Ceramic-metal composite heat sink and method of making same

Abstract

This invention discloses a ceramic-metal composite heat sink and its preparation method, belonging to the field of composite heat sink manufacturing. The ceramic-metal composite heat sink comprises several monomers bonded together with different orientations. Each monomer is composed of a composite layer of ceramic and metal layers, with the orientation of the monomers corresponding to the stacking direction of the ceramic and metal layers. By bonding the same or different monomers together with different orientations, the overall and local heat dissipation performance and coefficient of thermal expansion of the composite heat sink can be flexibly adjusted according to usage requirements, meeting customized needs. By creating holes in the monomers, interconnected cooling channels can be formed inside the ceramic-metal composite heat sink. These cooling channels connect to the outside environment, forming a loop channel, utilizing liquid cooling to improve the heat dissipation capacity of the composite heat sink.

Description

Technical Field

[0001] This invention belongs to the field of heat sink manufacturing, and more specifically, relates to a ceramic-metal composite heat sink and its preparation method. Background Technology

[0002] In the fields of power electronic devices and high-power LED packaging, with the continuous improvement of chip integration and the sharp increase in power consumption, how to effectively and quickly dissipate the heat generated by the chip to avoid overheating that could lead to performance degradation or even damage has become a pressing problem. Heat sinks are responsible for absorbing the heat generated by the chip and quickly transferring it to the surrounding environment; they are the first line of defense against heat transfer, and their performance significantly affects the safety and stability of electronic systems.

[0003] An ideal heat sink should possess high thermal conductivity and thermal stability. Besides rapidly transferring heat, it should also prevent deformation and cracking caused by thermal stress. Metals such as copper, aluminum, and copper alloys are widely used in heat sinks due to their high thermal conductivity. Taking pure copper heat sinks as an example... Figure 1 As shown, a direct copper cladding (DBC) process is used to sinter a DBC ceramic substrate onto a pure copper heat sink. Due to the significant difference in thermal expansion coefficients between pure copper and ceramic, severe deformation occurs between the two surfaces after sintering, leading to component bending. Under thermal cycling, cracks are prone to form at the interface between pure copper and ceramic, potentially causing the DBC ceramic substrate to fail.

[0004] Therefore, to reduce the mismatch in thermal expansion coefficients between metal and ceramic heat sinks, composite heat sinks of metal and ceramic have been developed. Chinese invention patent application CN119403305A discloses an integrated metal and ceramic substrate, in which metal sheets and ceramic substrates are alternately stacked and bonded together to form a composite heat sink. This composite heat sink can control the thermal expansion coefficient as a whole, keeping it between the thermal expansion coefficients of metal and ceramic. However, it is difficult to adjust the thermal expansion coefficient and heat dissipation performance locally. If, during use, a certain area of ​​the heat sink requires a larger thermal expansion coefficient or heat dissipation rate than other areas, then the heat sink needs to be able to control the local thermal expansion coefficient and heat dissipation performance. Summary of the Invention

[0005] 1. The problem to be solved

[0006] To address the issue that composite heat sinks made of metal and ceramic cannot simultaneously control the coefficient of thermal expansion and heat dissipation performance both as a whole and in specific areas, this invention provides a ceramic-metal composite heat sink. This heat sink combines ceramic and metal layers into a single unit with different orientations. Through modular design, it enables flexible adjustment of the coefficient of thermal expansion and heat dissipation performance of the composite heat sink as a whole and in different areas.

[0007] 2. Technical Solution To solve the above problems, the technical solution adopted by the present invention is as follows: The first aspect of the present invention provides a ceramic-metal composite heat sink, comprising a plurality of monomers bonded together in different orientations, wherein the monomers are composed of ceramic layers and metal layers stacked together, and the orientation of the monomers is the stacking direction of the ceramic layers and metal layers.

[0008] The thermal expansion coefficient and heat dissipation performance of the monomer fall between those of ceramics and metals. When combined in different orientations, the overall and local thermal expansion coefficients and heat dissipation performance of the composite heat sink can be controlled. In addition, the monomer can be miniaturized, mass-produced, and standardized. Compared with conventional ceramic-metallized products, the contact area between the ceramic and metal layers inside is smaller, which can reduce the interfacial stress caused by the inconsistency of their thermal expansion coefficients.

[0009] Preferably, the monomer has holes, and the holes are interconnected to form a cooling channel.

