High voltage power device structure based on flexible interconnection, method of fabrication and electric power device

Abstract

The application discloses a high-voltage power device structure based on flexible interconnection, a preparation method and power equipment, and belongs to the technical field of power semiconductor packaging. The high-voltage power device interconnection structure based on flexible interconnection provided by the application is a double-sided packaging structure, the conductive elastic sheet of the fusion middle deformation section and the two end fixed sections is used to overcome the inherent limitations of the double-sided interconnection packaging in the prior art, the rigid multi-chip interconnection structure in the traditional technology is converted into a flexible structure, and the flexible connection of the fixed copper plate and the movable copper plate is realized; based on the flexible connection, the height difference change caused by the machining tolerance of the chip, the solder layer, the metal pad and the like is compensated through the conductive elastic sheet, and the influence of the upper surface height difference on the welding quality during the multi-chip interconnection is avoided; meanwhile, through the high-voltage power device structure design based on flexible interconnection, the current-carrying capacity, the reliability and the ability to resist thermal stress aging of the high-voltage power device are improved.

Description

Technical Field

[0001] This invention relates to the field of power semiconductor packaging technology, specifically to a high-voltage power device structure and fabrication method based on flexible interconnection, and power equipment. Background Technology

[0002] With the rapid advancements in power electronics technology, the demand for power conversion systems with high power density, superior efficiency, and impeccable reliability is becoming increasingly urgent. Silicon carbide (SiC), a shining star among third-generation semiconductor materials, is gradually becoming a core driving force behind this revolution thanks to its excellent physical and chemical properties. Under extreme high-voltage and high-frequency operating conditions, the parallel connection technology of SiC power chips acts like a powerful east wind, greatly improving the current carrying capacity of the module and precisely meeting the stringent requirements of high-power power conversion and transmission. This technology not only gives the system unprecedented flexibility but also, through its built-in redundancy design, builds an unbreakable defense for the system's reliability and availability.

[0003] High-voltage, high-frequency power devices, especially those made of advanced materials such as silicon carbide, are gradually demonstrating their immeasurable application potential in several key fields, including industrial manufacturing, energy conversion, and transportation, thanks to their superior voltage withstand performance, low on-state loss, excellent thermal tolerance and thermal conductivity, and astonishing switching speed. In applications requiring high power output, multi-chip parallel current amplification technology for silicon carbide power modules is particularly important. Traditional packaging and interconnect structures fall short in meeting this demand, primarily due to their limited current carrying capacity, challenges in insulation performance, and the high-precision processing requirements and tolerance compensation issues.

[0004] Traditional packaging solutions, whether single-sided or double-sided, have significant limitations. While single-sided structures are simple, their reliance on bonding wires for electrical connections limits current carrying capacity and increases design complexity and operational risks due to parasitic inductance and insufficient insulation. Double-sided structures consist of two ceramic substrates. The power semiconductor chip is soldered onto the lower ceramic substrate, and a metal pad is soldered to the chip's upper surface. The upper ceramic substrate is then soldered to the upper surface of the metal pad. This method replaces bonding wires with metal pads and ceramic substrates, effectively improving device current carrying capacity and reducing parasitic parameters. The pads also prevent device termination discharge, making it highly suitable for high-voltage, high-power applications. However, existing double-sided interconnect structures, due to the rigidity of the upper and lower ceramic substrates, struggle to compensate for height differences caused by manufacturing tolerances in the chip, solder layer, and metal pad. This hinders parallel packaging of multiple chips. Furthermore, during device operation, the chip generates heat and expands, and this rigid connection structure cannot mitigate the thermal stress caused by chip temperature rise.

[0005] Therefore, how to provide a double-sided packaging structure for high-voltage power devices based on flexible interconnection to improve the current carrying capacity and reliability of high-voltage power semiconductor devices has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a high-voltage power device structure and fabrication method based on flexible interconnection, as well as a power equipment, to overcome the inherent limitations of rigid structure in existing double-sided interconnection packaging, which makes it difficult to compensate for height differences caused by processing tolerances of chips, solder layers, metal pads, etc., and to effectively alleviate the thermal stress problem generated during chip operation.

[0007] The present invention solves the above-mentioned technical problems through the following technical solution:

[0008] A high-voltage power device structure based on flexible interconnection includes a silver pillar, a movable copper plate, a fixed copper plate, a supporting copper pillar, a power terminal, a conductive spring, a ceramic substrate, and a power semiconductor chip.

