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July 1997

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Subject:
From:
Jim Herard <[log in to unmask]>
Date:
Wed, 16 Jul 1997 17:40:43 -0400
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You can have problems with wave soldering after BGA component placement, and
you have the correct concerns.  This is sometimes a design dependant issue --
how much heat do you transfer through the vias...  via size, cross section, Cu
thickness all have affects.

Most assembly shops will not only use LPI plugs on the back side of the bga
area, but they also tape them off with kapton tape.  I recommend you thermal
couple the board under the bga and run some through your wave process and look
for reflow temperatures on the BGA side of the board.  That's the safest way to
know if you are OK>  Stay as cool as you can and still get good reflow/solder
joints on the solder side of the board.

Hope that helps.

Jim Herard
KBL, Product Quality Engineering
IBM Microelectronics Endicott
t/l 857-7026

---------------------- Forwarded by Jim Herard/Endicott/IBM on 07-16-97 05:33 PM
 ---------------------------

        [log in to unmask]
        07-16-97 10:56 AM
Please respond to [log in to unmask] @ internet

To: [log in to unmask] @ internet
cc:
Subject: Wave and BGA

Hello all,

I will like to have comment on any effect that a wave can do on a BGA.

We have some boards with BGA on component side and many component on the solder
side. Our process will be reflow component side, glue solder side, install all
TH parts and go to wave.

Is anyone had or have  problems with BGA (solder joints problem) after wave? Our
via's are half tented with solder masks and the trace connecting the via to the
BGA pad is approx. 0.020"-0.030".

My concerns are:

- Re-reflow of BGA solder ball causing cold solder or any solder defect?
- Reliability problems?
- Etc.

Any advice will be well appreciated.

Thank you.

Andre Bisson
CAE Electronics
[log in to unmask]

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