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

Rokah Technologies

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?
>
>
>
> ______________________________________________________________________
> This email has been scanned by the MessageLabs Email Security System.
> For more information please contact helpdesk at x2960 or [log in to unmask]
> ______________________________________________________________________
>
> ---------------------------------------------------
> Technet Mail List provided as a service by IPC using LISTSERV 16.0
> To unsubscribe, send a message to [log in to unmask] with following text in
> the BODY (NOT the subject field): SIGNOFF Technet
> To temporarily halt or (re-start) delivery of Technet send e-mail to
> [log in to unmask]: SET Technet NOMAIL or (MAIL)
> To receive ONE mailing per day of all the posts: send e-mail to
> [log in to unmask]: SET Technet Digest
> Search the archives of previous posts at: http://listserv.ipc.org/archives
> For additional information, or contact Keach Sasamori at [log in to unmask] or
> 847-615-7100 ext.2815
> -----------------------------------------------------
>



-- 
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

**


______________________________________________________________________
This email has been scanned by the MessageLabs Email Security System.
For more information please contact helpdesk at x2960 or [log in to unmask] 
______________________________________________________________________

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 16.0
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
For additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------