Try IPC-SM-782, Suface Mount Design and Land Pattern Standard.  It is available through the IPC. $45 for member companies and $90 for nonmembers.

Contact the IPC Order Department at:
  847/509-9700       phone
  847/509-9798       fax
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  www.ipc.org          internet

Lisa Williams
IPC Technical Staff


>>> Johannes Sivula <[log in to unmask]> 09/10/97 08:04AM >>>
Hi Techneters

Does anyone know a good site/book/source , commercial/non-commercial for
SMD footprints library.
I have been assigned to update our footprint library, and I am not
satisfied with footprints
given in data books of component suppliers.  I presume that  those
footprints are not optimized
for IR reflow, nor carefully experimented.

Does anyone know any mathematical formula to be used to check roughly
dimensions of a pad ?

We make multilayer FR4 boards, HAL/Immersion Gold finish, no clean flux,
which is probably causing solder
balls. This problem is coped by reducing the size of stensil apertures. How
 much it can be reduced ?
Does anyone have comment on that ?


Thanks  for your time and cooperation.

Brs,

Johannes Sivula, Reliability Engineer, Tellabs Oy,