Liquid Metal Jetting for High-Performance Computing Applications

Gallium-based liquid metals (LMs) are materials that possess some unique properties. Just like any other metals, they have high thermal conductivity and low interfacial resistance, but they are in a liquid phase at room temperature. In contrast to mercury alloys, gallium alloys are non-toxic. They don’t evaporate, and they can’t be inhaled. The viscosity of those alloys is very similar to water, but they are six times as dense as water. All those properties make gallium-based liquid metals very good candidates for thermal interface material (TIM) in electronics applications. On the other hand, the reaction and incompatibility of those alloys with some metals is one of the challenges for this type of TIM. The other challenge is that those materials are not just thermally, but also electrically conductive, and that is not a desirable property for TIM. A suitable barrier that will prevent any leakage of LMs and the best way to apply the appropriate volume of LM in high-volume production (HVP) would be one of the most important things for any application. A key challenge is applying the liquid metal consistently through a traditional dispensing method due to its property and behavior which involves high surface tension. Through advanced dispensing techniques like jetting technology, liquid metal can be applied reliably on a flat, uneven surface or in arrays of minuscule confined spaces or cavities. This paper highlights the dispense quality, weight repeatability from one substrate to another, and valve hardware stability. This paper also addresses the challenges faced during dispensing of liquid metal in high volume manufacturing, and how to achieve desired bondline thickness with jet dispensing for higher throughput and process reliability.