Copper oxide-tungsten conductive paste adaptive to medium-temperature co-fired ceramic and preparation method of copper oxide-tungsten conductive paste

Abstract

The method comprises the following steps: (1) preparing high-temperature inorganic binding phase glass powder: heating silicon dioxide, aluminum oxide, calcium oxide, titanium oxide and barium oxide to a melting temperature, quenching, completely cooling, and crushing to obtain high-temperature inorganic binding phase glass powder; the inorganic binding phase glass powder is obtained; (2) weighing a conductive phase, a sintering framework, a catalyst and inorganic binding phase glass powder, and mechanically mixing to obtain composite powder; (3) preparing an organic carrier: uniformly mixing the additive solution with a solvent to obtain the organic carrier; and (4) preparing the copper oxide-tungsten conductive paste: mixing the composite powder with an organic carrier, grinding, and defoaming to obtain the copper oxide-tungsten conductive paste adaptive to the medium-temperature co-fired ceramic. The blank in the field of medium-temperature co-fired ceramic conductive paste is filled, and the medium-temperature co-fired ceramic conductive paste has an obvious price advantage.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic paste preparation, and particularly relates to a copper oxide-tungsten conductive paste adapted to medium-temperature co-fired ceramics and a preparation method thereof. Background Art

[0002] The electronic packaging housing is an important part of microelectronic devices. It can not only protect the chip, but also play a decisive role in signal transmission, amplification, emission, heat dissipation, etc. In the field of electronic packaging, ceramic packaging has become a common and important electronic packaging technology due to its good original stability, excellent microwave performance, good sealing performance, etc. At present, the processes of ceramic packaging mainly include substrate forming, co-firing, gold plating, soldering, etc. According to the co-firing temperature of the ceramic substrate, the ceramic substrate can be divided into low-temperature co-fired ceramics (LTCC) and high-temperature co-fired ceramics (HTCC).

[0003] LTCC has the advantages of good high-frequency characteristics, multi-function, and high density. The co-firing temperature with the paste is generally below 1000°C. Therefore, the melting point of the metal paste adapted to it must not be too high (usually gold paste, silver paste or copper paste is selected). HTCC has the advantages of high mechanical strength and large wiring density, and is usually applied to high-power devices. However, its sintering temperature reaches above 1400°C, and a metal with a high melting point must be selected to adapt to it (such as tungsten, molybdenum, etc.). For HTCC, although the mechanical strength of the substrate is large after sintering, since its conductive metal phase is tungsten and molybdenum, the conductive performance is relatively general. For some private enterprises that require general strength and certain conductive ability, medium-temperature co-fired ceramics (sintering temperature between 1000°C and 1400°C) are a better choice. However, in the field of medium-temperature ceramics, there is currently no corresponding conductive paste to adapt to it. Therefore, there is an urgent need to develop a new type of paste with a co-firing temperature above 1000°C and good conductive ability. Summary of the Invention

[0004] The purpose of the present invention is to provide a copper oxide-tungsten conductive paste adapted to medium-temperature co-fired ceramics and a preparation method thereof, which solves the problem of the lack of a suitable conductive paste in the field of medium-temperature ceramic substrates.

[0005] In one aspect of the present invention, a preparation method of a copper oxide-tungsten conductive paste adapted to medium-temperature co-fired ceramics is proposed. According to an embodiment of the present invention, the preparation method includes the following steps:

[0006] (1) Prepare a high-temperature inorganic binder glass powder: Heat silicon dioxide, aluminum oxide, calcium oxide, titanium oxide and barium oxide to the melting temperature and then quench, and perform pulverization after complete cooling to obtain an inorganic binder glass powder;

[0007] (2) Weigh the conductive phase, sintered framework, catalyst, and inorganic binder phase glass powder and conduct mechanical mixing to obtain a composite powder.

[0008] (3) Prepare the organic carrier: Mix the additive solution and the solvent evenly to obtain the organic carrier.

[0009] (4) Prepare the copper oxide-tungsten paste: Mix the composite powder and the organic carrier, grind, and degas to remove the air bubbles mixed inside the paste, thereby obtaining the copper oxide-tungsten conductive paste adapted to the medium-temperature co-fired ceramics.

[0010] In addition, according to the preparation method of a copper oxide-tungsten conductive paste adapted to medium-temperature co-fired ceramics in the above embodiments of the present invention, the following additional technical features may also be included:

[0011] In some embodiments of the present invention, in step (1): The mass ratio of the silica, alumina, calcium oxide, barium oxide, and titanium oxide is 6-1:2-1:2-1:2-1:2-1; The heating is carried out in a muffle furnace, and the heating temperature is 1500-1700 °C to ensure that the sintering temperature is above the melting points of all components, and all components can be completely melted.

