New mobile phones with built-in cameras and 3G functions consume much more power than conventional mobile phones, generating demand for high-volume lithium ion rechargeable batteries. Copper foil, used for negative electrodes, plays an important role in the adaptation of highly functional batteries to practical use. Hitachi Cable is one of the few manufacturers carrying out the entire process from copper casting to roll processing to supplying high-quality copper foil that lives up to the strict standards of battery manufacturers. Hitachi Cable is currently cooperating with battery manufacturers to develop copper foil for even more highly functional next-generation lithium ion batteries. Highly-flexible copper foil is also used for conductive FPC¹ substrates to connect folding mobile phones at the joint. In the latest terminals, multilayer wiring substrates using FPCs are replacing rigid substrates allowing higher-precision electrical parts necessary to achieve higher functionality. Hitachi Cable's copper foils are widely used in FPCs and thus contribute to the enhanced performance of mobile terminals.

* 1 FPC = Flexible Print Circuit

Gallium arsenide compound semiconductors are suitable for multifunction mobile phones due to their excellent performance at high frequencies and low power consumption. Currently, most mobile phones in Japan use gallium arsenide HEMT² transistors for their power amps, one of the most important parts of a mobile phone. The overwhelming majority of these power amps use Hitachi Cable's gallium arsenide epitaxial wafer materials. In recent years, with the move toward 3G services using high-frequency bands, there has been increasing demand for, and a wider range of applications using gallium arsenide compound semiconductors due to their excellent performance at high frequencies. In response to this, Hitachi Cable has not only developed gallium arsenide epitaxial wafer for use with highly functional HBT³ transistors, but is also developing gallium nitride semiconductors with high output and high pressure resistance properties to increase the power of 3.5G and 4G base stations for mobile phones.

* 2 HEMT = High Electron Mobility Transistor
* 3 HBT = Hetero-junction Bipolar Transistor