[0010] As the power density and size of power electronic devices, including high-power LEDs, increase, traditional passive cooling and air cooling are gradually becoming insufficient to meet heat dissipation requirements. Liquid cooling has thus taken on the crucial role of heat dissipation. However, commercially available liquid cooling equipment is large, complex to manufacture, and expensive. This invention provides through-holes or blind holes on the unit, which are connected through appropriate combinations to form cooling channels. These cooling channels are then connected to the outside environment to form a loop. In addition to holes, as a similar variation, slots can also be cut on the unit, forming cooling channels through connections between slots or between slots and holes.

[0011] Preferably, the shape of the monomer is a cube or a cuboid.

[0012] Preferably, the outermost layer of the monomer is a metal layer.

[0013] Preferably, the ceramic layer is one of an alumina layer, a zirconia-toughened alumina layer, an aluminum nitride layer, a silicon nitride layer, a diamond layer, or a pyrolytic graphite layer; the metal layer is one of a copper layer, an aluminum layer, a nickel layer, a copper alloy layer, an aluminum alloy layer, or a nickel alloy layer.

[0014] Preferably, at least one of the following parameters of the monomer is different: i) the type of ceramic layer; ii) the thickness of the ceramic layer; iii) the number of ceramic layers; iv) the type of metal layer; v) the thickness of the metal layer; vi) the number of metal layers.

[0015] In addition to combining the same monomers in different orientations, different monomers can also be combined in different orientations.

[0016] The second aspect of the present invention provides a method for preparing a ceramic-metal composite heat sink according to any embodiment of the first aspect of the present invention, comprising the following steps: S1. Prepare a ceramic-metal motherboard composed of composite ceramic and metal layers; S2. Cut the ceramic-metal motherboard into individual units of predetermined specifications; S3. Combine multiple monomers together according to different orientations and smooth the surface to obtain a ceramic-metal composite heat sink.

[0017] Preferably, in step S1, the ceramic layer and / or metal layer are pre-formed with holes; in step S3, the holes are connected to form a cooling channel.

[0018] Preferably, step S2 further includes the step of machining holes in the monomer; in step S3, the holes are connected to form a cooling channel.

[0019] A monomer with holes can be obtained by pre-forming holes in the ceramic layer and / or metal layer, or by fabricating the monomer and then machining the holes. The methods for machining the holes include laser drilling, machining, and chemical etching.

[0020] Preferably, in step S3, the combined methods include direct copper plating, direct aluminum plating, and active metal brazing.

[0021] Preferably, in step S1, the outermost layer of the ceramic-metal motherboard is a metal layer.

[0022] Preferably, in step S1, the method for preparing the ceramic-metal motherboard includes direct copper plating, direct aluminum plating, active metal brazing, direct copper electroplating, thin film metallization, and thick film printing.

[0023] Preferably, in step S2, the cutting method includes laser cutting, mechanical cutting, grinding machine processing, water jet cutting, and wire cutting.

[0024] 3. Beneficial effects Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The ceramic-metal composite heat sink provided by the present invention achieves modular design by pre-preparing a monomer composed of ceramic and metal layers. The same or different monomers can be combined together in different orientations to achieve the following functions: ① By reasonably designing and matching the monomers, the overall and local thermal expansion coefficients and heat dissipation performance of the composite heat sink can be flexibly adjusted according to the usage requirements to meet the customized requirements of the composite heat sink; ② By setting holes on the monomers, a connected cooling channel can be formed inside the ceramic-metal composite heat sink. The cooling channel is connected to the outside to form a loop channel, and the heat dissipation capacity of the composite heat sink is improved by liquid cooling.

[0025] (2) The ceramic-metal composite heat sink provided by the present invention has a smaller contact area between the ceramic layer and the metal layer in the monomer by miniaturizing the volume. On the one hand, it can reduce the interfacial stress caused by the inconsistency of the thermal expansion coefficients between the two and improve the structural stability of the composite heat sink. On the other hand, it can reduce the probability of problems such as bulging, protrusion and pitting at the bonding interface and improve the pass rate of the composite heat sink.

[0026] (3) The method for preparing the ceramic-metal composite heat sink provided by the present invention is simple. By pre-forming holes in the ceramic layer and / or metal layer, or by preparing the monomer and then processing the holes, a monomer with holes can be obtained. At the same time, this preparation method can flexibly combine the same or different monomers according to predetermined requirements, which is convenient to meet customized requirements. Attached Figure Description

[0027] Figure 1 This is a schematic diagram illustrating the incompatibility of thermal deformation between the DBC component and the pure copper composite heat sink. Figure 2 This is a schematic diagram of the structure of the alumina-copper composite heat sink prepared in Example 1 of the present invention; Figure 3 This is a schematic diagram of the aluminum nitride-copper composite heat sink prepared in Example 2 of the present invention; Figure 4 This is a schematic diagram of the alumina-aluminum nitride-copper composite heat sink prepared in Example 3 of the present invention; Figure 5 This is a schematic diagram of the cooling channel structure of the aluminum nitride-copper composite heat sink prepared in Example 4 of the present invention. Detailed Implementation

