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Parylene CVD vs. ALD vs. PECVD: Here's What R&D Leaders Should Know

Parylene CVD vs. ALD vs. PECVD: Here's What R&D Leaders Should Know

A side-by-side comparison of three thin film coating technologies for electronic applications. R&D product leaders like you and me drive innovation. We turn ideas and problems..

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Ensuring Parylene Adhesion: The Art of Proper Surface Prep

Ensuring Parylene Adhesion: The Art of Proper Surface Prep

If you're reading this article on ensuring good Parylene adhesion, chances are you already know a bit about Parylene and its properties, and now you're more curious about the..

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Conformal Coating Removal - How to Get Started W/Reference

Conformal Coating Removal - How to Get Started W/Reference

Conformal coatings are polymeric films on printed circuit boards (PCBs) that protect against hazards like moisture, pollution, chemicals, and temperature changes. This layer of..

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An Overview of Our Parylene Coating Equipment

An Overview of Our Parylene Coating Equipment

The development of our coating technology began in 2007. We've come a long way since, filing more than 200 patents and protecting millions of digital devices. Today, we want to..

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Parylene Coating Removal - Methods & Best Practices for Each

Parylene Coating Removal - Methods & Best Practices for Each

Parylene coatings present unique challenges when it comes to rework and removal. They often outperform other conformal coatings. Parylene has better barrier properties, uniform..

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Biocompatible Coatings - Coating Techniques, Applications, More

Biocompatible Coatings - Coating Techniques, Applications, More

Biocompatible coatings seamlessly integrate with the human body, offering benefits through their ability to promote healing and prevent adverse reactions. They can improve patient..

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Parylene Masking - General Concepts Explained

Parylene Masking - General Concepts Explained

Conformal coatings are an excellent way to increase the reliability of electronic components in harsh environments. However, this protection can be too much of a good thing..

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PECVD vs CVD – Chemical Vapor Deposition Overview

PECVD vs CVD – Chemical Vapor Deposition Overview

Thin-film deposition is the dynamic process used for depositing thin-film coatings onto a substrate, part, or assembly. Deposition methods, in general, can be grouped into three..

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IoT - Coating Consistency is Key

IoT - Coating Consistency is Key

IoT sensors aggregate and send data to IoT dashboards, simplifying critical, complex decisions quickly. One key area where this is particularly true is the utilization of sensor..

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6 Common Conformal Coating Defects & Their Solutions

6 Common Conformal Coating Defects & Their Solutions

When we say that a chain is only as strong as its weakest link, we aren’t talking about polymer chains – we’re talking about conformal coating defects. Regardless of the type, a..

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Conformal Coating vs Potting/Encapsulation - The Pros & Cons

Conformal Coating vs Potting/Encapsulation - The Pros & Cons

As the world of electronics continues to grow and evolve, printed circuit board assemblies (PCBAs) find their way into more and more products and industries. Whether you create..

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Parylene CVD vs. ALD vs. PECVD: Here's What R&D Leaders Should Know

May 1, 2025 / by Daniel Pulsipher posted in Coating Process, Coating Properties, PECVD Coatings, Thin Film Applications

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A side-by-side comparison of three thin film coating technologies for electronic applications.

R&D product leaders like you and me drive innovation. We turn ideas and problems into safe and manufacturable products by exploring new technologies, materials, and processes to meet technical needs and customer expectations. One such need and expectation is the development of smaller, "smarter," more reliable components and products. 

Protective coatings, particularly thin films (materials with thicknesses ranging from a few nanometers to a few micrometers), are one way to enable this development. Three of these coating techniques are thermal Chemical Vapor Deposition (CVD), Atomic Layer Deposition (ALD), and Plasma-enhanced Chemical Vapor Deposition (PECVD). Each of these techniques can deposit a wide range of materials. However, here we are going to refer to them as the techniques used to deposit HZO Guardian (Parylene), HZO Defender (thin ceramic), and HZO Sentinel Zero (layered hydrophobic) coatings using the respective methods.

Read more about HZO Guardian Plus Parylene Coatings

Learn about HZO Defender ALD Coatings

Understand Sentinel Zero PECVD Coatings

Let's examine the basic science behind each coating and the pros and cons of each. By the end of this overview, you should have a good idea of which option might be best for you, but I'll sum things up with some generalizations and questions you and your team can ask as you continue your research. This won’t be as much of a scientific paper, but rather a plain-language or conversational explanation of the concepts. If you’d like a deeper dive into the science, feel free to contact me personally and set up a meeting. 

 

What Makes a Good Protective Coating?

But before I dive in, let's align on what aspects of the coating you will likely be interested in. I realize everyone's knowledge of thin film coatings may vary. My company has a resource page, and I also recommend this paper by Vasilyev here to explore the science of thin film coatings further. However, in general, depending on your product, you might prioritize understanding the following:

Conformality: Can the coating reach deep crevices and cover 3D geometries evenly? 

Barrier Properties: How well does it block moisture, oxygen, or gases?

Mechanical Properties: Will it withstand abrasion or flexing?

Dielectric Performance: Is it insulating enough for sensitive or higher-power electronics?

UV Resistance: Will it hold up in direct sunlight or sterilization conditions?

Process Constraints: These include throughput, masking needs, temperature, etc.

With those criteria in mind, let's look at Parylene, ALD, and PECVD coatings. And for transparency, these are the coatings we offer at my company, HZO, which is also why I can speak to the science. I optimize and solve problems with these materials and processes every day.

 

Parylene: Flexible, Reliable, Conformal, Thicker 

Parylene is a vapor-deposited polymer known for uniformly coating complex shapes and internal crevices. This is thanks to its long-lived reactive species, which can travel deep into structures before reacting.

Parylene is deposited using a thermal chemical vapor deposition (CVD) process, which means it has a better “throw,” allowing you to get really conformal around components. The thermal activation of the precursor molecules typically allows the activation to last longer than an electrical activation. Parylene would be able to get inside smaller or deeper crevices, and you'd be able to coat hidden and difficult to reach areas that you normally can't conformally coat in a dip coating process. 

The coating is also flexible, but thick. And by thick - I mean relatively thick. Compared to an acrylic conformal coating, Parylene coatings are typically half as thick. But we're comparing it to the coatings yielded by the other two techniques in this overview - PECVD and ALD.

A common Parylene coating project is 7-25 microns thick, PECVD coatings could be 6 microns thick, but they are routinely 0.8-2.7 microns thick, and ALD coatings get even thinner. This is typical, but at HZO, we do a lot of customization, so if you have a question about a different thickness, please reach out

BL0147-Reliability-CVD vs ALD vs PECVD-Inline 1

A low magnification SEM image (left) and a corresponding Cl (chlorine) map (right) of a cross-section of a board-to-board connector. Note that the 10-micron thick coating covers the surfaces of the thin gap under the connector, reaching as far as the edge of the opening allowed it to.

If you need to coat underneath pins or if you need to coat in some crevices, then Parylene's a good balance between having something that's really conformal and not too thin versus something that's not conformal enough. I'll sum up Parylene's strengths and limitations below.

Strengths:
  • Excellent conformality, ideal for intricate 3D designs
  • Thick, flexible, and durable: its polymer backbone offers a good mix of pliability and robustness
  • Strong dielectric performance: effective at blocking electron flow
  • Water Vapor Transmission Rate (WVTR) is competitive at thicker layers
Limitations:
  • Soft surface: can be prone to scratching
  • UV degradation: prolonged UV exposure can lead to performance breakdown over time

 

ALD Coatings: Thinnest, Most Conformal, Superior Barrier Properties

BL0147-Reliability-CVD vs ALD vs PECVD-Inline 2

Snapshot of the ALD Process.

Atomic Layer Deposition (ALD) is a nanotechnology workhorse that builds coatings one atomic layer at a time in a coating chamber, similar to CVD. The result is an ultra-thin, pristine, and incredibly conformal film with unmatched barrier properties.

ALD is highly regarded for conformal coverage; it’s a lot more conformal than the CVD process used with Parylene. It is particularly suited for high aspect ratio structures because it can form a coating wherever the gas absorbs onto a surface. This gas is an unactivated gas or said another way, the gas is not in an excited state, instead it has a high chemical potential. When you send in the second gas, the second gas reacts with the first gas to make a film or an atomic layer coating. You can get this coating inside of many crevices, corners, and high-surface-area things, since anywhere both gases touch the surface, there could be a deposition. In contrast, Parylene has a limited number of times it can bounce off of a wall before it reacts and deposits on the wall. 

A problem with the ALD technique is that it takes a lot longer to deposit because the coating is built one layer at a time. If you want to build up a lot of layers, that takes a lot of time, which will be more costly. 

The layers that are deposited with ALD are normally of a ceramic nature including layers composed of alumina, titania, or silica, all of which are hard and brittle materials. Since the coatings are layered out atomically, there are less defects in the layers and that's great for protection because you could have a good barrier without any holes or gaps. 

