Ceramic copper-clad substrate and its preparation method

Abstract

This invention discloses a ceramic copper-clad substrate and its preparation method. The ceramic copper-clad substrate includes a ceramic base layer and a copper metal layer, as well as a reaction layer, a solid solution layer, and an intermetallic compound layer located between the ceramic base layer and the copper metal layer. The reaction layer is adjacent to the ceramic base layer and is formed by the reaction of Ti with ceramic. The solid solution layer is formed by the solid solution of Sn in Cu. The intermetallic compound layer contains Cu, Ti, and P. According to this invention, the ceramic base layer and the copper metal layer of the ceramic copper-clad substrate have high bonding strength, and the material cost of the substrate is low due to the use of low-cost Cu-P-Sn solder.

Description

Technical Field

[0001] This invention relates to the field of electronic materials technology, and more specifically to a ceramic copper-clad substrate and its preparation method. Background Technology

[0002] Common techniques for ceramic copper clad bonding include direct bonded copper (DBC) and active metal bonding (AMB). Direct bonded copper substrates have low reliability and are only suitable for alumina ceramics, limiting their applicability. Active metal bonding, on the other hand, utilizes the reaction of active elements with the ceramic to achieve copper-ceramic bonding, resulting in high reliability. However, it requires expensive traditional active solders such as Ag-Cu-Ti alloy solders, leading to higher overall costs.

[0003] Therefore, there is a need for a ceramic copper-clad substrate and its preparation method to at least partially solve the above problems. Summary of the Invention

[0004] The summary section introduces a series of simplified concepts, which will be further explained in detail in the detailed description section. The summary section of this invention is not intended to limit the key features and essential technical features of the claimed technical solution, nor is it intended to determine the scope of protection of the claimed technical solution.

[0005] To at least partially solve the above problems, the present invention provides a ceramic copper-clad substrate comprising a ceramic substrate and a copper metal layer, and a layer located between the ceramic substrate and the copper metal layer as follows:

[0006] A reaction layer, adjacent to the ceramic substrate, is formed by the reaction of Ti and ceramic.

[0007] A solid solution layer, wherein the solid solution layer is formed by Sn dissolved in Cu; and

[0008] An intermetallic compound layer containing Cu, Ti, and P.

[0009] Optionally, the intermetallic compound layer is adjacent to the copper metal layer, and the solid solution layer is located between the reaction layer and the intermetallic compound layer.

[0010] Optionally, the thickness of the reaction layer is less than 3 μm;

[0011] And / or the thickness of the solid solution layer is 1 μm to 8 μm;

[0012] And / or the thickness of the intermetallic compound layer is 1 μm to 10 μm.

[0013] According to another aspect of the present invention, a method for preparing a ceramic copper-clad substrate as described in any of the above aspects is provided, comprising the following steps:

[0014] A copper metal component, Cu-P-Sn solder, and Ti-containing solder are laminated onto a ceramic substrate to form a laminate, wherein the Cu-P-Sn solder and the Ti-containing solder are located between the copper metal component and the ceramic substrate, the Ti-containing solder is adjacent to the ceramic substrate, and the Cu-P-Sn solder is adjacent to the copper metal component; and

[0015] The laminate is subjected to sintering treatment.

[0016] Optionally, the Ti-containing solder is adjacent to the ceramic substrate, and the Cu-P-Sn solder is adjacent to the copper metal part; or the Ti-containing solder and the Cu-P-Sn solder are mixed evenly and then laminated onto the ceramic substrate.

[0017] Optionally, the preparation method further includes:

[0018] The Ti-containing solder is prepared into a Ti-containing solder paste, and a first solder layer formed by coating the Ti-containing solder paste is stacked on the ceramic substrate; and

[0019] The Cu-P-Sn solder is made into a copper-based solder paste, and a second solder layer formed by coating the copper-based solder paste is stacked on the first solder layer or the copper metal part.

[0020] Optionally, the mass ratio of the Ti-containing solder paste to both the Ti-containing solder paste and the copper-based solder paste is 8% to 30%.

[0021] Optionally, the areal density of the Ti-containing solder paste after coating is 15–35 g / m³. 2 The areal density of the copper-based solder paste after application is 80–115 g / m³. 2 .

[0022] Optionally, the Ti-containing solder paste includes titanium hydride and a binder, wherein the mass ratio of the binder to the Ti-containing solder paste is 40% to 70%.

[0023] And / or, the copper-based solder paste comprises Cu-P-Sn solder and a binder, wherein the mass ratio of the binder to the copper-based solder paste is 10% to 20%.

