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Accurate knowledge of the heat flux characteristics provided by optical heat sources of long heating time non-destructive infrared thermography techniques is essential to determine the adequate application of such techniques, however detailed characterizations are scarce. Therefore, a thermal and statistical characterization of a halogen lamp was developed. A highly repeatable experimental procedure was used to characterize the heat flux generated at an ideal inspection sample top surface. The characteristics studied were: lamp distance, bulb color, lamp orientation, heat quality, and heating time. The heat flux was determined by using readings of temperature and heat flux from the sample back, and a finite differences lumped capacitance thermal model. Detailed studies using three sensors determined that the heat flux was non-uniform (13% maximum variation). Therefore, a full quantitative characterization of the lamp was developed by using the average of such sensors readings, determining that: this halogen lamp can provide consistent top heat fluxes (although not uniformly distributed) adequate for non-destructive testing infrared thermography, the lamp distance and bulb color affected the amount of heat provided as well as the heat flux uniformity, and lamp orientation did not affect the mean top heat fluxes. This research approach can be used to determine an approximation of the lamp time-averaged heat fluxes for any material with similar top surface optical characteristics. Moreover, the technical data provided are useful to determine the adequacy of heating time, lamp distance, lamp orientation, and bulb color for long heating time non-destructive testing infrared thermography.

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It is essential for electronics reliability to develop effective methodologies to detect hidden solder joint defects. Active infrared thermography is an alternative to X-ray detection methodologies. The limits of active infrared thermography to detect solder ball defects on plastic ball grid arrays (PBGA) components (missing, open, cracked, and head on pillow defects) are investigated here. A FEM was used to simulate the thermal phenomena during the infrared thermography inspection of a PBGA component. The FEM was proven to be temporal and spatial grids size independent. The average temperature difference (ΔT) amid regions with and without defects was used as a detectability indicator. Defects detectability was found to decrease as the number of blocking objects increases. Missing solder balls were barely detected when blocked by the substrate and moulding compound with detectability numbers close to 1 °C. Head on pillow and cracked defects were impossible to detect with a maximum ΔT = 0.6 °C. Open solder balls were not detected below two objects with a maximum ΔT = 0.3 °C. These results clearly suggest that infrared thermography can be effectively used to detect hidden missing and open solder ball defects on PBGA components composed by a substrate and a die.