A Study on Stretchable Electrical Contacting Techniques for Embedded Chiplet Components

This paper presents a comparison of different manufacturing techniques for the electrical contacting of embedded chiplet components within multi-material flexible and stretchable polymers for the fabrication of stretchable electronics to be applied to 3-dimensional surfaces and biological tissue interfaces. Additive manufacturing processes were used to specifically integrate and contact a rigid chip component, such as an LED chip, within a substrate. As a reference for comparing subtractive versus additive technologies, identical LED components were soldered onto TPU substrates with etched copper conductors. In this study, the following additive manufacturing techniques were used to contact the LEDs: screen printing, dispensing, cavity filling using doctor blades, inkjet printing, wire bonding, and soldering. Various technological processes were compared in terms of conductor trace formation, LED contacting, and the pre- and posttreatment of the materials used in order to develop an integration concept for chiplets in flexible substrates towards application on 3D surface as well as for biological tissue compatible (TPU) interfaces.