Chip thick film micro-coating method

Abstract

The invention provides a chip thick film micro-coating method which comprises the following steps: S1, mixing a gas sensitive material, an organic solvent and an adhesive to prepare a mixed solution; s2, micro-coating the surface of a chip electrode with the mixed solution, and then curing; the gas sensitive material comprises tin dioxide and precious metal salt; the adhesive comprises at least one of organic acid and alcohol; the thickness of the micro coating is 8 [mu] m to 12 [mu] m; and the pressure of the micro coating is 0.1 MPa to 0.5 MPa. The adhesive is organic acid and alcohol, so that the gas sensitive material can be adhered, and a mixed solution formed by the gas sensitive material, the adhesive and the organic solvent has excellent flowability and stability, so that the gas sensitive material is uniformly dispersed in the mixed solution; and in the subsequent sintering process, the adhesive and the organic solvent are removed from the mixed solution system, so that the surface of the chip electrode is uniformly coated with the gas sensitive material, and the micro-coating of the thick film is realized.

Description

Technical Field

[0001] The present application relates to the field of sensor technology, and in particular to a chip thick film micro-coating method. Background Art

[0002] Thick film gas sensor is an important branch in the field of thick film sensors. It can sense the external atmosphere information and convert it into usable signals according to certain rules. Its principle is to use the fact that the surface state of metal oxides will change due to the adsorption of certain gases, so that the surface potential value can be obtained through the change of surface conductivity value.

[0003] The production method of gas sensors in related technologies is as follows: The gas-sensitive material is coated on the chip electrode and sintered by direct writing with a brush. The amount of gas-sensitive material added each time varies, resulting in poor consistency of the products. Different products need to be screened and graded during the test and screening process, resulting in low production efficiency.

[0004] Printing is used for production, which can improve product consistency; however, the loss of gas-sensitive materials during the printing process is too large, resulting in high production costs; at the same time, some harmful gases are also produced, which require subsequent recycling and treatment. Summary of the invention

[0005] The present application is made in view of the above-mentioned problems, and its purpose is to provide a chip thick film micro-coating method, which has low production cost.

[0006] Specifically, the present application provides a chip thick film micro-coating method, comprising the following steps: S1. Mixing a gas sensitive material, an organic solvent and an adhesive to obtain a mixed liquid; S2, applying the mixed solution to the chip electrode surface and then solidifying; The gas sensitive material includes tin dioxide and a noble metal salt; The adhesive includes at least one of an organic acid and an alcohol; The thickness of the micro-coating is 8 μm to 12 μm; The micro-covering pressure is 0.1MPa~0.5MPa.

[0007] According to one of the technical solutions of the method of this application, at least the following beneficial effects are achieved: In the present application, the adhesive is an organic acid and an alcohol, which help the diffusion of nanomaterials during bonding; it can not only achieve bonding of gas-sensitive materials, but also make the mixed liquid formed by the gas-sensitive materials, the adhesive and the organic solvent have excellent fluidity and stability, so that the gas-sensitive materials are evenly dispersed in the mixed liquid; in the subsequent sintering process, the adhesive and the organic solvent are removed from the mixed liquid system, so that the gas-sensitive material is evenly coated on the surface of the chip electrode, thereby realizing thick film micro-coating; it achieves uniform coating of the gas-sensitive material, and at the same time makes the gas-sensitive material stably solidified on the surface of the chip electrode.

[0008] According to some embodiments of the present application, the organic solvent includes an alcohol solvent.

[0009] According to some embodiments of the present application, the alcohol solvent includes one of methanol, ethanol and propanol.

[0010] According to some embodiments of the present application, at least one of amino acid and / or organic phosphonic acid is further added to the mixed solution.

[0011] According to some embodiments of the present application, the amino acid includes cysteine.

[0012] The present application introduces cysteine ​​into the mixed liquid. On the one hand, cysteine ​​has a certain coordination ability, which can effectively inhibit the agglomeration of the gas-sensitive material in the mixed liquid, thereby preparing a gas-sensitive material layer with uniform thickness and smooth surface; on the other hand, the interaction between the lone pair electrons in cysteine ​​and the tin (Sn) atoms in the gas-sensitive material promotes the reduction of oxygen vacancy defects in SnO2, helps to reduce defect sites in the gas-sensitive material, and optimizes its electronic structure; thereby optimizing the performance of the gas-sensitive material.

