Abstract
This study will focus on the drop durability of printed conductive traces that are ubiquitous in Printed Hybrid Electronics (PHEs). There are several methods, such as syringe extrusion printing, inkjet printing, and aerosol jet printing (AJP) to print conductive traces. Silver is a popular material for printing conductive elements due to its low sintering temperature and low susceptibility to oxidation and is the material of study in this paper. Silver conductive elements are usually printed using either AJP or extrusion printing, and these methods will be used in this study.
In this paper, silver traces are printed on 1.6 mm thick FR4 cantilever beams that are dropped with a drop tower at accelerations in excess of 40,000 Gs at room temperature. The silver is printed near the base of the cantilever beam (near the edge clamp fixture) to maximize the strain experienced by the traces. Two sets of samples are prepared with different printing methods: extrusion and AJP. The AJP samples are plated with a layer of copper ink and sintered. The traces are then covered with a printed polyimide layer to increase durability. Flexural strain of the cantilever beam and electrical resistance of the traces are measured in-situ during drop, to monitor the dominant response eigen-modes and resulting damage in the samples. High-speed footage of the drop (at 20,000 fps) is used to measure the tip displacement. Strain and tip displacement measurements are used to calibrate and verify a 3D shell finite element model (FEM) of the drop loading of the cantilever beam. This model is used to predict the strain history in the printed traces as well as the resulting dynamic eigen-modes in the sample, caused by drops at different G-levels. Damage in the silver traces is optically inspected.
The long-term goal is to provide insights into the drop-durability of printed silver traces quantitatively, establish the foundation for a high strain-rate damage model, and provide suggestions to improve the durability of 3D printed electronics using optimization of specimen design features and the printing process parameters.
