Method for preparing ceramic circuit substrate and ceramic circuit substrate

Abstract

The present invention discloses a method for preparing a ceramic circuit substrate and a ceramic circuit substrate. The method comprises: forming a silver-copper-titanium alloy layer corresponding to a desired circuit pattern on the surface of the ceramic substrate, wherein at least one wet metal layer is added to the silver-copper-titanium alloy layer; forming a desired conductive circuit layer on the silver-copper-titanium alloy layer; and after or during the formation of the conductive circuit layer, placing the entire ceramic substrate in a vacuum sintering furnace for sintering. During the vacuum sintering process, the silver, copper, and titanium in the silver-copper-titanium alloy layer diffuse into each other, forming an active brazing layer that is mutually alloyed. The method of the present invention not only prevents the ceramic circuit substrate and the circuit layer from easily falling off under high and low thermal cycles, but also reduces the difficulty of the ceramic circuit substrate preparation process and the sintering temperature, thereby significantly reducing the preparation cost.

Description

Technical Field

[0001] The present invention relates to the technical field of circuit boards, and in particular to a preparation method of a ceramic circuit substrate and the ceramic circuit substrate. Background Art

[0002] As industrial equipment performance improves, power module output power continues to increase. This drives the operating temperature of power module semiconductor components to 125°C to 150°C, and may even rise to 175°C or above. Ceramic metal PCBs can address the high-temperature operating requirements of power module semiconductor components, but they must also withstand high and low thermal cycles.

[0003] Currently, ceramic metal circuit boards (CMPCBs) that can withstand high and low thermal cycling typically use a ceramic substrate made of nitride, silicon oxide, or carbide. A highly conductive thick copper circuit (i.e., conductive circuit) is then applied to the ceramic substrate. A hard active brazing alloy layer is then brazed between the thick copper circuit and the ceramic substrate. This active brazing alloy layer must not only securely bond the ceramic substrate and the thick copper circuit; more importantly, it must be able to withstand the stresses generated by the high and low thermal cycling of the power module, ensuring that the thick copper circuit and the ceramic substrate do not become detached.

[0004] In the existing technology, the active metal brazing process (AMB) is currently widely used to produce the active brazing layer between the ceramic substrate and the thick copper circuit. The specific method is: a solder sheet or paste made of a silver-copper-titanium alloy material with an appropriate ratio is placed on the ceramic substrate, and then an oxygen-free copper foil is placed on the solder sheet or paste. The oxygen-free copper foil and the solder sheet or paste are then placed in a vacuum furnace for high-temperature sintering at a temperature of approximately 850 degrees. The oxygen-free copper foil and the solder sheet or paste are sintered into a copper-clad laminate, and then a circuit pattern is etched on the copper-clad laminate to form a thick copper circuit.

[0005] However, the active metal brazing process has the following drawbacks: 1) The soldering sheets or paste coatings made of silver-copper-titanium alloy materials need to be supplied, and in order to avoid external contamination or oxidation, they need to be carried out in a sealed space during the production, storage and use processes, which invisibly increases the cost and operation difficulty; 2) A higher sintering temperature is required, which increases the cost; 3) The active brazing layer is thicker; 4) Since the active brazing layer is not easily etched to form a pattern, it is difficult to etch out the circuit pattern. At the same time, the etching pattern production process is not environmentally friendly, the cost is expensive, and the process can easily harm the human body. Summary of the Invention

[0006] In view of the deficiencies in the prior art, the present invention aims to provide a method for preparing a ceramic circuit substrate and a ceramic circuit substrate, aiming to solve at least one of the above technical problems.

