A LTCC resistor paste and preparation method thereof

Abstract

The present invention provides an LTCC resistor paste and a preparation method thereof. The LTCC resistor paste comprises the following components by weight: 5% to 30% ruthenium oxide, 0.5% to 3% inorganic additives, 40% to 60% glass frit, 25% to 35% organic vehicle, and 0.1% to 2% aerosol. The organic vehicle comprises a resin composed of a high molecular weight resin and a low molecular weight resin, wherein the low molecular weight resin has a number average molecular weight of no more than 20,000, and the high molecular weight resin has a number average molecular weight of no less than 70,000. The LTCC resistor paste provided by the present invention exhibits excellent thixotropy and leveling properties, achieving good printing performance, avoiding screen marks, and ensuring a good surface quality of the paste after sintering.

Description

Technical Field

[0001] The present invention relates to the technical field of low temperature co-fired ceramic electronic paste, in particular to an LTCC resistor paste and a preparation method thereof. Background Art

[0002] Low-temperature co-fired ceramics (LTCC) have excellent high-frequency characteristics and can achieve reliable, three-dimensional, highly integrated, miniaturized designs through multi-layer wiring and layered inspection. They are widely used in the radio frequency field. Their interlayer circuits are thick-film pastes printed via screen printing. Ruthenium-based resistor pastes are one type of paste that acts as a resistor after sintering. During the sintering process, the glass in the resistor paste softens, wetting and dragging the ruthenium powder, thereby transforming the dispersed ruthenium powder particles into multiple conductive networks that conduct electricity through the contact conduction principle or tunneling effect. For cost considerations and to achieve a certain resistance value, ruthenium powder is typically nano-ruthenium powder with a high specific surface area. As a result, it often has poor leveling properties, resulting in defects such as severe mesh marks, rough surfaces, and low printing resolution during printing, which affect the normal use of the product. Summary of the Invention

[0003] To solve the above technical problems, the present invention provides an LTCC resistor paste and a preparation method thereof. The LTCC resistor paste provided by the present invention has good thixotropy and leveling properties, can avoid printing mesh marks, and ensure good surface quality of the paste after sintering.

[0004] Specifically, the technical solutions provided by the present invention are as follows.

[0005] In a first aspect, the LTCC resistor paste provided by the present invention comprises the following components in percentage by mass: 5% to 30% ruthenium oxide, 0.5% to 3% inorganic additives, 40% to 60% glass powder, 25% to 35% organic vehicle, and 0.1% to 2% aerosol; the organic vehicle comprises a resin, the resin being composed of a high molecular weight resin and a low molecular weight resin, the number average molecular weight of the low molecular weight resin being not higher than 20,000, and the number average molecular weight of the high molecular weight resin being not lower than 70,000.

[0006] In the present invention, the LTCC resistor paste utilizes a mixture of high- and low-molecular-weight resins, particularly in combination with aerosols, to achieve excellent printing performance. The high-molecular-weight resin provides the main network structure, maintaining internal knots in a defined shape at zero shear and resulting in high viscosity. However, when subjected to shear, the network structure is disrupted, causing a decrease in viscosity, thereby achieving excellent thixotropy. The silica / alumina aerosol has an extremely small particle size and a high specific surface area, which can increase zero-shear viscosity under van der Waals forces. Its combination with the high-molecular-weight resin further enhances thixotropy and improves printing quality. Furthermore, the low-molecular-weight resin has segments with greater freedom of movement, enabling the solid particles in the paste to be adjusted within a small range under the influence of gravity and surface tension, resulting in better leveling and avoiding screen marks, thereby ensuring a high-quality paste surface.

[0007] Preferably, the resin is ethyl cellulose, methyl cellulose or acrylic resin.

[0008] More preferably, the number average molecular weight of the low molecular weight resin is 10,000 to 20,000; and / or the number average molecular weight of the high molecular weight resin is 70,000 to 85,000.

[0009] Preferably, the mass ratio of the high molecular weight resin to the low molecular weight resin is 1:2 to 2:1, for example, 2:1, 1:2, 1:1, 7:9, 9:7, etc.

