喷印金属双液滴撞击固体形成气泡的模拟研究

Simulation of Bubble Formation by the Impact of Printed Metal Double Droplets on Solids

摘要:

喷墨打印镓金属液滴撞击固体表面时会产生空气夹带，造成气泡沉积出现喷墨打印导线不互联现象，深入理解气泡形成的影响因素是解决此问题的关键。为消除气泡，提高打印导线互联性，本研究使用Ansys Fluent软件，采用VOF耦合水平集方法，建立了二维镓金属双液滴撞击固体铜基板过程的仿真模型，研究了水平壁面温度、双液滴间距、倾斜壁面角度、倾斜壁面温度等参数对金属双液滴撞击固体壁面形成气泡过程的影响规律。研究结果表明，对于水平基板，在不同基板温度下气泡的大小呈现双向变化，金属双液滴间距的增加更有利于液滴铺展。当金属双液滴间距S=D₀-2.38D₀时，有气泡形成；当S=2.38D₀-2.5 D₀时，液滴铺展出现断裂，且气泡随温度的增加没有明显变化；当金属双液滴间距S=2.6 D₀时，随着温度的增加不再产生气泡，此时喷墨打印液滴表现出最佳精度，提高了打印导线的互联性。对于倾斜基板，使用参数韦伯数（We_⊥ )和参数（K_⊥ )表征金属双液滴形成的气泡，当撞击倾斜壁面韦伯数We_⊥>15、K_⊥>0. 035时，液滴会在固体表面上形成气泡；当We_⊥>16、K_⊥>0.04时，形成的气泡直径随壁面温度的增加而减小；当15<We_⊥<16、0.035<K_⊥< 0.04 时，液滴出现铺展断裂，并且气泡直径随着壁面温度的增加而减小；当5<We_⊥<15、0.015<K_⊥<0.035时，液滴铺展断裂且气泡直径变大；当We_⊥<5、K_⊥<0.01时，液滴在基板形成的气泡消失，此时为喷墨打印液滴的最佳精度，可提高打印导线的互联性。该研究为优化喷墨打印金属液滴的工艺提供了重要理论依据，有望在实际应用中消除气泡，进一步提高喷墨打印导线的互联性。

Abstract:

Inkjet printing gallium metal droplets impacting the solid surface will produce air entrainment，resulting in bubble deposition and the phenomenon of inkjet printing wires are not interconnected，in order to solve this problem，in-depth study of relevant parameters affecting the formation of bubbles is needed. Using Ansys Fluent software，a 2-dimensional simulation model was established using the VOF coupled level set method to simulate the bubble formation process of a gallium metal double droplet impacting a solid copper substrate. Through the study of horizontal wall temperature，double droplet spacing，tilted wall angle，tilted wall temperature and other parameters on the metal double droplet impact solid wall bubble formation law，so as to achieve the purpose of eliminating bubbles，improve the interconnectivity of the printed wire. For the horizontal substrate，the size of bubbles shows a bi-directional variation at different substrate temperatures，while the increase in the metallic double droplet spacing is more favorable for droplet spreading. For the horizontal substrate，the size of bubbles at different substrate temperatures shows a bi-directional change，while the increase of metal double droplet spacing is more favorable for droplet spreading. When the metal double droplet spacing S=D₀-2.38D₀，there are bubbles formed；when S=2.38D₀-2.5D₀ there is a break in the droplet spreading，and the bubbles do not change significantly with the increase of temperature；when the metal double droplet spacing S=2.6D₀，with the increase in temperature no longer produces bubbles，this time the inkjet printing droplets show optimal accuracy，thereby improving the print wire interconnectivity of the printed wires. For tilted substrates，the bubbles formed by metallic double droplets are characterized by the parameter Weber number（We_⊥） and the parameter（K_⊥） . When hitting the tilted wall with Weber number We_⊥>15，K_⊥>0.035，the droplet will form bubbles on the solid surface；when We_⊥>16、K_⊥>0.04，the diameter of the formed bubbles decreases with the increase of the temperature of the wall；when 15<We_⊥<16，0.035<K_⊥<0.04，the droplet appears to be spreading and breaking，and the diameter of the bubbles decreases with the increase of the wall temperature；the droplet spreading and breaking occurs. The bubble diameter decreases with the increase of wall temperature；when 5<We_⊥<15，0.015<K_⊥<0.035，the droplet spreads and breaks，and the bubble diameter becomes larger；when We_⊥<5，K_⊥<0.01，the bubble formed by the droplet in the substrate disappears，and this time is the best precision of inkjet printing droplet，which can make the interconnectivity of the printed wires improve.