| Ball Grid Array (BGA) packaging is the current mainstream of IC packaging technology. With the development of domestic semiconductor industry, and electronic products are lighter and multi-function, domestic IC market demand more and more BGA chips and associated equipments. However, the domestic IC industry started late, the corresponding study towards inspection techniques and equipment is very weak, and the industry in inspection equipment manufacturing totally fall behind the developed country, which lead to the quality inspection of BGA connector is relatively difficult, and the quality and reliability of the BGA chip is not easy to get guarantee. To solve this problem, in this paper, a BGA solder ball height real-time inspection system was designed, and a normal method of inspection system formal modeling was proposed. The main research contents were listed as follows:1) The shadow characteristic of the BGA solder ball lighted by a certain angle parallel beams was analyzed, the calculation formula for measuring solder ball height was demonstrated, the influence on the result of the inspection from incident angle was studied, and the structure and workflow of the BGA solder ball height real-time inspection system was designed.2) To resolve the difficulty in real-time inspection system modeling, a method of formal modeling based on Timed Automata was proposed. The mathematics model of real-time inspection system was established by using the description models of timed automata. This paper studied the method of model checking based on BNF grammar, and built a timed automata network model of the designed system in the tool of UPPAAL. The system requirements, including reachability, safety, time-property, activity, were verified, using strict mathematical method, by simulating the whole workflow and checking the possible situations in the tool of UPPAAL. According to the simulation results, the system optimization was completed.3) The design of BGA solder ball height real-time inspection system was realized under the guidance of the timed automata model. The motion control was based on PLC and servo system, the microcontroller of AT89C52was the core of the light source control, and the CCD camera connected PC based on 1394interface. The whole system was composed with the PC as the core.4) On the basis of the system hardware structure, it was necessary to divide the system software into submodule. Application software of those submodule were designed, including the motion control program of PLC based on SFC, the light source control program based on C language, the PC and PLC communication program based on Lab VIEW, and the interface design based on Lab VIEW. After the realization of software and hardware design, system performance should be debugged and the validity and stability of the system was verified by completing a task of a certain number of BGA solder ball inspection. |
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