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Proceedings Paper

Diffractive/refractive hybrid f-theta lens for laser drilling of multilayer printed circuit boards
Author(s): Keiji Fuse; Takeshi Okada; Keiji Ebata
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Paper Abstract

A new type of f-theta lens has recently been developed for microvia laser drilling of multilayer printed circuit boards. It employs a diffractive/refractive hybrid lens which has a blazed surface-relief microstructure on an aspheric surface. By introducing that hybrid lens for CO2 laser system, and by stopping the use of germanium that is optically much sensitive to temperature, the f-theta lens that consists of all zinc selenide lenses is obtained with its optical performance stable on temperature. Achromatic properties against the wavelength fluctuations of actual lasers are also achieved. A prototype is fabricated through the development of single point diamond turning of hybrid surfaces. The performance of the lens is first examined by measuring wavefront error with a tunable infrared interferometer. The results show diffraction-limited performance at all conditions, including different temperatures (up to 50°C) and wavelengths. The temperature dependence of the focal length of the lens is also measured and found to be 5 times as insensitive to temperature as that of a conventional one. Laser drilling experiments are performed for a polymide film on copper foil. The result shows good uniformity of hole size and circularity all over the 50×50 mm2 scan field.

Paper Details

Date Published: 19 February 2003
PDF: 6 pages
Proc. SPIE 4830, Third International Symposium on Laser Precision Microfabrication, (19 February 2003); doi: 10.1117/12.486556
Show Author Affiliations
Keiji Fuse, Sumitomo Electric Industries, Ltd. (Japan)
Takeshi Okada, Sumitomo Electric Industries, Ltd. (Japan)
Keiji Ebata, Sumitomo Electric Industries, Ltd. (Japan)

Published in SPIE Proceedings Vol. 4830:
Third International Symposium on Laser Precision Microfabrication
Isamu Miyamoto; Kojiro F. Kobayashi; Koji Sugioka; Reinhart Poprawe; Henry Helvajian, Editor(s)

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