Re: Open Source Bitcoin ASIC miner project that uses 2x BM1387 (Antminer S9)
Or do you think the metal of the cooler will short out the asic?
That's the issue all along, indeed. 
These chips expose their local ground on the top. Since the grounds have a voltage potential between them though, a common heatsink would allow undesired current flow, i.e. magic smoke.
If this is the issue then maybe the best solution is indeed a thermal pad.The best ones should be: https://kriticalpads.com
However they are expensive and compared to paste pretty bad. (20 W/mK)
20W/mK is good. Sidehack uses that, too, as quoted by me earlier.However they are expensive and compared to paste pretty bad. (20 W/mK)