Copper-clad ceramic substrate and preparation method thereof

Abstract

The invention discloses a copper-clad ceramic substrate and a preparation method thereof. A silicon nitride ceramic substrate is used in the preparation of the copper-clad ceramic substrate. The silicon nitride ceramic substrate is firstly cleaned and degreased with acetone, anhydrous ethanol and deionized water in sequence to remove surface impurities. A solder guide groove is then pre-cut at the surface edge by laser processing. A photoresist is then spin-coated on the surface of the ceramic substrate, and a solder groove pattern is exposed and developed. The solder groove pattern is consistent with a preset subsequent circuitization pattern. An ICP etching is then performed to form a solder groove, and the solder groove and the solder guide groove are connected to each other. The process design of the invention is reasonable and the operation is simple. The prepared copper-clad ceramic substrate has excellent strength, good bonding performance between the ceramic substrate and the copper foil, and solder can be controlled during the processing of the copper-clad ceramic substrate to avoid overflow and diffusion. The product has an excellent overall appearance and a high yield, can be used for mass production, and has high practicality.

Description

Technical Field

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

[0002] Copper-clad ceramics, also known as copper-clad ceramic substrates, are a type of electronic basic material made by directly sintering copper foil onto the ceramic surface using DCB (Direct Copper Bond) technology. With in-depth research and development, active metal brazing technology has become a more commonly used processing technology for copper-clad ceramic boards.

[0003] Active metal brazing involves placing active metal powder (such as Ti and Zr) and a metal solder (such as Ag and Cu) that can form an alloy with the active metal powder at a certain temperature between a ceramic substrate and copper metal. The process then heats and melts the metal in a vacuum or inert atmosphere to seal the copper metal to the ceramic substrate. However, the metal solder is prone to overflowing during the high-temperature sintering process, affecting the overall product appearance and hindering mass production.

[0004] Therefore, based on this situation, the present application discloses a copper-clad ceramic substrate and a preparation method thereof to solve this technical problem. Summary of the Invention

[0005] The object of the present invention is to provide a copper-clad ceramic substrate and a preparation method thereof, so as to solve the problems raised in the above background technology.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] A method for preparing a copper-clad ceramic substrate comprises the following steps:

[0008] (1) Take the ceramic substrate and ultrasonically clean it with acetone solution for 10-15 minutes, then ultrasonically clean it with anhydrous ethanol and deionized water in sequence, with the ultrasonic cleaning time being 10-15 minutes each, and blow dry it with nitrogen;

[0009] (2) Pre-cutting a solder guide groove on the edge of one side of the ceramic substrate, washing with deionized water, drying, and then spin-coating photoresist on the surface of the ceramic substrate, baking at 100-110°C for 10-15 minutes, UV-exposing, developing, exposing the solder groove pattern, placing the ceramic substrate in an ICP etcher for ICP etching, and etching a solder groove on the surface of the ceramic substrate, wherein the solder groove and the solder guide groove are connected to each other;

[0010] After ICP etching, the surface photoresist was removed from the ceramic substrate, and then ultrasonically cleaned with acetone, anhydrous ethanol, and deionized water in sequence. The ultrasonic cleaning time was 10-15 minutes each, and the substrate was dried with nitrogen.

[0011] (3) Take modified graphene, aluminum oxide, calcium carbonate, silicon carbide, and silicon nitride, mix them evenly, and then ball mill them. Add dispersant, binder, and water, stir evenly to obtain a transition coating material, apply it to a solder tank, and sinter at a high temperature of 1500-1600°C for 30-40 minutes to obtain a transition layer.

[0012] (4) Take silver powder, copper powder, titanium hydride powder and modified graphene, mix and stir evenly, grind for 5-10 minutes, and ball mill at a speed of 160-180 r / min for 40-50 minutes. After ball milling, add thickener, dispersant, solvent, antioxidant and thixotropic agent, mix and stir evenly to obtain solder;

[0013] Applying solder to the solder guide groove and the solder tank and covering the transition layer to obtain an active solder layer;

[0014] (5) Repeat steps (2) to (4) to process interconnected solder grooves and solder guide grooves on the other side of the ceramic substrate, and apply a transition layer and an active solder layer, rinse with deionized water, and dry;

[0015] The copper foil is fixed on both sides of the ceramic substrate and brazed at high temperature to obtain a copper-clad plate; the copper-clad plate is subjected to circuit patterning treatment and a preset circuit pattern is etched to obtain the copper-clad ceramic substrate.

[0016] In a more optimized solution, in step (2), the thickness of the ceramic substrate is h, the width of the solder guide groove is 0-5 mm, and the depth is ≦0.5h; the depth of the solder groove is ≦0.5h, and the depth of the solder groove is greater than the depth of the solder guide groove.

[0017] In a more optimized solution, in step (2), the thickness of the active solder layer coated in the solder trough and the solder guide trough is 30-50 μm, and the thickness of the transition layer is 5-10 μm.

[0018] In a more optimized solution, in step (2), the depth difference between the solder groove and the solder guide groove is 5-7 μm, and the solder guide groove is formed by any one of laser processing, ultrasonic grinding, electric spark processing, and electrolytic processing.

[0019] In a more optimized solution, in step (2), the pattern of the solder groove is the same as the preset circuit pattern, and when the width of the preset circuit pattern is a, the width of the solder groove is 0.6a~0.8a.

