Air sintering conductive molybdenum slurry and preparation method thereof

Abstract

The present invention provides an air-sintered conductive molybdenum slurry and a preparation method thereof, wherein the conductive molybdenum slurry comprises the following components in weight percentage: 40% to 55% of conductive metal powder, 0.5% to 15% of reducing metal powder, 10% to 30% of glass powder and 20% to 30% of organic carrier, wherein the conductive metal powder is one or two of molybdenum powder and molybdenum alloy powder. The present invention adds reducing metal powder and glass powder with good wettability to oxides, and in the process of sintering the conductive molybdenum slurry in air, there is no need to pre-coat the conductive metal powder for oxidation resistance, and there is no need to place the sintering process under a protective atmosphere, thereby simplifying the preparation process, reducing production costs, and avoiding the danger of using hydrogen, and has the characteristics of environmental protection and high efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic pastes, and in particular to an air-sintered conductive molybdenum paste and a preparation method thereof. Background Art

[0002] Tungsten, molybdenum, manganese and their alloys are a class of high melting point, corrosion-resistant metals with good thermal conductivity, electrical conductivity, low thermal expansion coefficient, high temperature strength, low vapor pressure and wear resistance, and have become important materials for electronic power equipment manufacturing, metal material processing, glass manufacturing, high temperature furnace structural component manufacturing, aerospace and defense industry applications. Electronic pastes prepared from tungsten, molybdenum and manganese powders are widely used in high temperature co-fired electronic components, integrated circuit packaging, thick film circuit ceramic surface metallization and connection. In some fields, they replace precious metal electronic pastes such as gold and silver with their low cost advantage, so they have a wide range of uses.

[0003] In the prior art, the sintering of tungsten, molybdenum and manganese slurries is basically carried out in a reducing atmosphere or a vacuum environment. Tungsten, molybdenum and manganese slurries that can be sintered in air have not yet been seen. The reducing atmosphere involves the safety and cost of hydrogen use and the hydrogen embrittlement of the furnace, resulting in harsh sintering conditions and complex processes for tungsten, molybdenum and manganese slurries. For example, patent CN116477969A discloses an active molybdenum-silver-copper-titanium slurry for ceramic metallization packaging, which is composed of the following mass fractions: molybdenum powder or Ti15Mo alloy powder 50%-60%, AgCu28Ti2-4.5 alloy powder 20%-25%, SZ-1 15%-20%, alcohol ester twelve 1%-2%, organic additives 1%-3%, inorganic additives (one or more of micron TiB2 powder, TiH2 powder, TiN powder, tin powder, indium powder) 1%-6%, after the alumina substrate is coated with molybdenum-silver-copper-titanium slurry, it is slightly dried to a semi-wet state, and then an oxygen-free copper foil of the same size is covered on the slurry, and a tungsten block is pressed on the top, and it is placed in a vacuum brazing furnace with a vacuum degree of <5×10 -3 , sintered at 950℃ for 30min. The slurry prepared by this method can form a dense oxide layer when printed on the ceramic substrate, making the ceramic and metal bonding layer structure dense and uniform. The sintering process in this process needs to be carried out in a vacuum environment.

[0004] For example, patent CN115286431A discloses an active molybdenum-manganese slurry for solvent-free ceramic metallization packaging. The Mn glass phase contained in the slurry migrates to the voids of the metal phase Mo and the ceramic phase in a molten state. After the Mn element enters the glass phase in the ceramic, it drives the glass phase in the ceramic to migrate to the metallization layer. Through the mutual migration of glass in the two phases, the ceramic and the metallization layer are tightly combined. This process requires sintering at 1300~1700℃ in a mixed atmosphere of wet hydrogen or hydrogen and nitrogen.

