Where is the Complexity of Rheocasting?

Telecommunications are evolving rapidly, and with each new generation, technical requirements increase, but so do expectations for efficiency, sustainability, and performance. As 5G antennas integrate more electronics and operate at higher frequencies, the thermal and structural demands on the housing rise sharply.

Traditional materials and casting methods struggle to keep pace, limiting output power, shrinking range, and increasing network cost. This is where Rheocasting has changed the game for telecom. By enabling alloys with higher thermal conductivity, dramatically lower carbon footprints, and superior castability, Rheocasting provides manufacturers with the tools they need to build more efficient, more powerful, and more reliable 5G antennas. At the same time, it unlocks new design freedoms that directly improve cooling performance. The result is simple: better-performing antennas, lower environmental impact, and a clear competitive advantage for companies adopting Rheocasting for their applications.

Developments in Telecommunication

Telecom transforms in these large tsunami waves. The latest wave was the change from 4G to 5G. In 4G networks, radios were external units operating mainly in lower-frequency bands (700–2600 MHz), which propagate well over long distances. These radios handled only a few transmit paths, produced about 80–150 W of heat, and the antenna itself stayed passive and thermally neutral.

With 5G, especially in the mid-band (3.3–4.2 GHz) and mmWave (>24 GHz) bands, frequencies are much higher, increasing path loss and reducing range. To compensate, 5G systems use massive-MIMO with dozens of independent transmitters, advanced beamforming, and larger bandwidths, all integrated directly into the antenna housing. This shift from passive panels to active, electronics-dense antenna arrays dramatically increases power consumption and heat output, with modern 5G antennas dissipating 300–1300 W. The combination of higher frequencies, reduced reach, and the need for beamforming makes 5G antennas not only faster but also significantly more thermally demanding than their 4G counterparts.

New Alloys are the Solution

Given this steep increase in thermal load, conventional HPDC alloys, often used in telecom antenna housings, are no longer sufficient. HPDC alloys typically achieve thermal conductivities of up to 140 W/m·K due to high silicon content and dendritic microstructures, which hinder efficient electron flow. That limitation is particularly problematic in 5G antenna systems where every watt of conduction counts; inadequate thermal paths translate into reduced output power, diminished range, and ultimately higher network cost.

Thankfully, Rheocasting offers a solution. In this semi-solid casting process, the alloy is kept in a slurry state, eliminating the typical dendritic structure and allowing lower-silicon compositions to reach as low as 1.7 % Si. This results in cast parts with thermal conductivities in the 180–195 W/m·K range, approaching that of pure aluminum (~220–225 W/m·K). One telecom OEM has already adopted the Rheocool-alloy and has been switching from standard HPDC to Rheocasting to enhance both the power output and range of its 5G antennas.

In addition, the carbon footprint of the Rheocool alloy is well below that of any available alloy on the market. Coal-based primary aluminium alloys are around 20 kg CO2 per kg Al. The best primary alloys reach 4.0 kg CO2 per kg Al. Most secondary alloys are around 1.5-2.0 kg CO2 per kg Al. The Rheocool does not require any addition of pure aluminium or silicon and is entirely based on post-consumer scrap. That is reflected in the carbon footprint of 0.36 kg CO2 per kg Al.

The Design Freedom of Rheocasting

Improving the alloy’s thermal conductivity and reducing its carbon footprint weren’t the only reasons for Rheocasting. In high-solid-fraction Rheocasting (above 35% solid fraction), the filling behaviour changes. In liquid HPDC, the baseplate would fill first, then the fins are backfilled. This leads to a lot of entrapped air and unfilled fins. In Rheocasting, the baseplate and fins fill simultaneously. This pushes the air towards the overflow system.

For the HPDC heat sinks, the fins require a higher draft of around 1° angle to be filled. In Rheocasting, you can reduce the draft angle to 0.2° for fins. This leads to a higher fin density, which improves cooling performance.

Additionally, the outstanding castability of Rheocasting allows for further design improvements. Instead of top-to-bottom parallel fins, Rheocasting allows the fins to be tilted towards each other. When running the antenna, the parallel fins form a stable surface layer of stationary air. Heat dissipation has to go through that layer. With the tilted fins, turbulences are introduced. These turbulences prevent the air layer from forming. This further increases the thermal conductivity of the Rheocasting antenna housing.

More insights are in the Rheocasting Masterclass

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