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How to Remove Conformal Coating - Which Method is Best?

How to Remove Conformal Coating - Which Method is Best?

Conformal coatings are polymeric films applied directly to PCBAs and electronic components to provide a barrier layer of protection from the environment in which they operate...

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Polyurethane Conformal Coatings - Benefits & Applications

Polyurethane Conformal Coatings - Benefits & Applications

Conformal coatings are polymeric materials applied to a PCB to improve device reliability. These films protect electronics from environmental threats, including humidity, liquids,..

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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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Epoxy Conformal Coating Evaluation Guide

Epoxy Conformal Coating Evaluation Guide

Conformal coatings are polymeric materials applied to substrates. These films are a barrier to protect electronics from environmental hazards, such as corrosion, humidity,..

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How to Remove Conformal Coating - Which Method is Best?

June 17, 2021 / by Mallory McGuinness-Hickey posted in Conformal Coatings, Coating Process

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Conformal coatings are polymeric films applied directly to PCBAs and electronic components to provide a barrier layer of protection from the environment in which they operate. There are five primary conformal coating materials: acrylics, epoxies, silicones, urethanes, and Parylene. Each material presents its advantages, limitations, challenges, and application methods.


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)

Understand conformal coating vs potting

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

Read the definitive paper on electronic protection methods

Every so often, conformal coatings must be removed. This may be for several reasons, including electrical or functional failures that require rework, PCBA malfunctions, initial design process issues, poor adhesion, conformal coating defects, or improper choice of coating material. Whatever the reason, the first step in the removal process is to determine which coating material you are working with, as this will help determine how to remove the PCB coating.

 

How to Remove Conformal Coating

Confirm the coating material applied to the PCB you want to remove to determine the best conformal coating method. Confirmation can typically be achieved by either contacting your coating supplier or looking for a JEDEC or IPC label placed on the board. Coatings are designated as AR, SR, ER, UR, or XY, indicating with which coating you are working. If there are no labels, you can still ID the material via methods outlined by the IPC below.

Because each conformal coating has distinct properties, methods such as testing transparency, solubility, hardness, thermal removal, and thickness can show you which type of coating you are working on. For more information, see IPC’s “Coating Removal, Identification of Conformal Coating” guidelines.

 

Conformal Coating Removal Techniques

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

Peeling Method

Typically used for RTV silicone or thick rubber coatings, use a dull blade or knife to slit the coating material and peel it off.

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 harder to remove, but you can typically use the micro-blasting, grinding, scraping, and thermal methods. However, at HZO, we have simplified the reworking process using technology. In the next blog in this series, we 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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Polyurethane Conformal Coatings - Benefits & Applications

June 23, 2020 / by Mallory McGuinness-Hickey posted in Conformal Coatings, Coating Properties

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Conformal coatings are polymeric materials applied to a PCB to improve device reliability. These films protect electronics from environmental threats, including humidity, liquids, and corrosive substances.

Different conformal coating materials include acrylic coatings, silicone, epoxy, and Parylene. Polyurethane is another common conformal coating material.

Learn how to choose the best conformal coating

 

 What is Polyurethane Conformal Coating?

Polyurethane coatings are tough, hard, protective layers resistant to solvents and abrasion.

Polyurethane conformal coatings have the following attributes:

  • Moisture and oil-resistant
  • Fungicidal
  • Good flexibility
  • Can be thinned to achieve a chosen viscosity
  • Class F temperature rating (160°C/320°F)

  • Retain excellent electrical insulation properties after the MIL-I-46058 cycling test.

 

Polyurethane Conformal Coating Benefits

Polyurethane can augment devices, extending their lifetime and ensuring they dependably operate wherever deployed.

These coatings exhibit sturdiness and strong resistance to humidity and organic solvents. The tough coatings are resistant to mechanical wear. Additionally, Polyurethane can mitigate the growth of tin whiskers.

 

Polyurethane conformal coating on a PCB

 

Polyurethane Conformal Coatings Applications

 

Polyurethane coatings are ideal in areas with technology that will face excessive chemical exposure.

Urethane coatings protect and insulate motors, generators, relays, transformers, and other components. This coating material is also common in automotive and aerospace environments. Urethane coatings protect these electronics from chemicals and salt sprays throughout temperature fluctuations.

