Si3n4 ceramic clad copper plate and its preparation method

Abstract

The application relates to the technical field of ceramic surface metallization, in particular to a Si3N4 ceramic Cu-coated plate and a preparation method thereof. The Si3N4 ceramic Cu-coated plate comprises Si3N4 ceramic plates, an interface bonding layer and an oxygen-free copper layer arranged in sequence, the interface bonding layer comprises a filler metal layer and a foam copper layer, and the filler metal layer is located on at least one side of the foam copper layer. The filler metal layer is connected to the Si3N4 ceramic by forming a reaction layer through reaction with the Si3N4 ceramic, the foam copper layer is arranged between the Si3N4 ceramic plate and the oxygen-free copper layer, the AgCu eutectic structure in the filler metal has a relatively low melting point (779 DEG C), the foam copper intermediate layer is softened and agglomerated, under the action of tension, a periodic columnar array solid solution structure is uniformly distributed on the bonding interface, the periodic columnar array can form a mechanical engagement effect, plastic deformation occurs on the interface under stress, energy in the strain process is absorbed, the bonding strength of the interface is improved, and the mechanical properties of the brazed joint are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ceramic surface metallization, in particular to a Si3N4 ceramic Cu-coated plate and a preparation method thereof. BACKGROUND

[0002] Ceramic substrates have high chemical stability, high corrosion resistance, high thermal conductivity, similar thermal expansion coefficient to chips, low dielectric constant and low dielectric loss, etc. According to the application of ceramic substrates, they can be divided into two categories: one is high-thermal-conductivity substrate, and the other is co-fired multilayer ceramic substrate, which has low dielectric constant and is suitable for high-speed devices.

[0003] With the increasing of power density and operating temperature of the third-generation SiC-based power module devices, the heat dissipation capacity and reliability of the packaging substrate are also required to be higher. The direct copper clad ceramic substrate (DBC) widely used in the past is prepared by eutectic bonding method, and there is no adhesive material between copper and ceramic. During high-temperature service, a large thermal stress is often generated due to the large difference in the coefficient of thermal expansion between copper and ceramic, which leads to the peeling of the copper layer from the ceramic surface, and finally causes the device to fail. Therefore, the traditional DBC ceramic substrate has been difficult to meet the packaging requirements of high temperature, high power, high heat dissipation and high reliability.

[0004] The copper / ceramic interface formed by the active metal brazing (AMB) process has higher bonding strength, and Si3N4 ceramic has more excellent mechanical properties and good thermal conductivity than traditional Al2O3 ceramic and AlN ceramic. The bending strength of Si3N4 ceramic is much higher than that of Al2O3 ceramic and AlN ceramic, and the theoretical thermal conductivity is higher. Therefore, the Si3N4-AMB copper-coated substrate has stronger service reliability at high temperature, and is the first choice for packaging substrates of future high-power SiC devices.

[0005] Brazing is a method widely used for connecting ceramic and metal materials, which has the advantages of high reliability and simple operation. However, the mechanical properties of the copper and Si3N4 ceramic brazed joint are not ideal, which is mainly because the copper of the base material matrix and the Si3N4 ceramic have a large difference in the coefficient of thermal expansion (CTE). The CTE of Si3N4 ceramic is about 2.2x10 -6 / ℃, while the CTE of Cu is about 16-17x10 -6The volume shrinkage of Cu is much greater than that of Si3N4 ceramic during the temperature decreasing from the joining temperature (870-900℃) to room temperature, so the ceramic is subjected to the compressive stress of the interface, while the Cu is subjected to the tensile stress of the interface. In order to keep the stable state of the internal static force balance, the residual tensile stress is generated in the Si3N4 ceramic, while the residual compressive stress is generated in the Cu. When the Si3N4 ceramic copper clad plate is subjected to the stress, the external stress is superimposed with the internal residual stress, and the material is easy to fail when the stress exceeds the strength limit of the Si3N4 ceramic. The great difference in CTE between the copper and the Si3N4 ceramic makes the residual thermal stress of the joint be large, and the mechanical properties of the joint are reduced. Therefore, making the filler metal organization in the brazing seam be uniformly distributed and reducing the residual thermal stress of the joint are the problems to be solved for improving the brazing performance of the copper and the Si3N4 ceramic. SUMMARY

[0006] Therefore, the application provides a Si3N4 ceramic copper clad plate and a preparation method thereof, so as to solve the problem of the large residual stress of the joint and the poor mechanical properties of the joint caused by the serious thermal mismatch of the base material during the connection of the Si3N4 ceramic and the copper.

