Thermal Conductivity from 1.0 to 10.0 W/mK: How to Choose the Right Thermal Grease Grade

Thermal greases are commonly available with thermal conductivity ratings from 1.0 to 6.0 W/m·K (Hanast HN100-HN600), and buyers often assume that higher is always better. In practice, the right grade depends on the heat flux, the gap geometry, the assembly process and the cost target. This guide explains what each conductivity level is really for and how to choose the correct thermal grease grade for your product.

What the Conductivity Range Means in Practice

The Real Performance Equation

Interface thermal resistance depends on conductivity and layer thickness. A 1.0 W/m·K grease applied at 0.03 mm has the same resistance as a 6.0 W/m·K grease applied at 0.18 mm. Since thick layers are usually caused by rough surfaces, excessive dispensing or tall components, process control often delivers a bigger improvement than switching to a higher grade.

When 1.0 W/m·K Is the Smart Choice

For LED lamps, LED drivers, phone chargers, adapters and low-power industrial electronics, the total heat is small and the heat sink is large. A 1.0 W/m·K white silicone grease provides ample performance at the lowest cost, with good insulation and easy handling. Hanast's 1.0 W/m·K grades are popular for LED driver and power supply mass production.

When 3.0 W/m·K Is the Sweet Spot

PC cooling, gaming hardware, IGBT modules, motor controllers and EV battery cooling plates typically need 2.0-3.0 W/m·K. This range balances performance, price and processability, and is the most widely specified conductivity in the industry.

When You Need 4.0-6.0 W/m·K (HN400-HN600)

Very high heat flux - laser diodes, RF power amplifiers, high-current traction inverters, high-end CPUs and GPUs - leaves little margin for interface resistance. HN400 at 4.0 W/m·K and the metal-filled HN500/HN600 at 5.0-6.0 W/m·K reduce junction temperature by several degrees, which can decide whether a design meets its reliability target. Note that HN400 is intended for non-exposed surfaces, and the metal-filled HN500/HN600 must stay inside enclosed interfaces away from exposed circuitry.

How to Choose: A Simple Decision Flow

1. Calculate heat flux (W/cm²) at the interface;
2. Below 5 W/cm²: 1.0-2.0 W/m·K is usually enough;
3. 5-15 W/cm²: choose 3.0-4.0 W/m·K;
4. Above 15 W/cm²: consider 6.0 W/m·K or higher;
5. Confirm by measuring the real junction temperature;
6. Check that the chosen grade dispenses reliably on your line.

Avoid Over-Specifying Conductivity

Over-specification adds 2-5 times the material cost, increases density and settling, and can make dispensing harder - all without a measurable temperature benefit. Always validate with a thermal test on production samples before finalizing the specification.

Hanast HN100-HN600 Selection Ladder

Conductivity Grades in the Real Product Range

The Hanast HN series forms a complete selection ladder from 1.0 to 6.0 W/m·K. When you request samples, ask for two adjacent grades and test them in your real assembly: the temperature difference tells you whether the higher grade pays for itself. In many LED and consumer designs HN100 wins on cost; in high-performance computing and automotive power, HN500 and HN600 justify their price with measurable temperature reductions.

FAQ

What does 6 W/mK thermal grease cost compared with 1.0 W/mK?

Typically 3-6 times more per kilogram, because of expensive fillers such as aluminum nitride and higher filler loading. That is why over-specifying conductivity wastes money.

Can one thermal grease grade cover all factory products?

Not optimally. A 1.0 W/m·K grade is weak for IGBT modules, while a 6.0 W/m·K grade is overkill and overpriced for LED drivers. Two grades - one standard and one high-performance - cover most factories.

Conclusion

Choosing between 1.0 and 6.0 W/m·K thermal grease is about matching the grade to the heat flux, geometry and process - not about buying the biggest number. Hanast offers the full HN100-HN600 range from 1.0 to 6.0 W/m·K with consistent batch quality; contact us for free samples and application guidance.