Partial Discharge Control In A Power Electronic Module

许多工业应用都使用高压电力电子器件。例如牵引、船舶电力和基于电力电子的电力系统。航空航天领域目前正在发生进一步的发展，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要求可靠运行。反过来，这意味着在设计绝缘系统时必须小心。目前已有电压超过5千伏的模块可用，而且总会有通过提高电压或小型化来提高模块功率密度的驱动力。要做到这一点，必须逐步改善介电系统中的薄弱环节。电力电子模块通常由焊接在基板上的金属化基板组成。可以使用不同的技术来实现这一点，例如直接粘合铜材或活性金属铜焊。高压硅IGBT/二极管通常焊接在由氮化铝(AlN)制成的衬底上，AlN是一种具有良好绝缘强度的陶瓷。然后使用焊线在各个IGBT/二极管端子和栅极驱动器/母线的外部连接之间建立连接。整个组件浸泡在软电介质中，通常是硅胶，以便沿基板表面、母线和模块的任何其他部件之间提供承受高电场的介电强度。然后，可以在整个介电系统的顶部放置环氧层。功率模块绝缘系统极其薄弱的关键区域位于衬底的金属化边缘。硅凝胶的性能在该位置上尤其关键，不仅在于防止凝胶本身内的放电，而且在于防止在靠近金属的凝胶-衬底界面处放电。由曼彻斯特大学开发的本发明涉及对模块的介电系统的改进，从而降低在该界面处的放电概率。正在开发的技术的使用将有助于降低目前在小批量生产高价值电力电子模块时可能出现的高故障率。这也将显著提高电力电子模块的可靠性，因为这种技术将降低绝缘缺陷的严重性，这些缺陷在最初的测试中没有表现出来，但存在并有能力造成累积损坏。通过后续基金机制为该项目提供资金，将使该技术的技术案例能够通过更彻底地了解技术增强介电系统的能力以及通过了解制造工艺和电气性能之间的关系来增强。同时，讨论的商业活动将通过完成成本效益分析、评估将用于下一代电力电子模块的技术并确定潜在合作伙伴来加强该技术的商业理由。与曼彻斯特大学知识产权团队的密切合作也将使该技术的长期推广和开发机制得到确定，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.