Method for improving compactness of via hole of AMB ceramic substrate

Abstract

The invention discloses a method for improving the compactness of a via hole of an AMB ceramic substrate, and relates to the technical field of ceramic substrate preparation. According to the invention, laser drilling is adopted to process via holes in the ceramic substrate; composite brazing filler metal containing alloy powder and graphene-TiO2 composite powder is prepared, and the via holes are filled with the composite brazing filler metal; and then carrying out segmented heating degreasing, pressure sintering, hot isostatic pressing, gradient cooling and other treatments, and finally carrying out ultrasonic cleaning and vacuum drying to obtain the AMB ceramic substrate. According to the prepared AMB ceramic substrate, the via hole compactness is remarkably improved, meanwhile, the excellent electric conduction and heat conduction performance and mechanical strength are achieved, the AMB ceramic substrate is suitable for high-power electronic device packaging and other harsh scenes, and a key basic material support is provided for development of the advanced electronic packaging technology.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic substrate preparation, and in particular to a method for improving the density of via holes in an AMB ceramic substrate. Background Art

[0002] As the core packaging material for power electronic devices, AMB ceramic substrates have high thermal conductivity, high insulation and good mechanical properties, and are widely used in new energy vehicles, smart grids, power modules and other fields.

[0003] Active Metal Brazing (AMB) technology is a process that achieves direct bonding between ceramics and metals using an active brazing filler metal. Its core principle is to utilize active elements to chemically react with the ceramic surface at high temperatures, forming a transition layer, thereby achieving a high-strength, high-reliability connection between the ceramic and metal. AMB ceramic substrates offer advantages such as high thermal conductivity, excellent insulation, and the ability to carry high currents, making them widely used in power semiconductor packaging.

[0004] Vias are key structures for achieving interlayer electrical connections in AMB ceramic substrates, and their density directly impacts the substrate's conductivity, reliability, and service life. However, during the traditional AMB ceramic substrate via preparation process, defects such as voids and cracks can easily appear within the vias due to issues such as insufficient metal affinity on the ceramic surface, uneven metal slurry filling, and incomplete gas discharge during sintering. These defects severely impact the via's density and connection performance.

[0005] At present, existing technologies mainly improve the density of vias by optimizing metal slurry formula, improving printing process or adjusting sintering parameters, but the effect still needs to be improved. There is an urgent need for an efficient and reliable method to improve the density of vias in AMB ceramic substrates. Summary of the Invention

[0006] The object of the present invention is to provide a method for improving the density of through-holes in an AMB ceramic substrate, so as to solve the problems raised in the above background technology.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0008] A method for improving the density of through-holes in an AMB ceramic substrate comprises the following steps:

[0009] S1: Through-hole processing

[0010] Laser drilling technology is used to process holes on a ceramic substrate to obtain a ceramic substrate A;

[0011] S2: Preparation and filling of composite solder

[0012] Preparation of composite solder: Alloy powder, graphene-TiO2 composite powder, and organic carrier are added to a mixing container. Nano-dispersant, thixotropic agent, and nano-diamond powder are also added. The mixture is first mixed at a low speed and then dispersed at a high speed to obtain a composite solder. The composite solder is then filled into the vias to obtain ceramic substrate B.

[0013] S3: Vacuum brazing

[0014] The ceramic substrate B is subjected to segmented heating degreasing, pressure sintering, hot isostatic pressing, gradient cooling and post-processing to obtain an AMB ceramic substrate.

[0015] Furthermore, the ceramic substrate can be pretreated before S1 via processing: select the ceramic substrate to be processed, place it in a sodium hydroxide solution with a concentration of 5-10%, soak it at a temperature of 50-60°C for 10-15 minutes, rinse it with deionized water, and place it in a vacuum drying oven and dry it at 80-100°C for 2-3 hours.

[0016] Furthermore, after the S2 via hole processing, the ceramic substrate A can be subjected to plasma treatment: argon is selected as the plasma gas, the gas flow rate is 50-200 sccm, the power is 300-500 W, and the processing time is 3-5 minutes.

[0017] Furthermore, the process conditions of laser drilling are as follows: the laser type is infrared laser, the laser wavelength is 1064nm, the pulse width is 10-20ns, the repetition frequency is 10-50kHz, the drilling speed is 5-10mm / s, the aperture of the via hole is 0.1-0.3mm, and the hole depth is 0.2-0.5mm.