Problems do arise because the ALD coatings are so thin and brittle, they can easily be broken or fractured. So, if you keep the ALD coating intact by making them the correct thickness, or adding other material layers, then it'll shield your products from many harmful gases, liquids, and harsh environments with very little thickness.

Usually, when you have an ALD process, you want to layer the coating. The coatings are layered with some other material that is deposited at a much faster rate, such as adding a CVD or PECVD layer that'll help protect the ALD layer, add flexibility, and add capabilities that outperform CVD and PECVD coatings alone. ALD is better at blocking gases. For example, if you want no oxygen, water, water vapor, or any kind of gas to pass through, then ALD would help you do that with a really thin layer.

Here are some strengths and limitations of Atomic Layer Deposition coatings.

Strengths:
  • The best conformality of the three processes, even in ultra-high aspect ratio features
  • Pristine chemical layer with very little defects: excellent for gas and moisture barriers
  • Extremely thin coatings: great when size and weight matter
Limitations:
  • Slow deposition process: less ideal for high-throughput production
  • Fragile: typically, a ceramic film is best used as part of a multi-layer stack to prevent defect formation and cracking

 

PECVD: Fast, Versatile, and UV-Resistant

BL0147-Reliability-CVD vs ALD vs PECVD-Inline 3

Snapshot of the PECVD Process. 

Plasma Enhanced Chemical Vapor Deposition (PECVD) is a plasma-assisted deposition technique that offers flexibility and speed. At HZO, our PECVD applied coatings excel in applications requiring thinner coatings (<6 microns) and at these thinner coating levels they give better protection than the equivalent thickness of a parylene coating. They can be hydrophobic, more oleophobic, transparent to high frequencies, and UV resistant.

Get Technical Datasheet for Sentinel Zero – UV resistant, PFOS & PFAS-free PECVD Coatings  

Get Technical Datasheet for EX – Transparent to High Frequencies (Low Loss Tangent), Omniphobic


Have more questions about the different properties of our PECVD coatings? Contact me.

PECVD-applied coatings can be deposited quickly and made in layers. For example, you can have a hard layer that is less conformal and more of a line-of-sight coating, and you could include that with a more conformal layer that is softer, but penetrates deeper into crevices. Then, the last or top layer could be a highly hydrophobic layer to prevent liquid water from ingressing into the stack or it could be harder layer to prevent the stack from being scratched.

PECVD coatings are a lot more conformal than many other coating techniques, but out of the three coatings we are discussing here, the PECVD coatings are less conformal because you have to activate your species electrically in a plasma, and that activated chemical has a limited lifetime.

In other words, if the travel time required before your activated gas reacts with a surface is too great because the area to coat is too far away or around too many corners, then that area will get less to no coating. The activated species has a limited time remaining active once it leaves the plasma zone. 

Our PECVD coatings are often chosen for their hydrophobic properties and UV resistance, which are crucial in specific applications. Take hydrophobicity. Water carries ions, and those ions help transport electricity and water itself. All devices run on some kind of electricity. So we want to prevent the water from staying on the board and causing damage from the ions. The hydrophobicity prevents the water from staying on the board if the board isn’t immersed in water.

Think about the typical use case for electronic devices—most entail only temporary exposure to water.  Even though our PECVD coatings can be tailored for longer exposure to water, sweat, or other harmful solutions in tests such as the IPX7 or IPX8 tests, all of our PECVD coatings are significantly hydrophobic regardless of thickness.  For example, we will probably spill water on our laptop; we won't use it underneath a pool. Hydrophobicity helps a lot with that. If the water gets into a little crack, capillary forces keep it in. If everything is hydrophilic, the water will want to stay in these cracks.

Of course, this causes problems you may not see with your computer right after the spill, but later on, corrosion develops because the water is still stuck in there.

Hydrophobicity helps the water not want to be there anymore. It pushes it out and helps it evaporate quickly, preventing the water from sitting on your device for too long. Meanwhile, UV resistance is critical for any application outside and not already in some kind of housing. Other coatings will degrade and break down in UV exposure, and so will their protection. This isn't the case with PECVD coatings. 

A huge benefit of going with a thinner PECVD coating is the potential for cost savings. Six microns or less is generally the cut-off for costs.  If you can keep close to this thickness layer, you can have punch-through capabilities. This means that when you have a connection that's often removed and put back on, you're punching through the coating once you plug in that connection. 

It is true that if you remove that connection from where it was plugged in, it isn't protected anymore. But other products like greases can help protect that area from water ingress, so if you want to plug in and unplug something while it's underwater, then greasing up that connection will help a lot, but as mentioned above a product with a thin plasma coating wouldn’t be constantly used in an underwater environment.

This will drastically reduce or eliminate the need for masking parts, reducing the price of the coating process and the cost of repairing it. If you need some areas without coating, you can use shadow masking, which is much cheaper than actual masking with glues.

Another benefit of the thin PECVD coatings is their ability to be transparent for high-frequency signals like radio waves, Wi-Fi, Bluetooth, or other signals that your device will be sending or receiving. One reason for this is the thin nature of the PECVD coatings, and the other is the low loss tangent of the chemistry used in our Sentinel EX coatings.

Strengths:
  • Better for thinner coatings with high hydrophobicity
  • UV resistance: performs well in sunlight or sterilization environments (Zero)
  • Shadow mask & punch-through capable: supports selective patterning
  • Faster processing, particularly for high-volume needs
  • Flexibility with layered chemistries beyond our standard coatings
  • Transparent to higher frequency signals (EX)
Limitations:
  • Sentinel EX: Softer than Parylene, offering less abrasion resistance
  • Extended immersion protection requires thicker films
  • Part size height limitations due to electrode-based chambers
Masking & Process Considerations

Masking can make or break your process regarding costs, especially when integrating coatings into production. The more your part is handled, and the more time is spent with it, the more costly the process could become. Here's how each technology compares:
  • Parylene: Complex to mask, but excellent for full encapsulation >6µm thick
  • ALD: Higher masking complexity. Best conformality of the three.
  • PECVD: Compatible with shadow masks and patterning

Comparison Table: Quick Reference

Feature Parylene ALD Coatings PECVD Coatings
Conformality High Highest

Moderate 

Dielectric Properties Excellent Moderate

Good

Mechanical Properties Flexible, relatively thick Fragile (ceramic) Softer than Parylene
WVTR/Barrier Performance Good, relatively thick Excellent, thin Moderate
UV Resistance Low  Moderate High
Hydrophobicity Moderate Low High
Process Speed Moderate Slow Fast
Masking Complexity High High Moderate-Low
Coating Cost (Speed+Masking) Moderate High Low-Moderate
Best Use Case Flexible, dielectric Ultra-thin, barrier UV, incidental

 

How to Choose the Right Coating: A Guide for R&D Engineers

BL0147-Reliability-CVD vs ALD vs PECVD-Inline 4

What are the common factors influencing the choice of one coating technology over another?

Factors to think about are what environment your end product is going to be in and what the coating will cost. Do you have something that's going to be underwater all the time and can cost more? Parylene is your best bet. Do you need to ensure that there's no particular ingress of a certain gas species in your environment? You might need an ALD coating to help with the protection you need. And if you need this to be out in a UV environment where we don't want any of it to degrade, then a plasma coating is a better choice. Do you just need to extend the life of your product by keeping water and sweat away? Then, a hydrophobic PECVD coating would work great.

Another factor is longevity. Do you want your product to last for years? Tens of years? Hundreds? We know that the longer you want a coating and its protection and enhancement to last, usually, the bigger, the thicker, and the more durable the coating needs to be. Most of our plasma coatings are thinner and help you protect a product from incidentals, but not for continuous immersion uses, although mass production coatings with a harder outer layer are being developed. 

Ultimately, though, I'm afraid there's no "winning" coating here. Only the right tool for the job. Some good questions to ask as you continue your research might be:

  • What are you protecting against? (moisture, UV, abrasion?)
  • What is the geometry of your part?
  • Are dielectric properties critical?
  • What's your target thickness, cost, and scalability?
  • Does your design require masking or selective coverage?

And some general advice?

  • Choose Parylene when flexibility and conformality are essential.
  • Use ALD when you need ultra-thin, ultra-pure, and gas-impermeable films.
  • Go with PECVD when UV exposure, hydrophobicity, or transparency to high frequencies are requirements, and cost is a concern. 

 

Final Thoughts: Match the Coating to the Mission

As electronic products evolve, so do the challenges we face in protecting them. At the R&D level, your coating decision shapes product performance, manufacturability, and regulatory compliance.

If you're unsure which path to take, consider running early coating tests with your development partner. We have found that in some situations, a hybrid or stacked solution (combining strengths from multiple technologies) yields the best results.

