As part of BEST’s services we offer Automated Optical Inspection or AOI PCB inspection services. This allows us to inspect either reworked or newly assembled boards faster, more repeatably and with greater precision. With the density of boards continuing to increase, the potential for neighboring part reflow during rework increases. With this greater density also comes the necessity to use automation during the PCB inspection process in order to catch any anomalies. With manual inspection being only slightly better than 80 per cent effective, a lot of assembly errors can be missed.
For board assembly there are numerous defects that an AOI inspection of the PCB can “catch”. One of the easiest things to catch is wrong or missing parts. The inspection system, once properly programmed, that can “flag” those areas of the board that do not have a component in the required location, have a different component in the required location or if a given location is “covered over” with different incorrect components or materials. Other problem areas in the initial assembly of the board that can be caught with the AOI inspection process include component (wrong part number, wrong lot or date code) anomalies, solder bridges and other gross soldering defects, mis-orientation of components like LEDs.
For rework areas AOI inspection can inspect the component rework location as well as the surrounding locations in addition to the underside areas of the rework location. This insures faster rework throughput, allows more complex rework (ie many device locations) all with a higher yield. In addition, the consistency of the rework quality is maintained.
The AOI system consists of a high speed, high precision camera as well as a linear actuator in order to “drive” either the board or the camera over the component locations. There are a multitide of different camera types and lightening option in order to optimize the AOI inspection process.
In order to be able to Inspect the PCB using AOI, the details for an acceptable board as well as the component location must be programmed into the system. This programming must be carried out correctly if the AOI system is to be able to correctly detect any defects on the PCB assemblies passing through. One of the methods used to insure proper programming is through the use of a perfect or “golden board”. This “perfect” board is passed through the system so that it can learn the relevant attributes. It will look at the components, the solder profiles of each joint, and many other aspects. In order to provide the system with enough data. PCB data in terms of some combination of X-Y data, BOM and GERBER data is provided to the system and it then generates its own profile for the board.
It is essential that any printed circuit board manufacturing area is able to check the quality of the boards coming off the end of the line. Only in this way are they able to monitor quality and when problems are detected to rectify the process so that further boards are not affected by the same problems. In this way automatic optical inspection and where necessary X-ray inspection are two essential tools for the manufacturing industry.
BEST can provide AOI inspection service for your boards. This means that a supplier can be evaluated for the quality (may be used in conjunction with other testing services like x-ray inspection) of their workmanship. In addition, AOI inspection may offer first article inspection of PCB assemblies being built for the first time. Call BEST to see how we can be of service with AOI services.