Laser Drilling of Epoxy-Glass Printed Circuit Boards

Abstract

In this paper, for the first time, excimer laser micromachining is applied to create new electrooptical devices called substrate integrated modulators, consisting of new optical and microwave waveguides on LiNbO 3 substrates. The fact of having both optical and microwave waveguides, offers the possibilities to modulate high-frequency optical signal (wavelength of 1.55 μm) by either millimeter or microwave signal (frequency of 60 GHz). Because LiNbO 3 is transparent between 370 nm to 5000 nm, 248 nm KrF excimer laser is one of the best candidates for performing fine micromachining of this material. Cutting the LiNbO 3 wafer, making holes, creating a ridge optical waveguide and fabricating a specific pattern of holes for microwave applications by 248 nm excimer laser are presented in this paper.

Laser Beam MicroMachining (LBMM) – A review

“…They found that the laser peak power and the focal position significantly affect the hole dimension. The effect of pulse duration and pulse frequency on the thickness of the carbonized layer around the drilled microvias of epoxy-glass printed wiring board was investigated by Takeno et al [36]. It was observed that due to heat accumulation around the drilled area the increase of pulse frequency increases the thickness of carbonized layer.…”

Laser Drilling of Metallic and Nonmetallic Substrates

“…The choice of a laser is decided by the type of material to be drilled, the quality and precision of hole required, and the cost effectiveness. ; therefore, pulsed TEA CO 2 lasers are used in drilling holes in these materials (24,68,96). Pulsed Nd:YAG lasers are most commonly used for percussion drilling in thick metallic, as well as in semiconducting and ceramic, materials because of their higher pulse energy capability (31,94,95).…”

“…Dell'Erba et al (21) compared the drilling by excimer and CO 2 lasers in Kevlar, glass, and carbon-reinforced epoxy composites, and found that while the quality of holes drilled by excimer laser was better but the ablation rate was lower compared to that by CO 2 laser. More recently, Takeno et al (68) investigated the effect of laser pulse duration and repetition frequency on the quality of microvia holes in glass epoxy-printed circuit board with a CO 2 laser and found that the carbonization took place at frequencies higher than a certain value due to heat accumulation and that the frequency limit increased with the reduction of laser pulse duration. The laser drilling was more energy efficient for aramid/epoxy composite and quality was also better than for glass epoxy composite.…”