A kind of silver via filling conductor paste for high thermal expansion coefficient LTCC green tape co-firing

Abstract

This invention discloses a via-filling conductor paste for high thermal expansion coefficient LTCC green tape and its preparation method. The paste comprises: I: Inorganic components, containing 80-90 wt% Ag silver powder, 1.0-3.0 wt% inorganic oxide or ceramic powder, and 2.0-5.0 wt% high thermal expansion coefficient glass powder. The inorganic oxide is one or a mixture of several of Al, Si, Cu, Ti, and Zr, and the ceramic powder is one or a combination of two of quartz or cordierite; II: 20-10 wt% organic carrier. This via-filling paste is specifically designed for via filling of high thermal expansion coefficient LTCC substrates, exhibiting excellent substrate compatibility and perfectly solving the problems of cracking around vias and interconnect failure after multiple temperature cycles, greatly improving the reliability of electronic packaging.

Description

Technical Field

[0001] This invention belongs to the field of electronic packaging materials, specifically relating to a silver through-hole filling conductor paste for co-firing green tape of low temperature co-fired ceramics (LTCC) with high thermal expansion coefficient and its preparation method. Background Technology

[0002] Low-temperature co-fired ceramic (LTCC) technology has been widely used in high-end electronic packaging fields such as microwave RF, automotive electronics, and aerospace due to its advantages such as high integration, excellent high-frequency transmission characteristics, and multilayer wiring capabilities. In recent years, with the increasing demand for high coefficient of thermal expansion (High CTE) substrates in specific semiconductor packaging and heterogeneous integration scenarios, developing high-reliability co-fired metal conductor materials that can match the high CTE LTCC ceramic raw materials has become a core issue in this field.

[0003] Currently, while existing technologies have developed matching surface wiring silver conductor pastes for LTCC substrates with high thermal expansion coefficients, effectively addressing the conductivity and adhesion issues of lateral (XY axis) wiring on ceramic surfaces, these surface wiring conductor pastes cannot be directly applied to longitudinal (Z axis) via-filling processes. The core mechanism flaw lies in: First, the inorganic solid content of surface wiring paste is usually low (generally less than 75 wt%), while the glass phase content used to assist surface anchoring is relatively high (usually 8-22 parts). If it is directly filled into 3D vias with a depth of tens to hundreds of micrometers, the large amount of organic matter volatilization and excessive glass melting during co-firing will cause severe volume collapse and sinking in the Z-axis direction, which can easily lead to open circuits or voids. Secondly, the interior of the through-hole is under constrained three-dimensional stress. During the heating and cooling processes of co-firing, the contraction trajectory and stress release behavior of metallic silver, due to its inherent high coefficient of thermal expansion, would lead to enormous tangential stress between the metal body and the ceramic hole wall if controlled solely by traditional low-thermal-expansion-coefficient glass. This would not only cause severe bulging and sinking of the through-hole surface in the early stages of sintering, but also induce severe microcracks in the ceramic body around the through-hole and at the interface after long-term temperature cycling fatigue (thermal shock), which would gradually propagate and ultimately lead to complete failure of the longitudinal interconnect.

[0004] Therefore, existing high thermal expansion surface silver pastes cannot meet the stringent technical requirements of isotropic matching of three-dimensional volume shrinkage and ultra-high thermal shock reliability for through-hole filling. There is an urgent need to develop a special through-hole filling silver paste with high solid phase, multi-graded particle size packing, and specific thermal expansion and sintering trajectory control mechanism.

[0005] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0006] This invention aims to solve the problems of mismatch between existing co-fired pastes and LTCC substrates with high thermal expansion coefficients, easy cracking after co-firing, and interconnect failure after multiple temperature cycles. It provides a silver through-hole filling paste with good compatibility with LTCC substrates with high thermal expansion coefficients and can significantly improve the reliability of through-hole interconnects, as well as its preparation method.

