Heat conduction substrate with low interface stress and preparation method thereof

Abstract

The invention discloses a heat conduction substrate with low interface stress and a preparation method thereof, and the method comprises the steps: providing a ceramic substrate which comprises a silicon nitride substrate, an aluminum nitride substrate, a diamond substrate or a silicon carbide substrate, and is provided with a first surface and a second surface which are oppositely arranged; providing at least one copper composite board; performing a copper coating process to arrange the at least one copper composite plate on at least one surface of the ceramic substrate so as to form a ceramic copper-clad plate to realize heat conduction; the copper composite plate comprises a metal plate made of invar alloy or kovar alloy, a transition metal layer formed on the metal plate and a copper layer formed on the transition metal layer, a plurality of up-down through micropores are formed in the metal plate, and the micropores are filled with copper materials. By adopting the heat-conducting substrate, the interface stress of the ceramic substrate and the copper-clad layer in the heat-conducting substrate at high and low temperatures can be reduced, the stability of the heat-conducting substrate is improved, and the service life of the heat-conducting substrate is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of metal composite boards in the circuit board industry, and more particularly to a thermally conductive substrate with low interface stress and a preparation method thereof. Background Art

[0002] Currently, thermal conductive substrates include silicon nitride thermal conductive substrates, aluminum nitride thermal conductive substrates, diamond thermal conductive substrates, and silicon carbide thermal conductive substrates. The basic structure is that oxygen-free copper material is used on both sides of a ceramic substrate and a copper layer is formed by active metal brazing (AMB), direct plating copper (DPC), or bonding. The thermal expansion coefficient (CTE) of oxygen-free copper material is 17*10 -6 / ℃about.

[0003] The CTE values ​​of ceramic substrates in current thermal conductive substrate technology solutions are low. The CTE values ​​of silicon nitride, aluminum nitride, silicon carbide and diamond materials are 2.5*10 -6 / ℃、4.5*10 -6 / ℃、4.2*10 -6 / ℃ and 1~1.5*10 -6 / ℃, copper is clad on both sides by AMB, DPC or bonding. The interface stress between the copper layer of the substrate and the ceramic substrate after copper cladding is large at high and low temperatures. Taking a 0.32mm thick ceramic substrate with 0.3mm thick oxygen-free copper foil clad on both sides by AMB as an example, at ΔT = +125℃, the theoretical values ​​of the interface stress are +57.4MPa, +72.3MPa, +78.1MPa and +121MPa, respectively. At ΔT = -70℃, the theoretical values ​​of the interface stress are -32.1MPa, -40.5MPa, -43.7MPa and -67.8MPa, respectively. Thermal shock after copper cladding is prone to poor interface bonding.

[0004] With the development of the circuit board industry, the negative impact of thermal expansion on process accuracy and the interface stress between the copper material and the insulating dielectric layer of the substrate at high and low temperatures has become increasingly prominent. Therefore, it is necessary to reduce the interface stress between the copper cladding layer and the ceramic substrate layer at high and low temperatures to increase the stability and life of the thermally conductive substrate. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention proposes a thermally conductive substrate, which can have lower interface stress at high and low temperatures.

[0006] According to one aspect of the present invention, an embodiment of the present invention provides a method for preparing a thermally conductive substrate, the method comprising:

[0007] Providing a ceramic substrate, the ceramic substrate including a silicon nitride substrate, an aluminum nitride substrate, a diamond substrate or a silicon carbide substrate, the ceramic substrate having a first surface and a second surface disposed opposite to each other;

[0008] providing at least one copper clad plate;

[0009] Implementing a copper cladding process to dispose the at least one copper composite board on at least one of the first surface and the second surface of the ceramic substrate to form a ceramic copper clad board to achieve heat conduction;

[0010] The copper composite plate includes a metal plate made of Invar alloy or Kovar alloy, a transition metal layer formed on the metal plate, and a copper layer formed on the transition metal layer; and the metal plate is provided with a plurality of micropores running through the metal plate, and the micropores are filled with copper material.

[0011] In an optional embodiment, implementing a copper cladding process to set the at least one copper composite board on at least one of the first surface and the second surface of the ceramic substrate to form a ceramic copper clad board includes directly completing copper cladding on the surface of the ceramic substrate using active metal brazing (AMB).

[0012] In another optional embodiment, implementing a copper cladding process to set the at least one copper composite board to at least one of the first surface and the second surface of the ceramic substrate to form a ceramic copper clad board includes using PVD sputtering Ti, TiC, TiN, Mo, W, Ni on the surface of the ceramic substrate, and then sputtering a layer of copper, and then implementing a copper cladding process with the copper composite board by copper-copper bonding.

[0013] In another optional embodiment, a copper clad process is implemented to set the at least one copper composite board to at least one of the first surface and the second surface of the ceramic substrate to form a ceramic copper clad board, including using PVD sputtering Ti, TiC, TiN, Mo, W, Ni on the surface of the ceramic substrate, and then sputtering a layer of copper, coating a metal brazing slurry between the ceramic substrate after the copper layer is sputtered and the copper composite board and implementing a copper clad process by sintering, wherein the metal brazing slurry includes but is not limited to nano copper slurry.

