Thanks all for your comments and suggestions. The response from the fabricator is that the blue blob is blue resist film that did not strip off, and it should be an easy repair. It does seem strange that this defect got through their inspection, but our QA also missed it!

Thanks,
Howard



-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Louis Hart
Sent: Tuesday, June 02, 2015 5:47 PM
To: [log in to unmask]
Subject: Re: [TN] PCB blob defect

Let me disagree with Ted and say I think it is a fragment of plating resist that did not get developed away. Compunetics has blue plating resists, if I have observed correctly. I've never done that job myself but have seen stuff in process.  The solder resist did not seem to set the area around the blob.  I'm not going to speculate about that behavior.  Louis Hart

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Theodore J Tontis
Sent: Tuesday, June 02, 2015 7:09 PM
To: [log in to unmask]
Subject: Re: [TN] PCB blob defect

It looks like a solder resist repair and they used blue instead of green. It would be interesting to find out when the repair happened, at the board house or assembly house. It's difficult to tell because the silkscreen looks to be repaired as well. 

Ted T.

Sent from my iPhone

> On Jun 2, 2015, at 5:56 PM, Watson, Howard August <[log in to unmask]> wrote:
> 
> Hi all,
> 
> My PCB fab knowledge is limited, and a very unusual defect was discovered (too late) in assembly. I'm wondering if anyone has seen something like this before, or has an idea what this could be. The blue color seems noteworthy to me. This is for IPC class III, space. I will return this to the fabricator, but I wanted to get educated in case there is a debate regarding the cause. Thanks for your help!
> 
> Steve put the pictures here:
> 
> http://stevezeva.homestead.com/Howards_Blob.jpg
> 
> http://stevezeva.homestead.com/Howards_Blob_close.jpg
> Howard A. Watson
> 
> ______________________________________________________________________
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