[0007] In order to achieve the above object, the present invention is implemented through the following technical solution: A method for preparing a ceramic circuit substrate comprises the following steps:

[0008] Forming a silver-copper-titanium alloy layer corresponding to a desired circuit pattern on the surface of a ceramic substrate, wherein at least one wet metal layer is added to the silver-copper-titanium alloy layer;

[0009] Fabricating a required conductive circuit layer on the silver-copper-titanium alloy layer;

[0010] After or during the process of manufacturing the conductive circuit layer, the entire ceramic substrate is placed in a vacuum sintering furnace for sintering;

[0011] During the vacuum sintering process, silver, copper and titanium in the silver-copper-titanium alloy layer diffuse into each other, so that the silver-copper-titanium alloy layer is formed into an active brazing layer of mutual alloying.

[0012] Furthermore, the step of forming a silver-copper-titanium alloy layer corresponding to the required circuit pattern on the surface of the ceramic substrate includes:

[0013] sputtering one or more laminated titanium-copper metal layers on the ceramic substrate;

[0014] Laying a photosensitive dry film on the titanium-copper metal layer, and exposing and developing the photosensitive dry film at a position corresponding to the desired circuit pattern to expose the titanium-copper metal layer at the position corresponding to the desired circuit pattern;

[0015] A silver-copper metal layer is stacked on the exposed titanium-copper metal layer to obtain the silver-copper-titanium alloy layer.

[0016] Furthermore, the method for preparing the ceramic circuit substrate further includes:

[0017] During the process of stacking the silver-copper metal layer on the exposed titanium-copper metal layer, the at least one wet metal layer is added by a method of pause addition or alloy co-electrolysis.

[0018] Furthermore, in the silver-copper-titanium alloy layer, the weight ratio of silver is 52%-68%, the weight ratio of copper is 20%-35.25%, and the weight ratio of titanium is 1.75%-3%.

[0019] Furthermore, the material of the wet metal layer includes at least one of tin, zinc and indium metals, and the weight of the wet metal layer accounts for 0.5%-3% of the total weight of the silver-copper-titanium alloy layer.

[0020] Furthermore, the step of making the required conductive circuit layer on the silver-copper-titanium alloy layer includes:

[0021] Thickening the remaining photosensitive dry film that has not been exposed and developed;

[0022] Depositing a conductive circuit layer having a thickness required by the application circuit design on the exposed silver-copper-titanium alloy layer;

[0023] The remaining photosensitive dry film is removed, and the silver-copper-titanium alloy layer on the non-circuit portion covered by the remaining photosensitive dry film is etched away.

[0024] Furthermore, the step of making the required conductive circuit layer on the silver-copper-titanium alloy layer includes:

[0025] Removing the remaining photosensitive dry film and etching away the silver-copper-titanium alloy layer on the non-circuit portion covered by the remaining photosensitive dry film;

[0026] Place an oxygen-free copper foil of the required thickness for the application circuit design on the silver-copper-titanium alloy layer, and place a pressing sheet of appropriate weight on top of the oxygen-free copper foil;

[0027] The ceramic substrate as a whole and the pressed sheet are placed in a vacuum sintering furnace for sintering;

[0028] A photosensitive film is coated on the sintered oxygen-free copper foil layer, and the photosensitive film on the unnecessary oxygen-free copper foil layer is etched away by exposure and development to expose the unnecessary oxygen-free copper foil layer;

[0029] The exposed oxygen-free copper foil layer is etched away, and the remaining oxygen-free copper foil layer that has not been etched away is formed into the conductive circuit layer.

[0030] Furthermore, the sintering conditions of the entire ceramic substrate are: sintering temperature 600-850° C., and sintering holding time 60-240 min.

[0031] Furthermore, the titanium-copper metal layer is produced by sputtering, and the sputtering thickness is 0.3 μm-2 μm.

[0032] Another aspect of the present invention provides a ceramic circuit substrate, which is prepared using the above-mentioned method for preparing the ceramic circuit substrate.

