Power supply substrate structure and preparation method thereof

Abstract

The invention provides a power supply substrate structure and a preparation method thereof. The preparation method comprises the following steps: coating a stripping layer on the surface of a first carrier; manufacturing a first plastic package body which is arranged in a snakelike shape; a hole is formed in the first plastic package body to form a molding through hole penetrating through the first plastic package body, and the molding through hole is filled with a conductive material; mounting a functional device in a reserved area on the first carrier; forming a second plastic package body through second packaging molding, wherein the second plastic package body covers all the functional devices and the first plastic package body; manufacturing a front rewiring layer on the upper surface of the second plastic package body; and manufacturing a back rewiring layer and a welding bump on the other surface of the second plastic package body. Functional devices such as a power device, an intermediate layer, a passive device and an active device are integrated in the power supply substrate in a three-dimensional manner, so that the integration level is remarkably improved, and the occupied space of the substrate is greatly reduced; the plurality of TMVs surround the functional device and provide a plurality of interconnection paths; the step-by-step molding reduces the internal residual stress of the packaging layer, reduces the warping degree of the substrate, and significantly reduces the cracking risk.

Description

Technical Field

[0001] This invention relates to the field of semiconductor packaging technology, and in particular to a power supply substrate structure and its fabrication method. Background Technology

[0002] As electronic devices evolve towards higher-density integration, thinner designs, and longer battery life, stringent requirements are being placed on the performance of power supply boards. As the core interconnect and power supply carrier for electronic devices, the integration level, interconnection efficiency, and reliability of the power supply board directly affect the overall performance of the device.

[0003] In existing technologies, traditional circuit boards (substrates) only have simple winding functions and do not integrate core components such as power devices and active devices. This forces electronic devices to be assembled from discrete components to form complete functional modules. Therefore, existing power supply substrates have the following drawbacks: (1) Discrete components are packaged independently and then assembled, which takes up a lot of space and has low integration, and cannot meet the development needs of miniaturization and high-density integration of electronic devices. (2) The interconnection path between devices is long, and parasitic parameters (such as parasitic resistance, capacitance and inductance) have a significant impact, resulting in low power supply efficiency and poor signal transmission stability, making it difficult to adapt to high-frequency communication scenarios. (3) The uniformity of the EMC thickness after overall molding is difficult to control, resulting in poor consistency of the drilling depth of subsequent through-hole (TMV) and affecting interconnect reliability; (4) Uneven resin flow during the overall molding process can easily generate residual stress inside the EMC, leading to an increased risk of substrate warping and cracking.

[0004] To address the aforementioned issues, there is an urgent need in this field to develop a highly integrated, high-precision, and highly reliable power supply substrate structure and its fabrication method, enabling efficient integration and stable interconnection of various types of devices. Summary of the Invention

[0005] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a power supply substrate structure to solve the problems of low integration, long power supply path, poor processing reliability, and high packaging stress in the prior art. At the same time, this invention will also provide a method for preparing the power supply substrate structure.

[0006] To achieve the above and other related objectives, the present invention provides the following technical solutions: A first aspect of the present invention provides a method for fabricating a power supply substrate structure, comprising the following steps: S1. Provide a first carrier and coat its surface with a release layer; S2. Fabricate a first plastic seal in a serpentine arrangement on the first carrier; S3. A through-hole (TMV) is formed by opening a hole in the first molding body to penetrate the first molding body, and conductive material is filled in the through-hole; S4. A functional device is mounted in a reserved area on the first carrier. The functional device is selected from at least one of power devices, interposers, passive devices, and active devices. S5. Use an integral mold to cover the mounted functional device and the first molding compound, perform a second encapsulation molding to form the second molding compound, and grind the surface of the second molding compound. S6. Fabricate a front redistribution layer (front RDL) on the upper surface of the second molding compound. S7. Attach the second carrier to the side forming the front rewiring layer and remove the first carrier; S8. Fabricate a back redistribution layer (back RDL) and solder bumps on the other side of the second molding compound; S9. Remove the second carrier to obtain the power supply substrate structure.

