LTCC (Low Temperature Co-Fired Ceramic) external electrode silver paste with high printing adaptability and co-firing process thereof

Abstract

The invention belongs to the technical field of silver paste materials, and particularly relates to LTCC external electrode silver paste with high printing adaptability and a co-firing process thereof. The LTCC external electrode silver paste with high printing adaptability comprises the following components in parts by weight: 90 to 100 parts of silver powder, 10 to 20 parts of an organic carrier, 4 to 8 parts of glass powder, 3.6 to 4.8 parts of an auxiliary agent, 0.2 to 0.4 part of a plasticizer, 0.2 to 0.4 part of a leveling agent, 0.2 to 0.4 part of a surfactant and 10 to 20 parts of a solvent, the organic carrier is phosphate modified hydroxyethyl cellulose. The silver paste can be ensured to have proper solid content, viscosity and thixotropy, the fineness of the silver paste is reduced, the resistivity after sintering is reduced, and the silver paste has high printing adaptability.

Description

Technical Field

[0001] This invention belongs to the field of silver paste material technology, specifically relating to a highly printable LTCC external electrode silver paste and its co-firing process. Background Technology

[0002] Low-temperature cofired ceramics (LTCC) technology involves preparing low-temperature sintered ceramic powder into precisely thick and dense green ceramic tapes. Using processes such as laser drilling, micro-hole injection, and precision conductor paste printing, predetermined circuit patterns are formed on the green ceramic tapes. Multiple passive components are then embedded within these tapes. Multiple layers of green ceramic sheets with printed conductive patterns are stacked together and sintered below 900°C to form passive integrated components with three-dimensional circuit networks. Simultaneously, ICs and active devices can be mounted on the surface to create three-dimensional circuits containing passive components, thus forming passive / active integrated functional modules. Therefore, LTCC technology can be used to completely manufacture a wide variety of high-tech LTCC products. LTCC is a type of ceramic packaging substrate that can meet the technical requirements of multi-chip assembly and single-chip packaging for digital, low-frequency RF, and microwave devices. It has been widely used in substrates, packaging, and microwave devices, and is a very important approach to achieving system-in-package (SIP). Currently, products that combine different functions into one device have been developed and have been successfully applied to terrestrial digital broadcasting, wireless local area networks, microwave systems, GPS receivers, and other power supply sub-modules and digital circuit boards.

[0003] Conductive silver paste is one of the core raw materials for LTCC technology. Electrodes are formed by printing or dipping silver paste and then sintering it. Its composition and properties have a significant impact on the conductivity, solderability, and co-firing compatibility with the substrate of the sintered thick film. With the rapid development of device manufacturing processes, LTCC products will be widely used in the future, and the added value of LTCC low-temperature co-firing silver paste companies will be further enhanced. Therefore, conductive silver paste urgently needs to be developed in conjunction with LTCC technology to further accelerate the practical application of LTCC products.

[0004] Therefore, there is an urgent need for an external electrode silver paste for LTCC. By selecting appropriate silver powder, glass phase and organic carrier, and combining various additives, the silver paste can be guaranteed to have suitable solid content, viscosity and thixotropy, and the fineness of the silver paste can be reduced. At the same time, the resistivity after sintering can be reduced, so that it has high printability. Summary of the Invention

[0005] The purpose of this invention is to provide a highly printable LTCC external electrode silver paste and its co-firing process. This invention uses spherical silver powder and nano silver powder as composite silver powder, uses phosphate-modified hydroxyethyl cellulose as an organic carrier, and adds Bi-B-Zn ternary system bismuthate glass powder, composite additives, etc. to prepare a low-fineness LTCC external electrode silver paste and reduce the resistivity after sintering. This makes the silver paste of this invention highly printable and has a wider range of applications.

[0006] To achieve the above objectives, the present invention provides the following technical solution: The first aspect of the present invention provides a highly printable LTCC external electrode silver paste, comprising, by weight, the following components: 90-100 parts silver powder, 10-20 parts organic carrier, 4-8 parts glass powder, 3.6-4.8 parts additives, 0.2-0.4 parts plasticizer, 0.2-0.4 parts leveling agent, 0.2-0.4 parts surfactant and 10-20 parts solvent.

[0007] As a preferred embodiment, the weight of the silver powder in this invention can be 90 parts, 92 parts, 94 parts, 96 parts, 98 parts, or 100 parts, etc.