[0009] The conductive spring includes a deformable section in the middle and fixed sections at both ends. A fixed copper plate is provided below the fixed section, and power terminals are provided on the fixed copper plate. The power terminals are used to realize the electrical connection between the high-voltage power device and the external circuit. A supporting copper column is fixed below the fixed copper plate, and the lower surface of the supporting copper column is completely attached to the ceramic substrate. Below the deformable section, a movable copper plate, a silver column and a power semiconductor chip are sequentially fixed to the ceramic substrate. The deformable section is used to compensate for the height difference between the upper surfaces of the silver columns when the power semiconductor chips are interconnected.

[0010] The silver pillar and the supporting copper pillar are at the same height, as are the movable copper plate and the fixed copper plate.

[0011] Furthermore, the deformable section in the middle of the conductive spring is a corrugated protrusion with intervals, and the intervals are consistent with the height of the fixed section of the conductive spring.

[0012] Furthermore, the conductive spring is made of spring steel.

[0013] Furthermore, the thickness of the conductive spring is 0.2 mm to 0.5 mm.

[0014] Furthermore, the height of the silver pillar and the supporting copper pillar is 3 mm to 5 mm.

[0015] Furthermore, the thickness of the movable copper plate and the fixed copper plate is 0.5 mm to 1 mm.

[0016] A method for fabricating a high-voltage power device structure based on flexible interconnection includes the following steps:

[0017] Step 1: Use computer-controlled precision machining to process the integrated structure of fixed copper plate, supporting copper column and power terminal; level the supporting copper column to make the lower surface of the supporting copper column uniform in height, and fix the supporting copper column to the ceramic substrate.

[0018] Step 2: Fix the fixed copper plate to the lower part of the fixed section of the conductive spring, and fix the movable copper plate to the lower part of the deformable section of the conductive spring. The flexible connection between the fixed copper plate and the movable copper plate is achieved through the conductive spring.

[0019] Step 3: Fix the lower surface of the movable copper plate to the upper surface of the silver column; fix the lower surface of the silver column to the upper surface of the power semiconductor chip; fix the lower surface of the power semiconductor chip to the ceramic substrate.

[0020] Furthermore, the fixed copper plate is fixedly connected to the lower part of the fixed section of the conductive spring by laser welding; the movable copper plate is fixedly connected to the lower part of the deformable section of the conductive spring by laser welding.

[0021] Furthermore, the supporting copper pillars are fixedly welded to the ceramic substrate using tin-based solder pads.

[0022] An electrical device includes: the aforementioned high-voltage power device structure based on flexible interconnection.

[0023] Compared with the prior art, the positive and progressive effects of the present invention are as follows:

[0024] This invention provides a high-voltage power device structure based on flexible interconnection. By integrating conductive springs in the middle deformation section and the fixed sections at both ends, it overcomes the inherent limitations of rigid structures in existing double-sided interconnect packaging. It transforms the rigid multi-chip interconnection structure in traditional technology into a flexible structure, realizing a flexible connection between fixed and movable copper plates. Based on the flexible connection, the conductive springs compensate for height differences caused by processing tolerances of chips, solder layers, and metal pads, thus avoiding the impact of upper surface height differences on welding quality in multi-chip interconnection.

[0025] Furthermore, the conductive spring is made of spring steel, which effectively alleviates the thermal stress generated during chip operation and improves the ability of high-voltage power devices to resist thermal stress aging during operation.

[0026] Furthermore, by controlling the height of the silver pillar and the supporting copper pillar to 3 mm, the insulation distance of the power semiconductor chip is effectively increased, meeting the insulation requirements of chip packaging interconnection.

[0027] The present invention provides a method for fabricating a high-voltage power device structure based on flexible interconnection. This method utilizes computer-controlled precision machining (integrated CNC machining) to achieve high-precision integrated manufacturing of the fixed copper plate, supporting copper pillars, and power terminals, eliminating the increased process complexity and contact resistance issues caused by subsequent welding. By leveling the lower surface of the supporting copper pillars, the height of the pillars is made consistent, thereby ensuring the quality and stability of subsequent welding operations. This not only demonstrates process reliability but also simplifies complex steps in traditional manufacturing processes, making it suitable for large-scale market applications.

