Fabricating sound copper/thermosetting polyimide joint via in-situ generated chemical bonding by chemical plating and hot pressing

The hard-to-weld combination, thermosetting polyimide (PI) and copper (Cu) was strongly joined via a new joining method combining chemical plating and hot pressing. Mechanical-roughened PI sheet was chemical plated with a thin Cu layer, then a thick Cu plate was bonded onto the PI sheet via hot pressing. Influence of heating temperature on macro-/microstructure, mechanical properties and interfacial bonding status was carefully investigated. The results showed that the Cu/PI interface achieved a ∼70.8 % increment in tensile-shear strength compared to the chemical-plated-only Cu/PI interface due to the in-situ formation of -C-O-Cu chemical bonding between -C=O of PI and in-situ generated Cu 2 O during hot pressing. To further enhance the mechanical performance of Cu/PI interface, different surface modification methods were applied to PI, among which, UV nanosecond laser treatment was proved to be the most suitable one owing to its ability to increase surface roughness, improve hydrophilicity and introduce active functional groups -COOH. Based on the experimental and simulation results, both -C=O and -COOH on laser-treated PI could react with Cu 2 O to form -(C=O)-O-Cu and -C-(O-Cu)2 chemical bonding, finally improving the tensile-shear strength of Cu/PI interface by 112.5 % in comparison to that of the chemical-plated-only one, from ∼2.4 MPa to ∼5.1 MPa.