[0033] Compared with the existing technology, the present invention adopts the method of transient liquid phase (TLP) to produce the active brazing layer. Compared with the traditional AMB process, it has at least the following advantages:

[0034] 1) The thickness of the active brazing layer can be made very thin, the thinnest can reach 3 microns, which greatly reduces the thickness of the active brazing layer;

[0035] 2) The composition ratio of the intermetallic active solder layer is determined by diffusion of the metal alloy at the sintering holding temperature. This composition ratio can be freely adjusted according to the actual application needs of the user and is not restricted by the ratio of traditional solder sheets or paste coatings. At the same time, because the active solder layer is obtained by diffusion of the metal alloy during the vacuum sintering process, traditional solder sheets or paste coatings are not required, reducing costs and operating difficulty.

[0036] 3) By adding a wet metal layer into the silver-copper-titanium alloy layer, the wet metal layer melts first during the sintering process, and uses its wetting properties to diffuse and melt the high-melting-point metal, lowering the melting point of the high-melting-point metal, thereby reducing the overall sintering temperature. This makes it applicable to a wider range of ceramic and metal materials and reduces costs;

[0037] 4) By making the circuit pattern before sintering, or sintering during the process of making the circuit pattern, compared with the AMB process of sintering first and then making the circuit pattern, the difficulty, cost and safety risks of circuit pattern production can be reduced.

[0038] Additional aspects and advantages of the present invention will be given in part in the description which follows and in part will be obvious from the description which follows, or may be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments with reference to the accompanying drawings, in which:

[0040] Figure 1 Flowchart of a method for preparing a ceramic circuit substrate according to an embodiment of the present invention;

[0041] Figure 2 is a schematic diagram of a preparation process of a ceramic circuit substrate according to an embodiment of the present invention;

[0042] Figure 3 is a flow chart of a method for preparing a ceramic circuit substrate according to another embodiment of the present invention;

[0043] Figure 4 FIG. 4 is a schematic diagram of a preparation process of a ceramic circuit substrate according to another embodiment of the present invention. DETAILED DESCRIPTION

[0044] To make the objectives, features, and advantages of the present invention more readily apparent, the following detailed description of specific embodiments of the present invention is provided in conjunction with the accompanying drawings. The accompanying drawings illustrate several embodiments of the present invention. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the present invention.

[0045] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be an element centered thereon. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be an element centered thereon. The terms "vertical", "horizontal", "left", "right", "up", "down" and similar expressions used herein are for illustrative purposes only and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be understood as limiting the present invention.

[0046] Example 1

[0047] A first embodiment of the present invention provides a method for preparing a ceramic circuit substrate, the method specifically comprising the following steps:

[0048] Step S01: forming a silver-copper-titanium alloy layer corresponding to a desired circuit pattern on a surface of a ceramic substrate, wherein at least one wet metal layer is added to the silver-copper-titanium alloy layer;

[0049] Step S02: fabricating a required conductive circuit layer on the silver-copper-titanium alloy layer;

[0050] Step S03: After the conductive circuit layer is produced, the entire ceramic substrate is placed in a vacuum sintering furnace for sintering. During the vacuum sintering process, the silver, copper, and titanium in the silver-copper-titanium alloy layer diffuse with each other, so that the silver-copper-titanium alloy layer forms an active brazing layer of interalloying.

[0051] In one case of this embodiment, the ceramic substrate can be made of 95wt.% silicon nitride. At the same time, the ceramic substrate can be pretreated first. For example, the pressureless sintered ceramic substrate can be polished to optical smoothness using diamond grinding paste to ensure that its surface roughness is ≤1.6μm. After polishing, the ceramic substrate is placed in acetone and alcohol for ultrasonic cleaning at room temperature for 20 minutes, and finally dried.