[0005] For example, patent CN117292870A discloses a controllable low-consumption molybdenum-based resistor slurry system and its preparation method, using tetrahydrate heptahydrate ammonium molybdate to prepare MoO3 functional phase powder, using ascorbic acid and sodium hydroxide to modify sodium hydroxide to prepare modified nano copper powder, MoO3 functional phase powder and modified nano copper powder are mixed with organic carriers prepared from pine alcohol, butyl carbitol acetate, tributyl citrate, modifier and ethyl cellulose, and then ground by a low-speed ball mill to obtain resistor slurry. The slurry prepared by this method can form a uniform conductive layer without holes, and its stability and conductive uniformity are greatly improved. The slurry system also needs to be dried in a muffle furnace under protective gas conditions, and the drying temperature is 600~900℃.

[0006] For another example, patent CN118405941A discloses a molybdenum slurry for aluminum nitride ceramic electrostatic chuck and its preparation method; the slurry is composed of 70% to 85% molybdenum powder, 5% to 10% aluminum nitride powder, and 10% to 20% organic carrier by mass percentage. After the aluminum nitride powder is added to the slurry, during the high-temperature sintering process, the aluminum nitride powder can wet and penetrate into the metal structure to improve the compactness of the metallization layer, and can also penetrate into the ceramic substrate to improve the bonding strength between the metal layer and the ceramic layer. The slurry also needs to be sintered at 1800°C to 1950°C in a nitrogen atmosphere before use.

[0007] Therefore, it is necessary to design an air-sintered conductive molybdenum slurry and a preparation method thereof to solve the above problems. Summary of the invention

[0008] The purpose of the present invention is to provide an air-sintered conductive molybdenum paste, which can adjust the square resistance of the paste circuit and simplify the sintering conditions while ensuring the sintering adhesion. The obtained paste can be used for thick film circuits, conductor connections, air welding or electroplating.

[0009] To achieve the above-mentioned purpose, the present invention adopts the following technical scheme: an air-sintered conductive molybdenum slurry, which includes the following components in weight percentage: 40%~55% conductive metal powder, 0.5%~15% reducing metal powder, 10%~30% glass powder and 20%~30% organic carrier, wherein the conductive metal powder is one or two of molybdenum powder and molybdenum alloy powder.

[0010] As a further improved technical solution of the present invention, the reducing metal powder is aluminum powder and / or aluminum-silicon alloy powder, and the weight ratio of the reducing metal powder to the glass powder is 0.1-1.5.

[0011] As a further improved technical solution of the present invention, the weight percentage of silicon element in the aluminum-silicon alloy powder is 10% to 30%.

[0012] As a further improved technical solution of the present invention, the glass powder includes sodium borosilicate bismuth system glass powder and Bi2O3, and the weight ratio of the sodium borosilicate bismuth system glass powder to Bi2O3 is 12~25, or the glass powder includes sodium borosilicate bismuth system glass powder and PbO, and the weight ratio of the sodium borosilicate bismuth system glass powder to PbO is 12~25; the melting point range of the glass powder is 300~900℃.

[0013] As a further improved technical solution of the present invention, the particle size of the conductive metal powder is 0.2-10 μm, and the particle size of the reducing metal powder is 0.2-10 μm.

[0014] As a further improved technical solution of the present invention, it includes the following components in weight percentage: 45%~50% molybdenum powder, 2%~5% aluminum powder or aluminum-silicon alloy powder, 10%~20% glass powder and 25%~30% organic carrier, and the weight ratio of the aluminum powder or aluminum-silicon alloy powder to the glass powder is 0.1~0.4.

[0015] As a further improved technical solution of the present invention, the organic carrier is composed of the following components in weight percentage: 20-50% acrylic resin and 50-80% solvent, and the solvent is composed of two water-resistant and mutually soluble organic solvents in a weight ratio of 1:1.

[0016] As a further improved technical solution of the present invention, the solvent is a mixture of two of petroleum ether, dibutyl butyric acid dicarboxylate and butyric acid acetate.

