Multi-phase power substrate, multi-phase power module, and method of manufacturing a power substrate

Abstract

The application discloses a multi-phase power substrate, a multi-phase power module and a preparation method of the power substrate, and aims at solving the technical problems of large space occupation, low heat dissipation efficiency and long current path of the existing multi-phase power module. The application provides a multi-phase power substrate, which comprises a substrate body, a first solder pad, a second solder pad, a circuit structure and a plurality of inductance units. The substrate body has a first surface and a second surface opposite in the thickness direction. The first solder pad is arranged on the first surface, and the second solder pad is arranged on the second surface. The circuit structure is arranged in the substrate body. The inductance unit comprises an input end, an output end and a conductor composed of part of the circuit structure. At least part of the output end extends to the first surface. The first solder pad, the second solder pad and the input end are sequentially electrically connected through the circuit structure. The application further provides a multi-phase power module comprising the multi-phase power substrate. The application further provides a preparation method for preparing the multi-phase power substrate.

Description

Technical Field

[0001] This invention relates to the field of circuit board technology, and in particular to multiphase power boards, multiphase power modules, and methods for preparing power boards. Background Technology

[0002] Multiphase DC-DC converters, with their advantages of high current output, low ripple, and high dynamic response, are widely used in high-power-density power supply scenarios such as servers, AI chips, and new energy vehicles. As the core energy storage component of a multiphase power supply, the performance and integration of the power inductor directly determine the overall size, efficiency, and reliability of the power module.

[0003] Currently, the industry's technical approaches to improving the integration of multiphase power supplies are mainly divided into three categories, each with its own limitations.

[0004] Category 1: Discrete Multiphase Power Supply Solution. This solution involves soldering multiple independent power inductors one by one onto an organic PCB substrate, connecting them to the respective phase output terminals of the power supply chip. While this solution boasts mature technology and high versatility, the numerous discrete inductors occupy a significant amount of PCB area, resulting in an excessively large power module. Furthermore, the one-to-one mounting assembly method is inefficient and costly. Additionally, the long horizontal traces between the inductors and the chip introduce significant parasitic resistance and inductance, leading to additional voltage drop losses and EMI issues.

[0005] The second category is power module solutions using encapsulated monolithic inductors. Multiple monolithic power inductors are encapsulated inside or on the surface of an organic substrate, and then integrated with the power chip within the same package. This solution saves some space compared to discrete inductors, but the extremely low thermal conductivity of the organic substrate makes it difficult to quickly dissipate the heat generated by the power inductors, resulting in excessive module temperature rise and limiting further increases in power density. Furthermore, the inductors and the chip still require horizontal traces on the organic substrate for connection, resulting in a relatively long current path and significant voltage drop losses. Additionally, some solutions using leadframe connections are prone to cracking at the solder joints after cyclic thermal shock, leading to increased contact resistance and reduced product reliability.

[0006] The third type: Magnetic laminate integrated multi-inductor array scheme. Multiple helical conductors are formed inside a single magnetic laminate (such as a ferrite laminate chip). Each helical conductor is connected in series through a via conductor to form an independent inductor coil, thus integrating multiple inductors within a single laminate chip for use in multi-phase DC-DC converters. For details, refer to Chinese invention patent application CN103608877A, entitled "Inductor Array Chip and DC-DC Converter." This scheme integrates multiple inductors into a single component, reducing the number of components and mounting steps compared to the above schemes. However, since the laminate chip itself is an independent component, it still needs to be mounted on a PCB substrate by soldering and then connected to the power chip via PCB wiring; the current path from each inductor to the chip is still relatively long, and parasitic parameters and conduction losses are not fundamentally resolved; furthermore, the internal space of the laminate chip is limited, and magnetic crosstalk exists between inductors when integrating multi-phase inductors, making phase-to-phase isolation design difficult. Summary of the Invention

[0007] To overcome the shortcomings of the prior art, this invention proposes a multiphase power substrate, a multiphase power module, and a method for fabricating the power substrate, in order to solve the technical problems of large space occupation, low heat dissipation efficiency, and long current path in the prior art for multiphase power modules.

[0008] To achieve the above technical objectives, the multiphase power substrate proposed in this invention includes: A substrate body formed by stacking multiple insulating magnetic dielectric layers along the thickness direction has a first surface and a second surface that are opposite to each other in the thickness direction. The first pad for connecting the PCB board is located on the first surface; A second pad for connecting the power chip is provided on the second surface; The circuit structure disposed within the substrate body consists of a vertical conduction structure and a horizontal conduction structure. The vertical conduction structure constitutes the portion of the circuit structure extending along the thickness direction, and the horizontal conduction structure constitutes the portion of the circuit structure extending along the layer direction of the magnetic dielectric layer. A plurality of inductor units, each inductor unit including an input terminal, an output terminal and a conductor formed by a portion of the circuit structure, wherein at least a portion of the output terminal extends to the first surface; The first pad, the second pad, and the input terminal are electrically connected sequentially through the circuit structure.

[0009] The multiphase power substrate proposed in this invention has a substrate body formed by stacked magnetic dielectric layers that has three functions: magnetic core, coil carrier and interconnection substrate. It integrates independent inductors, PCB traces and substrate carrier into one, reducing the size of the power module and the number of components. In the circuit structure, at least part of the electrical connection path from the first pad and the second pad to the inductor unit runs through the substrate thickness direction. The current transmission distance in the vertical direction is on the order of the substrate thickness. Compared with planar PCB wiring, the parasitic resistance and parasitic inductance are lower, making it suitable for high-frequency and high-current scenarios. The conductor of the inductor unit is formed by part of the circuit structure. The conductor of the inductor unit and the circuit structure are an integrated continuous structure. There is no additional soldering interface or mechanical connection interface between the two. This eliminates the procurement, mounting and soldering process of discrete inductor components. At the same time, it also eliminates the parasitic resistance and reliability risks introduced by the solder joints between discrete inductors and the substrate. The magnetic dielectric layer is self-insulating, and electrical isolation can be achieved between multiple inductor units embedded in the same substrate without the need for additional insulating spacers or shielding structures. The first pad and the output terminal are on the first surface, and the second pad is on the second surface. The connection with the external PCB board and the power chip is completed on both sides of the substrate, making the assembly process simpler. The magnetic dielectric layer not only forms the magnetic circuit but also serves as the mechanical carrier of the substrate, eliminating the need to embed discrete magnetic cores inside the substrate.

[0010] Preferably, the plurality of magnetic dielectric layers are provided with through holes extending along their thickness direction, and the vertical conductive structure is a conductor filling the through holes.

[0011] Using the aforementioned technical solution, vertical through-hole processing is simple and helps to reduce processing difficulty. The conductor is filled in the through-hole, and the inner wall of the through-hole forms a surrounding constraint on the conductor. The conductor and the magnetic medium layer are tightly bonded, and vertical conduction across the magnetic medium layer can be achieved without setting an additional interlayer connection structure.

[0012] Preferably, a portion of the magnetic dielectric layer has grooves extending along the layer direction, and horizontal conductors filling the grooves constitute the horizontal conductive structure for conducting current.

[0013] Using the aforementioned technical solution, the horizontal conductor filled in the groove constitutes a horizontal conductive structure. The cross-sectional area of ​​the horizontal conductor is determined by the groove depth and groove width. Under the same current carrying capacity, the groove depth can be increased to narrow the width, thereby reducing the outer dimension of the conductive path in the plane direction, shortening the crossing distance of the loop in the plane direction, and reducing the loop area, thereby reducing the parasitic inductance of the circuit structure.

