Good evening from Spain.

The problem we have is the following. After soldering, we conformal coating a 
class 3 polyamide board (blind vias) with Parylene C. Until this moment, all is 
OK.

Then, the board pass the ESS -thermal cycling-, and it is at this moment 
when appears a halo around the solder joints. The test tape performed in that 
area fails. I’ll send some pictures to Steeve Gregory for reference.

We have coated at the same time (and processed in the same conditions, 
that is soldering, cleaning…) the “suspicions” polyamide boards with other type 
of boards (polyamide & rigid). We only obtain negative results with the first 
ones.

We have sent some boards to an external lab for FTIR testing, and we are 
waiting for the final results.

Our though is that cause of the problem is the PCB, but we need to 
demonstrate it. It's like some contaminant appears under the conformal 
coating caused by the temperature (from the inner layers of the PCB?)

So, what we need is that somebody turns the ”light” on.

Thank you for your help.



Juan T. Marugán López
Supply Chain Management
Indra Sistemas SA (Spain)

[log in to unmask]
www.indra.es

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