3M™ Thermally Conductive Silicone Interface Pad 5591 is a highly conformable and ultra-soft pad with thermal conductivity of 1.0 W/m-K (ASTM D5470). This pad consists of a slightly tacky silicone elastomeric sheet filled with thermally conductive ceramic particles. It is designed to transfer heat from heat-generating components to heat sinks and cooling devices, improving device reliability and extending the component’s life.
3M™ Thermally Conductive Silicone Interface Pad 5591 has an ultra-soft pad that conforms to uneven substrates, providing excellent wettability to fill gaps for improved thermal performance. The thin, firm, low-tack layer provides easy handling for pre-assembly and die-cutting. This pad provides robust thermal management for applications in a variety of market segments, such as consumer electronics, automotive, LED lighting, medical devices, communication infrastructure, and aerospace & defense.
Good thermal stability of the base polymer with excellent softness of the thermal pad.
Good thermal conductivity in an ultra soft silicone polymer base.
The product tack is such that a mechanical means to support the pad in a final assembly is required.
Filled Silicone Polymer
0.5 mm, 1.0 mm, 1.5 mm, 2.0 mm
3M pad 5591S – 12 µm PET Film
These interface pads are designed to provide heat transfer path between heat generating components and heat sinks, heat spreaders or other cooling devices.
3M™ Thermally Conductive Silicone Interface Pads 5591 and 5591S
Thermal Conductivity (W/m-K)
3M Test Method with low pressure (<10 psi)
Operating Temperature Range²
-60°C to 130/140°C Long Term (Weeks-Months) 3M Test Method -60°C to 160/180°C Short Term (Hours-Days)
3M Test Method
Hardness Shore 00³
Shore 00 results depend on test method and thickness of the sample tested. Typical results are in the 10-15 Shore 00 range @ 6 mm test thickness without the PET film. Ask 3M for more details on pad softness.
Modified ASTM D2240
200 V/mil AC (3M pad 5591S tested)
3M TM (ASTM D149)
2 x 1012 Ohms (3M pad 5591S tested)
3M pad 5591 has not been tested for UL 3M pad 5591S tested: UL 94 V-1 (0.5mm) and UL 94 V-1 (1.0mm - 5.0mm)
Storage and Shelf Life
The shelf life of 3M™ Thermally Conductive Interface Silicone Pad 5591 and 55921 is 12 months from the manufacture
date when stored in original packaging at 21°C (70°F) and 50% relative humidity