[0012] In some embodiments of the present invention, in step (1), the pulverization method is as follows: Put the cooled raw materials into a ball mill for high-energy ball milling. The ball-to-material ratio of tungsten carbide and the cooled raw materials is 6-3:3-1; The diameter of the tungsten carbide balls used for ball milling is 6-3 mm. Use absolute ethanol as a grinding aid, and the ball milling time is 2-4 hours. After the ball milling is completed, conduct drying and sieving. The particle size of the finally obtained inorganic binder phase glass powder is 1-5 μm.

[0013] In some embodiments of the present invention, in step (2): The conductive phase is copper oxide powder, the sintered framework is tungsten powder, and the copper oxide powder is spherical copper oxide powder with a diameter of 1-5 μm; The catalyst is triethanolamine and manganese dioxide; The weight parts of the copper oxide powder, tungsten powder, inorganic binder phase glass powder, triethanolamine, and manganese dioxide are 60-75 parts, 5-20 parts, 3-5 parts, 0.1-0.5 parts, and 0.05-0.2 parts respectively.

[0014] In some embodiments of the present invention, in step (3): The solvent is one or a mixture of more of terpineol, butyl carbitol, and ethyl acetate; The additives include a thickener, a dispersant, a thixotropic agent, a leveling agent, and a plasticizer.

[0015] In some embodiments of the present invention, the thickener is one or more of ethyl cellulose, hydrogenated castor oil, dibutyl titanate, and acrylic resin, the dispersant is one or both of tristearate and polyethylene glycol, the thixotropic agent is polyvinyl butyral, the leveling agent is a silane coupling agent, and the plasticizer is castor oil; the mass ratio of the thickener, dispersant, thixotropic agent, leveling agent and plasticizer is 1-7:1-2:1-2:1-2:2-3.

[0016] In some embodiments of the present invention, in step (4): the weight proportion of the composite powder is 83-90 parts, and the weight proportion of the organic carrier is 10-17 parts.

[0017] In some embodiments of the present invention, in step (4), the grinding is performed using a three-roll grinder. The grinding method is as follows:

[0018] a. The ratio of the initial spacing between the medium-speed roller and the slow-speed roller of the three-roll mill to the initial spacing between the medium-speed roller and the fast roller is 2:1;

[0019] b. After grinding 3-4 times, reduce the distance between the medium speed roller and the slow speed roller, and the distance between the medium speed roller and the fast speed roller, and the ratio of the reduced distance is 2:1;

[0020] c. Repeat step b until the distance between the medium-speed roller and the slow-speed roller, and the distance between the medium-speed roller and the fast roller reach the required value;

[0021] d. Grind 7-8 times.

[0022] In some embodiments of the present invention, in step (4): during the degassing operation, the speed is 800-1000r / min, 1600-1800r / min, 800-1000r / min in the order of degassing for 60-50s, 30-20s, and 60-50s, respectively. This prevents the speed from being too low, resulting in incomplete degassing, and also prevents the speed from being too high and the time from being too long, resulting in a large amount of heat generated, causing the internal organic carrier to volatilize and affecting the performance of the slurry.

[0023] In another aspect of the present invention, the present invention provides a copper oxide-tungsten conductive paste suitable for medium temperature co-fired ceramics prepared by a method for preparing a copper oxide-tungsten conductive paste suitable for medium temperature co-fired ceramics.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1) The present invention utilizes the property that copper oxide decomposes into copper at high temperatures, and designs and prepares a conductive paste suitable for co-fired ceramics at medium temperatures. By adding a certain amount of catalyst, the copper oxide in the paste undergoes two decompositions during sintering with medium-temperature co-fired ceramics, and finally completely forms copper. The formed copper adheres to the tungsten skeleton to form a copper-tungsten film, constructing a conductive network, thereby enabling the ceramic substrate to have good electrical conductivity. In addition, compared with conventional copper pastes with sintering temperatures below 1000°C, the copper oxide-tungsten paste can form a copper film with a tungsten skeleton after sintering the ceramic substrate, but the sintering temperature of the copper oxide-tungsten paste can reach 1100 - 1300°C. This greatly increases the temperature for co-sintering with the ceramic substrate to form a copper-tungsten film.

[0026] 2) The argon atmosphere is adopted as the sintering atmosphere when the copper oxide-tungsten conductive paste suitable for medium-temperature co-fired ceramics of the present invention is sintered. Compared with high-temperature hydrogen sintering, it has a certain price advantage and does not have the same dangers and potential hazards as hydrogen sintering. This enables companies and research institutes without high-temperature hydrogen sintering qualifications to also mass-produce conductive products obtained by co-sintering this paste with medium-temperature ceramics, improving the popularity of medium-temperature co-fired ceramic conductive products.

[0027] 3) Part of the copper oxide in contact with the alumina ceramic will also react with the alumina ceramic during the sintering process to form a spinel structure mainly composed of CuAlO 2 , strengthening the bonding between the copper-tungsten film and the alumina substrate.