[0052] In some preferred embodiments of this embodiment, the weight ratio of silver in the silver-copper-titanium alloy layer is 52%-68%, for example, 55%, 57%, 63%, 65%, 66%, 67%, etc.; the weight ratio of copper is 20%-35.25%, for example, 23%, 25%, 30%, 33.25%, etc.; and the weight ratio of titanium is 1.75%-3%, for example, 1.75%, 1.8%, 2.2%, 2.75%, etc. The material of the wet metal layer includes at least one of tin, zinc, and indium. The weight of the wet metal layer accounts for 0.5%-3% of the total weight of the silver-copper-titanium alloy layer, for example, 1%, 2%, 2.5%, etc.

[0053] In addition, it should be noted that since the present invention adopts the method of liquid phase transient metal diffusion to make the active brazing layer and also adds a wet metal layer to the silver-copper-titanium alloy layer, during the sintering process, the wet metal layer melts first, and uses its wetting properties to diffuse and melt the high-melting-point metal, so that the high-melting-point metal lowers its melting point, thereby reducing the entire sintering temperature. Specifically, the sintering conditions of the entire ceramic substrate in the embodiment of the present invention can be: sintering temperature 600-850°C, sintering holding time 60-240min, for example, the sintering temperature can be specifically selected as 650°C, 700°C, 750°C, 800°C, etc., and the sintering holding time can be specifically selected as 100min, 120min, 180min, 200min, etc. Compared with the traditional AMB process requiring a sintering temperature of at least 850°C, the sintering temperature is significantly reduced, and the cost is significantly reduced.

[0054] Example 2

[0055] See also Figure 1 , which shows a method for preparing a ceramic circuit substrate according to a second embodiment of the present invention, and the method specifically comprises the following steps:

[0056] Step S11: sputtering one or more laminated titanium-copper metal layers on a ceramic substrate.

[0057] The titanium-copper metal layer is produced by sputtering, and the overall sputtering thickness is 0.3 μm-2 μm, for example, 0.6 μm, 1 μm, 1.5 μm, etc. Specifically, when sputtering a single titanium-copper metal layer, titanium and copper can be deposited together by co-sputtering; when sputtering multiple stacked titanium-copper metal layers, titanium and copper can be sputtered one layer at a time, with an unlimited number of sputtering layers, that is, each layer is a single pure metal layer, or each layer can be co-sputtered by titanium and copper, with an unlimited number of sputtering layers, that is, each layer is an alloy layer of titanium and copper.

[0058] More specifically, in some optional methods, copper and titanium can be sputtered layer by layer on the cleaned ceramic substrate using a physical vapor deposition method, with a total sputtering thickness of 2 μm. The sputtering environment can be: working pressure 1-5 Pa, sputtering gas is argon, and the argon pressure can be maintained between 0.2-0.4 MPa. The actual pressure can be adjusted according to the size and flow of the cavity and the specific equipment. The sputtering power is 2000W-10 kilowatts, which can be adjusted according to the target material and the processing batch. The vacuum degree is 4.9×10 -4 Pa or above.

[0059] By way of example and not limitation, Figure 2As shown in part S11 , a titanium layer 21 may be sputtered on the ceramic substrate 10 , and then a copper layer 22 may be sputtered on the titanium layer 21 . The titanium layer 21 and the copper layer 22 are sandwiched to form a titanium-copper metal layer 20 .

[0060] Step S12: laying a photosensitive dry film on the titanium-copper metal layer, and exposing and developing the photosensitive dry film at positions corresponding to the required circuit patterns to expose the titanium-copper metal layer at positions corresponding to the required circuit patterns.

[0061] like Figure 2 As shown in part S12 , a photosensitive dry film 30 may be laid on the titanium-copper metal layer 20 , and then the photosensitive dry film 30 may be selectively etched to expose the titanium-copper metal layer 20 at a position corresponding to the desired circuit pattern.

[0062] Step S13: superimposing a silver-copper metal layer on the exposed titanium-copper metal layer to obtain a silver-copper-titanium alloy layer, and in the process of superimposing the silver-copper metal layer on the exposed titanium-copper metal layer, adding at least one layer of wet metal layer by pausing in the middle or by alloy co-electrolysis.

