Thin film deposition and laser patterning for high volume manufacture of electrical structures

S. Duby, B. Ramsey

The aim of this research project has been to lay the foundation for the development of a generic, low-cost, high-volume, reel-to-reel process for the manufacture of functional electrical thin film structures. There are an increasing number of applications for an effective low-cost integrated production system for patterned conductive thin films, including RFID, large area displays and flexible electrical interconnect. This study however has focused on the manufacture of low-cost thermoelectric devices.

A novel three-step production technique has been developed that allows the manufacture of complete bi-material thermocouple arrays or thermoclusters. This means that entire devices can be manufactured using one reel-to-reel, non-stop processing envelope on a single piece of deposition equipment. This process negates the need for costly and time consuming pattern registration and involves no sacrificial process agents, both of which have been obstacles previously preventing low-cost, high-volume manufacture of these multi-material devices.

Figure 1: Bimetal thermocluster sheets produced by vacuum deposition and laser patterning.

The current climate of increasingly stringent legislation on environmental issues, represented by directives such as WEEE and RoHS implies a sharpening focus on environmental manufacturing techniques. This process could very conceivably provide a significant competitive advantage in terms of compliance with this legislation. There are good prospects that this approach could also complement other disruptive technologies such as carbon based electronics, identified as areas of focus in the recent EIGT report.

Applications of thermocluster arrays are wide and varied and include infrared imaging, process monitoring, airflow measurement for meteorological application or to aid the design of turbine blades or wing sections and the provision of power for autonomous microsystems or medical implants. It is anticipated that a successful low-cost thermoelectric power generation system could find application in sectors as diverse as the electricity generation industry in which large amounts of ‘low-grade’ heat is vented using cooling towers, to the automotive industry, which has already identified the benefits of capturing otherwise wasted engine heat. Much interest has already been expressed in the application of this technology to the capture of solar energy, either by augmenting the output from photovoltaic cells or to generate electrical power from the sun directly. This has particular relevance in a developing world context. One of the project collaborators is actively involved in this aspect of the research and a number of possible applications have been investigated including the accretion of minerals from seawater for the production of artificial coral reefs and the manufacture of carbon-positive building materials.

This work has been a joint collaboration with the Laser Group at Hull University, and has been supported generously by Teer Coatings Ltd.