[0018] Furthermore, in the preparation of the composite solder, the process conditions for low-speed mixing are: speed 4000-5000 rpm, time 4-6 minutes; the process conditions for high-speed mixing are: speed 11000-12000 rpm, time 15-20 minutes.

[0019] Furthermore, the composite solder includes the following components by mass: 47.5-63.7 parts of Ag-Cu-In alloy powder, 5-10 parts of graphene-TiO2 composite powder, 30-40 parts of organic carrier, 0.5-1 part of nano-dispersant, 0.3-0.5 part of thixotropic agent, and 0.5-1 part of nano-diamond powder.

[0020] Furthermore, the speed of filling the via hole is 0.1-5 mm / s and the filling pressure is 0.1-1 MPa.

[0021] Furthermore, Ag-Cu-In alloy powder is prepared by the following process: silver powder, copper powder, and indium powder are added to a high-purity graphite crucible and placed in a vacuum induction furnace for melting; the molten alloy is sprayed into an inert gas to prepare Ag-Cu-In alloy powder.

[0022] Furthermore, the Ag-Cu-In alloy powder includes the following components by mass: 55-75 parts of silver powder, 20-30 parts of copper powder, and 5-15 parts of indium powder.

[0023] Furthermore, the organic carrier includes the following components by weight: 15-30 parts of ethyl cellulose, 65-75 parts of terpineol, and 5-10 parts of polyethylene glycol.

[0024] Furthermore, the nano-dispersant is a mixture of one or more of oleic acid, polyvinyl pyrrolidone, BYK-110, and Disperbyk-163.

[0025] Furthermore, the thixotropic agent is one of hydrogenated castor oil and fumed silica, or a mixture of the two.

[0026] Furthermore, the graphene-TiO2 composite powder is prepared by the following process:

[0027] Step 1: adding graphene oxide to deionized water and performing ultrasonic dispersion to obtain a graphene oxide suspension;

[0028] Step 2: adding a titanium source and a reducing agent to the graphene oxide suspension, stirring evenly, then adding ethanol dropwise, and continuing to stir to obtain a mixed solution;

[0029] Step 3: reacting the mixed solution at 180-200°C for 10-14 hours and naturally cooling to room temperature to obtain product A;

[0030] Step 4: After centrifuging product A, wash it alternately with ethanol and deionized water to obtain product B;

[0031] Step 5: Dry the product B, grind and sieve it to obtain graphene-TiO2 composite powder.

[0032] Furthermore, the process conditions for ultrasonic dispersion in step 1 are: ultrasonic power 300-500W, time 30-60min.

[0033] Furthermore, the concentration of the graphene oxide suspension is 0.5-1.0 mg / mL.

[0034] Furthermore, in step 2, the titanium source is tetrabutyl titanate, and the mass ratio of graphene oxide suspension to titanium source is 1:(5-10); the reducing agent is hydrazine hydrate, and the concentration of the reducing agent in the mixed solution is 0.1-0.5 mol / L.

[0035] Furthermore, in step 2, the volume ratio of ethanol to water is (1-2):1, the stirring speed is 100-200 rpm, and the stirring time is 1-2 h.

[0036] Furthermore, in step 4, the centrifugal speed of product A is 8000-10000 rpm, and the centrifugation time is 10-15 min.

[0037] Furthermore, in step 5, the drying temperature of product B is 60-80° C., and the drying time is 12-24 h.

[0038] Furthermore, the operation process of staged heating degreasing is as follows: first, react at 150-300℃ for 1-2h, then heat to 400-600℃, react for 1-2h, and the vacuum range is 1×10 -3 Pa-5×10 -3 Pa.

[0039] Furthermore, the process conditions of pressure sintering are: temperature 800-850° C., nitrogen pressure 0.5-1.0 MPa, and time 30-60 min.

[0040] Furthermore, the process conditions of the hot isostatic pressing treatment are: temperature 800-850° C., argon pressure 80-100 MPa, and time 45-60 min.

[0041] Furthermore, the operation process of the gradient cooling is: reducing the temperature to 400°C at 5-10°C / min, and then cooling to room temperature in the furnace.

