A tungsten-copper electronic paste for medium-temperature co-fired ceramic substrates and its preparation method

Abstract

This invention discloses a tungsten-copper electronic paste for medium-temperature co-fired ceramic substrates and its preparation method, belonging to the field of electronic pastes. By mass percentage, the paste consists of 80%–85% tungsten-copper powder, 5%–15% organic carrier, and 5%–10% binder phase. The preparation method includes: first preparing the organic carrier, then uniformly mixing the tungsten-copper powder and binder phase, followed by adding the organic carrier, and then thoroughly grinding and dispersing the mixture using a stirring and three-roll mill to obtain a uniform and stable tungsten-copper electronic paste. This invention, by optimizing the powder size and paste ratio, significantly reduces the sheet resistance of the conductive layer after sintering and improves conductivity while ensuring good co-firing compatibility with medium-temperature co-fired ceramics. The resulting paste exhibits excellent printability and rheological stability, with clear printed lines and a smooth surface. It shows no bubbling or delamination during sintering and is suitable for high-performance, high-reliability electronic packaging and substrate circuit manufacturing.

Description

Technical Field

[0001] This invention belongs to the field of electronic pastes, specifically relating to a tungsten-copper electronic paste for medium-temperature co-fired ceramic substrates and its preparation method. Background Technology

[0002] Medium-temperature co-fired ceramic substrates (MTCCs) have important applications in electronic packaging due to their excellent thermal stability and mechanical strength. Compared to high-temperature co-fired ceramics (HTCCs), they have a lower sintering temperature, expanding the range of paste options; and compared to low-temperature co-fired ceramics (LTCCs), they exhibit superior physical and thermal properties. However, MTCCs still face limitations in material selection during metallization: although the sintering temperature is lower, low-melting-point metals such as Au, Ag, and Cu cannot be used directly because these metals will burn off during sintering, leading to decreased conductivity and structural defects.

[0003] Currently, high-melting-point metals or alloy systems, such as W / Mo / W-Mo, are typically used for MTCC metallization. While these materials can withstand sintering temperatures, they suffer from insufficient conductivity and high sheet resistance, leading to increased signal transmission loss and power loss, thus affecting the high-frequency performance of the device.

[0004] Based on this, the present invention provides a tungsten copper electronic paste for medium-temperature co-fired ceramic substrates. This paste can maintain structural stability at the MTCC sintering process temperature, greatly alleviate the burn-off phenomenon, and at the same time reduce sheet resistance, reduce signal and power transmission losses, thereby improving the electrical performance and reliability of the substrate. Summary of the Invention

[0005] The purpose of this invention is to provide a tungsten-copper electronic paste for medium-temperature co-fired ceramic substrates and its preparation method, which solves the problems of poor conductivity and high sheet resistance of existing tungsten electronic pastes. At the same time, this paste will not cause delamination or substrate warping under high-temperature sintering.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A tungsten-copper electronic paste for medium-temperature co-fired ceramic substrates, comprising the following components by mass percentage (100% total weight):

[0008] 80%~85% tungsten copper powder, 5%~15% organic carrier, 5%~10% binder phase.

[0009] As a preferred embodiment of the present invention, the tungsten-copper electronic paste for medium-temperature co-fired ceramic substrates comprises:

[0010] The tungsten-copper powder is composed of tungsten powder and copper powder. Based on the total mass of the tungsten-copper powder (100%), the tungsten powder content is 70%–78%, and the copper powder content is 22%–30%. The median particle size D of the tungsten powder is… 50 The particle size is 0.82~6.2 μm, and the shape is an irregular cubic structure; the copper powder has a dendritic structure, and the median particle size D of the copper powder is... 50 The range is 3.4~9.7 µm.

[0011] The binder phase is selected from one or more combinations of alumina, silicon dioxide, barium titanate, and zirconium silicate.

[0012] The organic carrier, based on a total mass percentage of 100%, consists of the following components by mass percentage:

[0013] 75%~80% organic solvent, 15%~20% thickener, 1%~5% additives.

