隨著國內IC封裝產業蓬勃發展，電子封裝之錫粉、錫膏用量與日俱增。但目前仍是以進口為主，如果國內可以自行生產，則可免受制於人，自給自足。然而封裝業所用之錫粉相當強調顆粒大小均勻，目前國內噴霧技術已能生產達到電子封裝業的形狀(球型)及大小需求的錫粉，唯粒徑分佈仍過於分散，須經篩分的過程以取其適用範圍之粒徑。一般常用振動式篩分機篩分，但對極微細(<38μm)的金屬而言，顆粒易阻塞篩網，所以並不適合量產時使用。
本研究則嘗試利用空氣動力原理，藉由側風對大小不同顆粒阻力之差異性來篩分其粒徑。在理論模式方面，連續相採用低雷諾數k-ε紊流模式(low-Reynolds-number k-ε turbulence model)以獲得流場結構；分散相利用拉氏法(Lagrangian approach) 之SSF(stochastic separated flow)模式，來獲得紊流場中的粒子運動軌跡。本文中並探討顆粒對氣相及氣相對顆粒的影響，檢視顆粒在側風下之運動特性及偏移量，比較各項參數對於顆粒運動軌跡的差異。由本研究的結果得知，流場中有顆粒的負載(two way coupling)，會改變整個流場的紊態結構。顆粒愈大受側風影響較小，側偏距離短。反之，顆粒小者側偏距離遠，且小顆粒(約<20μm)易懸浮於流場中不易收集。粒徑小於100μm之顆粒在沒有考慮相互碰撞(僅適用於稀薄兩相流)及氣相流速不大時(約17cm/s)，篩分效果不錯。

The growth of the integrated circuit (IC) and semiconductor industry causes a need of great amount of solder paste, which is mainly imported from foreign countries. There exists an urgent need to produce the solder paste domestically; however, the specification of the solder powder requires very narrow size distribution. It leads to a requirement of classification step in the process to be developed. Conventional classification technique does not work effectively for the powder sizes less than 38μm which are the main constituent of the solder paste.
To predict non-dense two-phase flows nowadays, the most popular approach is the combines Eulerian -Lagrangion models that treat the fluid as a continuum and the particles as discrete entities. In this study, the classification of powder is done by means of transverse blowing. The carrier-phase flow field is described by the Reynolds averaged Navier-Stokes equations with the low-Reynolds-number k-ε turbulence model. The particle trajectories are solved by using stochastic separated flow (SSF) method in Lagrangian framework. For SSF model, the turbulent dispersion effects are simulated by using Monte-Carlo method. A parametric study on geometric of the classifier dimension, particles size and gas phase velocity are performed. The results show that in the two-way coupling regime the momentum transfer from the particles is large enough to alter the turbulence structure. The influences of transverse blowing wind on large particle are less than small particle. The small particle responsed to the fluid motion easily. The classification by means of gas dynamics of particles (less than 100μm) is possible in the present modeling without considering particle collision process.

Abe, K., Kondoh T. and Nagano Y., 1994, “A New Turbulence Model for predicting Fluid Flow and Heat Transfer in Separating and Reattaching Flow - 1,Flow Field Calculation,” Int. J. Heat Mass Transfer, vol.137, pp.139-151.
Asano, K., Funayama, Y., Yatsuzuka, K., and Higashiyama, Y., 1995, “Spherical Particle Sorting by Using Droplet Deflection Technology,” J. Electrostatics, Vol. 35, pp. 3-12.
Armaly, B. F., Durst, F., Pereira, J. C. F. and Schonung, B., 1983, “Experimental and Theoretical investigation of Backward-Facing Step Flow,” J. Fluid Mech., Vol. 127.
Bird, G. A., 1976, “Molecular Gas Dynamics,” Clarendon, Oxford.
Chang, K. C., Wang, M. R., Wu, W. J., and Liu, Y. C., 1993, “Theoretical and Experimental Study on Two-phase Structure of Planar Mixing Layer,” AIAA J., Vol. 31, No. 1, pp. 68-74.
Chang, K. C., and Wu, W. J., 1994, “Sensitivity Study on Monte Carlo Solution Procedure of Two-phase Turbulent Flow,” Numerical Heat Transfer, Part B, Vol. 25, No. 2, pp. 223-244.
Chang, K. C., Wu, W. J., and Yang, J. C., 1997, “Lagrangian Transport Equation of Fluctuating Kinetic Energy in the Dispersed Phase,” Proceedings of 7th Int. Conf. on Liquid Atomization and Spray Systems, Seoul Korea, pp. 860-867.
Chen, C. P., Shang, H. M., and Jiang, Y., 1991, “A Novel Gas-Droplet Numerical Method for Spray Combustion,” AIAA paper 91-0286.
Chen, C. P., and Wood P. E., 1984, “Turbulence Closure Modeling of Two-Phase Flows,” Chem. Eng. Commun., Vol. 29, pp. 291-310.
