Hi Toby,
What is wrong is that you did not drill the hole into the pad and place the
thermocouple inside the ball. You need to measure the T of the solder balls,
not the air space underneath the BGA nor the PWB. At the very least, the T of
the BGA should be measured.

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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