[0028] 4) The formula process parameters of the present invention can be flexibly adjusted, that is, according to different copper oxide contents, the content of the catalyst can be adjusted to control the degree of self-decomposition of copper oxide to adapt to different requirements.

[0029] 5) All raw materials of the present invention are relatively inexpensive and widely sourced. At the same time, the preparation process of the copper oxide-tungsten conductive paste is simple, easy to control and adjust, and is very suitable for mass production. This paste fills the gap in the field of conductive pastes for medium-temperature co-fired ceramics, broadening the horizons for a wide range of civil packaging fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is the finished copper oxide-tungsten conductive paste obtained in step (4) of Embodiment 1 of the present invention;

[0031] Figure 2 is the thick film sample diagram formed after argon atmosphere sintering of the screen-printed sample of the copper oxide-tungsten conductive paste in Embodiment 1 of the present invention;

[0032] Figure 3 is the surface morphology diagram of the thick film after the cross-cut test in Embodiment 2 of the present invention, where (a) is the macroscopic morphology diagram of the thick film after the cross-cut test, and (b) is the metallographic microscope morphology diagram of the thick film after the cross-cut test;

[0033] Figure 4 This is the surface SEM image after sintering of the printed sample of the copper oxide-tungsten conductive paste in Example 4 of the present invention;

[0034] Figure 5 Among them, a) is the surface point scanning energy spectrum diagram after sintering of the printed sample of the copper oxide-tungsten conductive paste in Example 4 of the present invention, b) and c) are respectively the elemental contents of the copper film represented by points 11 and 12 in Figure a), and d) is the elemental distribution of the tungsten skeleton represented by point 13 in Figure a);

[0035] Figure 6 This is the energy spectrum diagram of the sintered cross-section after printing of the tungsten-copper electronic paste for slowing down copper loss in Example 4 of the present invention. Among them, a) is the cross-section EDS elemental distribution diagram, b) is the EDS elemental content diagram, and c) is the cross-section EDS copper elemental distribution diagram. Detailed implementation manners

[0036] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0037] Example 1

[0038] A preparation method of a copper oxide-tungsten conductive paste adapted to medium-temperature co-fired ceramics, the specific steps are as follows:

[0039] (1) Prepare the inorganic binder glass powder

[0040] Select 6 parts by weight of silicon dioxide, and then the weight ratios of added aluminum oxide, calcium oxide, barium oxide, and titanium oxide to silicon dioxide are 1:1:1:1:6.

[0041] Melting and quenching: Spread the weighed inorganic binder mixed powder evenly in an alumina crucible, and then place the crucible in a muffle furnace for heating. After the temperature in the muffle furnace reaches 1500 °C, keep it warm for two hours, then wear heat-insulating gloves to take out the crucible, and pour the molten inorganic binder into deionized water. After the inorganic binder is completely cooled, take it out and put it into a mortar for preliminary crushing.

[0042] Ball milling of the inorganic binder: Weigh the cooled inorganic binder and record it as 1 part, then put it into a ball milling tank, and weigh 6 parts by weight of tungsten carbide balls (diameter 6 mm). The ball milling process is wet ball milling, using ethanol as a grinding aid. After ball milling in the ball mill for 4 hours, take it out and dry it, and sieve the dried inorganic binder to obtain inorganic binder glass powder with a diameter of 1-5 μm.

[0043] (2) Weighing and mechanical mixing of conductive phase, catalyst, and inorganic binder phase

[0044] Weigh copper oxide powder, tungsten powder, inorganic binder phase, triethanolamine, and manganese dioxide and grind and mix them in a mortar. The weight of copper oxide is 75 parts, the weight of tungsten powder is 5 parts, the weight of inorganic binder phase is 5 parts, the weight of triethanolamine is 0.5 parts, and the weight of manganese dioxide is 0.2 parts. Put the weighed raw materials into a powder mixer and mix them thoroughly for 24 hours to obtain a mixed powder.

[0045] (3) Preparation of organic carrier

[0046] Take 50 parts of organic carrier solvent pine alcohol, 30 parts of butyl carbitol, 10 parts of ethyl acetate, 3 parts of thickener high viscosity acrylic resin, 0.5 parts of dispersant tristearate glyceryl, 0.5 parts of polyethylene glycol, 1 part of thixotropic agent polyvinyl alcohol butyrate, 1 part of leveling agent silane coupling agent, 1 part of plasticizer castor oil, put them into a beaker and stir them evenly with a glass rod. Put the stirred solvent into an oil bath pot and stir it further at a heating temperature of 70°C and a stirring speed of 20r / min. After stirring for 5 hours, the solvent in the beaker forms a uniform organic carrier, then stop stirring and keep warm for 0.5 hours to ensure the stability of the organic carrier.

