Are these "dimpled" BGAs?  Are the component pads recessed below the bottom
surface?  If so, perhaps you might try screening the flux instead of
dispensing.  This might give you a better flux deposit without voids.

Jim Marsico
AIL Systems Inc.
(516) 595-5879
[log in to unmask]



Fumiaki Shigeoka wrote:

My problem is dropping solder ball from BGA devices after ball attachment
process.
First, I suspected the temperature of reflow oven, but that was sufficient to
melt
solder ball. After reflow, some balls(5-10% of strip) are missing, and empty
pads
are not wetting or partially wetting.
I found voids in flux on pad before placing ball, so I guess the void will
expand
in reflow furnace, and ball doesn't touch to pad. I use dispensing system to
provide
flux, which sometimes contaminates air void to flux on pad.
Does anyone have any experiences and suggestions to solve this problem ?

Thanks in advance.

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