Inspecting for Parylene Conformal Coating

Press Office, VersaLogic Corporation, 08/14/24

Although it is difficult to apply, conformal coating with Parylene is renowned for its exceptional protective properties in the electronics industry. It offers excellent moisture resistance, electrical insulation, and chemical stability, making it a popular choice for safeguarding sensitive components.

However, it can be a challenge to inspect for Parylene conformal coating. Parylene is transparent and forms a thin flawless, continuous layer, making inspection difficult with the naked eye. It does not glow when inspected under a black light. So how can you tell if a board has been coated?

How to Inspect for Parylene
The easiest way to inspect for the presence of Parylene conformal coating is to inspect for the de-masking lines under a higher magnification, such as 10X. There can also be a subtle difference in the gloss of the solder mask (semi-gloss) and the Parylene (satin).

Spotting the de-masking lines is a very simple way of validating the presence of Parylene.

A picture of the ground point on a VersaLogic EPM-E2A.
The de-masking lines around the ground terminal,
the mounting annular ring, and connector housing are visible.

Step-by-Step Instructions for Inspecting Parylene Conformal Coating

1. Prepare Equipment
• Obtain a binocular microscope.
• Set the magnification to ten times (10x).
2. Initial Inspection with Microscope
• Place the item to be inspected under the binocular microscope.
• Focus on the de-masking lines around the conductors or non-coated components (e.g., connectors, annular rings, test pins, ground terminals).
3. Identify the Coating
• Observe the difference in gloss between the solder mask and the Parylene coating:
  – Solder Mask: Semi-gloss finish.
  – Parylene: Satin finish.
• Confirm the presence of Parylene conformal coating and ensure it is not on areas that must remain mask-free.
4. Switch to Unaided Inspection
• Once Parylene conformal coat presence and correct masking are verified, move to a visual inspection without the microscope.
5. Inspect the Conformal Coat
• Examine the conformal coat for any conditions listed in the inspection criteria.
• Ensure adherence to the standards specified in IPC-A-610.
6. Document Findings
• Record observations and any discrepancies found during the inspection process.
• Report any non-compliance with the criteria outlined in IPC-A-610.
7. Final Verification
• Conduct a final check to ensure all areas meet the inspection standards before concluding the inspection process.

Notes:

• Ensure proper lighting conditions during both microscope and unaided inspections.
• Handle the item carefully to avoid any damage during the inspection.
• Follow safety protocols while using the microscope and during the inspection process.

By following these steps, you can effectively validate the presence and correct application of Parylene conformal coating.

Not conformally coated (left), and Parylene conformal coating (right)

Questions or Concerns?
If you have any further questions or concerns regarding your inspection for Parylene conformal coating, please contact VersaLogic Customer Support.