Parylene Coating Blog by Diamond-MT

Are Parylene Noodles a Defect?

Posted by Sean Horn on Fri, Apr 06, 2018 @ 07:30 AM

Unlike liquid conformal coatings joined to substrate surfaces by wet application methods, polymeric parylene (XY) uses a unique chemical vapor deposition (CVD) process to assure adherence.  There is no intermediate liquid phase.  Rather, cross-link polymerization of powdered raw XY-dimer converts the solid to a vapor at the molecular level, polymerizing XY directly as a transparent film on assembly surfaces.

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Tags: parylene inpsection, conformal coating defects, parylene properties

Conformal Coating Removal Standards

Posted by Sean Horn on Fri, Feb 17, 2017 @ 08:00 AM

If problems in a conformal coating defy reliable repair, coating removal may be the only solution.  Removing conformal coating from PCBs requires matching removal methodology with coating type and the component’s function.  A variety of factors – bubbles/voids, coating thickness, component failure, inadequate masking, poor adhesion, surface finish, among many others – can necessitate coating removal.     

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Tags: conformal coating rework, conformal coating removal, conformal coating removal services, conformal coating defects, conformal coating issues

Cracking in Conformal Coating:  Major Causes and Preventative Strategies

Posted by Sean Horn on Fri, Feb 10, 2017 @ 07:45 AM

Conformal coatings protect printed circuit boards (PCBs) and similar electronic assemblies used for a wide range of aerospace, automotive, consumer, defense and medical applications.  Coatings effectively cover PCBs, shielding them from contaminants, liquid incursions, temperature fluctuations and other conditions potentially hazardous to component performance.  However, problems can develop if their preparation, application, and drying processes are inappropriately managed. 

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Tags: conformal coating, conformal coating rework, conformal coating defects, conformal coating issues, conformal coating process

When to Use Conformal Coating Removal Services

Posted by Sean Horn on Fri, Dec 02, 2016 @ 07:33 AM

It is possible to remove unwanted conformal coatings from PCBs in-shop.  The process can often be accomplished by either the assembly’s original equipment manufacturer (OEM) or an end-user, but the capacity to do so doesn’t always exist.  For these parties, conditions affecting the poor coating may:

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Tags: conformal coating, conformal coating rework, conformal coating removal, conformal coating defects, conformal coating removal services

Removing Conformal Coating Instead of Repairing It

Posted by Sean Horn on Fri, Nov 25, 2016 @ 07:34 AM

Sometimes problems with conformal coating are too complicated or difficult to repair.  This can occur when bubbles develop in the coating during the application process; bubbles cause voids in the coating that defeat its protective, insulating purpose, suggesting the need for removal.  Other situations that lead to inadequate coverage, and may favor coating removal, rather than repair include: 

  • Coating application that’s either too thick or thin for the project’s purposes.
  • Component surface finishes that adapt poorly to the conformal material chosen for coverage.
  • Disparities in surface tension/surface energy.
  • Gravity issues that negatively impact application of liquid coating.
  • Improper mixture of two-part materials.
  • Inadequate fixturing or placement of assembly components in the coating area.
  • Inadequate masking implementation.
  • Incorrect interpretation of coating requirements.
  • Residue on the coating surface during coating application.
  • Poor, uneven coating application.

Overly thick film application or use of coating equipment/materials unsuited to the assignment are major causes of coating problems.  In these cases, complete or partial removal of the conformal film from the PCB may be the best solution. 

Thus, it is important before beginning any conformal coating assignment for designers and users to recognize the various types of conformal coatings and their interactions with the parts/materials they cover, to protect the products in their respective end-use environments, for the expected design-life of each component. 

Industry Standards

             When removal is the best option for your coating problem, it is advisable to consult prevailing industry standards for appropriate process guidelines.  For instance, IPC-7711/7721 delineates recommended procedures for conformal coating removal from, and replacement onto, PCBs.  IPC-A-610 is a widely-held standard for electronic assemblies, offering users limited but valuable criteria for conformal coating applications.   Designed and constructed with the intent of obtaining maximum confidence in the materials with minimum test redundancy, IPC-CC-830B qualifies the definition, use and conformance of all conformal coatings types for PCBs.  In most cases, coating removal is required when assemblies don’t meet the requirements of IPC-CC-830, concerning overall quality conformance of each

The Logistics of Coating Removal                                                               

The logistics of coating removal are largely dependent on the type of coating material, its position on the PCB, and the board’s components.  Proper identification of the coating material, and the methods used for its original application, are essential to correct determination of the removal method.  Once these have been identified, determination of the appropriate removal method can be achieved. 