[0047] (4) Preparation of copper oxide-tungsten slurry

[0048] The mixed powder and organic carrier with a mass ratio of 88:12 were weighed and placed in a mortar for pre-stirring. After forming a viscous fluid slurry, it was placed in a three-roll mill for further grinding. The initial spacing between the medium-speed and slow-speed rollers of the three-roll mill was selected to be 100 μm, and the initial spacing between the medium-speed roller and the fast roller was 50 μm (the spacing ratio between the two was controlled to be 2:1). After grinding 4 times, the spacing between the medium-speed and slow-speed rollers was reduced by 15 μm, and the corresponding spacing between the medium-speed roller and the fast roller was reduced by 7.5 μm, and so on. The spacing between the medium-speed and slow rollers in the final grinding was 10 μm, the spacing between the medium-speed roller and the fast roller was 5 μm, and the final number of grindings was 8 times.

[0049] Then put it into the degassing machine to remove the bubbles inside. During the degassing operation, the rotation speed is 800r / min, 1600r / min, 800r / min in this order for degassing for 60s, 30s, and 60s respectively to finally obtain the finished slurry.

[0050] Figure 1 That is the finished copper oxide-tungsten conductive paste. The fineness of the conductive paste is measured to be 4.5 μm, and the viscosity is 180 Pa·s.

[0051] Performance test: The prepared copper oxide-tungsten conductive paste was screen-printed on a 50×50mm square ceramic substrate to form a copper oxide-tungsten thick film. After printing, the substrate was placed in a 60℃ oven for 5 hours and then degreased and sintered in an argon atmosphere. The sintering temperature was 1100℃ and the holding time was 1h. After sintering, the sample was taken out. The actual picture of the thick film sample after sintering is shown in Figure 2 The appearance after sintering can be observed. It is found that the surface of the film layer is smooth and the interface is clear after sintering. The surface slurry has good printability and no shrinkage occurs after sintering, indicating that its sintering shrinkage rate is small. The conductivity is tested, and the surface square resistance is 50.1mΩ / □ using a four-probe tester.

[0052] Example 2

[0053] A method for preparing a copper oxide-tungsten conductive slurry suitable for medium-temperature co-fired ceramics, the specific steps are as follows:

[0054] (1) Preparation of inorganic binder glass powder

[0055] 6 parts by weight of silicon dioxide was selected, and the weight ratio of aluminum oxide, calcium oxide, barium oxide and titanium oxide added thereafter to silicon dioxide was 1:1:1:1:6.

[0056] Melting and quenching: Spread the weighed inorganic binder phase mixed powder into an alumina crucible, and then heat the crucible in a muffle furnace. When the temperature in the muffle furnace reaches 1500°C, keep it warm for two hours, then take out the crucible wearing heat-insulating gloves, and pour the molten inorganic binder phase into deionized water. After the inorganic binder phase is completely cooled, take it out and put it in a mortar for preliminary crushing.

[0057] Ball milling of inorganic binder phase: weigh the cooled inorganic binder phase as 1 part, then put it into a ball mill, and weigh 6 parts by weight of tungsten carbide balls (diameter 6mm). The ball milling process is wet ball milling, with ethanol as a grinding aid. After ball milling in the ball mill for 4 hours, take it out and dry it. After sieving the dried inorganic binder phase, obtain an inorganic binder phase powder with a diameter of 1-5μm.

[0058] (2) Weighing and mechanical mixing of conductive phase, catalyst, and inorganic binder phase

[0059] Weigh copper oxide powder, tungsten powder, inorganic binder phase, triethanolamine, and manganese dioxide and grind and mix them in a mortar. The weight of copper oxide is 70 parts, the weight of tungsten powder is 10 parts, the weight of inorganic binder phase is 5 parts, the weight of triethanolamine is 0.45 parts, and the weight of manganese dioxide is 0.18 parts. Put the weighed raw materials into a powder mixer and mix them thoroughly for 24 hours to obtain a mixed powder.

[0060] (3) Preparation of organic carrier

[0061] Take 50 parts of the organic carrier solvent terpineol, 30 parts of butyl carbitol, 10 parts of ethyl acetate, 3 parts of the thickener high-viscosity acrylic resin, 0.5 parts of the dispersant glyceryl tristearate, 0.5 parts of polyethylene glycol, 1 part of the thixotropic agent polyvinyl butyral, 1 part of the leveling agent silane coupling agent, and 1 part of the plasticizer castor oil and place them in a beaker. Stir them evenly initially with a glass rod. Put the stirred solvent into an oil bath and further stir it at a heating temperature of 70 °C and a stirring speed of 20 r / min. After stirring for 5 h, stop stirring and keep warm for 0.5 h after the solvent in the beaker forms a uniform organic carrier to ensure the stability of the organic carrier.

