Mechanical Size Effects in Miniaturized Lead-Free Solder Joints

Future reliability and quality control of microelectronics will greatly depend on a detailed understanding of the complex mechanical and thermal properties of miniaturized lead-free solder joints. Therefore, the question of the occurrence of size effects or dimensionally induced constraints, which could change the mechanical properties of solder joints in small dimensions dramatically, has become the focus of investigation. In this study we investigated the influence of decreasing gap size on the tensile, shear, and stress relaxation behavior of solder joints to investigate the occurrence of size effects and dimensionally induced constraints, which could change the mechanical properties of solder joints significantly in micrometer dimensions. Residual stresses might remain in the solder joints during high-temperature dwell in thermomechanical fatigue. Model solder joints (Sn3.5Ag/Cu) of rectangular shape with gap sizes varying between 25 μm and 850 μm were prepared by reflow soldering to achieve near-industrial soldering processing. Scanning electron microscopy was used for analyzing the microstructure and the complex modes of fracture and crack propagation in the solder interconnect. The observed tensile behavior can be interpreted in terms of an existing theory for brazed joints to complement finite-element analysis that is usually used for a description of these phenomena.

[1]  C. R. Barrett,et al.  The effect of cooling rate on the strength of brazed joints , 1971 .

[2]  C. R. Barrett,et al.  Deformation and failure of brazed joints—macroscopic considerations , 1971 .

[3]  C. R. Barrett,et al.  Deformation and failure of thin brazed joints—microscopic considerations , 1971 .

[4]  William D. Nix,et al.  Mechanical properties of thin films , 1989 .

[5]  I. Noyan,et al.  Effect of the specimen size in predicting the mechanical properties of PbSn solder alloys , 1992, 1992 Proceedings 42nd Electronic Components & Technology Conference.

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

[7]  S. V. Harren,et al.  The effect of mechanical constraint on the flow and fracture of 63/37 Sn/Pb eutectic alloy , 1995 .

[8]  John P. Ranieri,et al.  Plastic constraint of large aspect ratio solder joints , 1995 .

[9]  B. Moran,et al.  Creep, stress relaxation, and plastic deformation in Sn-Ag and Sn-Zn eutectic solders , 1997 .

[10]  E. Arzt.  Size effects in materials due to microstructural and dimensional constraints: a comparative review , 1998 .

[11]  K. Chawla,et al.  Mechanical Behavior of Materials , 1998 .

[12]  M. Abtew,et al.  Lead-free Solders in Microelectronics , 2000 .

[13]  K. N. Subramanian,et al.  Stress relaxation behavior of composite and eutectic Sn-Ag solder joints , 2001 .

[14]  Golta Khatibi,et al.  Characterization of mechanical and thermal properties of thin Cu foils and wires , 2002 .

[15]  B. Michel,et al.  Determination of Packaging Material Properties Utilizing Image Correlation Techniques , 2002 .

[16]  Hwa-Teng Lee,et al.  Influence of intermetallic compounds on the adhesive strength of solder joints , 2002 .

[17]  Raymond J. Matela,et al.  Structural Integrity and Reliability in Electronics: Enhancing Performance in a Lead-Free Environment , 2003 .

[18]  K. N. Subramanian,et al.  Effects of prestrain, rate of prestrain, and temperature on the stress-relaxation behavior of eutectic Sn-3.5Ag solder joints , 2003 .

[19]  Hwa-Teng Lee,et al.  Influence of interfacial intermetallic compound on fracture behavior of solder joints , 2003 .

[20]  A. Antoniou,et al.  Deformation characteristics of tin-based solder joints , 2003 .

[21]  W. J. Plumbridge,et al.  Long term mechanical reliability with lead‐free solders , 2004 .

[22]  Thirumany Sritharan,et al.  Tensile fracture of tin–lead solder joints in copper , 2004 .

[23]  H. C. Lin,et al.  Reliability of Sn-Ag-Sb lead-free solder joints , 2005 .

[24]  K. N. Subramanian.  A parametric approach for assessment of thermomechanical fatigue performance of Sn-based solder joints , 2005 .

[25]  Nikhilesh Chawla,et al.  Deformation analysis of lap-shear testing of solder joints , 2005 .

[26]  John Botsis,et al.  Size and Constraining Effects in Lead‐Free Solder Joints , 2006 .