Surface-modified si-ca-al lead-free glass powder for resistive paste and method of making the same

Abstract

The application provides a surface modified Si-Ca-Al lead-free glass powder for resistance paste and a preparation method thereof, and belongs to the technical field of resistance paste materials. The application provides a surface modified Si-Ca-Al lead-free glass powder for resistance paste, which comprises a glass powder matrix and a modification layer on the surface of the glass powder matrix; the material of the modification layer is bismuth oxide or tellurium oxide. In the application, a low-melting-point oxide (bismuth oxide or tellurium oxide) modification layer is constructed on the surface of the glass powder, and when the modification layer is used in resistance paste, the modification layer will soften preferentially in the sintering process, thereby significantly improving sintering fluidity and wettability with silver-palladium alloy powder, avoiding floating of the glass phase in the sintering process, and improving the uniformity, compactness and re-sintering stability of the film structure.

Description

Technical Field

[0001] This invention belongs to the field of resistive paste material technology, specifically relating to a surface-modified Si-Ca-Al lead-free glass powder for resistive paste and its preparation method. Background Technology

[0002] With the development of electronic devices towards higher power, higher reliability, and miniaturization, chip resistors are increasingly widely used in power management, automotive electronics, and industrial control. For resistors, the resistive paste needs to balance good conductivity, stable resistance values, and excellent structural consistency during the sintering process. Existing ultra-low resistance resistive pastes typically use silver-palladium alloy powder as the conductive phase, combined with lead-free glass powder as the binder phase. To meet the demands of high-power applications, the glass powder needs to ensure the heat resistance and mechanical stability of the sintered film. However, existing glass powders have insufficient fluidity within the sintering temperature range and poor wettability with silver-palladium alloy powder, easily leading to problems such as glass phase floating, uneven film structure, and significant resistance drift after re-firing, severely restricting the reliability of ultra-low resistance resistive pastes. Therefore, how to improve the sintering fluidity of glass powder and its wettability with silver-palladium alloy powder to obtain a resistive film with uniform structure, density, and excellent re-firing stability has become a pressing technical challenge in this field. Summary of the Invention

[0003] The purpose of this invention is to provide a surface-modifying Si-Ca-Al lead-free glass powder for resistive pastes and its preparation method. The glass powder provided by this invention can improve the sintering fluidity of the glass powder and its wettability with silver-palladium alloy powder, thereby obtaining a resistive film layer with uniform structure, density, and excellent re-firing stability.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a surface modification of resistive paste using Si-Ca-Al lead-free glass powder, comprising a glass powder matrix and a modification layer on the surface of the glass powder matrix; The material of the modified layer is bismuth oxide or tellurium oxide.

[0005] Preferably, the mass of the modified layer accounts for 0.5 to 5% of the total mass of the surface-modified Si-Ca-Al lead-free glass powder.

[0006] Preferably, the glass transition temperature T of the glass powder matrix is... g The temperature is 700~750℃.

[0007] Preferably, the glass powder matrix comprises the following components by mass percentage: 45-60% SiO2, 20-35% CaO, 10-20% Al2O3, 2-5% MgO, 2-5% ZnO, 1-3% B2O3 and 1-2% Li2O.

[0008] Preferably, the particle size of the glass powder matrix is ​​2.5~5.0μm.

[0009] The present invention also provides a method for preparing Si-Ca-Al lead-free glass powder for surface modification of resistive paste as described in the above technical solution, comprising the following steps: (1) Mix the glass powder matrix, inorganic solvent and bismuth tellurium salt to obtain a mixed solution; (2) After mixing the mixed solution obtained in step (1) and the reducing agent solution, a reduction reaction is carried out to obtain Si-Ca-Al lead-free glass powder for surface modification of resistor paste.

[0010] Preferably, in step (1), the mass ratio of glass powder matrix to bismuth / tellurium salt is (9~11):1.

