Review and Prospect of New Electroplating Processes and Technologies
Keywords: electroplating new process alloy electroplating electroplating functional electroplating nanomaterials
1. Preface
We have entered the twenty-first century. How to deal with the electroplating industry in the face of this new century? Is it true that the sun is thin and there is no reason for it? To answer this question, it is necessary to review the new electroplating processes and new technologies in the last century, and at the same time, to look into the future of electroplating technology in the new century.
Due to the application of new surface treatment technology and the reduction of the amount of ferrous metal materials in the product structure, the application of the traditional plating technology is shrinking. In this sense, the electroplating industry is a good sunset industry. However, we can also see that the industrial development after the Second World War, especially the development of the electronics industry, since the 1950s, and the subsequent need for many resources such as resources, energy, the environment, military and aerospace Electroplating technology has made great progress in the development of new processes. The need in social reality has always been the driving force behind technological development. Modern companies are based on the needs of the market to develop products. Therefore, the research and development of new electroplating processes are also based on actual needs, taking into account the trend of technological advancement or potential future demand. In response to these demands, many new technologies and new technologies emerged in the 20th century.
The so-called new process is a relatively old, old, traditional process. For example, alkaline zincate zinc plating, which has become popular recently, was a new process in the 1970s and 1980s. It is now not a new process. The new process means that the entire process, from process recipes to operating conditions, process flow, etc., has new and innovative process systems that are different from the original processes. For the improvement of additives and brighteners, the application of a new brightener in the old process can only be said to be a new product. It cannot be said to be a new process.
For the electroplating process, a system characterized by main salts and ligands. A new process often uses a new main salt, or a new complex. Taking copper plating as an example, the traditional method is cyanide copper plating, characterized by complexes. With acid bright copper plating, copper sulfate and sulfuric acid systems are used. New products such as brighteners are added to the cathode moving device. This is a new process for acid bright copper plating. Also pyrophosphate copper plating, HEDP copper plating, etc., are relatively new cyanide copper plating process. The development of alkaline, highly disperse copper plating with copper sulfate as the main salt is also a new process.
Due to the development of science and technology and industry, the demand for new processes is also dynamic, so even in the traditional industrial field, the electroplating process has new opportunities. As for the new century, it is known as the century of high information technology, and some people say it is the century and the green century. The emergence and development of these new basic industries have provided a broad space for the development of electroplating technology. Due to space limitations, this article only briefly introduces new processes that are mainly related to materials and functions. It is not a comprehensive review of new electroplating processes.
2. Introduction of new electroplating process
2.1 Alloy Plating
Alloy plating has always been an important area for the development of new electroplating processes. Copper-tin alloys, previously developed to replace expensive nickel plating, were once a new process. The current generation of nickel and nickel plating are also various alloys. Because the alloy can combine the advantages of a single metal, and has new characteristics that are not possessed by a single metal, such as hardness, corrosion resistance, and functionality. It has now been recognized that electroplating, as a hydrometallurgical technique, can produce new alloys that cannot be made electrically or thermally. Including the production of amorphous materials and nano materials, electroplating technology is an advantage.
The principle of alloy plating in traditional theory is that the electrode potentials of two co-deposited metals should be close. If one has a more positive potential and the other has a negative potential, a complexing agent should be used to make positive potential metal ions. Complexation, so that the discharge potential to move in the negative direction, close to the potential of another metal, to achieve the purpose of co-deposition. This is still instructive in the development of new alloy processes.
However, nowadays more and more alloys have very small amounts of another component, which is the small amount of metal dispersed in the other metal, which changes the properties of the metal. The view from traditional metallurgy is that these doped metals occupy certain lattice sites of the host metal, thus changing the physical properties of the metal. However, in fact, it is difficult to disperse trace metals into another metal by pyrometallurgy, and it is easier to use electroplating. However, whether the structure of the alloy obtained by the electroplating method meets the principle of metallurgy is a subject worthy of discussion.
The new alloy processes that have been applied now include zinc series, nickel series, copper series, tin series, and silver series. Zinc is widely used as an excellent and inexpensive protective coating for steel, but since the Japanese car entered the European and North American markets, the car's salt-resistant protection has been mentioned on the agenda. [1] In the study of high corrosion resistant coatings, the study of zinc alloys has attracted attention. The tin-zinc alloy is the first to appear. When the zinc content of this alloy is about 30%, the salt spray time is the longest, and the red rust time can be more than 1,500 hours.