[0014] Preferably, the horizontal conductive structure includes conductive sheets extending along the layer direction of the magnetic dielectric layer, with the conductive sheets disposed on a portion of the magnetic dielectric layer. Multiple conductive sheets spaced apart in the thickness direction constitute the coil structure of one inductor unit, and adjacent conductive sheets are connected in series through a vertical conductive structure to form the conductor of the inductor unit.

[0015] Using the aforementioned technical solution, the horizontal conduction structure includes a conductive sheet that constitutes the conductor of the inductor unit. The conductive sheet is bonded to the magnetic dielectric layer with a strip-shaped wide surface. Under the same number of turns and the same substrate area, a higher single-turn inductance value can be obtained than that of conventional wire winding, which helps to achieve a larger inductance within a limited substrate size.

[0016] Preferably, the output terminal and the second pad are spaced apart in the thickness direction, and the vertical conduction structure includes a through structure that extends from the second pad to the output terminal through the magnetic dielectric layer. The through structure constitutes the conductor portion of the inductor unit, and the magnetic dielectric layer surrounding the through structure constitutes the magnetic portion of the inductor unit.

[0017] Using the aforementioned technical solution, the through structure is a single continuous conductive column that runs through multiple magnetic dielectric layers. It has a large cross-sectional area, a straight conductive path, and a short total length. There are no interlayer series connection points, resulting in low DC resistance and strong current carrying capacity. The magnetic dielectric layers surround the through structure circumferentially, forming a closed magnetic circuit and constituting a vertical inductor. Multiple through structures can be spaced apart in the layer direction, and each inductor unit has an independent magnetic circuit. The through structure fabrication process of this solution is simple and more suitable for multi-phase power supply scenarios with high current and low inductance.

[0018] Preferably, the circuit also includes a third pad disposed on the second surface. The third pad is disposed corresponding to the inductor unit and is used to connect a capacitor. The capacitor soldered to the third pad is connected in parallel with the inductor unit through the circuit structure.

[0019] Using the aforementioned technical solution, in scenarios where capacitors and inductors are required to work together for filtering and voltage regulation, the third pad for connecting the capacitor is located on the second surface, and the capacitor and power chip are soldered on the same side, which helps to reduce the soldering difficulty.

[0020] Preferably, the plurality of inductor units are arranged at intervals in a plane parallel to the first surface.

[0021] Using the aforementioned technical solution, multiple inductor units are arranged at intervals in a plane parallel to the first surface, so that each inductor unit occupies a relatively independent magnetic dielectric layer region inside the magnetic substrate. Since the magnetic dielectric layer itself is insulated, magnetic circuit coupling or magnetic circuit independence can be achieved between adjacent inductor units by controlling the spacing. That is, when the spacing is small, a coupled inductor is formed, and when the spacing is large, an uncoupled inductor is achieved, taking into account different circuit topology requirements without changing the layer structure of the substrate. In addition, multiple inductor units are dispersed in the plane of the layer, and the heat generated by each unit is distributed in different areas of the substrate body, avoiding heat concentration in a single hot spot and improving the heat dissipation uniformity of the substrate. Meanwhile, since each inductor unit is arranged in the same plane and not stacked along the thickness direction, the total thickness of the substrate is not affected by the increase in the number of inductors, which helps to keep the power module thin.

[0022] Preferably, the circuit structure is made of solid metal, and the solid metal is selected from copper and silver.

[0023] The aforementioned technical solution helps to reduce the resistance of the circuit structure.

[0024] Preferably, the magnetic dielectric layer is formed by sintering soft magnetic alloy powder, and the surface of the soft magnetic alloy powder has an insulating layer.

[0025] Using the aforementioned technical solution, the magnetic dielectric layer is sintered from soft magnetic alloy powder with an insulating layer, which gives the magnetic dielectric layer high permeability, high saturation magnetic flux density, good thermal conductivity and reliable insulation performance. On the one hand, it provides an efficient magnetic circuit with low magnetic resistance for the inductor unit. On the other hand, the insulating coating layer between the particles realizes electrical isolation between adjacent particles and adjacent inductor units. At the same time, the high thermal conductivity helps to quickly dissipate the heat generated by the inductor unit and the power chip, reducing the operating temperature of the substrate.

[0026] Preferably, the soft magnetic alloy powder is an iron-silicon-chromium alloy powder.

[0027] Using the aforementioned technical solution, the iron-silicon-chromium alloy powder achieves a good balance between thermal stability of the insulation layer, eddy current loss, oxidation resistance and cost, and is especially suitable for the preparation of magnetic dielectric layers that require high-temperature co-firing and have high requirements for insulation reliability.

[0028] The present invention also proposes a multiphase power module, including a power chip and a power substrate of any of the aforementioned technical solutions, wherein the power chip is soldered onto a second pad.

[0029] The multiphase power module of the present invention, since it adopts the power substrate of any of the aforementioned technical solutions, has all the technical effects of the power substrate of all the aforementioned technical solutions.

[0030] This invention also proposes a method for preparing a power substrate, used to prepare a power substrate according to any of the foregoing technical solutions. The preparation method includes the following steps: Soft magnetic alloy powder, binder, dispersant and solvent are mixed to form a magnetic slurry; The magnetic slurry is coated onto the membrane tape, and after the magnetic slurry is dried, a magnetic raw tape supported on the membrane tape is obtained. A vertical through hole is machined into the magnetic strip; A conductive paste pattern is formed on the magnetic strip and the conductive paste is filled into the vertical through hole to obtain a horizontal conductive structure and a vertical conductive structure, respectively. Multiple magnetic strips are stacked to form a strip structure; The stacked green strip structures are pressed together to form a single green blank; The green blank is sintered to form a substrate.

[0031] The power substrate preparation method proposed in this invention uses the same conductive paste for the inductor coil and the interconnect circuit, and is integrally formed in the same co-firing process, eliminating the need for additional winding or purchasing discrete inductor components, thus reducing component procurement, mounting and soldering processes. The processing of vertical through holes and the printing of conductive patterns on each magnetic strip can be completed in the same screen printing process, simplifying the manufacturing process. Multilayer magnetic raw tapes are visually aligned and stacked layer by layer, then pressed and sintered in one step. The conductive layers are sintered and interconnected in co-firing to form a continuous conductive structure, and the interlayer electrical connection is reliable. The entire preparation process is compatible with the stacked co-firing process, enabling mass production.

[0032] Preferably, the specific composition and mass percentage of the magnetic paste are as follows: The soft magnetic alloy powder is iron-silicon-chromium powder, accounting for 71.0% to 83.0%; The solvents are toluene and alcohols, accounting for 15.5% to 25.0%; The adhesive is polyvinyl acetal resin, accounting for 1.25% to 2.55%; The dispersant is an organosilicon wetting and dispersing agent, accounting for 0.25% to 1.5%.

[0033] Using the aforementioned technical solution, the proportions of each component in the formula are coordinated, the slurry viscosity is suitable for casting, and the surface of the raw tape is smooth and the thickness is uniform, which is beneficial to the accuracy of subsequent through-hole processing and lamination alignment.

[0034] Preferably, the magnetic slurry further includes a plasticizer, which is a modified ester and / or a polyol derivative, and the plasticizer accounts for no more than 0.42% of the total mass of the magnetic slurry.

