| YANG Hai-tao,YAN Biao.Effect of Plasma Surface Treatment on Interface Adhesive Performance of Low Roughness Copper Foil and Resin[J],52(7):278-287 |
| Effect of Plasma Surface Treatment on Interface Adhesive Performance of Low Roughness Copper Foil and Resin |
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| DOI：10.16490/j.cnki.issn.1001-3660.2023.07.025 |
| KeyWord:plasma treatment electronic copper foil roughness adhesion surface modification |
| Author | Institution |
| YANG Hai-tao |
School of Materials Science and Engineering, Tongji University, Shanghai , China |
| YAN Biao |
School of Materials Science and Engineering, Tongji University, Shanghai , China |
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| Abstract: |
| Low surface roughness is required for electronic copper foils in high frequency and high speed printed circuit board (PCB) substrates for reducing signal loss. However, the reduction of surface roughness will inevitably lead to the decrease of the adhesion between copper foil and resin, so that it cannot meet the requirements of industrial application. In this work, an atmospheric plasma treatment technology was developed to modify the resin surface for improving the adhesion between low roughness copper foil and resin. This new preparation process of PCB substrates mainly included the roughening treatment of copper foil, plasma treatment of resin, and hot pressing of copper foil/resin composites. The changes in adhesive properties between an epoxy resin or polyphenylene oxide resin and copper foil with and without plasma treatment were studied exhaustively. Surface morphologies of copper foil and resin were studied with a scanning electron microscope (SEM). The 3D morphologies and roughness of the samples were investigated with a laser scanning confocal microscope (LSM). An X-ray photoelectron spectroscopy (XPS) was used to analyze the chemical state change of the resin surface before and after plasma treatment. Peel strength tests were performed to investigate the adhesion of copper foil/resin composites with different treatment. By studying the roughness of four types of copper foils obtained by the electrodeposition roughening method and their adhesion to epoxy resin, it was found that the adhesion decreased with the decrease of roughness. Among them, the peel strength of PCB substrates for high-frequency and high-speed circuits did not meet the application standards, so the plasma treatment should be introduced. There was no obvious change in the surface morphology of the resin after plasma treatment, and the changes were mainly reflected in the surface chemical state, including the increase of O/C value, the appearance of N signal, and the increase of reactive groups such as COOH and COH that were favorable for adhesion. The peel strengths of the plasma-treated epoxy resin with bare and low-roughness copper foil were 0.31 N/mm and 0.86 N/mm, and the adhesion was increased by 48% and 43%, respectively, compared with the untreated samples. For the plasma-treated polyphenylene oxide resin, it had peel strength of 0.20 N/mm and 0.63 N/mm for bare and low-roughness copper foil, and the adhesion was increased by 67% and 50%, respectively, compared with the untreated samples. Moreover, the surface morphology characteristics after peeling of the copper foil/resin interface with and without plasma treatment showed obvious differences, which was related to the change in the chemical state of the surface after plasma treatment. More copper particles remained on the resin side after peeling for the copper/epoxy interface with plasma treatment. The copper/ polyphenylene oxide with plasma treatment tended to break from the resin side, and most of the resin was found to remain in the copper particle gaps. The research indicates that plasma treatment can effectively improve the adhesion performance between the low-roughness copper foil and epoxy resin or polyphenylene ether resin, which is attributed to the improvement of the chemical bonding performance of the treated resin surfaces. |
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