TWI874807B - Manufacturing method of liquid leakage sensor - Google Patents

Abstract

The present invention relates to a liquid leakage sensor and a manufacturing method thereof, and more specifically, to a liquid leakage sensor and a manufacturing method thereof which can be manufactured by continuously arranging a non-conductive layer and a conductive layer and then compressing them by a compressor, and thus is inexpensive and easy to manufacture. To this end, the present invention includes: a substrate formed into a flat plate shape by a non-conductive and chemically resistant material; a conductive mold product formed into a pattern for detecting liquid leakage by a conductive and chemically resistant material, and arranged on the top surface of the substrate, and in a state where the conductive mold product is arranged on the substrate, a compressor is used to apply pressure and heat to the top and bottom surfaces of the substrate to sinter the substrate and the conductive mold product.

Description

Manufacturing method of liquid leakage sensor

The present invention relates to a liquid leakage sensor and a manufacturing method thereof, and more specifically, to a liquid leakage sensor and a manufacturing method thereof which can be manufactured by continuously arranging a non-conductive layer and a conductive layer and then compressing them by a press, and thus is low-cost and easy to manufacture.

Korean Patent No. 10-2084721 (capacitive leakage sensor) granted to the present applicant has a structure for detecting various types of leaks of water, conductive and non-conductive chemical solutions, oils, and organic solvents. The structure has a "structure including a base film made of a material having excellent chemical resistance and chemical resistance and a pair of conductive wires formed at intervals on the top surface of the base film, the pair of conductive wires being configured to form a capacitor based on the area and interval of the conductive wires, wherein each conductive wire includes three metal layers, the first layer of the lowest layer is formed using copper by etching, the second layer formed on the first layer has a nickel-copper layer formed therein by electroplating, and the third layer is formed on the second layer using a gold plating method."

Therefore, when a leaked liquid is introduced into an adjacent conductive line, water, a conductive or non-conductive chemical solution, oil, or an organic solvent can be determined based on the change in capacitance value.

Capacitive leak sensors are also used in detection devices that detect liquid leakage based on the conductivity or resistance value of the leaking liquid rather than the change in capacitance value.

However, according to such prior art, since the conductive wire is made by forming a conductive metal material such as copper, nickel copper or gold on the top surface of the base using a plating method, the capacitive leakage sensor has very excellent conductivity. However, the capacitive leakage sensor has a problem in that the number of times of repeated use is limited, because if the capacitive leakage sensor is in contact with a chemical solution such as an alkaline solution or an acid solution, it is easily corroded and peeled off, and errors in detection signals often occur due to corrosion, and has the disadvantages of being very cumbersome and expensive in the manufacturing process.

If a conductive wire is formed using a carbon material according to a method such as printing, the conductive wire is less susceptible to chemical solutions than a metal material. In this case, there is a problem that if a protective film is stacked on a base film, the protective film for protecting the conductive wire is easily peeled off due to the step between the base film and the conductive wire.

<Previous technical literature>

1. Korean Patent No. 10-2084721

(Capacitive Leakage Sensor)

An embodiment of the present invention provides a liquid leakage sensor, which is manufactured by: molding a cylindrical compressed product, which is formed by alternately stacking a non-conductive mold product and a conductive mold product on a cylindrical mold and then compressing the mold product using a compressor, then sintering the compressed product, and then scraping the sintered product along the side of the sintered product to a given thickness; and a manufacturing method thereof.

In addition, the purpose of the present invention is to provide a liquid leakage sensor, which is manufactured by stacking a conductive material with a pattern on a non-conductive flat material, then applying heat and compressing it with a compressor to form a flat liquid leakage sensor.

To achieve the above-mentioned purpose, an embodiment of the present invention provides a liquid leakage sensor.

Its characteristic is that a conductive layer made of conductive material, a non-conductive layer made of non-conductive material, and a conductive layer are stacked in sequence, and then compressed to form a compressed product, and the side of the compressed product is scraped to a given thickness.

