Pads and microscale vias with aerosol jet printing technique

Abstract

Flexible printed electronic circuits find application in many fields including electrical engineering, bioengineering or textronic. Commonly used screen printed circuits, despite their low cost, have simply too wide paths (typical line width is about 100 μm) and require flat substrate. Due to the technical limitations more accurate and sophisticated technique was developed — aerosol jet printing. The possibility to print 3D structures with the line about 0,5 μm thick and 10 μm wide make it even comparable to the expensive, many-staged photolithography. Nevertheless still some important steps are missing to print completely unified microscale circuit with aerosol jet printing technique. One is microvia formation, which is the primary condition to obtain highly dense circuit. The other is external electrical elements assemblage to increase the functionality and application ability. The fulfilment of both gaps will allow to print microscale flexible circuits. Our work presents the essential research of microvia and pad formation made with aerosol jet printing technique. We have tested various pad shapes and sizes suitable for industrial smd elements for lead-free soldering and grade them in the terms of connection strength and resistance. We have located and investigated the break point to define the joint weak point. The SEM images provide the information about the microstructure appearance. The via materialization thickness and its transition resistance shows the connection electrical properties.