Unwetting leads of Palladium Plated Pins

Hello! SMT professionals,

I do not know if anyone posted this question before. Last week, I reflowed our newly designed thin Rigid-Flex pcb with 0.040" thickness. I found all of pins of a TQFP48 ic did not get wetted. I could see on the heel side of pin foot there is a clear unwetting line between pin and solder. Other components including bigger IC and heavy thermal mass parts on the board are soldered very good. I found this TQFP48 is made by Texas Instruments, and is Palladium Plated leads.

Does anyone have this unwetting problem on Palladium Plated leads? How do you solve the problem? I thank for any help, advise and suggestion you could give.

By the way, I am using a Vitronics Unitherm520 air convection oven with 5 heat zone. The profile gets peak temp. of 225 degree c.

Regards,

Dennis

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