Detection of air in helium filled thermal conduction modules

Two thermal conductance techniques for detecting air contamination in a helium-filled thermal conduction module (TCM) used to package silicon chips are described. A silicon majority carrier thermistor was used to detect as little as 15% air contamination in a container filled with helium. The technique directly measured the internal cooling ability of the package. Both a static test and a transient test were developed. The transient test is shown to be independent of the thermistor packaging. The technique did not require any modification to a TCM. Most importantly, the technique directly measured the cooling ability of the fill gas. The measurement could be performed simply and routinely after assembly, or on return from the field