[0014] The organic solvent is selected from one or more combinations of terpineol, butyl benzyl phthalate, tributyl citrate, and diethylene glycol butyl ether; the thickener is selected from one or more combinations of ethyl cellulose and acrylic resin; the additives include dispersants and thixotropic agents, wherein the dispersant is selected from one or more combinations of lecithin, sodium polyacrylate, castor oil, and methylcellulose; and the thixotropic agent is selected from one or more combinations of hydrogenated castor oil and methyl methacrylate.

[0015] This invention also proposes a method for preparing tungsten-copper electronic paste for medium-temperature co-fired ceramic substrates, comprising the following steps:

[0016] S1. Preparation of organic carrier: Stir and mix the components of the organic carrier at 60~80℃ for 3~5 h until the system is homogeneous and transparent to obtain the organic carrier;

[0017] S2. Powder premixing: Tungsten powder, copper powder and binder phase are mixed in a mixer for 15 h to obtain mixed powder;

[0018] S3. Slurry preparation: The mixed powder and the organic carrier are added to a stirring device and stirred at a speed of 1000~2000 rpm for 2~5 min for preliminary mixing. Then, the mixture is ground in multiple steps by a three-roll mill until the slurry fineness is ≤10 µm, thus obtaining the tungsten copper electronic slurry.

[0019] In addition, this invention also proposes a medium-temperature co-fired ceramic substrate, wherein the conductive lines on its surface or inner layer are formed by the aforementioned tungsten-copper electronic paste through a printing and sintering process. The sintering process is carried out in a hydrogen-nitrogen mixed atmosphere at a sintering temperature of 1350 °C.

[0020] Compared with the prior art, the beneficial effects of the present invention are mainly reflected in:

[0021] 1) This tungsten-copper paste uses tungsten powder and copper powder to directly form a conductive phase, avoiding the problems of incomplete reduction and residual oxides that can lead to decreased conductivity in traditional processes using copper oxide powder. The tungsten-copper composite metal phase forms a stable conductive network during medium-temperature sintering. Compared to pure tungsten paste, the sheet resistance is significantly reduced, and the conductivity is effectively improved, thereby enhancing the electrical performance and signal transmission efficiency of the medium-temperature co-fired ceramic substrate.

[0022] 2) This tungsten-copper slurry, by selecting specific morphologies and optimizing the particle size distribution and content ratio of tungsten-copper powder, facilitates powder stacking and sintering densification, thereby enhancing the connectivity of conductive pathways. The selected raw materials are readily available, the cost is controllable, and the preparation process is simple and stable, exhibiting good process adaptability and potential for large-scale production.

[0023] 3) This tungsten-copper paste possesses excellent rheological properties and printability, enabling high-resolution circuit printing with clear edges and a smooth surface. During co-firing, the paste exhibits good thermal matching with the ceramic substrate, resulting in strong adhesion after sintering without defects such as warping, delamination, or blistering. It boasts a high yield and is suitable for high-reliability electronic packaging and multilayer substrate circuit manufacturing. Attached Figure Description

[0024] Figure 1 This is a picture of the printed product of the tungsten copper paste prepared in Example 2.

[0025] Figure 2 The image shows a SEM image of the film surface of the tungsten copper paste prepared in Example 2. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings.

[0027] The main purpose of this invention is to obtain an electronic paste for medium-temperature co-fired ceramic substrates with superior performance and low sheet resistance by controlling the particle size and ratio of tungsten copper powder, as well as the reasonable ratio of it with organic carrier and binder phase.

[0028] The following examples use tungsten copper powder with different particle size ratios as examples to introduce tungsten copper powder obtained by different particle size combinations. The properties of the tungsten copper slurry prepared are shown in Table 1 below.

[0029] Table 1

[0030] Example Tungsten powder particle size Copper powder particle size Tungsten copper powder mass ratio Shear resistance 1 1.21 µm 6.29 µm 70%:30% 11.3475 mΩ / □ 2 3.13 µm 6.29 µm 72%:28% 10.2629 mΩ / □ 3 5.07 µm 6.29 µm 74%:26% 13.7796 mΩ / □

[0031] Example 1

[0032] In this embodiment, the mass ratio of tungsten copper powder, organic carrier, and binder phase is 81%:14%:5%.

