Evaluation of application limits for inkjet-printed MIDs

Many factors influence and determine the quality and reliability of inkjet-printed MIDs. Therefore a holistic view and understanding of the process chain is of importance. Even though different limiting factors have been evaluated partly by previous research, a systematic examination on three topics along the whole process chain is presented in this work for the first time. First, the influence of surface roughness on printing quality for a 50% glass fiber reinforced PPA is evaluated. Using DOEmethodology on injection molding parameters the roughness of plate specimen was decreased, whereby width and outline shape of printed lines were improved significantly. Second, limits for the printing process are evaluated. On a ramp with continuous angle of gradient areas where precise printing is possible are defined. Afterwards the precision of printed droplets on coated inkjet-paper for different printing-heights and frequencies is evaluated using a novel method. For the equipment used, a process window for height and frequency was found. Finally, the operating conditions are evaluated by measuring ampacity for single layer conductor tracks (width 0.5 mm and 1 mm). By using a semi-automated novel method increasing current loads are applied on polymer substrates and temperature increase is evaluated using thermographic measurements. For polymers with different thermal conductivity the maximum ampacity and heat spreading are investigated and layout recommendations are given based on the results. The methods used are supposed to be transferred to evaluate other materials and machines.