When it comes to thermal interface materials (TIMs), silicone-free thermal pads have grown in popularity. They address some of the pain points engineers and assemblers encounter with silicone-based products, especially in sensitive applications. But despite their benefits, silicone-free pads haven’t replaced silicone-based gap fillers entirely — and there are good reasons why.
The Benefits of Silicone-Free Thermal Pads
Silicone-free thermal pads are engineered to eliminate certain risks that can arise with traditional silicone products. Key advantages include:
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No Siloxane Outgassing
Silicone materials can release volatile siloxanes, which may migrate, condense, or cause contact issues in sensitive optical or electronic systems. Silicone-free pads avoid this. -
Safe for Optical and Display Applications
Outgassing can create fogging or film on lenses, displays, or sensors. Silicone-free pads are often chosen in cameras, sensors, or LED assemblies where optical clarity is critical. -
Improved Long-Term Stability in Some Environments
Certain silicone-free formulations show excellent resistance to contamination issues in harsh environments where siloxanes are undesirable. -
Regulatory or Customer Preference
Some industries (aerospace, medical, optics) specify silicone-free materials as a requirement due to risk mitigation. -
Alternative Chemistries Available
Silicone-free gap fillers often use urethane, acrylic, or other proprietary chemistries that still provide compliance and solid conductivity.
The SF Lines: Closing the Gap
Historically, silicone-free pads lagged behind in conductivity, and compliance compared to silicone-based solutions. However, Laird’s TFLEX SF line (SF4, SF7, SF10) has almost completely closed that gap:
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TFLEX SF4 → 4.0 W/m·K
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TFLEX SF7 → 7.8 W/m·K
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TFLEX SF10 → 10 W/m·K (and often tests closer to ~12 W/m·K in real-world results)
These numbers place the SF materials squarely in the same performance range as traditional silicone-based gap fillers. In many applications, they are a true drop-in replacement.
The only area where silicone-free pads still trail is in temperature ratings. While silicone-based pads often maintain performance well above 200 °C, silicone-free chemistries sometimes cap out lower. For most electronics, this isn’t a dealbreaker, but in extremely high-temperature environments, silicone materials still have the edge.
The Drawbacks of Silicone-Free Pads
So if silicone-free pads solve outgassing and deliver strong performance, why aren’t they used everywhere? A few key reasons:
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Temperature Limitations → not always rated as high as silicone-based pads.
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Portfolio Breadth → silicone-free lines don’t yet cover every niche thickness, and performance option.
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Cost and Availability → sometimes more expensive and less widely stocked.
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Field History → silicone-based pads have decades of data across industries; silicone-free is newer by comparison.
Why Silicone Pads Still Dominate
In most applications, the combination of high thermal conductivity, extreme softness, wide availability, and robust thermal stability makes silicone-based gap fillers the default. They’re proven, plentiful, and cost-effective.
But in industries sensitive to contamination — like optics, displays, aerospace, and medical — silicone-free materials like the TFLEX SF line are quickly becoming the preferred option.