2022年, 第31卷, 第1期　
刊出日期：2022-08-13

  

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  Research progress on solder thermal interface materials

  江阳, 邹贵生, 杜成杰, 刘磊

  中国焊接. 2022, 31(1): 1-5. https://doi.org/10.12073/j.cw.20211216001

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  Down to the road of miniaturization and high power density, the heat dissipation is becoming one of the critical factors restricting further development of advanced microelectronic devices. Traditional polymer-based thermal interface materials (TIMs) are not competitive for the high efficiency thermal management, mainly due to their low intrinsic thermal conductivity and high interface thermal resistance. Solder-based TIM is one of the best candidates for the next generation of thermal interface materials. This paper conducts a perspective review of the state of the art of solder TIM, including low melting alloy solder TIM, composite solder TIM and nanostructured solder TIM. The microstructure, process parameters, thermal performance and reliability of different TIMs are summarized and analyzed. The future trends of advanced TIMs are discussed.
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  Review on failure analysis of interconnections in power devices

  黄伟, 陈志文

  中国焊接. 2022, 31(1): 6-14. https://doi.org/10.12073/j.cw.20211227001

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  Interconnections in microelectronic packaging are not only the physical carrier to realize the function of electronic circuits, but also the weak spots in reliability tests. Most of failures in power devices are caused by the malfunction of interconnections, including failure of bonding wire as well as cracks of solder layer. In fact, the interconnection failure of power devices is the result of a combination of factors such as electricity, temperature, and force. It is significant to investigate the failure mechanisms of various factors for the failure analysis of interconnections in power devices. This paper reviews the main failure modes of bonding wire and solder layer in the interconnection structure of power devices, and its failure mechanism. Then the reliability test method and failure analysis techniques of interconnection in power device are introduced. These methods are of great significance to the reliability analysis and life prediction of power devices.
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  Thermal fatigue behaviors of SiC power module by Ag sinter joining under harsh thermal shock test

  陈传彤, 张浩, 酒金婷, 龙旭, 菅昭克昭

  中国焊接. 2022, 31(1): 15-21. https://doi.org/10.12073/j.cw.20211130001

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  The excellent properties of SiC bring new challenges for the device packaging. In this study, the bonding strength, fracture behaviors and microstructural evolution of micron-porous Ag joint were elevated during thermal cycling (–50 oC–250 oC) in SiC/DBC (direct bonding copper) die attachment structure for different time. During harsh thermal shock test, the strength of sintered joint deceased gradually with the increase of cycling number, and the value just was half of the value of as-sintered after 1000 cycles. Coarsening of Ag grains was observed in micron-porous joint with the structure inhomogeneity and defects increasing, which were the reasons of the strength decease. In addition, it was also found that the fracture behavior of sintered joints was changed from ductile deformation of Ag grain to brittle fracture of crack propagation after 1000 cycles. This study will add the understanding in the mechanical properties of Ag sinter joining and its applications at high temperature.
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  Interfacial enhancement of Ag and Cu particles sintering using (111)-oriented nanotwinned Cu as substrate for die-attachment

  郭如梦, 肖宇博, 高悦, 周士祺, 刘洋, 刘志权

  中国焊接. 2022, 31(1): 22-28. https://doi.org/10.12073/j.cw.20220101001

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  The electroplated (111)-oriented nanotwinned-Cu (nt-Cu) film was utilized as substrate for Ag and Cu sinter joining to improve the weak interface connection between the metal paste and the substrate. It was found that both Cu and Ag sinter joints using (111)-oriented nt-Cu film exhibited a higher bonding strength than that using traditional random-oriented Cu film. Especially, the joints sintered with Cu paste on (111)-oriented nt-Cu film possessed a higher bonding strength of 53.7 MPa at the sintering condition of 300 °C, 0.4 MPa in N₂ atmosphere, compared to that on random-oriented Cu film with a value of 31.3 MPa. The results show that as metal substrate layer, the (111)-oriented nt-Cu film can improve the connection performance of Ag and Cu sinter joints, which could further promote their application in die-attachment technology for the next-generation power semiconductors.
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  Study on the performance of silver paste sintered sealing joints for hermetic packaging

