New developments for highest integration density in Polymer Thick-film Technology

The development of innovative electronic devices is characterized by increasing demands with respect to functionality, further miniaturization, high reliability and simultaneously lower manufacturing costs. The study of Polymer Thick-film Technology (PTF) regarding improvements in print resolution and conductivity demonstrates its potential for an application in microelectronics. Polymeric thick-film technology is implemented in the production of electronic circuits since the 50psilas. It was primarily used in the production of cost saving hybrid circuits. However the used materials in the past did not match the now common specifications regarding thermal properties and migration behaviour. Now the requirements regarding resolution, material cleanness and reliability are unlikely higher. Therefore different materials and processes of this technology are described. Particularly the screen-printing of polymer pastes filled with silver particles is characterized. While the minimal line width of thick-film circuits was 120...200 mum 10 years ago, one now is capable to reduce line width to fewer than 100 mum. But line widths with a pitch fewer than 120 mum are necessary for a wafer level package because of always increasing requirements regarding the number of chip connections. Today we already find thick-film circuits with line resolutions smaller than 30 mum. With an additional process step not only the conductivity but also the reliability of such printed structures can be improved. Surface topography, shear strength and electrical parameters (square resistance, impedance and current carrying capacity) were determined using various methods. The conducted studies in fine-line screen-printing of polymer pastes could demonstrate that the normally used thin-film technology for wafer level redistribution can be replaced in low-cost applications.