Lead-free glass powder, lead-free glass paste, preparation methods of lead-free glass powder and lead-free glass paste, and capacitive pressure sensor

Abstract

The invention discloses lead-free glass powder, lead-free glass paste, a preparation method of the lead-free glass powder and the lead-free glass paste and a capacitive pressure sensor. The lead-free glass powder comprises the following raw materials in percentage by weight: 63-72% of bismuth oxide, 4-10% of silicon oxide, 5-11% of zinc oxide, 2-7% of boric oxide, 0.5-4% of aluminum oxide, 1-5% of copper oxide, 1-5% of antimony oxide, 1-3% of zirconium oxide and 1-3% of titanium oxide. According to the lead-free glass powder, different network forming bodies and network outer bodies are introduced into a Bi-Si-Zn glass system to change the formula composition of the sealing glass and adjust the characteristics of the sealing glass.

Description

Technical Field

[0001] This application relates to the field of sealing glass technology, and in particular to a lead-free glass powder, a lead-free glass slurry, a method for preparing the same, and a capacitive pressure sensor. Background Technology

[0002] As the most fundamental key technology and raw material in the upstream of the electronic information industry chain, new ceramic circuit components are a class of new ceramic materials with unique electrical, optical and magnetic properties that are widely used in the field of electronic information. They are basic components in optoelectronic, microelectronic and electronic manufacturing industries and are high-tech materials with fierce international competition.

[0003] Ceramic capacitive pressure sensors, due to their advantages such as corrosion resistance, impact resistance, no hysteresis, and strong media compatibility, can be widely used for pressure detection in various media including water, gas, and liquid, and are particularly suitable for fields such as automotive and industrial process control. They employ a structure of a fixed alumina ceramic substrate and a movable alumina ceramic diaphragm. The movable diaphragm is sealed and fixed to the substrate using methods such as sealing glass paste. Electrode patterns are printed on the inner side between the two, forming a variable capacitor. When the pressure of the medium on the diaphragm changes, the capacitance between the two changes accordingly. This signal is converted and conditioned by a conditioning chip before being output to subsequent stages. Ceramic capacitive technology offers advantages such as moderate cost, wide measuring range, good temperature characteristics, consistency, and good long-term stability.

[0004] Currently, the sealing glass used in commonly used ceramic capacitive pressure sensors is mostly lead borosilicate glass. Its main advantages are excellent processability and heat resistance, and its physicochemical properties such as thermal expansion coefficient, refractive index, softening temperature, and sealing temperature are adjustable. However, these traditional sealing glasses contain the heavy metal lead, which is extremely harmful to the environment and human health. When lead-containing glass is discarded, long-term contact with water and acidic substances causes lead to leach into the soil and groundwater, resulting in lead pollution. Its use is currently restricted or banned by many countries worldwide. Therefore, the lead-free development of low-melting-point sealing glass slurries will be the main direction of future development.

[0005] The development of a lead-free glass paste for sealing alumina substrates of ceramic capacitive pressure sensors will help improve the international competitiveness of domestic manufacturers of ceramic capacitive pressure sensors and other related products. Summary of the Invention

[0006] This invention provides lead-free glass powder, lead-free glass slurry, their preparation method, and a capacitive pressure sensor to solve the technical problem that lead-containing glass in the prior art does not meet environmental protection requirements.

[0007] To achieve the above objectives, the technical solution provided by the present invention is as follows: In a first aspect, the present invention provides a lead-free glass powder comprising the following raw materials in weight percentage: 63%–72% bismuth oxide, 4%–10% silicon oxide, 5%–11% zinc oxide, 2%–7% boron oxide, 0.5%–4% aluminum oxide, 1%–5% copper oxide, 1%–5% antimony oxide, 1%–3% zirconium oxide, and 1%–3% titanium oxide.

[0008] Furthermore, it includes the following raw materials in weight percentage: bismuth oxide 68%, silicon oxide 7%, zinc oxide 8%, boron oxide 5%, aluminum oxide 2%, copper oxide 2%, antimony oxide 4.5%, zirconium oxide 2%, and titanium oxide 1.5%.

