气动膜片式精密焊球微滴喷射制作方法

为满足面积阵列封装对所需焊球越来越高的要求,提出了利用气动膜片式微滴喷射原理制作焊球的新方法。介绍了该方法的基本原理及所采用的实验装置,使用由自制电火花微孔加工机床加工的直径50μm不锈钢喷嘴,成功实现了直径100μm以下焊球的制作,研究了主要控制参数对焊球直径的影响。结果表明,气动膜片式微滴喷射方法制作的焊球直径精确、表面闪亮、球形完美,填补了国内直径100μm以下超精密微焊球制作技术的空白。     

纳米银均匀喷射过程的数值计算与仿真

微滴喷射均匀液滴喷射过程受到多种因素的制约,包括压力波幅值、液滴物性(黏度、表面张力等)、喷嘴尺寸等。为深入理解微滴喷射过程机理,基于流体体积法建立了均匀液滴喷射数值模型,研究了压电驱动电压幅值对低粘度纳米银墨水稳定喷射行为的影响。通过数值仿真,给出了驱动电压幅值与液滴断裂长度、液滴飞行速度的数值关系,以及液滴飞行速度与卫星液滴的变化关系。采用27μm喷嘴直径的工业喷头构建微滴喷射系统,低粘度纳米银墨水为喷射材料,通过观测喷印到光面相纸的液滴尺寸及卫星液滴数量对数值模型进行实验验证。结果表明,液滴飞行速度取决于驱动电压幅值,液滴尺寸分布及卫星液滴数量取决于液滴飞行速度,与数值模型相吻合。通过数值模型仿真,针对纳米银墨水物性指标匹配合适的驱动电压幅值,生成均匀液滴流,对微液滴成型的工业化应用具有重要的理论指导意义。     

微电子封装用焊滴按需喷射装置设计及试验研究

为满足先进电子线路柔性、快速钎焊,设计开发了机械振动式焊滴喷射装置,该装置由电磁驱动、焊滴喷射、同轴供气、温度控制等模块组成。采用锡铅合金进行了喷射试验,在供气流量7.5 L/min~10 L/min范围内,可制备出球形度较好的颗粒;通过调节振动参数,实现了单颗均匀微滴的可控稳定喷射;本文试验条件下焊滴飞行平均速度约为2.43 m/s,有利于焊滴充分铺展以充分钎焊,为高质量的电子线路快速钎焊奠定了基础。     

气动式微滴喷射中液滴稳定生成的动力学特性研究

微滴喷射增材制造技术作为制造领域的新兴前沿技术有着广泛的应用前景,微滴生成特性对增材制造中微滴在基板铺展、搭接、凝固等过程影响较大,研究微滴生成特性对于提高液滴生成尺寸、频率和稳定性有重要意义。通过试验研究气动按需喷射作用下的微滴喷射行为,探究喷嘴尺寸、黏度和供给压力等因素对射流断裂过程及液滴生成稳定性的影响关系,并进一步研究形成角的变化对液桥断裂顺序及卫星液滴产生的影响关系。研究结果表明,随着喷嘴直径减少,韦伯数（We）显著减少,当喷嘴直径减少到100 μm时,We变为0.33,液滴尺寸与喷嘴直径的比值急剧增大;随着黏度的增加,射流颈缩段的液桥显著增长,液滴尺寸明显增大。在保证生成单个液滴的压力条件下,当供给压力较小时,液桥两端先后断裂形成卫星滴,并最终与半月面融合;随着压力的增大,液桥只发生一次断裂,剩余射流回缩到喷嘴内。在气动式喷射方式中由于上形成角始终大于下形成角,所以液桥总是在靠近液滴端首先断裂,该研究结果有助于提高气动式微滴喷射装置的液滴生成质量。     

