A microcapsule-type latent curing agent is prepared by solvent evaporation method with diaminodiphenylmethane (DDM) as the core material and PMMA as the wall material. The chemical structure, surface morphology, core content, and curing characteristics of as-prepared microcapsule-type curing agent are characterized by FTIR, SEM, TGA, and DSC. The results show that the obtained microcapsules have smooth surface and the core content is about 20 wt %. The one-component adhesive consisting of DDM-PMMA microcapsule and epoxy resin can be cured within 30 min at 130 C, and the room temperature latent period is more than 30 days. In addition, the internal reasons influencing the core content of microcapsules are analyzed by comparing and analyzing the structural compatibility of three kinds of wall material PMMA, PS, and polyetherimide with DDM. The results show that the core content is affected by the compatibility of wall material and core material.

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The IZ‐PU microcapsule‐type curing agent was prepared by interfacial polymerization method. The shell‐core structure of the IZ‐PU microcapsules was demonstrated by IR and SEM. The core content and coating efficiency of the IZ‐PU microcapsules were analyzed by DSC test of the one‐component adhesive consisting of IZ‐PU microcapsules and epoxy resin. The results showed that the IZ‐PU microcapsules is a proper latent curing agent to epoxy resin, its latency at room temperature is longer than 30 days.

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Sn 3.0 Ag 3.0 Bi 3.0 In (SABI333) solder is easy to form solder joints with different crystal structures during solidification. Solder joints with different crystal structures can exhibit different failure behaviors during creep. Five kinds of SABI333 solder joints with different crystal structures were selected to study the effect of grain boundary on the failure behavior of creep. The scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD) were utilized to characterize the surface morphologies and crystal orientations of solder joints. When there were only low angle grain boundaries or twin boundaries in the solder joints, it was not easy to generate cracks inside the solder joints during creep but easy to generate cracks at the interfaces between the copper bars and solder matrices. However, when there were high angle grain boundaries greater than 70° in the solder joints, the cracks would propagate along such grain boundaries during creep. This phenomenon depends on the difference of grain boundary energy and the difference of deformation degrees of grains on both sides of grain boundaries during creep. The grain boundary energy of the high angle grain boundaries is relatively high and the deformation degrees of grains on both sides of high angle grain boundaries are quite different during creep. This research is conducive to further understand the creep failure behavior of SABI333 solder joints under the service environment.