A method for preparing a three-dimensional aluminum nitride ceramic substrate for chip packaging

Abstract

This invention relates to the field of electronic packaging materials technology, and provides a method for preparing a three-dimensional aluminum nitride ceramic substrate for chip packaging, which solves the problems of poor airtightness, poor thermal stability, low reliability, and low precision of metal circuit layers in ceramic substrates prepared by existing technologies; the method includes the following preparation steps: 1) preparing an AlN ceramic substrate; 2) preparing an AlN ceramic substrate; 3) preparing a dammed substrate; 4) pretreatment; 5) preparing a three-dimensional aluminum nitride ceramic substrate.

Description

Technical Field

[0001] This invention relates to the field of electronic packaging materials technology, and in particular to a method for preparing a three-dimensional aluminum nitride ceramic substrate for chip packaging. Background Technology

[0002] Electronic packaging processes include chip mounting, electrical interconnection, and casing. For electronic packaging, the packaging substrate plays a crucial role in providing electrical connections, mechanical support, and a channel for heat dissipation between the internal and external components. Commonly used electronic packaging substrate materials mainly fall into three categories: organic polymers, metals and metal-based composites, and ceramics. Ceramic substrates, due to their high thermal conductivity, good high-temperature resistance, low coefficient of thermal expansion, and high mechanical strength, are widely used in aerospace, detection lighting, high-temperature sensing, and other fields.

[0003] For semiconductor power devices, the heat generated internally during operation is dissipated to the environment through the substrate. Therefore, the mechanical, electrical, and heat dissipation properties of the substrate are crucial to the reliability of semiconductor devices. Chinese Patent Application No. 202410675590.1 discloses a method for preparing aluminum nitride ceramic for chip packaging. The preparation method includes the following steps: 90-100 parts by weight of aluminum nitride ceramic powder, 5-6 parts of binder, 4-5 parts of sintering aid, 0.6-0.8 parts of leveling agent, 0.05-0.06 parts of rheology modifier, 0.2-0.3 parts of defoamer, and 40-50 parts of solvent are mixed by wet ball milling, followed by casting and slicing to obtain a green ceramic sheet. After debinding, the sheet is sintered to obtain an aluminum nitride ceramic for chip packaging. To prepare aluminum nitride ceramics with high thermal conductivity, the density of Al4SiC4 powder treated with sintering aids (rare earth metal oxides) and binders (aminosilane coupling agents) was increased. Oxygen atoms were minimized from dissolving into the aluminum nitride lattice, resulting in aluminum nitride ceramics that simultaneously possess high thermal conductivity and high flexural strength. However, this aluminum nitride ceramic for chip packaging lacks a three-dimensional cavity structure, making it unable to prevent corrosion and damage to the chip from external moisture, harmful gases, or dust.

[0004] Chinese Patent Application No. 202110746310.8 discloses a silicon nitride-based ceramic welding sealing component and its preparation method. The silicon nitride-based ceramic welding sealing component includes a silicon nitride ceramic substrate and a metallization layer. The silicon nitride ceramic substrate is prepared from modified silicon nitride, mullite fiber, aluminum nitride, calcium oxide, titanium oxide, binder, and dispersant raw materials through steps such as modified silicon nitride preparation, mixing, granulation, primary sintering, and secondary sintering. The metallization layer raw materials include copper powder, tungsten powder, copper oxide, yttrium oxide, zinc oxide, and an organic binder. The preparation method of the welded sealing component specifically includes the following steps: S1, ultrasonically cleaning the surface of the silicon nitride ceramic substrate with anhydrous ethanol, and then uniformly coating the surface of both ends of the ceramic substrate with metallizing paste using screen printing, wherein the printing thickness of the metallizing paste is 30-50μm; S2, sintering the prepared ceramic substrate coated with metallizing paste under vacuum or inert gas protection at a sintering temperature of 1300-1500℃ and a sintering holding time of 60-90min, thereby obtaining the silicon nitride-based ceramic welded sealing component. The silicon nitride-based ceramic welded sealing component provided by this invention improves the density of the silicon nitride ceramic substrate, has excellent strength, hardness and fracture toughness, increases the tensile strength of the sealing component, and has excellent high-temperature resistance. The preparation process of this silicon nitride-based ceramic welded sealing component uses screen printing technology, first coating the metallizing paste onto the ceramic substrate and then sintering at high temperature. However, screen printing cannot guarantee the accuracy of the pattern and cannot meet the requirements of applications with high precision requirements for the circuit layer. Summary of the Invention