[0020] In the optimized solution, in step (5), the high temperature brazing temperature is 900~950℃ and the vacuum degree is 5×10 -4 ~8×10 - 4Pa; during high-temperature brazing, ultrasonic vibration is applied to the surface of the copper foil, the ultrasonic frequency is 20-25kHz, the power is 100-200w, and the ultrasonic time is 30-60s.

[0021] In a more optimized solution, the raw materials of the components of the transition layer include 90wt% powder and 10wt% organic solvent, the powder includes 8wt% modified graphene, 82wt% aluminum oxide, 4wt% silicon carbide, 5wt% silicon nitride, and 1wt% calcium carbonate; the organic solvent includes 4wt% dispersant, 3wt% binder and 93wt% water, the dispersant is sodium polyacrylate, and the binder is silica sol.

[0022] In the optimized solution, the raw materials of the solder components include 88wt% solder powder and 12wt% organic vehicle. The solder powder includes 70wt% silver powder, 20wt% copper powder, 5wt% titanium hydride powder and 5wt% modified graphene; the organic vehicle includes 12wt% thickener, 5wt% dispersant, 70wt% solvent, 7wt% antioxidant and 6wt% thixotropic agent.

[0023] The thickener is polyethylene glycol, the dispersant is stearic acid, the thixotropic agent is stearamide, the antioxidant is oxalic acid, and the solvent is diethylene glycol dimethyl ether and terpineol in a mass ratio of 2:3.

[0024] A more optimized solution, the modified graphene preparation method is: take copper sulfate pentahydrate and silver nitrate, mix them, add graphene oxide aqueous solution, deionized water, sodium citrate and sodium borohydride, stir and react at 25~30℃ for 1~2h, let it stand for 2~3h after the reaction is completed, filter and wash, and vacuum dry to obtain modified graphene.

[0025] A more optimized solution is a copper-clad ceramic substrate prepared according to the above-mentioned method for preparing a copper-clad ceramic substrate.

[0026] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0027] The present invention discloses a copper-clad ceramic substrate and a preparation method thereof. A silicon nitride ceramic substrate is used in the preparation of the copper-clad ceramic substrate. The silicon nitride ceramic substrate is firstly cleaned and degreased with acetone, anhydrous ethanol and deionized water in sequence to remove surface impurities. Then, a solder guide groove is pre-cut at the edge of the surface by laser processing. Then, photoresist is spin-coated on the surface of the ceramic substrate, and a solder groove pattern is formed by exposure and development. The solder groove pattern is consistent with a preset subsequent circuit pattern. Then, ICP etching is performed to form a solder groove, and the solder groove and the solder guide groove are interconnected. In this process step, the present application must meet the following parameter conditions:

[0028] (1) The thickness of the ceramic substrate is h, the width of the solder guide groove is 0~5mm, and the depth is ≤0.5h; the depth of the solder groove is ≤0.5h.

[0029] (2) The pattern of the solder groove is the same as the preset circuit pattern. When the width of the preset circuit pattern is a, the width of the solder groove is 0.6a~0.8a.

[0030] (3) The depth of the solder groove is greater than the depth of the solder guide groove, and the depth difference between the solder groove and the solder guide groove is 5~7μm.

[0031] The reason for limiting condition (1) is that this application is used to prepare copper-clad ceramic boards. In the subsequent steps, copper foil needs to be fixed on both sides of the ceramic substrate and vacuum brazed. To ensure its actual processing, this application limits the depth of the solder guide groove and the solder groove to less than 0.5h to avoid the ceramic substrate from breaking or bending due to excessive etching during the subsequent processing, which affects actual use; and the width of the solder guide groove is 0~5mm. The width limitation is to avoid the groove being too wide and affecting the subsequent copper foil surface circuit patterning.

[0032] (2) The reason for the limitation of the conditions is that: the present application etches a solder groove through photolithography and ICP, and the pattern of the solder groove is the same as the preset circuit pattern. Therefore, when applying solder, the present application can apply a patterned solder layer, and then fix it with copper foil to perform circuit patterning. After the subsequent etching of the copper foil image circuit, there is no need to etch the solder layer again, thereby avoiding the problem of solder residue between circuits caused by the subsequent etching process and reducing the risk of circuit short circuit.

[0033] At the same time, since circuit graphic etching is required later, the etching solution will etch the copper foil while also slightly etching the solder layer underneath the copper foil. In order to ensure the bonding strength between the copper foil and the ceramic substrate, this application limits the solder groove width to 0.6a~0.8a. On the one hand, it can reduce the influence of the etching solution. On the other hand, during subsequent vacuum brazing, active solder sometimes overflows the groove and spreads at the groove mouth. The width limitation can avoid the influence of solder between the circuits to a great extent, reduce the process difficulty, and make the actual operation simpler.

[0034] (3) The reason for limiting the conditions is that this application will subsequently coat active solder in the solder trough and solder guide groove to form an active solder layer. In order to ensure that the solder layer can be evenly distributed in the groove and to avoid solder overflow to the greatest extent, this application limits the depth of the solder trough and solder guide groove. The depth of the solder guide groove at the edge is designed to be slightly smaller than the solder trough. In this way, when the active solder is coated, the solder can flow from the solder trough to the solder guide groove and spread, avoiding the accumulation of solder in the groove, and further reducing the process difficulty.

