In-situ manufacturing method of self-heating sintered thick film heater

Abstract

A method for in-situ production of a self-heating sintered thick film heater is characterized in that: the electrode and resistor slurry are printed on a substrate through a nozzle according to a designed thick film pattern, and the slurry is dried using a heating platform, and a wire is led out from the dried heating film to connect the electrode to a heating control circuit. The heating circuit is used to control the heating and sintering of the heating film, and finally a layer of insulating ceramic is coated on the heating film for encapsulation to obtain a finished thick film heater. The process steps of the present invention are simple, no sintering furnace is required, and it can effectively save energy and improve the efficiency of thick film preparation.

Description

Technical Field

[0001] The invention relates to an electric heating technology, in particular to a preparation technology of a thick film heater, specifically to an in-situ preparation method of a self-heating sintered thick film heater. Background Art

[0002] Thick film heaters are widely used in semiconductors, medical devices, small household appliances and various industrial heating equipment due to their small size, light weight, high thermal efficiency, fast heating speed, long service life, energy saving and environmental protection. The existing thick film heater manufacturing method is to first cover the base material with a mask, and then use the regular reciprocating motion of the screen printer to evenly deposit the resistor paste on the substrate, and then pass through the static leveling, infrared drying furnace and high-temperature sintering furnace in turn, and finally obtain a clear and complete printing pattern, that is, the heating thick film itself. During the screen printing process, the film thickness of the resistor paste can be adjusted by adjusting the printing parameters.

[0003] The manufacturing method of the above-mentioned thick film heater must use a mask plate and a screen printer, and the processing equipment cost is relatively high; at the same time, the high-temperature sintering furnace must not only heat the slurry, but also heat the entire substrate. The commonly used substrate material is ceramic material, which has a large heat capacity and consumes a lot of energy for overall heating; when the thickness of the thick film heater is large, the thickness of each printing is about 1.5μm, and each printing requires a sintering process of up to half an hour, which has a high time cost. In summary, a new manufacturing method of thick film heaters is needed to solve the shortcomings of high cost, low efficiency, and low yield in the prior art, so as to obtain a higher yield at a lower cost. Summary of the invention

[0004] The purpose of the present invention is to solve the problems of high manufacturing cost, low efficiency and low yield of thick film heaters at present, and to invent an in-situ manufacturing method of self-heating and sintering thick film heaters to improve the manufacturing efficiency and yield of thick film heaters.

[0005] The technical solution of the present invention is:

[0006] A method for manufacturing a self-heating sintered thick film heater, characterized in that it comprises the following steps:

[0007] Step 1: Design the thick film heater pattern according to the thick film resistor value required by the process. The pattern includes the electrode pattern and the resistor circuit pattern, which mainly includes the line width, line spacing, resistor thickness and other dimensions. First, draw the flat design pattern of the heating film in the plane drawing software, then introduce the resistor thickness in the 3D modeling software, draw the 3D model of the resistor circuit, and finally import the 3D model into the 3D printing auxiliary software to automatically plan the motion trajectory of the nozzle 1;

[0008] Step 2: Place the substrate 2 on the heating plate 3 of the machine tool. The machine tool used is a machine tool with a movable and replaceable nozzle and a heating plate (can be purchased commercially or designed and manufactured by yourself). The width and installation height of the nozzle are selected and replaced according to the designed heater pattern line width and thickness. The moving speed of the nozzle is mainly based on the resistance thickness test or existing theoretical calculations. The commonly used substrate material is metal ceramic, which has the toughness and bending resistance of metal and the high temperature resistance, high strength and oxidation resistance of ceramic, and is made into the size required to carry the resistance pattern. Turn on the machine tool, use the nozzle 1 to move relative to the substrate 2 according to the programmed trajectory, and at the same time spray the electrode slurry 4 on the substrate 2;

[0009] Step 3: Adjust the drying temperature to the solidification temperature of the slurry, that is, the volatilization temperature of the organic carrier in the slurry. Start the heating plate 3 to dry the sprayed heating membrane electrode slurry 4;