Want help evaluating coatings for your next product? Are you facing a problem with your current solution and starting to feel like you need an unprecedented solution? Let's talk. Use the contact us form to message me, and I will reply. I'm happy to share more about what I know to help you solve a problem, innovate a solution, or develop new technology.
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Ensuring Parylene Adhesion: The Art of Proper Surface Prep

March 11, 2025 / by Sara Nguyen posted in Coating Process, About HZO

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If you're reading this article on ensuring good Parylene adhesion, chances are you already know a bit about Parylene and its properties, and now you're more curious about the process. As the Process Engineer Manager at HZO, I can't stress enough how beneficial streamlined, optimized production processes are when bringing our customer concepts to life. 

Read more about Parylene masking

Our customers come from different industries but tend to want one thing in common—a durable, high-performance coating. Parylene needs good adhesion to do that

You already understand the importance of a clean, well-prepared surface from daily life. When was the last time you waxed your car without washing it first? If you applied wax over a dirty, dusty, or greasy surface, the wax wouldn't bond adequately; there would be streaks, uneven coverage, and poor protection. 

Similarly, if a PCBA isn't adequately cleaned before applying a Parylene coating, contaminants prevent it from adhering well, leading to weak coverage and potential failure. Surface preparation is understood and used across various industries—from chefs thoroughly cleaning a non-stick pan of debris before cooking to nail salons, filing and buffing nails, and swabbing them with acetone before applying paint. 

Yet, it is a concept that I feel isn't discussed enough when we talk about coating reliability. I'm going to explain why surface prep and cleaning might be more important than you think and give you an overview of the process so you can walk away with some actionable tips to use on your production line. I will go into precise cleaning techniques, so if you are an assembler and your goal is to clean your PCBAs and components before sending them to be coated, you will also find value in this post.

But first, let's talk about why your assemblies and components need surface prep. 

 

Careful! That Sample May Not Be As Clean As You Think 

Surface preparation and board cleaning are hot topics in our industry, and an entire history of why this is a debate would be beyond the scope of this article. If you are looking for that type of deep dive, Aqueous has a great reference.

I've observed, anecdotally, in my career that prospective customers often choose to skip surface preparation during sampling, and this can correlate with poor coating adhesion. Despite explaining the importance of surface preparation for achieving strong adhesion, we've encountered situations where, when we first recommend cleaning and outline the risks of not doing so—such as encapsulating contaminants like dust or dirt—prospects often decline to proceed with cleaning in order to save on costs or processing time. 

While there are cases where the outcome is acceptable, failures frequently occur due to contaminants trapped on the board. Given that not all potential sources of contamination on the manufacturing floor are immediately visible to the naked eye, our partners may be misled into skipping this crucial step. This can lead to issues down the line, as even invisible contaminants can compromise the quality of the coating adhesion and ultimately can lead to corrosion and other reliability issues.

This can frustrate our partners because of wasted time and resources, as we will have to start again, this time with surface preparation. However, it's somewhat understandable if you don't consider all of the possible sources of contamination on the manufacturing floor that may not even be visible to the human eye. 

Contamination Sources 

●    Flux residues 
●    Material handling 
●    Upstream/ Downstream 
●    Touch up and Repair 
●    Fingerprints
●    Dirt 
●    Lint
●    Skin oils 
●    Hand Lotions
●    Salts from worker perspiration 
●    Particulate matter in the air from cardboard 

 

surface cleaning contaminants commonly found on the manufacturing floor

 

Think of these tiny contaminants as ticking time bombs when they come between the Parylene coating and your component. The coating may not lift right away - causing delamination - but only time will tell if you have a huge issue on your hands. If you're not a fan of risk, read about how to ensure good Parylene adhesion with surface prep and precise cleaning techniques.

Read about Parylene removal


Ensuring Adhesion with The Surface Prep Process

Again, proper preparation of the substrate is crucial for the coating to adhere correctly. The surface should be clean (as possible) and free of contaminants that could interfere with the bonding process. First, use appropriate cleaning agents for the substrate to remove grease, dirt, oil, and other contaminants. 

The choice of cleaning agent depends on the type of contamination and the material of the substrate. Common cleaning agents include:

Solvent and Aqueous-Based Cleaners

●    Isopropyl Alcohol (IPA): Effective for removing light oils, grease, and flux residues.
●    Alkaline Detergents: Solutions containing surfactants, such as sodium hydroxide or potassium hydroxide, break down organic contaminants.
●    Citrus-Based Cleaners: Environmentally friendly options that dissolve oils and grease.
●    Deionized (DI) Water with Detergents: Used for water-soluble contaminants and light residues.

At HZO, we commonly recommend an ultrasonic wash and bake for precision removal and less abrasive cleaning. The ultrasonic wash uses high-frequency sound waves in a cleaning solution to remove contaminants such as dust, oils, and residues from the substrate at a microscopic level.

This method provides deep, uniform cleaning, especially for intricate or delicate components. Following this, the bake step involves heating the substrate to eliminate moisture and volatile residues that could interfere with the adhesion and uniformity of the parylene coating. Together, these steps enhance coating reliability, ensuring a clean and stable surface for deposition.

Specific pre-treatment surface modification steps may be required depending on the material, such as aluminum, steel, or plastic. You can use physical surface modification to give the Parylene physical roughness to latch onto. At HZO, we use plasma to roughen the surface and increase the surface area for adhesion. In this process, bombardment by active Argon atoms causes roughening at the molecular level.

You can also use chemical surface modification methods. These give coatings like Parylene a chemically attractive surface on which to bond. We use adhesion promotors such as silane to create a stronger bond. 

Precise Cleaning Techniques  

Cleaning is not just about removing visible dirt; it also involves eliminating microscopic contaminants that could prevent the coating from bonding or make customer parts appear aesthetically unappealing. We tailor the cleaning method to the contamination and the substrate. Sensitive substrates cannot handle all cleaning methods. 

For example, isopropyl alcohol is sometimes used to clean surfaces. We avoid solvent cleaning unless we know it's the proper solvent for the material to prevent damage or ensure no residues that could affect adhesion. After using solvents, we recommend using dry, filtered air to blow off any remaining residues or moisture. 

The following chart describes types of substrate materials and their reactions to cleaning methods. 

Substrate Materials Reactions to Cleaning Methods
Electronic Components Generally tolerate all cleaning methods, but items such as displays, MEMS, and optical components can be sensitive.
 Solder Mask Very robust but can be discolored by plasma. A known point of delamination and contamination in surface energy.
Other Conformal Coatings Some conformal coatings have very low surface energy, and some can inhibit cure of other coatings (acrylics and silicones, for instance).
Solder Joints Combined with the standoff gap of components and chips, these are areas most likely to hold contaminants both before cleaning (flux) and after (the solvent or detergent).
Other Metallic Surfaces Copper and silver can be discolored by aqueous/acidic/basic solutions in cleaning, as well as possible oxidation or tarnishing.

 

Compressed Air and Ionizers 

Compressed air and air ionizers play a crucial role in the final stages of surface preparation for Parylene coating by ensuring no residual contaminants remain on the substrate. Dry, filtered compressed air, used in short bursts to avoid dislodging components, can remove any remaining dust, lint, or microscopic debris that may have settled after previous cleaning steps. This step is crucial for intricate or delicate components where trapped particles could compromise coating uniformity. 

Alongside compressed air, air ionizers are often used to help neutralize static charges that attract dust and contaminants to the surface, especially in environments with sensitive electronics or plastic components. By eliminating electrostatic forces, air ionizers prevent airborne particles from re-adhering, ensuring a clean, contamination-free surface for optimal Parylene adhesion and performance.

Environmental Considerations and Safe Handling Procedures

Environmental conditions, such as room cleanliness, can affect the quality of a coating application. Specks of dirt, lint, or other particulates in the air could easily land on the components or assemblies. Keep items such as cardboard boxes off the floor and the production line orderly. 

The process is always essential. To avoid contamination before coating, ensure that the coated parts are not exposed to contaminants like dust, as contaminants on the surface may interfere with adhesion.

Additionally, industry standards, such as IPC-A-610, provide recommended practices for safely handling electronic assemblies to minimize the amount of contamination. Recommendations include: 

  1. Keep workstations clean and neat. Do not eat, drink, or use tobacco products in the work area. 
  2. Minimize the handling of electronic assemblies and components to prevent damage. 
  3. When gloves are used, change as frequently as necessary to prevent contamination from dirty gloves. 
  4. Do not handle solderable surfaces with bare hands or fingers. Body oils and salts reduce solderability, promote corrosion and dendritic growth. They can also cause poor adhesion of subsequent coatings or encapsulates.
  5. Do not use hand creams or lotions containing silicone since they can cause solderability and conformal coating adhesion problems. 
  6. Never stack electronic assemblies, or physical damage may occur. Special racks may be provided in assembly areas for temporary storage.
  7. Always assume the items are ESDS (Electrostatic Discharge Sensitive) even if they are not marked.
  8. Personnel must be trained and follow appropriate ESD practices and procedures.