In many cases, chemical strippers can dissolve conformal coatings from PCBs.  Acrylic films are typically removed easily by soaking in a solution of stripping fluid, followed by mild mechanical abrasion if necessary.  These two processes also work for coatings such as epoxy, silicone and urethane; however, since these substances have higher levels of chemical resistance than acrylic, complete coating removal is more difficult and time-consuming.  In all cases, the stripping solution’s compatibility with the PCB’s components needs to be verified to minimize potential damage during the removal process.

Chemical removal does the least damage to PCBs; it is effective for the liquid coatings -- acrylic, epoxy, silicon and urethane.   Chemical methods work less well for parylene films, since the substance is chemical inert.  Abrasion, laser, mechanical, plasmatic and thermal removal methods are more successful for parylene films; they also work for liquid coatings in many cases.

Recently applied coating is more easily detached from substrate surfaces than older coatings, regardless of the material, unless the coating itself has begun to decay with age.  Larger areas of the board respond best to complete submersion in a tank of stripping fluid.  Gentle abrasion using a soft bristle brush will also eradicate coatings.  


Please remember that the removal of conformal coating generally requires use of exceptionally caustic and potentially dangerous chemicals; the safety of process operators, the product being treated and the immediate environment can be jeopardized by use of inappropriate  removal materials and methods.  Consultation with a certified conformal coating specialist is highly recommended prior to removing conformal coating.  To this end, the professionals at Diamond MT are eminently qualified, and would be glad to be of assistance.

To discover more about conformal coating rework and removal, download our whitepaper now:

Conformal Coating Rework  Whitepaper

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Tags: conformal coating, conformal coating rework, conformal coating defects, conformal coating removal

Reapplying Conformal Coating After Its Removal

Posted by Sean Horn on Fri, Nov 18, 2016 @ 07:44 AM

Defects to either the PCB assembly or its conformal coating can be sufficient to cause coating removal.  Whether repair technologies address the circuit board’s components or the conformal film, subsequent post-repair coating (recoating) processes need to address:

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Tags: conformal coating, conformal coating rework, conformal coating removal, conformal coating defects

Removing Conformal Coating

Posted by Sean Horn on Fri, Nov 11, 2016 @ 07:43 AM

Conformally coated PCBs are expected to work without fail, largely because of the protection the coatings provide them.  In addition to PCB-manufacturing issues, coating problems can trigger failure mechanisms for the assembly.  For instance,
  • Conformal coating applied incorrectly can cause PCB malfunction.
  • Selecting the wrong coating material from among acrylic, epoxy, parylene, silicone or urethane can be a source of board failure, if it does not support the PCB’s operating environment.

Removing the coating may be necessary if these conditions prevail.

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Tags: conformal coating, conformal coating rework, conformal coating removal, conformal coating defects

Help!! My Board is Failing, but It's Already Coated!

Posted by Sean Horn on Fri, Nov 04, 2016 @ 07:44 AM

Conformal coatings are designed to protect printed circuit boards (PCBs), assuring they work under all operational circumstances.  However, cases emerge where boards fail to function despite conformal coating protection.  Such non-performance can be a consequence of:

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Tags: conformal coating, conformal coating rework, conformal coating removal, conformal coating companies, conformal coating defects

9 Questions to Ask About Contamination, Cleaning, Failures, and Defects in Conformal Coating

Posted by Sean Horn on Fri, May 13, 2016 @ 07:30 AM

How do you ensure that a potential conformal coating provider has the professional credentials and expertise necessary to avoid costly mistakes?

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Tags: conformal coating, conformal coating service, conformal coating issues, conformal coating bubbles, conformal coating defects

How to Avoid Bubbles in Conformal Coating

Posted by Sean Horn on Fri, Apr 08, 2016 @ 07:54 AM

Bubbles and foam are two of the leading causes of failure during conformal coating inspections. Because of this, it’s worth looking at these defects more closely.

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Tags: conformal coating, conformal coating bubbles, conformal coating defects