Hi, Werner,
I'm a little puzzled. I believed the reason why so many folks drill up into
the central ball of a BGA to place a T/C, is because it's these central
contacts that generally suffer from insufficient heating owing to the
shading effect of the overlying body of the component. If the BGA's outer
body temperature only is measured, isn't this going to be much hotter than
the balls underneath, and especially those in the centre of the array?
Which, then, is the best way to thermally profile a BGA, in your
experience, or does it depend on BGA size versus T/C size?
Peter
Werner Engelmaier <[log in to unmask]> 12/11/2002 07:54 AM
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Subject: Re: [TN] profiling BGAs
Hi Toby,
Your question is a good one.
What I have done--and it works--was to grind a depression in the ceramic
component body deep enough for the T/C beat to fit flush into it. Than I
epoxy the beat into this depression; the surface is still flush so not to
affect the heat transfer. I also epoxy the length of T/C wires which ends
with the T/C onto the the surface of the commponent; thus, the impact of
the
wires being heated faster than the component body and thus a giving me a
higher t-reading at the T/C is minimized. This works for both IR and
Convection reflow ovens.
Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL 32174 USA
Phone: 904-437-8747, Fax: 904-437-8737
E-mail: [log in to unmask], Website: www.engelmaier.com
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