Process Development and Solder Joint Reliability of a New Lead-Free Solder: Sn3wt%Ag0.5wt%Cu0.019wt%Ce (SACC)

The effects of a very low level (0.019wt%) of doping of Ce (cerium) on the SnAgCu (SAC) solder joints of lead-free PQFP (plastic quad flat pack), PBGA (plastic ball grid array), wafer-level chip scale package (WLCSP), and BCC (bumped chip carrier) components on lead-free PCB (printed circuit boards) are investigated in this study. Emphasis is placed on the PCA (PCB assembly) process developments and the solder joint reliability of these components on PCB with the newly proposed lead-free solder: Sn3wt%Ag0.5wt%Cu0.019wt%Ce (SACC). For process development of the SACC, important parameters such as the stencil printing, solder paste volume, void, and reflow temperature are determined and discussed. For SACC solder joint reliability, the mechanical fatigue of PQFP, PBGA, CSP, and BCC on PCB has been determined by 4-point bending fatigue tests. The test samples are prepared with 5 different aging conditions, namely, room temperature, 150degC for 1 hour, 150degC for 10 days, 150degC for 20 days, and 150degC for 30 days. After the tests, failure analyses have been performed and the IMC (intermetallic compound) thickness due to aging has also been determined and examined by SEM (scanning electron microscopy) and EDX (energy dispersive X-ray spectrometry).