RU2858815C1 - Coating polymerisation chamber - Google Patents

Abstract

FIELD: coating.

SUBSTANCE: invention relates to a polymerisation chamber. The technical result is achieved by a polymerisation chamber, which includes a housing with an inlet and an outlet opening, ultraviolet LED modules, and an exhaust pipe. The housing is made in the form of a channel. At least three ultraviolet LED modules are placed along the axis of the channel around the circumference. In the irradiation zone, a guide transparent to ultraviolet light is installed, configured to work with UV-transparent pallets. The inlet and outlet openings are equipped with labyrinth light-protective curtains made of UV-resistant elastomer.

EFFECT: reduction of shadow zones and uniform irradiation of the entire surface of the product, prevention of ultraviolet radiation leakage beyond the working area, increase in energy efficiency of the process, protection of service personnel from harmful vapours, as well as simplification of operation and the possibility of direct integration of the device into the production line.

6 cl, 3 dwg

Description

The invention relates to devices for polymerizing protective coatings after application, particularly moisture-resistant (conformal) coatings, onto sensitive elements and electronic components. The device can be used in instrument making and microelectronics, for example in the production of printed circuit boards, sensors, and medical devices, to improve their reliability and durability in high-humidity conditions.

Various devices for curing coatings using ultraviolet radiation are known. For example, US Patent 9,565,771 B1 describes a device based on UV LEDs for curing coatings on electronic assemblies, comprising a conveyor for moving parts through the UV curing zone and a system for controlling the thermal profile and radiation dose. However, this design uses a standard conveyor (belt or mesh), which does not provide optimal, uniform irradiation of the part from all sides due to the lack of a closed reflective channel. UV radiation losses to the lower hemisphere in such systems can reach 40-50%. Furthermore, there is no specialized transport system based on UV-transparent pallets and a guide with a transmittance of at least 90%, reducing the efficiency of radiation energy use.

Another example of a well-known solution is a UV oven with a conveyor and a moving lamp carriage (patent EP 4 228 379 A1), which allows for adjustable distance to the part to improve uniformity of curing. However, this design uses a flat chamber architecture with moving elements, which increases the number of mechanical components, increases the risk of failure, and requires complex control mechanisms. Furthermore, it lacks a compact cylindrical housing approximately 120 mm in diameter with a reflective inner surface, which creates an optically effective polymerization zone, and it lacks a UV-transparent transport system.

Computer-controlled UV curing units using LEDs are also known in the art. These units allow for through-feeding and even rotation of parts to improve uniformity, such as the device described in WO 2014/048436 A1. However, this design lacks a highly specialized cylindrical channel with a diameter of approximately 120 mm, which creates a closed and optically efficient work zone. Furthermore, there is no transport system based on UV-transparent pallets and a guide to minimize energy loss (in the proposed device, losses do not exceed 15%). The overall dimensions of such solutions typically exceed 1000 mm in length, making them difficult to integrate into compact production lines.

A UV curing chamber with a conveyor, upper and lower UV lamps, and a ventilation system for air removal is also known (patent CN 204800914 U). However, this design uses traditional mercury lamps with a service life of 1,000-2,000 hours and energy efficiency of approximately 30%, while modern UV LEDs last up to 20,000 hours and have energy efficiency exceeding 80%. Furthermore, the common industrial "box" design of the known device does not provide the compactness and optimal radiation distribution achieved in a cylindrical housing, and it lacks a UV-transparent product transport system.

A UV curing device using LEDs, according to patent RU 2401703 C2, is considered as a prototype. This solution is designed for UV curing of coatings, but does not disclose the design of a through-pass tunnel for the continuous transport of boards within a production line. Furthermore, it does not describe a circular arrangement of radiation sources with an angular pitch of approximately 120° for 360-degree irradiation of the product, nor does it provide for the use of UV-transparent carriers (pallets) to minimize energy loss (in the proposed device, losses do not exceed 15%). The device according to patent RU 2401703 C2 is accepted as the prototype for the proposed invention.