[0007] To achieve the above objectives, the present invention provides a conductor paste for co-fired silver through-hole filling of LTCC green tape with high thermal expansion coefficient, comprising inorganic components and an organic carrier, wherein the inorganic components include silver powder, inorganic oxide or ceramic powder, and high thermal expansion coefficient glass powder; the conductor paste comprises 80-90 wt% silver powder, 1.0-3.0 wt% inorganic oxide or ceramic powder, 2.0-5.0 wt% high thermal expansion coefficient glass powder, and 20-10 wt% organic carrier by mass percentage. The silver powder is composed of one or more of the following four particle size ranges: Silver powder 1: D50 is 0.6-0.8μm; Silver powder 2: D50 is 1.0-2.0μm; Silver powder 3: D50 is 1.5-2.5μm; Silver powder 4: D50 is 2.5-4.0μm; The inorganic oxide is one or a mixture of Al, Si, Cu, Ti, and Zr; the ceramic powder is one or a mixture of two of quartz or cordierite. The high thermal expansion coefficient glass powder composition includes the following molar percentage components: 10.0-25.0 mol% SiO2, 10.0-25.0 mol% B2O3, 5.0-10.0 mol% BaO, 50.0-65.0 mol% MgO, 0.5-5.0 mol% ZrO2, 0.2-3.0 mol% P2O5, and 0.2-5.0 mol% M2O, where M represents one or a mixture of alkali metals from Li, Na, and K; it also includes optional components, which may be 0-5.0 mol% CaO and / or CuO. The organic carrier comprises an organic solvent, an organic resin, and a dispersant; its overall ratio includes 5-20 wt% organic resin and 80-95 wt% organic solvent. The organic resins include ester resins and cellulose resins, preferably at least one selected from ethyl cellulose, polyvinyl butanol, and acrylic resins; The organic solvents include alcohols or alcohol esters, such as diethylene glycol butyl ether, 2,2,4-trimethylpentanediol monoisobutyrate (Texanol), α-terpineol, β-terpineol, γ-terpineol, tridecyl alcohol, diethylene glycol ethyl ether (Carbitol), diethylene glycol butyl ether (Butyl Carbitol), terpineol, and mixtures thereof; the organic solvents are prepared by mixing at least two of the above solvents. The organic carrier may also include a thixotropic agent, such as castor bean or its oxidized derivative; furthermore, the organic matter of the present invention does not contain phthalates.

[0008] A preparation and filling process for a conductor paste for co-fired silver through-hole filling of LTCC raw tape with high thermal expansion coefficient, comprising the following steps: (1) Mixing: Weigh the raw materials according to the ratio of inorganic component to organic carrier of 80-90wt%: 20-10wt% and put them into a mixing device for mixing; wherein, the silver powder in the inorganic component is one or more of silver powder 1 to silver powder 4; the organic carrier contains 5-20wt% organic resin and 80-95wt% organic solvent; the mixing time is 20-30 minutes. (2) Grinding: Take out the mixed slurry and put it into a three-roll mill for dispersion grinding; use a scraper fineness gauge to test the fineness of the slurry, so that the fineness of the slurry is less than 20μm, preferably less than 15μm; (3) Through-hole filling: using a metal stainless steel mask and a typical through-hole printing method, the through-hole silver paste is directly printed into the through-hole of the green ceramic sheet; the thickness of the stainless steel wire mask is 25-75μm; the printing table is made of porous stone or other structures with vacuum adsorption table, and the table maintains a vacuum adsorption state on the green ceramic sheet during the printing process. (4) Drying: After the through holes are filled, dry the raw ceramic pieces at 70°C for 10-15 minutes in a ventilated oven or conveyor belt drying oven.

[0009] Compared with the prior art, the present invention has the following beneficial effects: The via-hole filling paste of this invention exhibits excellent substrate compatibility when used for via filling in LTCC substrates with high thermal expansion coefficients. It effectively solves the problem of cracking around vias after co-firing and maintains excellent conductive interconnect reliability even after multiple temperature cycles. Detailed Implementation

[0010] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and test data.

