Thick-film electric heating element and preparation method thereof

Abstract

The invention discloses a thick-film electric heating element and a preparation method, and belongs to the technical field of electric heating materials, the thick-film electric heating element comprises a base material, and a glass insulating layer, a conductor layer, a heating layer and a protective layer which sequentially cover the surface of the base material; the glass insulating layer and the protective layer are both obtained by sintering dielectric paste, and the dielectric paste comprises the following components in percentage by mass: 70-80% of a glass phase and 20-30% of an organic carrier; the conductor layer is obtained by sintering silver paste; the heating layer is obtained by sintering resistance paste, and the resistance paste comprises the following components in percentage by mass: 20-30% of silver powder, 15-40% of tin antimony oxide, 10-30% of glass phase and 20-40% of organic carrier; the thickness of the glass insulating layer is 80-100 microns, the thickness of the conductor layer is 8-12 microns, the thickness of the heating layer is 8-12 microns, and the thickness of the protective layer is 85-110 microns. The thick-film electric heating element has a good application prospect in the fields of household appliances, industrial heating and the like.

Description

Technical Field

[0001] The invention relates to the technical field of electric heating materials, and in particular to a thick film electric heating element and a preparation method thereof. Background Art

[0002] Thick film heating technology has the characteristics of high efficiency, fast response and flexible design. The thick film resistors produced have good stability and are an important electronic component. They are widely used in household appliances, industrial heating, automobiles, medical equipment and other fields. The resistance characteristics of thick film resistors mainly depend on the resistance layer (heating layer) therein. The resistance layer is generally prepared by firing the resistance paste onto the substrate through printing, drying and other methods. The resistance paste needs to have excellent conductivity, heat resistance, good film forming properties and viscosity. It is usually composed of a conductive phase, a glass phase and an organic carrier (or other carrier). The conductive phase is used to form a conductive path. The glass phase softens and melts during the sintering process to connect, tighten and fix the conductive particles so that the resistor film layer is firmly bonded to the substrate. The organic carrier plays the role of dispersing the conductive phase and the glass phase.

[0003] Most of the research in the prior art focuses on the optimization of the components of resistor pastes. For example, the Chinese patent document with publication number CN116525173A discloses a stainless steel substrate high-power thick film silver platinum tungsten resistor paste, firing method and application. The paste includes the following components by mass percentage: 40-70% monodisperse spherical silver powder, 0.1-40% monodisperse spherical platinum powder, 0.1-10% monodisperse spherical tungsten powder, 0.1-40% glass powder, and 18-25% organic carrier. Since the price of tungsten powder is relatively low, adding an appropriate amount of high melting point tungsten element to the silver platinum resistor paste can improve the high temperature stability of the resistor paste. However, the high price of platinum powder will increase the paste cost, and the easy oxidation of tungsten powder will lead to complicated processes. The Chinese patent document with publication number CN114883027A discloses a thick film resistor paste, which includes the following components in mass percentage: 30-55% conductive phase, 3-22% glass phase, 9-73% organic solvent, and 2-16% resin; wherein the conductive phase includes Ag powder, the glass phase includes PbO and SiO2, the mass ratio of PbO to Ag powder is ≤0.18, and the mass ratio of SiO2 to PbO is 0.5-5. However, the use of PbO does not meet the requirements of green environmental protection.

[0004] In order to optimize the performance of thick film electric heating elements, in addition to optimizing the components of the resistor slurry, the design of its coating structure is also critical. For example, the Chinese patent document with publication number CN106686770A discloses a thick film element, including a carrier, a thick film coating coated on the carrier, and a covering layer covering the thick film coating. The heat transfer rate of each layer of the invention meets certain conditions, has high thermal conductivity, and has low heat loss. In summary, combining the optimization of the components of the resistor slurry and the design of the coating structure of the thick film electric heating element is conducive to obtaining a thick film electric heating element with better performance. Summary of the invention

[0005] The present invention provides a thick film electric heating element, which has the advantages of low cost, high working stability, high power density, etc., and the maximum working temperature can reach 800°C with a fast heating speed. It has good application prospects in the fields of household appliances, industrial heating, etc.

