Fabrication of Roughened Electrodeposited Copper Coating on Steel for Dissimilar Joining of Steel and Thermoplastic Resin

Susumu Arai,Masaomi Horita,Masami Itabashi,Junki Inoue,Takashi Nagaoka,Masahiro Shimizu,Ryosuke Iwashita

doi:10.3390/met11040591

Abstract

Electrodeposition of a roughened copper coating onto steel was carried out to produce a bonding surface for thermoplastic resin (polyphenylenesulfide). The roughened copper film was electrodeposited using a copper sulfate bath containing polyacrylic acid (PAA). Following injection molding of the resin, the bonding strength was evaluated in a tensile lap shear strength test, followed by durability testing at high temperature and humidity (85 ± 2 °C and 85 ± 2% relative humidity, respectively) for 2000 h, and a thermal shock test (−50 °C–150 °C) for 1000 cycles. An analysis of the boundary microstructure showed that the PAA concentration had a large effect on the surface morphology of the copper film. The shear strength of the joint between the coated steel substrate and the resin was more than 40 MPa, and the bonding strength also remained above 40 MPa throughout the durability test. During the thermal shock test, although the bonding strength gradually decreased with increasing number of cycles, it remained at over 20 MPa, even after 1000 cycles. This method achieves not only high initial bonding strength, but also durability for joints between dissimilar materials such as steel and resin.

Highlights

To tackle issues such as reducing CO2 emissions and mitigating global climate change, one effective method is the use of multiple materials for reducing the weight of vehicles, such as cars [1]
A homogeneous surface morphology consisting of grains with sizes of 100 to 200 nm was observed on the film (Figure 3a)
Roughened copper films were electrodeposited on a steel substrate using polyacrylic acid (PAA) as a roughening agent to enhance the anchor effect

Summary

Introduction

To tackle issues such as reducing CO2 emissions and mitigating global climate change, one effective method is the use of multiple materials for reducing the weight of vehicles, such as cars [1]. To form the joint, an injection molding machine or hot press is used to apply the resin to the roughened metal at high temperature and pressure This causes the plastic to fill the irregularities on the metal surface. To produce a rough metal surface, methods such as laser treatment [5,6,7,8,9,10,11], chemical etching [12,13], and abrasive blasting [14,15,16] have been shown to be effective All of these methods give rise to a different surface morphology, which depends on the type of metal or alloy used. One promising approach is plating, because the final surface morphology depends only on the plating conditions

Methods

Results

Conclusion