[0028] The power equipment based on the flexible interconnection high-voltage power device structure provided by this invention improves the current carrying capacity, reliability and resistance to thermal stress aging of the high-voltage power device through the design of the flexible interconnection high-voltage power device structure. Attached Figure Description

[0029] The accompanying drawings are provided to further understand the invention and constitute a part of this invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0030] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0031] Figure 2 This is a structural diagram of the power semiconductor chip, silver pillar, movable copper plate, fixed copper plate, and conductive spring of the present invention.

[0032] Figure 3 This is a schematic diagram of the fixed copper plate, supporting copper column, and power terminal of the present invention;

[0033] Figure 4 This is a schematic diagram of the welding structure of the present invention;

[0034] In the diagram, 1 is the silver pillar; 2 is the movable copper plate; 3 is the fixed copper plate; 4 is the supporting copper pillar; 5 is the power terminal; 6 is the conductive spring; 7 is the ceramic substrate; 8 is the power semiconductor chip; 9 is the first weld joint; and 10 is the second weld joint. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0036] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0037] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0038] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing the present 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, and therefore should not be construed as a limitation of the present invention. Furthermore, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0039] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0040] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" 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 the present invention according to the specific circumstances.

[0041] A high-voltage power device structure based on flexible interconnection includes a silver pillar 1 soldered above a power semiconductor chip 8, a conductive spring 6 connecting a movable copper plate 2 and a fixed copper plate 3, a ceramic substrate 7, a supporting copper pillar 4, and power terminals 5. The lower surface of the silver pillar 1 is connected to the upper surface of the power semiconductor chip 8, and the supporting copper pillar 4 and the lower surface of the power semiconductor chip 8 are connected to the upper surface of the ceramic substrate 7. The connection of the above structure realizes the flow and control of electrical energy during the interconnection of power semiconductor chips. During the process, when the fixed copper plate 3 is connected to the ceramic substrate 7 through the supporting copper pillar 4, the upper surface of the power semiconductor chip 8 is connected to the movable copper plate 2 through the silver pillar 1. At this time, the conductive spring 6 undergoes slight deformation, compensating for the height difference caused by the chip and the silver pillar 1 during processing, and realizing a reliable connection of multiple power semiconductor chips 8.

[0042] Among them, the silver column 1, movable copper plate 2, fixed copper plate 3, supporting copper column 4, power terminal 5, and conductive spring 6 are all machined; the fixed copper plate 3, supporting copper column 4, and power terminal 5 are integrated CNC machined and sheet metal for bending metal, omitting the welding process and eliminating the increased process complexity and contact resistance problems caused by subsequent welding; the fixed copper plate 3, supporting copper column 4, and power terminal 5 are integrated in that the bottom surfaces of multiple copper support columns are kept at the same height and connected to the ceramic substrate below through tin-based solder pads; the two ends of the conductive spring 6 are connected to the movable copper plate 2 and the fixed copper plate 3 by laser welding.

[0043] The upper surface of the power semiconductor chip 8 is connected to the lower surface of the silver pillar 1 via a tin-based solder pad. The upper surface of the silver pillar 1 is connected to the lower surface of the movable copper plate 2 via a tin-based solder pad. In this process, the height difference of the upper surfaces of the multiple silver pillars 1 is compensated by the deformation of the conductive spring 6. The thickness of the conductive spring 6 is 0.2 mm; the height of the silver pillars and the height of the supporting copper pillars are both 3 mm; the thickness of the fixed copper plate and the movable copper plate is 1 mm.

[0044] The position of the power semiconductor chip 8 is arranged according to the position of the copper layer on the ceramic substrate and the first welding is completed. The silver pillar is welded on top of the chip according to the chip position and the second welding is completed. The third welding realizes the welding of the upper surface of the silver pillar to the lower surface of the movable copper plate, and the upper copper layer of the ceramic substrate to the supporting copper pillar, and the welding position is arranged according to the upper layer of the substrate.

[0045] The present invention discloses a method for fabricating a high-voltage power device structure based on flexible interconnection as follows:

[0046] The movable copper plate structure and the fixed copper plate structure with supporting copper pillars are manufactured by machining (integrated CNC machining). The power terminals are made by sheet metal process, and then the lower surface of the supporting copper pillars is leveled. Tin-based solder pads are used to weld the movable copper plate structure and the fixed copper plate structure with supporting copper pillars to the corresponding positions on the upper surface of the silver pillars and the upper surface of the ceramic substrate to achieve flexible interconnection of multi-chip structure.

[0047] The present invention will be further described in detail below with reference to the accompanying drawings. These descriptions are for explanation purposes only and not for limitation.