[0009] A second aspect of the present invention provides a method for preparing the above-mentioned lead-free glass powder, comprising the following steps: S1. Weigh each raw material according to the proportion and mix and grind them to obtain a mixed powder; S2. The mixed powder obtained in step S1 is heated to 700℃~900℃, kept at that temperature, and then heated to 1100℃~1300℃, kept at that temperature again to obtain glass melt. S3. Pour the molten glass obtained in step S2 into water for water quenching to obtain glass slag; ball mill the glass slag and grind it into powder to obtain lead-free glass powder.

[0010] Furthermore, in step S2, the duration of each heat preservation cycle is 15 min to 45 min.

[0011] In a third aspect, the present invention provides a lead-free glass paste comprising the following raw materials in weight percentage: 70% to 76% of the aforementioned lead-free glass powder; 20% to 30% of an organic carrier; 0.1% to 5% of an organic functional additive; and 0.5% to 3.5% of an inorganic blue pigment.

[0012] Furthermore, the organic carrier comprises the following raw materials in weight percentage: 10%–20% terpineol, 40%–50% diethylene glycol butyl ether, 10%–20% diethylene glycol butyl ether acetate, 10%–20% dodecyl alcohol ester, 2%–6% acrylic resin, 1%–5% polyvinyl alcohol resin, and 1%–5% thixotropic acrylic resin.

[0013] Further, the preparation method of the organic carrier includes the following steps: weighing each raw material according to the proportion, mixing and stirring the acrylic resin, the polyvinyl alcohol resin, the terpineol, the diethylene glycol butyl ether, the diethylene glycol butyl ether acetate, and the alcohol ester dodecyl to obtain a mixed solution, heating to dissolve, then cooling and adding the thixotropic acrylic resin to the mixed solution to obtain the organic carrier.

[0014] Furthermore, the organic functional additive is selected from one or more of dispersants, leveling agents, and defoamers.

[0015] Furthermore, the inorganic blue pigment is selected from one or more of aluminum cobaltate, cobalt oxide, and cobalt suboxide.

[0016] A fourth aspect of the present invention provides a method for preparing the above-mentioned lead-free glass paste, comprising the following steps: weighing each raw material according to a certain proportion, mixing and stirring to disperse, grinding, and filtering with a sieve to obtain the lead-free glass paste.

[0017] In a fifth aspect, the present invention provides a capacitive pressure sensor comprising an alumina ceramic substrate, an alumina ceramic membrane, and a sealing glass, wherein the sealing glass is disposed between the alumina ceramic substrate and the alumina ceramic membrane and fixes both thereto; the sealing glass is formed by sintering the aforementioned lead-free glass paste.

[0018] The lead-free glass powder provided by this invention adjusts the coefficient of thermal expansion, sealing temperature, and heat resistance of the sealing glass by introducing boron oxide and aluminum oxide. The introduction of boron oxide network forgings reduces the softening temperature of the sealing glass, lowers the coefficient of thermal expansion, and improves its heat resistance. The introduction of aluminum oxide intermediates improves the chemical stability, surface tension, and hardness of the sealing glass. The introduction of zirconium oxide and titanium oxide improves the crystallization characteristics and surface hardness of the sealing glass, enhances its chemical stability and resistance to acid and alkali corrosion, and improves the durability of ceramic capacitive sensors in harsh environments. The introduction of copper oxide, based on the high-temperature chemical reaction between copper oxide and aluminum oxide to form copper aluminate, improves the wettability of the molten sealing glass on the alumina substrate, thereby increasing the sealing strength. The introduction of antimony oxide, with its oxidizing properties, reduces the volume effect and secondary reactions of bismuth induced by the reduction of bismuth glass at high temperatures, effectively reducing porosity during the sealing process and improving sealing strength. Detailed Implementation

[0019] To enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] A first aspect of this application provides a lead-free glass powder comprising the following raw materials in weight percentage: bismuth oxide 63%–72%, silicon oxide 4%–10%, zinc oxide 5%–11%, boron oxide 2%–7%, aluminum oxide 0.5%–4%, copper oxide 1%–5%, antimony oxide 1%–5%, zirconium oxide 1%–3%, and titanium oxide 1%–3%.