[0013] According to some embodiments of the present application, the organic phosphoric acid includes aminomethylphosphonic acid.

[0014] Aminomethylphosphonic acid has a phosphonic acid group, which has excellent bonding ability with the metal in the gas sensitive material; thus, it can provide an anchoring effect and can be effectively coordinated to the surface of the gas sensitive material; This strong anchoring effect not only helps to improve the surface stability of gas-sensitive materials, but also promotes the efficient transmission of electrons in gas-sensitive materials, thereby improving the performance of gas-sensitive materials.

[0015] According to some embodiments of the present application, the mass ratio of cysteine ​​to the gas sensitive material is 2~4:100.

[0016] According to some embodiments of the present application, the mass ratio of the aminomethylphosphoric acid to the gas sensitive material is 1~2:100.

[0017] According to some embodiments of the present application, the organic acid includes at least one of formic acid, acetic acid, propionic acid and butyric acid.

[0018] According to some embodiments of the present application, the alcohol includes at least one of a monohydric alcohol, a dihydric alcohol, and a trihydric alcohol.

[0019] According to some embodiments of the present application, the monohydric alcohol includes at least one of methanol, ethanol, propanol and butanol.

[0020] According to some embodiments of the present application, the diol includes at least one of ethylene glycol and propylene glycol.

[0021] According to some embodiments of the present application, the triol includes at least one of glycerol.

[0022] According to some embodiments of the present application, the propanol includes n-propanol and isopropanol.

[0023] According to some embodiments of the present application, the butanol includes at least one of n-butanol, isobutanol, sec-butanol and tert-butanol.

[0024] According to some embodiments of the present application, the mass ratio of the organic acid to the alcohol is 1:2~4.

[0025] According to some embodiments of the present application, the method for preparing tin dioxide comprises the following steps: The tin salt and the solvent are mixed and then subjected to a solvothermal reaction; The tin salt includes at least one of tin dichloride, tin tetrachloride and dimethyltin dichloride.

[0026] According to some embodiments of the present application, the solvent includes methanol and dimethylformamide.

[0027] According to some embodiments of the present application, the solvent thermal temperature is 170°C to 200°C.

[0028] According to some embodiments of the present application, the solvent thermal time is 12h~24h.

[0029] According to some embodiments of the present application, the noble metal salt includes dichlorotetraamminepalladium.

[0030] According to some embodiments of the present application, the molar ratio of the tin dioxide to the noble metal atoms in the noble metal salt is 100:2-5.

[0031] According to some embodiments of the present application, the mixing method is ball milling.

[0032] According to some embodiments of the present application, the rotation speed of the ball mill is 100r / min~200r / min.

[0033] According to some embodiments of the present application, the ball milling time is 10 h to 20 h.

[0034] According to some embodiments of the present application, the delivery pressure of the mixed liquid during the micro-coating process is 0.2MPa~0.4MPa.

[0035] According to some embodiments of the present application, the micro-coating is performed on a thick film micro-coating device.

[0036] According to some embodiments of the present application, the thick film micro-coating device is provided with a micro-coating nozzle.

[0037] According to some embodiments of the present application, the micro-overburden nozzle is a zirconium oxide micro-overburden nozzle.

[0038] According to some embodiments of the present application, the driving gas pressure of the thick film micro-coating device is 0.4MPa~0.6MPa.

[0039] According to some embodiments of the present application, the delivery pressure of the thick film micro-coating equipment is 0.2MPa~0.4MPa.

[0040] According to some embodiments of the present application, the micro-coating gas pressure of the thick film micro-coating equipment is 0.1 MPa~0.3 MPa.

[0041] According to some embodiments of the present application, the micro-coating area of ​​the thick film micro-coating process is 0.8 mm 2 ~1.2mm 2 .

[0042] According to some embodiments of the present application, the micro-coating space of the thick film micro-coating device is 2 mm to 4 mm.

[0043] According to some embodiments of the present application, the curing temperature is 400°C to 600°C.

