High-thermal-conductivity silicon nitride substrate embedded with liquid metal and preparation method of high-thermal-conductivity silicon nitride substrate

Abstract

The invention provides a high thermal conductivity silicon nitride substrate embedded with liquid metal and a preparation method thereof, and the high thermal conductivity silicon nitride substrate comprises a first heat dissipation layer which is provided with an embedded closed cavity, and the cavity is filled with the liquid metal; the first brazing layer is located on one side of the first heat dissipation layer; the second heat dissipation layer is located on the side, away from the first heat dissipation layer, of the first brazing layer; the second brazing layer is located on the side, away from the first brazing layer, of the first heat dissipation layer; the third heat dissipation layer is located on the side, away from the first heat dissipation layer, of the second brazing layer. The high-thermal-conductivity silicon nitride substrate transfers heat generated by the semiconductor device from the second heat dissipation layer to the first heat dissipation layer with the liquid metal, and because the liquid metal is low in melting point and is heated to be molten into a liquid state, the heat is quickly transferred to the third heat dissipation layer through convection heat dissipation, so that the passive heat conduction capability of the substrate is enhanced. The problem that in the prior art, the heat conduction capacity of a silicon nitride substrate cannot meet the heat dissipation requirement of packaging of a miniaturized integrated high-power-density power module is solved.

Description

Technical Field

[0001] The present application relates to the technical field of semiconductor devices, and in particular to a high thermal conductivity silicon nitride substrate with embedded liquid metal and a preparation method thereof. Background Art

[0002] In the prior art, the thermal conductivity of the substrate prepared by the active metal brazing ceramic substrate (AMB) is mainly improved by changing the ratio of silicon nitride powder and sintering aid when preparing the substrate and optimizing the sintering process parameters. Although the thermal conductivity of the substrate is improved by improving the powder formula and sintering process parameters, the theoretical thermal conductivity and the actual thermal conductivity of the AMB substrate material are not high, which makes it unable to meet the heat dissipation requirements of miniaturized integrated high power density power module packaging. Summary of the invention

[0003] The main purpose of the present application is to provide a high thermal conductivity silicon nitride substrate with embedded liquid metal and a preparation method thereof, so as to solve the problem that the thermal conductivity of the silicon nitride substrate in the prior art cannot meet the heat dissipation requirements of miniaturized integrated high power density power module packaging.

[0004] In order to achieve the above-mentioned purpose, according to one aspect of the present application, a high thermal conductivity silicon nitride substrate with embedded liquid metal is provided, including: a first heat dissipation layer, having an embedded closed cavity, the cavity is filled with liquid metal, forming a passive fluid heat dissipation embedded in the silicon nitride substrate; a first brazing layer, located on one side of the first heat dissipation layer; a second heat dissipation layer, located on the side of the first brazing layer away from the first heat dissipation layer; a second brazing layer, located on the side of the first heat dissipation layer away from the first brazing layer; a third heat dissipation layer, located on the side of the second brazing layer away from the first heat dissipation layer.

[0005] Optionally, the liquid metal includes at least: pure gallium, gallium-indium alloy and gallium-indium-tin alloy.

[0006] Optionally, the silicon nitride substrate further includes a penetrating structure, and the penetrating structure sequentially penetrates the third heat dissipation layer and the second brazing layer to the first heat dissipation layer and contacts with the liquid metal.

[0007] In order to achieve the above-mentioned purpose, according to one aspect of the present application, a method for preparing a high thermal conductivity silicon nitride substrate with embedded liquid metal is provided, which is used to prepare the high thermal conductivity silicon nitride substrate, and the preparation method comprises: providing a first preliminary heat dissipation layer, the first preliminary heat dissipation layer having an embedded closed cavity; forming a first brazing layer and a second heat dissipation layer on one side of the first preliminary heat dissipation layer, and the first brazing layer is located between the first preliminary heat dissipation layer and the second heat dissipation layer; forming a second brazing layer and a third heat dissipation layer on the side of the first preliminary heat dissipation layer away from the first brazing layer, and the second brazing layer is located between the first preliminary heat dissipation layer and the third heat dissipation layer; filling the cavity with liquid metal to obtain a first heat dissipation layer, and the first heat dissipation layer, the first brazing layer, the second heat dissipation layer, the second brazing layer and the third heat dissipation layer form a high thermal conductivity silicon nitride substrate.

