Pulsed laser milling process of CVD single crystal diamond

Chemical vapor deposition (CVD) diamond has high thermal conductivity and a low coefficient of thermal expansion, making it a good thermal conductive material. However, conventional processing methods are often difficult to balance processing quality while pursuing high efficiency. In view of this, this study focuses on the milling of CVD single crystal diamond using nanosecond and picosecond laser technology, aiming to optimize its processing accuracy and efficiency. By systematically investigating the effects of laser incidence angle, pulse width, and spot size on the milling angle of diamond. It is found that the slope angle of the machined surface can be effectively reduced by decreasing the laser incidence angle, shortening the pulse width, and reducing the spot size. With an average power of 200 W, a pulse width of 12 ps, a spot diameter of 60 µm, an incidence angle of 3°, and a scanning speed of 30 mm/s, the milling angle of diamond can be optimized to 1.30°, and at the same time, the surface roughness Sa is 0.42 µm, the maximum height difference of the surface Sz is 2.76 µm, and the machining efficiency reaches 32.57mm³/h. When the pulse width is adjusted to 150 ns and the rest of the parameters are kept unchanged, the milling angle of diamond is 2.45°, the Sa is 0.45 µm, the Sz is 2.88 µm, and the machining efficiency is improved to 66.10mm³/h. The present study proposes a high-efficiency and low-damage machining strategy for chip bonding diamond, which provides an important reference for the application of diamond in the field of microelectronics encapsulation.