Review and prospect of new electroplating processes and new technologies

Review and prospect of new electroplating processes and new technologies

Abstract: A brief review of the new electroplating process, such as alloy electroplating, electroplating and functional electroplating, was carried out in the late 20th century. The future of electroplating technology in the development of new materials, especially nanomaterials, in the 21st century is prospected. .

Keywords: electroplating new process alloy plating electroplating functional plating nano-material

1. Preface

We have entered the 21st century. In the face of this new century, how does the electroplating industry respond? Is it really thin, not doing it? To answer this question, it is necessary to make a review of the new electroplating process and new technology of the last century, and to make an outlook on the role of electroplating technology in the new century.

Due to the application of new surface treatment technology and the reduction of the amount of ferrous materials used in the product structure, the application of traditional electroplating technology is shrinking. In this sense, the electroplating industry is a good sunset industry. But 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 needs of resources, energy, environment, military, aerospace, etc. Electroplating technology has made great progress and progress in the development of new processes. The need in social reality has always been the driving force behind technology development, and modern enterprises are based on the needs of the market. Therefore, the research and development of new electroplating processes is based on real needs, while taking into account the trend of technological advancement or potential future needs. Stimulated by these demands, many new processes and technologies were created in the twentieth century.

The so-called new process is relatively old, old, and traditional. For example, alkaline zincate galvanizing, which is now popular, was a new process in the 1970s and 1980s, and it is no longer a new process. The new process refers to a new process system that is different from the original process from the process recipe to the operating conditions and process flow. 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, can not be said to be a new process.

For the electroplating process, a system characterized by a main salt and a ligand. A new process often uses a new main salt, or a new complex. Taking copper plating as an example, the traditional cyanide copper plating is characterized by a complex. With acid bright copper plating, the use of copper sulfate and sulfuric acid system, plus a new brightener, plus a cathode moving device, this is a new process of acid bright copper plating. There are also pyrophosphate copper plating, HEDP copper plating, etc., compared to cyanide copper plating is a new process. It is also a new process to develop copper plating with high alkaline dispersibility of copper sulfate as the main salt.

Due to the development of technology and industry, the demand for new processes is also dynamic, so even in the traditional industrial field, the plating process has new opportunities. As for the new century, it is called the century of high informationization, and some people say that it is the nano century, the green century. The emergence and development of these new basic industries provide a broad space for the development of electroplating technology. Due to space limitations, this article only introduces the new technology mainly related to materials and functions. It is not a comprehensive review of the new electroplating process. It is inevitable that it will be inevitable. If it is inappropriate, please advise.

2, introduction of new plating process

2.1 alloy plating

Alloy plating has always been an important area for the development of new plating processes. Copper-tin alloys that were previously developed to replace expensive nickel plating have been a new process. Today's nickel and nickel plating are also various alloys. Because alloys can combine the advantages of a single metal and have new properties not found in a single metal, such as hardness, corrosion resistance, and functionality. It has now been recognized that electroplating, as a hydrometallurgical technique, produces new alloys that cannot be made by electrical or thermal methods. Electroplating technology is advantageous in the production of amorphous and nanomaterials.

In the traditional theory, the principle of alloy plating requires that the electrode potentials of two co-deposited metals should be close. If one potential is positive and the other potential is negative, it is necessary to use a complexing agent to positively metal ions. The complexation causes the discharge potential to move in a negative direction, which is close to the potential of another metal, and achieves the purpose of co-deposition. This is still guiding the development of new alloy processes.

But now the amount of another component in more and more alloys is very small, that is, the small amount of metal dispersed in another metal changes the properties of the metal. The traditional metallurgical point of view is that these incorporated metals occupy some of the lattice sites of the host metal, thereby altering the physical properties of the metal. But in fact, it is difficult to disperse trace metals into another metal by pyrometallurgy, and the electroplating method is relatively easy to do. However, whether the structure of the alloy obtained by the electroplating method conforms to 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, silver series and so on. Zinc is widely used as an excellent and inexpensive protective coating for steel, but since Japanese cars have entered the European and North American markets, the salt-resistance of automobiles has been mentioned on the agenda. [1] In the study of high corrosion resistance coatings, the study of zinc alloys has attracted attention. The first to appear is tin-zinc alloy. The zinc content of this alloy is about 30%, the salt spray resistance is the longest, and the red rust time is more than 1500 hours.

