Thermal Management – Ƶۻ /news-and-events/applications/thermal-management Mon, 20 Jan 2025 20:52:40 +0000 en-US hourly 1 https://wordpress.org/?v=6.8.1 /wp-content/uploads/2024/12/momentive-favicon-150x150.png Thermal Management – Ƶۻ /news-and-events/applications/thermal-management 32 32 Thermal Fillers Enable Next-Gen Thermal Management for Electric Vehicles /news/thermal-fillers-enable-next-gen-thermal-management-for-electric-vehicles Thu, 02 Jan 2025 17:24:26 +0000 /news/thermal-fillers-enable-next-gen-thermal-management-for-electric-vehicles-2025-eng/
High power high frequency transmission devices are being used extensively to enable faster data transmission and smarter function in many applications, such as automotive radar sensors, 5G telecommunication devices and infrastructures.
Higherpower,faster data transmission,lighter weight,andsmaller sizearedesiredbytoday’sand next generation’s high performance high frequency devices. These demands lead to increasing concerns about the dissipation of significantly increased heat and the prevention of transmission loss.
Thermally conductive dielectric polymer composites with high dielectric strength and low dielectric constant were widely used as thermal management materials in these electronic devices to enable fast heat dissipation while achieving excellent electrical insulation and low signal loss at high frequency.
As these dielectric polymers are naturally thermal insulative, ceramic thermal fillers must be added to the polymer matrix during the compounding process to improve bulk thermal conductivity while maintaining electric resistance.Dielectric properties ofceramicthermal fillers play a critical role inmaintainingthe highdielectric strength and low dielectric constant of filled polymer composites.

As illustrated in the table below, among all the typical ceramic thermal fillers used in developing dielectric thermally conductive polymer composites, high purity crystalline hexagonal boron nitride (h-BN) and silica are the only two ceramic fillers with dielectric constants <4. Therefore, both have been popular as thermal fillers in polymer based thermal management materials for high frequency applications. The enhanced performance (power) and higher integration density of next generation high frequency devices inevitably drive up the power density which results in substantially increased heat to be dissipated within shrinking space. High purity h-BN powder, which has the highest thermal conductivity, highest electric resistivity, and lowest hardness, now has been the most attractive thermal fillers for high performance thermal management materials used in high frequency environment.

TYPICAL PROPERTIES BN AIN AI2O3 SiO2 ZnO
Thermal Conductivty (W/m-K)
300*
260
30
1.4
54
Specific Heat (J/kg-K @ 25°C)
800
730
800
690
520
Theoretical Density (g/cc)
2.2
3.2
4.0
2.2
5.6
Dielectric Constant
3.9
8.8
9.7
3.8
9.9
Volume Resistivity (ohm-cm)
1015
1014
1014
1014
1014
Coefficient of Thermal Expansion (ppm/K)
<1
4.4
6.7
<1
<1
Mohs Hardness
2
7
9
6
5

* Thermal conductivity in crystal plane

]]> Thermal Management for Electric Vehicles /news/thermal-management-for-electric-vehicles Thu, 02 Jan 2025 17:24:46 +0000 /news/thermal-management-for-electric-vehicles-2025-eng/

improving thermal conductivity with Boron Nitride

Thermal management plays a vital role in maximizing the safety, performance, efficiency and overall longevity of electric vehicles (EV). Multiple components in EVs, such as power electronics, e-motors, and batteries require adequate thermal management as the industry is pushing for higher power, higher voltage, faster data transmission, lighter weight, and smaller size. Thermally conductive, but electrically insulating thermal interface materials (TIMs) with high dielectric strength and low dielectric constant are needed to meet these thermal management challenges. Since TIMs made of dielectric polymers are naturally thermally insulative, ceramic fillers need to be added to improve thermal conductivity while maintaining electrical resistance. Superior thermal and dielectric properties of the ceramic thermal fillers are key to the success of thermal management materials.