In addition, in one embodiment, a method for manufacturing a liquid leak sensor includes: a first step: using a non-conductive powder to form a non-conductive mold product having a flat top surface and a bottom surface; a second step: using a conductive raw material to form a conductive mold product having a flat top surface and a bottom surface; a third step: stacking the non-conductive mold product and the conductive mold product alternately up and down on a die; a fourth step: forming a single compressed product by applying pressure up and down to the stacked non-conductive mold product and the conductive mold product using a compressor; a fifth step: sintering the compressed mold product; and a sixth step: performing a scraping process on the side surface of the sintered compressed product to a given thickness.

The non-conductive layer or conductive powder is made of polytetrafluoroethylene (PTFE). The conductive layer or conductive raw material is made of a raw material mixed with PTFE and carbon nanotubes (CNT).

The liquid leak sensor and the manufacturing method thereof according to the embodiment of the present invention have the advantage that the liquid leak sensor can be manufactured cheaply and very easily because the non-conductive molded product made of PTFE and the conductive molded product made of PTFE and CNT are alternately stacked on a stamping die having a cylindrical shape, the non-conductive molded product and the conductive molded product are compressed by a compressor to form a single cylindrical compressed product, and the compressed product is sintered and scraped along the side of the molded product to a given thickness.

In addition, it has the advantage that since the non-conductive wire and the conductive wire are sintered, they do not peel off as in the previous technology, and the drug resistance and chemical resistance are very excellent.

100: Stamping die

110:Lower compressor

120: Upper compressor

210, 230, 250: Non-conductive mold products

220, 240: Conductive mold products

300:Liquid leak sensor

310, 330, 350: non-conductive layer

320, 340: Conductive layer

400: Scraper

500: Base

600: Conductive mold products

610, 620: Conductive wire

611, 621: detection line

612, 622: Connection line

710:Lower compressor

720: Upper compressor

L: Leaking solution

Figures 1 to 3 are diagrams for describing the steps of manufacturing a liquid leakage sensor according to an embodiment of the present invention.

FIG4 is a diagram showing the structure of a liquid leakage sensor according to an embodiment of the present invention.

FIG5 is a diagram showing a cross-section of a liquid leakage sensor according to an embodiment of the present invention.

FIG6 is a diagram showing another form of a liquid leakage sensor.

FIG7 is a flow chart showing a method for manufacturing a liquid leak sensor.

FIG8 is a diagram showing the structure of a liquid leakage sensor according to another embodiment of the present invention.

FIG9 is a diagram showing a structure in which a conductive mold product is compressed and sintered to a substrate by a compressor.

The aforementioned purposes, features and advantages are described in detail with reference to the attached drawings, so that ordinary technicians in the field to which the present invention belongs can easily implement the technical spirit of the present invention.

When describing the contents of the present invention, if it is considered that a detailed description of the prior art related to the contents of the present invention unnecessarily obscures the main idea of the present invention, the detailed description will be omitted.

By considering the functions in the present invention, the general terms widely used now are selected as the terms used in the present invention, and these terms may be different according to the intentions of technicians in this field, precedents, or the emergence of new technologies.

In addition, in certain cases, the applicant randomly selects some terms. In this case, the meaning of the corresponding terms will be described in detail in the description part of the corresponding invention.

Therefore, the terms used in the present invention should not be simply defined based on their names, but should be defined based on their substantial meanings and contents based on the present invention.

Hereinafter, an embodiment of the present invention is described in detail with reference to the accompanying drawings.

However, the embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the following embodiments.

The embodiments of the present invention are provided to persons of ordinary skill in the art to more fully describe the present invention.

Figures 1 to 3 are diagrams for describing the steps of manufacturing a liquid leak sensor according to an embodiment of the present invention. Figure 4 is a diagram showing the structure of a liquid leak sensor according to an embodiment of the present invention. Figure 5 is a diagram showing a cross-section of a liquid leak sensor according to an embodiment of the present invention. Figure 6 is a diagram showing another form of a liquid leak sensor. Figure 7 is a flow chart showing a method of manufacturing a liquid leak sensor.

In order to manufacture a liquid leakage sensor according to an embodiment of the present invention, first, as shown in FIG1 , a cylindrical non-conductive mold product having flat top and bottom surfaces is manufactured using non-conductive powder. The non-conductive powder may include polytetrafluoroethylene (PTFE) powder having drug resistance and chemical resistance.

In addition to PTFE, various materials in powder form such as fluorinated ethylene propylene copolymer (FEP), perfluoroalkoxy (PFA), and ethylene tetrafluoroethylene (ETFE) can also be used as non-conductive powders.

