Circuit location sensor for component placement apparatus

• US 4,876,656 A
• Filed: 08/28/1987
• Issued: 10/24/1989
• Est. Priority Date: 08/28/1987
• Status: Expired due to Term

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Leitheiser, Jeffrey D., Leicht, John L.
• Primary Examiner(s): Arnold, Bruce Y.
• Assistant Examiner(s): Callaghan, Terry S.
• Application Number:
  US07/090,997
• Time in Patent Office: 788 Days
• Field of Search: 364/491, 364/490, 364/489, 364/488, 364/559
• US Class Current: 716/103
• CPC Class Codes: G05B 19/4083 Adapting programme, configuration
• CPC Class Codes: G05B 2219/36417 Programmed coarse position, fine position by alignment, follow line, path adaptive
• CPC Class Codes: G05B 2219/37572 Camera, tv, vision
• CPC Class Codes: G05B 2219/41104 Start fine position after coarse position stopped
• CPC Class Codes: G05B 2219/45035 Printed circuit boards, also holes to be drilled in a plate
• CPC Class Codes: H05K 13/081 Integration of optical monitoring devices in assembly lines; Processes using optical monitoring devices specially adapted for controlling devices or machines in assembly lines

Abstract

Unique circuit location sensing apparatus for component placement robots (100) utilizes a high-resolution optical reflective sensor (110) for detecting the location of selected circuit runners (300, 301) on a printed circuit board (350). The sensor (110) is mounted to the robot arm (106) and coupled by A/D converting circuitry (104) to the robot computer (102). The robot computer (102) positions sensor (110) over a selected runner (300, 301) and steps sensor (110) across the selected runner (300, 301), storing the digitized sensor output for each step. The robot computer (102) processes the digitized sensor outputs to determine the actual location of the selected runner (300, 301) and then calculates location offsets for the component placement program to be subsequently run on the robot computer (102). As a result, variations in actual location of circuitry on different printed circuit boards (350) are automatically compensated for and components are more accurately placed thereon. The unique circuit location sensing apparatus of the present invention may be advantageously utilized in any component placement robot for accurately detecting the location of circuitry prior to placement of components on the printed circuit board.

Claims

1. Component placement apparatus including processing means and a robot arm for placing components on a circuit board having at least one circuit element thereon with first and second edge portions, the processing means producing a control signal for positioning the robot arm and producing a strobe signal when the robot arm is positioned, said component placement apparatus further comprising:

sensing means attached to the robot arm and including a light source producing light for illuminating the circuit board and an optical reflective light sensor for producing an output signal having a magnitude proportional to the light reflected from the illuminated circuit board; and

converting means coupled to said sensing means for converting said output signal to a digitized signal in response to the strobe signal; and

said processing means coupled to the robot arm for producing the control signal to step said sensing means across said at least one circuit element and coupled to the converting means for processing the digitized signal produced at each step for detecting the location of said at least one circuit element on the circuit board.

2. The component placement apparatus according to claim 1, wherein said converting means includes an analog to digital converter.

3. A method for use in a component placement apparatus for determining the location of at least one circuit element with first and second edge portions on a circuit board, the component placement apparatus including processing means as a robot arm for placing components on the circuit board, said method comprising the steps of:

illuminating the circuit board with light produced by a light source in sensing means attached to the robot arm;

sensing the light reflected from the circuit board with an optical reflective light sensor in the sensing means, the optical reflective light sensor producing an output signal having a magnitude proportional to the light reflected form the illuminated circuit board;

stepping the optical reflective light sensor across said at least one circuit element;

processing the output signal of the optical reflective light sensor for each step for detecting the location of said at least one circuit element.

4. The method according to claim 3, wherein the output signal of the optical reflective light sensor has rising and falling portions when sensing light reflected from the first and second edge portions, respectively, and said processing step further includes the steps of:

detecting the rising and falling portions of the output signal of the optical reflective light sensor to determine the location of the first and second edge portions of said at least one circuit element; and

computing the location of said at least one circuit element using the determined location of the first and second edge portions of said at least one circuit element.

5. The method according to claim 3, wherein said processing step further includes the steps of:

converting the output signal of the optical reflective light sensor to a digitized signal for each step;

storing the digitized signal from each step; and

computing the location of said at least one circuit element using the stored digitized signals.

6. The method according to claim 3, wherein said stepping step includes for a first path across said at least one circuit element the steps of:

stepping the optical reflective light sensor across the first edge of said at least eon circuit element; and

stepping the optical reflective light sensor across the second edge of said at least one circuit element.

7. The method according to claim 6, further including the step of repeating said stepping steps for a second path across said at least one circuit element substantially perpendicular to said first path.

8. A method of operating component placement apparatus including processing means and a robot arm for placing components on a circuit board having at least one circuit element thereon with first and second edge portions, said method comprising the steps of:

(a) loading a component placement program into said processing means;

(b) determining the location of said at least one circuit element by the steps of;

(i) illuminating the circuit board with light produced by a light source in sensing means attached to the robot arm;

(ii) sensing the light reflected from the circuit board with an optical reflective light sensor in the sensing means, the optical reflective light sensor producing an output signal having a magnitude proportional to the light reflected from the illuminated circuit board;

(iii) stepping the optical reflective light sensor across said at least one circuit element;

(iv) processing the output signal of the optical reflective light sensor for each step for detecting the location of said at least one circuit element;

(c) modifying the component placement program using the location determined for said at least one circuit element; and

(d) executing the modified component placement program.

9. Component placement apparatus including processing means and a robot arm for placing components on a circuit board having at least one circuit element thereon with first and second edge portions, the processing means producing a control signal for positioning the robot arm and producing a strobe signal when the robot arm is positioned, said component placement apparatus further comprising:

sensing means attached to the robot arm and including a light source producing light for illuminating the circuit board and an optical reflective light sensor for producing an output signal having a magnitude proportional to the light reflected from the illuminated circuit board; and

converting means coupled to said sensing means for converting said output signal to a digitized signal in response to the strobe signal; and

said processing means coupled to the robot arm for producing the control signal to step said sensing means across said at least one circuit element at least two times along the same path and coupled to the converting means for processing the digitized signal produced at each step for detecting the location of said at least one circuit element on the circuit board.

10. Component placement apparatus including processing means and a robot arm for placing components on a circuit board having at least one circuit element thereon with first and second edge portions, the processing means producing a control signal for positioning the robot arm and producing a strobe signal when the robot arm is positioned, said component placement apparatus further comprising:

sensing means attached to the robot arm and including a light source producing light for illuminating the circuit board and an optical reflective light sensor for producing an output signal having a magnitude proportional to the light reflected from the illuminated circuit board; and

converting means coupled to said sensing means for converting said output signal to a digitized signal in response to the strobe signal; and

said processing means coupled to the robot arm for producing the control signal to step said sensing means across said at least one circuit element and coupled to the converting means for processing the digitized signal produced at each step for detecting the location of the first and second edge portions of said at least one circuit element on the circuit board.