[0035] By adopting the aforementioned technical solution, the addition of plasticizer can reduce the glass transition temperature of the adhesive (polyvinyl acetal resin), improve the flexibility of the magnetic raw tape, and make the raw tape less brittle during the peeling, punching and stacking process, thereby reducing the breakage rate of the raw tape. Modified esters and / or polyol derivatives (such as DINCH and Optifilm) have good compatibility with polyvinyl acetal resin, moderate volatilization temperature, and can be fully decomposed and discharged during the debinding stage, leaving little residue. The plasticizer accounts for no more than 0.42% of the mass. While improving the flexibility of the green strip, it does not significantly reduce the mechanical strength of the green strip, nor does it significantly increase the amount of volatilization during the debinding stage. This is beneficial for maintaining the density of the green body after sintering.

[0036] Preferably, the method of forming the horizontal conductive structure is selected from at least one of the following: Conductive paste is printed onto the magnetic strip to form a conductive sheet; On the magnetic tape, a dielectric paste is printed around a preset conductive pattern area. After the dielectric paste cures, it forms a dam structure. The dam structure encloses at least one groove, and conductive paste is filled into the groove to form a horizontal conductor.

[0037] The two methods of forming a horizontal conductive structure using the aforementioned technical solutions can be flexibly selected or combined according to current carrying requirements, which facilitates flexible design based on the current carrying requirements at different locations within the substrate.

[0038] These features and advantages of the present invention will be disclosed in detail in the following detailed description and accompanying drawings. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of a multiphase power substrate in an embodiment of the present invention; Figure 2 This is a perspective view of the multiphase power substrate in an embodiment of the present invention; Figure 3 This is a top view of the multiphase power substrate in an embodiment of the present invention; Figure 4 This is a bottom view of the multiphase power substrate in an embodiment of the present invention; Figure 5 This is a cross-sectional view of a multiphase power substrate in an embodiment of the present invention; Figure 6 This is another cross-sectional view of the multiphase power substrate in an embodiment of the present invention; Figure 7 This is another cross-sectional view of the multiphase power substrate in an embodiment of the present invention; Figure 8 This is another cross-sectional view of the multiphase power substrate in an embodiment of the present invention.

[0040] Figure label: 10. PCB board; 20. Power supply chip; 30. Capacitor; 40. External electrode; 100. Substrate body; 101. First surface; 102. Second surface; 200. Circuit structure; 210. Vertical conduction structure; 211. Straight-through structure; 220. Horizontal conduction structure; 221. Horizontal conductor; 222. Conductive sheet; 230. Inductor unit; 231. Input terminal; 232. Output terminal. 300, First pad; 400, Second pad; 500, third pad. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be explained and described below with reference to the accompanying drawings. However, the following embodiments are only preferred embodiments of the present invention and not all of them. Other technical solutions obtained by those skilled in the art based on the embodiments without creative effort are all within the protection scope of the present invention.

[0042] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0043] Furthermore, the terms "first" and "second" (if any) are used to distinguish similar objects, not to describe a specific order or sequence. In the description of this invention, unless otherwise stated, "a plurality of" or "several" means two or more, unless otherwise expressly defined.

[0044] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0045] like Figures 1 to 8 As shown, the multiphase power substrate proposed in this embodiment of the invention includes a substrate body 100, a first pad 300, a second pad 400, a circuit structure 200, and multiple inductor units 230.

[0046] The substrate body 100 is formed by stacking multiple magnetic dielectric layers along the thickness direction. The substrate body 100 has a first surface 101 and a second surface 102 opposite to each other in the thickness direction, and the magnetic dielectric layers are insulating.

[0047] The first pad 300 is located on the first surface 101 and is used to connect with the external PCB board 10, which can be achieved by soldering. The material of the first pad 300 can be conductive metals such as silver or copper.

[0048] The second pad 400 is located on the second surface 102 and is used to connect the power chip 20. The two can be connected by soldering. The material of the second pad 400 can be conductive metals such as silver or copper.

[0049] The circuit structure 200 is embedded in the substrate body 100. The circuit structure 200 is composed of a vertical conductive structure 210 and a horizontal conductive structure 220. The vertical conductive structure 210 constitutes the part of the circuit structure 200 that extends along the thickness direction, and the horizontal conductive structure 220 constitutes the part of the circuit structure 200 that extends along the layer direction of the magnetic dielectric layer.

[0050] Specifically, multiple magnetic dielectric layers have through-holes that penetrate vertically along their thickness direction. The vertical conductive structure 210 is a conductor filling the through-holes.

[0051] The conductor can be formed by sintering a conductive paste, such as silver or copper paste, which is then co-fired to form a solid metal conductive pillar. Conductive paste is existing technology.

[0052] The horizontal conductive structure 220 includes a conductive sheet 222 extending along the layer direction of the magnetic dielectric layer, formed by printing conductive paste on a portion of the magnetic raw tape surface and then co-firing it.

[0053] The horizontal conductive structure 220 can also be formed by setting a groove extending along the layer direction in the magnetic dielectric layer and filling the groove with conductive paste to form a conductor, thereby forming a horizontal conductive structure 220 extending along the layer direction.

[0054] Inductor unit 230 includes an input terminal 231, an output terminal 232, and a conductor connecting the two. The conductor of each inductor unit 230 is formed by a portion of the circuit structure 200. Specifically, the conductor of an inductor unit 230 may include a plurality of horizontal conductive segments spaced apart along the thickness direction, and a plurality of vertical conductive segments connected end-to-end in series with adjacent horizontal conductive segments, thereby forming a spiral winding extending along the thickness direction. Each horizontal conductive segment is formed by at least a partially horizontal conductive structure 220, and each vertical conductive segment is formed by at least a partially vertical conductive structure 210. A magnetic dielectric layer surrounding the spiral winding constitutes the magnetic core of the inductor unit 230.

[0055] At least a portion of the output terminal 232 extends to the first surface 101 to connect to the PCB board 10. The output terminal 232 may be a bottom electrode disposed on the first surface 101 to connect to the PCB board 10. In some other embodiments, the output terminal 232 may also be configured as other structures, such as pads, pins, conductive bumps, etc., and the pads on the PCB board 10 that connect to the output terminal 232 are adapted to the structure of the output terminal 232.

[0056] The first pad 300, the second pad 400, and the input terminal 231 are sequentially electrically connected through the circuit structure 200. After the power chip 20 is soldered onto the second pad 400 of the power substrate, the first pad 300, the second pad 400, and the inductor unit 230 are electrically connected. The current input from the first pad 300 flows through the second pad 400 and the inductor unit 230 and is output from the output terminal 232 of the inductor unit 230. When the power chip 20 is soldered onto the multiphase power substrate and mounted on the PCB board 10, the output current of the PCB board 10 flows from the first pad 300 to the second pad 400 through the circuit structure 200. The power chip 20 is used for current distribution and chopping. The output current of the power chip 20 flows from the circuit structure 200 to the input terminal 231 of the inductor unit 230 and is finally output to the load of the PCB board 10 from the output terminal 232 of the inductor unit 230.