聚合物熔体微滴喷射装置设计

针对现有3D打印制造技术对材料种类与形状的限制,结合现有微滴喷射制造技术,设计出了一种由螺杆挤出建压系统,电磁铁驱动的机械冲击系统,加热系统,温控系统和三维移动平台组成的聚合物熔体微滴喷射装置,并介绍了其工作原理。采用PP(聚丙烯)粉料作为熔体微滴喷射装置试验用料,通过调节加热温度,螺杆转速,机械冲击脉冲频率,喷嘴和基台距离等工艺参数和机械参数,实现了均匀可控的熔体输送和熔滴喷射,极大的拓展了传统聚合物3D打印所需材料种类与形状限制。     

微滴喷射工艺参数与液滴形态关系的数值模拟

以微滴喷射的增材制造技术为研究对象,采用守恒水平集方法建立了液滴喷射过程的数值仿真的物理数学模型.通过仿真实验分析了液滴喷射的流场分布,采用曲面响应法的中心复合设计建立了拟合模型并进行了修正,提出了液滴喷射过中液滴成球距离和断裂高度分别与入口处压强脉冲的幅值与脉宽的拟合关系式.模拟结果表明:在液滴喷射过程中喷嘴入处的压...     

热处理工艺对BCu58ZnMn钎料钎焊接头组织与性能的影响

研究了焊后冷却方式、固溶后冷却速率及时效工艺对BCu58ZnMn铜基硬钎料显微组织和硬度的影响,在此基础上分析了淬火、回火工艺对其钎焊YG13C硬质合金和42Cr Mo钢钎焊接头剪切强度的影响。结果表明:焊后快冷将使钎料的硬度增大,焊后固溶时效热处理可显著改善钎料的组织,提高其硬度;焊后缓冷钎焊接头的剪切强度明显高于快冷的,焊后空冷及高温回火后的钎焊接头能够保持理想的剪切强度(190.4 MPa),优于相关标准规定的指标要求。     

等离子熔积直接制造小电流熔积枪的设计

针对等离子熔积金属零件直接制造的焊道精细和持续熔积时间长的要求,设计了小电流金属等离子熔积枪.熔积枪采用了环形凸台送粉通道,钨极中心定位环,直接水冷却压缩喷嘴等改进措施.等离子熔积焊道实验结果表明,小电流条件下焊道尺寸较小,焊道平整均匀,表面光洁度好.该型小电流熔积枪适用于金属零件的等离子熔积直接制造中,同时枪体、喷嘴、送粉通道和冷却通道的特殊设计可以保证熔积枪的持续稳定工作.     

直写快速成型机中背压系统的设计

介绍了直写快速成型技术的工作原理、特点和应用.喷嘴背压系统是用来控制喷嘴喷出液滴,选用合适的背压对喷嘴产生均匀的液滴有着重要的影响.为此,设计一套稳定、可靠的喷嘴背压系统是必要的.作者根据直写快速成型机液体喷射的要求,设计了液体喷射背压系统.     

数字化微喷射用玻璃基组合微喷嘴设计及实验

为提高液滴微喷射的喷效率和粉体微喷射的喷射方向性,选用普通硼硅酸盐毛细管和石英玻璃管为原材料,基于稳定的拉制和锻制工艺,设计并制作了直列式组合微喷嘴和同轴式组合微喷嘴.在基于微流体数字化的微喷射实验平台上,利用4×2直列式组合微喷嘴单次喷射得到了形状规则、圆整,大小均匀,无卫星液滴的液滴阵列,液滴平均直径为180 μm;相对于单微喷嘴,直列式组合喷嘴提高了单次微喷射的效率.另外,进行了粉体微喷射实验,相对于单微喷嘴,同轴式组合微喷嘴在相同驱动条件下,出射角由33°减小至10°,成形粉线的宽度由450 μm降低至300 μm.结果表明,同轴式组合微喷嘴中的辅助喷嘴有效地约束了主喷嘴出射的粉体流动,粉体喷射的方向性有显著提高.     