[0005] Therefore, in view of the above problems, the present invention provides a method for preparing a three-dimensional aluminum nitride ceramic substrate for chip packaging, which solves the problems of poor airtightness, poor thermal stability, low reliability, and low precision of metal circuit layers in ceramic substrates prepared by the prior art.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for preparing a three-dimensional aluminum nitride ceramic substrate for chip packaging includes the following steps:

[0008] Preparation of S1 and AlN ceramic substrates: AlN, Ce2O3 and CeF3 are mixed evenly in a mass fraction ratio of 96-98wt%:1-3wt%:1wt% to obtain a first mixture. The first mixture and anhydrous ethanol are ball-milled for 5-6 hours in a solid-liquid ratio of 1:1-1.5. The mixture is then dried at 75℃ for 10-12 hours and passed through a 100-200 mesh sieve. Under a N2 atmosphere, the temperature is increased to 1700-1800℃ at a heating rate of 10℃ / min under a pressure of 30-35MPa. The mixture is then hot-pressed and sintered for 3-5 hours and then cooled to room temperature at a cooling rate of 5℃ / min to obtain the AlN ceramic substrate.

[0009] S2. Preparation of AlN ceramic substrate: A laser is used to drill holes in the AlN ceramic substrate to form a first through hole. Then, a seed layer is sputtered on the surface of the AlN ceramic substrate and the inner wall of the through hole to complete the metallization of the hole wall. Photolithography is used to form a metal line layer. The metal line layer is thickened to 50-80μm by electroplating. Then, the AlN ceramic substrate is obtained by chemical plating, film removal and etching processes.

[0010] S3. Preparation of the dam substrate: Laser drilling is performed on a copper plate to form a second through hole, and then wire cutting is performed to obtain the dam substrate;

[0011] S4. Pretreatment process: The AlN ceramic substrate and the dammed substrate are sequentially subjected to degreasing, micro-etching and acid immersion treatment, and then dried to complete the pretreatment process.

[0012] S5. Three-dimensional aluminum nitride ceramic substrate: An electroplating bonding process is used to add plating solution to the electroplating tank to connect the AlN ceramic substrate and the dammed substrate into a whole, thereby obtaining the three-dimensional aluminum nitride ceramic substrate for chip packaging.

[0013] Furthermore, the thickness of the AlN ceramic substrate is 0.5-1 mm.

[0014] Furthermore, the thickness of the copper plate is 1-3 mm.

[0015] Furthermore, the diameters of both the first and second through holes are 100-120 μm.

[0016] Furthermore, the wire cutting process uses N2 as the cutting gas, with a cutting speed of 6-8 m / min, a cutting gas pressure of 1-1.5 MPa, a cutting power of 2500-3000 W, and a cutting frequency of 4500-5000 HZ.

[0017] Furthermore, the height of the dam substrate is 700-1000 μm.

[0018] Further, the degreasing treatment is as follows: the AlN ceramic substrate and the dammed substrate are ultrasonically treated in a 5-8% H2SO4 solution for 5-10 minutes and then washed with water; the micro-etching treatment is as follows: the AlN ceramic substrate and the dammed substrate are ultrasonically treated in a micro-etching solution for 5-10 minutes and then washed with water, wherein the micro-etching solution is a mixture of Na2S2O8 and 98% concentrated sulfuric acid with a solid-liquid ratio of 8:3-5; the acid leaching treatment is as follows: the AlN ceramic substrate and the dammed substrate are ultrasonically treated in a 5-8% H2SO4 solution for 5-10 minutes and then washed with water.

[0019] Furthermore, the electroplating bonding process is as follows: dry film is attached to the lower surface of the AlN ceramic substrate and the upper surface of the dam substrate, exposing the area to be electroplated. Then, the AlN ceramic substrate and the dam substrate are aligned, clamped and fixed, and placed in the electroplating tank. Electroplating is performed by applying electricity. After electroplating is completed, the substrate is removed and the dry film is removed.

