Simulation and experimental study on temperature field of fluid jet-dispenser
Fluid jet-dispensing technology has been widely used in micro-electronic encapsulation industry. The fluid viscosity varies as temperature changes, while it affects the process remarkably. Besides basic method on temperature field solution, some thermal behaviors, including heat conduction and heat exchange, boundary conditions and some physical parameters are overall analyzed in this paper. Based on the simulation software platform ANSYS, a two-dimensional transient temperature field model of jet-dispenser was built, and simulation programs on temperature field for two sorts of fluid with obviously different thermal conductivity were performed. Then heating experiments were finished to validate the feasibility of FEA, and results show that temperature distribution is homogeneous along fluid area and it meets the conditions of jetting.
Nozzle and needle during high viscosity adhesive jetting based on piezoelectric jet dispensing
A piezoelectric impinging jet valve is used as a study object to investigate the effect of the ball needle in the existing impinging jet and nozzle structure of the valve on the performance of the jet. First, FLUENT software is used under different ball needle and nozzle structural parameters to simulate the pressure distribution that the ball needle and nozzle in the pressure cavity form when the ball needle hits the nozzle, by arranging the structure model of the ball needle and impact valve nozzle. The piezoelectric impact injection valve and the experiment test system are then designed. Test results show that the ball needle and nozzle structural parameters are closely related to the injection performance of the impact valve. Under certain conditions, a greater needle radius corresponds to a smaller nozzle aperture and taper. Moreover, high-viscosity liquid jetting is easily achieved. By using a ball needle with a radius of 1.5 mm, a taper angle of 60°, and a nozzle diameter of 0.1 mm, we can realize the industrial viscosity of 58 000 cps in glue spray, and the injection plastic fluid volume is 0.62 μl.
EFFECT OF SAMPLE PREPARATION ON WATER TREE RESISTANCE OF XLPE/SEBS BLENDS
The effects of an aromatic polymer, such as poly[styrene-b-(ethylene-co-butylene)b-styrene] (SEBS), and its preparation processes on water tree resistance, morphology, crystallinity, dielectric constant and dielectric loss tangent of crosslinked polyethylene (XLPE)/SEBS and XLPE/SEBS/ethylene vinyl acetate (EVA) blends were investigated. The XLPE/SEBS samples were characterized by means of differential scanning calorimetry, scanning electron microscopy, dielectric spectral analysis and the accelerated water treeing experiment. The results clearly showed that although SEBS was partially compatible with LDPE and it was dispersed evenly in XLPE matrix, the blends demonstrated excellent dielectric performances, such as dielectric constant and dissipation factor. The crystallinity of XLPE/SEBS blends was decreased with increase in SEBS content and it was further decreased with the addition of EVA. SEBS could effectively improve the water-tree resistance of XLPE and both SEBS and EVA were found to improve the water tree resistance of XLPE synergistically as expected. The differences in sample preparation processes could change the phase morphology and dielectric performance of the blends, and could also influence the dispersion of SEBS in XLPE matrix as well as the crystallinity of the blends. Different preparation processes led to different water tree resistance behaviours of the samples. The improvement of SEBS dispersion in XLPE matrix helped to improve the water tree resistance of XLPE.