A Manufacturing Process for Producing Thick Films with Controlled Microstructures

图案厚膜用于制造集成电路和传感器，应用范围从相机传感器、医疗植入物到计算机网络。目前，大多数厚膜是通过丝网印刷工艺生产的，其中包括沉积含有细小金属颗粒的糊状物，然后加热到高温以粘合颗粒，从而将导电性提高到可接受的水平。对高加工温度的需求限制了薄膜沉积基板的选择，并且通常需要昂贵且坚硬的玻璃或陶瓷基板。该奖项支持研究推进沉积厚膜的新方法，该方法可以显着降低加工温度，并允许在低成本和柔性基板上沉积，同时也允许有潜力生产具有优越性能的薄膜的新型材料结构。这种具有改进性能的图案薄膜将应用于许多设备，包括高功率电子设备和太阳能电池，以及其他可以提高美国制造业竞争力的应用。多学科的方法，包括计算机模拟和实验的结合，将使研究生的教育，推广活动将把这项研究与一个经过验证的计划结合起来，使高中教师能够有效地教授工程，鼓励和准备他们的学生进入工程和科学事业。激光烧蚀微粒气溶胶工艺是沉积具有纳米结构特征的图案微尺度厚膜的一种较新的工艺。纳米颗粒是通过气溶胶烧蚀从常见的廉价粉末中产生的，然后以高速撞击到基板上。高生产率允许在室温下将无机（金属，半导体或陶瓷）厚膜直接写入聚合物，金属或陶瓷基板上，而无需掩膜。通过烧蚀和沉积参数可以控制薄膜的晶粒尺寸和孔隙度。然而，目前的工艺仅限于生产最大沉积相对密度约为70%的多晶或非晶薄膜。计划结合预测分子动力学计算机模拟和纳米颗粒撞击和薄膜生长过程的实验研究，以了解加工参数如何影响纳米到微观尺度上的沉积效率、薄膜形态和薄膜结构。计算机模拟将用于系统地研究颗粒尺寸、撞击能量、衬底温度、材料组成和结晶度、缺陷取向和浓度以及颗粒/衬底错误取向对所得薄膜的影响。与计算机模拟相结合，实验装置将被修改，以允许在可以验证模拟的条件下进行实验。实验数据将用于根据需要修改计算机模拟，以便对所得到的薄膜微观结构做出准确的预测。预计通过研究控制沉积和薄膜生长的因素，将导致比目前可能的更大范围的微结构和密度，包括相对密度接近100%的单晶图案薄膜。

Patterned thick films are used in the manufacture of integrated circuits and sensors for applications ranging from camera sensors, to medical implants, to computer networks. Currently, most thick films are produced by a screen printing process, which involves deposition of pastes containing fine metal particles which are then heated to high temperatures to bond the particles so that the conductivity is increased to an acceptable level. The need for high processing temperature limits the choices of substrates upon which the films can be deposited, and often requires expensive and rigid glass or ceramic substrates. This award supports research towards advancing a new method for depositing thick films that can dramatically reduce processing temperatures and would allow deposition on lower-cost and flexible substrates, while also allowing novel material structures that have the potential to produce films with superior properties. Such patterned films that exhibit improved properties would have applications in many devices including high power electronics and solar cells, and other applications that could advance US competitiveness in manufacturing. The multidisciplinary approach which involves a combination of computer simulations and experiments will enable the education of graduate students, and the outreach activities will integrate this research with a proven program that enables high school teachers to effectively teach engineering to encourage and prepare their students to enter engineering and science careers.The laser ablation of microparticle aerosol process is a relatively new process for depositing patterned, micro-scale thick films with nanostructured features. Nanoparticles are produced from commonly available and inexpensive powders via an aerosol ablation and then impacted at high velocities onto a substrate. High production rates allow direct writing of inorganic (metallic, semiconductor, or ceramic) thick films without a mask at room temperature onto polymeric, metallic, or ceramic substrates. The grain size and porosity in the films can be controlled through the ablation and deposition parameters. The current process, however, is limited to producing polycrystalline or amorphous films with a maximum as-deposited relative density of about 70 percent. A combination of predictive molecular dynamics computer simulations and experimental studies of the nanoparticle impaction and film growth processes are planned to develop an understanding of how processing parameters influence deposition efficiency, the film morphology, and film structure on a nano- to-micro scale. Computer simulations will be used to systematically study the influence of particle size, impaction energy, substrate temperature, material composition and crystallinity, defect orientation and concentration, and particle/substrate misorientation on the resulting films. In combination with the computer simulations, the experimental apparatus will be modified to allow experiments to be conducted under conditions in which the simulations can be validated. The experimental data will be used to modify the computer simulations as needed so that accurate predictions of the resulting film microstructures can be made. It is expected that by studying the factors that control deposition and film growth will lead to a much larger range of microstructures and densities than is currently possible, including single crystal patterned films with relative densities approaching 100 percent.