喷射打印和化学沉积成形微细电路中微滴可控喷射研究

针对智能纺织品中微细线路制备工艺复杂、成本高、柔性差等问题,提出了喷射打印与化学沉积技术相结合制作微细线路的方法。利用构建的气动式微滴喷射系统,以100μm的喷嘴对抗坏血酸和硝酸银溶液进行了可控稳定喷射及沉积成形试验。试验获得了两溶液可控稳定喷射的工艺参数,且微滴在基板上沉积的点阵均匀、成形线宽基本一致,成形银线具有一定导电性。     

气动式微滴喷射过程仿真与尺寸均匀性试验研究

为使气压驱动式微滴喷射装置能产生均匀的微滴和稳定的喷射过程,使用FLUENT建立了二维轴对称计算模型并对微喷过程进行了模拟仿真。研究了气压驱动式微滴按需产生过程及腔体内压力峰值对单颗微滴成形的影响规律,利用构建的喷射系统对水进行喷射试验,并对产生微滴的均匀性进行了研究。仿真获得了单颗微滴的成形过程并得到了腔体内较低压力峰值有利于提高微喷稳定性的结论。实验结果表明,产生的微滴附着直径最大变化率为1.82%,均匀性较好。     

Predication and measurement of deflected trajectory and temperature history of uniform metal droplets in microstructures fabrication

The deposition of metal droplets has been attracted wide interests for potential applying in microstructures fabrication. A uniform droplet generator with image acquiring system and droplet temperature measuring system was established. A coupling analysis method on combination of droplets dynamic and thermal models was proposed. Effect of experimental parameters on deflected trajectory and the temperature history of the uniform droplets was investigated. The measured trajectory and temperature history agreed well with the predicted results, indicating the validity of the proposed analysis method. The predicted results with different experimental parameters showed that the deflected trajectories and thermal histories of the droplets with diameters close to 100???m or less were strongly dependent on their sizes. Small droplets had a narrow deposition length for obtaining parts with good metallurgical bonding. The predicted results also showed that it was effective in controlling the deflected trajectories and thermal histories of droplets by adjusting the pressure when it was low. At last, micro alloy tubes with good metallurgical bonding were obtained using 50???m diameter nozzle when the experimental parameters were chosen according to theoretical models. The deposited results show that proper parameters for microstructures deposition can be obtained according to the proposed analysis method.     

Investigation of design parameters for droplet generators driven by piezoelectric actuators

This paper presents a numerical analysis of a drop-on-demand (DOD) piezoelectric (PZT) actuated droplet generator. A finite difference numerical model was established to analyze the design parameters of droplet ejection. First, we discussed the influence of the driving conditions on the droplet ejection characteristics, such as the driving time and the driving volume change in the pressure chamber. The volume factor, an important design parameter, was proposed from the analysis. The ejected droplets can maintain the same ejection velocity at different nozzle diameters, as long as the volume factor remains the same. Two empirical formulas, based on the analysis data, are suitable for the design of PZT actuated droplet generator. The first empirical formula is a linear relationship between the droplet velocity and the volume factor with a slope of 0.3422 for different nozzle diameters. The second empirical formula defines the driving volume of PZT and nozzle diameter to eject the desired droplets. The geometrical design parameters of droplet generator, such as the nozzle thickness, the pressure chamber width and depth, as well as the driving conditions of the PZT actuator, are all included in the analysis. The sensitivity of geometrical design parameters which affect the droplet volume, the droplet velocity, and the lowest driving condition is established. The quantitative criterion for ejection of droplet, liquid jet, and no droplet is presented. The proposed empirical formula and figures provide easy-to-use tool for design of DOD PZT actuated droplet generators.     

Modeling of sessile droplet oscillation on electrohydrodynamic jetting nozzle at constant back pressure

In this study, we present a theoretical model for an oscillating meniscus along with changing the volume of the sessile droplet on the electrohydrodynamic nozzle under various voltage waveforms, supported by experimental data. The transient volume change of the sessile droplet upon step electric pressure was modeled by a one-dimensional flow. The meniscus oscillation upon cyclic electric pressure was analyzed by a harmonic oscillator model. By combining these two models, the behavior of the sessile droplet, under a bi-directional square voltage pulse train with a different bias voltage, was analyzed. It is expected that this theoretical model can provide effective information in optimizing the voltage waveform for drop-on-demand electrohydrodynamic jetting.     

