Preparation method of high-reliability and high-precision multilayer ceramic substrate

Abstract

The invention discloses a preparation method of a high-reliability and high-precision multilayer ceramic substrate, and relates to the technical field of multilayer ceramic substrates. The method specifically comprises the following steps that S1, ceramic micropores are machined; s2, magnetron sputtering is carried out; s3, patterning the sputtering ceramic; s4, silk-screen hole filling; s5, foil pasting and sintering; s6, carrying out metal foil image etching and alignment screen printing; s7, pre-laminating a plurality of layers of ceramic substrates; s8, secondary sintering is carried out; s9, manufacturing a DPC fine circuit on the outer layer; the advantages of AMB and DPC technologies are combined, the DPC technology and the multilayer board technology are combined, the high-precision multilayer ceramic substrate with high wiring density is achieved, and the high-precision multilayer ceramic substrate is higher in reliability, lower in cost and capable of meeting the requirement for high-density integrated circuit packaging in the future.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and particularly to a method for preparing a high-reliability and high-precision multi-layer ceramic substrate. Background Art

[0002] With the proposal and development of multi-chip packaging and microsystem packaging technologies, the application of multi-layer boards is becoming more and more extensive. The existing multi-layer ceramic substrates are mainly prepared by high-temperature co-firing HTCC process or low-temperature co-firing LTCC process. However, the thermal conductivity of LTCC products limits their use in high-power packaging modules. The traditional HTCC method for preparing multi-layer ceramic substrates is difficult, costly, and there are differences in sintering shrinkage between batches, resulting in low product consistency. In addition, the metallization of multi-layer boards is usually achieved by screen printing, but the graphic accuracy of screen printing is limited, the flatness is poor, the microwave transmission loss is large, and it is difficult to break through 30 μm for line width and line pitch. The ceramic thin film process (DPC) mainly uses photolithography, etching, deposition, etc., and has advantages such as no shrinkage and the ability to produce fine lines. It can easily achieve a 20-μm line width and line pitch, meet high-density wiring, and has a high metallization flatness and low microwave transmission loss. However, its wiring layer is limited and the multi-layer wiring is difficult. At present, there is no relevant report on high-precision multi-layer ceramic substrates prepared based on the DPC process.

[0003] In summary, to solve the above problems, it is of great significance to prepare a high-reliability and high-precision multi-layer ceramic substrate. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing a high-reliability and high-precision multi-layer ceramic substrate to solve the problems raised in the prior art.

[0005] In the first aspect of the present invention, a high-reliability and high-precision multi-layer ceramic substrate is provided, having the following technical features: including multi-layer ceramic layers, interlayer metal circuit layers, internal ceramic vias, and surface metallization layers.

[0006] Further, in the high-reliability and high-precision multi-layer ceramic substrate provided by the present invention, the multi-layer ceramic is aluminum nitride or silicon nitride ceramic, and the ceramic thickness is 0.1 - 0.5 mm;

[0007] Further, the interlayer metal circuit in the present invention can be metal foil, and the composition of the foil includes, but is not limited to, metals such as W, Mo, Nb, Ta, Cu, etc.

[0008] Further, in a highly reliable and high-precision multi-layer ceramic substrate provided by the present invention, the internal vias of the ceramic are formed by processing on the ceramic surface with a laser device. The internal vias are filled with conductive metal. The main component of the via filling metal paste for the internal vias is one or both of W and Mo, and also includes one or more of metals such as Cu, Ti, Cr, and Ni; the vias can be one or more of through vias, blind vias, and buried vias.

[0009] Further, in a highly reliable and high-precision multi-layer ceramic substrate provided by the present invention, the surface metallization layer is prepared by the DPC process, and the surface metallization layer is interconnected with the interlayer metal layer through the internal vias of the ceramic.

[0010] To achieve the above object, in the second aspect of the present invention, the following technical solutions are provided:

[0011] A method for preparing a highly reliable and high-precision multi-layer ceramic substrate includes the following steps:

[0012] S1: Micropore process the ceramic sheet to form positioning holes and internal vias; clean to obtain ceramic sheet A;

[0013] S2: Sequentially perform ion bombardment cleaning and surface sputtering of a metal layer on the surface of ceramic sheet A to obtain a single-sided ceramic sheet and a double-sided ceramic sheet;

[0014] S3: Perform sputtering ceramic patterning on the metal layers of the single-sided ceramic sheet and the double-sided ceramic sheet to obtain a patterned single-sided ceramic sheet and a patterned double-sided ceramic sheet;

[0015] S4: Perform alignment screen printing and filling of the vias on the patterned single-sided ceramic sheet and the patterned double-sided ceramic sheet, and dry to obtain an outer layer ceramic sheet and an intermediate ceramic sheet A respectively;