The first process to enter the practical process was the neutral plating solution of organic carboxylic acid in the late 1970s. Later, there was a citric acid plating solution. Now our company has developed a bright zinc tin plating process. What emerges after the tin-zinc process is the zinc-nickel process. This process is rapidly gaining popularity because the nickel content is 5-10% and the cost is lower than that of tin zinc. The first to appear was the sulphate process for continuous plating of steel sheets, which was around 1982. The ammonium chloride type process was developed in the future, and the alkaline zincate process is now more mature. This process is characterized by particularly good corrosion resistance. The unpassivated coating is resistant to salt spray to red rust for more than 150 hours. It also maintains its excellent protection at high temperatures. Therefore, there are many applications in the automotive industry.

In the two years after the development of zinc-nickel, the zinc-iron process has entered into practical use. Zinc iron differs from the previous process in that the iron content is very small, only about 0.2 to 0.6. Although there have been zinc-iron alloys used for steel plate plating, the iron content is 10-20%, but it is still practical to use such a low-iron coating. More mature zincate process. Its 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 salt spray time of red rust can reach more than 1500 hours. Now, our company has developed a new process of sodium chloride type zinc iron, and has passivation products with high corrosion resistance such as yellow and color.

In Europe, there is also a zinc-cobalt alloy process. Like zinc-iron, this process can make a black passivation film without using silver salts. The amount of cobalt contained is also only about 1%.

Nickel has always been an important plating in the electroplating industry. Due to the tightness and high cost of nickel resources, the development of nickel alloy plating is an option for nickel. At the same time, the functional properties of some nickel alloys are also required by the market. Therefore, nickel-based alloys are also widely used.

Nickel-iron alloy not only saves a part of nickel, but also has better coating performance than pure nickel coating. The iron content of this coating is about 7%-30%, and the iron content in the coating is proportional to the ratio of nickel to iron in the plating solution. There are also reports of nickel-manganese-iron alloy plating processes. [2] More nickel alloys for decoration, especially for black plating, many of which are nickel alloys, such as nickel tin, nickel cobalt, nickel cadmium and the like. 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 a large number of applications. The main direction of this new process is to replace cyanide with non-cyanide complexes, such as pyrophosphate, citrate copper plating alloy.

Tin is used as a brazing coating mainly in the electroplating industry, but it can also be used in decoration and protection, such as tin alloys for silver, tin plating for cans. But there are still a lot of applications in the electronics industry, and the tin-lead alloy is still the most used. There are also tin bismuth, tin bismuth and so on. The current trend is to replace old processes with new processes that are free of fluorine and lead. [4]

Alloys of other precious metals are mainly used for decoration and functionality, and are not introduced here. As mentioned earlier, the development of alloy plating technology may produce some new alloys, which are not only important in the surface treatment industry, but also important in the material science. Therefore, in the new century, research on alloy plating will continue to be intensified. Especially in the development of multi-alloys, including ternary and quaternary alloys, there is still a lot of room.

2.2 Electroplating

As mentioned earlier, the 21st century is known as the high information age. The so-called high information century is the century of information explosion with the Internet as a means of communication. In this century, the variety and output of electronic products will have faster and greater development, which brings great opportunities and challenges to the electroplating industry. Therefore, a large proportion of the development of new processes will now be placed in electronic plating.

Electroplating is the electroplating technology used in electronics or the electronics industry. There are many 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.

Except for a few, the electroplating process utilizes traditional processes, most of which are new processes developed in recent decades. For example, new non-metal plating processes, new electroless plating processes, new precious metal plating processes, and new alloy plating processes. Taking electroplating of printed circuit boards as an example, it is a process combining pre-treatment, electroless plating, electroplating, and deplating, which is centered on hole metallization.

Printed circuit boards have been used in electronic products since the 1960s. With the high density and integration of electronic components, single-sided and double-sided circuit boards have been unable to meet the demands of high density and miniaturization. Circuit board technology came into being. Now, the multi-layer plate hole and pattern plating technology represents the level of a national electronics industry.

Various electroless nickel plating techniques in electroless plating play an important role in the electronics industry. Electroless nickel plating is used for electroplating from electromagnetic shielding to hard disk. 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 pipes is using electroless nickel plating technology. [5]

2.3 functional plating

Functional plating is actually a broader concept that covers electroplating, anti-friction plating, wear-resistant plating, and all plating techniques with special requirements. It can be said that any coating that meets the requirements of electrical, mechanical, optical, biological, etc. on the surface of a product or material and can meet its requirements by electroplating can be called a functional coating. Obviously, to meet the above various requirements, it is impossible to rely on the old process, so the proportion of new processes in functional plating is the highest.

