High Functional Material

1. Silicon Nitride Circuit Board for Power Modules

While past practice has been to use alumina and aluminum nitride for the insulated substrate used in the power modules of automobiles, new forms of energy, industrial equipment, and other such applications, silicon nitride substrates are increasingly being adopted because of their excellent material strength, thermal conductivity, and insulation.

In the past, commercial-scale production of silicon nitride substrates by Hitachi Metals, Ltd. has largely been of the insulated substrates themselves. Recently, however, Hitachi Metals has embarked on the full-scale production of silicon nitride substrates for power modules that are composed of a silicon nitride insulated substrate brazed to copper sheet.

Hitachi Metals already has the materials used in a silicon nitride circuit board (the silicon nitride substrate and the brazing material and copper sheet), and is able to satisfy a wide variety of customer requirements. A newly developed silicon nitride substrate with high thermal conductivity (130 W/m•K) is also available.

There is a trend toward the use of thicker copper (0.6 mm or more) to enhance the heat dissipation of circuit boards for power modules. Hitachi Metals has come up with a wide product range to coincide with silicon nitride circuit boards for power modules entering full-scale production. Hitachi Metals has also started to offer surface treatment of copper circuit in the form of plating with nickel (Ni), silver (Ag), etc., and the intention is to expand the options for material characteristics, copper thickness, and copper circuit patterns in the future.

(Hitachi Metals, Ltd.)

[1] Silicon nitride circuit board (left) and specifications of silicon nitride substrates and copper thickness range (right)

2. Electric Motor Operated Segment Ball Valve with Variable Open/Close Time

3. LAN Cable for Overseas Rolling Stock

Factors such as the greater use of Ethernet in the electronic equipment on rolling stock and the provision of wireless local area network (LAN) services for passengers mean that more information than ever is being handled. This is boosting demand for rolling stock communication cabling.

Hitachi Metals has developed a category 7 (CAT. 7) high-speed LAN cable that complies with the EN45545-2^* European fire safety standard for railways.

Rolling stock cables use halogen-free materials that do not emit smoke or toxic gases in the event of a fire and are required to satisfy the flammability criteria stipulated by European fire safety standards. To achieve the criteria for near-end crosstalk up to 600 MHz and other electrical characteristics requirements for CAT. 7 LAN cable, the insulation uses micro foam technology and multi-layer extrusion to reduce its dielectric constant and flammability, while each twisted pair of cores is covered with aluminum foil tape. All of the fire safety requirements are satisfied, with the sheathing being made from a mix of materials that meet the low-smoke and low toxicity requirements.

(Hitachi Metals, Ltd.)

* :

EN: European Norm

[3] Cable wires (left), test results for EN45545-2 European fire safety standard (top right), and attenuation and near-end crosstalk graphs (bottom right)

4. More than Century-long Tradition of Cutlery Steel Production

Knives are one of the conveniences of civilization and essential for daily life. In 2020, Hitachi Metals will mark the 121st consecutive year of production of the specialty steel used to make kitchen and other cooking knives in the San’in region of Japan that has supported traditional Japanese tatara iron-making since the Yasugi Works first commenced operation. The steel is used both in wabocho Japanese kitchen knives and in western-style knives.

Among the many different characteristics required for knives are hardness and the fineness of the microstructure, which are needed for the particularly important requirement of ensuring sharpness. Electron backscatter diffraction (EBSD) using an electron scanning microscope provides a way to analyze the fine microstructure (crystal grains) at the knife edge. The technique was used to view the microstructure of kitchen knives made from Aogami Super cutlery steel, a steel commonly used for this purpose. The steel contains a large number of hard carbide particles with microstructural features in the sub-2 µm range that give it a hardness of 804 HV.

By applying micro-control techniques for achieving fine control over microstructure to the Yasugi Specialty Steel brand of high-quality specialty steel, which includes cutlery steel, the company intends to support knife-making by supplying cutlery steel that enables users to enjoy the sharpness of kitchen and other knives.

(Hitachi Metals, Ltd.)

[4] Knife made from Aogami Super cutlery steel and EBSD image of blade edge (knife made by Moriya Munemitsu Co., Ltd.)

5. Scintillator Array for Security Applications that Combines High Performance with Low Cost