Semiconductor pick-and-place machine automatic calibration apparatus

• US 5,237,622 A
• Filed: 12/04/1991
• Issued: 08/17/1993
• Est. Priority Date: 12/04/1991
• Status: Expired due to Term

• Current Assignee: Plexus Services Corporation (Plexus Corporation)
• Original Assignee: Micron Technology, Inc.
• Inventors: Howell, David A.
• Primary Examiner(s): Mancuso, Joseph
• Application Number:
  US07/802,310
• Time in Patent Office: 622 Days
• Field of Search: 382/8, 382/57, 382/48, 358/101, 358/106, 358/107
• US Class Current: 382/151
• CPC Class Codes: H05K 13/089 Calibration, teaching or correction of mechanical systems, e.g. of the mounting head

Abstract

An apparatus and method of automatically performing a calibration of the accuracy of placement of semiconductor chips or devices by a pick-and-place machine. The parts are placed on an adhesive-backed glass plate that has calibrated black marks whose dimensions match those of a specific part lead footprint. A gray scale camera mounted on the machine above the inverted glass plate records and sends a signal to a machine computer identifying the coordinates of exposed part silver lead area. The computer calculates part placement error and sends error data to a CRT or camera screen and alarm to alert an operator.

Claims

1. In a semiconductor chip manufacturing process, an apparatus that automatically monitors a pick-and-place machine part placement accuracy comprising:

a. a movable downward scanning gray scale camera mounted above a movable "Y" table section of the machine;

b. a glass plate having dimensions the same as a plurality of PC boards in an inverted position above the table;

c. a plurality of black calibration marks on the glass plate that match a part lead footprint;

d. an adhesive layer above the glass plate affixing a plurality of parts to a top of the plate;

e. a signal output from the gray scale camera to a machine computer; and

f. an output from the computer to a readout device wherein a misplaced part below the inverted glass plate exposes a silver chip lead and the camera senses a white area and sends a signal to the computer and readout device indicating part placement error.

2. The apparatus of claim 1 and wherein:

the camera is mounted on a movable pick-and-place head.

3. The apparatus of claim 2 and wherein:

the readout device is a CRT.

4. The apparatus of claim 2 and wherein:

the readout device is a camera screen.

5. The apparatus of claim 2 and wherein:

the computer output actuates a part placement error alarm at a first error magnitude.

6. The apparatus of claim 5 and wherein:

the computer output shuts down the machine at a second higher error magnitude.

7. In a semiconductor chip manufacturing process, an apparatus that automatically monitors a pick-and-place machine part placement accuracy comprising:

a. a movable downward scanning gray scale camera mounted to a pick-and-place head above "Y" table section of the machine;

b. a glass plate having dimensions the same as a plurality of PC boards in an inverted position above the "Y" table section;

c. a plurality of black calibration marks on the glass plate that match a part lead footprint;

d. an adhesive layer above the glass plate affixing a plurality of parts to a top of the plate;

e. a signal output from the gray scale camera to a machine computer; and

f. an output from the computer to a CRT and a camera screen wherein a misplaced part below the inverted glass plate exposes a silver part lead and the camera senses a white area and sends a signal to the computer and to the CRT and the camera screen indicating a part placement error.

8. The apparatus of claim 7 and wherein:

the computer output actuates a part placement error alarm at a first error magnitude.

9. The apparatus of claim 8 and wherein:

the computer output shuts down the machine at a second higher error magnitude.

10. A method of monitoring and indicating the accuracy of part placement of a semiconductor pick-and-place machine comprising the steps of:

a. placing a calibrated glass plate having black marks and an adhesive on a top surface of the glass plate, on a machine PCB in-conveyor;

b. conveying the glass plate to a "Y" table;

c. placing a plurality of parts on the adhesive on the glass plate by a place head;

d. conveying the glass plate and parts to a PCA out-conveyor;

e. removing the glass plate from the out-conveyor and inverting the glass plate;

f. conveying the inverted glass plate to the "Y" table;

g. moving the place head and an attached gray scale camera over the inverted glass plate;

h. sensing a white area adjacent the glass plate black marks by the camera;

i. transmitting a signal to a machine computer to indicate coordinates of the white area sensed; and

j. indicating on a readout device a magnitude of a part placement error.

11. The method of claim 10 and wherein:

an alarm is actuated by the computer at a first error magnitude.

12. The method of claim 11 and wherein:

the machine is shutdown at a second higher error magnitude.

13. The method of claim 10 and wherein:

the readout device is a CRT.

14. The method of claim 10 and wherein:

the readout device is a camera screen.