[0044] According to some embodiments of the present application, the curing time is 1 min to 30 min.

[0045] According to some embodiments of the present application, the chip electrode includes a substrate and a circuit.

[0046] According to some embodiments of the present application, the substrate includes an aluminum oxide substrate.

[0047] According to some embodiments of the present application, the circuit includes a metal circuit.

[0048] According to some embodiments of the present application, the metal circuit includes at least one of a gold circuit, a silver circuit, and a platinum circuit.

[0049] According to some embodiments of the present application, the thickness of the circuit is 1 μm to 10 μm. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the embodiments of the present drawings or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present drawings. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0051] Figure 1 This is a schematic diagram of the chip structure in this application.

[0052] Figure 2 for Figure 1 Schematic diagram of part of the area after the middle circle area is enlarged.

[0053] The purpose, features and advantages of this figure will be further described in conjunction with the embodiments with reference to the accompanying drawings. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application is described and illustrated below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application. Based on the embodiments provided in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present application.

[0055] Obviously, the following descriptions are only some examples or embodiments of the present application. For ordinary technicians in this field, the present application can also be applied to other similar scenarios without creative work. In addition, it can also be understood that although the efforts made in this development process may be complicated and lengthy, for ordinary technicians in the field related to the content disclosed in this application, some changes in design, manufacturing or production based on the technical content disclosed in this application are just conventional technical means, and should not be understood as insufficient content disclosed in this application.

[0056] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended or closed-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0057] If not specifically stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist); The method for preparing tin dioxide in the embodiment of the present application comprises the following steps: Dimethyltin dichloride, water, methanol (the volume ratio of methanol to water is 1:1; the mass volume ratio of dimethyltin dichloride to methanol is 1 g:20 mL) and dimethylformamide (the volume ratio of methanol to dimethylformamide is 10:1) are mixed to prepare a mixed solution; The mixed solution was added into a high-pressure reactor and subjected to solvent heating at 180°C for 16 h. After the reaction was completed, the solid and liquid were separated, and the solid phase was collected, dried at 60°C for 2 h, and then dried at 120°C for 2 h.

[0058] The schematic diagram of the structure of the chip in the embodiment of the present application is shown in FIG. Figure 1~Figure 2 The details are as follows: like Figure 1 As shown in , a number of chip units are distributed on the substrate.

[0059] like Figure 2 As shown in , a round hole is provided on the chip unit; the round hole needs to be filled with gold paste for connecting the circuits on both sides.

[0060] Example 1 This embodiment is a chip thick film micro-coating method, which consists of the following steps: S1, mixing the gas sensitive material and the organic solvent (ethanol) and then ball milling for the first time; The mass volume ratio of the gas sensitive material and the organic solvent during the first ball milling process was 1 g:50 mL; The ball milling speed was 150 r / min, and the ball milling time was 5 h; After the first ball milling is completed, the adhesive is added and the ball milling is repeated; During the second ball milling process, the mass ratio of the gas sensitive material to the adhesive was 1:20; The ball milling speed is 150r / min, the ball milling time is 10h, and a mixed solution is obtained after the ball milling is completed; The gas sensitive material is composed of tin dioxide and noble metal salt (tetraamminedichloropalladium); The adhesive is composed of an organic acid (acetic acid) and an alcohol (1,2-propylene glycol), and the mass ratio of the organic acid to the alcohol is 1:3; The molar ratio of tin dioxide in the gas sensitive material to the noble metal atom (platinum atom) in the noble metal salt is 100:3; S2, applying the mixed solution to the chip electrode surface and then solidifying; Micro-coating is carried out on thick film micro-coating equipment; The micro-coating thickness of the mixed liquid is 10μm; the micro-coating area of ​​the mixed liquid is 1mm 2 ; The driving pressure of the mixed liquid is 0.5MPa, the delivery pressure is 0.3MPa, and the micro-covering pressure is 0.2MPa; The chip electrodes include a substrate (alumina ceramic sheet) and a gold electrode (5 μm thick); The curing temperature is 500°C and the curing time is 5 minutes.

