A review of conducting polymers in electrical contact applications

A review of recent developments in fretting studies in electrical contacts is presented, focusing on developments in conducting polymer surfaces. Fretting is known to be a major cause of contact deterioration and failure; commonly exhibited as the contact resistance increases from a few milliohms, in the case of a new metallic contacts, to in excess of several ohms for exposed contacts. Two technologies are discussed; firstly extrinsically conducting polymer (ECP), where highly conductive interconnects are formed using metallized particles embedded within a high temperature polymer compound, and secondly; intrinsically conducting polymers (ICPs) are discussed. These latter surfaces are new developments which are beginning to show potential for the application discussed. This paper presents the work on the ICPs using poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) (PEDOT /PSS) and its blends from secondary doping of dimethylformamide (DMF)PEDOT/PSS. Two different processing techniques namely dropcoating and spin coating have been employed to develop test samples and their functionality were assessed by two independent studies of temperature and fretting motion. The review leads to a number of recommendations for further studies into the application of conducting polymers for contacts with micro-movement.<br/

Low force electrical switching using gold coated vertically aligned multi-walled carbon nanotubes surfaces

Gold coated vertically aligned multi-walled carbon-nanotubes (Au/MWCNT) surfaces are investigated to determine the electrical contact performance under low force conditions with repeated load cycling. The multi-walled CNT's are synthesized on silicon planar and sputter coated with a gold film. These planar surfaces are mounted on the tip of a PZT actuator and mated with a coated Au hemispherical probe. The load is typical of MEMs devices, with a 4V supply, 1 and 10mA current, and applied force of 1mN. The contact resistance (Rc) is monitored with the repeated loading cycles (over 1000 and a million cycle) to determine reliability and durability testing. The surfaces are compared with a reference Au-Au contact under the same experimental conditions. This study shows the potential for the application of CNT surfaces as an interface in low force electrical contact applications

Evaluation of the volumetric erosion of spherical electrical contacts using the defect removal method

Volumetric erosion is regarded as a significant index for studying the erosion process of electrical switching contacts. Three-dimensional (3-D) surface measurement techniques provide an approach to investigate the geometric characteristics and volumetric erosion of electrical contacts. This paper presents a concrete data-processing procedure for evaluating volumetric erosion of spherical electrical contacts from 3-D surface measurement data using the defect removal method (DRM). The DRM outlined by McBride is an algorithm for evaluating the underlying form (prior to erosion) parameters of the surfaces with localized erosion and allowing the erosion characteristics themselves to be isolated. In this paper, a number of spherical electrical contacts that had undergone various electrical operations were measured using a 3-D surface profiler, the underlying form parameters of the eroded contacts were evaluated using the DRM, and then the volumetric erosions were isolated and calculated. The analysis of the correlations between the volumetric erosion and the number of switching cycles of electrical operation that the contacts had undergone showed a more accurate and reliable volumetric erosion evaluation using the DRM than that without using the DRM

Gold coated carbon nanotube surfaces as low force electrical contacts for MEMS devices: part 1

An experimental investigation of a gold coated vertically aligned carbon nanotube surfaces is undertaken to determine the limits of the electrical contact performance over a large number of switching cycles under low force conditions and with current loading (1mA-50mA at 4V). The multi-walled CNT’s (MWCNT’s) are synthesized on a silicon planar and sputter coated with a gold film. The planar surfaces are mounted on the tip of a PZT actuator and mated with a coated Au hemispherical probe. The electrical load is selected to reflect typical MEMs relay loads with a 4V supply, 1 and 10mA current load with an applied force of 1mN. The surfaces tested maintain a stable contact resistance over 106 switching cycles. To determine the limits, the contact force is increased to 3mN under dry circuit conditions and the current increased at the 1mN load to 20mA-50mA. The surfaces are compared with a reference Au-Au contact under the same experimental conditions. For the surfaces investigated the current loading limit was determined to be 20mA where the contacts failed after 50x106 cycles

Degradation of road tested automotive connectors

The automotive environment is particularly demanding on connector performance, and is characterized by large temperature changes, high humidity and corrosive atmospheres. This paper presents an initial study of connector performance in terms of temperature profiles taken from road vehicles. The temperature profiles are then simulated using empirical relationships to allow prediction of connector performance. Wire harnesses have been investigated to seek evidence of the connector degradation predicted from the temperature data. Initial indications are that the wire harness shows the type of fretting behavior associated with the temperature changes. Evidence of fretting corrosion was found at the contact interface on tin plated terminals from sealed and unsealed connectors

Motion studies of high current arcs using an optical fibre array imaging system

This paper presents an integrated portable measurement system for thestudy of high speed and high temperature unsteady plasma flows such as thosefound in the vicinity of high current switching arcs. The system permits direct andnon-intrusive measurement of arc light emission images with a capture rate of 1million images per second (1MHz), and 8 bit intensity resolution. Novel softwaretechniques are reported to measure arc trajectories. Results are presented on singlehigh current (2kA) discharge events where the electrode and arc runner surfaces areinvestigated using 3D laser scanning methods; such that the position of the arc rootson the runner can be correlated to the measured trajectories. The results showevidence of the cathode arc root stepping along the arc runners<br/

Motion studies of high current arcs using an optical fibre array imaging system

This paper presents an integrated portable measurement system for thestudy of high speed and high temperature unsteady plasma flows such as thosefound in the vicinity of high current switching arcs. The system permits direct andnon-intrusive measurement of arc light emission images with a capture rate of 1million images per second (1MHz), and 8 bit intensity resolution. Novel softwaretechniques are reported to measure arc trajectories. Results are presented on singlehigh current (2kA) discharge events where the electrode and arc runner surfaces areinvestigated using 3D laser scanning methods; such that the position of the arc rootson the runner can be correlated to the measured trajectories. The results showevidence of the cathode arc root stepping along the arc runners<br/

Motion studies of cathode roots in high current arcs using an optical fibre array based imaging system

This paper presents an integrated portable measurement system for the study of high speed and high temperature unsteady plasma flows such as those found in the vicinity of high current switching arcs. The system permits direct and non-intrusive measurement of arc light emission images with a capture rate of 1 million images per second (1MHz), and 8 bit intensity resolution. Novel software techniques are reported to measure arc trajectories. Results are presented on single high current (2kA) discharge events where the electrode and arc runner surfaces are investigated using 3D laser scanning methods; such that the position of the arc roots on the runner can be correlated to the measured trajectories. The results show evidence of the cathode arc root stepping along the arc runners, and regions of where the arc runner is eroded by a stationary arc

Numerical analysis of switching performance evaluators in low-voltage switching devices

An arc modelling is a valuable and useful tool to evaluate the switching performance of low-voltage switching devices (LVSDs) during breaking operation before testing real products. Moreover, it helps improve interruption capability of LVSDs and optimize them. This paper focuses on the numerical simulation of the arc behavior in AC devices before zero current and prediction of the re-ignition after current zero based on the simulated arc voltage. The 3-D arc modelling is based on the conventional magnetohydrodynamics theory and it considers the motion of a contact, arc root, radiation and air properties which vary with the temperature and pressure