Effects of Lignin Derivatives on Cross-Link Density and Dielectric Properties in the Epoxy-Based Insulating Materials for Printed Circuit Boards

Bio-plastics are made from renewable biomass sources. We focus on lignin and develop epoxy resins containing lignin derivatives. We describe the preparation and application of epoxy resin containing lignin as a matrix. Soda-lignin (SLG) is obtained from black liquor in a soda pulp process. First, we use a lignin manufacturing process in which a methanol extraction method enabled reduction in the molecular and hydroxyl equivalent weights of lignin and removal of ${\rm SiO}_{2}$ and cellulose. Second, we investigate the ratio of diglycidyl ether of bisphenol-A (DGEBA) and methanol extraction SLG (me-SLG). From the viewpoint of cross-linking density and dielectric properties, 100/84 phr in the DGEBA/me-SLG casting system is found to be preferable. Finally, we try to fabricate an insulating material made up of DGEBA/me-SLG for an aluminum-based printed circuit board, and it achieves standard values.