Laser Soldering of Fine Pitch QFP Devices Using Lead-Free Solders

In this paper, soldering experiments of fine pitch quad flat package (QFP) devices were carried out when soldered with Sn–Ag–Cu and Sn–Cu–Ni lead-free solders by means of diode laser soldering system, and compared with the experimental results soldered with Sn–Pb solders and with infrared (IR) reflow soldering method. The results indicate that under the conditions of laser continuous scanning mode and the fixed laser soldering time, an optimal power is obtained when the optimal mechanical properties of QFP microjoints are achieved. Mechanical properties of QFP microjoints soldered with laser soldering system are better than that of QFP microjoints soldered with IR soldering method. Results also indicate that adding rare earth element Ce to Sn–Ag–Cu and Sn–Cu–Ni lead-free solders improves mechanical properties of QFP microjoints, and the optimal amount of Ce is about 0.03%.