[0024] Optionally, the Ti-containing solder paste includes titanium hydride, and the step of sintering the laminate includes:

[0025] A first sintering process involves sintering the laminate at a first sintering temperature, which is greater than the decomposition temperature of titanium hydride and less than the melting point of the Cu-P-Sn solder; and

[0026] The second sintering process involves sintering the laminated body after the first sintering process at a second sintering temperature greater than or equal to 650°C.

[0027] Optionally, the ceramic substrate is a substrate composed of at least one of alumina ceramic, aluminum nitride ceramic, and silicon nitride ceramic.

[0028] According to the present invention, a ceramic copper-clad substrate and its preparation method can be used to prepare a ceramic copper-clad substrate using Ti-containing solder and Cu-P-Sn solder. The Ti element in the Ti-containing solder can form a Ti-ceramic reaction layer with elements such as N in the ceramic, thus wetting the ceramic and facilitating better bonding of the Cu-P-Sn solder to the ceramic substrate through the Ti-ceramic reaction layer, reducing welding defects. The Ti element in the Ti-containing solder and the Cu-P-Sn solder can form a Cu-Sn solid solution layer and a Cu-Ti-P intermetallic compound layer. The ceramic copper-clad substrate provided by the present invention has a high bonding ability between the ceramic substrate and the copper metal layer, and the material cost of the substrate is low due to the use of low-cost Cu-P-Sn solder. Attached Figure Description

[0029] The following drawings, which are incorporated herein by reference as part of this invention, are provided for understanding the invention. The drawings illustrate embodiments of the invention and their descriptions, serving to explain the principles of the invention.

[0030] In the attached image:

[0031] Figure 1 This is a schematic structural diagram of the ceramic copper-clad substrate according to the present invention;

[0032] Figure 2 An image of a ceramic copper-clad substrate according to the present invention;

[0033] Figure 3 This is a flowchart of a preparation method according to a preferred embodiment of the present invention;

[0034] Figure 4 This is a flowchart of a preparation method according to another preferred embodiment of the present invention.

[0035] Explanation of reference numerals in the attached figures:

[0036] 10 Ceramic copper-clad substrate

[0037] 11 Ceramic base layer

[0038] 12 Copper metal layers

[0039] 13 Reaction Layer

[0040] 14 Solid solution layer

[0041] 15 Intermetallic compound layer Detailed Implementation

[0042] In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention can be practiced without one or more of these details. In other instances, certain technical features well-known in the art have not been described in order to avoid obscuring the invention.

[0043] To fully understand the present invention, a detailed description will be set forth in the following description. It is obvious that the implementation of embodiments of the present invention is not limited to the specific details familiar to those skilled in the art. Preferred embodiments of the present invention are described in detail below; however, in addition to these detailed descriptions, the present invention may have other embodiments.

[0044] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms “comprising” and / or “including” are used in this specification, they indicate the presence of the stated features, integrals, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or combinations thereof.

[0045] The ordinal numbers such as "first" and "second" used in this invention are merely identifiers and do not have any other meaning, such as a specific order. Moreover, for example, the term "first component" does not imply the existence of "second component," and the term "second component" does not imply the existence of "first component."

[0046] It should be noted that the terms “up,” “down,” “front,” “back,” “left,” “right,” “inner,” “outer,” and similar expressions used in this article are for illustrative purposes only and are not intended to be restrictive.

[0047] Exemplary embodiments according to the present invention will now be described in more detail with reference to the accompanying drawings. However, these exemplary embodiments may be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein. It should be understood that these embodiments are provided so that the disclosure of the invention is thorough and complete, and that the concept of these exemplary embodiments is fully conveyed to those skilled in the art.

[0048] like Figure 1 and Figure 2 As shown, the present invention provides a ceramic copper-clad substrate 10, which is obtained using active metal brazing technology. Figure 1 As shown, the ceramic copper-clad substrate 10 includes multiple layers: a ceramic substrate 11, a copper metal layer 12, a reaction layer 13, a solid solution layer 14, and an intermetallic compound layer 15. The reaction layer 13, solid solution layer 14, and intermetallic compound layer 15 are located between the ceramic substrate 11 and the copper metal layer 12. The reaction layer 13 is adjacent to the ceramic substrate 11 and is formed by the reaction of Ti with ceramic. The solid solution layer 14 is formed by the solid solution of Sn in Cu. The intermetallic compound layer 15 contains Cu, Ti, and P.

