I may try to introduce a hot soak zone in order to get uniform heat. In
other words, have a 30-60 second soak zone in the reflow profile just below
the reflow temperature. This will allow for the board to heat up evenly
with the larger BGA temperatures catching up to the temperatures of the
smaller BGA's.
Christopher J. Nash
Mid-West Technical Support Engineer
Indium Corporation of America
www.indium.com
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Macko, Joe @ IEC
Sent: Friday, January 05, 2007 7:21 PM
To: [log in to unmask]
Subject: [TN] Reflowing different sized BGAs without exceeding
manufacturer's p eak body temperatures?
Hello Fellow techs,
One of our CMs is having great difficulty developing a thermal profile for a
small, double sided, densely populated board with different sized BGAs on
one side. One of the BGAs is rather large and higher in thermal mass than
the surrounding smaller BGAs. The issue is that when he gets the solder ball
temperature of the larger BGA up to at least 205 C, the peak body
temperature of 2 adjacent but much smaller and thinner BGAs exceeds their
manufacturer's recommended peak body temperature of only 220 C by ~ 10 C.
The CM does not think he can make any more adjustments to the 9-heating zone
Heller oven to accomplish this task.
Does anyone have any suggestions/ideas on how to heat the larger BGA
sufficiently without over heating the smaller adjacent BGA components?.
Possibly, he can insulate the smaller BGAs with a piece(s) of tape on the
top (prior to assembly) to lower the body temperature - has anyone tried
this?
Look forward to reading anyone's idea. thanks
Joe
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