[0020] Furthermore, the plating solution comprises the following raw materials in parts by weight: 100-120 parts CuSO4, 50-60 parts H2SO4, 50-60 parts NaCl, 1-5 parts accelerator, 1-5 parts inhibitor, and 1-5 parts leveling agent; the accelerator is any one of sodium dithiopropane sulfonate, sodium thiazolinyl dithiopropane sulfonate, and sodium 3-mercapto-1-propane sulfonate; the inhibitor is any one of polyethylene glycol, polypropylene glycol, and fatty alcohol polyoxyethylene ether; and the leveling agent is nitrotetrazole blue chloride.

[0021] By adopting the aforementioned technical solution, the beneficial effects of the present invention are as follows:

[0022] 1. AlN ceramic substrates prepared by hot pressing sintering have the advantages of high thermal conductivity, good high temperature resistance, low coefficient of thermal expansion, and high mechanical strength, with thermal conductivity reaching 190 W / m. -1 ·K -1 Compared to other ceramic substrates, the coefficient of thermal expansion of AlN ceramic substrates is very similar to that of silicon with temperature, making them more suitable for chip packaging applications. Furthermore, planar AlN ceramic substrates have the advantages of high precision of metal circuit layers, controllable thickness of metal circuit layers, and the ability to be vertically interconnected with dammed substrates.

[0023] 2. Ceramic substrates are relatively hard and brittle, and traditional mechanical drilling methods can easily damage the substrates. Laser drilling technology is used to avoid damaging the substrates.

[0024] 3. Using copper as the raw material for the dam substrate has the advantages of high purity, good thermal conductivity, corrosion resistance and low cost;

[0025] 4. An electroplating bonding process is used to connect the AlN ceramic substrate and the copper dam substrate into a whole. This can be completed in three simple steps. First, the AlN ceramic substrate and the copper plate are micro-processed to form the AlN ceramic substrate and the dam substrate. Then, the two substrates are aligned and clamped together. Finally, they are immersed in an electroplating solution, and current is applied to the anode and cathode. The electroplating process is completed. Moreover, the electroplating bonding process does not easily contaminate the circuit layer during encapsulation and connection, and the bonding strength of the packaged chip is high.

[0026] 5. Electroplating and bonding form a three-dimensional ceramic substrate with a cavity structure. When packaging optoelectronic chips, it has good hermeticity, can eliminate interference from external factors, provide a stable working environment for the chip, improve device reliability and lifespan, and meet the hermetic packaging requirements of high-precision and high-reliability devices.

[0027] 6. The AlN ceramic substrate and the dammed substrate are sequentially subjected to degreasing, micro-etching and acid immersion treatments. The degreasing process can remove the oily substances adhering to the substrate; the micro-etching process can remove the copper oxide on the substrate surface, and the micro-etching process can increase the bonding strength between the electroplated copper layer and the substrate; the acid immersion process can remove the residual waste liquid on the substrate, so as to avoid affecting the composition of the base plating solution and the additive plating solution. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of the three-dimensional aluminum nitride ceramic substrate in an embodiment of the present invention;

[0029] Figure 2 This is a cross-sectional view of the three-dimensional aluminum nitride ceramic substrate in an embodiment of the present invention;

[0030] Figure 3 This is a schematic diagram of the front structure of the aluminum nitride ceramic substrate in an embodiment of the present invention.

[0031] Figure 4 This is a schematic diagram of the structure of the dam substrate in an embodiment of the present invention;

[0032] The labels in the figure are as follows: 1-AlN ceramic substrate, 2-dam substrate, 3-electroplated bonding layer, 4-first through hole, 5-second through hole, 6-metal circuit layer, 7-third through hole. Detailed Implementation

[0033] Example 1

[0034] like Figures 1 to 4 As shown, a method for preparing a three-dimensional aluminum nitride ceramic substrate for chip packaging includes the following steps:

[0035] Preparation of S1 and AlN ceramic substrates: AlN, Ce2O3 and CeF3 were mixed evenly in a mass fraction ratio of 96wt%:3wt%:1wt% to obtain a first mixture. The first mixture and anhydrous ethanol were ball-milled for 5 hours in a solid-liquid ratio of 1:1. The mixture was dried at 75°C for 10 hours and passed through a 100-mesh sieve. Under a N2 atmosphere, the pressure was set at 30MPa and the temperature was increased to 1700°C at a heating rate of 10°C / min. The mixture was hot-pressed and sintered for 3 hours and then cooled to room temperature at a cooling rate of 5°C / min to obtain the AlN ceramic substrate with a thickness of 0.5 mm.