[0011] This invention provides a conductor paste for co-fired silver through-hole filling of LTCC green tape with high thermal expansion coefficient, comprising inorganic components and an organic carrier. To eliminate ambiguity in understanding the proportions of each component, it is clarified that the addition amount of each component in this invention is calculated based on the total weight of the paste. Specifically, based on a total weight of 100 wt% of the conductor paste, its composition includes: 80.0-90.0 wt% silver powder, 1.0-3.0 wt% inorganic oxide or ceramic powder, 2.0-5.0 wt% high thermal expansion coefficient glass powder, and 10.0-20.0 wt% organic carrier.

[0012] The silver powder is composed of one or more of four different particle size ranges of silver powder (silver powder 1, silver powder 2, silver powder 3, and silver powder 4). Through the dense packing of multi-level particle sizes at the microscale, the rheological filling and extrusion printing performance of the paste at high solid content is guaranteed, and a dense three-dimensional conductive network is formed in the micropores.

[0013] The inorganic oxide is one or a mixture of several of Al, Si, Cu, Ti, and Zr, and the ceramic powder is one or a combination of two of quartz powder or cordierite powder.

[0014] In order to be compatible with LTCC substrates with high thermal expansion coefficients (typically around 10*10), -6 / ℃ to 15*10 -6 To achieve perfect physical shrinkage matching (between / ℃) and eliminate residual thermal stress around the through-hole, this invention provides a high coefficient of thermal expansion glass powder. Based on a total molar amount of 100 mol% of the high coefficient of thermal expansion glass powder, its composition includes the following components in molar percentage: 10.0-25.0 mol% SiO2, 10.0-25.0 mol% B2O3, 5.0-10.0 mol% BaO, 50.0-65.0 mol% MgO, 0.5-5.0 mol% ZrO2, 0.2-3.0 mol% P2O5, 0.2-5.0 mol% M2O (where M represents one or a mixture of alkali metals from Li, Na, and K); also includes optional components, which may be 0-5.0 mol% CaO and / or CuO; The aforementioned glass powder system is based on a high-content MgO main crystalline network, modified with a specific proportion of barium borosilicate system and trace amounts of ZrO2 and P2O5, resulting in a glass with an excellent high coefficient of thermal expansion. During the co-firing stage, this glass powder can uniformly wet the silver grain interface and exhibit excellent isotropic thermal stress buffering capacity.

[0015] The following provides six specific formulations of high thermal expansion coefficient glass powder (see Table 1) and four specific slurry formulation examples (see Table 2), but the scope of protection of this invention is not limited thereto.

[0016] Table 1. Specific formulation of high thermal expansion coefficient glass powder (mol%) <![CDATA[SiO2]]> 15 22.2 13.5 13.5 13.5 15 <![CDATA[B2O3]]> 17 11.7 17 17 22 17 BaO 6 6.7 6 6 5.4 6 MgO 57 52.5 62 59 51.2 57 <![CDATA[ZrO2]]> 2.5 2.0 0.6 1.6 2.3 2.5 <![CDATA[P2O5]]> 2 0.4 0.4 2.4 1.8 2.0 <![CDATA[Li2O]]> 0.5 0.5 0.5 0.5 3.8 - CaO - 2.9 - - - - CuO - 1.1 - - - - <![CDATA[Na2O]]> - - - - - 0.5 <![CDATA[K2O]]> - - - - - - Table 2. Formulation of specific examples of through-hole filling silver paste (wt%) Quartz powder 2.5-2.8 - 2.0-2.5 1.5-2.0 Cordierite powder - 1.5-2.5 - - Glass powder #6 2.5-4.0 2.0-3.6 - 2.5-3.0 Glass powder #4 - - 3.2-3.6 - Silver powder 1 23 10.4 - - Silver Powder 2 - 12.6 42.5 - Silver Powder 3 17.5 41.3 41.6 41.6 Silver Powder 4 40.8 16.5 - 42.5 organic carrier 11.5 12.2 10.2 10.2 The organic carrier formulation is as follows: 10-20wt% ethyl cellulose, 40-60wt% 2,2,4-trimethylpentanediol monoisobutyrate (Texanol), and 10-20wt% terpineol. Example 1