[0021] The lead-free glass powder in this embodiment is a Bi-Si-Zn system with a coefficient of thermal expansion of 6 to 10*10. -6 / ℃, the above lead-free glass powder is introduced into the Bi-Si-Zn glass system with different network forgings and network exogens to change the composition of the sealing glass formulation and adjust the properties of the sealing glass.

[0022] The lead-free glass powder in this application adjusts the coefficient of thermal expansion, sealing temperature, and heat resistance of the sealing glass by introducing boron oxide and aluminum oxide. Introducing a boron oxide network forging reduces the softening temperature of the sealing glass, lowers the coefficient of thermal expansion, and improves its heat resistance. Introducing an aluminum oxide intermediate improves the chemical stability, surface tension, and hardness of the sealing glass. Introducing zirconium oxide and titanium oxide improves the crystallization characteristics and surface hardness of the sealing glass, enhances its chemical stability and resistance to acid and alkali corrosion, and improves the durability of ceramic capacitive sensors in harsh environments. Introducing copper oxide, based on the high-temperature chemical reaction between copper oxide and aluminum oxide to form copper aluminate, improves the wettability of the molten sealing glass on the alumina substrate, thereby increasing the sealing strength. Introducing antimony oxide, which has oxidizing properties, reduces the volume effect and secondary bismuth reactions induced by bismuth metal during the high-temperature reduction of bismuth glass, effectively reducing porosity during the sealing process and improving sealing strength.

[0023] Furthermore, the lead-free glass powder comprises the following raw materials in weight percentage: bismuth oxide 68%, silicon oxide 7%, zinc oxide 8%, boron oxide 5%, aluminum oxide 2%, copper oxide 2%, antimony oxide 4.5%, zirconium oxide 2%, and titanium oxide 1.5%.

[0024] A second aspect of this application provides a method for preparing the above-mentioned lead-free glass powder, comprising the following steps: S1. Weigh each raw material according to the proportion and mix and grind them to obtain a mixed powder; S2. The mixed powder obtained in step S1 is heated to 700℃~900℃, kept at that temperature, and then heated to 1100℃~1300℃, kept at that temperature again to obtain glass melt. S3. Pour the molten glass obtained in step S2 into water for water quenching to obtain glass slag; ball mill the glass slag and grind it into powder to obtain lead-free glass powder.

[0025] The preparation method of lead-free glass powder in this application embodiment involves thoroughly mixing and grinding the raw materials using a horizontal ball mill. A portion of the mixed powder is added to water; the water temperature can be increased to facilitate dissolution, for example, to 80°C, and the mixture is stirred thoroughly to obtain a mixed solution. After allowing the mixed solution to stand and cool to room temperature, its conductivity and pH value are tested to determine if it is uniformly mixed. A conductivity of 200–300 μS / cm and a pH value of 5.5–6.5 indicate uniform mixing. The glass slag is transferred to a zirconia-lined ball mill jar for high-speed ball milling, and then dried and pulverized. The median particle size D50 of the above lead-free glass powder is controlled within 1–2 μm.

[0026] The lead-free glass powder prepared by the above method has a large sealing temperature window on the alumina substrate of the ceramic capacitive piezoelectric sensor, strong sintering uniformity, and a smooth, flat, and transparent surface without defects such as pores.

[0027] Furthermore, in step S2, the duration of both heat preservation sessions is 15 min to 45 min.

[0028] A third aspect of this application provides a lead-free glass paste comprising the following raw materials in weight percentage: 70%–76% of the aforementioned lead-free glass powder; 20%–30% of an organic carrier; 0.1%–5% of an organic functional additive; and 0.5%–3.5% of an inorganic blue pigment.

[0029] The lead-free glass paste of this application embodiment does not contain harmful lead elements and meets environmental protection requirements; in addition to lead-free glass powder, it also includes an organic carrier, which enables the lead-free glass powder to be better wetted and dispersed to form a uniform glass paste, and can help the organic functional additives to fully exert their effects.

