In recent years, the decrease in fatigue life of solder joints at high temperatures has been a major problem in semiconductor packages for automotive applications. In this paper, to improve the accuracy of predicting the fatigue life of solder joints when considering high-temperature degradation, we studied the correlation between high-temperature holding conditions and the decrease in fatigue life by using the mechanical fatigue test results of solder joints after high-temperature holding. The decrease in the fatigue life of solder joints after high-temperature holding was explained by the change in the fatigue ductility coefficient of Coffin-Manson’s law, and this fatigue life decrease can be quantitatively estimated using Arrhenius’ law with the holding time and holding temperature. We found that the fatigue life predicted by Miner’s law using the fatigue ductility coefficient under the test conditions of thermal cyclic tests agreed well with the experimental results.

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In this study the debonding strength of an adhesively bonded joint is investigated in terms of the intensities of the singular stress fields. Two types of models are used to evaluate the tensile adhesive strength σ_c; one is the perfectly bonded model, and the other is a fictitious crack model assuming different fictitious crack lengths. Previous experimental data, which were obtained for S35C JIS medium carbon steel plates bonded with epoxy resin, are then examined. From the comparison between the results, it is found that the critical values of the stress intensity factors are almost constant. In other words, the adhesive strength can be estimated from the intensities of the singular stress, usually with less than 17% error for both the perfectly bonded model and fictitious crack models. The usefulness of assuming the fictitious crack is put at the singular point is also discussed on the basis of the analysis for stress intensity factor.

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Various metal molds are made by an electroforming process. We fabricated a Ni structure using the electroforming process, and evaluated the effects of adding various agents to the trench substrates. The trench substrate was made using a photolithography process. When electrodeposition is applied to the trench substrate, voids are formed in the trench. In this work, void free electrodeposition is achieved by adding certain agents. We investigated the mechanisms of these added agents by performing electrochemical measurements.

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