In the embodiment of the present invention, an example of using PTFE powder has been described, but the present invention is not limited to this.

A conductive molded product stacked on a non-conductive molded product is molded using PTFE powder and carbon nanotubes (CNT). After inputting and stirring 10-30 wt% of PTFE powder, 1-10 wt% of multi-walled carbon nanotubes (MWCNT), 59.9-88.1 wt% of an organic solvent, and 0.1-0.9 wt% of a metal coupling agent, the organic solvent is removed, and the remaining mixture is dried at a low temperature and formed into a cylindrical shape with flat top and bottom surfaces, similar to the non-conductive molded product.

CNT is made of carbon and has a tube form with a diameter of nanometer size. CNT has the characteristics of high thermal/electrical conductivity, high strength and chemical stability. In addition to CNT, materials such as graphene can also be used.

PTFE has high electrical conductivity, which is a characteristic of CNTs, and at the same time, the unique properties are maintained through the coupling of PTFE and CNTs.

As shown in FIG. 2 , non-conductive mold products and conductive mold products are alternately stacked in a stamping die 100 having a cylindrical shape. A first non-conductive mold product 210 is located on a lower compressor 110 inserted into a lower side of the stamping die 100. A first conductive mold product 220 is stacked on the first non-conductive mold product 210. A second non-conductive mold product 230 is stacked on the first conductive mold product 220.

In addition, the second conductive mold product 240 is stacked on the second non-conductive mold product 230. The third non-conductive mold product 250 is stacked on the second conductive mold product 240.

In addition, the conductive mold products and the non-conductive mold products may be alternately stacked on the third non-conductive mold product 250. In this case, the number of conductive lines formed by the conductive mold products may be increased as needed.

When the non-conductive mold product and the conductive mold product are stacked as described above, a single cylindrical compressed product is formed by compressing the lower compressor 110 and the upper compressor 120.

The compressed product has a state in which the non-conductive mold product and the conductive mold product have not been firmly bonded. Therefore, the non-conductive mold product and the conductive mold product are bonded by sintering. Since the non-conductive mold product is formed using PTFE and the conductive mold product also contains PTFE, the non-conductive mold product and the conductive mold product are easily sintered and bonded by the same material.

As a result, bonding by sintering is easily performed only when the non-conductive molded product and the conductive molded product are formed using the same material.

The steps of pre-molding the non-conductive molded product into a cylindrical shape and inputting the molded non-conductive molded product into the die 100 have been described. However, as another form, PTFE powder may be directly stacked.

That is, after stacking the PTFE powder at the same height instead of the first conductive mold product 220, the top surface of the PTFE powder is flattened. The second conductive mold product 240 is stacked on the PTFE powder. After that, the PTFE powder is stacked on the second conductive mold product 240 and flattened.

By repeating such steps, non-conductive powder can be stacked instead of non-conductive molded products.

Thereafter, after a cylindrical compressed product is formed by applying pressure using the lower compressor 110 and the upper compressor 120 and then sintered, the non-conductive powder and the conductive mold product are combined together.

In the cylindrical compressed product formed as described above, as shown in FIG. 3, the first non-conductive layer 310 is formed from the lowermost side by the first non-conductive mold product 210. The first conductive layer 320 is bonded and stacked by the first conductive mold product 220. The second non-conductive layer 330 is formed by the second non-conductive mold product. The second conductive layer 340 is bonded and stacked by the second conductive mold product 240. The third non-conductive layer 350 is formed by the third non-conductive mold product 250.

If a scraper 400 is used to scrape the cylindrical compressed product from the outer circumferential surface to a given thickness, a liquid leakage sensor 300 having a long strip shape is formed as shown in FIG. 4 .

That is, the sides of the first non-conductive layer 310, the first conductive layer 320, the second non-conductive layer 330, the second conductive layer 340, and the third non-conductive layer 350 are sintered and bonded laterally. The second non-conductive layer 330 acts as an insulator between the first and second conductive layers 320 and 340. The first non-conductive layer 310 and the third non-conductive layer 350 located at the outermost side protect the sides of the first and second conductive layers 320 and 340 so that the sides are not exposed to the outside.