[0014] In an optional embodiment, the preparation method further includes polishing one surface of the copper composite board to a surface roughness Ra value of 5 to 200 nm before implementing the copper cladding process, and the surface is used to directly contact the first surface or the second surface of the ceramic substrate when implementing the copper-copper bonding copper cladding process.

[0015] In an optional embodiment, providing at least one copper clad plate includes: providing a metal plate having a certain thickness, the metal plate having an upper surface and an opposite lower surface; forming a transition metal layer on the upper and lower surfaces of the metal plate and on the walls of a plurality of micropores; plating a copper layer on the surface of the transition metal layer through a copper electroplating process; and filling the plurality of micropores of the metal plate with copper plating until the copper layer formed along the axis of the micropores connects the copper layers on the upper and lower surfaces of the metal plate, thereby forming the copper clad plate.

[0016] In an alternative embodiment, the transition metal layer has a multi-layer metal layer including a titanium layer formed on the metal plate, a nickel layer formed on the titanium layer, and a copper layer formed on the nickel layer.

[0017] In an optional embodiment, the transition metal layer has a multi-layer metal layer including a titanium layer formed on the metal plate and a copper layer formed on the titanium layer.

[0018] In an optional embodiment, the transition metal layer is a metal layer including a nickel layer formed on the metal plate.

[0019] In an optional embodiment, the thickness of the ceramic substrate is in the range of 150-1000 microns, and the thickness of the copper composite board is in the range of 250-800 microns.

[0020] In an optional embodiment, the diameter of the microhole is the same as the thickness of the metal plate.

[0021] In an optional embodiment, the thickness of the metal plate is in the range of 50 to 600 microns, and the thickness of the copper layer formed by electroplating on the upper and lower surfaces of the metal plate is in the range of 10 to 400 microns.

[0022] In an optional embodiment, the distance between the centers of two adjacent micropores is 1.5 to 2 times the diameter of the micropores.

[0023] In an optional embodiment, forming a transition metal layer on the upper surface and lower surface of the metal plate and the walls of the multiple micropores includes using physical vapor deposition (PVD) to sequentially sputter a titanium layer and a copper layer on the upper surface and lower surface of the metal plate and the walls of the multiple micropores, wherein the thickness of the titanium layer ranges from 0.015 to 0.25 microns, and the thickness of the copper layer formed by sputtering is 0.5 to 1 micron.

[0024] In an optional embodiment, forming a transition metal layer on the upper surface and lower surface of the metal plate and the walls of the multiple micropores includes using physical vapor deposition (PVD) to sequentially sputter a titanium layer, a nickel layer and a copper layer on the upper surface and lower surface of the metal plate and the walls of the multiple micropores, wherein the thickness of the titanium layer is in the range of 0.015 to 0.25 microns, the thickness of the nickel layer formed by sputtering is in the range of 0.015 to 0.25 microns, and the thickness of the copper layer formed by sputtering is 0.5 to 1 micron.

[0025] In an optional embodiment, forming the transition metal layer on the upper and lower surfaces of the metal plate and the walls of the plurality of micropores includes plating a nickel layer by chemical plating or electroplating, and the thickness of the nickel layer ranges from 5 to 120 microns.

[0026] In an optional embodiment, the preparation method further comprises completing pattern production on the ceramic copper clad laminate using laser or photolithography according to a predetermined pattern layout to obtain a desired thermally conductive substrate.

[0027] According to another aspect of the present invention, an embodiment of the present invention further provides a thermally conductive substrate with low interface stress, which is prepared using the preparation method described above.

[0028] The copper composite sheet material of the present invention utilizes a combination of Invar or Kovar alloy and copper. Using this as the conductive metal layer can reduce the thermal expansion coefficient of the conductive metal layer material and reduce stress between the metal layer and the ceramic substrate at high and low temperatures, thereby improving the stability and lifespan of the thermally conductive substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 FIG. 4 is a flow chart of a method for preparing a thermally conductive substrate according to an embodiment of the present invention.

[0030] Figure 2 The figure is a flow chart of a method for preparing a copper composite board for a thermally conductive substrate according to an embodiment of the present invention.

[0031] Figure 3 is an implementation according to an embodiment of the present invention Figure 2 The preparation method shown is a schematic diagram of the process of preparing copper composite boards.

[0032] Figure 4 According to another embodiment of the present invention Figure 2 The preparation method shown is a schematic diagram of the process of preparing copper composite boards.

[0033] Figure 5 Is to choose to use Figure 2 Schematic diagram of the process of preparing a thermally conductive substrate from a copper composite plate prepared by the method shown.

[0034] Figure 6 The figure is a flow chart of a method for preparing a copper clad plate for a thermally conductive substrate according to another embodiment of the present invention. DETAILED DESCRIPTION

[0035] The following will clearly and completely describe the technical solutions of the embodiments in conjunction with the drawings in the specification of this application. Those skilled in the art will understand that the embodiments described in the specification are only some of the embodiments of the invention, not all of them. Based on the embodiments described in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this invention.

