The quality of the hanger determines the quality of the electroplating
The role of the electroplating hanger is very clear. If you give it a definition, that is: the hanger is a tool used to hang and load the plated parts, and to conduct the cathode current to the plated parts. It's that simple. However, it is such a simple hanger that plays a very important role in the quality and efficiency of electroplating. Whether the design or selection of the hanger is appropriate is sometimes related to the success or failure of electroplating processing. Therefore, after its definition, a sentence should be added, that is, its structure, shape and conductivity are directly related to the efficiency and quality of electroplating. Therefore, the management of electroplating racks is very important for electroplating production. Unfortunately, many electroplating workers pay little attention to the hanger, thinking that the hanger is all about conducting electricity and hanging the product. It is often used to pick up a hanger and put the product into the plating tank for electroplating. It is difficult to guarantee the quality and efficiency of this kind of electroplating. Of course, some electroplating processing enterprises have a special hanger production department, and the operator can only use the rationed hanger (or pick it up by himself) for electroplating, which will be better. However, whether these rationed racks are in line with the conditions of the products to be plated, that is to say, whether the selected racks are reasonable is not completely certain, and once the racks are selected, the fate of this batch of electroplating products will also be determined. It has been determined, and it is all about the hanger. Is this really the case? Let everyone carefully study the role of the hanger.
1, Suspension and loading function
Most of the electroplated products are indeed hung on the hook for electroplating, and the name of the hanger also comes from this, but it is by no means hung up. The position, direction, quantity of the plated parts on the hanger, as well as the distance and relative position of the front and rear, left and right, upper and lower parts to be plated, etc., all have an important impact on the quality and production efficiency of this (or this batch) product. Properly suspended and loaded, the maximum output per unit time can be obtained, and the product quality is in line with the design requirements. If you load too little, the impact on quality may be small (and not necessarily), but the efficiency will drop; if you load too much, the quality will be affected, and the non-conforming product or rework will increase. quality. Therefore, how to ensure the loading capacity of the hanger, and how to ensure that each piece of the plated piece on the hanger is in a position suitable for obtaining a uniform coating layer, requires effort. What is needed now is reasonable and effective suspension and loading, so as to ensure that the capabilities of electroplating production are properly utilized.
2, Conductive effect
Electroplating requires current, so the hanger must not only carry the electroplating parts, but also conduct current for it. Isn't that just conductive? Yes, but don't think you can just use metal to make the hanger, it's not that simple. As a manager of an electroplating enterprise, one thing that must be done is to test the temperature of the hook being electroplated by hand. See if it gets hot. If the hanger is always hot to the touch, then the design or selection of the hanger is inappropriate. Because a part of the electric energy is doing useless work at this time, it is used to heat the plating solution. In this way, the electric energy distributed to the plated product will be reduced. To ensure that the electroplating can still work at the current density required by the process, the current can only be increased. Not to mention the quality impact, the first is the increase in power consumption. , the production cost increases. With this kind of hanger production, the temperature of the plating solution will rise continuously. For the plating species that do not need to be heated, this will affect the plating quality (such as acid plating of bright copper), and will also increase the evaporation of the plating solution. At the same time, the increase of the current will also cause passivation of the anode, which will have a greater impact on the quality of electroplating. Not only will the concentration of the main salt decrease and the plating solution become unbalanced, but also the distribution of the power lines will be affected, making the dispersion of the plating solution. Decrease inability. It can be seen that the conductivity problem of the hanger is not the end of the electricity. If it is not selected properly, it will not only affect the quality of electroplating but also waste electricity.
3. The form and type of hanger
When it comes to the role of the hanger, it is about hanging and loading, which means that the form of the hanger is not only the hook shape but also other methods, such as the plate plating method, the continuous plating method, the barrel plating method, etc., all of which are An extension of the hanger method. Therefore, it is necessary to explain that the hanger discussed here refers to the hanger used for hanging plating. Even the racks for rack plating can be divided into several types.
①Universal hanger. The characteristic of the universal hanger for electroplating is that a hanger can be used for parts of various shapes. It is divided into several specifications according to the size of the outer frame of the plated part to set the density of the hook and allows the outer dimension of the plated part to exceed this When the specifications are within the range, the hanger is used by jumping off one hook and hanging one, so as to make the hanger more versatile. In this way, a variety of products with the same frame size and different shapes can use the same type of hanger, which is the mainstream method in the design and manufacture of hangers at present.
②Special hanger. Due to the special shape or very large output of some products, a hanger needs to be specially designed for this kind of product, and it is only used for this kind of product, which is a special hanger. The special hanger can better ensure the quality and efficiency of the product, and this mode should be used when mass-producing fixed-form products.
③ Small parts hanger. Small parts that are not suitable for rack plating need a rack that is suitable for small parts. This is the plate, drum, etc. mentioned above. The plate is similar to rack plating, that is, it is still connected to the cathode by the main conductive rod. However, the conductive rods are no longer hooks, but small discs or screens made of metal mesh. The mesh of these mesh discs or screens is determined according to the size of the parts to be electroplated.