[0007] In step S2, the first encapsulation molding is performed using the corresponding first mold to form a first encapsulated body arranged in a serpentine pattern. The first encapsulated body is composed of two or more annular frames, with reserved areas for mounting functional devices inside the annular frames. There are through-holes or gaps between adjacent annular frames to provide a flow path for the molding compound of the second encapsulation molding.

[0008] In step S3, the surface of the first molding compound is ground, and then a through-hole (TMV) is formed in the first molding compound by laser drilling or mechanical drilling, and a conductive material is filled in by deposition and / or electroplating.

[0009] Furthermore, multiple molded through-holes are arranged at intervals along the shape of the first molding compound, so that each functional device is surrounded by multiple TMVs, providing multiple interconnection paths; and the TMVs are interconnected with the functional devices in close proximity, shortening the interconnection path; thereby effectively improving power supply efficiency, reducing signal transmission loss, and meeting the performance requirements of high-frequency communication scenarios.

[0010] In step S5, a second encapsulation molding process ensures complete encapsulation of the functional devices and TMV channels, avoiding space waste and providing more integrated functions while maintaining high current density. Furthermore, grinding exposes the pads and TMV of the functional devices, enabling electrical connection to the front-side RDL.

[0011] In step S8, the back redistribution layer is electrically connected to the TMV.

[0012] In step S8, the welding bump is a ball-mounted bump or an electroplated bump.

[0013] Furthermore, the first molding compound and the second molding compound are made of the same or different molding compounds.

[0014] Furthermore, when the first molding compound and the second molding compound are made of different molding compounds, the first molding compound is composed of an epoxy resin composition with low viscosity, low modulus, and high toughness, while the second molding compound is composed of an epoxy resin composition with high modulus and low coefficient of thermal expansion.

[0015] Specifically, the first molding compound comprises the following components in parts by weight: 100 parts of first epoxy resin, 20-40 parts of first curing agent, 0.5-3 parts of first curing accelerator, 400-600 parts of first filler, 5-20 parts of toughening agent, 1-5 parts of coupling agent, and 0.5-3 parts of release agent.

[0016] The first epoxy resin is selected from at least one of bisphenol A type epoxy resin, phenolic modified epoxy resin, and naphthalene-based epoxy resin. The first curing agent is selected from at least one of phenolic resin and acid anhydride curing agents; The first curing accelerator is selected from imidazole or phosphorus-based accelerators; The first filler is selected from spherical SiO2 with a particle size D50 of 1-10 μm and a purity of ≥99.9%. The toughening agent is selected from at least one of core-shell rubber (CSR) and carboxyl-terminated butadiene-acrylonitrile rubber (CTBN); The coupling agent is a silane coupling agent; The release agent is a fatty acid amide or polytetrafluoroethylene release agent.

[0017] The molding compound formulated with this method, due to its low filler content, exhibits reduced viscosity and minimizes material jamming during the preparation of the first molded body. The viscosity at 25°C is 3000-12000 mPa. The s ensures that the molding compound quickly and fully fills the serpentine mold, avoiding air bubble residue; while its low elastic modulus and high fracture toughness can adapt to the interfacial stress concentration characteristics of the slender structure of TMV.

[0018] Specifically, the second molding compound comprises the following components in parts by weight: 100 parts of second epoxy resin, 30-50 parts of second curing agent, 1-4 parts of second curing accelerator, 600-900 parts of second filler, 3-15 parts of toughening agent, 2-6 parts of coupling agent, and 1-4 parts of release agent.