[0008] Optionally, the step of providing the first preliminary heat dissipation layer includes: providing a first sub-preparation heat dissipation layer, and cutting the first sub-preparation heat dissipation layer to form a hollow area in the first sub-preparation heat dissipation layer; arranging the second sub-preparation heat dissipation layer on one side of the first sub-preparation heat dissipation layer; arranging the third sub-preparation heat dissipation layer on the side of the first sub-preparation heat dissipation layer away from the second sub-preparation heat dissipation layer, and the first sub-preparation heat dissipation layer, the second sub-preparation heat dissipation layer and the third sub-preparation heat dissipation layer form the first preliminary heat dissipation layer.

[0009] Optionally, the preparation method also includes: before providing the third sub-preparatory heat dissipation layer, filling the hollow area with a sacrificial material; after forming the first preliminary heat dissipation layer, heat-treating the first preliminary heat dissipation layer to remove the sacrificial material, and sintering the first preliminary heat dissipation layer after the heat treatment to obtain a second preliminary heat dissipation layer.

[0010] Optionally, the steps of forming the second soldering layer and the third heat dissipation layer include: forming the second soldering layer on one side of the second preliminary heat dissipation layer; forming the third heat dissipation layer on the second soldering layer, the second heat dissipation layer, the first soldering layer, the third heat dissipation layer, the second soldering layer and the second preliminary heat dissipation layer forming a third preliminary heat dissipation layer; opening a hole in the third preliminary heat dissipation layer so that the third heat dissipation layer, the second soldering layer and the second preliminary heat dissipation layer have at least one potting hole, and the potting hole and the cavity are connected.

[0011] Optionally, the preparation method further comprises: pouring liquid metal into the cavity through the potting hole, and sealing the potting hole.

[0012] Optionally, before the step of pouring liquid metal into the cavity, the preparation method further comprises: heat treating the liquid metal to make the liquid metal fluid.

[0013] Optionally, the step of closing the potting hole includes: squeezing a high temperature resistant adhesive into the potting hole, and closing the potting hole after the high temperature resistant adhesive solidifies.

[0014] The technical solution of the present application is applied to provide a high thermal conductivity silicon nitride substrate embedded with liquid metal, including: a first heat dissipation layer, a first brazing layer, a second heat dissipation layer, a second brazing layer and a third heat dissipation layer, wherein the first heat dissipation layer is embedded in a closed cavity, the cavity is filled with liquid metal, and passive fluid heat dissipation is formed in the silicon nitride substrate; the first brazing layer is located on one side of the first heat dissipation layer; the second heat dissipation layer is located on the side of the first brazing layer away from the first heat dissipation layer; the second brazing layer is located on the side of the first heat dissipation layer away from the first brazing layer; the third heat dissipation layer is located on the side of the second brazing layer away from the second brazing layer. The semiconductor device located on the substrate will generate high heat when working, and the substrate transfers the heat from the second heat dissipation layer to the first heat dissipation layer embedded with liquid metal. Since the melting point of liquid metal is low, it melts into liquid state by heat, and the heat is quickly transferred to the third heat dissipation layer by convection heat dissipation, and the passive thermal conductivity of the substrate is enhanced without adding external equipment. The problem that the thermal conductivity of silicon nitride substrates in the prior art cannot meet the heat dissipation requirements of miniaturized integrated high power density power module packaging is solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The drawings constituting part of the present application are used to provide a further understanding of the present application. The exemplary embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0016] Figure 1 A schematic cross-sectional structure diagram of a high thermal conductivity silicon nitride substrate with embedded liquid metal provided in an embodiment of the present application is shown;

[0017] Figure 2 A schematic diagram of an exploded structure of a high thermal conductivity silicon nitride substrate with embedded liquid metal provided in an embodiment of the present application is shown;

[0018] Figure 3 A schematic flow chart of a method for preparing a high thermal conductivity silicon nitride substrate embedded with liquid metal provided in an embodiment of the present application is shown;

[0019] Figure 4 Shown in Figure 3 In the preparation method, a first sub-preparation heat dissipation layer is provided, and a top view schematic diagram of the substrate after a hollow area is formed in the first sub-preparation heat dissipation layer;

[0020] Figure 5 Shows the Figure 4A schematic diagram of the cross-sectional structure of the substrate after the first sub-prepared heat dissipation layer provided in the embodiment is placed on the second sub-prepared heat dissipation layer and a high-temperature adhesive is filled in the hollow area;

