Pete, Ronnie & the group,
Mechanical Testing (T & E or Ductility testing) of the copper plated
from the copper plating baths is much more likely to detect a columnar
grain structure if the samples are not annealed prior to mechanical
testing and samples are tested from both sides in the X & Y directions.
If testing is done before annealing it represents a process control test
while testing after annealing the copper in an oven changes and somewhat
normalizes the grain structure and represents more of a capability test.
On the negative side of these particular mechanical tests one must also
consider that the performance of copper plated into a hole may not be
represented well by copper plated on the stainless steel plate used for
obtaining Mechanical test samples.
Unless the grain structure is severely deformed it is quite difficult to
rate how a grain structure will perform mechanically. If you look into
the microsection at the copper foil's grain structure you will see that
it is markedly different that of typical PTH copper although the foil in
many cases mechanically outperforms the PTH copper. There are many
plating bath characteristics that determine mechanical performance (i.e.
ASF, leveling chemicals, aspect ratio, etc., etc.) and grain structure
is only a simple visual indicator. Hardness of the copper in the PTH
microsection by a Vickers hardness test can sometimes shed some light on
eventual mechanical performance but is difficult to perform and does not
have much historical precedence.
Best Regards,
Bob Neves
President
Microtek Laboratories
+1.714.999.1616
[log in to unmask]
www.TheTestLab.com
-----Original Message-----
From: IPC-600-6012 [mailto:[log in to unmask]] On Behalf Of Ronnie
Walker
Sent: Monday, June 20, 2005 7:10 AM
To: [log in to unmask]
Subject: Re: [IPC-600-6012] Grain Structure
In my mind, that issued should be picked up in process control measures
like T & E of the copper bath, thermal shocks of the bath, thermal
shocks
of the procuct and chemical process control..
I do not understand how you received boards with such a condition.
"Menuez, Pete"
<Pete.Menuez@L-3C To:
[log in to unmask]
OM.COM> cc:
Sent by: Subject: [IPC-600-6012]
Grain Structure
IPC-600-6012
<IPC-600-6012@ipc
.org>
06/20/2005 08:44
AM
Please respond to
"(Combined Forum
of D-33a and
7-31a
Subcommittees)"
All:
We are currently completing an investigation of some bare board failures
and found the cause to be poor grain structure of the plated through
holes.
The plating is columnar which provides weaker copper and eventually
plating
cracks throughout the holes. Our testing showed 100% failure of this
lot
after thermal stress.
Has there been any discussion in this group regarding adding grain
structure as inspection criteria? Does anyone know of any references or
standards regarding grain structure? I have talked with several of our
suppliers and some of them have commented back that they don't have a
good
reference to good/bad plating grain structure.
If you would like to see a report with pictures email me with your
address
and I'll send the report to you.
Pete
Pete Menuez
Supplier Quality Engineer
L-3 Communications Cincinnati Electronics
7500 Innovation Way
Mason, Ohio 45040
[log in to unmask]
513-573-6401 Voice
513-573-6767 Fax
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