[0062] (4) Prepare copper oxide-tungsten paste

[0063] Weigh the mixed powder mainly composed of copper oxide powder with a mass ratio of 88:12 and the organic carrier and place them in a mortar for pre-stirring. After the initial paste in the form of a viscous fluid is formed, put it into a three-roll mill for further grinding. The initial spacing between the medium-speed and slow-speed rollers of the three-roll mill is selected as 100 μm, and the initial spacing between the medium-speed and fast-speed rollers is 50 μm (the spacing ratio between the two is controlled at 2:1). After grinding 4 times, reduce the spacing between the medium-speed and slow-speed rollers by 15 μm, and correspondingly reduce the spacing between the medium-speed and fast-speed rollers by 7.5 μm, and so on. The final spacing between the medium-speed and slow-speed rollers after grinding is 10 μm, and the spacing between the medium-speed and fast-speed rollers is 5 μm. The final number of grinding times is 8 times.

[0064] Then put it into a defoamer to remove the internal bubbles. During the defoaming operation, defoam for 60 s, 30 s, and 60 s in sequence at rotational speeds of 800 r / min, 1600 r / min, and 800 r / min respectively, and finally obtain the finished paste. The fineness of the conductive paste is measured to be 5 μm, and the viscosity is 180 Pa·s.

[0065] Print the prepared copper oxide-tungsten conductive paste on a 50×50 mm square ceramic substrate through screen printing to form a copper oxide-tungsten thick film. After printing, place the substrate in an oven at 60 °C and dry it for 5 hours, then degrease and sinter it in an argon atmosphere. The sintering temperature is 1100 °C, and the holding time is 1 h. Take out the sample after sintering is completed. According to the international standards I.S.EN ISO2409:2007 and I.S.EN ISO 2409:2013, conduct a cross-cut test on the sintered sample to test the adhesion. Use a cross-cut knife to vertically draw multiple parallel lines evenly on the surface of the sample, and then draw multiple parallel lines perpendicular to the just-drawn parallel lines again. The intersecting parallel lines drawn twice form multiple small grids. Stick a tape on the grid table and tear it off forcefully, and observe the degree of film layer peeling. The final result is as Figure 3As shown in the figure, according to the definition in the international standard, this test result meets the 0-level standard and is the test rating with the strongest bonding strength, indicating that the film layer formed after surface sintering fully meets the bonding strength requirements. Its conductivity was tested, and the surface square resistance was 20.6mΩ / □ using a four-probe tester.

[0066] Example 3

[0067] A method for preparing a copper oxide-tungsten conductive slurry suitable for medium-temperature co-fired ceramics, the specific steps are as follows:

[0068] (1) Preparation of inorganic binder glass powder

[0069] 6 parts by weight of silicon dioxide was selected, and the weight ratio of aluminum oxide, calcium oxide, barium oxide and titanium oxide added thereafter to silicon dioxide was 1:1:1:1:6.

[0070] Melting and quenching: Spread the weighed inorganic binder phase mixed powder into an alumina crucible, and then heat the crucible in a muffle furnace. When the temperature in the muffle furnace reaches 1500°C, keep it warm for two hours, then take out the crucible wearing heat-insulating gloves, and pour the molten inorganic binder phase into deionized water. After the inorganic binder phase is completely cooled, take it out and put it in a mortar for preliminary crushing.

[0071] Ball milling of inorganic binder phase: weigh the cooled inorganic binder phase as 1 part, then put it into a ball mill, and weigh 6 parts by weight of tungsten carbide balls (diameter 6mm). The ball milling process is wet ball milling, with ethanol as a grinding aid. After ball milling in the ball mill for 4 hours, take it out and dry it. After sieving the dried inorganic binder phase, obtain an inorganic binder phase powder with a diameter of 1-5μm.

[0072] (2) Weighing and mechanical mixing of conductive phase, catalyst, and inorganic binder phase

[0073] Weigh copper oxide powder, tungsten powder, inorganic binder phase, triethanolamine, and manganese dioxide and grind and mix them in a mortar. The weight of copper oxide is 65 parts, the weight of tungsten powder is 15 parts, the weight of inorganic binder phase is 5 parts, the weight of triethanolamine is 0.4 parts, and the weight of manganese dioxide is 0.16 parts. Put the weighed raw materials into a powder mixer and mix them thoroughly for 24 hours to obtain a mixed powder.

[0074] (3) Preparation of organic carrier

[0075] Take 50 parts of the organic carrier solvent terpineol, 30 parts of butyl carbitol, 10 parts of ethyl acetate, 3 parts of the thickening agent high-viscosity acrylic resin, 0.5 parts of the dispersant glyceryl tristearate, 0.5 parts of polyethylene glycol, 1 part of the thixotropic agent polyvinyl butyral, and 1 part of the leveling agent silane coupling agent, and 1 part of the plasticizer castor oil. Put them into a beaker and stir evenly initially with a glass rod. Put the stirred solvent into an oil bath and stir further at a heating temperature of 70 °C and a stirring speed of 20 r / min. After stirring for 5 h, stop stirring and keep warm for 0.5 h after the solvent in the beaker forms a uniform organic carrier to ensure the stability of the organic carrier.