[0011] Preferably, in step (1), the mass ratio of glass powder matrix to bismuth / tellurium salt is 10:1.

[0012] Preferably, the temperature of the reduction reaction in step (2) is 120~160℃ and the time of the reduction reaction is 2~8h.

[0013] The present invention also provides a resistive paste, comprising silver-palladium alloy powder, glass powder, organic carrier and additives; The glass powder is the Si-Ca-Al lead-free glass powder for surface modification of resistor paste described in the above technical solution or the Si-Ca-Al lead-free glass powder for surface modification of resistor paste prepared by the preparation method described in the above technical solution.

[0014] This invention provides a surface-modified Si-Ca-Al lead-free glass powder for resistive pastes, comprising a glass powder matrix and a modification layer on the surface of the glass powder matrix; the modification layer is made of bismuth oxide or tellurium oxide. By constructing a low-melting-point oxide (bismuth oxide or tellurium oxide) modification layer on the surface of the glass powder, this invention allows the modification layer to soften preferentially during sintering when used in resistive pastes, significantly improving sintering fluidity and wettability with silver-palladium alloy powders, preventing the glass phase from floating during sintering, and improving the uniformity, density, and re-firing stability of the film structure. Experimental results show that the resistive paste prepared using the glass powder provided by this invention forms a uniform and dense resistive film structure after sintering, with no glass phase floating, and the relative change rate of the resistive film after re-firing at 600℃ is less than 3%. Detailed Implementation

[0015] This invention provides a surface modification of resistive paste using Si-Ca-Al lead-free glass powder, comprising a glass powder matrix and a modification layer on the surface of the glass powder matrix; The material of the modified layer is bismuth oxide or tellurium oxide.

[0016] This invention does not impose any special restrictions on the source of the raw materials; commercially available products familiar to those skilled in the art can be used.

[0017] The Si-Ca-Al lead-free glass powder for surface modification of resistive paste provided by this invention includes a glass powder matrix; the glass transition temperature T of the glass powder matrix is... g The preferred temperature is 700~750℃.

[0018] In this invention, the glass powder matrix preferably comprises the following components by mass percentage: 45-60% SiO2, 20-35% CaO, 10-20% Al2O3, 2-5% MgO, 2-5% ZnO, 1-3% B2O3, and 1-2% Li2O. The composition design of the glass powder matrix of this invention improves wettability compared to existing glass powders, preventing the glass powder from floating.

[0019] In one embodiment, the mass percentage of SiO2 can be 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, or 59%; the mass percentage of CaO can be 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, or 19%; the mass percentage of Al2O3 can be 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, or 19%; the mass percentage of MgO can be 3% or 4%; the mass percentage of ZnO can be 3% or 4%; and the mass percentage of B2O3 can be 2%.

[0020] In this invention, the particle size of the glass powder matrix is ​​preferably 2.5~5.0 μm.

[0021] The present invention does not impose any special limitation on the preparation method of the glass powder matrix; it can be prepared by a preparation method well known to those skilled in the art.

[0022] As one embodiment, the preparation method of the glass powder matrix can be as follows: SiO2, CaCO3, Al2O3, MgO, ZnO, B2O3 and Li2CO3 are mixed in a planetary mixer for 30 min to obtain a mixture; then the mixture is loaded into a corundum crucible and heated to 1500℃ in a resistance furnace at a rate of 10℃ / min and held for 60 min to obtain a glass melt; then the glass melt is poured into deionized water for water quenching to obtain glass fragments; then the glass fragments are dried at 120℃ for 4 h, then coarsely crushed using a jaw crusher, then ball-milled in a planetary ball mill with anhydrous ethanol as the medium for 24 h, and finally centrifuged and dried to obtain the glass powder matrix.

