A low sheet resistance tungsten copper electronic paste and its preparation method

Abstract

This invention relates to the field of electronic paste preparation technology, and discloses a low sheet resistance tungsten-copper electronic paste and its preparation method, comprising the following steps: Step 1, preparing tungsten-copper composite powder: spherical tungsten powder with a diameter of 1-10 μm and copper powder with a size of 1-3 μm are mixed by mechanical mixing, with a tungsten to copper weight ratio of 3:1-6:1. Before mixing, the copper powder needs to undergo graphene coating pretreatment; Step 2, preparing an inorganic binder: the inorganic binder includes, but is not limited to, the following components: glass powder, CuO, TiO2, La2O3, Pu6O11; Step 3, preparing an organic carrier: the organic carrier includes a solvent, an organic binder, and a thickener; Step 4, preparing the tungsten-copper paste. The tungsten-copper paste of this invention has widely available raw materials, a simple preparation process, and is suitable for mass production. Although graphene, a high-priced material, is added, the amount added is small and the performance is particularly excellent, making the cost of the tungsten-copper paste of this invention far lower than that of similar foreign products, resulting in a very high cost-performance ratio.

Description

Technical Field

[0001] This invention relates to the field of electronic paste preparation technology, and in particular to a low sheet resistance tungsten copper electronic paste and its preparation method. Background Technology

[0002] Electronic packaging is a crucial component of microelectronic devices, not only protecting the chip but also playing a decisive role in signal transmission, amplification, emission, and heat dissipation. With the development of microelectronics technology, semiconductor devices are increasingly moving towards higher density, higher power, more functions, higher speed, and smaller size, placing higher performance demands on microelectronic packaging. Ceramic packaging, primarily using high-temperature ceramic shells, offers advantages over plastic and metal packaging, including a lower dielectric constant, extremely high insulation resistance, a lower coefficient of thermal expansion, and higher strength. This results in superior stability, strong heat dissipation, excellent microwave performance, and good sealing properties. Currently, ceramic packaging has become a key component of mainstream electronic packaging.

[0003] High-temperature co-firing (HTCF) is a common method for manufacturing ceramic packaging shells. The process involves drilling holes in each layer of green ceramic wafer, filling them with a metal conductor paste, printing the paste onto the surface, and finally stacking and co-firing these multiple layers at high temperature to form a substrate with interconnected conductors. Therefore, the metal conductor paste is a key material for obtaining high-performance ceramic packaging shells, as it affects the transmission performance of the ceramic packaging shell. Tungsten paste has good HTCF performance, excellent thermal conductivity, and a low coefficient of thermal expansion, making it a commonly used conductor paste in the production of high-temperature ceramic shells. However, its high sheet resistance limits its conductivity, affecting the transmission performance of the ceramic shell after HTCF and making it difficult to apply in high-frequency optoelectronic devices in fields such as optical communication, data centers, and phased-array radar. Therefore, developing tungsten-based conductor pastes with lower sheet resistance is of great significance in both military and civilian fields to meet the requirements of higher bandwidth and faster transmission rates.

[0004] Currently, the sheet resistance of mainstream tungsten-based paste products in China is approximately 12-15 mΩ / □, while Kyocera's tungsten-copper paste from Japan can achieve a sheet resistance as low as 4-5 mΩ / □, representing a revolutionary breakthrough. However, the technology for producing tungsten-copper paste is strictly embargoed against China, and the corresponding ceramic packaging shells have also been banned from sale to China.

[0005] Due to the addition of copper, the sheet resistance of tungsten copper paste is significantly reduced compared to pure tungsten paste. However, in practical applications, tungsten copper paste needs to be co-fired with ceramic substrates at temperatures exceeding 1500°C. During this process, copper in the tungsten copper paste often escapes due to its low melting point, leaving numerous pores. This results in an insufficiently dense sintered film, ultimately leading to a decrease in conductivity, sometimes even worse than that of pure tungsten paste. Therefore, ensuring that copper does not escape is crucial for achieving low sheet resistance in tungsten copper paste. Currently, there is no tungsten copper paste formulation or preparation process that can meet these requirements. Summary of the Invention

[0006] To address the technical problems mentioned in the background section, this invention provides a low sheet resistance tungsten copper electronic paste and its preparation method.

