An integrated conjugate inductor structure and method of manufacturing the same

Abstract

This invention discloses an integrated conjugate inductor structure and its manufacturing method. The structure includes: a plurality of copper pillars serving as a support and interconnection framework; a magnetic encapsulation layer with at least one block magnetic core embedded therein, the lower ends of the copper pillars being embedded therein; and redistribution layers respectively disposed on the upper and lower surfaces of the magnetic encapsulation layer. The planar helical wire patterns in the two layers are electrically connected in series through the copper pillars to jointly form a three-dimensional helical coil surrounding the magnetic core. This invention directly integrates a high-performance block magnetic core inductor into the fan-out package, achieving high-density, high-performance integration of the power management system, and possessing excellent heat dissipation and reliability.

Description

Technical Field

[0001] This invention relates to the field of advanced semiconductor packaging technology, and more specifically, to a method for integrating a conjugate inductor within a fan-out package structure and the resulting module structure, which is particularly suitable for high-density, high-performance power management integrated systems. Background Technology

[0002] With the rapid development of 5G communication, artificial intelligence and portable electronic devices, power systems have placed stringent requirements on the miniaturization, high efficiency and low electromagnetic interference of the core passive component, the inductor.

[0003] In the prior art, patent CN113053849A discloses an embedded support frame for an integrated inductor. This solution includes a core dielectric layer, a through-hole penetrating the core dielectric layer, and a magnetic core embedded within the core dielectric layer. The inductor coil includes inductance circuit layers on the upper and lower surfaces of the magnetic core and conductive copper pillars connecting the inductance circuit layers on both sides of the magnetic core. However, this solution has the following limitations: First, the method of forming the magnetic core is limited. This method forms the magnetic core by etching a layer of magnetic material, and the resulting magnetic core is essentially a thin-film magnetic core with limited magnetic properties (such as permeability and saturation current density), making it difficult to meet the high-performance requirements of power inductors.

[0004] Second, the core dielectric layer is a non-magnetic material. In this scheme, the core dielectric layer (such as polyimide, epoxy resin, etc.) is an insulating material that only serves a mechanical support function and cannot participate in the construction of the magnetic circuit. The magnetic flux is confined inside the magnetic core, resulting in low magnetic circuit utilization.

[0005] Third, the copper pillars are segmented and stacked. The conductive copper pillars in this design require two electroplating processes and precise alignment and connection, which is complex, has a low fault tolerance rate, and limits the structural reliability.

[0006] Fourth, the manufacturing process is complex. This solution requires multiple steps such as applying magnetic material layers, etching, bonding dielectric layers, and thinning, making the process cumbersome and unsuitable for large-scale production.

[0007] Therefore, there is an urgent need for an innovative packaged integrated inductor solution that can simplify the process while achieving the integrated integration of high-performance bulk magnetic cores and three-dimensional coils. Summary of the Invention

[0008] The present invention aims to overcome the shortcomings of the prior art and provide an integrated conjugate inductor structure and its manufacturing method. In the fan-out packaging process, the present invention innovatively introduces a magnetic molding layer and embeds a block magnetic core. By combining it with the redistribution layer process, a high-performance three-dimensional inductor structure is constructed inside the package, realizing the true integration of passive devices and active chips.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides an integrated conjugate inductor structure.

[0010] The structure is formed within an encapsulation body and is characterized by comprising: Several vertically extending copper pillars serve as an electrical interconnection and structural support framework; A magnetic encapsulation layer is provided, the copper pillar is disposed through the magnetic encapsulation layer, and at least one block-shaped magnetic core is embedded in the magnetic encapsulation layer; The first wiring layer and the second wiring layer are respectively disposed on the upper surface and the lower surface of the magnetic encapsulation layer, and each of them contains a planar spiral wire pattern. The planar spiral wire patterns in the first and second wiring layers are electrically connected through the copper pillars to form a three-dimensional spiral coil surrounding the block magnetic core. The magnetic encapsulation layer contains soft magnetic powder, and the magnetic encapsulation layer serves as a magnetic circuit extension of the bulk magnetic core, so that the magnetic flux forms a closed magnetic loop between the magnetic encapsulation layer and the bulk magnetic core.

