DOWSIL 3-6635 CLEAR DIELECTRIC GEL

Harmonization Code : 3910.00.00.90 | Silicones in Primary Forms; Others

DOWSIL 3-6635 CLEAR DIELECTRIC GEL

Main features

  • 80 to 200 deg C Service Range
  • Ultra-Soft Dielectric Gel
  • 20 kV/mm Dielectric Strength

Product Description

DOWSIL™ 3-6635 Dielectric Gel is a one-part, heat-curable silicone dielectric gel designed to protect sensitive electronic assemblies operating in demanding environments, including extreme low-temperature applications. It provides 700 cP viscosity, 20 kV/mm dielectric strength, and operating capability from -80°C to 200°C, while curing into an ultra-soft, resilient gel that cushions delicate components against thermal and mechanical stress. This makes it suitable for PCB assemblies, electrical insulation, encapsulation, and high-voltage electronics requiring long-term environmental protection and stress relief, subject to application-specific testing and qualification.

Key features

  • One-part silicone gel - supplied as a ready-to-use material with no mixing required, reducing processing complexity and minimizing mixing errors.
  • Excellent low-temperature performance - remains flexible and resilient across a wide operating temperature range from -80°C to 200°C, helping protect electronics exposed to severe thermal cycling.
  • Heat-curing system - cures under heat with a typical gel time of approximately 10.8 minutes at 135°C, supporting efficient manufacturing processes.
  • Low viscosity for easy dispensing - approximately 700 cP viscosity enables good flow beneath components and into complex geometries using manual or automated dispensing equipment.
  • Soft stress-relieving gel - cures into an extremely soft, self-healing silicone gel that helps absorb thermal expansion mismatch (CTE) while reducing mechanical stress on sensitive electronic components.
  • High electrical insulation - provides approximately 20 kV/mm dielectric strength, low dielectric constant, and high volume resistivity for reliable electrical insulation in high-voltage electronic assemblies.
  • Environmental protection - helps isolate circuits from moisture, contaminants, and environmental exposure while maintaining long-term electrical performance.

Applications

DOWSIL™ 3-6635 Dielectric Gel is suitable for electronic assemblies requiring soft silicone encapsulation, electrical insulation, moisture protection, and mechanical stress relief, particularly in applications exposed to extreme temperature environments.

  • Printed circuit board (PCB) encapsulation: provides protective encapsulation for PCB assemblies while cushioning delicate electronic components.
  • High-voltage electrical insulation: suitable for power electronics, electrical modules, connectors, and assemblies requiring reliable dielectric insulation.
  • Low-temperature electronics: supports aerospace, defense, scientific instrumentation, and industrial electronics operating under severe cold environments where flexibility must be maintained.
  • Stress-sensitive electronic assemblies: helps reduce thermal and mechanical stresses caused by coefficient of thermal expansion (CTE) mismatch between components and substrates.
  • Optoelectronic devices: suitable for optoelectronic assemblies where long-term optical stability and stress relief are important.

Additional information

  • Compatible with manual dispensing and automated dispensing equipment.
  • The cured gel remains soft and resilient, allowing localized repair or component replacement when required using appropriate silicone removal procedures.
  • Storage life is typically 6 months at 25°C when stored in the original unopened container.
  • As with all silicone encapsulants, compatibility testing with substrates, flux residues, curing agents, and surrounding materials is recommended before production implementation.

 

Product Family

DOWSIL 3-6635

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TDS, SDS & Technical Documents

Technical Specifications

Physical Properties
Viscosity
Viscosity is a measurement of a fluid’s resistance to flow. Viscosity is commonly measured in centiPoise (cP). One cP is defined as the viscosity of water and all other viscosities are derived from this base. MPa is another common unit with a 1:1 conversion to cP. A product like honey would have a much higher viscosity -around 10,000 cPs- compared to water. As a result, honey would flow much slower out of a tipped glass than water would. The viscosity of a material can be decreased with an increase in temperature in order to better suit an application
700 mPa.s
General Properties
Specific Gravity
Specific gravity (SG) is the ratio of the density of a substance to the density of a reference substance; equivalently, it is the ratio of the mass of a substance to the mass of a reference substance for the same given volume. For liquids, the reference substance is almost always water (1), while for gases, it is air (1.18) at room temperature. Specific gravity is unitless.
1 (uncured)
Electrical Properties
Dielectric Strength
Dielectric strength is measured in kV per mm and is calculated by the Breakdown voltage divided by the thickness of the tested material. Those two properties go hand in hand and while Breakdown voltage is always thickness dependent, dielectric strength is a general material property. As an example, the dielectric strength of Polyimide is 236 kV/mm. If we place 1mm of Polyimide between two electrodes, it will act as an insulator until the voltage between the electrodes reaches 236 kV. At this point it will start acting as a good conductor, causing sparks, potential punctures and current flow.
20 kV/mm
Volume Resistivity
Volume resistivity, also called volume resistance, bulk resistance or bulk resistivity is a thickness dependent measurement of the resistivity of a material perpendicular to the plane of the surface.
4.8 E+13 Ohms⋅cm

Additional Information

Unlike conventional rigid encapsulants, DOWSIL™ 3-6635 Dielectric Gel cures into an ultra-soft silicone gel that combines electrical insulation with mechanical cushioning. Its resilient gel structure helps absorb thermal expansion mismatch (CTE), reducing stress transferred to delicate solder joints, wire bonds, sensors, and electronic packages during temperature cycling. The material also maintains its flexibility at temperatures as low as -80°C, making it suitable for electronics operating in aerospace, industrial, scientific, and other harsh-environment applications.

PCB encapsulation

Protects populated PCB assemblies against moisture, dust, contaminants, vibration, and mechanical shock while maintaining electrical insulation.

High-voltage electronics

Provides dielectric insulation for power electronics, power supplies, converters, transformers, sensors, and electrical modules requiring long-term insulation performance.

Optoelectronic assemblies

Suitable for LEDs, photonic devices, optical sensors, and optoelectronic modules where stress relief and long-term optical stability are important.

Traditional rigid potting DOWSIL™ 3-6635 Dielectric Gel
High mechanical stress on components Ultra-soft gel cushions delicate components
Can crack during thermal cycling Flexible gel accommodates CTE mismatch
Limited repairability Localized rework is possible using Dow-recommended removal methods
High modulus Low modulus helps minimize stress on solder joints and interconnections

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