[0036] In the description of this patent specification, the directions or positional relationships indicated by "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", "outside", "longitudinal", "lateral", "center", "vertical", "horizontal", "length", "width", "thickness", "clockwise", "counterclockwise", etc. are based on the drawings in the specification. These directions and positional relationships are only for the convenience of describing the embodiments involved in the technical innovation of the present invention and cannot be understood as limiting the scope of protection of the claims. In addition, those skilled in the art will understand that the terms "first" and "second" used in this specification to describe various components are only for the purpose of distinguishing one component from another, and have no meaning of order, and the corresponding components should not be limited by these terms.

[0037] refer to Figure 1 An embodiment of the present invention provides a method for preparing a thermally conductive substrate, the method comprising:

[0038] S101, providing a ceramic substrate having a first surface and a second surface disposed opposite to each other. The ceramic substrate may include a silicon nitride substrate, an aluminum nitride substrate, a diamond substrate, or a silicon carbide substrate;

[0039] S102, providing at least one copper clad plate;

[0040] S103 , performing a copper cladding process to dispose the at least one copper composite board on at least one surface of the ceramic substrate to form a ceramic copper clad board to achieve heat conduction.

[0041] In one embodiment of the present invention, an active metal brazing (AMB) process can be used to directly coat copper on a ceramic substrate, wherein the active metal brazing (AMB) process can be a commonly used AMB process.

[0042] In another embodiment of the present invention, a transition metal layer may be deposited on a ceramic substrate using PVD, and then copper-clad with a copper clad plate using copper-copper bonding. In this embodiment, depositing the transition metal layer on the ceramic substrate includes depositing one or more of Ti, TiC, TiN, Mo, W, and Ni on the surface of the ceramic substrate using PVD, followed by depositing a copper layer.

[0043] In another embodiment of the present invention, a copper cladding process can be performed by PVD-ing a transition metal layer onto a ceramic substrate and then sintering a metal slurry between the ceramic substrate and the copper clad plate. In this embodiment, PVDing the transition metal layer onto the ceramic substrate involves PVD-sputtering one or more of Ti, TiC, TiN, Mo, W, and Ni onto the surface of the ceramic substrate, followed by sputtering a copper layer. A metal brazing slurry, including but not limited to nano-copper slurry, is then applied between the ceramic substrate and the copper clad plate after the copper layer has been sputtered.

[0044] In an embodiment of the present invention, a copper clad plate comprises a metal plate made of Invar or Kovar alloy, a transition metal layer formed on the metal plate, and a copper layer formed on the transition metal layer. The metal plate has a plurality of micropores extending vertically therethrough, and the micropores are filled with copper. In one embodiment, the transition metal layer comprises titanium (Ti) and copper (Cu) layers. In another embodiment, the transition metal layer comprises titanium (Ti), nickel (Ni), and copper (Cu) layers. In yet another embodiment, the transition metal layer comprises a nickel layer formed by electroplating or chemical plating.

[0045] In an embodiment of the present invention, the thickness of the ceramic substrate is in the range of 150-1000 microns, and the thickness of the copper composite board is in the range of 250-800 microns.

[0046] In an embodiment of the present invention, the preparation method further includes polishing the bonding surface of the copper composite board to a surface roughness Ra value of 5 to 200 nm before implementing the copper cladding process in step S103, and the bonding surface is in direct contact with the first surface or the second surface of the ceramic substrate when implementing the copper-copper bonding copper cladding process.

[0047] In an embodiment of the present invention, the metal sheet of the copper clad plate has a certain thickness and includes an upper surface and an opposing lower surface. The upper and lower surfaces of the metal sheet and the walls of the plurality of micropores include a transition metal layer of Ti and Cu, or Ti, Ni, and Cu, or directly electroplated nickel, and an electroplated copper layer formed on the transition metal layer. The plurality of micropores of the metal sheet are filled with copper plating until the copper layer formed along the axis of the micropores is electrically connected to the copper layers on both sides of the metal sheet. The copper layer is then electroplated on both sides of the metal sheet to form the copper clad plate.

[0048] The following describes the method for preparing the copper clad plate according to the embodiment of the present invention. Figure 2 A method for preparing a copper clad plate according to an embodiment of the present invention comprises the following steps:

[0049] Step S201: providing a metal plate with a certain thickness, wherein the metal plate comprises Invar alloy or Kovar alloy.

[0050] The metal plate has two surfaces, an upper surface and a lower surface opposite to the upper surface.

[0051] In step S202 , the surface of the metal plate is pierced by etching, so that a plurality of micro-holes penetrating the upper surface and the lower surface of the metal plate are formed in the metal plate.