[0007] The technical scheme of the application is as follows:

[0008] In a first aspect, the application provides a Si3N4 ceramic copper clad plate, which comprises a Si3N4 ceramic plate, an interface bonding layer and an oxygen-free copper layer arranged in sequence, the interface bonding layer comprises a filler metal layer and a foamed copper layer, and the filler metal layer is located at least on one side of the foamed copper layer. The connection is realized by the reaction of the filler metal layer and the Si3N4 ceramic to form a reaction layer, and the foamed copper layer is made into soft shell aggregation by the filler metal layer, so that the periodic columnar array solid solution structure is uniformly distributed between the Si3N4 ceramic plate and the oxygen-free copper layer. The filler metal layer contains AgCu eutectic phase

[0009] In the present application, a foamed copper layer is introduced between the Si3N4 ceramic plate and the oxygen-free copper layer, which can form a good interface bonding with the Si3N4 ceramic plate and the oxygen-free copper layer. Under the action of high temperature, the active Ti element in the filler metal reacts with the Si3N4 ceramic to form a reaction layer to realize the connection of the metal and the ceramic, and the AgCu eutectic structure in the filler metal melts, thereby softening and agglomerating the foamed copper intermediate layer. The softened foamed copper intermediate layer can form a periodic columnar array solid solution structure under the action of tension, which can be uniformly distributed between the ceramic plate and the oxygen-free copper layer, providing good connection and buffering effect, and enhancing the bonding strength of the interface. In the use process of the Si3N4 ceramic Cu plate, the interface will be affected by stress due to temperature change and mechanical load. The columnar solid solution structure formed by the foamed copper layer can relieve the residual thermal stress between the Si3N4 ceramic plate and the oxygen-free copper layer, form a good stress gradient transition, reduce the formation and expansion of cracks, and improve the stability and durability of the joint. The columnar solid solution structure formed by the foamed copper layer has a certain plastic deformation capacity, and when the Si3N4 ceramic Cu plate is subjected to external impact or vibration, the structure can plastically deform to absorb strain energy and reduce the impact on the ceramic and copper layer, thereby protecting the integrity of the overall structure.

[0010] On the basis of the above technical scheme, preferably, the filler metal layer comprises a first filler metal layer, and the first filler metal layer is located between the Si3N4 ceramic plate and the foamed copper layer, and the first filler metal layer is partially and uniformly filled into the porous structure of the foamed copper layer.

[0011] On the basis of the above technical scheme, preferably, the filler metal layer further comprises a second filler metal layer, and the second filler metal layer is located between the foamed copper layer and the oxygen-free copper layer, and the second filler metal layer is partially and uniformly filled into the porous structure of the foamed copper layer.

[0012] In the present application, the foamed copper has a porous structure, and the first filler metal layer and the second filler metal layer can be melted and filled into the porous structure on the side in contact with the foamed copper, so that the filler metal layer is uniformly distributed in the interface; meanwhile, the foamed copper skeleton provides more nucleation sites, which can promote grain refinement, optimize grain boundary structure, and increase the resistance of dislocation movement, thereby effectively preventing crack propagation and improving the tensile and compressive properties of the material.

[0013] On the basis of the above technical scheme, preferably, the pore diameter of the porous structure of the foamed copper layer is 80-100 μm, and the porosity is ≥85%. If the pore diameter is too small, the filler metal cannot flow into the interface to form holes, and if the pore diameter is too large, the foamed copper skeleton structure becomes loose, which reduces the stress relief effect.

