Excimer laser
drilling of polymers
Y. H. Chena, H. Y. Zhenga, K. S. Wonga
, and S. C. Tamb
(a) Gintic Institute of Manufacturing Manufacturing
71 Nanyang Drive, Singapore 638075
(b) School of Electrical & Electronic Engineering
Nanyang Technological University
Nanyang Avenue, Singapore 639798
ABSTRACT
Laser micro-drilling technology plays a more and more
important role in industry, especially in the fabrication of
multi-layer electronic packages. In such applications, non-metals
are often used as insulators, in which via holes are formed to
provide vertical interconnections for densely packed three
dimensional wiring networks. Mechanical punch tools have been the
primary means to form holes in ceramic sheets and in polymer
boards since the 1970's. As the cost of fabricating punch heads
increases drastically and the demand for quick turn around part
build becomes more routine, flexible via forming technologies,
such as laser drilling, have become more prevalent. In laser
drilling, CO2, Nd:YAG, and excimer lasers are often used. Their
drilling capabilities, drilling mechanisms, and hole qualities
are different because of the different laser beam characteristics
such as wavelength and beam energy distribution. In this paper,
the mechanisms of laser drilling are briefly reviewed. The
results of the experiments on excimer laser drilling of two types
of polymer: polyimide and polyethylene terephthalate, are
reported. It is found that the etch rate increases with increase
of fluence, and the wall angle of drilled holes is dependent on
the fluence. The material removal by a laser pulse is highly
controllable. There exists an optimal fluence range to obtain
clean and smooth edges of quality holes for a given material at a
given laser wavelength.
Keywords: excimer laser,
laser drilling, laser etching, laser micro-machining, polymers.
Full
paper in PDF
Reprinted from Proc. of SPIE, Vol.
3184 (1997), 202-210
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