Via-in-Pad for BGA
Has anyone had experience with via-in-pad for BGA devices?  

As I see it, there are some advantages and disadvantages of the concept:

Advantages:
1)  Secondary-side test access for ALL nodes of the BGA, possibly eliminating
the need for an expensive clam-shell ICT test fixture.
2)  Less stressful BGA removal, since bottom-side heat will help liquify the
ball/solder interface EQUALLY over the entire IC without the need of extensive
component package heating.
3)  Trace routing for inside nodes can use any of several inner layers, thus
making line density (width and space) more manageable and NOT eat up top-side
PCB real estate.

Disadvantages:

1)  The via pattern does eat up inner layer and bottom-side PCB real estate.
2)  It does punch a lot of holes in the ground/power planes, making shielding
in the BGA area more difficult. 

Are there any other items to be considered before embarking on this bold
concept?  Does IPC cover this type of assembly with an industry "standard"? 

Bill Fabry
Truevision, Inc.
[log in to unmask]