Apart from scientific considerations, aesthetics also play a role in
evaluating and selecting a product. A zigzag underfill may raise some
eyebrows.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Graham Collins
Sent: Thursday, June 04, 2009 11:57 AM
To: [log in to unmask]
Subject: [TN] Underfill Workmanship Pass/fail Criteria Proposal - underfill
on top surface

OK.  From the replies to my postings I don't think I'm explaining myself
well enough.  Here goes again:

Let's say for argument sake that I'm underfilling a Texas Instruments
part TMS320C670.  This part has an aluminum cap on top, the cap is also
stepped.  Details of the part can be seen at:
http://focus.ti.com/docs/prod/folders/print/tms320c6701.html#pricingpack
aging

Obviously it is best to avoid getting underfill onto the top of this
component, but let's assume a bit of underfill is on top, and the
operator did not notice it before curing the material.

Provided it does NOT interfere with mounting a heatsink, I am at a loss
to understand how underfill on the top surface of this component could
possibly impact the reliability of this component.  Therefore I would be
against a statement in a specification that would call it a defect and
make me rework it.

I do know there are brighter folks than I on TechNet, if you can explain
to me how this should be a defect I'm listening!  

regards,
 - Graham

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