[0057] The multiphase power substrate proposed in this invention has a substrate body 100 formed by stacking magnetic dielectric layers, which has three functions: magnetic core, coil carrier and interconnection substrate. It integrates independent inductors, PCB traces and substrate carrier into one, reducing the size of power modules and the number of components. In the circuit structure 200, at least part of the electrical connection path from the first pad 300 and the second pad 400 to the inductor unit 230 runs through the substrate thickness direction. The current transmission distance in the vertical direction is on the order of the substrate thickness. Compared with planar PCB wiring, the parasitic resistance and parasitic inductance are lower, making it suitable for high-frequency and high-current scenarios. The conductor of the inductor unit 230 is formed by part of the circuit structure 200. The conductor of the inductor unit 230 and the circuit structure 200 are an integrated continuous structure. There is no additional soldering interface or mechanical connection interface between the two. This eliminates the procurement, mounting and soldering process of discrete inductor components. At the same time, it also eliminates the parasitic resistance and reliability risks introduced by the solder joints between the discrete inductor and the substrate. Since the magnetic dielectric layer is itself insulating, electrical isolation can be achieved between multiple inductor units 230 embedded in the same substrate body 100 without the need for additional insulating spacer layers or shielding structures. The first pad 300 and the output terminal 232 are on the first surface 101, and the second pad 400 is on the second surface 102. The connection with the external PCB board 10 and the power chip 20 is completed on both sides of the substrate, making the assembly process simpler. The magnetic dielectric layer forms a magnetic circuit and also serves as a mechanical carrier of the substrate, eliminating the need to embed discrete magnetic cores inside the substrate.

[0058] It should be noted that the substrate body 100 is formed by sintering. Before sintering, the magnetic dielectric layer is a magnetic green tape. Multiple magnetic green tapes are stacked, compacted, and then sintered to form the substrate body 100. In the substrate body 100, the thickness of a single magnetic dielectric layer is on the order of μm, ranging from approximately 10 μm to 125 μm. The thickness of the substrate body 100, formed by stacking multiple magnetic dielectric layers, is on the order of mm, typically from 1 mm to 3 mm.

[0059] In one embodiment, the magnetic dielectric layer is formed by sintering soft magnetic alloy powder, such as at least one of iron-silicon-chromium (FeSiCr), iron-silicon-aluminum (FeSiAl), and iron-nickel (FeNi) alloy powder. The surface of the soft magnetic alloy powder has an insulating coating layer, which insulates the magnetic dielectric layer.

[0060] The magnetic dielectric layer formed by sintering soft magnetic alloy powder has a good thermal conductivity. The heat generated by the inductor unit 230 and the power chip 20 can be rapidly diffused along the layer direction and thickness direction through the magnetic dielectric layer. The heat is finally transferred to the PCB board 10 through the first pad 300, which reduces the temperature of the inductor unit 230 and the power chip 20 and reduces the local temperature rise of the substrate body 100, which is beneficial to the continuous and stable operation of the power module under high power density.

[0061] The insulating coating layer on the surface of the soft magnetic alloy powder makes the sintered magnetic dielectric layer as a whole insulated, electrically isolating adjacent alloy powder particles from each other, preventing eddy currents from flowing between particles and reducing eddy current losses at high frequencies. At the same time, the sidewalls of the vertical conducting structure 210 and the horizontal conducting structure 220 embedded in the magnetic dielectric layer are surrounded by the insulating magnetic dielectric layer, preventing short circuits through the magnetic dielectric layer.

[0062] The insulating coating can be formed in the following ways: Method 1: Oxidation Treatment. Taking FeSiCr as an example, FeSiCr powder is heat-treated in an oxygen-containing atmosphere to oxidize the powder surface and form an oxide insulating layer. The heat treatment temperature is, for example, 400~650℃. The oxide layer includes Fe2O3, Fe3O4, and oxides of elements such as Cr, Si, and Al in the alloy. It should be noted that if the subsequent sintering temperature is too high (e.g., exceeding 800℃) or if the sintering is carried out in a reducing atmosphere, the iron oxides will be reduced at high temperatures and lose their insulating properties. Therefore, when using an oxide insulating layer, the sintering temperature should be controlled below 650℃ and carried out in a non-reducing atmosphere to preserve the oxide insulating layer on the powder surface.

[0063] Method 2: Sol-gel coating of silica. Soft magnetic alloy powder is dispersed in a sol containing a silicon source (e.g., tetraethyl orthosilicate, TEOS). A silica gel coating layer is formed on the surface of the powder particles through a hydrolysis-condensation reaction. Following heat treatment, a dense SiO2 insulating coating layer is obtained. SiO2 has high chemical stability and is not easily decomposed or reduced during subsequent co-firing, reliably maintaining electrical isolation between particles. Compared to a simple oxide layer, the SiO2 coating layer offers better insulation and temperature resistance, making it suitable for high-temperature sintering processes.

[0064] In this embodiment, the magnetic dielectric layer is sintered from soft magnetic alloy powder with an insulating layer, which gives the magnetic dielectric layer high permeability, high saturation magnetic flux density, good thermal conductivity and reliable insulation performance. On the one hand, it provides a high-efficiency magnetic circuit with low magnetic resistance for the inductor unit 230. On the other hand, the insulating coating layer between the particles realizes electrical isolation between adjacent particles and adjacent inductor units 230. At the same time, the high thermal conductivity helps to quickly dissipate the heat generated by the inductor unit 230 and the power chip 20, thereby reducing the operating temperature of the substrate body 100.

[0065] In this embodiment, the preferred soft magnetic alloy powder is an iron-silicon-chromium alloy powder.

[0066] Iron-silicon-chromium alloy powder is mainly composed of iron, with an iron content of, for example, 89%–94%, a silicon content of, for example, 3%–6%, and a chromium content of, for example, 1.5%–6%. The addition of silicon can improve the resistivity and permeability of the alloy, while the addition of chromium can enhance the alloy's oxidation resistance and corrosion resistance. The combined introduction of both also helps to form a composite oxide insulating layer containing Cr and Si on the powder surface.

[0067] Before pulping, the iron-silicon-chromium alloy powder undergoes surface insulation treatment, as described above.

[0068] Surface-insulated iron-silicon-chromium alloy powder is mixed with binder and solvent to form a magnetic paste, which is then cast to form a magnetic green tape. Through-holes, conductive patterns, or grooves filled with conductive paste are machined onto the magnetic green tape. Multiple layers of magnetic green tape are then laminated and co-fired in a non-oxidizing atmosphere (e.g., nitrogen). The co-firing temperature is, for example, 700–900°C. Within this temperature range, sintering necks form and densification occurs between the powder particles, giving the magnetic dielectric layer sufficient mechanical strength. Simultaneously, the insulating coating layer on the particle surface is retained, resulting in an overall insulating magnetic dielectric layer after sintering. The insulating coating layer between the particles electrically isolates each alloy powder particle from the others, blocking the large-scale flow path of eddy currents between the particles and effectively reducing eddy current losses at high frequencies.

[0069] In one embodiment, such as Figures 1 to 8 As shown, the power substrate also includes a third pad 500 disposed on the second surface 102. The third pad 500 is correspondingly disposed to each inductor unit 230, with one inductor unit 230 corresponding to one third pad 500. The third pads 500 are spaced apart from the second pads 400 on the second surface 102, and each third pad 500 is arranged along the width direction of the substrate body 100. When the power substrate includes multiple inductor units 230, each group of third pads 500 is connected to a capacitor 30 to achieve multi-phase independent filtering.

[0070] The third pad 500 is used to connect the capacitor 30, which is, for example, a multilayer ceramic capacitor, and is soldered onto the third pad 500 by surface mounting. The capacitor 30 soldered onto the third pad 500 is connected in parallel with the corresponding inductor unit 230 through the circuit structure 200 to form an LC filter network.

