| The micro,precise and rapid distribution of high viscosity droplets such as adhesives and underfills is an indispensable technical means in the field of microelectronic packaging.With the development of the field of integrated circuit.the demand for droplets viscosity is getting higher and higher,and the volume of droplets that need to be dispensed is getting smaller and smaller,even reaching micro-nano upgrades.The requirements for the distribution speed,accuracy and precision are continuously increased.The industrial dispensing usually adopts open-loop control mode,which has low distribution precision and poor anti-interference ability.It is difficult to complete the rapid distribution of different expected volumes and the placement of chips of different sizes and package types when the dispensing of the droplets changes requires manual adjustion of the distribution parameters.The task restricts the development of droplets distribution in the field of microelectronic packaging to a micro-accurate.volume-controlled,and fast dispensing operation.Therefore,it is very necessary to study the droplets distribution process,realize the self-adjustment of the distribution process parameters and volumetric precision control.According to the distribution requirements of high-viscosity liquid materials in the field of microelectronic packaging,the problem of high-viscosity liquids is not easy to be precise and micro-dispensing.Combined with the latest research in the field of micro-spraying at home and abroad,it is found that the piezoelectric driven needle-txype dispenser is fast and precise in high-viscosity droplets.The ad.vantages of distribution are outstanding.Therefore,the research on the micro-disrpensing method of the piezoelectric driving needle type dispenser is carried out.and the piezoelectric dri.ving needle type dispenser for the micro-dispensing liquid micro-distribution is developed.The piezoelectric-driven dispensing structure adopts piezoelectric actuator.and has the characteristics of high output precision,fast response,and easy control by voltage.However,the hysteresis nonlinearity of the piezoelectric drive seriously affects the output accuracy.In this paper,the piezoelectric needle dispenser is taken as the research object to improve the displacement accuracy,ensure the droplet volume and enhance the adaptive control ability of the double closed loop control system.In order to reduce the hysteresis of the piezoelectric actuator magnifying mechanism system in the dispenser,this paper adopts the neural network fuzzy self-tuning fractional-order PI?D? control scheme.As the fractional order control method can improve the hysteresis characteristics of the piezoelectric actuator effectively,the paper combine the fractional-order controller with fuzzy control to realize the self-tuning of parameters and dynamically control the displacement of the piezoelectric actuator in real time.Since the mathematical model of the controlled object is not needed,the calculation amount is greatly reduced.The neural network and the fuzzy control are combined by the Adaptive Network-based Fuzzy Inference System(ANFIS)module in MATLAB.After a certain amount of data experiments,the fuzzy control rules and membership function parameters are obtained through computational training and learningIn the next step,a double closed-loop intelligent adaptive control method is constructed to accurately control the amplitude of the needle and the real-time detection of the droplet volume.The experimental platform consisting of five parts:circuit control,pneumatic control,three axis motion,temperature control,feedback detection was developed.The circuit part was controlled by the signal generating board of the upper computer interface of the industrial computer to generate a voltage signal,which is amplified by the power amplifier to act on the micro-injection valve.The pneumatic part is generated by the air pump.and is filtered by the filter unit and adjusted by the electric proportional valve to the glue storage barrel.The three-axis motion part realizes the fixed-point dispensing by controlling the three-axis linkage by the motion control card.Through the PID temperature controller,the temperature control part maintains constant temperature en-ironment of droplets among the nozzle part.The detection part is divided into micrometer needle strike displacement detection and balance quality inspection.The micrometer detects the displacement data of the needle,and the balance detects the quality feedback of the glue to the upper computer.After the treatment,a new control voltage is generated to act on the micro-dispenser to precisely control the displacement of the needle and the volume of the droplet to form a closed loop control to realize accurate and fast dispensing operation of adhesive droplet.In addition,VC++6.0 is used to establish the Microsoft Foundation Classes(MFC)host computer interface,the feedback data is read in real time,and the fuzzy fractional-order PI?D? operation is performed and the control signal is output,which realizes the human-computer interaction,and can set the parameters of the fractional-order PI?D?.Finally,experiments were carried out based on the above described injection valve and micro-injection control system.Firstly,the accurate test of the inner loop needle amplitude was performed,and the followability of the fuzzy fractional PI?D? was verified by the triangular wave signal.Secondly,the same PI?D? parameters were set for the piezoelectric needle square wave signal under the conditions of integer order,fractional order and fuzzy fractional order.The parameters were obtained by real-time displacement under the control of the system and the displacement under the stabilized rear-wave signal,and were compared from the aspects of stable time,steady-state deviation and square wave displacement followability.Finally,combined with the outer ring volume detection system,the volume was detected under the conditions of integer order.fractional order and fuzzy fractional order.Experimental results indicated that the self-tuning fuzzy fractional-order PI?D? controller could significantly improve the tracking performances of the PI?D? and the integer-order PID with regard to the amplifying mechanism with the advantages of good dynamic character and regulation precision.The followability of the output displacement for the square wave signal and the control precision of the droplet volume were improved.Among them,the displacement of the piezoelectric dispenser under the fuzzy fractional PI?D? control was stable within 0.40%,and the volume deviation of the stabilized droplet was maintained below 2.86%,which reduced hysteresis of the piezoelectric actuator amplification mechanism,improved the stability of the system.The whole process realized parameter self-adjustment and precise control of droplets volume during the distribution process. |
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