Sigi,
 Before redesigning the whole board, which is really the proper cure to
this problem
 you can try the following.
 Vias on the bottom( opposite) side should have the solder mask almost
closing the hole:
  : Drill + 4 mils - provided they are  not used for Ict. This will
eliminate some of the paste loss.
  Then add extra solder past to the troublesome locations either by
enlarging the
 stencil opening (opening may be larger then the pad size) or by
injecting paste in rework
 station or even in line if your line is so configured.

 Mickey


>>> [log in to unmask] 15-Apr-02 6:08:35 PM >>>
Hello to all

We have to redesign different board's because of Via in Pad:
Situation now:
FR4, thickness 1,5 mm, OCC finish
Through Hole Vias in Pads (middle, diameter 0,15..0,3 mm)

The problem is the sucking of solder form to the top to the bottom
side
(causing low solder on top and bumps on test points on the bottom
side)
Because of place limitations dog bones can't probably not be used.

What is your recommendation?
Using Blind Vias (problem of Voids in the solder joint?) ?
Epoxy (with Ag or what else) filled Vias?
Vias on the edge of the pad?
More ideas?

All input is welcome

Best regards

Siggi


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Kind regards / Mit freundlichen Gr??en

Dr. Siegmund Zweigart

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