[0021] Figure 6 Shown in Figure 5 A schematic diagram of the cross-sectional structure of the substrate after a third sub-preparatory heat dissipation layer is arranged on the first sub-preparatory heat dissipation layer to form a second preliminary heat dissipation layer;

[0022] Figure 7 Shows the Figure 6 A schematic diagram of the cross-sectional structure of the substrate after the second preliminary heat dissipation layer formed in the embodiment is heat treated;

[0023] Figure 8 Shown in Figure 7 A schematic diagram of the cross-sectional structure of the substrate after the second preliminary heat dissipation layer in the substrate is brazed to form a third preliminary heat dissipation layer;

[0024] Fig. 9 Shows the Figure 8 Schematic diagram of the cross-sectional structure of the substrate after the third preliminary heat dissipation layer is subjected to a hole opening treatment.

[0025] The above drawings include the following reference numerals:

[0026] 10. First heat dissipation layer; 11. Liquid metal; 12. First preliminary heat dissipation layer; 13. Cavity; 131. Hollow area; 14. First sub-preparatory heat dissipation layer; 15. Second sub-preparatory heat dissipation layer; 16. Third sub-preparatory heat dissipation layer; 17. Sacrificial material; 18. Second preliminary heat dissipation layer; 19. Third preliminary heat dissipation layer; 20. Potting hole; 21. First brazing layer; 22. Second brazing layer; 31. Second heat dissipation layer; 32. Third heat dissipation layer; 40. Through structure. DETAILED DESCRIPTION

[0027] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0028] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0029] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so as to describe the embodiments of the present invention described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0030] It should be understood that when an element (such as a layer, film, region, or substrate) is described as being "on" another element, the element may be directly on the other element, or there may be intermediate elements. Moreover, in the specification and claims, when an element is described as being "connected" to another element, the element may be "directly connected" to the other element, or "connected" to the other element through a third element.

[0031] As introduced in the background technology, the prior art mainly adopts the method of changing the ratio of silicon nitride powder and sintering aid when preparing the substrate, and optimizing the sintering process parameters to improve the thermal conductivity of the substrate prepared by the AMB active metal welding technology. Although the thermal conductivity of the substrate is improved by improving the powder formula and sintering process parameters, the theoretical thermal conductivity and the use thermal conductivity of the AMB substrate material are still not high enough. In order to solve the problem that the thermal conductivity of the substrate in the prior art cannot meet the heat dissipation requirements of the miniaturized integrated high power density power module packaging, the embodiments of the present application provide a high thermal conductivity silicon nitride substrate with embedded liquid metal and a preparation method thereof.

[0032] The embodiment of the present application provides a high thermal conductivity silicon nitride substrate with embedded liquid metal, such as Figure 1 and Figure 2 As shown, it includes: a first heat dissipation layer 10, having an embedded closed cavity, the cavity is filled with liquid metal 11, forming a passive fluid heat dissipation embedded in a silicon nitride substrate; a first brazing layer 21, located on one side of the first heat dissipation layer 10; a second heat dissipation layer 31, located on the side of the first brazing layer 21 away from the first heat dissipation layer 10; a second brazing layer 22, located on the side of the first heat dissipation layer 10 away from the first brazing layer 21; a third heat dissipation layer 32, located on the side of the second brazing layer 22 away from the first heat dissipation layer 10.

[0033] By utilizing the convection heat dissipation of liquid metal, the thermal conductivity of the silicon nitride substrate is improved. The semiconductor device located on the second heat dissipation layer will generate high heat during operation. When the surface temperature of the second heat dissipation layer is higher than the temperature of the surrounding environment, the heat is transferred from the surface of the second heat dissipation layer to the liquid metal through heat conduction, so that the temperature of the liquid metal rises and melts into a liquid flowable substance (hereinafter referred to as fluid). After the liquid metal is heated, the temperature will rise, resulting in a temperature difference inside the fluid. This temperature difference will drive the movement of the fluid, forming natural convection, which can effectively take away the heat, thereby achieving heat dissipation and preventing damage caused by overheating of the semiconductor device. Passive convection heat dissipation is used to quickly transfer heat to the third heat dissipation layer, which enhances the thermal conductivity of the substrate without adding external equipment, and also saves the cost of external equipment. The problem that the thermal conductivity of the substrate in the prior art cannot meet the heat dissipation requirements of miniaturized integrated high power density power module packaging is solved.

