Soldering Surface Mount Components Onto Inkjet Printed Conductors on Paper Substrate Using Industrial Processes

This paper describes mounting of standard surface mount component packages on a paper substrate using an industrial solder process with a low-temperature solder. The use of paper as a substrate for printed flexible electronics is becoming more and more widespread as an alternative to the more commonly used plastic substrates, such as polyethylene and polyimide. Paper has the benefits of being environmentally friendly, recyclable, and renewable, as well as inexpensive. It is shown that it is possible to mount standard surface mount device components on paper substrates using low-temperature solder in an industrial soldering process. The contact resistances obtained are mostly low, although the yield of functioning contacts is low. The reason is cracking of the substrate coating layer that goes through the printed silver tracks. It was observed that the cracks appear mostly close to the contact pads, the most likely cause is thermal mismatch between the coating layer and solder and also thermal expansion of the photo paper resin coating. The smallest component package size, 0201, resulted in the highest yield of >80% with decreasing yield for larger package sizes.