Effect of actual surface area on adhesion strength of copper electroplated on ABS plastic micro-textured by hot embossing

Acrylonitrile-butadiene-styrene (ABS plastic) is one of the most widely used thermoplastic resins for electroplating. In electroplating, a glossing metallic layer is coated on the ABS plastic surface. Yet, the electroplated coating has poor adhesion to ABS plastics. Thus, polymer producers strive to develop more adhesive electroplating grades of ABS plastic. Unfortunately, there is no reliable method to quantify the polymer chemistry-induced adhesion to electroplated coating separately from the interlocking. Herein, the chemical adhesion at the metal-polymer is measured via precision manipulation with the actual surface area of the ABS plastic, without introducing interlocking and chemical modifications. We fabricated 9 moulds with 2, 4 and 6 µm wide and 2, 4 and 6 µm deep pillars, hot-embossed the pillars into ABS plastic, electroplated the ABS plastic with a copper coating, peeled the copper coating to measure the adhesion strength, and observed the micro-textured ABS plastic/copper interface in SEM. We found that the adhesion strength at the ABS plastic/copper interface is linearly proportional to the actual surface area of the texture (1), independent of the non-interlocking texture size (2), and strongly depends on the grade of the ABS plastic (3). The method can be employed to compare the adhesivity of different polymers while developing a new electroplating grade of ABS plastic.