What is causing various concerns now is various composite plating technologies. Composite plating refers to the dispersion of some functional particles in a single metal plating or alloy plating solution to co-deposit with a metal or alloy during electroplating, so that the surface to be plated has certain properties.

One of the nickel plating processes that you often see on the sand surface is to use a method of dispersing particles. Most of the early composite plating carriers were nickel plating processes, and have now been developed to use galvanizing processes as carriers and further developed to be electrolessly plated. The particles used for the dispersion include perfumes, abrasives such as silicon carbide, SiC, Al2O3, etc., as well as pigments, graphite, molybdenum disulfide, and the like. From the properties of these fine particles, it is possible to know what kind of function the plating layer in which they are dispersed has. There are many new processes that can be included in the range of functional plating. It is expected that the future development of new electroplating processes will be mainly applied to functional electroplating technologies in the electronics industry or industries with special requirements.

3 prospects of electroplating technology in the new century

3.1 close to the needs of modern industry

The 21st century has many demands on industry, requiring high quality, high reliability, high efficiency, and energy saving and environmental protection. Therefore, it is a long-term task to develop new electroplating processes that are energy efficient and have 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 on the equipment. The high-speed electroplating process with high current and short time will be popularized, and the control and plating solution of temperature, concentration, pH, etc. Purification and so on will gradually develop into full automation. A non-emission plating process will emerge. These are all more suitable for the needs of the industrial sector for electroplating. Only the various industries that are close to modern industry need to develop new technologies, and the electroplating processing industry itself has a foothold in the new century.

3.2 Manufacturing new materials

Electroplating technology has traditionally been used for protection and decorative purposes, but with advances in electroplating technology, electroplating has become more than just a protective and decorative field, and can be an important new material production tool. Electroplating techniques have been successfully used to make amorphous materials. Amorphous materials are new materials relative to crystalline materials, which 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 nano is a state of aggregation of matter, showing some new properties when the atom or molecule is in the range of one millionth of a meter to one billionth of a meter. When the size of the material crystallizes between a few or a few tens of nanometers, this material has unexpected new properties. For example, a few nanometers of electrodes can increase the operating speed of the chip by tens of thousands of times; the strength of the metal made of nanomaterials is ten times higher than that of ordinary metals, and it is as flexible as rubber; nanoceramics retain the high temperature resistance of ceramics. And high-strength properties show plasticity. There are also many stories about the magical properties and applications of nano. In short, people have placed great expectations on nanometers.

At present, the fabrication technology of nanocrystalline materials in the world can be divided into three categories: one is external force synthesis method, such as mechanical grinding; the other is electrodeposition method, such as electroplating deposition, plasma deposition; the third is phase transformation interface formation method. Among them, the electroplating method has its own characteristics compared with other methods. First, many single metals can be electroplated, and second, 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 a long way.

3.3 electroplating

Speaking of electroplating, it is easy to think of electroforming. But the electroplating described here is different from the traditional electroforming. Electroforming requires a parent or a molded tire, which is then molded after electroforming. Electroplating refers to electrodeposition by selective intermittent discharge of electrodes in a special electrolyte without a mother type. When such discharge is controlled by a computer, it can be plated according to information stored in the computer. The shape you need. It sounds like science fiction, but many inventions are derived from scientific fantasy. It is believed that with the efforts of more imaginative electroplating technicians, more applications of electroplating technology will be developed.

Reference material

[1] Koga Takao. Progress of the lead-based alloy. Surface technology (Japan). VOL40, NO1, 1989

[2] MVAnanth Tuxture.Development in Electrodeposited Nanocrystalline Ni-Mn-Fe Alloys.Trans IMF, p222,77,(6),1999

[3]SSAbd El Rehim S.AbdEl Wahab.Electrodeposition of Copper-Nickel Alloys from a Citraet Bath Containing Boric Acid.Trans IMF, p242,77,(6),1999

[4] China Electroplating Committee. Non-fluoroboric acid Sn-Pb solderable coating and lead-free fluorine-free solderability long-term coating overview. Electroplating Communication. No. 4, 2000

[5] Jiang Xiaoxia Shen Wei. Electroless plating theory and practice. National Defense Industry Press. 2000

[6] Xiong Yi et al. Study on spray electrodeposition of nanocrystalline nickel. Electroplating and finishing. VOL22, NO5, 2000