Hi Tom - Just an correction - the IPC-7095B guideline document and not a 
requirement specification document. The solder voiding requirement of BGAs 
is per JSTD-001. I don't believe that there is an underfill voiding 
requirment in the JSTD-001 specification yet.

Dave Hillman
Rockwell Collins
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"Gervascio, Thomas" <[log in to unmask]> 
Sent by: TechNet <[log in to unmask]>
11/02/2007 08:49 AM
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Re: [TN] verifying BGA underfill coverage






Curious what criteria are you using for BGA underfill (i.e. voiding,
coverage, etc). IPC-7095B section 7.2.2? 


 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Joe Macko
Sent: Wednesday, October 31, 2007 7:34 PM
To: [log in to unmask]
Subject: [TN] verifying BGA underfill coverage

Fellow Techs

 

We purchased a GPD automated epoxy dispenser and I want to proof out the
new automated underfill application process on BGAs. We use a wickable
Loctite underfill that requires an elevated temperature to flow properly
under BGAs, etc..  Currently we successfully underfill by hand and want
to switch to an automated process using the GPD. 

 

I want to verify the underfill coverage under BGAs using a
non-destructive test method. The only non-destructive method I am aware
of is acoustic imaging using an instrument such as Sonoscan, which I
believe will show voids in the underfill material. I do not know how
industry non-destructively verifies underfill coverage.  I plan on
physically removing some BGAs on scrap boards to verify coverage but do
not want to do this on good boards for obvious reasons.

 

Question - What is the commonly accepted non-destructive method for
verifying BGA underfill coverage?  Look forward to your comment. thanks

 

Best Regards,

- Joe

 


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