[0008] As a preferred embodiment, the organic carrier in this invention can be in the following weight proportions: 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, or 20 parts, etc.

[0009] As a preferred embodiment, the weight parts of the glass powder in this invention can be 4 parts, 5 parts, 6 parts, 7 parts, or 8 parts, etc.

[0010] As a preferred embodiment, the weight parts of the adjuvant in this invention may be 3.6 parts, 3.8 parts, 4.0 parts, 4.2 parts, 4.4 parts, 4.6 parts, or 4.8 parts, etc.

[0011] As a preferred embodiment, the plasticizer described in this invention may be 0.2 parts, 0.3 parts, or 0.4 parts by weight, etc.

[0012] As a preferred embodiment, the leveling agent described in this invention may be present in weight parts of 0.2 parts, 0.3 parts, or 0.4 parts, etc.

[0013] As a preferred embodiment, the surfactant in this invention may be 0.2 parts, 0.3 parts, or 0.4 parts by weight, etc.

[0014] As a preferred embodiment, the solvent in this invention may be in the form of 10, 12, 14, 16, 18, or 20 parts by weight.

[0015] As a preferred embodiment, the silver powder is spherical silver powder or nano silver powder; The mass ratio of the spherical silver powder to the nano silver powder is (8~9):1.

[0016] As a preferred embodiment, the spherical silver powder has a particle size distribution D90 of 1.75~2.10 μm and a tap density of 5.8~6.1 g / cm³. 3 Its specific surface area is 0.38~0.41 m². 2 / g; The nano-silver powder has a particle size distribution (D90) of 0.6–0.8 μm and a tap density of 4.5–5.5 g / cm³. 3 Its specific surface area is 1.0~1.2m². 2 / g.

[0017] This invention uses spherical silver powder and nano silver powder as a compound silver powder. It selects silver powder with suitable particle size distribution, tap density and specific surface area, and controls the mass ratio of spherical silver powder and nano silver powder. Through the good matching of particle size, morphology and other properties, the performance of silver paste is improved.

[0018] The spherical silver powder of this invention has good flowability, and its high tap density allows the silver particles to bond together in a shorter time during sintering, resulting in fewer voids between the silver particles. At the same time, by controlling the specific surface area of ​​the spherical silver powder and the nano silver powder, the wettability of the silver paste in organic solvents is ensured and shrinkage is reduced. The density of sintering is controlled by adjusting the tap density and specific surface area of ​​the compounded silver powder, ensuring good processability of the silver paste.

[0019] As a preferred embodiment, the organic carrier is phosphate-modified hydroxyethyl cellulose.

[0020] As a preferred embodiment, the preparation method of the phosphate-modified hydroxyethyl cellulose is as follows: by weight, 20-30 parts of hydroxyethyl cellulose and 8-10 parts of anhydrous ethanol are added to 100-120 parts of deionized water and stirred and mixed. Then, 4-6 parts of urea and 10-20 parts of sodium dihydrogen phosphate are added, the temperature is raised to 140-150℃ for esterification reaction for 30-40 minutes, and the mixture is dried under vacuum to obtain phosphate-modified hydroxyethyl cellulose.

[0021] This invention uses hydroxyethyl cellulose as raw material. Under the catalysis of urea, the hydroxyl groups on hydroxyethyl cellulose undergo an esterification reaction with phosphate, introducing negatively charged phosphate groups, thereby obtaining phosphate ester modified hydroxyethyl cellulose.

[0022] As a preferred embodiment, the glass powder is bismuthate glass powder; The bismuthate glass powder adopts a Bi-B-Zn ternary system with a melting point of 410℃.

[0023] This invention uses bismuthate glass powder of the Bi-B-Zn ternary system. The Bi-based material provides low melting point characteristics and enhances the silver dissolving ability, the B-based material forms a glass network skeleton to adjust the coefficient of thermal expansion, and the Zn-based material enhances the interfacial bonding between the glass powder and the silver powder. By adding the Bi-B-Zn ternary system bismuthate glass powder, the silver paste obtains good comprehensive performance.

[0024] As a preferred embodiment, the additives are nano-zinc oxide and titanium dioxide quantum dots; The mass ratio of the nano-zinc oxide and titanium dioxide quantum dots is (1~2):1.

