Additive preparation of conductive circuit based on template transfer process using a reusable photoresist.

The widely used lithography and etching process to fabricate conductive circuits is considered to be wasteful, environment harmful and limited in line width. Nowadays, many additive processes have been developed to solve these problems, such as screen printing of conductive paste, inkjet printing of nanoparticle conductive ink, selective electroless plating and laser-induced pattern transferring. However, they respectively face the problems of poor electric property, low precision, high cost, low adhesion, limited in substrate, etc. In this paper, a novel template transfer process was developed to additively fabricate conductive circuits. This process includes two steps: the fabrication of the template and the transfer of the circuit. The template was fabricated by preparing a permanent photoresist on a carrier metal foil, followed by dip-coating of a polysiloxane anti-adhesion nano-layer on the photoresist and the exposed carrier metal area. The nano-layer can reduced the adhesion between the carrier metal foil with the electrodeposited metal film, as well as the adhesion between the photoresist with the adhesive. Afterwards, electroplating was used to deposit metal circuit on the template with designed thickness. The metal circuit can be transferred to the flexible substrate such as PET, cloth, paper, etc. with an adhesive layer for the large adhesion difference between the metal circuit/template and the metal circuit/adhesive interfaces, thus forming the designed conductive circuit. After being re-immersed into the anti-adhesion coating, the template with the photoresist can be reused to prepare the conductive circuit again, significantly reduce the pollution and cost of photolithography. The prepared conductive circuit demonstrates a same resistivity with bulk metal, a high adhesion meeting the industrial standard of FPC, an extremely fine line width of 10 um which has greatly exceeded the limitation of current subtractive process and a low cost without repeatedly photoresist preparation. As a result, the template transfer process shows high potential in the large-scale manufacturing of the conductive circuit with high electrical properties, high adhesion and high precision, such as FPCs, RFID tags, paper electronics, wearable electronics, etc.