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Subject:	Re: Heat-sinked BGA Bridging...
From:	"Ingemar Hernefjord (EMW)" <[log in to unmask]>
Reply To:	TechNet E-Mail Forum.
Date:	Thu, 1 Mar 2001 12:48:15 +0100
Content-Type:	text/plain
Parts/Attachments:	text/plain (39 lines)

Hi,
another thought is this. We had IBM people here today for discussing PAM, you know Precision Alignment Macros, funny things. And saw same again: IBM have all since the 70s oftenly used to omit one or two balls in each corner of their FCs or BGAs, so just empty places instead of balls. And they have had no soldering or bridging problems for two decades (at least they say so). I looked on some of their old supercomputer modules with thousands of balls on each module, same thing : some corner pads omitted.  Maybe there is a good trick with those inexisting corner balls. Have seen others too with that concept, think TI had something like....Kyocera too.. Go to your cellar and pick up your dusty and dumped IBM machine and have a look.  Just a thought.
Ingemar

-----Original Message-----
From: To My E-Mail Address [mailto:[log in to unmask]]
Sent: den 28 februari 2001 18:10
To: [log in to unmask]
Subject: Re: [TN] Heat-sinked BGA Bridging...

To the assembly people, just a thought.

It seems that the total flexing of BGA due to size and mismatched CTEs is a
given.  WHY not try high temp balls that do not collapse as much and hence
reduced or no bridging.  It may cost a bit more but I am sure it is worth
considering what you pay for reworking those BGAs.  I am sure TI will be
willing to work with you guys because that may be quick fix, without doing
extensive studies on finding materials and/or narrowing process window too
much.

Steve may be you can try this at the rework level.  Reball the BGAs using
high temp balls.

Just an engineer thinking.

Rush

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