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Ceramic Crack Detection by Oblique U.v.-blue Illumination

IP.com Disclosure Number: IPCOM000061875D
Original Publication Date: 1986-Jul-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Cerniglia, TJ: AUTHOR [+3]

Abstract

:AB Disclosed is a method and apparatus for visually inspecting minute cracks in a ceramic substrate by illuminating the substrate with ultra violet - blue light (e.g. that from Xenon l source) at an oblique angle of incidence.

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Ceramic Crack Detection by Oblique U.v.-blue Illumination

:AB Disclosed is a method and apparatus for visually inspecting minute cracks in a ceramic substrate by illuminating the substrate with ultra violet - blue light (e.g. that from Xenon l source) at an oblique angle of incidence.

In the manufacture of ceramic substrates for packaging semiconductor chips it is important to inspect the substrate for tiny cracks. Conventional techniques for crack inspection such as by means of a 4 DM Model dynascope system manufactured by Vision Engineering are not fully effective since they utilize a tungsten halogen light source and focusing fiber optics. The halogen light which produces long wavelength yellow-red light and rendered more red due to attenuation introduced by the fiber optics, does not get properly scattered to enable crack inspection. By substituting the long wavelength light with short wavelength light shining the light at an oblique angle, the present process overcomes the deficiencies of the conventional techniques.

The present method comprises illuminating the substrate with a u.v. Xenon light source (of short wavelength in the range of 380-450 nm) at an oblique angle of incidence (55-70 degrees from the perpendicular to the substrate surface) and observing the illuminated substrate in a direction perpendicular to the substrate surface. Since the intensity of the scattered light i inversely proportional to the fourth power of the wavelength (Rayleigh scatt...