[0023] The surface modification of Si-Ca-Al lead-free glass powder for resistive slurry provided by this invention includes a modification layer on the surface of the glass powder matrix; the modification layer is made of bismuth oxide or tellurium oxide. This invention achieves preferential interface softening by constructing a low-melting-point oxide (bismuth oxide or tellurium oxide) modification layer on the surface of the glass powder, significantly improving sintering fluidity and wettability with silver-palladium alloy powder, preventing the glass phase from floating during sintering, and improving the uniformity, density, and re-firing stability of the film structure.

[0024] In this invention, the mass of the modification layer preferably accounts for 0.5% to 5% of the total mass of the surface-modified Si-Ca-Al lead-free glass powder. As one embodiment, the mass of the modification layer can account for 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, or 4.5% of the total mass of the surface-modified Si-Ca-Al lead-free glass powder. Limiting the mass of the modification layer within the above range further significantly improves sintering fluidity and wettability with the silver-palladium alloy powder.

[0025] The present invention does not impose any special limitation on the thickness of the modified layer, as long as the quality of the modified layer meets the above requirements.

[0026] In this invention, the modification layer is preferably grown in situ on the surface of the glass powder matrix.

[0027] Compared with the prior art, the present invention has the following beneficial effects: 1) By introducing low-melting-point oxides onto the surface of glass powder through surface modification, when used in resistance slurry, the modified layer will soften preferentially during sintering, significantly improving sintering fluidity and wettability; 2) Significantly improves the interfacial compatibility between glass powder and silver-palladium alloy powder, avoids the glass phase from floating during sintering, and improves the uniformity and density of the film structure; 3) The prepared resistor paste has excellent reheating stability, which meets the requirements for use in high-reliability power chip resistors.

[0028] The present invention also provides a method for preparing Si-Ca-Al lead-free glass powder for surface modification of resistive paste as described in the above technical solution, comprising the following steps: (1) Mix the glass powder matrix, inorganic solvent and bismuth / tellurium salt to obtain a mixed solution; (2) After mixing the mixed solution obtained in step (1) and the reducing agent solution, a reduction reaction is carried out to obtain Si-Ca-Al lead-free glass powder for surface modification of resistor paste.

[0029] This invention does not impose any special restrictions on the source of the raw materials; commercially available products familiar to those skilled in the art can be used.

[0030] This invention involves mixing a glass powder matrix, an inorganic solvent, and a bismuth / tellurium salt to obtain a mixed solution. In this invention, the bismuth precursor is adsorbed onto the surface of the glass powder.

[0031] This invention does not impose any particular limitation on the type of inorganic solvent; any inorganic solvent well-known to those skilled in the art can be used. As one embodiment, the inorganic solvent may be deionized water.

[0032] This invention does not specifically limit the types of bismuth salt and tellurium salt; any bismuth salt and tellurium salt well known to those skilled in the art can be used. As one embodiment, the bismuth salt can be bismuth nitrate; the tellurium salt can be tellurium chloride or sodium tellurate.

[0033] The present invention does not have a special limitation on the amount of inorganic solvent used, as long as the glass powder matrix is ​​uniformly dispersed in the inorganic solvent and the bismuth / tellurium salt is completely dissolved in the inorganic solvent.

[0034] In this invention, the preferred mass ratio of the glass powder matrix to bismuth / tellurium salt is (9~11):1, more preferably 10:1. Limiting the mass ratio of the glass powder matrix to bismuth / tellurium salt within the above range allows this invention to influence the mass percentage of the modified layer, thereby further improving the sintering fluidity of the glass powder and its wettability with the silver-palladium alloy powder.

[0035] In this invention, the preferred mixture of the glass powder matrix, inorganic solvent, and bismuth / tellurium salt is: Bismuth / tellurium salt and a portion of the solvent are mixed to obtain a bismuth / tellurium salt solution; The glass powder matrix and the remaining solvent are mixed to obtain a dispersion; A bismuth / tellurium salt solution was added dropwise to the dispersion.

[0036] The present invention preferably involves mixing bismuth / tellurium salt with a portion of the solvent to obtain a bismuth / tellurium salt solution.

