Specification of the hottest electroplating proces

2022-10-16
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Third, standardize the copper plating process. Copper should not only cover the defects of steel rollers, but also show the best working face for the next process - electric carving. Copper plating is an extremely complex process, and its control should be extremely strict. If it is a little careless, it will take a lot of time, manpower and material resources to correct the problems

(I) copper plating process flow

metalworking drum → inspection → drum distribution → drum pretreatment → pre nickel plating → grinding and cleaning → copper plating → drum unloading → vehicle delivery grinding

(II) drum copper plating principle

the copper plating layer is pink, soft and has good ductility

the main components of the electrolytic solution in the copper plating bath are sulfuric acid (H2SO4) and copper sulfate (CuSO4 · 5H2O). Copper exists as copper ion (cu2+) in this solution. Electrolytic copper is used as anode, which is distributed in the electrolytic solution according to semi-circular arc and connected with the power anode. The drum is placed horizontally in the electrolytic cell. Some of its surface is fully immersed in the electrolytic solution, some are semi immersed or 1/3 immersed in the electrolytic solution. It is connected with the cathode and rotates at a certain speed. After being electrified, chemical reaction takes place at both anode and cathode. Copper ions are positively charged and attracted by the cathode. Electrons are obtained at the cathode to form copper atoms, which are attached to the drum to complete electroplating. But in fact, due to some reasons that will interfere with this reaction process, the positive and negative ions will never be balanced, so it is not easy to make a very satisfactory electroplating roller in actual production. In view of this situation, we can only try our best to reduce interference factors, and match various equipment and processes according to the conditions of our company, so as to make a satisfactory electroplating roller

(III) strengthen conductivity management

to improve the quality of the copper layer, it is important to control the current difference, ensure that the conductive parts are clean and in good contact, make the current value evenly distributed, and make the hardness of the copper layer at both ends of the drum and in the middle consistent

(IV) main components of copper plating solution

intaglio plating adopts sulfate copper plating, and the basic components of the plating solution are copper sulfate and sulfuric acid. Copper sulfate is used to supply copper ions in the plating solution, while sulfuric acid can prevent the hydrolysis of copper salt, improve the electrical capacity of the plating solution to guide out the sample and cathodic polarization. Due to the high current efficiency of the bath (nearly 100%), a thicker coating can be plated. Of course, we should ensure the purity and stability of various chemicals. The main components of copper plating solution are as follows:

1 Copper sulfate (CuSO4 · 5H2O) is a blue crystal, and its particle size is like corn grain. It should be free of yellow as far as possible, and it is available in industrial grade. According to the production conditions and different requirements, the content of copper sulfate is 200 ~ 250g/l, 210 ~ 230g/l and 180 ~ 220g/L. The content of copper sulfate is low, the allowable working current density is low, and the cathode current efficiency is low. Sulfur this will include kiefel's business in freilassing, Germany. The increase of copper sulfate content is limited by its solubility, and the solubility of copper sulfate decreases with the increase of sulfuric acid content in electroplating. Therefore, the content of copper sulfate must be lower than its solubility to prevent its precipitation

2. Sulfuric acid (H2SO4) can significantly reduce the resistance of the plating solution and prevent the hydrolysis and precipitation of copper sulfate. Its chemical reaction formula is as follows:

CuSO4 + 2H2O Cu (OH) 2 +h2so4

if it emits an odor like ammonia, there is a problem. If the concentration of bath solution is not appropriate, cu2+ will be produced, causing pitting and needle holes on the copper plated surface

sulfuric acid the Institute of plastics processing (IKv) of Aachen University of technology in Germany and its skilled crafts are conducting a research on polypropylene composites filled with graphene. When the content is low, the coating is rough and the anode is passivated. Increasing the content of sulfuric acid can improve the average plating ability, but some brighteners are easy to decompose. It includes the service content of load frame coaxiality correction. Some company specifications are 40 ~ 60g/l, some are 55 ~ 65g/, and some are 60 ~ 70g/L

some companies control the content of copper sulfate at 180 ~ 270g/l and the content of sulfuric acid at 55 ~ 65g/L, which has achieved good results, making the copper layer reach the best hardness and extending the storage period

under the condition of 15 ℃, the corresponding relationship between copper sulfate + sulfuric acid content and Baume degree is shown in Table 2

3. Chloride ion (cl-), obtained by adding a little hydrochloric acid. Chloride ion is an indispensable non-polar anion in acid bright copper plating. The ideal bright copper layer cannot be obtained without chloride ion, but too high chloride ion content will cause pitting on the copper coating and affect the brightness and smoothness. It should be used according to the requirements of additives. For example, megino additive is 50 ~ 60ppm, hard is about 50ppm, and Daiwa G is 80 ~ 120ppm

(V) preparation method of plating solution

first dissolve the calculated amount of copper sulfate in 2/3 of the prepared volume of warm water. When the copper sulfate is completely dissolved and cooled, slowly add sulfuric acid under continuous stirring (adding sulfuric acid is an exothermic reaction), quiesce the plating solution and filter it, and then add the specified additives. After the trial plating is qualified, it can be put into production

(to be continued)

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