[0033] In this embodiment, the tungsten-copper powder is composed of tungsten powder and copper powder in a mass ratio of 70%:30%, and the particle size of the tungsten powder is 1.21 µm and the particle size of the copper powder is 6.29 µm.

[0034] In this embodiment, the organic carrier is composed of terpineol, diethylene glycol butyl ether, tributyl citrate, ethyl cellulose, acrylic resin, lecithin, and hydrogenated castor oil in a mass percentage ratio of 40%:25%:10%:12%:8%:2%:3%.

[0035] In this embodiment, the binder phase is composed of silicon dioxide, aluminum oxide, barium titanate, and zirconium silicate in a mass percentage ratio of 60%:20%:10%:10%.

[0036] The preparation process of the tungsten-copper electronic paste in this embodiment is as follows:

[0037] Step 1: Preparation of organic carrier

[0038] Weigh out terpineol, diethylene glycol butyl ether, tributyl citrate, ethyl cellulose, acrylic resin, lecithin, and hydrogenated castor oil, mix them according to the specified ratio, heat to 80°C, add to the mixture and stir with a rotor for 5 hours until the system is homogeneous and transparent to obtain the organic carrier.

[0039] Step 2: Mixing the conductive phase and the binder phase

[0040] According to the preset ratio, tungsten powder and copper powder, which are conductive phases, are mixed with silicon dioxide, aluminum oxide, barium titanate and zirconium silicate, which are binder phases, and loaded into a material tank. The mixture is then uniformly mixed at a speed of 15 h using a three-dimensional powder mixer to obtain premixed powder.

[0041] Step 3: Grinding the slurry

[0042] An organic carrier is added to the premixed powder and placed in a mixing device for initial grinding at 1200 rpm for 4 minutes. The ground slurry is then subjected to multi-step grinding using a three-roll mill until the slurry fineness is ≤10 µm, thus obtaining the tungsten-copper electronic slurry.

[0043] Step 4: Sintering of slurry

[0044] Tungsten-copper electronic paste is screen-printed onto alumina green ceramic belt using a screen printing machine. The belt is then sintered at 1350 °C using a hydrogen-nitrogen mixed gas. After furnace cooling, the final product is obtained.

[0045] Performance testing: The surface sheet resistance of the sintered sample was tested using a four-probe tester, and the sheet resistance value was measured to be 11.3475 mΩ / □. Cross-cut adhesion testing showed that the sintered film layer was firmly bonded to the ceramic substrate, and no peeling was observed.

[0046] Example 2

[0047] In this embodiment, the mass ratio of tungsten copper powder, organic carrier, and binder phase is 81%:14%:5%.

[0048] In this embodiment, the tungsten-copper powder is composed of tungsten powder and copper powder in a mass ratio of 72%:28%, with the tungsten powder having a particle size of 3.13 µm and the copper powder having a particle size of 6.29 µm.

[0049] In this embodiment, the organic carrier is composed of terpineol, diethylene glycol butyl ether, tributyl citrate, ethyl cellulose, acrylic resin, lecithin, and hydrogenated castor oil in a mass percentage ratio of 40%:25%:10%:12%:8%:2%:3%.

[0050] In this embodiment, the binder phase is composed of silicon dioxide, aluminum oxide, barium titanate, and zirconium silicate in a mass percentage ratio of 60%:20%:10%:10%.

[0051] The preparation process of the tungsten-copper electronic paste in this embodiment is as follows:

[0052] Step 1: Preparation of organic carrier

[0053] Weigh out terpineol, diethylene glycol butyl ether, tributyl citrate, ethyl cellulose, acrylic resin, lecithin, and hydrogenated castor oil, mix them according to the specified ratio, heat to 80 °C, add to a stirring rotor and stir for 5 h until the system is homogeneous and transparent to obtain the organic carrier.