[0030] In some embodiments, the organic carrier comprises, by weight percentage, the following raw materials: 10%–20% terpineol, 40%–50% diethylene glycol butyl ether, 10%–20% diethylene glycol butyl ether acetate, 10%–20% dodecyl alcohol ester, 2%–6% acrylic resin, 1%–5% polyvinyl alcohol resin, and 1%–5% thixotropic acrylic resin. The organic functional additives are selected from one or more of dispersants, leveling agents, and defoamers. The inorganic blue pigment is selected from one or more of aluminum cobaltate, cobalt oxide, and cobalt(II) oxide.

[0031] In this embodiment, the organic carrier containing thixotropic acrylic resin and the organic functional additives have a dual synergistic effect, enabling the lead-free glass powder particles to be uniformly dispersed in the organic carrier to form a paste-like slurry. This ensures that the lead-free glass slurry can be printed smoothly on the alumina substrate and thin film of the ceramic capacitive sensor for a long time, with clear printed patterns, regular and full lines, stable wet weight, and uniform thickness. After drying, the lines are smooth, without grooves, and the film thickness is uniform. After medium-temperature sintering, the patterns are clear and without abnormalities, and the lines are smooth and rounded, without pores, residues, or other appearance defects. The organic part undergoes cracking and carbonization during the pre-sintering stage; the lead-free glass powder, as an inorganic binder phase, hardens and shrinks between glass powder particles during high-temperature sintering, initially melting, while the inorganic pigments also melt into the glass body and adhere to the alumina substrate to form a sealing glass layer.

[0032] Furthermore, the preparation method of the organic carrier includes the following steps: weigh each raw material according to the proportion, mix and stir acrylic resin, polyvinyl alcohol resin, terpineol, diethylene glycol butyl ether, diethylene glycol butyl ether acetate and alcohol ester dodecyl to obtain a mixture, heat to dissolve, then cool and add thixotropic acrylic resin to the mixture to obtain the organic carrier.

[0033] In the embodiments of this application, during the preparation of the organic carrier, terpineol, diethylene glycol butyl ether, diethylene glycol butyl ether acetate, and dodecyl alcohol ester are used as solvents; the resin and solvent can be added to a stirred tank, cooling water is circulated, the temperature inside the stirred tank is raised and maintained at about 80℃~100℃, and the temperature is kept for 2h~3h to dissolve; then the temperature is lowered, and thixotropic acrylic resin is added while stirring, and after constant temperature, a flowing paste is obtained, which is the organic carrier.

[0034] A fourth aspect of the embodiments of this application provides a method for preparing the above-mentioned lead-free glass paste, comprising the following steps: weighing each raw material according to the proportion, mixing and stirring to disperse, grinding, and filtering with a sieve to obtain lead-free glass paste.

[0035] In this embodiment, the raw materials are dispersed by planetary mixing, then thoroughly ground using a three-roll mill, and finally filtered through a sieve of 200-500 mesh. The resulting lead-free glass paste is a homogeneous paste with special rheological properties.

[0036] The lead-free glass paste of this application embodiment has a viscosity controlled at 120 Pa·s to 180 Pa·s, a thixotropic index of 2 to 3, a lead-free glass powder content of 70% to 76%, a median particle size (D50) of 1.5 μm to 2.5 μm, and a fineness controlled at less than 15 μm. The sealing lead-free glass paste has a light blue appearance, the printing screen is 90 mesh to 280 mesh, the drying temperature is 150°C, the drying time is 10 min, the pre-firing temperature is 400°C to 500°C, the sealing temperature is 580°C to 680°C, and the coefficient of thermal expansion is 5 to 7 × 10⁻⁶.-6 / ℃.

[0037] The lead-free glass paste of this application has the advantages of a wide sealing temperature window, high sealing strength, excellent airtightness, and concentrated capacitance distribution.

[0038] A fifth aspect of the embodiments of this application provides a capacitive pressure sensor, including an alumina ceramic substrate, an alumina ceramic film, and a sealing glass, wherein the sealing glass is disposed between the alumina ceramic substrate and the alumina ceramic film and fixes both thereto; the sealing glass is sintered from the aforementioned lead-free glass paste.

[0039] The lead-free glass paste of this embodiment is screen-printed onto the alumina substrate and sheet of the ceramic capacitive pressure sensor, dried, and then placed in a high-temperature chain sintering furnace for pre-sintering. After debinding, it is sintered again in a high-temperature chain sintering furnace. After cooling, the alumina ceramic substrate and sheet are sealed and fixed together using sealing glass.

