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Novel interlayer alloys for bonding high conductivity metals to silicon using laser powder bed fusion



Prime contractor
Organisational Unit
19 October 2023

Duration: 18 months


The development of high-power electronic devices requires innovative cooling systems. One promising approach is laser powder bed fusion (LPBF). While LPBF has been used for metallic cooling systems (e.g. microchannel heat sinks), a remaining challenge is the direct integration of these structures onto silicon-based electronic devices. Limited efforts have been made to establish a mechanically robust connection between metals and silicon due to thermal and compositional incompatibility. To address this issue, we employ LPBF to develop an interlayer between a metal heat sink (copper or aluminium) and silicon, enhancing metallurgical bonding and reducing thermal stresses. This goal is pursued through three objectives:
Objective 1
To select interlayer materials for crack-free, strong metal/silicon bonds: interlayer alloys are chosen through literature review and computational simulations based on two requirements: (i) avoiding the formation of brittle intermetallic compounds and (ii) good thermal compatibility of the interlayer with both silicon and heat sink, mitigating thermal stresses and cracking.
Objective 2
To optimize LPBF process: LPBF parameters are optimized and post-processing heat treatments are conducted to ensure strong Si/interlayer/metal bonding and minimize thermal stresses and defects.
Objective 3
To establish composition-property-performance relationships: materials analyses are performed for deep understanding of the microstructural evolution across silicon/interlayer/metal during LPBF, and phase transformations/homogenisation after heat treatments. Physical properties (e.g. thermal conductivity), and thermal/mechanical performance of the interface will also be assessed
The novel interlayer alloys and approaches developed in this proposal will enable the production of the first-ever metal microchannel heat sinks on silicon substrate by LPBF, a breakthrough in the electronic package without using thermal interface materials for space cooling applications.

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Open Channel
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Generic for multiple space applications
Novel interlayer alloys for bonding high conductivity metals to silicon using laser powder bed fusion