[0014] Preferably, the first filler metal layer comprises an AgCuTi foil, and the second filler metal layer comprises an AgCuTi foil or an AgCu foil.

[0015] Specifically, the first filler metal layer is located between the ceramic plate and the foam copper, and the AgCuTi foil is used as the first filler metal layer. On one hand, the active Ti element in the AgCuTi foil can react with the ceramic to form a reaction layer with a certain thickness, which can provide a larger contact area, thereby forming a reliable connection between the ceramic and the metal interface and improving the stability and reliability of the interface. On the other hand, the active element Ti will react with copper in the foam copper at high temperature to form fine Cu-Ti intermetallic compounds, which have good bonding properties and can enhance the bonding strength between the foam copper and the ceramic. The AgCuTi foil or the AgCu foil as the second filler metal layer can form a stronger connection between the foam copper and the oxygen-free copper layer, thereby enhancing the stability and strength of the overall structure. Preferably, the second filler metal layer is an AgCuTi foil.

[0016] Preferably, the content of Ti in the AgCuTi foil is 2wt%-8wt%. The AgCuTi foil in this range can better ensure the stability of the connection.

[0017] Preferably, the thickness of the oxygen-free copper layer is 0.5-5mm, the thickness of the foam copper layer is 100-300μm, the thickness of the first filler metal layer is 50-100μm, and the thickness of the second filler metal layer is 50-100μm.

[0018] Specifically, when the foam copper layer is too thin, it cannot effectively alleviate the thermal stress generated during the preparation of the Si3N4Cu-coated plate, resulting in an insignificant reduction in residual thermal stress. When the foam copper layer is too thick, the filler metal cannot completely fill the pores of the foam copper, resulting in the formation of holes in the interface and a decrease in the mechanical properties of the Si3N4Cu-coated plate. A too thick foam copper layer also increases the thickness of the interface layer, resulting in a longer heat conduction path of the Si3N4Cu-coated plate and a decrease in the heat conduction performance. A too thin first filler metal layer and a too thin second filler metal layer result in low connection strength, and a too thick first filler metal layer and a too thick second filler metal layer result in an increased thickness of the interface layer. In the present application, the thickness of the first filler metal layer and the second filler metal layer can be the same or different, which is not limited in the present application.

[0019] In a second aspect, the present application provides a method for preparing a Si3N4 ceramic Cu-coated plate, comprising the following steps

[0020] S1, stacking a Si3N4 ceramic plate, an interface bonding layer and an oxygen-free copper layer in sequence to obtain a to-be-connected piece;

[0021] S2, placing the to-be-connected piece in a vacuum tube furnace, heating to a connection temperature and holding for 5-15 min, then cooling and furnace cooling to 25-27℃, to obtain the Si3N4 ceramic coated Cu plate.

[0022] On the basis of the above technical scheme, preferably, step S1 further comprises pretreating the oxygen-free copper layer, the interface bonding layer and the oxygen-free copper layer,

[0023] S i3 The Si3N4 ceramic, the first filler metal layer, the second filler metal layer and the oxygen-free copper are polished with 240-mesh, 400-mesh, 600-mesh and 1200-mesh sandpaper in turn, and then ultrasonic treated with anhydrous ethanol for 15-20 min; the foamed copper layer is ultrasonic treated with anhydrous ethanol for 15-20 min.

[0024] By pretreating each layer, the surface can be effectively cleaned, the surface roughness can be reduced and the activity can be improved, promoting the bonding and connection effect of each layer of the Si3N4 ceramic coated Cu plate. These pretreatment steps help to ensure the connection quality and stability during preparation, and improve the performance of the prepared Si3N4 ceramic coated Cu plate.

[0025] On the basis of the above technical scheme, preferably, in step S2, the to-be-connected piece is placed in a vacuum tube furnace, heated to a connection temperature and held for 5-15 min, specifically comprising: placing the to-be-connected piece in a vacuum tube furnace, applying a pressure of 3 MPa to the to-be-connected piece, holding at a pressure of 2x10 -5 Pa-1x10 -3 Pa, a temperature of 870℃-900℃, and holding for 5-15 min.