[0011] Preferably, the volume content of soft magnetic powder in the magnetic encapsulation layer is 30% to 70%.

[0012] Preferably, the bulk magnetic core is a prefabricated ferrite, nanocrystalline, or amorphous alloy magnetic core, and the surface of the bulk magnetic core has an insulating coating.

[0013] Preferably, the copper pillar is a one-time electroplated integral through-structure with a diameter of less than 100 micrometers.

[0014] Preferably, it further includes an insulating molding layer covering the magnetic molding layer and the redistribution layer, wherein the insulating molding layer is a non-magnetic material.

[0015] Preferably, the surface of the insulating encapsulation layer is provided with an external interconnect structure.

[0016] Preferably, it further includes at least one semiconductor chip mounted on the redistribution layer.

[0017] Secondly, the present invention provides a method for manufacturing the above-mentioned integrated conjugate inductor structure.

[0018] The method includes the following steps: S1: A temporary substrate is provided, and a plurality of copper pillars are formed by electroplating on the substrate; S2: The copper pillar is first encapsulated with magnetic encapsulation material to form a magnetic encapsulation layer, and the copper pillar is embedded in the magnetic encapsulation layer; a cavity is processed on the magnetic encapsulation layer, a prefabricated block magnetic core is placed in the cavity, and the cavity is filled and fixed with magnetic encapsulation material. S3: Remove the temporary substrate and perform double-sided grinding on the structure after substrate removal, so that the two ends of the copper pillar are exposed from the upper and lower surfaces of the magnetic encapsulation layer, respectively. S4: Redundancy layers are fabricated on the upper and lower surfaces of the ground magnetic encapsulation layer to form planar spiral wire patterns. The planar spiral wire patterns on the upper and lower surfaces are electrically connected in series through the copper pillars to form a three-dimensional spiral coil. S5: Use non-magnetic insulating molding material to perform a second molding process on the overall structure to form an insulating molding layer.

[0019] Preferably, after step S4 and before step S5, the method further includes: mounting a semiconductor chip on the redistribution layer.

[0020] Preferably, in step S2, the magnetic encapsulating material is a polymer composite material mixed with soft magnetic powder.

[0021] Thirdly, the present invention provides a power management module.

[0022] The module includes an integrated conjugate inductor structure as described above and a power semiconductor chip mounted on the redistribution layer; the power semiconductor chip and the three-dimensional spiral coil are interconnected through the redistribution layer to form a power conversion circuit.

[0023] Compared with the prior art, the technical solution provided by the present invention has the following significant advantages: Fundamental improvement in magnetic core performance: This invention uses a prefabricated high-performance bulk magnetic core (ferrite / nanocrystalline / amorphous alloy) instead of a thin-film magnetic core formed by etching magnetic material layers, which fundamentally ensures high permeability and large saturation current capability, meeting the stringent requirements of power inductors.

[0024] A functional breakthrough in the magnetic encapsulation layer: The magnetic encapsulation layer of this invention not only serves as an encapsulation layer but also acts as a magnetic circuit extension for the bulk magnetic core, enabling the magnetic flux to form a closed magnetic loop between the magnetic encapsulation layer and the bulk magnetic core. In contrast, the core dielectric layer of prior art document 1 is a non-magnetic material and cannot participate in the construction of the magnetic circuit. This is the essential difference between the two in terms of magnetic circuit design.

[0025] The integrated and highly reliable copper pillar structure of this invention features a one-time electroplated, through-type structure with both ends exposed after double-sided grinding. In contrast, the copper pillar in prior art document 1 requires two electroplating processes with precise alignment and connection, resulting in a complex process and low reliability.

[0026] The process is simple and efficient: the manufacturing process of this invention requires only one magnetic encapsulation, one double-sided grinding, two RDL fabrications and one overall encapsulation, which greatly simplifies the process flow, is highly compatible with existing fan-out packaging production lines, and has the potential for large-scale production.