[0040] The present application will be further described below through specific embodiments. All reagents in the following embodiments are commercially available.

[0041] Example 1 The formulas for each raw material in lead-free glass powder are shown in Table 1, model SG-01; the formulas for each raw material in lead-free glass paste are shown in Table 2.

[0042] Table 1. Weight percentage of each raw material in lead-free glass powder

[0043] Table 2. Weight percentage of each raw material in lead-free glass paste in Examples 1 to 5

[0044] The preparation method of lead-free glass powder includes the following steps: 1. According to the different mass percentages listed in Table 1, accurately weigh bismuth oxide, silicon oxide, zinc oxide, boron oxide, aluminum oxide, copper oxide, antimony oxide, zirconium oxide and titanium oxide, and then use a horizontal ball mill to fully mix and grind them to obtain a mixed powder.

[0045] 2. Take 10g of the ground mixed powder and add it to 300mL of deionized water at 80℃. Stir thoroughly for 30min and let it stand and cool to room temperature to obtain a mixed solution. The conductivity of the above mixed solution is 249μs / cm and the pH value is 6, indicating that it has been ground evenly.

[0046] 3. The qualified mixed powder from step 2 is placed into an alumina crucible, heated to 800°C, held for 30 minutes, then heated to 1200°C and held for 30 minutes to obtain the molten glass liquid.

[0047] 4. Quickly pour the molten glass into deionized water for water quenching to obtain colorless and transparent glass shards.

[0048] 5. The glass slag was transferred to a zirconia-lined ball mill jar for high-speed ball milling, dried, and then pulverized to obtain the finished glass powder. The median particle size D50 of the glass powder was tested to be 1.8 μm.

[0049] The organic carrier comprises the following raw materials in weight percentage: 15% terpineol, 45% diethylene glycol butyl ether, 15% diethylene glycol butyl ether acetate, 15% dodecyl alcohol ester, 5% acrylic resin, 3% polyvinyl alcohol resin, and 2% thixotropic acrylic resin.

[0050] The preparation method of the organic carrier includes the following steps: The weighed resins (acrylic resin and polyvinyl alcohol resin) and solvents (terpineol, diethylene glycol butyl ether, diethylene glycol butyl ether acetate, and dodecyl alcohol ester) are added to a stirred tank. Cooling water is circulated, and the temperature inside the stirred tank is raised and maintained at 85°C for 2 hours. The temperature is then lowered to 50°C, and thixotropic acrylic resin is added while dispersing. After maintaining the temperature for 30 minutes, a uniform, flowing paste is obtained, which is the organic carrier.

[0051] The preparation method of lead-free glass paste includes the following steps: First, accurately weigh the above-mentioned lead-free glass powder, organic carrier, organic functional additives and inorganic blue pigment according to the mass percentages listed in Table 2, disperse them by planetary dynamic mixing, then grind them thoroughly with a three-roll mill to adjust the fineness to below 12μm, and finally filter them with a 300-mesh sieve to prepare a uniform paste with special rheological properties. Then adjust the viscosity to 120-180 Pa·s to finally obtain lead-free glass paste.

[0052] The lead-free glass paste of this embodiment was screen-printed onto the alumina substrate and sheet of the ceramic capacitive pressure sensor using a 120-mesh screen. It was dried at 150°C for 10 minutes and then placed in a high-temperature chain sintering furnace for pre-sintering at a peak temperature of 450°C for 60 minutes. Then, it was sintered again in a high-temperature chain sintering furnace at a peak temperature of 580°C for 60 minutes. After cooling, the surface appearance and pattern of the sealing glass paste after sintering were observed. The comprehensive performance is shown in Table 3.

[0053] Example 2 The formulas for each raw material in lead-free glass powder are as shown in Table 1 (model SG-02); the formulas for each raw material in lead-free glass paste are as shown in Table 2.

