The economic realities of quality control, rework cost and need for customer confidence make automated optical inspection (AOI) a necessity in circuit board manufacturing environments. AOI can take a number of roles on the PCB production line.
There are a number of 'captive' applications such as accurate component positioning in the pick-and-place system, or screen checking in the paste printer, and there are also standalone functions to which AOI is ideally suited.
For PCB verification, the ScanPoint from Diagnosys is a fully-functional colour AOI solution designed to operate before and after reflow, inspecting PCBs for component and solder faults. Handling boards up to 300 by 420 mm, ScanPoint is easily and rapidly programmed and performs a fast, comprehensive inspection. It has a minimal footprint to optimise space in the production line and can be easily networked for full process control activities.
The DiagnoSYS TestVue 32 software uses two basic algorithm groups to inspect component and soldering. The first algorithm checks the component-related parameters at once, with these being entered to a Model training phase. The second algorithm group is for solder and lead inspection and offers the ability to use the optimum algorithm for the type of inspection to be carried out. In addition, the solder inspection and lead inspection can be attached to a package style, rather than component type, to assist in programming.
Benchtop models
The company's desktop AOI models, the DT 10 and DT 30 use the same high performance scanner and software features as the in-line ScanPoint 50. The board is loaded and unloaded using the drawer feed facility allowing the operator to place the board on predefined blocks. The positional accuracy of the board is not critical as the fiducial alignment of the board ensures test repeatability. The DT 10 model has less emphasis on speed of test. This is a lower cost system designed for low volume assemblies but still has high speed capabilities when compared to existing camera systems.
Automated inline AOI
The ScanPoint 50 is a fully-automated inline AOI incorporating a dual scan with full colour fluorescent and LED lighting. This allows the user to read both printed and laser-marked devices. Optical alignment to on-board fiducials maintains positional accuracy from board to board. Most AOI systems on the market today find faults such as incorrect polarity, shifted part, solder defects, bent leads, incorrect part, missing, solder bridges, tombstone, billboard and skew. ScanPoint can find the same faults down to 0201 device sizes by using scanning technology, and in most cases this method is not only faster than camera systems with XY stages, but is more cost-effective with very low maintenance.
Faults are reported with panel and board position and all faults can be stored with pictures. Full fault classification facility for SPC analysis comes as standard. ScanPoint has a simple programming and user interface so that programs can be quickly and easily created for production.
Operation
This operator interface is user friendly so that training time period is short (around 30 minutes). The operator is presented with a board preview at 'Select Board' stage ensuring the correct board has been selected and the displayed orientation is used for loading. The automatic scanner and conveyor adjustment removes the possibility of operator error as well as significantly reducing set up times. A simple 'Blue' pass and 'Red' fail quickly indicates suspect devices while a review mode allows closer examination and classification of the devices with the option of collecting the information for full SPC analysis. The 'Test Board' environment interacts with the rework server allowing offline rework for high volume applications.
Simple icons can be tagged to the fault allowing the easy classification and an understanding of the defect displayed. Program Studio is the application for the creation of test programs used in the 'Test Board' environment. By using the pick-and-place information or CAD, programs are created by importing the device placement data onto the board. Existing devices are automatically placed from the library and unknown devices require identification only once. 95% of programs can be created using the mouse and shortcut keys and high-level board programs can be created in less than one hour.
With TestVue 32 the CAD import facility requires only basic placement information such as Ref ID, Part No, Package Type, X, Y and rotation. Any adjustments to scaling, rotation, polarity and positioning can be adjusted in realtime on the displayed board.
Offline programming and debug is simplified as TestVue 32 software allows the actual board for test or debug to be saved in its TPD format. The saved images and software are exactly the same as the ScanPoint's, making program creation and updates easy, without impacting on the production schedule.
Vu-Point comparator
For the inspection of low to medium volume PCB assemblies, an innovative scanner system, Vu-Point, is incorporated into the TestVue 32 inspection software. The system compares between a known good (Gold) board and a sample board. Vu-Point automatically aligns and flips between the two images testing the board using a predefined test routine for the board under inspection. The 'Test Board' function allows the comparison of specific areas of the board ensuring a precise and consistent method of test from inspector to inspector.
Being Windows-based, ScanPoint can be networked and can communicate with a central server and other ScanPoint products. The transfer of programs from one system to another is made painless since each system's calibration parameters are applied to all test programs being loaded.
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