[0042] Furthermore, the post-treatment operation process is: ultrasonic cleaning with deionized water for 3-5 times, and drying at 60-80° C. for 12-24 hours.

[0043] Compared with the existing technology, the beneficial effects achieved by the present invention are: the present invention adopts laser drilling technology to process the via hole, which can achieve micron-level precision aperture control, smooth hole wall and high verticality, avoiding defects such as substrate cracking and rough hole wall that may be caused by traditional mechanical drilling, and providing a regular space for uniform filling of composite solder.

[0044] The composite solder of the present invention has multiple components that enhance density: the alloy powder as the main body provides good electrical conductivity and mechanical strength; the graphene-TiO2 composite powder, with its high specific surface area and excellent thermal conductivity, can fill the gaps between alloy powder particles to form a tightly packed structure, while enhancing interfacial bonding strength; the nano-dispersant ensures that the composite powder is evenly dispersed in the organic carrier to avoid agglomeration.

[0045] The vacuum brazing process of the present invention regulates densification in multiple stages: the staged heating and thorough degreasing can volatilize the organic carrier in the composite brazing material in stages, avoiding the formation of pores due to the retention of volatile gases caused by rapid heating; the vacuum environment inhibits the oxidation of the brazing material, and ensures good metallurgical bonding between the alloy powder and the ceramic substrate during the brazing process; pressure sintering forces the composite brazing material to further fill the pores of the via hole, while accelerating the diffusion of alloy atoms and ceramic surface atoms to form a strong interface bonding layer and reduce the interface gap; hot isostatic pressing can effectively close the residual tiny pores through the synergistic effect of high temperature, eliminate internal stress concentration, and make the internal structure of the via hole reach a nearly completely dense state, significantly improving the mechanical properties and reliability; gradient cooling can avoid the sudden increase of internal stress caused by the difference in thermal expansion coefficient between the ceramic substrate and the composite brazing material due to rapid cooling, reduce the risk of crack generation, and ensure the stability of the overall structure of the substrate.

[0046] The present invention can completely remove residual brazing additives and processing debris on the surface of the substrate by ultrasonic cleaning with deionized water 3-5 times, thereby preventing impurities from affecting the electrical performance and reliability of the substrate; vacuum drying ensures that there is no residual moisture inside the substrate, preventing electrochemical corrosion or degradation of insulation performance caused by moisture penetration during long-term use, and ultimately obtaining a high-density and high-reliability AMB ceramic substrate.

[0047] In summary, through the synergistic effect of the above-mentioned processes, the density of the through-holes of the AMB ceramic substrate prepared in the present invention is significantly improved, while also having excellent electrical and thermal conductivity and mechanical strength, making it suitable for harsh scenarios such as high-power electronic device packaging, and providing key basic material support for the development of advanced electronic packaging technology. DETAILED DESCRIPTION

[0048] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0049] In the following specific embodiments:

[0050] The “parts” mentioned below are all parts by mass unless otherwise specified.

[0051] The alloy powder is Ag-Cu-In alloy powder, which is prepared by the following process: silver powder, copper powder and indium powder are added into a high-purity graphite crucible in a mass ratio of 65:25:10, and then placed in a vacuum induction furnace for melting. The vacuum degree of melting is 1×10 - 3Pa, temperature 1200℃, time 40min; the molten alloy was sprayed into argon gas with a pressure of 3MPa and a flow rate of 80L / min at a spray speed of 1m / s to prepare 30μm Ag-Cu-In alloy powder.

[0052] Graphene-TiO2 composite powder is prepared by the following process:

[0053] Step 1: Add graphene oxide to deionized water and perform ultrasonic dispersion at an ultrasonic power of 300 W for 60 min to prepare a 1.0 mg / mL graphene oxide suspension;

[0054] Step 2: adding tetrabutyl titanate and hydrazine hydrate to the graphene oxide suspension, with the mass ratio of the graphene oxide suspension to tetrabutyl titanate being 1:5; stirring evenly, and then adding ethanol dropwise, with the volume ratio of ethanol to water being 2:1, stirring at a speed of 150 rpm and a stirring time of 2 h to obtain a mixed solution; the concentration of hydrazine hydrate in the mixed solution is 0.2 mol / L;

[0055] Step 3: The mixed solution was reacted at 180°C for 14 hours and naturally cooled to room temperature to obtain product A;

[0056] Step 4: centrifuge product A at 8000 rpm for 15 min, and then wash alternately with ethanol and deionized water 5 times to obtain product B;

[0057] Step 5: Dry product B at 80°C for 18 hours, grind it through a 500-mesh sieve to obtain a 25 μm graphene-TiO2 composite powder.

