Ultra-Millisecond Flip-Chip Bonding Process via Intense Pulsed Light Irradiation

Abstract

In this study, an intense pulsed light (IPL) flip-chip bonding process was investigated to enhance the mechanical reliability of solder joints in flip-chip ball grid array (FC-BGA) packages. The process was characterized by using in situ temperature and resistance monitoring systems to provide real-time data during bonding. In addition, a numerical thermal transient simulation model was developed and validated by comparison with in situ monitoring results. The temperature profiles according to IPL parameters (pulse on-time, frequency, and pulse number) were investigated to effectively reduce bonding process time and maximum temperature of the flip-chip bonding process. The microstructure of the solder joint was observed using scanning electron microscope (SEM). The thickness of intermetallic compounds (IMC) was effectively reduced from 6 μm in the conventional reflow process to approximately 800 nm in the IPL flip-chip bonding process, as the process time was significantly shortened from 90 s to 56.4 ms, and the maximum temperature was lowered from 250 to 221.7 °C. Die shear tests demonstrated that the IPL flip-chip bonding process improved die shear force by 30% compared to conventional reflow processes. This study demonstrates that the IPL flip-chip bonding process could produce FC-BGA packages with excellent mechanical reliability.