Inverse Derivation of Constants for the Constitutive Equation and Fatigue Model of Pb-Free Solder Joints Based on Experiment Results, Finite Element Simulation and Virtual Optimization Methodology

2012 ◽  
Author(s):  
Weidong Xie ◽  
Mudasir Ahmad
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Constitutive Equation ◽  
Solder Joint ◽  
Test Results ◽  
Solder Joint Reliability ◽  
Joint Reliability ◽  
Fatigue Model ◽  
End Use ◽  
Free Solder

Solder joint reliability of Pb-free ball grid array (BGA) components, one of the most commonly used microelectronic devices, is one of the major concerns in product development and qualification. Accelerated Thermal Cycling (ATC) testing, though very time consuming and costly, remains the most prevalent means to evaluate solder joint reliability under certain end-use conditions. Wherever the test results are not readily available, a fine-tuned and well-benchmarked modeling methodology is of significance in producing quick-turn judgments and risk assessments to expedite product development. The two most critical elements in simulating solder joint reliability are 1) the solder constitutive equations, which describe the solder creep behavior under different working conditions, and 2) the fatigue model which ties the damage index from finite element modeling together with the experimental results. In this study, a novel approach has been explored in which the constants of the constitutive equation and fatigue model for Sn-based Pb-free solder joints were derived inversely based on ATC results of a ceramic BGA test vehicle. In order to cover the typical end-use conditions of the targeted products, the test vehicle was assembled onto PCBs with two different thicknesses and then thermal cycled under three different temperature profiles. The basic idea was that all of the constants, both for the constitutive equation and the fatigue life prediction model, were initially given as a range. Then by utilizing modeFrontier®, a multi-objective optimization software, the finite-element model was coupled with the virtual optimization algorithm to derive simultaneously all the constants that yielded the best fatigue life predictions compared to the test results. To simplify the problem without compromising the generality, a hyperbolic sine creep constitutive equation and Coffin-Manson fatigue model were selected in the analysis. There were a total of 6 constants to be determined; the initial ranges of the constants were defined by fitting the creep experimental data for a variety of Sn-based solder materials. Available in other publications, the selected solder materials cover a wide range of both Ag and Cu content which therefore represent the typical behavior of the most commonly adopted solder materials by the industry. To reduce the computational cost and enable fast convergence of multiple-generation iterations required by the multiple objective optimization algorithms, a very-well benchmarked submodel has been employed. Furthermore, by utilizing ANSYS® high performance computing (HPC) capability and cloud computing, the computational time was reduced significantly. An overall good correlation was achieved between the fatigue life prediction using the constants derived by this approach and the test characteristic life.

Thermal Cycling Reliability Predictions for PBGA Assemblies That Include Aging Effects

2013 ◽  
Author(s):  
Mohammad Motalab ◽  
Muhannad Mustafa ◽  
Jeffrey C. Suhling ◽  
Jiawei Zhang ◽  
John Evans ◽  
...  
Keyword(s):  
Finite Element ◽  
Solder Joint ◽  
Thermal Cycling ◽  
Failure Criteria ◽  
Lead Free ◽  
Aging Effects ◽  
Solder Joint Reliability ◽  
Reliability Models ◽  
Joint Reliability ◽  
Free Solder

The microstructure, mechanical response, and failure behavior of lead free solder joints in electronic assemblies are constantly evolving when exposed to isothermal aging and/or thermal cycling environments. Traditional finite element based predictions for solder joint reliability during thermal cycling accelerated life testing are based on solder constitutive equations (e.g. Anand viscoplastic model) and failure models (e.g. energy dissipation per cycle model) that do not evolve with material aging. Thus, there will be significant errors in the calculations with lead free SAC alloys that illustrate dramatic aging phenomena. In this research, we have developed a new reliability prediction procedure that utilizes constitutive relations and failure criteria that incorporate aging effects, and then validated the new approach through correlation with thermal cycling accelerated life testing experimental data. As a part of this work, a revised set off Anand viscoplastic stress-strain relations for solder have been developed that included material parameters that evolve with the thermal history of the solder material. The effects of aging on the nine Anand model parameters have been determined as a function of aging temperature and aging time, and the revised Anand constitutive equations with evolving material parameters have been implemented in commercial finite element codes. In addition, new aging aware failure criteria have been developed based on fatigue data for lead free solder uniaxial specimens that were aged at elevated temperature for various durations prior to mechanical cycling. Using the measured fatigue data, mathematical expressions have been developed for the evolution of the solder fatigue failure criterion constants with aging, both for Coffin-Manson (strain-based) and Morrow-Darveaux (dissipated energy based) type fatigue criteria. Similar to the findings for mechanical/constitutive behavior, our results show that the failure data and associated fatigue models for solder joints are affected significantly by isothermal aging prior to cycling. After development of the tools needed to include aging effects in solder joint reliability models, we have then applied these approaches to predict reliability of PBGA components attached to FR-4 printed circuit boards that were subjected to thermal cycling. Finite element modeling was performed to predict the stress-strain histories during thermal cycling of both non-aged and aged PBGA assemblies, where the aging at constant temperature occurred before the assemblies were subjected to thermal cycling. The results from the finite element calculations were then combined with the aging aware fatigue models to estimate the reliability (cycles to failure) for the aged and non-aged assemblies. As expected, the predictions show significant degradations in the solder joint life for assemblies that had been pre-aged before thermal cycling. To validate our new reliability models, an extensive test matrix of thermal cycling reliability testing has been performed using a test vehicle incorporating several sizes of fine pitch PBGA daisy chain components. Before thermal cycling began, the assembled test boards were divided up into test groups that were subjected to several sets of aging conditions (preconditioning) including different aging temperatures (T = 25, 55, 85 and 125 C) and different aging times (no aging, and 6 and 12 months). After aging, the assemblies were subjected to thermal cycling (−40 to +125 C) until failure occurred. As with the finite element predictions, the Weibull data failure plots have demonstrated that the thermal cycling reliabilities of pre-aged assemblies were significantly less than those of non-aged assemblies. Good correlation was obtained between our new reliability modeling procedure that includes aging and the measured solder joint reliability data.

