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Parylene Coating Thickness – How Much is Enough?

Dr. Sean Clancy August 18, 2020

If you are considering a Parylene coating for your printed circuit board assembly, you may wonder what thickness you should use. You may have surmised that the more coating, the better, but that is not always true. The thicker the coating, the longer it takes to coat – you will face diminishing returns at some point. Additionally, no universal thickness is ideal for all operating environments and applications. Different applications have different functional requirements.

To gain a better understanding, let’s look into how Parylene coating works and how to determine what Parylene thickness is most suitable for your requirements.

 

What is the Parylene Coating Process?

The Parylene chemical vapor deposition process begins with dimer, which is a powdered chemical. The more dimer that is in the first chamber, the thicker the coating will be. The dimer is heated into vapor, pulled by a vacuum into a connected chamber, and heated to an even higher temperature, further pyrolyzing the dimer. It is pulled into a final deposition chamber, penetrating crevices, coating exposed surfaces, and becoming a polymer. The resulting coating exhibits strong barrier properties at 50% thickness of conventional conformal coatings.

Read about Parylene biocompatibility and Parylene removal.

 

What Parylene Thickness is Best?

  • Are there Parylene cost considerations to meet, or do you need to meet the highest level of protection, no matter the price?
  • Are there time constraints?
  • Do you need to meet industry-standard requirements?

When Time is an Issue

Do you have a project that needed to be completed yesterday? A thinner coating may be your best bet. However, you risk breaches or pinholes in the coating when you go thin, say, 0.1 to 5 μm (microns). If your product has simple geometry or relatively flat structures, your coating will probably be pinhole-free.

But for products with more substantial differences in structural or component heights or components with more complex geometry, this level of thinness may not offer enough coating material to form a coherent film, leaving voids or pinholes. And any breaches in the film are potential pathways for the ingress of corrosive compounds and would require Parylene removal.

On the other hand, a thinner coating may provide a sufficient level of protection for products not exposed to corrosives, such as products requiring only a quality barrier against minimal exposure to contamination. Additionally, you decrease the time to coat and cost when you go thin.

 

Learn More About Parylene’s Chemical Resistance

 

a coating expert double checking the parylene coating on a PCB

 

For Product Reliability

Is product reliability the largest of your concerns? The IPC-CC-830 and MIL-I-46058 coating standards might be good references. According to these standards, thickness ranges of 12.5 to 18 and 12.5 to 25 μm, respectively, are thick enough for protection against very harsh environments. Coatings this thick are pinhole-free for a myriad of products and are time-tested, with decades of usage in demanding industries such as defense, aerospace, medical device, and telecommunications.

For products in the most demanding of environments, the NASA-STD 8739.1 standard calls for a range of thicknesses from 13 to 51 μm. This thickness is more than sufficient to provide a level of protection for incredibly harsh environments. Bear in mind, however, that at thicknesses around 50 μm, a single coating run may take well over a day, depending on the Parylene type you have selected.

 

Read about Parylene C and Parylene N

 

The Big Picture

There is no optimal Parylene coating thickness across all applications and requirements. Instead, you should select a thickness based upon several factors, such as the operating environment that your product will be exposed to, and how your customers expect to use the product. Additionally, budget and timeframe are essential factors. Although there is no perfect thickness of coating suitable for every application, with enough planning, you can find the perfect thickness suitable for yours. 

 

Read more about Parylene's temperature range

Although there is no perfect thickness of coating suitable for every application, with enough planning, you can find the perfect thickness suitable for yours.

Not Sure Which Parylene Thickness is Ideal for Your Product?

If you have questions or problems with Parylene, we’ve got a solution. To speak to an applications engineer about your specific requirements, Parylene coating cost, and how to determine which thickness is best, contact us today for a quote. We can help with automated Parylene masking and scalable Parylene coating equipment.

Additional Resources

Download the HZO Parylene Datasheet
Datasheet

Download the HZO Parylene Datasheet

Learn About Corrosion Resistance From An Industry-Leading Engineer
Webinar

Learn About Corrosion Resistance From An Industry-Leading Engineer

Learn About HZO Coatings With Our Resource Page
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Learn About HZO Coatings With Our Resource Page

Learn About the Parylene Process With Our Resource Page
Resource

Learn About the Parylene Process With Our Resource Page

Learn About Parylene Properties With Our Resource Page
Resource

Learn About Parylene Properties With Our Resource Page

Understand Parylene's Benefits for Optical Applications
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Understand Parylene's Benefits for Optical Applications

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Parylene Thickness - How Much is Enough?

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Understand Parylene Masking

Learn How to Remove Parylene Coating
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Learn How to Remove Parylene Coating

Download a Parylene C Datasheet and Learn About the Coating
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Download a Parylene C Datasheet and Learn About the Coating

Understand More About Parylene's Superior Chemical Resistance
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Understand More About Parylene's Superior Chemical Resistance

Learn About the Benefits of Parylene's Biocompatibility
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Learn About the Benefits of Parylene's Biocompatibility

Download a Parylene N Datasheet and Learn About the Coating
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Download a Parylene N Datasheet and Learn About the Coating

Is Parylene Right For Your Project?
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Is Parylene Right For Your Project?

How HZO Makes Parylene Scalable
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How HZO Makes Parylene Scalable

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Why is Parylene Coating Conformal?
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Why is Parylene Coating Conformal?

The Illustrated Guide to CVD
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The Illustrated Guide to CVD

Learn How To Incorporate Conformal Coating Into Your Manufacturing Process
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Learn How To Incorporate Conformal Coating Into Your Manufacturing Process

Parylene Coating for Reliable Product Design Webinar
Webinar

Parylene Coating for Reliable Product Design Webinar

Download the HZO Parylene SDS
Datasheet

Download the HZO Parylene SDS

Learn How to Bring Parylene Deposition In-House
Technical Paper

Learn How to Bring Parylene Deposition In-House