[0035] Based on the above-mentioned limiting conditions, the present application introduces a transition layer in the solder tank. The transition layer is composed of a mixture of modified graphene oxide, aluminum oxide, calcium carbonate, silicon carbide, and silicon nitride, with aluminum oxide as the main component in this ratio. The transition layer is laid in a loose and porous state in the solder tank, which can improve the bonding between the active solder layer and the ceramic substrate, so that the active solder is in full contact with the bottom and surrounding areas of the groove, and reacts and bonds during subsequent brazing, which can further improve the bonding performance between the copper foil and the ceramic substrate.

[0036] After the transition layer is coated and sintered at high temperature, the present application applies active solder in the solder trough and solder guide groove, and performs vacuum brazing. Ultrasonic vibration is used to assist in vacuum brazing. On the one hand, under ultrasonic vibration, a uniform and dense welding surface can be formed between the copper foil and the ceramic substrate, ensuring the bonding between the two; on the other hand, ultrasonic vibration can homogenize the high-temperature molten solder, and combined with the depth setting of the solder trough and solder guide groove, the solder can be distributed more evenly, greatly reducing the overflow and outward diffusion of the solder flow.

[0037] Based on the above scheme, the present application introduces modified graphene oxide into the transition layer and the solder. The modified graphene is graphene with nickel and silver modified on the surface. The modification of its surface nanoparticles can, on the one hand, introduce alloy elements to promote the bonding between the solder and the ceramic substrate and copper foil, thereby improving its bonding performance. On the other hand, due to the properties of graphene itself, its introduction into the solder can also improve the strength and wettability of the solder.

[0038] The present invention discloses a copper-clad ceramic substrate and a preparation method thereof. The process design is reasonable and the operation is simple. The prepared copper-clad plate has excellent strength, and the bonding performance between the ceramic substrate and the copper foil is good. In addition, during the processing of the copper-clad ceramic substrate, the solder can be controlled to avoid overflow and diffusion. The product has an excellent overall appearance and a high yield, can be used for mass production, and has high practicality. DETAILED DESCRIPTION

[0039] The following is a clear and complete description of the technical solutions in the examples of the present invention. Obviously, the examples described are only some of the examples of the present invention, not all of them. All other examples derived by persons of ordinary skill in the art based on the examples of the present invention without inventive effort are also within the scope of protection of the present invention.

[0040] The graphene oxide model is SE3122, provided by Changzhou Sixth Element Materials Technology Co., Ltd.; the aluminum oxide particle size is 20-100 nm; and the silicon carbide particle size is 10 μm.

[0041] Example 1:

[0042] A method for preparing a copper-clad ceramic substrate comprises the following steps:

[0043] (1) Take a ceramic substrate, ultrasonically clean it with acetone solution for 10 minutes, then ultrasonically clean it with anhydrous ethanol and deionized water in sequence, each ultrasonic cleaning time is 10 minutes, and blow dry with nitrogen; the ceramic substrate is a silicon nitride ceramic substrate with a size of 50 mm × 50 mm × 0.32 mm;

[0044] (2) A solder guide groove is pre-cut on the edge of one side of the ceramic substrate by laser processing. The width of the solder guide groove is 5 mm and the depth is 53 μm. The ceramic substrate is washed with deionized water and dried. Then, photoresist is spin-coated on the surface of the ceramic substrate, baked at 100°C for 15 minutes, exposed to ultraviolet light, and developed to expose the solder groove pattern. The ceramic substrate is placed in an ICP etcher for ICP etching. A solder groove is etched on the surface of the ceramic substrate. The depth of the solder groove is 60 μm. The solder groove and the solder guide groove are connected to each other.

[0045] The pattern of the solder groove is the same as the preset circuit pattern. When the width of the preset circuit pattern is a, the width of the solder groove is 0.8a.

[0046] After ICP etching, the surface photoresist was removed from the ceramic substrate, and then ultrasonic cleaning was performed in acetone, anhydrous ethanol, and deionized water in sequence, with the ultrasonic cleaning time being 15 min each, and then dried with nitrogen.

[0047] (3) 8wt% modified graphene, 82wt% alumina, 4wt% silicon carbide, 5wt% silicon nitride, and 1wt% calcium carbonate were mixed and ball-milled to obtain a powder. The powder was prepared in a ratio of 90wt% powder and 10wt% organic solvent, wherein the organic solvent includes 4wt% dispersant, 3wt% binder, and 93wt% water. The mixture was stirred to obtain a transition coating material, which was applied to a solder bath and sintered at 1500°C for 40 minutes to obtain a transition layer. The dispersant was sodium polyacrylate, and the binder was silica sol. The thickness of the transition layer was 10μm.

[0048] (4) Take graphene oxide and deionized water, and ultrasonically disperse them for 20 minutes to obtain a graphene oxide aqueous solution (1 mg / mL); take 0.25 g of copper sulfate pentahydrate and 0.16 g of silver nitrate, mix them, add 10 mL of graphene oxide aqueous solution, 20 mL of deionized water, 10 mL of sodium citrate (0.02 mol / L) and sodium borohydride (0.2 mol / L), and stir the reaction at 25°C for 2 hours. After the reaction is completed, let it stand for 2 hours, filter and wash, and vacuum dry to obtain modified graphene.