[0058] The purity of silver powder is 99.9%; the purity of copper powder is 99.9%; the purity of indium powder is 99.99%;

[0059] Ethyl cellulose CAS is 9004-57-3;

[0060] The density of terpineol is 0.937g / cm 3 , CAS is 8000-41-7;

[0061] Polyethylene glycol CAS is 25322-68-3;

[0062] Nanodispersant: Oleic acid density is 0.895g / cm 3 , CAS is 112-80-1;

[0063] Nanodispersant: Polyvinylpyrrolidone with a density of 1.144 g / cm 3 , CAS is 9003-39-8;

[0064] Nanodispersant: BYK-110 density is 1.103 g / mL;

[0065] Nanodispersant: Disperbyk-163 density is 0.99 kg / m 3 ;

[0066] Thixotropic agent: hydrogenated castor oil with a density of 1.02 g / cm 3 , CAS is 8001-78-3;

[0067] Thixotropic agent: fumed silica with a specific surface area of ​​200m 2 / g, CAS is 112945-52-5;

[0068] The particle size of graphene oxide is 5 μm, and the CAS number is 7782-42-5;

[0069] Tetrabutyl titanate has a density of 1.00 g / mL and a CAS number of 5593-70-4;

[0070] The particle size of nano diamond powder is 10nm, and the CAS number is 7782-40-3;

[0071] The density of hydrazine hydrate is 1.032 g / cm 3 , CAS is 7803-57-8;

[0072] Ethanol CAS is 64-17-5.

[0073] Example 1: A method for improving the density of via holes in an AMB ceramic substrate, comprising the following steps:

[0074] S1: Through-hole processing

[0075] Laser drilling technology is used to process via holes on a ceramic substrate to obtain ceramic substrate A. The laser drilling process conditions are as follows: infrared laser is selected as the laser type, the laser wavelength is 1064nm, the pulse width is 10ns, the repetition frequency is 20kHz, the drilling speed is 5mm / s, the via hole diameter is 0.2mm, and the hole depth is 0.3mm.

[0076] S2: Preparation and filling of composite solder

[0077] Composite solder preparation: 60 parts of 30 μm Ag-Cu-In alloy powder, 8 parts of 25 μm graphene-TiO2 composite powder, 30 parts of organic vehicle, 0.5 parts of oleic acid, 0.5 parts of hydrogenated castor oil, and 1 part of nano-diamond powder were added to a mixing container and mixed at 4000 rpm for 6 minutes and then at 11000 rpm for 20 minutes to obtain a composite solder. The composite solder was then filled into the via holes at a speed of 1 mm / s and a pressure of 0.5 MPa to obtain a ceramic substrate B. The organic vehicle comprised the following components by weight: 20 parts of ethyl cellulose, 70 parts of terpineol, and 10 parts of polyethylene glycol.

[0078] S3: Vacuum brazing

[0079] The ceramic substrate B was reacted at 200℃ for 2h, then heated to 500℃ for 2h, and the vacuum degree was 5×10 -3 Pa; then react at 800°C and nitrogen pressure of 1.0 MPa for 30 minutes; then react at 850°C and argon pressure of 80 MPa for 60 minutes; then reduce the temperature to 400°C at a rate of 10°C / min, and then cool to room temperature with the furnace; finally, ultrasonically clean with deionized water for 5 times and dry at 80°C for 18 hours to obtain an AMB ceramic substrate.

[0080] Example 2: A method for improving the density of via holes in an AMB ceramic substrate, comprising the following steps:

[0081] S1: Through-hole processing

[0082] Laser drilling technology is used to process via holes on a ceramic substrate to obtain ceramic substrate A. The laser drilling process conditions are as follows: infrared laser is selected as the laser type, the laser wavelength is 1064nm, the pulse width is 15ns, the repetition frequency is 10kHz, the drilling speed is 8mm / s, the via hole diameter is 0.3mm, and the hole depth is 0.2mm.

