A color-coded light-induced heating technology for Pb-free solder joints of advanced multi-semiconductor packaging

The complexity of semiconductor packaging is increasing due to artificial intelligence, heterogeneous integration, and chiplet technology, necessitating precise thermal control in multi-component soldering. Conventional reflow soldering requires multiple heating cycles to accommodate different solder alloys, leading to process inefficiencies, excessive thermal exposure, and mechanical degradation. This study introduces a color-coded intense pulsed light (IPL) reflow process, leveraging differential light absorption for localized thermal modulation, enabling simultaneous soldering of multiple alloys in a single reflow cycle. The results show that IPL-soldered joints exhibit superior or comparable mechanical integrity to conventional reflow, with thinner, more stable intermetallic compound (IMC) layers, refined Ag 3 Sn precipitates, and reduced void formation, enhancing reliability. The rapid, transient heating of IPL suppresses excessive IMC growth while optimizing microstructural evolution. Substrate color engineering offers a scalable method for selective thermal regulation, positioning color-coded IPL as a high-efficiency, energy-conscious alternative for next-generation semiconductor packaging.