Development of nano-columnar carbon coating for dry micro-stamping

In parallel with down-sizing of electrical devices and products, manufacturing is forced to be also miniatured to fabricate small-sized electrical parts with the geometric size in millimeters. This type of micro-stamping, suffers from two issues: stamping in dry with strict accuracy in clearance. Residual lubricating oils and cleansing agents are completely disliked by electrical parts; elimination of these oils and agents becomes difficult and costly task after stamping. Since the clearance is designed to be much less than 5% of sheet material thickness, the conventional hard coating has a risk of break-away, or, the formability in stamping is significantly shortened. Nano-columnar carbon coating is developed to solve the above two issues in micro-stamping. Amorphous carbon coating is employed as a starting film. Electron-beam irradiation is performed to chemically modify this microstructure having a fine nano-structured columnar composite. After precise HRTEM observation and Raman spectroscopy, this nano-columnar carbon film is found to be composed of graphitized inter-columnar network with amorphous columns. Nano-indentation proves that this film has remarkable reversibility in deformation up to 8 to 10% of film thickness after loading and unloading. The scratching test verifies that this coating has sufficiently high resistance over 100 N. Furthermore, a micro-stamping test is designed and performed to demonstrate the feasibility of this coating in practical operation.