[0061] Example 2 This embodiment is a chip thick film micro-coating method, which consists of the following steps: S1, mixing the gas sensitive material and the organic solvent (ethanol) and then ball milling for the first time; The mass volume ratio of the gas sensitive material and the organic solvent during the first ball milling process was 1 g:50 mL; The ball milling speed was 150 r / min, and the ball milling time was 5 h; After the first ball milling is completed, the binder and modifier are added and ball milled again; During the second ball milling process, the mass ratio of the gas sensitive material to the adhesive was 1:20; The ball milling speed is 150r / min, the ball milling time is 10h, and a mixed solution is obtained after the ball milling is completed; The gas sensitive material is composed of tin dioxide and noble metal salt (tetraamminedichloropalladium); The adhesive is composed of an organic acid (acetic acid) and an alcohol (1,2-propylene glycol), and the mass ratio of the organic acid to the alcohol is 1:3; The molar ratio of tin dioxide in the gas sensitive material to the noble metal atom (platinum atom) in the noble metal salt is 100:3; The modifier is cysteine, and the mass ratio of cysteine ​​to the gas sensitive material is 3:100; S2, applying the mixed solution to the chip electrode surface and then solidifying; Micro-coating is carried out on thick film micro-coating equipment; The micro-coating thickness of the mixed liquid is 10μm; the micro-coating area of ​​the mixed liquid is 1mm 2 ; The driving pressure of the mixed liquid is 0.5MPa, the delivery pressure is 0.3MPa, and the micro-covering pressure is 0.2MPa; The chip electrodes include a substrate (alumina ceramic sheet) and a gold electrode (5 μm thick); The curing temperature is 500°C and the curing time is 5 minutes.

[0062] Example 3 This embodiment is a chip thick film micro-coating method, which is different from the embodiment 2 in that: In this embodiment, the modifier is aminomethylphosphoric acid; The mass ratio of aminomethylphosphoric acid to the gas sensitive material is 1.8:100.

[0063] Example 4 This embodiment is a chip thick film micro-coating method, which is different from the embodiment 2 in that: In this embodiment, the modifier is composed of cysteine ​​and aminomethylphosphonic acid; The mass ratio of cysteine ​​to gas sensitive material is 2:100; The mass ratio of aminomethylphosphoric acid to the gas sensitive material is 2:100.

[0064] Example 5 This embodiment is a chip thick film micro-coating method, which is different from the embodiment 2 in that: In this embodiment, the modifier is composed of cysteine ​​and aminomethylphosphonic acid; The mass ratio of cysteine ​​to gas sensitive material is 4:100; The mass ratio of aminomethylphosphoric acid to the gas sensitive material is 1:100.

[0065] Example 6 This embodiment is a chip thick film micro-coating method, which is different from the embodiment 2 in that: In this embodiment, the modifier is composed of cysteine ​​and aminomethylphosphonic acid; The mass ratio of cysteine ​​to gas sensitive material is 3.5:100; The mass ratio of aminomethylphosphoric acid to the gas sensitive material is 1.2:100.

[0066] Comparative Example 1 This comparative example is a chip thick film micro-coating method, which differs from Example 1 in that: In this comparative example, the adhesive is acetic acid.

[0067] Comparative Example 2 This comparative example is a chip thick film micro-coating method, which differs from Example 1 in that: The adhesive in this comparative example is 1,2-propylene glycol.

[0068] Gas Sensitive Performance Test Method The gas sensor dynamic test system used in this application mainly includes a gas distribution system, a sensor heating part, a temperature and humidity control part, and a data acquisition part. The gas distribution part refers to the gas from the gas cylinder through the pressure reducing valve and the gas mass flow controller (MFCs) to the mixing chamber, the test chamber, and the temperature and humidity chamber. Different gases can be controlled by MFCs to control the ratio of gas flow (the total gas flow is set to 100mL / min) to obtain methane gas, interference gas, and mixed gas of different concentrations.

[0069] The response value of the sensor is defined as R a / R g, where R a and R g represents the resistance of the sensor in air environment and the resistance of the sensor in test gas environment (the volume fraction of CO is 5×10 -4 , the volume fraction of CH4 is 5×10 -4 ) in the figure; the test results are shown in Table 1.

[0070] Table 1 .

