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Reference Number EP/R032203/1
Title Quasi-ambient bonding to enable cost-effective high temperature Pb-free solder interconnects
Status Started
Energy Categories ENERGY EFFICIENCY(Transport) 3%;
OTHER POWER and STORAGE TECHNOLOGIES(Electric power conversion) 2%;
NOT ENERGY RELATED 95%;
Research Types Basic and strategic applied research 100%
Science and Technology Fields PHYSICAL SCIENCES AND MATHEMATICS (Metallurgy and Materials) 50%;
ENGINEERING AND TECHNOLOGY (Electrical and Electronic Engineering) 50%;
UKERC Cross Cutting Characterisation Not Cross-cutting 100%
Principal Investigator Professor C Liu
No email address given
Wolfson Sch of Mech, Elec & Manufac En
Loughborough University
Award Type Standard
Funding Source EPSRC
Start Date 01 July 2018
End Date 30 April 2023
Duration 58 months
Total Grant Value £437,621
Industrial Sectors Electronics; Manufacturing
Region East Midlands
Programme Manufacturing : Manufacturing
 
Investigators Principal Investigator Professor C Liu , Wolfson Sch of Mech, Elec & Manufac En, Loughborough University (99.999%)
  Other Investigator Dr Z Zhou , Inst of Polymer Tech and Materials Eng, Loughborough University (0.001%)
  Industrial Collaborator Project Contact , The Manufacturing Technology Centre: MTC (0.000%)
Project Contact , Oclaro (0.000%)
Project Contact , Dynex Semiconductor Ltd (0.000%)
Project Contact , Indium Corporation, USA (0.000%)
Project Contact , Datalink Electronics (0.000%)
Project Contact , TT Electronics (0.000%)
Project Contact , Tribus-D (0.000%)
Web Site
Objectives
Abstract 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.
Publications (none)
Final Report (none)
Added to Database 06/02/19