[0019] The second epoxy resin is selected from at least one of high crosslinking density epoxy, BMI modified epoxy, and biphenyl type epoxy; The second curing agent is selected from at least one of phenolic resin and amine curing agents; The second curing accelerator is an imidazole or tertiary amine accelerator; The second filler is selected from a mixture of spherical SiO2 and thermally conductive filler, wherein the thermally conductive filler is selected from at least one of boron nitride (BN) and aluminum nitride (AlN), and the total particle size of the filler is D50 = 2-15 μm; The toughening agent is selected from at least one of core-shell rubber (CSR) and carboxyl-terminated butadiene-acrylonitrile rubber (CTBN); The coupling agent is a silane coupling agent; The release agent is a fatty acid amide or polytetrafluoroethylene release agent.

[0020] When the molding compound of this formulation is used to prepare the second molding compound, the high filler content and high elastic modulus provide sufficient mechanical support to prevent the functional devices from shifting or deforming in subsequent processes; while the low coefficient of thermal expansion can significantly reduce the residual stress of the encapsulation layer after molding and during high and low temperature cycling, thereby reducing substrate warping.

[0021] A second aspect of the present invention provides a power supply substrate structure, including a front redistribution layer, a back redistribution layer, and a plurality of functional devices and a TMV disposed between the two, wherein the functional devices are electrically connected to the front redistribution layer, and both ends of the TMV are electrically connected to the front redistribution layer and the back redistribution layer, respectively; the TMV is encapsulated in a first molding compound, the functional devices are encapsulated in a second molding compound, and the second molding compound simultaneously encapsulates the first molding compound.

[0022] Furthermore, the back redistribution layer is also provided with solder bumps.

[0023] Furthermore, the functional device is selected from at least one of power devices, interposers, passive devices, and active devices. Two or more functional devices are disposed between the front redistribution layer and the back redistribution layer.

[0024] As described above, the power supply substrate structure and its fabrication method of the present invention have the following beneficial effects: 1. This invention integrates functional devices such as power devices, interposers, passive devices, and active devices into the power supply substrate in three dimensions, replacing the traditional discrete device assembly mode, which significantly improves the integration level and greatly reduces the space occupied by the substrate.

[0025] 2. This invention transforms the power supply path from traditional planar wiring to three-dimensional wiring through the vertical conduction structure of TMV, significantly shortening the power supply path; and multiple TMVs surround the functional device, providing multiple interconnection paths; at the same time, TMVs work in conjunction with the front rewiring layer and the back rewiring layer to effectively reduce power supply resistance and parasitic inductance, reduce signal transmission loss, and meet the performance requirements of high-frequency communication scenarios.

[0026] 3. This invention achieves physical separation between the TMV area and the functional device area by completing the process sequence of TMV fabrication first and then mounting the device, thereby improving the accuracy of TMV hole positions and increasing the overall packaging yield of the power supply substrate. Moreover, the step-by-step molding reduces residual stress inside the packaging layer, reduces substrate warpage, and significantly reduces the risk of cracking. Furthermore, the shape, size, TMV hole diameter, and distribution of the first molding body can be flexibly adjusted through mold and laser parameters to adapt to different types and specifications of functional devices.

[0027] 4. This invention uses two formulations of molding compounds for two-stage encapsulation. The first encapsulation body is composed of a low-viscosity, low-modulus, and high-toughness epoxy resin composition, which ensures that the molding compound quickly and fully fills the serpentine mold, avoids air bubble residue, and is adapted to the interface stress concentration characteristics of the slender TMV structure. The second encapsulation body is composed of a high-modulus and low-thermal-expansion-coefficient epoxy resin composition, which provides sufficient mechanical support to prevent functional devices from shifting or deforming in subsequent processes, and can significantly reduce the residual stress of the encapsulation layer after molding and during high and low temperature cycling, thereby reducing substrate warpage.

[0028] 5. The core processes of this invention all adopt mature technologies in the semiconductor packaging field, with good equipment compatibility, easy control of process parameters, and the ability to achieve large-scale mass production. Attached Figure Description

[0029] Figure 1 The diagram shown is a structural schematic of the power supply substrate structure disclosed in this invention.