[0026] Specifically, the melting point of AgCu eutectic structure is relatively low at 779℃, and in the temperature range of 870℃-900℃, the AgCu eutectic structure can be softened and melted, thereby promoting the softening and agglomeration of the foamed copper intermediate layer, and the softened foamed copper intermediate layer can form a periodic columnar array under the action of tension, which can increase the bonding area between the Si3N4 ceramic plate and the oxygen-free copper layer, and is beneficial to improving the bonding strength and interface quality; by applying pressure, the density of the bonding interface can be improved, the defects such as pores can be reduced, and the bonding strength and quality can be further improved.

[0027] On the basis of the above technical scheme, preferably, in step S2, the to-be-connected piece is cooled and furnace cooled to 25-27℃, specifically comprising: reducing the to-be-connected piece after heating to 500℃ at a rate of 2-5℃ / min, and then furnace cooling to 25-27℃.

[0028] The temperature is reduced at a rate of 2-5℃ / min, which helps to relieve the thermal stress of the material formed in the process of temperature reduction, reduces the material deformation, crack and other problems caused by thermal stress, and protects the integrity of the Si3N4 ceramic Cu plate.

[0029] The Si3N4 ceramic Cu plate and the preparation method thereof have the following beneficial effects relative to the prior art:

[0030] (1) The foam copper layer and the filler metal layer are arranged between the Si3N4 ceramic plate and the oxygen-free copper layer, the active Ti element in the filler metal reacts with the Si3N4 ceramic to form a reaction layer to realize the connection of the metal and the ceramic, the AgCu eutectic structure has a lower melting point (779℃), which makes the foam copper intermediate layer soften and agglomerate, and the softened foam copper intermediate layer can form a periodic columnar array solid solution structure under the action of tension, so that the periodic columnar solid solution array can form a mechanical engagement effect, and plastic deformation occurs when the interface is stressed to absorb the energy in the strain process and improve the bonding strength of the interface, thereby significantly improving the mechanical properties of the brazed joint; (2) The first filler metal layer and the second filler metal layer are arranged on both sides of the foam copper layer, the porous structure of the foam copper makes the holes filled with melted filler metal to uniformly distribute in the interface, and the foam copper skeleton provides more nucleation sites to refine the grains, optimize the grain boundary structure and increase the resistance of dislocation movement, so that the crack is not easy to expand;

[0031] (3) During the process of reducing the temperature from the bonding high temperature to room temperature, the interface structure formed by the foam copper and the first filler metal layer and the second filler metal layer can relieve the residual thermal stress in the Si3N4 ceramic, so that a good stress gradient is formed at the interface between the Si3N4 ceramic and the oxygen-free copper, thereby making the crack not easy to form in the process of stress and thermal cycle;

[0032] (4) The filler metal layer material is AgCuTi foil, and the active element Ti in the AgCuTi foil reacts in situ with the foam copper to generate fine Cu-Ti intermetallic compounds uniformly distributed in the weld, which has obvious strengthening effect. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0034] Figure 1 The structure schematic diagram of the Si3N4 ceramic Cu plate prepared for the embodiment 2 of the present application;

[0035] Figure 2 Shear property test graph of Si3N4 ceramic coated Cu plate prepared for example 2 of the present application;

[0036] Figure 3 Interface scanning electron microscope graph of Si3N4 ceramic coated Cu plate prepared for example 2 of the present application;

[0037] Figure 4 Interface scanning electron microscope graph of Si3N4 ceramic coated Cu plate prepared for example 2 of the present application;

[0038] Figure 5 Interface XRD graph of Si3N4 ceramic coated Cu plate prepared for example 2 of the present application;

[0039] Figure 6 Interface scanning electron microscope graph of Si3N4 ceramic coated Cu plate prepared for comparative example 1 of the present application;

[0040] Figure 7 Shear property graph of Si3N4 ceramic coated Cu plate prepared for example 2 of the present application;