[0063] In practice, a silver-copper metal layer can be formed by electrolytic deposition on the exposed titanium-copper metal layer. The silver-copper metal layer can be deposited one layer of silver and one layer of copper at a time, with no limit on the number of layers. Alternatively, the silver-copper alloy can be deposited by co-electrolytic plating, where each layer is a silver-copper alloy layer, with no limit on the number of layers. The number of wet metal layers is unlimited, and the wet metal layer can be added anywhere in the silver-copper metal layer, for example, at the bottom, top, or middle layers of the silver-copper metal layer, preferably at the bottom or middle layers, for optimal diffusion and melting point reduction.

[0064] By way of example and not limitation, Figure 2 As shown in part S13, the silver-copper metal layer 40 includes a wet metal layer 41, a silver layer 42 and a copper layer 43 which are stacked in sequence, that is, a wet metal layer 41 is first electrolytically deposited, a silver layer 42 is electrolytically deposited on the wet metal layer 41, and then a copper layer 43 is electrolytically deposited on the silver layer 42 to form a silver-copper metal layer 40 with a wet metal layer added thereto. The silver-copper metal layer 40 is stacked on the titanium-copper metal layer 20 to form a silver-copper-titanium alloy layer.

[0065] Step S14: thickening the remaining photosensitive dry film that has not been exposed and developed.

[0066] Among them, in this embodiment, the thickness of the dry film can be consistent with the thickness required by the application circuit design (that is, the thickness of the subsequent conductive circuit), such as Figure 2 As shown in the S14 part.

[0067] Step S15: depositing a conductive circuit layer of the required thickness on the exposed silver-copper-titanium alloy layer. Specifically, the conductive circuit layer is a thick copper layer, such as Figure 2 As shown in S15 , a conductive circuit layer 50 of a desired thickness can be grown on the exposed silver-copper-titanium alloy layer by electrolytic copper.

[0068] Step S16: removing the remaining photosensitive dry film and etching away the silver-copper-titanium alloy layer on the non-circuit portion covered by the remaining photosensitive dry film.

[0069] Specifically, you can use some etching solutions that will not cause too much damage to the circuit layer (for example, 40g / L superfluous potassium hydrogen phosphate + 4%-5% sulfuric acid to etch copper, and then use 5% sodium hydroxide + 2.5% hydrogen peroxide to etch titanium, or use 25-30% hydrofluoric acid to etch away the non-circuit part of the titanium-copper alloy layer under a protective film on the prepared circuit, leaving only the circuit metal layer, such as Figure 2 As shown in the S16 part.

[0070] Step S17: Place the entire ceramic substrate (i.e., the product of step S16) in a vacuum sintering furnace and sinter it at a sintering temperature of 600-850°C. When the temperature reaches 600-850°C, keep it warm for 60-240 minutes. During the vacuum sintering process, the silver, copper, and titanium in the silver-copper-titanium alloy layer diffuse with each other, so that the silver-copper-titanium alloy layer forms an active brazing layer of alloy intermetallicization. After being taken out of the furnace, the ceramic circuit substrate is completed.

[0071] Example 3

[0072] A third embodiment of the present invention provides a method for preparing a ceramic circuit substrate, the method specifically comprising the following steps:

[0073] Step S21: forming a silver-copper-titanium alloy layer corresponding to a required circuit pattern on the surface of a ceramic substrate, wherein at least one wet metal layer is added to the silver-copper-titanium alloy layer.

[0074] Step S22: forming a required conductive circuit layer on the silver-copper-titanium alloy layer, and during the process of forming the conductive circuit layer, placing the entire ceramic substrate in a vacuum sintering furnace for sintering;

[0075] During the vacuum sintering process, silver, copper and titanium in the silver-copper-titanium alloy layer diffuse into each other, so that the silver-copper-titanium alloy layer is formed into an active brazing layer of mutual alloying.