Another well-known solution is a UV curing system with a ring-shaped housing containing radiation sources for uniform illumination of the object around its perimeter (US Patent 6,972,413 B1). However, this solution is designed for curing large objects (e.g., vessel contents) and is not suitable for continuous transport of parts through the polymerization zone in a linear process. Furthermore, the design lacks exhaust ventilation with a capacity of approximately 40-60 ^m³ /h to remove volatile vapors, making it unsuitable for environments requiring personnel protection from hazardous emissions.

The objective of the present invention is to create a compact device for polymerizing protective coatings that can be integrated into a production line and ensure a highly uniform and efficient curing process in a single-pass mode. This solution enables the technical result of reducing shadow zones and uniformly irradiating the entire surface of the product, eliminating ultraviolet radiation leakage outside the work area, increasing the energy efficiency of the process, protecting maintenance personnel from harmful fumes, and simplifying operation and enabling direct integration into the production line.

The technical result is achieved in a polymerization chamber (hereinafter also referred to as the "chamber"), comprising a housing with an inlet and an outlet opening, ultraviolet LED modules (hereinafter also referred to as the "UV modules") and an exhaust pipe; the housing is made in the form of a channel, at least three UV modules are placed circumferentially inside the housing along the channel axis, and a guide (hereinafter also referred to as the "guide"), transparent for ultraviolet light, is installed in the irradiation zone. The UV modules are made in the form of LED strips and are arranged with an angular pitch of 110-130°; the radiation sources have a peak wavelength of 395-405 nm; the UV-transparent guide is made of polymethyl methacrylate or quartz glass, or UV-stabilized polycarbonate; the inner surface of the channel has a reflectivity of at least 92% in the working spectral range; The inlet and outlet openings are equipped with labyrinth protective curtains made of UV-resistant elastomer (hereinafter also referred to as "curtains"); the guide is configured to work with UV-transparent pallets (hereinafter also referred to as "pallets"); the chamber contains a fitting for the purge unit.

Brief description of the drawings:

Fig. 1 - isometric view of the camera;

Fig. 2 - internal structure of the chamber (labyrinth shutters are not shown);

Fig. 3 - internal structure of the chamber, top view.

In the figures, the positions denote the following elements: 1 - exhaust pipe of the ventilation system; 2 - polymerization chamber doors at the inlet and outlet openings; 3 - housing; 4 - ultraviolet LED modules; 5 - guide transparent for ultraviolet light; 6 - UV-transparent pallet; 7 - purge unit fitting; 8 - labyrinth protective curtains.

The curing chamber for moisture-resistant coatings on electronic devices (boards) is designed as an elongated cylindrical housing 3 (channel) with a diameter of approximately 120 mm and a working area length of 500 mm. Housing 3 is oriented horizontally and has an inlet and outlet, allowing the chamber to be integrated directly into a production conveyor. Essentially, the chamber forms a tunnel through which the components pass for irradiation. The inner surface of housing 3 is polished and has a high reflectivity (at least 92% in the 395-405 nm range), creating a closed, optically efficient space for curing the coating on the electronic component placed on a UV-transparent pallet 6.

A hole in the top of housing 3 contains a hermetically sealed exhaust port 1, 60 mm in diameter, connected to the external ventilation system. Exhaust port 1 is located in the zone of maximum volatile emissions during curing. It provides forced extraction of monomer vapors and ozone generated during UV irradiation of the coatings. The exhaust ventilation capacity is approximately 40-60 ^m3 /h, providing an airflow velocity of 0.7-1.2 m/s in the work area. This mode ensures the effective capture and removal of harmful vapors, preventing their accumulation inside the chamber. The selected airflow intensity does not significantly cool the workpieces (the temperature difference on the board surface does not exceed ±2°C from the initial temperature) and does not create noticeable air turbulence near the light sources, ensuring a stable spectral irradiation density at the workpiece surface. Removing ozone and organic volatile compounds before external ventilation prevents them from entering the operator's work area, ensuring compliance with occupational safety regulations. Specifically, ozone concentrations are maintained below the maximum permissible concentration (MPC ~0.1 mg/ ^m³ according to GOST 12.1.007-76 for the work area), and acrylate monomer vapor concentrations are maintained within sanitary standards.

