Soft magnetic cores play a crucial role in RF applications. Traditionally, materials like silicon steel, ferrite, and amorphous cores have dominated the solutions available. However, a promising alternative has emerged in the form of nanocrystalline cores, vs these conventional soft magnetic cores, offering a paradigm shift in performance and efficiency.

Nanocrystalline Core Basics and Properties

Nanocrystalline materials are characterized by extremely small grain sizes, typically in the nanometer range. These materials boast remarkable properties compared to conventional soft magnetic cores. Exhibiting significantly lower losses with a staggering 1000 times reduction compared to Silicon Iron (SiFe) cores, nanocrystalline cores feature high saturation induction (1.2T), broadband frequency range, and can achieve very high inductances.

What are Some Fabrication Techniques of Nanomaterials?

Fabrication of nanocrystalline materials involves a rapid solidification process where raw materials are heated to over 1000 degrees and sprayed onto a water-cooled wheel to lower temperatures in a fraction of a second.

The resulting thin strip is then processed into a structured nanocrystalline tape via heat treatment. From there, it a protective toroidal core with an epoxy coating or plastic housing is applied to prevent breakage.

Why Do Materials Change Their Behavior at Nano-Level?

At the nano-level, nanocrystalline materials, primarily composed of iron and silicon, also include minerals like boron. The additional minerals form around each grain to yield technical advantages such as reduced eddy currents and minimal losses. Moreover, the manufacturing process allows for the precise control of grain sizes, leveraging nanometer-sized scales, to optimize performance in various applications. 

Nanocrystalline Core Features

• Adjustability of very high permeabilities (about 20,000 – 200,000μ)
• Saturation flux density Bs = 1.2T
• Vanishing saturation magnetostriction <5ppm
• Temperature resistance up to 150°C
• Excellent HF/RF attenuation

Nanocrystalline Core Markets and Applications

• All RF filters in Industry
• Automotive
• Aviation
• Medical Technology
• Special Applications

What Are Soft Magnetic Cores?

Soft magnetic cores serve as the backbone of various electrical and electronic systems, enabling the efficient manipulation of magnetic fields. Understanding the fundamentals and applications of these cores is essential for optimizing performance across a wide range of RF devices.

Why Use Soft Magnetic Materials in Transformers?

Grain-oriented silicon iron steel, a common soft magnetic material, boasts a high saturation induction of up to 2 Tesla. However, its usage is limited to frequencies up to 1kHz due to its significant frequency-dependent losses. Soft magnetic materials, including nanocrystalline cores, offer lower core losses and comparable saturation inductions (ranging from 1.2T-1.5T). Notably, the low magnetostriction that nanocrystalline materials exhibit allow for higher frequency ranges, such as 200 kHz in transformers.

What is an Inductive Absorber?

An inductive absorber utilizes a soft magnetic nanocrystalline toroidal core to absorb the high-frequency component of an interference current, converting it into thermal energy, this process effectively dampens harmful interference peaks, contributing to improved system stability and performance.

• Soft magnetic, nanocrystalline toroidal core that absorbs the high-frequency part of an interference current and converts it into thermal energy. This dissipates and thus smooths down the harmful peaks of the interference current.

Top Nanocrystalline Advantages

Nanocrystalline cores represent a technological advancement in soft magnetic core technologies, offering unparalleled performance and versatility across a diverse range of applications. Their unique properties make them indispensable in modern electronic systems, ensuring optimal efficiency and reliability. Nanocrystalline core inductors offer a wide range of benefits, including:

• Compact sizing
• Extensive permeability (up to 100.000µ @10kHz)
• Lightweight construction
• High dampening at low frequencies
• Low copper losses
• Low magnetostriction
• Linear behavior
• Thin hysteresis loop
• Adaptability to different currents
• Stable inductance across frequencies
• Constant temperature of 120-180°C (only limited by plastic cover)
• Curie temperature of about 570°C
• Minimal temperature dependence
• Low Q-Factor
• High linearity of magnetization curve

Overview and Comparison of Traditional Soft Magnetic Materials

In comparison to one another, each type of soft magnetic material offers distinct advantages and considerations.

1.     Silicon Steel (Electrical Steel)

Application: Commonly utilized in transformers and electric motors.

Advantages: Silicon steel boasts very low losses and high permeability, making it ideal for efficient energy transfer.

Comparison: Compared to silicon steel, nanocrystalline material offers significantly lower losses and higher permeability. This enables the construction of smaller and lighter transformers, simplifying cooling mechanisms and enhancing overall efficiency.

2.     Ferrite Cores

Application: Widely employed in high-frequency applications.

Advantages: Ferrite cores offer good performance at high frequencies with low losses.

Comparison: Nanocrystalline material surpasses ferrite in terms of permeability, resulting in smaller component sizes. Additionally, nanocrystalline cores exhibit lower core and copper losses, allowing for open designs and efficient air cooling. Moreover, their temperature stability eliminates the need for extensive temperature extrapolation during the design phase.

3.     Amorphous Cores

Application: Utilized in various applications requiring high efficiency and low losses.

Advantages: Amorphous cores offer high saturation induction and low losses, contributing to energy-efficient operation.

