Metallic soft magnetic inductors play a crucial role in the power management systems of AI chips. Due to their efficient power conversion capabilities and exceptional stability, they are irreplaceable in supporting high-speed, low-loss computations in AI chips.
With the continuous advancement of AI technology and the growing demand for more efficient and compact hardware solutions, metallic soft magnetic inductors are expected to play an increasingly significant role in the AI industry, driving the future development of AI chips.
What is an Inductor?
An inductor is a component that converts electrical energy into magnetic energy. It is responsible for functions such as signal selection, noise filtering, current stabilization, and electromagnetic shielding in servers. Traditional inductors use ferrite as a magnetic core, which has a relatively low saturation current, is bulky, and suffers from higher losses, making it increasingly inadequate for the miniaturization of power modules and the increase in current demand.
What Are Metallic Soft Magnetic Inductors?
Metallic soft magnetic inductors adopt a new integrated molding process. The pre-formed tightly wound hollow coils are embedded in magnetic powder and pressed into a specific shape using molds, resulting in a unique structure. This type of inductor replaces the traditional winding and core structure, achieving integration between the inductor coil and the base. Compared to traditional ferrite inductors, metal soft magnetic chip inductors have many advantages.
Advantages of Metallic Soft Magnetic Inductors
| Miniaturization: The integrated design significantly reduces the size of the inductor. For the same inductance value, the volume of an integrated molding inductor is only about 20% of a conventional inductor. Additionally, the integrated molding process allows for the simultaneous molding of multiple coils, achieving the integration of several inductors and further reducing the space occupied by the product. In the future, metallic soft magnetic inductors are expected to become the mainstream inductor solution for high-power AI chips. Currently, Nvidia’s H100 uses metal soft magnetic chip inductors.
| High Current Capacity: Compared to traditional ferrite materials, metal soft magnetic materials perform better in high-power and high-frequency scenarios. They have a higher saturation flux density (Bs value) and better temperature stability, allowing them to withstand higher currents. The saturation flux density of metal soft magnetic materials is more than twice that of ferrite. Although traditional ferrite chip inductors have low losses, their low Bs value (0.3-0.5T) and poor temperature stability make them less suitable for applications where the chip power exceeds 300W. Notably, AI chips are expected to exceed 700W in power in the future.
| Voltage Management: AI chips (such as GPUs, TPUs, NPUs, etc.) require a fast and stable voltage supply when processing complex computational tasks. Due to the close integration of the inductor coil and the magnetic core, metallic soft magnetic inductors can fully leverage magnetic permeability to respond more quickly to current changes, providing a more stable power supply. Especially in DC-DC converters and voltage regulator circuits, metallic soft magnetic inductors can effectively smooth out current fluctuations and prevent damage to chips from voltage instability.
Core Materials for Metallic Soft Magnetic Inductors
The core material of metallic soft magnetic inductors is metal soft magnetic powder, and its formulation determines the key parameters of the integrated molding inductor. By adding different elements, the performance can be optimized to meet specific requirements.
For example, adding silicon can reduce coercivity and increase resistivity, thus reducing losses; chromium can improve rust resistance and thermal stability; elements such as boron, niobium, chromium, and copper can promote the formation of amorphous and nanocrystalline materials. However, adding non-ferromagnetic elements can reduce the saturation magnetic induction strength, affecting the DC bias characteristics of the inductor.
Therefore, the powder formulation needs to be adjusted based on actual requirements. Currently, the main types of metal powder used in integrated molding inductors are carbonyl iron powder, iron-silicon-chromium alloy powder, and amorphous and nanocrystalline powders.
| Carbonyl Iron Powder: Carbonyl iron powder is one of the main raw materials for integrated inductors. It is produced by thermally decomposing iron pentacarbonyl Fe(CO)5, resulting in a hard powder with an onion-like structure. After high-temperature annealing to eliminate this structure, it becomes the soft powder needed for integrated molding inductors. Carbonyl iron powder has a high saturation magnetic induction (2.2T), making it ideal for applications that require high current handling. However, it has drawbacks such as low permeability and poor corrosion resistance, which can be addressed through post-processing like coating to improve salt spray and humidity resistance, though this increases manufacturing and environmental costs.
| Iron-Silicon-Chromium Alloy: Adding chromium to iron-silicon enhances the formation of Cr2O3 films, improving rust resistance and aging resistance. It also offers higher saturation flux density (usually 1.3-1.5T), high magnetic permeability, and low cost. Iron-silicon-chromium powders are produced through gas atomization and water atomization.
The gas atomization process uses high-speed airflow to impact the molten metal, breaking it into fine droplets that quickly solidify in the air, producing larger powder particles with a spherical shape. Water atomization produces smaller powder particles and is more cost-effective and environmentally friendly, though the powder may contain more oxygen and the spherical shape may be less uniform.
| Nanocrystalline Materials: Nanocrystalline materials offer higher resistivity, lower coercivity, and reduced hysteresis and eddy current losses, making them an important development direction for soft magnetic materials in integrated molding inductors. The most advanced amorphous powder preparation process is the rotary water atomization method, where high-pressure gas and rotating water streams rapidly break up the molten metal and accelerate cooling, forming amorphous materials. This process helps achieve higher saturation flux density for nanocrystalline materials.
Magnets Manufacturer
At Tengye, we’re thrilled to be early participants in your new projects. Our passion for magnets extends from material selection and design optimization to providing magnetic solutions. We hope to bring our knowledge and experience to the forefront by actively engaging in your upcoming projects. Work with our magnet experts to get the right magnet solution.
Image Source: Eepower & Iqsdirectory & Sciencekitstore & Americancarbonyl & Tdk & Usiglobal
