Bonding Process of Copper Foam-Silver Composite and Performance Characterization of the Joint

As a key heat-dissipating and electrical interconnecting component in high-temperature power modules, die-attach and substrate-attach layers play an important role in effectively reducing the thermal resistance and improving the long-term reliability. Traditional substrate-attach materials limit the high-temperature applications of packaging modules due to their high thermal resistance and high-temperature reliability. To solve the above deficiency, a copper foam-silver composite was proposed in this paper, which was prepared by mixing copper foam solid skeleton with micron silver paste. According to the results of thermogravimetric analysis (TGA) of silver paste, the preheating process was determined and sintered at 270°C and 10MPa. The influence of different preparation technology on the quality of sintered joint was investigated. The morphology characteristics and distribution of sintered silver in the copper foam were observed by scanning electron microscope (SEM). The results show that the sintered silver of group C samples can be uniformly filled into the solid skeleton of copper foam, and the densification degree is high, without cracks, delamination, and holes. The shear strength can reach 55MPa.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Electronic Components, Technology and Material

Molecular Dynamics Simulation of Sintering Densification of Multi-Scale Silver Layer

Based on molecular dynamics (MD), in this study, a model was established to simulate the initial coating morphology of silver paste by using a random algorithm, and the effects of different sizes of particles on sintering porosity were also analyzed. The MD result reveals that compared with the sintering process using large-scale silver particles, the sintering process using multi-scale silver particles would enhance the densification under the same sintering conditions, which authenticates the feasibility of adding small silver particles to large-scale silver particles in theory. In addition, to further verify the feasibility of the multi-scale sintering, a semi in-situ observation was prepared for a sintering experiment using micro-nano multi-scale silver paste. The feasibility of multi-scale silver sintering is proved by theoretical and experimental means, which can provide a meaningful reference for optimizing the sintering process and the preparation of silver paste for die-attach in powering electronics industry. In addition, it is hoped that better progress can be made on this basis in the future.Electronic Components, Technology and Material

Effects of Thermal Reflowing Stress on Mechanical Properties of Novel SMT-SREKs

A novel silicone rubber elastic key (SREK) is proposed in this paper for surface mounting technology (SMT) applications. Effects of thermal reflowing stress on the mechanical properties of SMT-SREKs are investigated. The manufactured SMT-SREKs, which underwent various reflowing conditions in advance, are subjected to pressing force and fatigue pressing tests. Fatigue lifetime projection model and its predicted error are then assessed systematically. The thermal degradation of silicone rubber materials is illustrated through the dynamic mechanical analysis and the Fourier transform infrared spectroscopy experiments. The mechanical finite element modeling is also conducted to simulate the pressing process. The results show that the pressing force and tactility of the SMT-SREKs are strongly affected by the reflowing condition, which contributes to the degradation of the silicone rubber materials. During the fatigue pressing test, the change rate of tactility increases with the reflowing peak temperature ( T-{p} ) and is accelerated by the repeated reflowing process. Moreover, a linear model can precisely project the tactility before the fatigue pressing number of 2.0E+6 times, and the impact rate of T-{p} on tactility with the increasing fatigue pressing number can be predicted effectively by using a logarithm model.Electronic Components, Technology and Material