Showing papers on "Contact resistance published in 1976"

About Some D-C Conduction Processes in Carbon Black Filled Polymers

Abstract: The conductive properties of carbon black filled polymers have already found many qualitative applications while quantitative ones remain infrequent because of the number of unexpected parameters which influence the conductance of samples of the material. We have tried to connect the anomalous electrical behaviour of such materials with three particular phenomena which influence d-c conduction: –Percolation, which is a process expected to occur in mixtures of conducting and insulating solids. –Volumic polarization and ionic heterocharge near the electrodes which supply a new explanation for the variable contact resistance. –Filamentary conduction and localized thermal effects which produce under some conditions, regions of negative resistance in the current-voltage characteristics of samples. Possible electrical applications for filled polymers are deduced from this analysis.

Effect of the electric arc and the ambient air on the contact resistance of silver, tungsten, and silver-tungsten contacts

Abstract: Contact pairs of Ag, W, and Ag‐W were operated 6000 times in a 20‐A 110‐V ac circuit. The effect of contact‐resistance change was observed by measuring the temperature rise (TR) at the fixed contact while passing the steady‐state 20 A. The TR was measured before the switching had begun and after each 1000 operations. A large number of contact pairs were used in order to ensure a good statistical interpretation of the data. The chemical composition of the contact surfaces was measured using a Debye‐Scherer x‐ray analysis. The distribution of contact resistance for Ag contacts remained the same throughout the experiment. For W contacts, the distribution was initially higher than that for Ag: the result of conductivity and hardness differences. During the switching experiments, the formation of tungsten oxides on the contact surface resulted in high contact‐resistance values. For Ag‐W, the distribution was initially closer to that for Ag contacts: the result of a thin surface layer of Ag on the Ag‐W. During ...

1/f noise measurements for characterizing multispot low-Ohmic contacts

Abstract: The patchiness of contacts can be determined from measurements of 1/f noise and contact resistance on a number of contacts of different diameters made by the same method. If a contact consists of k conducting spots with average radius a, k and a can be determined if the distance between the spot centers is at least 2.5 times the spot diameter. Using the developed multispot contact model, the results of the 1/f noise analysis are in good agreement with multispot parameters obtained from microscopic investigations.

Electrical plug-type connector

Abstract: To provide low contact resistance, long life, and resistance against tarnishing under corrosive, particularly sulfur atmospheres, a substrate carrier has a layer of palladium applied thereto, of a thickness between 0.5 and 5 μm, preferably between 1 and 3 μm, to which a coating of gold is applied which is porous and has a thickness of only between 0.05 μm and 0.1 μm; the porous gold coating forms islands of gold on the palladium which, in use and as the terminal is wiped against a counter element, smears over the palladium, thus effectively covering the palladium, preventing tarnishing, and maintaining low contact resistance throughout the useful life of the terminal element.

Fabrication and Thermal Stability of W‐Si Ohmic Contacts

Abstract: W‐Si ohmic contacts have been fabricated using rf‐sputtered W and bulk‐doped n‐ and p‐type Si. The investigated doping range is for B (p‐type) and for As (n‐type); with corresponding contact resistance ranging as and , respectively. Steam‐grown and deposited oxide were used as the mask to study the effect of impurity redistribution during steam oxidation on contact resistance. Chemical (100:1 buffered ) and sputter etch cleaning were used to remove the native oxide from contact windows before W deposition. Metallurgical and electrical stability of these contacts was studied up to ~830°C. The unannealed contacts (using steam oxide mask) are ohmic if the Si has >1019/cm3 As but the minimum B needed is ~1020/cm3. This difference stems from two reasons: (i) B is lost from Si during steam oxidation whereas As concentrates in Si; (ii) the native oxide growing on p‐Si seems to be electrically quite different from that on n‐Si. Contacts improve with anealing up to ~800°C (1 hr treatments), but if higher temperatures are used high resistance or "opens" may occur. Sputter etching is found to be more effective in cleaning the contact windows than the chemical cleaning.