[0037] The present invention does not have a special limitation on the amount of solvent used, as long as it is sufficient to fully dissolve the bismuth / tellurium salt.

[0038] In one embodiment, the concentration of the bismuth salt solution can be 0.05~0.3 mol / L, or 0.1 mol / L or 0.2 mol / L; the concentration of the tellurium salt solution can be 0.1~0.3 mol / L, or 0.15 mol / L or 0.2 mol / L.

[0039] The present invention does not have any special limitations on the operation of mixing the bismuth / tellurium salt and a portion of the solvent; any technical solution for preparing the mixture well known to those skilled in the art can be used.

[0040] In this invention, the glass powder matrix and the remaining solvent are preferably mixed to obtain a dispersion.

[0041] In one embodiment, the mass ratio of the glass powder matrix to the remaining solvent can be 1:(8~12), or it can be 1:9, 1:10 or 1:11.

[0042] In this invention, the mixing of the glass powder matrix and the remaining solvent is preferably carried out under stirring conditions; the stirring time is preferably 20-40 minutes. This invention does not impose a particular limitation on the stirring rate, as long as uniform dispersion of the glass powder matrix is ​​achieved. As one embodiment, the stirring time can be 30 minutes.

[0043] After obtaining the bismuth / tellurium salt solution and the dispersion, the present invention preferably adds the bismuth / tellurium salt solution dropwise to the dispersion.

[0044] The present invention does not impose any particular limitation on the dropping rate; any operation familiar to those skilled in the art can be used. The dropping method used in this invention facilitates the full adsorption of the bismuth or tellurium precursor onto the surface of the glass powder matrix.

[0045] In this invention, the dropwise addition is preferably carried out under stirring conditions. This invention does not impose a particular limitation on the stirring rate; any stirring operation well-known to those skilled in the art can be used.

[0046] In this invention, the dispersion treatment is preferably carried out under stirring conditions; the stirring time is preferably 20-40 minutes. This invention does not impose any particular limitation on the stirring rate; stirring operations well-known to those skilled in the art can be used.

[0047] After obtaining the mixed solution, the present invention mixes the mixed solution and the reducing agent solution and carries out a reduction reaction to obtain Si-Ca-Al lead-free glass powder for surface modification of resistor paste.

[0048] In this invention, the reducing agent in the reducing agent solution is preferably at least one selected from sulfite, borohydride, ascorbic acid, and alcohol reducing agents; the concentration of the reducing agent solution is preferably 0.05~0.15 mol / L, more preferably 0.1 mol / L; the mass ratio of the reducing agent to bismuth salt is preferably 1:(4~6), more preferably 1:5; the mass ratio of the reducing agent to tellurium salt is preferably 1:(4~6), more preferably 1:5. By limiting the mass ratio of the reducing agent to bismuth / tellurium salt within the above ranges, this invention can further promote the reduction of the bismuth / tellurium precursor, thereby increasing the content of the modified layer.

[0049] This invention does not specifically limit the type of sulfite; any sulfite well-known to those skilled in the art can be used. As one embodiment, the sulfite may be sodium sulfite.

[0050] The present invention does not have any particular limitation on the specific type of alcohol reducing agent, and any alcohol reducing agent well known to those skilled in the art can be used.

[0051] In this invention, the reducing agent solution is preferably added dropwise. There is no particular limitation on the rate of dropwise addition; any operation familiar to those skilled in the art can be used.

[0052] The present invention does not impose any special limitations on the mixing operation, and any technical solution for preparing the mixture well known to those skilled in the art can be used.

[0053] In this invention, the preferred temperature of the reduction reaction is 120-160°C; the preferred time of the reduction reaction is 2-8 hours; the reduction reaction is preferably carried out under stirring conditions; and the preferred stirring rate is 20-40 r / min. As one embodiment, the temperature of the reduction reaction can be 130°C, 140°C, or 150°C; the preferred time of the reduction reaction can be 3 hours, 4 hours, 5 hours, 6 hours, or 7 hours; and the preferred stirring rate can be 25 r / min or 30 r / min. By limiting the process parameters of the reduction reaction to the above ranges, this invention can further promote the in-situ formation of a modification layer on the surface of the glass powder, thereby increasing the content of the modification layer.