[0025] As a preferred embodiment, the size of the nano-zinc oxide is 30~80nm, and the size of the titanium dioxide quantum dots is 2~5nm.

[0026] This invention selects nano zinc oxide and titanium dioxide quantum dots as compounding additives, and selects nano zinc oxide with a size of 30~80nm and titanium dioxide quantum dots with a size of 2~5nm. By controlling the mass ratio of the two, a good synergistic effect is achieved, thereby improving the performance of silver paste.

[0027] As a preferred embodiment, the plasticizer is selected from one or more of dibutyl phthalate, dioctyl phthalate, and tributyl citrate.

[0028] As a preferred option, the leveling agent is selected from BYK-333, BYK-358, and Tego900.

[0029] As a preferred embodiment, the surfactant is tributyl phosphate or sodium dodecylbenzenesulfonate.

[0030] As a preferred embodiment, the solvent is selected from one or more of terpineol, cyclohexanone, and diethylene glycol ethyl ether.

[0031] The second aspect of the present invention provides a co-firing process for silver paste as described in the first aspect, wherein the silver paste is printed onto a ceramic substrate using a 250-mesh stainless steel screen, and then sintered in a tunnel furnace under atmospheric atmosphere at a sintering temperature of 890~910℃ for 8~10 min.

[0032] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows: 1. This invention uses micron-sized spherical silver powder and nano silver powder to form a compound. The organic carrier is phosphate-modified hydroxyethyl cellulose. The glass phase is Bi-B-Zn ternary system bismuthate glass powder. The additives are nano zinc oxide and titanium dioxide quantum dots. Plasticizers, leveling agents, surfactants and solvents are added to obtain LTCC external electrode silver paste with high printability. This ensures that the silver paste has suitable solid content, viscosity and thixotropy, and reduces the fineness of the silver paste, while also reducing the resistivity after sintering.

[0033] 2. The present invention uses a combination of spherical silver powder and nano silver powder. The coarser spherical silver powder has good flowability and sintering skeleton effect, while the finer nano silver powder can fill the gaps between large particles, thereby increasing the powder packing density and effectively reducing fineness. At the same time, the synergistic effect of nano silver powder and micron-sized spherical silver powder can significantly reduce porosity, improve the continuity of the conductive network, and thus reduce volume resistivity.

[0034] 3. The phosphate groups in the phosphate-modified hydroxyethyl cellulose of this invention are excellent anchoring groups. They can effectively deagglomerate the hard agglomerates of nanoparticles through the anchoring effect, and prevent particles from agglomerating again by forming steric hindrance through the full extension of long-chain polymers, thereby effectively reducing the fineness. At the same time, the phosphate-modified hydroxyethyl cellulose forms an ordered network during the drying process, which guides the silver powder to align along the electric field direction, forming a continuous conductive channel and reducing the resistivity of the silver paste.

[0035] 4. The Bi-B-Zn ternary system of the bismuthate glass powder of the present invention enables it to achieve excellent dispersion in an organic carrier, preventing hard agglomeration of the original particles. The fineness is guaranteed by the well-dispersed ultrafine glass powder. At the same time, the melting point of the bismuthate glass powder is controlled to achieve early melting and form a continuous liquid phase. The capillary force pulls the silver particles to rearrange and fill the pores, thereby increasing the density and reducing the resistivity.

[0036] 5. The silver paste of this invention uses a compound additive of nano zinc oxide and titanium dioxide quantum dots. The titanium dioxide quantum dots can be adsorbed on the surface of silver powder and prevent silver powder agglomeration through steric hindrance. The nano zinc oxide, as a secondary dispersant, further hinders the formation of large particles, thereby significantly reducing the fineness of the silver paste. In addition, the gaps formed by the accumulation of silver powder are the main bottlenecks for electron transport, which easily lead to gap scattering and increased resistivity. The nano zinc oxide in the compound additive can accurately fill the mesoscale gaps between silver powder, while the titanium dioxide quantum dots further fill the microscale gaps between zinc oxide and silver powder. Through multi-level gap filling, a dense conductive network is constructed, which effectively reduces resistivity. Attached Figure Description

[0037] Figure 1 The infrared spectra of phosphate-modified hydroxyethyl cellulose and hydroxyethyl cellulose in Example 1 are shown. Detailed Implementation

