Roger,
I'm working on electroplated Nickel on copper, I would like to more about your
experience with Copper diffusion into Nickel layer. We work on silicon wafers here. Any
input from you will be greatly appreciated.
Yasmeen
Roger Massey-G14195 wrote:
> 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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