UHF radio frequency tag with a highly sealed protective housing

Description

[0001] The utility model relates to the field of radio frequency identification, namely to radio frequency tags operating in the UHF range and designed to operate in a hole in a metal object at a depth of the order of the thickness of the tag itself under the simultaneous influence of high pressure, temperature and an aggressive chemical environment.

[0002] Various designs of UHF radio frequency tags for identifying objects, including metal, are known in the art. However, most known solutions only ensure stable tag operation when placed on the surface of metal objects. The need to mark various objects, including drill pipes and tubing, with radio frequency tags requires placing the tags inside a small metal hole, which may be located in the wall of the metal object. Therefore, ensuring tag functionality when placed inside a metal hole, especially under conditions of simultaneous exposure to high temperatures, pressures, and aggressive chemicals, remains a pressing issue.

[0003] The tag's protective casing must be hermetically sealed when exposed to high pressure, temperatures, and aggressive chemical environments simultaneously. Otherwise, the chemically aggressive environment may penetrate down to the tag's electronic components (antenna and microcircuit) and lead to deterioration of its radiation characteristics, which means a decrease in the reading range and a shift in the tag's operating frequency.

[0004] A RFID tag resistant to corrosion, high temperatures, and high pressure is known, according to patent document No. CN 20408725 1U [1]. In the design description, the antenna and RFID chip are located in a ceramic "core," which is placed in a special groove in the housing. The remaining space inside the housing is filled with a sealant, and the housing itself is then closed with a lid. However, the tag itself does not provide the necessary protection from an aggressive chemical environment, allowing it to penetrate under high pressure into the groove between the housing and the lid due to a leaky seal between the lid and the main body.Further, similar to the previous patent, the aggressive chemical environment, due to the different coefficients of thermal expansion of the housing and sealant materials, penetrates the space between the groove and the thin layer of sealant surrounding the core containing the electronic component. This environment then fills the space near the electronic component, affecting the near-field electrical properties of the antenna. The utility model solves this problem by using a completely sealed housing.

[0005] A known solution under patent No. US 8690066 B2 [2] provides for the operation of an RFID tag at elevated temperatures, pressures, and in chemically aggressive environments. Furthermore, the tag housing is primarily designed to protect against mechanical impacts. In this design, the tag antenna and microchip are contained in a capsule, which is positioned in a side opening of the housing and then filled with a sealant. This sealant does not prevent chemicals from penetrating the housing through the sealant-housing interface under high pressure due to the different temperature expansion coefficients of the sealant and housing. At high temperatures, this leads to the formation of micropores through which an aggressive chemical environment can penetrate under high pressure, which can ultimately lead to a significant deterioration in radiation characteristics.

[0006] Also known is a RFID tag design, according to patent No. RF222297 U1 [3], where the components of the protective housing are joined using an adhesive. The use of an adhesive does not ensure the tag's resistance to chemical exposure at high pressures due to the ability of aggressive chemicals to penetrate the housing through the adhesive-housing interface, all the way to the tag's antenna.

[0007] The closest analogue in technical essence is the radio frequency tag described in patent document No. CN 110097166 A [4], the design of which, like that of the utility model, is formed by casting a polymer material. In this case, the electronic component is rigidly fixed to a metal holder, which serves as an additional radiating part of the entire tag and holds this component in the desired position. This technical solution provides only partial resistance to the declared harsh operating conditions typical of oil exploration. However, the known design does not ensure complete chemical resistance and hermetic sealing of the housing under exposure to high pressure (up to 80 MPa), sinceAt high temperatures, the different thermal expansion coefficients of the metal housing, metal holder, and casting material form micropores and channels at the interfaces between these materials. These channels allow the aggressive chemical environment, under high pressure, to penetrate the tag's housing, reaching the electronic component, negatively impacting its emission characteristics. Therefore, the prototype is not suitable for long-term operation in environments containing aggressive chemical compounds, whereas the utility model ensures complete hermetic sealing and chemical resistance of the tag.

[0008] The utility model proposes a design for a cased radio tag, the functionality of which is maintained during prolonged exposure to an aggressive chemical environment at high temperature and pressure.