[0071] Capacitor 30 typically has two solder pads, which are soldered to two solder areas on the third pad 500. One solder area is connected to the first pad 300 via a vertical conductive structure 210, or to the capacitor 30 pad located on the first surface 101, so that one end of capacitor 30 is grounded through the PCB board 10; the other solder area extends downward into the substrate body 100 via the vertical conductive structure 210, directly connected to the output terminal 232 of the corresponding inductor unit 230, or connected to the output terminal 232 of the corresponding inductor unit 230 via a horizontal conductive structure 220, so that the other end of capacitor 30 forms a power supply terminal. Thus, capacitor 30 and inductor unit 230 are connected in parallel.

[0072] For the DC component, capacitor 30 is open-circuit in steady state, and all current flows through inductor 230 to the output terminal 232. For the AC ripple component, capacitor 30 presents low impedance, and the ripple current forms a bypass path across inductor 230 through the charging and discharging of capacitor 30, reducing the ripple reaching the output terminal 232. Capacitor 30 and inductor 230 thus constitute a low-pass filter structure, smoothing the output voltage.

[0073] The capacitor 30 and the power chip 20 are co-located on the second surface 102, allowing them to be soldered in the same process, simplifying the assembly procedure. Simultaneously, the electrical connection between the capacitor 30 and the inductor unit 230 can extend along the substrate thickness direction via the vertical conduction structure 210, with a path on the order of substrate thickness. This results in a compact filtering circuit, which helps suppress high-frequency switching noise.

[0074] In other embodiments, a decoupling capacitor 30 can be placed on the PCB board 10 near the output terminal 232 of the inductor unit 230. This decoupling capacitor 30 can also work with the inductor unit 230 to achieve a filtering and voltage regulation effect. However, the decoupling capacitor 30 occupies additional space on the PCB board 10, and also increases the length of the horizontal traces on the PCB board 10, introducing additional parasitic inductance and weakening the bypass effect of the decoupling capacitor 30 on high-frequency ripple. In addition, the physical loop area from the output terminal 232 of the inductor unit 230 to the decoupling capacitor 30 through the horizontal traces increases, which is not conducive to suppressing electromagnetic interference.

[0075] In contrast, in this case, capacitor 30 is directly soldered to the second surface 102 of the magnetic substrate via the third pad 500. Capacitor 30 and the output terminal 232 of inductor unit 230 are connected along the thickness direction of the substrate via vertical conduction structure 210. The loop path is on the order of substrate thickness, resulting in lower parasitic parameters and smaller loop area. The filtering effect is better than the scheme of arranging decoupling capacitor 30 on PCB board 10.

[0076] like Figure 8 As shown, an external electrode 40 is provided on the substrate body 100. The external electrode 40 is used to connect the capacitor 30 and the PCB board 10 so that one end of the capacitor 30 is grounded. Using the external electrode 40 can simplify the circuit structure 200 connected to the capacitor 30 in the substrate body 100. For example, the external electrode 40 is configured with an L-shaped electrode that extends from the first surface 102 to the side wall of the substrate body 100. The circuit structure 200 has a conductor reserved on the side wall of the substrate body and is connected by soldering to the L-shaped electrode. In this way, the connection between the capacitor 30 and the PCB board 10 is realized by using the external electrode 40, which helps to reduce the extension length of the circuit structure 200 in the substrate body 100.

[0077] In one embodiment, such as Figures 2 to 8 As shown, multiple magnetic dielectric layers are provided with vertical through holes that extend along their thickness direction, and the vertical conductive structure 210 is a conductor filling the through holes.

[0078] Vertical vias are formed when the magnetic dielectric layer is not stacked. The vertical arrangement of the vias makes the processing easier and helps to reduce the processing difficulty.

[0079] After filling the vertical vias with conductive paste, co-firing is performed to form a solid conductor filling the vertical vias. The conductive paste can be, for example, silver paste or copper paste. Multiple magnetic dielectric layers are stacked, with the conductive paste in each layer's vertical vias aligned with each other in the thickness direction. After co-firing, the solid conductor layers are sintered and interconnected, forming a vertically conductive structure 210 that extends continuously along the thickness direction.

[0080] In one embodiment, such as Figures 5 to 8 As shown, a groove extending along the layer direction is provided in a portion of the magnetic dielectric layer, and at least a portion of the horizontal conductive structure 220 is composed of a horizontal conductor 221 filling the groove. The horizontal conductor 221 is used to carry large currents, rather than being a conductor constituting the inductor unit 230.

[0081] In some embodiments, the groove is formed when the magnetic dielectric layer is in a green state, for example by laser etching. The cross-sectional shape of the groove can be rectangular, trapezoidal, semi-circular, etc., and the depth of the groove is not greater than the thickness of the magnetic dielectric layer. After the groove is filled with conductive paste, the surface of the conductive paste is approximately flush with the surface of the magnetic dielectric layer.

[0082] In other embodiments, the groove can also be formed by printing a dielectric paste around a predetermined conductive pattern area on the surface of the magnetic dielectric layer. After the dielectric paste cures, it forms a dam structure around the predetermined area. The space enclosed by the dam structure constitutes the groove, which is then filled with conductive paste. The dielectric paste, for example, is a paste of the same material as the magnetic dielectric layer, which fuses with the magnetic dielectric layer after co-firing. This method eliminates the need for material removal from the magnetic dielectric layer. The depth of the groove is controlled by the printing thickness of the dielectric paste, not limited by the thickness of the magnetic dielectric layer, and the width of the groove is determined by the printing pattern of the dam structure, offering greater flexibility. Furthermore, since the dam structure and the magnetic dielectric layer are made of the same material after co-firing, their thermal expansion is matched, reducing the likelihood of interfacial stress.

[0083] The horizontal conductive structure 220 proposed in this embodiment is used to transmit current, rather than constituting a conductor of the inductor unit 230. The two ends of the horizontal conductive structure 220 are connected to the vertical conductive structure 210 in the adjacent magnetic dielectric layer, allowing the two parts connected by the circuit structure 200 to cross over each other in the direction of the magnetic dielectric layer. Examples include: the crossing between the second pad 400 and the input terminal 231 of the inductor unit 230; the crossing between the second pad 400 and one end of the capacitor 30; the crossing between the external electrode 40 and the capacitor 30; and the crossing between the second pad 400 and the external electrode 40.

[0084] Compared to printing conductive patterns on the surface of a magnetic dielectric layer, the horizontal conductor 221 filling the groove has a larger cross-sectional area. Under the condition of carrying the same current, the width of the conductive path can be narrowed, thereby reducing the area of ​​the current loop and lowering the parasitic inductance of the horizontal conducting structure 220 itself. The lower the parasitic inductance, the smaller the induced voltage spike generated by the large current transmission path during high-frequency switching, which is beneficial to improving the stability of circuit operation.

[0085] Furthermore, the horizontal conductor 221 is embedded in the groove, and its surface is flush with the magnetic dielectric layer, which does not affect the flatness of the stacking of adjacent magnetic dielectric layers and is beneficial to the interlayer bonding quality of multi-layer stacking. The sidewall of the groove constrains the horizontal conductor 221, making it less prone to lateral expansion during pressing and sintering, thus maintaining the dimensional accuracy of the horizontal conductor 221.