Therefore, as shown in FIG. 5 , the first conductive layer 320 and the second conductive layer 340 are positioned in parallel while maintaining a spacing therebetween by the second non-conductive layer 330, thereby serving as electrodes. Therefore, when the leaking solution L is located on the top surface of the first conductive layer 320 and the second conductive layer 340, the leakage state of the solution L can be detected using a capacitance method, a resistance method, or a conductivity method.

Since the bottom surface and the top surface of the liquid leak sensor 300 have a flat state by the scraping process, the adhesive member to be attached to the bottom of the liquid leak sensor 300 can be attached to the bottom surface without being lifted. In addition, the protective film can be closely attached to the top surface.

That is, as in the prior art, if a conductive line is formed on the top surface of the base film, the protective film is easily lifted and peeled off due to the step between the base film and the conductive line. However, in the embodiment of the present invention, since the non-conductive layers 310, 330, and 350 and the conductive layers 320 and 340 are formed flat at the same height, the protective film can be attached very stably.

The non-conductive layers 310, 330, and 350 and the conductive layers 320 and 340 contain PTFE, so their surfaces have very smooth lubricity. Therefore, when the leakage solution L is introduced to the top surface, the leakage solution slides easily. This may make it difficult for the leakage solution to be positioned between the conductive layers 320 and 340.

To solve such a problem, as shown in (a) of FIG. 5 , lines 321 and 341 made of PTFE material are backstitched in the length direction of the conductive layers 320 and 340. Therefore, the tops of the backstitched lines 321 and 341 are located higher than the surfaces of the conductive layers 320 and 340. Therefore, the leaked solution L is positioned between the backstitched lines 321 and 341. As a result, since the leaked solution L flows down, the conductive layers 320 and 340 can detect the leaked solution L very easily.

The reverse stitching of the lines 321 and 341 may be performed in the length direction of the conductive layers 320 and 340. As shown in FIG5(b), the lines 321 and 341 may be formed at the outer edge portions of the conductive layers 320 and 340, that is, in the length direction between the first conductive layer 320 and the first non-conductive layer 310 and between the second conductive layer 340 and the third non-conductive layer 350.

Lines 321 and 341 have been described as being made of PTFE material, but various materials other than PTFE may be used, such as fluorinated ethylene propylene copolymer (FEP), perfluoroalkoxy (PFA), or ethylene tetrafluoroethylene (ETFE) having drug resistance and chemical resistance.

FIG. 6 is a diagram showing another form of the liquid leakage sensor 300. The liquid leakage sensor 300 may have a structure in which conductive layers 320 and 340 are positioned in parallel on both sides of the second non-conductive layer 330.

In this case, since the second non-conductive layer 330 is located between the two conductive layers 320 and 340 functioning as electrodes, the two conductive layers 320 and 340 can maintain a given interval and can be insulated. In addition, the liquid leakage sensor 300 does not have five layers as shown in FIG. 5, but may have only three layers, i.e., two conductive layers 320 and 340 and the second non-conductive layer 330. Therefore, the manufacturing cost can be greatly reduced.

In addition, the conductive layers 320 and 340 may be reverse-stitched in their length direction by lines 321 and 341.

FIG8 is a diagram showing the structure of a liquid leakage sensor according to another embodiment of the present invention.

In the first embodiment of the present invention, a liquid leakage sensor with a longer length is exemplified, while another embodiment of the present invention shows an area-type liquid leakage sensor structure for detecting large-area liquid leakage.

To this end, a conductive mold product 600 having a liquid leakage detection pattern is arranged on the top surface of a substrate 500 having a large area, and is compressed by a large pressure to thereby achieve integration.

The substrate 500 has a thickness of 2-3 mm, a transverse length of 30-70 cm, and a longitudinal length of 30-70 cm. It has a flat plate shape, and the thickness, transverse length, and longitudinal length can be arbitrarily reduced or increased.

The substrate 500 may be made of various materials such as PTFE, fluorinated ethylene propylene copolymer (FEP), perfluoroalkoxy (PFA), and ethylene tetrafluoroethylene (ETFE) that are resistant to drugs or chemicals.

