The creep deformation mechanism of Sn–Ag–Cu alloy doped with Bi and Sb (SACBiSb) alloys is theoretically and experimentally analyzed in order to clarify the effect of solid solution additives in Sn–Ag–Cu alloys. The theoretical prediction results and test results are found to mostly agree with each other. The breakaway stress which is the stress at the transition from Class II to Class I in particular is finely reproduced in the theoretical prediction, with a stress of 25 MPa found both by the prediction and test results. In the stress range where the stress is higher than the breakaway stress, the creep strength of SACBiSb is higher than that of Sn–Ag–Cu, while it was predicted that the creep strength of Sn–Ag–Cu would be superior to that of SACBiSb in the range of stress lower than the breakaway stress. The thermal fatigue life of SACBiSb was predicted to be longer than that of Sn–Ag–Cu in the temperature profile mainly used above the breakaway stress. However, in the temperature profile mainly used in the low-stress range, a reversal of the creep strength between SACBiSb and Sn–Ag–Cu was predicted to occur and the loss of the superiority of SACBiSb in the thermal fatigue life was also predicted. 

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Class I Creep Deformation of Sn–Ag–Cu Containing Solid Solution Elements and Its Effect on Thermal Fatigue Life of Solder Joints

Ball grid array (BGA) technology is one of the technologies used in surface mount technology (SMT). It provides many interconnection points via the solder ball and thus give advantages such as good heat dissipation, improved the PCB design, BGA package become robust and reliable. In electronic industry, the reliability of BGA package is being concerned. Thermal cycling test (TCT)is one of typical reliability test used to investigate the reliability of the BGA package. This study investigates on the thermal cycling effect on the crack formation of solder joint in ball grid array package. The BGA package was subjected to thermal cycle test with temperature cyclic of -40°C and 85°C for 500, 750 and 1000 cycles. The finding shows that the cracks were observed in solder joint in 750 and 1000 cycles. This shows that the BGA package is sensitive to the thermal cycling and effect its reliability. The package was modified with adding underfill materials and tested through the same cycles. Cross sectional and Dye and pry test show no crack formation and dye penetration for all thermal cycles in the BGA package with underfill.

https://doi.org/10.1088/1742-6596/2169/1/012006

Thermal cycling effect on the crack formation of solder joint in ball grid array package


 Miniaturization as well as manufacturing processes that electronics devices are subjected to, often results to increase in operational parameters such as current density, temperature, mechanical load, with potential to induce stresses that may be detrimental to device reliability. Past studies have identified some failure mechanisms common to these devices. Examples of these failure mechanisms include fatigue, electromigration, stress induced voiding, corrosion, conduction filament formation and time dependent dielectric breakdown. While some review activities related to reliability model development based on these failure mechanisms can be easily found in literature, to the best of our knowledge, a single review paper, which captures the reliability model progresses made over the past four decades across these failure mechanisms in comparison with Standards such as Joint Electron Device Engineering Council (JEDEC) and Institute for Printed Circuits (IPC) is to the best of our knowledge lacking. To fill this gap, a detailed review of failure mechanism driven reliability models, with emphasis on physics of failure (PoF) for power electronics was carried out in this paper. Although, other failure mechanisms exist, our review is only limited to fatigue, electromigration, stress induced voiding, corrosion, conduction filament formation and time dependent dielectric breakdown. It was found that, most reliability research modelling efforts are yet to be fully integrated into Standards.

Failure Mechanisms Driven Reliability Models for Power Electronics: A Review

The eight papers were selected for the best paper award in 2021 to 2022 from Materials Transactions. Here, the awarded papers are briefly summarized as current trends in research of Materials Transactions. Among the eight best papers, four were specially selected for young scientists whose ages are 35 or below. An important trend in the year of 2021 is that three best papers are from a special issue with the title of “Materials Science on Hypermaterials”, which is based on an ongoing national research project, Grant-in-Aid for Scientific Research on Innovative Areas. 

https://www.jstage.jst.go.jp/article/matertrans/advpub/0/advpub_MT-M2023035/_pdf

Best Papers Awarded in 2022 by Materials Transactions

Microstructures and shear strengths of W-ball solder joints aged under isothermal and cyclic thermal conditions

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Kouichi Morooka

Papers

Thermal fatigue life prediction of BGA solder joints using a creep constitutive equation incorporating microstructural coarsening effect