[0049] Take 70wt% silver powder, 20wt% copper powder, 5wt% titanium hydride powder and 5wt% modified graphene, mix and stir evenly, grind for 5 minutes, and ball mill for 50 minutes at a speed of 160r / min to obtain solder powder, mix 88wt% solder powder and 12wt% organic carrier in a ratio, the organic carrier includes 12wt% thickener, 5wt% dispersant, 70wt% solvent, 7wt% antioxidant and 6wt% thixotropic agent, mix and stir evenly to obtain solder; the thickener is polyethylene glycol, the dispersant is stearic acid, the thixotropic agent is stearamide, the antioxidant is oxalic acid, and the solvent is diethylene glycol dimethyl ether and terpineol, and the mass ratio of the two is 2:3.

[0050] The solder is applied to the solder guide groove and the solder tank, and covered on the transition layer to obtain an active solder layer; the thickness of the active solder layer applied in the solder guide groove and the solder tank is 50 μm;

[0051] (5) Repeat steps (2) to (4) to process interconnected solder grooves and solder guide grooves on the other side of the ceramic substrate, and apply a transition layer and an active solder layer, rinse with deionized water, and dry;

[0052] Take copper foil with a thickness of 50mm×50mm×0.4mm, fix it on both sides of the ceramic substrate, and braze it at a high temperature of 900℃ and a vacuum degree of 5×10 -4 Pa; applying ultrasonic vibration to the surface of the copper foil during brazing, with an ultrasonic frequency of 20kHz, a power of 100W, and an ultrasonic time of 60s to obtain a copper-clad laminate; taking the copper-clad laminate, performing circuit patterning processing, etching a preset circuit pattern, and obtaining the copper-clad ceramic substrate.

[0053] Example 2:

[0054] A method for preparing a copper-clad ceramic substrate comprises the following steps:

[0055] (1) Take a ceramic substrate, ultrasonically clean it with acetone solution for 12 minutes, then ultrasonically clean it with anhydrous ethanol and deionized water in sequence, each ultrasonic cleaning time is 12 minutes, and blow dry with nitrogen; the ceramic substrate is a silicon nitride ceramic substrate with a size of 50 mm × 50 mm × 0.32 mm;

[0056] (2) A solder guide groove is pre-cut on the edge of one side of the ceramic substrate by laser processing. The width of the solder guide groove is 5 mm and the depth is 53 μm. The substrate is washed with deionized water and dried. Then, photoresist is spin-coated on the surface of the ceramic substrate, baked at 105°C for 12 minutes, exposed to ultraviolet light, and developed to expose the solder groove pattern. The ceramic substrate is placed in an ICP etcher for ICP etching. A solder groove is etched on the surface of the ceramic substrate. The depth of the solder groove is 60 μm. The solder groove and the solder guide groove are connected to each other.

[0057] The pattern of the solder groove is the same as the preset circuit pattern. When the width of the preset circuit pattern is a, the width of the solder groove is 0.8a.

[0058] After ICP etching, the surface photoresist was removed from the ceramic substrate, and then ultrasonic cleaning was performed in acetone, anhydrous ethanol, and deionized water in sequence, with the ultrasonic cleaning time being 15 min each, and then dried with nitrogen.

[0059] (3) 8wt% modified graphene, 82wt% alumina, 4wt% silicon carbide, 5wt% silicon nitride, and 1wt% calcium carbonate were mixed and ball-milled to obtain a powder. The powder was prepared in a ratio of 90wt% powder and 10wt% organic solvent, wherein the organic solvent includes 4wt% dispersant, 3wt% binder, and 93wt% water. The mixture was stirred to obtain a transition coating material, which was applied to a solder bath and sintered at 1550°C for 35 minutes to obtain a transition layer. The dispersant was sodium polyacrylate, and the binder was silica sol. The thickness of the transition layer was 10μm.

[0060] (4) Take graphene oxide and deionized water, and ultrasonically disperse them for 20 minutes to obtain a graphene oxide aqueous solution (1 mg / mL); take 0.25 g of copper sulfate pentahydrate and 0.16 g of silver nitrate, mix them, add 10 mL of graphene oxide aqueous solution, 20 mL of deionized water, 10 mL of sodium citrate (0.02 mol / L) and sodium borohydride (0.2 mol / L), and stir the reaction at 28°C for 1.5 hours. After the reaction is completed, let it stand for 2.5 hours, filter and wash, and vacuum dry to obtain modified graphene.

[0061] Take 70wt% silver powder, 20wt% copper powder, 5wt% titanium hydride powder and 5wt% modified graphene, mix and stir evenly, grind for 8 minutes, and ball mill for 45 minutes at a speed of 170r / min to obtain solder powder, which is mixed with 88wt% solder powder and 12wt% organic carrier in a ratio of 12wt% thickener, 5wt% dispersant, 70wt% solvent, 7wt% antioxidant and 6wt% thixotropic agent, and mix and stir evenly to obtain solder; the thickener is polyethylene glycol, the dispersant is stearic acid, the thixotropic agent is stearamide, the antioxidant is oxalic acid, and the solvent is diethylene glycol dimethyl ether and terpineol, with a mass ratio of 2:3.