[0048] See Figures 1-4 A high-voltage power device structure based on flexible interconnection includes a silver pillar 1, a movable copper plate 2, a fixed copper plate 3, a supporting copper pillar 4, a power terminal 5, a conductive spring 6, a ceramic substrate 7, a power semiconductor chip 8, a first welding point 9, and a second welding point 10. The conductive spring 6 includes a deformation section in the middle and fixed sections at both ends. The fixed copper plate 3 is disposed below the fixed section, and the power terminal 5 is disposed on the fixed copper plate 3. The power terminal 5 is used to realize the electrical connection between the high-voltage power device and the external circuit. The supporting copper pillar 4 is fixed below the fixed copper plate 3, and the lower surface of the supporting copper pillar 4 is completely attached to and fixed on the ceramic substrate 7. The deformation section is fixed to the ceramic substrate 7 in sequence via the movable copper plate 2, the silver pillar 1, and the power semiconductor chip 8. The deformation section is used to compensate for the height difference between the upper surfaces of the silver pillars when the power semiconductor chips 8 are interconnected. The silver pillar 1 and the supporting copper pillar 4 have the same height, and the movable copper plate 2 and the fixed copper plate 3 have the same height.

[0049] Preferably, the conductive spring 6 is made of spring steel, and the deformation section in the middle of the conductive spring 6 is a corrugated protrusion with intervals, the intervals being consistent with the height of the fixed section of the conductive spring 6.

[0050] Preferably, the ceramic substrate 7 is made of ceramic material.

[0051] Preferably, the thickness of the conductive spring 6 is 0.2 mm to 0.5 mm.

[0052] Preferably, the height of the silver pillar 1 and the supporting copper pillar 4 is 3 mm to 5 mm.

[0053] Preferably, the thickness of the movable copper plate 2 and the fixed copper plate 3 is 0.5 mm to 1 mm.

[0054] A method for fabricating a high-voltage power device structure based on flexible interconnection includes the following steps:

[0055] Step 1: Use computer digital control precision machining to realize the integrated structure of fixed copper plate 3, supporting copper column 4 and power terminal 5; level the supporting copper column 4 to make the lower surface of the supporting copper column 4 uniform in height, and fix the supporting copper column 4 to the ceramic substrate 7.

[0056] Step 2: Fix the fixed copper plate 3 below the fixed section of the conductive spring 6, and fix the movable copper plate 2 below the deformable section of the conductive spring 6. The flexible connection between the fixed copper plate 3 and the movable copper plate 2 is achieved through the conductive spring 6.

[0057] Step 3: Weld the lower surface of the movable copper plate 2 to the upper surface of the silver pillar 1 to create a second weld 10; fix the lower surface of the silver pillar 1 to the upper surface of the power semiconductor chip 8; fix the lower surface of the power semiconductor chip 8 to the ceramic substrate 7.

[0058] Preferably, the fixed copper plate 3 is fixedly connected to the lower part of the fixed section of the conductive spring 6 by laser welding; the movable copper plate 2 is fixedly connected to the lower part of the deformable section of the conductive spring 6 by laser welding.

[0059] Preferably, the supporting copper pillar 4 is fixedly welded to the ceramic substrate 7 by tin-based solder pads, forming the first weld joint 9.

[0060] This invention discloses a high-voltage power device structure based on flexible interconnection, with reference to... Figure 1 The system consists of a parallel ceramic substrate, a movable copper plate, a fixed copper plate, and conductive springs. A power semiconductor chip is soldered onto the ceramic substrate. A silver pillar is soldered to the upper surface of the power semiconductor chip, and a movable copper plate is soldered to the upper surface of the silver pillar. The movable copper plate is flexibly connected to the fixed copper plate via conductive springs. Supporting copper pillars are positioned at corresponding locations on the fixed copper plate and are soldered to the ceramic substrate. Power terminals are located on the fixed copper plate of the high-voltage power device to achieve electrical connection between the device and external circuits.

[0061] High-voltage power semiconductor chips are soldered onto a ceramic substrate, with silver pillars soldered on top. During the interconnection process, the upper surfaces of the silver pillars exhibit height differences due to tolerances in the manufacturing of the chip, the silver pillars, and the solder layer. However, the supporting copper pillars undergo leveling during manufacturing, eliminating these height differences and ensuring a reliable connection. Therefore, to ensure a reliable connection between the copper pillars and the ceramic substrate during soldering, a conductive spring is applied to compensate for the height differences on the upper surfaces of the silver pillars. When a 10N pressure is applied to the upper surface of the movable copper plate, the plate descends by more than 0.5mm, effectively compensating for the height differences.