[0049] According to this embodiment, a ceramic copper-clad substrate 10 can be prepared using Ti-containing solder and low-cost Cu-P-Sn solder. The Ti element in the Ti-containing solder can form a Ti-ceramic reaction layer 13 with elements such as N in the ceramic, which wets the ceramic, reduces welding defects, and facilitates better bonding of the Cu-P-Sn solder to the ceramic substrate 11 through the Ti-ceramic reaction layer 13. The Ti element in the Ti-containing solder and the Cu-P-Sn solder can form a Cu-Sn solid solution layer 14 and a Cu-Ti-P intermetallic compound layer 15, which can improve the bonding ability between the ceramic substrate 11 and the copper metal layer 12. On the other hand, the low cost of Cu-P-Sn solder can reduce material costs.

[0050] The Cu-Ti-P intermetallic compound layer 15 can be adjacent to the copper metal layer 12, and the Cu-Sn solid solution layer 14 can be located between the Ti-ceramic reaction layer 13 and the Cu-Ti-P intermetallic compound layer 15. The copper metal layer 12, reaction layer 13, solid solution layer 14 and intermetallic compound layer 15 can be stacked on one side or opposite sides of the ceramic substrate 11. Figure 1 An exemplary embodiment is shown of the structure of the copper-clad ceramic substrate 10 in a configuration where it is laminated to one side of the ceramic substrate 11; for configurations where it is laminated to opposite sides of the ceramic substrate 11, the copper-clad ceramic substrate 10 has the following layering sequence: copper metal layer 12, intermetallic compound layer 15, solid solution layer 14, reactive layer 13, ceramic substrate 11, reactive layer 13, solid solution layer 14, intermetallic compound layer 15, and copper metal layer 12.

[0051] The thickness of the ceramic substrate 11 can be less than or equal to 2 mm, for example, 0.5 mm, 0.6 mm, 0.8 mm, 1.0 mm, 1.2 mm, 1.4 mm, 1.6 mm, 1.8 mm, 2 mm, etc. The thickness of the Ti-ceramic reaction layer 13 can be less than or equal to 3 μm, for example, 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.8 μm, 3 μm, etc. The thickness of the copper metal layer 12 can be 0.1–1.5 mm, for example, 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm. The preferred thickness of the copper metal layer 12 is 0.3–0.8 mm. The thickness of the Cu-Sn solid solution layer 14 can be from 1 μm to 8 μm, for example, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 6 μm, 7 μm, 8 μm, etc. The thickness of the Cu-Ti-P intermetallic compound layer 15 can be from 1 μm to 10 μm, for example, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, etc.

[0052] According to another aspect of the present invention, a method for preparing a ceramic copper-clad substrate 10 for any of the above aspects is provided, comprising the following steps:

[0053] S1: Clean the ceramic substrate and copper metal parts.

[0054] Cleaning can remove oil and foreign matter from the surfaces of ceramic substrates and copper metal parts.

[0055] S2: Copper metal parts, Cu-P-Sn solder, and Ti-containing solder are laminated onto a ceramic substrate to form a laminate.

[0056] In this step, Cu-P-Sn solder and Ti-containing solder are located between the copper metal component and the ceramic substrate. The copper metal component, Cu-P-Sn solder, and Ti-containing solder can be stacked on one surface or two opposite surfaces of the ceramic substrate.

[0057] One implementation is as follows: Ti-containing solder and Cu-P-Sn solder are stacked independently, with the Ti-containing solder adjacent to the ceramic substrate and the Cu-P-Sn solder adjacent to the copper metal part.

[0058] Another implementation method is to mix Ti-containing solder with Cu-P-Sn solder evenly and then laminate it onto a ceramic substrate.

[0059] The ceramic substrate is composed of at least one of alumina ceramic, aluminum nitride ceramic, and silicon nitride ceramic. The copper metal component can be copper sheet or thinner copper foil. Cu-P-Sn solder, as a raw material, can reduce material costs compared to Ag-Cu-Ti solder. Ti-containing solder can be, for example, titanium hydride or titanium, specifically titanium hydride powder or titanium powder. In this paper, titanium hydride is preferred as the Ti-containing solder.

[0060] S3: Sinter the laminate.

