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Parameters For Good Contacts Contact Physics
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By: Reichle & De- Massari
Although connection blocks, connectors and jacks are generally considered rather unimpressive and simple to handle connection elements, electro-technical contacting is based on complex physical connections. Therefore, as a matter of good form it must be noted that we will discuss only a few basic aspects here that are helpful in understanding the IDC technology. The point known as the contact transfer is the most important point in the development and production of contacts. All parameters are subject to the electrical resistance of the junction, i.e., the contact resistance.
The contact resistance is composed of the constriction resistance and the surface contamination resistance. The constriction resistance is caused by irregularities in the contact surfaces. As a result of these irregularities (microscopically small rough spots), the electrical contacts do not touch tightly over their entire surface, but rather at a large number of convex micro-surfaces. With current loads, the current path is constricted.
The surface contamination resistance takes into consideration components of resistance caused by wafer-thin surface layers, e.g., oxide or corrosion skins. To avoid this, tinning and coating with precious metals such as gold, silver, palladium or platinum are used. Both the constriction resistance and the surface contamination resistance depend on the force of the contact pressing the two contact surfaces together. The total of the micro-surfaces can be increased with increasing force, through elastic or plastic deformation, and surface contamination layers can be destroyed in part, thus reducing the total resistance.
Depending on the range of application, contact or connector developers must take into consideration a series of additional criteria both directly and indirectly related to the actual contact transfer. Among these are, in addition to the above-mentioned contact film, for example the contact pin materials (or basic materials), the contact geometry, mechanical contact wear, sliding characteristics, and any locking mechanisms and seals.
IDC Contacts:
IDC (Insulation Displacement Contact) is a connection solution that works without soldering, screwing or stripping. The wiring principle is quite easy, the conductor, together with its insulation, is pressed into a V-shaped crimped contact. When pressed, the sharp edges of the crimped contact cut through the insulation (insulation displacement) and create an electrically-conductive connection, a contact transfer, between the conductor and the displacement clamp. This creates a gas-tight, corrosion-resistant connection. The clamping effect is achieved by the pre-established displacement geometry.
High contact force, good conductivity and the right shape of the basic material determine the transfer quality and long-term reliability of the IDC contact. Based on the good electrical and mechanical properties, IDC is appropriate for a multitude of applications calling for reliable connections between an electrical conductor and a connection element, including twisted pair cabling or RJ45 connections and power cabling.
Advantages and disadvantages of various connecting technologies:
Developments in the IT/Telecommunication sector and electronics over the past few years have produced a variety of electromechanical connection types. Some are predecessors, and others competitors, to the current IDC technology.
A general distinction can be drawn between non-destructive detachable and non-detachable connections. In addition, there are connections, in part rewirable, in which the jacket must be cut through or penetrated by a cut or a pin. IDC is among the non-destructive detachable connections and does not make use of soldering, screwing or stripping; it is, in short, the IDC method.
Posted by ROOT Technologies
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