[0017] A preparation and filling process for a conductor paste for co-fired silver through-hole filling of LTCC raw tape with high thermal expansion coefficient, comprising the following steps: (1) Mixing: Weigh out 2.5-2.8 wt% quartz powder, 2.5-4.0 wt% glass powder 6#, 23 wt% silver powder 1, 17.5 wt% silver powder 3, 40.8 wt% silver powder 4, and 11.5 wt% organic carrier and put them into a mixing device for mixing; wherein, the organic carrier contains 10-20 wt% ethyl cellulose, 40-60 wt% alcohol ester, and 10-20 wt% terpineol; the mixing time is 20-30 minutes; (2) Grinding: Take out the mixed slurry and put it into a three-roll mill for dispersion grinding; use a scraper fineness gauge to test the fineness of the slurry, so that the fineness of the slurry is less than 15μm; (3) Through-hole filling: using a metal stainless steel mask and a typical through-hole printing method, the through-hole silver paste is directly printed into the through-hole of the green ceramic sheet; the thickness of the stainless steel wire mask is 25-75μm; the printing table is made of porous stone or other structures with vacuum adsorption table, and the table maintains a vacuum adsorption state on the green ceramic sheet during the printing process. (4) Drying: After the through holes are filled, the raw ceramic pieces are dried in a ventilated oven or conveyor belt drying oven at 70°C for 10-15 minutes to obtain experimental sample 1. Example 2

[0018] A preparation and filling process for a conductor paste for co-fired silver through-hole filling of LTCC raw tape with high thermal expansion coefficient, comprising the following steps: (1) Mixing: Weigh out 1.5-2.5wt% cordierite powder, 2.0-3.6wt% glass powder 6#, 10.4wt% silver powder 1, 12.6wt% silver powder 2, 41.3wt% silver powder 3, 16.5wt% silver powder 4, and 12.2wt% organic carrier and put them into a mixing device for mixing; wherein, the organic carrier contains 10-20wt% ethyl cellulose, 40-60wt% alcohol ester, and 10-20wt% terpineol; the mixing time is 20-30 minutes; (2) Grinding: Take out the mixed slurry and put it into a three-roll mill for dispersion grinding; use a scraper fineness gauge to test the fineness of the slurry, so that the fineness of the slurry is less than 15μm; (3) Through-hole filling: using a metal stainless steel mask and a typical through-hole printing method, the through-hole silver paste is directly printed into the through-hole of the green ceramic sheet; the thickness of the stainless steel wire mask is 25-75μm; the printing table is made of porous stone or other structures with vacuum adsorption table, and the table maintains a vacuum adsorption state on the green ceramic sheet during the printing process. (4) Drying: After the through holes are filled, the raw ceramic pieces are dried in a ventilated oven or conveyor belt drying oven at 70°C for 10-15 minutes to obtain experimental product 2. Example 3

[0019] A preparation and filling process for a conductor paste for co-fired silver through-hole filling of LTCC raw tape with high thermal expansion coefficient, comprising the following steps: (1) Mixing: Weigh out 2.0-2.5 wt% quartz powder, 3.2-3.6 wt% glass powder 4#, 42.5 wt% silver powder 2, 41.6 wt% silver powder 3 and 10.2 wt% organic carrier and put them into a mixing device for mixing; wherein, the organic carrier contains 10-20 wt% ethyl cellulose, 40-60 wt% alcohol ester and 10-20 wt% terpineol; the mixing time is 20-30 minutes; (2) Grinding: Take out the mixed slurry and put it into a three-roll mill for dispersion grinding; use a scraper fineness gauge to test the fineness of the slurry, so that the fineness of the slurry is less than 15μm; (3) Through-hole filling: using a metal stainless steel mask and a typical through-hole printing method, the through-hole silver paste is directly printed into the through-hole of the green ceramic sheet; the thickness of the stainless steel wire mask is 25-75μm; the printing table is made of porous stone or other structures with vacuum adsorption table, and the table maintains a vacuum adsorption state on the green ceramic sheet during the printing process. (4) Drying: After the through holes are filled, the raw ceramic pieces are dried at 70°C for 10-15 minutes in a ventilated oven or conveyor belt drying oven to obtain experimental product 3. Example 4

