Effects of Surface Modifications on the Peel Strength of Copper Based Polymer/Metal Interfaces with Characteristic Morphologies

Abstract

This paper summarizes a study on the effect of changes in surface chemistry on the peel strength of copper/polymer interfaces. Two different surface topographics were created and evaluated, one produced by cleaning and etching in sodium persulfate, the other by etching then mechanically roughening using 180 grit sandpaper. Both surfaces were then oxidized in an alkaline/oxidizing treatment to form cupric oxide. Ion implantation and benzotriazole priming modified the surface chemistry of the cupric oxide samples. After lamination to form an epoxy/copper interface, peel strength measurements were taken. The results showed that ion implantation degraded the peel strength while priming with benzotriazole improved the peel strength compared with the unmodified cupric oxide. In a separate comparison study, peel strength measurements were taken on interfaces formed from copper oxides with the same oxide structure but with widely different gross morphologies, “As laminated” adhesive strength was virtually the same. The bonded interfaces were aged at elevated temperature and the peel strength obeyed first order degradation kinetics. Two terms can be determined from the degradation studies, the first is the long term peel strength, A(∞), and the other is Ω, the degradation rate with units of time⁻¹. A value of A(∞) was 3.0 lbs/in for etched copper interfaces while A(∞) was 0.5 lbs/in for the sanded interfaces.

Key Words:

• surface chemistry of copper/polymer interfaces
• effect of topography on peel strength
• mechanical roughening
• ion implantation
• time dependent degradation of interface
• chemical pretreatments
• epoxy/glass prepreg.