[0076] Example 4

[0077] See also Figure 3, which shows a method for preparing a ceramic circuit substrate according to a fourth embodiment of the present invention, and the method specifically comprises the following steps:

[0078] Step S31 : sputtering one or more laminated titanium-copper metal layers on a ceramic substrate.

[0079] By way of example and not limitation, Figure 4 As shown in S31 , a titanium layer 21 may be sputtered on the ceramic substrate 10 , and then a copper layer 22 may be sputtered on the titanium layer 21 . The titanium layer 21 and the copper layer 22 are sandwiched to form a titanium-copper metal layer 20 .

[0080] Step S32 , laying a photosensitive dry film on the titanium-copper metal layer, and exposing and developing the photosensitive dry film at positions corresponding to the required circuit patterns to expose the titanium-copper metal layer at positions corresponding to the required circuit patterns.

[0081] like Figure 4 As shown in step S32 , a photosensitive dry film 30 may be laid on the titanium-copper metal layer 20 , and then the photosensitive dry film 30 may be selectively etched to expose the titanium-copper metal layer 20 at positions corresponding to the desired circuit patterns.

[0082] Step S33: superimposing a silver-copper metal layer on the exposed titanium-copper metal layer to obtain a silver-copper-titanium alloy layer, and in the process of superimposing the silver-copper metal layer on the exposed titanium-copper metal layer, adding at least one layer of wet metal layer by pausing in the middle or by alloy co-electrolysis.

[0083] By way of example and not limitation, Figure 4 As shown in the S33 part, the silver-copper metal layer 40 includes a wet metal layer 41, a silver layer 42 and a copper layer 43 which are stacked in sequence, that is, a wet metal layer 41 is first electrolytically deposited, and then a silver layer 42 is electrolytically deposited on the wet metal layer 41, and then a copper layer 43 is electrolytically deposited on the silver layer 42 to form a silver-copper metal layer 40 with a wet metal layer added. The silver-copper metal layer 40 is stacked on the titanium-copper metal layer 20 to form a silver-copper-titanium alloy layer 1.

[0084] Step S34: remove the remaining photosensitive dry film and etch away the silver-copper-titanium alloy layer on the non-circuit portion covered by the remaining photosensitive dry film. Figure 4 As shown in the S34 part.

[0085] Step S35: Place a piece of oxygen-free copper foil of the required thickness for the application circuit design on the silver-copper-titanium alloy layer, and place a pressing sheet of appropriate weight on the oxygen-free copper foil. Figure 4 The S35 part is shown in the figure.

[0086] Step S36: Place the entire ceramic substrate together with the pressed sheet (i.e., the product of step S35) in a vacuum sintering furnace for sintering at a sintering temperature of 600-850°C. When the temperature reaches 600-850°C, keep the temperature for 60-240 minutes. During the vacuum sintering process, the silver, copper, and titanium in the silver-copper-titanium alloy layer diffuse with each other, so that the silver-copper-titanium alloy layer forms an alloyed active brazing layer. That is, after sintering, the silver-copper-titanium alloy layer 1 is transformed into an alloyed active brazing layer 2, as shown in FIG. Figure 4 As shown in the S37 part.

[0087] Step S37 : coating a photosensitive film on the sintered oxygen-free copper foil layer, and etching away the unnecessary photosensitive film on the oxygen-free copper foil layer by exposure and development to produce the final required application circuit.

[0088] It should be noted that after sintering, the oxygen-free copper foil layer and the active solder layer formed by sintering are integrated. Figure 4 As shown in S37 , a photosensitive film 70 is first coated on the oxygen-free copper foil layer 60 , and then the photosensitive film on the unnecessary oxygen-free copper foil layer (ie, non-circuit portion) is etched away to expose the unnecessary oxygen-free copper foil layer.