[0007] This invention is achieved using the following technical solution: a method for preparing a low sheet resistance tungsten copper electronic paste, comprising the following steps:

[0008] Step 1: Preparation of tungsten-copper composite powder: Select spherical tungsten powder with a diameter of 1-10 μm and copper powder with a size of 1-3 μm and mix them by mechanical mixing. The weight ratio of tungsten to copper is 3:1-6:1.

[0009] Step 2: Preparation of Inorganic Adhesive: The inorganic adhesive includes, but is not limited to, the following components: glass powder, CuO, TiO2, La2O3, Pr6O. 11 ;

[0010] Step 3: Prepare the organic carrier: The organic carrier includes solvent, organic binder and thickener. When preparing, weigh the solvent and thickener according to the ratio, put them into a container and stir evenly. Heat the container in a water bath to 50°C, and add the organic binder while stirring until it is evenly mixed. Then seal and store for later use.

[0011] Step 4: Preparation of tungsten-copper paste: During preparation, the tungsten-copper composite powder is first mechanically mixed with the prepared inorganic binder, and then put together with the organic carrier into a high-speed mixer for rapid and uniform mixing. The mixed paste is then ground 3-5 times on a three-roll mill to obtain the final tungsten-copper electronic paste.

[0012] As a further improvement to the above scheme, before mixing copper powder and tungsten powder in step one, the surface of the copper powder is coated with graphene.

[0013] As a further improvement to the above scheme, in step one, graphene coating of copper powder is performed using high-energy ball milling. A certain weight of 8-layer graphene with a size of 10 μm is prepared and placed in a ball mill jar along with a certain amount of copper powder and a certain amount of rare earth element Ce for high-energy ball milling. The weight ratio of graphene, rare earth, and copper powder is 0.5-1.5:1-3:95.5-98.5. The high-energy ball milling time is 1-4 hours, and the atmosphere inside the ball mill jar is argon. After high-energy ball milling, graphene-coated copper powder is obtained.

[0014] As a further improvement to the above scheme, in step two: glass powder, CuO, TiO2, La2O3, and Pr6O 11 The weight ratio is: 50-70: 5-20: 5-15: 1-5: 1-5;

[0015] As a further improvement to the above scheme, in step three, the weight ratio of solvent, organic binder and thickener is 60-80:5-20:5-20.

[0016] As a further improvement to the above scheme, in step three, the solvent is terpineol, the organic binder is ethyl cellulose and polyvinyl butyral, and the thickener is dibutyl phthalate.

[0017] As a further improvement to the above scheme, the weight ratio of ethyl cellulose to polyvinyl butyral is 1:1.

[0018] As a further improvement to the above scheme, in step four, the weight ratio of tungsten-copper composite powder, inorganic binder and organic carrier is 75-85:4-8:10-20.

[0019] As a further improvement to the above scheme, the stirring speed is 1000-5000 r / min and the stirring time is 3-6 min.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] This invention first employs a high-energy ball milling method to coat copper powder with graphene. Because graphene has a very high melting point, it will not melt during co-firing and can effectively encapsulate the molten copper powder, thereby preventing copper loss. Furthermore, due to graphene's excellent electrical conductivity, its addition does not reduce the conductivity of the slurry but rather further enhances it. Adding an appropriate amount of rare earth element Ce during the high-energy ball milling graphene coating of copper powder can improve the surface activity of the copper powder, which is beneficial for graphene coating and thus improves the coating effect.

[0022] Due to the addition of copper, the formulation of the inorganic binder in this invention should be modified accordingly. A small amount of CuO is added to the inorganic binder, using CuO as a bridge between Cu and the ceramic substrate. This improves the bonding strength between the tungsten copper paste and the ceramic substrate after sintering. Simultaneously, CuO can be partially reduced by hydrogen in the sintering atmosphere during sintering to obtain pure copper, thus supplementing the copper content in the paste. Furthermore, adding a small amount of rare earth oxides with good electrical conductivity to the inorganic binder can further improve the bonding strength between the tungsten copper paste and the ceramic substrate after sintering, while also improving the electrical conductivity of the tungsten copper paste.

