US 4,065,212 A · Inspection tool

Abstract

This patent discloses an improved inspection tool for rapidly inspecting miniature electronic conductor patterns, circuits and the like. The tool focuses a laser beam to a small laser spot that raster scans a large conductor pattern area on the workpiece being inspected. Reflected laser light from the workpiece impinges upon a light detector that generates electrical signals according to the presence or absence of conductor pattern material on the workpiece at the momentary X and Y coordinate of the scanning laser spot. The light detector signals are compared with a previously encoded data image of the correct circuit pattern for the X and Y coordinates of the scanning laser spot. When the signals and the data agree at all X and Y coordinate points the workpiece is accepted. If the signals and the data do not agree at one or more X and Y coordinate points a defect in the circuit pattern is indicated. A defect may indicate out-of-tolerance dimensions, possible electrical short circuits, and/or open circuits. The extent of a defect may be determined by adjacent X and Y coordinate points and suitable computer programming, while workpieces having extended or out-of-tolerance defects are rejected. The improved disclosed inspection tool includes apparatus for automatically compensating for variations in the workpieces, and to effect registration for the scanning laser spot.

Claims17

Dependent claims

An inspection tool comprising:

means to feed a workpiece to be inspected into a work zone, said workpiece having a pattern thereon to be inspected;
a source of coherent light and means to effect a sweep of said coherent light across said work zone;
a grating having a plurality of parallel interdigitated light receiving and light transmitting lines thereon;
means intermediate said source of coherent light and said work zone to reflect at least a portion of said coherent light into a light beam onto and traversing said grating across said lines with said lines extending at an angle transverse said light beam imaging thereon as the light is swept across said work zone;
light detector means positioned to continuously receive and sense light transmitted by said light transmitting lines of said grating so that the position of said sweep of coherent light across said work zone may be determined;
and means to alter said angle of said lines transverse said reflected light beam as it sweeps across said lines on said grating to compensate for differences in the position of the pattern on a workpiece relative to a nominal pattern position.

3 more elements

An inspection tool comprising:

means to feed a workpiece to be inspected into a work zone, said workpiece having a pattern thereon to be inspected;
a source of coherent light and means to effect a sweep of said coherent light across said work zone;
first light detector means positioned adjacent said work zone to receive light reflected from a workpiece in said zone from said sweep of coherent light;
a grating having a plurality of interdigitated light receiving and light transmitting lines thereon wherein said light transmitting and receiving lines on said grating are positioned at an oblique angle relative to said reflected portion of said sweep of coherent light;
means intermediate said source of coherent light and said work zone to reflect at least a portion of said coherent light onto said grating at an oblique angle relative to said lines and as the light is swept across said work zone;
second light detector means positioned to receive light transmitted by said light transmitting lines of said grating so that the position of said sweep of coherent light across said work zone may be determined, means to alter the angle said reflected portion of said light intercepts said lines on said grating to change the angle and thereby compensate for differences in the position of the pattern on a workpiece relative to a nominal pattern position;
and including a frame;
a sub-frame mounting said grating;
actuator means interconnecting said sub-frame and said frame to effect changes in the position of said sub-frame and thus said grating relative to said frame.

6 more elements

Dependencies are inferred from the claim text.

Inspection tool

Life of this patent

Inspection tool

Life of this patent

Abstract

Claims17