As a kind of connector, Splicing Connector ,the wiring terminal is an important component in the electrical industry and plays an irreplaceable and non negligible role. Because engineers and technicians start with the interface inspection, that is, the terminal, when overhauling, the design of the wiring terminal is particularly important.

Product design is a comprehensive design integrating product standard, material, structure, electroplating, certification, mold and manufacturing process, and the terminal is no exception.

（1） The product standard plays a general guiding ideology, and almost all considerations are based on it. Our terminal design standards are first subject to UL and CSA, but some electrical parameters can also be based on other standards, such as high and low temperature test.

（2） The selection of materials directly affects the performance of the whole product and is the key to the design. Take plastic materials as an example: if the design is based on the flame retardant of UL94 and V-0, it is necessary to carefully review whether the technical parameters of each material property table can meet the product standards, such as whether the impact voltage resistance and aging resistance tests can be passed, In terms of hardware materials, the selection of tabletting materials, mainly TP, is particularly important, because this tabletting should not only meet a certain conductivity (current) but also have a certain elasticity, which has brought difficulties to our engineers in selecting materials, which is precisely the trend pursued by connector manufacturers in elastic components, and many manufacturers of hardware materials are making efforts in this regard, The conductivity directly affects the temperature rise and contact resistance. The elasticity is related to the chemical elements, elastic modulus, hardness and tensile strength of the material. The elastic modulus is calculated by the fourth strength theoretical formula of material mechanics. The greater the conductivity of the material, the smaller the contact resistance and the lower the temperature rise. The relationship between the plugging force and the contact resistance is a quadratic curve. The contact resistance is mainly divided into compression resistance, film resistance and volume resistance (the resistance of the conductor itself). Among them, the film resistance accounts for 70 ~ 80% of the total resistance, which is also the main factor affecting the service life of the connector. We should pay full attention to it. Compared with gold plating and silver plating, although the conductivity of silver is higher than gold, its chemical stability is not as good as gold, and the resulting film resistance is much greater than gold plating. Therefore, understanding the relationship between the above is of guiding significance for us to select materials, Is a prerequisite for product design.

（3） The design of product structure is also very important, which is completely empirical, and there is no shortcut. In this regard, each series has its own characteristics, such as anti falling of screws, arc before and after the spliced products, long digit deformation, shrinkage deformation caused by uneven wall thickness, etc. the anti falling of screws mainly includes the following: anti falling of three bars, anti falling of hoop mouth and anti falling of neck mouth, Due to the influence of technical process, the neck mouth is not used much, but most of them are used. The realization of the above structure is based on the plastic material PA66. Here, it is necessary to explain the neck mouth anti falling. Take the screw m3 as an example, and the actual outer diameter of M3 screw is φ 2.90mm, so the size of the shell neck shall be designed in: φ 2.5～ φ 2.6. The thickness of the shell neck shall be 0.4 ~ 0.5mm, and there shall be a smooth rod less than the shell neck under the screw head, so as to ensure that the screw can be screwed into the thread smoothly. The production process should also be adjusted accordingly. Here is a statistical and solution to the structural problems of various series of products.

1. The main reason for the deformation of the long digits of the spliced product portfolio is that the two spliced falcons are unbalanced in front and back, up and down, left and right due to the unreasonable structure. As shown in the figure, the stress and deformation direction of the spliced Falcon should be considered in the structural design.

2. In this regard, I suggest using the neck to prevent the screw from falling, because it avoids the trouble caused by the tolerance accuracy of the screw smooth rod and the hoop compared with the hoop. Moreover, the structure is reliable and the tolerance is easy to control.

3. There are two methods to solve the problem of salt spray test of screws and threaded steel parts after electroplating according to the company's thread electroplating standard in 2012 (the coating is limited, but the corresponding coating thickness of the thread remains to be further determined). Under the normal electroplating process, there are two methods: selecting the correct sealing agent and using the coating for multiple electroplating. Both methods are to cover the pores generated by the screw that cannot be seen by the naked eye. The cost of multiple plating is high, so the first method is recommended, and the key of this method is to study the formula of sealing agent.

4. The problem of plug-in force involves many contents. It is related to materials, electroplating, structure and applied industries. It is an important mechanical performance requirement in the connector industry, especially for plug-in terminals. In terms of plug-in force, the selection of materials is limited by conductivity (current), contact resistance and temperature rise. It will not be explained in detail here. Electroplating is mainly affected by the type of coating and whether it is pre plated or not.

