In contemporary electrical and electronic facilities, the density of the elements and the gradual increase in performance between them, the electromagnetic disturbance put forward a strict limit. Therefore, the connector is usually closed with a metal shell to stop the internal electromagnetic energy radiation or by the external electromagnetic field annoyance.
At low frequencies, the only magnetic material can be significant shielding effect on the magnetic field. At this point, there is an absolute delineation of the electrical continuity of the metal shell, which is the shell touch resistance.
Second, the safety properties of insulation resistance
Insulation resistance refers to the insulation of the connector to some voltage, so that the insulation of some of the exterior or the exterior of the current leakage and show the resistance value.
It is mainly affected by the insulation material, heat, humidity, dirt and other reasons involved. Connector samples supplied on the insulation resistance value is usually all in the standard atmospheric premise of the indicator value, in a certain type of scenario premise, the insulation resistance value will not have to level of decline.
In addition to focus on the insulation resistance of the experimental voltage value. According to the insulation resistance (MΩ) = the voltage (V) added to the insulator / leakage current (μA) to different voltages, there is no need for the results. In the connector experiment, the voltage is usually 10V, 100V, 500V three grades. Withstand voltage
Any connector in the work can not be separated from the current, which there is the risk of anger. Therefore, the connector not only needs to be able to prevent ignition, but also needs to be able to self-extinguish in a short time once ignition and anger. In the selection of the selection should focus on the selection of flame-retardant, self-extinguishing insulation material electrical connectors.
Third, the machine properties touch pressure (single foot separation force and total separation force)
Connector touch pressure is a primary indicator, it is directly linked to the size of the touch resistance and touch the amount of wear and tear on the pair.
In most constructions, it is quite difficult to measure the touch pressure directly. Therefore, the touch pressure is usually measured directly by the single foot separation force. For round pinhole touching pairs, the standard pin with a defined weight is often used to check the ability of the negative touching part to hold the weight, and usually the diameter of the standard pin is the lower limit of the diameter of the positive touching part taken as -5μm.
The total separation force is usually twice the sum of the upper line of the single foot separation force. Total separation force beyond 50N, with manual plugging has been quite difficult. Of course, some of the test facilities or a particular type of special needs of the site, you can use zero plug force connectors, intelligent drop connectors and so on. Machine life
Connector machine life refers to the plug life, often delineated as 500 to 5000 times.
In reaching this specified machine life, the connector's touch resistance, insulation resistance and voltage resistance and other indicators should not exceed the specified value.
Strictly speaking, today's machine life is a class of vague concepts. Machine life should be absolutely linked to time, 10 years after 500 times and 1 year after 500 times, obviously its condition is not the same. Only now there is not a more economic class
Oscillation, impact, collision
The primary reference connector in the delineated frequency and speed premise oscillation, impact, collision when the electrical continuity of the touch pair.
The contact pair in this dynamic stress condition will produce instantaneous disconnection. The defined transient break time is usually 1μs, 10μs, 100μs, 1ms and 10ms, and it is important to focus on how to determine the transient break failure of the touch pair.
Nowadays, it is usually determined that when the voltage drop at both ends of the closed contact pair (contact) exceeds 50% of the power supply potential, the closed contact pair (contact) can be judged to be faulty. In other words, there are two prerequisites to determine whether a transient break can be generated: continuous time and voltage drop, the absence of one cannot. Connection method
Connector is usually composed of plugs and sockets, in which the plug is also known as the free end connector, socket is also known as a fixed connector. Through the plug, socket insertion and separation to implement the circuit connection and disconnection, thus constituting a plug and socket connection method of various types.
For circular connectors, the primary ribbed connection, bayonet connection and self-locking (bullet) type connection three types of methods.
The ribbed connection is the most common, it has a simple processing technology, low production costs, wide range of applications and other benefits, but the connection rate is not suitable for frequent plugging and unplugging and rapid connection of the site.
Bayonet type connection because of its three bayonet slot guide is long, so the connection rate is faster, but it is more difficult to produce, the cost is also very high.
Self-locking (bullet) type connection is the fastest connection rate of the three types of connection methods
Four, scene attributes
Scene properties are the primary scene heat, humidity, heat rush, atmospheric pressure and erosion scenes. Connector in the application and storage, transportation process in the scene of its function has obvious implication, so the actual scene must be based on the premise of the choice of the corresponding connector. Scene heat
Connector metal materials and insulation materials determine the connector's work scene heat. High heat will destroy the edge of the material, triggering insulation resistance and voltage resistance function is reduced; for metal high heat can make touching the pair to get elastic, accelerate oxidation and produce plating degradation. Often the scene of heat for -55 ~ 100 ℃ special places may need to be higher. Humidity
Relative humidity greater than 80% is the primary cause of electrical breakdown. Wet scene triggers the absorption and diffusion of water vapor in the insulator exterior, easier to make the insulation resistance reduced to MΩ level below, persistent in high humidity scene, will trigger physical distortion, decomposition, overflow formation, constitute the breathing effect and electrolysis, erosion and cracking. Especially in the facility outside the connector, often to refer to the wet, water infiltration and pollution scenario premise, such conditions should be selected to seal the connector. For water-tight and dust-tight connectors usually take GB4208 shell protection grade to express. Heat rapid change
Humidity rapid change experiment is to imitate the application of connector facilities in the cold scene into the warm scene of the actual application of the situation, or imitate the space flyer, detector scene heat rapid change in the situation. The thermal shock may cause the insulation material to crack or pucker. Atmospheric pressure
In the air thin low altitude, plastic release gas pollution touch pair, and make the corona constitutes the situation increase, the voltage resistance function drop, so that the circuit constitutes a short-circuit fault. At low altitude to a certain absolute value, the plastic function becomes worse. Therefore, when applying non-sealed connectors at low altitude, it is necessary to derate the application. Erosion scenario
According to the different applications of the connector erosion scenarios, the use of metal, plastic, plating structure of the connector, such as the application of the connector in the salt spray scenario, if there is no corrosion-resistant metal exterior, will make the function quickly improve. In the scene containing a considerable concentration of SO2, should not apply silver-plated touch pair of connectors. In hot and humid places, mold is also the primary problem.