[0027] Integrated design of structure, material and magnetic circuit: The present invention uses the magnetic encapsulation layer as the structural matrix, magnetic circuit extension and electromagnetic shield at the same time, realizing the functional integration of "three-in-one" and producing a synergistic effect that cannot be achieved in prior art 1. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the manufacturing method and final structure according to an embodiment of the present invention.

[0029] The diagram is labeled as follows: 1. Temporary glass substrate; 2. Copper pillar; 4. Block magnetic core; 31. Magnetic encapsulation layer; 32. Redundancy layer (including coil); 33. Insulating encapsulation layer; 34. Patterned groove; 35. Electroplated pattern; 36. Solder resist layer; 5. Semiconductor chip. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0031] Example: Integrated Inductor and its Manufacturing Method Reference Figure 1 This embodiment describes in detail the manufacturing process and final form of an integrated conjugate inductor structure.

[0032] S1: Copper Pillar Construction A temporary glass substrate 1 with a release layer on its surface is provided. Through-hole patterns are formed by sputtering a seed layer, thick photoresist photolithography, and copper electroplating to form an array of copper pillars 2 with a height of approximately 100-150 μm. The diameter and spacing of the copper pillars 2 are designed according to the current and inductance value of the target inductor. In this step, the copper pillars are formed by a single electroplating process.

[0033] S2: Magnetic encapsulation and core embedding Using a molding process, an epoxy resin-based magnetic composite material containing 30%-70% by volume of soft magnetic powder such as Fe-Si-Al and Fe-Si-Cr is encapsulated on a substrate 1 covered with copper pillars 2 to form a magnetic encapsulation layer 31, in which the copper pillars 2 are embedded.

[0034] Subsequently, using a laser ablation process, a cavity of precise dimensions is fabricated on the magnetic encapsulation layer 31 corresponding to the future center of the coil. A pre-fabricated block magnetic core 4, such as a ferrite, nanocrystalline, or amorphous alloy core, is then placed into the cavity. The cavity gaps are then filled again using the same magnetic encapsulation material to complete the fixation and encapsulation of the magnetic core 4.

[0035] This step is the core of the invention: the magnetic encapsulation layer 31 serves both as a structural support and as a magnetic flux extension and closure path for the magnetic core 4. The soft magnetic powder contained in the magnetic encapsulation layer 31 and the bulk magnetic core 4 together form a continuous magnetic path in three-dimensional space.

[0036] S3: Carrier Removal and Double-Sided Grinding The temporary glass substrate 1 is removed by laser lift-off. Subsequently, the upper and lower surfaces of the structure are chemically and mechanically polished (CMP) until both ends of the copper pillar 2 are flatly exposed from the upper and lower surfaces of the magnetic encapsulation layer 31.

[0037] S4: Three-dimensional coil formation After planarization, standard fan-out redistribution layer (RDL) technology is applied to the upper and lower surfaces of the structure. Using polyimide or benzocyclobutene (BCB) as the dielectric layer, planar spiral copper wire patterns are fabricated on the upper and lower surfaces through photolithography, sputtering of seed layers, and pattern plating. Crucially, the spiral wire patterns on the upper and lower surfaces are electrically connected in series through pre-fabricated one-time electroplated copper pillars 2, thereby forming a complete spiral coil surrounding the embedded magnetic core 4 in three-dimensional space.

[0038] S5: Chip Mounting The power semiconductor chip 5 is mounted onto the designated pads of the top redistribution layer 32 using a reflow soldering process.

[0039] S6: Overall package Using conventional non-magnetic epoxy molding compound, the entire structure with chip 5 mounted is encapsulated by compression molding process to form an external insulating molding layer 33.

[0040] S7-S9: External interconnect fabrication: On the surface of the insulating molding layer 33, patterned grooves 34 extending to the pads of the bottom redistribution layer 32 are created using laser or photolithography. Subsequently, copper plating is applied to the grooves 34 through seed layer sputtering and pattern electroplating to form an electroplated pattern 35 that connects to the external PCB board. Finally, a solder mask layer 36 is applied to the non-connection areas for protection.

[0041] The technical scope of this invention is not limited to the content described above. Those skilled in the art can make various modifications and variations to the above embodiments without departing from the technical concept of this invention, and all such modifications and variations should fall within the protection scope of this invention.