[0052] In an alternative embodiment, the thickness of the metal sheet is in the range of 50 to 600 microns. In an alternative embodiment, the diameter of the micropores is the same as the thickness of the metal sheet. In an alternative embodiment, the center-to-center distance between two adjacent micropores is 1.5 to 2 times the diameter of the micropores. However, those skilled in the art will appreciate that other multiples of the diameter of the micropores are also acceptable.

[0053] Step S203: Using physical vapor deposition, a transition metal layer is sputtered onto the upper and lower surfaces of the metal plate and the walls of the plurality of micropores. The transition metal layer comprises one or more metal layers. For example, the transition metal layer comprises a titanium layer formed on the metal plate, a nickel layer formed on the titanium layer, and a copper layer formed on the nickel layer. In another example, the transition metal layer comprises a titanium layer formed on the metal plate and a copper layer formed on the titanium layer. In another example, the transition metal layer comprises a nickel layer directly electrolessly plated or electroplated on the metal plate as the transition metal layer.

[0054] In an optional embodiment, the thickness of the titanium layer is in the range of 0.015 to 0.25 micrometers. In an optional embodiment, the thickness of the nickel layer formed by sputtering is in the range of 0.015 to 0.25 micrometers, and the thickness of the copper layer formed by sputtering is in the range of 0.5 to 1 micrometers.

[0055] In an optional embodiment, the thickness of the nickel layer plated by chemical plating or electroplating is in the range of 5 to 120 microns.

[0056] In step S204 , a copper electroplating process is performed on the metal plate having the transition metal layer to form a copper layer on the transition metal layer, and a copper electroplating filling process is performed on the plurality of micro-holes of the metal plate.

[0057] During the copper electroplating process, the copper layer formed along the axis of the microvia connects to the copper layers on the upper and lower surfaces of the metal plate. The entire surface is then electroplated with copper to form a copper composite plate. In an optional embodiment, the copper layer on the transition metal layer has a thickness ranging from 10 to 400 microns.

[0058] In an optional embodiment, the preparation method further includes, after step S204, performing a vacuum annealing heat treatment on the copper-plated metal sheet at a temperature of 100 to 700° C., with a treatment time of about 60 minutes and a heating and cooling rate of 5° C. / min.

[0059] Step S205 , polishing the surface of the copper-plated metal plate so that the composite copper layer has a desired thickness and desired flatness.

[0060] Figure 3 is an implementation according to an embodiment of the present invention Figure 2 The preparation method shown is a schematic diagram of the process of preparing a copper composite plate, which is shown in the form of a cross-sectional view of a metal plate and various sputtered or electroplated metal layers. Figure 2 and Figure 3 The embodiments of the present invention can be better understood by reading the above-described preparation method. The copper composite board 10 for the thermal conductive substrate can be prepared. Figure 3 As shown in Figures 3a and 3b, the copper clad plate comprises a metal plate 12 of a certain thickness, wherein the metal plate has two opposite surfaces, an upper surface and a lower surface. The metal plate is etched with a plurality of micropores 14 passing through the upper surface and the lower surface. The metal plate comprises Invar alloy or Kovar alloy. Figure 3 As shown in Figures 3c and 3d, a titanium layer 16 and a copper layer 20 located on the titanium layer 16 are sequentially sputtered on the upper and lower surfaces of the metal plate 12 using a physical vapor deposition (PVD) process. Figure 3 As shown in Figures 3e and 3f, a copper layer 20 is electroplated on the copper layer formed by sputtering on the upper and lower surfaces of the metal plate 12. An electroplating filling process is performed on the multiple micropores in the metal plate, filling each micropore with copper material until the surface of the copper layer 20 in the micropore 14 is flush with the surface of the copper layer 20 formed by electroplating on the upper and lower surfaces of the metal plate, thereby forming a copper composite plate. At this point, the thickness of the copper layer extending along the axis of the micropore 14 is the same as the thickness of the metal plate after the copper layer is plated.

[0061] Figure 4 According to another embodiment of the present invention Figure 2 The preparation method shown is a schematic diagram of the process of preparing a copper composite plate, which is shown in the form of a cross-sectional view of a metal plate and various sputtered or electroplated metal layers. Figure 2 and Figure 3The embodiments of the present invention can be better understood by reading the above-described preparation method. The copper composite board 10 for the thermal conductive substrate can be prepared. Figure 4 As shown in Figures 4a and 4b, the copper clad plate comprises a metal plate 12 of a certain thickness, wherein the metal plate has two opposite surfaces, an upper surface and a lower surface. The metal plate is etched with a plurality of micropores 14 passing through the upper surface and the lower surface. The metal plate comprises Invar alloy or Kovar alloy. Figure 4 As shown in 4c, 4d and 4e in FIG, a titanium layer 16, a nickel layer 18 on the titanium layer 16, and a copper layer 20 on the nickel layer 18 are sequentially sputtered on the upper and lower surfaces of the metal plate 12 using a physical vapor deposition (PVD) process. Figure 4 As shown in Figures 4f and 4g, a copper layer 20 is electroplated on the copper layer sputtered on the upper and lower surfaces of the metal plate 12. Electroplating is then performed on the multiple micropores in the metal plate, filling each micropore with copper material until the surface of the copper layer 20 in the micropore 14 is flush with the surface of the copper layer 20 electroplated on the upper and lower surfaces of the metal plate, thereby forming a copper composite plate. At this point, the thickness of the copper layer extending along the axis of the micropore 14 is the same as the thickness of the metal plate after the copper layer is plated.

