Key Theories And Technologies Research On The Precision Printing System Of High Efficient Cystalline Silicon Solar Cells

The photovoltaic (PV) power generation technology is the new energy leader tosolve the global energy crisis. Various materials are applied to solar cells, but themost prevalent material for solar cells is bulk crystalline silicon in the PV market,and its product technology also is mature. After the2008global financial crisis, thesovereign debt crisis break out in European, the global PV industry has been greatlychallenged. Against this background the whole PV industry is seeking a way toreduce the cost of production and increase the efficiency of a solar cell. Therefore,the wafer tends to become thinner and thinner, ask for the lower breakage rate andthe higher throughput, and new technologies of selective emitter and double printingare applied to the metallization of crystalline silicon solar cells. These bring newchallenges to the equipments on the metallization production line.Fully automatic vision-based screen printing system is one of the key productionfacilities on the crystalline silicon solar cells production line, so are the mainactuators that implement the technologies of selective emitter and double printing.And its productivity and breakage affect the output of solar cells of the whole line.Therefore, key theories and technologies on the precision printing system of highefficient crystalline silicon solar cells is thoroughly investigated in this paper,especially in the field of precision positioning base on vision metrology. The maincontributors of the thesis are listed as follows:(1) Based on the requirement of high accuracy, high speed and low breakage rate,a novel precision vision-based screen printing system is proposed, which has amodular design and the highest flexibility. And then a positioning calibrationalgorithm applied to multi-cameras screen printing system is presented, which canquickly establish the mapping relationship of local coordinate systems. awafer-positioning method based on the square fitting and a finger-inspection methodbased on parallel lines fitting are proposed using vision metrology, and somebreakage inspection methods and its logical grouping are also introduced in thissection.(2) The three degree-of-freedom (3-DOF) planar alignment positioningmechanism is a key part of precision vision-based screen printing system, and itspositioning accuracy directly impacts the quality of printing. A novel3-DOF planar parallel alignment stage for screen printing, being named XY-Theta parallelalignment stage, is proposed in this paper. Its two direct and inverse kinematicmodels are obtained by a geometrical method and a vector combined with analyticmethod. An useful method is presented to analyze the kinematic accuracy ofXY-Theta parallel alignment stage, to obtain the maximum position and orientationerrors in the workspace subjected to input errors and structure parameter errors, andthen some conclusions are drawn.(3) Based on the characteristics of XY-Theta parallel alignment stage, animproved error modelling method is proposed using the vector method and theanalytical method. The mapping relationship between the errors of position andorientation and the errors of geometric parameters is derived, and the Jacobin errormatrix is also obtained. Then, the influences of all geometric error sources ofXY-Theta parallel alignment stage on the terminal pose errors are estimated via asensitivity analysis method.(4) For the calibration of XY-Theta parallel alignment stage, an orientationinterpolation method using a triangular area to position the alignment point based ona moving camera, and a step kinematic calibration method based on two cameras aredesigned. The orientation interpolation method differs from the traditional kinematiccalibration methods, and can calibrate the equipment itself automatically withoutcomplicated error modelling and identification for all geometric errors and the needfor any background in parallel robot calibration. By contrast, the step and gradualkinematic calibration including step measurement, step identification and stepcompensation can lead to a higher accuracy.Finally, concentration and academic future of the precision vision-based screenprinting system for crystalline silicon solar cells is speculated based on thesummarization of the whole paper.