[0016] S5: Double-sidedly attach metal foil to some of the intermediate ceramic sheets A, perform high-temperature sintering and cooling; obtain a metal-foil-attached intermediate ceramic sheet A;

[0017] S6: Perform metal foil pattern etching and alignment screen printing of dielectric paste on the surface of the metal-foil-attached intermediate ceramic sheet A; obtain an intermediate ceramic sheet B;

[0018] S7: Align and install the outer layer ceramic sheet, the intermediate ceramic sheet A, and the intermediate ceramic sheet B using the positioning holes to form a stacked structure; obtain a pre-stacked multi-layer ceramic substrate;

[0019] S8: Perform secondary sintering and cooling on the pre-stacked multi-layer ceramic substrate to obtain a basic multi-layer ceramic substrate;

[0020] S9: Grind and polish the surface of the basic multi-layer ceramic substrate and perform DPC fine circuit manufacturing to obtain a high-precision multi-layer ceramic substrate.

[0021] More preferably, in step S7, in the stacked structure of the pre-stacked multi-layer ceramic substrate: outer ceramic chips are provided on both sides of the outermost layer of the multi-layer ceramic substrate; in the middle part of the multi-layer ceramic substrate, intermediate ceramic chip A is provided in the odd-numbered layers, and intermediate ceramic chip B is provided in the even-numbered layers; the number of stacked intermediate ceramic layers in the multi-layer ceramic substrate is odd.

[0022] More preferably, in step S2, during the ion bombardment cleaning process, the specific process conditions are as follows: the vacuum degree is 20-1200 Pa, the argon pressure is 0.2-1 Pa, the voltage is 0.6-0.8 KV, and the cleaning time is 180-300 seconds;

[0023] During the sputtering process, it is magnetron sputtering, and the specific process conditions are as follows: the vacuum degree of the furnace chamber is 10 -4 ~10 -3 Pa, the argon pressure is 0.2-1 Pa, the sputtering power is 15-25 KW, the voltage is 500-800 V, the time is 60-180 min, and the temperature is 200-300 °C.

[0024] More preferably, in step S5, during the high-temperature sintering process, the specific process is as follows: the temperature is 900-1500 °C, the heat preservation time is 20-90 min, the vacuum degree in the furnace is <0.01 Pa, and the pressure is 10-30 Mpa;

[0025] In step S8, during the secondary sintering process, the specific process is as follows: the temperature is 900-1500 °C, the heat preservation time is 20-90 min, the vacuum degree in the furnace is <0.01 Pa, and the pressure is 10-30 Mpa.

[0026] More preferably, in step S2, the thickness of the metal layer is 0.5-5 μm; the metal layer includes an active metal layer and other metal layers, and the active metal layer is on the side close to the ceramic; the active metal layer includes one of titanium and zirconium; the other metal layer includes one or more of copper, nickel, and silver;

[0027] In step S5, the metal foil includes one of tungsten foil, molybdenum foil, tungsten-molybdenum foil, molybdenum-copper foil, tungsten-copper foil tantalum foil, and niobium foil, and the thickness is 5-30 μm;

[0028] In step S7, the dielectric paste includes one of an insulating paste and a functional paste.

[0029] More preferably, in step S4, during the alignment screen printing and hole filling process, the paste used is a metal paste;

[0030] The metal paste comprises the following raw materials by mass parts: 85 to 92 parts of metal powder and 8 to 15 parts of organic matter; the metal powder comprises infusible metal powder and fusible metal powder with a mass ratio of 16:3 to 4; the infusible metal powder comprises one or more of tungsten powder, molybdenum powder, and tungsten-molybdenum powder; the fusible metal powder comprises one or more of copper powder, silver powder, and nickel powder; the organic matter is a terpineol system.

[0031] Among them, the terpineol system comprises the following raw materials by mass fraction: 60 to 85% of terpineol, 5 to 15% of ethyl cellulose, 2 to 4% of acrylic resin, 2 to 4% of hydrogenated castor oil, 2 to 6% of KH550, 2 to 5% of tributyl citrate, and 0.5% to 1.5% of BYK-111.

[0032] Among them, the metal paste is different from the existing commercial pastes, does not contain inorganic phase, oxides, glass phase, etc., and is dried using an oven after ceramic hole filling is completed.

[0033] More preferably, the metal paste comprises the following raw materials by mass parts: 85 to 92 parts of metal powder, 14 to 16 parts of water-based binder, and 0.3 to 0.5 part of defoamer RJ-6501; the metal powder comprises the following raw materials by mass parts: 14 to 15 parts of silver-coated copper powder and 70 to 76 parts of tungsten powder.

[0034] More preferably, the water-based binder comprises the following raw materials by mass parts: 13 to 14 parts of modified polyacrylic resin aqueous solution and 1 to 2 parts of hydroxyethyl cellulose.

