Papers by Keyword: Contact Resistance

Abstract: The silver pastes containing Ag₂O powder, Ag powder, α-terpineol, ethyl-cellulose and Pb-free glass were synthesized for crystalline silicon (c-Si) solar cells. It was found that α-terpineol assisted the decomposition of Ag₂O powder and effectively lowered the decomposition temperature of Ag₂O. Ag nanoparticles were produced during the decomposition of Ag₂O, which helped to reduce the sintering temperature of the silver pastes. The Ag₂O-aided silver pastes were fired on polycrystalline silicon solar cells at various temperatures, and large plate-shaped Ag crystallites appeared at the interfaces between the sintered pastes and the emitter, which ensured a good electrical contact. The contact resistivity of Ag₂O-aided silver paste with an optimal ratio of Ag₂O to Ag was lower than that of the paste with pure Ag powder. The lowest contact resistivity of Ag₂O-aided Pb-free silver pastes sintered at 800°C was 0.029 Ω⋅cm², which was close to that of commercial silver paste that contained Pb-based glass (0.026 Ω⋅cm²). The experimental data demonstrated that the addition of Ag₂O reduced the contact resistance and promoted the sintering of Pb-free silver pastes, and Ag₂O-aided Pb-free silver paste could be a promising candidate used for front-contact electrode of c-Si solar cells.

Abstract: In this work, fabrication and characterisation of graphene photodiodes and transfer length method structures is presented. Graphene growth is carried out using a thermal chemical vapor deposition process on copper foils and subsequently transferred onto silicon-dioxide/silicon substrate. Comparison of electrical and optical characteristics of the photodiodes, which are fabricated on both n-type and p-type silicon, is shown. The photodiodes fabricated on n-type silicon show good rectifying behaviour when compared with photodiodes fabricated on p-type silicon. Spectral response of graphene photodiodes is measured to be less than 0.2 mAW^-1 which is attributed to the light absorbance of 2.3% for single layer graphene. Transfer length method device structures are also fabricated and contact resistance is calculated and plotted as a function of spacing between the contacts. The calculated contact resistance (R_cW) is 0.87 kΩ.µm. The latter structures are also characterised under various ambient conditions, before and after annealing. The value of contact resistance reduces from 0.87 kΩ.µm to 0.75 kΩ.µm after annealing. This reduction is attributed to the improvement in bonding between graphene and metal. Measurements under vacuum show an increase in contact resistance which is attributed to the removal of adsorbed water molecules on the surface on graphene. The sheet resistivity of graphene is calculated to be between 1.17 kΩ/□ and 3.67 kΩ/□.

Abstract: Gold-based alloys are widely used in electrical contact environment which requires small contact resistance, and friction pair components consisting of electrical contact has a direct impact on the properties of electrical contact. In this thesis, an experiment of AuNI9 brushes/AuCuAgZn gold sheets in a organization is designed to show the elastic properties of the brush, friction pair wear properties and environmental adaptability of the contact resistance, whose result indicates that the elastic properties of the brushes are stable, alloy sheets mainly produce wear when the brushes and gold sheets are used in matched pair and environmental assessment tests do not significantly increase the degree of wear of the friction pair components in low load condition.

Abstract: Contact resistance is one of the key parameters of main bus bar. The bus performance is decided by the value of Contact resistance. By test of the typical rectangular copper bus-bar, it is analyzed that the effects of force on DC contact resistance. The results show that metal surface contact resistance decreases with the increment of pressure. The resistance is mental nature property, which is determined by material’s performance. At the same time the effect of contact distance is studied in detail.

Abstract: Study on contact resistance is a fundamental content of electrical contact field. The causes of contact resistance are complex, and a reasonable theoretical model poses significant impacts on the study and practical application of contact resistance. This paper describes the generating mechanism and components of contact resistance, highlights the summary on the development of the model, and gives the calculation method of contact resistance in practical engineering application.