  9. Never transport ESDS devices unless proper packaging is applied.


Parylene Adhesion Tests 

Regarding customer projects, we never make any assumptions, no matter how optimized or streamlined the process is. Test everything. We use cross-hatch testing internally to ensure our coating bonded well. 

Cross-hatch testing is a widely used method for evaluating the adhesion strength of coatings to a substrate. This test involves making precise cuts in the coating, typically in a grid or cross-hatch pattern, using a sharp blade or specialized cutter. After scoring the surface, adhesive tape is applied and quickly removed to assess how much the coating detaches. The adhesion is then rated based on the percentage of coating removed, with classifications ranging from excellent adhesion (no coating loss) to poor adhesion (significant peeling or flaking). Cross-hatch testing provides a quick and reliable way to assess coating durability and performance, ensuring that coatings meet quality and industry standards before being subjected to real-world conditions.


A Good Cleaning Process Brings Parylene to Life

When people contact us about Parylene coating, it's typically about a property they’ll need to meet a spec or solve a problem. For example, they need superior corrosion resistance. They'll also need good adhesion, which means they'll need good surface prep. 

My team and I work daily to bring customer visions to life through streamlined, dependable processes. Our problem-solving skills save our customers money and time and enable and enhance our amazing technology at HZO. 

In the coming months, I'll share more about how you can use the process to do the same for your company. Of course, I can't share the custom solutions we've developed for our partners, but I'm happy to provide value where I can. 

Do you have questions about process engineering in Parylene or surface preparation? Use the contact form to send me a message, and I'll get back to you. Otherwise, learn more about the Parylene coating process in its entirety. 

 

 

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Conformal Coating Removal - How to Get Started W/Reference

October 10, 2024 / by Mallory McGuinness-Hickey posted in Conformal Coatings, Coating Process

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Conformal coatings are polymeric films on printed circuit boards (PCBs) that protect against hazards like moisture, pollution, chemicals, and temperature changes. This layer of material is vital for the longevity and reliability of electronic parts. But sometimes, conformal coating removal or rework is necessary.

There are five primary conformal coating materials: acrylics, epoxies, silicones, urethanes, and Parylene. Each material presents its advantages, limitations, challenges, and application methods. Understanding these details can help operators determine how best to remove each material. This is why we will start with a brief summary of each coating material's properties.


Acrylic (AR) Conformal Coating Properties

  • Low moisture absorption
  • Relatively short drying times
  • Clear protective coating
  • Good electrical and physical properties
  • Typically brushed, sprayed, or dipped

Epoxy (ER) Conformal Coating Properties

  • Very robust
  • Excellent chemical and abrasion resistance
  • Very rigid conformal coating
  • High dielectric strength
  • Typically brushed, sprayed, or dipped

Read more about epoxy conformal coating

Silicone (SR) Conformal Coating Properties

  • Good humidity and moisture resistance
  • Low toxicity
  • Easy to apply
  • Easy to repair
  • Typically brushed, sprayed, or dipped

Properties of Urethane (UR) Conformal Coatings 

  • Moisture and oil-resistant
  • Fungicidal
  • Good flexibility
  • Can be thinned to achieve a chosen viscosity
  • Typically brushed, sprayed or dipped

Read more about polyurethane conformal coating

Properties of Parylene (XY) Conformal Coatings

  • Biostable, biocompatible
  • Excellent chemical resistance
  • Superior conformality
  • Exceptional corrosion resistance
  • Applied by chemical vapor deposition (CVD)

Learn about Parylene coating

engineer looking at PCB to determine how to best remove conformal coating

Why Does Conformal Coating Need to be Removed?

  • Incorrect application - this may lead to incomplete coverage, bubbles, or excessive thickness. If these defects hurt the circuit board's function or reliability, operators must remove and reapply the coating.
  • Need for repairs - during repairs, removal allows for precise soldering and component replacement.
  • Rework - this often involves altering circuits, necessitating access that is obstructed by existing coatings.
  • Failure analysis - failure analysis can prevent future errors. But, technicians must examine the original circuit materials without obstruction.

Read the definitive paper on electronic protection methods

Before Removing Conformal Coatings - Safety Precautions

Safety is paramount before removing conformal coatings from electronic components. The compounds and methods for stripping conformal coatings can be risky. If proper precautions are not followed, they can harm health.


Essential Safety Measures

Dedicated working environments with adequate ventilation are required. This is non-negotiable. Solvent fumes can be harmful if inhaled in high concentrations. So, a well-ventilated area, using natural means or fume extractors, minimizes inhalation risks. Also, some coating removal techniques create dust or aerosols. So, use suitable air filtration systems.

Flammability is another factor to consider. Several solvents and chemicals employed in the removal processes are highly flammable. To prevent combustion, keep the workspace free of ignition sources, like sparks or open flames.


Electricity poses a significant risk. Turn off and unplug all devices. This will prevent accidents during the conformal coating removal process.

How to Remove Conformal Coating - First Step

Check the coating on the PCB you want to remove. This will help find the best method to remove the conformal coating. You can usually confirm this by contacting your coating supplier. Or, look for a JEDEC or IPC label on the board. Coatings are designated as AR, SR, ER, UR, or XY, indicating which coating you are working with. If there are no labels, you can still identify the material via methods outlined by the IPC below.
Each conformal coating has distinct properties. So, you can test for transparency, solubility, hardness, thermal removal, and thickness. These tests will show you which type of coating you have. For more information, see
IPC’s “Coating Removal, Identification of Conformal Coating” guidelines.

 

Coating Removal Techniques

After identifying your coating, the next step is to choose the removal technique. Popular methods are briefly discussed below:

Peeling Method

For RTV silicone or thick rubber coatings, use a dull blade or knife to slit and peel off the coating.

Chemical Solvent Method

This process effectively removes urethane, acrylic, and silicone coatings. Prep the area with high-temperature tape and apply solvent using a foam swab.

Grinding and Scraping Method

This removal technique can grind away thin, hard coatings with a micro motor or rotary-style tool or soft coatings with a rotary brush.

Thermal Method

Using low-temperature heat, gently burn and melt the coating material.

Micro Sandblaster Method

This technique involves projecting a fine abrasive powder onto the coating to flake off the material.

engineer observing PCB with equipment

 

Which Technique is Best for My Conformal Coating Material?

Urethane Coatings

  • Grinding and scraping method
  • Solvent method
  • Micro-blasting method

Acrylic Coatings

  • Thermal removal method
  • Chemical solvent method
  • Scraping and grinding method
  • Micro-blasting method

Epoxy Coatings

  • Thermal removal method
  • Grinding and scraping method
  • Micro-blasting method

Silicone Coatings

  • Grinding and scraping method
  • Micro-blasting method
  • Chemical solvent method
  • Thermal method

Parylene Coatings

Parylene coatings are often hard to remove. You can usually use micro-blasting, grinding, scraping, and thermal methods. But at HZO, we have simplified the reworking process using technology. The next blog in this series, will discuss reworking Parylene in general and detail how we simplify the process.

For more information on thin-film coatings for your project, contact us today.

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An Overview of Our Parylene Coating Equipment

September 26, 2024 / by Ryan Moore posted in Parylene, Coating Process

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The development of our coating technology began in 2007. We've come a long way since, filing more than 200 patents and protecting millions of digital devices. 

Today, we want to nod to our origin story. We also want to introduce, at a high level, a key material that is a building block of our technology.


Learn more about the Parylene process and Parylene properties.

Parylene Protection

Parylene (or Poly(p-xylylene) as it’s also known) is a protective coating. It's deposited using a chemical vapor deposition process. The material is a moisture-resistant, dielectric thin film barrier. It has been used for over five decades on many corrosion-resistant products. Parylene is biocompatible, has superior barrier properties at 50% thickness and is chemical-resistant. Think big. Think powerful. Parylene has been protecting equipment and products in some of the world's most advanced industries for decades.

Read more about WHY ENGINEERS USE PARYLENE

HZO has developed its proprietary technology using Parylene as a building block. Over the years, it has improved its chemistry and processes. It also automated its Parylene masking and removal equipment. These innovations form a unique and powerful conformal protective solution.

 

Parylene Overview

So why have most people never heard of it? A major obstacle to wider adoption of Parylene is its high cost. This affects many products, including consumer devices.

Learn more about Parylene coating cost considerations

The Parylene deposition system and its raw material are expensive. There have been challenges with scalability, manufacturing, and device complexity. There has also been a manual process for masking and demasking sensitive areas that need protection from protective layering.

To the credit of Parylene companies that have been in that market for much of this journey, the technology has improved dramatically over time. The material has a sterling reputation in certain markets where development has been focused. But what about other industries that need the same kind of powerful protection?