[0062] The connection between the supporting copper pillars and the power terminals and the fixed copper plate is achieved through integrated machining, eliminating the increased process complexity and contact resistance issues caused by subsequent welding.

[0063] The conductive spring can alleviate thermal stress during chip operation, and its high fatigue resistance can effectively reduce the risk of failure due to fatigue aging at the conductive spring.

[0064] This invention proposes a high-voltage power device structure based on flexible interconnection. By using conductive springs, a rigid multi-chip interconnect structure is transformed into a flexible structure, effectively compensating for height differences during multi-chip interconnection and improving process reliability and redundancy. Through flexible design, the thermal stress generated by chip heat during operation is effectively mitigated, enhancing the overall electrothermal stability of the module.

[0065] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A high-voltage power device structure based on flexible interconnection, characterized in that, It includes a silver column (1), a movable copper plate (2), a fixed copper plate (3), a supporting copper column (4), a power terminal (5), a conductive spring (6), a ceramic substrate (7), and a power semiconductor chip (8); The conductive spring (6) includes a deformation section in the middle and fixed sections at both ends. A fixed copper plate (3) is provided below the fixed section. A power terminal (5) is provided on the fixed copper plate (3). The power terminal (5) is used to realize the electrical connection between the high voltage power device and the external circuit. A supporting copper column (4) is fixed below the fixed copper plate (3). The lower surface of the supporting copper column (4) is completely attached to the ceramic substrate (7). The deformation section is fixed to the ceramic substrate (7) in sequence via a movable copper plate (2), a silver column (1) and a power semiconductor chip (8). The deformation section is used to compensate for the height difference between the upper surfaces of the silver column (1) when the power semiconductor chip (8) is interconnected. Among them, the silver column (1) and the supporting copper column (4) are at the same height, and the movable copper plate (2) and the fixed copper plate (3) are at the same height; the deformation section in the middle of the conductive spring (6) is a raised corrugated section with intervals, and the intervals are at the same height as the fixed section of the conductive spring (6).

2. The high-voltage power device structure based on flexible interconnection according to claim 1, characterized in that, The conductive spring (6) is made of spring steel.

3. A high-voltage power device structure based on flexible interconnection according to claim 1, characterized in that, The thickness of the conductive spring (6) is 0.2 mm to 0.5 mm.

4. A high-voltage power device structure based on flexible interconnection according to claim 1, characterized in that, The height of the silver column (1) and the supporting copper column (4) is 3 mm to 5 mm.

5. A high-voltage power device structure based on flexible interconnection according to claim 1, characterized in that, The thickness of the movable copper plate (2) and the fixed copper plate (3) is 0.5 mm to 1 mm.

6. A method for fabricating a high-voltage power device structure based on flexible interconnect according to any one of claims 1 to 5, characterized in that, Includes the following steps: Step 1: Use computer digital control precision machining to process the integrated structure of fixed copper plate (3), supporting copper column (4) and power terminal (5); perform leveling treatment on the supporting copper column (4) so ​​that the lower surface of the supporting copper column (4) is uniform in height, and fix the supporting copper column (4) to the ceramic substrate (7). Step 2: Fix the fixed copper plate (3) below the fixed section of the conductive spring (6), and fix the movable copper plate (2) below the deformable section of the conductive spring (6). A flexible connection between the fixed copper plate (3) and the movable copper plate (2) is achieved through the conductive spring (6). Step 3: Fix the lower surface of the movable copper plate (2) to the upper surface of the silver column (1); fix the lower surface of the silver column (1) to the upper surface of the power semiconductor chip (8); fix the lower surface of the power semiconductor chip (8) to the ceramic substrate (7).

7. The method for fabricating a high-voltage power device structure based on flexible interconnection according to claim 6, characterized in that, The fixed copper plate (3) is fixedly connected to the lower part of the fixed section of the conductive spring (6) by laser welding; the movable copper plate (2) is fixedly connected to the lower part of the deformable section of the conductive spring (6) by laser welding.

8. The method for fabricating a high-voltage power device structure based on flexible interconnection according to claim 6, characterized in that, The supporting copper column (4) is fixedly welded to the ceramic substrate (7) by tin-based solder pads.

9. An electrical device, characterized in that, include: The high-voltage power device structure based on flexible interconnection as described in any one of claims 1 to 5.

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