[0017] The present invention also aims to provide a method for preparing the air-sintered conductive molybdenum slurry described in any one of the above items, which comprises the following steps:

[0018] Step 1: Stir the solvent and acrylic resin until they are evenly mixed to obtain an organic carrier;

[0019] Step 2: then add the conductive metal powder, the reducing metal powder and the glass powder into the organic carrier, transfer them into a homogenizer for homogenization to obtain a conductive molybdenum slurry semi-finished product;

[0020] Step 3: The semi-finished conductive molybdenum slurry obtained in step 2 is transferred to a three-roll grinder for grinding, and finally decompressed and degassed to obtain an air-sintered conductive molybdenum slurry.

[0021] As a further improved technical solution of the present invention, in step 1, after the acrylic resin and the solvent are mixed, they are placed in a constant temperature water bath at 75-85° C., stirred at 300-800 r / min, and kept warm for 1 hour after being completely dissolved;

[0022] In step 3, the roller speed of the three-roll mill is 60-120 r / min, the pressure is 3 MPa, and the rollers are rolled 3-6 times; the pressure during the reduced pressure degassing is -80 KPa.

[0023] It can be seen from the above technical solutions that the present invention has at least the following technical effects:

[0024] (1) The air-sintered conductive molybdenum slurry of the present invention is added with reducing metal powder and glass powder with good wettability to oxides. During the sintering process of the conductive molybdenum slurry in the air, especially during the sintering temperature rise process, the reducing metal powder provides reducing properties, that is, the reducing metal powder preferentially undergoes a reduction reaction with the surface oxide layer of the conductive metal to obtain a metal conductive phase, aluminum oxide, and silicon oxide. These formed oxides are then infiltrated by the glass powder and melted into the glass phase. The flow of the glass drives the conductive metal powder to approach and connect to form a conductive channel, while driving out excess air. In the cooling stage, the glass phase solidifies on the surface of the conductive layer to form a sealing layer to prevent the continued oxidation of the conductive phase, thereby forming a stable conductive circuit, that is, achieving the purpose of sintering into a conductive circuit in the air.

[0025] (2) The conductive molybdenum slurry of the present invention does not require the conductive metal powder to be pre-coated for oxidation resistance, nor does it require the sintering process to be carried out under a protective atmosphere, which greatly simplifies the preparation process, reduces equipment requirements, reduces production costs, and avoids the danger of using hydrogen. It is environmentally friendly and highly efficient.

[0026] (3) The present invention can adapt to different resistance requirements by adjusting the ratio of conductive metal powder, reducing metal powder and glass powder, thereby enriching the application scenarios of the air-sintered conductive molybdenum slurry of the present invention.

[0027] (4) The present invention adjusts the softening point of glass by adding bismuth oxide or lead oxide to glass powder, thereby achieving optimal control of resistance at different sintering temperatures. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The figure is a trend diagram of the square resistance of the conductive molybdenum paste of the comparative example and embodiments 1-4 of the present invention at temperatures of 600°C, 800°C, and 1000°C.

[0029] Figure 2 The figure is a trend diagram of the square resistance of the conductive molybdenum paste of the comparative example and embodiments 1-4 of the present invention at a temperature of 1200°C.

[0030] Figure 3 This is a comparison chart of the square resistance values ​​of the conductive molybdenum paste of Example 2 of the present invention at temperatures of 600°C, 800°C, 1000°C, and 1200°C. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is described in detail below in conjunction with examples and laboratory data. Example 1

[0032] The preparation of air-sintered conductive molybdenum slurry A1 specifically includes the following steps:

[0033] Step 1: Accurately weigh 20g of acrylic resin, 40g of petroleum ether and 40g of dibutyl carboxylate and add them into a container, place it in a constant temperature water bath at 80°C, and stir it at 500r / min. After it is completely dissolved, keep it warm for 1h to obtain an organic carrier for standby use;

[0034] Step 2: Accurately weigh 45g of molybdenum powder, 3g of AlSi10 alloy powder, 25g of commercially available sodium borosilicate bismuth system glass powder, 1g of Bi2O3 powder and 27g of organic carrier, add them into a homogenizer and homogenize to obtain a conductive molybdenum slurry semi-finished product;

[0035] Step 3: The conductive molybdenum slurry semi-finished product obtained in step 2 is transferred to a three-roll grinder for grinding. The roller speed of the three-roll grinder is 100r / min, the pressure is 3MPa, and the roller is rolled 5 times; finally, the pressure is reduced and degassed, and the pressure during the reduced pressure degassed is -80KPa to obtain air-sintered conductive molybdenum slurry A1.

