Foreword contributions from the 1998 intersociety conference on thermal and thermomechanical phenomena in electronic packages

HE Thermomechanical analysis of electronic packages is a critical aspect of reliability assessment. Although the focus of earlier Intersociety Conferences on Thermal and Thermomechanical Phenomena in Electronic Packages (ITherm) was on thermal analysis, thermomechanical issues that ensue from thermally-induced strains and stresses are receiving increased attention at the Conference. ITherm has been making steady progress in terms of quantity and quality of papers in this area over the years and we expect it to hold for ITherm 2000. In this special section of this TRANSACTIONS ,w e showcase outstanding papers that were presented at ITherm 98 on thermomechanical issues related to electronic packaging. Seven papers are selected for this special issue based on a rigorous review process. The majority of the papers deal with various aspects of the solder joint reliability, mainly in the flip-chip ball grid array (BGA) packages. Based on a parametric study of the effect of voids in the underfill of a ceramic BGA, Niu et al. have concluded that the edge voids decrease C4 fatigue life where as middle and center voids have less impact. A comparison of solder joint reliability for ceramic quad-flat-pack and CBGA packages for two typical accelerated temperature cycles (0 C to 100 C and 40 C to 125 C) of interest for microprocessors has been carried out by Gerke et al. They have also looked at the effect of temperature gradient on solder joint reliability by using experimentally measured temperatures. Bailey et al. have integrated the effect of fluid flow, heat transfer during solidification, and stress evolution on solder joint formation. Ayhan and Nied have applied enriched crack tip finite elements for prediction of interface fracture parameters. They have evaluated two-dimensional and three-dimensional models for moisture absorption and thermal cycling. Material properties and BGA model validation issues are addressed in the last three papers. Using a three-point bending test, Tay and Lin have measured the effect of temperature and moisture on interfacial fracture toughness for molded QFPs. They have also examined the effect of interfacial defect location of fixed initial size on interfacial crack growth. Tran et al. have characterized fracture toughness for various underfill materials for improved adhesion. Finally, Zhang et al. have Publisher Item Identifier S 1521-3331(99)10361-1. used a combined experimental and numerical approach to evaluate various material and geometric assumptions made in the analyses of area-array packages. We hope the papers presented here will add to the knowledge of predictive engineering. We wish to acknowledge the efforts of many individuals who helped with this special section on mechanics. We would like to thank all the reviewers for their tireless efforts in completing the reviews in a short period of time. In some cases, this involved two rounds of reviews. We would like to thank J. Starbird and K. Mauch of the Editor’s office for administrative assistance. Last, but not least, this effort would not have been possible but for the encouragement and guidance of Editor-in-Chief Avram Bar-Cohen.