Thermal Management Solutions

Thermal Management for Microelectronics

Thermal Spreaders & Tabs

Make-to-print thermal tabs engineered for reliable heat transfer paths and assembly integration.

Thermal Management Base Plates

Base plates designed to support high-power modules and demanding thermal/mechanical environments.

Heat Dissipation Materials

Advanced heat spreader materials and composites optimized for thermal conductivity, stability, and system lifetime.

When heat rises, performance drops, and reliability is at risk. Hi-Rel Group engineers thermal management solutions that protect sensitive electronics in hermetic and non-hermetic packages, from ultra-high-conductivity materials like CVD Diamond and DiaCool® diamond metal matrix composites to proven legacy metals such as MoCu, WCu, and copper-molybdenum laminates. Whether your application is a high-power RF amplifier, a photonics submount, an avionics module, or a medical implant, we help engineering teams meet demanding thermal, mechanical, and lifecycle requirements with materials and manufacturing methods matched to the design.

The Thermal Reliability Challenge in High-Reliability Electronics


Power densities continue to climb across aerospace, defense, medical, telecom, and industrial electronics. Wide-bandgap semiconductors like SiC, GaN, and GaAs deliver more output in smaller footprints, but they also concentrate heat in smaller die areas, raising junction temperatures and accelerating failure mechanisms. Conventional copper and aluminum heat spreaders frequently fall short on two fronts. Their coefficient of thermal expansion (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 well below what next-generation devices need.

When CTE mismatches go unaddressed, repeated thermal cycling stresses solder joints and die-attach layers, leading to voiding, cracking, and eventual device failure. When thermal conductivity is insufficient, hot spots develop, junction temperatures rise, and device lifetime is compromised. Designing for high reliability means addressing both, and that requires materials and manufacturing approaches built for the application.


A Capability-First Approach to High-Reliability Thermal Solutions

Hi-Rel doesn't sell off-the-shelf thermal parts. We engineer them. Our process starts with your device requirements, including power dissipation, package type, target CTE, operating environment, and mechanical constraints, and works backward to the right material selection and fabrication approach

What We Deliver:

Make-to-print fabrication of heat spreaders, base plates, carriers, thermal tabs, and integrated assemblies

Material options matched to CTE and thermal performance requirements.



High flatness and dimensional control that reduce voiding at bond lines


Nadcap™-accredited plating, when required, fully integrated into the workflow


Prototype-through-volume manufacturing with consistent quality across runs


Our team works directly with your engineers, early in the design cycle when it matters most, to recommend material stack-ups, machining approaches, and finishing processes aligned to your reliability goals.

DiaCool® Diamond Metal Matrix Composites Engineered for Extreme Heat Flux 

DiaCool® is Hi-Rel's family of isotropic diamond metal matrix composites, manufactured for applications where conventional materials simply can't move heat fast enough. By combining synthetic diamond particles with copper, silver, or aluminum matrices, DiaCool® delivers thermal conductivity up to 850 W/m·K (roughly twice that of pure copper) while maintaining a coefficient of thermal expansion compatible with SiC, GaN, GaAs, and other wide-bandgap semiconductors. Hi-Rel owns the DiaCool® intellectual property and manufactures the material in-house.

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

DiaCool® Variants

VariantThermal ConductivityCTEDensityBest Suited For
 DiaCool-Ag850 850 W/m·K 5–6 ppm 6.07 g/cm³Highest thermal performance applications, including high-power laser diodes, photonics, and mission-critical RF
 DiaCool-Ag700 700 W/m·K 6–7 ppm 6.2 g/cm³

High-performance silver-diamond applications where Ag850's properties exceed design needs

 DiaCool-Cu600 600 W/m·K 6–8 ppm 6.3 g/cm³

High-conductivity applications requiring robust mechanical strength, such as power modules and microwave packages

 DiaCool-Al500 500 W/m·K 6–8 ppm 3.2 g/cm³Weight-sensitive aerospace electronics; x-ray friendly density supports 100% void inspection when required


All four variants are available in stock thicknesses from 0.89 mm (.035") through 3 mm (.120"), with custom thicknesses on request. DiaCool® is also available as raw material in dimensions up to 9" x 9" x 1" thick. Solder preforms (AuSn, SOT305, AuSi, AuGe and others) can be shipped separately or pre-attached, and standard plating chemistries or thin-film processing can be applied to meet your assembly requirements.