[0036] S2. Preparation of AlN ceramic substrate: A first through hole 4 is formed on the AlN ceramic substrate by laser drilling. The diameter of the through hole is 100 μm. Then, a seed layer is sputtered on the surface of the AlN ceramic and the inner wall of the through hole to complete the metallization of the hole wall. Then, a metal line layer 6 is formed by photolithography and development. The metal line layer is thickened to 50 μm by electroplating. Then, the AlN ceramic substrate 1 is obtained by chemical plating, film removal and etching processes.

[0037] The sputtering seed layer was deposited in a vacuum magnetron sputtering coating machine with a vacuum level of 0.3 Pa. First, the magnetron sputtering power supply for the titanium target was turned on, with a sputtering power of 200 W, a sputtering pressure of 1.2 Pa, and a deposition time of 50 minutes. A high-density titanium ion stream was sputtered from the target surface and deposited on the surface of the AlN ceramic substrate and the inner walls of the through-holes to form a titanium underlayer. Then, the magnetron sputtering power supply for the copper target was turned on, with a sputtering pressure of 4 × 10⁻⁶ Pa. -2 Pa, sputtering power of 200W, deposition time of 20 minutes, copper ions form plasma in the vacuum chamber and deposit on the titanium substrate to form a copper layer, and then naturally cool to complete the metallization of the hole wall;

[0038] The photolithography and development process is as follows: I. First, the AlN ceramic substrate is photolithographically processed in a photolithography machine according to a preset pattern, with an exposure time of 120s; II. Then, a developing solution is added in a developing machine. The developing solution is tetramethylammonium hydroxide solution, and the development time is 10s.

[0039] The electroplating process is carried out in an electroplating tank, using a 1.5 mol / L copper sulfate solution as the plating bath, and a current density of 0.5 A / dm³. 2 The electroplating temperature is 50℃; the chemical plating is carried out in an electroplating bath, where a tin layer is electroplated on the surface of the metal circuit layer as a protective layer. The electroplating solution is a 1.5 mol / L stannous sulfate solution with a current density of 0.1 A / dm³. 2 The electroplating temperature is 50℃; the film removal is performed by using a 0.5mol / L NaOH solution to remove the dry film on the surface of the AlN ceramic substrate; the etching is performed by immersing the AlN ceramic substrate in a 0.5mol / L sulfuric acid solution to remove excess seed layer in non-patterned areas.

[0040] S3. Preparation of the dam substrate: Laser drilling is performed on a copper plate with a thickness of 1 mm to form a second through hole 5. Then, wire cutting is performed using N2 as the cutting gas, the cutting speed is 6 m / min, the cutting gas pressure is 1 MPa, the cutting power is 2500 W, and the cutting frequency is 4500 HZ to obtain the dam substrate 2 with a height of 700 μm.

[0041] S4. Pretreatment process: The AlN ceramic substrate and the dammed substrate are ultrasonically treated in a 5% H2SO4 solution for 5 minutes and then washed with water. Then, the AlN ceramic substrate and the dammed substrate are ultrasonically treated in a micro-etching solution for 5 minutes and then washed with water. The micro-etching solution is a mixture of Na2S2O8 and 98% concentrated sulfuric acid with a solid-liquid ratio of 8:3. Finally, the AlN ceramic substrate and the dammed substrate are ultrasonically treated in a 5% H2SO4 solution for 5 minutes and then washed with water and dried to complete the pretreatment process.