[0036] The components and weight percentages of the air-sintered conductive molybdenum paste A1 of this embodiment are: 44.6% molybdenum powder, 3% AlSi10 alloy powder, 24.8% commercially available sodium borosilicate bismuth glass powder, 1% Bi2O3 powder and 26.7% organic carrier, among which the weight ratio of molybdenum powder to the total weight of sodium borosilicate bismuth glass powder and Bi2O3 powder is 1.7, and the weight ratio of AlSi10 alloy powder to the total weight of sodium borosilicate bismuth glass powder and Bi2O3 powder is 0.12. Example 2

[0037] The preparation of air-sintered conductive molybdenum slurry A2 specifically includes the following steps:

[0038] Step 1: Same as Example 1;

[0039] Step 2: Accurately weigh 45g of molybdenum powder, 8g of AlSi10 alloy powder, 20g of commercially available sodium borosilicate bismuth system glass powder, 1g of Bi2O3 powder and 27g of organic carrier, add them into a homogenizer and homogenize to obtain a conductive molybdenum slurry semi-finished product;

[0040] Step 3: Same as Example 1.

[0041] The components and weight percentages of the air-sintered conductive molybdenum paste A2 of this embodiment are: 44.6% molybdenum powder, 7.9% AlSi10 alloy powder, 19.8% commercially available sodium borosilicate bismuth glass powder, 1% Bi2O3 powder and 27.6% organic carrier, among which the weight ratio of molybdenum powder to the total weight of sodium borosilicate bismuth glass powder and Bi2O3 powder is 2.1, and the weight ratio of AlSi10 alloy powder to the total weight of sodium borosilicate bismuth glass powder and Bi2O3 powder is 0.4. Example 3

[0042] The preparation of air-sintered conductive molybdenum slurry A3 specifically includes the following steps:

[0043] Step 1: Same as Example 1;

[0044] Step 2: Accurately weigh 45g of molybdenum powder, 13g of AlSi10 alloy powder, 15g of commercially available sodium borosilicate bismuth system glass powder, 1g of Bi2O3 powder and 27g of organic carrier, add them into a homogenizer and homogenize to obtain a conductive molybdenum slurry semi-finished product;

[0045] Step 3: Same as Example 1.

[0046] The components and weight percentages of the air-sintered conductive molybdenum paste A3 of this embodiment are: 44.6% molybdenum powder, 12.9% AlSi10 alloy powder, 14.9% commercially available sodium borosilicate bismuth glass powder, 1% Bi2O3 powder and 26.7% organic carrier, among which the weight ratio of molybdenum powder to the total weight of sodium borosilicate bismuth glass powder and Bi2O3 powder is 2.8, and the weight ratio of AlSi10 alloy powder to the total weight of sodium borosilicate bismuth glass powder and Bi2O3 powder is 0.8. Example 4

[0047] The preparation of air sintering type conductive molybdenum slurry A4 specifically includes the following steps:

[0048] Step 1: Same as Example 1;

[0049] Step 2: Accurately weigh 45g of molybdenum powder, 18g of AlSi10 alloy powder, 12g of commercially available sodium borosilicate bismuth system glass powder, 1g of Bi2O3 powder and 27g of organic carrier, add them into a homogenizer and homogenize to obtain a conductive molybdenum slurry semi-finished product;

[0050] Step 3: Same as Example 1.

