Hard gold is harden by Ni or Co. Intend for contact interface, not soldering. Why you solder it?
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----- Original Message -----
From: Reuven Rokah [mailto:[log in to unmask]]
Sent: Sunday, July 10, 2011 01:53 AM
To: [log in to unmask] <[log in to unmask]>
Subject: Re: [TN] Micro voids when soldering to hard gold
1. Pls send the cross section you have
2. If micro-voids manifest itself in the component junction (not PCB), you
should send the component manufacturer a failure analysis request form.
3. You have to pass samples of components without PCBs / solder paste
through reflow, in order to see if the phenomena happened again.
Reuven
On Fri, Jul 8, 2011 at 11:23 PM, Crandall, Ken <
[log in to unmask]> wrote:
> All -
>
> I have a situation where we are experiencing micro-voids in solder joints
> after SMT reflow. Problem manifest itself primarily in BGA to solder ball
> interface ( at the device junction interface and not the PWB to solder ball
> interface) confirmed with cross sectioning. BGA solder joints are weak
> resulting in electrical failures and removal with minimal mechanical stress.
>
> We are using a Kester 256 HA (62-36-2) solder paste on a electrolytic PWB
> finish. The same board with the same process using ENiG does not exhibit
> this problem.
>
> Ionic, XRF and SIMS analysis does not reveal any surface or interlayer
> organic contamination. I have seen old publications indicating this
> phenomena has been observed before with hard gold chemistries.
>
> DOEs conducted by varying reflow dwell times / surface cleaning / pre-bake
> does not remedy the situation
>
> Any thoughts or experience with salvaging built CCAs or reclaiming bare
> boards to eliminate this issue?
>
>
>
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