[0061] In this step, the sintering treatment of the laminate can result in the following reaction:

[0062] The Ti element in the Ti-containing solder can chemically react with elements in the ceramic substrate to form a Ti-ceramic reaction layer 13. Specifically, the Ti element can chemically react with Al and O elements in alumina ceramic to produce titanium oxide, thereby forming a reaction layer 13 comprising titanium oxide, Ti, and Al. The Ti element can chemically react with N elements in aluminum nitride ceramic to produce titanium nitride, thereby forming a reaction layer 13 comprising titanium nitride, Ti, and Al. The Ti element can chemically react with N elements in silicon nitride ceramic to produce titanium nitride, thereby forming a reaction layer 13 comprising titanium nitride, Ti, and Si.

[0063] When copper metal parts are heated to high temperatures, they will melt, causing some of the Ti elements in the Ti-containing solder and the P elements in the Cu-P-Sn solder to diffuse into the molten copper metal parts. They will react at the interface of the copper metal parts to form an intermetallic compound layer 15 containing Cu-Ti-P.

[0064] Because the P element in the Cu-P-Sn solder is used to form the Cu-Ti-P intermetallic compound layer 15, a Cu-Sn solid solution layer 14 is formed.

[0065] The Ti-containing solder of this invention preferably contains titanium hydride. Titanium hydride has high chemical stability, does not react with air or water, and begins to decompose and release hydrogen when heated to 400°C, providing fresh active Ti elements for welding. This is beneficial for the wetting of the solder and ceramic, reducing welding defects. During sintering, when the temperature rises to 400°C or above, titanium hydride decomposes, and H elements volatilize, releasing active Ti elements. Some of the active Ti elements diffuse and accumulate at the ceramic interface. As the Ti element concentration increases, Ti elements react with elements in the ceramic. With further increases in Ti element concentration, Ti no longer diffuses towards the ceramic side, but rather towards the copper metal side to form the Cu-Ti-P intermetallic compound layer 15 as described above.

[0066] For implementations where Ti-containing solder and Cu-P-Sn solder are independently stacked, such as Figure 4As shown, the preparation method also includes:

[0067] S21: Prepare Ti-containing solder paste from Ti-containing solder and stack a first solder layer formed by coating Ti-containing solder paste on a ceramic substrate.

[0068] In this step, the Ti-containing solder paste may include titanium hydride powder and a binder. The titanium hydride powder and binder are mixed uniformly in a predetermined ratio to obtain the titanium hydride solder paste. An example is that the particle size of the titanium hydride powder is 500 nm to 50 μm; the mass ratio of the binder to the Ti-containing solder paste is 40% to 70%, for example, 40%, 45%, 50%, 55%, 60%, 65%, 70%, etc. By controlling the proportion of the binder in the Ti-containing solder paste, the ratio of the Ti-containing solder paste to the copper-based solder paste can be controlled within a desired range (described below), thereby facilitating the formation of the reaction layer 13, the solid solution layer 14, and the intermetallic compound layer 15.

[0069] Alternatively, the Ti-containing solder paste may include titanium powder and a binder. The titanium powder and binder are mixed uniformly in a predetermined ratio to obtain a titanium solder paste. The Ti-containing solder paste is applied to one surface or both opposite surfaces of a ceramic substrate and baked to obtain a ceramic substrate with a first solder layer.

[0070] S22: The Cu-P-Sn solder is made into a copper-based solder paste, and a second solder layer formed by coating the copper-based solder paste is stacked on the first solder layer or copper metal part.

[0071] In this step, Cu-P-Sn solder and binder are mixed uniformly in a predetermined ratio to obtain copper-based solder paste. An example is that the Cu-P-Sn solder has a particle size of 20 μm to 80 μm; the mass ratio of binder to copper-based solder paste is 10% to 20%, for example, 10%, 12%, 14%, 16%, 18%, 20%, etc., preferably 10% to 15%. By controlling the proportion of binder in the copper-based solder paste, the ratio of Ti-containing solder paste to copper-based solder paste can be controlled within a desired range (described below), thereby facilitating the formation of the reaction layer 13, the solid solution layer 14, and the intermetallic compound layer 15. The copper-based solder paste is applied to the surface of the first solder layer located on one or both sides of the ceramic substrate, and baked to obtain a ceramic substrate with the first solder layer and the second solder layer.

[0072] For the embodiment where Ti-containing solder and Cu-P-Sn solder are uniformly mixed and then stacked, the preparation method further includes:

[0073] S121: A mixed solder paste is made by combining Ti-containing solder with Cu-P-Sn solder, and a mixed solder layer formed by coating the mixed solder paste is stacked on a ceramic substrate.

