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April 2003

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Subject:
From:
Eli Sarig <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Sat, 26 Apr 2003 10:08:32 +0200
Content-Type:
text/plain
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text/plain (66 lines)
Rick,
If you have good Rework machine, you can try the following:
After finishing the assembly process (Without the BGA component)
put solder paste on the BGA pads. You can use dispenser for that
(put the maximum paste that you can) . Activate your Rework machine
within new profile which enable melting the solder paste dots with the
bottom heater only (selectively). During the process, make sure that the
BGA component is about 1 to 2 cm above the surface of the PCB.
Adjust the sequence : When the paste melt put down the BGA on board
and cool down immediatly.

Eli.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Rick Thompson
Sent: Thursday, April 24, 2003 6:46 PM
To: [log in to unmask]
Subject: [TN] 'Unique' BGA Reflow Problem


We have a customer who had a custom BGA built with some additional
components besides the die under the encapsulant. Unfortunately, these parts
were soldered with Sn63Pb37 and the solder reflows and bridges under the
encapsulant during reflow.  Due to time constraints they would like to find
a way to use these while they wait for new parts to be fabbed.  We've tried
various types of shielding, but the convection systems we have heat the
entire part causing the internal reflow.  Does anyone know of a focused
reflow system that would allow reflowing the eutectic balls of a BGA but not
apply enough heat to the top of the component to reflow the other parts?
Would one of the focused IR systems (Ersa, PDR) do this?  Other
possibilities?

Thanks in advance.

Rick Thompson

Sr. SMT Process Engineer
SMTEK International, Inc.
+1 (805) 532-2800
[log in to unmask]

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