Members | About Us | Contact Us | Sitemap |
 |
|
SMD-9000 PLCC/SOJ/SO Vision-Based Inspection System A high resolution, fully programmable, image processing based system for the inspection of PLCC, SOJ and SOIC surface mount devices. The SMD 9000 consists of two fully integrated subsystems: an in The handling system moves the devices to be inspected through the SMD 9000 in a controlled manner. It positions the devices at each inspection station and sorts the inspected devices into the appropriate output tubes. All operations are performed in a manner which protects the leads and contents of the IC package from damage. Devices are handled at a cycle rate of 1800 to 2200 UPH. The inspection system consists of five solid-state video cameras and optics interfaced with a computerized image processing system. Specific inspection routines enable the user to program criteria for coplanarity, lead spacing and tweeze tolerances. The image processing system digitizes images acquired by the cameras and analyzes them using the system's sophisticated software. Specific measurements are taken and compared against pre-selected criteria to determine a pass or fail decision. Finally, the image processing subsystem sends instructions to the handling subsystem to sort the passed or failed device into one of the four output tubes. Key features include:
Inspection System The SMD 9000 inspection subsystem is an integrated combination of precision optics, electronic hardware and highly sophisticated software working together to provide a system that is both highly accurate and easy to operate. Its flexibility allows the operator to pre-select the inspection criteria in accordance with specific customer requirements. Five solid-state video cameras provide analog outputs which are then digitized for software program evaluation. The cameras and optics are mounted to maximize system resolution and allow fast and easy adjustment between device sizes. The three inspections performed by the SMD 9000 are Coplanarity, Lead Spacing and Tweeze (outside lead dimension). Calibration Calibration is achieved through the use of special gauges. Each gauge resembles and simulates the actual device leads, providing a known reference from which to calibrate the system. These precision gauges have been inspected in accordance with the National Bureau of Standards. The calibration process is very simple. The operator places the gauge on its respective inspection stage. The calibration menu is accessed and, one by one, each camera is calibrated. The calibration process is fail-safe. If the operator makes an error, the procedure will not be accepted. Coplanarity Inspection In measuring coplanarity, it is most important to accurately define the seating plane and then measure the height of each lead relative to this plane. In the SMD 9000, devices are placed live-bug on a highly polished, precision-flat stage. This stage is the true seating plane. Errors encountered in calculating the theoretical seating plane used in dead-bug inspection machines are eliminated. A diffuser provides the source to backlight the leads allowing inspection of all leads regardless of their finish. The camera transmits a silhouette of the leads and their mirror images. The mirror surface of the stage enhances the resolution of the coplanarity measurement, providing an image twice the size of the coplanarity gap to the image processing system. Each side of the device is viewed with a separate camera. The coplanarity of SOIC-gull wing leads is determined in the same manner as for J-leads. Lead Spacing Lead spacing or pitch is the center-to-center distance between the device leads. The SMD 9000 image software performs lead spacing inspection using the same image provided by the coplanarity cameras. Lead spacing measurements are then taken from centerline to centerline and compared to the rejection criteria. Tweeze Tweeze is the distance from the device centerline (top view) to the outermost point on the end of the lead. Using a single overhead camera, the SMD 9000 offers two methods of tweeze inspection. The Outside Dimension Method calculates the distance between the outermost points on opposing lead pairs without first referencing the centerline. This distance will be compared against a rejection dimension selected by the user. This method is the fastest, requiring less processing time than the centerline method. The Centerline Method is designed to be a more stringent evaluation than the outside dimension method. Instead of measuring the opposing lead pair dimension and comparing this to the outside dimension specification, this routine measures the distance between the outermost point on each lead and the lead frame centerline. This value is then compared to one-half the outside dimension specification. This technique permits the detection of lead frame errors. Handling The handling subsystem removes devices from tubes that have been loaded into the two-position input shuttle. It then deposits them on an input conveyor which singulates and positions the devices. A vacuum pick and place system progressively transports each device from the coplanarity stage to the tweeze stage for respective inspections. After the tweeze inspection, the devices are placed on an output conveyor where, based on the pass/fail results from the image processing computer, they are sorted into one of four output stations. Each output station contains a two-position tube shuttle. The horizontal handler subsystem provides gentle, anti-static, safe handling of all packages. Standard bus electronics control the handler subsystem logic. Low Jam Rate The SMD 9000 has a jam rate of less than 0.1%. This rate is supported by extensive factory testing and feedback from units operating in production environments throughout the world. If a jam does occur in the SMD 9000, it is sensed by the handling system electronics and a message appears on the operating screen indicating the problem. Jams are typically cleared with ease on the SMD 9000, resulting in no significant effect on the throughput rate. Device Protection The handling system of SMD 9000 causes no measurable damage to devices as they are processed. Extensive performance testing of these systems has shown no drift in lead measurements resulting from repeated handling through the system. User Friendly The SMD 9000 is designed for easy operation. Very little operator training is required. The system is menu driven and the operator merely moves about the screen, using the arrow keys, and selects options using + or - keys. The operator's keyboard does not provide alphabetic characters as a safety precaution. Where these characters are required (lot name, or other data base header information) an on-screen prompt appears, allowing the operator to toggle through characters and symbols. A removable engineer's keyboard has all the necessary keys for ASCII operation of a personal computer to allow access for file manipulation and software usage. The image processing computer can be used by engineers to run other applications, analyze inspection data bases and maintain the system data files. Specifications Performance
General
Options
|
||
American Tech Manufacturing, Inc.
All Rights Reserved
|
|
spection system and a handling system.