[0062] Figure 5 According to one embodiment of the present invention, Figure 2 Schematic diagram of the process of preparing a thermally conductive substrate from a copper composite plate prepared by the method shown. Figure 4 and Figure 5 The embodiments of the present invention can be better understood by reading them together. Figure 5 As shown in FIG5a, a ceramic substrate 30 is provided. Active metal brazing material AMB 32 is printed on the ceramic substrate. Figure 5 As shown in b. Provided by Figure 2 and Figure 4 The copper clad plate 10 prepared by the process described above is double-sided copper-clad on the ceramic substrate 30 and the copper clad plate 10 using the AMB method to obtain a ceramic copper-clad plate. Figure 5 Then, the ceramic copper clad laminate is patterned by laser or photolithography according to a predetermined pattern design, thereby obtaining a thermally conductive substrate with a desired pattern. Figure 5 The figure shows a schematic diagram of the process of completing the copper cladding process on the ceramic substrate by using the existing active metal brazing AMB method.

[0063] In other embodiments of the present invention, the method for preparing a thermally conductive substrate further includes sputtering one or more of Ti, TiC, TiN, Mo, W, and Ni on the first surface and / or the second surface of the ceramic substrate by PVD, then sputtering a layer of Cu, and then completing the copper clad process with the copper composite plate by copper-copper bonding (not shown in the drawings).

[0064] In other embodiments of the present invention, the method for preparing a thermally conductive substrate further includes sputtering one or more of Ti, TiC, TiN, Mo, W, and Ni on the first and / or second surfaces of the ceramic substrate using PVD, then sputtering a Cu layer, and then coating the sputtered Cu layer with a metal brazing slurry, including but not limited to a nano-copper slurry. The copper composite plate and the ceramic substrate are then sintered to complete the copper cladding process (not shown in the accompanying drawings).

[0065] In an optional embodiment of the present invention, the copper plating process can be completed by using the AMB method under certain temperature, pressure and vacuum conditions. The environmental conditions in this case can be a temperature of 800-900°C, a physical pressure of 3-10 MPa and a vacuum requirement of 10 -3 Pa.

[0066] In an optional embodiment of the present invention, the copper-copper bonding process can be completed under certain temperature, pressure and vacuum conditions. The environmental conditions in this case can be a temperature of 200-800°C, a physical pressure of 10-50 MPa and a vacuum requirement of 10 -3 Pa~10 -7 Pa. Plasma activation can be performed using formic acid or the like.

[0067] In an optional embodiment of the present invention, the copper coating process can be completed by sintering under certain temperature, pressure and vacuum conditions or nitrogen environment. The environmental conditions in this case can be a temperature of 150-350°C, a physical pressure of 5-30 MPa and a vacuum requirement of 10 -3 Pa.

[0068] The physical pressure described above refers to pressurized physical pressure, that is, the pressure generated by a suitable object directly applied to the thermally conductive substrate.

[0069] refer to Figure 6 Another embodiment of the present invention provides a method for preparing a copper composite board for a thermally conductive substrate, comprising the following steps:

[0070] Step S601: providing a metal plate with a certain thickness, wherein the metal plate comprises Invar alloy or Kovar alloy.

[0071] The metal plate has two surfaces, an upper surface and a lower surface opposite to the upper surface.

[0072] In step S602 , the surface of the metal plate is pierced by an etching process, so that a plurality of micro-holes are formed on the metal plate and penetrate the upper surface and the lower surface thereof.

[0073] In an alternative embodiment, the thickness of the metal plate is in the range of 50 to 600 microns. In an alternative embodiment, the diameter of the micropores is the same as the thickness of the metal plate. In an alternative embodiment, the distance between the centers of two adjacent micropores is 1.5 to 2 times the diameter of the micropores.

[0074] In step S603 , a nickel layer is plated on the upper surface, the lower surface and the walls of the plurality of micropores of the metal plate by chemical plating or electroplating.

[0075] In an optional embodiment, the thickness of the nickel layer plated by chemical plating or electroplating is in the range of 5 to 20 microns.

[0076] In step S604, the nickel-plated metal sheet is subjected to a copper electroplating process to form a copper layer on the nickel layer, and the plurality of micropores in the metal sheet are filled with copper. The copper filling process is performed until the copper layer formed along the axis of the micropores is connected to the copper layers on the upper and lower surfaces of the metal sheet to form a single, integrated surface. Copper electroplating is then continued on this integrated copper surface to a desired thickness. During the copper electroplating process, the thickness of the copper layer formed along the axis of the micropores is equal to the thickness of the metal sheet after the copper electroplating, thereby forming a copper composite plate.