[0074] Specifically, Ti-containing solder and Cu-P-Sn solder are first mixed in a certain proportion, and then the mixed materials are mixed with binder in a predetermined proportion to obtain a mixed solder paste. The mixed solder paste is applied to one surface or two opposite surfaces of a ceramic substrate and baked to obtain a ceramic substrate with a mixed solder layer.

[0075] The above-mentioned Ti-containing solder paste, copper-based solder paste, and mixed solder paste can be applied using any suitable method, such as screen printing. When using screen printing, the mesh count of the screen printing stencil can be 100–500 mesh. The solder paste can be baked in an oven at a temperature of 50–100°C for 10–30 minutes.

[0076] Furthermore, the mass ratio of Ti-containing solder paste to both Ti-containing solder paste and copper-based solder paste can be 8%–30%, for example, 8%, 10%, 15%, 20%, 25%, 30%, etc. By controlling the ratio of Ti-containing solder paste to copper-based solder paste, the proportional relationship between Ti and Cu, P, and Sn elements can be controlled, which is more conducive to the formation of the reaction layer 13, the solid solution layer 14, and the intermetallic compound layer 15. The areal density of the Ti-containing solder paste after coating can be 15–35 g / m³. 2 For example, 15g / m 2 18g / m 2 20g / m 2 22g / m 2 25g / m 2 28g / m 2 30g / m 2 32g / m 2 35g / m 2 The areal density of copper-based solder paste after application can be 80–115 g / m³. 2 For example, 80g / m 2 85g / m 2 90g / m 2 95g / m 2 100g / m 2 105g / m 2 110g / m 2 115g / m 2 By controlling the areal density of Ti-containing solder paste and / or copper-based solder paste, the ratio between Ti and Cu, P, and Sn elements can be controlled, which is more conducive to the formation of reaction layer 13, solid solution layer 14, and intermetallic compound layer 15.

[0077] In the scheme where the Ti-containing solder is titanium hydride, step S3, which involves sintering the laminate, includes:

[0078] S31: First sintering treatment, in which the laminate is sintered at a first sintering temperature, which is greater than the decomposition temperature of titanium hydride and less than the melting point of Cu-P-Sn solder. For example, the first sintering temperature is greater than 400℃ and less than or equal to 600℃, and can be 410℃, 430℃, 450℃, 480℃, 500℃, 520℃, 550℃, 580℃, 600℃, etc.

[0079] The specific process is as follows: heat from room temperature to the first sintering temperature at a certain heating rate and hold at that temperature. Holding at this temperature for a period of time helps decompose titanium hydride and prevents fresh Ti elements from dissolving into the Cu-P-Sn solder. The holding time can be 10–50 minutes.

[0080] S32: Second sintering treatment, wherein the laminate after the first sintering treatment is sintered at a second sintering temperature, which is higher than the melting point of the Cu-P-Sn solder, for example, greater than or equal to 650℃. Optionally, the second sintering temperature is 650℃~850℃, and can be 650℃, 680℃, 700℃, 720℃, 750℃, 780℃, 800℃, 820℃, 850℃, etc.

[0081] In the specific process, after the first sintering treatment and holding, the temperature is further increased to the second sintering temperature and held. The CuPSn solder melts, and some of the active Ti elements react with the elements in the ceramic substrate, while another portion of Ti reacts with Cu. P in the Cu-P-Sn solder diffuses into the Cu-Ti reaction layer 13 to form a Cu-Ti-P intermetallic compound layer 15. The holding time can be 10–50 minutes.

[0082] The use of a two-stage sintering process for the laminated body improves the layer structure formation of the copper-clad ceramic substrate 10. Alternatively, a single-stage sintering process can be used if needed and / or desired. In this case, the sintering temperature is higher than the melting point of the Cu-P-Sn solder, for example, greater than or equal to 650°C; in other words, it is approximately the same as the second sintering temperature mentioned above. The holding time is 30–60 minutes.

[0083] S4: After sintering, the laminate is cooled to obtain the ceramic copper-clad substrate 10.

[0084] Example 1

[0085] The ceramic substrate is a silicon nitride ceramic substrate with a thickness of 0.32mm. The solder system is titanium hydride solder paste + CuP7Sn7 solder paste. The copper metal parts are oxygen-free copper foil with a thickness of 0.3mm.