[0028] It should be noted that when a component is referred to as being "mounted" on another component, it can be directly on the other component or the two components can be integrated as one unit; when a component is referred to as being "connected" to another component, it can be directly connected to the other component or the two components can be integrated as one unit. Furthermore, terms such as "upper," "lower," "left," "right," and "middle" used in this specification are merely for clarity of description and are not intended to limit the scope of implementation. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0029] Any step described in any method or process claim (e.g., steps S1, S2, S3... or steps (1), (2), (3)... or steps 1), 2), 3)...) may be performed in any order and is not limited to the order set forth in the claims.

[0030] In this invention, the direct copper plating process involves first introducing oxygen onto the copper surface through pre-oxidation, and then using an oxygen-containing eutectic solution of copper to directly sinter the copper with the ceramic.

[0031] In this invention, the direct aluminum coating process is a technique that involves sintering aluminum and ceramic together under high temperature and protective gas or high vacuum conditions, depending on the ceramic material, with or without the introduction of transition metals.

[0032] In this invention, the active metal brazing process is a method of achieving the bonding of ceramics and metals by utilizing the active metal elements in the solder.

[0033] In this invention, the direct electroplating copper process refers to the process of sequentially sputtering titanium and copper onto a ceramic substrate using magnetron sputtering, and finally thickening the metal layer by electroplating.

[0034] In this invention, the thin film metallization process is a process in which the surface layer of a metal material is ionized into ions by physical methods under high vacuum conditions, and then the required thin film is deposited on the surface of a ceramic substrate by low-pressure gas. It mainly includes magnetron sputtering, ion plating, and arc plating.

[0035] In this invention, the thick film printing process is a technique that involves applying a metal paste to the ceramic surface via screen printing, followed by high-temperature drying and heat treatment to form a metallized ceramic substrate.

[0036] The present invention will be further described below with reference to specific embodiments.

[0037] Example 1 S1. Using a direct copper plating process, two sides of an alumina ceramic substrate are sintered together with a copper substrate to obtain an alumina-copper motherboard, wherein the alumina ceramic substrate has dimensions of 138 mm × 190 mm × 0.50 mm and the copper substrate has dimensions of 134 mm × 184 mm × 1.25 mm.

[0038] S2. Using diamond wire cutting, the alumina-copper motherboard is cut into 3 mm × 3 mm × 3 mm units along the thickness direction.

[0039] S3. The monomers are placed in a pre-oxidation furnace for oxidation, introducing oxygen into the copper surface to form a cuprous oxide layer. The oxygen content in the oxidation atmosphere is 500 ppm, the oxidation time is 30 min, and the oxidation temperature is 560 ℃. The monomers are arranged in two mutually perpendicular orientations on a boron nitride material mold to form a 45 mm × 24 mm × 3 mm matrix array. The monomers are sintered together using a direct copper plating process, and then the surface is smoothed using mechanical grinding to obtain a 45 mm × 24 mm × 3 mm alumina-copper composite heat sink. The sintering conditions are: sintering temperature 1070 ℃, holding time 20 min, and oxygen content in the sintering furnace approximately 100 ppm.

[0040] The structure of the alumina-copper composite heat sink prepared in this embodiment is as follows: Figure 2 As shown, this structure regulates the thermal expansion coefficient and heat dissipation performance of the composite heat sink as a whole.

[0041] Example 2 S1. Using a direct copper plating process, two sides of an aluminum nitride ceramic substrate are sintered together with a copper substrate to obtain an aluminum nitride-copper motherboard, wherein the aluminum nitride ceramic substrate has dimensions of 138 mm × 190 mm × 1.0 mm and the copper substrate has dimensions of 134 mm × 184 mm × 1.0 mm.

[0042] S2. Using a grinding wheel, cut the aluminum nitride-copper motherboard into 3 mm × 3 mm × 3 mm units along the thickness direction.

[0043] S3. The monomers are placed in a pre-oxidation furnace for oxidation, introducing oxygen into the copper surface to form a cuprous oxide layer. The oxygen content in the oxidation atmosphere is 350 ppm, the oxidation time is 26 min, and the oxidation temperature is 560 ℃. The monomers are arranged in two mutually perpendicular orientations on an alumina material mold to form a central spiral matrix array of 45 mm × 42 mm × 3 mm. The monomers are sintered together using a direct copper plating process, and then the surface is smoothed by mechanical grinding to obtain a 45 mm × 42 mm × 3 mm aluminum nitride-copper composite heat sink. The sintering conditions are: sintering temperature 1070 ℃, holding time 20 min, and oxygen content in the sintering furnace approximately 100 ppm.