[0042] S5. Three-dimensional aluminum nitride ceramic substrate: Using an electroplating bonding process, a dry film is attached to the lower surface of the AlN ceramic substrate and the upper surface of the dammed substrate, exposing the area to be electroplated. Then, the AlN ceramic substrate and the dammed substrate are aligned, as shown below. Figure 4 As shown, the pin is inserted into the third through hole 7 around the perimeter of the dam substrate, and the entire system is clamped after positioning. After fixing, it is placed in an electroplating tank, and a plating solution is added to the electroplating tank. The plating solution includes the following raw materials by weight: 100 parts CuSO4, 50 parts H2SO4, 50 parts NaCl, 1 part sodium polydisulfide dipropane sulfonate, 1 part polyethylene glycol, and 1 part chlorinated nitrotetrazole blue. Electroplating is performed by applying an electric current to form an electroplated bonding layer 3 between the AlN ceramic substrate 1 and the dam substrate 2. After electroplating, the substrate is removed, the dry film is removed, and the AlN ceramic substrate and the dam substrate are connected as a whole to obtain the three-dimensional aluminum nitride ceramic substrate for chip packaging.

[0043] Example 2

[0044] like Figures 1 to 4 As shown, a method for fabricating a three-dimensional aluminum nitride ceramic substrate for chip packaging includes the following steps:

[0045] Preparation of S1 and AlN ceramic substrates: AlN, Ce2O3 and CeF3 were mixed evenly in a mass fraction ratio of 97wt%:2wt%:1wt% to obtain a first mixture. The first mixture and anhydrous ethanol were ball-milled for 5.5h in a solid-liquid ratio of 1:1. The mixture was dried at 75℃ for 11h and passed through a 100-mesh sieve. Under a N2 atmosphere, the pressure was set at 35MPa and the temperature was increased to 1750℃ at a heating rate of 10℃ / min. The mixture was hot-pressed and sintered for 4h and then cooled to room temperature at a cooling rate of 5℃ / min to obtain the AlN ceramic substrate with a thickness of 0.8mm.

[0046] S2. Preparation of AlN ceramic substrate: A first through hole 4 is formed by drilling holes in the AlN ceramic substrate using a laser. The diameter of the through hole is 120 μm. Then, a seed layer is sputtered on the surface of the AlN ceramic substrate and the inner wall of the through hole to complete the metallization of the hole wall. A metal line layer 6 is formed by photolithography and development. The metal line layer is thickened to 60 μm by electroplating. Then, the AlN ceramic substrate is obtained by chemical plating, film removal and etching processes.

[0047] The sputtering seed layer was deposited in a vacuum magnetron sputtering coating machine with a vacuum level of 0.3 Pa. First, the magnetron sputtering power supply for the titanium target was turned on, with a sputtering power of 200 W, a sputtering pressure of 1.2 Pa, and a deposition time of 50 minutes. A high-density titanium ion stream was sputtered from the target surface and deposited on the surface of the AlN ceramic substrate and the inner walls of the through-holes to form a titanium underlayer. Then, the magnetron sputtering power supply for the copper target was turned on, with a sputtering pressure of 4 × 10⁻⁶ Pa. -2 Pa, sputtering power of 200W, deposition time of 20 minutes, copper ions form plasma in the vacuum chamber and deposit on the titanium substrate to form a copper layer, and then naturally cool to complete the metallization of the hole wall;

[0048] The photolithography and development process is as follows: I. First, the AlN ceramic substrate is photolithographically processed in a photolithography machine according to a preset pattern, with an exposure time of 120s; II. Then, a developing solution is added in a developing machine. The developing solution is tetramethylammonium hydroxide solution, and the development time is 10s.

[0049] The electroplating process is carried out in an electroplating tank, using a 1.5 mol / L copper sulfate solution as the plating bath, and a current density of 0.5 A / dm³. 2 The electroplating temperature is 50℃; the chemical plating is carried out in an electroplating bath, where a tin layer is electroplated on the surface of the metal circuit layer as a protective layer. The electroplating solution is a 1.5 mol / L stannous sulfate solution with a current density of 0.1 A / dm³. 2 The electroplating temperature is 50℃; the film removal is performed by using a 0.5mol / L NaOH solution to remove the dry film on the surface of the AlN ceramic substrate; the etching is performed by immersing the AlN ceramic substrate in a 0.5mol / L sulfuric acid solution to remove excess seed layer in non-patterned areas.