 

HZO Parylene Coating Equipment Broadens the Scope

 

HZO Parylene coating equipment

 

HZO has expanded the use of this powerful, organic material. It has made it available to companies and manufacturers that had not considered it an option until now. The application’s utility is what separates HZO from other companies in the Parylene space.


We talk a lot about the power of the Total HZO Solution. This includes more than our thin-film protective layering technology. That technology protects digital devices from corrosive liquids. It also includes advances in equipment, integration, and specialized processes. These are required to protect some of the world's most complex digital devices. HZO is a leader in custom solutions for digital devices. Years of work on the technology have made it so. Parylene is part of that solution.


Our ongoing innovations benefit every company we work with. HZO has made Parylene's benefits more accessible and affordable than ever. As a result, more sweat and corrosion-resistant products are reaching consumers. The change in performance is starting to get noticed, and the cry for better protection on consumer devices has never been stronger.

 

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Parylene Coating Removal - Methods & Best Practices for Each

September 12, 2024 / by Mallory McGuinness-Hickey posted in Parylene, Coating Process

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Parylene coatings present unique challenges when it comes to rework and removal. They often outperform other conformal coatings. Parylene has better barrier properties, uniform coverage, and performance in thinner layers

Learn more about what Parylene is used for.

Additionally, Parylene's chemical resistance can withstand corrosive gases and liquids. It also performs in extreme temperatures and high electrical activity.

 

 

Want to know if HZO Parylene meets your specifications?

 

But, the properties that make Parylene the "gold standard" of conformal coating can also make it hard to remove. Thankfully, you can use methods to remove and rework Parylene when needed.

 

When Do You Need to Remove Parylene?

 

From time to time, it is necessary to rework or remove coating. Sometimes, job specifications change or a Parylene vendor incorrectly applies the coating.

What is Parylene Delamination?

One example of poor application is Parylene delamination. This is when the conformal coating separates from the coated surface. This results in an unattached, torn, non-conformal coating and an unacceptable finish. Delamination defeats the purpose of Parylene coatings. It must be avoided at all costs. Even partial lifting can render the protective coating useless.

What Causes Parylene Delamination?

Many causes of Parylene delamination exist. One is demasking, a standard process. It creates a need for high-quality inspections after production. Other causes include:

Coating porosity: A vapor pressure difference creates a risk of moisture intrusion into the substrate. Pressure fluctuations and temperature changes create osmotic pressures. These separate the coating from the component.

Incompatible materials: The Parylene coating must bond with the component surface for successful coverage. When the Parylene and the surface are incompatible, they create incongruous surface energies. This causes minimal bonding.

Contaminated surfaces: Improperly cleaned component surfaces do not support adhesion.

Regardless of the reason, the resulting Parylene removal must be efficient and safe. It must protect the coated substrate's integrity.

The following methods are popular ways to approach Parylene removal.

 

How Do You Do Mechanical Parylene Removal?

Parylene's strength and uniformity make it tough to remove. So, be careful with mechanical methods. They may damage the final product. However, Parylene is a soft polymer. So, mechanical methods may remove it.

Methods like picking, cutting, and scraping are effective. But, they may damage components, substrates, and delicate track lines. This type of removal requires considerable attention and care. Good spot removal is possible with proper masking. But, mechanical methods may be unreliable for larger surfaces.

 

How to Remove Parylene with Micro-Abrasion

Micro-abrasion is a process performed with automated or handheld systems. It targets a specific area by blasting the Parylene coating with inert gas or dry air and abrasive media. This removal method is suitable for both whole board and spot removal. It is generally easy to put in place, quick, cost-effective, and environmentally friendly.

 

Can You Use Thermal Removal With Parylene?

Parylene can withstand high temperatures. But, a high-temperature oven or soldering iron can remove it in small, specific areas. As heat is applied, the coated component rises from the board and lifts off.

This technique may be adequate for small repairs. It is less reliable for large surfaces. But, it can still be effective for some jobs. However, residues and discoloration may occur. Parylene's high melting point may damage heat-sensitive substrates. Thermal removal can be hard to manage. It's not recommended without Parylene experts' help.

thermal removal parylene removal method

 

 

Which Chemical Can Remove Parylene?

Parylene is chemically inert, resisting chemical degradation. But, one chemical has been used to strip Parylene from substrates and components. It is a colorless organic compound, tetrahydrofuran (THF), with the formula (CH2)4O. This solvent softens the Parylene coating. It temporarily loosens the bond between the substrate and the coating. At this point, the Parylene can be lifted off with tweezers. THF can remove Parylene, but it may damage the coated part. Use the solvent only for complete coating removal. For the security of the components under the coating, consider other removal methods before using TFH.

 

Laser Ablation for Parylene Removal

Laser ablation is a process that removes material from a surface by irradiating it with a laser beam. The beam can cut, drill, or mark delicate materials, providing precise removal. At HZO, a laser ablation process converts Parylene to gas or plasma with pulsed laser sources. This method is cost-effective for complex removals. It gives better results. It can also service 3D devices and Parylene-free areas.

Conclusion

There are many effective methods to remove Parylene should the need arise. Each method has its strengths. So, you must know your options. Then, choose the best method for your project.

If you need Parylene removal or want to discuss your project with experts, please message us today. Removing Parylene can be tough. But, a skilled company can simplify and lower the cost of the job. We can help with scalable Parylene equipment and Parylene masking automation. We can also address concerns about the cost of Parylene services.

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Biocompatible Coatings - Coating Techniques, Applications, More

September 13, 2023 / by Mallory McGuinness-Hickey posted in Protection Capabilities, Coating Process, Coating Properties, Thin Film Applications

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Biocompatible coatings seamlessly integrate with the human body, offering benefits through their ability to promote healing and prevent adverse reactions. They can improve patient outcomes, reduce complications, and enhance device functionality. As such, biocompatible coatings have become an indispensable tool in various medical applications.

 

What is Biocompatibility, and What Affects the Biocompatibility of Coatings?

 

Biocompatibility refers to the ability of a material to function without causing any harmful effects to the living tissues or organs it comes into contact with.

Several factors influence the biocompatibility of coatings. One such factor is the material composition. The choice of materials used in a coating can significantly impact its compatibility with the human body. Additionally, the surface properties of the coating play a vital role in determining its biocompatibility. Roughness, porosity, and surface energy can affect how the coating interacts with biological tissues and fluids.

When it comes to achieving biocompatibility in coatings, there are key considerations. First and foremost, the material should be non-toxic and non-allergenic. It should not trigger any adverse immune responses or elicit any toxic effects. Furthermore, the coating should withstand the physiological environment it will be exposed to, such as changes in pH, temperature, and mechanical stress.

Coating application processes also play a significant role in achieving biocompatibility. The application technique must ensure uniform coverage and adherence. Proper surface preparation and application techniques are essential to avoid issues arising from poor coating adhesion or inconsistencies.

 

Why are Biocompatible Coatings Important?

Biocompatible coatings can significantly influence the body's response to medical devices and implants. A well-designed biocompatible coating can minimize inflammatory responses, prevent bacterial adhesion, and promote tissue integration. Furthermore, by providing a protective and biologically compatible barrier, these coatings enhance the safety and effectiveness of medical devices, improving patient outcomes.

There have been several successful applications of biocompatible coatings in medicine and biomedical engineering. Here are a few examples:

  • Orthopedic implants: Biocompatible coatings have been used on orthopedic implants to improve their longevity and reduce inflammation and tissue rejection.
  • Drug delivery systems: Coatings have been developed to encapsulate and protect drugs, allowing for targeted delivery and controlled release within the body.
  • Stents: Biocompatible coatings on stents help to prevent blood clot formation and promote healing in cardiovascular applications.
  • Dental implants: Coatings on dental implants enhance biocompatibility, improving the integration of the implant with the surrounding bone.

 

Coating Technologies

Various coating technologies are employed to achieve biocompatibility in different medical devices. These technologies involve using specific materials and techniques to create coatings that meet the required standards:

Chemical Composition

Different biocompatible coating materials, including polymers, such as Parylene, ceramics, and metals, are used. Each type has its unique characteristics and advantages for medical applications. Polymers, for example, are known for their flexibility and ability to mimic natural tissues. Ceramics offer excellent wear resistance and can provide a stable surface for cell growth, while metals are valued for their durability and strength.

Coating Techniques

Each coating technique has its advantages and limitations. The selection of a particular method depends on factors such as the desired coating properties, the substrate material, and the intended application. The deposition of biocompatible coatings requires specific techniques to ensure uniformity and adherence to the substrate. Several coating techniques are commonly employed in the medical industry, including:

  • Chemical vapor deposition (CVD): In this technique, a precursor gas is introduced into a chamber and reacts to form a coating on the surface of the substrate. CVD offers excellent coating conformity and is frequently used for coating stents and catheters.
  • Electrochemical deposition: Also known as electrodeposition, this technique involves using an electric current to deposit a material onto a substrate. It is typical for coating electrodes and medical implants.
  • Dip coating: This technique entails immersing the substrate into a bath of the coating material and then withdrawing it at a controlled rate. Dip coating provides a uniform and controlled coating and is often used in the fabrication of medical devices.
  • Spray coating: The coating material is atomized and applied to the substrate in a fine spray. This is a popular technique for coating dental implants and prosthetics.