[0035] More preferably, the preparation method of the modified polyacrylic resin aqueous solution comprises the following steps: (1) Add sodium dodecyl sulfonate and alkylphenol polyoxyethylene ether to deionized water and stir evenly, then add methyl methacrylate, butyl acrylate, acrylic acid, and acrylamide, and stir evenly at 150 to 160 r / min to obtain a monomer emulsion;

[0036] (2) Add the monomer emulsion and 0.1 to 0.2 part of ammonium persulfate to the reaction kettle, stir at 75 to 80 °C for 50 to 70 min, dropwise add the monomer emulsion and ammonium persulfate, control the dropping time to be 2 to 3 h, after dropping is completed, stir at 85 to 90 °C for 1 to 1.5 h, adjust the pH to 6 to 8, filter to obtain a filtrate, and add water to dilute to a solid content of 60% to obtain a water-based polyacrylic resin aqueous solution;

[0037] (3) Add ferrocene amine to the water-based polyacrylic resin aqueous solution and stir evenly, add an activator, and stir at 50 to 60 °C for 3 to 5 h to obtain a modified polyacrylic resin aqueous solution.

[0038] More preferably, the monomer emulsion comprises the following raw materials in parts by mass: 2-3 parts of sodium dodecyl sulfonate, 1-2 parts of alkylphenol polyoxyethylene ether, 40-45 parts of deionized water, 8-10 parts of acrylic acid, and 2-4 parts of acrylamide;

[0039] The aqueous polyacrylic resin solution comprises the following raw materials in parts by mass: 96-104 parts of monomer emulsion, and 0.5-0.7 parts of ammonium persulfate;

[0040] The modified polyacrylic resin solution comprises the following raw materials in parts by mass: 2-3 parts of aminoferrocene, 100 parts of aqueous polyacrylic resin solution, and 1-2 parts of activator.

[0041] Compared with the prior art, the beneficial effects of the present application are as follows:

[0042] (1) The multi-layer ceramic substrate prepared by the present invention uses well-performing fired ceramic chips instead of the green ceramic chips used in traditional HTCC. There is no problem of different shrinkage rates of different batches of HTCC, and the sintering shrinkage can be ignored, resulting in a high yield. Compared with the generally thinner green body of HTCC, the present invention can select appropriate number of layers and ceramic chip thickness according to product requirements, with a wide range of ceramic chip selection, and the number of layers can be appropriately reduced, reducing the process difficulty and production cost.

[0043] (2) The connection between layers of the multi-layer ceramic substrate prepared by the present invention is based on the principle of active metal brazing. The method of active metal brazing + metal foil makes the brazing layer between ceramics continuous, uniform and dense, with firm bonding and higher airtightness; the interlayer metal foil neither melts nor shrinks during the sintering process, so the graphic resistance has high controllability; in addition, when the fired ceramic chips are sintered at high temperature, the ceramic grains will grow synchronously, and the glass phase in the ceramic will soften at high temperature and undergo viscous flow under the dual action of external load, thereby reducing the porosity inside the ceramic and reducing ceramic defects, improving the airtightness and reliability of the multi-layer ceramic substrate.

[0044] (3) The graphic circuit of the multi-layer ceramic board prepared by the present invention is made by thin film etching process and DPC process, with higher graphic accuracy and larger wiring density compared with the traditional HTCC screen printing, and is more in line with the requirements of future high-density integrated circuit packaging.

[0045] (4) The present invention also provides an aqueous metal paste, which mainly comprises an aqueous solution of aqueous polyacrylic resin with water as the solvent. The combination of the traditional terpineol system and metal powder is accompanied by strong volatilization of organic substances during the drying process, which will cause irritation to the human body or the environment. By preparing the aqueous polyacrylic resin, the present invention can provide good adhesive properties without introducing low-melting metals or glass phases, thereby improving conductivity. In the preparation process of the present invention, acrylamide is introduced to participate in copolymerization, which helps to improve the wettability to ceramics and the dispersibility of the system. Further, ferrocene is grafted onto the aqueous polyacrylic resin. During the subsequent vacuum sintering process, organic substances can be used as a carbon source to promote the graphitization of carbon, improving the densification and conductivity after sintering. At the same time, in the selection of metal powders, a compound of silver-coated copper and tungsten powder is selected: on the one hand, it is difficult for copper to contact the outside world after being wrapped, which helps to reduce the oxidation of copper; on the other hand, the introduction of a small amount of silver helps to further optimize the conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 is a process flow chart of the present invention;

[0047] Figure 2 is a schematic cross-sectional view of the multi-layer ceramic substrate structure of Example 1 of the present invention;

[0048] Figure 3 is a schematic cross-sectional view of the single-layer structure of Example 1 of the present invention;

