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A shorter laser pulse provides smaller heat affected zones and higher ablation accuracy, which are demanded for metal micro-fabrication processes. In particular, picosecond laser systems, which are suitable for operation in industrial environments, are of great interest for many practical applications. However, low productivity has been a limitation to broadening their industrial application. It was recently reported that when micromachining copper with a 1064 nm picosecond laser, a desirable pulse energy and repetition rate exist for achieving the maximum volume ablation rate. In this paper, we used a 515 nm picosecond laser, which is more efficient for micromachining copper in terms of laser energy absorption, and determined its optimum pulse energy and repetition rate. A theoretical analysis based on the experimental data on copper ablation showed that using a 515 nm picosecond laser instead of a 1064 nm picosecond laser is favorable in that the calculated threshold fluence is 75 % lower and the optical penetration depth is 50 % greater.

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