[0020] A preparation and filling process for a conductor paste for co-fired silver through-hole filling of LTCC raw tape with high thermal expansion coefficient, comprising the following steps: (1) Mixing: Weigh out 1.5-2.0 wt% quartz powder, 2.5-3.0 wt% glass powder 6#, 41.6 wt% silver powder 3, 42.5 wt% silver powder 4 and 10.2 wt% organic carrier and put them into a mixing device for mixing; wherein, the organic carrier contains 10-20 wt% ethyl cellulose, 40-60 wt% alcohol ester and 10-20 wt% terpineol; the mixing time is 20-30 minutes; (2) Grinding: Take out the mixed slurry and put it into a three-roll mill for dispersion grinding; use a scraper fineness gauge to test the fineness of the slurry, so that the fineness of the slurry is less than 15μm; (3) Through-hole filling: using a metal stainless steel mask and a typical through-hole printing method, the through-hole silver paste is directly printed into the through-hole of the green ceramic sheet; the thickness of the stainless steel wire mask is 25-75μm; the printing table is made of porous stone or other structures with vacuum adsorption table, and the table maintains a vacuum adsorption state on the green ceramic sheet during the printing process. (4) Drying: After the through holes are filled, the raw ceramic pieces are dried in a ventilated oven or conveyor belt drying oven at 70°C for 10-15 minutes to obtain experimental product 4.

[0021] To fully compare and highlight the technical effects of the present invention, experimental sample 5 was prepared as a comparative example using conventional methods. Experimental sample 5 did not contain the high thermal expansion coefficient glass powder of the present invention, but instead used commercially available low-expansion borosilicate glass powder from the electronic paste industry. Furthermore, the silver powder used was only ordinary single-peak silver powder with a single particle size (D50 of 2.0 μm). Its total inorganic content, organic carrier ratio, solvent type, as well as the three-roll milling, through-hole filling process, and drying and sintering conditions, were completely identical to those of Example 3.

[0022] The above-mentioned experimental samples 1-4 (examples of the present invention) and experimental sample 5 (comparative example) were printed and filled into the through holes of the high thermal expansion coefficient LTCC substrate. After being processed by standard stacking, isostatic pressing and co-firing in air atmosphere at 850-900℃, the initial physical properties of the through holes were tested, as shown in Table 3.

[0023] Table 3 Performance of through-hole filling silver paste in test samples 1-4 Through-hole diameter (μm) 200 200 200 200 200 Hole resistance (mΩ) 1.3 1.8 1.4 1.8 2.8 Height of through-hole protrusion after sintering (μm) -25 -5 -10 2 -40 From Table 3, we can conclude that: To further verify the compatibility of the slurry of this invention with the high thermal expansion coefficient LTCC substrate and its reliability in thermal cycling, the microstructure of test samples 1-4 and 5 after co-firing was observed, and thermal cycling tests were conducted (test conditions: -40℃ to 125℃, holding for 30 min each time, 1000 cycles). The test results are shown in Table 4: Table 4: Crack resistance and interconnect reliability test results of test samples 1-5 Microcracks around the through-hole after co-firing (SEM) No cracks, tight bonding No cracks, tight bonding No cracks, tight bonding No cracks, tight bonding Obvious microcracks are visible at the interface between the through-hole and the substrate. Through-hole cracking rate after 1000 temperature cycles 0% 0% 0% 0% 82.5% Pore ​​resistivity change rate after 1000 temperature cycles ＜ 5.0% ＜ 3.0% ＜ 4.5% ＜ 2.5% The resistance increases sharply (>300%). Interconnection failure status (whether a circuit break occurred) no no no no Yes (partial open circuit). The results in Tables 3 and 4 show that: 1. The synergistic effect of multi-level silver powder on improving the conductivity and densification of through-hole foundations was verified. According to the test results in Table 3, in the initial state, the through-hole resistances of Experiment 1 and Experiment 3, which contain fine-grained silver powder, are as low as 1.3 mΩ and 1.4 mΩ, respectively, significantly better than the comparative example (Experiment 5) without scientific gradation. This indicates that the present invention, by limiting the multi-peak blending of four different particle size ranges of silver powder, enables the fine-grained silver powder to accurately and densely fill the microscopic gaps between larger-particle silver powder. During the co-firing stage, this high-density stacked framework effectively promotes local micro-melting and grain neck development, constructing a continuous and dense three-dimensional conductive network with a larger contact area and fewer defects inside the 3D deep pores, thereby significantly reducing the longitudinal resistance.