Comparison: While nanocrystalline material may have a slightly lower saturation induction compared to amorphous cores, its adjustable permeability and exceptionally low losses provide a significant advantage. Nanocrystalline cores also exhibit minimal noise development, making them preferable in noise-sensitive applications.

Loss Analysis

Understanding and mitigating core losses is critical for optimizing the performance and efficiency of magnetic cores, particularly in high-frequency applications where losses can be significant. Hysteresis losses result from rapid magnetic switching within the core material. These losses can be mitigated by utilizing materials with smaller hysteresis loop areas. While laminated silicon steel exhibits a small hysteresis area, it also suffers from very high losses.

In contrast, nanocrystalline material, with its tape technology comprising much thinner layers, effectively reduces eddy currents and hysteresis losses. The result is a significantly smaller hysteresis range and an impressive reduction of losses by a factor of 1000. Moreover, the high permeability of nanocrystalline material enables the creation of smaller core sizes, further enhancing efficiency.

Minimizing Core Losses in Transformers

To minimize core losses in transformers, it is essential to utilize soft magnetic materials such as nanocrystalline or amorphous ribbon technology. These advanced materials offer lower losses compared to traditional options, leading to improved overall efficiency in transformer operation.

Eddy Current Loss

At elevated frequencies, eddy current losses become a significant consideration. Nanocrystalline cores exhibit reduced eddy current losses compared to conventional cores, contributing to improved performance in high-frequency applications.

By contrast, conventional cores, such as laminated silicon steel, may experience higher losses due to their larger hysteresis loop areas and susceptibility to eddy currents at elevated frequencies. Therefore, the adoption of nanocrystalline cores presents a compelling solution for minimizing losses and maximizing efficiency in modern magnetic core designs.

Nanocrystalline Use Cases

Nanocrystalline cores find applications and use cases across a broad range of electromagnetic devices. In power transformer cores, nanocrystalline solutions are increasingly favored for their high magnetic permeability and low losses.

Similarly, in filtercores used for noise suppression and filtering in electronic circuits, nanocrystalline cores boast high saturation magnetization and low core loss. Additionally, their high permeability allows for a significant reduction in size compared to alternatives. With the ability to exhibit up to ten times higher permeability than ferrite cores, nanocrystalline materials contribute to a substantial decrease in core size without compromising efficiency.

Soft magnetic pearls, crafted from nanocrystalline materials, exhibit excellent AC magnetic characteristics, making them well-suited for applications where minimizing core loss is critical.

In common mode chokes (CMCs), which suppress electromagnetic interference (EMI), nanocrystalline cores play a vital role in minimizing energy losses and enhancing overall performance.

Additionally, nanocrystalline cores feature prominently in rolls and cut cores used in various electromagnetic applications, including inductors and transformers.

Design Challenges and Considerations

When designing with nanocrystalline cores, careful consideration of mechanical properties such as yield strength, ductility, and fatigue resistance is essential, ensuring the core material withstands mechanical stress without permanent deformation. Moreover, attention to magnetic/electrical properties, including saturation magnetization, resistivity, and thermal conductivity, is crucial for optimizing performance and minimizing losses. While nanocrystalline cores offer unique advantages, proper material selection and design optimization are paramount for successful applications.

Cost and Manufacturing

The adoption of nanocrystalline cores in place of conventional cores necessitates an evaluation of both cost implications and manufacturing considerations. Comparing the cost of both nanocrystalline cores and their conventional counterparts is important if developers want to make well-informed decisions.

While nanocrystalline cores may have an initially higher up-front cost, their superior performance and efficiency often justify the up-front investment. Factors such as reduced losses, smaller core sizes, and enhanced energy efficiency contribute to long-term cost savings and improved system performance.

When integrating nanocrystalline cores into existing manufacturing processes, several considerations come into play:

1. Compatibility with Existing Processes (Short Term)

Manufacturers must assess the compatibility of nanocrystalline core production with their current manufacturing processes. This involves evaluating whether existing equipment and procedures can accommodate the fabrication of nanocrystalline cores without significant disruption or reconfiguration.

2. Modifications to Manufacturing Processes (Intermediate Term)

In the intermediate term, manufacturers may need to make modifications to their manufacturing processes to fully optimize the production of nanocrystalline cores. This could involve adjusting parameters such as temperature, pressure, or production line setup to achieve optimal results with nanocrystalline materials.

3. Major Process Overhaul (Long Term)

In the long term, a major process overhaul may be necessary to fully integrate nanocrystalline core production into existing manufacturing facilities. This could involve investing in new equipment, retraining staff, or redesigning production layouts to accommodate the unique properties and fabrication requirements of nanocrystalline materials.

Overall, while there may be initial challenges in adopting nanocrystalline cores in terms of cost and manufacturing processes, the long-term benefits in terms of improved performance, efficiency, and cost savings justify the investment and effort required for their implementation.

Nanocrystalline Solutions Available

In conclusion, nanocrystalline cores bring many advantages over conventional soft magnetic cores. The advent of nanocrystalline cores represents a significant advancement in soft magnetic core technology, offering unparalleled performance, efficiency, and versatility across a diverse range of applications.

If you’re a developer seeking industry-leading core solutions, you can learn more about nanocrystalline solutions from MRC Components, an RFMW Company. For ordering information, contact our expert sales team or view MRC Components’ full nanocrystalline portfolio.