The first process to be put into practical use was the neutral plating solution of organic carboxylic acid at the end of the 1970s. Later, there was a citric acid plating solution. Now, our company has developed a process of bright tinned zinc sulfate. What appears after the tin-zinc process is a zinc-nickel process. Because of the nickel content of 5-10%, the cost of this process is lower than that of tin-zinc, and it has quickly gained popularity. The first to emerge was the sulphate process for the continuous plating of steel plates around 1982. After the development of ammonium chloride type process, now more mature is alkaline zincate process. This process is characterized by a particularly good resistance to corrosion, and the duration of the red rust is not less than 150 hours for a non-passivated coating. It can still maintain its excellent protection performance under high temperature. Therefore, there are many applications in the automotive and other industries.
Two years after the development of zinc and nickel, the zinc-iron process was put into practical use. The difference between zinc iron and the previous process is that the iron content is very small, only about 0.2 to 0.6. Although there were zinc-iron alloys for steel plate plating in the past, and their iron content was in the range of 10-20%, it is now practical to use such low iron content coatings. More mature zincate process. The corrosion resistance is also very good, but it must be passivated to have high corrosion resistance. When the iron content is around 0.4, the red rust salt spray time can reach more than 1500 hours. Now, our company has developed a new process of sodium chloride zinc iron, and there are yellow, color and other high corrosion resistance of passivation products.
In Europe, there is also a zinc-cobalt alloy process, which, like zinc and iron, can be used to make black passive films without silver salts. The cobalt content is only about 1%.
Nickel has always been an important plating species in the electroplating process industry. Because nickel resources are strained and expensive, the development of nickel alloy electroplating is an option for nickel. At the same time, the functional properties of some nickel alloys are also needed by the market. Therefore, nickel-based alloys are also widely used.
Nickel-iron alloys not only save part of nickel, but also have better plating properties than pure nickel coatings. The iron content of this coating is about 7% to 30%, and the iron content in the coating is proportional to the nickel-iron ratio in the plating solution. Nickel-manganese alloy plating techniques have also been reported. [2] There are more nickel alloys used for decoration, especially black coatings. Many nickel alloys are used, such as nickel-tin, nickel-cobalt, and nickel-cadmium. Copper-nickel alloys have more applications in decorative plating. [3]
Copper alloys such as copper-tin alloys and copper-zinc alloys have long been used in large quantities. The main direction of this new process is to replace cyanide with non-cyanide complexes such as pyrophosphate and citrate copper plating alloys.
Tin as a brazing coating is mainly used in the electroplating industry, but it can also be used in decoration and protection, such as tin alloys of silver substitutes, tin plating process for corrosion protection of cans, etc. However, there are still a large number of applications in the electronics industry, and tin-lead alloys are still the most used ones. There are also tin, tin, etc. The current trend is to replace the old process with a new, non-fluorine and lead-free process. [4]
Other precious metal alloys are mainly used for decoration and functionality, and they will not be introduced here. As mentioned earlier, the development of alloy plating technology may produce some new alloys. This is not only important in the surface treatment industry, but also important in materials science. Therefore, in the new century, the study of alloy plating will continue to be carried out. Especially in the development of multiple alloys, including ternary and quaternary alloys, there is still a lot of room for development.
2.2 Electroplating
As mentioned earlier, the 21st century is known as the century of high information technology. The so-called high information century is the century of information explosion that uses the Internet as a means of communication. In this century, the variety and output of electronic products will have faster and greater development, which also brings great opportunities and challenges to the electronic plating industry. Therefore, the development of new processes will now have a large proportion of electronic plating.
Electroplating is the plating technology used in the electronics or electronics industry. There are many kinds of coatings used in the electronics industry, including conductive coatings, brazing coatings, information carrier coatings, electromagnetic shielding coatings, electronic functional coatings, printed circuit board plating, protective coatings for electronic components, and decorative coatings for electronic products.
Apart from a few of the electronic plating processes that utilize traditional processes, most of them are new processes that have been developed in recent decades. Such as new non-metal plating process, new chemical plating process, precious metal plating new process, new alloy plating process. Taking electroplating of printed circuit boards as an example, it is a process that integrates pre-treatment, electroless plating, electroplating, and deposition-reduction technologies centered on hole metallization.
Printed circuit boards began to be used in electronic products in the 1960s. With the increasing density and integration of electronic components, single-sided and double-sided circuit boards have been unable to meet the demand for high density and miniaturization. Circuit board technology came into being. Now, the multi-layer plate's hole and pattern plating technology represent the level of a national electronics industry.