[0054] After the reduction reaction is completed, the present invention preferably performs post-processing on the product obtained from the reduction reaction to obtain surface-modified Si-Ca-Al lead-free glass powder for resistive paste.

[0055] In this invention, the post-processing preferably includes sequentially performing cooling, centrifugation, washing, and drying.

[0056] The present invention does not impose any special limitations on the cooling operation; the cooling can be carried out naturally to room temperature using an operation known to those skilled in the art.

[0057] The present invention does not impose any special limitations on the centrifugation operation; any operation well known to those skilled in the art can be used to obtain a solid.

[0058] In this invention, the detergent used for washing is preferably deionized water; the number of washing cycles is preferably 2 to 4. This invention does not have a specific limitation on the washing rotation speed; any operation familiar to those skilled in the art can be used. This invention uses washing to remove unreacted precursors and byproducts.

[0059] In this invention, the drying temperature is preferably 60~90℃; the drying time is preferably 8~16h. As one embodiment, the drying temperature can be 70℃ or 80℃; the drying time can be 9h, 10h, 11h, 12h, 13h, 14h or 15h.

[0060] This invention generates a modification layer in situ on the surface of a glass powder matrix using a chemical reduction method. The modification layer is distributed on the outer surface of the glass powder particles and does not enter the glass phase structure.

[0061] The present invention also provides a resistive paste, comprising silver-palladium alloy powder, glass powder, organic carrier and additives; The glass powder is the Si-Ca-Al lead-free glass powder for surface modification of resistor paste described in the above technical solution or the Si-Ca-Al lead-free glass powder for surface modification of resistor paste prepared by the preparation method described in the above technical solution.

[0062] The present invention does not impose any special limitations on the types and amounts of the silver-palladium alloy powder, organic carrier and additives, which can be adjusted according to actual needs in a manner known to those skilled in the art.

[0063] The present invention does not have a special limitation on the amount of glass powder used; any amount of glass powder known to those skilled in the art can be used.

[0064] This invention utilizes a chemical reduction method to generate a modification layer in situ on the surface of glass powder, effectively improving the sintering fluidity of the glass powder and its wetting properties to silver-palladium alloy powder. The resistive film layer formed after sintering the resistive slurry prepared using this glass powder has a uniform and dense structure, with no glass phase floating to the surface. After re-firing at 600℃, the relative change rate of the resistive film layer is less than 3%, making it suitable for the fabrication of high-reliability power-type chip resistors.

