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High-Voltage Electronics and Superior Electrical Insulation
PCB Potting and Encapsulation: Advanced Dielectric and Arc Resistance
Silicone oil of an industrial grade begins the manufacturing process with the useful property of an oil's dielectric strength. This oil's dielectric strength is over 15 kV/mm, which is useful for stopping dangerous electrical arcing for components such as transformers, power modules, and battery systems for electric vehicles. Insulation breach can cause serious issues such as the thermal runaway. This is due to the failure of the insulation. Silicone, being a polymer, has stable chains that do not undergo significant changes under bombardment by electrons, which helps with cooling. This oil is also corona and dendrite discharge free, making it useful for sealing printed circuit boards in the medical, aerospace, and automotive manufacturing industries. Silicone oil is also unique in that it can self-heal following electrical stress, and can regain dielectric strength after stress without permanent damage. This property is essential in systems that cannot tolerate failure.
Performance Analysis of Silicone Oil, Mineral Oil, and PAO Fluids
Once temperatures reach about 130 °C, traditional mineral oils quickly begin to break down. PAO fluids may have greater heat stability than traditional mineral oils, but silicone fluids are still superior, exhibiting twenty percent greater arc resistance. This is particularly relevant for high frequency applications, especially in the case of rapidly growing insulation material wear due to frequent electrical discharges, such as in DC fast charging stations. Silicone is also more resistant to oxidation; therefore, sealed transformers filled with silicone fluids are less likely to accumulate sludge. As a result, silicone fluid filled transformers require less frequent replacement, typically lasting 3 to 5 years longer than those that use traditional hydrocarbon fluids.
Thermal Stability in Automotive Domains
Resistance at Above 200 degrees C in Engine Bay and Power Electronics
It is common for automobile engines and their components to reach and operate at 200 degrees Celsius and beyond. This heat causes lubricants and coolants like oils to evaporate or break down. Engine fluid breakdown generates harmful sludge and acid that increases friction and accelerates the wear and tear on engine components. Silicone oil on the other hand does not breakdown because of its better silicon-oxygen structure which is stronger than that of common oils. In an experiment simulation, at 220 degrees Celsius for 500 hours of continuous flow, silicone oil retained about 95 percent of its initial fluid viscosity, whereas the other mineral oil lost nearly half its viscosity at the same conditions. This is important because it keeps engine and turbocharger fluid systems clean. Silicone oil increases the life of engine components two or even three times over the life of conventional hydrocarbon oil.
Real-World Validation in EV Power Electronics
These benefits provide proof for real world applications in EVs. Field analysis was done on a peer leading moderately sized EV model using silicone oil coolant in its power inverter over a period of 100K+ miles. The key measurements were:
Parameter Silicone Oil Traditional Coolant
Viscosity change at 200°C <5% >35%
Acid number increase 0.1 mg KOH/g 2.8 mg KOH/g
Inverter failure rate 0.2% 1.7%
This resulted in a 40% decrease of thermal related warranty claims. In addition, silicone oil’s non-corrosive characteristic prevented any chemical degradation of copper windings and polyimide substrates, and because of its stable viscosity, it helped to ensure a constant flow within microchannel cooling systems, thus eliminating hot spots which are caused by failures of semiconductors.
Use of Silicone Oil as Heat Transfer Fluid and Lubricant
`Viscosity Index > 300` = Excellent Lubrication and Heat Transfer
Silicone oil has one of the highest viscosity index values in commercial fluids. In fact, the viscosity index of silicone oil is above 300. This means that silicone oil does not change its viscosity by much as temperature changes. This means that silicone oil can operate efficiently in both extremely high and extremely low temperatures; from -50 °C to 200 °C. What does this mean? This means that silicone oil can be used as an effective lubricant, as well as an effective heat transfer fluid, with no issues to be had. In the case of standard oils, as the temperature drops, the oil can become too viscous and in turn can lose the ability to properly flow, which can lead to issues such as pump cavitation. On the other hand, silicone oil continues to properly flow, ensuring that heat is continuously dissipated. On the other side of the temperature spectrum, silicone oil has stable film strength that prevents metals from touching one another in bearings and still allows heat to be transferred from the hotter areas. The ability to act as both a lubricant and heat transfer fluid means that engineers are able to design less complicated systems as there is no need to include separate circuits for lubrication and cooling. This has the potential to reduce the number of components needed by 30 to 40 percent in the thermal management systems used in the batteries of electric vehicles.
Situations where reliability is key include component cooling systems of powerful semiconductors, aircraft actuators, etc., and critical applications like these call for silicone oil. No surprise, then, that experts rely on silicone oil.
Long-Term Reliability and Material Compatibility with Sensitive Electronics
Non-Corrosive Behavior with Polyimide Substrates, Solder Masks, and Copper
Silicone oil used in the industry is responsible for the reliability of sensitive electronic components and their longevity. This is because silicone oil does not cause chemical reactions, unlike petroleum-based oils, which can lead to problems. For instance, silicone does not cause corrosion to copper, solder masks, and polyimide substrates in modern PCB and flexible circuit boards. Because of this, issues like electrochemical migration and insulation resistance lose their importance, especially concerning the moisture and repeated temperature changes the equipment is subjected to. Furthermore, the silicones protective non-reactive characteristic means that the adhesive and protective coatings can withstand operational changes. This increases the lifespan of the overall system, especially sophisticated systems where material failures are costly.
FAQs
What is the industrial-grade silicone oil's dielectric strength?
Industrial-grade silicone oil's dielectric strength is more than 15 kV per millimeter.
What advantages does silicone oil have over mineral oil and PAO fluids?
Compared to mineral oil and PAO fluids, silicone oil demonstrates greater dielectric strength, temperature operational range, resistance to oxidation, and stability of viscosity.
What about silicone oil makes it useful for extreme temperatures within automotive applications?
Because silicone oil can withstand an extreme temperature rise in excess of 200°C and continue to perform as required, it can be utilized to for extreme automotive applications.
Why is silicone oil used in sensitive electronics?
Silicone oil does not chemically interact with the copper, solder masks, or polyimide substrates, which increases the reliability of sensitive electronic parts.
