Simulation And Experimental Research Of Needle-typed Micro Jet Dispenser Driven By Piezoelectric Actuator

Dispensing adhesive materials accurately and quickly is applied extensively to micro-electronics packaging field. With the rapid development of micro-electronics packaging technology, the traditional contact dispensing technology, for the shortage of low efficiency, big dispensing space, poor consistency and big droplets, is gradually replaced by the non-contact dispensing technology. And limited by the air switch speed and the air fluctuation, the same problems of low dispensing efficiency and poor droplet control ability are also apparent in needle-typed jetting technology driven by air, which is a key member of the non-contact adhesive materials dispensing technology. Given the demand of micro-electronics packaging tasks and the drawbacks of all the dispensing technology above, a kind of needle-typed jetting dispenser driven by piezoelectric actuator is proposed. Combining the piezoelectric actuator that has precise output displacement, and the needle-typed jetting dispenser which has big driving force, the proposed dispenser can dispensing high viscous adhesive materials more quickly and accurately. Based on the forming process of the droplet, the performance of the needle’s output displacement, the construction of the system platform, and the experiment of the liquid’s micro-dispensing, the following research is conducted in this paper:1) Jetting process research of the adhesive materials based on the piezo-needle valve. Firstly the simulation model is built based on the Fluent, a kind of fluid dynamics simulation software. And the adhesive materials’ dispensing process based on the jetting valve is simulated by the dynamic mesh technique. Then by means of the simulation, the influence on the droplet’s volume and the adhesive liquid’s velocity, from the needle’s open time, adhesive viscosity, driving air pressure and needle’s stroke is analyzed. Finally via the orthogonal experiment, the priority of all the above parameters’ influence is researched, and in commonly used dispensing conditions, the smallest droplet diameter and the maximum flow velocity of the developed jetting valve is obtained.2) Output displacement performance analysis of the piezo-needle valve. Firstly the diamond displacement amplification mechanism, a key element of the displacement output module, is designed. Next through finite element simulation, the structure parameters of the amplification mechanism is optimized, and the performance of the optimized amplification mechanism is analyzed, which is aimed to instruct the structure design of the jetting dispenser. Then the dynamic model of the jetting valve’s displacement output module is built, and via the Matlab simulation, the amplification mechanism’s amplification multiple and the relationship between the needle and the piezoelectric actuator is analyzed. Finally the experiment is conducted to test the needle’s output displacement in working conditions.3) Development of the piezo-needle adhesive materials micro jetting system. Firstly a set of needle-typed jetting dispenser driven by piezoelectric actuator, and a set of three dimensional adhesive dispensing platform, are developed. Next a control cabinet is designed to integrating the control components, and an experimental platform consisting of control module, pneumatic module and monitoring module is built. Finally the PC program interface is developed via the VC++ 6.0 software,which consists of jetting valve control module, digital balance measure module, dispensing parameters adjustment module, moving platform control module and application experiments module.4) Experimental research of dispensing adhesive materials. Firstly the adhesive materials’ dispensing performance in various control parameters is researched. Next a PID control algorithm is designed, which is used to obtain the expected droplet volume through adjusting the dispensing frequency quickly. According to this algorithm, the dispensing repeat-precision and accuracy can be controlled within 4% and ±6%. Finally based on the micro dispensing valve, the underfill experiment involving single point injection, single line injection, L path injection and square path injection is conducted. And the experimental results indicate that the shape accuracy and the location accuracy of the droplet and the liquid line is fine.