[0050] S3. Preparation of the dam substrate: Laser drilling is performed on a 2mm thick copper plate to form a second through hole 5. Then, wire cutting is performed using N2 as the cutting gas, with a cutting speed of 7m / min, a cutting gas pressure of 1.2MPa, a cutting power of 2800W, and a cutting frequency of 4800HZ, to obtain the dam substrate with a height of 800μm.

[0051] S4. Pretreatment process: The AlN ceramic substrate and the dammed substrate are ultrasonically treated in a 6% H2SO4 solution for 8 minutes and then washed with water. Then, the AlN ceramic substrate and the dammed substrate are ultrasonically treated in a micro-etching solution for 8 minutes and then washed with water. The micro-etching solution is a mixture of Na2S2O8 and 98% concentrated sulfuric acid with a solid-liquid ratio of 8:5. Finally, the AlN ceramic substrate and the dammed substrate are ultrasonically treated in a 6% H2SO4 solution for 8 minutes and then washed with water and dried to complete the pretreatment process.

[0052] S5. Three-dimensional aluminum nitride ceramic substrate: Using an electroplating bonding process, a dry film is attached to the lower surface of the AlN ceramic substrate and the upper surface of the dammed substrate, exposing the area to be electroplated. Then, the AlN ceramic substrate and the dammed substrate are aligned, as shown below. Figure 4 As shown, the pin is inserted into the third through hole 7 around the perimeter of the dam substrate, and the entire system is clamped after positioning. After fixing, it is placed in an electroplating tank, and a plating solution is added to the electroplating tank. The plating solution includes the following raw materials by weight: 100 parts CuSO4, 50 parts H2SO4, 50 parts NaCl, 1 part sodium polydisulfide dipropane sulfonate, 1 part polyethylene glycol, and 1 part chlorinated nitrotetrazole blue. Electroplating is performed by applying an electric current to form an electroplated bonding layer 3 between the AlN ceramic substrate 1 and the dam substrate 2. After electroplating, the substrate is removed, the dry film is removed, and the AlN ceramic substrate and the dam substrate are connected as a whole to obtain the three-dimensional aluminum nitride ceramic substrate for chip packaging.

[0053] Example 3

[0054] A method for preparing a three-dimensional aluminum nitride ceramic substrate for chip packaging includes the following steps:

[0055] Preparation of S1 and AlN ceramic substrates: AlN, Ce2O3 and CeF3 were mixed evenly in a mass fraction ratio of 98wt%:1wt%:1wt% to obtain a first mixture. The first mixture and anhydrous ethanol were ball-milled for 6 hours in a solid-liquid ratio of 1:1.5. The mixture was dried at 75°C for 12 hours and passed through a 200-mesh sieve. Under a N2 atmosphere, the pressure was set at 35MPa and the temperature was increased to 1800°C at a heating rate of 10°C / min. The mixture was hot-pressed and sintered for 5 hours and then cooled to room temperature at a cooling rate of 5°C / min to obtain the AlN ceramic substrate with a thickness of 1 mm.

[0056] S2. Preparation of AlN ceramic substrate: A laser is used to drill holes in the AlN ceramic substrate to form a first through hole 4 with a diameter of 120 μm. Then, a seed layer is sputtered on the surface of the AlN ceramic substrate and the inner wall of the through hole to complete the metallization of the hole wall. Photolithography is used to form a metal line layer 6. The metal line layer is thickened to 80 μm by electroplating. Then, the AlN ceramic substrate is obtained by chemical plating, film removal and etching processes.

[0057] The sputtering seed layer was deposited in a vacuum magnetron sputtering coating machine with a vacuum level of 0.3 Pa. First, the magnetron sputtering power supply for the titanium target was turned on, with a sputtering power of 200 W, a sputtering pressure of 1.2 Pa, and a deposition time of 50 minutes. A high-density titanium ion stream was sputtered from the target surface and deposited on the surface of the AlN ceramic substrate and the inner walls of the through-holes to form a titanium underlayer. Then, the magnetron sputtering power supply for the copper target was turned on, with a sputtering pressure of 4 × 10⁻⁶ Pa. -2 Pa, sputtering power of 200W, deposition time of 20 minutes, copper ions form plasma in the vacuum chamber and deposit on the titanium substrate to form a copper layer, and then naturally cool to complete the metallization of the hole wall;

[0058] The photolithography and development process is as follows: I. First, the AlN ceramic substrate is photolithographically processed in a photolithography machine according to a preset pattern, with an exposure time of 120s; II. Then, a developing solution is added in a developing machine. The developing solution is tetramethylammonium hydroxide solution, and the development time is 10s.