[0086] Using a 400-mesh screen printing stencil, prepared titanium hydride solder paste was uniformly screen-printed onto the upper and lower surfaces of a silicon nitride ceramic substrate, and baked at 70°C for 15 minutes to obtain a silicon nitride ceramic substrate with a first solder layer. Using a 300-mesh screen printing stencil, prepared CuP7Sn7 solder paste was uniformly screen-printed onto the surfaces of the first solder layer on both sides of the silicon nitride ceramic substrate, and baked at 70°C for 15 minutes to obtain a silicon nitride ceramic substrate with both first and second solder layers (also called a screen-printed sheet). Copper foil-screened sheet-copper foil were stacked in a "sandwich" manner within a graphite fixture, with alumina ceramic sheets separating the copper foils, and a counterweight was pressed onto the top layer of copper foil. Sintering was performed at two temperatures: a first sintering temperature of 550°C for 30 minutes and a second sintering temperature of 800°C for 30 minutes.

[0087] The image obtained by performing ultrasonic scanning or X-ray scanning on the cooled ceramic copper-clad substrate (e.g.) Figure 2 As shown, no welding voids can be observed. The sintered ceramic copper-clad substrate interconnect layer includes: a titanium nitride layer on the ceramic side, an intermetallic compound layer 15 containing Cu, Ti and P on the copper metal side, and a Cu-Sn solid solution layer 14 in which Sn is dissolved in Cu between the titanium nitride layer and the intermetallic compound layer 15.

[0088] Example 2

[0089] The ceramic substrate is an alumina ceramic substrate with a thickness of 0.32mm. The solder system is titanium hydride solder paste + CuP7Sn7 solder paste. The copper metal parts are oxygen-free copper foil with a thickness of 0.3mm.

[0090] The preparation process of the ceramic copper-clad substrate in Example 2 is largely the same as that in Example 1, and the description is omitted for the sake of brevity.

[0091] Ultrasonic scanning or X-ray scanning of the cooled ceramic copper-clad substrate revealed no weld voids. The bonding layers of the sintered ceramic copper-clad substrate include: a titanium oxide and Ti-Al layer on the ceramic side, an intermetallic compound layer 15 containing Cu, Ti, and P on the copper metal side, and a Cu-Sn solid solution layer 14 in which Sn is dissolved in Cu between the titanium nitride layer and the intermetallic compound layer 15.

[0092] Example 3

[0093] The ceramic substrate is a silicon nitride ceramic substrate with a thickness of 0.32mm. The solder system is titanium hydride solder paste + CuP7Sn7 solder paste. The copper metal parts are oxygen-free copper foil with a thickness of 0.3mm.

[0094] The prepared titanium hydride and CuP7Sn7 mixed solder paste was uniformly screen-printed onto the upper and lower surfaces of a silicon nitride ceramic substrate and baked at 70°C for 15 minutes to obtain a silicon nitride ceramic substrate with a mixed solder layer (also known as a screen-printed sheet). Copper foil-screened sheet-copper foil were stacked in a "sandwich" manner within a graphite fixture, with alumina ceramic sheets separating the copper foils, and a counterweight was pressed onto the top layer of copper foil. Sintering was then performed: the first sintering temperature was 550°C for 30 minutes, and the second sintering temperature was 800°C for 30 minutes.

[0095] Ultrasonic scanning or X-ray scanning of the cooled ceramic copper-clad substrate revealed no weld voids. The bonding layer of the sintered ceramic copper-clad substrate includes: a titanium nitride layer on the ceramic side, an intermetallic compound layer 15 containing Cu, Ti, and P on the copper metal side, and a Cu-Sn solid solution layer 14 in which Sn is dissolved in Cu between the titanium nitride layer and the intermetallic compound layer 15.

[0096] Example 4

[0097] The ceramic substrate is a silicon nitride ceramic substrate with a thickness of 0.32mm. The solder system is titanium solder paste + CuP7Sn7 solder paste. The copper metal parts are oxygen-free copper foil with a thickness of 0.3mm.

[0098] Using a 400-mesh screen printing stencil, prepared titanium solder paste was uniformly screen-printed onto the upper and lower surfaces of a silicon nitride ceramic substrate, and baked at 70°C for 15 minutes to obtain a silicon nitride ceramic substrate with a first solder layer. Using a 300-mesh screen printing stencil, prepared CuP7Sn7 solder paste was uniformly screen-printed onto the surfaces of the first solder layer on both sides of the silicon nitride ceramic substrate, and baked at 70°C for 15 minutes to obtain a silicon nitride ceramic substrate with both first and second solder layers (also called a screen-printed sheet). Copper foil-screened sheet-copper foil were stacked in a "sandwich" manner within a graphite fixture, with alumina ceramic sheets separating the copper foils, and a counterweight was pressed onto the top layer of copper foil. Sintering was performed at two temperatures: a first sintering temperature of 550°C for 30 minutes and a second sintering temperature of 800°C for 30 minutes.

