PARAMETER OPTIMISATION IN LASER MICROENGRAVING
OF PHOTOMASKS WITH TAGUCHI METHOD  

Chen Yi Hong  and Chen Wei Long  
Gintic Institute of Manufacturing Technology
Nanyang Technological University Nanyang Avenue, Singapore 2263  

Tam Siu Chung
School of Electrical & Electronic Engineering
Nanyang Technological University Nanyang Avenue, Singapore 2263  
 

ABSTRACT
 
 Photomasks are required to generate various patterns for different designs in the fabrication of liquid crystal displays (LCDs). This paper reports on the use of the Taguchi method of experimental design in optimising the process parameters for engraving on iron oxide coated glass by a Q-switched Nd:YAG laser.  The effects of five process parameters - beam expansion ratio, focal length, laser average power, pulse repetition rate and engraving speed - have been explored.  The primary response under study is the engraving line width.  An L16 orthogonal array was used to accommodate the experiments.  The study indicated that a minimum line width of 18 mm could be obtained with beam expansion ratio of 5 times,  focal length of 5mm,  laser average power of 0.4W,  pulse  repetition rate of 5 kHz, and engraving speed of 5000 mm/min.
 
Reprinted from Proc. of Int. Conf. on Precision Engineering (1995), 194-198

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