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Assembly Technique for Placing Electronic Components on Printed Circuit Wiring Patterns

IP.com Disclosure Number: IPCOM000034565D
Original Publication Date: 1989-Mar-01
Included in the Prior Art Database: 2005-Jan-27
Document File: 7 page(s) / 194K

Publishing Venue

IBM

Related People

Brennemann, AE: AUTHOR [+4]

Abstract

This article describes an automated electronic assembly system for accurately placing surface mount components (SMCs) on printed circuit board wiring patterns. The system can accommodate a large variety of components including bottom lead SMCs. Surface mount technology (SMT) is being used in electronic circuit assemblies as the integrated circuit module. Now the surface mount component, can perform more functions. This results in an increase in the number of input-output (I/O) connections or leads needed to access the SMC. The demands on automated system accuracy for circuit assembly becomes more severe as the spacing between the I/O leads becomes smaller. Commercially available state of the art SMCs have I/O lead (Image Omitted) spacings from 20 to 50 mils (0.020 to 0.050 inch).

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Assembly Technique for Placing Electronic Components on Printed Circuit Wiring Patterns

This article describes an automated electronic assembly system for accurately placing surface mount components (SMCs) on printed circuit board wiring patterns. The system can accommodate a large variety of components including bottom lead SMCs. Surface mount technology (SMT) is being used in electronic circuit assemblies as the integrated circuit module. Now the surface mount component, can perform more functions. This results in an increase in the number of input-output (I/O) connections or leads needed to access the SMC.

The demands on automated system accuracy for circuit assembly becomes more severe as the spacing between the I/O leads becomes smaller. Commercially available state of the art SMCs have I/O lead

(Image Omitted)

spacings from 20 to 50 mils (0.020 to 0.050 inch). Circuits using 50- mil SMCs are being assembled with state of the art automation, some with the aid of industrial machine vision. Some automation machinery builders have demonstrated component placement systems for devices with smaller I/O lead spacing. The basic areas of a typical pick and place method SMC placement system (Fig. 1) are: 1. Printed circuit board (PCB) conveyor line. 2.

Robot (manipulator) with component pick-up device and camera for registering the board to the robot coordinates. 3. Component feeder station where SMC is picked up. 4. SMC I/O lead finder using a second camera and vision techniques.

(Image Omitted)

The SMC placement sequence for assembly is as follows: 1. The robot registers or calibrates the PCB to the robot coordinate system using a camera and the board fiducials. 2. The robot moves to pick up the SMC at the component feeder and presents it to the lead finder station. A

silhouette of the SMC lead pattern is shown to the

camera by the proper illumination technique, and the

location of the SMC leads with respect to the robot

coordinates is determined by vision/image processing.

At this stage lead inspection can be done, if desired. 3. The robot moves to a predetermined SMC location on the PCB and registers the component footprint to the robot

coordinates using the robot-mounted camera and image

processing. This requires that the robot move the

camera to each of the two footprint fiducials

independently before determining the footprint

location.

(Image Omitted)

1

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4. The

component is then placed on the PCB based on the

parameters obtained from the above sequence. The above procedure has been demonstrated for smaller lead spacing SMCs (25-mil spacing) with placement times in the range of 5 to 10 seconds. This technique puts severe demand on the accuracy of the mechanical systems. The system disclosed herein does SMT assembly more accurately for the smaller lead spacing SMCs with improved throughput. The system of this disclosure (Fig. 2) consists of the following units: 1. PCB conveyor line. 2. Component feeder station. 3. Robot...