Kyoto metal powder traditional technique surface treatment
In 1990, Fukuda Metal Foil Powder Company began developing metal powder for electromagnetic shielding paint, for which there was then a growing need in America’s electronics industry. The company worked on commercializing copper powder that offered excellent conductivity and cost effectiveness, yet was vulnerable to rust. First, they fabricated dendrite copper powder having favorable conductivity. Then, hydroxyl on the powder surface was removed, followed by surface treatment using a coupling agent to promote the affinity with acrylic resin, the base material of paint.
Thus, the company successfully developed copper powder that shows no deterioration in its properties over the passage of time, and which has been used worldwide in the electromagnetic shielding paint for PCs, mobile phones, and other electronic products. Currently, silver is being used for electromagnetic shielding due to stricter regulations governing electromagnetic waves, but the use of copper powder has been expanded to the wiring of printed circuit boards, surface treatment for insulation to facilitate heat dissipation and other applications.
Fukuda Metal Foil Powder Co., Ltd. http://www.fukuda-kyoto.co.jp/
Since being established in 1700 (the 13th year of Japan’s Genroku Era), the company has specialized in the production of metal foil for the past 300 years. With the beginning of the Meiji Period, the company soon entered the field of industrial materials. In 1936, they became the first Japanese manufacturer of electrolytic copper powder. This development proved to be a core technology for copper powder used in conductive paints along with related surface treatment technology that was developed. The company’s various methods and products based on traditional technology are applied to a wide array of industrial products ranging from the lids of noodle pots, to the disc brake pads of Shinkansen bullet trains and other applications.
Metal foil and powder are widely applied to a variety of product, such as mechanical parts, electronic parts, and packages for food or medicine.
Because there are at least seven major methods of producing metal powder, the factory has various plants that employ each of these methods. On the other hand, the laboratory for developing new products is small and simple.
The photo shows the complex form of copper powder for conductive paint.
“If you want to see where the copper powder is used, you would have to disassemble your mobile phone or PC. The copper powder we developed is used in the electromagnetic shielding paint applied to the back of the body of these devices.”
It is believed that the electromagnetic waves emitted from electronic devices can cause other electronic devices to malfunction, as well as have harmful effects on the human body. Such electromagnetic interference can be prevented by covering the inside of these devices with a paint mixed with metal powder having good conductivity.
“The ideal material is silver, but the price is not reasonable. Consequently, nickel was used in the United States during the 1980s, but nickel lacks sufficient shielding performance. At that time, the American computer industry needed metal materials offering better performance at lower cost.”
The regulations governing electromagnetic waves are self-imposed in Japan, but legally enforced in the United States. When a popular product can be manufactured for the American market, its sales will be huge and eventually reach worldwide markets. Mr. Kajita, who has an engineering and sales background, set up a project team by recruiting members with a strong motivation in the company. However, the company did not officially condone the team’s activities, which were considered too adventurous.
“We immediately decided on the material to be newly developed: copper. It has far better conductivity than nickel, though is inferior to silver.”
If so, why wasn’t copper used until then? The reason is that copper oxidizes easily, and thus suffers significant deterioration in its performance. Yet, by solving this problem, copper would prove quite satisfactory in terms of performance and cost. This is exactly what Mr. Kajita thought about copper.
Metal powder comes in a great variety of shapes and sizes according to the intended use and method of production. To improve conductivity, the desired shape of metal powder needs a larger surface area and more contact points so as to ensure easy contact with other metal particles. By employing the electrolytic method, the team devised copper powder of a dendritic shape having many tiny projections. The problem was how to conduct surface treatment for rust prevention on this powder without lowering its conductivity.
“The reason why electrolytic copper powder oxidizes is because moisture inevitably remains on its surface during the process of electrolyzing copper from copper sulfate solution. This moisture must be transformed into another substance through chemical reactions. In addition, copper powder must have favorable wettability (in this case, the contacting characteristics with resin materials) since it is mixed with acrylic resin to be used as paint. As an additive to satisfy both conditions, we finally decided to use such coupling agents as titanate and aluminate.”
Since the company did not officially sanction this research, the team had to work on it after regular working hours. The members tried new methods of surface treatment almost everyday until late at night. The results would then be revealed the following morning. They analyzed the results and then tried another method that night. They repeated this procedure many times.
“No matter how favorable the characteristics were shown initially, marketing in the form of a product is not possible without proving long-term reliability. We then conducted an evaluation test on a number of paint samples mixed with copper powder under environmental conditions of 65°C temperature and 95% humidity for a continuous one-year period to check the deterioration in performance of the layer of paint. Those samples proving defective during the course of the test were eliminated one by one. Finally, of the dozens of samples at the start of the test, only a few remained.”
The last obstacle was mass production. Although surface treatment was successful at the laboratory level, the team still had to prove that it was really possible to conduct uniform coating on each particle having a complex, dendritic shape at the mass production level. If even a small spot is not coated, the layer of paint will begin deteriorating from that spot. Moreover, stirring and mixing too hard in order to avoid such a situation will damage the delicate shape of the powder particles.
“Once you conduct surface treatment on copper powder, you cannot recycle it even if it proves defective. It simply becomes a large volume of industrial waste. Thus, we had to purchase a special machine for ensuring successful surface treatment. This machine could mix the copper powder and coupling agents in a ‘fluffy’ fashion. This idea resulted from the experience and wisdom of the longtime, skilled operators of our plants.”
IBM, Apple, and other computer makers then began adopting the company's newly developed copper powder for conductive paint. This accomplishment was publicized in academic circles as well.
“Upon hearing about the metal foil or powder produced in a factory based in Kyoto, one might think of traditional Japanese gilded folding screens, gold-lacquered artifacts, beautifully handcrafted Buddhism altars, or other ritualistic objects. Sadly, the demand for such traditional handicrafts has been constantly declining. That doesn’t mean that we can allow the craftsman skills employed in producing these items to just fade away. Our role in this regard is to preserve such traditional skills and continue developing it so as to utilize traditional technology in the industrial fields of our time.”
Through the success achieved in this challenging development, which has been widely recognized in America, the world’s leading computer country, we have demonstrated the underlying capabilities of traditional Japanese technology.
In fact, Fukuda Metal Foil Powder Company had been skillfully manufacturing metal powder and foil materials some 76 years before America gained its independence as a sovereign nation.
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