The reasons for the rough surface of the acid copper plating layer are as follows: the pre-plated nickel layer on the surface of the part is too thin or rough; the pre-plated nickel is not energized in the sulphate copper plating solution; the chrome layer on the hook of the hanger is not completely removed; The phosphorus content is small; the copper sulfate content in the plating solution is too high, the temperature is too high, or there is "copper powder" and other suspended matter, etc., which will cause the copper plating layer to appear rough.
There are many reasons for this kind of failure. What kind of cause is caused? In actual production, people have accumulated certain experience. For example, the copper plating layer is too thin due to the too thin nickel plating layer, because it is related to the substrate. If the combination is not strong, the point can be scraped off with a knife to observe the phenomenon. It can also be judged by extending the time of pre-nickel plating to see if the rough phenomenon of the copper plating layer disappears.
The roughness caused by the pre-nickel plating in the copper plating solution that is not energized in time is not well-bonded, and the coating can be wiped off by one rub. When this phenomenon occurs, all contact points should be brushed to reduce the contact resistance and make the contact parts of the conductive parts good.
In addition, the pre-nickel-plated parts enter the sulphate copper plating solution. If it is not energized in time, the nickel can also replace the copper to form a loose and rough replacement layer. If there is a chrome layer on the hook of the hanger, the plated layer on the chrome layer is not firmly bonded. It will fall off in the form of small particles and fall on the surface of the lower part of the hanger to make the copper plating of the lower part rough. . The copper layer roughness caused by these factors should be carefully checked first.
If the copper plating solution contains iron impurities, the iron can replace the copper in the solution through the pores of the pre-nickel layer (too thin or rough) to form a point-like loose replacement, giving the copper plating layer a rough appearance.
When a normal copper anode is electroplated, a monochromatic film is formed on the surface, which can dissolve the copper anode in the form of divalent copper, suppressing the production of "copper powder" and monovalent copper. If the phosphorus content in the copper anode is low, it is difficult to form a brown-black film on the anode surface during electroplating. Thus, there are many "copper powders", and there is a monovalent copper dissolved into the solution, which is easier to reduce on the cathode to form a rough coating. Therefore, anodes with low phosphorus content should not be used. It is well known that "copper powder" or solid suspensions can roughen the copper plating layer. Careful observation of the roughness of the coating reveals that the coarse particles suspended in the solution or the roughness caused by the "copper powder" often appear on the top of the part because these particles are denser and tend to deposit on the upper surface of the part. When such roughness occurs, it is checked whether the anode bag is broken, and the plating solution is filtered to remove solid particles in the solution.
Copper powder is formed by monovalent copper ions in the copper plating solution, which causes pinhole phenomenon caused by rough copper plating, burrs and copper powder falling off. Is the roughness of the copper plating layer produced by monovalent copper ions? It can be added to the plating solution by adding 0.03mL/L to 0.05mL/L of 30% hydrogen peroxide and then plating. If it is caused by monovalent copper ions, it will be over a period of time. Copper powder will be produced in time, indicating that monovalent copper ions in the plating solution are easy to produce. At this point, the way to produce copper powder should be checked.
One of the ways to produce copper powder is a phosphor bronze anode. First check whether the surface of the phosphor bronze anode has a black film and whether the phosphorus content of the phosphorus copper anode is appropriate. Also check that the phosphorus copper anode can not exceed the copper plating liquid level, the phosphorus copper anode beyond the liquid surface has no black film protection, when the phosphorus copper anode in the titanium basket gradually declines, the phosphor bronze anode without black film protection falls on the copper plating In the case of liquid, a monovalent copper ion is quickly formed to form a copper powder, which causes a rough copper plating layer; in addition, a surface of a phosphorous-copper anode which is not protected by a black film is liable to form a cuprous sulfate crystal, and a falling copper plating solution also rapidly produces a monovalent copper. Ions form copper powder, causing the copper plating to be rough. It is observed that there is no copper crystal adhesion on the conductive rod, and the copper crystal on the conductive rod itself is a monovalent copper ion, which falls into the plating solution, and rapidly generates monovalent copper ions to form copper powder, resulting in a rough copper plating layer.
The second way to produce copper powder is the content of chloride ions in the plating solution. If the chloride ions are too low, they cannot fully combine with the monovalent copper ions. In the process of forming divalent copper ions, copper cannot fully utilize monovalent copper ions (chlorine). The cuprous copper is converted into divalent copper ions (copper sulfate) to form copper powder, which causes the copper plating layer to be rough; the reduction of chloride ions is mainly caused by the large anode area and the small cathode area. When the chloride ion in the plating solution is too high, an excessive amount of cuprous chloride is formed, and the disproportionation reaction 2Cu+=Cu+Cu2+ is generated to form copper powder, which causes the copper plating layer to be rough, and the increase of the chloride ion content in the plating solution mainly comes from the washing water. Add water, etc. The very fine copper powder produced by the disproportionation reaction becomes the anode slime. When the air is stirred, part of the copper powder enters the plating layer to form a rough type of burr.
When there is a chrome layer on the hook of the hanger, although the part will appear rough to the top, the phenomenon is slightly different. In addition to making the part rough to the top, the coating on the hanger is also rough and loose, and the handle is touched by hand. The upper plating layer is peeled off by powdery fine particles. When this phenomenon is discovered, the chrome removal treatment of the pre-plating hanger should be strengthened.
If the temperature of the copper plating solution is too high or the copper sulfate content is too high, the cathode polarization of the plating solution will be lowered, and the temperature of the plating solution is too high, which is not conducive to the adsorption of the bright additive on the surface of the cathode, so that the effect of the bright additive is weakened, thereby causing plating. The copper layer is rough in crystals. Excessive temperature of the bath or the influence of monovalent copper not only makes the copper plating layer rough, but also makes the coating of the low current density region of the part not bright.
The main measures to eliminate the above faults are: controlling the phosphorus content of the phosphor bronze anode, ensuring that the anode mud and the small copper particles do not enter the solution during the dissolution process of the anode bag and the anode hanging basket; and avoiding various kinds of copper or other metal particles entering the plating solution. Channels, such as copper powder on the hanger; copper plating liquid continuous filtration to remove various particulate matter in the plating solution, generally more than 3 cycles / h; all anode and anode hanging baskets must be in good contact with the anode bar (This is the key to ensure the normal dissolution of the copper anode. If some anode baskets are poorly conductive, the dissolution current of other anodes will be greatly improved, which is not only unfavorable for anode dissolution, but also increases the possibility of copper powder generation).
Therefore, in the bright acid copper plating process, the use of a suitable amount of copper anode (using an anode bag and an anode hanging basket) is ensured to avoid external impurities, continuous plating of the plating solution, and good contact between the copper anode and the anode bar. It can basically solve the problem of causing the "copper powder" to cause the copper plating layer to be rough.
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Tag: Phosphorus Copper Hanger Plating Copper Powder Nickel Plated
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