Hi, Antonio,

As the other two respondants have indicated, voids in BGA joints are
principally caused by volatile compounds in the flux out-gassing into the
joint. Voids in these cases tend to be small and of no significance as long
as they don't blow out through the side of the ball, which is rare. Larger,
more irregularly-shaped voids can occur when you have via holes in the
pads, unfilled holes especially, although these holes are normally plugged
nowadays.

Voids in BGA joints are common and are not considered to be a problem
unless they are very large and/or found at the top of the ball next to the
compnoent substrate. These weaken the balls' adherence to the component.
Careful selection of flux and tight soldering process control can eliminate
voiding, but the cost of this will be high with no real advantage gained
unless your voids are a problem.

Best wishes

Peter




                    Antonio Souza
                    <[log in to unmask]        To:     [log in to unmask]
                    INPE.BR>             cc:     (bcc: DUNCAN Peter/Asst Prin Engr/ST
                    Sent by:             Aero/ST Group)
                    TechNet              Subject:     [TN] Voids on BGA
                    <[log in to unmask]
                    ORG>


                    04/10/02
                    08:25 PM
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Does anybody know the main causes for Voids on BGA solder joints?

Thanks

Antonio
Brazil

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