[0054] Step 2: Mixing the conductive phase and the binder phase

[0055] According to the preset ratio, tungsten powder and copper powder, which are conductive phases, are mixed with silicon dioxide, aluminum oxide, barium titanate and zirconium silicate, which are binder phases, and loaded into a material tank. The mixture is then uniformly mixed at a speed of 15 h using a three-dimensional powder mixer to obtain premixed powder.

[0056] Step 3: Grinding the slurry

[0057] An organic carrier is added to the premixed powder and placed in a mixing device for initial grinding at 1200 rpm for 4 minutes. The ground slurry is then subjected to multi-step grinding using a three-roll mill until the slurry fineness is ≤10 µm, thus obtaining the tungsten-copper electronic slurry.

[0058] Step 4: Sintering of slurry

[0059] Tungsten-copper electronic paste is screen-printed onto alumina green ceramic belt using a screen printing machine. The belt is then sintered at 1350 °C using a hydrogen-nitrogen mixed gas. After furnace cooling, the final product is obtained.

[0060] Performance testing: The surface sheet resistance of the sintered sample was tested using a four-probe tester, and the sheet resistance value was measured to be 10.2629 mΩ / □.

[0061] Simultaneously, its morphology and printability are analyzed: such as Figure 1 As shown, the conductive patterns formed after printing and sintering of the slurry have clear lines, neat edges, high resolution, and a smooth film surface without warping or cracking, indicating that the slurry and ceramic substrate have good thermal matching and interfacial bonding during the sintering process.

[0062] Microstructure characterization: The sample surface was observed using scanning electron microscopy (SEM). Figure 2 As can be seen, the tungsten and copper powder particles are densely packed with sufficient inter-particle connections, and no obvious pores or structural defects are observed. This uniform and dense microstructure is conducive to the formation of continuous conductive paths, which is the structural basis for obtaining low sheet resistance. Cross-cut adhesion testing showed that the sintered film layer was firmly bonded to the ceramic substrate, and no peeling was observed.

[0063] Example 3

[0064] In this embodiment, the mass ratio of tungsten copper powder, organic carrier, and binder phase is 81%:14%:5%.

[0065] In this embodiment, the tungsten-copper powder is composed of tungsten powder and copper powder in a mass ratio of 74%:26%, with the tungsten powder having a particle size of 5.07 µm and the copper powder having a particle size of 6.29 µm.

[0066] In this embodiment, the organic carrier is composed of terpineol, diethylene glycol butyl ether, tributyl citrate, ethyl cellulose, acrylic resin, lecithin, and hydrogenated castor oil in a mass percentage ratio of 40%:25%:10%:12%:8%:2%:3%.

[0067] In this embodiment, the binder phase is composed of silicon dioxide, aluminum oxide, barium titanate, and zirconium silicate in a mass percentage ratio of 60%:20%:10%:10%.

[0068] The preparation process of the tungsten-copper electronic paste in this embodiment is as follows:

[0069] Step 1: Preparation of organic carrier

[0070] Weigh out terpineol, diethylene glycol butyl ether, tributyl citrate, ethyl cellulose, acrylic resin, lecithin, and hydrogenated castor oil, mix them according to the specified ratio, heat to 80 °C, add to a stirring rotor and stir for 5 h until the system is homogeneous and transparent to obtain the organic carrier.

[0071] Step 2: Mixing the conductive phase and the binder phase

[0072] According to the preset ratio, tungsten powder and copper powder, which are conductive phases, are mixed with silicon dioxide, aluminum oxide, barium titanate and zirconium silicate, which are binder phases, and loaded into a material tank. The mixture is then uniformly mixed at a speed of 15 h using a three-dimensional powder mixer to obtain premixed powder.

[0073] Step 3: Grinding the slurry

[0074] An organic carrier is added to the premixed powder and placed in a mixing device for initial grinding at 1200 rpm for 4 minutes. The ground slurry is then subjected to multi-step grinding using a three-roll mill until the slurry fineness is ≤10 µm, thus obtaining the tungsten-copper electronic slurry.