Estimating the Vibration Fatigue Life of Quad Leaded Surface Mount Components

1993 ◽  
Vol 115 (2) ◽  
pp. 195-200 ◽  
Author(s):  
D. B. Barker ◽  
Y. S. Chen ◽  
A. Dasgupta
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Solder Joint ◽  
Finite Element Modeling ◽  
Stress Analysis ◽  
Empirical Equation ◽  
Solder Joint Reliability ◽  
Surface Mount ◽  
Joint Reliability ◽  
Vibration Fatigue

This paper discusses the assumptions and details of the fatigue life calculations required to predict the fatigue life of quad leaded surface mount components operating in a vibration environment. A simple approximate stress analysis is presented that does not require complex finite element modeling, nor does it reduce the problem to a simple empirical equation or rule of thumb. The goal of the new method is to make PWB vibration solder joint reliability information available to the designer as early as possible and in an easily understood and implemented manner.

Reliability Analysis of WLCSP Using Tie-Release Crack Prediction Finite Element Technique

2005 ◽  
Author(s):  
Chang-Chun Lee ◽  
Kuo-Ning Chiang
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Solder Joint ◽  
Solder Joints ◽  
Wafer Level ◽  
Element Analysis ◽  
Solder Joint Reliability ◽  
Joint Reliability ◽  
Prediction Technique ◽  
Packaging Structure

For the purpose of enhancing the solder joint reliability of a wafer level chip scaling package (WLCSP), the WLCSP adopted the familiar design structure where both the stress compliant layer with low elastic modulus and the dummy solder joints are considered as structural supports. However, the predicted fatigue life of the solder joints at the internal part of the packaging structure using the conventional procedures of finite element simulation are higher than under actual conditions as a result of the perfect bonding assumption in the modeling. In this research, in order to improve the thermo-mechanical reliability of the solder joints, a node tie-release crack prediction technique, based on non-linear finite element analysis (FEA), is developed and compared with the estimation of the solder joint reliability using conventional methodology. The predicted results of reliability, using the novel prediction technique, show a lower fatigue life of the solder joint than that when using conventional one when the fracture regions in the dummy solder joints are simulated under quasi-steady state. At the same time, the result of the thermal cycling test also shows good agreement with the simulated result when using the proposed node tie-release crack prediction analysis.

Effects of load and thermal conditions on Pb-free solder joint reliability

2004 ◽  
Vol 33 (12) ◽  
pp. 1507-1515 ◽  
Author(s):  
J. Liang ◽  
S. Downes ◽  
N. Dariavach ◽  
D. Shangguan ◽  
S. M. Heinrich
Keyword(s):  
Solder Joint ◽  
Thermal Conditions ◽  
Solder Joint Reliability ◽  
Joint Reliability ◽  
Free Solder

Experimental Evaluation on Solder Joint Reliability of PBGA Assembly Under Mechanical Drop Test

2002 ◽  
Author(s):  
Shi-Wei Ricky Lee ◽  
Yin-Lai Tracy Li ◽  
Hoi-Wai Ben Lui
Keyword(s):  
Solder Joint ◽  
Failure Modes ◽  
Solder Joints ◽  
Drop Test ◽  
Solder Joint Reliability ◽  
Joint Reliability ◽  
Free Solder ◽  
Board Level ◽  
Better Than ◽  
Mechanical Drop Test

The present study is intended to investigate the board level solder joint reliability of PBGA assemblies under mechanical drop test. During the course of this study, a five-leg experiment was designed to investigate various combinations of solder materials and peak reflow temperatures. Two major failure modes, namely, solder cracking and copper trace breakage, were identified. In addition, the critical location of solder joints was characterized. It was found that Sn-Pb eutectic solder joints performed better than Pb-free solder joints under mechanical impact loading.

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