hi,

assuming that this board has plated through holes, there will always be a
layer of electroplated copper on top of the foil.  the failure may be at
this interface.

i have seen two layers of electrodeposited copper on top of foil.  when
speaking to the fabricator about this they essentially said that the cross
section after pattern plating indicated insufficient copper; so they put it
back in the tank to add more.  if this happened, your failure may be at this
interface.

only a microsection will tell.

phil

-----Original Message-----
From: Stephen R. Gregory [mailto:[log in to unmask]]
Sent: Wednesday, October 06, 1999 12:57 PM
To: [log in to unmask]
Subject: [TN] Two distinct layers of copper...


Hi ya'll!

Here's something weird I've never come across, but maybe some of you have.
We
built this Hi-Rel board here that the PCB drawing calls out for 2-ounce
copper.

The board has this leaded SMT multi-capacitor part (it's like 3 huge ceramic
capacitors stacked on top of each other) and has 8-leads. After assembly,
and
before we test then conformal coat it, we put the assembly on this vibration
table to go through some ESS.

There's been a few of these capacitor deals come loose because they're so
top
heavy, but that's a whole 'nuther issue...

What we've been seeing on some of these boards, is that either the pad
completely lets go from the laminate (it's a polyimide), or sometimes we'll
see the pad come up in what looks like a layer of copper, yet there's still
copper down on the PCB...as if the copper has split horizontally in two
distinct layers? Is this possible? Does 2-ounce copper clad laminate get the
copper plated an ounce at a time? Is this a defect? I've never seen
something
like this before, and I can take a picture and send it to ya' if you want me
to....

Thanks!

-Steve Gregory-

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