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Purpose This paper aims to discuss the effect of surface treatment on the wettability between copper and a lead-free solder paste. The industrial applications of laser technologies are increasing constantly. A specific laser treatment can modify the surface energy of copper and affect the wetting properties. Design/methodology/approach The surfaces of copper plates were treated using an Nd:YAG laser with varying laser powers. After laser surface treatment, wetting experiments were performed between the copper plates and SAC305 lead-free solder paste. The effect of laser treatment on copper surface was analysed using optical microscopy and scanning electron microscopy (SEM). Findings The experimental results showed that the wetting contact angles changed with the variation in laser power. Furthermore, it means that the surface energy of copper plates was changed by the laser treatment. The results demonstrated that the contact angles also changed when a different soldering paste was used. Originality/value Previous laser surface treatment can be a possible way to optimize the wettability between solders and substrates and to increase the quality of the soldered joints.

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The wettability of graphite by the silver-gold (Ag-Au) liquid alloy was measured using the sessile drop method at a temperature interval of 1273 -1473 K. The measured alloys are in the solid solution range. The system is found poorly wetting with the contact angle at an interval of 112. . . 136 degrees. Typical alloying effects are found, as the Ag host metal is gradually replaced by Au alloying element. The results of the contact angle measurements were compared to the change of electrical resistance. The wetting angle measurement is complicated because several environmental variables affect the results. The wetting experiments were performed in a wetting angle measuring system which has changeable atmosphere, so the measurements can be performed in inert atmosphere and has a resistance-heated tube furnace which can ensure the wetting angle measuring temperature up to 1473 K.