Updated Life Prediction Models for Solder Joints with Removal of Modeling Assumptions and Effect of Constitutive Equations

Abstract

There are two sources of errors in any finite element based life prediction model: the finite element mesh and assumptions, and the material properties usedspecifically the constitutive model used to describe the behavior of solder joints during temperature cycling. The use of these assumptions may prohibit the application of life prediction model to conditions beyond the ones used to develop the model.The author has previously proposed life prediction models for SnPb and SnAgCu solder joints using advanced finite element modeling techniques such as substructuring and multi-point constraints. The assumptions were necessary to increase the efficiency of solution with available computing power. With the advances in computing technology, these assumptions are no longer necessary, and more accurate life prediction can be achieved by eliminating most of the modeling assumptions.In this paper, the updated life prediction model parameters for SnAgCu solder joints are presented without the use of sub-structuring and multi-point constraints. All joints for a particular package-board interconnection are modeled as having non-linear properties. In addition, a detailed mesh refinement study is done to determine the minimum mesh density required to yield near mesh-independent results.In addition to modeling assumptions, the constitutive equation used for solder joints may also influence the life prediction model parameters. To investigate this further, the creep behavior of SnAgCu solder joints is represented by using published constitutive equations (double power law creep and hyperbolic sine equation). The results show a significant influence of constitutive equation on creep strain based life prediction model but minimum impact when energy density based approach is used.

Effect of Static and Dynamic Aging on Fatigue Behavior of Sn3.0Ag0.5Cu Solder Alloy

“…However, Syed [8] did similar study and found that the energy-based method yielded a more consistent prediction with different constitutive models than strain-based approach. Zhang et al [9] used energy-partitioning model to predict the reliability As mentioned earlier in Section 1.2.1, aging has a strong influence on the reliability of solder joints and therefore, it is essential to include aging effect in fatigue prediction.…”

Considerations in solution stabilization for thermal fatigue modeling of lead-free solder joints

“…In order to characterize the thermal fatigue damage accumulated inside the solder joint per temperature cycle according to the common modeling approaches [1][2][3][4], a critical volume (CV) is required to be defined. There are, unfortunately, no universal guidelines provided in the field for the selection of this volume.…”

“…A consistent prediction can then be made in Step (3). The common modeling approaches [1][2][3][4][5], however, have no universal guidelines for the number of necessary temperature cycles. Results from one temperature cycle have been used by Dudek et al [5] to evaluate the lead-tin solder joint thermal fatigue life.…”

“…The use of the finite element (FE) method is a common practice in the field for this task [1][2][3][4][5]. In order to adopt the modeling method to evaluate the long-term solder joint reliability, there are three major steps need to be implemented: (1) Although the modeling procedures appear to be "standardized", there is ambiguity when following them.…”

“…Results from one temperature cycle have been used by Dudek et al [5] to evaluate the lead-tin solder joint thermal fatigue life. Two temperature cycles are suggested to be solved by Syed [3][4] for the acquisition of stabilized damage results of lead-free SnAgCu (SAC) solder joints. Up to three temperature cycles are simulated by Darveaux [1] in his fatigue life prediction approach.…”