[0076] (4) Prepare the copper oxide-tungsten paste

[0077] Weigh the mixed powder mainly composed of copper oxide powder with a mass ratio of 88:12 and the organic carrier and place them in a mortar for pre-stirring. After the initial paste in the form of a viscous fluid is formed, put it into a three-roll grinder for further grinding. The initial spacing between the medium-speed and slow-speed rollers of the three-roll grinder is selected as 100 μm, and the initial spacing between the medium-speed and fast-speed rollers is 50 μm (the spacing ratio of the two is controlled at 2:1). After grinding 4 times, reduce the spacing between the medium-speed and slow-speed rollers by 15 μm, and correspondingly reduce the spacing between the medium-speed and fast-speed rollers by 7.5 μm, and so on. The final spacing between the medium-speed and slow-speed rollers for grinding is 10 μm, and the spacing between the medium-speed and fast-speed rollers is 5 μm, and the final number of grinding times is 8 times.

[0078] Then put it into a defoamer to remove the internal bubbles. During the defoaming operation, defoam for 60 s, 30 s, and 60 s in sequence at rotational speeds of 800 r / min, 1600 r / min, and 800 r / min respectively, and finally obtain the finished paste. The fineness of the conductive paste is measured to be 6 μm, and the viscosity is 175 Pa·s.

[0079] Print the prepared copper oxide-tungsten conductive paste on a 50×50 mm square ceramic substrate by screen printing to form a copper oxide-tungsten thick film. After printing, place the substrate in an oven at 60 °C and dry it for 5 hours, then degrease and sinter it in an argon atmosphere. The sintering temperature is 1100 °C, and the holding time is 1 h. Take out the sample after sintering is completed. Conduct a bonding strength test on it, and it is found that the sintered film layer also meets the requirements of the bonding strength in the international standard. Conduct a conductivity test on it, and use a four-probe tester to measure its surface sheet resistance to be 10.6 mΩ / □.

[0080] Example 4

[0081] A preparation method of a copper oxide-tungsten conductive paste adapted to medium-temperature co-fired ceramics, the specific steps are as follows:

[0082] (1) Prepare the inorganic binder glass powder

[0083] 6 parts by weight of silicon dioxide was selected, and the weight ratio of aluminum oxide, calcium oxide, barium oxide and titanium oxide added thereafter to silicon dioxide was 1:1:1:1:6.

[0084] Melting and quenching: Spread the weighed inorganic binder phase mixed powder into an alumina crucible, and then heat the crucible in a muffle furnace. When the temperature in the muffle furnace reaches 1500°C, keep it warm for two hours, then take out the crucible wearing heat-insulating gloves, and pour the molten inorganic binder phase into deionized water. After the inorganic binder phase is completely cooled, take it out and put it in a mortar for preliminary crushing.

[0085] Ball milling of inorganic binder phase: weigh the cooled inorganic binder phase as 1 part, then put it into a ball mill, and weigh 6 parts by weight of tungsten carbide balls (diameter 6mm). The ball milling process is wet ball milling, with ethanol as a grinding aid. After ball milling in the ball mill for 4 hours, take it out and dry it. After sieving the dried inorganic binder phase, obtain an inorganic binder phase powder with a diameter of 1-5μm.

[0086] (2) Weighing and mechanical mixing of conductive phase, catalyst, and inorganic binder phase

[0087] Weigh copper oxide powder, tungsten powder, inorganic binder phase, triethanolamine, and manganese dioxide and grind and mix them in a mortar. The weight of copper oxide is 60 parts, the weight of tungsten powder is 20 parts, the weight of inorganic binder phase is 5 parts, the weight of triethanolamine is 0.35 parts, and the weight of manganese dioxide is 0.14 parts. Put the weighed raw materials into a powder mixer and mix them thoroughly for 10 hours to obtain a mixed powder.

[0088] (3) Preparation of organic carrier

[0089] Take 50 parts of organic carrier solvent pine alcohol, 30 parts of butyl carbitol, 10 parts of ethyl acetate, 3 parts of thickener high viscosity acrylic resin, 0.5 parts of dispersant tristearate glyceryl, 0.5 parts of polyethylene glycol, 1 part of thixotropic agent polyvinyl alcohol butyrate, 1 part of leveling agent silane coupling agent, 1 part of plasticizer castor oil, put them into a beaker and stir them evenly with a glass rod. Put the stirred solvent into an oil bath pot and stir it further at a heating temperature of 70°C and a stirring speed of 20r / min. After stirring for 5 hours, the solvent in the beaker forms a uniform organic carrier, then stop stirring and keep warm for 0.5 hours to ensure the stability of the organic carrier.

