Assembly of electronic components with Optoelectronic Tweezers

在这个项目中，我们将使用一种控制电力与光模式的方法来移动和组装成电路的小电子元件。这与当前使用的技术形成对比，在当前使用的技术中，末端具有真空尖端的机器人臂用于拾取这些组件并将其放置到印刷电路上。我们的目标是在最小组件的尺寸上产生一个阶跃变化，可以从目前最小的标准组件尺寸400x200微米（0402公制），例如小于半毫米，下降到几微米的组件，甚至纳米结构的组件（例如基于石墨烯，纳米线或纳米管）。这将通过开发一种全新的组装策略来实现，该策略基于称为光电镊子（OET）的无接触光电流技术。OET使用光电导装置将光的图案转变成电场的图案。通过设计该装置，使得液体层在其被照射的地方经历更大的偏压，产生电梯度，其通过介电泳在液体内的任何颗粒上产生力。改变光图案改变电力的图案，从而允许微粒的连续运动和定位。显示600微米长的电子元件的运动的概念实验的证明已经被证明，并且在该项目的18个月期间，目的是将这项研究和开发技术到我们能够将其纳入自动化工艺流程的程度。我们将组装的电子元件在所有消费电子设备中很常见，例如，典型的智能手机中有400到500个。组件的尺寸不断缩小，以便它们占用更少的空间，并减少笔记本电脑，相机和手机等便携式产品的重量。随着组件变得越来越小，机器人手臂上真空吸头的可靠性降低，但OET等非接触式技术越来越容易移动它们。在第一个实例中，我们将把电子元件组装到电路中的特定位置，该电路是通过在OET设备上图案化金属线来创建的，然后通过加热每个元件上的焊料来将它们固定到位。该测试系统将使我们能够评估该方法的速度，位置精度和可靠性，同时展示该方法并行组装多个组件的灵活性（机器人手臂无法实现）。通过展示标准组件的组装，该项目将展示其对工业的直接适用性。在本项目的下一阶段，我们将展示OET如何通过放置比当前最小标准更小的组件，在装配行业中创造真实的步骤变化。我们将从muRata在2013年发布的250x125微米的新范围开始，预计将创建一个新的标准。然后，我们将通过创建从1000微米到1微米长的整个尺寸范围的模型元件来向下扩展尺寸范围。在演示了使用OET放置小型元件的优势之后，我们将研究如何在传统的印刷电路板（PCB）上这样做。我们还将研究使用OET器件本身的创新方法，通过将导电金属纳米线图案化为线来创建电路中的线，以连接分立元件。

In this project we will use a method of controlling electrical forces with light patterns to move and assemble small electrical components into circuits. This is in contrast to the current techniques used where a robotic arm with a vacuum tip on the end is used to pick up and place these components onto printed circuits. We aim to produce a step change in the size of the smallest components that can be handled from the current smallest standard component size of 400x200 microns (0402 metric) e.g. less than half a millimetre across, down to components a few microns across and even nanostructured components (based upon graphene, nanowires or nanotubes, for example). This will be accomplished by developing a radically new assembly strategy based on a touch-less opto-electro-fluidic technique known as optoelectronic tweezers (OET). OET use a photoconductive device to turn patterns of light into patterns of electrical field. By designing the device so that a liquid layer experiences a larger bias across it where it is illuminated, electrical gradients are created which create forces on any particles within the liquid through dielectrophoresis. Changing the light pattern changes the pattern of electrical forces allowing the continuous movement and hence positioning of microparticles.Proof of concept experiments showing the movement of electronic components 600 microns long have already been demonstrated and during the 18 months of this project the aim is to take this research and to develop the technique to a degree where we are able to incorporate it into an automated process flow. The electrical components we will be assembling are common in all consumer electronic equipment with, for example, 400 to 500 being present in a typical smart phone. The size of the components is constantly shrinking so that they take up less space and add less weight to portable products such as laptops, cameras and phones. As the components get smaller the reliability of the vacuum tips on robotic arms decreases but it becomes increasingly easier for contactless techniques such as OET to move them. In its first instance we will assemble electrical components into specific positions within a circuit created by patterning metal wires onto an OET device and then fix them into place by heating the solder which comes on each component. This test system will allow us to assess the speed, positional accuracy and reliability of this methodology whilst demonstrating the flexibility of this approach to assemble multiple components in parallel (something not possible with a robotic arm). By demonstrating the assembly of standard components this project will demonstrate its immediate applicability to industry. In the next phase of this project we will demonstrate how OET can create a real step change in the assembly industry by placing components smaller than the current smallest standard. We will start with the new range being released in 2013 by muRata which are 250x125 microns and are expected to create a new standard. We will then extend the size range downwards by creating model components of the whole size range from 1000 microns in length down to 1 micron long.After demonstrating the advantages of using OET to place small components we will then investigate how to do so onto a conventional printed circuit board (PCB). We will also investigate the innovative approach of using the OET device itself to create the wires in the circuit by patterning conductive metallic nanowires into lines in order to connect the discrete components.