Author(s):  
T. E. Wong ◽  
C. Chu

A thermal fatigue life prediction model of a ceramic column grid array (CCGA) solder joint assembly has been developed when the 90Pb/10Sn solder columns of the CCGA package are soldered onto the printed circuit board with either tin-lead or lead-free solder paste. This model was evolved from an empirically derived formula by correlating the solder nonelastic strain energy density increment to the fatigue life test data. To develop the solder joint fatigue life prediction model, a nonlinear finite element analysis (FEA) was conducted using the ABAQUS computer code. A thermal fatigue life prediction model was then established. The test results, obtained from various sources in which tin-lead and lead-free solder pastes on PCB were used, combined with the FEA derived nonelastic strain energy density per temperature cycle, ΔW, were used to calibrate the proposed life prediction model. In the analysis, 3-D finite element global- and sub-modeling techniques were used to determine the ΔW of the CCGA solder joints when subjected to temperature cycling. The analysis results show that: 1) solder joint would typically fail across solder column instead of along solder pad interfaces; and 2) higher nonelastic strain energy densities of solder occur at the solder columns at the package corners and these solder joints would fail first. These analysis predictions are consistent with the test observations. In the model calibration process, the 625- and 1657-pin CCGA test results, which were cycled between 20°C/90°C, 0°C/100°C, -55°C/110°C, or -55°C/125°C, were reasonably well correlated to the predicted values of ΔW. Therefore, the developed life prediction model could be used and is recommended to serve as an effective tool to determine the integrity of the CCGA solder joints during temperature cycling. In addition, the following future work is recommended: 1) selecting more study cases with various solder joint configurations, package sizes, environmental profiles, etc. to further calibrate this life prediction model; 2) using this model to conduct parametric studies to identify critical factors impacting solder joint fatigue life and then seek an optimum design; and 3) developing a simplified method instead of the FEA approach to make preliminary thermal fatigue life estimates of the CCGA solder joints.


2003 ◽  
Vol 125 (1) ◽  
pp. 120-125 ◽  
Author(s):  
Hong Tang ◽  
Cemal Basaran

A thermomechanical fatigue life prediction model based on the theory of damage mechanics is presented. The damage evolution, corresponding to the material degradation under cyclic thermomechanical loading, is quantified thermodynamic framework. The damage, as an internal state variable, is coupled with unified viscoplastic constitutive model to characterize the response of solder alloys. The damage-coupled viscoplastic model with kinematic and isotropic hardening is implemented in ABAQUS finite element package to simulate the cyclic softening behavior of solder joints. Several computational simulations of uniaxial monotonic tensile and cyclic shear tests are conducted to validate the model with experimental results. The behavior of an actual ball grid array (BGA) package under thermal fatigue loading is also simulated and compared with experimental results.


Author(s):  
T. E. Wong ◽  
C. Chu

A simplified method was developed to determine the fatigue life of a ceramic column grid array (CCGA) solder joint when exposed to thermal environments. The CCGA package with 90Pb/10Sn solder columns is soldered onto the printed circuit board with a tin-lead solder paste. Failure of the solder joint occurs at the CCGA solder column. A closed-form solution with the equilibrium of displacements of electronic package assembly was first derived to calculate the solder joint strains during the temperature cycling. In the calculation, an iteration technique was used to obtain a convergent solution in the solder strains, and the elastic material properties were used for all the electronic package assembly components except for the solder materials, which used elastic-plastic properties. A fatigue life prediction model, evolved from an empirically derived formula based upon a modified Coffin-Manson fatigue theory, was then established. CCGA test results, obtained from various sources, combined with the derived solder strains were used to calibrate the proposed life prediction model. In the model calibration process, the 625- and 1657-pin CCGA test results, which were cycled between 20°C/90°C, 0°C/100°C, −55°C/110°C, or −55°C/125°C, were reasonably well correlated to the calculated values of solder strains. In addition, this calibrated model is remarkably simple compared to the model used in an evaluation by a finite element analysis. Therefore, this model could be used and is recommended to serve as an effective tool to make a preliminarily estimate at the CCGA solder joint thermal fatigue life. It is also recommended to 1) select more study cases with various solder joint configurations, package sizes, environmental profiles, etc. to further calibrate this life prediction model, 2) use this model to conduct parametric studies to identify critical factors impacting solder joint fatigue life and then seeking an optimum design, and 3) develop a similar life prediction model for lead-free solder materials.


Author(s):  
T. E. Wong ◽  
C. Y. Lau ◽  
H. S. Fenger

A simple analysis method was developed to determine the fatigue life of a ceramic ball grid array (CBGA) solder joint when exposed to thermal environments. The solder joint consists of a 90Pb/10Sn solder ball with eutectic solder on both top and bottom of the ball. Failure of the solder joint occurs at the eutectic solder. A closed-form solution with the equilibrium of displacements of electronic package assembly was first developed to calculate the solder joint strains during the temperature cycling. In the calculation, an iteration technique was used to obtain a convergent solution in the solder strains, and the elastic material properties were used for all the electronic package assembly components except for the solder materials, which used elastic-plastic properties. A fatigue life prediction model, evolved from an empirically derived formula based upon a modified Coffin-Manson fatigue theory, was then established. CBGA test results, obtained from Motorola, combined with the derived solder strains were used to calibrate the proposed life prediction model. In the model calibration process, the 255- and 304-pin CBGA test results, which were cycled between 0°C and 100°C or −40°C and 125°C, were reasonably well correlated to the calculated values of solder strains. In addition, this calibrated model is remarkably simple compared to the model used in an evaluation by finite element analysis. Therefore, this model could be used and is recommended to serve as an effective tool to preliminarily estimate the CBGA solder joint thermal fatigue life.


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