[0023] Compared with existing tungsten-copper pastes, the tungsten-copper paste prepared in this invention has a dense structure after sintering, with no delamination, shrinkage cavities, or cracks. It also exhibits a small copper content loss, significantly improved conductivity, a sheet resistance as low as 5.3-8.2 mΩ / □, and a bonding strength with the ceramic substrate greater than 15N. The tungsten-copper paste of this invention uses widely available raw materials, has a simple preparation process, and is suitable for mass production. Although graphene, a high-priced material, is added, the amount added is small and its performance is exceptionally superior, resulting in a significantly lower cost than similar foreign products, offering outstanding cost-effectiveness. Attached Figure Description

[0024] Figure 1 These are photographs of the tungsten-copper slurry prepared according to Embodiment 2 of the present invention.

[0025] Figure 2 This is a cross-sectional microstructure photograph of the tungsten copper paste prepared in Embodiment 2 of the present invention after sintering on a ceramic substrate;

[0026] Figure 3 This is a photograph of the surface structure of the tungsten copper paste prepared in Embodiment 2 of the present invention after sintering on a ceramic substrate. Detailed Implementation

[0027] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0028] Example 1:

[0029] This embodiment presents a low sheet resistance tungsten copper electronic paste formulation and preparation method, including the following steps:

[0030] Step 1: Preparation of Tungsten-Copper Composite Powder: Spherical tungsten powder with a diameter of 6 μm and copper powder with a size of 2 μm are mixed mechanically at a tungsten to copper weight ratio of 5:1. Before mixing the tungsten and copper powders, the copper needs to be pretreated by coating its surface with graphene. The specific process is as follows: Graphene coating of copper powder is performed using high-energy ball milling. Several weights of 8-layer graphene with a size of 10 μm are prepared and placed in a ball mill jar along with a certain amount of copper powder and a certain amount of rare earth element Ce for high-energy ball milling. The weight ratio of graphene, rare earth element, and copper powder is 0.5:1:98.5. The high-energy ball milling time is 4 hours, and the atmosphere inside the ball mill jar is argon. After high-energy ball milling, graphene-coated copper powder is obtained, which is then mechanically mixed with tungsten powder according to the required proportions to obtain the final tungsten-copper composite powder.

[0031] Step 2: Preparation of Inorganic Adhesive: The inorganic adhesive consists of glass powder, CuO, TiO2, La2O3, and Pr6O. 11 It consists of several components, including glass powder, CuO, TiO2, La2O3, and Pr6O. 11 The weight ratio is 70:15:8:3:3. The components are weighed according to the above ratio and mechanically mixed to obtain the final inorganic adhesive.

[0032] Step 3: Preparation of the organic carrier: The organic carrier consists of a solvent, an organic binder, and a thickener, with a weight ratio of 70:20:10. The solvent is terpineol, the organic binder is ethyl cellulose and polyvinyl butyral in a 1:1 weight ratio, and the thickener is dibutyl phthalate. Preparation process: Weigh the solvent and thickener according to the ratio and place them in a container, stirring thoroughly. Heat the mixture in a water bath to 50°C, adding the organic binder while stirring until evenly mixed. Then seal and store for later use.

[0033] Step 4: Preparation of Tungsten-Copper Paste: The tungsten-copper paste consists of the tungsten-copper composite powder obtained in Step 1, the inorganic binder obtained in Step 2, and the organic carrier obtained in Step 3. The weight ratio of the tungsten-copper composite powder, inorganic binder, and organic carrier is 80:4:16. The preparation process is as follows: First, the tungsten-copper composite powder is mechanically mixed with the prepared inorganic binder. Then, it is placed together with the organic carrier in a high-speed mixer and rapidly stirred until uniform. The stirring speed is 1000-5000 r / min, and the stirring time is 3-6 min. Finally, the stirred paste is ground 3-5 times on a three-roll mill to obtain the final tungsten-copper electronic paste.

[0034] The tungsten-copper paste obtained through the above steps is screen-printed onto a ceramic substrate and then formed into a thick-film circuit at 1450°C in a hydrogen atmosphere. The surface sheet resistance was measured to be 8 mΩ / □ and the adhesion strength to be 14 N using a four-probe tester. The film layer was dense and free of defects such as delamination, shrinkage cavities, and cracks.

