Contacting Inkjet-Printed Silver Structures and SMD by ICA and Solder

Digitally printed conductive structures often need to be electrically connected to batteries, microcontrollers, or other devices. A consensus of industry and research is that such hybrid printed electronics will play a major part in the future of printed electronics. To promote the technology of hybrid printed electronics, surface mount technologies for electronic components using isotropic conductive adhesives (ICAs) and low melting tin bismuth solders on inkjet-printed silver structures on injection molded liquid crystal polymer (LCP) substrates were investigated in this publication. The special needs for inkjet-printed electronics were considered as well as the reliability of assembled surface mounted devices (SMDs) and their failure mechanisms. Connected 0603 and 1206 SMD components achieved a characteristic fatigue life of more than 3500 cycles during thermal cycling at +125 degrees C/-40 degrees C and withstood over 1000 h under a damp-heat atmosphere of +85 degrees C/85% RH. The coefficient of thermal expansion (CTE) of the substrate and the selection of solder have major impacts on the reliability of the assemblies.