Processing of nano copper materials for the production of conductive circuits

Dispersions of nano-metals such as copper, silver and nickel allow the production of conductive circuitry using an appropriate printing and curing/ sintering process. This additive approach to electronic circuit manufacture allows large area devices to be manufactured with minimal waste and fewer production steps. The technology has applications in a number of large area markets including PV, EM shielding, smart windows, distributed power systems and large batteries. The dominant material for printed circuitry is silver but this has a cost and resource sustainability limitations. Copper is earth abundant and has the potential to significantly reduce cost but the rapid reactivity of the nano-copper leads to oxidation, destroying the conductivity of the copper. In order to sustain conductivity the nano-copper must undergo a rapid (<1s) controlled nano-particle to bulk copper transition. In this way the kinetics of nano particle coalescence occur more rapidly than the kinetics of oxidation.
The project will examine means by which nano-copper can be deposited and sintered at production speeds which are compatible with volume manufacturing. This will utilize relevant printing process (inkjet, screen and electrostatic deposition) and curing equipment (laser, NIR, UV and pulsed white light). Laboratory studies of macro changes in properties will need to be correlated to changes in the micro structure and composition of the nano-copper. The project will initially target nano-copper materials, but other technologies such as rapid reduction of copper oxide and decomposition of copper complexes may also be within scope. Having produced circuitry, there is also scope for examining the interaction between the copper circuitry and its environment or its interaction with other materials in a device, such as organic conductors. 1. The key objectives/aims of the research. What questions does the project intend to answer?
The project aims to identify and understand the physical and chemical mechanisms which occur during the sintering of nano copper ink. The project will address the inter relationship between the nano copper sintering mechanism and the copper particle size, temperature, kinetic rate of energy input and local gaseous environment. The highly reactive copper nano particles are subject to competing processes physical melting and chemical oxidation, with an ideal transition from a porous nano copper framework to coherent continuous un-oxidized metallic structure. Understanding the impact of material and processing properties on the sintered film is a key objective of the research study.
2. The novel physical sciences/engineering methodology that will be carried out during the course of the project. What will the students be doing?
The project will examine the working envelope of sintering process, through sintering of a selection of materials (variations in particle size distribution) within thermal and gaseous environments (Inert, air and reducing). Printed samples subjected to these sintering environments will be assessed macroscopically in terms of conductivity, adhesion and contact resistance. Identification of mechanisms on a micro scale will be examined using a combination of analytical methods including AFM, XRD, XPS and SEM. The student will also examine high speed sintering processes such as near infra-red, laser and photonic sintering which offer a potential productivity and carbon footprint benefit. Through iterative studies with refinement of methods, the potential of these potentially attractive processes will be examined. This work will focus on glass substrates of 50 x 50 mm to provide a thermally stable (over the 250C range considered).

3. It would be helpful to include a sentence at the end identifying the research area - please select from
The project materials lie within (Materials engineering - metals and alloys) and its interaction with novel Manufacturing technologies with a likely end user in the