[0041] Figure 8 Interface maximum principal stress distribution graph of Si3N4 ceramic coated Cu plate prepared for example 2 and comparative example 1 of the present application;

[0042] Figure 9 Shear property graph of Si3N4 ceramic coated Cu plate prepared for example 6 of the present application;

[0043] Figure 10 Mechanical property graph of Si3N4 ceramic coated Cu plate prepared for example 2, example 5 and comparative example 1 of the present application. DETAILED DESCRIPTION

[0044] The technical solutions in the embodiments of the present application will be apparently and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by those of ordinary skill in the art without any creative work, fall within the protection scope of the present application.

[0045] Example 1

[0046] The embodiment provides a Si3N4 ceramic covered Cu plate and a preparation method thereof, which comprises a Si3N4 ceramic plate, an interface bonding layer and an oxygen-free copper layer (2.5 mm) arranged in sequence, wherein the interface bonding layer is a first filler metal layer (100 μm) and a foamed copper layer (300 μm), the foamed copper porosity is 85%, and the pore size is 90-100 μm; the first filler metal layer is an AgCuTi foil (the Ti content is 3.3 wt%), and the specific preparation method is as follows:

[0047] S1, the oxygen-free copper, the first filler metal layer and the Si3N4 ceramic plate are polished in sequence by using 240 mesh, 400 mesh, 600 mesh and 1200 mesh sandpaper, and then are subjected to ultrasonic treatment with anhydrous ethanol for 15-20 min, so that the oxygen-free copper, the first filler metal layer and the Si3N4 ceramic with surface impurities removed are obtained;

[0048] S2, the foamed copper foil is subjected to ultrasonic treatment with anhydrous ethanol for 15-20 min, and then is placed in a 60 ℃ drying box for drying for 1 hour, so that the foamed copper foil with surface impurities removed is obtained;

[0049] S3, the oxygen-free copper with surface impurities removed, the foamed copper foil and the Si3N4 ceramic are stacked in sequence to obtain a connecting piece, the connecting piece is placed in a vacuum tube furnace, a pressure of 3 MPa is applied to the connecting piece, the pressure is 1x10 -4 Pa and the temperature is 880 ℃, the temperature is reduced to 500 ℃ at a cooling rate of 3.5 ℃ / min, and finally the furnace is cooled to room temperature, so that the Si3N4 ceramic covered Cu plate is obtained.

[0050] Embodiment 2

[0051] The embodiment provides a Si3N4 ceramic covered Cu plate and a preparation method thereof, which has the same structure and preparation method as those of embodiment 1, and the difference lies in that the interface bonding layer is a first filler metal layer (100 μm), a foamed copper layer (300 μm) and a second filler metal layer (100 μm), the first filler metal layer and the second filler metal layer are both AgCuTi foils (the Ti content is 3.3 wt%),

[0052] In the preparation process, the first filler metal layer is pretreated in step S1, and the oxygen-free copper with surface impurities removed, the first filler metal layer, the foamed copper foil, the second filler metal layer and the Si3N4 ceramic are stacked in sequence in step S3 to obtain a connecting piece, so that the Si3N4 ceramic covered Cu plate is obtained.

[0053] Embodiment 3

[0054] The embodiment provides a Si3N4 ceramic covered Cu plate and a preparation method thereof, which comprises a Si3N4 ceramic plate, an interface bonding layer and an oxygen-free copper layer (1 mm) placed in sequence, wherein the interface bonding layer is a first filler metal layer (50 μm), a foamed copper layer (200 μm) and a second filler metal layer (50 μm), the pore size of the foamed copper layer is 80-90 μm, the first filler metal layer and the second filler metal layer are both AgCuTi foil (the Ti content is 2 wt%), and the specific preparation method is as follows:

[0055] S1, the oxygen-free copper, the first filler metal layer, the second filler metal layer and the Si3N4 ceramic plate are polished in sequence by using 240-mesh, 400-mesh, 600-mesh and 1200-mesh sandpaper, and then are treated by ultrasonic treatment with anhydrous ethanol for 15-20 min, so that the oxygen-free copper and the Si3N4 ceramic with surface impurities removed are obtained;