Three extended UV LED modules 4 are installed within housing 3 along its entire length. These modules can be configured, for example, as LED strips, evenly spaced around a circle at angular intervals of ~120° relative to the channel's central axis. All UV modules 4 are equidistant from one another, forming a ring-shaped irradiation system. The spectral range of the modules' radiation is 395-405 nm (near ultraviolet), which corresponds to the maximum sensitivity of typical photopolymer materials used in moisture-protective coatings. The total UV radiation power in the working area is approximately 70-75 W (e.g., three linear UV modules 4, each 0.5 m long, with a specific power of ~48 W/m each). The close circumferential arrangement of multiple sources and the high reflectivity of housing 3's walls create an intense and uniform radiation field around the product. This ensures uniform polymerization of the coating across the entire surface of the printed circuit board or other product in a single pass. The irradiation dose variation across different surface areas does not exceed ±8-10%. For example, the use of a transparent transport system (described below) enables a uniformity index of Δ ≤ ±8% to be achieved even in areas beneath suspended components, whereas in systems with a mesh conveyor this figure is typically around ±20-25%. Furthermore, the circular arrangement of the sources and multiple reflection in the cylindrical channel reduce UV energy loss: virtually all radiation is directed at the product or repeatedly reflected before being absorbed by the coating. As a result, the required integral irradiation dose to achieve a given degree of curing (e.g., ≥95%) is achieved with lower energy consumption – approximately 15-20% lower than in systems with a traditional "box" chamber and overhead lamp placement, where a significant portion of the radiation is scattered outside the product. The use of ultraviolet LED modules 4 as light sources instead of mercury lamps further increases the energy efficiency and reliability of the device: the efficiency of the emitters exceeds 80%, there is virtually no heating of the external structures, and the estimated service life of the LEDs reaches 20,000 hours, which significantly reduces the need for maintenance compared to lamp systems.

A flat guide 5, transparent to ultraviolet light, is located in the center of housing 3 along its axis. It forms the supporting base of the transport system along which the products move through the chamber. In this example, guide 5 is made of 2 mm thick polymethyl methacrylate (organic glass). This material has high ultraviolet transmittance in the specified spectral range (at least 90%) and sufficient mechanical strength. The guide platform is rigidly fixed within the housing and maintains its geometry at operating temperatures (the heat resistance of organic glass is 70-90°C). Furthermore, PMMA is chemically resistant to ozone and acrylates vapors released during polymerization, ensuring long-term operation without clouding or loss of clarity. The flexural strength of the material used, approximately 80-120 MPa, ensures the reliability of the structure under the load of moving pallets 6. Alternatively, for special conditions, other UV-transparent guide materials can be used: for example, quartz glass (which is completely resistant to harsh UV radiation and any chemical influences) or UV-stabilized polycarbonate (a type of polycarbonate plastic modified with special additives (stabilizers) that protect the material from destruction under the influence of ultraviolet (UV) radiation). If high transparency at peak wavelengths of 395-405 nm is important, UV-stabilized PC can be a compromise between quartz glass and polymethyl methacrylate. It combines strength, stability, and acceptable UV transparency, depending on the desired modification.

UV-transparent pallets 6 are used to transport parts through the chamber. These are flat holders on which printed circuit boards or other coated objects are placed. Pallets 6 match the dimensions of guide 5 and are made of the same UV-transparent material. Pallets 6 are not part of the stationary chamber structure, but rather operate in a single system with the guide, forming a moving extension of the optical platform. Parts on pallets 6 are fed into the chamber entrance and continuously move along guide 5 through the irradiation zone at a speed of up to ~5 m/min, after which they exit the chamber for further processing. The guide 5 and pallet 6 system have a combined UV transmittance of at least ~85%, allowing virtually unimpeded irradiation of the underside (shadow) of parts. This eliminates "dead" zones and shadows from components, allowing UV radiation to reach even hard-to-reach areas beneath components. The uniform movement of 6 pallets through the irradiation zone ensures uniform exposure time for all products and promotes a uniform polymerization process. The conveyor system's simple design contains no moving parts (only the pallet containing the product moves), increasing reliability and simplifying maintenance compared to motorized conveyors.

