Interconnecting embroidered hybrid conductive yarns by ultrasonic plastic welding for e-textiles

Abstract

This article presents a novel approach for the electrical interconnection of embroidered conductive yarns with each other at defined cross-points using ultrasonic spot welding. The electrically conductive yarns are made of silver-coated copper microwires plied with polyester filament fibers into a hybrid embroidery yarn. In this study we evaluated the influence of different material properties (number of microwires of conductive yarn, fabric substrate, and adhesive film), the embroidery designs of contact pads, and the main parameters of the welding process (energy, force, amplitude, and tools) on the welded interconnection. The results were evaluated by the process yield and the contact resistance of the welded contacts. The electrical contacts were then tested for long-term reliability (elevated temperature and humidity, temperature shock change, bending, washing and drying) and analyzed. In addition, the contacts were examined with scanning electron microscopy (SEM) and micro-computed tomography and in the form of cross-sections with optical and SEM techniques to discuss interconnection and failure mechanisms. The results show that ultrasonic spot welding can enable the production of highly reliable interconnections of textile-integrated conductive yarns with contact resistances of a few milliohms that are resistant to mechanical, environmental, and washing conditions, leading to potential new manufacturing processes of e-textiles.

Porous Conductive Textiles for Wearable Electronics

“…Strategies have been proposed to reduce the heat stress from the adhesive-bonding process in order to minimize any potential damage to heat-sensitive textiles. For example, Dils et al 756 employed ultrasonic spot-welding for the electrical interconnection of embroidered conductive yarns with each other at defined cross-points. A welding tool was used to transfer the vibration energy from the welding machine and apply the pressing force of the machine to the crossing contact area.…”

Wearable textile antennas: investigation on material variants, fabrication methods, design and application

“…This joining process is frequently found in the literature: for example, in Micus et al (2021) a method is presented to connect wires for cable-based applications to the functional textiles by ultrasonic welding. The authors in Dils et al (2022) focused on the realization of stable, low-impedance electrical contacts between crossing hybrid conductive yarns by ultrasonic spot welding (Fig. 4b).…”

“…In the course of these experiments (Micus et al, 2021;Atalay et al, 2019;Dils et al, 2022) some results appeared, which are to be considered depending on the application. Contact resistance is one of the crucial quantities in the analysis of electrical contacts.…”

Novel SMD Component and Module Interconnection and Encapsulation Technique for Textile Substrates Using 3D Printed Polymer Materials

“…An effort has been made to transfer this technology to e-textile; however, due to textile substrate low-temperature resistance, dimension instability, large areas of character, and poor wettability, textile-based conductors create difficulties that limit the soldering in e-textile applications. There are other interconnection techniques that are more compatible with textiles (Table 2), such as sewing of electronic modules on flexible polyamide foil by conductive yarns [27,28], manual low-temperature soldering by bismuth solder [29,30], ultrasonic welding [31][32][33], resistance welding [34], and joining by conductive or nonconductive UV-cured and melt adhesives [35][36][37] conductive silver-plated hook and loop strips [25,36,38], snap fasteners [39][40][41], the 3D-printed press-fit socket using filaments filled by carbon [42], etc. However, all these techniques also have certain weaknesses, such as the instability of electrical contact resistance based on the gradual loosening of fibers of yarns of sewed contacts, increasing electrical resistance due to the silver tendency to peel off quickly out of hook and loop strips, the high electrical contact resistance of carbon-filled filaments for 3D printing, cost of adhesives, or the risk of some electrical components becoming damaged during ultrasonic welding interconnection process.…”