[0034] In some embodiments, the material of the first heat dissipation layer may also be any one of aluminum oxide and aluminum nitride. The first heat dissipation layer may also be a direct bonded copper ceramic substrate (DBC) or an AMB ceramic substrate. The material and type of the first heat dissipation layer are not specifically limited in this application.

[0035] The above-mentioned miniaturized integrated high power density power module package may specifically be a silicon carbide power module package.

[0036] In the above optional embodiment, the liquid metal has the characteristics of high thermal conductivity, low melting point, and high boiling point. The liquid metal is injected into the embedded cavity of the first heat dissipation layer to form a heat dissipation medium flowing in the embedded cavity. The flow of liquid metal can significantly improve the heat transfer efficiency, especially in high power density power module packaging. By using liquid metal as the embedded heat dissipation material, not only the thermal conductivity of the substrate is greatly improved, but also due to the flow characteristics of the liquid metal, the thermal resistance of the heat of the semiconductor power device in the heat transfer path is further reduced, thereby further improving the heat dissipation efficiency of the semiconductor power device, and meeting the high requirements of miniaturized integrated high power density power module packaging for heat dissipation capabilities.

[0037] The above-mentioned liquid metal includes at least: pure gallium, gallium-indium alloy and gallium-indium-tin alloy. The melting point of pure gallium is about 29.76°C, the melting point of gallium-indium alloy is about 16.5°C to 17.5°C at room temperature, and the melting point of gallium-indium-tin alloy is about -19°C to 10°C at room temperature. The melting point of the liquid metal mixed with these three metals will vary due to different composition ratios. Generally, it will be in a liquid state at room temperature, or in a liquid state after absorbing the heat generated by the semiconductor device, so as to realize passive fluid heat dissipation embedded in the silicon nitride substrate.

[0038] In some optional embodiments, such as Figure 1 and Figure 2 As shown, the silicon nitride substrate further includes a through structure 40 , which sequentially penetrates the third heat dissipation layer 32 and the second soldering layer 22 to the first heat dissipation layer 10 and contacts the liquid metal 11 .

[0039] In the above optional embodiment, the through structure is a potting hole before being formed, and the potting hole is used for pouring liquid metal, and after pouring, it is sealed with a high temperature resistant adhesive to form a through structure. The material of the high temperature resistant adhesive can include any one of high temperature resistant epoxy resin, heat resistant acrylic glue, high temperature resistant silicone and high temperature resistant epoxy ceramic glue, and this application does not make specific limitations.

[0040] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0041] Figure 3 1 is a flow chart of a method for preparing a high thermal conductivity silicon nitride substrate with embedded liquid metal according to an embodiment of the present application. Figure 3 As shown, the method comprises the following steps:

[0042] Step S201, providing a first preliminary heat dissipation layer, wherein the first preliminary heat dissipation layer has an embedded closed cavity;

[0043] Specifically, the material of the first preliminary heat dissipation layer can be any one or more of silicon nitride, aluminum oxide and aluminum nitride. The first preliminary heat dissipation layer can be an AMB ceramic substrate or a DBC ceramic substrate. The first preliminary heat dissipation layer is formed by combining a plurality of sub-preparatory heat dissipation layers.

[0044] Step S202, forming a first soldering layer and a second heat dissipation layer on one side of the first preliminary heat dissipation layer, wherein the first soldering layer is located between the first preliminary heat dissipation layer and the second heat dissipation layer;

[0045] Specifically, the material of the first soldering layer may be any one or more of titanium, silver and copper, or any one or more of titanium, silver and tin, and the material of the second heat dissipation layer may be any one of copper, aluminum and tungsten.

[0046] Step S203, forming a second soldering layer and a third heat dissipation layer on a side of the first preliminary heat dissipation layer away from the first soldering layer, wherein the second soldering layer is located between the first preliminary heat dissipation layer and the third heat dissipation layer;

[0047] Specifically, the material of the second soldering layer is the same as that of the first soldering layer, and the material of the third heat dissipation layer is consistent with that of the second heat dissipation layer, and a repeated description thereof will not be made.

