any vapor therein is cooled this cooling causes most of the liquid 20 that is evaporated and contained therein is condensed back into liquid form and becomes part of the liquid 20 again a controller 31 starts the filling of the enclosure 12 with the liquid 20 when the operator activates the start cold switch 33 the liquid 20 is subsequently pumped into the enclosure 12 until a float switch 32 by its position afloat in the liquid 20 is activated and indicates that the enclosure 12 is sufficiently full the float switch 32 by operator action or by action of a simple switching circuit stops further filling the liquid 20 is cooled to a low temperature such as 273 degrees kelvin or lower and since the liquid 20 has a high density and a high heat capacity it can absorb heat from the pcb or pcb assembly under test very rapidly thus in a short time the pcb or pcb assembly will be cooled down to essentially 273 degrees kelvin after substantially reaching the first temperature and a short delay which may be as long as the controller 31 takes to stop the pump 22 and open the valve 36 the liquid 20 is drained through pipes 38 40 into the cold bath 21 a filter 42 is preferably included between the enclosure 12 and the pipe 38 to filter out water hydrofloric acid formed by the action of water on perfluorinated liquids any other liquid contaminates and particulate matter from the pcb or pcb assembly under test.