[0049] Among them, Figure 2 01, 03, and 05 in are single-layer ceramics, 02 and 04 are double-layer ceramics, and 06 is a fine circuit prepared by the DPC process on the surface of the multi-layer board; Figure 3 In, 02 is a double-layer ceramic, 021 is a via filled with paste, 022 is a graphic circuit after etching of the metal foil, and 023 is a screen-printed dielectric paste DETAILED DESCRIPTION OF THE EMBODIMENTS

[0050] Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0051] It should be noted that there are no special restrictions on the purchase manufacturers of all raw materials involved in the present invention, and they exemplarily include: aluminum nitride ceramics with a thickness of 0.3 mm; tungsten powder with a particle size of 5 to 10 μm; copper powder with a particle size of 5 to 10 μm; silver-coated copper powder with a silver content of 15 wt% and a particle size of 5 to 10 μm, provided by Chengdu Nuclear 857 New Materials Co., Ltd.; tungsten foil with a thickness of 15 μm; CAS number of methyl methacrylate: 80-62-6; CAS number of acrylic acid: 79-10-7; CAS number of acrylamide: 79-06-1; CAS number of aminoferrocene: 1273-82-1.

[0052] In the following examples, parts are by mass, and the raw materials mentioned above and used but not mentioned below are all commercially available.

[0053] Example 1: The preparation of a high-precision multilayer ceramic substrate comprises the following steps:

[0054] S1: using a laser drilling device to perform drilling processing on aluminum nitride ceramics to form positioning holes and internal vias; cleaning the drilled ceramics to remove slag at the edges of the micropores to obtain a ceramic sheet A;

[0055] S2: The surface of the ceramic sheet A is sequentially subjected to ion bombardment cleaning and magnetron sputtering to deposit a metal layer; the outermost two ceramic sheets are sputtered on one side to obtain a single-sided ceramic sheet; the rest are sputtered on both sides to obtain a double-sided ceramic sheet; the sputtered metal layer is divided into two layers, the copper layer is sputtered first, and the titanium layer is sputtered later; the sputtering vacuum is 10 -4 Pa, argon pressure is 0.2Pa; titanium target sputtering power is 8KW, sputtering time is 30min; copper target sputtering power is 15KW, sputtering time is 100min, sputtering temperature is 240℃;

[0056] S3: performing sputtering ceramic patterning processing on the metal layer of the single-sided ceramic sheet and the double-sided ceramic sheet: exposing and developing the film, etching out fine circuit patterns; obtaining a patterned single-sided ceramic sheet and a patterned double-sided ceramic sheet;

[0057] S4: performing screen printing of hole-filling metal slurry on the patterned single-sided ceramic sheet and the patterned double-sided ceramic sheet, and drying the same at a temperature of 120° C. for 15 min; and obtaining an outer layer ceramic sheet and an intermediate ceramic sheet A accordingly;

[0058] S5: attaching metal foils to both sides of the middle ceramic sheet A located in an even number of layers in the multilayer board, sintering at high temperature, and cooling down; the metal foil is a rolled tungsten foil; the sintering temperature is 1150°C, the heat preservation time is 30min, the vacuum degree in the furnace is <0.01Pa, and the pressure is 10Mpa; and the foil-attached middle ceramic sheet A is obtained;

[0059] S6: Etch the surface of the middle ceramic sheet A of the foil sticker: Apply a film, expose it, develop it, and etch out the required corresponding pattern; Align and screen-print the dielectric paste: Align and screen-print the dielectric paste in the gaps of the graphic circuit and dry it. The model of the dielectric paste is 07HD290; The drying temperature is 100 °C and the time is 15 min; Obtain the middle ceramic sheet B;

[0060] S7: Align and install the outer porcelain sheet, the middle ceramic sheet A, and the middle ceramic sheet B using the positioning holes to form a laminated structure: The outer porcelain sheets are arranged on both sides of the outermost layer of the multi-layer ceramic substrate; In the middle part of the multi-layer ceramic substrate, the middle ceramic sheet A is arranged in the odd-numbered layers and the middle ceramic sheet B is arranged in the even-numbered layers; The number of laminated layers of the middle ceramic layer in the multi-layer ceramic substrate is 3; Obtain the pre-laminated multi-layer ceramic substrate;

[0061] S8: Sinter the pre-laminated multi-layer ceramic substrate for the second time and cool it down; The sintering temperature is 1100 °C, the heat preservation time is 40 min, the vacuum degree in the furnace is <0.01 Pa, and the pressure is 15 Mpa; Obtain the basic multi-layer ceramic substrate;

[0062] S9: Grind and polish the surface of the basic multi-layer ceramic substrate; Use the DPC process to prepare high-density circuits on the surface of the multi-layer ceramic substrate to obtain a high-precision multi-layer ceramic substrate.