[0048] Step S204, filling liquid metal into the cavity to obtain a first heat dissipation layer, and the first heat dissipation layer, the first soldering layer, the second heat dissipation layer, the second soldering layer and the third heat dissipation layer form a high thermal conductivity silicon nitride substrate.

[0049] Specifically, the liquid metal is a liquid metal with a relatively low melting point, such as any one or more of pure gallium, gallium-indium alloy and gallium-indium-tin alloy.

[0050] The silicon nitride substrate prepared by this embodiment can improve the thermal conductivity of the substrate by utilizing the convection heat dissipation of liquid metal. The semiconductor device located on the second heat dissipation layer will generate high heat when working. When the surface temperature of the second heat dissipation layer is higher than the temperature of the surrounding environment, the heat is transferred from the surface of the second heat dissipation layer to the liquid metal through heat conduction, so that the temperature of the liquid metal rises and melts into a liquid fluid. After the liquid metal is heated, the temperature will rise, resulting in a temperature difference inside the fluid. This temperature difference will drive the movement of the fluid and form natural convection, which can effectively take away the heat, thereby achieving passive heat dissipation and preventing damage caused by overheating of the semiconductor device. The heat is quickly transferred to the third heat dissipation layer by convection heat dissipation, which enhances the passive thermal conductivity of the substrate. The problem that the thermal conductivity of the substrate in the prior art cannot meet the heat dissipation requirements of miniaturized integrated high power density power module packaging is solved.

[0051] In the specific implementation process, the above step S201 can be implemented by the following steps:

[0052] Step S2011, as Figure 4 As shown, a first sub-prepared heat dissipation layer 14 is provided, and the first sub-prepared heat dissipation layer 14 is cut to form a hollow area 131 in the first sub-prepared heat dissipation layer 14;

[0053] Specifically, the first sub-prepared heat dissipation layer can be a DBC ceramic substrate or an AMB ceramic substrate. The cut first sub-prepared heat dissipation layer is placed in a laser punching machine mold and fixed, and a hollow area (prepared embedded sealed cavity) is formed by laser cutting according to the pre-designed embedded cavity design size.

[0054] Step S2012, as Figure 5 and Figure 6 As shown, the second sub-preparatory heat dissipation layer 15 is arranged on one side of the first sub-preparatory heat dissipation layer 14; the third sub-preparatory heat dissipation layer 16 is arranged on the side of the first sub-preparatory heat dissipation layer 14 away from the second sub-preparatory heat dissipation layer 15, and the first sub-preparatory heat dissipation layer 14, the second sub-preparatory heat dissipation layer 15 and the third sub-preparatory heat dissipation layer 16 form the first preparatory heat dissipation layer 12.

[0055] Specifically, the first sub-prepared heat dissipation layer forming the hollow area is stacked with the second sub-prepared heat dissipation layer and the third sub-prepared heat dissipation layer, and then the above structure is subjected to isostatic pressing to form the first preparatory heat dissipation layer with a cavity.

[0056] In some optional embodiments, such as Figures 5 to 7 As shown, the preparation method further includes: before providing the third sub-prepared heat dissipation layer, filling the hollow area with a sacrificial material 17; after forming the first preparatory heat dissipation layer 12, heat-treating the first preparatory heat dissipation layer 12 to remove the sacrificial material 17, and sintering the first preparatory heat dissipation layer 12 after the heat treatment to obtain the second preparatory heat dissipation layer 18. Filling the sacrificial material 17 in the cavity can prevent the preparatory cavity formed by the hollow area and the second sub-prepared heat dissipation layer 15 from deforming during the isostatic pressing process.

[0057] In the above optional implementation, if Figure 5 As shown, the first sub-prepared heat dissipation layer 14 and the second sub-prepared heat dissipation layer 15 are stacked, and a sacrificial material 17, such as paraffin, is filled in the hollow area. Figure 6 As shown, the third sub-preparation heat dissipation layer 16 is stacked on the first sub-preparation heat dissipation layer 14, and the stacked structure is subjected to isostatic pressing to form adhesion between the first sub-preparation heat dissipation layer 14, the second sub-preparation heat dissipation layer 15 and the third sub-preparation heat dissipation layer 16, thereby forming the first preparatory heat dissipation layer 12. Figure 7 As shown, the first preliminary heat dissipation layer 12 after isostatic pressing is placed in a vacuum debinding furnace for debinding treatment, and the organic matter contained in the first preliminary heat dissipation layer 12 and the sacrificial material filled in the cavity are thermally decomposed and removed, and the first preliminary heat dissipation layer 12 after debinding is placed in a customized graphite crucible and subjected to air pressure sintering in a nitrogen atmosphere to obtain a second preliminary heat dissipation layer 18.