Applications in Electric Vehicles

  • Tims for power electronic components such as Inverters/converters
  • Pcb laminates for ev electronics
  • Thermal management materials for e-motors
  • Tims for battery assemblies

Boron Nitride Meets The Challenge

Thermal interface materials loaded with hexagonal Boron Nitride (BN) meet the challenges of offering high thermal conductivity (TC), high dielectric breakdown strength (DBS), low dielectric constant (Dk), low coefficient of thermal expansion (CTE), and low density to EV systems.

Ceramic thermal filler properties

TYPICAL PROPERTIES BN AIN AI2O3 SiO2 ZnO
Thermal Conductivty (W/m-K)
300*
260
30
1.4
54
Specific Heat (J/kg-K @ 25°C)
800
730
800
690
520
Theoretical Density (g/cc)
2.2
3.2
4.0
2.2
5.6
Dielectric Constant
3.9
8.8
9.7
3.8
9.9
Volume Resistivity (ohm-cm)
1015
1014
1014
1014
1014
Coefficient of Thermal Expansion (ppm/K)
<1
4.4
6.7
<1
<1
Mohs Hardness
2
7
9
6
5

Advantages of BN Fillers

  • HIGH THERMAL CONDUCTIVITY
  • HIGH BREAKDOWN VOLTAGE
  • LOW DIELECTRIC CONSTANT
  • LIGHT WEIGHT
  • MECHANICAL COMPLIANCE
  • THERMALLY STABLE
  • CHEMICALLY INERT
  • WHITE COLOR

High Thermal Conductivity

Boron Nitride has one of the highest thermal conductivities and electrical insulative properties of ceramic fillers. This, along with low dielectric loss characteristics, makes BN a highly desired filler in epoxies, silicones, and PU systems. Compared to other ceramic fillers such as spherical alumina, BN enables superior thermal and electrical performance, capable of providing more than 2x thermal conductivity and improved electrical breakdown properties. This is achieved with less volume loading compared to other fillers, and less impact to mechanical properties such as hardness. Higher thermal conductivities enable higher power through the circuits.

The inherent softness of BN as a filler ensures good contact between the component, heat sink and the TIM thereby minimizing contact resistances.

CHART 1: Thermal conductivity measured in silicone resin system, via HotDisk® method. Performances in other resin systems would be similar.

High Dielectric Breakdown Strength

Package and board level thermal management, higher thermal conductivities coupled with thinner bond lines of the dielectric layers enables lower thermal resistance. With increasing voltages in power electronics such as in EVs, maximizing electrical isolation in these thin dielectric layers becomes crucial. BN has one of the highest breakdown strengths (Eb) among fillers, enabling lower bond line thicknesses compared to others. The breakdown strength of BN filled system compares favorably with spherical alumina filled system at equivalent volume loadings.

CHART 2: Breakdown strength measured in an epoxy resin system. Relative performances in other resin systems would be similar.

High-quality signal transmission

For high-speed data transmission and high-voltage, high frequency applications related to EVs, dielectric constant impacts the signal integrity and impedance. Lower Dk materials are preferred for high-speed signals to reduce losses, signal distortion, and minimize cross talk between closely spaced traces and vias.

Boron Nitride has one of the lowest Dk of thermal fillers. Coupled with its very low dielectric loss properties, Df, Boron Nitride fillers enable low loss and excellent signal transmission/ low attenuation at high frequencies and for high voltage applications.

These combined properties of Boron Nitride make it a very attractive material for use in thermal management materials in power electronics, electric motors, battery assemblies, and high frequency signal processing components in EV applications.

CHART 4:Dielectric properties measured in a silicone resin system. Relative performances in other resin systems would be similar.

Our experts are ready

Ƶۻ is a leading supplier globally for high quality Boron Nitride products with a broad portfolio of more than 50 grades. Our MT Therm series of Boron Nitride powders are tailored to thermal management needs of EV applications. Our application development engineering team can provide detailed technical support to help customers select the best BN products for their specific requirements.

