Hi, 

  We experience some void in BGA.  We try different paste and profile but
nothing seem to eliminate those void. We try something, we took a BGA and
put only  flux on the ball( Flux 297DX from AIM) and we didn't see any
voiding after that...

  We use stencil of .006mil, and .005mil of thickness, and we had some
medium to large void

  We also try a .004 stencil ( like a mini-stencil) where we put some paste
and we had some little BGA.

  My question is, could the paste and the ball of the BGA could not be
compatible( we use a no clean solder paste, 63/37, our Solder ball under BGA
are also 63/37).

  Or is the stencil thickness is very important??

  We use a 10% reduction on the stencil whti round pad

Thanks You

Yannick Brisson
============================
Technicien SMT
Technician SMT
M2S Électronique
2855, Rue de Celles 
Québec, Québec
G2C 1K7
Téléphone: (418) 842-1312 Ext: 264
Télécopie: (418) 842-0123
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