[0051] The components and weight percentages of the air-sintered conductive molybdenum paste A4 of this embodiment are: 44.6% molybdenum powder, 17.5% AlSi10 alloy powder, 11.7% commercially available sodium borosilicate bismuth glass powder, 1% Bi2O3 powder and 26.2% organic carrier, among which the weight ratio of molybdenum powder to the total weight of sodium borosilicate bismuth glass powder and Bi2O3 powder is 3.5, and the weight ratio of AlSi10 alloy powder to the total weight of sodium borosilicate bismuth glass powder and Bi2O3 powder is 1.4. Comparative Example

[0052] The preparation of air-sintered conductive molybdenum slurry B specifically comprises the following steps:

[0053] Step 1: Same as Example 1;

[0054] Step 2: Accurately weigh 45g of molybdenum powder, 25g of commercially available sodium borosilicate bismuth system glass powder, 1g of Bi2O3 powder and 27g of organic carrier, add them into a homogenizer and homogenize to obtain a conductive molybdenum slurry semi-finished product;

[0055] Step 3: Same as Example 1.

[0056] The components and weight percentages of the air-sintered conductive molybdenum paste B of this embodiment are: 45.9% molybdenum powder, 25.5% commercially available sodium borosilicate bismuth system glass powder, 1% Bi2O3 powder and 27.6% organic carrier, wherein the weight ratio of molybdenum powder to the total weight of sodium borosilicate bismuth system glass powder and Bi2O3 powder is 1.7.

[0057] Table 1 Content of each component of the air-sintered conductive molybdenum slurry of Examples 1-4 and Comparative Examples

[0058]

[0059] The performance tests were performed on the air-sintered conductive molybdenum slurries of Examples 1 to 4 and the comparative example:

[0060] Preparation of electrodes: The air-sintered conductive molybdenum pastes prepared in Examples 1 to 4 and the comparative example were respectively used to print thick film circuits on alumina ceramics, and then sintered in batches at different temperatures. The sintering temperatures and sintering times are shown in Table 2. The resistance of the sintered circuits was further measured, and the square resistance was calculated. The results are shown in Table 2.

[0061] Table 2 Performance parameters of air-sintered conductive molybdenum slurry after sintering of Examples 1-4 and Comparative Examples

[0062]

[0063] Please refer to Figure 1 It can be seen that when the sintering temperature is 800°C and 1000°C, the air-sintered conductive molybdenum pastes of Examples 1-4 all have lower square resistance (all ≤50kΩ / □), and when the weight ratio of AlSi10 alloy powder to the total weight of sodium borosilicate bismuth system glass powder and Bi2O3 powder is between 0.1-1.5, as the above ratio increases, the square resistance first decreases and then increases, and reaches the lowest square resistance when the above ratio is about 0.4; when the sintering temperature is 600°C, the square resistance of the air-sintered conductive molybdenum paste of Example 1 is greater than 20MΩ / □, and the square resistance of the air-sintered conductive molybdenum pastes of Examples 2-4 first decreases and then increases as the above ratio increases, and reaches the lowest square resistance when the above ratio is about 0.8. Please refer to Figure 2As shown, when the sintering temperature is 1200°C, the air-sintered conductive molybdenum pastes of Examples 1-4 all have relatively high square resistance values ​​(all > 1MΩ / □), and when the weight ratio of AlSi10 alloy powder to the total weight of sodium borosilicate bismuth system glass powder and Bi2O3 powder is between 0.1-1.5, as the above ratio increases, the square resistance value first decreases and then increases, and reaches the lowest square resistance value when the above ratio is about 0.4. Figure 1 , Figure 2 It can be seen that when the sintering temperature is 800-1200°C and the weight ratio of the AlSi10 alloy powder to the sodium borosilicate bismuth system glass powder and the total weight of the Bi2O3 powder is about 0.4, the air-sintered conductive molybdenum pastes of Examples 1-4 all have the lowest square resistance. Figure 3 As shown, when the weight ratio of AlSi10 alloy powder to sodium borosilicate bismuth system glass powder and Bi2O3 powder is 0.4, with the increase of sintering temperature, the square resistance shows a trend of first decreasing and then increasing. When the sintering temperature is about 1000℃, the square resistance reaches the lowest value.