]]> Boron Nitride for Thermal Management /news/boron-nitride-for-thermal-management Thu, 02 Jan 2025 17:25:12 +0000 /news/boron-nitride-for-thermal-management-2025-eng/

The challenge of heat

Heat is one of the major enemies of today’s electronic components and assemblies. It shortens service life and threatens reliability. The challenge grows greater as designers and fabricators are asked to produce assemblies that are smaller and faster, making the need for heat dissipation greater than ever before.

Hexagonal Boron Nitride (BN) Fillers solve the problem. When used in a variety of polymeric materials, BN’s heat dissipating capability helps extend the service life and enhance the reliability of electronic components and assemblies.

Comparing the thermal conductivity of BN fillers to other fillers such as fused silica, aluminum oxide, and aluminum nitride, BN outperforms these materials when used as a filler in polymeric materials. Some BN-polymer materials have achieved thermal conductivity levels as high as 15 w/mK.

BN fillers meet today’s electronic fabrication needs in other ways, too. They are excellent insulators with a dielectric constant of 3.9. That is especially important in today’s thermal management designs in EV and 5G telecommunication. BN fillers are easy to work with because they are made from a soft, lubricious material that provides good flow properties at high loadings. This chemically inert material resists moisture and provides high volume resistivity (above 10 15 ohm-cm).

Thermal Interface Materials Solutions

Various material solutions are available to fulfill these roles, each with its own advantages and disadvantages. Let’s explore some common options:

Adhesives

Adhesive-based TIMs provide excellent mechanical stability and can be used to bond components together securely. They offer good thermal conductivity but may have limitations in terms of re-workability or ease of application.

Greases:

Thermal greases are widely used due to their high thermal conductivity and ease of application. They fill microscopic gaps between surfaces, enhancing thermal transfer efficiency. However, they may require periodic reapplication due to drying out over time.

Gels:

Thermal gels provide good conformability and can fill larger gaps effectively. They offer moderate thermal conductivity but may exhibit higher viscosity, making them more suitable for specific applications where gap filling is critical.

Phase Change Materials (PCMs)

PCMs undergo a phase transition when exposed to temperature changes, allowing them to absorb or release large amounts of energy during operation. This property makes them ideal for applications with varying temperature conditions; however, their relatively low thermal conductivity may limit their use in high-power applications.

Pads

Thermal pads are pre-formed sheets made of materials like silicone or graphite. They offer ease of installation and reworkability, making them suitable for applications where frequent maintenance or component replacement is expected. However, their thermal conductivity may be lower compared to other TIM options.

Exploring Thermal Interface Materials for CHip Devices

In the world of chip devices, the efficient management of heat is crucial for optimal performance and reliability. Figure 1 illustrates a cross-sectional view of a flip chip device with a heat spreader and heat sink attached, highlighting the importance of thermal interface materials (TIMs) in this setup.

The TIM-2 layer acts as an intermediary between the heat spreader and the heat sink, facilitating efficient heat transfer to dissipate it into the surrounding environment.

The TIM-1 layer serves as an interface between the chip and the heat spreader. It plays a vital role in transferring heat from the chip to the spreader, ensuring effective thermal dissipation.

At its core, a Printed Circuit Board (PCB) serves as a platform that provides channels and pathways for electricity and signals to flow within an electronic device. These pathways connect various components such as resistors, capacitors, transistors, and integrated circuits, allowing them to communicate and work together harmoniously.

Die attach plays a vital role in establishing electrical connections between the die and the substrate. It ensures proper signal transmission and power distribution within the device. Additionally, it facilitates efficient heat dissipation from the die to prevent overheating and maintain optimal performance.

Zoom in on image

Test data. Actual data may vary.

]]> High Performance Lightweight Ceramics for Critical Thermal Management in Electronic Devices /news/high-performance-lightweight-ceramics-for-critical-thermal-management-in-electronic-devices Thu, 02 Jan 2025 17:25:24 +0000 /news/high-performance-lightweight-ceramics-for-critical-thermal-management-in-electronic-devices-2025-eng/

BEI XIANG , Ph.D.