Generally speaking, under the same material and structure, the pre plated tablet is more stable in plug-in force than the first stamping and then electroplating tablet, because in the post electroplating process, the hardware materials are virtually hardened, and the first stamping just eliminates this phenomenon. In terms of structure, the main consideration is the contact between the pressing plate and the guide needle. Most of the contact between the guide needle and the pressing plate is line contact, which results in the sudden large insertion at the moment of cooperation, and then suddenly becomes smaller, which gives customers a very unstable feeling in the process of use and affects its service life. If the contact between the pressing plate and the guide needle is changed into surface contact in terms of structure, Then it not only solves the problem of plug-in force, but also reduces the contact resistance and temperature rise.

（4） Product application: mainly used in lighting, communication, security and other industries. The application industries of plug-in terminals are the most extensive, such as frequency conversion, anti riot, CNC panel, access control controller, sensor, PLC, instrument, power supply and servo drive. The common requirements of these application industries for plug-in terminals are: the plug-in force should be stable, the contact resistance should be small, and it should meet a certain life and fatigue. Therefore, the requirements for hardware shrapnel materials are high. This requires product designers to have certain experience in structure and material selection. Fence type terminals are mainly used in: power supply, relay (especially double-layer terminal), frequency converter, elevator industry (less), air conditioning.

The requirements of this series of terminals are that the torque of the screw is high during crimping, the distance from the screw to the highest position shall be greater than the maximum crimping range, the terminals with long digits shall not have warpage deformation, and the corrosion resistance of the screw is high.

（5）With the beginning of China's 3C certification system, the state has put forward higher requirements for the safety and electromagnetic compatibility of electrical products. The relevant standards are: gb16836-2003 General requirements for the safety design of measuring relay protection devices, GB / t14598 3-1993 insulation test of electrical relays, JB / T 9568-2000 general technical conditions for relays, protection and automatic devices in power system, international standard iec60255-27 (CD: 2002) product safety requirements for measuring relays and protection devices. The safety items involved in gb16836-2003 mainly include: mechanical structure, shell protection, insulation coordination, heating Fire test, anti electric shock, safety signs and safety instructions.

1. The safety of mechanical structure requires the terminal to ensure personal safety in terms of chemistry, structural materials and live moving parts, such as the edges and corners of the shell, the burrs of hardware, the connection strength of various parts, and even the stability of the product under conditions such as movement. These are the requirements of mechanical structure for the terminal in the power industry.

2. The protection requirements of the shell are mainly the provisions on the protection grade in JB / T 9568-2000. It is mainly divided into two types: one is the protection grade of solid foreign matters, and the other is the harm caused by water to equipment and products.

3. The insulation coordination requirements are mainly to select the electrical clearance and creepage distance according to the materials used, working voltage and environmental pollution level, so as to protect the safety of workers and products, and prevent insulation damage of products under overvoltage.

4. According to the requirements of leakage trace index, the surface of solid insulating material forms a conductive path under the action of electric field and electrolyte during the use of the product, which reduces the insulation performance of shell insulating material and affects the safety of the product. If the creepage distance of the product can be reduced when the leakage trace index is high under the same insulation voltage level, if the product enters the power industry, please pay full attention to it.

5. Thermoplastic materials have deformation requirements in work. It mainly affects the temperature rise and contact resistance of the terminal during work. The high temperature caused by it softens the deformation of the shell, resulting in electrical short circuit and serious accidents. Therefore, the selection of current carrying component materials of the terminal is very important.

6. Anti electric shock requirements: in terms of structure, the operating elements shall not be charged, and the terminals connected internally shall not be accessible. This is mainly the requirement for the reliability of screw torque, and the accidental loosening and short circuit of screws and wires with accessible terminals shall be prevented. As required by the grounding terminal, the grounding resistance of class I safety products shall not be greater than 0.5 Ω.

（6） In terms of mold, at least in the connector industry, almost all important parts are realized through mold, with high efficiency, good precision and convenient maintenance. The main surface of the terminal is mainly plastic mold and hardware continuous mold. In terms of plastic mold, it mainly lies in design. First, the selection of product parting surface is very important. It decides the design of the mold structure, There is also the design of the rubber inlet and direction of the side core pulling (most can be four sides). The mold secondary system is also a very important item. As for the design of some structures will be affected by the type of plastic material, the uniformity of the insulating shell structure will have an impact on the mold, and the inserts on the front mold and rear mold should avoid the phenomenon of opposite insertion, As a product design engineer, if we only consider the function and standard of the product, it will lead to the normal production and appearance of the mold. We should take into account the mold manufacturing and processing process. In addition, the molding process of the injection molding machine. The impact of this aspect is also very important: injection temperature, molding time, mold locking force, injection speed, etc.

（7） Other manufacturing processes, including instrument, casting, heat treatment, etc. The above process is not only to understand, but also to accumulate experience, summarize in time and step by step. Therefore, in terms of R & D, greatly improving the quality of product project engineers and increasing the responsibility management system of project engineers are the key to complete product development.