Help: Low Outgassing epoxy to seal between metal and PCB for vacuum sealing?

I'm looking to seal between an aluminum flange and a PCB assembly that will pass thru the flange. This will act as a vacuum sealing barrier, and hopefully operate just fine down to 10\^-7 mBar. Of importance for is low outgassing of the epoxy after curing (think NASA low outgassing, ASTM E595). Does anyone have any recommendations?