[0077] In an optional embodiment, the thickness of the copper layer on the nickel layer ranges from 10 to 400 microns. In an optional embodiment, the preparation method further includes, after step S604, performing a vacuum annealing heat treatment on the copper-plated metal sheet at a temperature of 100 to 700° C., with a treatment time of about 60 minutes and a heating and cooling rate of 5° C. / min.

[0078] Step S605 , polishing the surface of the copper-plated metal plate to achieve the target thickness and uniformity of the copper layer.

[0079] Those skilled in the art will understand how to directly electroplate or chemically plate a nickel layer on the metal plate 12 as a transition metal layer, and then electroplate a copper layer and implement copper plating and hole filling. In order to clearly and concisely illustrate the embodiments of the present invention, the process schematic diagram is not illustrated here.

[0080] A copper composite board for a thermally conductive substrate can be prepared by implementing the preparation method described above, which includes:

[0081] A metal plate having a certain thickness, the metal plate having an upper surface and an opposite lower surface, the metal plate being etched with a plurality of micropores penetrating the upper surface and the lower surface, wherein the metal plate comprises Invar or Kovar;

[0082] Electroplating nickel layers on the upper surface, lower surface and walls of the plurality of micropores of the metal plate;

[0083] Each of the plurality of micropores in the metal sheet is filled with copper material, so that the copper layer formed along the axis of the micropore connects the upper and lower copper layers of the metal sheet, thereby increasing the thickness of the surface copper layer to form a copper composite plate. In a preferred embodiment, the surface of the copper composite plate is polished by a grinding process to achieve a predetermined thickness of the copper layer on the surface of the copper composite plate and a predetermined flatness of the entire copper layer surface.

[0084] Furthermore, specific examples are given below to better understand the innovative technical solutions of the present invention.

[0085] Example 1

[0086] The copper composite plate with a total thickness of 300 μm is made of Invar alloy with a thickness of 150 μm and a CTE value of 7.8×10 -6 / ℃. The diameter of the micropores etched into the Invar alloy sheet metal is 150μm, and the center-to-center distance between two adjacent micropores is 350μm. A physical vapor deposition (PVD) sputtering process is used to deposit one or more of Ti, Ni, and Cu on the Invar alloy sheet metal to form a titanium (Ti) layer with a thickness of 15nm to 500nm and a copper (Cu) layer with a thickness of 15 to 800nm. Alternatively, a nickel (Ni) layer with a thickness of 15 to 500nm and a copper (Cu) layer with a thickness of 15 to 800nm ​​are deposited after the titanium (Ti) layer is deposited. Alternatively, a nickel (Ni) layer with a thickness of 5μm is electroplated on the Invar sheet metal. After the transition layer metal deposition is completed, hole-filling electroplating and conventional copper electroplating processes are used to fill the micropores with copper material, and a copper layer with a thickness of 75 microns is electroplated on each surface, thereby obtaining a copper composite plate containing Invar alloy material.

[0087] A ceramic substrate with a thickness of 300 μm is selected. Ceramic substrates include silicon nitride (Si3N4) substrates, aluminum nitride (AlN) substrates, silicon carbide (SiC) substrates, and diamond substrates. The copper composite board and these types of ceramic substrates are copper-clad using one of the following three processes:

[0088] The first type is to use active brazing AMB process to achieve copper cladding on ceramic substrates such as silicon nitride, silicon carbide or diamond and copper composite plates;

[0089] The second method is to metallize a ceramic substrate such as silicon nitride, silicon carbide or diamond first, and then use PVD sputtering to sputter one or more of Ti, TiC, TiN, Mo, tungsten W, and Ni, and then sputter a layer of Cu, and then use copper-copper bonding with a copper composite plate to complete copper cladding;

[0090] The third type is to metallize a ceramic substrate such as silicon nitride, silicon carbide, or diamond first, and then sputter one or more of Ti, TiC, TiN, Mo, tungsten W, or Ni using PVD sputtering, and then sputter a layer of Cu. The copper clad is then sintered with a copper composite board using solder to complete the copper cladding. The solder includes but is not limited to nano copper paste, or paste based on Sn, Zn, or In. Specifically, a layer of nano copper paste or other paste with a thickness of about 20um to 100um is printed on both sides of the metallized ceramic substrate, and the copper paste is dried in an oven at 50 to 100 degrees. After drying, a copper composite board of corresponding size is placed on the surface of the paste layer on both sides of the substrate, and sintered at a temperature of 200 to 500 degrees Celsius and a pressure of 5 to 20 MPa for 5 to 30 minutes to complete the copper cladding. According to tests, the interface stress between the copper composite board and the ceramic substrate is significantly improved compared to the interface stress between the oxygen-free copper material and the ceramic substrate. Table 1 shows a data comparison table of the interface stress of these types of thermally conductive substrates.

