Testing and validating the lifetime of stretchable electronic circuits

Abstract

Researchers at imo-imomec are using a novel technology consisting of a silicone encapsulation with galinstan traces and small rigid components to produce stretchable electronic devices. This study focuses on testing and validating the lifetime of these devices.

To obtain comparable results, two reference devices were designed: a device containing an LED, and a stretchable wire with contact points for four wire measurements. Subsequently, the devices were produced in batches and exposed to the following stress factors: temperature, humidity, UV radiation, and stretching in accelerated lifetime tests. The performance of the stretchable LED strip was assessed based on the functioning of the LED, while resistance measurements were the prominent parameter for the stretchable wires. During the exposure, both in situ and ex situ measurements and observations were performed.

The LED strips endure 859 cycles of 50% stretch on average. The manageable stretch is reduced by the damp heat test. Failures result from the silicone detachment from the LED which causes trace disconnection from the LED contacts. UV radiation increases silicone stiffness and extends the operation. The lifetime of the stretchable wires was significantly longer, as those devices lasted hundreds to thousands of cycles. Additionally, the resistance of the traces increased both during stretching and during exposure to increased temperature and humidity. However, UV radiation alone did not appear to have any direct effect on trace resistance.