[0062] The solder is applied to the solder guide groove and the solder tank, and covered on the transition layer to obtain an active solder layer; the thickness of the active solder layer applied in the solder guide groove and the solder tank is 50 μm;

[0063] (5) Repeat steps (2) to (4) to process interconnected solder grooves and solder guide grooves on the other side of the ceramic substrate, and apply a transition layer and an active solder layer, rinse with deionized water, and dry;

[0064] Take copper foil with a thickness of 50mm×50mm×0.4mm, fix it on both sides of the ceramic substrate, and braze it at high temperature, the temperature is 930℃, and the vacuum degree is 5×10 -4 Pa; applying ultrasonic vibration to the surface of the copper foil during brazing, with an ultrasonic frequency of 25kHz, a power of 100W, and an ultrasonic time of 40s to obtain a copper-clad laminate; taking the copper-clad laminate, performing circuit patterning processing, etching a preset circuit pattern, and obtaining the copper-clad ceramic substrate.

[0065] Example 3:

[0066] A method for preparing a copper-clad ceramic substrate comprises the following steps:

[0067] (1) Take a ceramic substrate, ultrasonically clean it with acetone solution for 15 minutes, then ultrasonically clean it with anhydrous ethanol and deionized water in sequence, each ultrasonic cleaning time is 15 minutes, and then blow dry with nitrogen; the ceramic substrate is a silicon nitride ceramic substrate with a size of 50 mm × 50 mm × 0.32 mm;

[0068] (2) A solder guide groove is pre-cut on the edge of one side of the ceramic substrate by laser processing. The width of the solder guide groove is 5 mm and the depth is 53 μm. The substrate is washed with deionized water and dried. Then, photoresist is spin-coated on the surface of the ceramic substrate, baked at 110°C for 10 minutes, exposed to ultraviolet light, and developed to expose the solder groove pattern. The ceramic substrate is placed in an ICP etcher for ICP etching. A solder groove is etched on the surface of the ceramic substrate. The depth of the solder groove is 60 μm. The solder groove and the solder guide groove are connected to each other.

[0069] The pattern of the solder groove is the same as the preset circuit pattern. When the width of the preset circuit pattern is a, the width of the solder groove is 0.8a.

[0070] After ICP etching, the surface photoresist was removed from the ceramic substrate, and then ultrasonic cleaning was performed in acetone, anhydrous ethanol, and deionized water in sequence, with the ultrasonic cleaning time being 15 min each, and then dried with nitrogen.

[0071] (3) 8wt% modified graphene, 82wt% alumina, 4wt% silicon carbide, 5wt% silicon nitride, and 1wt% calcium carbonate were mixed and ball-milled to obtain a powder. The powder was prepared in a ratio of 90wt% powder and 10wt% organic solvent, wherein the organic solvent includes 4wt% dispersant, 3wt% binder, and 93wt% water. The mixture was stirred to obtain a transition coating material, which was applied to a solder bath and sintered at 1600°C for 30 minutes to obtain a transition layer. The dispersant was sodium polyacrylate, and the binder was silica sol. The thickness of the transition layer was 10μm.

[0072] (4) Take graphene oxide and deionized water, and ultrasonically disperse them for 20 minutes to obtain a graphene oxide aqueous solution (1 mg / mL); take 0.25 g of copper sulfate pentahydrate and 0.16 g of silver nitrate, mix them, add 10 mL of graphene oxide aqueous solution, 20 mL of deionized water, 10 mL of sodium citrate (0.02 mol / L) and sodium borohydride (0.2 mol / L), and stir the reaction at 30°C for 1 hour. After the reaction is completed, let it stand for 2 hours, filter and wash, and vacuum dry to obtain modified graphene.

[0073] Take 70wt% silver powder, 20wt% copper powder, 5wt% titanium hydride powder and 5wt% modified graphene, mix and stir evenly, grind for 10 minutes, and ball mill for 40 minutes at a speed of 180r / min to obtain solder powder, mix 88wt% solder powder and 12wt% organic carrier in a ratio, the organic carrier includes 12wt% thickener, 5wt% dispersant, 70wt% solvent, 7wt% antioxidant and 6wt% thixotropic agent, mix and stir evenly to obtain solder; the thickener is polyethylene glycol, the dispersant is stearic acid, the thixotropic agent is stearamide, the antioxidant is oxalic acid, and the solvent is diethylene glycol dimethyl ether and terpineol, and the mass ratio of the two is 2:3.

[0074] The solder is applied to the solder guide groove and the solder tank, and covered on the transition layer to obtain an active solder layer; the thickness of the active solder layer applied in the solder guide groove and the solder tank is 50 μm;

[0075] (5) Repeat steps (2) to (4) to process interconnected solder grooves and solder guide grooves on the other side of the ceramic substrate, and apply a transition layer and an active solder layer, rinse with deionized water, and dry;

[0076] Take copper foil with a thickness of 50mm×50mm×0.4mm, fix it on both sides of the ceramic substrate, and braze it at a high temperature of 950℃ and a vacuum degree of 5×10 -4 Pa; applying ultrasonic vibration to the surface of the copper foil during brazing, the ultrasonic frequency is 25kHz, the power is 200W, and the ultrasonic time is 60s to obtain a copper-clad laminate; taking the copper-clad laminate, performing circuit patterning processing, etching a preset circuit pattern, and obtaining the copper-clad ceramic substrate.

[0077] Comparative Example 1: Comparative Example 1 is based on Example 2. Modified graphene oxide is not introduced in Comparative Example 1, and the remaining process steps and reaction parameters are consistent with Example 2.

