Improving Performance of Laser-Printed Conductive Silver Lines

Abstract

Within the last decade, large efforts were made to implement digital printing as a production method for printed electronics. Especially in production of thick-film electronics, innovation is pushed forward to overcome the lacks of established screen-printing regarding flexibility and tooling. Besides the numerous approaches in using ink-jet printing for printed electronics, researchers at Helmut Schmidt University already showed huge progress in applying electrophotography (“laser printing”) as a method to print conductive silver lines in order to form a conductive layout for thick-film circuits. Electrophotography is a solvent-free method, able to directly print silver toner onto ceramic substrates, forming a conductive line after firing. Benefits are high speeds and flexibility and a huge potential regarding precision. Now, after the feasibility of the method was proven and even functional conductive layouts like RFID coils were printed, the next steps have to be taken towards developing electrophotography to an applicable method in a thick-film production process. Thus, this paper describes the efforts in improving the method's performance. Different kinds of silver particles are tested towards their possibility of forming a silver toner. The resulting silver lines are examined regarding conductivity and printing precision. Also, surface treatment of substrates is considered as a method to reduce the number of required print cycles. Corresponding tests are performed. Furthermore, different firing profiles are tested towards their influence onto the resulting silver lines. Combining the results of these examinations, the performance of conductive silver lines could be improved significantly.