[0058] In order to be able to apply the first heat dissipation layer to a semiconductor device, such as Figure 8 and Fig. 9 As shown, the above-mentioned step S203 of the present application can be specifically implemented by the following steps: forming a second brazing layer 22 on one side of the second preliminary heat dissipation layer 18; forming a third heat dissipation layer 32 on the second brazing layer 22, and the second heat dissipation layer 31, the first brazing layer 21, the third heat dissipation layer 32, the second brazing layer 22 and the second preliminary heat dissipation layer 18 form a third preliminary heat dissipation layer 19; opening the third preliminary heat dissipation layer 19 so that the third heat dissipation layer 32, the second brazing layer 22 and the second preliminary heat dissipation layer 18 have at least one potting hole, and the potting hole and the cavity 13 are connected.

[0059] Specifically, Figure 8As shown, the second preliminary heat dissipation layer 18, the second heat dissipation layer 31 and the third heat dissipation layer 32 are placed in an ethanol or acetone cleaning device for cleaning, and the second preliminary heat dissipation layer 18 with the second heat dissipation layer 31 and the third heat dissipation layer 32 attached thereto is fixed with a clamp and then placed in a vacuum brazing furnace for brazing to obtain the third preliminary heat dissipation layer 19. Fig. 9 As shown, the third heat dissipation layer 32, the second soldering layer 22 and part of the second preliminary heat dissipation layer 18 are subjected to hole opening treatment so that the cavity 13 is connected to the outside through the potting hole 20. The hole opening treatment can be laser etching or chemical wet cleaning.

[0060] In some optional embodiments, the liquid metal is heat treated to make the liquid metal fluid.

[0061] In the above optional implementation, in order to smoothly fill the liquid metal into the cavity through the filling hole, the liquid metal can be heated to reach the melting point of the liquid metal, so that the liquid metal becomes liquid and flows into the cavity through the filling hole.

[0062] In some optional embodiments, the preparation method further includes: pouring liquid metal into the cavity through the potting hole, and sealing the potting hole.

[0063] In the above optional implementation, the third preliminary heat dissipation layer is placed in a container containing liquid metal, and the liquid metal is slowly injected into the cavity of the third preliminary heat dissipation layer through the potting hole by a potting device; the third preliminary heat dissipation layer filled with liquid metal is taken out from the liquid metal container, and the potting hole is sealed with a high temperature resistant adhesive to obtain a substrate.

[0064] The step of sealing the above-mentioned potting hole includes: squeezing a high-temperature resistant adhesive into the above-mentioned potting hole, and sealing the above-mentioned potting hole after the above-mentioned high-temperature resistant adhesive is solidified. The material of the high-temperature resistant adhesive may include any one of high-temperature resistant epoxy resin, heat-resistant acrylic glue, high-temperature resistant silicone and high-temperature resistant epoxy ceramic glue, and this application does not make specific limitations.

[0065] In order to enable those skilled in the art to more clearly understand the technical solution of the present application, the implementation process of the method for preparing a high thermal conductivity silicon nitride substrate embedded with liquid metal of the present application will be described in detail below in combination with specific embodiments.

[0066] This embodiment relates to a specific method for preparing a high thermal conductivity silicon nitride substrate with embedded liquid metal, comprising the following steps:

[0067] Step S1: Cut the 0.18μm thick silicon nitride green sheet (first sub-prepared heat dissipation layer) into green sheets with a size of 245mm×180mm, put the cut silicon nitride green sheet into the laser punching machine mold and fix it, and form a hollow area (prepared embedded closed cavity) by laser cutting according to the design size of the embedded cavity. Then use a CNC milling machine (Computer Numerical Control, CNC) milling cutter to grind the inner surface of the hollow area to meet the liquid metal flow requirements;

[0068] Step S2: Place the lower green sheet (second sub-preparation heat dissipation layer) in the lamination mold, then stack the first sub-preparation heat dissipation layer on the second sub-preparation heat dissipation layer and fix them. Then fill the preparation cavity with paraffin wax, and then stack the third sub-preparation heat dissipation layer on the first sub-preparation heat dissipation layer. The purpose of filling paraffin wax is to prevent the preparation cavity from deformation during the isostatic pressing process.