[0086] In one embodiment, such as Figure 5 , Figure 6 As shown, the horizontal conductive structure 220 includes a conductive sheet 222 extending along the layer direction of the magnetic dielectric layer. The conductive sheet 222 is provided on a portion of the magnetic dielectric layer, and is formed by printing conductive paste onto the surface of a magnetic raw tape and then co-firing it. The conductive sheet 222 is, for example, a rectangular strip or an arc-shaped strip, extending a predetermined length along the layer direction.

[0087] Multiple conductive sheets 222 arranged at intervals along the thickness direction constitute the coil structure of an inductor unit 230. Specifically, the conductive sheets 222 on different magnetic dielectric layers are arranged in layers along the thickness direction, with adjacent conductive sheets 222 staggered by a predetermined distance in the layer direction, and their near ends connected in series through a vertical conduction structure 210. One end of a conductive sheet 222 is connected downwards to one end of the next conductive sheet 222 via the vertical conduction structure 210, and the other end of the next conductive sheet 222 is connected downwards to one end of an even lower conductive sheet 222 via another vertical conduction structure 210, and so on, layer by layer, to form a multi-turn spiral coil extending along the thickness direction. The magnetic dielectric layer surrounding this coil constitutes the magnetic core of the inductor unit 230.

[0088] The conductive sheet 222 is a planar strip conductor extending along the layer direction, with its width dimension being much larger than its thickness dimension. Compared to conventional wire-wound coils, the conductive sheet 222 is a flat strip with a larger surface area facing the upper and lower magnetic dielectric layers. When current flows through the conductive sheet 222, the generated magnetic field links with the magnetic dielectric layer through this surface area. The larger the linking area, the greater the magnetic flux in the magnetic circuit, and the higher the inductance of a single-turn coil. In other words, by attaching the conductive sheet 222 to the magnetic dielectric layer with its wide strip surface, a higher single-turn inductance value can be obtained than conventional wire-wound coils with the same number of turns and the same substrate area, which helps to achieve a larger inductance within a limited substrate size.

[0089] In one embodiment, such as Figure 7 , Figure 8 As shown, unlike the previous embodiment, the output terminal 232 and the second pad 400 are spaced apart in the thickness direction, and the vertical conduction structure 210 between them includes a through structure 211 extending from the second pad 400 to the output terminal 232. The through structure 211 continuously penetrates multiple magnetic dielectric layers along the thickness direction, forming the conductor portion of the inductor unit 230. The magnetic dielectric layer surrounding the through structure 211 forms the magnetic portion of the inductor unit 230.

[0090] It should be noted that the through structure 211 is a type of vertical conduction structure 210 in terms of physical morphology. Compared with the ordinary vertical conduction structure 210 that only penetrates one or a few magnetic dielectric layers, the through structure 211 continuously penetrates multiple or even all magnetic dielectric layers along the thickness direction, and has a longer longitudinal extension length.

[0091] Specifically, the through structure 211 is a conductive pillar extending along its thickness direction. Through holes are machined at the same planar position on multiple magnetic strips and filled with conductive paste. After lamination and pressing, the through holes of each layer are aligned. After co-firing, the conductive layers are longitudinally sintered together to form a continuous conductive pillar extending from the layer where the second pad 400 is located to the layer where the output terminal 232 is located. The second pad 400 is located on the second surface 102. The top end of the through structure 211 is electrically connected to the second pad 400; the bottom end of the through structure 211 extends to the first surface 101 and is electrically connected to the output terminal 232.

[0092] Current enters the through structure 211 from the second pad 400, flows along the entire length of the through structure 211 in the thickness direction, and exits from the output terminal 232. The magnetic dielectric layer surrounding the through structure 211 surrounds it circumferentially, providing a closed magnetic circuit for the current path, thus forming a vertical inductor.

[0093] Compared to the spiral coil formed by multiple conductive sheets 222 connected in series via a vertical conductive structure 210 in the previous embodiment, the straight-through structure 211 has a larger cross-sectional area, thus providing stronger current carrying capacity. Furthermore, the straight-through structure 211 is a single straight conductive post with a straight conductive path, short total length, and no interlayer series connection points, resulting in lower DC resistance. This makes the straight-through structure 211, as the conductor of the inductor unit 230, more suitable for multi-phase power supply scenarios with high current and low inductance.

[0094] When the magnetic substrate contains multiple inductor units 230, multiple through structures 211 spaced apart from each other in the layer direction can be provided, and the magnetic dielectric layer around each through structure 211 constitutes an independent magnetic circuit of each inductor unit 230.

[0095] In one embodiment, such as Figure 2 , Figure 5As shown, multiple inductor units 230 are arranged at intervals in a plane parallel to the first surface 101.

[0096] For an inductor unit 230 that uses a coil structure as a conductor, the coil of a single inductor unit 230 has a certain extension area in the layer direction, occupying a large space. Multiple such inductor units 230 are usually arranged at intervals along the length direction of the substrate body 100 to avoid the substrate body 100 being too wide, thereby improving the overall compactness of the substrate body 100 while ensuring that the magnetic circuits of each inductor unit 230 are independent of each other.

[0097] For the inductor unit 230 that uses the through structure 211 as the conductor, the cross-sectional dimension of the through structure 211 (i.e., the diameter of the through hole) is much smaller than the layer area of ​​the coil structure, and the area occupied by a single inductor unit 230 is extremely small. The arrangement of multiple such inductor units 230 in the layer plane is more flexible. They can be arranged at intervals along the length direction, at intervals along the width direction, or even in a two-dimensional array to adapt to the requirements of different package sizes and pad layouts.

[0098] The spaced arrangement of multiple inductor units 230 separates the magnetic dielectric layer regions surrounding each inductor unit 230. The degree of magnetic coupling between adjacent inductor units 230 depends on their spacing: when the distance between the edges of adjacent coils is small (e.g., ≤0.22mm), magnetic coupling occurs between adjacent inductor units 230, and the magnetic fields partially overlap. In this case, the inductors of each phase can work together to achieve the function of coupled inductors (e.g., improving transient response); when the distance between the edges of adjacent coils is large (e.g., ≥0.3mm), the magnetic coupling between adjacent inductor units 230 is negligible, and the magnetic circuits of each inductor unit 230 work independently, making them uncoupled inductors.

[0099] Therefore, by adjusting the spacing of multiple inductor units 230 in the layer plane, coupled or uncoupled inductors can be realized on the same magnetic substrate without changing the layer structure or material of the substrate body 100 to adapt to different circuit topology requirements.

[0100] The power substrate of the present invention, the substrate body 100 formed by the stacking of magnetic dielectric layers has three functions: magnetic core, coil carrier and interconnection substrate. It integrates independent inductors, PCB traces and substrate carrier into one, reducing the size of the power module and the number of components. The circuit structure 200 built into the substrate body 100 connects the pads on the first surface 101 and the second surface 102 of the power substrate. The current is transmitted along the thickness direction of the substrate through the vertical conduction structure 210. The transmission distance is on the order of the substrate thickness. The current path is short and has few detours. The parasitic resistance and parasitic inductance are low. At the same time, the first pad 300 and the output terminal 232 are on the first surface 101 and the second pad 400 is on the second surface 102. The connection with the external PCB board 10 and the power chip 20 is completed on both sides of the substrate. The assembly process is simple and there is no need to reserve additional layout space for the input and output pads on the same side of the substrate.

[0101] A portion of the circuit structure 200 embedded in the substrate body 100 constitutes the conductor of the inductor unit 230, making the inductor unit 230 and the circuit structure 200 a continuous conductor. There is no soldering interface or mechanical connection interface, which eliminates the procurement, mounting and soldering process of discrete inductor components, reduces the number of components and assembly steps, and reduces the parasitic resistance and reliability risks introduced by the solder joints of discrete components.