[0091] Table 1 Interface stress data comparison table of Example 1

[0092]

[0093] Example 2

[0094] The copper composite plate with a total thickness of 250 μm is made of Invar alloy with a thickness of 100 μm and a CTE value of 10.4×10 -6 / ℃. The diameter of the micropores etched into the Invar alloy sheet metal is 100μm, and the center-to-center distance between two adjacent micropores is 250μm. A physical vapor deposition (PVD) sputtering process is used to deposit one or more of Ti, Ni, and Cu on the Invar alloy sheet metal. A titanium (Ti) layer with a thickness of 15nm to 500nm and a copper (Cu) layer with a thickness of 15 to 800nm ​​can be formed; or a nickel (Ni) layer with a thickness of 15 to 500nm and a copper (Cu) layer with a thickness of 15 to 800nm ​​can be deposited after the titanium (Ti) layer is deposited; or a nickel (Ni) layer with a thickness of 5μm can be electroplated on the Invar sheet metal. After the transition layer metal deposition is completed, hole-filling electroplating and conventional copper electroplating processes are used to fill the micropores with copper material, and a copper layer with a thickness of 75 microns is electroplated on each surface, thereby obtaining a copper composite plate containing Invar alloy material.

[0095] A ceramic substrate with a thickness of 300 μm is selected. Ceramic substrates include silicon nitride (Si3N4) substrates, aluminum nitride (AlN) substrates, silicon carbide (SiC) substrates, and diamond substrates. The copper composite board and these types of ceramic substrates are copper-clad using one of the following three processes:

[0096] The first type is to use active brazing AMB process to achieve copper cladding on ceramic substrates such as silicon nitride, silicon carbide or diamond and copper composite plates;

[0097] The second method is to metallize a ceramic substrate such as silicon nitride, silicon carbide or diamond first, and then use PVD sputtering to sputter one or more of Ti, TiC, TiN, Mo, tungsten W, and Ni, and then sputter a layer of Cu, and then use copper-copper bonding with a copper composite plate to complete copper cladding;

[0098] The third type is to metallize a ceramic substrate such as silicon nitride, silicon carbide, or diamond first, and then sputter one or more of Ti, TiC, TiN, Mo, tungsten W, or Ni using PVD sputtering, and then sputter a layer of Cu. The copper clad is then sintered with a copper composite board using solder to complete the copper cladding. The solder includes but is not limited to nano copper paste, or paste based on Sn, Zn, or In. Specifically, a layer of nano copper paste or other paste with a thickness of about 20um to 100um is printed on both sides of the metallized ceramic substrate, and the copper paste is dried in an oven at 50 to 100 degrees. After drying, a copper composite board of corresponding size is placed on the surface of the paste layer on both sides of the substrate, and sintered at a temperature of 200 to 500 degrees Celsius and a pressure of 5 to 20 MPa for 5 to 30 minutes to complete the copper cladding. According to tests, the interface stress between the copper composite board and the ceramic substrate is significantly improved compared to the interface stress between the oxygen-free copper material and the ceramic substrate. Table 2 shows a data comparison table of the interface stress of these types of thermally conductive substrates.

[0099] Table 2 Comparison table of interface stress data of Example 2

[0100]

[0101]

[0102] Example 3

[0103] The copper composite plate with a total thickness of 300 μm is made of Kovar alloy with a thickness of 150 μm and a CTE value of 11.7×10 -6 / °C. The diameter of the micropores etched into the Kovar alloy sheet is 150 μm, and the center-to-center distance between adjacent micropores is 250 μm. A physical vapor deposition (PVD) sputtering process is used to deposit one or more of Ti, Ni, and Cu on the Invar sheet. This can form a titanium (Ti) layer with a thickness of 15 nm to 500 nm and a copper (Cu) layer with a thickness of 15 to 800 nm; or, after depositing the titanium (Ti) layer, a nickel (Ni) layer with a thickness of 15 to 500 nm and a copper (Cu) layer with a thickness of 15 to 800 nm are deposited; or, alternatively, a nickel layer with a thickness of 5 μm is electroplated on the Invar sheet. After the transition layer metal is deposited, the micropores are filled with copper using hole-filling electroplating and conventional copper electroplating processes, and a copper layer with a thickness of 75 μm is electroplated on each surface, thereby producing a copper composite sheet containing Invar alloy.

[0104] A ceramic substrate with a thickness of 300 μm is selected. Ceramic substrates include silicon nitride (Si3N4) substrates, aluminum nitride (AlN) substrates, silicon carbide (SiC) substrates, and diamond substrates. The copper composite board and these types of ceramic substrates are copper-clad using one of the following three processes:

[0105] The first type is to use active brazing AMB process to achieve copper cladding on ceramic substrates such as silicon nitride, silicon carbide or diamond and copper composite plates;

[0106] The second method is to metallize a ceramic substrate such as silicon nitride, silicon carbide or diamond first, and then use PVD sputtering to sputter one or more of Ti, TiC, TiN, Mo, tungsten W, and Ni, and then sputter a layer of Cu, and then use copper-copper bonding with a copper composite board to complete copper cladding.