[0030] Figures 2a-2h The diagram shown illustrates the fabrication process of the power supply substrate structure disclosed in this invention.

[0031] Figure 3 The diagram shown is a structural schematic of the first encapsulated body disclosed in this invention.

[0032] Component designation explanation: 1. First carrier; 2. Release layer; 3. First encapsulation; 4. Molded through-hole; 5. Functional device; 6. Second encapsulation; 7. Front redistribution layer; 8. Second carrier; 9. Back redistribution layer; 10. Solder bump. Detailed Implementation

[0033] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0034] Example 1 This embodiment provides a method for fabricating a power supply substrate structure, including the following steps: S1, such as Figure 2aAs shown, a first carrier 1 is provided, and a release layer 2 is coated on its surface. The first carrier 1 is silicon-based or glass-based.

[0035] S2. The first encapsulation molding is performed on the first carrier 1 using the corresponding first mold to form a first encapsulated body 3 arranged in a serpentine pattern. The first encapsulated body 3 is composed of two or more annular frames, and the annular frames contain reserved areas for mounting functional devices 5. There are through channels or gaps between adjacent annular frames to provide a flow path for the molding compound of the second encapsulation molding.

[0036] S3, such as Figure 2b As shown, the surface of the first molding compound 3 is ground, and then a through-hole 4 (TMV) is formed in the first molding compound 3 by laser drilling or mechanical drilling, resulting in the following: Figure 3 The first molding compound 3 shown is then subjected to a sputtering process to deposit a seed layer on the hole walls and bottom, followed by electroplating to fill with conductive material. Multiple molded vias 4 are arranged at intervals along the shape of the first molding compound 3, so that each functional device 5 is surrounded by multiple molded vias 4, providing multiple interconnection paths, and allowing the molded vias 4 to be interconnected with the functional devices 5 in close proximity, shortening the interconnection path, thereby effectively improving power supply efficiency and reducing signal transmission loss.

[0037] S4, such as Figure 2c As shown, two or more functional devices 5 are mounted in a reserved area on the first carrier 1. The functional devices 5 are selected from at least one of power devices, interposers, passive devices, and active devices. A high-precision pick-and-place machine is used to accurately mount the functional devices 5 in the reserved area within the annular frame, ensuring the flatness of the functional devices 5.

[0038] S5, such as Figure 2d As shown, an integral mold is used to cover the mounted functional device 5 and the first molding compound 3, and a second molding process is performed to form the second molding compound 6. The surface of the second molding compound 6 is then ground to expose the pads and molded vias 4 of the functional device 5, enabling electrical connection with the front redistribution layer 7. The first molding compound 3 and the second molding compound 6 can be made of the same molding compound.

[0039] S6, such as Figure 2e As shown, a front redistribution layer 7 is fabricated on the upper surface of the second molding compound 6 through processes such as photolithography and electroplating to achieve electrical connection with the pads of the functional device 5 and the molded via 4.

[0040] S7, such as Figure 2f As shown, the second carrier 8 with the release layer 2 is attached to the surface of the front redistribution layer 7, and then the first carrier 1 is removed by a peeling process to expose the other side of the second encapsulation 6.

[0041] S8, such as Figure 2g As shown, the entire structure is flipped 180° to create a back redistribution layer 9 and solder bumps 10 on the other side of the second molding compound 6. The back redistribution layer 9 is electrically connected to the molded through-hole 4; the solder bumps 10 are either ball-mounted or electroplated bumps, forming the final electrical connection interface.

[0042] S9, such as Figure 2h As shown, removing the second carrier 8 yields the following result: Figure 1 The power supply substrate structure shown includes a front redistribution layer 7, a back redistribution layer 9, and a plurality of functional devices 5 and molded vias 4 (TMVs) disposed between the two. The functional devices 5 are electrically connected to the front redistribution layer 7, and the two ends of the molded vias 4 (TMVs) are electrically connected to the front redistribution layer 7 and the back redistribution layer 9, respectively. The molded vias 4 (TMVs) are encapsulated in a first molding compound 3, and the functional devices 5 are encapsulated in a second molding compound 6, which in turn encapsulates the first molding compound 3. The back redistribution layer 9 is also provided with solder bumps 10.