 

Learn about protective coatings vs potting

 

What Do Polyurethane Conformal Coatings Protect Against?

The coatings protect electronics from thermal shock, moisture, chemical solvents, and other elements. Compared with other materials, Polyurethane has a lower degree of friction and high abrasion resistance.

 

The Polyurethane Conformal Coating Process

Polyurethane is available as either single or two-component formulations and can be applied with dipping, spraying, and brushing methods. After application, the films are cured to complete the coating process, which takes an hour to several days. Single-component urethanes are easy to apply but take up to days to finalize. Meanwhile, two-component formulations cure within hours. The length of the process is also related to temperature, curing faster at moderately elevated temperatures. UV curing and heat catalyzed, and moisture curing are common methods to cross-link urethane polymers.

 

View a webinar about designing conformal coatings for reliability

 

Polyurethane Disadvantages

As mentioned, Polyurethane conformal coatings have benefits, such as abrasion, thermal shock, and moisture resistance. That said, the coating also has disadvantages. The curing process can be timely and requires a long post-cure time, and moisture impacts the cure rate and cured properties. The coating can also turn yellow with age.

 

The Big Picture

Choosing a conformal coating material extends beyond just looking at the material and application methods. It is important to consider various variables, including the components’ complexity, environmental regulations, and coating rework and removal. Repeatable processes that avoid defects may be important, especially for high-reliability applications.

Please read our definitive guide for more information on choosing the best conformal coating for your PCB. Alternatively, contact our Applications Engineering team for a consultation if you require more assistance. Or, you can learn more about the protection capabilities of coatings.

 
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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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Epoxy Conformal Coating Evaluation Guide

May 21, 2020 / by Ryan Moore posted in Conformal Coatings, Coating Properties

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Conformal coatings are polymeric materials applied to substrates. These films are a barrier to protect electronics from environmental hazards, such as corrosion, humidity, chemicals, and liquids. Popular conformal coating materials include silicone, acrylic, Parylene, and urethane. Epoxy is another coating material of choice in applications where chemical and abrasion resistance are priorities.

 

What is Epoxy Conformal Coating?

Epoxy coatings are protective layers with excellent electrical, thermal, mechanical, and moisture barrier properties. 

Epoxy coatings have the following attributes:

  • Very robust, difficult to remove the protective coating
  • Excellent chemical and abrasion resistance
  • Very rigid conformal coating
  • High dielectric strength

Epoxy Conformal Coating Applications

Epoxies are highly abrasion-resistant and tough and, therefore, common in applications with harsh environments, including automotive, marine, and military. Different types of epoxies have different benefits as well. For example, thermally conductive epoxy can protect boards with components that give off heat. Meanwhile, flame retardant epoxy is useful for fire hazard protection, and clear epoxy allows for board visualization.

 

epoxy conformal coating
 

 

What Does Epoxy Conformal Coating Protect Against?

Epoxy conformal coatings resist chemicals, alkalis and acids, moisture, organic solvent, and salt spray. They are known for excellent adhesion to various substrates without needing primers and retain adhesion under many conditions. Additionally, they have good electrical characteristics, and these parameters remain stable despite humidity or elevated temperature.

 

The Epoxy Conformal Coating Process

Applying epoxies with dip coating, brush, or spray application techniques is easy. With dip coating, a component is immersed in a tank of coating material, while brushing entails manual application by an operator. The spraying method can be automated or manual, depending on production needs. Epoxy materials come as either a single or two-part compound and require curing with UV or heat exposure.

Learn About Conformal Coating vs. Potting

 

Why Choose Epoxy Conformal Coating to Protect Your Electronic Devices?

Epoxies are a common coating material choice due to their strong barrier properties, ease of processing, and low cost. That said, the toughness and durability of epoxy coating may pose challenges with rework and removal. Film shrinkage may occur during polymerization, potentially causing issues, and the suggested thickness for epoxy coatings can reach up to 130 micrometers. This thickness may prove too bulky for applications that entail miniaturization.

Understanding material properties and how they meet your requirements is a good start if you are trying to determine which coating material is best for your PCB. However, other factors must be considered, including masking, cleaning, inspection, scalability, coating removal, and avoiding and addressing defects. For a big-picture view, read our guide to choosing the best coating or learn more about coatings’ protection capabilities. Alternatively, please contact us to speak to a coating service expert about your application one-on-one. 

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