HMC590LP5 Evaluation board assembly process

During my assembly process I am damaging the HMC590LP5 by creating shorts to ground on the RF input and output.

I’m trying to solder the HMC590LP5 to a .010” thick RO4350 PCB and solder the PCB to a heat sink carrier using SN63PB379 (melting point of 183C.)    

In my assembly process I pre-tin the carrier with SN63PB37. Place the carrier and PCB on a hot plate. Bring the hot plate up to ~183C to reflow the solder.  Pre-tin the pads for the HMC590.   Place the HMC590 on the PCB and immediately remove the assembly from the hot plate. During the process the carrier temperature never exceeds 185C.

The data sheet indicates the parts can handle a maximum reflow temperature of 260C.  What is the maximum duration the part can be at 260C?

What solder and process is used to assemble the HMC590LP5 Evaluation board where there are 2 plates attached to the bottom of the PCB assembly?

 

Is it possible that I have a defective batch?

I have lost at least 5 parts and need a solution.