V. Termination method
Termination method refers to the method of connecting the connector's touch pair to the wire or cable. Reasonable selection of termination methods and accurate application of termination techniques, but also the application and selection of connectors is a primary aspect. Solder
The most common type of soldering is soldering.
The most important thing about soldering connections is the continuity of the metal that should be generated between the solder and the soldered surface. Thus, for connectors, the primary concern is solderability. The most common plating on the solder side of the connector is tin alloy, silver and gold. The reed type touch on the common solder end of the solder lug type, punch eye solder lug type and notched solder lug type: pinhole type touch on the common solder end of the drilled circular arc notch type. Crimping
Crimping is a type of technique for making metal compression and displacement within a defined limit and connecting the wire to the contact pair.
A good crimp connection can constitute a mutual fusion of metal flow, so that the wire and touch the material symmetrically twisted. This type of connection is similar to a cold weld connection, which gives good machine strength and electrical continuity, and it can withstand more difficult scenarios. It is now widely recognized that taking accurate crimp connections is better than soldering, especially in high-current places must apply crimp. Crimping must take a special crimping pliers or intelligent, semi-intelligent crimping machine.
Should be based on the cross-section of the wire, the accurate choice of touching the wire copper. To focus on the crimp connection is a permanent connection, can only be applied once. Winding
Winding is the wire directly wrapped around the prongs of the touch piece around the column.
When winding, the wire is wound under controlled tension, pressed into and secured to the prongs of the contact winding post to create an airtight contact. Winding wire has several needs: the nominal value of the wire diameter should be in the range of 0.25mm ~ 1.0mm; wire diameter is not greater than 0.5mm, the conductor material derived rate of not less than 15%; wire diameter greater than 0.5mm, the conductor material derived rate of not less than 20%. Winding tools include cover winding gun and fixed winding machine. Puncture connection
Puncture connection, also known as insulation displacement connection, is invented by the United States in the 1960s, a class of chic end technology, with high reliability, low cost, easy to use and other features, has now been fully used in all types of printed circuit board connectors.
It is used in the connection of ribbon cable. Connection does not need to strip the cable insulation, relying on the top of the connector's "U" touch reed stabbed into the insulation layer, so that the cable conductor slides into the slot of the touch reed and is clamped, so that the cable conductor and the connector reed between the generation of a discreet electrical connectivity. It requires only simple tools, but it is necessary to use cables with specified wire gauge. Screw connection
Screw connection is to take the screw type terminal connection method.
Pay attention to the maximum and minimum cross-section of the allowable connection wire and the maximum tightening torque allowed for different sizes of screws.
Finishing words
The above from the electrical properties, safety properties, machine properties, scene properties and termination methods and other aspects of the connector selection method, but because the connector variety is cumbersome, coupled with the use of industry is cumbersome, we must combine the actual situation to select the best connection plan.
It does not require rotational movement, but only linear movement to implement the performance of connection, separation and locking. Because it belongs to the push-pull connection method, it is only used in connectors where the total separation force is not large. It is usually more common in small connectors. Loading method and shape
Connector loading front loading and back loading, loading and fixing method rivets, screws, card ring or connector itself card pin quickly locked. There is also a class of plugs and sockets are free end connector, the so-called relay connector.
The shape of the connector is varied, the customer is primarily from the straight, curved shape, the outer diameter of the wire or cable and with the shell of the fixed needs, volume, weight, whether the need to connect metal hoses and other aspects imposed by the selection, the application of the connector in the panel but also from the good-looking, appearance, color and other aspects imposed by the selection.
A more scientific way to weigh. Touch on the number and pinhole sex
The number of touch pairs can be selected according to the needs of the circuit, while referring to the volume of the connector and the size of the total separation force. Touch the number of pairs, of course, its volume is large, the total separation force is relatively large. In a certain type of fastness needs high, and the size of the situation allows, can take two even contact pairs in parallel to improve the fastness of the connection.
Connector plugs, sockets, pins (Yang touch pieces) and jacks (Yin touch pieces) can usually be exchanged for removal. The actual application, according to the plug and socket at both ends of the charged condition to choose. If the socket needs to be often charged, you can choose to install the jack socket, due to the jack socket, its charged touch piece buried in the insulator, the body is not easy to touch the charged touch piece, relatively speaking, safer.