[0090] (4) Preparation of copper oxide-tungsten slurry

[0091] Weigh a mixed powder mainly composed of copper oxide powder with a mass ratio of 88:12 and an organic carrier, place them in a mortar for pre-stirring. After forming a thick and viscous initial slurry, put it into a three-roll grinder for further grinding. The initial spacing between the medium-speed and slow-speed rollers of the three-roll grinder is selected as 100 μm, and the initial spacing between the medium-speed and fast-speed rollers is 50 μm (the spacing ratio between the two is controlled at 2:1). After grinding 4 times, reduce the spacing between the medium-speed and slow-speed rollers by 15 μm, and correspondingly reduce the spacing between the medium-speed and fast-speed rollers by 7.5 μm, and so on. The final spacing between the medium-speed and slow-speed rollers after grinding is 10 μm, and the spacing between the medium-speed and fast-speed rollers is 5 μm. The final number of grinding times is 8 times.

[0092] Then put it into a defoamer to remove the internal bubbles. During the defoaming operation, defoam for 60 s, 30 s, and 60 s in sequence at rotation speeds of 800 r / min, 1600 r / min, and 800 r / min respectively, and finally obtain the finished slurry. The fineness of the obtained finished conductive slurry is measured to be 4.3 μm, and the viscosity is 160 Pa·s.

[0093] Print the prepared copper oxide-tungsten conductive slurry on a 50×50 mm square ceramic substrate through screen printing to form a copper oxide-tungsten thick film. After printing, place the substrate in an oven at 60 °C for drying for 5 hours, and then degrease and sinter it in an argon atmosphere. The sintering temperature is 1100 °C, and the holding time is 1 h. Take out the sample after sintering is completed. Conduct a bonding strength test on it, and it is found that the sintered film layer also meets the requirements of the bonding strength in the international standard. Test its conductivity, and use a four-probe tester to measure the surface sheet resistance to be 6.6 mΩ / □.

[0094] Macroscopically, there are no cracks and voids on the surface of the sample, and the surface structure is dense. Subsequently, analyze the microscopic morphology of the copper oxide-tungsten electronic slurry sample. The surface morphology is as Figure 4 shown. It can be seen that fine particles are attached to a thick film. In order to verify that this thick film is a copper film, further EDS analysis is performed on its surface morphology, as Figure 5 shown. Figure 5 Points 11 and 12 in the middle are point scans of the elemental content of the unknown film layer. It can be seen that the weight percentage of copper element reaches 70% - 80%, indicating that the unknown film layer is indeed a copper film. Figure 5 Point 13 in the middle is a scan of the particles attached to the copper film. It can also be obtained that the elemental content of tungsten reaches 85%, indicating that these small particles are the added tungsten skeleton. In addition, in order to see the cross-section of this film layer, EDS analysis is performed on the cross-section, and it can also be seen that copper adheres to the tungsten skeleton to form a large-area copper film, constructing a conductive network, and having a good combination with the cross-section. Generally speaking, under the action of a catalyst, copper oxide undergoes self-decomposition during sintering in an argon atmosphere to generate copper, which adheres to the tungsten skeleton to form a large-area copper film, constructing a good conductive network.

[0095] Figure 6 It reflects the morphology and element distribution of the cross-section of the copper-tungsten thick film after sintering. From Figure 6 (a), it can be seen that green represents copper element and red represents tungsten element. Copper adheres to the tungsten skeleton to form a large-area copper film, constructing a conductive network. Figure 6 (b) and Figure 6 (c) The cross-section element content and the distribution of copper element can also indicate the presence of copper and tungsten in the cross-section, that is, a copper-tungsten thick film is formed.

[0096] In summary, the copper oxide-tungsten conductive paste described in the present invention fills the blank of the compatible paste in the medium-temperature ceramic field, that is, by adding a catalyst, the copper oxide undergoes self-decomposition in advance under an argon atmosphere and adheres to the tungsten skeleton to form a copper film. When the content of copper oxide in the paste is different, the content of the added catalyst also needs to be adjusted. It can be seen from the sintering results of the above examples that when a small amount of tungsten skeleton is added, the sheet resistance is large because there is not enough tungsten skeleton for the formed copper film to adhere to, resulting in serious agglomeration, thus generating more pores and making the sheet resistance large. As the content of the added tungsten skeleton increases, the copper film formed by adhering to the tungsten skeleton will be denser, resulting in a decrease in sheet resistance. However, it is not that the more tungsten skeleton, the better. Since the conductivity of tungsten is poor, adding more tungsten will also affect the conductivity of the thick film. Therefore, the addition amount of tungsten needs to be considered comprehensively.

[0097] The above content is only an example and explanation of the present invention. Those skilled in the art of this technology can make various modifications or supplements to the described specific embodiments or use similar methods to replace them. As long as it does not deviate from the structure of the present invention or exceed the scope defined by this claim book, it shall fall within the protection scope of the present invention.