均匀液滴喷射过程仿真与试验研究

针对液滴喷射增材制造试验参数调整困难、实施难度较大的现存问题,基于流体体积(Volume of fluid,VOF)两相流模型,建立均匀液滴喷射过程流场的计算模型。采用数值模拟的方法,对液滴喷射过程中的液滴流形态、压力场和速度场及其影响因素进行了研究,揭示了形成均匀液滴流的内在变化规律,得到了均匀液滴喷射过程的最优频率。在模拟结果的基础上,建立了液滴喷射装置并配置了相应的高速拍照系统,对射流断裂形态、喷射过程、喷射速度进行了试验研究。结果表明,射流速度主要取决于喷射压强,液滴流均匀性主要取决于扰动频率和扰动振幅,射流的压力场则呈周期性变化。模拟结果与试验结果吻合较好,说明所提出的建模方法是可行的,为不同情况下射流内部流场的计算提供了实用的方法,也为液滴喷射增材制造技术的应用奠定了理论基础。     

Droplet analysis in an inkjet-integrated manufacturing process for nylon 6

With the recent progress in inkjet technology, it has been employed to develop manufacturing processes to deposit a range of functional materials for various applications. The authors have researched the possibility of a novel inkjet-integrated process for nylon 6. The concept requires stable jetting and deposition of activator and catalyst mixtures of caprolactam. This paper reports on droplet formation characteristics of the molten mixtures in the inkjet system using high-speed imaging and quantitative image analysis. By varying the process parameters, the droplet shape and kinetics were studied in addition to the stability of droplet generation. Results showed the jetting frequency did not have an effect; and with low jetting voltages, instability occurred due to the low kinetic energy, which made the droplets vulnerable to the air motion caused by convection around the heated printhead. The catalyst mixture which had a particulate nature was also investigated for consistency, to ensure the droplet characteristics were unaffected by this. Increasing the vacuum level decreased the droplet kinetics due to the higher surface energy which existed on the meniscus, which was found to be inside the nozzle. It was possible to have satellite-free and stable droplet generation conditions.     

撞击型雾化喷嘴流量特性及喷雾降温性能试验研究

针对空冷机组在夏季高温天气不能满发的问题,采用喷雾增湿以降低入口空气的干球温度,选用撞击型雾化喷嘴AM4进行流量特性及喷雾降温特性的实验研究。分析试验数据拟合得到撞击型喷嘴流量与喷雾压力的关系,并计算得出喷嘴的流量系数。通过对不同类型喷嘴组合喷雾降温效果的比较,得到加入1排AM4有利于冷却效果的提高;加入两排AM4的喷雾降温效果并没有明显提高,且由于撞击式喷嘴价格较高,加入两排AM4的经济性较差。     

航空发电机风阻实验及匹配冷却风扇设计

为研究航空发电机匹配风扇设计的实用性方法,通过相应的实验装置,对某型航空发电机进行了风阻特性实验。通过强迫通风实验测得发电机不同状态下的风阻、流量及温升,根据实验结果及该发电机设计要求,利用正交设计方法设计出一种宽弦、大转折角、高稠度的轴流冷却风扇,同时设计了特殊的扩张轮毂结构,以进一步提高冷却性能。对加装设计风扇的发电机进行实验,验证了该风扇适用于该发电机冷却系统的高压差、小流量工况。     

A fast full-field 3D measurement system for BGA coplanarity inspection

Ball-Grid-Array (BGA) has become one of the most popular packaging techniques in the electronics industry. Coplanarity inspection of BGA solder balls is critical for process and quality control in BGA manufacturing. Currently, the 3D measurement systems for BGA coplanarity inspection are mainly based on laser scanning techniques. However, they suffer from low inspection speed due to the physical line-scanning process. In this paper, a fast and cost-effective 3D measurement system for coplanarity inspection of BGA solder balls is proposed. The proposed system uses an LCD-based phase measuring technique to perform full-field 3D measurement of BGA solder balls with high accuracy. Experiments have shown that the coplanarity measurement of BGA solder balls is very efficient and effective with the proposed system. The measurement repeatability is in the micrometer range. The processing time of the proposed 3D measurement system for an image of 640×480 pixels is less than 2 s on a typical personal computer.