Browse Prior Art Database

Module Cap Etch Quality Monitor

IP.com Disclosure Number: IPCOM000043446D
Original Publication Date: 1984-Sep-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Murphy, RJ: AUTHOR [+3]

Abstract

In the encapsulation of circuit modules, the aluminum module caps must be etched to insure reliable bonding of the adhesive. The described device measures the degree of etching or surface roughness of a cap by measuring the ratio of diffuse to specular reflection of light from the module cap. Fig. 1 is an optical schematic. A fiber-optic light guide 1 transmits light from an incandescent source through a color filter (not shown) to the surface of the cap 3. A portion of the light undergoes specular reflection and is measured by a silicon diode detector 5. Another portion of the light undergoes diffuse reflection and is measured by another silicon diode detector 7. These detectors have an aperture of 3Πto reduce the influence of stray light.

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Module Cap Etch Quality Monitor

In the encapsulation of circuit modules, the aluminum module caps must be etched to insure reliable bonding of the adhesive. The described device measures the degree of etching or surface roughness of a cap by measuring the ratio of diffuse to specular reflection of light from the module cap. Fig. 1 is an optical schematic. A fiber-optic light guide 1 transmits light from an incandescent source through a color filter (not shown) to the surface of the cap 3. A portion of the light undergoes specular reflection and is measured by a silicon diode detector 5. Another portion of the light undergoes diffuse reflection and is measured by another silicon diode detector 7. These detectors have an aperture of 3OE to reduce the influence of stray light. The reflectivity of a surface depends on both the wavelength of the light and the angle of incidence. In this application, best results were obtained with yellow (600 nm) light and an angle of incidence of 60OE. In practice, the optics are aligned and locked in place to insure reproducibility. The electrical schematic is shown in Fig. 2. The signals from the specular and diffuse detectors are passed through amplifiers 8 and 9 which, in conjunction with a multi-position switch 10 and an analog-to-digital converter 23, provide means for setting the zeros (light off) and calibrating each channel with a standard opal diffuser. The ratio between the signals is established at 11, and this ratio is c...