Where DiaCool® fits in the design: heat spreaders, die tabs, submounts, package base plates, and custom integrated assemblies for high-power laser mounts, photonics, radar systems, jammers, electronic countermeasures, microwave and millimeter-wave packages, RF power amplifiers, and 5G/optical networking thermal control.

View all DiaCool® datasheets →

The Complete Hi-Rel Thermal Material Portfolio

DiaCool® is one piece of a broader portfolio. For applications that don't require diamond composite performance, or that need it taken even further, Hi-Rel manufactures across the full spectrum of thermal management materials.

CVD Diamond

Ultra-High Conductivity: CVD Diamond
For applications where even DiaCool® can't dissipate heat fast enough, CVD Diamond delivers thermal conductivity up to 2000 W/m·K, the highest performance available in any thermal material. Available through Hi-Rel's strategic collaboration with WD Advanced Materials, CVD Diamond is suited to the most extreme power-density designs in semiconductor, photonics, and defense electronics. CVD Diamond and DiaCool® are not interchangeable; the right choice is driven by application requirements, not by raw conductivity numbers alone.

Learn more about CVD Diamond Heat Spreaders →

Diamond Metal Matrix Composites: DiaCool®Ultra-High Conductivity: CVD Diamond

Isotropic silver-, copper-, and aluminum-diamond composites delivering up to 850 W/m·K with CTE values tuned for compatibility with SiC, GaN, and other wide-bandgap semiconductors.

Explore DiaCool® Diamond Metal Composites →

 

Legacy Thermal Materials

For traditional semiconductor packaging, RF housings, power modules, and moderate-to-high-power thermal applications where predictable performance and trusted reliability are essential, Hi-Rel machines a full range of legacy materials:

  • - Copper-Molybdenum 
  • - Composite (CuMo / MoCu)
  • - Copper-Molybdenum Laminate (Cu/Mo/Cu, also known as CMC)
  • - Tungsten Copper (WCu)
  • - Molybdenum (Mo)
  • - Copper and Aluminum

See Legacy Thermal Materials →



Thermal Spreaders and Tabs


Make-to-print thermal tabs and spreaders engineered for reliable heat transfer in hermetic RF packages, power amplifiers, laser mounts, and submount applications. Multiple material options are matched to CTE requirements, with proprietary processing that supports complex geometries and demanding flatness specifications.

Explore Thermal Spreaders & Tabs →

Thermal Management Base Plates


Custom thermal base plates designed to support high-power modules and demanding thermal/mechanical environments. Materials include MoCu, WCu, DiaCool® diamond composites, and CVD Diamond integration, with EDM, waterjet, and high-tolerance CNC machining, plus Nadcap™ plating when required.

Explore Thermal Management Base Plates → 

Heat Dissipation Materials


Advanced heat spreader materials and composites optimized for thermal conductivity, CTE matching, and system lifetime, covering the full Hi-Rel material portfolio from CVD Diamond through DiaCool® to legacy metals.

Explore Heat Dissipation Materials →

Why Engineers Choose Hi-Rel for Thermal Management 

Proprietary EDM Process for Industry-Leading Flatness

Most thermal spreaders are produced by stamping, a fast process, but one that introduces dimensional inconsistencies that compromise bond-line quality at scale. Hi-Rel developed a proprietary EDM-based mass-production process specifically for heat spreaders, delivering linear dimensional compliance and flatness that conventional stamping cannot match. The result is higher yield rates, more consistent bond lines, and lower voiding at the interfaces that matter most for thermal performance. 