[0069] Step S3: After the laminated green sheets are fixed, they are placed in a bag, vacuumed and sealed. The vacuum-sealed green sheets are placed in an isostatic press, and are statically pressed at 20 MPa and 75°C for 15 minutes to complete the isostatic pressing of the green sheets and form the first preliminary heat dissipation layer;

[0070] Step S4: placing the first preliminary heat dissipation layer after isostatic pressing into a vacuum debinding furnace, heating it to 300° C., keeping it warm for 3 hours, then heating it to 500° C., keeping it warm for 4 hours, and performing debinding treatment to remove organic matter and paraffin contained in the first preliminary heat dissipation layer by thermal decomposition, thereby forming an embedded closed cavity;

[0071] Step S5: placing the first preliminary heat dissipation layer after the glue is discharged into a customized graphite crucible, and performing air pressure sintering in a nitrogen atmosphere, with a sintering pressure of 3Mpa, and heating the temperature to 1750-1850°C at a heating rate of 10°C per minute, and sintering time of 24-48 hours to obtain a second preliminary heat dissipation layer;

[0072] Step S6: Put the second preliminary heat dissipation layer, the second heat dissipation layer (copper sheet) and the third heat dissipation layer (copper sheet) into an ethanol or acetone cleaning device for cleaning, then print active metal solder paste on both sides of the second preliminary heat dissipation layer, and paste the copper sheet on the surface of the second preliminary heat dissipation layer, use a clamp to fix the second preliminary heat dissipation layer pasted with the copper sheet, and then put it into a vacuum brazing furnace for brazing at a brazing temperature of 800-900°C to obtain the third preliminary heat dissipation layer;

[0073] Step S7: Before pouring the liquid metal, firstly make holes in the third preliminary heat dissipation layer, so that the second soldering layer, the third heat dissipation layer and part of the third preliminary heat dissipation layer have at least one potting hole, the potting hole connects the cavity with the outside, and then preheats the liquid metal to a temperature exceeding its melting point to ensure its fluidity during the potting process. Put the third preliminary heat dissipation layer with the potting hole into a container containing liquid metal, and slowly inject the liquid metal into the cavity of the third preliminary heat dissipation layer through the potting equipment;

[0074] Step S8: Take out the third preliminary heat dissipation layer filled with liquid metal from the liquid metal container, then squeeze the high temperature resistant adhesive into the sealing hole, and after the high temperature resistant adhesive is initially solidified, put the third preliminary heat dissipation layer into a heat curing furnace, heat it to 120°C, and cure it for 2 hours. The high temperature resistant adhesive is cured and formed to ensure a firm bond between the high temperature resistant adhesive and the third preliminary heat dissipation layer to obtain a substrate.

[0075] The high thermal conductivity silicon nitride substrate with embedded liquid metal of the present application will be described in detail below with reference to specific embodiments.

[0076] Example 1

[0077] The present application provides a high thermal conductivity silicon nitride substrate with embedded liquid metal, comprising:

[0078] The first heat dissipation layer has a cavity filled with liquid metal, wherein the first heat dissipation layer is an AMB silicon nitride ceramic substrate, the size of the cavity is 35mm×25mm×0.15mm, and the liquid metal includes gallium-indium alloy.

[0079] The first brazing layer and the second brazing layer are respectively located on two opposite sides of the first heat dissipation layer, and the materials of the first brazing layer and the second brazing layer are silver-based alloy;

[0080] A second heat dissipation layer is located on a side of the first soldering layer away from the first heat dissipation layer, and the material of the second heat dissipation layer is copper;

[0081] The third heat dissipation layer is located on the side of the second soldering layer away from the first heat dissipation layer, and the material of the third heat dissipation layer is copper. The performance of the substrate using three groups of different alloys in the above embodiment 1 was tested, and the test results are as follows:

[0082] Table 1

[0083]

[0084] It can be seen from the above-mentioned multiple sets of experimental data that in the present application, an embedded closed cavity is set in the substrate, and the cavity is filled with liquid metal, and passive heat dissipation is adopted. Compared with the thermal conductivity of the substrate in the prior art, the thermal conductivity of the existing conventional silicon nitride substrate is 80W / (m·K), which can meet the heat dissipation requirements of miniaturized integrated high power density power module packaging.

