Diamond Metal Matrix Composites for Thermal Management


A diamond metal matrix composite combines synthetic diamond particles with a metal matrix to move heat that conventional spreaders cannot. Diamond has one of the highest thermal conductivities of any material, and pairing it with copper, silver, or aluminum produces an isotropic composite that delivers high thermal conductivity and a coefficient of thermal expansion (CTE) tuned to the semiconductor it sits beneath. Hi-Rel's DiaCool® family reaches up to 850 W/m·K, roughly twice that of pure copper, while holding a CTE compatible with SiC, GaN, GaAs, and other wide-bandgap devices. Hi-Rel owns the DiaCool® intellectual property and manufactures the material in-house.


The DiaCool® Family

DiaCool® variants are application-specific rather than tiered. The right choice depends on thermal load, weight constraints, mechanical environment, and inspection requirements, not on which number is largest.

Variant
Thermal Conductivity
CTE
Density
Best suited for

DiaCool-Ag850

850 W/m·K
5–6 ppm
6.07 g/cm³

Highest thermal performance: high-power laser diodes, photonics, mission-critical RF

DiaCool-Ag700
700 W/m·K
6–7 ppm
6.2 g/cm³
Silver-diamond applications where Ag850 exceeds design needs
DiaCool-Cu600
600 W/m·K
6–8 ppm
6.3 g/cm³
High conductivity with robust mechanical strength: power modules, microwave packages
DiaCool-Al500
500 W/m·K
6–8 ppm
3.2 g/cm³
Weight-sensitive aerospace electronics; x-ray friendly density supports 100% void inspection

Why Diamond Composites Outperform Conventional Heat Spreaders

Conventional copper and aluminum spreaders fall short on two fronts. Their CTE is mismatched to the semiconductor (copper's CTE is roughly six times that of GaN or SiC), and their bulk thermal conductivity caps out below what high-power devices need. The mismatch drives thermal cycling stress into solder joints and die-attach layers, leading to voiding and cracking over time. Insufficient conductivity lets hot spots form and junction temperatures climb. Diamond metal matrix composites address both at once: high conductivity to pull heat away from the die, and a matched CTE to keep the bond line stable through thermal cycles.

Matching a Composite to Your Semiconductor

For SiC, GaN, and GaAs designs, CTE control matters as much as raw conductivity. A spreader that moves heat quickly but expands at a different rate than the die will still fail at the bond line. DiaCool® CTE values (5 to 8 ppm depending on variant) are selected to track wide-bandgap semiconductors, which is why these composites are specified into power amplifiers, photonics submounts, and radar modules where both heat flux and reliability are non-negotiable. For applications that need even higher conductivity than diamond composites provide, CVD Diamond reaches up to 2000 W/m·K.

Formats, Plating, and Make-to-Print

DiaCool® is available in stock thicknesses from 0.89 mm (.035") through 3 mm (.120"), with custom thicknesses on request, and as raw material up to 9" x 9" x 1". Solder preforms (AuSn, SOT305, AuSi, AuGe, and others) ship separately or pre-attached, and standard plating chemistries or thin-film processing can be applied to meet assembly requirements. Every part is available make-to-print, including Nadcap™-accredited plating where required.

Share your power dissipation, package type, target CTE, and mechanical constraints, and our team will recommend the right variant and fabrication approach.


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