[0024] 2. This study confirmed the precise control of the matching of sintering volume shrinkage between the ceramic conditioning phase and the silver powder grade. The smoothness (roughness) of the through-hole filler surface after sintering directly affects the planarization quality of subsequent multilayer integration. Tests show that the through-hole protrusion height of Experiment 4 is only +2 μm, while that of Experiment 2 is -5 μm, with extremely low absolute values, exhibiting near-perfect smoothness. This is because Experiment 4 introduced a high proportion of large-particle silver powder 4, while Experiment 2 synergistically introduced trace amounts (1.0-3.0 wt%) of quartz powder or cordierite powder. The introduction of trace ceramic powder significantly hindered and dragged the grain growth and capillary shrinkage of the silver powder in the early stages of sintering, precisely delaying the excessive "premature" shrinkage of metallic silver within the through-hole. This ensured that the volume shrinkage trajectory of the entire metal column in the Z-axis direction remained highly parallel and synchronous with the high thermal expansion coefficient LTCC green zone, perfectly preventing the deep collapse or large protrusions that are easily observed in traditional slurries.

[0025] 3. The decisive technical contribution of high thermal expansion coefficient glass powder to eliminating thermal stress and preventing substrate cracking is elucidated. The core advantages of this invention lie in its excellent substrate compatibility, complete resolution of cracking around vias after co-firing, and maintenance of reliable interconnects under long-term, multiple temperature cycles. These advantages are directly and strongly supported by the quantitative comparison in Table 4: Table 4 shows that after co-firing, experimental samples 1-4 of this invention showed no cracks around the vias as observed by scanning electron microscopy (SEM). Even after undergoing 1000 extremely harsh thermal cycles, the via cracking rate remained at 0%, and the change in pore resistance was only slightly controlled within 5.0%, with no interconnect failures. Conversely, the comparative sample (experiment 5) produced using conventional glass powder and methods showed obvious microcracks at the interface between the via wall and the ceramic substrate immediately after co-firing. After thermal cycling, these cracks rapidly expanded under external stress, with the via cracking rate soaring to 82.5%, leading to large-scale tearing, peeling, and even volumetric cracking of the micro-conductive network. The pore resistance increased dramatically by over 300%, resulting in catastrophic via interconnect failures (open circuits).

[0026] The glass powder of this invention, composed of a high MgO molar ratio and a specific silicon-boron-barium-zirconium system, exhibits thermal expansion matching behavior (CTE matching) that is highly compatible with the high thermal expansion coefficient LTCC substrate during co-firing. It successfully releases and buffers the residual shear stress accumulated at the via interface due to the inherent differences in thermodynamic behavior between metal and ceramic, fundamentally overcoming the industry pain point of longitudinal interconnect failure in high thermal expansion coefficient LTCC systems during long-term mechanical and thermal shock service.

[0027] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A paste for filling conductor vias in co-fired silver-coated LTCC green tape with high thermal expansion coefficient, characterized in that, Its composition includes inorganic components and organic carriers, wherein the inorganic components include silver powder, inorganic oxide or ceramic powder, and high thermal expansion coefficient glass powder; the mass percentage composition of the conductor paste is 80-90 wt% silver powder, 1.0-3.0 wt% inorganic oxide or ceramic powder, 2.0-5.0 wt% high thermal expansion coefficient glass powder, and 20-10 wt% organic carrier; the silver powder is composed of one or more combinations of four different particle size ranges of silver powder.

