Fabrication of conductive patterns by selective electroless plating is a widely studied process in recent years for its advantages of lower waste, simpler process, less pollution and lower cost compared to the traditional subtractive process. But the poor adhesion of the as-fabricated patterns is the prior problem of this process, which limits the thickness of the conductive patterns in sub micrometer range and thus degrades the electrical properties of the patterns. Many chemical and physical modifications have been used to increase the chemical bonding or physical interaction between substrates and deposited metal, but the effects are limited, especially after thick metal is deposited. However, increasing the interfacial mechanical anchor is an effective alternative to enhance the adhesion but has often been neglected. In our previous work, we have developed a novel patterning-adsorption-plating (PAP) process to additively fabricate copper patterns on flexible polymer substrates. In this paper, polystyrene (PS) microspheres are added into the ion-adsorption ink as templates to fabricate three-dimensional (3D) porous polysiloxane films. Thereafter, the as-fabricated copper patterns show excellent conductivity competitive to that of bulk copper and good adhesion with a distinct increase of mechanical anchor.