[0056] S2, the foamed copper foil is treated by ultrasonic treatment with anhydrous ethanol for 15-20 min, and then is dried in a 60 ℃ drying box for 1 hour, so that the foamed copper foil with surface impurities removed is obtained;

[0057] S3, the oxygen-free copper with surface impurities removed, the foamed copper foil and the Si3N4 ceramic are stacked in sequence to obtain a connecting piece, the connecting piece is placed in a vacuum tube furnace, a pressure of 3 MPa is applied to the connecting piece, the pressure is 2x10 -5 Pa and the temperature is 870 ℃, the temperature is reduced to 500 ℃ at a cooling rate of 2 ℃ / min, and finally the furnace is cooled to room temperature, so that the Si3N4 ceramic covered Cu plate is obtained.

[0058] Embodiment 4

[0059] The embodiment provides a Si3N4 ceramic covered Cu plate and a preparation method thereof, which comprises a Si3N4 ceramic plate, an interface bonding layer and an oxygen-free copper layer (5 mm) placed in sequence, wherein the interface bonding layer is a first filler metal layer (80 μm), a foamed copper layer (100 μm) and a second filler metal layer (80 μm), the pore size of the foamed copper layer is 80-90 μm, the first filler metal layer is AgCuTi foil (the Ti content is 8 wt%), and the second filler metal layer is AgCu foil, and the specific preparation method is as follows:

[0060] S1, the oxygen-free copper, the first filler metal layer, the second filler metal layer and the Si3N4 ceramic plate are polished in sequence by using 240-mesh, 400-mesh, 600-mesh and 1200-mesh sandpaper, and then are treated by ultrasonic treatment with anhydrous ethanol for 15-20 min, so that the oxygen-free copper and the Si3N4 ceramic with surface impurities removed are obtained;

[0061] S2, the foamed copper foil sheet is treated with anhydrous ethanol for 15-20 min, and then is placed in a 60℃ drying oven for drying for 1 h to obtain a foamed copper foil sheet with surface impurities removed;

[0062] S3, the oxygen-free copper with surface impurities removed, the foamed copper foil sheet and the Si3N4 ceramic are sequentially stacked to obtain a connecting piece, the connecting piece is placed in a vacuum tube furnace, a pressure of 3 MPa is applied to the connecting piece, the pressure is 1×10 -3 Pa and the temperature is 900℃, heat preservation is performed for 15 min, then the temperature is reduced to 500℃ at a cooling rate of 5℃ / min, and finally the furnace is cooled to room temperature, to obtain a Si3N4 ceramic coated Cu plate.

[0063] Example 5

[0064] This example provides a Si3N4 ceramic coated Cu plate and a preparation method thereof, the structure and the preparation method are the same as those of Example 2, and the difference lies in that the first filler metal layer and the second filler metal layer are both AgCuTi foil (the Ti content is 4.5wt%).

[0065] Example 6

[0066] This example provides a Si3N4 ceramic coated Cu plate and a preparation method thereof, the structure and the preparation method are the same as those of Example 2, and the difference lies in that in step S3, a pressure of 3 MPa is applied to the connecting piece, the pressure is 1×10 -4 Pa and the temperature is 870℃, heat preservation is performed for 10 min.

[0067] Example 7

[0068] This example provides a Si3N4 ceramic coated Cu plate and a preparation method thereof, the structure and the preparation method are the same as those of Example 2, and the difference lies in that the first filler metal layer is an AgCu foil.

[0069] Example 8

[0070] This example provides a Si3N4 ceramic coated Cu plate and a preparation method thereof, the structure and the preparation method are the same as those of Example 2, and the difference lies in that the thickness of the foamed copper layer is 50μm.

[0071] Example 9

[0072] This example provides a Si3N4 ceramic coated Cu plate and a preparation method thereof, the structure and the preparation method are the same as those of Example 2, and the difference lies in that the thickness of the foamed copper layer is 350μm.

