Hi Lee!  The primary issue are need to address is "how much wetting is 
required". As other TechNetees have described, you are not melting the 
solder ball so you will end up with various levels of wetting. Your BGA 
left solderball is acceptable and the BGA right solderball may also be 
just fine despite its visual appearance. IMHO the BGA left solderball is 
acceptable as it has good wetting for a non melting solder alloy situation 
(it just doesn't have the anticipated wetting height). My recommendation 
is to sacrifice a couple of BGAs, do some cross sectioning and setup a 
go/no go wetting scale for inspection use. You could also play with your 
stencil apertures to potentially increase wetting characteristics. Good 
Luck.


Dave Hillman
Rockwell Collins
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Lee Whiteman <[log in to unmask]> 
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05/17/2010 08:52 AM
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[TN] MORE 90 / 10 SOLDER BALL QUESTIONS






I just posted a photograph of a 90 Pb / 10 Sn BGA solder joint on the
IPC Photo Gallery, that was soldered with eutectic SnPb solder and an
eutectic SnPb solder thermal profile.

The BGA on the left hand side is "acceptable", but the BGA on the right
hand side shows a clear line of demarcation. My initial thoughts was to
check the thermal profile, to see if it got to a high enough
temperature.

Any thoughts and comments?

Thanks.

Lee Whiteman, PMP
Senior Member Engineering Staff
L-3 Communications East
Telephone: (856) 338-3508
FAX: (856) 338-2906
E-Mail: [log in to unmask]

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