[0107] The copper composite sheet in the embodiments of the present invention utilizes a combination of Invar or Kovar alloy and copper conductive material. Using this as the conductive metal layer can reduce the thermal expansion coefficient of the conductive metal layer material and reduce stress between the copper cladding layer and the ceramic substrate at high and low temperatures, thereby improving the stability and lifespan of the thermally conductive substrate.

[0108] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a thermally conductive substrate, the method comprising: Providing a ceramic substrate, the ceramic substrate including a silicon nitride substrate, an aluminum nitride substrate, a diamond substrate or a silicon carbide substrate, the ceramic substrate having a first surface and a second surface disposed opposite to each other; providing at least one copper clad plate; Implementing a copper cladding process to dispose the at least one copper composite board on at least one of the first surface and the second surface of the ceramic substrate to form a ceramic copper clad board to achieve heat conduction; The copper composite plate includes a metal plate made of Invar alloy or Kovar alloy, a transition metal layer formed on the metal plate, and a copper layer formed on the transition metal layer; and the metal plate is provided with a plurality of micropores running through the metal plate, each of which is filled with copper material.

2. The method for preparing a thermally conductive substrate according to claim 1, wherein: Implementing a copper cladding process to dispose the at least one copper composite board on at least one of the first surface and the second surface of the ceramic substrate to form a ceramic copper clad board includes: Active metal brazing (AMB) is used to directly coat the surface of the ceramic substrate with copper. One or more of Ti, TiC, TiN, Mo, W, and Ni are sputtered on the surface of the ceramic substrate by PVD, and then a copper layer is sputtered, and then a copper-copper bonding method is used to perform a copper cladding process with the copper composite plate; or One or more of Ti, TiC, TiN, Mo, W, and Ni are sputtered on the surface of the ceramic substrate by PVD, and then a copper layer is sputtered. Then, a metal brazing slurry is coated between the ceramic substrate after the copper layer is sputtered and the copper composite plate, and a copper cladding process is performed by sintering. The metal brazing slurry includes but is not limited to nano copper slurry.

3. The method for preparing a thermally conductive substrate according to claim 2, wherein: The preparation method also includes polishing one surface of the copper composite board to a surface roughness Ra value of 5 to 200 nm before implementing the copper cladding process. This surface is used to directly contact the first surface or the second surface of the ceramic substrate during the copper-copper bonding copper cladding process.

4. The method for preparing a thermally conductive substrate according to any one of claims 1 to 3, wherein: Providing at least one copper clad plate including: providing a metal sheet having a certain thickness, the metal sheet having an upper surface and an opposite lower surface; A transition metal layer is formed on the upper and lower surfaces of the metal plate and on the walls of the multiple micropores. A copper layer is plated on the surface of the transition metal layer through a copper electroplating process. The multiple micropores of the metal plate are copper-plated and filled until the copper layer formed along the axial direction of the micropores connects the copper layers on the upper and lower surfaces of the metal plate, thereby forming a copper composite plate.

5. The method for preparing a thermally conductive substrate according to claim 4, wherein: The transition metal layer has one or more metal layers, which include: a titanium layer formed on the metal plate, a nickel layer formed on the titanium layer, and a copper layer formed on the nickel layer; a titanium layer formed on the metal plate and a copper layer formed on the titanium layer; or A nickel layer is formed on the metal plate.

6. The method for preparing a thermally conductive substrate according to claim 4, wherein: The thickness of the ceramic substrate is in the range of 150 to 1000 microns, the thickness of the copper composite plate is in the range of 250 to 800 microns, and the diameter of the micropores is the same as the thickness of the metal plate.

7. The method for preparing a thermally conductive substrate according to claim 4, wherein: The thickness of the metal plate is in the range of 50 to 600 microns, and the thickness of the copper layer formed by electroplating on the upper and lower surfaces of the metal plate is in the range of 10 to 400 microns; and / or, The distance between the centers of two adjacent micropores is 1.5 to 2 times the diameter of the micropores.

8. The method for preparing a thermally conductive substrate according to claim 5, wherein: Forming a transition metal layer on the upper surface and the lower surface of the metal plate and on the walls of the plurality of micropores comprises: A titanium layer and a copper layer are sequentially sputtered on the upper surface, the lower surface and the walls of the plurality of micropores of the metal plate by physical vapor deposition (PVD), or a titanium layer, a nickel layer and a copper layer are sequentially sputtered, or a nickel layer is plated by chemical plating or electroplating; The thickness of the titanium layer is in the range of 0.015 to 0.25 microns, the thickness of the nickel layer formed by sputtering is in the range of 0.015 to 0.25 microns, and the thickness of the copper layer formed by sputtering is in the range of 0.5 to 1 micron. The thickness of the nickel layer plated by chemical plating or electroplating ranges from 5 to 120 microns.

9. The method for preparing a thermally conductive substrate according to claim 1, wherein: The preparation method further comprises: The ceramic copper clad plate is patterned by laser or photolithography according to a predetermined pattern layout to obtain a desired thermally conductive substrate.

10. A thermally conductive substrate with low interfacial stress, prepared by the preparation method according to any one of claims 1 to 9.

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