[0063] Among them, the metal paste includes the following raw materials, by mass: 89 parts of metal powder, 11 parts of organic matter; The metal powder includes tungsten powder and copper powder with a mass ratio of 16:3; The organic matter is a terpineol system.

[0064] Example 2: The preparation of the high-precision multi-layer ceramic substrate includes the following steps:

[0065] Step 1: Preparation of modified polyacrylic acid: (1) Add 2.5 parts of sodium dodecyl sulfonate and 1.5 parts of alkylphenol polyoxyethylene ether to 40 parts of deionized water, stir evenly, add 50 parts of methyl methacrylate, 34 parts of butyl acrylate, 9 parts of acrylic acid, and 3 parts of acrylamide, and stir evenly at 150-160 r / min to obtain a monomer emulsion;

[0066] (2) Add 30 parts of the monomer emulsion and 0.15 parts of ammonium persulfate to the reaction kettle, stir at 80 °C for 60 min, dropwise add 70 parts of the monomer emulsion and 0.5 parts of ammonium persulfate, control the dropping time to 2.5 h, after the dropping is completed, stir at 90 °C for 1.5 h, adjust the pH to 7.5, filter to obtain the filtrate, and dilute it with water to a solid content of 60% to obtain an aqueous polyacrylic acid resin aqueous solution;

[0067] (3) Add 2.5 parts of aminoferrocene to 100 parts of the aqueous polyacrylic acid resin aqueous solution, stir evenly, add 1.5 parts of the activator, and stir at 55 °C for 4 h to obtain a modified polyacrylic acid resin aqueous solution.

[0068] Step 2: S1: Use a laser drilling device to drill holes in the aluminum nitride ceramic to form positioning holes and internal vias; clean the drilled ceramic to remove the slag at the edges of the micro-holes, and obtain ceramic sheet A;

[0069] S2: Clean the surface of ceramic sheet A by ion bombardment and deposit a metal layer by magnetron sputtering in sequence; for the outermost two ceramic sheets, single-sided sputtering is performed to obtain single-sided ceramic sheets; for the rest, double-sided sputtering is performed to obtain double-sided ceramic sheets; the sputtered metal layer is divided into two layers, first sputter the copper layer and then sputter the titanium layer; the sputtering vacuum degree is 10 -4 Pa, the argon pressure is 0.2 Pa; the sputtering power of the titanium target is 8 KW, and the sputtering time is 30 min; the sputtering power of the copper target is 15 KW, the sputtering time is 100 min, and the sputtering temperature is 240 °C;

[0070] S3: Perform sputtering ceramic patterning on the metal layers of the single-sided ceramic sheets and double-sided ceramic sheets: laminate, expose, develop, and etch out fine circuit patterns; obtain patterned single-sided ceramic sheets and patterned double-sided ceramic sheets;

[0071] S4: Screen-print and fill the via hole metal paste on the patterned single-sided ceramic sheets and patterned double-sided ceramic sheets, and dry it. The drying temperature is 120 °C and the drying time is 15 min; correspondingly obtain outer ceramic sheets and intermediate ceramic sheet A;

[0072] S5: Double-sidedly attach metal foils to the intermediate ceramic sheet A located in the even layers of the multi-layer board, sinter at high temperature and cool down; the metal foil is tungsten foil after rolling; the sintering temperature is 1150 °C, the heat preservation time is 30 min, the vacuum degree in the furnace < 0.01 Pa, and the pressure is 10 Mpa; obtain the intermediate ceramic sheet A with attached foils;

[0073] S6: Etch the metal foil pattern on the surface of the intermediate ceramic sheet A with attached foils: laminate, expose, develop, and etch out the required corresponding patterns; screen-print the dielectric paste in alignment: screen-print the dielectric paste in alignment in the gaps of the graphic circuits and dry it. The dielectric paste model is 07HD290; the drying temperature is 100 °C and the time is 15 min; obtain intermediate ceramic sheet B;

[0074] S7: Install the outer ceramic sheets, intermediate ceramic sheet A, and intermediate ceramic sheet B in alignment using the positioning holes to form a stacked structure: the outermost two sides of the multi-layer ceramic substrate are provided with outer ceramic sheets; in the middle part of the multi-layer ceramic substrate, intermediate ceramic sheet A is provided in the odd layers and intermediate ceramic sheet B is provided in the even layers; the number of stacked intermediate ceramic layers in the multi-layer ceramic substrate is 3; obtain a pre-stacked multi-layer ceramic substrate;

[0075] S8: Secondary sintering and cooling of the pre-laminated multi-layer ceramic substrate; the sintering temperature is 1100 °C, the heat preservation time is 40 min, the vacuum degree in the furnace is <0.01 Pa, and the pressure is 15 Mpa; the basic multi-layer ceramic substrate is obtained;

[0076] S9: Grind and polish the surface of the basic multi-layer ceramic substrate; use the DPC process to prepare high-density circuits on the surface of the multi-layer ceramic substrate to obtain a high-precision multi-layer ceramic substrate.