Senior Application Development Engineer

Ƶۻ

Strongsville, OH 44149

Summary

Thermal management materials loaded with boron nitride (BN) match the challenge of offering thermal conductivity, electrical insulation, low coefficient of thermal expansion and low density. As electronic devices continue to shrink in size while simultaneously increasing power output, new materials are required to dissipate heat more efficiently. Electronic devices used in telecommunications, electric vehicles, and LED lighting are just a few examples requiring innovation in thermal conductivity and electrical insulation. Ƶۻ produces several types of BN for varying needs in thermal management.

BN is one of the most attractive fillers for improving thermal conductivity while maintaining the electrical insulation of polymeric thermal management materials used in electronic devices. Agglomerate BN particles exhibit much better isotropic thermal performance than platelet BN powders. The impact of compounding conditions on the morphology of agglomerate BN, which is critical to the final composite thermal performance, is studied herein. It is demonstrated that the final thermal conductivity of polymer composites filled with the same percentage of agglomerate BN could have as much as 4x difference in thermal conductivity depending on compounding conditions.

Introduction

As more and higher power chips are incorporated into smaller size electronic devices used in electric vehicles, 5G telecommunication, LED lighting, etc., power density increases tremendously. In these electronic devices, heat generated within the diminished space must be dissipated more efficiently to help avoid heat buildup that could quickly throttle the device performance and possibly result in failure. The miniaturization of many mobile electronic devices makes active cooling more often than before not a feasible choice for thermal management design in current and future devices. The desire for an enhanced passive heat dissipation solution combined with the requirement for weight reduction of the whole package has forced thermal designers to look for innovative, high performance, lightweight thermally conductive materials to use in different components of the electronic devices, such as thermal interface materials (TIM), housing materials, heat sink fins, and heat spreaders [1].

Thermoset polymers, such as silicone and epoxy, have been extensively used for preparing thermal interface materials for decades. Because of the thermally insulative nature of polymers (thermal conductivity ~0.2 W/mK), ceramic fillers such as Al2O3, ZnO, etc. have been used for improving the thermal conductivity of polymer composites. However, the thermal performance criteria of TIM are increasingly demanding. TIM makers are facing greater challenges in achieving the thermal management requirements of today’s high performance electronic devices. h-BN is a superior thermal filler with the highest in-plane thermal conductivity (>300 W/mK) and lowest dielectric constant when compared to typical ceramic fillers found in polymer composites. However, the anisotropy in h-BN’s thermal conductivity greatly limits the thermal performance of the TIM made of BN-polymer composite in the direction needed. To solve this issue, agglomerate BN, whose particles are the random agglomeration of fine platelets, has been developed. Because of the random orientation of the platelets in the agglomerates, the thermal performance in all directions is very close if not equal. Significant improvement of all-direction thermal conductivity (TC) has been achieved for polymer TIM filled with agglomerate BN [2]. However, the optimal thermal and rheological performance are often not obtained by (new) users because of the lack of understanding on the compounding conditions impact on BN morphology, which directly influence the thermal and rheology performance of BN filled polymer composites. Therefore, a study was conducted on the correlation of compounding conditions and BN morphology with final polymer composites’ thermal performance.

Studies and Results

Impact of BN morphology on BN-polymer composite’s thermal performance

Ƶۻ h-BN powder can be categorized into two major morphologies – platelets and agglomerates. Among agglomerates, there are also agglomerates in irregular shape or close to spherical shape. Various sizes and shapes of platelet BN and agglomerated BN were compounded at specified levels (wt. or vol.%) in silicone resin with a crosslinker at 3500 rpm for 30 seconds in a SpeedMixer. The mixture was then cured in a compression mold to produce ~0.5-1.3mm thick pads for through-plane thermal conductivity measurement by Netzsch Laser Flash LFA447. A comparison of in-plane and through-plane TC of BN-silicone composites made with 40wt% platelet BN and spherical agglomerated BN is demonstrated in Figure 1 Spherical BN powder grades delivered higher & more isotropic thermal conductivity than platelet BN at the same loading level and compounding conditions.

