Feature: Power management
A high-density server circulating silicone-based dielectric fluid to efficiently remove heat for improved performance and energy efficiency
cycling, in which they are subjected to repeated fluctuations between high and low temperatures. In data centre electronics, thermal cycling occurs when semiconductor devices such as CPUs and GPUs turn on or off. In addition, silicones can absorb some
of the stresses that occur when electronic components made from different materials expand and contract at different rates. Te coefficient of thermal expansion (CTE) is a measure of size change in response to temperature, and varies between electronic materials such as plastics, glass, ceramics and metals. When there are CTE mismatches, the resulting stress can damage solder joints and wire bonds. Because silicones are soſt and flexible, they can absorb this differential expansion and contraction.
Thermal conductivity and resistance Termal conductivity (TC) is a measure of the ability to transfer heat and it is considered a key variable in Fourier’s Law; it is measured in watts per metre Kelvin (W/m·K). Metals and ceramics have significantly higher TC values than thermally conductive silicones, which then have significantly higher thermal conductivities than air that would otherwise fill the gaps between heat sources and heat sinks. For context, copper has a TC of ~ 400W/m·K, aluminum ~ 200W/m·K, whilst thermally conductive silicones typically range from 1-12W/m·K. At room temperature (~ 20°C), the
thermal conductivity of air is around 0.024-0.026 (W/m·K). Termal conductivity increases as temperatures rise, but air has a TC value of just 0.71W/m·K at 800°C, a temperature far greater than data centres reach or electronics can withstand. By contrast, thermally conductive silicones for data centre electronics have TC values that far exceed 1.0W/m·K when tested at elevated temperatures. Although thermal conductivity is a
key thermal management specification, designers must also consider thermal resistance, a measure of resistance to the flow of heat. In electronic design, thermal resistance is used to measure a package’s
heat dissipation and avoid overheating. Typically, IC manufacturers specify a device’s junction-to-ambient thermal resistance and list this value in degrees °C/W. Termally conductive silicones are
designed to have low thermal resistance, which is crucial for dissipating heat from electronic components to heat sinks. Tey can also support thinner (< 100µm) and more uniform bond lines for efficient heat transfers. Tin bond lines are important because they minimise thermal resistance and improve heat transfer efficiency. Importantly, these advanced materials flow readily and conform to uneven surfaces, filling tiny gaps that would otherwise contain air. Teir ability to thoroughly wet- out substrates minimise contact resistance, which can cause energy loss as heat.
Thermal interface materials Termally conductive compounds, a category of thermally conductive silicones for data centre electronics, have a low thermal resistance of 0.03 or 0.04°C-cm²/W, a unit of measure that normalises thermal resistance by contact area. In electronics, °C-cm²/W is used to standardise thermal interface material (TIM) performance independent of a component’s physical size. A gap in µm is given to account for interruptions in the conductive path for heat transfers. Termally conductive compounds can
have TC values that range from about 3W/m·K to 6W/m·K. Silicone compounds with higher thermal conductivities are
18 February 2026
www.electronicsworld.co.uk
used with bare dies in ASICs, which are critical for optimising AI performance. Oſten, these bare dies are made from silicon carbide, which operates at higher temperatures. Bare dies are also used to create higher-density power modules such as IGBTs. Among their advantages, thermally
conductive silicone compounds do not require curing, a chemical process in which a material transitions from a liquid or semi-liquid state to a solid and achieves its final properties. Curing that requires heat from an oven increases energy consumption and overall costs, but some thermally conductive silicones that require curing can use moisture from the air instead. Silicone thermal gels, another type of
thermal interface material, are non-curing liquids that are used to fill large gaps for efficient heat transfers. Because they are highly conformable and reworkable, these thermally conductive silicones can also fill complex geometries in stackable dies, which are used in high-performance components like CPUs and GPUs and high-bandwidth memory for data- intensive AI applications. Some thermally conductive gels cure
from a liquid into a solid elastomer for greater long-term stability. Tese silicone gels can have thermal conductivities as high as 12W/m·K for data centre applications such as optical interconnects, arrayed power chips and 5G communications. Although they are not reworkable, curable silicone thermal
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