Effect of Isothermal Aging on Sn-Ag-Cu Solder Joints on Electroless Ni-P/Au Plating in Laser Reflow Soldering

With the miniaturization of electronic productions and the use of heat sensitive electronic components, the traditional reflow soldering process often has difficulties. As an alternative soldering process, the laser reflow soldering has been recently proposed. The laser process brings several advantages in terms of localized heating, rapid rise and fall in temperature, non-contact and easily automated process. Therefore, to clarify joint properties in laser reflow  soldering, we investigated the effect of isothermal aging on Sn-Ag-Cu solder joints on electroless Ni-P/Au plating in laser reflow soldering. The laser used in a laser soldering system is a high power diode laser (λ=940 nm), equipped with a 1.2 mm beam diameter, a 120 mm focal distance objective and a 50 W maximum laser output power. Laser irradiation conditions were determined by laser power and irradiation time. Especially, the microstructure at the interface between Sn-Ag-Cu solder and Ni-P/Au plating and mechanical properties of solder joints were studied.