[0099] Ultrasonic scanning or X-ray scanning of the cooled ceramic copper-clad substrate revealed no weld voids. The bonding layer of the sintered ceramic copper-clad substrate includes: a titanium nitride layer on the ceramic side, an intermetallic compound layer 15 containing Cu, Ti, and P on the copper metal side, and a Cu-Sn solid solution layer 14 in which Sn is dissolved in Cu between the titanium nitride layer and the intermetallic compound layer 15.

[0100] Peel strength test

[0101] Peel strength tests were conducted on the ceramic copper-clad substrates prepared in Examples 1 to 4. The test conditions included: a universal testing machine, a peel speed of 50 mm / min, and a peel stroke greater than 25 mm.

[0102] Test Procedure: First, the copper-clad ceramic substrate was etched into a peel strip according to the sample preparation requirements for the peel test. Then, the copper layer protruding from the ceramic portion was bent at a 90-degree angle. The peel strip was clamped on a universal testing machine, and the copper layer was stretched in a direction perpendicular to the ceramic substrate. The minimum peel force when the copper layer peels from the ceramic was measured. The value obtained by dividing the minimum peel force by the width of the peel strip can be taken as the 90-degree peel strength. The test results are shown in Table 1 below.

[0103] Ultrasonic scanning weld layer test

[0104] Ultrasonic scanning solder layer tests were performed on the ceramic copper-clad substrates prepared in Examples 1 to 4. Test conditions included: the testing equipment being an ultrasonic non-destructive testing instrument. The quality requirement was a solder layer void rate of less than 3%.

[0105] Experimental procedure: The ceramic copper-clad substrate was tested using an ultrasonic non-destructive testing instrument. The experimental results are shown in Table 1 below.

[0106] Product reliability test

[0107] Product reliability tests were conducted on the ceramic copper-clad substrates prepared in Examples 1 to 4. The test conditions included: the test equipment was a thermal shock chamber, the holding time was -50℃ for 30 min, the holding time was 150℃ for 30 min, and the transition time from low temperature to high temperature was less than 30 s.

[0108] Experimental Procedure: First, the ceramic copper-clad substrate was etched into a specific pattern and laser-cut into individual units. Units with no solder defects, no ceramic cracks, and no copper peeling were selected and placed in a thermal shock chamber. The test was initiated according to the test requirements. Every 100 cycles, the samples were removed for ultrasonic scanning and optical microscopy to check for solder defects, ceramic cracks, and copper peeling, until any of these defects were detected. The test results are shown in Table 1 below.

[0109] It should be noted that the weld layer mentioned in the ultrasonic scanning weld layer test and product reliability test includes the reaction layer 13, the solid solution layer 14, and the intermetallic compound layer 15.

[0110] Table 1 Comparison of Experimental Results

[0111]

[0112] The experimental results can be seen from Table 1:

[0113] Examples 1 to 4 use low-cost CuP7Sn7 solder, and the average peel strength of the resulting ceramic copper-clad substrates is greater than 10 N / mm. Furthermore, the method of forming two different solder layers achieves even higher peel strength. Therefore, compared to traditional ceramic copper-clad substrates, the ceramic copper-clad substrate of this invention, using a lower-cost solder, also meets performance requirements in terms of peel strength. The ceramic substrate and copper metal layer of this invention exhibit high bonding strength and adhesion; the preferred method of forming two different solder layers is also present in this invention.

[0114] Examples 1 to 3 used a titanium hydride + CuP7Sn7 solder system, and the resulting copper-clad ceramic substrates all exhibited good solder layer structures, i.e., dense soldering without voids. However, Example 4 used a titanium + CuP7Sn7 solder system. Since titanium is a highly reactive element and readily oxidizes in air, this oxidation of the solder can lead to the formation of some solder voids. Therefore, the present invention preferably uses a titanium hydride + Cu-P-Sn solder system.

[0115] Example 2 used alumina ceramic, while Examples 1, 3, and 4 used silicon nitride ceramic. The reliability of the copper-clad ceramic substrate made with silicon nitride ceramic was higher than that made with silicon nitride ceramic. This is because alumina ceramic has lower fracture toughness and bending strength compared to silicon nitride ceramic. During reliability testing, rapid changes in high and low temperatures can generate thermal stress within the alumina ceramic substrate. Due to its lower fracture toughness, alumina ceramic is more prone to cracking or even breakage, thus reducing the substrate's reliability.

