LMK00301: allowed maximum Mechanical pressure when fastening heatsink

Part Number:LMK00301

Hi

we are designing heatsink to be mounted on the top of 2 pcs of LMK00301, 2Watt for each one, and we use compressible thermal pad for interfacing material placed between case top of IC and metal heatsink.

According to supplier of thermal pad , we must add some pressure to keep the thermal pad contact with IC surface tightly to ensure the good thermal conductivity.

So what is the recommended Mechanical Pressure for LMK00301 chip (unit is PSI ,Pounds per square inch ), or what is the pressure limit so as to keep IC from being destroyed by over stressed. Thanks.

I think mechanical characteristic of this kind of QFN packages may be similar , independent of specific part number, but I not sure of this, because different manufacturer may have difference. So I hope TI expert could give some suggestions. And we also use BGA ICs on board which also need heatsink, any comments are welcome. 

Thanks.