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July 2011

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Subject:
From:
Joyce Koo <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Joyce Koo <[log in to unmask]>
Date:
Sun, 10 Jul 2011 06:12:11 -0400
Content-Type:
text/plain
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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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-- 

Best Regards,

*Reuven Rokah*

Mobile: 972-52-60-120-18
Tele-fax: 97239360688
<http://www.rokah-technologies.com/>[log in to unmask]
[log in to unmask]
www.rokah-technologies.com

**


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