[0102] The inductor unit 230 in the power substrate can be a coil structure, that is, a coil structure is formed by multiple conductive sheets 222 distributed in each magnetic medium layer, and multiple conductive sheets 222 spaced apart in the thickness direction are connected end to end through a vertical conduction structure 210 to form an inductor unit 230 conductor in a phase output.

[0103] The inductor unit 230 in the power substrate can also be a through-structure 211, that is, the conductor of the inductor unit 230 is formed by a conductive pillar that continuously penetrates multiple magnetic dielectric layers along the thickness direction. This conductive pillar is formed by co-firing conductive paste filled with vertically aligned through holes in each magnetic dielectric layer, and the conductive layers are sintered and interconnected into a whole. The magnetic dielectric layers surrounding the conductive pillar form the magnetic core of the inductor unit 230, forming a vertical inductor. Compared with the coil structure, the through-structure 211 has a straight conductive path, short total length, no interlayer series connection points, and lower DC resistance, making it suitable for multi-phase power supply scenarios with high current and low inductance.

[0104] It should be noted that the interphase coupling coefficient K can be adjusted by controlling the spacing between the conductors of adjacent inductor units 230. The smaller the spacing, the more the magnetic circuits overlap between adjacent inductor units 230, the larger the K value, and the stronger the coupling; the larger the spacing, the less the magnetic circuits overlap between adjacent inductor units 230, the smaller the K value, and the weaker the coupling, until the spacing exceeds a certain threshold and the K value approaches zero, at which point the adjacent inductor units 230 achieve uncoupled operation.

[0105] Therefore, the spacing between adjacent inductor units 230 can be adjusted according to the actual application requirements of the power substrate. When multi-phase coupling is required to improve transient response, a smaller spacing is used to achieve coupled inductance; when independent operation of each phase is required, a larger spacing is used to achieve uncoupled inductance. By adjusting the spacing, the same power substrate design can adapt to different multi-phase power supply topology requirements without changing the substrate's layer structure or material.

[0106] Taking the inductor unit 230 as an example of a coil structure, when the distance between adjacent coils is greater than 0.3mm, K < 0.05, and the output of each phase of the power board is considered to be in a non-coupled state; when the distance between adjacent coils is less than 0.22mm, K > 0.05, and the output of each phase of the power board is considered to be in a coupled state.

[0107] The embodiments of the present invention also propose a power module, such as Figures 5 to 8 As shown, the system includes a power chip 20 and a power substrate from any of the aforementioned embodiments. The power chip 20 is soldered onto the second pad 400. The power module is mounted on the PCB board 10 and is used to convert the input voltage provided by the PCB board 10 into the output voltage required by the load.

[0108] Specifically, the input voltage of PCB board 10 enters the power substrate via the first pad 300, is chopped and phase-distributed by the power chip 20, and then smoothed by energy storage in each inductor unit 230 and filtered by capacitor 30. Finally, a stable DC voltage is output from the output terminal 232 of the first surface 101 to the load on PCB board 10. The power module integrates the power chip 20, multi-phase inductors, and filter capacitors 30 onto a single substrate and is mounted on PCB board 10 in a modular form, reducing the number and layout area of ​​discrete components on PCB board 10 and simplifying system-level power supply design.

[0109] In this embodiment, the power supply chip 20 is a DC-DC chip.

[0110] This invention also proposes a method for fabricating a power substrate, used to prepare the power substrate of any of the foregoing embodiments. The fabrication method includes the following steps: Soft magnetic alloy powder, binder, dispersant, and solvent are mixed in a predetermined ratio and stirred to form a uniform magnetic slurry. The soft magnetic alloy powder is, for example, iron-silicon-chromium (FeSiCr) alloy powder with a particle size of, for example, 1–30 μm. The binder is polyvinyl acetal resin, the dispersant is, for example, an organosilicon wetting and dispersing agent, and the solvent is toluene and alcohols. Before slurry preparation, the soft magnetic alloy powder undergoes surface insulation treatment (e.g., oxidation treatment or sol-gel coating with SiO2) to give the powder particles an insulating coating layer.

[0111] The casting process involves applying a magnetic paste onto a film strip (e.g., PET release film) using a doctor blade, with the blade gap controlling the wet film thickness. After drying (e.g., at 60-80°C), the solvent evaporates, forming a magnetic green tape carried on the film strip. The thickness of the magnetic green tape is approximately 10-125 μm. The casting process is performed using a casting machine, which is existing technology.

[0112] A vertical through-hole, running along the thickness direction, is machined at a predetermined position on the magnetic tape. The machining method can be, for example, laser drilling. The diameter of the through-hole is, for example, 50~300μm. The vertical through-hole is formed in one pass, simplifying the process and reducing alignment requirements.

[0113] On the surface of the magnetic strip, a predetermined conductive pattern is formed by screen printing a conductive paste. This conductive pattern constitutes at least a partial horizontal conductive structure. After a subsequent sintering process, the conductive pattern forms a conductive sheet. This conductive sheet is used to form the coil structure of the conductor in an inductor unit. The conductive paste is, for example, silver paste or copper paste. Simultaneously or before this, the conductive paste is filled into vertical through-holes to form conductors in the vertical conductive structure. The printing of the surface conductive pattern and the filling of the vertical through-holes can be completed in the same screen printing process—during screen printing, the conductive paste is pressed into the through-holes and simultaneously forms a conductive pattern on the surface, resulting in high process efficiency.

[0114] In some embodiments, the horizontal conductive structure is formed using a groove-filling method: first, a dielectric paste is printed around a predetermined conductive pattern area on the magnetic raw tape. After the dielectric paste cures, it forms a dam structure surrounding the predetermined area. The space enclosed by the dam structure constitutes a groove extending along the layer direction. The dielectric paste, for example, is a paste of the same material as the magnetic raw tape. This method eliminates the need for material removal from the magnetic raw tape itself. The depth of the groove is controlled by the printing thickness of the dielectric paste, not limited by the thickness of the magnetic raw tape. The width and shape of the groove are determined by the printing pattern of the dam structure, offering greater flexibility. Conductive paste is then filled into the groove, forming a horizontal conductor after a subsequent sintering process. This horizontal conductor is used to construct a structure in the circuit structure that transmits current across the layer direction of the magnetic dielectric layer.

[0115] Multiple magnetic green tapes, supported by a membrane tape, are peeled off and then stacked sequentially according to a predetermined layer sequence to form a green tape structure. The magnetic green tapes are stacked using a precision thin film stacking machine, which is existing technology.

[0116] High pressure is applied to the stacked green tape structures for pressing, for example, using isostatic pressing, to ensure that adjacent magnetic green tapes are tightly bonded together and that each layer of conductive paste is pressed into contact with each other, eliminating the interfacial gaps between adjacent magnetic green tapes and connected conductive pastes, thus forming a dense and integrated green tape structure. The pressure value of isostatic pressing is 500MPa~680MPa.

