Paul,
Another thought to echo what others have said. Copper build-up in
electroless nickel solutions, while not necessarily visible to the naked
eye, will be incorporated into the nickel deposit. Then, as if by magic, the
copper can migrate along grain boundaries in the nickel (solid
State diffusion) and basically relocate to the surface of the nickel. This
is one possible scenario for the copper you are seeing.
Good luck,
Mike Carano
-----Original Message-----
From: Roger Massey-G14195 [SMTP:[log in to unmask]]
Sent: Thursday, August 26, 1999 3:02 AM
To: [log in to unmask]
Subject: Re: [TN] Nickel plating contaminants ; cracking
propagations
Paul,
If the CuSn intermetallics are forming randomly across the
surface,
have you considered that the Ni layer is not strictly
continuous, or
more likely its porous. This would result with rapid Cu
diffusion (via
pore and grain boundaries) up onto the Ni layer, and hey presto
theres
yer CuSn chunks.
Have you tried a surface scan of incoming boards looking for
Cu?
follow this with "reflowing" a board (without any components)
and
repeating the surface scans, if you see Cu at any time, then
your
boards are bad, and should be returned for cleaning, and
replating if
it can be done
For the analysis, you may need to use a low penetration
technique
like auger, EDX may just punch through any small or thin Cu
deposits.
alternativly, cross sectioning and doing a Cu Xray map or line
scan
may show an increase in Cu concentration through the Ni layer
Ive experienced this before with an electroplated Ni layer
on Cu.
Then the Hydrogen embrittled plating was cracking during
transit, and
also reflow. This resulted with rapid Cu diffusion up onto the
surface, which was giving the same style of thing.
Hope it helps,
Roger
Motorola AIEG
______________________________ Reply Separator
_________________________________
Subject: [TN] Nickel plating contaminants ; cracking propagations ?
Author: "TechNet E-Mail Forum." <[log in to unmask]> at #email
Date: 26/08/99 10:51
This must be a problem season :
after flakes, cabbages and roses , I have this copper "boulders"
alloy
problem :
On our routine microsectioning of (4umNi + 0.3umAu; 63/37) joints we
discovered we have rather interesting phenomenon :
After the obvious dissolution of gold ; there are sitting on top of
Nickel
(admittedly bit thin ; still , continuous) microcracked boulders
(about same
dia as the Ni layer) .
when we zoomed scan on them ; we found they're CuSn alloy ! Looks
like a
smallpoxed nickel face .
Now our regular profiling 's telling us we're nowhere near this
alloying
scenarios ;
and we ponder about the cracking propagations ; the Q is :
Where are this aliens coming from ?
Contaminants of tubs from some previous process ?
Smudged sample polish ?
Appears only on one specific fab supply .
Paul Klasek
http://www,resmed,com
##############################################################
TechNet Mail List provided as a free service by IPC using LISTSERV
1.8c
##############################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with
following text
in
the body:
To subscribe: SUBSCRIBE TECHNET <your full name>
To unsubscribe: SIGNOFF TECHNET
##############################################################
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for
additional
information.
If you need assistance - contact Gayatri Sardeshpande at
[log in to unmask] or
847-509-9700 ext.5365
##############################################################
##############################################################
TechNet Mail List provided as a free service by IPC using LISTSERV
1.8c
##############################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with
following text in
the body:
To subscribe: SUBSCRIBE TECHNET <your full name>
To unsubscribe: SIGNOFF TECHNET
##############################################################
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for
additional
information.
If you need assistance - contact Gayatri Sardeshpande at
[log in to unmask] or
847-509-9700 ext.5365
##############################################################
##############################################################
TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
##############################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in
the body:
To subscribe: SUBSCRIBE TECHNET <your full name>
To unsubscribe: SIGNOFF TECHNET
##############################################################
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information.
If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or
847-509-9700 ext.5365
##############################################################
|