  林丽婷, 章永飞, 李欣

  中国焊接. 2022, 31(1): 29-36. https://doi.org/10.12073/j.cw.20211129001

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  The traditional hermetic packaging methods, which require high temperatures and high voltages, would have adverse effects on electronics devices. Based on current-assisted sintering technology, we proposed a new hermetic packaging method using silver paste. Comparing the microstructure of the joints sintered with different currents, we found that with the increasing sintering current from 4.7 kA to 5.3 kA, the density of the joint increases, which improves the hermeticity and bonding strength of the joints. The results of thermal cycling tests showed that the sealing joints sintered at 4.7 kA with larger porosity are more prone to fail because pores tend to be sources of defects under thermal cycling. After 250 ℃ high thermal storage, there is the coarsening of the pores and the delamination near the Ag/Au interface, degrading the sealing performance of the sintered joint. Besides, the sealing joints sintered at 5.3 kA exhibit superior reliability when exposed to high temperatures.
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  Drop impact analysis of TSV-based 3D packaging structure by PSO-BP and GA-BP neural networks

  毛明晖, 刘建松, 田梦珂, 林鹏荣, 龙旭

  中国焊接. 2022, 31(1): 37-46. https://doi.org/10.12073/j.cw.20211111001

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  Particle swarm algorithm (PSO) and genetic algorithm (GA) were used to optimize the back propagation (BP) artificial neural network for predicting the dynamic responses of the through silicon via (TSV) based three-dimensional packaging structures. A finite element model of the TSV packaging structure with a strain-rate dependent constitutive model for solder joints was created to simulate the drop impact due to a free fall of 0.8 m to the rigid ground to investigate the structural dynamic responses during the whole impact process. The spatial coordinates of the solder joints were used as the input parameters of the hybrid neural network model for the drop impact responses, while the maximum Von Mises stress and PEEQ (plastic strain) values are identified the output parameters. The correlation coefficient (R), the mean absolute percentage error (MAPE) and the training time were used as the measures to validate and compare the proposed PSO-BP and GA-BP neural networks. The results show that both the PSO-BP model and the GA-BP model can achieve high accuracy predictions with strong generalization capability. Apparently, both optimized algorithms outperform the original BP model, but the PSO-BP model is slightly more superior than the GA-BP model. It is also demonstrated that the proposed optimized algorithms efficiently predict the drop impact responses of TSV packaging structures by greatly saving the computational and experimental cost of drop impact tests.
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  Mg₂Sn-induced whisker growth on the surfaces of Mg/Sn/Mg ultrasonic-assisted soldering joints

  操慧珺, 李世钦, 张英干, 朱轶辰, 李明雨, 张志昊

  中国焊接. 2022, 31(1): 47-59. https://doi.org/10.12073/j.cw.20211209001

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  In this paper, the phenomena of Mg₂Sn-induced Sn whisker growth were explored on the surfaces of Mg/Sn/Mg ultrasonic-assisted soldering joints after aging treatment. The in-situ observation and thermal analysis confirmed that the formation and the corrosion of Mg₂Sn nanoparticles were the dominant reason of Sn whisker growth. The Mg₂Sn accumulation at the grain boundaries would pin the dislocation slip and affect the continuity of whisker growth, and the boundary angle would thus play a decisive role in the growth shape of Sn whiskers due to the pining effect of Mg₂Sn. This study might be conducive to elucidating the growth behavior of Sn whiskers and provide the exploration strategy to further improve the bonding strength of Mg/Sn/Mg ultrasonic-assisted soldering joints.
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  Effect of surface finish metallization on interfacial bonding behavior of sintered Ag joints

  杨帆, 吴炜祯, 杜建军, 李明雨

  中国焊接. 2022, 31(1): 60-64. https://doi.org/10.12073/j.cw.20211130002

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  In this work, the sandwich joints were joined by low temperature pressureless sintering Ag paste. The morphology and thermal behavior of Ag nanoparticle paste was characterized and analyzed. The sintered Ag joints with different metallization were prepared and tested. The joints with Ag metallization exhibited superior shear strength and interface bonding ratio. However, the joints with Cu metallization showed lowest shear strength and interface delamination. The interfacial microstructures were observed and the diffusion kinetics between Ag and Au atoms were both calculated. The excessive diffusion of Ag atoms towards the Au layer deteriorated the interface bonding ratio and shear strength. This work will help understand the bonding mechanism between sintered Ag and other metallization.