6 February 2013

Mitsubishi Electric develops multi-wire electrical discharge process for SiC ingot slicing

Tokyo-based Mitsubishi Electric Corp says that it has developed a prototype multi-wire electrical discharge processing technology to cut very hard 4-inch polycrystalline silicon carbide (SiC) ingots into 40 pieces simultaneously.

Up to now, because SiC is the third hardest compound on earth, sliced wafers have been produced by using multi-wire saws with diamond particles. However, this method requires lengthy machining time and large kerf widths.

The new parallel multi-wire electrical discharge machining method uses Mitsubishi Electric’s proven electrical discharge technology for difficult-to-cut material, and employs a dedicated power supply specially developed for SiC. The technology is expected to improve both the productivity of SiC slicing and the effective use of SiC material.

Specifically, 40 wire electrodes (each with a diameter of 0.1mm) aligned at 0.6mm intervals are rotated to cut 40 slices at once, improving productivity. Also, the non-contact, thermal process-wire electrical discharge method slices faster and at closer intervals compared to contact cutting (220 microns or less cut at a speed of 80 microns per minute). More wafer slices extracted per SiC ingot for improved efficiency.

Regarding the power supply dedicated to SiC slice processing, Mitsubishi Electric says that simultaneous wire cuts with even energy enabled by 40 electrically independent power feed contacts to the wire electrodes. Also, there is uninterrupted processing with even very thin (0.1mm) wire electrodes due to a newly developed high-frequency power supply tailored to the characteristics of SiC material, adds the firm.

Pending patents for the technology number 22 in Japan and 10 overseas. Mitsubishi Electric aims to market its multi-wire electrical discharge slicer by 2015.

The firm notes that SiC is expected to be used increasingly in power semiconductors due to its superior energy-saving and CO2 emissions-reduction properties compared with silicon.

Tags: Mitsubishi Electric SiC

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