Good Evening to you too Juan!

I have your pictures posted. They're at:

http://stevezeva.homestead.com/files/Parylene_1.jpg

http://stevezeva.homestead.com/files/Parylene_2.jpg

http://stevezeva.homestead.com/files/Parylene_3.jpg

Boy, don't you have a mess on your hands! So you say that you had other flex circuits that did okay during ESS after coating? Were they from the same fab vendor? Did you do the parylene coating yourself or did you sub-contract that out? Sorry for all the questions, just thinking out loud.

I feel for you man, this sucks. These boards being parylene coated makes things all the more difficult...

Steve

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Juan T. Marugán
Sent: Monday, September 29, 2008 2:41 PM
To: [log in to unmask]
Subject: [TN] Big problem when coating with Parylene C.

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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