[0071] In Example 1, the gas sensitive material will not fall off the chip under a thrust of 1 kg, that is, the combination of the gas sensitive material and the chip electrode is stable and has excellent stability.

[0072] In comparative example 1 of the present application, a single organic acid is selected as the adhesive; in comparative example 2, a single organic alcohol is selected as the adhesive; from the data in Table 1, it can be seen that when a single organic acid or alcohol is used as an adhesive, the response value of the chip actually obtained is small and the performance is relatively poor; that is, the present application further improves the performance of the gas sensor chip by selecting a compound adhesive.

[0073] The thick film micro-coating method in the present application solves the problem of precisely coating gas-sensitive materials on gas sensor chips; the present application optimizes the formula of the adhesive, and all the raw materials used are organic acids and alcohols. After high-temperature sintering, they are basically converted into water and a small amount of carbon dioxide, which are almost pollution-free to the environment; at the same time, the fluidity and stability are in the best state; the present application adopts thick film micro-coating technology, and the minimum micro-coating amount can be accurately controlled at 10pL, and the thickness can be accurately controlled at 5μm~200μm; no splashing occurs during micro-coating, and the edge of the thick film is neat and perfect; because the gas-sensitive material is extremely susceptible to contamination by metal objects, the micro-coating nozzle needs to use zirconia ceramic material with a pore size less than 0.08 mm.

[0074] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A chip thick film micro-coating method, characterized in that: The following steps are involved: S1. Mixing a gas sensitive material, an organic solvent and an adhesive to obtain a mixed liquid; S2, applying the mixed solution to the chip electrode surface and then solidifying; The gas sensitive material includes tin dioxide and a noble metal salt; The adhesive includes at least one of an organic acid and an alcohol; The thickness of the micro-coating is 8 μm to 12 μm; The micro-covering pressure is 0.1MPa~0.5MPa; The noble metal salt is dichlorotetraamminepalladium; The organic acid is at least one of formic acid, acetic acid, propionic acid and butyric acid; The alcohol is at least one of a monohydric alcohol, a dihydric alcohol and a trihydric alcohol; The monohydric alcohol is at least one of methanol, ethanol, propanol and butanol; The diol is at least one of ethylene glycol and propylene glycol; The triol is glycerol.

2. The chip thick film micro-coating method according to claim 1, characterized in that: At least one of an amino acid and an organic phosphonic acid is also added to the mixed solution; The amino acids include cysteine; The organophosphoric acid includes aminomethylphosphonic acid; The mass ratio of cysteine ​​to the gas sensitive material is 2-4:100; The mass ratio of the aminomethylphosphoric acid to the gas sensitive material is 1-2:

100.

3. The chip thick film micro-coating method according to claim 1, characterized in that: The mass ratio of the organic acid to the alcohol is 1:2-4.

4. The chip thick film micro-coating method according to claim 1, characterized in that: The preparation method of tin dioxide comprises the following steps: The tin salt and the solvent are mixed and then subjected to solvothermal reaction; The tin salt includes at least one of tin dichloride, tin tetrachloride and dimethyltin dichloride; The solvent includes methanol and dimethylformamide; The solvent heat temperature is 170°C to 200°C; The solvent thermal time is 12h~24h.

5. The chip thick film micro-coating method according to claim 1, characterized in that: The molar ratio of the tin dioxide to the noble metal atoms in the noble metal salt is 100:2-5.

6. The chip thick film micro-coating method according to claim 1, characterized in that: The mixing method is ball milling; The rotation speed of the ball mill is 100r / min~200r / min; The ball milling time is 10h~20h.

7. The chip thick film micro-coating method according to claim 1, characterized in that: The conveying pressure of the mixed liquid during the micro-coating process is 0.2MPa~0.4MPa.

8. The chip thick film micro-coating method according to claim 1, characterized in that: The curing temperature is 400°C to 600°C.

9. The chip thick film micro-coating method according to any one of claims 1 to 8, characterized in that: The chip electrode includes a substrate and a circuit; The substrate comprises an aluminum oxide substrate; The circuit includes a metal circuit; The metal circuit includes at least one of a gold circuit, a silver circuit and a platinum circuit.

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