SUBSTRATE POSITIONED DETERMINATION STRUCTURE AND METHOD

• US 3,758,745 A
• Filed: 09/07/1971
• Issued: 09/11/1973
• Est. Priority Date: 09/07/1971
• Status: Expired due to Term

• Current Assignee: Graham A. Neathway, Paul S. Wilker, William B. Kiss
• Original Assignee: Graham A. Neathway, Paul S. Wilker, William B. Kiss
• Inventors: Wilker, Paul S., Kiss, William B., Neathway, Graham A.
• Primary Examiner(s): Staubly, R. F.
• Assistant Examiner(s): Montanye, George A.
• Application Number:
  US05/177,997
• Time in Patent Office: 735 Days
• Field of Search: 219/121L,121EB,125 318/572 250/49.5 83/63,522
• US Class Current: 219/121.68
• CPC Class Codes: B23K 26/351 for trimming or tuning of electrical components
• CPC Class Codes: H05K 1/167 incorporating printed resistors
• CPC Class Codes: H05K 3/027 the conductive material being removed by irradiation, e.g. by photons, alpha or beta particles
• CPC Class Codes: Y10T 29/49099 Coating resistive material on a base

Abstract

A resistive strip adherently deposited on a substrate is progressively cut by a laser beam while the resistance of the strip is monitored. As the last edge becomes cut, the resistance approaches infinity, and the relative position of the laser beam with respect to the substrate is registered, providing a high resolution coordinate on the substrate which is useable as a base from which further laser trimming of circuitry deposited on the substrate may be performed.

Claims

1. A substrate position determining apparatus comprising:

a. means for restraining a substrate having a first resistive strip and another element fixed to its surface, the first resistive strip being located in a predetermined position with respect to the other element, b. means adjacent the substrate position for progressively cutting the first resistive strip from one of its edges toward the other, thereby increasing its resistance, c. means for causing relative movement between the (b) means and substrate along a predetermined line so as to effect the progression of the cut, d. means for measuring the resistance of the first resistive strip transversely to the direction of movemenT, and e. means connected to the (d) means for reacting to the increase in measured resistance above a predetermined value to accurately register the relative position of the (b) means relative to a point on the first resistive strip. on the substrate.

2. An apparatus as defined in claim 1, in which the (b) means is comprised of a laser beam adapted to cut a path through the resistive material of the first resistive strip as the substrate and (b) means are relatively moved.

3. An apparatus as defined in claim 2, wherein the first resistive strip is comprised of a thin film of sputtered tantalum adherent to the surface of the substrate, and a pair of contact pads for measuring the resistance of the resistive strip, ohmically contacting the resistive strip on opposite sides of the path of the laser beam.

4. An apparatus as defined in claim 3, further comprising a second resistive strip ohmically connected between the pair of contact pads in parallel with the first resistive strip and at a predetermined position on the substrate;

the second resistive strip having a step so as to have a portion thereof lying transverse to the direction of the first resistive strip;

the (c) means comprising means for moving the (b) means or the substrate relative to the other along a first predetermined line so as to effect progression of the cut of the first resistive strip;

the line extending to a position adjacent and central of the transverse portion of the second resistive strip, and for then moving the (b) means or the substrate relative to the other along a second predetermined line transverse to the first, so as to effect progression of the cut of the transverse portion of the second resistive strip;

the resistance of the second resistive strip being more than double the resistance of the first resistive strip.

5. An apparatus as defined in claim 4, in which the (e) means comprises means for reacting to the resistance of the second resistive strip as it increases above a predetermined value to accurately register the relative position of the (b) means, and hence a point on the second resistive strip, on the substrate, whereby co-ordinates on two transverse lines on the surface of the substrate are accurately registered.

6. An apparatus as defined in claim 3 further comprising a second resistive strip at right angles to the first resistive strip and adherent at a predetermined position on said surface, means for moving the cutting means in a direction transverse to the second resistive strip so as to cause the laser beam to cut through the second resistive strip after cutting through the first resistive strip, means for measuring the resistance of the second resistive strip transverse to the direction of movement of the cutting means, and means for reacting to the resistance of the second resistive strip as it increases in resistance above a predetermined value and accurately registering the position of a point on the second resistive strip, and hence of the substrate, whereby the accurate co-ordinates on two transverse lines on the surface of the substrate are accurately registered.

7. An apparatus as defined in claim 1, further including means for holding the substrate in a fixed position, whereby the cutting means is moved relative to the substrate.

8. A method of determining the position of elements adherent to the surface of a substrate, comprising the steps of:

a. continuously measuring the resistance between two points on a first resistive strip fixed at a predetermined position on the surface of a substrate, b. progressively cutting the first resistive strip from one edge transversely to a line of resistance between two points, c. accurately registering the position of the last cut decrement of the first resistive strip when the measured resistance increases above a predetermined value.

9. A method as defined in claim 8 including the additional steps of:

d. continuously measuring the resistance of a second resistive strip adheRent at a predetermined position on the surface of the substrate transverse to the first resistive strip, e. progressively cutting the second resistive strip transversely to and intersecting the line of resistance being measured, f. accurately registering the position of the last cut decrement of the second resistive strip when the measured resistance increases above another predetermined value, whereby the position of any elements related to said strips at the surface of the substrate may be accurately determined with respect to two transverse lines.