[0054] The organic carrier comprises the following raw materials in weight percentage: 15% terpineol, 45% diethylene glycol butyl ether, 15% diethylene glycol butyl ether acetate, 15% dodecyl alcohol ester, 4% acrylic resin, 3% polyvinyl alcohol resin, and 3% thixotropic acrylic resin.

[0055] In this embodiment, the preparation methods of lead-free glass powder, organic carrier, and lead-free glass paste are the same as in Example 1.

[0056] The lead-free glass paste of this embodiment was screen-printed onto the alumina substrate and sheet of the ceramic capacitive pressure sensor using a 120-mesh screen. It was dried at 150°C for 10 minutes and then placed in a high-temperature chain sintering furnace for pre-sintering at a peak temperature of 450°C for 60 minutes. Then, it was sintered again in a high-temperature chain sintering furnace at a peak temperature of 600°C for 60 minutes. After cooling, the surface appearance and pattern of the sealing glass paste after sintering were observed. The comprehensive performance is shown in Table 3.

[0057] Example 3 The formulas for each raw material in lead-free glass powder are shown in Table 1 (model SG-03); the formulas for each raw material in lead-free glass paste are shown in Table 2.

[0058] The organic carrier comprises the following raw materials in weight percentage: 15% terpineol, 45% diethylene glycol butyl ether, 15% diethylene glycol butyl ether acetate, 15% dodecyl alcohol ester, 3% acrylic resin, 4% polyvinyl alcohol resin, and 3% thixotropic acrylic resin.

[0059] In this embodiment, the preparation methods of lead-free glass powder, organic carrier, and lead-free glass paste are the same as in Example 1.

[0060] The lead-free glass paste of this embodiment was screen-printed onto the alumina substrate and sheet of the ceramic capacitive pressure sensor using a 120-mesh screen. It was dried at 150°C for 10 minutes and then placed in a high-temperature chain sintering furnace for pre-sintering at a peak temperature of 450°C for 60 minutes. Then, it was sintered again in a high-temperature chain sintering furnace at a peak temperature of 620°C for 60 minutes. After cooling, the surface appearance and pattern of the sealing glass paste after sintering were observed. The comprehensive performance is shown in Table 3.

[0061] Example 4 The formulas for each raw material in lead-free glass powder are shown in Table 1 (model SG-04); the formulas for each raw material in lead-free glass paste are shown in Table 2.

[0062] The organic carrier comprises the following raw materials in weight percentage: 10% terpineol, 50% diethylene glycol butyl ether, 10% diethylene glycol butyl ether acetate, 20% dodecyl alcohol ester, 5% acrylic resin, 3% polyvinyl alcohol resin, and 2% thixotropic acrylic resin.

[0063] In this embodiment, the preparation methods of lead-free glass powder, organic carrier, and lead-free glass paste are the same as in Example 1.

[0064] The lead-free glass paste of this embodiment was screen-printed onto the alumina substrate and sheet of the ceramic capacitive pressure sensor using a 120-mesh screen. It was dried at 150°C for 10 minutes and then placed in a high-temperature chain sintering furnace for pre-sintering at a peak temperature of 450°C for 60 minutes. Then, it was sintered again in a high-temperature chain sintering furnace at a peak temperature of 640°C for 60 minutes. After cooling, the surface appearance and pattern of the sealing glass paste after sintering were observed. The comprehensive performance is shown in Table 3.

[0065] Example 5 The formulas for each raw material in lead-free glass powder are shown in Table 1 (model SG-05); the formulas for each raw material in lead-free glass paste are shown in Table 2.

[0066] The organic carrier comprises the following raw materials in weight percentage: 10% terpineol, 50% diethylene glycol butyl ether, 15% diethylene glycol butyl ether acetate, 15% dodecyl alcohol ester, 5% acrylic resin, 3% polyvinyl alcohol resin, and 2% thixotropic acrylic resin.

[0067] In this embodiment, the preparation methods of lead-free glass powder, organic carrier, and lead-free glass paste are the same as in Example 1.

[0068] The lead-free glass paste of this embodiment was screen-printed onto the alumina substrate and sheet of the ceramic capacitive pressure sensor using a 120-mesh screen. It was dried at 150°C for 10 minutes and then placed in a high-temperature chain sintering furnace for pre-sintering at a peak temperature of 450°C for 60 minutes. Then, it was sintered again in a high-temperature chain sintering furnace at a peak temperature of 660°C for 60 minutes. After cooling, the surface appearance and pattern of the sealing glass paste after sintering were observed. The comprehensive performance is shown in Table 3.