[0035] Example 2:

[0036] A low sheet resistance tungsten copper electronic paste formulation and preparation method, comprising the following steps:

[0037] Step 1: Preparation of Tungsten-Copper Composite Powder: Spherical tungsten powder with a diameter of 6 μm and copper powder with a size of 1 μm are mixed mechanically, with a tungsten to copper weight ratio of 4:1. Before mixing the tungsten and copper powders, the copper needs to be pretreated by coating its surface with graphene. The specific process is as follows: Graphene coating of copper powder is performed using high-energy ball milling. Several weights of 8-layer graphene with a size of 10 μm are prepared and placed in a ball mill jar along with a certain amount of copper powder and a certain amount of rare earth element Ce for high-energy ball milling. The weight ratio of graphene, rare earth element, and copper powder is 1:1.5:97.5. The high-energy ball milling time is 4 hours, and the atmosphere inside the ball mill jar is argon. After high-energy ball milling, graphene-coated copper powder is obtained, which is then mechanically mixed with tungsten powder according to the required proportions to obtain the final tungsten-copper composite powder.

[0038] Step 2: Design and formulation of inorganic adhesive: The inorganic adhesive consists of glass powder, CuO, TiO2, La2O3, and Pr6O. 11 Composed of several components, including glass powder, CuO, TiO2, La2O3, and Pr6O. 11 The weight ratio is 66:18:10:4:2. The components are weighed according to the above ratio and mechanically mixed to obtain the final inorganic adhesive.

[0039] Step 3: Design and Preparation of the Organic Carrier: The organic carrier consists of a solvent, an organic binder, and a thickener in a weight ratio of 75:18:7. The solvent is terpineol, the organic binder is ethyl cellulose and polyvinyl butyral in a weight ratio of 1:1, and the thickener is dibutyl phthalate. Preparation process: Weigh the solvent and thickener according to the ratio and place them in a container, stirring until homogeneous. Heat the container in a water bath to 50°C, adding the organic binder while stirring until fully mixed. Then seal and store for later use.

[0040] Step 4: Preparation of Tungsten-Copper Paste: The tungsten-copper paste consists of the tungsten-copper composite powder obtained in Step 1, the inorganic binder obtained in Step 2, and the organic carrier obtained in Step 3, with a weight ratio of 82:4:14. Preparation: First, the tungsten-copper composite powder and the prepared inorganic binder are mechanically mixed. Then, the mixture is placed together with the organic carrier in a high-speed mixer and rapidly stirred until homogeneous. The stirring speed is 1000-5000 r / min, and the stirring time is 3-6 min. The stirred paste is then ground 3-5 times on a three-roll mill to obtain the final tungsten-copper electronic paste.

[0041] The tungsten-copper paste obtained through the above steps is screen-printed onto a ceramic substrate and then used to form a thick-film circuit at 1450°C in a hydrogen atmosphere. Using a four-probe tester, its surface sheet resistance is measured to be 5.3 mΩ / □, and its adhesion strength is 15 N. The film layer is dense and free of defects such as delamination, shrinkage cavities, and cracks. The internal and surface structures are as follows: Figure 2 and 3 As shown.

[0042] Example 3:

[0043] This embodiment presents a low sheet resistance tungsten copper electronic paste formulation and preparation method, including the following steps:

[0044] Step 1: Preparation of Tungsten-Copper Composite Powder: Spherical tungsten powder with a diameter of 6 μm and copper powder with a size of 1 μm are mixed mechanically, with a tungsten to copper weight ratio of 4:1. Before mixing the tungsten and copper powders, the copper needs to be pretreated by coating its surface with graphene. The specific process is as follows: Graphene coating of copper powder is performed using high-energy ball milling. Several weights of 8-layer graphene with a size of 10 μm are prepared and placed in a ball mill jar along with a certain amount of copper powder and a certain amount of rare earth element Ce for high-energy ball milling. The weight ratio of graphene, rare earth, and copper powder is 1:3:96. The high-energy ball milling time is 3 hours, and the atmosphere inside the ball mill jar is argon. After high-energy ball milling, graphene-coated copper powder is obtained, which is then mechanically mixed with tungsten powder according to the required proportions to obtain the final tungsten-copper composite powder.

