Brief discussion on the technology of insulation replacement connector

Insulation replacement Connector The technology is referred to as IDC for short. The insulation replacement connector (IDC) can realize multi-point cable termination and eliminate the stripping operation required for crimping. It is often used with multi strand cables and belongs to large-scale termination.

1. Insulation replacement Connector Design concept of Technology

The key difference between crimping method and IDC wiring method is the different way of crimping cable.

In the process of crimping, the pre stripped cable and terminal are seriously deformed under the action of high pressure crimping die, breaking through the oxide layer on it and obtaining the contact between metals.

A relatively large force is applied to each contact, and the deformation includes the plastic deformation of the terminal and the axial extrusion of the cable. Cold welding is usually produced by force, and little elastic energy is stored in the termination system. The key dimension of crimping contact is the crimping height tolerance obtained by crimping tool (as shown in Figure 1 below). This requires careful setting and continuous monitoring to maintain the quality of the long-term crimping height.

The IDC termination method requires much less force. Press the insulated cable into the terminal slot, which is designed to deform the cable by using the shear force that produces local plastic deformation, cut off the insulating layer and remove oxides. It is realized by one action, and a high-voltage contact surface is formed between the cable and the terminal. Because the terminals are elastic between terminals, a stable IDC system design stores a lot of energy in the terminals.

The slot width and insertion depth of the terminal are very important in IDC termination. The groove width can be easily controlled at 0.1 mils during blanking. In addition, the cable insertion tool can simply control the insertion depth, because the insertion depth tolerance is usually several mils, so the termination quality can be checked by visual inspection. IDC termination is easier to adapt to the production environment, so it has more advantages than crimping.

2. Insulation replacement Connector Advantages and disadvantages of Technology

IDC insulation replacement Connector The advantages of the technology are low application cost and high reliability. One disadvantage is that the geometry of the connector is limited.

Generally, the rectangular shape of double row contacts provides the best appearance size for the system. In addition, an anti withdrawal device is required because the contact surface with the terminal may not be stable enough in the case of cable vibration. In applications with high mechanical stress, double slots are often required, and sometimes cable insulation clamps are required.

3. Performance characteristics

The good crimping effect is due to the contact between metals in the crimping process and the axial extrusion of the cable, which stores a small amount of elastic energy. Over time, additional diffusion welding can improve the contact surface if the compression joint remains mechanically stable. However, the stress relaxation and creep processes in the terminal / cable system tend to reduce its mechanical stability. Therefore, depending on the mechanical design, the creep process may eventually lead to degradation. If the contact surface initially has marginal strength and is weakened due to vibration and stress relaxation, mechanical stability will limit its service life.

The mechanical stability of IDC end connection depends on the elasticity of the terminal and the load state of the cable. From a design point of view, this is easier to control. In addition, the anti return device of the cable can prevent the looseness of the contact between the cable and the terminal. If it is a solid wire, IDC end connection will have the same or even better performance as crimping due to its inherent good mechanical stability through appropriate anti withdrawal measures. This is because the elastic energy stored in the deflection terminal maintains the high pressure contact surface. Typically, for small wire rules such as awg26, the terminal design provides several pounds of force and several mils of elastic deflection on the contact surface. For larger wire rules, such as awg20, the pressure can be up to 15-20 pounds.

For multi strand wires, the mechanical stability of core bundle plays an important role in its performance. There are two factors affecting its performance. First, because the core bundle bears compressive load, the contact force tends to decrease when it is relaxed in the groove due to mechanical interference, stress relaxation and creep. The possible degree of relaxation depends on the type of stranded wire used. The number and level (or stranding) of cores, the top layer (coating) of conductors and the type of insulation play an important role in mechanical stability.

For some insulation types, multi strand wires without coating, large number of cores, few layers or no are the most difficult to terminate reliably; The coated 7-Strand wire is the simplest and often has the same performance as the solid wire. Second, since the contact point is composed of a limited number of cores (usually 4 of 7 strands), the conductivity between cores will affect the overall conductivity. If the cable is tinned, the overall conductivity can be optimized. Obviously, in the case of multi strand wires, the stress release of clamping cable insulation is very important. Sometimes, additional (or spare) IDC terminal slots can provide the necessary mechanical stability. The mechanical stability of IDC termination can be optimized by using the appropriate deflection (flexibility) of the terminal and effective stress release.

4. Cable load characteristics

Each cable has a unique parameter, so the load characteristics in each case must be evaluated to standardize the design criteria for terminating specific types of cables. The load characteristics of solid wires or multi strand wires can be measured in the laboratory and a fixed dynamometer is used to simulate a groove with guiding geometry. The determination results are used to determine the load requirements of the terminals. The load characteristics of the cable can be displayed on the force variation curve of a given design. Note that bevel, transition radius, and material thickness have significant effects on the load characteristics of a given cable.

After analysis, the design goal is to provide the terminal of cable curve through the predetermined design area. The design area of a given geometry is determined by checking the contact area after the cable is inserted into the simulator. According to the definition, the design area is the load curve area where the insulating layer is replaced and the conductor is effectively deformed to form the contact between high pressure metals. In the case of multiple strands, the design area usually represents the load curve area with the best mechanical stability. This area has good contact formed by as many cores as possible, and each core is not seriously damaged.

5. Test method

The mechanical stability of IDC contact surface plays an important role in practical performance. Therefore, vibration, mechanical, thermal shock and temperature / humidity cycle are important factors to be considered in the test. In order to enhance the laboratory test of simulating practical aging caused by these factors, it should be mainly considered in the product certification test. During this test project, the change of termination resistance should be the main performance characteristic of monitoring. The simple fault criterion 10rc can be used to judge its performance (10 times the minimum contact resistance of the contact surface between cable and terminal).

Considering the basic principle of IDC termination, it is obvious that this technology has the same excellent performance as crimping contacts in many applications. In addition, this termination can reduce the application cost. This ideal situation urges us to seriously consider the application of IDC technology in IDC technology operations. Many applications can provide opportunities to use IDC technology, reduce costs and maintain its termination performance.

Shenglan Technology Co., Ltd_ It focuses on the production of electronic connectors and research and development of precision components. Its products are widely used in consumer electronics, new energy vehicles, USB, 5g and other fields. Its industrial lines cover the Pearl River Delta, Southeast Asia and other regions. It has established long-term strategic cooperation relations with well-known enterprises such as Foxconn, Lixun precision, Huawei, Xiaomi, TCL, Hitachi Group, BYD and Great Wall Motors, with IATF 16949, ISO9001 ISO14001, QC080000 and other system certification and product safety certification, and provide professional connection and manufacturing solutions for the industry http://jctc.com.cn/