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October 1998

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Subject:
From:
"(Eden Chen)" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 21 Oct 1998 08:58:38 +0800
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Item Subject: [TN] BGA Assembly
     Tom,
     In the market, the nozzles for rework stations such as SRT,
     Conceptronic and Pace have the same shape as the BGA, namely square.

     There is more heat in the four corners than in other location due to
     more flow near the corner. When you set the temperature profile, you
     may put the thermal couple in the center of BGA. This cause that the
     temperature profile at the corner is too high.

     The solution may have:

     (1)Modify the nozzle---reduce the heat at the corners

     (2)Use more thermal couple for setting the temperature profile

     (3)If you print the solder paste for rework, stencil aperture at the
     corner should be smaller.

     (4)If you do not print solder paste for rework, consider the
     noe-cleaning tacky flux.

     Eden



______________________________ Reply Separator _________________________________
Subject: [TN] BGA Assembly
Author:  Non-HP-tomh3 ([log in to unmask]) at HP-Singapore,shargw51
Date:    10/21/98 7:48 AM


I had a lot of 15 boards that I mounted PBGA388 (35mmX35mm), using
Conceptronic BGA rework station.  As I was observing the reflow, I
noticed  bowing of the plastic laminate on the corners of the component.
Once the component was reflowed, it became level with the PCB, but the
bowing action caused several shorts between the balls under the corners.
Any suggestions on how to correct the problem?  The inspection following
the reflow reveal good wetting and reflow on rest of the balls.


Tom Han
Ardent Systems

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