Provided all ball size and coplanarity issues are relatively good, no paste
is best. If using paste, ensure the micro stencil thickness is as specified
over the entire foil or whatever material. Ensure the stencil is placed
accurately and located "permanently", with tape or tool system, until paste
dispensation has been properly effected. Doesn't hurt to look at paste
depositions under scope to get a good "feel" for consistency.

No paste is best as there is plenty of solder volume from balls. Going below
.8mm pitch is another story - sometimes. Of course, be sure specified pad
sizes are as required - relative to ball size. No solder bridging should be
apparent whatever the attachment method. Good profiles don't hurt either -
and on it continues.

MoonMan

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