Browse Prior Art Database

Double-Sided Ball Grid Array Arrangement

IP.com Disclosure Number: IPCOM000116979D
Original Publication Date: 1995-Dec-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Leddige, MW: AUTHOR [+4]

Abstract

Disclosed is a method which allows Ball Grid Array (BGA) modules to be mounted doublesided with little offset while not requiring blind vias.

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Double-Sided Ball Grid Array Arrangement

      Disclosed is a method which allows Ball Grid Array (BGA)
modules to be mounted doublesided with little offset while not
requiring blind vias.

      On card technologies that don't support blind vias, it is
impossible to

mount

BGA

modules directly across from each other on
opposite sides of the card.  This is because each module solder bump
has to go to a via and that via has to go all the way through the
card.  Therefore, if (for example) two 32mm BGA modules are to be
mounted on opposite sides of the card, they would have to be offset
by 32mm (more or less depending on local wirability constraints).
This leave a lot of card area wasted and makes wiring lengths longer
which is a performance problem.

      Instead of insisting on a minimum signal pitch on the BGA
modules (currently 50mils), double this pitch for the signals in one
dimension (i.e., to 100mils) so that a 50 mil offset of one module
relative to the other is all that is required to mount the modules
doublesided without need of card technology that supports blind
vias.  The module size does not necessarily double as power and
ground
solder bumps can be strategically placed to work on either site.