Daniel,
Glad to see the university is doing real world application.  Few points:
(1) flip chip (area array with HDI), normally required fine pitch fan out,
depend upon your overall board layout requirement, such as other components
on the board, it may be cost more at PCB level.  BGA avoid this problem...
(BGA pitch is very similar to the SMT parts).
(2) flatness of the PCB for flip chip is different compare to the BGA.  You
have to worry about CTE match between PCB/encap/chip... larger the size of
die, more "challenge" for Daniel.  BGA or LGA is better (the carrier
normally matches better to the PCB).
(3) If your operation temp is not large swing, flip chip works well.
Thermal shock, you need good design and encap.  BGA is a bit more
forgiving...
(4) before you take on flipchip, check the thermal requirement of the
chip... piggy back a heat sink at board level attach might be a headarch...
(5) if you got known good die, that's great... otherwise, rework of a bad
flipchip die is a pain.  (BGA come in pre-tested).  Not like direct chip
attach you pop a wire bond and replace it before you glab top... but you
have pain try to get a wire bondable gold PCB and clean to the extend that
you can wire bond after solder reflow... not every body's cup of tea.  Mr.
IngeMAR will tell you all the story...
Definitely, need someone like Daniel who has special knowledge in the
area...

                       jk (my 1.78 cents)

abcd

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Daniel Blass
Sent: Monday, June 05, 2006 10:59 AM
To: [log in to unmask]
Subject: Re: [TN] Use of BGA packaging in automotive applications


Since it is my area of research, I'd say this is the place to consider flip
chip.  We have helped several automotive suppliers with flip chip on board.
 Flip chip assembly can be integrated with the standard SMT process and give
a much smaller foot print than a leaded device or standard pitch BGAs.

However, the process knowledge required is a barrier to implementing FC.
Board cost is higher since it requires very small substrate features and
good tolerances.  Since all the decisions are the assembler's
responsibility, it is much more involved than selecting a BGA package.
Depending on your volumes and future needs, it may or may not make sense to
use flip chip on board.

Most of our research isn't publicly available but if you are interested in
FC for harsh environments, you can look at some of the work published by
Wayne Johnson's group at Auburn.

Regards,
Daniel Blass
Process Research Engineer
Area Array Consortium
Surface Mount Technology Lab
Universal Instruments Corporation
http://www.uic.com/wcms/WCMS2.nsf/index/Global_Svc_Support_31.html

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