2. The paste for filling through-hole conductors with co-fired silver in high thermal expansion coefficient LTCC green tape according to claim 1, characterized in that, The four silver powders with different particle size ranges are: silver powder 1 with a D50 of 0.6-0.8 μm, silver powder 2 with a D50 of 1.0-2.0 μm, silver powder 3 with a D50 of 1.5-2.5 μm, and silver powder 4 with a D50 of 2.5-4.0 μm.

3. The paste for filling through-hole conductors with co-fired silver in LTCC green tape according to claim 2, characterized in that, The weight percentage ranges of the four different particle size ranges of silver powder are: 10.0-25.0 wt% silver powder 1; 12.0-45.0 wt% silver powder 2; 17.0-50.0 wt% silver powder 3; and 16.0-50.0 wt% silver powder 4.

4. The paste for filling through-hole conductors with co-fired silver in LTCC green tape according to claim 3, characterized in that: The silver powder consists of 30.0-45.0 wt% silver powder 2 and 35.0-50.0 wt% silver powder 3.

5. The paste for filling through-hole conductors with co-fired silver in LTCC green tape according to claim 3, characterized in that: The silver powder consists of 35.0-45.0 wt% silver powder 3 and 35.0-50.0 wt% silver powder 4.

6. The paste for filling through-hole conductors with co-fired silver in LTCC green tape according to claim 1, characterized in that: The inorganic oxide is one or a mixture of Al, Si, Cu, Ti, and Zr; the ceramic powder is one or a mixture of two of quartz or cordierite.

7. The paste for filling through-hole conductors with co-fired silver in LTCC green tape according to claim 1, characterized in that, The high thermal expansion coefficient glass powder composition includes the following molar percentage components: 10.0-25.0 mol% SiO2, 10.0-25.0 mol% B2O3, 5.0-10.0 mol% BaO, 50.0-65.0 mol% MgO, 0.5-5.0 mol% ZrO2, 0.2-3.0 mol% P2O5, and 0.2-5.0 mol% M2O, where M represents one or a mixture of alkali metals such as Li, Na, and K; it also includes optional components, which may be 0-5.0 mol% CaO and / or CuO.

8. The paste for filling through-hole conductors with co-fired silver in LTCC green tape according to claim 1, characterized in that: The organic carrier includes organic solvent and organic resin; the overall ratio is 5-20 wt% organic resin and 80-95 wt% organic solvent; the organic resin includes ester resin and cellulose resin, and the organic solvent includes alcohol or alcohol ester solvent.

9. The paste for filling through-hole conductors with co-fired silver in LTCC green tape according to claim 8, characterized in that: The organic resin is selected from at least one of ethyl cellulose, polyvinyl butanol, and acrylic resin; the organic solvent is selected from at least two of diethylene glycol butyl ether, 2,2,4-trimethylpentanediol monoisobutyrate, α-pinene alcohol, β-pinene alcohol, γ-pinene alcohol, tridecyl alcohol, diethylene glycol ethyl ether, diethylene glycol butyl ether, and terpineol.

10. A preparation and filling process for a high thermal expansion coefficient LTCC raw tape co-fired silver through-hole filling conductor paste according to any one of claims 1-9, the steps of which are: (1) mixing, weighing raw materials according to the ratio of inorganic components to organic carrier of 80-90wt%: 20-10wt% and mixing them in a stirring device; the mixing time is 20-30 minutes; (2) Grinding: Take out the mixed slurry and put it into a three-roll mill for dispersion grinding; use a scraper fineness gauge to test the fineness of the slurry, so that the fineness of the slurry is less than 20μm; (3) Through-hole filling: using a metal stainless steel mask and a typical through-hole printing method, the through-hole silver paste is directly printed into the through-hole of the green ceramic sheet; the thickness of the stainless steel wire mask is 25-75μm; the printing table is made of porous stone or other structures with vacuum adsorption table, and the table maintains a vacuum adsorption state on the green ceramic sheet during the printing process. (4) Drying: After the through holes are filled, dry the raw ceramic pieces at 70°C for 10-15 minutes in a ventilated oven or conveyor belt drying oven.