[0089] Step S38: Etch away the exposed oxygen-free copper foil layer, and the remaining oxygen-free copper foil layer that has not been etched away is formed into a conductive circuit layer, and the ceramic circuit substrate is completed. Figure 4 As shown in the S38 part.

[0090] It should be noted that the difference between Examples 3 and 4 and Examples 1 and 2 is that in both Examples 3 and 4, the ceramic substrate as a whole is placed in a vacuum sintering furnace for sintering during the process of manufacturing the required conductive circuit layer on the silver-copper-titanium alloy layer, and a manufacturing method for the conductive circuit layer that is completely different from that of Examples 1 and 2 is also proposed.

[0091] In summary, the embodiment of the present invention adopts the method of transient liquid phase (TLP) to produce the active brazing layer, which has at least the following advantages compared with the traditional AMB process:

[0092] 1) The thickness of the active brazing layer can be made very thin, the thinnest can reach 3 microns, which greatly reduces the thickness of the active brazing layer;

[0093] 2) The composition ratio of the intermetallic active solder layer is determined by diffusion of the metal alloy at the sintering insulation temperature. This composition ratio can be freely adjusted according to the actual application needs of the user and is not restricted by the ratio of traditional solder sheets or paste coatings. At the same time, since the active solder layer is obtained by diffusion of the metal alloy during the vacuum sintering process, no traditional solder sheets or paste coatings are required, reducing costs and operating difficulty. At the same time, if the actual application temperature is lower than the eutectic secondary melting temperature, a lower temperature can be used for sintering during production and different alloy ratios can be given, which can reduce costs and match the process to actual applications.

[0094] 3) By adding a wet metal layer into the silver-copper-titanium alloy layer, the wet metal layer melts first during the sintering process, and uses its wetting properties to diffuse and melt the high-melting-point metal, lowering the melting point of the high-melting-point metal, thereby reducing the overall sintering temperature. This makes it applicable to a wider range of ceramic and metal materials and reduces costs;

[0095] 4) By making the circuit pattern before sintering, or sintering during the process of making the circuit pattern, compared with the AMB process of sintering first and then making the circuit pattern, the difficulty, cost and safety risks of circuit pattern production can be reduced;

[0096] 5) The alloy layer is prepared and formed using sputtering and electrolytic deposition, unlike soldering sheets or solder paste coating. Intermetallic metals are formed by liquid-phase transient diffusion, so precise and rigid alloy proportions are not necessary during alloy preparation. During sintering, the liquid-phase transient diffusion temperature can be used to determine the final alloy layer proportions, morphology, and properties.

[0097] 6) During the sintering process, a relatively long liquid phase transient holding process will inevitably increase the sintering time, but the advantage is that the temperature locking does not need to be as strict as the AMB eutectic, which captures a relatively narrow eutectic temperature range. This has the effect of relaxing the ratio of alloy materials and the process indicators of sintering furnace equipment;

[0098] 7) The new TLP method can lower the temperature much more than AMB. This of course also means that the secondary melting temperature of the intermetallic alloy layer will not reach the secondary melting temperature of the normal silver-copper-titanium alloy eutectic. However, it is emphasized that actual applications often do not require such a high secondary melting temperature. When the production cost can be reduced, the application range can also be expanded.

[0099] 8) It can reduce the cost of traditional AMB process by more than 50%.

[0100] Example 5

[0101] Embodiment 5 of the present invention provides a ceramic circuit substrate, which is prepared using the method for preparing the ceramic circuit substrate described in any one of the above embodiments 1-4.

[0102] In the thermal shock test of -50°C to 150°C, the ceramic circuit substrate and the circuit will not peel off after 5,000 thermal shocks, and can reach the national standard of 15 years of service life.

[0103] In the present invention, unless otherwise expressly specified or limited, the terms "installed," "connected," "connected," "fixed," and the like should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to mechanical connections or electrical connections; they may refer to direct connections or indirect connections through an intermediate medium; and they may refer to internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances. The term "and / or" as used herein includes any and all combinations of one or more of the relevant listed items.

