Hi Li Zheng,
That will depend on the type reflow machine you have, IR-dominant or
convection-dominant, the die sizes, the lead frame size on the QFP, etc. But
in general, you are likely have to increase the reflow spike temperature to
allow the solder balls near the center of the BGA to reach minimum reflow
temperature (about 205oC for near eutectic Sn/Pb solders).

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]

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