Novel Poly(benzoxazole-etherimide) Copolymer for Two-Layer Flexible Copper-Clad Laminate

Abstract

A new random co-polyimide (co-PI), poly(benzoxazole-etherimide), was prepared via the poly(amic acid) from the reaction of 5-amino-2-(4-aminobenzene)-1,3-benzoxazole (BOA) and 4,4′-oxydianiline (ODA) with 3,3′,4,4′-biphenyl tetracarboxylic dianhydride (BPDA) at a diamine molar ratio of 6:4. The BOA-type and ODA-type homo-PIs were also prepared for comparison. The aggregation structure and properties of the PI films were analyzed. The co-PI film showed a good balance in thermal properties, tensile strength, film toughness, and water absorption. The two-layer flexible copper-clad laminates made from these PIs were produced by coating poly(amic acid) solutions onto copper foils and then imidizing thermally. The adhesion properties and relative thermodimensional stability of the laminates were evaluated. The laminate based on the co-PI had higher relative thermodimensional stability as well as better adhesion property than those based on the two homo-PIs, which is due to the improvement in both the bonding strength of PI/copper at the interface and the cohesive strength of the co-PI itself in the boundary layer near the interface.

Keywords:

• adhesion strength
• copolymer
• flexible copper-clad laminate
• polyimide
• properties
• two-layer

Acknowledgment

The work was supported by the National Natural Science Foundation of China (Grant No. 50433010).