[0083] S2: Preparation and filling of composite solder

[0084] Composite solder preparation: 47.5 parts of 30 μm Ag-Cu-In alloy powder, 10 parts of 25 μm graphene-TiO2 composite powder, 40 parts of organic vehicle, 1 part of polyvinyl pyrrolidone, 0.5 parts of hydrogenated castor oil, and 1 part of nano-diamond powder were added to a mixing container and mixed at 4500 rpm for 5 minutes and then at 11000 rpm for 20 minutes to obtain a composite solder. The composite solder was then filled into the via holes at a filling speed of 0.1 mm / s and a pressure of 0.1 MPa to obtain a ceramic substrate B. The organic vehicle comprised the following components by weight: 15 parts of ethyl cellulose, 75 parts of terpineol, and 10 parts of polyethylene glycol.

[0085] S3: Vacuum brazing

[0086] The ceramic substrate B was reacted at 150℃ for 1.5h, then heated to 400℃ for 1.5h, and the vacuum degree was 1×10 - 3 Pa; then react at 850°C and nitrogen pressure 0.5MPa for 60min; then react at 850°C and argon pressure 90MPa for 55min; then reduce the temperature to 400°C at a rate of 5°C / min, and then cool to room temperature with the furnace; finally, ultrasonically clean with deionized water for 3 times, and vacuum dry at 60°C for 24h to obtain an AMB ceramic substrate.

[0087] Example 3: A method for improving the density of via holes in an AMB ceramic substrate, comprising the following steps:

[0088] S1: Through-hole processing

[0089] Laser drilling technology is used to process via holes on a ceramic substrate to obtain ceramic substrate A. The laser drilling process conditions are as follows: infrared laser is selected as the laser type, the laser wavelength is 1064nm, the pulse width is 20ns, the repetition frequency is 50kHz, the drilling speed is 10mm / s, the via hole diameter is 0.2mm, and the hole depth is 0.5mm.

[0090] S2: Preparation and filling of composite solder

[0091] Composite solder preparation: 63.7 parts of 30 μm Ag-Cu-In alloy powder, 5 parts of 25 μm graphene-TiO2 composite powder, 30 parts of organic vehicle, 0.5 parts of BYK-110, 0.3 parts of hydrogenated castor oil, and 0.5 parts of nano-diamond powder were added to a mixing container and mixed at 5000 rpm for 4 minutes and then at 12000 rpm for 15 minutes to obtain a composite solder. The composite solder was then filled into the via holes at a speed of 5 mm / s and a pressure of 1 MPa to obtain a ceramic substrate B. The organic vehicle comprised the following components by weight: 30 parts of ethyl cellulose, 65 parts of terpineol, and 5 parts of polyethylene glycol.

[0092] S3: Vacuum brazing

[0093] The ceramic substrate B was reacted at 300℃ for 1h, then heated to 600℃ for 1h, and the vacuum degree was 3×10 -3 Pa; then react at 830°C and nitrogen pressure 0.8MPa for 45min; then react at 830°C and argon pressure 100MPa for 45min; then reduce the temperature to 400°C at 8°C / min, and then cool to room temperature with the furnace; finally, ultrasonically clean with deionized water 4 times, and vacuum dry at 70°C for 12h to obtain an AMB ceramic substrate.

[0094] Comparative Example 1: Based on Example 1, S2 was adjusted, and no graphene-TiO2 composite powder was added to the composite solder, comprising the following steps:

[0095] S1: Through-hole processing

[0096] Laser drilling technology is used to process via holes on a ceramic substrate to obtain ceramic substrate A. The laser drilling process conditions are as follows: infrared laser is selected as the laser type, the laser wavelength is 1064nm, the pulse width is 10ns, the repetition frequency is 20kHz, the drilling speed is 5mm / s, the via hole diameter is 0.2mm, and the hole depth is 0.3mm.

