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In this paper, the influences of pretreatment and hard baking on the mechanical characteristics of SU-8 microstructures are described. Four types of samples with different combinations of O2 plasma ashing, primer coating and hard baking were prepared for shear strength tests and uniaxial tensile tests. Specially developed shear test equipment was used to experimentally measure the shear adhesion strength of SU-8 micro posts on a glass substrate. The adhesiveness was strengthened by hard baking at 200 °C for 60 min, whereas other pretreatment processes hardly affected the strength. The pretreatment and hard baking effects on the adhesive strength were compared with those on the fracture strength measured by uniaxial tensile testing. There were no influences of O2 plasma ashing on both the strengths, and primer coating affected only tensile strength. The primer coating effect as well as the hard baking effect on stress relaxation phenomena in uniaxial tension was observed as well. Fourier transform infrared spectroscopy demonstrated that surface degradation and epoxide-ring opening polymerization would have given rise to the primer coating effect and the hard baking effect on the mechanical characteristics, respectively.

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In this article, a new low temperature solder bonding technique using Al/Ni exothermic reactive film is described. Al/Ni reactive film is able to generate heat enough to melt SnAg solder film. During the reaction, the volume is definitely shrunk by 12% because of the changes in crystallographic structure and lattice constant. The volume shrinkage yields cracking in reacted NiAl. In this study we focus on the control of crack position and its propagation direction for realizing crack-less solder bonding using Al/Ni exothermic film. A multiple ignitions system to simultaneously start the reaction from several parts was developed. It was demonstrated that major cracks were produced at the portion where two reactions ran into each other. By changing reaction start point, Al/Ni film's thickness and the overlap width, crack-less solder bonding in 20mm-square silicon chips was achieved.

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