Liquid Gap Fillers

What are Liquid Gap Fillers?

Liquid gap fillers, also known as dispensable thermal gap fillers, are thermally conductive materials that dissipate heat in high-powered electronic devices. Liquid gap fillers are placed between an electronic component generating heat, such as an integrated circuit or transistor, and a mechanical component transferring heat away from the component, such as a heatsink.

Laird offers both one-part and two-part liquid gap filler solutions. One-part liquid gap fillers remain uncured and flowable and can be reworked. Two-part solutions cure after application. Two-part dispensable thermal gap fillers reduce pump out and offer more reliability in applications with temperature excursions or the possibility of mechanical deformation. This ensures the liquid gap filler solution maintains thermal conductivity while withstanding mechanical stress like vibration, shock, or thermal cycling. 

How do Liquid Gap Fillers Work?

Liquid gap fillers function as a flexible, high-performance conduit for moving heat away from sensitive components into external cooling systems. These solutions fill the gap between a heat-generating component and the heatsink, making sure no air remains between the two components. Liquid gap fillers are formulated to be thermally conductive and flowable, allowing them to conform to uneven surfaces and variable gap dimensions, enabling efficient thermal transfer.

How do dispensable thermal gap fillers compare to other types of thermal fillers?

Another common type of thermal interface material is thermally conductive gap filler pads. While both solutions perform the same core function – providing thermal transfer to enable more efficient heat dissipation – liquid gap fillers are made of a putty material while thermal gap filler pads are solid. Compared to traditional gap filler pads, liquid gap fillers offer superior coverage over complex geometries and variable gap thicknesses.

Furthermore, liquid gap fillers offer very low compressive forces during product assembly. Meaning, they can be deflected to high percentages without providing much force on the expensive electronic component they are mating to a heatsink. This provides a desirable tradeoff that allows boards with multiple varying heights to be assembled at faster rates while still protecting those valuable and fragile components.

Dispensable thermal gap fillers are more easily automated, as they are placed via dispensing equipment directly onto components, enabling precision and uniform contact to improve electronic cooling. Alternatively, thermal gap filler pads are applied manually or via pick-and-place robotics

The portfolio of Laird™ thermal interface materials also includes:

• Thermal greases for minimal bondline, constant pressure applications.
• Phase change materials, which soften at operating temperature to reduce pump out and offer long-term reliability.
• Specialty TIMs, which combine thermal conductivity with other benefits, such as electromagnetic interference absorption, to provide dual functionality.

What characteristics should you consider when selecting a liquid gap filler?

• Thermal conductivity: When selecting a liquid gap filler, thermal conductivity is the most important factor to consider. Thermal conductivity determines how efficiently the gap filler can transfer heat between the electronic component and the heatsink.
• Minimum bondline thickness: Bondline thickness – or the final thickness of a material once it’s in place – works hand-in-hand with thermal conductivity to impact the overall thermal resistance. In applications with tighter tolerances, thinner bond lines help maximize heat dissipation. Different products will be able to achieve varying minimum bond line thicknesses.
• Thermal resistance: Thermal resistance is the performance property that matters most in application. Here, you must consider bulk thermal conductivity of the liquid thermal interface material, the interfacial resistances that arise at the interface between the TIM and component, and bond line. This property is best understood and measured in application-based testing.
• Processing requirements: One-part formulations enable streamlined manufacturing processes, increase throughput, and allow for rework or removal. Two-part liquid gap fillers, while more robust and reliable, require manufacturers to mix the solution and maintain optimal consistency throughout application.
• Mechanical reliability: For applications exposed to shock, vibration, or temperature cycling, a cured two-part filler offers vertical and long-term reliability by resisting pump out.
• Chemical composition: Liquid gap fillers are available in both silicone and non-silicone-based versions. In optical or sensitive electronics applications, such as automotive cameras, non-silicone-based liquid gap fillers are preferred as they avoid the outgassing and oil bleed that can occur with silicone-based materials.

What are the benefits of Laird™ dispensable thermal gap fillers?

Laird offers a broad portfolio of liquid gap fillers, including one- and two-part solutions and silicone and non-silicone-based offerings, specifically designed for vertical stability and consistent dispensing. With Laird™ liquid gap filler solutions, engineers can specify the right product for their applications, including those with strict outgassing or oil bleed constraints (such as optical systems or camera modules) where silicone-based materials may not be suitable.

With extensive materials science and engineering expertise, Laird is a world leader in high-performance thermal interface materials. We offer fully automated application capabilities for thermal pads and dispensable thermal gap fillers, allowing customers to apply TIMs directly onto the component or board, ensuring precise placement and uniform coverage across complex topographies. See our short videos to learn more.

What are common applications for liquid gap fillers?

Liquid thermal interface materials are commonly used in datacom, automotive, industrial and aerospace and defense applications, where precise, efficient electronic cooling is essential.

Liquid gap fillers are used in data centers and AI systems, where powerful GPUs and CPUs are generating unprecedented levels of heat. These applications require maximum thermal conductivity along with reliability to ensure efficient electronics cooling and long-term device performance.

In automotive systems, liquid gap fillers are ideal for ADAS, automotive lighting and power converting unit applications as they can maintain mechanical integrity while withstanding shock and vibrations.

Non-silicone-based solutions are common in defense applications, such as drones and satellites, where manufacturers must avoid oil bleed and other challenges that can cause system failure.

These dispensable products are also ideal for high-volume production and automated application. For example, liquid gap fillers are used in consumer electronics, such as laptops and gaming devices, to enable thermal transfer in tightly packed designs.

Download our Thermal Interface Solutions brochure to learn more about our portfolio of liquid gap fillers and other TIMs.