Ti-Based Phonon-Bridged Cu/Diamond Interfaces for Ultra-High Thermal Performance

DIASEMI Technical Brie

Background
Diamond offers the highest known thermal conductivity, while copper remains the backbone of power electronic packaging. However, the Cu/diamond interface fundamentally limits heat dissipation due to weak bonding and severe phonon spectrum mismatch. Without interface engineering, most of diamond’s thermal potential is lost.

Core Insight: Phonon Bridging Determines Thermal Performance

Advanced atomistic simulations based on DFT-accurate machine-learning potentials reveal that interfacial thermal resistance (TBR) is governed by phonon transmission continuity across the Cu/diamond interface.

A key concept emerges:

Efficient heat transfer requires a “phonon bridge” that connects Cu’s low-frequency phonons to diamond’s high-frequency phonons.

Why Ti and TiC Are Critical

Among all investigated interlayer materials (Cr, Mo, Ti, W, TiC, WC):

✅ Ti and TiC are the most effective phonon bridges

• Ti interlayer reduces TBR by ~42%, achieving the lowest interface resistance.

• TiC provides dual phonon transmission channels, enabling parallel heat flow paths.

• Both materials:

• Strongly couple with Cu phonons

• Extend vibrational continuity toward diamond

• Reduce the phonon frequency gap (“phonon bridge length”)

❌ W and WC are ineffective

• W significantly widens the phonon gap, increasing TBR by ~66%.

• WC fails to form a continuous phonon pathway despite chemical compatibility.

➡️ Conclusion:
Chemical affinity alone is insufficient—phonon spectrum matching is decisive. Ti-based interlayers uniquely satisfy this requirement.

Implications for Thermal Conductivity of Cu/Diamond Composites

• The effective thermal conductivity of Cu/diamond is interface-limited, not diamond-limited.

• Ti / TiC interlayers unlock diamond’s intrinsic thermal conductivity, allowing heat to flow efficiently from Cu into diamond.

• Elevated operating temperatures further enhance phonon overlap, improving interface performance under real power-device conditions.

DIASEMI Design Strategy

DIASEMI’s Cu/diamond solutions are engineered around Ti-based phonon bridging, integrating:

• Ti or TiC metallization layers

• Carbide-mediated bonding

• Interface strain optimization

• Orientation-aware surface engineering

This approach transforms Cu/diamond from a theoretical concept into a practical, high-reliability thermal management platform.

Application Impact

• SiC & GaN power modules

• High-heat-flux heat spreaders

• Advanced packaging substrates

• Aerospace & RF power electronics

DIASEMI Advantage

We engineer the phonon pathway—not just the material stack