Automotive terminalWhat are the details of your design that need attention? How to design it? The editor of Keweite will give you a detailed explanation below.

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

The product design is a comprehensive design integrating product standards, materials, structure, plating, certification, molds, and manufacturing processes, and terminals are no exception.

(1) The product standard plays a general guiding ideology. Almost all considerations are based on it. First of all, our terminal design standards are based on UL and CSA. However, some electrical parameters can also be based on other standards, such as high Low temperature test.

(2) The choice of materials directly affects the performance of the entire product and is the key to the design. Take plastic materials as an example: if the design is based on UL94, V-0 flame retardancy, it is necessary to carefully review the technology of each material property table Whether the parameters can meet the standards of the product, such as whether the impulse withstand voltage and aging resistance test can be passed, the selection of the sheet material of TP in terms of hardware materials is particularly important, because the sheet must meet a certain conductivity (current) and To have a certain degree of flexibility has brought difficulties to our engineers in selecting materials. This is precisely the trend that connector manufacturers are pursuing in elastic components. Many manufacturers of hardware materials are working hard in this regard. The rate directly affects the temperature rise and contact resistance. The quality of 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 theory formula of material mechanics. The greater the electrical conductivity of the material, the lower the contact resistance, the lower the temperature rise. The plug-in force and the contact resistance have 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 layer resistance accounts for 70-80% of the total resistance, which is also the main factor affecting the life of the connector. Full attention should be paid to the terminal gold plating and silver plating. Although the conductivity of silver is higher than that of gold, its chemical Stability is not as good as gold, and the film resistance caused by it is much greater than gold plating. Therefore, understanding the relationship between the above has guiding significance for our choice of materials and is a prerequisite for product design.

(3) The design of the product structure is also very important. It is entirely a matter of experience, and there is no shortcut. In this regard, each series has its own characteristics, such as: screws prevent falling, and spliced ​​products are curved and long. Deformation of digits, shrinkage and deformation caused by uneven wall thickness, etc., the prevention of screws is mainly as follows: three ribs, hoop, neck, stamping, etc., due to the influence of technical processes There are not many necks to prevent falling, and most of them use necks to prevent falling. The realization of the above structure is based on the premise that the plastic material is PA66. Here we need to explain the prevention of necks. Take the screw for M3 as an example, M3 The actual outer diameter of the screw is φ2.90mm, so the size of the shell neck should be designed: φ2.5～φ2.6, the thickness of the shell neck should be 0.4～0.5mm, and there should be a section under the screw head smaller than the shell The polished rod at the neck can ensure that the screw can be smoothly screwed into the thread. The production process should also be adjusted accordingly. Below, we will make a statistics and solution for the structural problems of our company's various series of products.

1. The main reason for the deformation of the spliced ​​product portfolio is the unbalanced structure of the two spliced ​​falcons. The force and deformation of the spliced ​​falcon should be considered in the structural design. direction.

2. The problem of screw prevention. In this regard, I recommend using the neck to prevent it, because it avoids the troubles caused by the smooth rod of the screw and the tolerance of the hoop compared with the hoop. Moreover, the structure is reliable and the tolerance is easy to control.

3. The problem of the salt spray test of screws and threaded steel parts after electroplating is solved according to the company's standard of thread electroplating in 2012 (the coating is limited, but the thickness of the coating corresponding to the thread is still to be determined). There are two methods when the electroplating process is normal, choosing the correct sealing agent and using the plating layer to electroplate multiple times, both of which are to cover the holes produced by the screws that are invisible to the naked eye. The cost of electroplating in multiple times of plating is higher, so the first method is recommended, and the key to this method is the study of the sealant formulation.

4. The problem of plug-in force. This aspect involves more content. It is related to materials, electroplating, structure and the applied industry. It is an important mechanical performance requirement of the connector industry. Plug-in terminals Even more so, the choice of material is limited by conductivity (current), contact resistance, and temperature rise in terms of insertion force. I won’t go into details here. Electroplating is mainly affected by the type of plating and whether it is pre-plated.