[0010] In the present invention, based on the optimization of the above LTCC resistor paste formula system and resin composition, the molecular weight and ratio of the high molecular weight resin and the low molecular weight resin are optimized. This not only enables the formation of a stable structure during the sintering process and improves the performance and stability of the final product, but also, in particular, better maintains the paste shape while providing better rheological properties during the printing process, further improving the printing performance of the paste.

[0011] More preferably, the aerosol is aluminum oxide aerosol and / or silicon oxide aerosol.

[0012] In the present invention, by optimizing the aerosol, especially selecting low-cost alumina aerosol and silica aerosol, the aerosol can synergize with high and low molecular weight resins to more effectively adjust the viscosity and thixotropy of the slurry system, further improving the printing quality.

[0013] Preferably, the ruthenium oxide is nano-ruthenium oxide with a specific surface area of 8 to 15 m 2 In the present invention, by using nano-ruthenium oxide with a high specific surface area, the amount of ruthenium oxide used in the target resistance paste can be reduced, thereby reducing costs and facilitating the acquisition of a more uniform resistor paste.

[0014] Preferably, the glass powder particle size D50 is 1.5 to 3 microns, and D90 is ≤ 5 microns. In the present invention, the optimized glass powder particle size can further improve the slurry fineness and smoothness after sintering, and is also beneficial to particle bonding and densification during the sintering process.

[0015] Preferably, the inorganic additive is selected from one or more of CuO, MnO2, Fe2O3, and Nb2O5. In the present invention, by optimizing the selection of inorganic additives, the conductivity and temperature coefficient of the slurry after sintering can be adjusted, further improving the performance of the product.

[0016] More preferably, the organic vehicle is composed of the following components in weight percentage: 75% to 87% solvent, 10% to 20% resin, and 3% to 5% dispersant.

[0017] More preferably, the solvent is selected from one or more of terpineol, butyl carbitol, butyl carbitol acetate, and dibutyl phthalate.

[0018] More preferably, the dispersant is selected from one or more of Span 80, Span 85, Tween 60 and Tween 80.

[0019] In the present invention, by further optimizing the organic carrier and selecting organic solvents such as terpineol, butyl carbitol, and butyl carbitol acetate, the resin can be fully dissolved and removed during the drying stage. At the same time, combined with dispersants such as Span 80, Span 85, Tween 60, and Tween 80, the stability and uniformity of the slurry can be ensured, thereby improving the printing quality and sintering effect.

[0020] In a second aspect, the present invention provides a method for preparing the LTCC resistor paste, comprising the following steps:

[0021] 1) Mixing a solvent, a resin and an additive to obtain an organic carrier.

[0022] 2) Mixing the inorganic additive, ruthenium oxide, and part of the organic carrier to obtain a premix 1.

[0023] 3) The glass powder and the remaining organic vehicle are mixed to obtain a premix 2.

[0024] 4) The premix 1 and the premix 2 are mixed, aerosol is added, and rolling is performed.

[0025] Preferably, step 1) further comprises: stirring and cooling in a water bath.

[0026] Preferably, in step 2) and step 3), the mixing is carried out by homogenization, and the homogenization time is ≥5 min and the rotation speed is ≥900 r / min.

[0027] Preferably, in step 4), the rolling is performed using a three-roll mill with a minimum rolling pitch of 10 microns and a slurry viscosity of 100-300 Pa·s. The resistor slurry disclosed herein has the advantages of simple steps, low cost, and excellent results. The LTCC resistor slurry exhibits improved thixotropy and leveling properties during the preparation process, thereby enhancing printing quality, sintering performance, and the electrical properties of the final product. Optimized parameter manipulation yields even better results.

