The term contact resistance refers to the contribution to the total resistance of a material which comes from the electrical leads and connections as opposed to the intrinsic resistance, which is an inherent property, independent of the measurement method. Placing the test probes of an ohmmeter onto the leads of an 100 ohm resistor, a scientist might observe a total resistance of 1 megaohm, 1 kilohm or 101 ohms, depending on exactly how the connection is made. The contact resistance is then the difference between the measured resistance and 100 ohms. Electrical resistance is a measure of the degree to which an electrical component opposes the passage of current. ... An Ohmmeter is an electrical measuring instrument that measures electrical resistance, the opposition to the flow of an electric current. ... Resistor symbols (non-European) Resistor symbols (Europe, IEC) A pack of resistors A resistor is a two-terminal electrical or electronic component that resists an electric current by producing a voltage drop between its terminals in accordance with Ohms law. ... The ohm (symbol: Ω) is the SI unit of electric resistance. ...

Origin of contact resistance

There are two major determinants of contact resistance: geometry and insulating layers between the contacting surfaces (better known as "dirt.") The resistance of a contact is inversely proportional to its area, which is in turn dependent on the force holding the two surfaces together and their stiffness. Joining methods like soldering or wire bonding keep the force between two halves of a contact constant. Softer metals like gold tend to form larger area contacts and are therefore preferred for bonding pads. Gold also has the advantage of being non-reactive, which prevents the formation of oxides or other poorly conducting reaction products. Stiffness is the resistance of an elastic body to deflection by an applied force. ... (De)soldering a contact from a wire. ... Wire bonding is a method of making interconnections between a microchip and the outside world as part of semiconductor device fabrication. ... General Name, Symbol, Number gold, Au, 79 Chemical series transition metals Group, Period, Block 11, 6, d Appearance metallic yellow Atomic mass 196. ...

Experimental characterization

The specific contact resistance is experimentally defined as the slope of the I-V curve at V=0: IV may refer to: 4: The Roman numeral (there are also separate Unicode characters for this number, 0x2163 Ⅳ and 0x2173 ⅳ). Côte dIvoire: NATO country code; from Ivory Coast. ...

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where J is the current density = current/area. The units of contact resistance are typically therefore in Ω.cm² where Ω stands for ohms. When the current is a linear function of the voltage, the device is said to have ohmic contacts. An ohmic contact is a region on a semiconductor device that has been prepared so that the current-voltage (I-V) curve of the device is linear and symmetric. ...

The resistance of contacts can be crudely estimated by comparing the results of a four terminal measurement to a simple two-lead measurement made with an ohmmeter. In a two-lead experiment, the measurement current causes a potential drop across both the test leads and the contacts so that the resistance of these elements is inseparable from the resistance of the actual device, with which they are in series. In a four-point probe measurement, one pair of leads is used to inject the measurement current while a second pair of leads, in parallel with the first, is used to measure the potential drop across the device. In the four-probe case, there is no potential drop across the voltage measurement leads so the contact resistance drop is not included. The difference between resistance derived from two-lead and four-lead methods is a reasonably accurate measurement of contact resistance assuming that the leads resistance is much smaller. Specific contact resistance can be obtained by multiplying by contact area. Four-terminal sensing (4T sensing) is an electrical impedance measuring technique that uses separate pairs of current-carrying and voltage sensing electrodes to make more accurate measurements than traditional two-terminal (2T) sensing. ...

For development of integrated circuit fabrication processes, far more sophisticated measurements of contact resistance are used, the most popular being the transmission line measurement. The basic idea of the transmission line measurement is to plot the resistance of strips of constant width and varying length that are terminated by similar contacts. The slope of the resulting line is a function of the bulk film resistivity while the intercept is the contact resistance. Electrical resistivity (also known as specific electrical resistance) is a measure of how strongly a material opposes the flow of electric current. ...

