Inductive excited lock–in thermography for electronic packages and modules

In this paper for the first time inductive excited lock-in thermography (ILT) is applied on electronic packages and modules. This non-destructive evaluation method allows the detection of subsurface defects. Previous works in this field dealt with macroscopic applications or unpackaged devices. The main goal of this paper is the suitability estimation of ILT for electronic packages and modules mainly based on experimental investigations. Further points of interest are the characteristics for ILT on packages, optimum test parameters and the appreciation of loading capacity concerning magnetic field power. Therefore, an appropriate experimental setup is developed and different package types and assemblies are examined. For each tested device type a simple 1D-model based on the thermal wave propagation equation is created to determine a reasonable range for the test parameters. Theoretical considerations about load limits and experimental load tests are performed to ensure that the induced heating is really non-destructive.