Massive Synthesis in Vacuum of High Thermal Conductivity Boron Arsenide for Underfill Application

Abstract

The continuous miniaturization and increased integration density of semiconductor devices have intensified the demand for high thermal conductivity materials capable of efficiently dissipating heat generated within chips. Boron arsenide (BAs), predicted to exhibit an exceptionally high theoretical thermal conductivity of approximately 1000 W/m·K, has emerged as a promising next-generation thermal management material. However, studies on the synthesis of high-purity BAs powders and their applicability remain limited. In this work, BAs powder was synthesized via a solid-state reaction in vacuum, and the effects of annealing temperature and precursor molar ratio on phase formation and chemical composition were systematically investigated. Structural and compositional analysis revealed that annealing at 800 °C for 12 h with 2.02 mmol boron and 5.05 mmol arsenic yielded spherical, single-phase BAs with minimized B₁₂As₂ impurities and residual boron, representing the composition closest to the ideal 1:1 stoichiometry. Using the synthesized powder, BAs ceramics were fabricated via spark plasma sintering. Thermally stable ceramic discs without cracks were successfully obtained at 700 °C and 30 MPa, exhibiting a relatively low thermal conductivity of approximately 3.0 W/m·K at room temperature. When the synthesized powder was incorporated into epoxy for underfill applications, BAs/epoxy composites showed processable viscosities of 13–43 Pa·s, while their thermal conductivity increased from 0.250 to 0.416 W/m·K with increasing BAs filler content.

Graphical Abstract