I have assembled and soldered the Thermometry PCBs to be mounted into the Dewar for initial pump-down tests. These PCBs were soldered in the vent hood in the chem room with lead-based solder and acuu glass flux that is vacuum compatible.

Upon finishing the boards, they were then soaked in isopropyl alcohol and sonically cleaned for 5 minutes (as directed on the accu glass website). 

Please see the last photos for side-by-side comparison of post soldering and post-sonicating.