[0043] This power supply substrate structure integrates power devices, an interposer, passive devices, and active devices in three dimensions within the substrate, replacing the traditional discrete device assembly method. This significantly reduces the substrate space occupied and greatly improves integration. The molded through-hole 4 is closely interconnected with the functional device 5, shortening the interconnection path, effectively reducing the impact of parasitic parameters, improving power supply efficiency, and reducing signal transmission loss by more than 25%, meeting the performance requirements of high-frequency communication scenarios.

[0044] Example 2 This embodiment provides a method for fabricating a power supply substrate structure, including the following steps: S1, such as Figure 2a As shown, a first carrier 1 is provided, and a release layer 2 is coated on its surface. The first carrier 1 is silicon-based or glass-based.

[0045] S2. The first encapsulation molding is performed on the first carrier 1 using the corresponding first mold to form a first encapsulated body 3 arranged in a serpentine pattern. The first encapsulated body 3 is composed of two or more annular frames, and the annular frames contain reserved areas for mounting functional devices 5. There are through channels or gaps between adjacent annular frames to provide a flow path for the molding compound of the second encapsulation molding.

[0046] The first molding compound 3 is prepared using a low-viscosity, low-modulus, and high-toughness epoxy resin composition, comprising the following components in parts by weight: 100 parts of first epoxy resin, 20-40 parts of first curing agent, 0.5-3 parts of first curing accelerator, 400-600 parts of first filler, 5-20 parts of toughening agent, 1-5 parts of coupling agent, and 0.5-3 parts of release agent. The first epoxy resin is selected from at least one of bisphenol A type epoxy resin, phenolic modified epoxy resin, and naphthalene-based epoxy resin; the first curing agent is selected from at least one of phenolic resin and anhydride curing agent; the first curing accelerator is selected from imidazole or phosphorus-based accelerators; and the first filler is selected from spherical SiO2 with a particle size D50 of 1-10 micrometers and a purity ≥99.9%. Due to its low filler content, the molding compound formulated with this method has reduced viscosity and minimizes material jamming. At 25°C, its viscosity is 3000-12000 mPa·s, ensuring rapid and complete filling of the serpentine mold and preventing air bubble residue. Its low elastic modulus and high fracture toughness can be adapted to the interfacial stress concentration characteristics of the slender TMV structure.

[0047] S3, such as Figure 2b As shown, the surface of the first molding compound 3 is ground, and then a through-hole 4 (TMV) is formed in the first molding compound 3 by laser drilling or mechanical drilling, resulting in the following: Figure 3 The first molding compound 3 shown is then subjected to a sputtering process to deposit a seed layer on the hole walls and bottom, followed by electroplating to fill with conductive material. Multiple molded vias 4 are arranged at intervals along the shape of the first molding compound 3, so that each functional device 5 is surrounded by multiple molded vias 4, providing multiple interconnection paths, and allowing the molded vias 4 to be interconnected with the functional devices 5 in close proximity, shortening the interconnection path, thereby effectively improving power supply efficiency and reducing signal transmission loss.

[0048] S4, such as Figure 2c As shown, two or more functional devices 5 are mounted in a reserved area on the first carrier 1. The functional devices 5 are selected from at least one of power devices, interposers, passive devices, and active devices. A high-precision pick-and-place machine is used to accurately mount the functional devices 5 in the reserved area within the annular frame, ensuring the flatness of the functional devices 5.

[0049] S5, such as Figure 2d As shown, an integral mold is used to cover the mounted functional device 5 and the first molding compound 3, and a second encapsulation molding is performed to form the second molding compound 6. The surface of the second molding compound 6 is then ground to expose the pads and molded through holes 4 of the functional device 5, enabling it to make electrical connections with the front redistribution layer 7.