[0010] Step 4: Start the machine again, and use the nozzle 1 to spray the resistor slurry 5 on the substrate 2. The resistor slurry 5 should achieve good electrical connection with the electrode, and then dry it again to obtain a solidified heating film 6. The purpose of drying is to remove the organic solvent in the film layer of the heating film 6 and temporarily shape the film layer. The electrode slurry is selected in advance according to the resistance value of the heater, production conditions, use environment, etc., and the different ratios of the conductive phase, glass phase and organic carrier are selected;

[0011] Step 5: Lead wires from the two electrode ends electrically connected to the dried heating film 6, and connect the electrodes to the heating control circuit of the device;

[0012] Step 6: Cover the surface of the heating film 6 with a layer of heat-insulating film 7, set the heating temperature, start the heating control circuit, and change the self-heating power of the heating film 6 by adjusting the voltage and current in the control circuit. The main function of high-temperature sintering of the thick film (i.e., the heating film 6) is to remove the residual organic carrier on the film, so that the thick film (heating film 6) forms the required electrical properties, and bonds the heating film 6 to the substrate 2. In the early stage of sintering, with the increase of heating power and time, the temperature rises rapidly, the conductive phase and the glass phase gradually disperse, and the heating film generates a large amount of heat energy; when the temperature is higher than 600°C, the glass phase begins to soften, and a part of it begins to infiltrate the conductive particles, so that the conductive particles are close to each other and bonded to form a chain and mesh structure. Parameters such as current size, sintering time, and heat preservation time can be obtained through experiments or existing theoretical calculations, and will not be repeated here. After the heating film 6 reaches the sintering temperature and is kept warm for a period of time, the heating is stopped and the temperature is naturally reduced, that is, self-sintering is achieved to obtain a thick film heater; the heating parameters (such as heat preservation parameters, etc.) can be determined by referring to the requirements for the use of the raw materials of the heating film.

[0013] Step 7: After the self-heating sintering of the heating film is completed, in order to obtain better wear resistance, corrosion resistance, high temperature oxidation resistance, sealing and other properties, the heating film needs to be surface strengthened and modified. After removing the heat insulation film 7 on the surface of the heating film 6, a layer of insulating ceramic 8| (ceramic coating) is coated on the sintered heating film 6 for encapsulation, and the ceramic coating is sintered by heating the sintered thick film heater to obtain a complete thick film resistor.

[0014] The nozzle is selected with a corresponding width and installation height according to the heating film pattern.

[0015] The heating plate is a platform including an electric heater, which can controllably heat the object placed thereon.

[0016] The control circuit is a heating and temperature control system, which includes a heating circuit and a temperature measuring circuit. It can monitor the temperature of the heating film in real time while heating, so as to facilitate dynamic adjustment.

[0017] The thermal insulation film is a standard part with a double-layer structure. The upper layer is a thermal insulation layer and the lower layer is a heat preservation layer. Its size is selected according to the heating platform. When in use, it covers the entire heating platform, can isolate the outside air, and avoid heat loss during the heating process.

[0018] Beneficial effects of the present invention:

[0019] 1. The present invention is an additive manufacturing method. When using the method of the present invention to produce thick film heaters, no mask plate and screen printing machine are required, which saves the cost of process equipment and manufacturing equipment.

[0020] 2. During sintering, in-situ sintering is adopted, and there is no need to transfer the substrate to the sintering furnace, which reduces the processing auxiliary time and improves the processing efficiency.

[0021] 3. The sintering method of the present invention only needs to heat the thick film circuit part, and there is no need to heat the substrate. The heating temperature is greatly lower than that in the sintering furnace, which reduces energy consumption and saves processing costs.

[0022] 4. When sintering the heating film, the temperature control system can monitor the sintering temperature in real time and make flexible adjustments, which is beneficial to improving the yield rate.

[0023] 5. Compared with the traditional screen printing method, the present invention is more flexible and convenient for producing thick film heaters with different resistance values ​​according to process requirements, providing a new solution for small-batch production of thick film heaters. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic flow chart of the production method of the present invention.

[0025] Figure 2It is a schematic diagram of the heating film graphic of the present invention.

