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This study investigates the influence of adding Sb on the microstructure and adhesive strength of the Sn3.5Ag solder. Both solidus and liquidus temperatures increase as Sb additions increase. Adding 1.5wt.%Sb leads to the narrowest range (6.6°C) between the solidus and liquidus temperature of the solder. Adding Sb decomposes the as-soldered ringlike microstructure of Sn3.5Ag and causes solid-solution hardening. The as-soldered hardness increases with increasing Sb addition. For long-term storage, adding Sb reduces the size of the rodlike Ag 3 Sn compounds. The hardness also increases with increasing Sb addition. Adding Sb depresses the growth rate of interfacial intermetallic compounds (IMCs) layers, but the difference between 1% and 2% Sb is not distinct. For mechanical concern, adding Sb improves both adhesive strength and thermal resistance of Sn3.5Ag, where 1.5% Sb has the best result. However, adding Sb causes a variation in adhesive strength during thermal storage. The more Sb is added, the higher the variation reveals, and the shorter the storage time requires. This strength variation helps the solder joints to resist thermal storage.

This study adopts the application of the electrodischarge machining (EDM) hole-drilling method to the measurement of residual stress in AISI D2 cold work tool steel, AISI H13 hot work tool steel, and AISI 1045 medium carbon steel. A calibration procedure based on the thermal conductivity of the material is conducted to compensate for the additional compressive stress induced in the workpiece by the EDM hole-drilling operation. Since the formation of this white layer influences the magnitude of the induced stress, the scanning electron microscopy, transmission electron microscopy, and nanoindentation techniques are used to examine the microstructure and hardness of the white layer resolidified on the EDMed surface. The experimental results reveal that combination of the hole-drilling strain-gage method (ASTM standard E837) with an EDM drilling process provides the effective means of determining the residual stress in materials with high hardness and good wear resistance.

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