[0044] The structure of the aluminum nitride-copper composite heat sink prepared in this embodiment is as follows: Figure 3 As shown, this structure regulates the thermal expansion coefficient and heat dissipation performance of the composite heat sink as a whole.

[0045] Example 3 S1. Using a direct copper cladding process, two sides of an alumina ceramic substrate are sintered together with a copper substrate to obtain an alumina-copper motherboard. The dimensions of the alumina ceramic substrate are 138 mm × 190 mm × 1.0 mm, and the dimensions of the copper substrate are 134 mm × 184 mm × 1.0 mm. The oxidation parameters of the copper in the pre-oxidation furnace are: oxygen content 500 ppm, oxidation time 20 min, and oxidation temperature 900 ℃; the sintering parameters are: oxygen content 100 ppm, sintering time 25 min, and sintering temperature 1079 ℃.

[0046] An aluminum nitride ceramic substrate was sintered onto both sides of a copper substrate using a direct copper cladding process to obtain an aluminum nitride-copper motherboard. The aluminum nitride ceramic substrate measures 138 mm × 190 mm × 1.6 mm, and the copper substrate measures 134 mm × 184 mm × 0.7 mm. The oxidation parameters for the aluminum nitride ceramic were: oxidation time 120 min, oxidation temperature 1200 ℃; the oxidation parameters for the copper in the pre-oxidation furnace were: oxygen content 300 ppm, oxidation time 20 min, oxidation temperature 900 ℃; and the sintering parameters were: oxygen content 50 ppm, sintering time 25 min, sintering temperature 1070 ℃.

[0047] S2. Using a grinding wheel, cut both the alumina-copper motherboard and the aluminum nitride-copper motherboard into 3 mm × 3 mm × 3 mm units along the thickness direction.

[0048] S3. After the monomer undergoes pre-oxidation, such as Figure 4 As shown, alumina-copper monomers are arranged in a matrix array with two mutually perpendicular orientations. Figure 4 (Outside the black box in the middle) aluminum nitride-copper monomers are arranged in a matrix array with two mutually perpendicular orientations in a spiral pattern. Figure 4 (within the black box in the middle) The matrix array composed of aluminum nitride-copper monomers is embedded in the matrix array composed of alumina-copper monomers.

[0049] The array assembled above was placed on an alumina material mold, and the individual components were sintered together using a direct copper plating process. The surface was then smoothed using mechanical grinding to obtain a 54 mm × 24 mm × 3 mm alumina-alumina-copper composite heat sink. The sintering conditions were: sintering temperature of 1075 ℃, holding time of 25 min, and oxygen content in the sintering furnace of approximately 50 ppm.

[0050] The structure of the alumina-aluminum nitride-copper composite heat sink prepared in this embodiment is as follows: Figure 4As shown, since the coefficient of thermal expansion of aluminum nitride ceramics is less than that of alumina ceramics, and the former has a larger volume fraction in its monomers, the coefficient of thermal expansion of the region within the black frame composed of aluminum nitride-copper monomers is less than that of the region outside the black frame, thus achieving the adjustment of the coefficient of thermal expansion in a local area.

[0051] Example 4 S1. Using a direct copper plating process, two sides of an aluminum nitride ceramic substrate are sintered together with a copper substrate to obtain a first aluminum nitride-copper motherboard, wherein the aluminum nitride ceramic substrate has dimensions of 138 mm × 190 mm × 0.5 mm and the copper substrate has dimensions of 134 mm × 184 mm × 1.25 mm.

[0052] A second aluminum nitride-copper motherboard is obtained by sintering two sides of a copper substrate with an aluminum nitride ceramic substrate using a direct copper cladding process. The aluminum nitride ceramic substrate has dimensions of 138 mm × 190 mm × 0.5 mm, and the copper substrate has dimensions of 134 mm × 184 mm × 2 mm.

[0053] In the above steps, the parameters for the oxidation of aluminum nitride ceramics are: oxidation time of 120 min and oxidation temperature of 1200℃; the parameters for the oxidation of copper in the pre-oxidation furnace are: oxygen content of 300 ppm, oxidation time of 20 min and oxidation temperature of 900℃; and the parameters for sintering are: oxygen content of 50 ppm, sintering time of 25 min and sintering temperature of 1070℃.