[0059] The electroplating process is carried out in an electroplating tank, using a 1.5 mol / L copper sulfate solution as the plating bath, and a current density of 0.5 A / dm³. 2 The electroplating temperature is 50℃; the chemical plating is carried out in an electroplating bath, where a tin layer is electroplated on the surface of the metal circuit layer as a protective layer. The electroplating solution is a 1.5 mol / L stannous sulfate solution with a current density of 0.1 A / dm³. 2 The electroplating temperature is 50℃; the film removal is performed by using a 0.5mol / L NaOH solution to remove the dry film on the surface of the AlN ceramic substrate; the etching is performed by immersing the AlN ceramic substrate in a 0.5mol / L sulfuric acid solution to remove excess seed layer in non-patterned areas.

[0060] S3. Preparation of the dam substrate: Laser drilling is performed on a 1mm thick copper plate to form a second through hole 5. Then, wire cutting is performed using N2 as the cutting gas, with a cutting speed of 8m / min, a cutting gas pressure of 1.5MPa, a cutting power of 3000W, and a cutting frequency of 5000HZ, to obtain the dam substrate with a height of 1000μm.

[0061] S4. Pretreatment process: The AlN ceramic substrate and the dammed substrate are ultrasonically treated in an 8% H2SO4 solution for 10 minutes and then washed with water. Then, the AlN ceramic substrate and the dammed substrate are ultrasonically treated in a micro-etching solution for 10 minutes and then washed with water. The micro-etching solution is a mixture of Na2S2O8 and 98% concentrated sulfuric acid with a solid-liquid ratio of 8:5. Finally, the AlN ceramic substrate and the dammed substrate are ultrasonically treated in an 8% H2SO4 solution for 10 minutes and then washed with water and dried to complete the pretreatment process.

[0062] S5. Three-dimensional aluminum nitride ceramic substrate: Using an electroplating bonding process, a dry film is attached to the lower surface of the AlN ceramic substrate and the upper surface of the dammed substrate, exposing the area to be electroplated. Then, the AlN ceramic substrate and the dammed substrate are aligned, as shown below. Figure 4 As shown, the pin is inserted into the third through hole 7 around the perimeter of the dam substrate, and the entire system is clamped after positioning. After fixing, it is placed in an electroplating tank, and a plating solution is added to the electroplating tank. The plating solution includes the following raw materials by weight: 100 parts CuSO4, 50 parts H2SO4, 50 parts NaCl, 1 part sodium polydisulfide dipropane sulfonate, 1 part polyethylene glycol, and 1 part chlorinated nitrotetrazole blue. Electroplating is performed by applying an electric current to form an electroplated bonding layer 3 between the AlN ceramic substrate 1 and the dam substrate 2. After electroplating, the substrate is removed, the dry film is removed, and the AlN ceramic substrate and the dam substrate are connected as a whole to obtain the three-dimensional aluminum nitride ceramic substrate for chip packaging.

[0063] Although the invention has been specifically shown and described in conjunction with preferred embodiments, those skilled in the art should understand that various changes in form and detail may be made to the invention without departing from the spirit and scope of the invention as defined in the appended claims, all of which shall be within the scope of protection of the invention.

Claims

1. A method for preparing a three-dimensional aluminum nitride ceramic substrate for chip packaging, characterized in that, Includes the following steps: Preparation of S1 and AlN ceramic substrates: AlN, Ce2O3 and CeF3 are mixed evenly in a mass fraction ratio of 96-98wt%:1-3wt%:1wt% to obtain a first mixture. The first mixture and anhydrous ethanol are ball-milled for 5-6 hours in a solid-liquid ratio of 1:1-1.

