Thermal Fatigue Life Of Solder Joints Research Articles

Nonlinear Damage Accumulation Rule for Solder Life Prediction Under Combined Temperature Profile With Varying Amplitude

Due to a mismatch of the coefficient of thermal expansion, electronic solder joints experience cyclic shear strain, which ultimately leads to fatigue failure. Traditional predictions of solder joint thermal fatigue life that use the experimental data or the physics-of-failure model often assume a regular profile. For complex temperature profiles, the linear accumulation rule is typically used to integrate the superposition effect. However, the linear rule was proved not applicable to most of the complex loading or temperature conditions. Based on the damage curve theory and the fatigue crack propagation theory, a novel nonlinear accumulation rule has been deduced for solder joint life predictions under irregular profiles, which were composed of two standard temperature cycles and may be experienced by phased-mission system. Four groups of experiments were conducted for ball grid array package solder joints with different dimensions and materials to determine parameters of the proposed nonlinear accumulation rule. The finite-element simulation method was used to extend this rule to more general cases for application. Compared to Miner’s linear accumulation rule, prediction of solder joint thermal fatigue life via the proposed nonlinear accumulation rule is closer to the accelerated life test results of real-world electronic solder joints under a combined temperature profile.

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

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.

Application of Finite Element Method in Optimal Design of Flip-Chip Package

More and more solder joints in circuit boards and electronic products are changing to lead free solder, placing an emphasis on lead free solder joint reliability. Solder joint fatigue failure is a serious reliability concern in area array technologies. In this study, the effects of substrate materials on the solder joint thermal fatigue life were investigated by finite element model. Accelerated temperature cycling loading was imposed to evaluate the reliability of solder joints. The thermal strain/stress in solder joints of flip chip assemblies with different substrates was compared, and the fatigue life of solder joints were evaluated by Darveaux’s crack initiation and growth model. The results show the mechanisms of substrate flexibility on improving solder joint thermal fatigue.

Critical Review of the Engelmaier Model for Solder Joint Creep Fatigue Reliability

A solder interconnect fatigue life model was developed by Werner Engelmaier in the early 1980s as an improvement upon the inelastic strain range-based Coffin-Manson model. As developed, the model provides a first-order estimate of cycles to failure for SnPb solder interconnects under power and thermal cycles. While the model has been widely adopted for SnPb solder joint reliability prediction, many issues that arise from simplifications in formulating input model parameters as well as from the complex physics of solder degradation challenge the model's ability to accurately estimate cycles to failure. Deficiencies with the model have been reported by a number of researchers. This paper reviews and summarizes the major issues with the Engelmaier model in its applicability to predict solder joint thermal fatigue life.

Fracture mechanics analysis of the effect of substrate flexibility on solder joint reliability

Solder joint fatigue failure is a serious reliability concern in area array technologies, such as flip chip and ball grid array packages of integrated-circuit chips. The selection of different substrate materials could affect solder joint thermal fatigue life significantly. The reliability of solder joints in real flip chip assembly with both rigid and compliant substrates was evaluated by the accelerated temperature cycling test and thermal mechanical analysis. The mechanism of substrate flexibility on improving solder joint thermal fatigue lifetime was investigated by fracture mechanics methods. Two different methods (crack tip opening displacement, CTOD and virtual crack closure technique, VCCT) are used to determine the crack tip parameters which are considered as the indices of reliability of solder joints, including the strain energy release rate and phase angle for the different crack lengths and temperatures. It was found that the thermal fatigue lifetime of solder joints in flip chip on flex assembly (FCOF) was much longer than that of flip chip on rigid board assembly (FCOB). The flex substrates could dissipate energy that otherwise would be absorbed by solder joints, that is, substrate flexibility has a great effect on solder joint reliability and the reliability improvement was attributed to flex buckling or bending during thermal cycling.

Effect of substrate flexibility on solder joint reliability. Part II: finite element modeling

Solder joint fatigue failure is a serious reliability concern in area array technologies, such as flip chip and ball grid array packages of integrated-circuit chips. The selection of different substrate materials could affect solder joint thermal fatigue life significantly. The mechanism of substrate flexibility on improving solder joint thermal fatigue was investigated by thermal mechanical analysis (TMA) technique and finite element modeling. The reliability of solder joints in real flip chip assembly with both rigid and compliant substrates was evaluated by accelerated temperature cycling test. Finite element simulations were conducted to study the reliability of solder joints in flip chip on flex assembly (FCOF) and flip chip on rigid board assembly (FCOB) applying Anand model. Based on the finite element analysis results, the fatigue lives of solder joints were obtained by Darveaux’s crack initiation and growth model. The thermal strain/stress in solder joints of flip chip assemblies with different substrates were compared. The results of finite element analysis showed a good agreement with the experimental results. It was found that the thermal fatigue lifetime of FCOF solder joints was much longer than that of FCOB solder joints. The thermal strain/stress in solder joints could be reduced by flex buckling or bending and flex substrates could dissipate energy that otherwise would be absorbed by solder joints. It was concluded that substrate flexibility has a great effect on solder joint reliability and the reliability improvement was attributed to flex buckling or bending during temperature cycling.

Effect of substrate flexibility on solder joint reliability. Part II: finite element modeling

Solder joint fatigue failure is a serious reliability concern in area array technologies, such as flip chip and ball grid array packages of integrated-circuit chips. The selection of different substrate materials could affect solder joint thermal fatigue life significantly. The mechanism of substrate flexibility on improving solder joint thermal fatigue was investigated by thermal mechanical analysis (TMA) technique and finite element modeling. The reliability of solder joints in real flip chip assembly with both rigid and compliant substrates was evaluated by accelerated temperature cycling test. Finite element simulations were conducted to study the reliability of solder joints in flip chip on flex assembly (FCOF) and flip chip on rigid board assembly (FCOB) applying Anand model. Based on the finite element analysis results, the fatigue lives of solder joints were obtained by Darveaux’s crack initiation and growth model. The thermal strain/stress in solder joints of flip chip assemblies with different substrates were compared. The results of finite element analysis showed a good agreement with the experimental results. It was found that the thermal fatigue lifetime of FCOF solder joints was much longer than that of FCOB solder joints. The thermal strain/stress in solder joints could be reduced by flex buckling or bending and flex substrates could dissipate energy that otherwise would be absorbed by solder joints. It was concluded that substrate flexibility has a great effect on solder joint reliability and the reliability improvement was attributed to flex buckling or bending during temperature cycling.