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Quasi-ambient bonding to enable cost-effective high temperature Pb-free solder interconnects

准环境键合可实现经济高效的高温无铅焊料互连

基本信息

批准号：
EP/R032203/1
负责人：
Changqing LIU
金额：
$ 55.76万
依托单位：
Loughborough University
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2018
资助国家：
英国
起止时间：
2018 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FR032203%2F1
关键词：
Quasi ambient bonding enable cost

项目摘要

There is an increasing demand for electronics that can operate at temperatures in excess of 200 degrees C, well above the maximum operating temperature of traditional silicon microelectronics. Key application areas are in the power, automotive, aerospace and defence industries. Electronic devices capable of operating at such high temperatures are now available. However, new methods are also needed for integrating these devices into circuits and systems, and in particular for attaching them, both mechanically and electrically, to circuit boards and heatsinks. At present high-temperature devices are typically attached by soldering using high-melting-point, lead-rich solders. However, there is a strong environmental imperative to reduce the use of lead in all electronics, so this cannot be accepted as a long-term solution. Alternative solutions employing gold-rich solders or sintered nano-silver pastes can be used, but these are expensive and can suffer from reliability issues. Low-cost, lead-free high-temperature solder alloys are also available; however, these tend to require significantly higher soldering temperatures and longer processing times, leading to slower production and higher thermal load on the devices during soldering.This project will explore the use of quasi-ambient bonding (QAB) with reactive nanofoils as a route to lowering the process time and thermal load during packaging of high-temperature electronic devices. Reactive nanofoils are multilayer materials comprising alternating layers of two elements (typically nickel and aluminium) that react exothermically i.e. with the release of heat. Once the reaction is triggered, it is self-propagating and spreads throughout the foil. If the foil is sandwiched between two parts that are pre-coated with solder, the heat generated can be used to melt the adjacent solder layers momentarily and form a permanent bond. The heating is intense, but occurs over a short timescale, so that while the local temperature can reach up to 1500 degrees C, heating is confined to a narrow region around the foil, with negligible temperature rise occurring elsewhere. Up to now, quasi-ambient bonding applications have used traditional lower-temperature solders. In this project we will extend the application of QAB to a range of low-cost, lead-free high-temperature alloys. The primary aim will be to develop bonding processes tailored for applications in high-temperature power electronics and optoelectronics. We will also explore the use of QAB for sealing of hermetic packages which is another key area where low cost and low thermal load can be an advantage. The processes developed will be evaluated in terms of bonding strength and in-service reliability, and benchmarked against alternative processes based on lead- and gold-based solders. Alongside the process development and evaluation, we will carry out extensive modelling and characterisation aimed at gaining an improved understanding of the QAB process. Developments to date have been mainly empirical, and fundamental aspects of the process remain poorly understood. QAB is fundamentally different from traditional soldering because of the very short timescale over which the process takes place. In order for it to become established in mainstream electronics manufacturing, the potential detrimental effects of residual stresses and microstructural defects incorporated into QAB bonds need to be fully understood. The proposed research has the potential to provide a low-cost, sustainable joining technology for electronics manufacturing that can continue to meet the operating temperature requirements of high-temperature electronics for many years to come. At the same time it will yield new fundamental insights into processes involving rapid solidification of complex alloys that will be of wide interest to the materials science and manufacturing research communities.

对于可以在超过200摄氏度的温度下工作的电子器件的需求越来越大，远远高于传统硅微电子器件的最高工作温度。主要应用领域是电力、汽车、航空航天和国防工业。能够在这样的高温下工作的电子设备现在是可用的。然而，还需要新的方法来将这些器件集成到电路和系统中，特别是将它们机械地和电气地附接到电路板和散热器。目前，高温器件通常通过使用高熔点、富铅焊料的焊接来附接。然而，在所有电子产品中减少铅的使用是一个强烈的环境要求，因此这不能被接受为一个长期的解决方案。可以使用采用富含金的焊料或烧结的纳米银膏的替代解决方案，但是这些解决方案是昂贵的并且可能遭受可靠性问题。低成本、无铅的高温焊料合金也是可用的;然而，这些往往需要显著更高的焊接温度和更长的处理时间，导致生产速度较慢，焊接过程中器件的热负荷较高。本项目将探索使用反应性纳米箔的准环境键合（QAB），作为降低高性能封装过程中工艺时间和热负荷的途径。温度电子设备。反应性纳米箔是包括两种元素（通常是镍和铝）的交替层的多层材料，所述两种元素发生化学反应，即释放热量。一旦反应被触发，它就会自我传播并扩散到整个箔中。如果箔被夹在两个预先涂有焊料的部件之间，则产生的热量可以用于瞬间熔化相邻的焊料层并形成永久结合。加热是强烈的，但发生在很短的时间尺度上，因此虽然局部温度可以达到1500摄氏度，但加热仅限于箔周围的狭窄区域，其他地方的温度上升可以忽略不计。到目前为止，准环境焊接应用一直使用传统的低温焊料。在这个项目中，我们将QAB的应用扩展到一系列低成本，无铅高温合金。主要目标是开发适合高温电力电子和光电子应用的键合工艺。我们还将探索使用QAB密封的密封封装，这是另一个关键领域，低成本和低热负荷可以是一个优势。开发的工艺将在结合强度和使用可靠性方面进行评估，并与基于铅基和金基焊料的替代工艺进行基准测试。除了工艺开发和评估，我们还将进行广泛的建模和表征，旨在更好地了解QAB工艺。迄今为止的发展主要是经验性的，对这一进程的基本方面仍然知之甚少。QAB与传统焊接有着根本的不同，因为该过程发生的时间非常短。为了使其成为主流电子制造，潜在的有害影响的残余应力和微观结构缺陷纳入QAB债券需要充分了解。这项研究有可能为电子制造提供一种低成本、可持续的连接技术，可以在未来许多年内继续满足高温电子产品的工作温度要求。与此同时，它将产生新的基本见解，涉及复杂合金的快速凝固过程，这将引起材料科学和制造研究界的广泛兴趣。