Ramsey,

I am all too familiar with what you are going through. I have had the same
problems with some certain boards that I have built here. They sound like the
same layer count and have the same sort of delamination problems that you
speak of. I can send you some pictures if you want. I'm in Tulsa, Oklahoma,
and humidity is not something that we're short of.

It's been a month or so, ago, that I waved about a dozen of these particular
assemblies, almost 75% of them blistered on me. Dime, to quarter sized
blisters (again I can show you pictures of them, they're in our scrap pile
now) discovered that they hadn't been baked. Since that time, I've baked
these assemblies at 125-degrees centigrade for 2-hours prior to getting them
across the wave (within around 4-hours after bake), haven't had a blister so
far since I've been making sure they're baked.

I still would like to know why I should need to bake them, because I recieved
a few responses at the time I first had the problem that it was probably a
problem with the lamination process (resin starvation or something) that I
was getting the blisters...but for some reason, it seems that baking them
does prevent the blisters.

From my past experiences, baking is only needed to eliminate the problems
with laminate moisture absorption and the defects that may cause (like
blow-holes, pin-holes, etc. during wave solder) not blisters or delamination.
But it seems to be working for me... I've not had a delamination or blister
since I've been baking the boards...

Don't have a root cause yet..but I'll work on that when I get time. I bake
for now, and not worry about blisters.

-Steve Gregory-

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