| Solder paste printing is a key process of the surface mount production line(SMT).The performance of printing system usually degrades gradually with the increase of production quantity.Steel mesh cleaning is an important measure to maintain printing performance and ensure printing quality.Under the current printing conditions,engineers usually need to pre-determine the frequency of stencil cleaning before printing starts.In order to reduce the loss of printing quality,the cleaning frequency is often set relatively high,and frequent cleaning and maintenance not only cause a large number of production interruptions,but also increase the production cycle and cost.Therefore,it is very necessary to carry out in-depth research on the cleaning and maintenance of steel mesh.The thesis combined with the topic of "New Model of Intelligent Manufacturing for Mobile Terminal Motherboards",with the analysis of printing system performance degradation as an entry point,studied the cleaning and maintenance of steel mesh based on Hidden Markov Model(HMM),aiming The stencil cleaning control of the paste printing system provides a reasonable and effective decision-making method.Firstly,introduce the SMT production process flow and solder paste printing process,analyze the degradation of the printing system performance and causes,analyze the impact of cleaning and maintenance on the quality,cost and productivity of solder paste printing on the SMT production line;put forward the solder paste printing based on the hidden Markov model System stencil cleaning and maintenance methods,clarify the decision-making process of cleaning and maintenance issues;establish a research framework for stencil cleaning and maintenance methods based on HMM,clarify research ideas and research content.Secondly,study the definition of the status classification of the solder paste printing system;analyze the solder paste printing feature data,study the selection and data processing of the feature data;establish a hidden Markov model of the printing system performance degradation,study the initialization and training algorithm of model parameters,and use Viterbi The algorithm evaluates the degradation status of the printing system.Then,based on the established hidden Markov model,evaluate the quality loss caused by the degradation of the printing system performance;to minimize the cost,establish a cleaning and maintenance decision model of the solder paste printing system,and analyze the changes in parameters such as maintenance time and number of printed boards The impact of maintenance decisions.Finally,the effectiveness of the steel mesh cleaning and maintenance method based on hidden Markov model is verified through case analysis. |
