It sounds to me that you don't understand how a pcb is manufactured to
achieve your requirements, particularly about the manufacturing methods used
i.e acid copper plating and the problems of distribution of plating across a
board

Basically if you specify a 2 ounce surface copper a manufacturer will use 1
ounce copper laminate and plate the surface up to 2 ounce resulting in your
requirements of sufficient copper down the hole of a minimum of 25 microns

If a manufacturer used 0.5-ounce laminate and plated up to 2 ounce then you
could have problems (with certain holes because of plating distribution
problems)


Delamination of the copper plated layer can be caused by a vast number of
problems

1. Direct plate not being sufficiently etched (if used)
2. Poor adhesion of electroless copper deposit (problems with brushing ,
oxidation etc, etc prior to plating)
3. Poor developing of dry film laminate
4. Problems with acid cleaner prior to acid copper plating
5. Problems with microetch prior to acid copper plating
6. Low temperature of rinses after acid cleaner in acid copper plating line
(believe me it happens)

Etc , Etc

Get clued in to your pcb supplier and find out how a board is made

Paul



-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Stephen R. Gregory
Sent: 06 October 1999 20:57
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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