Additive Preparation of Conductive Circuit Based on Template Transfer Process Using a Reusable Photoresist

To solve the problems of a conventional subtractive process for preparing conductive circuits, numerous alternative additive processes have been investigated, such as screen or inkjet printing, selective electroless plating, laser-induced forward transfer, etc. They all lead to a simpler procedure, less pollution, and finer line width but are still faced with difficulties like low conductivity and thickness, poor adhesion, and high cost. PDMS is a kind of material with low surface energy, leading to low adhesion with adhesive. Under these circumstances, a simple template transfer process for additively preparing conductive circuits is reported. The process to form the template includes the preparation of a photolithographic mask on the carrier copper foil and adsorption of PDMS anti-adhesion coating. Followed by metal deposition through electroplating on the template, the conductive circuits are transferred to the target substrate. Thus, the designed conductive circuits on various substrates including paper and cloth are formed. The template can be used again after being reimmersed into PDMS anti-adhesion coating. The components and the concentration of the coating are carefully discussed, and the mechanism of anti-adhesion is also researched by EIS and XPS. The copper circuits show a line width of 10 mu m, a peeling strength of 7.11 N/cm, and a resistivity of 1.93 mu Omega.cm, which is similar to that of bulk copper. With low pollution and cost, high versatility, and good electrical and adhesion performance, the template transfer process shows a good application prospect in the large-scale production of flexible electronics like sensors, RFID tags, etc.