Development of very thin coaxial cable using fluorine resin covered with high adhesion electroless copper plating

近来，同轴电缆和印刷电路板需要在GHz频带中具有低介电常数和低介电损耗因子的材料。氟碳聚合物具有优异的高频性能。然而，由于它们的低表面能，很难在它们的表面上形成高粘附性的金属图案。氟碳聚合物在金属化前的表面改性是必不可少的步骤。我们已经提出了一种氟碳聚合物的表面改性技术，通过大气压等离子体处理与液相自组装相结合来增强化学镀铜（Cu）膜/氟碳聚合物的粘附力。本文研究了在中压或常压等离子体改性的四氟乙烯-全氟烷基乙烯基醚共聚物（PFA）表面化学镀铜层的结合强度。大气压He等离子体处理导致通过中压He等离子体处理获得的粘附强度的两倍。通过90°剥离试验后的FTIR分析，从化学镀铜膜表面观察到一个强的红外峰，归属于CF 2键，因此认为中压He等离子体辐照易在PFA基体中形成损伤层。

Recently, a material with a low dielectric constant and low dielectric loss factor in the GHz band is required for coaxial cable and printed circuit boards. Fluorocarbon polymers have excellent high-frequency properties. However, owing to their low surface energy, it is difficult to form highly adhesive metal patterns on their surface. The surface modification of fluorocarbon polymers before metallization is an essential step. We have proposed a surface modification technique for fluorocarbon polymers that enhances the adhesion of electroless copper (Cu) film/fluorocarbon polymers by a combination of atmospheric-pressure plasma treatment with liquid-phase self-assembly. We investigated the adhesion strength of an electroless Cu-plated layer on a tetrafluoroetylene-perfluoroalkylvinylethercopolymer (PFA) surface modified by medium-pressure or atmospheric-pressure plasma. The atmospheric-pressure He plasma treatment resulted in twice the adhesion strength of that obtained by the medium-pressure He plasma treatment. It is considered that a damaged layer is easily formed in the bulk of PFA by medium-pressure He plasma irradiation because a strong IR peak assigned to the CF2 bond was observed from the surface of the electroless Cu film by FTIR analysis after a 90° peel test.