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Substrate Crack Detection by Acoustic Microscope

IP.com Disclosure Number: IPCOM000040525D
Original Publication Date: 1987-Nov-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 2 page(s) / 45K

Publishing Venue

IBM

Related People

Clark, FE: AUTHOR [+2]

Abstract

Cracks in metallized ceramic substrates are commonly detected by a visual process in which the cracks are illuminated by the use of ultraviolet radiation. Residual resin flux in the cracks has fluorescent qualities and can be seen as a bright glow. This technique works well in a manually operated environment, but to automate crack detection a process of scanning laser acoustic microscope (SLAM) provides a non- destructive method of examining internal structures for voids or discontinuities. The method also is environmentally preferable as it is not dependent on residual flux. The method works as described in the following. SLAM works by propagating ultrasound from a source to the object to be viewed. The sound reaching the object is detected by a laser beam which scans the object's surface.

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Substrate Crack Detection by Acoustic Microscope

Cracks in metallized ceramic substrates are commonly detected by a visual process in which the cracks are illuminated by the use of ultraviolet radiation. Residual resin flux in the cracks has fluorescent qualities and can be seen as a bright glow. This technique works well in a manually operated environment, but to automate crack detection a process of scanning laser acoustic microscope (SLAM) provides a non- destructive method of examining internal structures for voids or discontinuities. The method also is environmentally preferable as it is not dependent on residual flux. The method works as described in the following. SLAM works by propagating ultrasound from a source to the object to be viewed. The sound reaching the object is detected by a laser beam which scans the object's surface. An acoustic image for those areas where the ultrasound has passed through relatively unobstructed appears as light areas. Dark areas indicate reduced levels of transmission where refraction or absorption occurs. The technique is seen in the photos of an acoustic image of a substrate. The light area is the substrate surface, and the dark circles are the pin rows on the substrate. A dark line, pointed to by arrows, indicates a crack in the substrate.

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