[0045] Step 2: Design and formulation of inorganic adhesive: The inorganic adhesive consists of glass powder, CuO, TiO2, La2O3, and Pr6O. 11 Composed of several components, including glass powder, CuO, TiO2, La2O3, and Pr6O. 11 The weight ratio is 64:18:14:2:2. The components are weighed according to the above ratio and mechanically mixed to obtain the final inorganic adhesive.

[0046] Step 3: Design and Preparation of the Organic Carrier: The organic carrier consists of a solvent, an organic binder, and a thickener, with a weight ratio of 80:13:7. The solvent is terpineol, the organic binder is ethyl cellulose and polyvinyl butyral in a 1:1 weight ratio, and the thickener is dibutyl phthalate. Preparation process: Weigh the solvent and thickener according to the ratio and place them in a container, stirring thoroughly. Heat the container in a water bath to 50°C, adding the organic binder while stirring until evenly mixed. Then seal and store for later use.

[0047] Step 4: Preparation of Tungsten-Copper Paste: The tungsten-copper paste consists of the tungsten-copper composite powder obtained in Step 1, the inorganic binder obtained in Step 2, and the organic carrier obtained in Step 3, with a weight ratio of 84:6:10. Preparation: First, the tungsten-copper composite powder and the prepared inorganic binder are mechanically mixed. Then, the mixture is placed together with the organic carrier in a high-speed mixer and rapidly stirred until homogeneous. The stirring speed is 1000-5000 r / min, and the stirring time is 3-6 min. The stirred paste is then ground 3-5 times on a three-roll mill to obtain the final tungsten-copper electronic paste.

[0048] The tungsten-copper paste obtained through the above steps is screen-printed onto a ceramic substrate and then formed into a thick-film circuit at 1450°C in a hydrogen atmosphere. The surface sheet resistance was measured to be 7 mΩ / □ using a four-probe tester, the adhesion strength was 13 N, the film layer was dense, and there were no defects such as delamination, shrinkage cavities, or cracks.

[0049] Example 4:

[0050] A low sheet resistance tungsten copper electronic paste formulation and preparation method, comprising the following steps:

[0051] Step 1: Preparation of Tungsten-Copper Composite Powder: Spherical tungsten powder with a diameter of 6 μm and copper powder with a size of 1 μm are mixed mechanically, with a tungsten to copper weight ratio of 6:1. Before mixing the tungsten and copper powders, the copper needs to be pretreated by coating its surface with graphene. The specific process is as follows: Graphene coating of copper powder is performed using high-energy ball milling. Several weights of 8-layer graphene with a size of 10 μm are prepared and placed in a ball mill jar along with a certain amount of copper powder and a certain amount of rare earth element Ce for high-energy ball milling. The weight ratio of graphene, rare earth, and copper powder is 0.5:2.5:97. The high-energy ball milling time is 3 hours, and the atmosphere inside the ball mill jar is argon. After high-energy ball milling, graphene-coated copper powder is obtained, which is then mechanically mixed with tungsten powder according to the required proportions to obtain the final tungsten-copper composite powder.

[0052] Step 2: Design and formulation of inorganic adhesive: The inorganic adhesive consists of glass powder, CuO, TiO2, La2O3, and Pr6O. 11It consists of several components, including glass powder, CuO, TiO2, La2O3, and Pr6O. 11 The weight ratio is 65:15:15:2.5:2.5. The components are weighed according to the above ratio and mechanically mixed to obtain the final inorganic adhesive.

[0053] Step 3: Design and Preparation of the Organic Carrier: The organic carrier consists of a solvent, an organic binder, and a thickener, with a weight ratio of 77:13:10. The solvent is terpineol, the organic binder is ethyl cellulose and polyvinyl butyral in a 1:1 weight ratio, and the thickener is dibutyl phthalate. Preparation process: Weigh the solvent and thickener according to the ratio and place them in a container, stirring until homogeneous. Heat the container in a water bath to 50°C, adding the organic binder while stirring until fully mixed. Then seal and store for later use.

