Correlation Studies Between Laser Ultrasonic Inspection Data and Finite-element Modeling Results in Evaluation of Solder Joint Quality in Microelectronic Packages

Laser Ultrasonic Inspection (LUI) is a non-destructive and non-contact technique to evaluate the quality of solder ball interconnections in area-array microelectronic packages. Dual-Fiber Array Laser Ultrasonic Inspection System was demonstrated identifying defects and failures in chip-scale packages, ball grid array packages, and flip-chip ball grid array packages. The location and severity of the defects and failures in packages have been identified accurately using this system. Further, it is important to establish the correlation between LUI results and the severity of the failures for failure mode analysis, which will enable us to eliminate the need for destructive testing and allow the study of failure evolution in a given sample under continued reliability testing. This paper discusses correlation studies between experimental LUI results and finite-element simulation results from the flip-chip ball grid array packages subjected to thermal cycling reliability testing. The correlation equations will help in predicting the severity of the failures at a given number of thermal cycles based on LUI results. Furthermore, the life of the microelectronic packages can be predicted accurately from LUI results at a fewer number of thermal cycles.

Uptake Rate of Hydrogen Getter for Effectively Removing Outgassed H2 from Microelectronic Packages

Hydrogen absorption kinetic properties of palladium foil-based getter elements have been studied by manometric method based pressure amplitude measurement. The getter H2 uptake rate can be simply converted by pressure amplitude change, and can be fairly described by a mixed gas sorption modeling analysis. It has been found that the sorption rate of Pd-based getter element has a maximum rate of 40 ppm/min at initial absorption stage but it gets slowly down to 0.5ppm/min when approaching maximum sorption capacity, determined by a getter foil thickness. Based on different H2 outgassing rates of metal and polymer based package materials, a safety factor based methodology has been proposed for down selecting an appropriate getter element that can effectively removing outgassed H2 from microelectronic packages.