A study on a stretchable conductive polymer of thermoplastic automotive device

Abstract

Advance of knowledge in material engineering has introduced stretchable electronic materials which can be stretched, bended or twisted and it is beneficial for consumer product manufacturing. This paper aims to study the effect of process combination of standard printing process in surface mount technology and thermoforming process on a stretchable conductive polymer to form a 3-dimensional electronic device. The polymer comprised of silver particles as fillers was prepared to produce a conductive and stretchable behavior which can withstand high temperature deformation. It was printed on a flat substrate using a screen printing technique and then being thermoformed to produce 3-dimensional shape of automotive rear lighting. Mechanical and electrical performances of the thermoformed product were characterized before and after thermoforming process to study the reliability of LEDs assembly with stretchable circuits. Four point probes instrument was used to measure resistivity of the printed circuit which was elongated due to thermoforming process. The elongation of circuit varied throughout the lighting prototype depending on complex geometry of mould. Conductivity of the circuit was also tested by LEDs illumination. Results of microscopy investigation, x-ray imaging and thermal cycling show good performances of LEDs joints. This new manufacturing process of printed circuit offers a promising future alternative method in manufacturing of 3dimensional electronic device. Keywords— Conductive polymer; printed electronics; thermoforming