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August 2004

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Subject:
From:
"Ingemar Hernefjord (KC/EMW)" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Ingemar Hernefjord (KC/EMW)
Date:
Mon, 2 Aug 2004 13:39:56 +0200
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We have done FEA (NASTRAN, ANSYS) on BGA balls by means of what they call Maxwell's rheological elasticity model. May be possible to
share with you, Shean, if you are interested I can ask the guy who did this huge job a couple of years ago. You need a good math background to understand this report.

Ingemar Hernefjord
Ericsson Microwave Systems

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Shean Dalton
Sent: den 28 juli 2004 21:04
To: [log in to unmask]
Subject: Re: [TN] BGA pad missmatch


Hi Phil,

I have been hoping for a response from someone who has practical
experience with this, as it is interesting to me.  That said, I suspect
areas of concern would be for TCE.  The larger pad size takes away
solder from the bulk joint, effectively reducing the standoff height.
Again, I suspect the reduced standoff height might reduce the "flexure"
ability of the solder joint to "absorb" the TCE mismatch.    And, using
a larger sphere diameter may compensate for the large pad size,
effectively raising the standoff height.


 Sure would be nice to do a
finite elemental analysis.

Have fun!,

Shean Dalton
Austin American Technology

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