Assembly of electronic components with Optoelectronic Tweezers

在这个项目中，我们将使用一种用光图案控制电动力的方法来移动和组装小的电气元件到电路中。这与目前使用的技术形成了鲜明对比，目前使用的技术是使用末端有真空尖端的机械臂来拾取这些元件并将其放置在印刷电路上。我们的目标是使可处理的最小组件的尺寸发生阶梯变化，从目前最小的400x200微米(0402公吨)的标准组件尺寸，例如直径不到半毫米的组件，到直径几微米的组件，甚至纳米结构组件(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，该组装策略基于一种称为光电子镊子(OET)的无接触光电流体技术。OET使用光导装置将光的图案转变为电场的图案。通过设计该装置，使液体层在其被照射的地方经历更大的偏压，产生电梯度，通过介电泳对液体中的任何粒子产生力。改变光模式改变了允许微小粒子连续运动的电动力模式。展示了600微米长的电子元件运动的概念实验的雏形已经被证明，在这个项目的18个月中，目标是进行这项研究，并将该技术开发到能够将其纳入自动化工艺流程的程度。我们将组装的电子部件在所有消费电子设备中都是常见的，例如，一部典型的智能手机中有400到500个。组件的尺寸不断缩小，因此它们占用的空间更小，对笔记本电脑、相机和手机等便携式产品的重量也更轻。随着部件变小，机械臂上真空触头的可靠性降低，但对于非接触式技术，如OET，移动它们变得越来越容易。在第一个实例中，我们将把电气元件组装到电路中的特定位置，该电路是通过将金属线图案化到OET设备上而创建的，然后通过加热每个元件上的焊料将它们固定到位。该测试系统将使我们能够评估这种方法的速度、位置精度和可靠性，同时展示这种方法并行组装多个部件的灵活性(这是机械臂所不可能做到的)。通过演示标准部件的组装，该项目将展示其在工业中的直接适用性。在这个项目的下一阶段，我们将演示OET如何通过放置比当前最小标准更小的零部件来在组装行业中创造真正的阶段性变化。我们将从村田2013年发布的250x125微米的新系列开始，预计将创造一个新的标准。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组件来向下扩展尺寸范围。在演示了使用OET放置小组件的优势后，我们将研究如何将其放置到传统的印刷电路板(PCB)上。我们还将研究使用OET器件本身在电路中创建导线的创新方法，方法是将导电金属纳米线图案化成线，以便连接离散元件。

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.