Competition is Heating Up in Thermal Interface Applications
Dec 16, 2019 Dr Richard Collins
Thermal interface materials (TIM) play a crucial role in numerous sectors, from lithium-ion batteries to 5G base stations, LEDs, consumer electronics and more. Heat dissipation is often on the of the limiting factors as many industries look to increase power and reduce the size.
Efficiently and uniformly transferring the heat generated from a device to a heat sink is typically aided by some form of interface material. TIM can take numerous forms (and names), from gap pads/fillers to conductive adhesives, thermal greases, and beyond. There are a variety of property considerations for a TIM given its specific applications this includes the adhesiveness, viscosity, coefficient of thermal expansion (CTE), bond line thickness, reworkability, and longevity. However, the most significant is the through-plane conductivity and the thermal contact resistance (the interface of the interface material).
IDTechEx has conducted an extensive analysis of this industry and have a leading market report on the industry: "Thermal Interface Materials 2020-2030: Forecasts, Technologies, Opportunities". This includes a detailed review of numerous industries and a review of the key players and material considerations.
Enhanced through-plane conductivity is becoming a key market pull in numerous sectors. Traditional materials and designs are not providing sufficient performance which opens the way for new material adoption and market entrants. For many industries this is progressing to above 10 W/mk, but for certain industries the key will be getting far beyond 25 W/mk.
The incumbent materials, such as ceramic filled silicone resins, still have markets to expand into (the most notable of which being lithium-ion batteries for electric vehicles) but are also under threat in more demanding areas. A previous article discussed the diversifying and growing markets.
This article will highlight some of the advanced materials being explored or adopted. In addition, it is important to consider routes to manipulating the alignment of conductive fillers. Alignment, particularly for anisotropic additives, can either provide a cost saving by using less material for same performance or improve the performance for the same filler content. This should also be considered in conjunction with the mechanical performance the matrix material provides. Achieving alignment can be done in multiple routes: mechanical, magnetic, electrical, dielectrophoresis, or in how the conductive fillers are grown.
Many are turning to advanced carbon for higher conductivity either as a conductive filler in a polymer matrix or standalone. This includes graphite, pitch-based carbon fiber, carbon nanotubes, and graphene.
As shown in the figure below, achieving vertical alignment gives the potential for high conductivity up to ca. 80 W/mk.
One of the most notable examples is the adoption of carbon fiber in the Samsung Galaxy Note9. IDTechEx has been informed that carbon fiber based TIM is also in use for power electronic devices in electric vehicles, a variety of military applications, high performance computing and more.
Graphite through to graphene as sheets, pastes or vertically aligned in pads have all received a significant amount of attention. All report significant conductivity improvements and show current and future promise in LEDs, consumer electronics, base stations and more.
Carbon nanotubes have been known since the early 1990s and have been explored as a conductive filler, but more notable is the extensive research in vertically aligned forests/arrays (VACNT). There are still notable challenges, from how the VACNT are transferred after growth through to how they achieve uniform contact resistance. However, significant collaborations and announcements from many of the leading players in China and Japan indicate that this a promising future area.
Figure 1: Benchmarking study of different carbon materials used as TIM in different forms. Source: "Thermal Interface Materials 2020-2030: Forecasts, Technologies, Opportunities"
One of the challenges of using advanced carbons is that they are electrically conductive; this means the device must be designed accordingly. Ceramics are preferred for this amongst other reasons. There are trends to more spherical or flake like particles where appropriate, but concerning emerging material there is more interest around boron nitride nanostructures. Boron nitride nanotubes (BNNT) or nanosheets (BNNS) are both starting to become commercial.
BNNTs have a wide variation in property and cost with still a limited number of players, but many are progressing from the lab to pilot plants and even full-scale production. Most cite TIM as a key target market with already some promising results and interest from significant industries.
Through extensive primary interviews and detailed analysis. The market report provides a view of all these advanced materials as well as incumbents such as phase change materials (PCM), thermal greases and more. The report gives 50 forecast lines on key sectors, providing a comprehensive overview and outlook for this industry.