[0028] The beneficial effects of the present invention are at least as follows: the resistor paste is required to have good rheological properties to ensure printing quality, that is, it needs to have both good thixotropy and leveling properties. The present invention uses a combination of high and low molecular weight resins. The high molecular weight resin provides the main network structure, and the internal knots maintain a certain shape under zero shear, with high viscosity. When subjected to shear force, the network structure is destroyed and the viscosity decreases, thereby achieving good thixotropy. The thixotropy can be further enhanced when used with an aerosol. The low molecular weight resin has segments with higher degrees of freedom, and can adjust the solid particles in the paste within a small range under the action of gravity and surface tension, thereby achieving good leveling, avoiding printing marks, and ensuring good surface quality of the paste after sintering. The resistor paste involved in the present invention has the advantages of simple steps, low cost, and good effect. DETAILED DESCRIPTION

[0029] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention are described clearly and completely below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0030] Unless otherwise noted, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods. Where specific techniques or conditions are not specified in the examples, all reactions were performed according to conventional methods, techniques or conditions described in literature in the field, or according to product specifications. Reagents and instruments used, for which the manufacturer is not specified, are all conventional products available through regular channels.

[0031] According to some embodiments of the present invention, the following steps are included:

[0032] Glass melting: Weigh the batch materials, mix them evenly, and melt them at the appropriate temperature. After melting, quench and grind them to obtain glass powder with a particle size D50 between 1.5 and 3 microns and D90 ≤ 5 microns.

[0033] Preparation of the organic vehicle: Weigh the solvent, resin, and dispersant and place them in a waterbath. Stir until completely dissolved, then cool and set aside. The weight ratio of the three components is 75%-87% solvent, 10%-20% resin, and 3%-5% dispersant. The solvent is one or more of terpineol, butyl carbitol, butyl carbitol acetate, and dibutyl phthalate. The resin is one of ethyl cellulose, methyl cellulose, and acrylic resin, and is composed of two resins: a high-molecular-weight resin with a number-average molecular weight between 10,000 and 20,000, and a high-molecular-weight resin with a number-average molecular weight between 70,000 and 85,000. The ratio of the two is between 1:2 and 2:1. The aerosol is one or more of aluminum oxide aerosol and silicon oxide aerosol. The dispersant is one or more of Span 80, Span 85, Tween 60, and Tween 80.

[0034] Preparation of resistor paste: 5% to 30% ruthenium oxide, 0.5% to 3% inorganic additives, 40% to 60% glass powder, 25% to 35% organic carrier, and 0.1% to 2% aerosol. First, the inorganic additives, ruthenium oxide, and part of the organic carrier are placed in a homogenizer for homogenization to obtain premix 1. Then, the glass powder and the remaining organic carrier are placed in a homogenizer for homogenization to obtain premix 2. Then, premix 1 and premix 2 are mixed, and aerosol is added to adjust the viscosity. The mixture is rolled evenly using a three-roller mill. The time of the above homogenization process is not less than 5 minutes, and the speed is not less than 900r / m. Finally, the mixture of the previous step is rolled evenly using a three-roller mill, with a minimum rolling spacing of 10 microns. The viscosity of the obtained resistor paste is 100 to 300Pa·s. The inorganic additive is one or more of CuO, MnO2, Fe2O3, and Nb2O5. The ruthenium oxide is nano-ruthenium oxide with a specific surface area of 8 to 15m 2 / g.

[0035] Resistor paste testing: The viscosity of the resistor paste at 1 rpm and 10 rpm was measured using a viscometer, and the ratio of the two was recorded as the thixotropic index. Fineness was measured using a fineness gauge according to the national standard GB / T 17473.2. The resistor paste was printed onto LTCC green sheets using a 325-mesh screen printer. The sheets were placed on a horizontal surface at room temperature for 10 minutes, then dried in an 80°C forced-air oven for 10 minutes. The sheets were then observed under a microscope for any printing marks. The LTCC green sheets with resistor paste were stacked, hot-pressed, and sintered, and their surfaces were observed under a microscope.

[0036] The present invention is further described below by the following examples and comparative examples, but the protection scope of the present invention is not limited thereto.