④ Electroless plating hanger. Due to the problems of pollution to the hanger in electroless plating, special hangers are required for electroless plating before electroplating non-metallic materials. In many cases, electroless plating is made of rubber wires or net bags as hangers. After electroless plating is completed, the electroplating hangers are added. Now, a hanger coating has been developed that does not participate in the chemical plating process in the non-metallic metallization process, which also produces a hanger used in the whole process of plastic electroplating from pre-treatment to electroplating to the end of the finished product. It is especially suitable for For the production of automatic electroplating lines.
The principle of selection of hangers is of course based on the requirements of production capacity and product quality. The connection between the electroplating product and the hanger depends on the weight of the metal part itself to contact the hook on the hanger, which is called gravity conduction. When performing non-metal electroplating, especially plastic electroplating, since the relative density is less than or close to the plating solution, the buoyancy generated by the plating solution will make the plated parts unstable on the hanger, and even the entire hanger will float. The selection of hangers has more requirements than metal plating.
1. First determine the quantity
The relationship should ensure that the hangers used can reach the production capacity required by the production program, that is, the loading capacity of the hangers, including weight and quantity. Both manual operation and automatic line production should consider the single hanging weight. It is necessary to proceed from the principle of ergonomics and consider the continuous operability of the operator. Even if it is a hanger used on an automatic production line, the loading and unloading of the final product still require manual operation, and it should not be too heavy, with a weight of 10kg. Inside is appropriate. Of course, for non-metal electroplating, the number of each hanger should be used as the basis, and its weight cannot be used as a requirement. The second is the size of the plating tank. The size of the plating tank determines how many hangers can be installed in a plating tank, as well as the size of the outer frame of each hanger. Generally, the top plated part of each hanger is at least 3-5cm away from the plating liquid surface, and the lower end is away from the tank. The bottom should be at least 10-15cm, and the left and right distances from the groove wall should be more than 10cm. Lastly is the size of the part being plated. The size of the parts is the basis for determining the number and distribution of hooks. The parts must never be too close to each other, let alone cover each other. On the premise of ensuring electrical conductivity, the current distribution on the surface of the plated part should be as uniform as possible, the gas discharge should be smooth, and the plating solution should not remain in the plated part and can be easily discharged.
2. To determine the material for making the hanger
Since the conductivity and cost of different metal materials are different, it is also very important to use what kind of material to meet the needs of electrical conductivity when selecting a hanger. Generally, brass is used more. Especially for hooks that rely on elastic contact, brass is ideal. Of course, the conductivity of copper is the best, but its strength is slightly insufficient. However, some companies still use brass for hangers, because the strength and elasticity are better. In fact, red copper can be used for the main conductive rod, but brass can be used for the hook part for good elasticity. This is because most of the hooks are in the plating solution, and the amount of current passing through the conductor in the plating solution can be It is twice as large as in the air, so the conductivity efficiency of using red copper as the main conductive rod is much higher than that of using brass completely.
3. Conductive cross-section of the main conductive rod
After the material for making the hanger is determined, it is necessary to know how thick the main conductive rod is to be selected. The determination of this parameter is related to the total current that will pass through the main conductive rod. The determination of the total current depends on the total surface area of the product plated on the rack and the maximum current density allowed by the process used.
4. Selection principles of non-metallic electroplating hangers
①The parts to be plated and the hanger should be tightly connected. When non-metal electroplating products are mounted on the hanger before electroplating, it is necessary to fully ensure a good connection between the product and the hanger. This connection must be fixed, and it is not easy to fall off after multiple processes.
②The hooks of elastic connection should be set symmetrically. When using elastic connection hooks, the force points must be symmetrically arranged, and the toughness of the hooks must be moderate, so that the plated parts should not be deformed due to excessive force. .Especially when the hook is asymmetrical, it is difficult to correct it once it is twisted.
③The contact surface of the conductive contact should be large. Since the plating thickness of non-metallic electroplating parts after electroless plating is only 0.1 ~ o.3pm, if the point contact during metal electroplating is used to conduct electricity, because the conductive cross section is too small, the connection point will be burnt out accidentally and the electroplating will fail. Therefore, for the contact of non-metallic electroplating hooks, the method of surface contact should be adopted, that is, the tip of the hook should no longer be pointed or point-shaped, but should be a small plane shape. A small wafer is welded to the contact part with the contact point, so that each conductive section is increased several times or even ten times, and its ability to pass current is greatly increased.
④The main conductive rod shall adopt the double-rod multi-point contact type. The metal plating hanger has a single-rod main conductive rod. In this way, when the cathode moves, the hanger will swing with it. But for non-metallic electroplating, when the resistance of this swing is too large, it will cause the plated parts to fall off. Therefore, for non-metallic electroplating, double main conductive rods are always used to increase the number of hangers and cathode conductive rods. relatively fixed connection.
⑤The non-conductive parts of the hanger should be shielded with insulating paint. Like the metal electroplating hanger, the non-conductive parts of the hanger should be shielded with insulating paint, which not only saves electricity and materials but also makes the current more concentrated on the plated area.
