Figure 14 - uploaded by David M Pierce
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Perspective view of BGA submodel geometry and solder joint mesh (note interface element layers, three elements of 0.0127mm thickness per element)
Source publication
The ubiquitous eutectic tin-lead (Sn-Pb) solder alloys are soon to be replaced with lead-free alternatives. In light of this transition, new computational tools for predicting the fatigue life of lead-free solders are required. Stress-strain, creep and isothermal fatigue data are generated for the 95.5Sn-3.9Ag-0.6Cu (wt.%) solder alloy; the latter...
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Citations
... It is evident that when the temperature is large, the strain components increases and the maximum strain concentration with a move to the diagonal edges of the solder interface and fails due to creep cracks propagation and rupture. [46] shows comparable outcomes with high strain regions in the critical solder ball determined with FEM analysis and observation of the thermomechanical fatigue crack localised in the solder bulk on the component side. ...
... This shows that the stress/deformation occurs near the substrate as seen from the results of our simulation. Similarly, results obtained byFu et al. (2017) [45] andPierce et al. (2007) ...
Solder joints of electronic components are the most critical part of any electronic device. Their untimely failure during the system’s operation often culminates in catastrophic failure of the device. The determination of creep damage in electronic component solder joint is vital to the prediction of crack initiation and prevention of premature failure. This paper presents the creep damage in solder joints in a ball grid array (BGA) soldered on a printed circuit board (PCB) and subjected to thermal cycling as well as isothermal ageing. ANSYS 19.0 package is employed to model the isothermal gaining at -40, 25, 75 and 150℃ temperatures for 45 days. Standard temperature cycle profile is used to simulate the effect of the coefficient of thermal expansion mismatch on the bonded materials in the BGA component. The solders studied are lead-based eutectic solder alloy and lead-free SAC396, SAC387, and SAC305. Based on the results obtained for the stress, strain and strain energy of the solders, the research investigation advises on the most effective solder for achieving improvement in the thermo-mechanical reliability of solder joints in BGA soldered on PCB.
... Conformément aux quelques résultats expérimentaux [170], une régression polynomiale de second ordre entre l'aire endommagée et le nombre de cycles de chargement est utilisé ici. La relation quadratique qui apparaît permet de dire qu'il existe une relation linéaire entre la longueur effective d'endommagement (longueur de fissure équivalente) et le nombre de cycles. ...
Cette thèse vise à réaliser des développements théoriques et numériques portant sur le comportement en cyclage thermomécanique de nouveaux alliages de brasure. L’objectif est de proposer une méthodologie de simulation de la fatigue des assemblages électroniques intégrant ce type de brasures. De nombreux modèles semi-empiriques de fatigue existent déjà mais ont montré leurs limites pour une prédiction suffisamment précise de la fiabilité. Il existe donc un besoin d’enrichir les approches existantes par une description des mécanismes de défaillance à l’échelle mésoscopique, en prenant en compte la microstructure fine de l’alliage d’étain. Une formulation décrivant la plasticité cristalline de l’étain et l’endommagement aux joints de grains a donc été développée et intégrée dans un code de calcul pour simuler les mécanismes de déformation dans le joint de brasure.
Fatigue of lead-free solder joints remains the most critical concern in thermo-mechanical reliability of high power modules. Due to size miniaturization requirement, fatigue properties become even more affected by features of the solder joint microstructure. Phenomenological fatigue models based on effective material properties at macro-scale only grossly predict the engineering lifetime for some specific boundary conditions while ignoring the important effects of the microstructural mechanisms of deformation. In this study, a 3D microstructure-informed model for reproducing the intergranular fatigue crack in the solder joint of a power module is developed. The submodeling technique is applied in order to investigate accurately the critical zone of the solder joint with reasonably reduced computational time. In the submodel, the anisotropic elasticity and crystal plasticity constitutive laws are integrated for the bulk grain material, while the decohesion at grain boundaries is modeled by the cohesive zone approach. The needed crystal plasticity parameters are calibrated using the Berveiller-Zaoui transition rule to fit tensile test data for the so-called InnoLot solder alloy, and physically-based concepts are used to estimate the cohesive zone parameters at the grain scale. Simulations demonstrate how fatigue cracking occurs and propagates at grain boundaries in the solder joint. A criterion is then presented to estimate the fatigue lifetime of the entire solder joint, based on specific quantities predicted numerically.
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