[0037] Example 1

[0038] First, prepare the organic vehicle. Weigh 81% terpineol, 5% ethyl cellulose with a number average molecular weight of 12634, 10% ethyl cellulose with a number average molecular weight of 70397, and 4% Span 85, based on the weight percentage of the total organic vehicle. Place in a 90°C water bath, stir until completely dissolved, and cool for later use. Then, prepare the resistor slurry. Homogenize 21% MnO, 22.5% ruthenium oxide, and 22.3% organic vehicle in a homogenizer, based on the weight percentage of the total resistor slurry, to obtain premix 1. Then, homogenize 44% glass powder and 10% organic vehicle in a homogenizer to obtain premix 2. The homogenization process lasts for 5 minutes at a speed of 900 rpm. Finally, mix premix 1 and premix 2, add 0.2% alumina aerosol, and roll using a three-roll mill to uniformly distribute the mixture, with a minimum rolling distance of 10 microns. The test showed that the resistor paste had a fineness of 11 μm, a thixotropic index of 4.19, good leveling, no mesh marks, clear printed graphics, and a smooth and dense surface after sintering.

[0039] Comparative Example 1

[0040] First, prepare the organic carrier. Weigh 76% terpineol, 20% ethyl cellulose with a number average molecular weight of 12634, and 4% Span 85, based on the weight percentage of the total organic carrier, place in a 90°C water bath, stir until completely dissolved, and cool for later use. Then prepare the resistor slurry. Homogenize 21% MnO, 22.5% ruthenium oxide, and 22.5% organic carrier in a homogenizer to obtain premix 1, based on the weight percentage of the total resistor slurry. Then, homogenize 44% glass powder and 10% organic carrier in a homogenizer to obtain premix 2. The homogenization process lasts for 5 minutes at a speed of 900 rpm. Finally, mix premix 1 and premix 2 and roll them evenly using a three-roll mill, with a minimum rolling spacing of 10 microns. Testing shows that the resistor slurry has a fineness of 13 μm, a thixotropic index of 1.36, good leveling properties, and no mesh marks. The printed pattern has poor clarity and dot gain. After sintering, the surface is smooth and dense.

[0041] Comparative Example 2

[0042] First, prepare the organic carrier. Weigh 86% terpineol, 10% ethyl cellulose with a number average molecular weight of 70397, and 4% Span 85 in proportion to the total weight of the organic carrier, place in a 90°C water bath, stir until completely dissolved, and cool for later use. Then prepare the resistor slurry. Homogenize 21% MnO, 22.5% ruthenium oxide, and 22.5% organic carrier in a homogenizer in proportion to the total weight of the resistor slurry to obtain premix 1. Then, homogenize 44% glass powder and 10% organic carrier in a homogenizer to obtain premix 2. The homogenization process lasts for 5 minutes at a speed of 900 rpm. Finally, mix premix 1 and premix 2 and roll them evenly using a three-roll mill with a minimum rolling spacing of 10 microns. Tests show that the resistor slurry has a fineness of 24 μm, a thixotropic index of 5.71, poor leveling, severe mesh marks, clear printed graphics, and a rough surface after sintering.

[0043] Example 2

[0044] First, prepare the organic vehicle. Weigh 50% terpineol, 10% butyl carbitol, 17.5% butyl carbitol acetate, 12% methyl cellulose with a number average molecular weight of 18020, 6% methyl cellulose with a number average molecular weight of 82503, 1.5% Span 85, 1.5% Tween 60, and 1.5% Tween 80, in percentages based on the total weight of the organic vehicle. Place the mixture in a 90°C water bath, stir until completely dissolved, and then cool for later use. Then, prepare the resistor slurry. Homogenize 1% CuO, 1% MnO2, 1% Nb2O5, 10% ruthenium oxide, and 15% organic vehicle in a homogenizer, in percentages based on the total weight of the resistor slurry, to obtain premix 1. Then, homogenize 56% glass powder and 15% organic vehicle in a homogenizer to obtain premix 2. The homogenization process lasts for 5 minutes at a speed of 900 rpm. Finally, premix 1 and premix 2 were mixed, and 1% silica aerosol was added. The mixture was then rolled uniformly using a three-roll mill with a minimum rolling pitch of 10 microns. Testing revealed a resistor paste with a fineness of 13 μm, a thixotropic index of 3.90, excellent leveling, no mesh marks, clear printed graphics, and a smooth, dense surface after sintering.