[0078] A method for preparing a copper-clad ceramic substrate comprises the following steps:

[0079] (3) 90 wt% alumina, 4 wt% silicon carbide, 5 wt% silicon nitride, and 1 wt% calcium carbonate were mixed and then ball-milled to obtain a powder. The powder was then mixed with 90 wt% of the powder and 10 wt% of an organic solvent, wherein the organic solvent included 4 wt% of a dispersant, 3 wt% of a binder, and 93 wt% of water. The mixture was stirred to obtain a transition coating material, which was applied to a solder bath and sintered at 1550°C for 35 minutes to obtain a transition layer. The dispersant was sodium polyacrylate, and the binder was silica sol. The thickness of the transition layer was 10 μm.

[0080] (4) Take 70wt% silver powder, 20wt% copper powder, and 10wt% titanium hydride powder, mix and stir them evenly, then grind them for 8 minutes, and ball mill them at a speed of 170r / min for 45 minutes to obtain solder powder, which is mixed with 88wt% solder powder and 12wt% organic carrier in a ratio of 12wt% thickener, 5wt% dispersant, 70wt% solvent, 7wt% antioxidant and 6wt% thixotropic agent, and mix and stir them evenly to obtain solder; the thickener is polyethylene glycol, the dispersant is stearic acid, the thixotropic agent is stearamide, the antioxidant is oxalic acid, and the solvent is diethylene glycol dimethyl ether and pineol, and the mass ratio of the two is 2:3.

[0081] The solder is applied to the solder guide groove and the solder tank, and covered on the transition layer to obtain an active solder layer; the thickness of the active solder layer applied in the solder guide groove and the solder tank is 50 μm;

[0082] Comparative Example 2: Comparative Example 2 is based on Example 2. In Comparative Example 2, the depth of the solder groove is 60 μm, the depth of the solder guide groove is 50 μm, and the remaining process steps and reaction parameters are consistent with those of Example 2.

[0083] Comparative Example 3: Comparative Example 3 is based on Example 2. No transition layer is introduced in Comparative Example 3, and the remaining process steps and reaction parameters are consistent with Example 2.

[0084] A method for preparing a copper-clad ceramic substrate comprises the following steps:

[0085] (1) Take a ceramic substrate, ultrasonically clean it with acetone solution for 12 minutes, then ultrasonically clean it with anhydrous ethanol and deionized water in sequence, each ultrasonic cleaning time is 12 minutes, and blow dry with nitrogen; the ceramic substrate is a silicon nitride ceramic substrate with a size of 50 mm × 50 mm × 0.32 mm;

[0086] (2) Pre-cutting a solder guide groove on the edge of one side of the ceramic substrate by laser processing, wherein the width of the solder guide groove is 5 mm and the depth is 50 μm; washing with deionized water, drying, and then spin-coating photoresist on the surface of the ceramic substrate, baking at 105°C for 12 minutes, ultraviolet exposure, and development to expose the solder groove pattern, placing the ceramic substrate in an ICP etcher for ICP etching, and etching a solder groove on the surface of the ceramic substrate, wherein the depth of the solder groove is 50 μm, and the solder groove and the solder guide groove are connected to each other.

[0087] The pattern of the solder groove is the same as the preset circuit pattern. When the width of the preset circuit pattern is a, the width of the solder groove is 0.8a.

[0088] After ICP etching, the surface photoresist was removed from the ceramic substrate, and then ultrasonic cleaning was performed in acetone, anhydrous ethanol, and deionized water in sequence, with the ultrasonic cleaning time being 15 min each, and then dried with nitrogen.

[0089] (3) Take graphene oxide and deionized water, ultrasonically disperse them for 20 minutes to obtain a graphene oxide aqueous solution (1 mg / mL); take 0.25 g of copper sulfate pentahydrate and 0.16 g of silver nitrate, mix them, add 10 mL of graphene oxide aqueous solution, 20 mL of deionized water, 10 mL of sodium citrate (0.02 mol / L) and sodium borohydride (0.2 mol / L), stir and react at 28°C for 1.5 hours, let it stand for 2.5 hours after the reaction is completed, filter and wash, and vacuum dry to obtain modified graphene.

[0090] Take 70wt% silver powder, 20wt% copper powder, 5wt% titanium hydride powder and 5wt% modified graphene, mix and stir evenly, grind for 8 minutes, and ball mill for 45 minutes at a speed of 170r / min to obtain solder powder, which is mixed with 88wt% solder powder and 12wt% organic carrier in a ratio of 12wt% thickener, 5wt% dispersant, 70wt% solvent, 7wt% antioxidant and 6wt% thixotropic agent, and mix and stir evenly to obtain solder; the thickener is polyethylene glycol, the dispersant is stearic acid, the thixotropic agent is stearamide, the antioxidant is oxalic acid, and the solvent is diethylene glycol dimethyl ether and terpineol, with a mass ratio of 2:3.

[0091] Applying solder to the solder guide groove and the solder tank to obtain an active solder layer; the thickness of the active solder layer applied in the solder guide groove and the solder tank is 50 μm;

[0092] Comparative Example 4: Comparative Example 4 is based on Example 2. Comparative Example 4 defines that "when the preset circuit pattern width is a, the solder groove width is 0.9a", and the remaining process steps and reaction parameters are consistent with Example 2.

