Research On Cleaning Control Of Stencil Printing Based On State Analysis

Solder paste printing is one of the three major processes in surface mount production.Studies have shown that more than 60% of PCB board assembly quality problems are rooted in the solder paste printing process.Stencil is an important factor affecting the printing quality of solder paste.The role of the stencil is to use the mesh to apply solder paste to the pad.As the printing process is repeated,the residual solder paste will more and more adhere to the stencil and gradually solidify,which will affect the printing quality.At present,periodic stencil cleaning methods are commonly used to remove stencil residual solder paste,but frequent cleaning will interrupt the printing process,increasing production cycle and production costs.This article mainly studies the stencil cleaning control method based on condition analysis,and reduces unnecessary cleaning operations on the premise of ensuring the printing quality.The main research contents of the paper are as follows:Firstly,the research background and stencil printing process are introduced.The influencing factors of printing quality are analyzed.A stencil cleaning control method is proposed based on states analysis.The control ideas of this method are analyzed.The main technical issues that this method needs to study is clarified,including real-time printing state modeling,cleaning control state analysis and stencil cleaning control.Secondly,the stencil printing process capability is analyzed,the printing process characteristic parameters are clarified,the printing process capability index calculation method based on the characteristic parameters is studied,the conversion relationship between the printing capability index and the printing state is studied,and the stencil printing performance is evaluated using the obtained state.Thirdly,the Markov model is used to establish the stencil printing state transition probability matrix to describe the degradation process of the stencil printing state,the stencil printing efficiency model is established by using the state transition matrix,the corresponding printing state at this time is solved according to the goal of maximizing the printing efficiency.Use this state as the cleaning control state of the stencil to provide a basis for decision-making for the stencil cleaning control.Finally,the stencil cleaning control logic is analyzed.Simulation is used to study the influence of typical influencing factors on stencil cleaning control.Comparing with traditional periodic stencil cleaning control methods is analyzed.The advantages and disadvantages of various cleaning control methods are sought to provide advice and guidance for companies to improve PCB printing.