[0064] The above embodiments are only used to illustrate the present invention but not to limit the technical solutions described in the present invention. The understanding of this specification should be based on the technicians in the relevant technical field. Although this specification has described the present invention in detail with reference to the above embodiments, ordinary technicians in the field should understand that technicians in the relevant technical field can still modify or replace the present invention with equivalents, and all technical solutions and improvements that do not depart from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. An air-sintered conductive molybdenum slurry, characterized in that: The invention comprises the following components in weight percentage: 40% to 55% of conductive metal powder, 0.5% to 15% of reducing metal powder, 10% to 30% of glass powder and 20% to 30% of organic carrier, wherein the conductive metal powder is one or both of molybdenum powder and molybdenum alloy powder, the reducing metal powder is aluminum powder and / or aluminum silicon alloy powder, and the weight ratio of the reducing metal powder to the glass powder is 0.1 to 1.5; the glass powder comprises sodium borosilicate bismuth system glass powder and Bi2O3, and the weight ratio of the sodium borosilicate bismuth system glass powder to Bi2O3 is 12 to 25, or the glass powder comprises sodium borosilicate bismuth system glass powder and PbO, and the weight ratio of the sodium borosilicate bismuth system glass powder to PbO is 12 to 25.

2. The air-sintered conductive molybdenum slurry according to claim 1, characterized in that: The weight percentage of silicon in the aluminum-silicon alloy powder is 10% to 30%.

3. The air-sintered conductive molybdenum slurry according to claim 1, characterized in that: The melting point of the glass powder ranges from 300 to 900°C.

4. The air-sintered conductive molybdenum slurry according to claim 1, characterized in that: The particle size of the conductive metal powder is 0.2-10 μm, and the particle size of the reducing metal powder is 0.2-10 μm.

5. The air-sintered conductive molybdenum slurry according to claim 1, characterized in that: The invention comprises the following components in weight percentage: 45% to 50% molybdenum powder, 2% to 5% aluminum powder or aluminum silicon alloy powder, 10% to 20% glass powder and 25% to 30% organic carrier, wherein the weight ratio of the aluminum powder or aluminum silicon alloy powder to the glass powder is 0.1 to 0.

4.

6. The air-sintered conductive molybdenum slurry according to claim 1, characterized in that: The organic carrier is composed of the following components in weight percentage: 20-50% acrylic resin and 50-80% solvent, and the solvent is composed of two organic solvents that do not absorb water and are mutually soluble in a weight ratio of 1:

1.

7. The air-sintered conductive molybdenum slurry according to claim 6, characterized in that: The solvent is a mixture of two of petroleum ether, dibutyl butyric acid dicarboxylate and butyric acid acetate.

8. A method for preparing an air-sintered conductive molybdenum slurry according to any one of claims 1 to 7, characterized in that: The following steps are involved: Step 1: Stir the solvent and acrylic resin until they are evenly mixed to obtain an organic carrier; Step 2: then add the conductive metal powder, the reducing metal powder and the glass powder into the organic carrier, transfer them into a homogenizer for homogenization to obtain a conductive molybdenum slurry semi-finished product; Step 3: The semi-finished conductive molybdenum slurry obtained in step 2 is transferred to a three-roll grinder for grinding, and finally decompressed and degassed to obtain an air-sintered conductive molybdenum slurry.

9. The method for preparing the air-sintered conductive molybdenum slurry according to claim 8, characterized in that: In step 1, after the acrylic resin and the solvent are mixed, they are placed in a constant temperature water bath at 75-85°C, stirred at 300-800 r / min, and kept warm for 1 hour after they are completely dissolved; In step 3, the roller speed of the three-roll mill is 60-120 r / min, the pressure is 3 MPa, and the rollers are rolled 3-6 times; the pressure during the reduced pressure degassing is -80 KPa.

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