Study On The Transfer And Spreading Behavior Of Liquid In Micro-dispensing Process

With the development of micro-electronics,the size of work pieces in micro-assembly engineering is developing in the direction of miniaturization,since the processing space is becoming more and more compact.In addition,the distribution of the used glue is becoming more difficult,demanding higher efficiency as well as precision of fluid dispensing technology.The accuracy of dispensing in continuous dispensing,while keeping the volume of the droplet between p L-f L,is a difficult task for the current dispensing technology.Therefore,the study of glue transfer and spreading is of great importance for the development of dispensing technology.Among the common dispensing methods,most of them cannot achieve the precise dispensing of ultra-micro glue.To address the difficulties of fluid dispensing technology,this paper proposes a dispensing method for micro-size processing,using a capillary tube to store the glue,a processed tungsten wire as a transfer needle,and a control system to drive the transfer needle to a specified position to complete the transfer and spreading process of tiny drops of glue.This method can achieve the requirement for precision dispensing of glue in the volume range of p L-f L.This paper introduces the current development of fluid dispensing technology and analyzes the rheological properties and fluid stresses from the fluid properties of the glue itself.The mathematical description of the glue in different dispensing stages is presented and the formula for calculating the glue transfer rate is derived.An experimental platform for micro-dispensing is built,and the process of dispensing experiments are described in detail.The key components are selected and processed.Combined with the theoretical analysis to determine the factors affecting the dispensing results,single-factor experiments were conducted on glue viscosity,dispensing speed and transfer needle diameter,and the maximum spreading diameter of glue was recorded in each case.An orthogonal experimental scheme was designed to rank the factors influencing the dispensing spread in order of priority according to the experimental results.Experiments were conducted to investigate the factors affecting the transfer rate by varying the viscosity of the glue,the surface tension of the glue,and the stretching speed of the transfer needle,respectively.By using the dimensionless number Ca to express the transfer rate,the pattern of conversion rate change was obtained.The experimental results showed that changes in individual factors had a significant effect on the dispensing results.The degree of influence on the glue spreading was ranked from largest to smallest: the diameter of the pipette needle,the glue viscosity,and the dispensing speed.As the viscosity of the glue increases or as the needle stretching speed increases,the rate of glue transfer decreases.Compared to epoxy resins of the same viscosity,the transfer rate of methyl silicone oil,which has a lower surface tension,is higher.The overall trend of the transfer rate under different conditions does not vary much,but decreases as the increase of the dimensionless number Ca,and finally converges to a certain value.