Mechanism And Experimental Research On Piezo-driven Injection Valve Dispensing Hot Melt Adhesive

Nowadays,due to rapid development of electronic technology and people’s higher demands for electronic products, change the direction of electronic products to diverse, intelligent, innovative and miniature. While the border of visual electronics becomes thinner, even to be of no borders, fixation and protection of electronic component becomes the core process during the packaging. Therefore, the accuracy of electronics packaging has a vital role in the development of electronic technology.Currently on the market,due to a lot of advantages, new dispensing process of hot melt adhesive is highly favored in electronic packaging industry.First,the curing speed is faster compared to other glue. At the same time,it has the properties of melt with heating and adhesion with cooling. Second,the performance of hot melt adhesive is very stable and the working environment is not affected by temperature and humidity changes. Thus,it can ensure the bonding strength. Third, hot melt adhesive does not contain any other solvent such as water.It is solid at room temperature and can even be stored in rubber cylinder with the form of solid.Fourth,it has extensive bonding objects. Whatever the bonding objects are, it always remains high bonding strength and good sealing performance.And it does not require post-drying process, so the bonding process is very simple.In the enterprise factory,needle dispenser is widely used to coat the hot melt adhesive.But this way is lack of accuracy and efficiency,and it always needs higher requirement of smoothness on the surface of workpiece.Therefore,this article proposes a piezoelectric and non-contact injecting mechanism of melt colloid.It can achieve droplet ejection of hot melt adhesive in the molten state.Then,the injection theory of hot melt adhesive is analyzed. At last, a prototype is produced through theoretical analysis and calculation,then tested systematically.Firstly,the performance of the stack of piezoelectric ceramics is analyzed. Secondly,the injecting mechanism of melt colloid is simulated and analyzed with the use of simulation software Fluent.Then,the impact of colloid injecting by ball striker of different diameter is studied.In addition, a relatively suitable insulated material is chose according to comparison and analysis.Then,the intensity of the firing pin is analyzed by Ansys simulation software to ensure stable operation at maximum load.According to the conclusions of simulation analysis,a piezo-driven injection valve of hot melt adhesive is designed and produced. Then the experiment platform is built and each component of platform is described in detail.Finally, a large number of experiments are carried out to test the performance of injection valve.The impact of some factors such as the inner diameter of the nozzle size, the level of the heating temperature, the size of the driving voltage and pressure on the performance of dispensing is mainly analyzed.When the driven voltage, inner diameter of nozzle,driven pressure and opening time of the valve is 90 V,0.1mm,0.1MPa and 1.5ms respectively,the droplet-ejecting precision of melt colloid is tested repeatedly.The results showed that the repeatability error of designed valve is less than ±3%.