[0026] Figure 3 It is a three-dimensional structural principle diagram of the overall device of the present invention (excluding the thermal insulation film).

[0027] Figure 4 It is a schematic diagram of the overall device of the present invention covered with a heat insulation film.

[0028] Figure 5 It is a schematic diagram of the production system of the present invention.

[0029] Figure 6 It is a partial cross-sectional view of the thick film heater structure of the present invention.

[0030] In the figure: 1. nozzle, 2. substrate, 3. heating plate, 4. electrode slurry, 5. resistor slurry, 6. solid heating film, 7. thermal insulation film, 8. insulating ceramic. DETAILED DESCRIPTION

[0031] The present invention will be further described below in conjunction with the accompanying drawings and examples.

[0032] like Figure 1-6 shown.

[0033] An in-situ manufacturing method of a self-heating sintered thick film heater comprises the following steps: Figure 1 As shown:

[0034] Step 1: Design the heating film pattern according to the thick film resistor required by the process. The pattern includes the electrode pattern and the resistor circuit pattern, which mainly includes the line width, line spacing, line thickness and other dimensions. In this example, the line width is designed to be 1mm and the line spacing is designed to be 2mm. Figure 2 First, draw the plane design of the heating film, then introduce the thickness of the resistor, draw the three-dimensional model of the resistor circuit, and finally import the three-dimensional model to automatically plan the motion trajectory of the nozzle 1;

[0035] Step 2: The machine tool used in this embodiment is a machine tool with a movable and replaceable nozzle and a heating plate. This example uses 96% alumina ceramic to make a 80×100mm single-layer substrate with a surface roughness of 3~5μm. First, the ceramic substrate is cleaned with deionized water and anhydrous ethanol and dried. Fix the substrate 2 on the heating plate 3 of the machine tool, select a nozzle with a width of 1mm according to the line width of the heating film, adjust the distance between the nozzle and the substrate according to the thickness of the heating film, and the moving speed of the nozzle is mainly based on the resistance thickness Test or existing theoretical calculations. Turn on the machine tool, use the nozzle 1 to move relative to the substrate 2 according to the programmed trajectory, and at the same time spray the electrode slurry 4 on the substrate 2. The electrode slurry in this example uses Ag / Pd electrode slurry C-1211 produced by Xi'an Hongxing Electronic Slurry Co., Ltd.

[0036] Step 3: Adjust the drying temperature to the solidification temperature of the selected electrode slurry. This example uses a common temperature of 150°C. Start the heating plate 3 and dry the sprayed heating film electrode slurry 4 for about 10 to 15 minutes. At this time, the organic solvent evaporates to obtain a solidified electrode. The electrode slurry and the resistor slurry have different compositions, that is, the electrode pattern and the resistor circuit pattern are different, and the nozzle scanning must be performed according to two different tracks.

[0037] Step 4: Start the machine again, and use the nozzle 1 to spray the resistor slurry 5 on the substrate 2. Since the resistor slurry needs to select different component ratios according to the resistance value of the heater, production conditions, and use environment, this example uses RuO2 as the conductive phase, lead borosilicate glass as the glass phase, and pine alcohol, butyl carbitol, etc. as solvents. The three are ground and mixed in a certain ratio (for example, 1:4:5 weight ratio) to obtain a thick film resistor slurry. Dry again for about 10 to 15 minutes to obtain a cured heating film 6. The purpose of drying is to remove the organic solvent in the film layer and temporarily shape the film layer;

[0038] Step 5: Lead wires from the two electrode ends of the dried heating film 6 to connect the heating film 6 to the heating control circuit of the device, such as Figure 3 ;