[0093] A method for preparing a copper-clad ceramic substrate comprises the following steps:

[0094] (1) Take a ceramic substrate, ultrasonically clean it with acetone solution for 12 minutes, then ultrasonically clean it with anhydrous ethanol and deionized water in sequence, each ultrasonic cleaning time is 12 minutes, and blow dry with nitrogen; the ceramic substrate is a silicon nitride ceramic substrate with a size of 50 mm × 50 mm × 0.32 mm;

[0095] (2) A solder guide groove is pre-cut on the edge of one side of the ceramic substrate by laser processing. The width of the solder guide groove is 5 mm and the depth is 55 μm. The substrate is washed with deionized water and dried. Then, photoresist is spin-coated on the surface of the ceramic substrate, baked at 105°C for 12 minutes, exposed to ultraviolet light, and developed to expose the solder groove pattern. The ceramic substrate is placed in an ICP etcher for ICP etching. A solder groove is etched on the surface of the ceramic substrate. The depth of the solder groove is 60 μm. The solder groove and the solder guide groove are connected to each other.

[0096] The pattern of the solder groove is the same as the preset circuit pattern. When the width of the preset circuit pattern is a, the width of the solder groove is 0.9a.

[0097] After ICP etching, the surface photoresist was removed from the ceramic substrate, and then ultrasonic cleaning was performed in acetone, anhydrous ethanol, and deionized water in sequence, with the ultrasonic cleaning time being 15 min each, and then dried with nitrogen.

[0098] Comparative Example 5: Comparative Example 5 is based on Example 2. Comparative Example 5 stipulates that "when the preset circuit pattern width is a, the solder groove width is 0.5a", and the remaining process steps and reaction parameters are consistent with Example 2.

[0099] A method for preparing a copper-clad ceramic substrate comprises the following steps:

[0100] (1) Take a ceramic substrate, ultrasonically clean it with acetone solution for 12 minutes, then ultrasonically clean it with anhydrous ethanol and deionized water in sequence, each ultrasonic cleaning time is 12 minutes, and blow dry with nitrogen; the ceramic substrate is a silicon nitride ceramic substrate with a size of 50 mm × 50 mm × 0.32 mm;

[0101] (2) A solder guide groove is pre-cut on the edge of one side of the ceramic substrate by laser processing. The width of the solder guide groove is 5 mm and the depth is 55 μm. The substrate is washed with deionized water and dried. Then, photoresist is spin-coated on the surface of the ceramic substrate, baked at 105°C for 12 minutes, exposed to ultraviolet light, and developed to expose the solder groove pattern. The ceramic substrate is placed in an ICP etcher for ICP etching. A solder groove is etched on the surface of the ceramic substrate. The depth of the solder groove is 60 μm. The solder groove and the solder guide groove are connected to each other.

[0102] The pattern of the solder groove is the same as the preset circuit pattern. When the width of the preset circuit pattern is a, the width of the solder groove is 0.9a.

[0103] After ICP etching, the surface photoresist was removed from the ceramic substrate, and then ultrasonic cleaning was performed in acetone, anhydrous ethanol, and deionized water in sequence, with the ultrasonic cleaning time being 15 min each, and then dried with nitrogen.

[0104] Comparative Example 6: Comparative Example 6 is based on Example 2. Ultrasonic assisted brazing is not performed in Comparative Example 6, and the remaining process steps and reaction parameters are consistent with those of Example 2.

[0105] A method for preparing a copper-clad ceramic substrate comprises the following steps:

[0106] (5) Repeat steps (2) to (4) to process interconnected solder grooves and solder guide grooves on the other side of the ceramic substrate, and apply a transition layer and an active solder layer, rinse with deionized water, and dry;

[0107] A copper foil with a thickness of 50 mm × 50 mm × 0.4 mm is fixed on both sides of a ceramic substrate and brazed at a high temperature of 930°C and a vacuum degree of 5 × 10-4 Pa to obtain a copper-clad laminate. The copper-clad laminate is subjected to circuit patterning processing and a preset circuit pattern is etched to obtain the copper-clad ceramic substrate.

[0108] Detection experiment:

[0109] The copper clad laminate samples prepared in Examples 1-3 and Comparative Examples 1-6 were subjected to the following performance tests; the thermal shock test was performed at -50°C for 10 min and 220°C for 10 min, with the temperature rising and cooling controlled at 20 s, and the treatment was cycled 100 times. The peel strength was retested and recorded.

[0110]

[0111] Conclusion: The copper clad laminates prepared in Examples 1-3 have no surface warping, clear and accurate circuits, no solder overflow between the circuits, excellent peel strength of the copper clad laminates, and no voids as a whole; while the copper clad laminates prepared in Comparative Example 4 have slight solder residues between the circuits and no warping; the peel strengths of the remaining Comparative Examples 1-3 and Comparative Examples 5-6 are all inferior to that of the present application.

[0112] The process of the present invention is reasonably designed and simple to operate. The prepared copper-clad laminate has excellent strength, and the bonding performance between the ceramic substrate and the copper foil is good. In addition, the solder can be controlled during the processing of the copper-clad ceramic substrate to avoid overflow and diffusion. The overall appearance of the product is excellent, the yield is high, and it can be used for mass production with high practicality.

