IC bond evaluation by transient thermal testing methodology using thermography

A new method for estimating the electrical contact resistance of Inner Lead Bonding (ILB) in a Tape Automated Bonding (TAB) package has been developed and investigated by utilizing transient thermal testing methodology. After characterizing the thermal contact resistance of TAB ILB by utilizing transient thermal testing methodology, the thermal contact resistance is converted into electrical contact resistance by utilizing the analogy between steady-state electrical circuits and thermal circuits.; An inner copper lead with multiple substrates, such as a plastic supporting ring and the air, is bonded onto a gold composite bump on a silicon die. The inner lead is considered a thermal transmission line. Thermal characterization for the inner lead, according to the thermal transmission line theory, is experimentally and theoretically accomplished. Bonding quality is modeled as thermal contact resistance.; For Transient Thermal Testing (T{dollar}sp3{dollar}), a finite argon laser pulse with wavelengths of 488 nm and 512 nm is used to heat an inner lead on the plastic substrate. An IR camera, with band width of 8 to 12 micrometers, measures the thermal radiation along the lead over the plastic. Most of the thermal energy is propagated through the inner lead toward a silicon die, and part of it is reflected when a thermal characteristic impedance change of the inner lead occurs. The thermal profile along the lead on the plastic substrate is influenced by the variation of the length of the lead over the air gap and the variation of the thermal contact resistance of the ILB. The radiation pattern is assumed to confirm the temperature profile for the small changes of temperature experienced.; A steady-state thermal transmission line model for an inner lead has been developed and solved. The model includes a thermal termination resistor at the end of a finite thermal transmission line, where the thermal termination resistor includes a thermal resistor for the lead over the air gap, a thermal contact resistor of the ILB, and thermal spreading resistance from a bump and through a silicon die.; By applying the steady-state thermal transmission line model to the Total Pulse Area (TPA) profile along the lead, the thermal termination resistance of the lead is estimated. Subtracting the thermal spreading resistance and the thermal resistance for the inner lead over the air gap from the measured thermal termination resistance, yields the estimation of the thermal contact resistance of the inner lead bonding. Finally, the electrical contact resistance of the inner lead bond is estimated utilizing the analogy between steady-state electrical and thermal circuits. The electrical contact resistance of the ILB ranges from 2 to 7 milliohms.; Basic measurement characteristics of Transient Thermal Testing {dollar}rm(Tsb3){dollar} methodology have been investigated. For instance, the noise characteristics, calibration method, spatial sampling scheme, and temporal sampling scheme have all been examined in this study.; TAB ILB geometries for the {dollar}rm Tsb3{dollar} analysis of the TAB inner lead bonding are measured. Some sample inner lead bonds are screened and selected for the {dollar}rm Tsb3{dollar} measurement, based on the investigation of inner lead geometry and location. An optical profilometer is utilized to measure the geometrical lead configurations. In conclusion, the {dollar}rm Tsb3{dollar} methodology results are confirmed with the current standard destructive method (lead-pull test) of evaluating the inner lead bonds.