Effect of compounding conditions on the through-plane thermal conductivity of BN-polymer composites

PTX60 is a special BN powder with particles close to spherical shape. These spherical shaped agglomerates provide the best isotropic thermal performance as shown in Figure 1. However, the agglomerate of the building platelets could be broken under high shear when aggressive compounding conditions are used in compounding process with polymers, leading to particle size reduction and the loss of spherical agglomeration. As shown in Figure 2, when compounding with silicone by SpeedMixer, different combinations of blending speed and time led to different levels of agglomerate breakdown. The morphology change resulted in a significant impact on final BN-silicone composite through-plane thermal conductivity. The final through-plane TC of the same formulation varies 4x between the lowest and highest values depending on the combination of blending RPM and blending duration. These results demonstrate the importance of choosing the right compounding conditions when processing agglomerated BN with polymers.

(a)

(a)

Test data and results. Actual results may vary.

Figure 1. (a) Platelet Vs Spherical agglomerate. (b) PTX60, PTX25, PT371, PT350 are agglomerate BN with different sizes and morphologies, while PT110 and PT120 are platelet BN.

(a)

(b)

Test data and results. Actual results may vary.

Figure 2. (a) Effect of mixing Speed & Time on BN agglomerate morphology. (b) Effect of mixing Speed & Time on through-plane thermal conductivity.

References

[1] Z. Carl, “Advances in composite materials for thermal management in electronic packaging’, JOM, June 1998, Volume 50, Issue6, pp 47–51.

[2] L. James, J. Peter, “Thermally conductive interface materials and methods of using the same”, U.S. Patent 5, 213,868 A, issued May 25, 1993.

]]> Ƶۻ’ high quality agglomerate h-BN powder delivers high performance in all directions /news/momentive-technologies-high-quality-agglomerate-h-bn-powder-delivers-high-performance-in-all-directions Thu, 02 Jan 2025 17:25:35 +0000 /news/momentive-technologies-high-quality-agglomerate-h-bn-powder-delivers-high-performance-in-all-directions-2025-eng/

improving thermal conductivity with Borone Nitride

Boron Nitride (BN) is one of the most attractive fillers for improving thermal conductivity while maintaining the electrical insulation of polymeric thermal management materials used in electronic devices. Thermal management materials loaded with Boron Nitride (BN) match the challenge of offering thermal conductivity, electrical insulation, low coefficient of thermal expansion, and low density. However, due to the anisotropic thermal transport in the laminar BN crystal structure, thermal management materials filled with platelet shape BN as thermal filler often have anisotropic thermal performance – one magnitude lower thermal conductivity in through-plane direction than in-plane direction. At the same loading in polymer thermal management materials, platelet BN particles lack the efficiency to form heat-conductive channels in a direction not aligned with the platelet orientation, typically caused by exposure to high shear in the compounding process.

As illustrated in the figure below, randomly oriented BN platelets composing the agglomerates can form more efficient heat conductive channels in all directions to enable high isotropic thermal performance in thermal management materials.

Ƶۻ (MT) have a large portfolio of high-quality BN powders for varying needs in thermal management. Besides different sizes of high-quality BN platelet powders, MT offers high thermal performance agglomerate BN powder grades with a variety of particle sizes, shapes, surface areas, etc. to enable highly isotropic thermal performance for thermal management materials, especially thermal interface materials with high thermal conductivity and good electrical insulation desired by today’s electronic, e-vehicle and high frequency telecommunication applications.

In MT’s high performance agglomerate BN powder portfolio, PTX series grades, benefiting from its spherical agglomerate shape, can enable users to achieve the best isotropic thermal performance in filled composites. As shown in the example below, in the thermal performance comparison between the spherical agglomerate BN powder grade PTX60 and platelet BN powder grade PT110 similar particle size, PTX60 enables almost identical excellent thermal conductivity in both in-plane and through-plane directions, while PT110 can be oriented during compounding process and exhibit very anisotropic thermal performance. Therefore, spherical agglomerate BN such as PTX60 has been the top choice for thermal management materials design requiring the best isotropic thermal performance.

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