Inductive and capacitive methods could be used in principle to measure an intrinsic impedance without the complication of contact resistance. In practice, direct current methods are more typically used to determine resistance. In electronics, inductive coupling refers to the transfer of energy from one circuit component to another through a shared magnetic field. ... In electronics, capacitive coupling is the transfer of energy from one circuit to another by means of the mutual capacitance between the circuits. ... Electrical impedance, or simply impedance, is a measure of opposition to a sinusoidal alternating electric current. ... Direct current (DC or continuous current) is the continuous flow of electricity through a conductor such as a wire from high to low potential. ...

Quantum limit

When a conductor has spatial dimensions close to (2 * π) / k_F, where k_F is Fermi wavevector of the conducting material, Ohm's law does not hold any more. These small devices are called quantum point contacts. Their conductance must be an integer multiple of the value 2e² / h, where e is the electronic charge and h is Planck's constant. Quantum point contacts behave more like waveguides than the classical wires of everyday life and may be described by the Landauer scattering formalism.^[1] Point-contact tunneling is an important technique for characterizing superconductors. In condensed matter physics, the Fermi surface is an abstract boundary useful for predicting the thermal, electrical, magnetic, and optical properties of metals, semimetals, and doped semiconductors. ... For the phase law, see Ohms Phase Law. ... The elementary charge (symbol e or sometimes q) is the electric charge carried by a single proton, or equivalently, the negative of the electric charge carried by a single electron. ... A commemoration plaque for Max Planck on his discovery of Plancks constant, in front of Humboldt University, Berlin. ... Look up waveguide in Wiktionary, the free dictionary. ... Rolf Landauer (1927 – 1999) was an IBM physicist who in 1961 demonstrated that when information is lost in an irreversible circuit, the information becomes entropy and an associated amount of energy is dissipated as heat. ... Quantum tunneling is the quantum-mechanical effect of transitioning through a classically-forbidden energy state. ... Superconductivity is a phenomenon occurring in certain materials at low temperatures, characterised by the complete absence of electrical resistance and the damping of the interior magnetic field (the Meissner effect. ...

Other forms of contact resistance

Measurements of thermal conductivity are also subject to contact resistance. Similarly, a drop in hydrostatic pressure (analogous to electrical voltage) occurs when fluid flow transitions from one channel to another. In physics, thermal conductivity, k, is the intensive property of a material that indicates its ability to conduct heat. ... Hydrostatic pressure is the pressure exerted by a fluid due to its weight. ... International safety symbol Caution, risk of electric shock (ISO 3864), colloquially known as high voltage symbol. ... This article or section should be merged with Fluid mechanics Fluid dynamics is the study of fluids (liquids and gases) in motion, and the effect of the fluid motion on fluid boundaries, such as solid containers or other fluids. ...

Significance

Bad contacts are the cause of failure or poor performance in a wide variety of electrical devices. For example, corroded jumper cable clamps can frustrate attempts to start a vehicle that has a dead battery. Dirty or corroded contacts on a fuse or its holder can give the false impression that the fuse is blown. A sufficiently high contact resistance can cause substantial heating in a high current device. Unpredictable or noisy contacts are a major cause of the failure of electrical equipment. An intermittent contact which alternates rapidly between a high and low resistance is the worst nightmare of anyone who has to troubleshoot equipment. A jump start is a colloquial term for a method of starting an automobile or other internal combustion engine-powered vehicle having a discharged battery. ... Karl Benzs Velo (vélo means bicycle in French) model (1894) - entered into the first automobile race 2005 MINI Cooper S. An automobile (also motor car or simply car) is a wheeled passenger vehicle that carries its own motor. ... Lead-acid batteries, invented in 1859 by French physicist Gaston Planté, are the oldest type of galvanic cell battery. ... Corrosion is deterioration of essential properties in a material due to reactions with its surroundings. ... Look up fuse in Wiktionary, the free dictionary. ... In electronics, and in physics more broadly, Joule heating refers to the increase in temperature of a conductor as a result of resistance to an electrical current flowing through it. ...

Notes

1. ^ Landauer, Rolf (August 1976). "Spatial carrier density modulation effects in metallic conductivity". Phys. Rev. B 14 (4): 1474-1479.