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Browse Prior Art Database

Thin Film Gauging Device

IP.com Disclosure Number: IPCOM000093963D
Original Publication Date: 1966-Apr-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 22K

Publishing Venue

IBM

Related People

Gow, J: AUTHOR [+3]

Abstract

This device measures the thickness of a thin film by sensing the attenuation of a laser beam. The device is particularly useful for detecting thickness variations of printed resistors and the like on ceramic substrates. In the manufacture of electrical component modules it is frequently necessary to accurately and rapidly check the thickness of resistor and electrode pastes deposited on a ceramic substrate.

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Thin Film Gauging Device

This device measures the thickness of a thin film by sensing the attenuation of a laser beam. The device is particularly useful for detecting thickness variations of printed resistors and the like on ceramic substrates. In the manufacture of electrical component modules it is frequently necessary to accurately and rapidly check the thickness of resistor and electrode pastes deposited on a ceramic substrate.

This film gauging device consists of laser device 10, positioned to direct a laser beam through a substrate 12 having a thin coating 14 to be measured, and a standard photomultiplier tube 16. The latter is positioned to receive the laser beam and detect the attenuation of the beam caused by coating 12. The degree of attenuation is directly related to the thickness of coating 14.

The laser beam as a light source improves the efficiency of the device. This is because the beam has a constant intensity, is very monochromatic, and has very little attenuation or beam spread in air.

When resistor paste is dried, it is normally dark in color which causes heavy attenuation of the beam. The use of a laser beam is particularly significant in this application in order to provide a very intense beam to eliminate noise and get a good signal-to-noise ratio. The attenuation caused by substrate 12 is relatively constant and small in comparison to the attenuation caused by coating 14. Thus variation of beam attenuation caused by substrate 12 does not ap...