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SDK Develops Halogen-Free, Heat-Resistant Electromagnetic Wave Absorption Sheets

July 1, 2004

Showa Denko K.K. (SDK) has developed a halogen-free, heat-resistant electromagnetic wave absorption sheet that controls noise and prevents malfunctioning of mobile electronic devices, such as cellular phones and digital cameras.

There is a growing need for noise-control material as mobile electronic devices are heading for still higher performances and compactness with the use of high frequency and dense mounting technologies. While electromagnetic wave absorption sheets are pasted on circuit boards and elements, conventional sheets contain halogenated resins or halides to ensure flame retardance and high loading of magnetic materials in base resins.

SDK has developed environment-friendly halogen-free sheets by combining proprietary technologies for the design/processing of resin compositions and the design/production of magnetic materials. By using magnetic properties of magnetic materials dispersed in resin, the new product effectively absorbs unnecessary electromagnetic wave and controls noise. The advantages of the new product are as follows:

  • 1.Free from halogen, antimony, lead or siloxane1)
  • 2. Granted the status of UL94V-02) (thickness: 0.1 mm-0.5 mm) (This level of flame retardance was not possible with existing halogen-free sheets.)
  • 3. High efficiency of noise control comparable to the best product on the market today
  • 4. Resistant to heat as high as 130°C (This enables the product to cope with the heat buildup resulting from the use of high-frequency LSIs. The product can also be used in the automotive engine room.)
  • 5.Superior flexibility and workability

Studies are now under way regarding the use of electromagnetic wave absorption sheets in non-contact electromagnetic induction IC cards.3) Demand for this type of IC cards is forecast to grow rapidly for such applications as electronic payment of train fare and short-distance communication.

SDK has started sample shipments of the new product, planning to start full-scale sales by the end of this year. Sales for 2010 are targeted at 2 billion.

SDK will further develop thinner halogen-free sheets—0.05 and 0.025 mm—while maintaining their high noise-control and heat-resistance characteristics to meet the demand for more compact electronic devices.

Under the ongoing medium-term consolidated business plan, the “Sprout Project,” SDK is positively allocating resources to its magnetic materials business as one of the “strategic growth businesses.” SDK intends to increase the annual sales of magnetic materials to 5 billion by 2010 by developing individualized products through interconnections of such proprietary technologies as high thermal conductivity inorganic fillers and formation of thin magnetic films.


  • 1)Siloxane
    A family of silica-based compounds. Silicone rubber is widely used as a halogen-free resin for this application. However, when there is residual low-molecular weight siloxane, it tends to vaporize, causing contact defects on circuit boards.
  • 2)UL
    An abbreviation for Underwriters’ Laboratories, Inc., a non-profit organization of the United States that sets wide-ranging safety standards. UL-94 represents a method for testing flame retardance of plastic materials. Class “V-0” means the highest level of flame retardance.
  • 3)Non-contact electromagnetic induction IC card
    In this system, the card’s IC chip is operated for reading and writing information using induced electric current. Specifically, electric current is passed through a reader & writer coil of a supporting device and the resultant magnetic field induces electric current in the card’s coiled antenna. Sony Corporation’s FeliCa™ card (for use in bitWallet, Inc.’s electronic money “Edy”) and East Japan Railway Co.’s Suica™ card are based on this system.

Samples of SDK’s newly developed halogen-free, heat-resistant electromagnetic wave absorption sheets