Thanks guys ; always helps to know you're not having heatsrokes ; mirages ;
LSD hangovers; etc.
Now I have to have a gentle chat with my fab buddy (poor fellow was
typhooned in HK).
see yo' paul
-----Original Message-----
From: Roger Massey-G14195 [mailto:[log in to unmask]]
Sent: Thursday, 26 August 1999 18:02
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
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