Claims

1. An integrated conjugate inductor structure, characterized in that, Formed within an encapsulation, the structure includes: Several vertically extending copper pillars serve as an electrical interconnection and structural support framework; A magnetic encapsulation layer is provided, the copper pillar is disposed through the magnetic encapsulation layer, and at least one block-shaped magnetic core is embedded in the magnetic encapsulation layer; The first wiring layer and the second wiring layer are respectively disposed on the upper surface and the lower surface of the magnetic encapsulation layer, and each of them contains a planar spiral wire pattern. The planar spiral wire patterns in the first and second wiring layers are electrically connected through the copper pillars to form a three-dimensional spiral coil surrounding the block magnetic core. The magnetic encapsulation layer contains soft magnetic powder, and the magnetic encapsulation layer serves as a magnetic circuit extension of the bulk magnetic core, so that the magnetic flux forms a closed magnetic circuit between the magnetic encapsulation layer and the bulk magnetic core.

2. The integrated conjugate inductor structure according to claim 1, characterized in that, The volume content of soft magnetic powder in the magnetic encapsulation layer is 30% to 70%.

3. The integrated conjugate inductor structure according to claim 1, characterized in that, The bulk magnetic core is a prefabricated ferrite, nanocrystalline, or amorphous alloy magnetic core, and the surface of the bulk magnetic core has an insulating coating.

4. The integrated conjugate inductor structure according to claim 1, characterized in that, The copper pillar is a one-time electroplated integral through-structure with a diameter of less than 100 micrometers, and the copper pillar penetrates the upper and lower surfaces of the magnetic encapsulation layer.

5. The integrated conjugate inductor structure according to claim 1, characterized in that, It also includes an insulating plastic encapsulation layer covering the magnetic plastic encapsulation layer and the redistribution layer. The insulating plastic encapsulation layer is made of a non-magnetic material. The surface of the insulating plastic encapsulation layer is provided with an external interconnect structure. The external interconnect structure includes a patterned groove, a conductive pattern electroplated in the groove, and a solder resist layer.

6. The integrated conjugate inductor structure according to claim 1, characterized in that, It also includes at least one semiconductor chip mounted on the redistribution layer, the semiconductor chip being electrically connected to the three-dimensional spiral coil through the redistribution layer.

7. A method for manufacturing an integrated conjugate inductor structure as described in any one of claims 1 to 6, characterized in that, Includes the following steps: S1: A temporary substrate is provided, and a plurality of copper pillars are formed by electroplating on the substrate; S2: The copper pillar is first encapsulated with magnetic encapsulation material to form a magnetic encapsulation layer, and the copper pillar is embedded in the magnetic encapsulation layer; a cavity is processed on the magnetic encapsulation layer, a prefabricated block magnetic core is placed in the cavity, and the cavity is filled and fixed with magnetic encapsulation material. S3: Remove the temporary substrate and perform double-sided grinding on the structure after substrate removal, so that the two ends of the copper pillar are exposed from the upper and lower surfaces of the magnetic encapsulation layer, respectively. S4: Redundancy layers are fabricated on the upper and lower surfaces of the ground magnetic encapsulation layer to form planar spiral wire patterns. The planar spiral wire patterns on the upper and lower surfaces are electrically connected in series through the copper pillars to form a three-dimensional spiral coil. S5: Use non-magnetic insulating molding material to perform a second molding process on the overall structure to form an insulating molding layer.

8. The method according to claim 7, characterized in that, After step S4 and before step S5, the method further includes: mounting a semiconductor chip on the redistribution layer.

9. The method according to claim 7, characterized in that, In step S2, the magnetic encapsulation material is a polymer composite material mixed with soft magnetic powder, and the volume content of the soft magnetic powder is 30% to 70%.

10. A power management module, characterized in that, include: The integrated conjugate inductor structure as described in any one of claims 1 to 6; A power semiconductor chip mounted on the redistribution layer; The power semiconductor chip and the three-dimensional spiral coil are interconnected through the redistribution layer to form a power conversion circuit, and the inductor structure and the power semiconductor chip are jointly encapsulated in the insulating plastic encapsulation layer.

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