Quasi-ambient bonding to enable cost-effective high temperature Pb-free solder interconnects
Lead Research Organisation:
Imperial College London
Department Name: Electrical and Electronic Engineering
Abstract
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Publications
Ramachandran S
(2022)
Fast in-situ synchrotron X-ray imaging of the interfacial reaction during self-propagating exothermic reactive bonding
in Materialia
| Description | This project is a three-way collaboration between Loughborough University, University of Manchester and Imperial College London. We are aiming to develop the quasi-ambient bonding process for electronics manufacturing where it has significant potential in the area of high-temperature electronics. At Imperial we are working on systematic process development with the aim of establishing an industrially viable process. This work is mainly experimental and has been severely impacted by the Covid-19 pandemic. Nevertheless we have made significant progress in establishing the process windows for several of the process parameters. This work is still ongoing, but it is expected to yield process specifications that can be picked up by our industrial partners towards the end of the project (June 2023). |
| Exploitation Route | This project is supported by several UK companies with a direct interest in the technology we are developing. If the research is successful there is a clear path to exploitation through these companies. The PIs at Loughborough and Imperial are also well connected to other companies in the electronics manufacturing sector. |
| Sectors | Aerospace Defence and Marine Electronics Energy |
| Title | Flip chip bonder |
| Description | We have developed a flip chip bonder suitable for quasi-ambient bonding which has in-built capability for nanofoil ignition by exposure to infrared radiation from a pulsed fibre laser. The tool allows bonding to be carried out under precisely controlled conditions (pre-heating, bonding force, alignment including coplanarity). |
| Type Of Material | Improvements to research infrastructure |
| Year Produced | 2020 |
| Provided To Others? | Yes |
| Impact | This tool was one of the primary sources of experimental data in the EPSRC project EP/R031770/1 (Quasi-ambient bonding...). |
| Title | Supplementary information files for Fast in-situ synchrotron X-ray imaging of the interfacial reaction during self-propagating exothermic reactive bonding |
| Description | Supplementary files for article Fast in-situ synchrotron X-ray imaging of the interfacial reaction during self-propagating exothermic reactive bonding Self-Propagating Exothermic Reactive (SPER) bonding with lead-free solders is potentially attractive for microelectronics assembly due to its highly localised heating and minimal thermal loading of the components and substrates. The transient dynamics of melting, wetting, solidification and defect formation during SPER bonding were observed using in-situ synchrotron X-ray imaging with sub-millisecond temporal resolution and the results were further analysed using electron microscopy and thermal modelling. In-situ imaging revealed the preferential melting of the solder and subsequent wetting of the substrate. Numerous air bubbles were observed to form at the bonding interface. The distribution of these bubbles was found to vary with the thermal conductivity and wettability of the substrates. These bubbles appear to reduce the effectiveness of bonding by promoting the formation of cracks and voids within the solder joint. Our results show that metallisation layers on the bonding substrate can influence the dynamics of melting for the solder materials and thereby directly influence the reliability of SPER interconnects. |
| Type Of Material | Database/Collection of data |
| Year Produced | 2023 |
| Provided To Others? | Yes |
| URL | https://repository.lboro.ac.uk/articles/dataset/Supplementary_information_files_for_Fast_in-situ_syn... |
| Title | Supplementary information files for Fast in-situ synchrotron X-ray imaging of the interfacial reaction during self-propagating exothermic reactive bonding |
| Description | Supplementary files for article Fast in-situ synchrotron X-ray imaging of the interfacial reaction during self-propagating exothermic reactive bonding Self-Propagating Exothermic Reactive (SPER) bonding with lead-free solders is potentially attractive for microelectronics assembly due to its highly localised heating and minimal thermal loading of the components and substrates. The transient dynamics of melting, wetting, solidification and defect formation during SPER bonding were observed using in-situ synchrotron X-ray imaging with sub-millisecond temporal resolution and the results were further analysed using electron microscopy and thermal modelling. In-situ imaging revealed the preferential melting of the solder and subsequent wetting of the substrate. Numerous air bubbles were observed to form at the bonding interface. The distribution of these bubbles was found to vary with the thermal conductivity and wettability of the substrates. These bubbles appear to reduce the effectiveness of bonding by promoting the formation of cracks and voids within the solder joint. Our results show that metallisation layers on the bonding substrate can influence the dynamics of melting for the solder materials and thereby directly influence the reliability of SPER interconnects. |
| Type Of Material | Database/Collection of data |
| Year Produced | 2023 |
| Provided To Others? | Yes |
| URL | https://repository.lboro.ac.uk/articles/dataset/Supplementary_information_files_for_Fast_in-situ_syn... |
| Description | QAB process development |
| Organisation | Indium Corporation |
| Country | United States |
| Sector | Private |
| PI Contribution | We have carried out process development on SPER (self-propagating exothermic reaction) nanofoils provided by Indium Corp, exploring new processing regimes. |
| Collaborator Contribution | Indium Corp have provided the nanofoil materials and guidance on established processing regimes. |
| Impact | The work has yielded new information on the useable parameter space for QAB (quasi-ambient bonding) with SPER nanofoils. The results will be published in due course. |
| Start Year | 2019 |
| Description | Sintered copper bonding |
| Organisation | Loughborough University |
| Department | Wolfson School of Mechanical and Manufacturing Engineering |
| Country | United Kingdom |
| Sector | Academic/University |
| PI Contribution | We have given our collaborators access to custom bonding equipment which we developed in the course of earlier projects. They used the equipment to carry out bonding trials with nanostructured copper samples which they had prepared in their labs. |
| Collaborator Contribution | Our collaborators provided test samples and also carried out analysis of the results. |
| Impact | This is a new collaboration and as yet there are no outputs. Based on initial results we are expecting the collaboration to result in joint publications in due course. |
| Start Year | 2023 |
| Description | Tribus-D |
| Organisation | Tribus-D Ltd |
| Country | United Kingdom |
| Sector | Private |
| PI Contribution | We have provided access to specialised equipment in our labs along with technical support. |
| Collaborator Contribution | They have provided applications expertise and materials. |
| Impact | New technological understanding in the area of advanced electronic packaging. |
| Start Year | 2017 |