Generally speaking, the press plate after pre-plating under the same material and structure is more stable in insertion and extraction force than the press plate which is stamped and then electroplated, because the hardware material is hardened in the process of the post-plating process. , And the prior stamping just eliminated this phenomenon. The main consideration in the structure is the contact between the pressing piece and the lead pin. The contact between the lead pin and the pressing piece is mostly line contact, which causes the sudden big moment when it is inserted during mating, and then suddenly becomes smaller. There is an extremely unstable feeling during use, which affects its life. If the contact between the pressing piece and the lead pin is changed to surface contact in terms of structure, it will not only solve the problem of insertion and extraction force, but also reduce 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 dominant, such as frequency conversion, vandal-proof, numerical control panels, access controllers, sensors, PLCs, instruments, power supplies, and servo drives. These application industries have common to plug-in terminals. The requirements are: the insertion and extraction force must be stable, the contact resistance must be small, and a certain life span and fatigue must be met. Therefore, the requirements for hardware shrapnel materials are higher. This requires product designers to have certain experience in structure and material selection. For barrier terminals, the main applications are: power supplies, relays (especially double-layer terminals), frequency converters, elevator industry (less), air conditioners.

The requirement of this series of terminals is that the screw has a higher torque requirement when crimping. The distance from the screw to the highest position is greater than the maximum crimping range. For long-digit terminals, there should be no warping and corrosion resistance. Higher.

(5): With the beginning of China's 3C certification system, the country has put forward higher requirements for the safety and electromagnetic compatibility of electrical products. The related standards are: GB16836-2003 "General Safety Design of Measuring Relay Protection Devices" Requirements", GB/T14598.3-1993 "Insulation Test of Electrical Relays", JB/T 9568-2000 "General Technical Conditions for Power System Relays, Protections and Automatic Devices", International Standard IEC60255-27 (CD: 2002) "Measurements "Product Safety Requirements for Relays and Protection Devices", the safety items involved in GB16836-2003 mainly include: mechanical structure, enclosure protection, insulation coordination, heat generation, fire test, electric shock prevention, safety signs and safety instructions.

1. The safety of mechanical structure requires that the terminal must ensure personal safety in terms of chemical and structural materials and live moving parts, such as the edges and corners of the shell, the burrs of the hardware, and the connection strength of various parts, even the product under the conditions of movement. Stability, the above are all requirements of the mechanical structure in the power industry for terminals.

2. The protection requirement of the shell is mainly the protection level of JB/T 9568-2000. It is mainly divided into two types, one is the protection level of solid foreign objects, and the other is the harm caused by water to equipment and products.

3. Insulation coordination requirements are mainly based on the materials used, the working voltage and the environmental pollution level, to select the electrical clearance and creepage distance, so as to protect the safety of the staff and the product, and at the same time, the product will not be damaged due to overvoltage. .

4. The tracking index is required. During the use of the product, the surface of the solid insulating material forms a conductive path under the action of the electric field and the electrolyte, which reduces the insulation performance of the housing insulating material and affects the safety of the product. If the creepage tracking index is high under the same insulation voltage level, the creepage distance of the product can be reduced. If the product enters the power industry, please pay full attention to research and development in this regard.

5. Thermoplastic materials require deformation during work. It mainly affects the temperature rise and contact resistance of the terminal during work. The high temperature it causes causes the shell to deform and soften, thereby causing electrical short-circuits and causing serious accidents. The choice of material for flow parts is obviously very important.

6. Anti-electric shock requirements. In terms of structure, operating elements should not be live, and the internally connected terminals should not be accessible. This aspect is mainly the requirement for the reliability of screw torsion, and the screw with the accessible terminal should be prevented. The wire was accidentally loose and short-circuited. For example, the grounding terminal requirements: the grounding resistance of Class I safety products should not be greater than 0.5Ω.

(6) In terms of molds, at least in the connector industry, almost all important parts are realized through molds, with high efficiency, good accuracy, and easy maintenance. The main surface of the terminal is mainly plastic mold and continuous metal mold. Aspect: Mainly lies in the design. First of all, the choice of the parting surface of the product is very important. He decides the design of the mold's own structure, as well as the design of the side core (mostly four sides) inlet and direction. The system is also a very important item. As for the design of some structures, it will be affected by the type of plastic material, and the uniformity of the insulating shell structure will affect the mold. The inserts on the front mold and the rear mold should be avoided as a product design. If the engineer only considers the function and standard aspects of the product, it will lead to the normal production and appearance of the mold. It is necessary to take into account the mold manufacturing process and the molding process of the injection molding machine. The impact of this aspect is also very important: injection temperature, molding time, Clamping force, injection speed, etc.

(7) Other manufacturing processes. The manufacturing processes of other parts used in the terminals include: instrumentation, casting, heat treatment, etc. It is not only to understand the above process, but also to accumulate experience, summarize in time, and make progress gradually. Therefore, in terms of research and development, greatly improving the quality of product project engineers and increasing the management system of project engineers are the keys to complete product development.

I believe that through the above explanation, everyone is rightAutomotive terminalThe design has a deeper understanding. Welcome customers to come to consult and purchase!

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