~ducking the flying objects~
Wow, that was blunt!!!
Franklin
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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