 

Biocompatible Coatings Applications

Biocompatible coatings can be employed in manufacturing electronic devices, food processing equipment, and cosmetic products, among others. With their ability to provide a safe and reliable surface, biocompatible coatings offer advantages beyond the medical field.

However, within various areas of medicine, biocompatible coatings play a crucial role in enhancing the compatibility of medical devices, improving tissue engineering techniques, and revolutionizing drug delivery systems. These coatings have transformed the field of medicine by reducing rejection and adverse reactions and improving the overall efficiency of medical interventions. Three use cases are described below.

Medical Implants

One of the critical applications of biocompatible coatings is in the field of medical implants. For instance, in orthopedic implants, biocompatible coatings create an optimal environment for the implant to integrate seamlessly with the surrounding tissues and bones. Similarly, dental and cardiovascular implants benefit from biocompatible coatings, promoting long-term stability and functionality.

Drug Delivery Systems

Biocompatible coatings have revolutionized the field of drug delivery systems by improving stability, enhancing bioavailability, and enabling targeted drug delivery. The efficacy and safety of drug delivery are significantly improved by coating drug carriers such as nanoparticles, microparticles, and implants with biocompatible materials. These coatings protect the drugs from degradation, facilitate controlled release, and ensure targeted delivery to specific tissues or cells.

Biomedical Devices

Biocompatible coatings find extensive applications in various biomedical devices, including biosensors, microfluidic devices, and prosthetics. These coatings enable seamless integration and interaction with biological systems, enhancing the device's functionality and reducing the risk of adverse reactions. For example, biocompatible coatings on biosensors allow accurate and reliable detection of biomarkers, while coatings on prosthetic limbs improve their integration with the human body and enhance user comfort and mobility.

 

Factors Influencing Biocompatible Coating Selection

Selecting the most suitable material for a specific application is essential to ensure optimal biocompatibility and overall performance of the coating. There are various factors to consider when selecting materials for specific medical applications. These factors include:

  • Chemical composition: The specific chemicals used in the coating formulation can significantly influence its biocompatibility with the surrounding environment.
  • Surface interactions: Understanding how the coating interacts with the surrounding biological tissues and fluids is crucial to ensure proper biocompatibility.
  • Thickness and uniformity: The thickness and uniformity of the coating play a vital role in its ability to protect the underlying substrate and provide the desired properties.
  • Physical properties: The physical properties, such as hardness, flexibility, and adhesion strength, must be considered when selecting a coating for a specific application.

Please contact our engineers if you require a biocompatible coating material for your application or have questions about protective thin film coating properties. Meanwhile, please browse our resource section to learn about other relevant properties, such as tensile strength, yield elongation, and corrosion resistance.

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Parylene Masking - General Concepts Explained

January 28, 2022 / by Mallory McGuinness-Hickey posted in Parylene, Coating Process

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Conformal coatings are an excellent way to increase the reliability of electronic components in harsh environments. However, this protection can be too much of a good thing without processes to ensure certain areas remain coating-free.

These polymeric films can inhibit the critical functions of specific functions, but the masking process resolves this issue. With proper masking, you can benefit from conformal coating protection without losing functionality.

 

What is Masking?

Masking is applying a temporary film, boot, tape, or plug to designated assembly components to prevent them from being coated. While masking is important for conventional coatings such as acrylics, epoxies, urethanes, and silicones, Parylene has unique qualities that create a critical need to ensure it is done right.

 

Quick Introduction to Parylene Masking Techniques

For general guidance on conformal coating masking, the IPC-HDBK-830A handbook provides a good reference. However, because the coating process causes Parylene molecules to penetrate any surface area accessible to air, operators must ensure that all coating keep-out areas resist Parylene coating application, which requires domain expertise.

HZO uses proprietary masking equipment, and our engineers build and customize techniques for every project. However, a short description of general methods follows below.

Parylene masking techniques typically involve precisely sizing materials such as tapes, form-in-place gaskets, and boots to designated masked regions. After applying materials to the appropriate areas, a masking operator will allow peelable masking materials to dry before starting the CVD process, coating the entire component. After coating, the masking material is carefully removed.

 

Why Proper Masking for Parylene Coating is So Critical

Parylene’s exceptionally high dielectric strength requires you to mask the right areas diligently. A PCBA coated with Parylene would benefit from electrical insulation protection. However, if the connectors on that same PCBA get covered, you won’t be able to plug it in or make connections.

Another reason you must get your Parylene masking process correct is the film's incredible conformality. Where Parylene is allowed to penetrate, pins and moving parts will be completely encapsulated. Although this cohesive and thorough presence of coating is typically considered a benefit, additional cost and labor to remove the Parylene from the keep-out areas will be required with incorrect masking implementation. In other words, it’s best to prevent instead of rework, which can be challenging due to Parylene’s strong chemical resistance properties. 

 

Why It Can Also Be More Complicated

When you mask for Parylene application, the stakes are higher. Once it’s on, removing the coating will be a struggle without a knowledgeable partner with tools and techniques to make rework easier. The fact that masking for Parylene is also more complex, requiring more skill, raises further complications.

Without skill and experience, masking for Parylene is more challenging than general conformal coating masking due to the chemical vapor deposition process (CVD) used to apply the coating.

Learn about Parylene Thickness 

Unlike conventional conformal coatings applied as liquids, Parylene is applied as a vapor, which means you are masking against a gas. Therefore, a much better barrier is required with the Parylene masking process, as vapor can more easily bypass masking materials.

Other masking considerations include:

  • The need to validate if all components are hermetically sealed or not due to the vacuum nature of the CVD process
  • Chamber maintenance
  • Masking more than just keep-out locations may be required
  • The need for specific fixturing
  • Materials need to be thoroughly cured before coating, and outgassing should be avoided

The list below includes components that, in many cases, should not be coated:

  • MEMs
  • Actuators
  • Mating connectors and pins
  • Test points needed before assembly
  • Ground contacts

Parylene Coating With HZO

Parylene Masking with HZO

 

If you are masking for Parylene, you must implement the process correctly. Further, Parylene masking requires considerable expertise and experience to identify factors affecting masking success. These might include Parylene masking materials, the Parylene type, and the different areas that must be coated. Proper timing is also essential, as there is a relationship between the masking and coating processes. Any timing issues can impede coating quality. Managing electrostatic discharge is also a concern when masking.

Fortunately, our engineers have years of this experience, creating custom masking plans for customers with electronic products of all sizes, shapes, and functions. We have also developed industry-leading masking equipment that can automate and semi-automate the process for larger productions.

Reach out today if you would like a consultation to discuss why to use Parylene, our scalable Parylene coating equipment, or our automated masking processes that decrease Parylene coating costs

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PECVD vs CVD – Chemical Vapor Deposition Overview

May 7, 2021 / by Ryan Moore posted in Coating Process, PECVD Coatings

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Thin-film deposition is the dynamic process used for depositing thin-film coatings onto a substrate, part, or assembly. Deposition methods, in general, can be grouped into three categories – liquid coating deposition techniques, physical vapor deposition, and chemical vapor deposition. This article will focus on chemical vapor deposition and one of its variants, plasma-enhanced chemical vapor deposition (PECVD).

 

Download our white paper on choosing the correct coating methodology for your next project:

 
 

Chemical Vapor Deposition Methods

Chemical vapor deposition (CVD) methods (including but not limited to CVD, PECVD, and atomic layer deposition, ALD) are done under vacuum, well below atmospheric pressure, as the process deposits layers of material molecule-by-molecule or atom-by-atom. With these techniques, thin-film layers can be deposited in the range of nanometers to sub-20-micron, compared to traditional deposition, which yields coatings at 50-500 microns.

No matter the method, vapor deposition produces coatings that alter the substrates’ electrical, mechanical, optical, thermal, and corrosion-resistance properties. The resulting dry coatings are durable and have reached optimal properties without curing at the end of the production cycle.

Below is an overview of the chemical vapor deposition process.

 

Overview of the Chemical Vapor Deposition Process

The CVD process deposits materials, including Parylene, in a vacuum chamber by vapor deposition polymerization. The item to be coated is exposed to one or more precursors, which decompose or react on the surface. In the instance of Parylene, a solid dimer is vaporized to gas. Before entering the deposition chamber, the gas travels through a pyrolysis chamber that cracks the dimer into two di-radical monomers. The monomers adsorb onto the substrate as a polymer.

