COOLTHERM SC-303
Harmonization Code : 3910.00.00.90 | Silicones in Primary Forms; Others
Main features
- 0.9 W/(m K) Thermal Conductivity
- 6,000 cP Application Viscosity
- 40 to 200 deg C Service Range
Product Description
CoolTherm® SC-303 Thermally Conductive Silicone Encapsulant is a two-component, addition-curing silicone system designed for thermally conductive electrical and electronic encapsulation. The white resin and grey hardener mix at a simple 1:1 ratio by weight or volume to form a light-grey material with a typical 6,000 cP viscosity at 25°C, 50-minute working life, and 60–120 minute gel time at 25°C. Supported cure schedules are 24 hours at 25°C, 25–30 minutes at 70°C, or 10–15 minutes at 100°C. The cured elastomer provides typical 0.9 W/m·K thermal conductivity, 45 Shore A hardness, 17.3 kV/mm dielectric strength, and an operating-temperature range of -40°C to 200°C.
Key features
- Two-component thermally conductive addition-cure silicone encapsulant
- Simple 1:1 mix ratio by weight or volume
- Low 6,000 cP mixed viscosity for encapsulation of electrical and electronic assemblies
- Low-shrinkage, low-stress cured silicone elastomer
- Room-temperature and accelerated heat-cure options
- Typical 0.9 W/m·K thermal conductivity and 17.3 kV/mm dielectric strength
- UL 94 V-0 certified, subject to the current listed formulation and test construction
Applications
- Thermally conductive electrical and electronic encapsulation
- Assemblies requiring heat dissipation with a flexible silicone encapsulant
- High-voltage or critical assemblies using validated vacuum-assisted void control
- Devices operating across the documented -40°C to 200°C temperature range
TDS, SDS & Technical Documents
Technical Specifications
General Properties
Physical Properties
Thermal Properties
Mechanical Properties
Chemical Properties
Electrical Properties
Additional Information
CoolTherm® SC-303 Thermally Conductive Silicone Encapsulant
A two-component silicone encapsulation system designed to combine heat dissipation, electrical insulation, low cured stress, flexibility, and broad-temperature operation. The 1:1 resin and hardener system supports manual cartridge application or automated meter/mix/dispense processing for electrical and electronic assemblies.
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Component and mixed-material properties
Both components have the same published viscosity and specific gravity, supporting a simple 1:1 ratio by either weight or volume. Thoroughly premix each component before combining.
| Property | SC-303 resin | SC-303 hardener | Mixed material |
|---|---|---|---|
| Appearance | White paste | Grey paste | Light-grey paste |
| Viscosity at 25°C | 6,000 cP | 6,000 cP | 6,000 cP |
| Specific gravity | 2.14 | 2.14 | 2.14 |
| Mix ratio | 1:1 by weight or volume | ||
| Gel time at 25°C | 60–120 minutes | ||
| Working life at 25°C | 50 minutes | ||
Premix both components, combine 1:1, minimise air, dispense, and cure
Thoroughly mix the resin and hardener separately before combining them at 1:1 by weight or volume. Continue mixing until the colour is uniform. Automatic meter/mix/dispense equipment may be used for higher-volume production.
- Use closed-chamber mixing where practical to reduce introduced air.
- For extremely high-voltage or other critical applications, evaluate vacuum processing to minimise bubbles and voids.
- Apply using same-day prepared handheld cartridges or automatic meter/mix/dispense equipment.
- Avoid surfaces containing cure-inhibiting amines, sulphur, or tin salts.
- When substrate compatibility is uncertain, apply a test patch and allow the normal cure time.
- Cure for 24 hours at 25°C, 25–30 minutes at 70°C, or 10–15 minutes at 100°C.
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Restore resin and hardener separately to a uniform condition.
Combine 1:1 by weight or volume and mix until uniformly light grey.
Minimise voids and verify questionable surfaces with a cured test patch.
Use room-temperature cure or the supported 70°C or 100°C accelerated schedule.
Storage and industrial handling
Each component has a nine-month shelf life when stored at 25°C in its original unopened container. The hardener evolves minute quantities of hydrogen gas; do not repackage or store it in unvented containers, and ventilate the work area to prevent gas accumulation. The resin and hardener safety documents also note that methylpolysiloxanes may generate formaldehyde at approximately 150°C and above in oxygen-containing atmospheres. Review the current regional SDS documents and labels, use trained industrial personnel, and provide suitable ventilation, gloves, eye protection, hygiene, spill, and waste controls.
Thermal, mechanical, moisture, and electrical properties
The values below are typical cured-material results and are not lot specifications. Installed thermal and electrical performance also depends on geometry, thickness, coverage, interfaces, voids, cure, voltage design, and the surrounding assembly.
| Property | Typical value | Context |
|---|---|---|
| Thermal conductivity | 0.9 W/m·K | Hot Disc Transient Method, ISO 22007-2. |
| Coefficient of linear thermal expansion | 200 ppm/°C | ASTM D864. |
| Hardness | 45 Shore A | ASTM D2240 flexible elastomer. |
| Tensile strength | 1.17 MPa (170 psi) | ASTM D412 bulk-material property. |
| Elongation at break | 90% | ASTM D412. |
| Moisture absorption | 0.05% | ASTM D570-81. |
| Volume resistivity at 25°C | 3.8 × 1015 ohm-cm | ASTM D257; not a finished-assembly working-voltage rating. |
| Dielectric strength | 17.3 kV/mm (440 V/mil) | ASTM D149; breakdown property rather than a design working voltage. |
| Dielectric constant | 4.20 at 1 MHz and 25°C | ASTM D150. |
| Dissipation factor | 0.02 at 1 MHz and 25°C | ASTM D150. |
Flexible thermal encapsulation for electrical and electronic assemblies
SC-303 is directly positioned for electrical and electronic encapsulation where heat dissipation, electrical insulation, flexibility, and broad-temperature operation are required. Final selection must account for component layout, pour depth, exotherm, void tolerance, cure inhibition, voltage, creepage and clearance, thermal path, enclosure design, repairability, and environmental exposure.
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Potting & Encapsulation Materials Catalogue — PC3002
The catalogue identifies SC-303 as a grey, two-component, 1:1 thermally conductive silicone with 6,000 cP viscosity, UL 94 V-0, UL RTI 200°C, 45 Shore A hardness, 17.3 kV/mm dielectric strength, and 0.9 W/m·K thermal conductivity.
Use the current technical datasheet for processing, shelf life, operating range, cure-inhibition precautions, and complete cured-property context. UL recognition must be verified against the current listing.
Validate SC-303 for your thermal encapsulation process
Krayden can help review mix-ratio control, component premixing, meter/mix/dispense equipment, vacuum processing, cure inhibition, pour geometry, void control, cure profile, thermal path, electrical insulation, operating temperature, UL scope, and assembly-level qualification for CoolTherm® SC-303.
