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Terminal Blocks Problems
- Sep 25, 2017 -

The terminal is a kind of accessory product which is used to realize electrical connection, which is divided into the category of connectors. With the increasing degree of industrial automation and more stringent and accurate industrial control requirements, the use of terminals gradually increases. With the development of the electronic industry, the use of terminal terminals is increasing and the variety is more and more. At present, the most widely used are not only the PCB terminal, but also hardware terminal, nut terminal, spring terminal and so on.

Terminal is applied for the convenience of the connection wire, it is actually a seal inside the insulation plastic pieces of metal, with a hole at both ends can be inserted into conductor, a screw is used to tighten or loosen, such as two wire, sometimes need to connection, sometimes need to disconnect, then connect them can use the terminal, and can be disconnected at any time, without having to weld them up or intertwined, very convenient. And suitable for a large number of wires connected, in the electric power industry is a special terminal, terminal box, above all terminal, single, double, current, voltage, ordinary, can be broken, and so on. A certain pressure area is to ensure reliable contact and to ensure sufficient current.

The design of the product is a comprehensive design of product standard, material, structure, electroplating, certification, mould, and manufacturing process, and the terminal is no exception.

(a) product standards play an overall guiding ideology, almost all considerations are based on it, our terminal design standards start with UL and CSA shall prevail, but in terms of some electric parameters can also be based on other criteria, such as high and low temperature test.

(2) the choice of materials directly affect the product performance, is the key to the design of plastic material, for example: if with UL94, V - 0 flame retardant for design basis to seriously review of technical parameter of material property table whether can meet the standards of products, such as impact resistance to voltage and aging test whether, in the aspect of metal material is mainly TP tablet material selection is particularly important, because this tablet to meet certain conductivity (current) and a degree of elasticity that choose our materials brought difficulties to our engineers, and precisely in this respect is the connector manufacturer in elastic components pursues trend, many manufacturer of metal material are the efforts, the conductivity directly affect the temperature rise and the contact resistance, flexibility and materials of chemical elements, elastic modulus, hardness, tensile strength, elastic modulus of choice with material mechanics calculation formula of the fourth strength theory. The conductivity of the material, the greater the resistance, the smaller the lower the temperature, the insertion force and contact resistance into a quadratic curve, the relationship between contact resistance main points: the compression resistance, membrane layer resistance and volume resistance (the resistance of the conductor itself). The film resistance is 70 ~ 80% of total resistance, is also the main factors affecting the service life of the connector, should give full attention, with terminal than gold and silver, while the conductivity of the silver is higher than gold, but its chemical stability is not as good as gold, gold-plated layer caused by the membrane resistance is far greater than so find out the relationship between the above have guiding significance for us to choose materials, is a prerequisite for product design.

(3) the structure of the product design is also very important, it is totally experience, there is no shortcut, each series in this area have their own characteristics, such as: screw off, joining together the product before and after an arc, long digits deformation, such as wall thickness caused by uneven shrinkage deformation, such as the screw fall prevention mainly has the following kinds: three rib fall prevention, hoop mouth, neck mouth off, stamping out, due to the affected by the technology of cervical mouth out with few, and most of the cervical mouth off, the realization of the above structure is plastic material PA66 the premise condition, in need of cervical mouth off here, for the M3 screw, for example, the M3 screw the actual outside diameter is 2.90 mm phi, so the size of the shell of cervical mouth should be designed in: from 2.5 ~ 2.5, the thickness of the shell of cervical mouth should be in 0.4 ~ 0.5 mm, and under the screw head should have a period of less than the polished rod of the shell of cervical mouth, so as to ensure the screw can be smoothly precession thread, also should make a corresponding adjustment in production process, the following to me all the series of problems in the aspect of structure make a statistics and solutions.

1, splicing portfolio growth figures deformation problem, the main reason is caused by unreasonable structure before and after the two splicing falcons in the up and down or so unbalanced force, as shown in the structure design should consider the splicing falcon direction of force and deformation.

2. The problem of screw preventing, in this respect I suggest to try to keep the neck out, because it avoids the trouble caused by the screw rod and the tolerance accuracy of the hoops. And the structure reliable tolerance is easy to control.

3, screw and take rebar after plating salt spray test, because in 2012 the company screw plating standards (coating is limited, but how much thread corresponding to the coating thickness I think remains to be determined), solve the problem under the normal operation of the electroplating process, there are two ways to select the correct hole sealing agent and by several times coating electroplating, the two methods are produced to cover screw with the naked eye can't see the pore. It is suggested to use the first method, and the key of this method is the study of the formulation of the sealing agent.

4, the problem of insertion force, involves the contents of this aspect is more, it has to do with material, electroplating, structure and application of industry, connector industry is an important mechanical performance requirements, plug type terminal, the choice of materials in terms of insertion force by the conductivity (current) and the limitation of the contact resistance and temperature rise. In this case, the details are not explained. Electroplating is mainly the type of coating and the influence of preplating.