[0073] Comparative Example 1

[0074] The comparative example 1 provides a Si3N4 ceramic covered Cu plate and a preparation method thereof, the structure and the preparation method are the same as those of the example 2, and the difference lies in that the interface bonding layer is a first filler metal layer and a second filler metal layer, and the thickness of the interface bonding layer is the same as that of the example 3.

[0075] Comparative example 2

[0076] The comparative example 1 provides a Si3N4 ceramic covered Cu plate and a preparation method thereof, the structure and the preparation method are the same as those of the example 2, and the difference lies in that the interface bonding layer is a first filler metal layer and a second filler metal layer, and the thickness of the interface bonding layer is the same as that of the example 3.

[0077] Performance detection

[0078] The shear performance of the Si3N4 ceramic covered Cu plates prepared from the examples 1-9 and the comparative example 1 is detected, and the test method is as follows Figure 2 The Si3N4 ceramic covered Cu plate is fixed by using a clamp, a load is applied to the Cu plate, the load change rate is 0.5 mm / s, and the detection result is shown in Table 1.

[0079] Table 1

[0080] Maximum shear strength Example 1 65 MPa Example 2 143 Mpa Example 3 96 MPa Example 4 51 MPa Example 5 98 MPa Example 6 133 Mpa Example 7 88 MPa Example 8 53 MPa Example 9 87 MPa Comparative Example 1 32 MPa

[0081] As shown in Table 1, the highest shear strength of the example 2 is the largest compared with the example 1, which indicates that the interface bonding layer formed by arranging the filler metal layers on both sides of the foam copper layer can improve the shear performance of the Si3N4 ceramic covered Cu plate; the shear performance of the Si3N4 ceramic covered Cu plate of the example 2-6 and the comparative example 1 is compared, which indicates that the shear performance of the Si3N4 ceramic covered Cu plate of the example 2 is better than that of the Si3N4 ceramic covered Cu plate without the foam copper layer in the prior art; the example 7 is compared with the example 2, which indicates that the first filler metal layer without Ti can reduce the shear performance of the Si3N4 ceramic covered Cu plate; the examples 8 and 9 are compared with the example 2, which indicates that the thickness of the foam copper layer can affect the shear performance of the Si3N4 ceramic covered Cu plate.

[0082] Figures 3-5 The interface scanning electron microscope image and the interface XRD image of the Si3N4 ceramic covered Cu plate prepared from the example 2 are shown. Figure 3 The interface structure diagram of the example 2 is shown, and it can be obviously seen that a large number of periodically arranged columnar arrays composed of copper are formed in the interface bonding area; Figure 4The interface structure diagram of example 2 is shown, and it can be seen from the diagram that the interface is tightly combined without obvious defects, the Cu plate and the filler metal are connected by interdiffusion without obvious interface, and it can be seen from the partial enlarged view that the ceramic and the filler metal form a reaction layer with a thickness of about 1 μm, the connection with the ceramic is realized through the reaction layer, the white part in the interface is an Ag solid solution, and the fine gray part is a Cu solid solution, the uniformly distributed fine Cu solid solution is beneficial to the improvement of the shear performance of the joint. Figure 5 The XRD diagram of the interface is shown, and it can be seen from the diagram that TiN and Ti5Si3 are generated in the interface, which are mainly the main components of the reaction layer of the filler metal and Si3N4 ceramic, and CuTi and CuTi2 are the reaction products of excess Ti and Cu in the interface. Figure 6 The SEM diagram of the interface of the Si3N4 ceramic coated Cu plate prepared in comparative example 1 is shown. It can be seen from the diagram that the Cu solid solution is unevenly distributed and not fine enough in the interface, and there is no Cu columnar array in the interface.

[0083] Figure 6 The shear performance diagram of the Si3N4 ceramic coated Cu plate prepared in example 2 is shown. It can be seen from the diagram that the highest shear strength can reach 143 MPa.

