Thanks Kagan.
The Thermal Resistance of LFCSP/QFN packaged HMC637LP5E marginally changed below 50% void, according to the info from Hittite's web. I do not know whether the info is correct. Bias sequencing has been reviewed and followed the recommendation from the datasheet. Not sure whether it was tested thru IPC-9701 compare to JESD22 standard on reliability for QFN packaged components. Else, what are the changes in manufacturing process and internal circuits between the 'A' and without the A parts? We had no issue with the 'A' parts.
