Synergistic reinforcement strategy of high performance dual component alkali soluble photosensitive resin composites for solder resist

Solder resist (SR) materials are indispensable in advanced packaging technologies. However, conventional SR are often constrained by inferior thermo-mechanical properties, high dielectric constants, limited resolution, and poor chemical resistance, hindering their application in high-frequency, high-speed electronics. Herein, we report a molecular design strategy to synthesize a flexible alkali-soluble photosensitive resin (PIPE-2) containing imide rings, which was chemically integrated with a rigid alkali-soluble photosensitive epoxy resin (PE-6) to establish a rigid-flexible hybrid SR matrix system. The rigid-flexible network architecture enables a finely tuned balance between crosslinking density, chain mobility and comprehensive performance. Among the formulations, SR-40 exhibits the highest elongation at break (7.3 %, a 70 % increase), attributed to the disruption of PE-6 ordered conjugated domains by PIPE-2 flexible chains. Molecular-level chemical blending effectively prevents phase separation, ensuring thermal-mechanical performance balance. Consequently, SR-40 achieves superior adhesion (0.45 N/mm), low dielectric constant (D_k: 3.24), high resolution (40 μm), hydrophobicity (WCA: 83.3°), thermal stability (T_g: 136.4 °C, T₅_%: 352.4 °C) and robust chemical resistance. This work demonstrates a rational design strategy for achieving property synergies in SR systems and provides a viable pathway toward next-generation high-performance SR materials for advanced electronic packaging.