Characterization of a laser-soldered avionic component using lead-free paste

Electrical cable-connector sets used in airplanes have been laser soldered using a lead-free paste. These connections are usually crimped using a hand tool, which necessarily leads to variable mechanical and electrical properties in the connection. Calorimetric studies have shown that paste melting occurs within tenths of a second at laser intensities of 400 or 500 W cm−2. However, when such laser intensities strike the connector surface, some boiling occurs. In order to avoid paste losses, a stepped heating curve is applied, which allows good weldability. It was verified that a reaction layer of 2 μm length exists between the wires and the solidified solder paste, and also that there is some diffusion of copper from the wires to the paste. The soldered joints are 38% more electrically conductible and have 113% more tensile strength resistance than crimped joints.