[0069] Table 3. Overall performance results of lead-free glass pastes from Examples 1 to 5

[0070] As can be seen from the comprehensive performance results of the lead-free glass paste in Table 3, the lead-free glass paste of this application has a smooth and flat surface without depressions after sintering, a uniform blue color, no pores, high sealing strength, uniform capacitance distribution, and excellent airtightness.

[0071] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A lead-free glass powder, characterized in that, Includes the following raw materials in weight percentage: Bismuth oxide 63%–72%, silicon oxide 4%–10%, zinc oxide 5%–11%, boron oxide 2%–7%, aluminum oxide 0.5%–4%, copper oxide 1%–5%, antimony oxide 1%–5%, zirconium oxide 1%–3%, titanium oxide 1%–3%.

2. The lead-free glass powder according to claim 1, characterized in that, It includes the following raw materials in weight percentage: bismuth oxide 68%, silicon oxide 7%, zinc oxide 8%, boron oxide 5%, aluminum oxide 2%, copper oxide 2%, antimony oxide 4.5%, zirconium oxide 2%, and titanium oxide 1.5%.

3. The method for preparing lead-free glass powder according to claim 1 or 2, characterized in that, Includes the following steps: S1. Weigh each raw material according to the proportion and mix and grind them to obtain a mixed powder; S2. The mixed powder obtained in step S1 is heated to 700℃~900℃, kept at that temperature, and then heated to 1100℃~1300℃, kept at that temperature again to obtain glass melt. S3. Pour the molten glass obtained in step S2 into water for water quenching to obtain glass slag; ball mill the glass slag and grind it into powder to obtain lead-free glass powder.

4. The method for preparing lead-free glass powder according to claim 3, characterized in that, In step S2, the two heat preservation times are both 15 min to 45 min.

5. A lead-free glass paste, characterized in that, Includes the following raw materials in weight percentage: The lead-free glass powder obtained by the method according to claim 1 or 2 or the method according to claim 3 or 4 accounts for 70% to 76% of the lead-free glass powder. Organic carrier 20%–30%; Organic functional additives 0.1-5%; Inorganic blue pigment 0.5%–3.5%.

6. The lead-free glass paste according to claim 5, characterized in that, The organic carrier comprises the following raw materials in weight percentage: 10%–20% terpineol, 40%–50% diethylene glycol butyl ether, 10%–20% diethylene glycol butyl ether acetate, 10%–20% dodecyl alcohol ester, 2%–6% acrylic resin, 1%–5% polyvinyl alcohol resin, and 1%–5% thixotropic acrylic resin.

7. The lead-free glass paste according to claim 6, characterized in that, The preparation method of the organic carrier includes the following steps: weighing each raw material according to the proportion, mixing and stirring the acrylic resin, the polyvinyl alcohol resin, the terpineol, the diethylene glycol butyl ether, the diethylene glycol butyl ether acetate, and the alcohol ester dodecyl to obtain a mixture, heating to dissolve, then cooling and adding the thixotropic acrylic resin to the mixture to obtain the organic carrier.

8. The lead-free glass paste according to any one of claims 5 to 7, characterized in that, The organic functional additive is selected from one or more of dispersants, leveling agents, and defoamers; and / or, The inorganic blue pigment is selected from one or more of aluminum cobalt oxide, cobalt oxide, and cobalt suboxide.

9. The method for preparing lead-free glass paste according to any one of claims 5 to 8, characterized in that, Includes the following steps: Weigh each raw material according to the specified proportions, mix and stir to disperse, grind, and filter through a sieve to obtain the lead-free glass paste.

10. A capacitive pressure sensor, characterized in that, It includes an alumina ceramic substrate, an alumina ceramic film, and a sealing glass, wherein the sealing glass is disposed between the alumina ceramic substrate and the alumina ceramic film and fixes both thereto; the sealing glass is sintered from the lead-free glass paste according to any one of claims 5 to 8.

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