Abstract
This paper discusses the detection process on the defect in the TAB bonds by infrared thermal imaging with laser irradiation. We have previously discussed about the detection process for QFP gullwing type lead. But TAB bonds have three different factors which differentiate the detection process from that of the QFP gullwing type lead, i.e., (1) large valid heat capacity (Si-chip) under the bond interface, (2) lead thickness and (3) two different structures (face-up type, face-down type). This paper discusses about the influence of these three factors using thermal analysis. (1) The influence of the TAB bonds large heat capacity on the temperature distribution is that the thermal flow through the bond interface is increased. (2) The influence of the lead thickness is that thermal flow reflection from the defective part on the bond interface is attenuated by the lead thickness value. (3) We can detect the defect of face-up type structure by using the same detection process as the QFP gullwing type and the face-down type structure by changing the position of the laser irradiation and observation from the lead surface above the bond part to an observable lead surface. Then a detection process of internal micro defect in TAB bonds is theoretically established by infrared thermal imaging with laser irradiation.