[0097] S2: Preparation and filling of composite solder

[0098] Composite solder preparation: 68 parts of 30 μm Ag-Cu-In alloy powder, 30 parts of an organic vehicle, 0.5 parts of oleic acid, 0.5 parts of hydrogenated castor oil, and 1 part of nanodiamond powder were added to a mixing container and mixed at 4000 rpm for 6 minutes and then at 11000 rpm for 20 minutes to obtain a composite solder. The composite solder was then filled into the via holes at a speed of 1 mm / s and a pressure of 0.5 MPa to obtain a ceramic substrate B. The organic vehicle comprised the following components by weight: 20 parts of ethyl cellulose, 70 parts of terpineol, and 10 parts of polyethylene glycol.

[0099] S3: Vacuum brazing

[0100] The ceramic substrate B was reacted at 200℃ for 2h, then heated to 500℃ for 2h, and the vacuum degree was 5×10 -3 Pa; then react at a temperature of 800°C and a nitrogen pressure of 1.0 MPa for 60 minutes; then react at a temperature of 850°C and an argon pressure of 80 MPa for 60 minutes; then reduce the temperature to 400°C at a rate of 10°C / min, and then cool to room temperature with the furnace; finally, ultrasonically clean with deionized water for 5 times and dry at 80°C for 18 hours to obtain an AMB ceramic substrate.

[0101] Comparative Example 2: Based on Example 1, S2 was adjusted to change the Ag-Cu-In alloy powder to Ag-Cu alloy powder, comprising the following steps:

[0102] S1: Through-hole processing

[0103] Laser drilling technology is used to process via holes on a ceramic substrate to obtain ceramic substrate A. The laser drilling process conditions are as follows: infrared laser is selected as the laser type, the laser wavelength is 1064nm, the pulse width is 10ns, the repetition frequency is 20kHz, the drilling speed is 5mm / s, the via hole diameter is 0.2mm, and the hole depth is 0.3mm.

[0104] S2: Preparation and filling of composite solder

[0105] Composite solder preparation: 60 parts of 30 μm Ag-Cu alloy powder, 8 parts of 25 μm graphene-TiO2 composite powder, 30 parts of organic vehicle, 0.5 parts of oleic acid, 0.5 parts of hydrogenated castor oil, and 1 part of nano-diamond powder were added to a mixing container and mixed at 4000 rpm for 6 minutes and then at 11000 rpm for 20 minutes to obtain a composite solder. The composite solder was then filled into the via holes at a speed of 1 mm / s and a pressure of 0.5 MPa to obtain a ceramic substrate B. The organic vehicle comprised the following components by weight: 20 parts of ethyl cellulose, 70 parts of terpineol, and 10 parts of polyethylene glycol.

[0106] S3: Vacuum brazing

[0107] The ceramic substrate B was reacted at 200℃ for 2h, then heated to 500℃ for 2h, and the vacuum degree was 5×10 -3 Pa; then react at a temperature of 800°C and a nitrogen pressure of 1.0 MPa for 60 minutes; then react at a temperature of 850°C and an argon pressure of 80 MPa for 60 minutes; then reduce the temperature to 400°C at a rate of 10°C / min, and then cool to room temperature with the furnace; finally, ultrasonically clean with deionized water for 5 times and dry at 80°C for 18 hours to obtain an AMB ceramic substrate.

[0108] Ag-Cu alloy powder was prepared by the following process: silver powder and copper powder were added into a high-purity graphite crucible in a mass ratio of 70:30, and then melted in a vacuum induction furnace. The vacuum degree of the melting was 1×10 -3 Pa, temperature 1200℃, time 40min; the molten alloy was sprayed into argon gas with a pressure of 3MPa and a flow rate of 80L / min at a spray speed of 1m / s to prepare 30μm Ag-Cu-In alloy powder.

[0109] Comparative Example 3: Based on Example 1, S3 was adjusted, and the staged heating degreasing operation was not performed, comprising the following steps:

[0110] S1: Through-hole processing

[0111] Laser drilling technology is used to process via holes on a ceramic substrate to obtain ceramic substrate A. The laser drilling process conditions are as follows: infrared laser is selected as the laser type, the laser wavelength is 1064nm, the pulse width is 10ns, the repetition frequency is 20kHz, the drilling speed is 5mm / s, the via hole diameter is 0.2mm, and the hole depth is 0.3mm.