[0104] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0105] The above-described embodiments merely illustrate several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A method for preparing a ceramic circuit substrate, characterized in that: The following steps are involved: Forming a silver-copper-titanium alloy layer corresponding to a desired circuit pattern on the surface of a ceramic substrate, wherein at least one wet metal layer is added to the silver-copper-titanium alloy layer; Fabricating a required conductive circuit layer on the silver-copper-titanium alloy layer; After or during the process of manufacturing the conductive circuit layer, the entire ceramic substrate is placed in a vacuum sintering furnace for sintering; During the vacuum sintering process, silver, copper and titanium in the silver-copper-titanium alloy layer diffuse into each other, so that the silver-copper-titanium alloy layer forms an active brazing layer of mutual alloying; The step of forming a silver-copper-titanium alloy layer corresponding to the required circuit pattern on the surface of the ceramic substrate comprises: sputtering one or more laminated titanium-copper metal layers on the ceramic substrate; Laying a photosensitive dry film on the titanium-copper metal layer, and exposing and developing the photosensitive dry film at a position corresponding to the desired circuit pattern to expose the titanium-copper metal layer at the position corresponding to the desired circuit pattern; Obtaining the silver-copper-titanium alloy layer; The step of fabricating the required conductive circuit layer on the silver-copper-titanium alloy layer includes: Thickening the remaining photosensitive dry film that has not been exposed and developed; Depositing a conductive circuit layer having a thickness required by the application circuit design on the exposed silver-copper-titanium alloy layer; The remaining photosensitive dry film is removed, and the silver-copper-titanium alloy layer on the non-circuit portion covered by the remaining photosensitive dry film is etched away.

2. The method for preparing a ceramic circuit substrate according to claim 1, wherein: Also includes: During the process of stacking the silver-copper metal layer on the exposed titanium-copper metal layer, the at least one wet metal layer is added by a method of pause addition or alloy co-electrolysis.

3. The method for preparing a ceramic circuit substrate according to claim 1, wherein: In the silver-copper-titanium alloy layer, the weight ratio of silver is 52%-68%, the weight ratio of copper is 20%-35.25%, and the weight ratio of titanium is 1.75%-3%.

4. The method for preparing a ceramic circuit substrate according to claim 1 or 2, wherein: The material of the wet metal layer includes at least one of tin, zinc and indium metals, and the weight of the wet metal layer accounts for 0.5%-3% of the total weight of the silver-copper-titanium alloy layer.

5. The method for preparing a ceramic circuit substrate according to claim 1, wherein: The steps of fabricating the required conductive circuit layer on the silver-copper-titanium alloy layer include: Removing the remaining photosensitive dry film and etching away the silver-copper-titanium alloy layer on the non-circuit portion covered by the remaining photosensitive dry film; Place an oxygen-free copper foil of the required thickness for the application circuit design on the silver-copper-titanium alloy layer, and place a pressing sheet of appropriate weight on top of the oxygen-free copper foil; The ceramic substrate as a whole and the pressed sheet are placed in a vacuum sintering furnace for sintering; A photosensitive film is coated on the sintered oxygen-free copper foil layer, and the photosensitive film on the unnecessary oxygen-free copper foil layer is etched away by exposure and development to expose the unnecessary oxygen-free copper foil layer; The exposed oxygen-free copper foil layer is etched away, and the remaining oxygen-free copper foil layer that has not been etched away is formed into the conductive circuit layer.

6. The method for preparing a ceramic circuit substrate according to claim 1, wherein: The sintering conditions of the entire ceramic substrate are: sintering temperature 600-850° C., and sintering holding time 60-240 min.

7. The method for preparing a ceramic circuit substrate according to claim 1, wherein: The titanium-copper metal layer is produced by sputtering, and the sputtering thickness is 0.3 μm-2 μm.

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