( ESNUG 398 Item 2 ) --------------------------------------------- [07/31/02]
From: Steve Gross <smgross@umich.edu>
Subject: How Thermally/Vibrationally/Soldering Reliable Is BGA Packaging?
Hi John,
I've got some questions on BGA reliability.
I work for the University of Michigan, I'm making a microwave radiometer for
use on an aircraft (a DC-8). The digital back-end processing is being done
in an FPGA. It looks like I need somewhere in the vicinity of 500 - 750 K
gates (and let's not get sidetracked on what a "gate" means in an FPGA...)
to implement the several hundred correlators and related control and data
readout logic.
There's no problem getting FPGA's of this capacity, but AFAIK they're only
available in BGA packaging. I've never progressed beyond 240-pin QFP
packaging. Do any ESNUGers have any reports on BGA reliability,
specifically in an environment which will experience thermal swings (ambient
temp can vary from about +50 to -60 C over the course of about 30 minutes,
although we have active thermal control to significantly reduce that range
within the system's enclosure... this is necessary to make the radiometer
data usable) and vibration (see "aircraft" above)?
A second issue is that we don't have BGA soldering and inspection capability
in-house. I can either send my board out to have the BGA directly mounted,
or I have found a vendor who can mount the BGA's on a carrier (through-hole
or SMT) that I can work with in-house. This latter vendor knows mil-spec
issues and can provide x-ray inspection of all joints, etc. A third option
is a socket from a company such as Emulation Technology. Any good or bad
experience reports with any of these techniques (preferably with pointers to
vendors) would be appreciated.
My alternative is to partition the design, but (of course) my schedule is
tight and I would like to be able to finalize the FPGA design in parallel
with board fab. I'd rather not have the additional complication of a
partition to deal with.
Thanks!
- Steve Gross
University of Michigan
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