[0050] The second encapsulation body 6 is prepared using a high-modulus, low-thermal-expansion-coefficient epoxy resin composition, comprising the following components in parts by weight: 100 parts of second epoxy resin, 30-50 parts of second curing agent, 1-4 parts of second curing accelerator, 600-900 parts of second filler, 3-15 parts of toughening agent, 2-6 parts of coupling agent, and 1-4 parts of release agent. The second epoxy resin is selected from at least one of high-crosslinking-density epoxy, BMI-modified epoxy, and biphenyl-type epoxy; the second curing agent is selected from at least one of phenolic resin and amine curing agent; the second curing accelerator is an imidazole or tertiary amine accelerator; the second filler is selected from a mixture of spherical SiO2 and thermally conductive filler, and the thermally conductive filler is selected from at least one of boron nitride and aluminum nitride. This second encapsulation molding ensures complete encapsulation of the functional device 5 and the molded through-hole 4, avoiding space waste and providing more integrated functions while maintaining high current density. High filler content and high elastic modulus provide sufficient mechanical support to prevent functional device 5 from shifting or deforming in subsequent processes, while low coefficient of thermal expansion can significantly reduce residual stress in the encapsulation layer after molding and curing and during high and low temperature cycling, thus reducing substrate warping.

[0051] S6, such as Figure 2e As shown, a front redistribution layer 7 is fabricated on the upper surface of the second molding compound 6 through processes such as photolithography and electroplating to achieve electrical connection with the pads of the functional device 5 and the molded via 4.

[0052] S7, such as Figure 2f As shown, the second carrier 8 with the release layer 2 is attached to the surface of the front redistribution layer 7, and then the first carrier 1 is removed by a peeling process to expose the other side of the second encapsulation 6.

[0053] S8, such as Figure 2g As shown, the entire structure is flipped 180° to create a back redistribution layer 9 and solder bumps 10 on the other side of the second molding compound 6. The back redistribution layer 9 is electrically connected to the molded through-hole 4; the solder bumps 10 are either ball-mounted or electroplated bumps, forming the final electrical connection interface.

[0054] S9, such as Figure 2h As shown, removing the second carrier 8 yields the following result: Figure 1 The power supply substrate structure shown includes a front redistribution layer 7, a back redistribution layer 9, and a plurality of functional devices 5 and molded vias 4 (TMVs) disposed between the two. The functional devices 5 are electrically connected to the front redistribution layer 7, and the two ends of the molded vias 4 (TMVs) are electrically connected to the front redistribution layer 7 and the back redistribution layer 9, respectively. The molded vias 4 (TMVs) are encapsulated in a first molding compound 3, and the functional devices 5 are encapsulated in a second molding compound 6, which in turn encapsulates the first molding compound 3. The back redistribution layer 9 is also provided with solder bumps 10.

[0055] This embodiment uses two formulations of molding compounds for two encapsulation processes. The first encapsulation body 3 is composed of a low-viscosity, low-modulus, and high-toughness epoxy resin composition, which ensures that the molding compound quickly and fully fills the serpentine mold, avoids air bubble residue, and is adapted to the interface stress concentration characteristics of the slender TMV structure. The second encapsulation body 6 is composed of a high-modulus and low-thermal-expansion-coefficient epoxy resin composition, which can provide sufficient mechanical support to prevent the functional device 5 from shifting or deforming in subsequent processes, and can significantly reduce the residual stress of the encapsulation layer after molding and during high and low temperature cycling, thereby reducing substrate warpage.

[0056] In summary, this invention significantly improves integration and greatly reduces substrate space by three-dimensionally integrating functional devices such as power devices, interposers, passive devices, and active devices within the power supply substrate. Furthermore, multiple TMVs surround the functional devices, providing multiple interconnect paths. Step-by-step molding reduces residual stress within the encapsulation layer, lowers substrate warpage, and significantly reduces the risk of cracking. Therefore, this invention effectively overcomes the various shortcomings of existing technologies and possesses high industrial applicability.

