Introduction

With the advent of the 5G era and the continued miniaturisation and densification of integrated circuits, power consumption in electronic devices has increased. This trend imposes higher demands on thermal management. Aluminium nitride (AlN) exhibits high thermal conductivity. Its theoretical value is 320 W/(m·K). Practical values range from 100 to 280 W/(m·K), which is five to ten times that of alumina. AlN also offers high strength, high volume resistivity, high insulation breakdown voltage, low dielectric loss, and a coefficient of thermal expansion compatible with silicon. These properties make AlN a promising next-generation high-thermal-conductivity filler powder, as well as a material for ceramic electronic substrates and packaging. Its crystal structure consists of AlN₄ tetrahedral units.

Hydrolysis Challenge

AlN powder has high reactivity with water. In humid environments, it readily reacts with hydroxyl groups to form aluminium hydroxide and release ammonia, a pungent gas. Oxygen atoms incorporate into the AlN lattice, reducing thermal conductivity. This creates difficulties for storage, transport and subsequent processing. Improving the hydrolysis resistance of AlN powder is therefore of practical significance for its wider application.

Research on AlN hydrolysis has been conducted systematically over an extended period. Key findings are summarised below.

Bestry's Production Method

Bestry produces AlN powder using a carbothermal reduction process with highly active aluminium and carbon sources. The resulting high-purity AlN achieves a thermal conductivity of 80 to 320 W/(m·K). However, untreated powder exhibits poor hydrolysis resistance. Conventional AlN powder (D50 ≈ 1 μm) after 30 minutes in a 60°C water bath produces an ammonia odour and forms large agglomerates of aluminium hydroxide. Untreated AlN therefore has weak hydrolysis resistance and is unsuitable for use in humid environments.

Hydrolysis-Resistant Modified Product

Based on published research and its expertise in powder modification, Bestry has developed an AlN powder with enhanced hydrolysis resistance using specialised processing techniques. The modified product effectively inhibits hydrolysis and expands the material's application range.

Bestry's TA-ST series AlN powder, treated with proprietary surface modification reagents and a proprietary process, demonstrates excellent hydrolysis resistance. After modification, the powder surface shows no significant visible change, but hydrolysis resistance is substantially improved. Under accelerated test conditions (90°C water bath), the pH of Bestry's modified product remained below 10 after 120 hours. No ammonia odour or agglomeration was observed.

Applications

The modified AlN powder significantly broadens the range of applications, particularly in high-loading nitride and high-thermal-conductivity materials. Key applications include:

• High-thermal-conductivity gels

• High-thermal-conductivity gap fillers (thermal pads)

• High-thermal-conductivity thermal greases

• High-thermal-conductivity film materials