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Phosphor X-Ray Imaging Quality Control System

IP.com Disclosure Number: IPCOM000047490D
Original Publication Date: 1983-Nov-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 3 page(s) / 36K

Publishing Venue

IBM

Related People

Chang, IF: AUTHOR [+3]

Abstract

An erasable X-ray sensitive medium and readout means is proposed for use in place of disposable X-ray film to inspect the conductor patterns of integrated circuit packaging substrates. One currently used technique for inspecting the conductor patterns of packaging substrates is to expose X-ray film through the packaging substrate. The developed X-ray exposure yields information about the quality of the packaging substrate. Unfortunately, this quality control method leaves much to be desired. The film development and visual study is extremely labor intensive, with the result that not every picture is even looked at. There is also considerable lag obtaining the necessary quality control information due to the time delay needed for film development.

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Phosphor X-Ray Imaging Quality Control System

An erasable X-ray sensitive medium and readout means is proposed for use in place of disposable X-ray film to inspect the conductor patterns of integrated circuit packaging substrates. One currently used technique for inspecting the conductor patterns of packaging substrates is to expose X-ray film through the packaging substrate. The developed X-ray exposure yields information about the quality of the packaging substrate. Unfortunately, this quality control method leaves much to be desired. The film development and visual study is extremely labor intensive, with the result that not every picture is even looked at. There is also considerable lag obtaining the necessary quality control information due to the time delay needed for film development. Another very important factor is that X-ray film is expensive and not reusable. We propose to replace the X-ray film with a reusable zinc silicate phosphor screen, and retrieve the necessary information through an energy storage effect in an automated system. We described this information storage effect of zinc silicate phosphors in an earlier article [*]. Zinc silicate phosphor may be used to improve fluorescent lamp efficiency and to reduce flicker or to form a gas discharge display or image storage device with an optical readout feature. The storage effect itself has the following characteristics. After X-ray exposure, there is a latent "excitation" trapped in the phosphor for several hours. This stored energy can be read out in the form of a green light output by stimulating the phosphor with a lower frequency radiation. The number of green photons produced is proportional to the intensity of the original X-ray exposure. The spatial resolution of the retrieval is only limited by the ability to focus the readout light beam. If, for instance, a He-Ne laser is used for readout, a 2-micron resolution can be achieved with good optics. Focusing and defocusing the readout beam automatically changes the readout resolution in accordance with need. An embodiment is shown in Figs. 1 and 2. After the phosphor screen 10 has been exposed to X-rays 12 through a packaging substrate 14, it contains the X-ray image of the packaging substrate. The...