Technological development for the reduction of out-of-plane deformation of metallic meander structures in thermoformed electronics

Abstract

This paper presents a novel approach for removing out-of-plane deformation in stretched metal interconnects by adding a fractal structure to the original meander shape and using an optimized fabrication stack. In thermoformed electronics, in cases where copper is used as conductor, the twisting of meander-shaped structures caused by excessive mechanical stress can cause a non-uniform surface, delamination of the metal interconnect from the substrate, and in some cases, a short circuit to the adjacent tracks. Typically, designers of stretchable electronics use various shapes and widths of the copper interconnect to tackle this issue. Using conventional meander shapes such as horseshoes and U-shapes is not universally practical, especially when stretching is higher than 30 percent leading to significant out-of-plane buckling. Limiting this out-of-plane buckling by reducing the track width is not always applicable, as a minimum width is needed from a technology and conductivity perspective. The presented approach is inspired by computational and experimental studies of multiple meander shapes and fabrication methods. A geometry- and fabrication-based approach is presented, reducing the mechanical stress of almost all possible meander shapes by increasing the meander's path length to accommodate the metal track's produced torque during stretching. An analytical approach is provided for calculating the optimal meander parameters and the optimal fabrication stack is achieved based on simulation results. Experiments and finite element modeling for a case study show the improvement in the stress distribution and reduction of out-of-plane buckling.

Methods to Improve Accuracy of Electronic Component Positioning in Thermoformed Electronics

“…Reference source not found. 13 shows the final thermoformed sample. In this experiment, we have used the mold with 60% elongation (same as in the first methodology).…”

“…Over several years, 3D-shaped electronics have become more popular, finding multiple applications in manufacturing, home appliances, and the car industry. A number of methods, including in-mold electronic technology (IME) [1-7], stretchable mold interconnect (SMI) [8][9][10][11][12][13], and 3D-MID [14], can be used to produce curve-shaped electronics. IME is a technique that combines conventional plastic molding with printed conductive inks that are flexible or even elastic on plastic surfaces.…”

Process Optimization of Injection Overmolding Structural Electronics with Regard to Film Distortion

“…This can cause the out-of-plane deformation of the laminated structures, such as the conductive tracks. Madadnia et al [ 8 ] were able to reduce this undesirable deflection by adding a fractal structure to the original meander-shaped conductors.…”

Innovative component positioning method for thermoformed electronics

“…3D shaped electronics have been emerging for several years and have a lot of applications in home appliances, the automotive industry, and manufacturing. Curve-shaped electronics can be manufactured using a variety of technologies, such as In-mold electronic technology (IME) [1][2][3][4][5][6][7], Stretchable mold interconnect (SMI) [8][9][10][11][12][13] and 3D-MID [14]. IME is a method that integrates traditional plastic molding with flexible or even elastic conductive inks printed on plastic substrates.…”