[0116] The order of steps in the method of this invention can be adjusted, combined, or deleted according to actual needs.

[0117] The processes described in all the preferred embodiments above are merely examples. Unless adverse effects occur, various processing operations can be performed in a different order than those described above. The order of steps in the above processes can also be added, combined, or deleted according to actual needs.

[0118] Unless otherwise defined, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for descriptive purposes only and is not intended to limit the invention. Features described in one embodiment may be applied, alone or in combination with other features, to another embodiment, unless that feature is not applicable in that other embodiment or is otherwise stated.

[0119] The present invention has been described through the above embodiments. However, it should be understood that the above embodiments are only for illustrative purposes. The present invention is not limited to the above embodiments. Many variations and modifications can be made according to the teachings of the present invention, and all such variations and modifications fall within the scope of protection claimed by the present invention.

Claims

1. A ceramic copper-clad substrate, characterized in that, It includes a ceramic substrate and a copper metal layer, and the following layer located between the ceramic substrate and the copper metal layer: A reaction layer, adjacent to the ceramic substrate, is formed by the reaction of Ti and ceramic. A solid solution layer, wherein the solid solution layer is formed by Sn dissolved in Cu; and An intermetallic compound layer, adjacent to the copper metal layer, comprising Cu, Ti, and P. The copper metal layer is formed from a copper metal component; The Ti in the reaction layer comes from Ti-containing solder; The solid solution layer is located between the reaction layer and the intermetallic compound layer; The intermetallic compound layer is formed by the diffusion of a portion of Ti from the Ti-containing solder and P from the Cu-P-Sn solder into the molten copper metal part, where a reaction occurs at the interface of the copper metal part.

2. The ceramic copper-clad substrate according to claim 1, characterized in that, The thickness of the reaction layer is less than 3 μm.

3. The ceramic copper-clad substrate according to claim 1, characterized in that, The thickness of the solid solution layer is 1μm~8μm; And / or the thickness of the intermetallic compound layer is 1 μm to 10 μm.

4. A method for preparing a ceramic copper-clad substrate according to any one of claims 1 to 3, characterized in that, Includes the following steps: A copper metal component, Cu-P-Sn solder, and Ti-containing solder are laminated onto a ceramic substrate to form a laminate, wherein the Cu-P-Sn solder and the Ti-containing solder are located between the copper metal component and the ceramic substrate; and The laminate is subjected to sintering treatment.

5. The preparation method according to claim 4, characterized in that, The Ti-containing solder is adjacent to the ceramic substrate, and the Cu-P-Sn solder is adjacent to the copper metal part; Alternatively, the Ti-containing solder can be mixed evenly with the Cu-P-Sn solder and then laminated onto a ceramic substrate.

6. The preparation method according to claim 4, characterized in that, Also includes: The Ti-containing solder is made into a Ti-containing solder paste, and a first solder layer formed by coating the Ti-containing solder paste is stacked on the ceramic substrate; as well as The Cu-P-Sn solder is made into a copper-based solder paste, and a second solder layer formed by coating the copper-based solder paste is stacked on the first solder layer or the copper metal part.

7. The preparation method according to claim 6, characterized in that, The mass ratio of the Ti-containing solder paste to both the Ti-containing solder paste and the copper-based solder paste is 8% to 30%.

8. The preparation method according to claim 6, characterized in that, The areal density of the Ti-containing solder paste after coating is 15~35 g / m³. 2 The areal density of the copper-based solder paste after application is 80~115 g / m³. 2 .

9. The preparation method according to claim 6, characterized in that, The Ti-containing solder paste comprises titanium hydride and a binder, wherein the mass ratio of the binder to the Ti-containing solder paste is 40% to 70%. And / or, the copper-based solder paste comprises Cu-P-Sn solder and a binder, wherein the mass ratio of the binder to the copper-based solder paste is 10% to 20%.

10. The preparation method according to claim 4, characterized in that, The Ti-containing solder is titanium hydride, and the step of sintering the laminate includes: A first sintering process involves sintering the laminate at a first sintering temperature, which is greater than the decomposition temperature of titanium hydride and less than the melting point of the Cu-P-Sn solder; and The second sintering process involves sintering the laminated body after the first sintering process at a second sintering temperature greater than or equal to 650°C.

11. The preparation method according to claim 4, characterized in that, The ceramic substrate is a substrate composed of at least one of alumina ceramic, aluminum nitride ceramic, and silicon nitride ceramic.

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