[0039] Step 6: Cover the surface of the heating film with a layer of heat insulation film 7, such as Figure 4 , set the heating temperature, run the heating control circuit to sinter the heating film 6, and change the self-heating power of the heating film by adjusting the voltage and current in the control circuit. The principle of the production system is as follows Figure 5 . The main function of high-temperature sintering of thick films is to remove residual organic carriers on the film, so that the thick film can form the required electrical properties and bond the film to the substrate. Parameters such as current size, sintering time, and holding time can be obtained through experiments or existing theoretical calculations, and will not be repeated here. In this example, according to the sintering curve provided by the manufacturer, the heating film 6 needs to go through three stages. First, the temperature is raised to 850°C at a rate of 30°C / min. In the process of rising from room temperature to 600°C, the conductive phase and glass phase in the resistor slurry gradually disperse. At 600°C to 850°C, the glass phase begins to soften, and a part of it begins to infiltrate the conductive particles, so that the conductive particles are close to each other and bonded to form chain and network structures; then keep warm for about 10 to 15 minutes to allow the conductive particles to fully bond, and finally stop heating. After natural cooling, self-sintering is achieved; a thick film heater is obtained;

[0040] Step 7: After the self-heating sintering of the heating film is completed, it is best to coat a layer of alumina insulating ceramic 8 on the sintered heating film 6 for encapsulation, and use the sintered thick film heater to heat and sinter the ceramic coating to obtain a complete thick film resistor. The thick film resistor structure is as follows: Figure 6Through this process, the heating film has better mechanical properties and high temperature resistance, which can better meet the working requirements.

[0041] The method for manufacturing a self-heating sintered thick film heater of the present invention can dynamically monitor the heating temperature, effectively save costs, improve processing efficiency, and facilitate improving the yield rate of thick film heater manufacturing.

[0042] The parts not involved in the present invention are the same as the prior art or can be implemented by using the prior art.

Claims

1. An in-situ method for manufacturing a self-heating sintered thick film heater, characterized in that: It includes the following steps: The first step is to design a thick film heater pattern according to process requirements, wherein the pattern includes an electrode pattern and a resistor circuit pattern, and to program the trajectory of the nozzle (1) according to the pattern to form an electrode pattern scanning trajectory and a resistor circuit pattern scanning trajectory; Step 2: placing the substrate (2) on a heating plate (3) of a machine tool, turning on the machine tool, and using the nozzle (1) to move relative to the substrate (2) along a scanning trajectory of the electrode pattern to spray the electrode slurry (4) onto the substrate; Step 3: Start the heating plate (3), adjust the temperature to the solidification temperature of the electrode slurry, and dry the electrode slurry (4) to obtain a solidified electrode; Step 4: restart the machine tool, use the nozzle (1) to spray the resistor slurry (5) onto the substrate (2) according to the resistor pattern scanning track and dry it again to obtain a solidified heating film (6), and at the same time make the resistor slurry overlap with the electrode to ensure subsequent electrical connection; Step 5: Leading out a wire from the electrode end electrically connected to the dried heating film (6), and connecting the heating film (6) to a heating control circuit; Step 6: Cover the surface of the heating film with a layer of heat-insulating film (7), start the heating control circuit, and change the heating power of the heating film (6) by adjusting the output power of the control circuit, so as to perform sintering by utilizing the heat generated by the heating film (6) itself; Step 7: Coat a layer of insulating ceramic (8) on the sintered heating film (6) for encapsulation, and then use the heating film (6) itself to heat and sinter again to obtain a complete thick film heater.

2. The method according to claim 1, characterized in that: The width and installation height of the nozzle (1) are selected according to the line width and thickness of the heating film pattern.

3. The method according to claim 1, characterized in that: The heating plate (3) is a platform including an electric heater, which can controllably heat an object placed thereon.

4. The method according to claim 1, characterized in that: The control circuit is a heating and temperature control system, which includes a heating circuit and a temperature measuring circuit. It can monitor the temperature of the heating film in real time while heating, so as to facilitate dynamic adjustment.

5. The method according to claim 1, characterized in that: The thermal insulation film (7) is a standard part with a double-layer structure, the upper layer is a thermal insulation layer, and the lower layer is a heat preservation layer. Its size is selected according to the heating platform. When in use, it covers the entire heating platform, isolating the outside air and preventing heat loss during the heating process.

6. The method according to claim 1, characterized in that: The substrate (2) is a metal ceramic having both the toughness and bending resistance of metal and the high temperature resistance, high strength and oxidation resistance of ceramic.

7. The method according to claim 1, characterized in that: The machine tool is a machine tool having a movable and replaceable nozzle and a heating plate (3).

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