[0065] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0066] Example 1 Surface-modified Si-Ca-Al lead-free glass powder consists of a glass powder matrix and a modification layer on the surface of the glass powder matrix; The material of the modification layer is bismuth oxide; The glass powder matrix comprises, by mass percentage: 52% SiO2, 28% CaO, 14% Al2O3, 2% MgO, 2% ZnO, 1% B2O3 and 1% Li2O; The particle size of the glass powder matrix is ​​2.5~5.0μm; The glass transition temperature Tg of the glass powder matrix is ​​720℃; The method for preparing the glass powder matrix is ​​as follows: Weigh the following raw materials by mass percentage: 52% SiO2, 28% CaCO3, 14% Al2O3, 2% MgO, 2% ZnO, 1% B2O3, and 1% Li2CO3. Mix these raw materials in a planetary mixer for 30 minutes to obtain a mixture. Then, place the mixture into a corundum crucible and heat it to 1500℃ in a resistance furnace at a rate of 10℃ / min, and hold it for 60 minutes to obtain a glass melt. Quickly pour the obtained glass melt into deionized water for water quenching to obtain glass fragments. Then, dry the glass fragments at 120℃ for 4 hours, coarsely crush them using a jaw crusher, and then ball mill them in a planetary ball mill with anhydrous ethanol as the medium for 24 hours. Finally, centrifuge and dry the mixture to obtain a Si-Ca-Al lead-free glass powder matrix. The mass of the modified layer accounts for 2% of the total mass of the surface-modified Si-Ca-Al lead-free glass powder; The preparation method of the surface-modified Si-Ca-Al lead-free glass powder is as follows: 50g of glass powder matrix was weighed and added to 500mL of deionized water. The mixture was dispersed under magnetic stirring for 30min to form a uniform suspension. Then, a 0.2mol / L bismuth nitrate solution was slowly added dropwise to the system, and stirring was continued for another 30min to obtain a mixed solution. Next, a 0.1mol / L ascorbic acid solution was added dropwise to the mixed solution, and the mixture was stirred at 120℃ at a stirring rate of 30r / min for 2h to carry out a reduction reaction. After the reaction was completed, the mixture was cooled to room temperature, and the solid product was obtained by centrifugation. The solid product was then washed three times with deionized water and finally dried in a 70℃ vacuum drying oven for 12h to obtain surface-modified Si-Ca-Al lead-free glass powder. The mass ratio of bismuth nitrate to glass powder matrix was 1:10, and the mass ratio of bismuth nitrate to ascorbic acid was 5:1.

[0067] Application Example 1 The surface-modified Si-Ca-Al lead-free glass powder prepared in Example 1 was added to 74wt% silver-palladium alloy powder (Pd content was 10wt%) at a ratio of 5wt%, and then 20wt% organic resin (terpineol / ethyl cellulose mass ratio of 5:1) and 1wt% additive (hydrogenated castor oil and BYK-333 mass ratio of 1:1) were added to obtain the resistive paste. The resistive film layer was obtained by screen printing on a 96% alumina ceramic substrate and sintering at 850°C for 10 minutes.

[0068] The resistive film prepared in Application Example 1 has a dense and uniform cross-sectional structure, and the glass phase did not float significantly. After being reheated at 600℃ for 30 min, the relative change rate of the resistance value was 2.6%.

[0069] Example 2 Surface-modified Si-Ca-Al lead-free glass powder consists of a glass powder matrix and a modification layer on the surface of the glass powder matrix; The material of the modified layer is tellurium oxide; The composition and preparation method of the glass powder matrix are the same as in Example 1; The mass of the modified layer accounts for 2.5% of the total mass of the surface-modified Si-Ca-Al lead-free glass powder; The preparation method of the surface-modified Si-Ca-Al lead-free glass powder is as follows: 50g of glass powder matrix was weighed and dispersed in 500mL of deionized water. The dispersion was carried out for 30min under magnetic stirring. Then, a 0.15mol / L sodium tellurate solution was added dropwise to the system and stirred for 60min to obtain a mixed solution. A 0.1mol / L sodium sulfite solution was added dropwise to the mixed solution and stirred and sonicated for 20min. Then, the mixture was reduced at 120℃ with a stirring rate of 20r / min for 3h. After the reaction was completed and cooled to room temperature, the solid product was obtained by centrifugation. The solid product was then washed three times with deionized water and finally dried in a vacuum drying oven at 70℃ for 12h to obtain surface-modified Si-Ca-Al lead-free glass powder. The mass ratio of sodium tellurate to glass powder matrix was 10:1, and the mass ratio of sodium tellurate to sodium sulfite was 5:1.

[0070] Application Example 2 The surface-modified Si-Ca-Al lead-free glass powder obtained in Example 2 was used to prepare a resistive paste (75wt% silver-palladium powder, 20wt% organic resin, 4wt% glass powder and 1wt% additives) according to the raw materials in Application Example 1. The paste was screen-printed onto a 96% alumina ceramic substrate and sintered at 850°C for 10 min to obtain a resistive film layer.