5. The mixture is then dried at 75℃ for 10-12 hours and passed through a 100-200 mesh sieve. Under a N2 atmosphere, the temperature is increased to 1700-1800℃ at a heating rate of 10℃ / min under a pressure of 30-35MPa. The mixture is then hot-pressed and sintered for 3-5 hours and then cooled to room temperature at a cooling rate of 5℃ / min to obtain the AlN ceramic substrate. S2. Preparation of AlN ceramic substrate: A laser is used to drill holes in the AlN ceramic substrate to form a first through hole. Then, a seed layer is sputtered on the surface of the AlN ceramic substrate and the inner wall of the through hole to complete the metallization of the hole wall. Photolithography is used to form a metal line layer. The metal line layer is thickened to 50-80μm by electroplating. Then, AlN ceramic substrate is obtained by chemical plating, film removal and etching processes. S3. Preparation of the dam substrate: Laser drilling is performed on a copper plate to form a second through hole, and then wire cutting is performed to obtain the dam substrate. S4. Pretreatment process: The AlN ceramic substrate and the dammed substrate are sequentially subjected to degreasing, micro-etching and acid immersion treatment, and then dried to complete the pretreatment process. S5. Three-dimensional aluminum nitride ceramic substrate: An electroplating bonding process is used to add plating solution to the electroplating tank to connect the AlN ceramic substrate and the dammed substrate into a whole, thereby obtaining the three-dimensional aluminum nitride ceramic substrate for chip packaging. The electroplating bonding process is as follows: dry film is attached to the lower surface of the AlN ceramic substrate and the upper surface of the dam substrate to expose the area to be electroplated. Then, the AlN ceramic substrate and the dam substrate are aligned, clamped and fixed and placed in the electroplating tank. Electroplating is performed by applying electricity. After the electroplating is completed, the substrate is removed and the dry film is removed. The plating solution comprises the following raw materials in parts by weight: 100-120 parts CuSO4, 50-60 parts H2SO4, 50-60 parts NaCl, 1-5 parts accelerator, 1-5 parts inhibitor, and 1-5 parts leveling agent; the accelerator is any one of sodium dithiopropane sulfonate, sodium thiazolinyl dithiopropane sulfonate, and sodium 3-mercapto-1-propane sulfonate; the inhibitor is any one of polyethylene glycol, polypropylene glycol, and fatty alcohol polyoxyethylene ether; and the leveling agent is nitrotetrazole blue chloride.

2. The method for preparing a three-dimensional aluminum nitride ceramic substrate for chip packaging according to claim 1, characterized in that: The thickness of the AlN ceramic substrate is 0.5-1 mm.

3. The method for preparing a three-dimensional aluminum nitride ceramic substrate for chip packaging according to claim 1, characterized in that: The thickness of the copper plate is 1-3mm.

4. The method for preparing a three-dimensional aluminum nitride ceramic substrate for chip packaging according to claim 1, characterized in that: The diameters of both the first and second through holes are 100-120 μm.

5. The method for preparing a three-dimensional aluminum nitride ceramic substrate for chip packaging according to claim 1, characterized in that: The wire cutting process uses N2 as the cutting gas, with a cutting speed of 6-8 m / min, a cutting gas pressure of 1-1.5 MPa, a cutting power of 2500-3000 W, and a cutting frequency of 4500-5000 Hz.

6. The method for preparing a three-dimensional aluminum nitride ceramic substrate for chip packaging according to claim 1, characterized in that: The height of the dam substrate is 700-1000μm.

7. The method for preparing a three-dimensional aluminum nitride ceramic substrate for chip packaging according to claim 1, characterized in that, The degreasing treatment is as follows: the AlN ceramic substrate and the dammed substrate are ultrasonically treated in a 5-8% H2SO4 solution for 5-10 minutes and then rinsed with water; the micro-etching treatment is as follows: the AlN ceramic substrate and the dammed substrate are ultrasonically treated in a micro-etching solution for 5-10 minutes and then rinsed with water, wherein the micro-etching solution is a mixture of Na2S2O8 and 98% concentrated sulfuric acid with a solid-liquid ratio of 8:3-5; the acid leaching treatment is as follows: the AlN ceramic substrate and the dammed substrate are ultrasonically treated in a 5-8% H2SO4 solution for 5-10 minutes and then rinsed with water.

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