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Details of Grant 

EPSRC Reference: EP/R021716/1
Title: Self-Healing of Open Interconnect Faults for Reliable Large Area Electronic Systems
Principal Investigator: Sambandan, Dr S
Other Investigators:
Researcher Co-Investigators:
Project Partners:
Department: Engineering
Organisation: University of Cambridge
Scheme: First Grant - Revised 2009
Starts: 01 January 2018 Ends: 31 December 2018 Value (£): 100,520
EPSRC Research Topic Classifications:
Complex fluids & soft solids Electronic Devices & Subsys.
EPSRC Industrial Sector Classifications:
Electronics Information Technologies
Related Grants:
Panel History:
Panel DatePanel NameOutcome
27 Nov 2017 EPSRC ICT Prioritisation Panel Nov 2017 Announced
Summary on Grant Application Form
Open circuit faults in interconnects can occur due to various reasons such as unexpected current spikes (e.g. during electrostatic discharge events), thermal stress, applied mechanical forces and fabrication faults. In the case of large area electronic systems (such as wearable electronics, active matrix systems on rigid and flexible substrates such as displays and image sensors) the occurrence of an open fault could make the system unusable. It is therefore of interest to improve the operational reliability of these systems.

To address this problem several passive and active approaches have been studied. Passive techniques such as adding redundancies, improving interconnect geometries and materials (e.g. meandering interconnects, stretchable interconnects etc.) make the electronic systems more fault tolerant. Active techniques imply the use of self healing mechanisms to completely restore electrical conductivity after the occurrence of the fault. One approach considers the encapsulation of conductive inks in dielectric shells (10.1002/adfm.201000159) embedded in the interconnect during fabrication. Upon the occurrence of an open circuit fault, the fracture in the interconnect also fractures the shells present in the local vicinity of the fault thereby spilling the conductive ink and immediately restoring conductivity. While this method provides a true healing of the fault, a downside is that the interconnect fabrication process flow must be modified to embed the shells.

We propose an alternate means to actively self heal open circuit faults using a dispersion of conductive particles in an insulating fluid. This dispersion is contained and isolated over each interconnect. When a current carrying interconnect experiences an open circuit fault, an electric field appears across the open gap. The field polarizes the conductive particles in the dispersion allowing some of them to chain up due to dipole-dipole attractive forces and create a bridge across the gap thereby healing the fault. The advantages of this approach is that the implementation does not disturb the existing techniques of fabrication of interconnects. The mechanism can be incorporated as an add-on feature.

A proof of concept of self healing using dispersion was demonstrated for printed circuits board (http://aip.scitation.org/doi/10.1063/1.4916513) but not for the much smaller length scales of integrated circuits using in large area electronic systems. The main goals of this proposal are (i) study and model the effectiveness of the self healing as we scale down particle size i.e. how quickly can we heal? how much current can the heal carry? (ii) to implement and demonstrate self healing of open faults at the much smaller length scales of interest on rigid and flexible substrates. (iii) Study the impact of the bending of a flexible substrate on the healing (iv) Implement self healing on integrated circuits used in large area electronic systems (thin film transistors on a rigid substrate) and study the performance of the circuit pre and post heal.

Apart from being of academic interest, this research would great help in developing modern manufacturing techniques that result in electronic circuits that last much longer. A wide variety of faults occurring in a wide variety of systems would benefit from this study eg. opens at solder joints in printed circuit boards, cracks in capacitive touch screen displays, open faults in photo-voltaic cell arrays, faults in foldable displays and wearable electronics etc. Certain critical systems such as health care devices, electronics used in satellites (where thermal stress is significant), electronics used to monitor dangerous or hard to reach environments etc. would operate with improved reliability. The research also has a direct impact on addressing social and environmental problems such e-wastes.
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