[0071] The resistive film prepared in Application Example 2 had a wetting angle of 28° with the silver-palladium alloy powder, a uniform film structure, and no obvious glass phase floating phenomenon. After reheating at 600℃ for 15 min, the relative change rate of the resistivity was 2.8%.

[0072] Comparative Example 1 The same glass powder matrix as in Example 1 was used, but no surface modification treatment was performed.

[0073] Comparative Application Example 1 Based on Application Example 1, a resistance paste was prepared using Comparative Example 1. During the sintering process, it was observed that the glass phase floated significantly and the film structure was uneven. After re-firing at 600°C for 15 minutes, the relative change rate of the resistance value was 4.7%, which was significantly higher than the results obtained in the Example.

[0074] As demonstrated by the above embodiments and comparative examples, by introducing bismuth oxide or tellurium oxide modification layers onto the surface of glass powder, the sintering behavior and interfacial stability of glass powder in ultra-low resistivity resistive slurries can be significantly improved without altering the glass bulk structure. The resulting resistive film exhibits excellent structural consistency and re-firing stability. This invention solves the challenges of flowability and stability of lead-free glass in ultra-low resistivity resistive slurries through surface engineering, and has promising prospects for industrial applications.

[0075] As can be seen from the above embodiments and comparative examples, the surface-modified Si-Ca-Al lead-free glass powder provided by the present invention can improve the sintering fluidity of the glass powder and its wettability with silver-palladium alloy powder, thereby obtaining a resistive film layer with uniform structure, density and excellent re-firing stability.

[0076] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A surface-modifying Si-Ca-Al lead-free glass powder for resistive paste, comprising a glass powder matrix and a modification layer on the surface of the glass powder matrix; The material of the modified layer is bismuth oxide or tellurium oxide.

2. The surface modified Si-Ca-Al lead-free glass powder according to claim 1, characterized in that, The mass of the modified layer accounts for 0.5 to 5% of the total mass of the surface-modified Si-Ca-Al lead-free glass powder.

3. The surface-modified Si-Ca-Al lead-free glass powder according to claim 1, characterized in that, The glass transition temperature T of the glass powder matrix g The temperature is 700~750℃.

4. The surface-modified Si-Ca-Al lead-free glass powder according to claim 3, characterized in that, The glass powder matrix comprises, by mass percentage, the following components: 45-60% SiO2, 20-35% CaO, 10-20% Al2O3, 2-5% MgO, 2-5% ZnO, 1-3% B2O3 and 1-2% Li2O.

5. The surface-modified Si-Ca-Al lead-free glass powder according to claim 1, characterized in that, The particle size of the glass powder matrix is ​​2.5~5.0μm.

6. The method for preparing surface-modified Si-Ca-Al lead-free glass powder for resistive paste according to any one of claims 1 to 5, comprising the following steps: (1) Mix the glass powder matrix, inorganic solvent and bismuth / tellurium salt to obtain a mixed solution; (2) After mixing the mixed solution obtained in step (1) and the reducing agent solution, a reduction reaction is carried out to obtain Si-Ca-Al lead-free glass powder for surface modification of resistor paste.

7. The preparation method according to claim 6, characterized in that, In step (1), the mass ratio of glass powder matrix to bismuth / tellurium salt is (9~11):

1.

8. The preparation method according to claim 7, characterized in that, The mass ratio of the glass powder matrix to the bismuth / tellurium salt is 10:

1.

9. The preparation method according to claim 6, characterized in that, The temperature of the reduction reaction in step (2) is 120~160℃, and the time of the reduction reaction is 2~8h.

10. A resistive paste, comprising silver-palladium alloy powder, glass powder, organic carrier, and additives; The glass powder is the Si-Ca-Al lead-free glass powder for surface modification of resistor paste as described in any one of claims 1 to 5, or the Si-Ca-Al lead-free glass powder for surface modification of resistor paste prepared by the preparation method described in any one of claims 6 to 9.