The main component of the leveling agent is a surfactant with a large difference in molecular structure. The role of the leveling agent is to improve the leveling performance of the bath because the leveling agent can be preferentially adsorbed on the crystal surface with high activity and fast growth speed. The growth rate of these crystal planes is reduced, so that crystals arranged neatly can be obtained and the plating layer can be made uniform. It can greatly expand the cathode current density upper limit, and can improve the brightness of the low current density area. The disadvantage is that due to the strong adsorption of this type of active agent on the cathode surface, a layer of ten water film is formed on the surface of the cathode to reduce the binding force of the coating. The scope of use of leveling agent is relatively narrow, when the content is too low, it will affect the leveling effect, the high current density area is easy to scorch, and if the content is too high, a large area of ​​peeling phenomenon is likely to occur, and the effect of the hardener will be inhibited, so that the plating layer The light effect is poor and the hardness is reduced, as shown in Figure 4.
7. Cathode move
In order to make the coating uniform in the circumferential direction, electroplating usually adopts the mode of rotation of the platen (cathode movement). The appropriate rotation speed of the plate roller can effectively reduce the polarization of the concentration difference and help to increase the upper limit of the cathode polarization and current density, thus shortening Plating time increases production efficiency. The line speed of the printing roller is too slow, and the allowable operating current density is low; the line roller rotates at a too fast line speed and it is easy to splash the plating solution. In addition, the rotational speed of the plate has little effect on the hardness of the plating.
8. temperature
In the production process, the plating temperature must be strictly controlled, the temperature is too low, and the concentration polarization of the cathode is enlarged, but the upper limit of the current density is also reduced, and the copper sulfate is easily crystallized, causing quality problems. At the same time, if the temperature is too low, there will also be a fixing direction when the hardness and hardness of the coating are maintained, as shown in FIG. 5 . High temperature, can increase the conductivity of the bath, reduce concentration polarization, but also reduce the bright coating, but if the temperature is too high, it will decompose additives, increase the consumption of additives.
9. Current density
The current density is a more important factor, which is closely related to the quality of the plating. The upper limit of the current density is affected by the factors such as bath temperature, stirring intensity, bath concentration, and additive ratio. Because the plating is generally thick, it is desirable to use a relatively high current density. It can be achieved by appropriately increasing the temperature of the bath, strengthening the stirring, increasing the concentration of the bath, adding a reasonable proportion of the additive and the amount of the additive (decreasing the content of the hardener, and increasing the leveling agent). Low current density, low production efficiency, low cathodic polarization, coarse crystals, rough coating, low hardness, and relatively short hardness retention time; increased current density, increased production efficiency, improved cathodic polarization, and crystal clear , Close, bright plating, and can increase the interaction force of the crystal atoms, to promote the inclusion of hardener in the copper layer lattice, thereby increasing the hardness of the copper layer, as shown in Figure 6. No excessive current density can be pursued in the production process.
10. anode
For phosphorous copper anodes, an appropriate amount of phosphorus content is an important quality indicator for phosphorus copper anodes. It is ensured that the black phosphor film forming Cu3P on the anode surface is not thick or thin, but its structure is tight and it is firmly bonded, which not only can effectively prevent monovalent copper. The production does not affect the normal dissolution of the anode. Anode with low phosphorus content is too thin on the surface of the anode to form a black phosphor film, which can not effectively prevent the generation of copper powder and inevitably contaminate the plating solution. Once infiltrated with the plating layer, there will be a large quality risk; high phosphorus content The black phosphorus film thickness produced by the copper anode in production, combined with the large current density and rapid black phosphor film formation, easily causes the black phosphor film to fall off and the black phosphide mud and mud to increase, which can also cause rough plating. In addition, because the phosphor film is too thick, the resistance of the plating solution increases. To maintain the original current, the tank voltage must be increased. In the case of a rise in the cell voltage, hydrogen ions are advantageously discharged to generate hydrogen, which is likely to cause pinholes. In addition, the area ratio of the cathode and the anode must also be given sufficient attention. If the area of ​​the anode is too small, anode passivation or local passivation is likely to occur, the cell voltage increases, and a large amount of oxygen is generated at the anode, which consumes excessive amounts of additives.
The bag sleeves outside the phosphor bronze anodes are also stressful. Acid-resistant polyester fabrics or acid and alkali-resistant polypropylene fabrics should be selected, and the density (density of latitude and longitude lines) should be appropriate. The density and thickness of the anode bag are different, and the effect of convection diffusion of blocking anode particles, black mud and copper ions is also different.
11. Cathode and anode distance
Proper cathode and anode distances can effectively reduce energy consumption on the premise of ensuring good dispersion ability and depth capability. The distance between the cathode and the anode is too close. The depth capability and throwing power of the plating layer are poor, and the uneven thickness and uneven hardness of the copper layer are likely to be caused. As a result, the raw material is wasted; the distance between cathode and anode is too large, and the resistance of the plating solution increases. To maintain the original current density, it is necessary to increase the cell voltage and increase the energy consumption.
12. Periodic maintenance of bath
The production capacity of the plate-making manufacturers is generally relatively large, and the consumption of additives is also relatively large. It is impossible for all the components in the additives to be consumed in the same proportion, and some of the components will accumulate. Exceeding the solubility will precipitate on the surface of the plating solution and affect the plating. The binding force, as well as other quality risks, must be dealt with on a regular basis. The treatment method is as follows: raise the bath temperature to 70°C, add 1-2ml of 30% hydrogen peroxide solution under stirring, stir for 2 hours, then slowly add 3-59/L of powdered activated carbon, let it stand overnight, and filter it. The assay was adjusted according to the additives required for the Hall tank experiment and used after 2 hours of electrolysis.
In addition, in the actual production process, although the current density of the cathode is high, it is impossible to reach 100% while the anode current efficiency exceeds 100%. Therefore, the dissolution amount of the anode is more than the amount of precipitation of the cathode, and because the current density used in the process is large, sufficient area of ​​the anode must be secured, so the content of the copper sulfate in the plating solution is gradually increased when the process exceeds the process. Range, it is necessary to dilute the plating solution, resulting in the waste of raw materials. Solution: 1-2 titanium blue phosphors can be replaced with high-density graphite to maintain the stability of the composition of copper sulfate, to pay special attention is that due to the current density used in the process is larger, the graphite surface will produce a lot of Oxygen causes the graphite powder on some surfaces to fall off. It is necessary to strengthen protective measures so as not to contaminate the plating solution.
The technological parameters of the fast electroplating hard copper introduced in this article are not all fixed values, and must be determined according to the specific conditions of production, and need to be slowly summarized in actual production.
Qingdao Hailian Plate Making Co., Ltd. Wang Qinghao
Source of information: printing and packaging. decorating technology
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