[0009] The technical problem addressed by this utility model is the insufficient sealing of existing UHF radio frequency tags used for marking industrial equipment operating under high pressure, temperature, and aggressive chemical environments. Insufficient sealing of existing tag housings leads to the penetration of chemically active substances into the housing, affecting the electronic component (chip and antenna), and, consequently, degrading the device's performance. The objective of this utility model is to ensure stable operation of the tag under the combined effects of extreme temperatures and pressures by precisely fixing the electronic component in a predetermined position during the molding process using a temporary holder that partially or completely dissolves and integrates into the structure of the plastic housing.

[0010] Ensures sufficient tightness and temperature stability of the RFID tag under high pressure, temperature and the presence of an aggressive chemical environment, which leads to stable operation and confident readability of the UHF RFID tag installed in a cavity or hole of a metal object.

[0011] This is achieved due to the fact that the UHF radio frequency tag has a highly hermetic protective housing made by casting from molten high-temperature thermoplastic material with low moisture absorption, which contains a temporary element that fixes the position of the antenna and microcircuit, which is made of the same material as the cast housing, and can partially or completely dissolve and integrate into the structure of the plastic housing.

[0012] This utility model is a UHF radio frequency tag with a highly hermetically sealed housing designed to operate under high temperatures, pressures, and aggressive chemical influences, including when installed in a hole or cavity in a metal object. The housing houses a transceiver electronic component. The tag's design and manufacturing technology ensure complete sealing of the electronic component and stable radio frequency characteristics during long-term operation in extreme environmental conditions. The electronic component is constructed using materials, including solders, adhesives, and plastics, that do not melt at temperatures up to 250°C.

[0013] The RFID tag contains an electronic component, including a microchip and antenna, housed in a sealed housing made of a heat-resistant and chemically resistant material. This housing material is characterized by high chemical resistance, resistance to organic solvents, saline solutions, and petroleum products, and maintains its mechanical strength and shape when exposed to high temperatures (up to 295°C and pressures up to 600 atm).

[0014] The electronic component is located inside the housing in such a way that the optimal spatial position of its antenna relative to the dimensions of the housing walls is maintained, ensuring effective interaction with the electromagnetic field when the tag is placed on or inside a metal surface.

[0015] The essence of the utility model is explained in Fig. 1-6, namely:

[0016] Fig. 1 - shows an isometric image of an electronic component placed inside a “spider”, where 1 is an electronic component, 2 is a “spider”;

[0017] Fig. 2 - shows an orthogonal image of an electronic component placed inside a “spider”;

[0018] Fig. 3 - shows an image of a tag containing an electronic component inside a "spider" positioned correctly inside a space filled with high-temperature plastic with low moisture absorption, where 3 is the formed housing;

[0019] Fig. 4 - shows an orthogonal image of a finished encased radio tag with an electronic component correctly placed in it;

[0020] Fig. 5 - shows an isometric image of a finished encased radio tag with an electronic component correctly placed inside it;

[0021] Fig. 6 - shows an image of a pipe with a hole prepared in it for installing a radio tag, where 4 is the pipe, 5 is the hole for installing the radio tag, 6 is the manufactured radio tag.

[0022] The RFID tag housing is manufactured using a hot-injection molding process from a molten, high-temperature, low-moisture-absorbing thermoplastic material. To precisely hold the electronic component in place during the molding process, a temporary holder—a fixing element, such as a "spider"—is used (Fig. 4).

[0023] The "Spider" is designed to secure the position of an electronic component in a mold during hot polymer injection. Since the position of the electronic component at least affects the tag's operating frequency, maintaining stable tag parameters (within acceptable tolerances) requires securing the electronic component within the molded housing. Measurements conducted using a hardware and software system such as Voyantic Tagformance Pro showed that when the electronic component shifts within the housing, the tag's operating frequency can vary significantly. When reading the tag with a handheld or stationary RFID reader at the standard Russian frequency of 867 MHz, the read range can be significantly lower than required.Moreover, in the absence of a fixing element during high-temperature injection molding, the electronic component may be shifted to the edge of the housing so that the poured material cannot cover its entire surface, leaving some part of the housing open to the penetration of various substances during operation, which also significantly affects the radiating characteristics of the antenna and, accordingly, the reading range of the tag.

[0024] The "spider" design can have various configurations, one of which is a design with multiple support beams securing the electronic component at the corners. However, the utility model is not limited to this option; other clamping arrangements that provide a similar function are also permitted.