 

an Overview of the Chemical Vapor Deposition Process

 

Chemical vapor deposition is used to augment substrate surfaces in ways that traditional modification techniques cannot. Polymerization by CVD allows for thin coatings with properties such as lubricity, weather resistance, and hydrophobicity.

Chemical vapor deposition is a repeatable process that produces consistent coverage and reliable results. Applications include:

Many hybrid application techniques arise from CVD, evolving to modify the properties of fabricated thin films. Among these variants, PECVD is a method that can extend the applicability of the technique for reactive and inorganic materials, inert materials, and various precursors. This technique is discussed below.

Overview of the Plasma Enhanced Chemical Vapor Deposition Process

Plasma-enhanced chemical vapor deposition is a variant of CVD; however, it uses plasma energy instead of only thermal energy to deposit thin films. The plasma is typically created by radio frequency, direct current, or microwave discharge that energizes reactant gases, such as silane or oxygen, to form a plasma. The deposition equipment uses a mixture of ions, free electrons, radicals, excited atoms, and molecules to deposit thin-film coatings to the substrate. Parts in the chamber are bombarded with energetic ions (plasma) that form a thin-film layer on the surface made from metals, oxides, nitrides, and/or polymers (fluorocarbons, hydrocarbons, silicones).

 

PECVD Process Diagram

 

 

PECVD-deposited films have excellent physical properties because they are uniform, highly cross-linked, and generally resistant to chemical and thermal changes. Plasma-applied polymers are extensively used in optical coating and dielectric films due to their lower cost and higher efficiency properties. Offering excellent control of material properties (stress, refractive index, hardness), PECVD also produces films used in the semiconductor industry for device encapsulation, surface passivation, and isolation of conductive layers.

Different film compositions can easily be adjusted to produce organic thin films on large substrates (glass and silicon) with varying chemical, thermal, optical, electrical, and mechanical properties. PECVD has also recently been used for many biological applications, including medical device protection, and is also used to avoid corrosion in optical and dielectric devices.

This nanocoating process can use various materials as coatings, including metals, oxides, or silicon, which may offer more flexibility than CVD. Applications include:

  • Fabrication of electronic devices to isolate multiple conductive layers, capacitors, and for surface passivation
  • Solar cells, semiconductor devices, and optically active device applications due to optical, mechanical, and electrical properties
  • Processing of printable electronic devices due to high process efficiency, large-scale patternability, lower cost, and environmentally friendly nature
  • SiN (silicon nitride) PECVD films are used for semiconductor applications due to higher capacitance density, breakdown voltage, and particle performance.
  • SiC (silicon carbide) PECVD films have demonstrated promise in developing high-temperature withstanding MEMs devices.

 

CVD Benefits

When used with Parylene, CVD brings many benefits to the table, including:

  • Ultimate thin-film barrier material for liquid water, water vapor, and harsh chemical corrosion (acid, alkali, organic reagents)
  • Excellent dielectric strength to provide dielectric and insulative protection across an extensive range of frequencies
  • Highly conformal and adherent to many surfaces (metals, glasses, plastics, silicon, ceramics)
  • Entirely non-toxic (safe for all human contact, including implantable devices) and green (non-hazardous processing)

Download our introductory guide to protective coatings

 

CVD Drawbacks

In comparison with PECVD, CVD can have the following drawbacks:

  • Higher cost: long deposition time (10-20 hrs) need for masking/demasking (80%-line cost), and high precursor (dimer) cost
  • Relatively thick film (typically 10µm minimum thickness needed for high integrity pinhole-free conformal coating)
  • Limited operating range/life due to the aging effects of heat (>50°C), oxygen (air), and UV (sunlight) exposure
  • Low wear resistance and mechanical durability limits use on exterior surfaces (cases, enclosures)

PECVD Benefits

PECVD offers the following benefits:

  • Ability to create “nano”-thin barrier films (50nm+) with low stress (room temperature process)
  • Lower cost: due to fast deposition times (accelerated by RF field) and relatively low cost/low use precursor materials
  • No need for masking/demasking to prevent coating on non-target part areas: the coating may be shielded using the part-holders
  • High tailorability: recipe changes facilitate diverse coating properties, including hydrophobic surfaces, UV protection, oxygen resistance, reworkability, and more

PECVD Drawbacks

In comparison with CVD, PECVD can have the following drawbacks:

 
  • Barrier performance is weaker than Parylene and highly dependent on the film thickness, layer count, and plasma type.
  • Limited wear resistance: materials are typically soft (enables rework but exacerbates handling issues).
  • Some coatings may be halogenated, raising health and environmental concerns.

Although this article has provided an overview of CVD and PECVD, it is only a high-level discussion. Chemical vapor deposition processes are a good choice for thin-film deposition, but selecting the proper method takes significant experience and technical acumen from a domain expert. HZO offers highly customizable protection solutions with both CVD and PECVD processes. If you have difficulty deciding which thin-film deposition method to use, contact us today to consult with our engineers.

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IoT - Coating Consistency is Key

September 25, 2020 / by Mallory McGuinness-Hickey posted in Parylene, Coating Process, Coating Properties, Value of Coatings

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IoT sensors aggregate and send data to IoT dashboards, simplifying critical, complex decisions quickly. One key area where this is particularly true is the utilization of sensor data for predictive maintenance, a process that reduces downtime and lowers the total cost of ownership. Myriad other applications incorporate these “smart” sensors too.

Today, IoT sensors are ubiquitous, touching almost every aspect of life. Gas pressure sensors monitor pressure changes in oil, energy, and utility applications. Photoelectric devices (photo sensors) are now common in the consumer electronics vertical. Sensors are responsible for temperature monitoring, a typical use case for warehouse and inventory management, and HVAC systems monitoring.

Accelerometers detect subnormal industrial machine applications, while ultrasonic flow meters are coupled with IoT modules to send data about smart metering to a remote location. Moisture sensors have been critical in recent advances in smart farming, allowing for constant soil health monitoring. In the automotive sector, tunneling magnetoresistive sensors (TMR) are an increasingly popular way to measure mechanical displacement. And Particulate Matter sensors detect pollution in the industrial landscape and smart cities.

 

The chemical vapor deposition (CVD) process used to deposit Parylene conformal coatings can efficiently accommodate these complex surfaces. Parylene’s usefulness is primarily founded upon its ability to cover PCBA configurations with exposed internal surfaces, sharp edges, flat surfaces, points, and crevices with consistent coverage free of voids.

 

HZO PRO750 Parylene Coating Equipment

HZO PRO750 Parylene Coating Equipment

 

The Parylene Deposition Process – Consistent Coverage

Rather than dipping, spraying, or brushing pre-formulated layers onto PCBAs and other components, Parylene’s application method synthesizes the protective film in-process. This deposition system comprises a series of vacuum chambers that produce Parylene vapor, pyrolyze the vapor, then deposit the vapor as a polymer sequentially.

During the CVD process, gaseous Parylene penetrates the layers of a PCBA. Its vaporous consistency surrounds all areas as it builds coating protection along the exterior. The coating layers are substantially thinner than those provided by liquid conformal coating materials, enhancing reliability and functional versatility.

It has repeatedly been demonstrated that CVD is valuable for thin-film deposition on irregular PCBAs. CVD's Conformal layers are exceptionally uniform, even in the nanometer range. Because these coating layers are exceptionally thin, non-uniformity is minimal.

 

Reach out to an Expert 

Choosing Parylene conformal coating services isn’t a failsafe decision, like anything else. Problems can occur with the process and the material. This is particularly true if the wrong Parylene type is used for a coating project while another type could provide better coverage. If you need a consultation to determine if Parylene is the right choice for your project, contact the HZO engineering team today, fill out a quote form, or leave a brief message.

 
 
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6 Common Conformal Coating Defects & Their Solutions

June 16, 2020 / by Mallory McGuinness-Hickey posted in Conformal Coatings, Coating Process

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When we say that a chain is only as strong as its weakest link, we aren’t talking about polymer chains – we’re talking about conformal coating defects. Regardless of the type, a single coating defect can affect the long-term reliability of a PCBA or component and must be repaired or removed. This can be costly and labor-intensive.

Therefore, it’s best to avoid defects from occurring in the first place. The following is a list of common defects and how to keep them from cropping up during your conformal coating application.

Learn how to remove conformal coating

 

The 6 Most Common Conformal Coating Defects and Solutions

Capillary Flow

Capillary flow, also known as scavenging, occurs when a conformal coating migrates from one area of a PCBA to another, leaving behind an inconsistent, uneven finish on the surface.

Common causes for capillary flow include:

  • The application of too much coating
  • Conformal coating with low viscosity or high surface tension
  • Low surface energy of component being coated

To avoid capillary flow from occurring:

  1. Ensure that the PCBA is entirely clean before coating.
  2. Use solvent-based coatings instead of water-based, and decrease the use of thinners to increase viscosity.
  3. Before coating, heat the board to decrease dry time.

