Does anyone did reliability test of the joint form with Ni/Pd/Au?  If my
memory serve me right, Pd and solder do form intermetallics relatively fast.
                                  jk
At 02:33 PM 12/9/99 -0700, you wrote:
>Larry,
>
>        You are absolutely correct.  However, in order for solder to make
>contact with Ni, it must first dissolve the Pd.
>
>        Several SMT solderability tests have used the technique of depositing
>solder and measuring how far it spreads during reflow.  How far solder
>will spread is a function of the surface energy interface of the liquid,
>solid and gas, and the wetting angle.  By increasing the surface energy
>of the solid, the liquid can more easily wet that surface.  Without
>referencing a chart, I would guess that the energy interface of liquid
>Tin is better for Gold than Palladium because Gold dissolves into Tin
>faster.  Improving the solderability of Palladium by using flash gold
>was suggested by Elizabeth Benedetto in her article in SMT Feb 99 titled
>"Evaluation of Palladium Lead Plating".
>
>        Dave Hillman did do solderability testing and wire bonding on Ni/Pd/Au
>and found that surface finish has very good wire bondability. (Published
>in SMI '96)  It is also corroborated by an NCMS consortium published in
>SMI '96. And ITRI reported the same results in IPC expo 97.
>
>        From the looks of the above stated articles, I guess I'm wrong about
>the Au being used to improve solderability.  It sounds like the gold is
>for wirebonding.
>
>Ryan Grant
>
>>-----Original Message-----
>>From:  Larry Tawyea [SMTP:[log in to unmask]]
>>Sent:  Thursday, December 09, 1999 11:16 AM
>>To:    [log in to unmask]
>>Subject:       Re: [TN] Ni/Pd/Au
>>
>>In a message dated 12/8/99 4:02:17 PM Central Standard Time,
>>[log in to unmask] writes:
>>
>><<
>>         The gold is an attempt to improve the solderability of the
>>palladium. >>
>>Ryan,
>>
>>Unless I am totally missing something from your response,  the issue is not
>>how long the solder is in contact with the Au or Pd but how long is the NI in
>>contact with the solder.  I'm not trying to take issue with your response,
>>but I think the issue is what is the solderability of the Ni and how good of
>>a solder joint have you made to the NI.
>>
>>Larry Tawyea
>>
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