[0084] Figure 7 The interface maximum principal stress distribution diagram of the Si3N4 ceramic coated Cu plate prepared in example 2 under Abaqus finite element simulation is shown. It can be seen from the diagram that the stress distribution of the interface (1 to 1.1 mm is the interface of the Si3N4 ceramic coated Cu plate) changes from step to gradient after the addition of the foamed copper.

[0085] Figure 8 The shear performance diagram of the Si3N4 ceramic coated Cu plate prepared in example 7 is shown. It can be seen from the diagram that the highest shear strength can reach 133 MPa.

[0086] Figure 9 The mechanical property diagram of the Si3N4 ceramic coated Cu plate prepared in example 2, example 5 and comparative example 1 is shown. It can be seen from the diagram that the mechanical properties of the Si3N4 ceramic coated Cu plate prepared in examples 2 and 5 are obviously better than those of comparative example 1.

[0087] The above only describes the preferred embodiments of the present application and is not used to limit the present application, and 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 Si3N4 ceramic clad Cu plate characterized by: The Si3N4 ceramic plate, the interface bonding layer and the oxygen-free copper layer are sequentially stacked, the interface bonding layer comprises a filler metal layer and a foamed copper layer, the filler metal layer is at least located on one side of the foamed copper layer, the foamed copper layer is softened and agglomerated by the filler metal layer to form a periodic columnar array crystal phase structure uniformly distributed between the Si3N4 ceramic plate and the oxygen-free copper layer; The filler metal layer comprises a first filler metal layer, the first filler metal layer is located between the Si3N4 ceramic plate and the foamed copper layer, and the first filler metal layer is partially and uniformly filled into the porous structure of the foamed copper layer; The filler metal layer comprises a second filler metal layer, the second filler metal layer is located between the foamed copper layer and the oxygen-free copper layer, and the second filler metal layer is partially and uniformly filled into the porous structure of the foamed copper layer; The first filler metal layer comprises an AgCuTi foil, and the second filler metal layer comprises an AgCuTi foil or an AgCu foil; The preparation method of the Si3N4 ceramic Cu-coated plate comprises the following steps: S1, sequentially stacking the Si3N4 ceramic plate, the interface bonding layer and the oxygen-free copper layer to obtain a connecting piece to be connected; S2, the to-be-connected piece is placed in a vacuum tube furnace, a pressure of 3 MPa is applied to the to-be-connected piece, the pressure is 2×10 -5 Pa~1×10 -3 Pa, the temperature is 870℃~900℃, the temperature is kept for 5~15 min, then the temperature is lowered, and the furnace is cooled to 25~27℃, to obtain the Si3N4 ceramic Cu plate.

2. A Si3N4 ceramic clad Cu plate as claimed in claim 1, wherein: The content of Ti in the AgCuTi foil is 2wt%-8wt%.

3. The Si3N4 ceramic clad Cu plate of claim 1, wherein: The thickness of the oxygen-free copper layer is 0.5-5mm, the thickness of the foamed copper layer is 100-300μm, the thickness of the first filler metal layer is 50-100μm, the thickness of the second filler metal layer is 50-100μm, and the pore diameter of the porous structure of the foamed copper layer is 80-100μm.

4. The Si3N4 ceramic clad Cu plate of claim 1 wherein: In step S1, the oxygen-free copper layer, the interface bonding layer and the Si3N4 ceramic plate are pretreated, S i3 The N4 ceramic, the first filler metal layer, the second filler metal layer and the oxygen-free copper are polished with 240-mesh, 400-mesh, 600-mesh and 1200-mesh sandpaper in sequence, and then are ultrasonically treated with anhydrous ethanol for 15 min to 20 min; the foamed copper layer is ultrasonically treated with anhydrous ethanol for 15 min to 20 min.

5. The Si3N4 ceramic clad Cu plate of claim 1 wherein: In step S2, the cooling and furnace cooling to 25-27℃ specifically comprises: After the heating of the connecting piece to be connected, the temperature is reduced to 500℃ at a rate of 2-5℃ / min, and then the furnace is cooled to 25-27℃.

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