At first glimpse, the apparent change in opacity of the soldermask makes it
look like the mask is lifting off the laminate.  Is that what you see?

You said the date codes are all the same.  How old are they?  For moisture
absorption related delamination on FR4 they either have to be pretty old
(months) or been stored in very humid conditions.


> ----------
> From:         [log in to unmask][SMTP:[log in to unmask]]
> Reply To:     TechNet E-Mail Forum.;[log in to unmask]
> Sent:         Wednesday, January 30, 2002 11:34 AM
> To:   [log in to unmask]
> Subject:      [TN] Laminate Blisters...
>
> 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-
>

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