Report from
saa
seess
Thin films: faster by computer
Arthur G. Gross and Harry M. Kalish
of Bell Telephone Laboratories have
developed a computer program whose
end product is a set of correctly sized
photographic ‘‘masks’' for making
prototype thin-film networks. The masks
control the deposition and shapes of
various widths and thicknesses of
conductive, resistive, and dielectric
materials that make up such circuits.
(These frequently begin as tantalum,
deposited onto a glass or ceramic substrate and chemically treated to produce
desired electrical properties.)
Controlled by the new program, a
computer feeds a precision microfilm
plotter which prints the masks on 35mm
film (photo above).
With this system, a prototype can be
ready in a day, as against the weeks
that may be involved in making high-
precision masks for volume circuit
production. Usually, for example, a
drattsman must make rough sketches
and prepare a list of numbers (coordinate points) accurately describing the
geometry of the final circuit. Then the
actual shapes—greatly enlarged—are
cut into plastic sheets on a ‘‘coordinatograph.” Later, the plastic patterns
are photographically reduced to circuitsized masks, perhaps % by 1 inch.
In addition to reducing time and
handling, Bell Laboratories’ new program relieves the engineer of
—
another tedious job: designing
the meandering lines that
constitute resistors in these
An experimental thin-film filter network
—in actual size—made from 35mm film
masks. In the top photo,A. G. Gross (left)
and H. M. Kalish hold three of the masks
used. Each mask controls the formation
of a layer of conductive, resistive, or dielectric material. The circuit is built up
of a number of such layers.
[_
-—
circuits. And the computer fesetéa
resistors are ‘‘optimized” ... fitted into
the smallest possible area.
To give the engineer freedom to use
irregular
plane
shapes,
the
program
inciudes a subroutine which closely
approximates geometric figures used
in making thin-film circuits.
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