Learn more about epoxy conformal coating

 

Cracking and Ripples

Cracking and ripples can compromise a conformal coating film, exposing a substrate or PCBA to potential contaminants.

Common causes for cracks and ripples include:

  • Coating that is too thick
  • Thermal shock
  • Coating that has been cured too quickly

To avoid cracks and ripples:

  1. Always apply the coating at an appropriate thickness.
  2. Allow for extra drying time at room temperature.
  3. Consider selecting a coating with a broader effective temperature range.

Dewetting

De-wetting is when a conformal coating will not evenly coat the surface to which it is being applied.

Many things cause dewetting, including:

  • An uneven coating application
  • An improper mixture of two-part materials
  • Residue on the coating surface
  • Variations in Surface Tension and Surface Energy

To avoid dewetting, thoroughly clean the material being coated before application.

Learn more about polyurethane conformal coating

 

a printed circuit board experiencing dewetting

 

Delamination

Delamination occurs when a coating has lifted away from the substrate. This hinders protection because the area below the coating is left exposed.

Delamination has many causes, including:

  • Too thick of a coating
  • Coating not adhering to the previous coating layer
  • Contamination on the coating surface prevented a good bond to the surface

To prevent delamination:

  1. Reduce the thickness of the coating.
  2. Thoroughly clean the substrate before coating.
  3. Apply a “primer material” that can bond with the substrate and material used for conformal coating.

Orange Peel

Orange peel is when a coating appears dull, resembling the skin of an orange.

It is caused by conditions including:

  • A substrate that is too hot
  • Improper coating mixture or solvent ratio
  • A local environment that is too dry during application
  • A second coat has been applied before the first coat is dry

To avoid orange peel:

  1. Apply coating at the specified thickness.
  2. Reduce the viscosity of the coating.

Learn more about conformal coating vs potting

 

Air bubbles, Pinholes, and Foam

Bubbles occur when pockets of air get trapped under a conformal coating layer. Foam is an extreme form of bubbling, and sometimes bubbles burst through the conformal coating, forming a pinhole.

Bubbles, pinholes, and foam happen when:

  • A coating is too viscous
  • The coating is too thick
  • Application equipment has not been setup correctly

To avoid air bubbles, pinholes, and foam:

  1. Use a lower viscosity conformal coating
  2. Ensure the coating is applied at the recommended thickness.
  3. When applying the coating, do so with thin coats.

Why This Doesn’t Happen at HZO

At HZO, we use a conformal coating application method called chemical vapor deposition (CVD) that circumvents these conformal coating issues. Using CVD, we produce uniform, pinhole-free conformal coatings every time. Contact us today to speak to an expert if you want to hear more about our proven technology and processes.

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Conformal Coating vs Potting/Encapsulation - The Pros & Cons

June 11, 2020 / by Mallory McGuinness-Hickey posted in Conformal Coatings, Coating Process

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As the world of electronics continues to grow and evolve, printed circuit board assemblies (PCBAs) find their way into more and more products and industries. Whether you create products for consumers, the automotive industry, the military, or some other field, PCBAs play a big part in your product design. You’ll need to protect them without impeding the rest of your design.
 

You have a few options for coating a PCBA: conformal coatings or potting and encapsulation resins. These organic polymers provide chemical and thermal resistance and electrical insulation to the delicate PCBA beneath them. But that’s where most of their similarities end. This guide will discuss the differences between encapsulation resin and conformal coating and their effects on a PCBA.

 

What’s the Difference Between Conformal Coatings and Potting?

While both potting/encapsulation and conformal coatings protect a PCBA, they do so differently.

Electronic encapsulation seals a PCBA within a thick resin layer to protect substantially against physical shock, chemical exposure, and excellent electrical properties. Usually, this resin is dark-colored, so you won’t be able to see the board underneath it. The resin is mixed with a hardener before application, which allows it to cure a cross-linked polymer.

So, what is potting? While “encapsulation” and “potting” are used interchangeably, potting sometimes refers to the process used for PCBA encapsulation.

Alternatively, a conformal coating is a protective dielectric layer that is non-conductive. It protects from dangers like salt spray, fungus, moisture, and corrosion. The film, composed of epoxy conformal coating, acrylic, or silicone, is very thin and lightweight, having almost no dimensional effect on the PCBA or added stress to the components. Processing and applying this single-component material is easy and versatile, providing flexible options for the finished product.

While traditional coatings are single-component, some newer ones use a two-part process with polyurethane conformal coating to blend the protective aspects of PCBA potting with the flexibility of coatings. Plus, they don’t use solvents, which reduces concerns about volatile organic compounds (VOCs) present in many low-viscosity single-component coatings and adversely affects people and the environment. Fortunately, even those have come a long way, as most manufacturers have worked to reduce VOCs in their coatings.

 

Which Is Better to Protect My PCBA — Conformal Coating or Potting?

To best protect your PCBA, you’ll have to consider several factors of your product and how PCB resin coating and potting contribute to them.

Environmental factors play a significant role in choosing a protective material. Will your PCBA be exposed to any of the following?

  • Extremely high or low temperatures: You will have to consider the way resin can behave during use in extreme temperatures, how sudden or gradual the change is, and how heat could affect production. Resin generates a lot of heat when mixed with its hardener, which can cause damage to the PCBA or the housing if it gets too hot.
  • Water, humidity, or moisture: Some conformal coatings are less waterproof than others. While the resin is typically always waterproof, you’ll have to double-check that your coating is, too.
  • Physical shock: If your component might be exposed to heavy physical shock, the resin can help spread the impact across the material and reduce or eliminate the damage to the PCBA.
  • Mechanical stress: Abrasion and scratches can become problematic in environments like assembly lines and manufacturing equipment, where high speeds and volumes are typical. Resin provides a thick layer to protect against that physical threat.
  • Chemical exposure: If your PCBA could be exposed to harsh chemicals, both resin and coatings provide exceptional protection from exposure and submersion.

While PCBA potting offers more protective benefits, coatings hold the upper hand in design flexibility and can still protect products in everyday environments, like consumer electronics. Only those that are in particularly challenging environments typically need PCBA encapsulation.

 

a printed circuit board being encapsulated with a coating

 

Below are some design factors that factor into the debate:

  • Weight: Resin adds a thick block of material on top of the board, significantly increasing its weight. In many products, heavyweight components aren’t an option.
  • Thickness: Many products can’t function with the added thickness of the resin added to their design.
  • Workability: Since resin is dark and thick, you can’t see through it or easily remove it to rework the board. It could rip up the PCBA if you tried to take it off. Coating, on the other hand, is usually clear, which allows you to see through it and make adjustments if needed. This helps address any conformal coating defects
  • Housing: If the housing of the PCBA doesn’t offer much protection, the resin may be a way to protect it more thoroughly. Coatings are often used as secondary protection within well-built housing.
  • Application: Depending on the design requirements, one option may be better for production. Resin can add risky heat during application and takes longer to cure. Conformal coatings tend to be quick-drying and can be applied in several ways, such as painting it with a brush, spraying it on, dipping the PCBA, and using robotic systems.

Conformal coatings are an excellent way to protect a PCBA from common threats without paying for the added weight and cost of encapsulation.

Here at HZO, we use a coating called Parylene, which is biocompatible — meaning it’s great for the medical devices industry — and extremely thin. It is clear and excellent for waterproofing and liquid protection.

 

Pros and Cons of Potting/Encapsulation

Designers often choose PCBA encapsulation for products in heavy-duty environments, as it protects against many damaging agents.

Some of the benefits of PCBA potting include the following:

  • Provides added protection against chemical, thermal, and physical risks, including water and shock.
  • Offers better performance for high-speed and high-volume work in industrial environments.
  • Has VOC-free options.

Some disadvantages of PCBA potting are:

  • It makes it difficult to inspect or rework the PCBA.
  • Causes possible design issues due to the added weight and thickness.
  • A more complex application process, especially regarding heat and two-part mixing.

Pros and Cons of Conformal Coating

Conformal coating is more popular than potting. It protects many consumer products outside dangerous exposure environments and provides more design flexibility. However, if your product is used in rough applications, it may not offer all the necessary protections.

Here are some of the pros of conformal coatings.

  • Thin and lightweight, offering superior design flexibility and no stressed components.
  • Offers protection from low-level issues like salt spray, dust, moisture, and corrosion.
  • Offers a variety of application methods.
  • Newer options with low VOCs.
  • Long lifespan.

The negatives of conformal coatings include:

  • Offers less robust protection against heavy-duty threats.
  • Contains VOCs within the solvents, though these are becoming less abundant.

Contact Us Today to Protect Your PCBA

If you’re still unsure about which option is best for your PCBA, our expert team of HZO engineers can help. We realize that your needs are just as unique as our coatings, so we will work closely with you to provide custom coating solutions.

To learn more, contact us or call us today at 1-877-757-4496.

 
 
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