Objective Epoxy resins have become one of the primary electronic packaging materials due to their excellent mechanical and electrical insulating properties. However, conventional epoxy resins heavily rely on non-renewable fossil resources and exhibit drawbacks such as poor dielectric performance and inadequate flame retardancy when used as encapsulants. Therefore, this study aims to replace petroleum-based feedstocks with renewable biomass (lignin), address its low reactivity and heterogeneity through structural modification, and thereby develop high-performance lignin-based epoxy resins for electronic packaging materials.

Method Industrial alkali lignin (AL) was purified to obtain purified alkali lignin (PAL). PAL was then hydroxymethylated to enhance its reactivity, followed by anti-solvent self-assembly to produce highly reactive nano-hydroxymethylated PAL particles (NHPAL). NHPAL fully replaced bisphenol A (BPA) and reacted with epichlorohydrin to introduce epoxy groups, yielding a nano-lignin-based epoxy resin (NHPAL-EP). Finally, carboxyl-terminated butadiene acrylonitrile rubber (CTBN) was employed to modify NHPAL-EP, optimizing its dielectric and insulating properties and resulting in a nano-lignin-based electronic packaging material (NHPAL/CTBN-EP).

Result High-purity and structurally homogeneous PAL was successfully prepared via purification. Subsequent hydroxymethylation and anti-solvent self-assembly yielded NHPAL with a particle size distribution of 60-120 nm. The multi-step modified NHPAL/CTBN-EP exhibited significantly enhanced mechanical properties. Compared with epoxy resin directly synthesized from AL (AL-EP), its tensile strength and compressive strength increased by 12.80-fold and 9.80-fold, respectively. Incorporation of CTBN improved the insulation and dielectric performance of NHPAL-EP. At an NHPAL-EP to CTBN mass ratio of 10∶1.5, the volume resistivity increased by 3.50-fold. In the medium-to-low frequency range (10²-10⁷ Hz), NHPAL/CTBN-EP demonstrated a low dielectric constant (≤3.44) and low dielectric loss (≤0.012). Additionally, water absorption decreased from 2.93% to 1.09%. Compared with diglycidyl ether of bisphenol A (DGEBA), the material achieved an HB flammability rating, indicating superior flame retardancy. These improvements enhance the long-term reliability of the packaging material. Practical encapsulation tests confirmed the flame resistance, water resistance, and alkaline solvent resistance of NHPAL/CTBN-EP, demonstrating its potential as an electronic packaging material.

Conclusion This study successfully developed a biomass-based NHPAL-EP that fully replaces BPA, using low-cost and biodegradable AL, thereby effectively reducing dependence on non-renewable petroleum resources. The CTBN-modified NHPAL/CTBN-EP exhibits low dielectric loss, HB-level flame retardancy, and low water absorption, making it suitable for medium-to-low frequency encapsulation applications in power electronics, integrated circuits, and capacitors.