[0006] The specific technical solutions adopted are as follows:

[0007] A thick film electric heating element comprises a substrate and a glass insulating layer, a conductor layer, a heating layer and a protective layer sequentially covering the surface of the substrate;

[0008] The glass insulating layer and the protective layer are both obtained by sintering a dielectric slurry, and the components of the dielectric slurry include 70-80% of a glass phase and 20-30% of an organic carrier by mass percentage;

[0009] The conductor layer is obtained by sintering silver paste;

[0010] The heating layer is obtained by sintering a resistor paste, and the components of the resistor paste include 20-30% silver powder, 15-40% antimony tin oxide (ATO), 10-30% glass phase and 20-40% organic carrier by mass percentage;

[0011] The thickness of the glass insulating layer is 80-100 μm, the thickness of the conductor layer is 8-12 μm, the thickness of the heating layer is 8-12 μm, and the thickness of the protective layer is 85-110 μm.

[0012] The present invention uses Ag / ATO-based resistor slurry as the heating layer. Compared with traditional precious metals, alloys, etc., ATO is resistant to high temperatures and is not easily oxidized, so that the prepared thick-film electric heating element has high high-power tolerance and can operate stably at higher temperatures. In addition, compared with components prepared using tungsten slurry, nickel slurry, etc., the thick-film electric heating element of the present invention has a simple preparation process and does not need to be sintered in a specific atmosphere, but can be sintered in the air. Moreover, the thick-film electric heating element does not contain heavy metals such as lead, and meets safety and environmental protection requirements.

[0013] Specifically, the substrate is made of stainless steel, aluminum alloy, nickel-based alloy or copper alloy, etc.; the substrate is in the shape of a sheet or a tube.

[0014] Specifically, the glass phase is CaO-Al2O3-SiO2-B2O3 glass powder, and its expansion coefficient is 80×10 -7 / ℃~90×10 -7 / ℃, the glass phase CaO-Al2O3-SiO2-B2O3 glass powder in the dielectric slurry includes 10-50% CaO, 10-40% Al2O3, 20-60% SiO2 and 5-15% B2O3 by mass percentage; the glass phase CaO-Al2O3-SiO2-B2O3 glass powder in the resistor slurry includes 10-40% CaO, 5-30% Al2O3, 20-60% SiO2 and 5-20% B2O3 by mass percentage.

[0015] Specifically, the organic carrier is at least one of terpineol, alcohol ester dodecanol, butyl carbitol, butyl carbitol acetate, dibutyl phthalate, tributyl phosphate, tributyl citrate, cellulose acetate, ethyl cellulose, polyvinyl butyral, Span-85, and polypropylene.

[0016] Preferably, in the medium slurry, the organic carrier includes, by mass percentage, 10-40% terpineol, 40-70% dodecanol, 1-10% ethyl cellulose, 0-6% cellulose acetate, 5-10% butyl carbitol, and 0-5% span-85.

[0017] Preferably, in the resistor paste, the organic carrier includes, by mass percentage, 50-70% terpineol, 5-10% butyl carbitol, 10-20% alcohol ester dodecyl, 2-5% ethyl cellulose and 0-5% Span-85.

[0018] Optionally, the average particle size of silver powder used to prepare resistor paste is 0.1-3 μm, the average particle size of antimony tin oxide used to prepare resistor paste is 0.5-7 μm, and the average particle size of glass phase CaO-Al2O3-SiO2-B2O3 glass powder used to prepare resistor paste and dielectric paste is 0.8-10 μm.

[0019] Furthermore, the medium slurry is first dried at a temperature of 500 to 700° C. for 10 to 20 minutes and then sintered, the peak sintering temperature is 700 to 950° C., and the peak holding time is 5 to 20 minutes;

[0020] The peak temperature of silver paste sintering is 600-750°C, and the peak holding time is 5-30 minutes;

[0021] The peak temperature of the resistor paste sintering is 700-850°C, and the peak holding time is 5-30 minutes.

