Silicone compounds find extensive application in numerous electronic systems to effectively seal, bond, coat, and encapsulate components. This enables these components to function reliably even in challenging conditions. Over the years, formulators have been continuously enhancing silicones to make them more user-friendly and to offer a wider range of properties.
The electronics industry has experienced remarkable growth since the 1980s, driven by higher transistor densities that have facilitated significant advancements in performance and paved the way for miniaturization. Initially developed for computers and communication systems, electronic circuits are now widely employed across various industries. They are utilized in applications ranging from satellite systems deployed in space to medical devices implanted in humans. To ensure the proper functioning of these systems, the electronic circuits must be safeguarded against extreme temperatures, contaminants, shock and vibration, and harsh environmental conditions.
Silicones have played a pivotal role in the electronics revolution by providing enhanced functionality through the sealing and coating of sensitive electronics. Silicones are relied upon in business, consumer, and military applications to protect electronic components from heat, moisture, contamination, and accidental damage. The range of applications benefiting from silicones has expanded over time, driven by the increased heat generated by additional transistors packed into smaller packages, necessitating higher temperature resistance for improved reliability. With their distinct properties, silicones offer the necessary protection that electronic systems require to deliver optimal performance in diverse environments.
Why is silicone used in electronics?
Silicone specifically designed for electrical applications offers numerous advantages over traditional materials, including:
Water Resistance, or Hydrophobicity: Instead of spreading out on silicone, water forms droplets, enhancing device reliability by reducing the risk of flashover due to contaminated surfaces.
Improved Elasticity: Silicone exhibits excellent elasticity that remains intact across a wide temperature range, enabling the installation and operation of components even in sub-zero temperatures.
Resistance to UV Radiation: The molecular structure of silicone grants it permanent resistance to high doses of UV radiation, making it an excellent choice for external applications.
Low Flammability: Silicone rubber ignites only at extremely high temperatures, making it ideal for locations with strict fire safety standards such as hospitals, high-rise buildings, ships, trains, and subway systems. In the event of a fire, silicone does not release halogens or toxins.
Dielectric Characteristics: Compared to other insulating materials, silicone exhibits high electrical resistivity and superior dielectric strength, which remains practically unaffected by high temperatures. These properties ensure a longer service life for silicone in similar operating environments compared to other insulating materials.
Long-Term Thermal Stability: Silicone’s thermal stability allows insulating materials to operate at higher temperatures, leading to better utilization and optimal use of transformer capacity. Manufacturers have developed various forms of silicone, including fluids, gels, polymers, and compounds.
What is silicone used for in electronics?
The unique combination of silicone’s properties, such as conductivity, thermal stability hydrophobicity, and durability make silicone a suitable material solution for a broad range of electrical applications, including:
Silicone Insulators
The service life of electrical insulators is affected by electrical, mechanical, and environmental stresses, with mechanical loads posing the greatest threats. Airborne pollutants and moisture can combine to form a conductive film, leading to leakage currents and dry band arcing. This process eventually triggers a contamination-based flashover, resulting in a fault in the electrical circuit. As the surface of the insulator loses its hydrophobicity and resistance, leakage currents increase.
Hydrophobicity in polluted environments is one of the key properties desired for electrical insulators. However, the hydrophobic properties of insulators decrease over time due to electric activity caused by wetting and pollution. During periods of inactivity, the insulator surface is able to recover. In the case of silicone insulators, water remains as droplets rather than forming a continuous film. As a result, silicone insulators demonstrate superior hydrophobic performance and require minimal cleaning and maintenance as time progresses.
Silicones protect sensitive electronic components
Silicone’s wide range of service temperatures, flexibility, superior electrical properties, and ability to shield components from environmental contaminants make them highly valuable as adhesives, sealants, coatings, and potting compounds. Their capability to withstand extreme environmental conditions gives them an advantage over other adhesive types and related compounds in certain applications.
Sealing and bonding:
Silicones are commonly employed to seal and bond substrates during the assembly of printed circuit boards (PCBs) and modules. They are the only adhesives that can adhere to a silicone substrate. Electrically conductive silicone adhesives can be used as an alternative to solder for component attachment. Thermally conductive grades are suitable for bonding microprocessors, LED arrays, and other heat-generating components to heat sinks, ensuring efficient heat transfer. Thanks to their stable properties under high temperatures, silicones can endure the heat prevalent in many operating environments.
Conformal coatings:
Silicone-based conformal coatings electrically isolate all conductors on a PCB while safeguarding the electronics from humidity, temperature extremes, corrosives, and vibration. Applied as a thin and uniform layer during the final stages of manufacturing, these coatings offer low viscosity and strong adhesion, allowing them to flow easily and conform to the contours of electronic assemblies. They minimize the accumulation of moisture and other harmful contaminants. Silicone-based coatings can be formulated to be optically clear or exhibit low outgassing.
Silicones are often used in low-stress applications to protect sensitive components in demanding environments due to their ability to maintain a low Shore durometer over a wide temperature range. Flexible silicone elastomeric coatings can be applied in thicker layers than their epoxy counterparts, providing a higher level of protection for applications that require maximum vibration damping. Additionally, silicone coatings offer the advantage of being easier to rework compared to other materials.
Potting and encapsulation:
Silicones are well-suited for potting and encapsulation applications due to their softness, high-temperature resistance, toughness, and electrical insulation properties. They are commonly used when extreme thermal insulation and robust electrical insulation are crucial. Thermally conductive silicone compounds are employed to encase devices such as power supplies, rectifiers, transformers, and sensors. These compounds transfer heat away from the components while safeguarding them from dust, humidity, temperature extremes, and vibration.
Silicone-based materials, including “glob-tops,” protect sensitive bare die and wire bonds. These specially formulated encapsulants exhibit thixotropic properties, flowing smoothly in response to stress during application. They cover the die and fill gaps between wires, increasing viscosity rapidly to prevent flow outside the target area. Silicone-based glob tops provide a resilient barrier against contaminants while supporting the delicate die and wires.
Display Protection
In the modern digital era, the demand for portable devices is constantly rising. This presents numerous challenges for manufacturers, as they must address issues such as varying temperatures, waterproofing, thinner designs, and drop resistance.
Silicone foam offers a solution for protecting displays and back pads by mitigating the effects of vibrations and temperature fluctuations. Additionally, it has the ability to absorb shocks and distribute energy from impacts, ensuring enhanced device durability.
Vibration Management
Silicone foams are excellent choices for vibration isolation applications. They possess the ability to deflect vibrations over extended durations, offering remarkable resilience while effectively dampening vibrations and absorbing impacts.
For more information on our silicone products and how they can be used in electrical manufacturing, please get in touch with A1 Silicones