CF4 fluorination onto Cu surface using atmospheric pressure non-equilibrium plasma for flux-less soldering with lead free solder

Atmospheric pressure non-equilibrium plasma inducted CF4 gas was irradiated to Cu printed board to obtain fluorinated Cu surface with a high affinity of a lead-free solder without fluxes. The plasma was produced by applying microwave power inducted with Ar–CF4–O2 mixed gasses with various flow gas ratios of CF4/O2. Fluorinated Cu surfaces were observed using a scanning electron microscopy (SEM) and analyzed using an X-ray photoelectron spectroscopy (XPS). The Cu surface fluorination was the most active when the ratio of CF4/O2 was 1/9. Contact angle of the solder mounted on Cu printed board was measured to evaluate the wettability. The contact angle was minimized at the flow ratio of CF4/O2 was 1/9. Surface fluorination by non-equilibrium plasma irradiation would be applicable to improve the wettability of flux-less solder.