Thermosonic Flip-bonding Bench Visual Positioning System Design And Research

With the development of microelectronics technology, the chip requests a smaller size, more I/Os, higher performance and reliability. The developing potential of traditional wire bonding is becoming smaller and smaller because of its technical characteristics. The flip chip packaging based on the surface array packaging technology becomes the mainstream of the next generation packaging technologies. The thermosonic flip chip Bonding technology becomes focus of studying, which can increase the density of packaging. At the same time, the thermosonic flip chip bonding equipment requires higher positioning precision, so the machine vision positioning technology is the key technology of flip chip equipments. In this paper, the software and hardware of vision based positioning in this thermosonic flip chip bonder are designed and studied.Firstly, this paper analyzes the function and objective of the thermosonic flip chip Bonding test stand vision alignment system, a new fixing method of dual CCD is raised by refering machine vision in other related microelectronics equipments.Secondly, According to the material characteristics of chip and substrate, CCD optical characteristics, experiment and theoretical study, the ring LED illumination with 6 LED bumps is adopted. Then a digital adjustable LED light power is developed, by which the brightness is regulated by software through serial port of the computer.Thirdly, the software development process based HexSight is summarized after analyzing the features of the flip chip bonder, the resources allocation method of double CCD cameras, the object Models controll method, the search function based gray histogram and the positioning method of reversed chip are worked out. In order to further improve the accuracy and speed of positioning, the acquired digital image is calibrated, the chip Model is optimizated. the error of the vision positioning system is analyzed according to the experiment results.Finally, based on the imaging model of ideal camera, the geometric relationship between two CCD panel is presented by spatial geometric transform algorithm. This vision positioning system has reached a sub-pixel accuracy, which realizes the die pickup and the alignment of die and substrate and lays a foundation for further study.