Characterization for dynamic micro wetting of lead-free solder paste

Novel characterization method for evaluating dynamic wetting on a tiny chip component device using an infrared noncontact position sensor during unsteady wetting process was proposed. Testing system consists of a programmable reflow profile-heating unit and a motion sensing unit. Copper traced FR-4 substrates with paired circle lands for each chip component terminal were used as the wetting test substrate. Standard chip capacitors and registers were used for the test. Time vs. z-position curve was analyzed around melting point of the solder paste. The height position of the chip component decreased after solder melting. Several wetting parameters (rate and change of the vertical position of the chip component device) were determined according to the acquired time vs. z-position curves. Dynamical vertical motion of a chip component device and steady state position were evaluated with several kinds of lead-free solder alloys.