I'd like to use bare chip like HMC1081 and HMC-ALH382.
I have multi layer PCB cutting 1 copper and 1 layer substrate(Teflon) as cavity PCB.
So I can see second copper layer. But the process is hard to make.
I found other solution. It is using through hole with metal like coin PCB.
I'm wondering what purpose is bare chip's bottom ground. I think it would be heat sink and GND for signal.
When I check on datasheet. they use microstirp line wihtout transformation. I know there are same ground microstip line and chip. If I use coin PCB, Do I have to transform microstip line to CPW for wiring signal and ground? or whatever is it okay?, If I wired signal and ground.
Please let me know bare chip ground's purpose.