[0038] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] The sources of some components in the examples and comparative examples are as follows: Spherical silver powder, type 429, with a particle size distribution D90 of 1.75~2.10μm and a tap density of 5.8~6.1g / cm³. 3 Its specific surface area is 0.38~0.41 m². 2 / g, purchased from Ningbo Jingxin Electronic Materials Co., Ltd.; Nano silver powder, model SC5002, with a particle size distribution D90 of 0.6~0.8μm and a tap density of 4.5~5.5g / cm³. 3 Its specific surface area is 1.0~1.2m². 2 / g, purchased from Ningbo Jingxin Electronic Materials Co., Ltd.; Hydroxyethyl cellulose, product number H104790, was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. Urea, CAS No. 57-13-6, purchased from Sinopharm Chemical Reagent Co., Ltd. Sodium dihydrogen phosphate, CAS No. 7558-80-7, was purchased from Sinopharm Chemical Reagent Co., Ltd. Bismuthate glass powder, Bi-B-Zn ternary system, melting point 410℃, purchased from Jiangsu Qiuzheng New Material Technology Co., Ltd. Conventional glass powder, product number A00109, purchased from Wuhan Jiyesheng Chemical Co., Ltd. Nano zinc oxide, item number XFI06, with a size of 30~80nm, was purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd. Titanium dioxide quantum dots, item number XF398, with a size of 2~5nm, were purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd. Dibutyl phthalate, CAS No. 84-74-2, was purchased from Shanghai Maclean Biochemical Technology Co., Ltd. Dioctyl phthalate, CAS No. 117-81-7, was purchased from Shanghai Maclean Biochemical Technology Co., Ltd. Tributyl citrate, CAS No. 77-94-1, purchased from Shanghai Maclean Biochemical Technology Co., Ltd. Tributyl phosphate, CAS No. 126-73-8, was purchased from Shanghai Maclean Biochemical Technology Co., Ltd. Sodium dodecylbenzenesulfonate, CAS No. 25155-30-0, was purchased from Shanghai Maclean Biochemical Technology Co., Ltd. Terpineol, CAS No. 8000-41-7, was purchased from Shanghai Maclean Biochemical Technology Co., Ltd. Cyclohexanone, CAS No. 108-94-1, purchased from Sinopharm Chemical Reagent Co., Ltd. Diethylene glycol ethyl ether, CAS No. 111-90-0, was purchased from Sinopharm Chemical Reagent Co., Ltd. Leveling agents: BYK-333, BYK-358, Tego900.

[0040] Example 1 This embodiment provides a highly printable LTCC external electrode silver paste, comprising the following components by weight: 100 parts silver powder (90 parts spherical silver powder and 10 parts nano silver powder), 20 parts organic carrier phosphate-modified hydroxyethyl cellulose, 8 parts bismuthate glass powder, 4.8 parts additives (3.2 parts nano zinc oxide and 1.6 parts titanium dioxide quantum dots), 0.4 parts plasticizer dibutyl phthalate, 0.2~0.4 parts leveling agent BYK-333, 0.4 parts surfactant tributyl phosphate and 20 parts solvent terpineol.

[0041] Preparation of the phosphate-modified hydroxyethyl cellulose: by weight, 30 parts of hydroxyethyl cellulose and 10 parts of anhydrous ethanol are added to 120 parts of deionized water and stirred and mixed. Then, 6 parts of urea and 20 parts of sodium dihydrogen phosphate are added, the temperature is raised to 150°C and the esterification reaction is carried out for 30 min. After vacuum drying, phosphate-modified hydroxyethyl cellulose is obtained.

[0042] Example 2 This embodiment provides a highly printable LTCC external electrode silver paste, comprising the following components by weight: 90 parts silver powder (80 parts spherical silver powder and 10 parts nano silver powder), 10 parts organic carrier phosphate-modified hydroxyethyl cellulose, 4 parts bismuthate glass powder, 3.6 parts additives (1.8 parts nano zinc oxide and 1.8 parts titanium dioxide quantum dots, 0.2 parts plasticizer dioctyl phthalate, 0.2~0.4 parts leveling agent BYK-358, 0.2 parts surfactant sodium dodecylbenzenesulfonate and 10~20 parts solvent cyclohexanone).

