Evaluation of printing parameters and substrate treatmet over the quality of printed silver traces

Abstract

Printed electronics provide a promising potential pathway towards the design of low cost products. Manufacturing electronic devices by printing techniques using nano-size material particles at low temperatures can revolutionize the electronics industry in coming years. Products based on printable electronics might include ultra cheap radio-frequency identification tags (RFID), inexpensive and disposable displays/electronic paper, interior connections, parts of electronic assemblies (e.g. PWB and phone chassis), sensors, memories, and wearable user interfaces. Moreover, PWBs could be replaced by an inkjet printed substrate. Direct printing of nanoparticle inks could also be used for the electrical interconnection of components (traces). Considering this scenario, the challenge is to provide sufficient quality of interconnecting traces considering the selection of appropriate material, more precise material deposition process and sintering. Adequate process control would lead to suitable electrical conductivity of printed interconnections.In this work the influence of the printing parameters - such as ink temperature, cartridge ink height and the plate temperature (surface over which the substrate that receives the ink is fixed) - in the print quality were evaluated. These parameters are very important in order to obtain conductive traces with good resolution and reproducibility. Another important factor is the treatment of the substrate. It also defines the quality and resolution of the traces since the chemical interaction between the ink and the surface (defined by the surface energy) determine how the ink will spread over the substrate. An optimized surface can be obtained by seeking the best relation between the metal trace adhesion and trace resolution. The surface treatment can be made in different ways aiming at an optimal value for the surface energy. Common surfaces treatments are plasma, corona treatment, and chemical treatment. In this work, polyimide substrates were submitted to surface treatment using corona and a chemical solution. The surface energy was evaluated and an optimum surface energy value was determined.