Hi Wee Mei - I haven't a clue what that stuff is but just because it 
passed isolation testing doesn't mean its ok to be on the board. I 
recommend you get the unknown material analyzed by FTIR and identify what 
it is. You can decide if it is acceptable once you have it identified.

Dave Hillman
Rockwell Collins
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From:   Lum Wee Mei <[log in to unmask]>
To:     <[log in to unmask]>
Date:   10/02/2013 07:21 PM
Subject:        [TN] Grey Matter
Sent by:        TechNet <[log in to unmask]>



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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