Coupled thermal and vibration numerical analysis of solder joints

Abstract

A heat transfer subroutine has been implemented into an existing finite element code developed in theCivil Engineering and Engineering Mechanics Department at the University of Arizona by Dr. Desai and students. The code is capable of performing non linear material and dynamic analysis. The heat transfer subroutine has been implemented such that any inelastic material behavior induced by a temperature increment is captured at every time step in a loading cycle. With the addition of the heat transfer routine, both thermal sources and sinks can be modeled. For example, power generating chips and power dissipating heat sinks, respectively. This will allow a more realistic representation of electronic packages under operational conditions. A 313 ball PBGA staggered area array package was used in all the analyses performed in this dissertation. The calibration of the models was based on research performed by the JPL consortium which included members such as Raytheon, Boeing and Xilinx. The focus of this dissertation was to determine the thermal and vibration fatigue lifetimes of electronic packages using the Disturbed State Concept. To achieve this goal, numerous analyses were performed, representing different test cases. The different test cases included thermal test chamber cycling (TCT), power cycling (PCT), vibration, thermal test chamber cycling with voids in solder balls, vibration with voids in solder balls, and coupled temperature with vibration. Based on the results of these analyses, the Disturbed State Concept was found to predict the fatigue lifetimes of the 313 PBGA package with excellent accuracy, when test results were available for comparison.