The full name of AOI is automatic optical inspection, which is a device based on optical principles to detect common defects encountered in welding production. AOI is a new type of testing technology, but it is developing rapidly, and many manufacturers have launched AOI testing equipment.
At present, the functions of AOI are generally relatively complete, and there is not much difference. The following is a brief description of some common functions.
1. Selection of resolution: The resolution of AOI should be measured by the size of the pixel as the criterion for discrimination, that is, the spatial resolution. The size of the pixel is not the criterion for judging the detection ability of AOI. To be precise, the size of the pixel is the factor that determines the size of the pixel per unit area. If the unit area is different, no matter how high the pixels are, there is no comparison.
2. Selection of special functions: If you want to test the PCBA with multiple boards, you must choose the AOI with the springboard function, that is, the AOI with the area selection function. If you use AOI as quality process control, then, when you choose AOI, you must choose AOI with RPC function, that is, AOI with real-time process control.
3. The choice of CAD: Now most AOIs have the function of importing CAD data, but the use of this function is not very efficient for PCBA boards with fewer components, while the use of PCBA boards with more components is not very efficient. Can play a multiplier effect.
4. Selection of SPC: SPC is process statistical control. Statistical control is not as important as real-time process control (RPC). RPC can not only perform real-time statistical analysis, but also provide early warning, which can keep the production line in normal working condition for a long time.
5. Selection of repeatability, false positive rate and missed judgment rate:
The higher the repeatability of the AOI, the more stable its performance, but because the AOI technology is not very mature, the repeatability of the AOI on the market is generally 20%-30%.
The lower the false positive rate, the better. The false positive rate of the best AOI is only about 0.5% (calculated by point).
The lower the missed judgment rate, the better. The best AOI missed judgment rate is only about 0.5% (calculated according to the bad points).
it is not difficult to see from the above discussion that a cost-effective AOI must meet the following conditions:
① If the AOI camera is a real area array digital camera (CCD), this camera does not need a frame grabber;
② AOI light source Z is preferably a coaxial bowl-shaped light source;
③The AOI mechanical system is preferably driven by a servo motor and driven by a screw rod and a guide rail;
④The best development language of AOI software system is VC++;
⑤The repeatability of AOI software should be high;
⑥The operability of AOI software should be humanized;
⑦ AOI has a low rate of misjudgment and missed judgment;
⑧The AOI detection function should be complete;
⑨AOI should be able to interface with RPC real-time process control software.