Similar to or similar to one embodiment of the present invention, a conductive mold product 600 stacked and attached to the top surface of the substrate 500 is formed using PTFE powder and carbon nanotubes (CNT), 10-30 wt% of PTFE powder, 1-10 wt% of multi-walled carbon nanotubes (MWCNT), 59.9-88.1 wt% of organic solvent, and 0.1-0.9 wt% of metal coupling agent are added and stirred, and placed in a die for molding, thereby molding the first conductive wire 610 and the second conductive wire 620.

The first conductive line 610 is a plurality of detection lines 611 arranged in parallel with intervals, and one side of the plurality of detection lines is formed into a pattern connected by a connection line 612. Similarly, the second conductive line 620 also maintains intervals and arranges a plurality of detection lines 621 in parallel, and one side thereof is formed into a pattern having a structure connected to each other by a connection line 622.

The first conductive wire 610 and the second conductive wire 620 formed as described above are placed on the top surface of the substrate 500, so that the multiple detection lines 611 and 621 are kept at a given interval and alternate with each other.

When molding the conductive mold product 600, as another method, not only injection molding but also sheet molding, flat mold molding, etc. can be used to mold it into a large area, and then the first conductive wire 610 and the second conductive wire 620 can be formed by cutting with a punching mold, laser processing, cutting rolls, etc.

Furthermore, in addition to CNT, materials such as graphene can also be used, and the conductive mold product 600 can be manufactured by a mixture of PTFE+CNT+graphene.

As described above, in a state where the first conductive wire 610 and the second conductive wire 620 are placed in parallel on the top surface of the substrate 500, the substrate 500 is placed on the top surface of the lower compressor 710 as shown in FIG. 9, and then the upper compressor 720 compresses the substrate 500 and the first conductive wire 610 and the second conductive wire 620.

Of course, the substrate 500 may be first placed on the top surface of the lower compressor 710, and then the first conductive wire 610 and the second conductive wire 620 may be placed on the top surface of the substrate 500, and then compressed by the upper compressor 720, with the applied compression force being about 200-250 ^cm3 /Kgf.

In addition, the conductive mold product 600 is firmly attached to the substrate 500 by heating during compression by the compressors 710 and 720, and the sintering temperature is firstly slowly heated from room temperature to 200°C for 3 hours; then kept at 200°C for 1 hour; then slowly heated from 200°C to 300°C for 3 hours; then kept at 300°C for 1 hour; then slowly heated from 300°C to 365°C for 2 hours; and then kept at 365°C for 5 hours while sintering.

Therefore, the PTFE constituting the base 500 and the PTFE contained in the conductive mold product 600 are sintered to each other and firmly attached.

After sintering is completed, the temperature is slowly lowered from 365°C to 200°C for 6 hours, and then slowly lowered from 200°C to room temperature for 5 hours, so that a firm sintering state can be maintained.

By sintering the substrate 500 and the conductive mold product 600 with each other and firmly integrating them by such a large pressure and heat, it is not only possible to prevent the conductive mold product 600 from being easily peeled off from the substrate 500 due to the chemical solution, but also because there is almost no step between the conductive mold product 600 and the top surface of the substrate 500, the protective film stacked on the upper side can be attached very stably.

Specific parts of the content of the present invention have been described above. For ordinary technicians in this field, such detailed descriptions are only preferred embodiments, and it is obvious that the scope of the present invention is not limited by these detailed descriptions.

Therefore, it can be said that the substantial scope of the present invention is defined by the attached patent application scope and its equivalents.

500: Base

600: Conductive mold products

710:Lower compressor

720: Upper compressor

Claims (1)

A method for manufacturing a liquid leakage sensor, characterized in that it includes: a step of forming a substrate of a non-conductive material and a chemically resistant flat plate; a step of forming a conductive mold product having a liquid leakage detection pattern from a conductive material; after arranging the conductive mold product on the top surface of the substrate, a step of applying pressure and heat by a compressor to sinter the substrate and the conductive mold product to integrate them, wherein the pressure applied by the compressor is 200-250 ^cm3 /Kgf, and the sintering temperature and time are: (a) slowly heated from room temperature to 200°C for 3 hours; (b) slowly heated from 200°C to 300°C for 3 hours; (c) kept at 300°C for 1 hour; (d) slowly heated from 300°C to 365°C for 2 hours; and (e) kept at 365°C for 5 hours.