[0077] Among them, the metal paste includes the following raw materials, by mass: 89 parts of metal powder, 15 parts of water-based binder, and 0.4 part of defoaming agent RJ-6501; the metal powder includes tungsten powder and copper powder with a mass ratio of 16:3.

[0078] Example 3: The preparation of the high-precision multi-layer ceramic substrate includes the following steps:

[0079] Step 1: Preparation of modified polyacrylic acid: (1) Add 2.5 parts of sodium dodecyl sulfonate and 1.5 parts of alkylphenol polyoxyethylene ether to 40 parts of deionized water, stir evenly, add 50 parts of methyl methacrylate, 34 parts of butyl acrylate, 9 parts of acrylic acid, and 3 parts of acrylamide, and stir evenly at 150-160 r / min to obtain a monomer emulsion;

[0080] (2) Add 30 parts of the monomer emulsion and 0.15 part of ammonium persulfate to the reaction kettle, stir at 80 °C for 60 min, dropwise add 70 parts of the monomer emulsion and 0.5 part of ammonium persulfate, control the dropping time to 2.5 h, after the dropping is completed, stir at 90 °C for 1.5 h, adjust the pH to 7.5, filter to obtain a filtrate, and dilute with water to a solid content of 60% to obtain an aqueous polyacrylic acid resin aqueous solution;

[0081] (3) Add 2.5 parts of aminoferrocene to 100 parts of the aqueous polyacrylic acid resin aqueous solution, stir evenly, add 1.5 parts of activator, and stir at 55 °C for 4 h to obtain a modified polyacrylic acid resin aqueous solution.

[0082] Step 2: S1: Use a laser drilling device to drill the aluminum nitride ceramic to form positioning holes and internal vias; clean the drilled ceramic to remove the slag at the edges of the micropores to obtain ceramic piece A;

[0083] S2: The surface of ceramic piece A is sequentially subjected to ion bombardment cleaning and magnetron sputtering deposition of a metal layer; the outermost two ceramic pieces are sputtered on one side to obtain a single-sided ceramic piece; the rest are sputtered on both sides to obtain a double-sided ceramic piece; the sputtered metal layer is divided into two layers, first sputter the copper layer, and then sputter the titanium layer; the sputtering vacuum degree is 10 -4Pa, the argon pressure is 0.2 Pa; the sputtering power of the titanium target is 8 KW, and the sputtering time is 30 min; the sputtering power of the copper target is 15 KW, the sputtering time is 100 min, and the sputtering temperature is 240 °C;

[0084] S3: Perform sputtering ceramic patterning on the metal layers of the single-sided ceramic sheet and the double-sided ceramic sheet: laminate, expose, develop, and etch out the fine circuit pattern; obtain the patterned single-sided ceramic sheet and the patterned double-sided ceramic sheet;

[0085] S4: Perform alignment screen printing to fill the hole metal paste on the patterned single-sided ceramic sheet and the patterned double-sided ceramic sheet, and dry it. The drying temperature is 120 °C, and the drying time is 15 min; correspondingly obtain the outer ceramic sheet and the intermediate ceramic sheet A;

[0086] S5: Double-sidedly attach the intermediate ceramic sheet A located in the even layers of the multi-layer board with metal foil, sinter at high temperature and cool down; the metal foil is the rolled tungsten foil; the sintering temperature is 1150 °C, the holding time is 30 min, the vacuum degree in the furnace < 0.01 Pa, and the pressure is 10 Mpa; obtain the intermediate ceramic sheet A with attached foil;

[0087] S6: Etch the metal foil pattern on the surface of the intermediate ceramic sheet A with attached foil: laminate, expose, develop, and etch out the required corresponding pattern; perform alignment screen printing of the dielectric paste: perform alignment screen printing of the dielectric paste in the gaps of the graphic circuit and dry it. The model of the dielectric paste is 07HD290; the drying temperature is 100 °C, and the time is 15 min; obtain the intermediate ceramic sheet B;

[0088] S7: Align and install the outer ceramic sheet, the intermediate ceramic sheet A, and the intermediate ceramic sheet B using the positioning holes to form a laminated structure: the outer ceramic sheets are arranged on both sides of the outermost layer of the multi-layer ceramic substrate; in the middle part of the multi-layer ceramic substrate, the intermediate ceramic sheet A is arranged in the odd layers, and the intermediate ceramic sheet B is arranged in the even layers; the number of laminated intermediate ceramic layers in the multi-layer ceramic substrate is 3; obtain the pre-laminated multi-layer ceramic substrate;

[0089] S8: Perform secondary sintering and cooling on the pre-laminated multi-layer ceramic substrate; the sintering temperature is 1100 °C, the holding time is 40 min, the vacuum degree in the furnace < 0.01 Pa, and the pressure is 15 Mpa; obtain the basic multi-layer ceramic substrate;

[0090] S9: Grind and polish the surface of the basic multi-layer ceramic substrate; use the DPC process to prepare a high-density circuit on the surface of the multi-layer ceramic substrate to obtain a high-precision multi-layer ceramic substrate.