[0112] S2: Preparation and filling of composite solder

[0113] Composite solder preparation: 60 parts of 30 μm Ag-Cu-In alloy powder, 8 parts of 25 μm graphene-TiO2 composite powder, 30 parts of organic vehicle, 0.5 parts of oleic acid, 0.5 parts of hydrogenated castor oil, and 1 part of nano-diamond powder were added to a mixing container and mixed at 4000 rpm for 6 minutes and then at 11000 rpm for 20 minutes to obtain a composite solder. The composite solder was then filled into the via holes at a speed of 1 mm / s and a pressure of 0.5 MPa to obtain a ceramic substrate B. The organic vehicle comprised the following components by weight: 20 parts of ethyl cellulose, 70 parts of terpineol, and 10 parts of polyethylene glycol.

[0114] S3: Vacuum brazing

[0115] The ceramic substrate B was reacted at a temperature of 800°C and a nitrogen pressure of 1.0 MPa for 30 minutes; then at a temperature of 850°C and an argon pressure of 80 MPa for 60 minutes; then the temperature was reduced to 400°C at a rate of 10°C / min, and then cooled to room temperature with the furnace; finally, it was ultrasonically cleaned with deionized water for 5 times and dried at 80°C for 18 hours to obtain the AMB ceramic substrate.

[0116] Experiment: The AMB ceramic substrates obtained in Examples 1-3 and Comparative Examples 1-3 were used to prepare samples, and their properties were tested and the test results were recorded:

[0117] Density test: Use Archimedes drainage method to test the density of the sample, and then calculate the density of the sample based on the actual density value and the theoretical density value;

[0118] Resistance test: Use the RTS-8 four-probe tester to test the resistance of the sample, compare the measured resistance with the theoretical resistance, and evaluate the density of the via filling (if the measured resistance is ≤1.2 times the theoretical resistance, the filling is considered good);

[0119] Temperature reliability test: Use KTHR-hot and cold shock test chamber, the temperature is 150℃ / -50℃, each cycle of high and low temperature is kept for 30 minutes, and the conversion time is less than 5 minutes to test the temperature reliability of the sample;

[0120] Thermal conductivity test: Use DRX-Ⅱ-JG laser flash thermal conductivity meter to test the thermal conductivity of the sample.

[0121] Table 1 AMB ceramic substrate performance test results

[0122] project density Measured resistance / theoretical resistance Temperature reliability (number of cycles) <![CDATA[Thermal conductivity (W·m- 1 ·K- 1 )]]> Example 1 99.87％ 1.02 3000 185 Example 2 99.79％ 1.07 2800 178 Example 3 99.81％ 1.05 2850 182 Comparative Example 1 98.50％ 1.35 1700 150 Comparative Example 2 99.20％ 1.28 1800 165 Comparative Example 3 99.00％ 1.25 1500 160

[0123] Conclusion: From the comparison of the data in the table, it can be seen that the performance of the AMB ceramic substrates prepared in Examples 1-3 is significantly better than that of the AMB ceramic substrates prepared in Comparative Examples 1-3; in Comparative Example 1, no graphene-TiO2 composite powder is added to the composite solder. Compared with the examples, the density of the AMB ceramic substrate prepared in Comparative Example 1 is reduced to 98.50%, the resistivity ratio is 1.35, and the number of cycles is reduced to 1700, indicating that the graphene-TiO2 composite powder can significantly improve the fluidity and interface bonding strength of the solder, thereby enhancing the density and thermal conductivity; in Comparative Example 2, Ag is added to the composite solder. -Cu-In alloy powder was adjusted to Ag-Cu alloy powder. Compared with the embodiment, the density of the AMB ceramic substrate prepared in Comparative Example 2 dropped to 99.20%, and the number of cycles was significantly reduced, indicating that the In element can lower the melting point and improve the wettability, thereby improving the density and thermal conductivity; Comparative Example 3 did not perform the segmented heating degreasing operation. Compared with the embodiment, the density of the AMB ceramic substrate prepared in Comparative Example 2 dropped to 99.00%, indicating that segmented degreasing can effectively remove the organic carrier, avoid pore defects caused by residual carbon impurities, and achieve the effect of enhancing the density.

[0124] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations that come within the meaning and range of equivalents of the claims be embraced therein.