[0045] Example 3

[0046] First, prepare the organic vehicle. Weigh 70% terpineol, 11% dibutyl phthalate, 9% acrylic resin with a number average molecular weight of 16331, 7% acrylic resin with a number average molecular weight of 80073, 1.5% Span 80, and 1.5% Tween 80, based on the weight percentage of the total organic vehicle, and place in a 90°C water bath. Stir until completely dissolved, then cool and set aside. Then, prepare the resistor slurry. Homogenize 1.5% CuO, 1% Fe2O3, 15.5% ruthenium oxide, and 10% organic vehicle in a homogenizer to obtain premix 1. Then, homogenize 53.5% glass powder and 17.5% organic vehicle in a homogenizer to obtain premix 2. The homogenization process lasts for 5 minutes at a speed of 900 rpm. Finally, premix 1 and premix 2 were mixed, and 0.5% silica aerosol and 0.5% alumina aerosol were added. The mixture was then rolled uniformly using a three-roll mill with a minimum rolling pitch of 10 microns. Testing revealed a resistor paste with a fineness of 12 μm, a thixotropic index of 3.82, excellent leveling, no mesh marks, clear printed graphics, and a smooth, dense surface after sintering.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A LTCC resistor paste, characterized in that: The invention comprises the following components in percentage by mass: 5% to 30% of ruthenium oxide, 0.5% to 3% of inorganic additives, 40% to 60% of glass powder, 25% to 35% of organic carrier, and 0.1% to 2% of aerosol; the organic carrier comprises a resin, and the resin is composed of a high molecular weight resin and a low molecular weight resin, the number average molecular weight of the low molecular weight resin is not higher than 20,000, and the number average molecular weight of the high molecular weight resin is not lower than 70,000.

2. The LTCC resistor paste according to claim 1, characterized in that: The resin is ethyl cellulose, methyl cellulose or acrylic resin.

3. The LTCC resistor paste according to claim 2, characterized in that: The number average molecular weight of the low molecular weight resin is 10,000 to 20,000; and / or the number average molecular weight of the high molecular weight resin is 70,000 to 85,000.

4. The LTCC resistor paste according to claim 3, characterized in that: The mass ratio of the high molecular weight resin to the low molecular weight resin is 1:2 to 2:

1.

5. The LTCC resistor paste according to any one of claims 1 to 4, characterized in that: The aerosol is aluminum oxide aerosol and / or silicon oxide aerosol.

6. The LTCC resistor paste according to any one of claims 1 to 4, characterized in that: The ruthenium oxide is nano-ruthenium oxide with a specific surface area of 8 to 15 m 2 / g.

7. The LTCC resistor paste according to any one of claims 1 to 4, characterized in that: The glass powder particle size D50 is 1.5 to 3 microns, and D90 is ≤ 5 microns.

8. The LTCC resistor paste according to any one of claims 1 to 4, characterized in that: The inorganic additive is selected from one or more of CuO, MnO2, Fe2O3, and Nb2O5.

9. The LTCC resistor paste according to any one of claims 1 to 4, characterized in that: The organic vehicle is composed of the following components in weight percentage: 75% to 87% solvent, 10% to 20% resin, and 3% to 5% dispersant; And / or, the solvent is selected from one or more of terpineol, butyl carbitol, butyl carbitol acetate, and dibutyl phthalate; And / or, the dispersant is selected from one or more of Span 80, Span 85, Tween 60, and Tween 80.

10. The method for preparing the LTCC resistor paste according to any one of claims 1 to 9, characterized in that: The following steps are involved: 1) mixing a solvent, a resin and an additive to obtain an organic carrier; 2) mixing the inorganic additive, ruthenium oxide, and part of the organic carrier to obtain a premix 1; 3) mixing the glass powder and the remaining organic vehicle to obtain a premix 2; 4) The premix 1 and the premix 2 are mixed, aerosol is added, and rolling is performed.

11. The method for preparing a resistor paste according to claim 10, wherein: In step 1), the method further comprises: stirring and cooling in a water bath; And / or, in step 2) and step 3), the mixing is carried out by homogenization, the homogenization time is ≥5 min, and the rotation speed is ≥900 r / min; And / or, in step 4), the rolling is performed using a three-roll mill, the minimum rolling spacing of the three-roll mill is 10 microns, and the slurry viscosity is 100-300 Pa·s.