[0091] Among them, the metal paste includes the following raw materials, by mass: 89 parts of metal powder, 14 - 16 parts of water-based binder, and 0.4 part of defoaming agent RJ-6501; the metal powder includes the following substances by mass: 15 parts of silver-coated copper powder and 74 parts of tungsten powder.

[0092] Performance test: The samples prepared according to the methods of the respective embodiments were tested for resistance at the through-holes, and the experimental data are as described in Table 1.

[0093] Table 1

[0094] Item Resistance / mΩ Example 1 296.1 Example 2 270.9 Example 3 265.3

[0095] Conclusion: As can be seen from Table 1, compared with Example 1, the water-based adhesive prepared was used in Example 2, and it can be seen that there is still good resistance, and due to the graphitization of carbon, the resistance decreases; compared with Example 2, copper powder was replaced with silver-coated copper powder in Example 3, which also has a certain improvement in reducing the resistance.

[0096] In summary, by combining the advantages of the AMB and DPC processes, the DPC process is combined with the multi-layer board technology to achieve a high-precision multi-layer ceramic substrate with a high wiring density. The products of the present invention have higher reliability and lower cost, can meet the requirements of future high-density integrated circuit packaging, and provide a water-based metal paste for through-hole metal filling, reducing the resistivity.

[0097] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of a high-reliability and high-precision multi-layer ceramic substrate, characterized in that, It includes the following steps: S1: Micro-machine the ceramic sheet to form positioning holes and internal vias; clean it to obtain ceramic sheet A. S2: Sequentially perform ion bombardment cleaning and surface sputtering of a metal layer on the surface of ceramic sheet A to obtain a single-sided ceramic sheet and a double-sided ceramic sheet. S3: Perform sputtering ceramic patterning on the metal layers of the single-sided ceramic sheet and the double-sided ceramic sheet to obtain a patterned single-sided ceramic sheet and a patterned double-sided ceramic sheet. S4: Perform alignment screen printing and hole filling on the patterned single-sided ceramic sheet and the patterned double-sided ceramic sheet, and dry it to obtain an outer ceramic sheet and an intermediate ceramic sheet A respectively. S5: Double-sidedly attach metal foil to part of the intermediate ceramic sheet A, perform high-temperature sintering and cooling; obtain a foil-attached intermediate ceramic sheet A. S6: Perform metal foil pattern etching and alignment screen printing of dielectric paste on the surface of the foil-attached intermediate ceramic sheet A; obtain intermediate ceramic sheet B. S7: Align and install the outer ceramic sheet, intermediate ceramic sheet A, and intermediate ceramic sheet B using the positioning holes to form a stacked structure; obtain a pre-stacked multi-layer ceramic substrate. S8: Perform secondary sintering and cooling on the pre-stacked multi-layer ceramic substrate to obtain a basic multi-layer ceramic substrate. S9: Grind and polish the surface of the basic multi-layer ceramic substrate and fabricate fine DPC circuits to obtain a high-precision multi-layer ceramic substrate.

2. The preparation method of a highly reliable and high-precision multi-layer ceramic substrate according to claim 1, characterized in that: In step S7, in the stacked structure of the pre-stacked multi-layer ceramic substrate: outer ceramic sheets are provided on both sides of the outermost layer of the multi-layer ceramic substrate; in the middle part of the multi-layer ceramic substrate, intermediate ceramic sheet A is provided on the odd-numbered layers, and intermediate ceramic sheet B is provided on the even-numbered layers; the number of stacked intermediate ceramic layers in the multi-layer ceramic substrate is odd.

3. The preparation method of a highly reliable and high-precision multi-layer ceramic substrate according to claim 1, characterized in that: In step S2, during the ion bombardment cleaning process, the specific process conditions are as follows: the vacuum degree is 20 - 1200 Pa, the argon gas pressure is 0.2 - 1 Pa, the voltage is 0.6 - 0.8 KV, and the cleaning time is 180 - 300 seconds. During the sputtering process, it is magnetron sputtering, and the specific process conditions are as follows: the vacuum degree of the furnace cavity is 10 -4 ~10 -3 Pa, the argon gas pressure is 0.2 - 1 Pa, the sputtering power is 15 - 25 KW, the voltage is 500 - 800 V, the time is 60 - 180 min, and the temperature is 200 - 300 °C.

