1. Field of Invention
The present invention relates to a method for manufacturing a diamond film applied to applications of diamond film such as acoustic diaphragm, dresser, and more particularly to a method for manufacturing a diamond film using a substrate can be thermally decomposed at a high temperature.
2. Related Art
Diamond material has excellent mechanical characteristics and strength, thus is suitable for manufacturing the acoustic diaphragm which is light weighted and highly rigid, and may be applied in intermediate-frequency, high-frequency loudspeakers. The sound to be sent is produced by the vibration of such an acoustic diaphragm. The higher the acoustic diaphragm vibration frequency is, the stricter the requirement for mechanical strength and quality of the diaphragm is, and the object can be achieved by using the diamond film to manufacture the diaphragm.
A diamond acoustic diaphragm generally adopts a metallic or non-metallic substrate with a preformed shape (which may be a powder, a block, or a film, etc.), which is provided for the diamond film to be grown on. For a metallic substrate, the diamond film attached thereon tends to crack during the process or in an atmospheric temperature due to a large thermal expansion coefficient of the metal. The non-metallic substrate can effectively solve the above problem since it has a thermal expansion coefficient smaller than that of the metallic substrate. However, the non-metallic material suitable for depositing the diamond film by using chemical vapor deposition tends to bond with the carbon atoms, such that it is difficult to split the diamond film off the non-metallic substrate and thereby to become a free body, therefore, not only the substrate tends to be worn out during the splitting off process, but also a defect exists early in the diamond film. From the other aspect, the thermal residual stress between the substrate and diamond film, and the mismatch of the atom crystal lattice still makes the diamond film in danger of cracking diamond film.