Ohmic contact to p-type GaP

Abstract: A study was made of the contact properties of a AuBe eutectic and a AuBeNi alloy on p -type GaP. The specific contact resistance varied from 1 × 10 −3 to 7.5 × 10 −5 ω cm 2 in the acceptor concentration range of 9 × 10 16 to 2 × 10 18 cm −3 . In the sintering temperature range resulting in good ohmic behaviour and low contact resistance the AuBe contacts do not form drops, whereas the AuBeNi contacts became molten; even after melting they wetted the surface of the GaP well. At the temperature of sintering Be diffuses from the contact into the GaP. The diffusion of Be gives rise to an additional acceptor concentration of 5 × 10 18 to 1 × 10 19 cm −3 beneath the contact surface. Taking this into consideration the concentration-specific contact resistance relationship appears to support a field emission FE conduction mechanism.

Silver-Ruthenium Dioxide Contacts

Abstract: This paper describes the development of a novel electrical contact material, silver-ruthenium oxide, for use in light duty switching applications where low contact resistance values must be maintained. Material fabrication and contact resistance behaviour after exposure to a tarnishing atmosphere are described. An explanation for the low contact resistance values obtained for silver-ruthenium dioxide in comparison with pure silver is offered.

Low temperature ohmic contacts to gallium arsenide using In and Al

Abstract: A method of making ohmic contact to n-type GaAs by means of micro-alloying at 320°C for 90 s, resulting in a specific contact resistance of approximately 0.1 Ω.cm2is described. This technique involves an aluminum overlay which prevents puddling and thus maintains contact geometry. Such contacts, having a relatively high specific contact resistance, have the advantage of being formed by low temperature micro-alloying for short times.

The use of Ag-W-CdO and AgSi 3 N 4 as Contact Materials

Abstract: Three different contact combinations were investigated: (a) Ag-W operated against Ag-CdO, (b) Ag-W-CdO contact pair, (c) Ag-Si 3 N 4 contact pair. A hot pressing technique was used to make the contacts for (b) and (c). The contacts were tested by switching a 20 A, 110V circuit and then examined using a Scanning Electron Microscope. It was found that: (a) The Ag-W vs Ag-CdO produced a high resistance contact pair which was the result of migration of a W layer onto the Ag-CdO contact. (b) The high temperature arc roots caused the W to reduce the CdO in the Ag-W-CdO contact material, which led to severe contact erosion and degradation. (c) The Si 3 N 4 dissociated in the switching arc and the Si formed a SiO 2 layer on the contact surface, which would eventually lead to a high contact resistance. These results are discussed in terms of the thermodynamics of the material combinations and their interaction with the switching arc.

Method of detecting heater resistance independent of contact resistance

Abstract: A constant current is applied through a heater by means of an electrical connector which mates with terminal pins of the tube. The applied current causes a voltage across the heater. A first voltage measurement is made across the heater at a first time. After a predetermined time interval has elapsed, a second voltage measurement is made across the heater. The value of the first voltage measurement is substracted from the value of the second voltage measurement and the value of the difference obtained is compared with a predetermined reference value. If the difference value is less than the reference value, a first nominal value of heater resistance is indicated. If the difference value is greater than the reference value, a second nominal value is indicated. The nominal heater resistance values are detected independent of the electrical connector contact resistance.

Technique for stabilizing contact resistance of gold plated electrical contacts

Abstract: A technique is described for stabilizing gold plated electrical contacts wherein the contacts are treated with an oxidizing agent at elevated temperatures, so resulting in a contact structure which does not evidence resistance drift during subsequent thermal aging. Additionally, the technique may be used to reduce the contact resistance of thermally aged contacts which were not subjected to the foregoing preparative process.

Method of calculating the thermal resistance of a contact between metal surfaces

Abstract: The physical nature of the thermal resistance at a contact between rough metal surfaces is considered. By analogy with the thermal resistance of a plate having a variable cross section and also by analogy with the identical form of Ohm's and Fourier's laws, an expression is derived for the thermal resistance of such a contact. Experiments are carried out to determine the thermal resistance of a contact in vacuo and in air. These investigations show that the calculated values of thermal contact resistance are in satisfactory agreement with experiment.

