Hi Fulton!  There has been some industry issues with BGA's and immersion
gold/electroless nickel finishes (there was a very good paper given at the
IPC PWB Surface Finishes Summit  by Z. Mei of HP). The problem is/has been
solder joint failure of large BGA packages at the nickel/solder interface
after assembly. There is a team of folks lead by Bruce Houghten of
Celestica looking into the issues and they will be reporting their
investigation results periodically. Also, because of the BGA's finite
solder volume the issue of gold embrittlement has sometimes been discussed.
Most problems surrounding the gold embrittlement of BGA solder joints were
due to  insufficient reflow time to allow the dissolution of the gold into
the solder joint. Good Luck.

Dave Hillman
Rockwell Collins
[log in to unmask]





Fulton Feng <[log in to unmask]> on 05/13/98 12:30:04 PM

Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please respond
      to Fulton Feng <[log in to unmask]>

To:   [log in to unmask]
cc:    (bcc: David D Hillman/CedarRapids/Collins/Rockwell)
Subject:  Re: [TN] Reliability of Immersion Gold PCB




Hi Steve, thank you for your comment! What I really want to know is the
reliability of the product by using immersion gold PCB, including solder
joint reliablity and integrity of the PCB after process. Do you know
whether
IPC has any standard or publication on this topic? Is it Bellcore
compliant?
What is the issue with BGA for immersion gold?

Thanks again!

Fulton Feng

> ----------
> From:
>
"STEVE_O\\'HARA"@HP-Vancouver-om10.om.hp.com[SMTP:"STEVE_O\\'HARA"@HP-Vanc
> ouver-om10.om.hp.com]
> Sent:         Wednesday, May 13, 1998 10:01 AM
> To:   Feng, Fulton [MPK:5221:EXCH]
> Cc:   [log in to unmask]
> Subject:      Re: [TN] Reliability of Immersion Gold PCB
>
>      What do you want to know??
>
>      Raw Board Reliability (solderability)
>      Contact Resistance Reliability?
>      Solder Joint Reliability
>
>      With regards to Solder Joint Reliability, the solder interface of
the
>
>      nickel to solder forms tin intermetallics which will not be as
strong
>
>      as solder to solder. These joints will still be acceptable for most
>      smt components but immersion gold and BGA's should be avoided.
>
>      Regards:
>
>      Steve O'Hara  HP
>
>
> ______________________________ Reply Separator
> _________________________________
> Subject: [TN] Reliability of Immersion Gold PCB
> Author:  Non-HP-Fulton.Feng.ffeng ([log in to unmask]) at
> HP-Vancouver,mimegw10
> Date:    5/12/98 5:39 PM
>
>
> Hi
> Has anyboy done any reliability study on Gold Immersion PCB finish?
>
> Thanks
> Fulton Feng
>
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