[0054] S2. Using diamond wire cutting, both the first aluminum nitride-copper mother plate and the second aluminum nitride-copper mother plate are cut into 3mm×3mm×3mm units to obtain the first aluminum nitride-copper unit and the second aluminum nitride-copper unit, respectively.

[0055] Holes were machined on the first aluminum nitride-copper monomer using chemical etching and laser cutting, with the copper holes having a diameter of 1.2 mm and the ceramic holes having a diameter of 1.0 mm. Through holes and corner holes with a diameter of 1.0 mm were then machined on the second aluminum nitride-copper monomer using a CNC machine tool.

[0056] S3. After the monomer undergoes pre-oxidation, such as Figure 5As shown in (a), a spatial rectangular coordinate system is displayed in the upper right corner. In this coordinate system, an array of porous aluminum nitride-copper monomers (first and second types) is placed on an alumina material mold, arranged according to the X orientation (the stacking direction of the ceramic and metal layers is parallel to the X direction), Y orientation (the stacking direction of the ceramic and metal layers is parallel to the Y direction), and Z orientation (the stacking direction of the ceramic and metal layers is parallel to the Z direction). The monomers are sintered together using a direct copper plating process, and then the surface is smoothed using mechanical grinding to obtain a 39 mm × 24 mm × 3 mm aluminum nitride-copper composite heat sink. The sintering conditions are: sintering temperature of 1070 ℃, holding time of 25 min, and oxygen content in the sintering furnace of approximately 50 ppm.

[0057] like Figure 5 As shown in (b), the interconnected pores inside the aluminum nitride-copper composite heat sink form a cooling channel, which can be connected to the outside to form a loop channel.

[0058] It should be noted that, in order to further improve the heat dissipation performance of the ceramic-metal composite heat sink in this invention, at least one of the side and bottom surfaces of the ceramic-metal composite heat sink can be connected to a metal substrate.

[0059] The above description provides an illustrative overview of the present invention and its embodiments. This description is not restrictive, and the embodiments shown are merely one example of the invention's implementation. Actual implementations are not limited to these examples. Therefore, if those skilled in the art are inspired by this description and design similar implementations and examples without departing from the spirit of the invention, such designs should fall within the scope of protection of the present invention.

Claims

1. A ceramic-metal composite heat sink, characterized in that: It includes several monomers bonded together in different orientations, wherein each monomer is composed of a composite of ceramic and metal layers, and the orientation of the monomer is the superposition direction of the ceramic and metal layers.

2. The ceramic-metal composite heat sink according to claim 1, characterized in that: The unit has holes, and the holes are connected to form a cooling channel.

3. The ceramic-metal composite heat sink according to claim 1 or 2, characterized in that: The shape of the individual unit is a cube or a cuboid.

4. The ceramic-metal composite heat sink according to claim 1 or 2, characterized in that: The outermost layer of the monomer is a metal layer.

5. The ceramic-metal composite heat sink according to claim 1 or 2, characterized in that: The ceramic layer is one of the following: an alumina layer, a zirconia-toughened alumina layer, an aluminum nitride layer, a silicon nitride layer, a diamond layer, or a pyrolytic graphite layer. The metal layer is one of a copper layer, an aluminum layer, a nickel layer, a copper alloy layer, an aluminum alloy layer, or a nickel alloy layer.

6. The ceramic-metal composite heat sink according to claim 1 or 2, characterized in that: The monomer has at least one of the following parameters that are different: i) the type of ceramic layer; ii) the thickness of the ceramic layer; iii) the number of ceramic layers; iv) the type of metal layer; v) the thickness of the metal layer; vi) the number of metal layers.

7. The method for preparing the ceramic-metal composite heat sink according to any one of claims 1 to 6, characterized in that, Includes the following steps: S1. Prepare a ceramic-metal motherboard composed of composite ceramic and metal layers; S2. Cut the ceramic-metal motherboard into individual units of predetermined specifications; S3. Combine multiple monomers together according to different orientations and smooth the surface to obtain a ceramic-metal composite heat sink.

8. The method for preparing a ceramic-metal composite heat sink according to claim 7, characterized in that: In step S1, the ceramic layer and / or metal layer are pre-formed with holes; in step S3, the holes are connected to form a cooling channel.

9. The method for preparing a ceramic-metal composite heat sink according to claim 7, characterized in that: Step S2 further includes the step of machining holes in the monomer; in step S3, the holes are connected to form a cooling channel.

10. The method for preparing a ceramic-metal composite heat sink according to any one of claims 7 to 9, characterized in that: In step S3, the combined methods include direct copper plating process, direct aluminum plating process, and active metal brazing process.

Images