The various electroless nickel plating technologies in electroless plating play an important role in the electronics industry. Electroless nickel plating is used for electroplating from electromagnetic shielding to hard disks. Of course, electroless plating is not only used in the electronics industry, but also has important value in many other industries. For example, in the petrochemical industry, the inner wall protection of some pipelines uses electroless nickel plating technology. [5]
2.3 Functional plating
Functional electroplating is actually a broad concept, covering electroplating, anti-friction electroplating, wear-resistant electroplating, and all plating techniques with special requirements. It can be said that any plating that meets the requirements of electrical, mechanical, optical, biological, etc. surfaces on the surface of a product or material and that can meet its requirements can be called a functional coating. Obviously, in order to meet the above requirements, the old process is not feasible. Therefore, the proportion of new processes in functional plating is the highest.
Now it is various composite electroplating technologies that have caused various concerns. Composite electroplating refers to the dispersion of functional particles in a single metal plating or alloy plating solution that is co-deposited with the metal or alloy during the electroplating process so that the surface to be plated has certain properties.
One common feature of sand-plated nickel plating that everyone sees is the use of dispersed particles. Most of the early composite electroplated carriers were nickel-plated and have now been developed using a galvanizing process as a carrier, and further developed to use electroless plating as a carrier. The particles used to make the dispersion are spices, abrasives such as corundum, SiC, Al2O3, etc., as well as pigments, graphite, molybdenum disulfide, and the like. From the properties of these fine particles, it can be known what kind of function the coating with dispersed them has. There are many new processes that can be included in the scope of functional plating. It can be expected that the development direction of the new electroplating process in the future will be mainly applied to the functional electroplating technology in the electronics industry or in industries with special requirements.
3 Prospects of electroplating technology in the new century
3.1 Close to the needs of modern industry
In the 21st century, there are many demands for industry, demanding high quality, high reliability, and high efficiency. At the same time, we must also save energy and save energy and protect the environment. Therefore, it is a long-term task to develop a new electroplating process that is highly efficient and energy-saving, with little or no pollution. With the popularization of automation technology and the renewal of concepts, the electroplating process in the new century will be more involved in the equipment. The high-current and short-time high-speed electroplating process will be popularized, and the temperature, concentration, pH, etc. will be controlled and bathed. Purification will gradually develop fully automated. Non-emission plating processes will appear. These are all more suitable for the needs of the industrial community for electroplating, and only the close proximity to the various needs of modern industry to develop new processes, the electroplating process industry itself has a foothold in the new century.
3.2 Manufacturing new materials
Electroplating technology has traditionally been used for protective and decorative purposes, but with the advancement of electroplating technology, electroplating has become more than just a protective and decorative field, but it can also be an important new material production tool. Electroplating technology has been successfully used to make amorphous materials. Amorphous materials are new materials in terms of relatively crystalline materials. They are better than traditional materials in terms of hardness, strength, and corrosion resistance.
Now everyone can often hear a word that is "nano." The 21st century is also known as the nano century. The so-called nanometer is a state of aggregation of matter, when the atom or molecule is in the range of 10 to 10 millionths of a meter, it shows some new properties. When the material crystallizes in the size of several or several tens of nanometers, this material has unexpected new features. For example, a few nanometers long electrodes can increase the running speed of the chip by tens of thousands of times; the strength of the metal made of nano materials is ten times higher than that of ordinary metals, and it is as elastic as rubber itself; and nano ceramics retain the high temperature resistance of ceramics. And the high-strength properties show plasticity. There are many stories about the magical properties and applications of nano. In short, people place great expectations on nanotechnology.
Currently, the world's nanocrystalline material production technology can be divided into three categories: First, the external force synthesis method, such as mechanical grinding; Second, the electrodeposition method, such as electroplating deposition, plasma deposition; Third, the phase change interface formation method. The electroplating method has its own characteristics compared with other methods. First, many single metals can be electroplated, and secondly, the technical difficulty is relatively small. [6] Therefore, with the growth of research and demand for nanomaterials, the use of electroplating technology to develop and produce nanomaterials will not be far-reaching.
3.3 Plating
Speaking of electroplating, it is easy to think of electroforming. However, the electroforming described here is different from traditional electroforming. Electroforming requires a master or mold and is molded after electroforming. Electroplating refers to electrodeposition of a selective intermittent discharge by an electrode in a special electrolyte without a parent. When the discharge is controlled by a computer, it can be plated according to the information stored in the computer. The desired shape. This sounds like science fiction, but many inventions come from science fiction. It is believed that with the efforts of more imaginative plating technicians, electroplating technology will have more uses to be developed.