The chamber's entrance and exit openings are equipped with flexible labyrinth-shaped protective shutters 8 made of UV-resistant elastomer (e.g., organosilicon). These shutters 8 are attached to the housing so that they fit snugly around the pallet 6 while passing through, but do not impede its movement. The multiple bends (labyrinth) prevent direct light from escaping from the chamber. This light-shielding system absorbs and reflects UV rays, significantly reducing radiation leakage through the process slots. Combined with the cylindrical shape of the housing, this reduces the level of outgoing UV radiation to less than 0.1 mW/cm² at a distance of 100 mm from the openings, which complies with strict standards for safe UV exposure in the workplace. For additional safety, doors 2 with a rotating mechanism and seal are also provided, allowing for servicing the chamber's internal components (module replacement, guide cleaning). When closed, the doors hermetically seal the workspace, completely preventing the leakage of ultraviolet radiation and vapors outside the housing, thereby protecting personnel.

The device's housing, 3, is made of 430 stainless steel (or equivalent in reflectivity). This material was selected based on several factors: it has high UV reflectivity after polishing (at least 92%), is corrosion-resistant to aggressive chemical fumes generated during polymerization, and provides the necessary mechanical strength. The wall thickness and stiffeners are designed to prevent vibration and housing deformation during long-term operation, while maintaining guide alignment and the correct relative positioning of the modules. Steel housing 3 is easy to manufacture (using bending and welding) and is convenient for integrating additional components, such as module mounts, sensors, or fitting 7, the inert gas purge unit. Fitting 7 of the purge unit can be used to supply, for example, dry nitrogen into the chamber to displace oxygen from the irradiation zone through fitting 7 of the purge unit. This eliminates the influence of oxygen on the polymerization and ozone formation processes, and also further stabilizes the temperature regime if required by the technology (nitrogen purging is often used to improve the quality of UV curing in critical coatings).

Thus, the combination of the listed design features ensures the achievement of the claimed technical result. The device according to the present invention enables the polymerization of moisture-protective coatings in a completely closed cycle, without the release of harmful radiation and vapors into the external environment. Single-pass curing of coatings to a minimum of 95% is ensured due to uniform, circular irradiation of the product. The chamber is seamlessly integrated into the technological process and simultaneously functions as a transport unit between adjacent operations and directly performs the polymerization function, which increases overall automation and production speed. A sealed, ventilated design guarantees personnel health protection, completely eliminating exposure to ozone and volatile organic compounds in the workplace (in accordance with the requirements of GOST 12.1.007-76 and sanitary standards for maximum permissible concentrations). The use of energy-efficient UV LEDs and optimized reflective geometry reduces energy consumption by approximately 15-20% while maintaining the required productivity. The use of heat- and UV-resistant materials (AISI 430 steel, plexiglass, etc.) ensures consistent performance throughout the device's service life, minimizes maintenance, and prevents premature component failure. The chamber's standardized, compact dimensions (diameter ~120 mm, length ~500 mm) and unified guide system allow for seamless integration into existing lines and, if necessary, scale-up or modification for other product sizes. Thus, the proposed polymerization chamber combines the advantages of highly efficient UV curing and industrial safety, a combination unmatched by any other known analog.

Claims (6)

1. A polymerization chamber comprising a housing with an inlet and outlet openings, ultraviolet LED modules, and an exhaust pipe, characterized in that the housing is made in the form of a channel, at least three ultraviolet LED modules are placed circumferentially along the axis of the channel, a guide transparent to ultraviolet light is installed in the irradiation zone, configured for operation with UV-transparent pallets, the inlet and outlet openings are equipped with labyrinth light-protective curtains made of UV-resistant elastomer. 2. The chamber according to paragraph 1, characterized in that the ultraviolet LED modules are made in the form of LED strips and are arranged with an angular pitch of 110–130°. 3. The chamber according to claim 1, characterized in that the ultraviolet LED modules have a peak wavelength of 395–405 nm. 4. The chamber according to item 1, characterized in that the guide is made of polymethyl methacrylate, or quartz glass, or UV-stabilized polycarbonate. 5. The chamber according to paragraph 1, characterized in that the inner surface of the channel is made with a reflectivity of at least 92% in the working spectral range. 6. The chamber according to item 1, characterized in that it contains a purge unit fitting.