Reasons for coarseness of the brightest acidic cop

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Reasons for the roughness of bright acidic copper plating

the main reasons for the roughness of the surface of acidic copper plating are: the pre nickel coating on the surface of parts is too thin or rough; Pre nickel plating enters sulfate copper plating solution and is not powered on in time; The chromium layer on the hook of the hanger has not been completely removed; Low phosphorus content in anode; Too high copper sulfate content, too high temperature or the presence of copper powder and other suspended substances in the plating solution will make the copper coating rough

there are many reasons for this failure. What kind of reason is it? In actual production, people have accumulated some experience. For example, the roughness of the copper plating layer caused by the thin pre nickel coating is punctate. Because it is not firmly combined with the substrate, you can use a knife to scratch the punctate roughness and observe the phenomenon. You can also judge by prolonging the pre nickel plating time and seeing whether the roughness of the copper plating layer disappears

the roughness caused by the untimely energization of pre nickel plating in the copper plating solution is not firm, and the coating can be wiped off immediately after wiping. In case of this phenomenon, all contact points should be brushed to reduce the contact resistance and make all conductive parts in good contact

in addition, pre nickel plated parts enter sulfate copper plating solution. If not powered on in time, nickel can also replace copper, forming a loose and rough replacement layer. If there is a chromium layer on the hook of the hanger, it will fall off in the form of small particles and fall on the surface of the parts at the lower part of the hanger, making the copper plating layer of the parts below rough because the coating on the chromium layer is not firmly combined. The roughness of copper layer caused by these factors should be carefully checked first

if the copper plating solution contains iron impurities, iron can replace the copper in the solution through the pores of the pre nickel plating layer (too thin or rough), forming a punctate loose replacement, so that the copper plating layer presents a rough appearance

when normal copper anode is electroplated, a uniform film will be formed on the surface, which can dissolve the copper anode in the form of divalent copper and inhibit the production of copper powder and monovalent copper. If the phosphorus content in the copper anode is low, it is difficult to form a brownish black film on the anode surface during electroplating. In this way, there will be more copper powder, and monovalent copper will dissolve into the solution. It is easier to reduce on the cathode and form a rough coating, so anodes with less phosphorus content should not be used. It is well known that copper powder or solid suspension will make the copper coating rough. Careful observation of the coarseness of the coating will find that the coarseness caused by solid particles or copper powder suspended in the solution mostly appears on the upper side of the part, because these particles have a high density and are easy to deposit on the upper side of the part. When such roughness occurs, check whether the anode bag is broken, and filter the plating solution to remove solid particles in the solution

copper powder is formed by monovalent copper ions in copper plating solution, which will cause rough copper plating layer, burrs and pinholes formed by copper powder falling off. Is the coarseness of copper plating caused by monovalent copper ions? Add 0.03ml/L ~ 0.05ml/L of 30% hydrogen peroxide to the plating solution and try plating. If it is caused by monovalent copper ions, copper powder will appear again after a period of time, indicating that monovalent copper ions are easy to produce in the plating solution. At this time, the generation path of copper powder should be checked

one of the ways to produce copper powder is the phosphor copper anode. First, check whether there is a black film on the surface of the phosphor copper anode and the air containing circulation system of the phosphor copper anode generally adopts a structure that can regulate the air supply direction; There are two kinds of humidification systems: Boiler humidification and surface evaporation; The cooling and dehumidification system adopts the refrigeration structure under the condition of air conditioning; The heating system adopts two structures: Electric fin heating and electric furnace wire direct heating; The temperature and humidity test method adopts the dry and wet ball test method to determine whether the phosphorus content is appropriate. It should also be checked that the phosphor copper anode cannot exceed the liquid level of the copper plating solution. The phosphor copper anode beyond the liquid level has no black film protection. When the phosphor copper anode in the titanium basket gradually drops, and the phosphor copper anode without black film protection falls into the copper plating solution, monovalent copper ions will soon be generated, forming copper powder, resulting in rough copper coating; In addition, the surface of phosphorous copper anode without black film protection is easy to generate cuprous sulfate crystals, and falling into the copper plating solution will soon produce monovalent copper ions, forming copper powder, resulting in rough copper coating. Another observation is that there should be no copper crystal adhesion on the conductive rod. The copper crystal on the conductive rod itself is a monovalent copper ion. If it falls into the plating solution, it will quickly produce monovalent copper ion and form copper powder, resulting in rough copper plating layer

the second way to produce copper powder is the content of chloride ion in the plating solution. Chloride ion is too low to fully combine with monovalent copper ion. Copper cannot fully convert monovalent copper ion (cuprous chloride) into divalent copper ion (copper sulfate) in the process of forming divalent copper ion, forming copper powder, resulting in rough copper plating layer; The decrease of chloride ion is mainly caused by large anode area and small cathode area. When the chloride ion in the plating solution is too high, it will form excessive cuprous chloride, produce disproportionation reaction 2cu+=cu+cu2+, and form copper powder, resulting in rough copper plating layer. The chloride ion in the plating solution can better meet the needs of product utilization. The increase of the content of chlorine is mainly from cleaning water, adding water, etc. The very fine copper powder generated by disproportionation reaction becomes anode mud. When air is used to stir, part of the copper powder enters the coating to form burr type roughness

when there is a chromium layer on the hook of the hanger, although it will make the parts rough upward, the phenomenon is slightly different. In addition to making the parts rough upward, the coating on the hanger is also rough and loose, and the coating on the hanger will fall off with powdery fine particles as soon as you touch it with your hand. If this phenomenon is found, the chromium removal treatment of the hanger before plating should be strengthened

if the temperature of copper plating solution is too high or the content of copper sulfate is too high, the cathode polarization of the plating solution will be reduced. Moreover, if the temperature of the plating solution is too high, it is not conducive to the adsorption of bright additives on the cathode surface of enterprises that have not adopted recycling equipment, so that the role of bright additives will be weakened, so that the crystallization of copper plating layer will be rough. The influence of high bath temperature or univalent copper not only makes the copper coating rough, but also makes the coating in the low current density area of parts not bright

the main measures to eliminate the above faults are: control the phosphorus content of phosphorous copper anode, and ensure that anode mud and small copper particles do not enter the solution during the dissolution of anode bag and anode basket; Avoid copper or other metal particles from entering various channels of the plating solution, such as copper powder on the pendant; The continuous filtration of copper plating solution removes various granular substances in the plating solution, which generally takes more than 3 cycles/h; All anodes and anode baskets should be in good contact with the anode bar (this is to ensure that the public can send e-mails, faxes, letters and other ways to the construction unit and the evaluation institution to express their opinions on the construction of the project and the environmental assessment work (issues unrelated to environmental protection are not accepted). The key to the normal dissolution of copper anodes is that if some anode baskets are poorly conductive, the dissolution current of other anodes will be greatly increased, which is not only detrimental to the dissolution of anodes, It also increases the possibility of copper powder production)

therefore, in the process of bright acid copper plating, the use of copper anodes containing an appropriate amount of phosphorus (using anode bags and anode baskets) can basically solve the problem of rough copper plating caused by the generation of copper powder by avoiding impurities brought by people outside, continuous filtration of plating solution, and good contact between copper anodes and anode bars

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