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August 1999

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Subject:
From:
nishath yasmeen <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Thu, 26 Aug 1999 11:04:42 -0500
Content-Type:
text/plain
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text/plain (107 lines)
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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