Modern power semiconductor devices and electronic assemblies are both subject to the same trend – miniaturisation. This is leading to ever higher operating temperatures.

WACKER’s thermally conductive silicone adhesives have a key dual role in this process. On the one hand, they transfer the device’s heat to the heat sink or other dissipation components. On the other, they create a firm yet flexible mechanical bond that doesn’t require further fixing.

Silicone-based thermally conductive adhesives  from WACKER exhibit outstanding durability. They remain virtually wear-free under permanent thermal stress, with an almost constant hardness even after thousands of operating hours at 150°C, and an elongation at break which changes minimally over the long term. The material does not become brittle. As a result, you have the assurance that the thermally conductive bond between the device and cooling element remains functional over the long term.

WACKER’s thermally conductive silicone encapsulants and potting compounds are optimized for bubble-free encapsulation. Despite their high filler content, they exhibit good flow properties with low viscosity. This property mix is achieved thanks to minimal thixotropic or pseudoplastic behavior, reducing the risk of air bubbles.


Features & Benefits

  • Thermal management of pcb assemblies, LED assemblies, power electronics
  • Efficiently dissipate heat, even for complicated shapes
  • Permanently withstand shocks, vibrations and temperature fluctuations due to their soft consistency
  • Thermal conductivity of up to 4.3 W/m⋅K
  • Reduction of manufacturing costs by acting as both thermal coupling and mechanical fixturing

Curing and Rheology

Product Type Cure Cure Time Colour Rheology Characteristics
Semicosil 975 TC Single part Thermal 10 min at 90°C
20 min at 100°C
10 min at 130°C
4 min at 150°C
Reddish-grey Thixotropic paste Adhesive with very high thermal conductivity 4.3 W/m⋅K. FIPG. CIPG. Meets MIL-A-46106
Elastosil RT 747 TC Single part Thermal 30 min at 130°C 15 min at 150°C White Low viscosity Self-levelling thermally conductive encapsulant with good primerless adhesion; cold storage required
Elastosil RT 428 Two part Condensation 8 hours at 23°C Reddish-brown 12,000 mPas Thermally conductive two part potting compound. Very good flow. Excellent heat resistance.
Semicosil 961 TC Two part Addition 5 hours at 23°C;5 mins at 100°C Yellow 130,000 mPas Thermally conductive gap filler; shear-thinning so easy dispensing; non-slump; cures to a soft and tacky rubber


Product Thermal conductivity (W/m⋅K) Hardness (Shore) Tensile strength (N/mm2) Elongation %
Semicosil 975 TC 4.3 A 98 3 10
Elastosil RT 747 TC 1.3 A 70 2 50
Elastosil RT 428 0.3 A 65 6 90
Semicosil 961 TC 2.3 OO 55

All Downloads

Filename Size Download
Thermally Conductive Silicones 0.12MB
  • Last updated: October 2018
  • Version: 1.2

Statements, technical information and recommendations contained herein are based on tests we believe to be reliable but they are not to be construed in any manner as warrantees expressed or implied. The user shall determine the suitability of the product for his intended use and the user assumes all risk and liability whatsoever in connection therewith.