Design And Experimental Research Of Laser Solder Bumping System

As one of micro-electronic packaging technologies, flip interconnection is widely used as the advantages of large contact area, short connecting distance, reliable signal transmission and so on. The fabrication of bumps is essential in flip interconnection in that it affects the packaging quality, however microelectronic devices are sensitive to pollution, and require no flux during bumping process. Therefore the laser solder bumping device which uses laser remelting technology to produce bumps emerges.According to the small object and high precision during the process of bumping, the laser solder bumping platform based on micro-vision technology is bulit. Then the technologies of the laser solder bumping, the quality detection of bumps'appearance and the repair work of bad bumps are researched. After that the software for system control is developed, and finally system experiments are carried out.Firstly, functions and criteria of laser solder bumping system are in-depth analyzied, then a program which uses the micro-vision technology to locate pads and detect qualities of bumps is determined to be used, and the laser solder bumping experimental platform that consists of mechanical, micro-vision, laser, pneumatic and control system is established.Secondly, the crucial link of the laser solder bumping process, namely visual location of the pad's center is researched. A center detecting algorithm for the pad image is raised, and it consists of binary filter, edge extraction and sub-pixel center detection. In order to realize sub-pixel center detection, an improved randomized Hough transform is raised, then it is combined with least squares method, the sub-pixel coordinates of the pad's center are quickly and accurately extracted by using rough location first and then using precise detection, and it can satisfy the precision requirement of image recognition.Thirdly, according to the analysis of the bump's image character, the accelerated normalized correlation matching algorithm is determined to be used, and a method for the bump's quality detection is rasied based on this matching algorithm. This method consists of connected area labeling and the bump's center detecting algorithm, and according to the detecting results of these algorithms, the bump's quality style is confirmed.After that, repair work is to be done in order to assure the quality of bumps, the eccentric bumps'repair work is laser remelting first and then laser solder bumping, the shedding bumps'repair work is laser solder bumping directly.Finally, the control software of laser solder bumping system is developed, and based on the software and hardware system, the precision experiment of center detecting algorithm, the laser parameter calibration experiment, the laser solder bumping experiment, the quality detecting experiment of bumps and the repair work experiment of bads bumps are carried out. At last, experimental results indicate that it can satisfy criteria requirements of the system, and can be applied to bumps'fabrication.