[0117] The green blank is sintered to form the substrate. Before sintering, the green blank needs to be cut to remove excess material and flatten its edges. During sintering, a low-temperature (e.g., 300-500℃) debinding process is first performed to allow the organic components such as binders and dispersants in the green blank to gradually decompose and volatilize. After debinding, sintering is carried out and held at that temperature for a certain period of time. Sintering necks form and densify between the soft magnetic alloy powder particles, and the particle contact gradually changes from point contact to surface bonding. The blank shrinks and densifies, and the magnetic dielectric layer acquires sufficient mechanical strength. At the same time, the metal particles (e.g., silver or copper) in the conductive paste sinter and densify, and the conductive layers are sintered and interconnected to form a continuous conductive structure. The magnetic dielectric layer and the conductive layers densify synchronously under the same sintering regime. After holding at that temperature, the temperature is gradually lowered to avoid rapid cooling that could cause warping or cracking of the substrate due to thermal stress, ultimately resulting in a multilayer stacked substrate.

[0118] It should be noted that the printing order of conductive paste in both vertical and horizontal conductive structures is not limited.

[0119] In some embodiments, conventional processes such as external electrode fabrication, electroplating, and surface treatment are performed on the sintered substrate to finally obtain a power substrate.

[0120] The specific composition and mass percentage of each component of the magnetic paste are as follows: the soft magnetic alloy powder is iron-silicon-chromium powder, accounting for 71.0% to 83.0%; the solvent is toluene and alcohols, accounting for 15.5% to 25.0%; the binder is polyvinyl acetal resin, accounting for 1.25% to 2.55%; and the dispersant is organosilicon wetting and dispersing agent, accounting for 0.25% to 1.5%.

[0121] Alcohols, such as methanol, ethanol, isopropanol, isooctanol, etc.

[0122] Polyvinyl acetal resins, such as B-72, B75, and SLEC series.

[0123] Organosilicon wetting and dispersing agents, such as DC-3 and BYK-163.

[0124] In some embodiments, the magnetic paste may further include a plasticizer, which is a modified ester and / or a polyol derivative, and the plasticizer accounts for no more than 0.42% of the total mass of the magnetic paste.

[0125] The role of plasticizers in magnetic raw tape is to improve flexibility and prevent the raw tape from cracking during processing.

[0126] Plasticizers can be modified esters and / or polyol derivatives, such as DINCH (diisononyl cyclohexane-1,2-dicarboxylate, BASF) and / or Optifilm (triethylene glycol diisooctanoate, Eastman). These plasticizers are non-phthalate esters, have good compatibility with PVB adhesives, moderate evaporation temperatures, and can be fully decomposed and discharged during the debinding stage, leaving little residue.

[0127] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that the present invention includes, but is not limited to, the contents described in the accompanying drawings and the specific embodiments above. Any modifications that do not depart from the functional and structural principles of the present invention will be included within the scope of the claims.

Claims

1. A multiphase power substrate, characterized in that, include: A substrate body formed by stacking multiple insulating magnetic dielectric layers along the thickness direction has a first surface and a second surface that are opposite to each other in the thickness direction. The first pad for connecting the PCB board is located on the first surface; A second pad for connecting the power chip is provided on the second surface; The circuit structure disposed within the substrate body consists of a vertical conduction structure and a horizontal conduction structure. The vertical conduction structure constitutes the portion of the circuit structure extending along the thickness direction, and the horizontal conduction structure constitutes the portion of the circuit structure extending along the layer direction of the magnetic dielectric layer. A plurality of inductor units, each inductor unit including an input terminal, an output terminal and a conductor formed by a portion of the circuit structure, wherein at least a portion of the output terminal extends to the first surface; The first pad, the second pad, and the input terminal are electrically connected sequentially through the circuit structure.

2. The power substrate as described in claim 1, characterized in that, The plurality of magnetic dielectric layers are provided with through holes extending along their thickness direction, and the vertical conductive structure is a conductor filling the through holes.

3. The power substrate as described in claim 1, characterized in that, The magnetic dielectric layer is provided with grooves extending along the layer direction, and the horizontal conductors filled in the grooves constitute the horizontal conductive structure for conducting current.

4. The power substrate as described in claim 1, characterized in that, The horizontal conductive structure includes conductive sheets extending along the layer direction of the magnetic dielectric layer. The conductive sheets are provided on a portion of the magnetic dielectric layer. Multiple conductive sheets spaced apart in the thickness direction constitute the coil structure of the inductor unit. Adjacent conductive sheets are connected in series through a vertical conductive structure to form the conductor of the inductor unit.

5. The power substrate as described in claim 1, characterized in that, The output terminal and the second pad are spaced apart in the thickness direction. The vertical conduction structure includes a through structure that extends from the second pad to the output terminal through the magnetic dielectric layer. The through structure constitutes the conductor portion of the inductor unit, and the magnetic dielectric layer surrounding the through structure constitutes the magnetic portion of the inductor unit.

6. The power substrate as described in claim 1, characterized in that, It also includes a third pad disposed on the second surface, the third pad being disposed corresponding to the inductor unit and used to connect a capacitor, and the capacitor soldered to the third pad being connected in parallel with the inductor unit through the circuit structure.

7. The power substrate as claimed in claim 1, characterized in that, The plurality of inductor units are arranged at intervals in a plane parallel to the first surface.

8. The power substrate as described in claim 1, characterized in that, The circuit structure is made of solid metal, which is selected from copper and silver.

9. The power substrate as claimed in claim 1, characterized in that, The magnetic dielectric layer is formed by sintering soft magnetic alloy powder, and the surface of the soft magnetic alloy powder has an insulating layer.

10. The power substrate as claimed in claim 9, characterized in that, The soft magnetic alloy powder is an iron-silicon-chromium alloy powder.

11. A power module, characterized in that, It includes a power chip and a power substrate as described in any one of claims 1 to 10, wherein the power chip is soldered onto a second pad.

12. A method for preparing a power substrate, used to prepare a power substrate as described in any one of claims 1 to 10, characterized in that, Includes the following steps: Soft magnetic alloy powder, binder, dispersant and solvent are mixed to form a magnetic slurry; The magnetic slurry is coated onto the membrane tape, and after the magnetic slurry is dried, a magnetic raw tape supported on the membrane tape is obtained. A vertical through hole is machined into the magnetic strip; A conductive paste pattern is formed on the magnetic strip and the conductive paste is filled into the vertical through hole to obtain a horizontal conductive structure and a vertical conductive structure, respectively. Multiple magnetic strips are stacked to form a strip structure; The stacked green strip structures are pressed together to form a single green blank; The green blank is sintered to form a substrate.

13. The preparation method according to claim 12, characterized in that, The specific composition and mass percentage of the magnetic slurry are as follows: The soft magnetic alloy powder is iron-silicon-chromium powder, accounting for 71.0% to 83.0%; The solvents are toluene and alcohols, accounting for 15.5% to 25.0%; The adhesive is polyvinyl acetal resin, accounting for 1.25% to 2.55%; The dispersant is an organosilicon wetting and dispersing agent, accounting for 0.25% to 1.5%.

14. The preparation method according to claim 13, characterized in that, The magnetic slurry also includes a plasticizer, which is a modified ester and / or a polyol derivative. Based on the total mass of the magnetic slurry, the mass percentage of the plasticizer does not exceed 0.42%.

15. The preparation method according to claim 12, characterized in that, The method of forming the horizontal conduction structure is selected from at least one of the following: Conductive paste is printed onto the magnetic strip to form a conductive sheet; On the magnetic tape, a dielectric paste is printed around a preset conductive pattern area. After the dielectric paste cures, it forms a dam structure. The dam structure encloses at least one groove, and conductive paste is filled into the groove to form a horizontal conductor.

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