RE>>BGA's - one user's perspective           1/15/96

Hi Jerry,

You have some very valid concerns regarding the increased costs at the present time regarding BGAs, but package cost is but one thing to look at.  It all depends on the specific application.  

We at Mercury Computer Systems implemented BGAs (361 I/O, 50 mil pitch, 25.4 mm ceramic bodies) over two years ago mainly for improved packaging density.  We "live" in a very tight VME space and have to get a lot into that 0.8" wide slot.  Going to a BGA from a PGA allowed us to significantly reduce the x-y area (about a 67% savings), to reduce the z-dimension so that we could fit additional devices on the corresponding motherboard/daughtercard stack, and to eliminate an additional wave soldering step.  Furthermore, we were able to design out Blind Vias on our daughtercards.  

We do not produce large volumes (we've placed 30-40,000 CBGAs over the last 2 years, and some of the larger motherboards have up to 11 BGAs each), but this move definitely made sense to us.  As you can probably guess, our boards are very high performance and aren't the cheapest things in the world.  We've also seen reduced defect levels, but this is more "gravy" when the big picture is considered.  

Regards,
Greg Bartlett
Mercury Computer Systems
Chelmsford, MA