Investigation of the Surface Adhesion Phenomena and Mechanism of Gold-Plated Contacts at Superlow Making/Breaking Speed

Surface adhesion phenomena of gold-plated copper contact materials are studied in conditions of nonarc load (5/15/25 V and 0.2/0.5/1 A) and superlow speed (25 and 50 nm/s) realized by a piezoactuator during the making and breaking processes. It is shown that softening and melting of local asperities leads to interface adhesion, which results from the joule heat generated by the contact resistance; it is determined that the change of contact force with time obeys the negative exponential distribution and the time constant is associated with the adhesion force directly. Based on the fitting experimental data, the relationship between the adhesion force F z and the contact resistance R d while breaking can be expressed as F z ∝ R d -1 , which indicates that the main component of contact resistance is the bulk resistance of weld nugget and the constriction resistance is negligible

Observation and Understanding of the Initial Unstable Electrical Contact Behaviors

Reliable and long-lifetime electrical contact is a very important issue in the field of radio frequency microelectromechanical systems (MEMS) and in energy transmission applications. In this paper, the initial unstable electrical contact phenomena under the conditions of micro-newton-scale contact force and nanometer-scale contact gap have been experimentally observed. The repetitive contact bounces at nanoscale are confirmed by the measured instantaneous waveforms of contact force and contact voltage. Moreover, the corresponding physical model for describing the competition between the electrostatic force and the restoring force of the mobile contact is present. Then, the dynamic process of contact closure is explicitly calculated with the numerical method. Finally, the effects of spring rigidness and open voltage on the unstable electrical contact behaviors are investigated experimentally and theoretically. This paper highlights that in MEMS systems switch, minimal actuation velocity is required to prevent mechanical bounce and excessive wear

High-Throughput Measurement of the Contact Resistance of Metal Electrode Materials and Uncertainty Estimation

Low and stable contact resistance of metal electrode materials is mainly demanded for reliable and long lifetime electrical engineering. A novel test rig is developed in order to realize the high-throughput measurement of the contact resistance with the adjustable mechanical load force and load current. The contact potential drop is extracted accurately based on the proposed periodical current chopping (PCC) method in addition to the sliding window average filtering algorithm. The instrument is calibrated by standard resistors of 1 mΩ, 10 mΩ, and 100 mΩ with the accuracy of 0.01% and the associated measurement uncertainty is evaluated systematically. Furthermore, the contact resistance between standard indenter and rivet specimen is measured by the commercial DMM-based instruments and our designed test rig for comparison. The variations in relative expanded uncertainty of the measured contact resistance as a function of various mechanical load force and load current are presented

Modeling and Experimental Verification of Material Welding Characteristics for Low Current Switching Devices

Material welding failure considerably influences the electrical lifetime and reliability of low current switching devices. However, relevant studies on methods for calculating the threshold welding current and welding area under milli-Newton scale load forces are very limited. In this paper, the welding characteristics of metal material, including the threshold welding current, welding area and welding force are studied by using theoretical calculations and experiments. The comparison between the theoretical calculation and experimental results shows the accuracy of the built model. Further, the effects of mechanical load force and load current on welding force and welding area of representative metal materials are investigated. It is found that the anti-welding ability of metal materials depends not only on the exerted load force and current, but also the electrical resistivity, the thermal conductivity, the tensile strength, and the melting temperature of the materials

On the Relationship between Contact Resistance and Load Force for Electrode Materials with Rough Surfaces

Higher contact resistance not only increases power consumption and temperature rise but also causes undesirable interconnectivity between electrode materials, which further influences the electrical lifespan and reliability of switching devices. However, relevant studies on the relationship between contact resistance and load force, and on the reduction of contact resistance by controlling the micro-structure of rough surfaces, especially for electrode materials with larger Sq (root mean square) values, are very limited. In this study, the contact resistance calculation method, based on classical Holm theory in combination with the elastic and plastic deformation, was reviewed. Then, typical curves of measured contact resistance and load force were analyzed and compared with the calculation results for smooth surfaces. Furthermore, experimental results for electrodes with bright and matt surfaces were compared. It was found that the average contact resistance of samples with matt surfaces was 0.162 mΩ for a load force of 5 N, which decreased by 18.52% compared to that of the bright surface. The standard deviation of the contact resistance greatly decreased to 0.008 mΩ for samples with matt surfaces, which indicated that the matt electrode surface could effectively produce low and stable contact resistance. In addition, the influences of the numbers and sizes of contact a-spots on the relationship between contact resistance and load force were investigated. It was found that denser asperities with smaller curvature radii for the matt surface were beneficial for lower contact resistance, even for the electrode material with larger Sq values. Finally, an empirical model of the contact resistance with error bands based on the experimental results was established and verified