Isothermal Aging Effects on the Mechanical Shock Performance of Lead-Free Solder Joints

Isothermal aging effects on lead-free solders have been extensively investigated in recent studies. Researches show that aging effects significantly degrade the mechanical properties of lead-free solders. However, limited work has been done on the effects of aging on the board-level dynamic performance of lead-free solder joints, especially for large flip-chip ball grid array (FCBGA) packages. Due to the sensitivity of aging effects on lead-free solders, it is crucial to investigate the aging effects on the board-level dynamic performance of lead-free solders. In this paper, dynamic performance of lead-free solder joints has been characterized and isothermal aging effects have been investigated. It was found that the dynamic shock performance of lead-free FCBGA packages significantly degrades up to 20-35% after aging at elevated temperatures. It was also observed that aging at 100°C shows more severe degradation than aging at 75°C and 150°C. This is an important finding because many electronic products operate in the 100°C range for long periods. The unique finding of aging effects is related to the growth of Cu3Sn and Cu6Sn5 intermetallics after aging. Even though failure analysis shows mixed failure of pad cratering and intermetallic compound (IMC) failures, the IMC growth is the most sensitive factor contributing to the failure observed.

[1]  Robert J. Asaro,et al.  Elastic-plastic analysis of cracks on bimaterial interfaces: interfaces with structure , 1993 .

[2]  P. Lall,et al.  The Influence of Elevated Temperature Aging on Reliability of Lead Free Solder Joints , 2007, 2007 Proceedings 57th Electronic Components and Technology Conference.

[3]  Hongtao Ma,et al.  Impact of Isothermal Aging on Long-Term Reliability of Fine-Pitch Ball Grid Array Packages with Sn-Ag-Cu Solder Interconnects: Surface Finish Effects , 2010 .

[4]  Luhua Xu,et al.  Effect of intermetallic and Kirkendall voids growth on board level drop reliability for SnAgCu lead-free BGA solder joint , 2006, 56th Electronic Components and Technology Conference 2006.

[5]  F. Che,et al.  Performance assessment on board-level drop reliability for chip scale packages (fine-pitch BGA) , 2006, 56th Electronic Components and Technology Conference 2006.

[6]  Young-Ho Kim,et al.  Drop impact reliability of Cu-Zn/Sn-Ag-Cu/Cu-Zn solder joints , 2008, 2008 International Conference on Electronic Materials and Packaging.

[7]  P. Lall,et al.  Reliability of the aging lead free solder joint , 2006, 56th Electronic Components and Technology Conference 2006.

[8]  C. Kim,et al.  Study of Fracture Mechanics in Testing Interfacial Fracture of Solder Joints , 2008 .

[9]  D. Frear,et al.  Intermetallic growth and mechanical behavior of low and high melting temperature solder alloys , 1994 .

[10]  Vito J. Colangelo,et al.  Fundamentals of Engineering Materials , 1985 .

[11]  T. Chiu,et al.  Effect of thermal aging on board level drop reliability for Pb-free BGA packages , 2004, 2004 Proceedings. 54th Electronic Components and Technology Conference (IEEE Cat. No.04CH37546).

[12]  J. W. Morris,et al.  Tensile behavior of pb-sn solder/cu joints , 1987 .