Structural Analysis of Power Devices and Assemblies by Thermal Transient Measurements

Abstract

Power modules composed of semiconductor dice, thermal interface layers, and cooling mounts can be characterized by thermal transient testing at their actual position (in situ). This paper demonstrates that transient testing enables tracking of changes in material quality and structural details on the raw heating or cooling curves. Higher precision can be achieved with the structure function technique where absolute and partial thermal resistance and capacitance values can be used for unambiguous identification of structural elements in a heat conducting path. Measurement techniques are presented to characterize the self-heating of a die and heat transfer between dice. Change of the thermal interface material layers in assembly during test sequences is also highlighted by the structure function concept. The power distribution between dice and wiring is analyzed by the newly introduced “accordion” principle.

Keywords

• thermal transient testing
• non-destructive testing
• thermal testability
• in-situ characterization