[0085] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A high thermal conductivity silicon nitride substrate with embedded liquid metal, characterized in that: include: The first heat dissipation layer has an embedded closed cavity, wherein the cavity is filled with liquid metal to form a passive fluid heat dissipation embedded in the silicon nitride substrate; A first soldering layer, located on one side of the first heat dissipation layer; a second heat dissipation layer, located on a side of the first soldering layer away from the first heat dissipation layer; a second brazing layer, located on a side of the first heat dissipation layer away from the first brazing layer; The third heat dissipation layer is located on a side of the second soldering layer away from the first heat dissipation layer.

2. The high thermal conductivity silicon nitride substrate according to claim 1, characterized in that: The liquid metal at least includes: pure gallium, gallium-indium alloy and gallium-indium-tin alloy.

3. The high thermal conductivity silicon nitride substrate according to claim 1, characterized in that: The silicon nitride substrate further includes a penetrating structure, which sequentially penetrates the third heat dissipation layer and the second brazing layer to the first heat dissipation layer and contacts the liquid metal.

4. A method for preparing a high thermal conductivity silicon nitride substrate embedded with liquid metal, characterized in that: For preparing a high thermal conductivity silicon nitride substrate according to any one of claims 1 to 3, the preparation method comprises: Providing a first preliminary heat dissipation layer, wherein the first preliminary heat dissipation layer has an embedded closed cavity; forming a first soldering layer and a second heat dissipation layer on one side of the first preliminary heat dissipation layer, wherein the first soldering layer is located between the first preliminary heat dissipation layer and the second heat dissipation layer; forming a second soldering layer and a third heat dissipation layer on a side of the first preliminary heat dissipation layer away from the first soldering layer, wherein the second soldering layer is located between the first preliminary heat dissipation layer and the third heat dissipation layer; The cavity is filled with liquid metal to obtain a first heat dissipation layer, and the first heat dissipation layer, the first soldering layer, the second heat dissipation layer, the second soldering layer and the third heat dissipation layer form the high thermal conductivity silicon nitride substrate.

5. The preparation method according to claim 4, characterized in that: The step of providing the first preliminary heat dissipation layer comprises: Providing a first sub-prepared heat dissipation layer, and cutting the first sub-prepared heat dissipation layer to form a hollow area in the first sub-prepared heat dissipation layer; Disposing a second preliminary sub-heat dissipation layer on one side of the first preliminary sub-heat dissipation layer; The third sub-preparation heat dissipation layer is disposed on a side of the first sub-preparation heat dissipation layer away from the second sub-preparation heat dissipation layer, and the first sub-preparation heat dissipation layer, the second sub-preparation heat dissipation layer and the third sub-preparation heat dissipation layer form the first preparatory heat dissipation layer.

6. The preparation method according to claim 5, characterized in that: The preparation method further comprises: Before providing the third preliminary sub-heat dissipation layer, filling the hollow area with a sacrificial material; After forming the first preliminary heat dissipation layer, the first preliminary heat dissipation layer is heat-treated to remove the sacrificial material, and the first preliminary heat dissipation layer after the heat treatment is sintered to obtain a second preliminary heat dissipation layer.

7. The preparation method according to claim 6, characterized in that: The steps of forming the second soldering layer and the third heat dissipation layer include: forming the second soldering layer on one side of the second preliminary heat dissipation layer; forming the third heat dissipation layer on the second soldering layer, wherein the second heat dissipation layer, the first soldering layer, the third heat dissipation layer, the second soldering layer and the second preliminary heat dissipation layer form a third preliminary heat dissipation layer; The third preliminary heat dissipation layer is perforated so that the third heat dissipation layer, the second soldering layer and the second preliminary heat dissipation layer have at least one potting hole, and the potting hole and the cavity are connected.

8. The preparation method according to claim 7, characterized in that: The preparation method further comprises: Liquid metal is poured into the cavity through the potting hole, and the potting hole is sealed.

9. The preparation method according to claim 7, characterized in that: Before the step of pouring liquid metal into the cavity, the preparation method further comprises: The liquid metal is heat treated to make it fluid.

10. The preparation method according to claim 8, characterized in that: The step of closing the potting hole comprises: squeezing a high temperature resistant adhesive into the potting hole, and closing the potting hole after the high temperature resistant adhesive solidifies.

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