[0025] The "spider" is made from the same material as the tag body. This eliminates the dividing lines between dissimilar materials in the final casting. During the casting process, the "spider" partially or completely dissolves and integrates into the structure of the plastic body. To achieve this, the melt temperature and pressure conditions are selected so that the retainer material melts when the polymer melt has completely filled the mold but has not yet cooled.

[0026] The hot melt injection temperature and pressure are selected within a range that simultaneously maintains the positioning accuracy of the electronic component and completely dissolves the retainer, resulting in the formation of a homogeneous, monolithic housing structure after cooling. The operating temperature range depends on the properties of the chemically resistant injection molding material used.

[0027] The selection of technological parameters for the hot injection molding method eliminates premature destruction of the retainer and ensures its gradual dissolution in the polymer melt, as a result of which, after molding, the housing is a monolithic shell that is uniform in structure and composition without internal boundaries and interphase transitions.

[0028] Highly hermetic enclosure integrity is achieved by completely and uniformly filling the space around the electronic component with a homogeneous material—a thermoplastic polymer with low moisture absorption, free of voids and microchannels. Unlike known analogs that used adhesive joints, glass capsules, or combinations of materials (such as a metal-polymer combination), the proposed design eliminates interfacial material boundaries outside the tag's electronic component (antenna and microcircuit), which could potentially allow aggressive chemicals to penetrate the enclosure under pressure.

[0029] The completely monolithic and homogeneous structure of the housing eliminates the formation of micropores, gaps, and channels through which liquid or gaseous reagents could penetrate. Thus, the internal electronic part of the tag is completely isolated from the external environment, ensuring absolute tightness and long-term stability of the device when used in aggressive chemical conditions with high temperatures and pressures.

[0030] Furthermore, the use of injection molding technology allows the production of RFID tag housings not only in cylindrical shapes, but also in shapes of arbitrary configurations, which expands the design possibilities of the device depending on the shape and characteristics of the object being labeled.

[0031] To confirm the operational characteristics and design integrity, a pilot batch of cylindrical radio frequency tags was manufactured and tested. These tags were produced using the described method of high-temperature injection molding of polyphenylene sulfide (PPS), a thermoplastic polymer, at a melt temperature in the range of 330-400°C. As an example, the tests used radio frequency antennas constructed as a short-circuited transmission line using thick-film technology on a ceramic substrate with a deposited silver conductive layer. This antenna design is provided as an example and does not limit the scope of application of the utility model, which permits the use of other antenna types and manufacturing technologies.

[0032] A total of 30 tags were manufactured, each of which was placed in a special autoclave and subjected to cyclic testing, namely, exposure to a high temperature of 150°C and a pressure of 60 MPa in a 5% NaCl saline solution, followed by cooling and a slow pressure release. Each round of testing lasted 72 hours.

[0033] The marks were also kept separately for 2 hours in a special chamber at a temperature of 250°C.

[0034] The read range of each RFID tag was measured before and after testing using a Chainway C72 handheld reader. Analysis of the results showed that the read range changed only slightly after testing and did not exceed the permissible tolerances, indicating that the housing remained completely sealed and the RFID characteristics of the tag were stable.

[0035] Thus, the test results confirm that the design of the RFID tag, manufactured by injection molding high-temperature thermoplastic polymer with low moisture absorption using a soluble fixative of a heat-resistant electronic component, ensures complete tightness and stable operation of the device when exposed to high temperatures, pressures and aggressive chemical environments.

[0036] Sources of information:

[0037] 1. Chinese Patent No. CN 204087251

[0038] 2. US Patent No. US 8690066

[0039] 3. RF Patent No. RU 222297

[0040] 4. Chinese Patent No. CN 110097166 - prototype

Claims

1. A UHF radio frequency tag designed for operation under the influence of high pressures, temperatures and aggressive chemical environments and having a highly hermetic protective housing made by casting from a molten high-temperature thermoplastic material with low moisture absorption, characterized in that there is a temporary element that fixes the position of the antenna and the microcircuit, which is made from the same material as the poured highly hermetic protective housing, which is designed with the ability to dissolve during the casting process and integrate into the structure of the highly hermetic protective housing, wherein the temporary fixing element is made in the form of a "spider" with support beams for fixing the electronic component in the required position.

2. A UHF radio frequency tag according to claim 1, characterized in that the tag body has a cylindrical shape.

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