Study Of High-density Circuit Boards Automatic Optical Inspection System

With the development of all kinds of mobile terminal equipments, the size of PCBboards become smaller and smaller, such as chip resistors, capacitors and so on. For thedetection of the small chips, the naked eye used before can not reach the result we want,machine vision instead of the human eye detection has become an inevitable trend. Herewe have developed an automatic optical inspection (Automatic Optical Inspection,referred AOI) equipment to replace the manual testing.The equipment is to be used in SMT (surface mount technology) production linebefore going into the oven, it can find out default elements automatically at theproduction stage. This is an integrated use of several majors which mainly includedigital image processing, servo motion control and track structure design of the threeaspects. The testing process is that camera capture the special picture of the PCB boards,computer then analyze all the elements and find out the fault ones by a good algorithm.The positioning of elements is the core of the inspection process, which mean computermust first find the location of elements to be analyzed. This paper presents the containpositioning and contour positioning of two methods, and make detail analysis of the twopositioning results. After validated the computer can quickly locate the position of theelements which improves the efficiency and convenient of detection. In addition, herepresents an orbital automatic control system to make AOI well embedded into the SMTproduction lines which main use of PLC and servo control, reducing human andmaterial resources. At last, this paper developed a statistical software to deal with testresults and data processing, which make the results of the test data present in a betterway by data collection and chart analysis.