[0043] Preparation of the phosphate-modified hydroxyethyl cellulose: by weight, 20 parts of hydroxyethyl cellulose and 8 parts of anhydrous ethanol are added to 100 parts of deionized water and stirred and mixed. Then, 4 parts of urea and 10 parts of sodium dihydrogen phosphate are added, the temperature is raised to 140°C and the esterification reaction is carried out for 40 min. After vacuum drying, phosphate-modified hydroxyethyl cellulose is obtained.

[0044] Example 3 This embodiment provides a highly printable LTCC external electrode silver paste, comprising the following components by weight: 95 parts silver powder (85 parts spherical silver powder and 10 parts nano silver powder), 15 parts organic carrier phosphate-modified hydroxyethyl cellulose, 6 parts bismuthate glass powder, 4.2 parts additives (2.6 parts nano zinc oxide and 1.6 parts titanium dioxide quantum dots), 0.3 parts plasticizer tributyl citrate, 0.3 parts leveling agent Tego900, 0.3 parts surfactant tributyl phosphate, and 15 parts solvent diethylene glycol ethyl ether.

[0045] Preparation of the phosphate-modified hydroxyethyl cellulose: by weight, 25 parts of hydroxyethyl cellulose and 9 parts of anhydrous ethanol were added to 110 parts of deionized water and stirred. Then, 5 parts of urea and 15 parts of sodium dihydrogen phosphate were added, and the mixture was heated to 145°C for esterification reaction for 35 min. The mixture was then dried under vacuum to obtain phosphate-modified hydroxyethyl cellulose.

[0046] Comparative Example 1 The difference between this comparative example and Example 1 is that 95 parts of spherical silver powder and 5 parts of nano silver powder were used instead of silver powder.

[0047] Comparative Example 2 The difference between this comparative example and Example 1 is that 80 parts of spherical silver powder and 20 parts of nano silver powder were used instead of silver powder.

[0048] Comparative Example 3 The difference between this comparative example and Example 1 is that all the silver powder used is now spherical.

[0049] Comparative Example 4 The difference between this comparative example and Example 1 is that all the silver powder used is replaced with nano silver powder.

[0050] Comparative Example 5 The difference between this comparative example and Example 1 is that hydroxyethyl cellulose (product number H104790) is used instead of phosphate-modified hydroxyethyl cellulose.

[0051] Comparative Example 6 The difference between this comparative example and Example 1 is that conventional glass powder (item number A00109) is used instead of bismuthate glass powder.

[0052] Comparative Example 7 The difference between this comparative example and Example 1 is that all the additives were replaced with nano zinc oxide.

[0053] Comparative Example 8 The difference between this comparative example and Example 1 is that all the additives were replaced with titanium dioxide quantum dots.

[0054] Performance testing (1) Solid content, fineness, and viscosity: Refer to GB / T 17473-2025 Test methods for electronic paste properties - Conductor paste testing. (2) Thixotropy: The thixotropy of the examples and comparative examples was tested at 25°C using a viscometer (model DV2T, Brookfield, USA). The thixotropy was expressed as a viscosity ratio of 10 rpm / 50 rpm.

[0055] (3) Resistivity: The silver paste of the examples and comparative examples was printed on the ceramic substrate using a 250-mesh stainless steel screen, and then sintered in an atmospheric tunnel furnace at a temperature of 850±5℃ for 10 min. The resistivity was then tested using a four-probe resistance meter (model MCP-T360, Mitsubishi, Japan).

[0056] Table 1 Performance Test Results The performance test results above show that Examples 1-3 have the best overall performance. This is mainly because they use micron-sized spherical silver powder and nano silver powder in combination, phosphate-modified hydroxyethyl cellulose as the organic carrier, Bi-B-Zn ternary bismuthate glass powder as the glass phase, and nano zinc oxide and titanium dioxide quantum dots as additives. Plasticizers, leveling agents, surfactants and solvents are added to obtain LTCC external electrode silver paste with high printability, ensuring that the silver paste has suitable solid content, viscosity and thixotropy, reducing the fineness of the silver paste, and reducing the resistivity after sintering.

