Unified Finite Element Modeling for Prediction of Solder Joint Fatigue

Author(s):  
Mohammad Masum Hossain ◽  
Dereje Agonafer ◽  
Puligandla Viswanadham ◽  
Tommi Reinikainen

The life-prediction modeling of an electronic package requires a sequence of critical assumptions concerning the finite element models. The solder structures accommodate the bulk of the plastic strain that is generated during accelerated temperature cycling due to the thermal expansion mismatch between the various materials that constitute the package. Finite element analysis is extensively used for simulating the effect of accelerated temperature cycling on electronic packages. There are a number of issues that need to be addressed to improve the current FEM models. One of the limitations inherent to the presently available models is the accuracy in property values of eutectic 63Sn/37Pb solder or other solder materials (i.e. 62Sn/36Pb/2Ag). Life prediction methodologies for high temperature solders (90Pb/10Sn, 95Pb/5Sn, etc.) or lead-free based inter-connects materials, are almost non-existent due to their low volume use or relative infancy. [1] Another major limitation for the models presently available is excluding the effect of intermetallic compound (Cu6Sn5, Cu3Sn) formation and growth between solder joint and Cu pad due to the reflow processes, rework and during the thermal aging. The mechanical reliability of these intermetallic compounds clearly influences the mechanical integrity of the interconnection. The brittle failures of solder balls have been identified with the growth of a number of intermetallic compounds both at the interfaces between metallic layers and in the bulk solder balls. In this paper, the effect of intermetallic compound in fatigue life prediction using finite element modeling is described. A Chip Scale Package 3D Quarter model is chosen to do the FE analysis. Accelerated temperature cycling is performed to obtain the plastic work due to thermal expansion mismatch between the various materials. Solder joint fatigue life prediction methodologies were incorporated so that finite element simulation results were translated into estimated cycles to failure. The results are compared with conventional models that do not include intermetallic effects. Conventionally available material properties are assumed for the eutectic 63Sn/37Pb solder and the intermetallic material properties. The importance of including intermetallic effect in finite element modeling will be discussed.


2015 ◽  
Vol 2015 (DPC) ◽  
pp. 000958-000972
Author(s):  
Betty Yeung

The solder joint reliability of semiconductor package interconnects to printed circuit boards is critical for product durability. A dominant failure mode is solder fatigue due to the CTE mismatch between the BGA component and PCB at thermal cycling. However, it is well known that other factors can impact fatigue behavior and time to failure such as solder joint geometry, die geometry, solder system, etc. Finite element modeling (FEM) and simulation can play an integral role in providing deeper insight into the impact of these package parameters on the overall assembly. However, a major challenge of accurately modeling these systems includes simulation of multiple length scales from the package, substrate, and solder joints. The FEM approach addressing these can lead to reduced cycle time, accurate simulation, and improved package performance. In this work, the finite element modeling and simulation procedure is demonstrated for a BGA package at accelerated temperature cycling conditions. At the component level, key details regarding the properties and constituents of the BGA package mold compound and substrate are established by coupling measured experimental warpage data and finite element modeling. Comparison of simulated & Thermoire measurements shows excellent agreement at the package level, with warpage correlation achieved over the entire temperature range. At the assembly level, the truncated sphere model is used to arrive at precise solder joint profiles for accurate representation to tie the package to the board. The combined validated package-level results and solder joint profiles are employed towards a subsequent thermo-mechanical analysis of the full BGA assembly. The entire simulation procedure is demonstrated for a BGA design, where inelastic creep and reliability test data are compared. High strain regions in the solder joint array are shown to compare closely with regions of failure from experimental reliability test data. The validated FEM model allows for extrapolating to similar package conditions allowing faster design cycle time and less time consuming experimental work.


1991 ◽  
Vol 3 (1) ◽  
pp. 235-253 ◽  
Author(s):  
L. D. Philipp ◽  
Q. H. Nguyen ◽  
D. D. Derkacht ◽  
D. J. Lynch ◽  
A. Mahmood

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