Characterization of IMC layer and its effect on thermomechanical fatigue life of Sn–3.8Ag–0.7Cu solder joints

• Published in: Journal of alloys and compounds Vol. 541; pp. 6 - 13
• Main Authors: Che, F.X., Pang, John H.L.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 15.11.2012; Elsevier
• Subjects: Applied sciences; Brazing. Soldering; Copper; Exact sciences and technology; Fatigue life; Finite element method; Finite element modeling; Intermetallic compound; Intermetallic compounds; Joining, thermal cutting: metallurgical aspects; Lead-free solder; Mathematical models; Metals. Metallurgy; Nanoindentation; Nanoindentation test; Scanning electron microscopy; Sn–Ag–Cu; Solders; Tin; Tin base alloys; Fatigue life; Lead-free solder; Finite element modeling; Nanoindentation test; Sn–Ag–Cu; Intermetallic compound; Scanning electron microscopy; Ageing; Nanoindentation; Thermal fatigue; Hardness; Tin base alloys; Thickness measurement; Young modulus; Finite element method; Soldered joint; Lead free solder; Sn-Ag-Cu; Microstructure; Thermomechanical treatment
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2012.06.104

► The IMC microstructure and growth were studied under thermal aging conditions. ► The Young’s modulus and hardness were determined for CuSn and CuNiSn IMC. ► Simulation results show that the thick IMC layer results in a lower fatigue life. ► The IMC layer with higher modulus results in a lower solder joint fatigue life. Intermetallic compound (IMC) growth was investigated under isothermal aging condition at 125°C for up to 500h. The evolution in the IMC morphology and microstructure were observed at four aging time conditions for 0, 120, 260 and 500h, respectively. Solid state IMC growth thickness measurements were determined from scanning electron microscope (SEM) observations for Cu–Sn and Cu–Ni–Sn IMC systems. The Young’s modulus and hardness of the IMCs were determined by nanoindentation tests. A finite element analysis (FEA) was carried out to model the effect of the IMC layer on the solder joint thermal fatigue life. The nanoindentation mechanical properties of Cu6Sn5 and CuNiSn IMCs were modeled with different IMC thicknesses in the FEA simulation to study the effect of the IMC growth on the fatigue life of the solder joint. It was shown that the IMC layer reduces the fatigue life of the solder joints and thick IMC layer results in a lower fatigue life. In addition, thermal cycling test and analysis for plastic ball grid array (PBGA) package with Sn–3.8Ag–0.7Cu Pb-free solder joints was performed. The mean-time-to-failure (MTTF) for the PBGA solder joints was determined, which was used for validating the FEA simulation results.