Quality Built for Inspections

Our process controls deliver consistent thermal continuity and uniform bond quality, supporting strong yields when x‑ray inspection is part of a customer’s qualification or final‑inspection protocol, and for applications requiring 100% void inspection, DiaCool‑Al500’s lower density provides an x‑ray‑friendly profile that enables clearer imaging and more reliable interpretation within customer inspection systems, making it well suited for aerospace, defense, medical, and high‑power RF environments where thermal reliability cannot be compromised. 

Low Voiding at Bond Lines

Voids at die-attach and bond-line interfaces are one of the most common causes of thermal failure in high-power devices. Hi-Rel's combination of proprietary EDM machining, tightly controlled finishing processes, and high-purity solder alloys produces some of the lowest voiding levels in the industry, translating directly into superior heat transfer efficiency, reduced thermal cycling stress, and extended device lifespan under high power loads. 

Built for High-Reliability Markets

Hi-Rel's quality systems, including AS9100 and ISO 9001 certifications, Nadcap™-accredited plating, ITAR registration, and RoHS/REACH compliance, are built around the demands of mission-critical electronics. Every part we ship is built to be one that an engineering team can trust in a fielded system. 

Designed for High-Performance Applications

Hi-Rel thermal management materials and components support designs across the most demanding electronics applications:

  • High-power laser mounts and photonics packages
  • Radar systems, jammers, and electronic countermeasures
  • Microwave/RF packages, high-RF modules, and power amplifiers
  • Chip mounting, circuit board cores, lids/covers, and package base plates


Medical instrumentation and implantable device electronics

  • 5G and high-speed telecom/optical networking thermal control
  • Semiconductor packaging for defense and commercial markets



Industries Served

Thermal management is fundamentally application-driven rather than industry-specific. The same DiaCool® variant that protects a high-power laser diode in a medical instrument may be specified into a defense RF amplifier or an industrial control system. Hi-Rel supports thermal management programs across:



Aerospace & Defense: radar, EW, avionics, space electronics



Medical Devices: imaging, instrumentation, implantables


Optical Networking & Telecoms: 5G infrastructure, photonics, high-speed optical


Petrochemical & Energy: high-temperature, harsh-environment electronics


Industrial and Commercial Electronics: power modules, semiconductor packaging

Engineering Collaboration: Bring Us Your Spec 

Need help selecting the right thermal solution? Share your operating temperature range, power dissipation, package type (hermetic or non-hermetic), target CTE, and mechanical constraints. Our team will recommend material options and fabrication approaches aligned to your reliability goals, and we'll work with you from prototype through volume production.

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Frequently Asked Questions 

What's the difference between a heat spreader and a heat sink?

Heat spreaders distribute heat laterally across a surface to reduce hot spots and even out temperature gradients. Heat sinks increase surface area to reject heat to ambient air or liquid cooling. Many high-reliability designs use both: a spreader to manage heat at the die, and a sink to move it out of the package.

When should I use diamond composites like DiaCool® for thermal management?

Choose diamond composites when your design needs extremely high thermal conductivity, tight CTE control to match SiC, GaN, or other wide-bandgap semiconductors, and stable performance at high power densities. If conventional copper or MoCu can't keep up with junction temperatures, DiaCool® is typically the next step.

Can Hi-Rel manufacture make-to-print thermal components?

Yes. Hi-Rel supports make-to-print parts and can also assist with design and integration, depending on project needs. Bring us a print, or bring us a problem. We work with both.

Do you support thermal management for hermetic packages?

Yes. Hi-Rel materials and components are used in both hermetic and non-hermetic packaging where reliability is critical. We also manufacture the hermetic lids, getters, and solder preforms that often accompany thermal management components in the same package.

What plating and finishing options are available?

Standard plating chemistries and thin-film processing are available across the portfolio. Nadcap™-accredited plating is provided where required by program specifications.