[0022] The present invention also provides a method for preparing the thick film electric heating element, comprising the following steps:

[0023] (1) mixing a glass phase and an organic carrier in proportion and grinding them to obtain a dielectric slurry, printing the dielectric slurry on a substrate surface, and then drying and sintering to obtain a glass insulating layer;

[0024] (2) printing silver paste on the substrate treated in step (1), and sintering to obtain a conductor layer;

[0025] (3) mixing silver powder, antimony tin oxide and glass phase in proportion and grinding them for 5 to 20 minutes to make them fully mixed, then adding an organic carrier and grinding them to obtain a resistor paste, printing the resistor paste on the substrate treated in step (2), and sintering to obtain a heating layer;

[0026] (4) The glass phase and the organic carrier are mixed in proportion and then ground to obtain a dielectric slurry, the dielectric slurry is printed on the substrate treated in step (3), and sintered to obtain a protective layer.

[0027] Furthermore, the printing process is screen printing.

[0028] By changing the content of the heating layer components, the operating temperature of the thick film electric heating element can be adjusted within the range of 200 to 800°C.

[0029] The invention also provides application of the thick film electric heating element in the field of household appliances or industrial heating.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) The heating layer of the thick film heating element of the present invention is prepared from a low-cost and relatively green and environmentally friendly resistor paste. The resistor paste has a low re-firing change rate, which reduces the manufacturing cost of the thick film heating element and increases the service life of the thick film heating element. In addition, the thick film heating element of the present invention has a high power density, which is conducive to the miniaturization of the element.

[0032] (2) The operating temperature of the thick film electric heating element provided by the present invention can be adjusted within the range of 200 to 800° C. and the heating time is fast. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is an optical picture of the resistor paste in Example 1.

[0034] Figure 2 It is a schematic diagram of the structure of the thick film electric heating element. DETAILED DESCRIPTION

[0035] The present invention will be further described below in conjunction with the examples and accompanying drawings. It should be understood that these examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. The operating methods of the following examples that do not specify specific conditions are usually performed under normal conditions or under conditions recommended by the manufacturer. The content that is not described in detail in this specification sheet belongs to the prior art known to professionals in the field. The experimental materials used in the following examples, if not otherwise specified, can be purchased by conventional biochemical reagent companies.

[0036] The silver paste used in the following examples is provided by Shenzhen Sai Ya Electronic Paste Co., Ltd. The expansion coefficient of the CaO-Al2O3-SiO2-B2O3 glass powder is 80×10 -7 / ℃~90×10 -7 / ℃.

[0037] Example 1

[0038] (1) Preparation of dielectric slurry: By mass percentage, 75% CaO-Al2O3-SiO2-B2O3 glass powder (average particle size of 1.2 μm) and 25% organic vehicle are ground by a three-roll grinder for 40 minutes to obtain dielectric slurry, wherein the CaO-Al2O3-SiO2-B2O3 glass powder comprises 50% CaO, 15% Al2O3, 25% SiO2 and 10% B2O3 by mass percentage; the components of the organic vehicle comprise 15% terpineol, 65% alcohol ester dodecahydrate, 5% ethyl cellulose, 2% cellulose acetate, 10% butyl carbitol and 3% Span-85 by mass percentage. The dielectric slurry is used for the preparation of both the glass insulating layer and the protective layer.

[0039] (2) Preparation of resistor paste: In terms of mass percentage, 20% silver powder (average particle size of 1 μm), 27% antimony tin oxide (average particle size of 1 μm), and 30% CaO-Al2O3-SiO2-B2O3 glass powder (average particle size of 1.5 μm) were manually ground for about 15 minutes using an agate mortar to fully mix them. Then, 23% of an organic vehicle was added to the mixed phase and ground using a three-roll mill to obtain a resistor paste ( Figure 1 ), wherein the CaO-Al2O3-SiO2-B2O3 glass powder includes 40% CaO, 20% Al2O3, 25% SiO2 and 15% B2O3 by mass percentage; the components of the organic carrier include 70% terpineol, 10% butyl carbitol, 12% alcohol ester dodecahydrate, 5% ethyl cellulose and 3% Span-85 by mass percentage.