[0057] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for fabricating a power supply substrate structure, characterized in that, Includes the following steps: S1. Provide a first carrier and coat its surface with a release layer; S2. Fabricate a first plastic seal in a serpentine arrangement on the first carrier; S3. A through-hole is formed in the first molding body to penetrate the first molding body, and conductive material is filled in the through-hole; S4. A functional device is mounted in a reserved area on the first carrier. The functional device is selected from at least one of power devices, interposers, passive devices, and active devices. S5. Perform a second encapsulation molding to form a second molded body, which covers all functional devices and the first molded body. Grind the surface of the second molded body. S6. Create a front redistribution layer on the upper surface of the second molding compound; S7. Attach the second carrier to the side forming the front rewiring layer and remove the first carrier; S8. Fabricate a back redistribution layer and solder bumps on the other side of the second molding compound; S9. Remove the second carrier to obtain the power supply substrate structure.

2. The preparation method according to claim 1, characterized in that, In step S2, the first molding compound is composed of two or more annular frames, the annular frames having reserved areas for mounting functional devices, and there are through holes or gaps between adjacent annular frames.

3. The preparation method according to claim 1, characterized in that, In step S3, the surface of the first molding compound is ground, and then a through hole is formed in the first molding compound by laser drilling or mechanical drilling to form a through hole that penetrates the first molding compound. The through hole is then filled with conductive material by deposition and / or electroplating.

4. The preparation method according to claim 1, characterized in that, The first and second molding compounds are made of the same or different molding compounds.

5. The preparation method according to claim 4, characterized in that, The first molding compound is composed of an epoxy resin composition with low viscosity, low modulus, and high toughness, while the second molding compound is composed of an epoxy resin composition with high modulus and low coefficient of thermal expansion.

6. The preparation method according to claim 5, characterized in that, The first molding compound comprises the following components in parts by weight: 100 parts of first epoxy resin, 20-40 parts of first curing agent, 0.5-3 parts of first curing accelerator, 400-600 parts of first filler, 5-20 parts of toughening agent, 1-5 parts of coupling agent, and 0.5-3 parts of release agent.

7. The preparation method according to claim 6, characterized in that, The first epoxy resin is selected from at least one of bisphenol A type epoxy resin, phenolic modified epoxy resin, and naphthalene-based epoxy resin; The first curing agent is selected from at least one of phenolic resin and acid anhydride curing agents; The first curing accelerator is selected from imidazole or phosphorus-based accelerators; The first filler is selected from spherical SiO2.

8. The preparation method according to claim 5, characterized in that, The second molding compound comprises the following components in parts by weight: 100 parts of second epoxy resin, 30-50 parts of second curing agent, 1-4 parts of second curing accelerator, 600-900 parts of second filler, 3-15 parts of toughening agent, 2-6 parts of coupling agent, and 1-4 parts of release agent.

9. The preparation method according to claim 8, characterized in that, The second epoxy resin is selected from at least one of high crosslinking density epoxy, BMI modified epoxy, and biphenyl type epoxy; The second curing agent is selected from at least one of phenolic resin and amine curing agents; The second curing accelerator is an imidazole or tertiary amine accelerator; The second filler is selected from a mixture of spherical SiO2 and thermally conductive filler, wherein the thermally conductive filler is selected from at least one of boron nitride and aluminum nitride.

10. A power supply substrate structure prepared by the preparation method according to any one of claims 1-9, characterized in that, It includes a front redistribution layer, a back redistribution layer, and several functional devices and a TMV disposed between the two. The functional devices are electrically connected to the front redistribution layer, and the two ends of the TMV are electrically connected to the front redistribution layer and the back redistribution layer, respectively. The TMV is encapsulated in a first molding compound, and the functional devices are encapsulated in a second molding compound, and the second molding compound also encapsulates the first molding compound.

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