Claims

1. A method for improving the density of via holes in an AMB ceramic substrate, characterized by: The following steps are involved: S1: Through-hole processing Laser drilling technology is used to process holes on a ceramic substrate to obtain a ceramic substrate A; S2: Preparation and filling of composite solder Preparation of composite solder: Alloy powder, graphene-TiO2 composite powder, and organic carrier are added to a mixing container. Nano-dispersant, thixotropic agent, and nano-diamond powder are also added. The mixture is first mixed at a low speed and then dispersed at a high speed to obtain a composite solder. The composite solder is then filled into the vias to obtain ceramic substrate B. S3: Vacuum brazing The ceramic substrate B undergoes segmented heating degreasing, pressure sintering, hot isostatic pressing, gradient cooling and post-processing to obtain an AMB ceramic substrate.

2. The method for improving the density of via holes in an AMB ceramic substrate according to claim 1, wherein: The process conditions of the laser drilling are as follows: the laser type is infrared laser, the laser wavelength is 1064nm, the pulse width is 10-20ns, the repetition frequency is 10-50kHz, the drilling speed is 5-10mm / s, the aperture of the via hole is 0.1-0.3mm, and the hole depth is 0.2-0.5mm.

3. The method for improving the density of via holes in an AMB ceramic substrate according to claim 1, wherein: The composite solder comprises the following components by mass: 47.5-63.7 parts of Ag-Cu-In alloy powder, 5-10 parts of graphene-TiO2 composite powder, 30-40 parts of organic carrier, 0.5-1 part of nano-dispersant, 0.3-0.5 part of thixotropic agent, and 0.5-1 part of nano-diamond powder.

4. The method for improving the density of via holes in an AMB ceramic substrate according to claim 3, wherein: The Ag-Cu-In alloy powder is prepared by the following process: silver powder, copper powder and indium powder are added into a high-purity graphite crucible, and the mixture is placed in a vacuum induction furnace for melting; and the molten alloy is sprayed into an inert gas to prepare the Ag-Cu-In alloy powder.

5. The method for improving the density of via holes in an AMB ceramic substrate according to claim 4, characterized in that: The Ag-Cu-In alloy powder includes the following components by mass: 55-75 parts of silver powder, 20-30 parts of copper powder, and 5-15 parts of indium powder.

6. The method for improving the density of via holes in an AMB ceramic substrate according to claim 3, wherein: The graphene-TiO2 composite powder is prepared by the following process: Step 1: adding graphene oxide to deionized water and performing ultrasonic dispersion to obtain a graphene oxide suspension; Step 2: adding a titanium source and a reducing agent to the graphene oxide suspension, stirring evenly, then adding ethanol dropwise, and continuing to stir to obtain a mixed solution; Step 3: reacting the mixed solution at 180-200°C for 10-14 hours and naturally cooling to room temperature to obtain product A; Step 4: After centrifuging product A, wash it alternately with ethanol and deionized water to obtain product B; Step 5: Dry the product B, grind and sieve it to obtain graphene-TiO2 composite powder.

7. The method for improving the density of via holes in an AMB ceramic substrate according to claim 3, wherein: The organic carrier comprises the following components by weight: 15-30 parts of ethyl cellulose, 65-75 parts of terpineol, and 5-10 parts of polyethylene glycol.

8. The method for improving the density of via holes in an AMB ceramic substrate according to claim 1, wherein: The operation process of the segmented heating degreasing is as follows: first, react at 150-300°C for 1-2 hours, then heat to 400-600°C, react for 1-2 hours, and the vacuum range is 1×10 -3 Pa-5×10 -3 Pa.

9. The method for improving the density of via holes in an AMB ceramic substrate according to claim 1, wherein: The process conditions of the pressure sintering are: temperature 800-850°C, nitrogen pressure 0.5-1.0 MPa, and time 30-60 min; the process conditions of the hot isostatic pressing treatment are: temperature 800-850°C, argon pressure 80-100 MPa, and time 45-60 min.

10. The method for improving the density of via holes in an AMB ceramic substrate according to claim 1, characterized in that: The gradient cooling process is as follows: cooling to 400°C at a rate of 5-10°C / min, and then cooling to room temperature in the furnace.