Abstract: Keywords: electrical contact lubricant contact resistance sliding wear Abstract. The contacts must be reliable in the required life time under practical application. Reliability means that the contact resistance can maintain low and stable. Au-plated contact pairs have been used widely for weak current connectors due to its well electrical and anti-corrosion performance. The high price of gold forces manufacturers to reduce the thickness of Au-plated while maintaining well performance. Increasing thin of Au plating causes the microporosity to increase rapidly, which has harmful effect on the performance of connectors. Appropriate lubricant coated on contact pair is a solution to improve the contact property. This paper focuses on sliding contact performance of gold plated contact pairs coupon with 0.25 m thickness and lubricated with water based lubricant named lub-E under damp heat and corrosion environment respectively. The contact pairs are also exposed in damp heat, corrosion environment respectively to evaluate the anti contamination property. The sliding experiment is conducted at frequency of 1Hz, amplitude of 1cm, and load of 0.5N, 1.0N and 1.5N. Contact resistance data is gotten in every sliding cycle at the condition of DC current 100mA and limited voltage 1.0V. Scanning electron microscopy (SEM) is used to observe the sliding track morphology and X-ray energy dispersive spectroscopy (EDS) is used to analyze the element.

Abstract: An ohmic contact process by using tri-layer materials for a source contact of a silicon carbide (SiC) metal oxide semiconductor field effect transistor (MOSFET) is proposed. The authors validate its extremely low contact resistance for both n-type and p-type SiC by a simple process. The characteristics of Ti/Al/Si ohmic contacts were measured by using the transfer length method (TLM). We examined the dependence of the contact resistance on the thickness of each layer of Ti/Al/Si. Then, it is found that Ti/Al/Si contacts with an appropriate thickness show excellent ohmic properties for both n-type and p-type SiC. N-type specific contact resistance (ρ_n) of 3.7 × 10^-6 Ω cm² and p-type specific contact resistance (ρ_p) of 1.7 × 10^-4 Ω cm² are obtained with Ti (20 nm) /Al (30 nm) /Si (30 nm).

Abstract: The knowledge of the temperature behavior of Ohmic contacts is an important issue to understand the device operation. This work reports an electrical characterization as a function of the temperature carried out on nickel silicide (Ni₂Si) Ohmic contacts, used both for n-type and p-type implanted 4H-SiC layers. The temperature dependence of the specific contact resistance suggested that a thermionic field emission mechanism dominates the current transport for contacts on p-type material, whereas a current transport by tunneling is likely occurring in the contacts on n-type implanted SiC. Furthermore, from the temperature dependence of the electrical characteristics, the activation energies for Al and P dopants were determined, resulting of 145 meV and 35 meV, respectively. The thermal stability of the electrical parameters has been demonstrated upon a long-term (up to ~100 hours) cycling in the temperature range 200-400°C.

Abstract: This paper mainly studies the effects of low temperature on the reliability of electrical connectors. Based on the theory of constant stress accelerated life test, this paper provides a kind of scheme of low temperature reliability test, which includes magnitude of the temperature stresses, the parameters measured during the test and so on. The detecting circuit is designed; the test is carried out and finally, according to the experimental data, it can be concluded that 1) both the absolute change and the relative change of contact resistance are small for each temperature stress; 2) the forecast data show a tendency toward slightly lower value of contact resistance for each low temperature stress; 3) the lower the test temperature stress, the smaller the value of contact resistance, but the difference in contact resistance is tiny; 4) stress analysis of samples under low temperature is also helpful for correctly evaluating the effects of low temperature on the reliability of electrical connectors.

Abstract: This paper mainly studies one kind of failure prediction method on electrical connectors at high temperature. One scheme of high temperature reliability test was provided based on the theory of constant stress accelerated life test. The test device was designed; the test data was analyzed. It can be seen that 1) both the absolute change and the relative change of contact resistance are small for each temperature stress; 2) there is a tendency toward slightly higher value of contact resistance for each low temperature stress; 3) the higher the test temperature stress, the larger the value of contact resistance, but the difference in contact resistance is not very big. 4) The data prediction method such as the gray theory model is helpful for rapid failure prediction of electrical connectors at high temperature.