Additively Manufactured in-Mold Electronics Reliability Under Thermal Cycling and Sustained High Temperature

Wire harnesses on the automotive platform may account for over 100 lbs of weight in a typical automobile. Significant weight saving can be achieved through the use of inmold electronics for integration of the wire harnesses with the structural body plastic. In this paper, additive process-performance-reliability interactions have been explored for functional in-mold circuits under thermal cycling and sustained high temperatures typical of the automotive platform. A specialized conductible ink designed for forming has been used for printing conductive traces, and the formable substrates used for this study are polyethylene terephthalate glycol (PETG) and polycarbonate (PC). The conductible ink printing has been achieved via direct-write and screen printing, and the samples have been thermoformed using a vacuum thermoforming system. For each of the print platforms, the interaction of process parameters and realized performance has been studied. The component attachment processes established for the individual substrates were then used to fabricate functional circuits, including integrator, differential, active low pass filter, and voltage-controlled oscillator. The impact of thermoforming on the realized performance, stability, and reliability has been explored. Functional circuits have been subjected to automotive environments of Grade-3 thermal cycling and sustained high temperatures. The performance, stability, and reliability of the circuits have been quantified. Circuit performance has been studied for encapsulated and unencapsulated circuits. The novelty of the presented work is the examination of process-performancereliability interaction for in-mold electronics under automotive extremes of grade- 3 sustained high temperature and thermal cycling. Process recipes for achieving grade- 3 reliability have been demonstrated. Both elements are previously unexplored.