4. The preparation method of a highly reliable and high-precision multi-layer ceramic substrate according to claim 1, characterized in that: In step S5, during the high-temperature sintering process, the specific process is as follows: the temperature is 900 - 1500 °C, the holding time is 20 - 90 min, the in-furnace vacuum degree < 0.01 Pa, and the pressure is 10 - 30 Mpa. In step S8, during the secondary sintering process, the specific process is as follows: the temperature is 900 - 1500 °C, the holding time is 20 - 90 min, the in-furnace vacuum degree < 0.01 Pa, and the pressure is 10 - 30 Mpa.

5. The preparation method of a highly reliable and high-precision multi-layer ceramic substrate according to claim 1, characterized in that: In step S2, the thickness of the metal layer is 0.5 - 5 μm; the metal layer includes an active metal layer and other metal layers, with the active metal layer adjacent to the ceramic side; the active metal layer includes one of titanium and zirconium; the other metal layer includes one or more of copper, nickel, and silver. In step S5, the metal foil includes one of tungsten foil, molybdenum foil, tungsten-molybdenum foil, molybdenum-copper foil, and tungsten-copper foil, and the thickness is 5 - 30 μm. In step S7, the dielectric paste includes one of an insulating paste and a functional paste.

6. The preparation method of a highly reliable and high-precision multi-layer ceramic substrate according to claim 1, characterized in that: In step S4, during the alignment screen printing and hole filling process, the paste used is a metal paste. The metal paste comprises the following raw materials by mass: 85 to 92 parts of metal powder and 8 to 15 parts of organic matter; the metal powder comprises infusible metal powder and fusible metal powder with a mass ratio of 16:3 to 4; the infusible metal powder comprises one or more of tungsten powder, molybdenum powder, and tungsten-molybdenum powder; the fusible metal powder comprises one or more of copper powder, silver powder, and nickel powder; the organic matter is a terpineol system.

7. The preparation method of a highly reliable and high-precision multi-layer ceramic substrate according to claim 6, characterized in that: The metal paste comprises the following raw materials by mass: 85 to 92 parts of metal powder, 14 to 16 parts of a water-based binder, and 0.3 to 0.5 part of defoamer RJ-6501; the metal powder comprises the following raw materials by mass: 14 to 15 parts of silver-coated copper powder and 70 to 76 parts of tungsten powder.

8. The preparation method of a highly reliable and high-precision multi-layer ceramic substrate according to claim 7, characterized in that: The water-based binder comprises the following raw materials by mass: 13 to 14 parts of a modified polyacrylic resin aqueous solution and 1 to 2 parts of hydroxyethyl cellulose.

9. The preparation method of a highly reliable and high-precision multi-layer ceramic substrate according to claim 8, characterized in that: The preparation method of the modified polyacrylic resin aqueous solution comprises the following steps: (1) Add sodium dodecyl sulfonate and alkylphenol polyoxyethylene ether to deionized water, stir evenly, add methyl methacrylate, butyl acrylate, acrylic acid, and acrylamide, and stir evenly at 150 to 160 r / min to obtain a monomer emulsion; (2) Add the monomer emulsion and 0.1 to 0.2 part of ammonium persulfate to a reaction kettle, stir at 75 to 80 °C for 50 to 70 min, dropwise add the monomer emulsion and ammonium persulfate, control the dropping time to be 2 to 3 h, after the dropping is completed, stir at 85 to 90 °C for 1 to 1.5 h, adjust the pH to 6 to 8, filter to obtain a filtrate, and add water to dilute to a solid content of 60% to obtain a water-based polyacrylic resin aqueous solution; (3) Add ferrocenylamine to the water-based polyacrylic resin aqueous solution, stir evenly, add an activator, and stir at 50 to 60 °C for 3 to 5 h to obtain a modified polyacrylic resin aqueous solution.

10. The preparation method of a highly reliable and high-precision multi-layer ceramic substrate according to claim 9, wherein: The monomer emulsion comprises the following raw materials by mass: 2 to 3 parts of sodium dodecyl sulfonate, 1 to 2 parts of alkylphenol polyoxyethylene ether, 40 to 45 parts of deionized water, 8 to 10 parts of acrylic acid, and 2 to 4 parts of acrylamide; The water-based polyacrylic resin aqueous solution comprises the following raw materials by mass: 96 to 104 parts of the monomer emulsion and 0.5 to 0.7 part of ammonium persulfate; The modified polyacrylic resin aqueous solution comprises the following raw materials by mass: 2 to 3 parts of ferrocenylamine, 100 parts of the water-based polyacrylic resin aqueous solution, and 1 to 2 parts of an activator.

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