Research On Precise Micro-scale Automatic Dispensing Method Based On Surface Tension

In the micro assembly engineering,with the rapid development of microelectronics technology,the size of the workpiece is gradually miniaturized,and the assembly space is becoming more and more narrow,which puts forward higher requirements for the fluid dispensing technology.Under the premise of ensuring the efficiency and accuracy,it also needs smaller droplet volume,which is generally between pL and fL.the conventional dispensing method is no longer suitable.Considering the characteristics of common dispensing methods,it is not suitable for micro assembly engineering,and can not meet the process requirements of micro assembly engineering.Therefore,this article proposes an ultra-micro dispensing method that can be automated and used for micro-size manufacturing,which can complete the precise dispensing of glue in the fL-pL range.In this method,the tungsten needle is used as the pipette and the capillary tube as the glue storage container.Through the designed control system,the pipette is driven to realize the precise distribution of micro glue at the specified position.This thesis introduces the research and development status of dispensing technology at home and abroad,and then from the fluid itself,analyzes the rheological characteristics and stress of the fluid.The dispensing process is divided into three stages,and the mathematical model of the glue force is carried out in each stage,and the factors influencing the result of dispensing are summarized through the model.An ultra micro dispensing system is designed and developed.Based on this,an automatic control system combiningLabview and PLC is developed.The system can realize the ultra precision dispensing experiment in X,Y,Z three-axis linkage.A comprehensive experimental platform of ultra precision dispensing was built,and the processing and selection of key parts were introduced in detail,including the preparation of pipette,the selection of rubber storage tube,the determination of gap,and the processing method of three-dimensional observation of rubber spots.The main factors influencing dispensing results were summarized through theoretical analysis.Single factor experiments were carried out for these factors,including adjusting the diameter of pipette,dispensing speed,residence time,contact distance and other parameters.The influence of different wettability materials on dispensing results was explored,and the influence rules of the above parameters on dispensing results were summarized.Through the design of orthogonal experiment,the factors affecting the dispensing results were sorted.Using the ultra precision dispensing automatic control system designed in this thesis,the comprehensive application experiment based on the automatic dispensing system is carried out,and the dispensing work is carried out at the designated position through programming.Including the application of automatic dispensing plane graphics drawing,automatic dispensing 3D three-dimensional dispensing experiment,micro hole filling experiment.The experimental results show that the diameter of pipette,residence time,dispensing speed,contact distance and other factors will have an impact on the drop volume.In the dispensing experiment with four kinds of materials as the substrate,the change order of droplet diameter from large to small is: PC,quartz slide,PTFE,PCB.Compared with other factors,the diameter of pipette is the most important factor.In the comprehensive application experiment based on the automatic dispensing system,the minimum drop diameter is 9.4 ?m and the volume is 24.468 fL.the drop has good uniformity and position accuracy,which meets the expected requirements of the experiment and realizes the ultra precision automatic dispensing.