Steve has kindly post this picture for me.

Anyone saw such phenomena before on delivered bare boards? Are those grey matter found on recess between solder pads and soldermask acceptable? My PCB supplier said that since the PCBs passed isolation test, those residues should not pose any problem. In addition, as IPC has no such reference in 6012 and 600, my PCB supplier suggest that I use them as UAI. I am concern about long term effect on reliability after assembly, especially such PCBs will be used for space application. Your expertise and opinion will be greatly appreciated.

Thanks and Regards,
~wee mei~

"Successful people aren't born that way. They become successful by establishing the habit of doing things unsuccessful people don't like to do. The successful people don't always like these things themselves; they just get on and do them." - William M Thackeray

From: Steve Gregory [mailto:[log in to unmask]]
Sent: Thursday, 3 October 2013 2:46 AM
To: Lum Wee Mei
Subject: RE: Grey Matter

Hi Wee Mei!

Hmmm, not so sure, depends on what it is? Is this on bare boards that have not been assembled yet? Have you tried cleaning it?

Anyways, I have your picture posted, it's here: http://stevezeva.homestead.com/LumWeeMei.JPG

Maybe you can get some good input from the group from someone who might have seen this before...

Kind regards,

Steve

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