I have used VIP (Via In Pads) a while ago when trying to adhere to
In Cicuit Test demands of having one-node-per-net bottom access on
100 mil centers, on very dense SMT boards. One of the very important
process changes I encountered was the solder paste stencil opening
had to be +.004 LARGER than the pad (.002 per side) to allow for the
seepage of solder into the holes. It worked out well, but it became less
important to do VIP due to advances in technology since then.
I'm talking top side 50 mil pitch ic's (every other pad is fanned-in).
For discretes 1206's it worked out well, and can be done on bottom side
wave ops as stated by [log in to unmask] 
But for the most part, I stay away from it now. Too much unpredictability
in results - I remember touching up some cold joints more than usual.


Tom Kavendek
Lucent Technologies
Murray Hill, N.J.

****************************************************************************
* The mail list is provided as a service by IPC using SmartList v3.05      *
**************************************************************************** 
* To unsubscribe from this list at any time, send a message to:            *
* [log in to unmask] with <subject: unsubscribe> and no text. *
****************************************************************************