Reliability Enhancement of 30 μm-Pitch Interconnections via Room-Temperature Laser-Assisted Bonding with Compression (LABC) Using Optimized Laser Non-Conductive Paste (LNCP)

As the trend in advanced semiconductor packaging continues toward finer pitch and higher integration, bonding technologies are increasingly expected to meet stricter thermal and mechanical performance requirements. However, conventional methods such as Thermo-Compression Bonding (TCB) often lead to problems including thermal stress, long processing times and limitations of fine-pitch bonding. To overcome these challenges, this study introduces Room-Temperature Laser-Assisted Bonding with Compression (LABC), a next-generation bonding technique that enables localized heating and rapid cooling, minimizing thermal stress while improving alignment accuracy and process efficiency. To further enhance the electrical and mechanical reliability of LABC, we developed two types of Laser Non-Conductive Paste (LNCP), designated LNCP-(A) and LNCP-(B). These eco-friendly materials, flux-free and solvent-free, not only prevent void formation and fume generation but also eliminate the need for post-bond cleaning and underfill processes. The bonding experiments were conducted on 30 µm-pitch daisy-chain bump structures formed on 11 mm × 7 mm silicon chips, simulating High Bandwidth Memory (HBM). The glass transition temperatures (Tg) of LNCP-(A) and LNCP-(B) were measured to be 36.27 °C and 51.23 °C, respectively, via Differential Scanning Calorimetry (DSC). Following the bonding process, electrical resistance measurements, cross-sectional microstructural analysis, and temperature cycling (TC) tests were performed. LNCP-(B), with its higher Tg, exhibited improved thermal stability and lower resistance variation compared to LNCP-(A). Furthermore, the LABC process effectively suppressed intermetallic compound (IMC) growth, resulting in consistently thinner IMC thickness compared to those formed by TCB. In addition, shear strength testing confirmed the mechanical robustness of the bonded joints. These results demonstrate the effectiveness of LABC with optimized LNCP materials as a promising solution for high-reliability, fine-pitch interconnections in next-generation semiconductor packaging.