Hi all!

Got another strange one again (why me?). Ran 70 peices of a double-sided SMT assembly. The board is a 6-layer FR4 board. PTH is hand-soldered.

Everything seemed to be going fine until the boards got to an inspector just prior to test. I get paged to look at some blisters she said she was seeing. I was pretty suprised because things were fine when they went through surface mount.

I went to the inspector, and sure enough, this is what I saw. Go to:

http://www.stevezeva.homestead.com

They appear randomly at one of four plated mounting holes on the board, and it's on random sides of the boards too...and it only happened on 19-assemblies. I can't find out when it happened. These mounting holes are off away from anything that was hand soldered too...

Funny thing is they look like blisters, but the laminate isn't displaced like you normally would see in a blister...to me, it's more like a sort of delamination.

I didn't see anything like that during SMT processing, I mean you can't miss something like that. But if it were due to excessive heat, I would expect to see it on more assemblies. The same thing would apply if it were caused by absorbed moisture wouldn't it? I would expect to see the problem on more assemblies. The fabs are all the same date code by the way...

Anybody ever see something like this before?

-Steve Gregory-