Partial Discharge Control In A Power Electronic Module

许多工业应用使用高压电力电子器件。示例包括基于电力电子的牵引、船舶电力和电力系统。目前，航空航天领域正在取得进一步的发展，这意味着此类设备的市场将继续增长。电力电子器件的大部分应用都需要可靠的运行。反过来，这意味着在绝缘系统的设计中必须小心。目前，在5 kV以上电压下工作的模块是可用的，并且总是存在通过提高电压或通过简化来提高模块的功率密度的驱动力。要做到这一点，必须逐步改善电介质系统中的薄弱环节。电力电子模块通常由焊接到基板上的金属化基板组成。使用不同的技术来实现这一点，例如直接结合铜或活性金属钎焊。高压硅IGBT/二极管通常焊接在该基板上，该基板本身由氮化铝（AlN）制成，氮化铝是一种具有良好绝缘强度的陶瓷。然后使用引线键合在各个IGBT /二极管端子与栅极驱动器/母线的外部连接之间进行连接。整个组件被浸入软电介质中，通常是硅凝胶，以便在母线和经受高电场的模块的任何其他部分之间沿着基板的表面沿着提供介电强度。然后可以将环氧树脂层放置在整个电介质系统的顶部上。功率模块的绝缘系统极其薄弱的关键区域位于基板金属化的边缘。硅胶的性能在该位置是特别关键的，不仅在防止凝胶本身内的放电方面，而且在防止紧邻金属化的凝胶-基底界面处的放电方面。曼彻斯特大学正在开发的发明涉及模块的介电系统的修改，从而降低在该界面处放电的可能性。正在开发的技术的使用将有助于降低目前在高价值电力电子模块的小批量生产运行中可能发生的高故障率。这项技术亦可大大改善电力电子模块的可靠性，因为即使在初步测试时并无发现绝缘缺陷，但该技术亦可减低绝缘缺陷的严重程度，并可造成累积损害。透过后续基金机制资助这项计划，可透过更深入了解有关技术的能力，增强介电系统并通过了解制造工艺与电气性能之间的关系。与此同时，所讨论的商业活动将通过完成成本效益分析来加强该技术的商业案例，对下一代电力电子模块中使用的技术进行评估，并确定潜在的合作伙伴。与曼彻斯特大学知识产权团队的密切联系也将使该机制能够长期推广，这一技术的发展有待确定，并了解该技术可用于其他技术领域的方式。

Many industrial applications make use of high voltage power electronic devices. Examples include traction, marine power and power system based power electronics. Further developments are currently taking place within the aerospace sector that will mean the market for such devices will continue to grow. Most of the applications that power electronic devices are used in demand reliable operation. In turn this means that care must be taken in the design of the insulation system. Modules that operate at voltages over 5kV are currently available and there will always be a drive to improve the power density of the module by raising voltages or by miniaturisation. To do this, weak points in the dielectric system must be progressively improved. A power electronic module is typically composed of a metallized substrate soldered onto a baseplate. Different techniques are used to achieve this such as directly bonded copper or active metal brazing. The high voltage silicon IGBTs / diodes are typically soldered this substrate that is itself made from aluminum nitride (AlN), a ceramic with a good insulation strength. Wire bonds are then used to make connections between the individual IGBT / diode terminals and external connections for gate drives / busbars. The whole assembly is immersed in a soft dielectric, typically silicone gel, in order to provide the dielectric strength along the surfaces of the substrate, between the busbars and any other parts of the module subject to high electric fields. An epoxy layer may then be placed over the top of the entire dielectric system. The critical area in which the insulation system of a power module is extremely weak is at the edge of the metallisation of the substrate. The performance of the silicon gel is particularly critical in this location not just in terms of preventing discharge within the gel itself but also in terms of preventing discharge at the gel-substrate interface in close proximity to the metallisation.The invention being developed by the University of Manchester relates to the modification of the dielectric system of a module thus reducing the probability of electric discharge at this interface. The use of the technology being developedwould help to reduce the high levels of failure rates that can currently occur on low volume production runs of high value power electronic modules. It would also significantly improve the reliability of power electronic modules as insulation defects that did not show up in initial testing but which exist and have the ability to cause cumulative damage would be reduced in severity by the technology.The funding of this project through the follow on fund mechanism will allow the technical case for the technology to be enhances through a more thorough understanding of the ability of technology to enhance the dielectric system and through the understanding of the relationship between the manufacturing process and the electrical performance. In parallel, the commercial activities that are discussed will allow the commercial case for the technology to be strengthened through the completion of a cost benefit analysis, the appraisal of the technology to be used in the next generation of power electronic modules and the identification of prospective partners.The close association with the University of Manchester Intellectual Property team will also allow the mechanism for long term promotion and development of this technology to be identified as well as understanding the ways in which the technology can be used in other technical areas.