[0075] Step 4: Sintering of slurry

[0076] Tungsten-copper electronic paste is screen-printed onto alumina green ceramic belt using a screen printing machine. The belt is then sintered at 1350 °C using a hydrogen-nitrogen mixed gas. After furnace cooling, the final product is obtained.

[0077] Performance testing: The surface sheet resistance of the sintered sample was tested using a four-probe tester, and the sheet resistance value was measured to be 13.7796 mΩ / □. Cross-cut adhesion testing showed that the sintered film layer was firmly bonded to the ceramic substrate, and no peeling was observed.

Claims

1. A tungsten copper electronic paste for an intermediate temperature co-fired ceramic substrate, characterized by, consists of the following components in mass percentage, based on 100% of the total mass: consists of the following components in mass percentage, based on 100% of the total mass: 80%~85% tungsten copper powder, 5%~15% organic carrier, 5%~10% binder phase.

2. The tungsten copper electronic paste for an intermediate temperature co-fired ceramic substrate according to claim 1, wherein The tungsten copper powder consists of tungsten powder and copper powder, with the content of tungsten powder being 70%~78% and the content of copper powder being 22%~30%, based on 100% of the total mass of the tungsten copper powder.

3. The tungsten copper electronic paste for an intermediate temperature co-fired ceramic substrate according to claim 2, wherein The tungsten powder has a median particle size D50 of 0.82 to 6.2 pm and an irregular cubic structure; the copper powder has a dendritic structure and a median particle size D50 of 3.4 to 9.7 pm. 50 The tungsten powder has a median particle size D50 of 0.82 to 6.2 pm and an irregular cubic structure; the copper powder has a dendritic structure and a median particle size D50 of 3.4 to 9.7 pm. 50 The tungsten powder has a median particle size D50 of 0.82 to 6.2 pm and an irregular cubic structure; the copper powder has a dend 4. The tungsten copper electronic paste for an intermediate temperature co-fired ceramic substrate according to claim 1, wherein The binder phase is selected from the group consisting of one or more of a combination of alumina, silica, barium titanate, zirconium silicate.

5. The tungsten copper electronic paste for an intermediate temperature co-fired ceramic substrate according to claim 1, wherein consists of the following components in mass percentage, based on 100% of the total mass of the organic carrier: 75%~80% organic solvent, 15%~20% thickening agent, 1%~5% auxiliary agent.

6. The medium temperature co-fired ceramic substrate electronic paste according to claim 5, wherein, The organic solvent is selected from the group consisting of one or more of a combination of terpineol, butyl benzyl phthalate, tributyl citrate, diethylene glycol butyl ether; the thickening agent is selected from the group consisting of one or both of a combination of ethyl cellulose, acrylic resin; the auxiliary agent includes a dispersing agent and a thixotropic agent, wherein the dispersing agent is selected from the group consisting of one or more of a combination of lecithin, sodium polyacrylate, castor oil, methyl cellulose; the thixotropic agent is selected from the group consisting of one or both of a combination of hydrogenated castor oil, methyl methacrylate.

7. The method of claim 1 to 6, wherein the method is characterized by, comprises the following steps: S1, preparing the organic carrier: stirring and mixing the components of the organic carrier at 60~80℃ for 3~5 h until the system is uniform and transparent, to obtain the organic carrier; S2, powder premixing: mixing the tungsten powder, copper powder and binder phase in a mixer for 15 h to obtain a mixed powder; S3, slurry preparation: adding the mixed powder and the organic carrier into a stirring device, first stirring at a speed of 1000~2000 rpm for 2~5 min for preliminary mixing, and then performing multi-step grinding by a three-roll grinder until the fineness of the slurry is ≤10 µm, to obtain the tungsten copper electronic slurry.

8. A medium-temperature co-fired ceramic substrate, the surface or inner layer of which has a conductive circuit formed by printing and sintering the tungsten copper electronic slurry according to any one of claims 1~6.

9. The mid-temperature co-fired ceramic substrate of claim 8, wherein, The sintering process is performed in a hydrogen-nitrogen mixed atmosphere, and the sintering temperature is 1350℃.

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