Chen, X. Q., and Pereira, J. C. F., 1996, “Stochastic-probabilistic Efficiency Enhanced Dispersion Modeling of Turbulent Polydispersed Sprays,” J. Propulsion and Power, Vol.12, No 4, pp.760-769.
Clift, R., Grace J. R., and Weber, M. E., 1978, Bubbles, Drops and Particles, Academic Press, New York.
Crowe, C. T., Sharma, M. P. and Stock, D. E., 1977, “The Particle-Source-In-Cell Model for Gas-Droplet Flows,” Trans. ASME J. Fluid Engng., Vol. 99, pp. 325-332.
Crowe, C. T., Troutt, T. R. and Chung J. N., 1996, “Numerical Models for Two-Phase Turbulent Flows,” Annual Review of Fluid Mechanics, Vol. 28, pp. 11-43.
Cundall, P. A., Strack, O. D., 1979, “A discrete numerical model for granular assemblies,” Geotechnique, Vol. 29, pp. 47.
Elghobashi, S. E., 1994, “On Predicting Particle-Laden Turbulent Flows,” Applied Scientific Research, Vol. 52, pp. 309-329.
Gosman, A. D., and Ioannides, E., June 1981, “Aspects of Computer Simulation of Liquid-Fuelled Combustors,” AIAA Paper 81-0323.
Hetsroni, G., 1989, “Particle-Turbulence Interaction,” Int. J. Multiphase Flow, Vol. 15, pp. 735-746.
Hsu, C. C. and Chang, K. C., 2001, “Prediction of Lagrangian Time Scales for Carrier Phase in Single-Phase and Droplet-Loading Two-Phase Mixing Layers,” Master Thesis, Institute of Aeronautics and Astronautics, National Cheng-Kung University, Tainan, Taiwan, R.O.C. .
Mostafa, A. A., and Mongia, H. C., 1987, “On the Modeling of Turbulent Evaporating Sprays: Eulerian Versus Lagrangian Approach,” Int. J. Heat Mass Transfer, Vol. 30, pp. 2583-2593.
Nagano, Y. and Tagawa, M., 1990, "An improved Model for Boundary Layer Flows," ASME J. Fluid. Engng., vol.112, pp.33-39.
Owen, P. R., 1964, "Saltation of Uniform Grains in Air," J. Fluid Mech., Vol. 20, pp. 225-242.
Pan, Y., 2000,”Numerical Analysis on Particle-Laden Rotating Turbulent Flow,” Ph. D. Thesis, Osaka University, Japan.
Patankar, S. V., 1980, Numerical Heat Transfer and Fluid Flow, McGraw Hill, New York.
Pourahmadi, F., and Humphrey, J. A. C., 1983, “Modeling Solid-Fluid Turbulent Flows with Application to Predicting Erosive Wear,” Physico Chemical Hydrodynamical, Vol. 4, pp. 191-219.
Shirolkar, J. S., Coimbra, C. F. M., and McQuay, M. Q., 1996, “Fundamental Aspects of Modeling Turbulent Particle Dispersion in Dilute Flows,” Progress Energy Combustion Science, Vol. 22, pp. 363-399.
Shuen, J.-S., Solomon, A. S. P., Zhang, Q.-F., and Faeth, G. M., 1983, “A Theoretical and Experimental Study of Turbulent Particle-Laden Jet,” NASA CR-168293.
Shyu, M. J. and Chang, K. C., 1998,” Re-examination of Damping Function and Energy Equation in Low-Reynolds-Number Turbulence Models,” Master Thesis, institute of Aeronautics and Astronautics National Cheng Kung University, Taiwan R.O.C.
Sirignano, W. A., September 1993, “Fluid Dynamics of Sprays-1992 Freeman Scholar Lecture,” J. Fluids Engineering, Vol. 118, pp. 345-378.
Soo, S. L., 1967, Fluid Dynamics of Multiphase System, Chap. 2, Blaisdell, Waltham, Massachusetts.
Tsuji, Y., Tanaka, T., and Yonemura, S., 1998, “ Cluster Patterns in Circulating Fluidized Beds Predicted by Numerical Simulation (Discrete Particle Model versus Two-Fluid Model),” Powder Technology, Vol. 95, pp. 254-264.
Yang, J. C. and Chang, K. C., 2000, Re-examination of the stochastic Eulerian-Lagrangian method for two-phase turbulent flow, Ph. D. Thesis, Institute of Aeronautics and Astronautics, National Cheng-Kung University, Tainan, Taiwan/R.O.C.
Wang, C. C. and Chang, K. C., 1995 “Numerical Simulation on the Wall Transport process via the Near-Wall Low-Reynolds-number Turbulence Model and Body Fitted Coordinates System,” Master Thesis, institute of Aeronautics and Astronautics National Cheng Kung University, Taiwan R.O.C.
Wu, W. J., 1992, “A Parametric Study of Monte-Carlo Method Capable of Predicting Two-Phase Turbulent Flows,” Ph. D. Thesis, Institute of Aeronautics and Astronautics, National Cheng-Kung University, Tainan, Taiwan, R.O.C..