| 摘要: | 半導體產業與微機電元件之發展使液滴現象的探討愈來愈重要。本研究針對不同黏滯度溶液在不同環境因素下，液滴撞擊基板後會產生不同型態的變化進行分析與探討。為觀察這些現象，以不同的液滴的撞擊速度、液滴溶液黏滯度及基板溫度作為實驗控制變數，輔以高速攝影機(CCD camera)觀測(400frames/s)液滴碰撞基板表面(該基板表面溫度控制在液滴之沸點（含）以下)，所產生擴展(spreading)、飛濺(splashing)、迴縮(recoil)、向上拉升(rebound)、震盪與穩定等現象。 本研究以無因次化參數雷諾數(Re=ρvDμ )與韋伯數(We=ρuD2/σ) 為指標，探討液滴最大擴展半徑與飛濺現象。實驗結果發現雷諾數增加會使液滴最大擴展半徑增加。另外，韋伯數是引發飛濺現象的主要因素，並比較水與矽油之飛濺現象，發現同撞擊速度下其矽油較水易發生飛濺，水需較大的撞擊速度來達到飛濺。在矽油μ為10 cp之情況發生飛濺的韋伯數為 420，而水為 580，而液滴撞擊後擴展時能量積於外緣產生指狀現象（finger pattern ），給予更高的撞擊速度便更易於碎裂。因此飛濺現象發生多在高韋伯數液滴。矽油溶液之液滴，增加基板溫度使撞擊液滴的表面張力以及黏滯力變小，其擴展半徑增大，故較不易發生飛濺現象。增加基板溫度若超過沸點於110°C時，水液滴在韋伯數下(We > 280)，也易形成破碎飛濺現象。 The phenomena of the droplet impact play an important role on the semiconductor industry and the development of micro-electro-mechanical (MEM)system. The different patterns of droplet will be obtained when it is impacted at different parameters such as impact velocities, liquid dynamics viscosity, and substrate temperatures. The high-speed camera (CCD camera) with four hundred frames per second is used to observe and analyze these phenomena including the expansion (spreading), the flying (splashing), the turning back (recoil), the going upward (rebound), the concussion and the stability and so on. The temperature imposes on substrate at the value which is higher than the boiling temperature for water droplet case is also studied. The results indicate that the droplet impacts with different Weber number (We), the higher We number is, the higher spreading coefficient obtains. If the impact velocity increases, the droplet will be become the instability finger pattern. After that, droplet will be breakout if the impact velocity is higher. This means that when the We number increases, the droplet pattern changes from spreading to finger and splashing. Therefore, the phenomenon of splashing occurred in high We number, which is compare to spreading (180). For instance, when the We number is higher than 420, the splashing is observed for silicon oil case. When the substrate temperature changes, the splashing occurs only if the impact velocity is higher than those in case of lower temperature and the height of recoil is also different. The higher temperature is, the higher recoil obtains. For different liquids, we also observed the We number for the splashing phenomena occur in the water is higher than in the silicon oil. When the substrate temperature is higher than the liquid boiling temperature(110°C), we also observe that the water droplet is immediately rebound after impact on solid surface. |
