Kallex recycles silicon carbide grinding waste in product manufacturing line and processes it to recycled high-purity silicon carbide, which is then used to produce vacuum suction cups for wafers.
The production of silicon carbide raw material powders requires considerable energy. By reducing the generation of waste during the manufacturing process, it is possible to decrease the need of virgin silicon carbide raw material powders. On its silicon carbide product production line, Kallex purifies and reuses silicon carbide grinding waste.
Calcination and Acid Washing to Extract Process Waste
The particle size distribution of silicon carbide grinding waste ranges from approximately 0.1 to 15 micrometers and consists primarily of silicon carbide particles, powders, diamond wheel fragments, and cutting fluid mixtures. By calcining this mixture at 900°C in an air furnace, the organic cutting fluid and diamond particles are burned off. At this temperature, a slight oxide layer may form on the surface of the silicon carbide particles. Subsequently, treatment with a mixed acid of nitric acid and hydrofluoric acid (1:1) yields silicon carbide particles with a purity of over 99.9%. After the calcination and acid washing, the material is mixed with sintering aids and binders to form a powder blend. This blend, through careful control of molding pressure and sintering temperature, results in a sintered body with a porosity of about 15–50%, which is suitable for making products such as wafer carriers.
Manufacturing Wafer Carriers with Recycled Silicon Carbide Powder
Currently, Taiwan lacks full control over the key factors and manufacturing techniques for the materials used in vacuum suction cups for wafer production, such as material formulations, conductivity, porosity, air permeability, and dust emission factors. These components are entirely reliant on imports. Kallex is developing vacuum suction cups using recycled silicon carbide powder to enhance domestic manufacturers' capabilities in the independent research, design, and production of silicon carbide vacuum suction cups.
Benefits
- Reduces expenditure on purchasing powder raw materials.
- Save NT$200,000 in processing costs by reducing 3 metric tons of grinding waste.