High Performance Thermal Fillers for Electronic Cooling

Thermal management represents an increasingly important role in electronics manufacturing, performance and reliability.  The single most frequent failure mode of electronic devices is heat. The power and heat generation in electronic systems has increased with technological advancement, requiring thermal management solutions at several levels of system design. Boron nitride powders are high performance thermal fillers that can bring enhanced thermal performance to polymer composites both in the board, such as in copper clad laminates, and on the board, in thermal interface materials. 
boron nitride electronics thermal management
In The Board

Printed circuit boards (PCBs) have become the standard in electronics circuitry. They are made by creating copper traces on electrically insulating backing, often referred to as the dielectric, and building up layers to create compact but complex circuits. While ceramic fillers have traditionally been used to adjust mechanical and dielectric properties, the thermal performance of these assemblies are becoming more important. Boron nitride fillers bring unique value to PCBs as both thermal and low loss fillers, with the added benefit of having low density & abrasion compared to alternative fillers.

Rigid PCB
Flex PCB
rigid printed circuit board pcb
flexible cable circuit
Rigid PCBs are what most people think of when they imagine a circuit board. As indicated by the name, circuit traces are created on stiff, typically glass-reinforced layers that create a rigid assembly to which components are attached. Copper clad laminates (CCLs) and prepreg, which are the base materials used to lay up a board, benefit from thermal or dielectric fillers like boron nitride.   
Flex PCBs are a newer technology that are designed with flexible dielectric material, often polyimide, to allow for even more compact designs that can better dissipate heat and withstand vibrations. Fillers like BN are still used here, often as part of the flexible copper clad laminate (FCCL) and the bondply or coverlay adhesives. 

Rigid-Flex PCBs, which are, as their name indicates, a combination of both rigid and flex PCBs, are also becoming a popular solution in electronics. While there are pros and cons to each type of PCB, boron nitride fillers can bring value for providing improved thermal performance while maintaining low loss dielectric properties.



On The Board

Thermal interface materials (TIMs) are used to enhance the heat transfer between heat generating components, like the computer processing unit (CPU), and heat sinks. They are typically silicone-based, but the type varies based on the dimensional and pressure constraints. 

  • Thermal greases and gels - one of the original TIM types, greases tend to be used in thin bond line thickness applications. They are fluid at room temperature, resulting in excellent spreading & filling, but can lead to pump out over time. 
  • Gap Fillers - available as cured pads or as dispensible systems, Saint-Gobain's BN Spherical Agglomerates are particularly well suited to these TIMs. These are used where the TIM needs to span spaces up to a few millimeters. Dispensibles have gained popularity in areas like automotive electronics, where automation is key.
  • Phase Change Materials - designed to take advantage of the benefits of gels and greases without the drawbacks, phase change materials are solids at room temperature for easy application but convert to liquid at temperature for optimal thermal transfer.
  • Adhesive Tapes & Films - doubling as a fastener, adhesive TIMs are ideal for use for pressure-sensitive components or where mechanical hardware is too bulky.
  • Potting Compounds - potting compounds are liquid when applied and cure in place, typically used to encapsulate sensitive components. These are often epoxy-based.



Considerations for BN Thermal Fillers
Size and Size Distribution
Different particle sizes and size distributions offer customers the ability to optimize the packing of thermal fillers in the matrix. When it comes to BN, our agglomerate grades provide improved flowability and typically improve thermal conductivity by providing larger contact area for heat flow. Key process parameters that can help determine the optimal size and particle morphology are (1) bond line or laminate thickness and (2) intensity of mixing forces.
Saint-Gobain offers a selection of shapes utilizing its expertise in manufacturing BN. High density agglomerates have a more irregular and random shape, whereas spherical agglomerates offer uniquely tight particle size distributions, and therefore better packing density. Platelets are best suited for high shear mixing operations, applications where heat spreading is desired, or where fine particle sizes are required.
Density is an important factor when working with BN agglomerates. Higher density improves the thermal performance by increasing the number of contact points within the agglomerate, providing an efficient heat transfer path. It also yields stronger agglomerates, improving the energy tolerance of BN agglomerates in maintaining their morphology.
Saint-Gobain can tune the purity and composition of BN agglomerated products to meet customer demands. Our standard suite of agglomerated powders offers over 99.5% purity which allows for the highest dielectric properties for increased breakdown voltage and signal strength in the final products.
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