[0057] Compared to Example 1, Comparative Example 1 used 95 parts spherical silver powder and 5 parts nano silver powder. Due to insufficient nano silver powder, the compounding effect was poor, resulting in a finer silver paste and increased resistivity after sintering. Compared to Example 1, Comparative Example 2 used 80 parts spherical silver powder and 20 parts nano silver powder. Due to excessive nano silver powder, the compounding effect was poor, resulting in a finer silver paste and increased resistivity after sintering. Compared to Example 1, Comparative Example 3 used only spherical silver powder, resulting in silver paste clogging. Compared to Example 1, Comparative Example 4 used only nano silver powder, resulting in silver paste clogging. Compared to Example 1, Comparative Example 5 used hydroxyethyl cellulose (product number H1). In Comparative Example 6, 04790) was used to replace phosphate-modified hydroxyethyl cellulose. The lack of phosphate groups resulted in a finer silver paste and increased resistivity after sintering. Compared to Example 1, Comparative Example 6 used conventional glass powder (item number A00109) instead of bismuthate glass powder. The lack of the Bi-B-Zn ternary system resulted in a finer silver paste and increased resistivity after sintering. Compared to Example 1, Comparative Example 7 used entirely nano-zinc oxide as an additive. The lack of synergistic effect from titanium dioxide quantum dots resulted in a finer silver paste and increased resistivity after sintering. Compared to Example 1, Comparative Example 8 used entirely titanium dioxide quantum dots as an additive. The lack of synergistic effect from nano-zinc oxide resulted in a finer silver paste and increased resistivity after sintering.

Claims

1. A highly printable LTCC external electrode silver paste, characterized in that, Based on parts by weight, it includes the following components: 90-100 parts silver powder, 10-20 parts organic carrier, 4-8 parts glass powder, 3.6-4.8 parts additives, 0.2-0.4 parts plasticizer, 0.2-0.4 parts leveling agent, 0.2-0.4 parts surfactant and 10-20 parts solvent; The organic carrier is phosphate-modified hydroxyethyl cellulose.

2. The LTCC external electrode silver paste with high printability according to claim 1, characterized in that, The silver powder is spherical silver powder and nano silver powder; The mass ratio of the spherical silver powder to the nano silver powder is (8~9):

1.

3. The LTCC external electrode silver paste with high printability according to claim 2, characterized in that, The spherical silver powder has a particle size distribution D90 of 1.75~2.10 μm and a tap density of 5.8~6.1 g / cm³. 3 Its specific surface area is 0.38~0.41 m². 2 / g; The nano-silver powder has a particle size distribution (D90) of 0.6–0.8 μm and a tap density of 4.5–5.5 g / cm³. 3 Its specific surface area is 1.0~1.2m². 2 / g.

4. The LTCC external electrode silver paste with high printability according to claim 1, characterized in that, The preparation method of the phosphate-modified hydroxyethyl cellulose is as follows: by weight, 20-30 parts of hydroxyethyl cellulose and 8-10 parts of anhydrous ethanol are added to 100-120 parts of deionized water and stirred. Then, 4-6 parts of urea and 10-20 parts of sodium dihydrogen phosphate are added, the temperature is raised to 140-150℃ for esterification reaction for 30-40 minutes, and the mixture is dried under vacuum to obtain phosphate-modified hydroxyethyl cellulose.

5. The LTCC external electrode silver paste with high printability according to claim 1, characterized in that, The glass powder is bismuthate glass powder; The bismuthate glass powder adopts a Bi-B-Zn ternary system with a melting point of 410℃.

6. The LTCC external electrode silver paste with high printability according to claim 1, characterized in that, The additives are nano zinc oxide and titanium dioxide quantum dots; The mass ratio of the nano-zinc oxide and titanium dioxide quantum dots is (1~2):

1.

7. The LTCC external electrode silver paste with high printability according to claim 6, characterized in that, The size of the nano-zinc oxide is 30~80nm, and the size of the titanium dioxide quantum dots is 2~5nm.

8. The LTCC external electrode silver paste with high printability according to claim 1, characterized in that, The surfactant is tributyl phosphate or sodium dodecylbenzenesulfonate.

9. The LTCC external electrode silver paste with high printability according to claim 1, characterized in that, The solvent is selected from one or more of terpineol, cyclohexanone, and diethylene glycol ethyl ether.

10. A co-firing process for silver paste as described in any one of claims 1-9, characterized in that, The silver paste was printed onto the ceramic substrate using a 250-mesh stainless steel screen, and then sintered in a tunnel furnace under atmospheric atmosphere at a temperature of 890-910℃ for 8-10 minutes.

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