An experimental study of the electrical properties of the contact between two similar semiconductor crystals

Abstract: Electrical measurements on pressure contacts between pairs of semiconductor crystals are reported with a view to understanding the properties of grain-grain contacts in powdered semiconductors. The materials used were Ge and GaAs, their surfaces being prepared chemically and exposed to room atmosphere. It is thus necessary to consider three contributions to the contact resistance-bulk spreading resistance, oxide film resistance and semiconductor surface barrier effects. By studying the contact resistance, shape of current voltage curves and the a.c. impedance, and comparing semiconductor-semiconductor and semiconductor-metal contacts, the following conclusions were reached: (i) for GaAs and light doped n-Ge surface barrier effects are dominant; (ii) for lightly doped p-Ge bulk spreading resistance is probably the controlling factor; (iii) for heavily doped p-Ge and oxide resistance is important.

Low resistance contacts for semiconducting ceramics

Abstract: A method of applying low contact resistance ohmic electrodes to semiconducting polycrystalline oxide ceramics is described. The electroding technique involves ultrasonically soldering indium or an indium alloy to the ceramic. The technique produces a low resistance ohmic contact which does not age and remains stable over a wide temperature range.

4Π space radiation of solar cells

Abstract: A study was conducted to evaluate the performance of various solar cell types exposed on both surfaces to isotropic irradiation by protons and electrons which approximate the effects of space irradiation. In addition to the normal damage mechanism of lifetime degradation in the base region, another important damage mechanism of series resistance increase was produced by the particles incident from the rear. This damage is produced in the contact region by the low-energy, or high-angle-of-incidence particles which penetrate only this far. The series resistance increase is at least as important as the lifetime degradation in causing the maximum power to degrade. An effective hardening technique is to p+-dope the back surface so that a higher fluence is required to remove enough carriers that the contact resistance increase becomes significant. On the other hand, lithium-doping of the cells hardens those irradiated from the front only by producing defects that are not as effective as the normal ones in degrading the lifetime. Therefore, it is not useful for cells irradiated from the back. This is because the lithium "hardening" mechanism involves additional carrier removal, which adversely affects the series resistance when significant damage is produced near the rear contract. This series resistance increase causes the lithium-doped cells, especially the float-zone ones, to degrade much more rapidly. The other findings of the study are essentially the same as results on cells irradiated from the front surface only. Lower sensitivity cells damage at a faster rate, and the spectral response shows a larger degradation in the red region. This latter point means that cells with an enhanced violet response would not degrade as rapidly as similar cells without the enhanced response.

Manufacturing method of a semiconductor apparatus

Abstract: PURPOSE:To obtain the semiconductor apparatus that the contact resistance is low, there is the reappearance quality and the interface is plain, by forming non-rectifier quality contact to the compound semiconductor, not hurting noncrystal quality of the base by the heat treatment.

Measurement of Land to Plated-Through-Hole Interface Resistance in Multilayer Boards

Abstract: Thermally induced cracks can occur at the interface between land and PTE barrel, hence, a measure of electrical continuity of the interface connection is important in product quality assessment and reliability projection. Series circuits with poor resolution are generally used to monitor circuit integrity during thermal tests. A much more sensitive method of measuring the interface directly is described.

The design of optimum high radiance double heterojunction (Al,Ga)As LED's for fiber-optical communication systems

Abstract: The differential equation for current flow in an etched-well type LED is solved. This solution leads to design criteria for the optimization of these devices. These criteria are that the sheet resistance of the p-layers be as large as possible (for a p-type active layer), the sheet resistance of the n-layer be as small as possible, and the ratio of contact diameter to well diameter be as large as possible. Measurements of optical power coupled into a fiber are in excellent agreement with predictions of the model assuming unity internal quantum efficiency.