As 5G communication technology rapidly evolves towards the Sub-6GHz and millimetre wave bands, the power density of base station power amplifiers (PA) and radio frequency front-end modules (FEM) has exceeded 15W/mm². The thermal conductivity of traditional aluminium oxide (Al₂O₃) substrates, at 24W/mK, is insufficient to meet cooling requirements, becoming a critical bottleneck limiting device reliability. Aluminium nitride (AlN) ceramics, with their ultra-high thermal conductivity of 170–220 W/mK, are emerging as the ultimate solution for thermal management in 5G power devices.
5G Thermal Management Challenges: Exponential Growth in Heat Flux Density
Thermal Accumulation Effect of GaN Devices
GaN-on-SiC power devices used in 5G Massive MIMO antennas can reach junction temperatures above 200°C during operation. If heat cannot be dissipated promptly, every 10°C increase in temperature will reduce the device's lifespan by 50% (Arrhenius model).
Dielectric Loss of High-Frequency Signals
Alumina substrates exhibit dielectric loss (tanδ ≈ 0.0004) at the 28 GHz frequency band, causing signal attenuation. In contrast, aluminium nitride has tanδ < 0.0001 (@40 GHz), combining high thermal conductivity with low signal loss characteristics.
Blocked heat dissipation paths in 3D packaging
AiP (Antenna in Package) technology integrates RF chips with antennas. Traditional metal heat sinks interfere with electromagnetic fields, necessitating lateral heat conduction via ceramic substrates.
Three Major Technological Breakthroughs in Aluminium Nitride
Significant Increase in Thermal Conductivity
Through the use of high-purity AlN powder (oxygen content < 0.8 wt%) and pressure sintering technology, thermal conductivity has exceeded 170 W/mK (measured at 195 W/mK), which is seven times higher than that of aluminium oxide, and can reduce the junction temperature of GaN chips by 45°C.
Precise CTE Matching
The thermal expansion coefficient of aluminium nitride (4.5×10⁻⁶/℃) closely matches that of GaN (3.5×10⁻⁶/℃), preventing cracking of the welded layer caused by thermal cycling.
Metalisation Process Innovation
The use of active metal brazing (AMB) technology achieves a thermal resistance of < 5×10⁶m² ·K/W at the Cu-AlN interface, meeting heat dissipation requirements of over 30W/mm².
Industry Evidence: Heat Dissipation Upgrade by Leading Base Station Manufacturers
After a certain 5G base station equipment manufacturer adopted AlN ceramic substrates:
1. The operating junction temperature dropped from 182°C to 137°C (as measured by infrared thermal imaging).
2. The MTBF (mean time between failures) of the device increased to 150,000 hours (compared to 60,000 hours with the original aluminium oxide solution).
3. The overall power consumption decreased by 8% (due to lower thermal efficiency degradation)
Future Trends: Integrated Cooling Solutions
1. The next generation of aluminium nitride substrates is moving towards multifunctional integration:
2. Embedded microchannels: Water cooling synergistic cooling reduces thermal resistance by another 30%.
3. Three-dimensional circuit co-firing: Achieves a three-dimensional architecture for signal transmission and cooling.
4. Nano-diamond composite: Thermal conductivity in laboratories has exceeded 400W/mK.
In the race from 5G to 6G, aluminium nitride ceramic materials are redefining the limits of power device heat dissipation through materials science. When every watt of power consumption affects signal coverage and energy efficiency, this ceramic, less than 1 mm thick, is becoming the 'thermal management hub' of wireless communication infrastructure.