Thermal pads and insulation materials are specified by a handful of units. W/m·K measures thermal conductivity. kV/mm measures dielectric strength. The insulation class gives the rated temperature. UL94 gives the flammability rating. Thickness is quoted in millimetres, mils or microns: 1 mil is 0.0254 mm and 1 micron is 0.001 mm.
Watts per metre-kelvin: the rate at which heat is conducted through a material, per unit thickness and per degree of temperature difference across it. A higher number conducts more heat through the same thickness. The silicone pads in our range run from 1.0 to 6.0 W/m·K, and the alumina ceramic pad is 24 W/m·K.
Kilovolts per millimetre: the electric field a material withstands before electrical breakdown, measured under defined test conditions and quoted per millimetre of thickness. Our silicone pads are rated from 4.0 to 6.0 kV/mm and our epoxy-glass sheets from 18 to 22 kV/mm.
The maximum continuous temperature an insulation system is rated for, defined in IEC 60085: Class B is 130 °C, Class F 155 °C, Class H 180 °C. See electrical insulation classes explained.
UL94 classifies how a plastic material behaves when exposed to a flame. For solid materials the ratings are HB, V-2, V-1 and V-0, with V-0 the most flame-resistant. For foams the ratings are HBF, HF-2 and HF-1, with HF-1 the most flame-resistant. Our micro-cellular PU foam is rated UL94 HF-1 / HBF.
| Unit | In millimetres |
|---|---|
| 1 mm | 1 mm |
| 1 mil (thou) | 0.0254 mm |
| 1 micron (µm) | 0.001 mm |
For example, aramid paper quoted as 2 to 30 mil is 0.05 to 0.76 mm, and a film quoted as 100 microns is 0.1 mm.
It is the thermal conductivity: watts of heat conducted per metre of thickness per kelvin of temperature difference. A higher number conducts more heat through the same thickness.
It is the dielectric strength: the voltage per millimetre of thickness the material withstands before electrical breakdown, under defined test conditions.
0.0254 mm. 10 mil is 0.254 mm.
The highest of the three UL94 flame ratings for foam materials: HBF, HF-2 and HF-1.
Perfect Insulations has manufactured thermal and electrical insulation in Bengaluru since 1995 and works to ISO 9001:2015. Send your drawing or specification with the material, thickness and quantity.