[0040] (3) Preparation of glass insulating layer: A tubular stainless steel substrate was used as the substrate. The dielectric slurry obtained in step (1) was printed on the surface of the substrate by screen printing. The substrate was then placed in a tubular furnace for drying at a temperature of 600° C. for 15 min. The substrate was taken out and placed in a muffle furnace for sintering. The peak sintering temperature was 850° C. and the peak holding time was 10 min.

[0041] (4) Preparation of the conductor layer: Silver paste is printed on the surface of the substrate treated in step (3) by screen printing, and then placed in a muffle furnace for sintering. The peak sintering temperature is 700° C. and the peak holding time is 10 minutes.

[0042] (5) Preparation of heating layer: The resistor paste prepared in step (2) is printed on the surface of the substrate treated in step (4) by screen printing, and then placed in a muffle furnace for sintering. The peak sintering temperature is 850° C. and the peak holding time is 10 minutes.

[0043] (6) Preparation of protective layer: The dielectric slurry prepared in step (1) is printed on the surface of the substrate treated in step (5) by screen printing, and then placed in a tube furnace for drying at a temperature of 600° C. for 15 min, and then placed in a muffle furnace for sintering at a peak temperature of 850° C. and a peak insulation time of 10 min; thereby preparing the thick film electric heating element.

[0044] The structural diagram of the thick film electric heating element is shown in Figure 2 As shown, the thickness of the glass insulating layer is about 85 μm, the thickness of the conductor layer is about 9 μm, the thickness of the heating layer is about 10 μm, the thickness of the protective layer is about 90 μm, and the maximum operating temperature of the thick film electric heating element is 230°C.

[0045] Example 2

[0046] In this embodiment, the preparation of the resistor paste is as follows: by mass percentage, 25% silver powder (average particle size of 1 μm) and 22% antimony tin oxide (average particle size of 1 μm), and 30% CaO-Al2O3-SiO2-B2O3 glass powder (average particle size of 1.5 μm) are manually ground using an agate mortar for about 15 minutes to fully mix them, and then 23% of an organic carrier is added to the above mixed phase, and ground using a three-roll grinder to obtain a resistor paste, wherein the CaO-Al2O3-SiO2-B2O3 glass powder includes 40% CaO, 20% Al2O3, 25% SiO2 and 15% B2O3 by mass percentage; the components of the organic carrier include 70% terpineol, 10% butyl carbitol, 12% alcohol ester dodecahydrate, 5% ethyl cellulose and 3% span-85 by mass percentage.

[0047] The medium slurry is the same as that in Example 1;

[0048] The preparation of the glass insulating layer is the same as in Example 1;

[0049] The preparation of the conductor layer is the same as in Example 1;

[0050] Preparation of the heating layer: The resistor paste prepared in the above step is printed on the conductor layer on the surface of the substrate by screen printing, and then placed in a muffle furnace for sintering, the peak sintering temperature is 850°C, and the peak holding time is 10 minutes;

[0051] The preparation of the protective layer is the same as in Example 1;

[0052] The maximum operating temperature of this thick film heating element is 550℃.

[0053] Example 3

[0054] In this embodiment, the preparation of the resistor paste is as follows: by mass percentage, 30% silver powder (average particle size of 1 μm) and 17% antimony tin oxide (average particle size of 1 μm), 30% CaO-Al2O3-SiO2-B2O3 glass powder (average particle size of 1.5 μm) are manually ground using an agate mortar for about 15 minutes to fully mix them, and then 23% of an organic carrier is added to the above mixed phase, and ground using a three-roll grinder to obtain a resistor paste, wherein the CaO-Al2O3-SiO2-B2O3 glass powder includes 40% CaO, 20% Al2O3, 25% SiO2 and 15% B2O3 by mass percentage; the components of the organic carrier include 70% terpineol, 10% butyl carbitol, 12% alcohol ester dodecahydrate, 5% ethyl cellulose and 3% span-85 by mass percentage.

[0055] The medium slurry is the same as that in Example 1;

[0056] The preparation of the glass insulating layer is the same as in Example 1;

[0057] The preparation of the conductor layer is the same as in Example 1;

[0058] Preparation of the heating layer: The resistor paste prepared in the above step is printed on the conductor layer on the surface of the substrate by screen printing, and then placed in a muffle furnace for sintering, the peak sintering temperature is 850°C, and the peak holding time is 10 minutes;

[0059] The preparation of the protective layer is the same as in Example 1;

[0060] The maximum operating temperature of this thick film heating element is 800℃.