Claims

1. A method for preparing a copper oxide-tungsten conductive slurry suitable for medium-temperature co-fired ceramics, characterized in that: The following steps are involved: (1) Preparing high-temperature inorganic binder phase glass powder: heating silicon dioxide, aluminum oxide, calcium oxide, titanium oxide and barium oxide to a melting temperature, quenching, and crushing after being completely cooled to obtain an inorganic binder phase glass powder; (2) weighing a conductive phase, a sintered skeleton, a catalyst, and an inorganic binder phase glass powder and mechanically mixing them to obtain a composite powder; (3) preparing an organic carrier: uniformly mixing the additive solution and the solvent to obtain an organic carrier; (4) Preparation of copper oxide-tungsten slurry: The composite powder is mixed with an organic carrier, ground, and degassed to obtain the copper oxide-tungsten conductive slurry suitable for medium-temperature co-fired ceramics.

2. The method for preparing a copper oxide-tungsten conductive slurry suitable for medium-temperature co-fired ceramics according to claim 1, characterized in that: In step (1): The mass ratio of silicon dioxide, aluminum oxide, calcium oxide, barium oxide and titanium oxide is 6-1:2-1:2-1:2-1:2-1; The heating is carried out in a muffle furnace at a heating temperature of 1500-1700°C.

3. The method for preparing a copper oxide-tungsten conductive slurry suitable for medium-temperature co-fired ceramics according to claim 1, characterized in that: In step (1), the crushing method is as follows: The cooled raw materials are placed in a ball mill for high-energy ball milling, and the ball-to-material ratio of tungsten carbide to the cooled raw materials is 6-3:3-1; the diameter of the tungsten carbide balls used for ball milling is 6-3mm, anhydrous ethanol is used as a grinding aid, and the ball milling time is 2-4 hours. After the ball milling is completed, it is dried and sieved, and the final particle size of the inorganic binder phase glass powder is 1-5μm.

4. The method for preparing a copper oxide-tungsten conductive slurry suitable for medium-temperature co-fired ceramics according to claim 1, characterized in that: In step (2): The conductive phase is copper oxide powder, and the copper oxide powder is spherical copper oxide powder with a diameter of 1-5 μm; The sintered skeleton is tungsten powder; The catalyst is triethanolamine and manganese dioxide; The weight proportions of the copper oxide powder, tungsten powder, inorganic binder glass powder, triethanolamine and manganese dioxide are 60-75 parts, 5-20 parts, 3-5 parts, 0.1-0.5 parts and 0.05-0.2 parts respectively.

5. The method for preparing a copper oxide-tungsten conductive slurry suitable for medium-temperature co-fired ceramics according to claim 1, characterized in that: In step (3), the solvent is a mixture of one or more of terpineol, butyl carbitol, and ethyl acetate; and the additives include a thickener, a dispersant, a thixotropic agent, a leveling agent, and a plasticizer.

6. The method for preparing a copper oxide-tungsten conductive slurry suitable for medium-temperature co-fired ceramics according to claim 5, characterized in that: The thickener is one or more of ethyl cellulose, hydrogenated castor oil, dibutyl titanate, and acrylic resin; the dispersant is one or both of tristearate and polyethylene glycol; the thixotropic agent is polyvinyl butyral; the leveling agent is a silane coupling agent; and the plasticizer is castor oil; The mass ratio of the thickener, dispersant, thixotropic agent, leveling agent and plasticizer is 1-7:1-2:1-2:1-2:2-3.

7. The method for preparing a copper oxide-tungsten conductive slurry suitable for medium-temperature co-fired ceramics according to claim 1, characterized in that: In step (4): the weight proportion of the composite powder is 83-90 parts, and the weight proportion of the organic carrier is 10-17 parts.

8. The method for preparing a copper oxide-tungsten conductive slurry suitable for medium-temperature co-fired ceramics according to claim 1, characterized in that: In step (4), the grinding is performed using a three-roll grinder, and the grinding method is as follows: a. The ratio of the initial spacing between the medium-speed roller and the slow-speed roller of the three-roll mill to the initial spacing between the medium-speed roller and the fast roller is 2:1; b. After grinding 3-4 times, reduce the distance between the medium speed roller and the slow speed roller, and the distance between the medium speed roller and the fast speed roller, and the ratio of the reduced distance is 2:1; c. Repeat step b until the distance between the medium-speed roller and the slow-speed roller, and the distance between the medium-speed roller and the fast roller reach the required value; d. Grind 7-8 times.

9. The method for preparing a copper oxide-tungsten conductive slurry suitable for medium-temperature co-fired ceramics according to claim 1, characterized in that: In step (4): during the degassing operation, the degassing is carried out at a rotation speed of 800-1000 r / min, 1600-1800 r / min, 800-1000 r / min for 50-60 s, 20-30 s, and 50-60 s, respectively.

10. A copper oxide-tungsten conductive paste suitable for medium temperature co-fired ceramics prepared by the method for preparing the copper oxide-tungsten conductive paste suitable for medium temperature co-fired ceramics according to any one of claims 1 to 9.

Images