[0054] Step 4: Preparation of Tungsten-Copper Slurry: The tungsten-copper slurry consists of the tungsten-copper composite powder obtained in Step 1, the inorganic binder obtained in Step 2, and the organic carrier obtained in Step 3, with a weight ratio of 84:6:10. The preparation process is as follows: First, the tungsten-copper composite powder and the prepared inorganic binder are mechanically mixed. Then, the mixture is placed together with the organic carrier in a high-speed mixer and rapidly stirred until homogeneous. The stirring speed is 1000-5000 r / min, and the stirring time is 3-6 min. Finally, the stirred slurry is ground 3-5 times on a three-roll mill to obtain the final tungsten-copper electronic slurry.

[0055] The tungsten-copper paste obtained through the above steps is screen-printed onto a ceramic substrate and then formed into a thick-film circuit at 1450°C in a hydrogen atmosphere. A four-probe tester was used to measure its surface sheet resistance at 7.8 mΩ / □, its adhesion at 12N, and the film layer was dense and free of defects such as delamination, shrinkage cavities, and cracks.

[0056] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing a low sheet resistance tungsten copper electronic paste, characterized in that, Includes the following steps: Step 1: Preparation of tungsten-copper composite powder: Select spherical tungsten powder with a diameter of 1-10 μm and copper powder with a size of 1-3 μm and mix them by mechanical mixing. The weight ratio of tungsten to copper is 3:1-6:

1. Step 2: Prepare the inorganic adhesive: The inorganic adhesive includes: glass powder, CuO, TiO2, La2O3, and Pr6O. 11 ; Step 3: Prepare the organic carrier: The organic carrier includes solvent, organic binder and thickener. When preparing, weigh the solvent and thickener according to the ratio, put them into a container and stir evenly. Heat the container in a water bath to 50°C, and add the organic binder while stirring until it is evenly mixed. Then seal and store for later use. Step 4: Preparation of tungsten copper paste: During preparation, the tungsten copper composite powder is first mechanically mixed with the prepared inorganic binder, and then put together with the organic carrier into a high-speed mixer for rapid and uniform mixing. The mixed paste is then ground 3-5 times on a three-roll mill to obtain the final tungsten copper electronic paste. In step one, copper powder is coated with graphene using high-energy ball milling. Several weights of 8-layer graphene with a size of 10μm are prepared and placed in a ball milling jar with a certain amount of copper powder and a certain amount of rare earth Ce for high-energy ball milling. The weight ratio of graphene, rare earth and copper powder is 0.5-1.5:1-3:95.5-98.

5. The high-energy ball milling time is 1-4 hours. The atmosphere in the ball milling jar is argon. After high-energy ball milling, graphene-coated copper powder is obtained. In step two: glass powder, CuO, TiO2, La2O3, and Pr6O 11 The weight ratio is: 50-70: 5-20: 5-15: 1-5: 1-5; In step four, the weight ratio of tungsten-copper composite powder, inorganic binder, and organic carrier is 75-85:4-8:10-20.

2. The method for preparing a low sheet resistance tungsten copper electronic paste as described in claim 1, characterized in that, Before mixing copper powder and tungsten powder in step one, the surface of the copper powder is coated with graphene.

3. The method for preparing a low sheet resistance tungsten copper electronic paste as described in claim 1, characterized in that, In step three, the weight ratio of solvent, organic binder and thickener is 60-80:5-20:5-20.

4. The method for preparing a low sheet resistance tungsten copper electronic paste as described in claim 1, characterized in that, In step three, the solvent is terpineol, the organic binder is ethyl cellulose and polyvinyl butyral, and the thickener is dibutyl phthalate.

5. The method for preparing a low sheet resistance tungsten-copper electronic paste as described in claim 4, characterized in that, The weight ratio of ethyl cellulose to polyvinyl butyral is 1:

1.

6. The method for preparing a low sheet resistance tungsten copper electronic paste as described in claim 1, characterized in that, In step four, the stirring speed is 1000-5000 r / min, and the stirring time is 3-6 min.

7. A low sheet resistance tungsten copper electronic paste, characterized in that: It is prepared by the preparation method described in any one of claims 1-6.

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