At the 7th MID Day on the 10th of August 2022 you can expect two exciting presentations from the MID world. The online event starts at 4 PM (CEST) and is open to everyone free of charge. Each presentation will last about 20 minutes and will be accompanied by a discussion.
First, Dr. David Bowen from the Chair Laboratory for Physical Sciences of the University of Maryland, USA will give the talk “Laser Direct Structured Circuits on Silicone”.
Silicone rubber is a remarkable material, known for high-temperature resistance and chemical inertness, but most interestingly for its elastomeric properties. Silicone applications include biocompatible sensors, soft robotics, sensitive mechanical sensors, and mechanically tunable devices. There is a strong desire to integrate electronics within silicone structures for these applications using a direct-write method, but silicone has low surface energy, making it difficult for direct ink writing inks to adhere. In this presentation, the research into using the laser direct structuring (LDS) process on highly-flexible silicone (Smooth-On Ecoflex 00-30) doped with copper chromite to form copper circuits will be discussed. With laser micro roughening and chemically grown copper, LDS traces will have superior adhesion while being highly conductive and solderable. Minimum process parameters such as doping level and average laser power will be presented. Mechanical properties such as elastic modulus and peel strength were measured to increase with doping level. Representative traces were mechanically tested to determine breakage strain and maximum 60% elongation cycles. Meander and Hilbert fractal inductors were fabricated and their inductance measured, pre and post strain. A hemispherical helical trace was fabricated on a silicone bowl to demonstrate 3D fabrication capability. Preliminary examples of LDS traces on silicone-impregnated fabric will also be presented.
Maximilian Kneidl from the Chair of Manufacturing Automation and Production Systems (FAPS) at FAU Erlangen-Nuremberg will then present the research project „INFINITE“ – Integrative functional expansion in electrical engineering for the automated production of intelligent insulation systems.
As part of the increasing electrification of the mobility sector, the demands on the electric drive are rising both in terms of performance and efficiency and on the production system in terms of the quantities to be output. The insulation system is becoming the limiting factor here, as it limits the operating point of a machine thermally and electrically. Current insulation processes take up a significant proportion of the total production time of a stator, with a lead time of around 40 minutes.
Within the insulation process, thermoset injection molding reveals new, previously untapped potential in the field of electromobility. On the materials side, thermoset compounds allow better mechanical and thermal properties through targeted modification compared with previously used resin systems. On the process side, injection molding can achieve higher reproducibility during processing than conventional casting methods and thus improved component quality, while at the same time reducing process time.
The research objective is to enable a thermoset injection molding process for the insulation of stators for electric motors. Material advantages and the degrees of freedom of the process are to be used to produce an optimized insulation system with reduced process time compared to conventional processes. In an iterative development process, suitable thermosets will first be selected, modified and characterized in preliminary tests. Demonstrators will then be produced and validated in accordance with the requirements for component preparation.
The research results will enable medium-sized companies in the field of plastics technology to transfer key technologies to electromobility and sustainably secure value creation and employment in Germany.
Figure 1: Composite figure of a spiral circuit on a silicone shell; Source: Laboratory for Physical Sciences at the University of Maryland, USA
