Fine transfer in electrical switching contacts using gold coated carbon-nanotubes

Multi-Walled CNT (MWCNT) are synthesized on a silicon wafer and sputter coated with a gold film. The planar surfaces are mounted on the tip of a piezo-electric actuator and mated with a gold coated hemispherical surface to form an electrical contact. These switching contacts are tested under conditions typical of MEMS relay applications; 4 V, with a static contact force of 1 mN, at a low current between 20 -50 mA. The evolution of contact resistance is considered in a newly developed test procedure. The contact resistance performance is then linked to a study of the contact changes in the surface. The contact surfaces have been shown to exhibit a transfer process over a large number of switching cycles. The continuous monitoring of contact resistance can be used for the identification of surface failure. The results show that for the surfaces presented the contact resistance remains stable for between 80 and 120 million switching cycles. Interestingly the number of bounces is related to the fine transfer failure mechanism.

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“…levels 30-50 mA were dominated by a delamination process but at a current level at 20 mA, the fine transfer process dominated [13][14][15].…”

mentioning

confidence: 99%

The Contact Resistance Performance of Gold Coated Carbon-Nanotube Surfaces under Low Current Switching

McBride

Chianrabutra

Jiang

et al. 2013

IEICE Trans. Electron.

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“…The actuation of the cantilever beam brings the substrate into contact with the goldcoated ball. In this work the contact force was kept constant at 1 mN in line with previous work and values typical for MEMS relays [19][20][21][22]. The load voltage was 4 V; this was switched using a square wave with a frequency of 20 Hz, which gave a contact duration of 25 ms per cycle.…”

Section: Methodsmentioning

confidence: 99%

The Effect on Switching Lifetime of Chromium Adhesion Layers in Gold-Coated Electrical Contacts under Cold and Hot Switching Conditions

Lewis

Down

Chianrabutra

et al. 2013

2013 IEEE 59th Holm Conference on Electrical Contacts (Holm 2013)

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-Gold is commonly used for electrical contacts due to its many desirable electrical and mechanical properties. Throughout the switch lifetime, the contacts are required to survive a large number of opening and closing cycles and therefore it is important to understand the failure mechanisms. Adhesion layers (e.g. chromium or titanium) can be deposited to increase the adhesion of the gold layer to the contact surface. In this work, the inclusion of a chromium adhesion layer shows an improvement of the switching lifetime of gold-coated electrical contacts under cold and hot switching conditions. These testing conditions further the understanding of the failure mechanisms (e.g. fine transfer, etc.). The mechanism of failure when no chromium adhesion layer was used is attributed to delamination of the gold layer from one contact to the other. This failure mechanism is different in the cases where a chromium adhesion layer is included. We present a model which was developed in line with experimental results. These describe the effect of load current on material transfer between gold contacts and the contact failure.

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“…It should be noted that the number of bouncing events closing processes have been neglected from the calculation of the number of cycles. The bouncing events result in a number of opening and closing events occurring per switching cycle [19]. Figure 5: Au-coated silicon substrate after ~600,000 switching cycles, where load current was 50 mA; the contact has failed (top).…”

Section: Pzt Test Rig: Dry-switching Versus Hot-switchingmentioning

confidence: 99%

Development of a MEMS test platform for investigating the use of multi-walled CNT composites electric contacts

Lewis

Chianrabutra

Jiang

et al. 2013

2013 IEEE 15th Electronics Packaging Technology Conference (EPTC 2013)

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The use of gold-coated multi-walled carbon nanotube (Au/MWCNT) composites have been shown to extend the life of electrical contacts, in previous work [1][2][3]. Due to the long lifetimes (which are of the order of 10 6 up to 10 8 cycles [4,5]) the lifetime testing tends to be highly time consuming. In this work we discuss the design and development of an electrostatically actuated MEMS cantilever beam which enables testing at higher frequencies than our previous experimental rig. Following calculations using fundamental cantilever beam equations, a computational model of the designed beam was developed to accurately predict the characteristics of the beam, including the resonant frequency, pull-in voltage and contact force. Where possible the values from the model have been compared with the fabricated MEMS cantilever beam. A MEMS-based electrostatically actuated cantilever beam has been fabricated and incorporated with Au/MWCNT composite surfaces to form a MEMS switch test platform. Initial results show the improved performance over a PZT based test platform.

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Fine transfer in electrical switching contacts using gold coated carbon-nanotubes

Cited by 12 publications

References 6 publications

The Contact Resistance Performance of Gold Coated Carbon-Nanotube Surfaces under Low Current Switching

The Contact Resistance Performance of Gold Coated Carbon-Nanotube Surfaces under Low Current Switching

The Effect on Switching Lifetime of Chromium Adhesion Layers in Gold-Coated Electrical Contacts under Cold and Hot Switching Conditions

Development of a MEMS test platform for investigating the use of multi-walled CNT composites electric contacts

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