[0113] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing a copper-clad ceramic substrate, characterized in that: The following steps are involved: (1) Take the ceramic substrate and ultrasonically clean it with acetone solution for 10-15 minutes, then ultrasonically clean it with anhydrous ethanol and deionized water in sequence, with the ultrasonic cleaning time being 10-15 minutes each, and blow dry it with nitrogen; (2) Pre-cutting a solder guide groove on the edge of one side of the ceramic substrate, washing with deionized water, drying, and then spin-coating photoresist on the surface of the ceramic substrate, baking at 100-110°C for 10-15 minutes, UV-exposing, developing, exposing the solder groove pattern, placing the ceramic substrate in an ICP etcher for ICP etching, and etching a solder groove on the surface of the ceramic substrate, wherein the solder groove and the solder guide groove are connected to each other; After ICP etching, the surface photoresist was removed from the ceramic substrate, and then ultrasonically cleaned with acetone, anhydrous ethanol, and deionized water in sequence. The ultrasonic cleaning time was 10-15 minutes each, and the substrate was dried with nitrogen. (3) Take modified graphene, aluminum oxide, calcium carbonate, silicon carbide, and silicon nitride, mix them evenly, and then ball mill them. Add dispersant, binder, and water, stir evenly to obtain a transition coating material, apply it to a solder tank, and sinter at a high temperature of 1500-1600°C for 30-40 minutes to obtain a transition layer. (4) Take silver powder, copper powder, titanium hydride powder and modified graphene, mix and stir evenly, grind for 5-10 minutes, and ball mill at a speed of 160-180 r / min for 40-50 minutes. After ball milling, add thickener, dispersant, solvent, antioxidant and thixotropic agent, mix and stir evenly to obtain solder; Applying solder to the solder guide groove and the solder tank and covering the transition layer to obtain an active solder layer; (5) Repeat steps (2) to (4) to process interconnected solder grooves and solder guide grooves on the other side of the ceramic substrate, and apply a transition layer and an active solder layer, rinse with deionized water, and dry; Taking copper foil, fixing it on both sides of the ceramic substrate, and high-temperature brazing to obtain a copper-clad laminate; taking the copper-clad laminate, performing circuit patterning processing, etching a preset circuit pattern, and obtaining the copper-clad ceramic substrate; In step (2), the pattern of the solder groove is the same as the preset circuit pattern, and when the width of the preset circuit pattern is a, the width of the solder groove is 0.6a~0.8a; The modified graphene preparation method comprises the following steps: taking copper sulfate pentahydrate and silver nitrate, mixing them, adding graphene oxide aqueous solution, deionized water, sodium citrate and sodium borohydride, stirring and reacting at 25-30° C. for 1-2 hours, standing for 2-3 hours after the reaction is completed, filtering and washing, and vacuum drying to obtain the modified graphene.

2. The method for preparing a copper-clad ceramic substrate according to claim 1, wherein: In step (2), the thickness of the ceramic substrate is h, the width of the solder guide groove is 0-5 mm, and the depth is ≦0.5h; the depth of the solder groove is ≦0.5h, and the depth of the solder groove is greater than the depth of the solder guide groove.

3. The method for preparing a copper-clad ceramic substrate according to claim 1, wherein: In step (2), the thickness of the active solder layer coated in the solder trough and the solder guide trough is 30-50 μm, and the thickness of the transition layer is 5-10 μm.

4. The method for preparing a copper-clad ceramic substrate according to claim 1, wherein: In step (2), the depth difference between the solder groove and the solder guide groove is 5-7 μm, and the solder guide groove is formed by any one of laser processing, ultrasonic grinding, electric spark processing, and electrolytic processing.

5. The method for preparing a copper-clad ceramic substrate according to claim 1, wherein: In step (5), the high temperature brazing temperature is 900~950℃ and the vacuum degree is 5×10 -4 ~8×10 -4 Pa; during high-temperature brazing, ultrasonic vibration is applied to the surface of the copper foil, the ultrasonic frequency is 20-25kHz, the power is 100-200w, and the ultrasonic time is 30-60s.

6. The method for preparing a copper-clad ceramic substrate according to claim 1, wherein: The raw materials of the components of the transition layer include 90wt% powder and 10wt% organic solvent, the powder includes 8wt% modified graphene, 82wt% aluminum oxide, 4wt% silicon carbide, 5wt% silicon nitride, and 1wt% calcium carbonate; the organic solvent includes 4wt% dispersant, 3wt% binder and 93wt% water, the dispersant is sodium polyacrylate, and the binder is silica sol.

7. The method for preparing a copper-clad ceramic substrate according to claim 1, wherein: The raw materials of each component in the solder include 88wt% solder powder and 12wt% organic vehicle, the solder powder includes 70wt% silver powder, 20wt% copper powder, 5wt% titanium hydride powder and 5wt% modified graphene; the organic vehicle includes 12wt% thickener, 5wt% dispersant, 70wt% solvent, 7wt% antioxidant and 6wt% thixotropic agent; The thickener is polyethylene glycol, the dispersant is stearic acid, the thixotropic agent is stearamide, the antioxidant is oxalic acid, and the solvent is diethylene glycol dimethyl ether and terpineol in a mass ratio of 2:

3.

8. A copper-clad ceramic substrate prepared according to the method for preparing a copper-clad ceramic substrate according to any one of claims 1 to 7.

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