Removing Conformal Coatings

Posted on June 17th, 2021 by

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 own set of advantages, limitations, and challenges, along with different application methods.

Read our blog post on conformal coating 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

Read more about acrylic conformal coatings

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 coatings

Silicone (SR) Conformal Coating Properties

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

Read more about epoxy conformal coatings

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 urethane conformal coatings

Properties of Parylene (XY) Conformal Coatings

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

Read more about urethane conformal coatings

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, 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

PCB Conformal Coating Removal 

To determine the best conformal coating removal method, confirm the coating material applied to the PCB you are looking to remove. 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, using methods such as testing transparency, testing solubility, testing hardness, testing thermal removal, and testing 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 is very effective for removing 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.

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 method, grinding and scraping method, and thermal method. However, at HZO, we have simplified the reworking process with the use of technology. In the next blog in this series, we will discuss reworking Parylene in general and go into detail about how we simplify the process.

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

Mallory McGuinnessMallory McGuinness

Mallory is an electronics protection evangelist who writes content for HZO. In her free time she is reading non-fiction, and hanging out with her beta fish, King Awesome.

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