[0061] The embodiments described above provide a detailed description of the technical solutions of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements or similar substitutions made within the scope of the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A thick film electric heating element, characterized in that: It includes a substrate and a glass insulating layer, a conductor layer, a heating layer and a protective layer sequentially covering the surface of the substrate; The glass insulating layer and the protective layer are both obtained by sintering a dielectric slurry, and the components of the dielectric slurry include 70-80% of a glass phase and 20-30% of an organic carrier by mass percentage; The conductor layer is obtained by sintering silver paste; The heating layer is obtained by sintering a resistor paste, and the components of the resistor paste include 20-30% silver powder, 15-40% antimony tin oxide, 10-30% glass phase and 20-40% organic carrier by mass percentage; The thickness of the glass insulating layer is 80-100 μm, the thickness of the conductor layer is 8-12 μm, the thickness of the heating layer is 8-12 μm, and the thickness of the protective layer is 85-110 μm.

2. The thick film electric heating element according to claim 1, characterized in that: The substrate material includes stainless steel, aluminum alloy, nickel-based alloy or copper alloy; the substrate shape is sheet or tube.

3. The thick film electric heating element according to claim 1, characterized in that: The glass phase is CaO-Al2O3-SiO2-B2O3 glass powder. The glass phase CaO-Al2O3-SiO2-B2O3 glass powder in the dielectric slurry includes 10-50% CaO, 10-40% Al2O3, 20-60% SiO2 and 5-15% B2O3 by mass percentage; the glass phase CaO-Al2O3-SiO2-B2O3 glass powder in the resistor slurry includes 10-40% CaO, 5-30% Al2O3, 20-60% SiO2 and 5-20% B2O3 by mass percentage.

4. The thick film electric heating element according to claim 1, characterized in that: The organic carrier is at least one of terpineol, alcohol ester dodecanol, butyl carbitol, butyl carbitol acetate, dibutyl phthalate, tributyl phosphate, tributyl citrate, cellulose acetate, ethyl cellulose, polyvinyl butyral, Span-85, and polypropylene.

5. The thick film electric heating element according to claim 1, characterized in that: The average particle size of silver powder is 0.1 to 3 μm, the average particle size of antimony tin oxide is 0.5 to 7 μm, and the average particle size of glass phase CaO-Al2O3-SiO2-B2O3 glass powder is 0.8 to 10 μm.

6. The thick film electric heating element according to claim 1, characterized in that: The medium slurry is first dried at a temperature of 500 to 700° C. for 10 to 20 minutes and then sintered. The peak sintering temperature is 700 to 950° C. and the peak holding time is 5 to 20 minutes. The peak temperature of silver paste sintering is 600-750°C, and the peak holding time is 5-30 minutes; The peak temperature of the resistor paste sintering is 700-850°C, and the peak holding time is 5-30 minutes.

7. The method for preparing a thick film electric heating element according to any one of claims 1 to 6, characterized in that: The following steps are involved: (1) mixing a glass phase and an organic carrier in proportion and grinding them to obtain a dielectric slurry, printing the dielectric slurry on a substrate surface, and then drying and sintering to obtain a glass insulating layer; (2) printing silver paste on the substrate treated in step (1), and sintering to obtain a conductor layer; (3) mixing silver powder, antimony tin oxide and glass phase in proportion and grinding them for 5 to 20 minutes to make them fully mixed, then adding an organic carrier and grinding them to obtain a resistor paste, printing the resistor paste on the substrate treated in step (2), and sintering to obtain a heating layer; (4) The glass phase and the organic carrier are mixed in proportion and then ground to obtain a dielectric slurry, the dielectric slurry is printed on the substrate treated in step (3), and sintered to obtain a protective layer.

8. The method for preparing a thick film electric heating element according to claim 7, characterized in that: The printing process is screen printing.

9. Application of the thick film electric heating element according to any one of claims 1 to 6 in the field of household appliances or industrial heating.

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