Radiation source and tube section for optically sterilising a liquid

Abstract

The invention relates to a radiation source (10) for optically sterilising a liquid (12), the radiation source comprising: an LED chip (14) for generating ultraviolet radiation, which LED chip has a first side and a second side (14b) opposite the first side (14a); and a protective layer (16), which is transparent to the ultraviolet radiation and is liquid-tight and has a first surface (16a) and a second surface (16b); wherein the first side of the LED chip (14) abuts the first surface (16a) of the protective layer (16) such that the protective layer (16) is thermally coupled to the LED chip (14), and wherein the second surface (16b) of the protective layer (16) is designed to come into contact with the liquid (12).

Description

[0001] DESCRIPTION

[0002] Radiation source and pipe section for optical disinfection of a liquid

[0003] Technical field

[0004] This disclosure relates to a radiation source for the optical disinfection of a liquid, which includes an LED chip for generating ultraviolet radiation.

[0005] This disclosure further relates to a pipe section for the optical disinfection of a liquid, which includes a pipe with a window and the radiation source.

[0006] This disclosure also relates to a method for producing a radiation source for the optical disinfection of a liquid, which includes providing an LED chip for generating ultraviolet radiation.

[0007] State of the art

[0008] In many areas, such as drinking water supply, the disinfection of liquids is of great importance for maintaining hygiene and human health. Disinfection means killing and / or removing microorganisms present in the liquid, such as viruses, bacteria, yeasts, and molds.

[0009] It is known that ultraviolet (UV) radiation is used for this purpose. Ultraviolet radiation is absorbed by the DNA of microorganisms, destroying their structure and / or inactivating living cells. At sufficiently high irradiance, UV disinfection is a reliable and environmentally friendly method, as the addition of chemicals and / or the use of filters is unnecessary.

[0010] Technical task

[0011] The present disclosure addresses the technical problem of providing improved optical sterilization. Summary of the disclosure

[0012] According to a first aspect, a radiation tray is provided for the optical sterilization of a liquid, optionally a flowing liquid. The radiation tray comprises an LED chip for generating ultraviolet radiation, a protective layer, and electrical contacts for supplying the LED chip with electrical energy. The LED chip has a first side and a second side opposite the first. The protective layer is transparent to ultraviolet radiation and liquid-tight. The protective layer also has a first surface and a second surface. The electrical contacts are located on or attached to the second surface of the LED chip. The first side of the LED chip rests against the first surface of the protective layer in such a way that the protective layer is thermally coupled to the LED chip. The second surface of the protective layer is designed to come into contact with the liquid.

[0013] According to a second aspect, a reactor is provided for the optical sterilization of a liquid. The reactor comprises a container with a window and the radioactive substance as described here. The window is at least partially covered by the radioactive substance.

[0014] According to a third aspect, a method for producing a radiation source for the optical sterilization of a liquid is provided. The method comprises the steps (a) providing an LED chip for generating ultraviolet radiation, wherein the LED chip has a first side and a second side opposite the first side, and (b) applying a protective layer, which is transparent to ultraviolet radiation and liquid-tight, and has a first surface and a second surface, to the first side of the LED chip such that the protective layer is thermally coupled to the LED chip and the second surface of the protective layer is formed when it comes into contact with the liquid.

[0015] In an optional embodiment, the protective layer has a thickness such that at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or 95% and at most 80%, 90% or 100% of the heat energy generated by the LED chip is conducted through the protective layer.

[0016] In an optional embodiment, the thickness of the protective layer is at most 200 pm, optionally at most 150 pm, and further optionally at most 100 pm.

[0017] In an optional embodiment, the protective layer comprises silicon oxide or aluminum oxide. In an optional embodiment, the LED chip has a substrate and a semiconductor layer system deposited on the substrate, in which the ultraviolet radiation is generated. Optionally, the substrate provides the first layer.

[0018] In an optional embodiment, the radiation source further comprises electrical contacts for supplying the LED chip with electrical energy. Optionally, the electrical contacts are arranged on the second side of the LED chip.

[0019] In an optional embodiment, the protective layer is flat. Optionally, the electrical contacts extend from the second side, forming a cavity between a side face of the LED chip and the electrical contacts to the first surface.

[0020] In an optional embodiment, the protective layer is curved. Optionally, the electrical contacts are flat and / or the protective layer extends from the first side, forming a cavity between a side face of the LED chip and the protective layer to the electrical contacts.

[0021] In an optional embodiment, the cavity is filled with air or a thermally conductive material, optionally a transparent paste.

[0022] In an optional embodiment, the protective layer is a coating of the first side and a side surface of the LED chip as well as at least a part of the electrical contacts, wherein optionally the electrical contacts are planar.

[0023] In an optional embodiment, the LED chip comprises a substrate and a semiconductor layer system deposited on the substrate, in which the ultraviolet radiation is generated. Optionally, the substrate provides the second side.

[0024] In an optional embodiment, the radiation source comprises a heat sink that is thermally coupled to the second side of the LED chip, rests against the electrical contacts, or is formed by the electrical contacts.

[0025] The radiation source, reactor, and process described here provide passive cooling of the LED chip via the liquid, which is sterilized by the radiation source. This eliminates the need for additional active cooling of the radiation source. Furthermore, passive cooling allows for high power density with relatively little technical effort. Reliable and / or high cooling can increase the lifespan of the radiation source and / or enable it to operate at high power. Exemplary radiation densities are described below. Due to the cooling mechanisms described here, the maximum temperature occurring in the LED chip (e.g., the junction temperature) can be limited to a continuous operating temperature in the range of 40°C to 70°C, for example, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, or 70°C.For short periods when the power of the LED chip is increased, the maximum temperature occurring in the LED chip can be limited to 70°C to 90°C, for example 70°C, 75°C, 80°C, 85°C or 90°C.

[0026] This can be achieved by thermally coupling the protective layer, which acts as a barrier between the LED chip and the liquid, to the LED chip. This allows the heat generated by the LED chip to transfer through the protective layer into the liquid. Because the liquid flows along the radiation source during sterilization, a continuous heat exchange occurs between the protective layer and the portion of the liquid in contact with it, thus providing continuous cooling of the radiation source. This is particularly important because the radiation source is typically only switched on when the liquid is moving along it. Even at low flow rates, the liquid has a significantly higher thermal conductivity than, for example, air.In known radiation sources, a cavity filled with air is typically provided between a disk, which acts as a barrier between the radiation source submerged in liquid, and the radiation source itself, particularly the LED chip. This results in minimal heat exchange between the liquid and the LED chip. Cooling is then usually achieved via a heat sink on the other side of the LED chip. In the radiation source described here, this is resolved by thermally coupling the protective layer to the LED chip.

[0027] In addition to conducting heat, the protective layer has two further functions: transmitting UV light from the LED chip into the liquid and acting as a barrier to prevent, at least in some areas, the liquid from penetrating the radiation source. The radiation source may have other liquid barriers, such as seals, a frame, a mounting, and the like. However, the protective layer represents an outer surface of the radiation source that comes into contact with the liquid during sterilization. Specifically, the liquid flows past the protective layer along its direction of expansion.

[0028] The protective layer can thus be part of the surface of the pipe section that contains the liquid. The second surface of the protective layer can therefore be an outer surface of the radiation source. This second surface of the protective layer can be free of further layers and / or components and therefore in direct contact with the liquid. The protective layer can be a single component, for example, a (glass) disc to cover the LED chip.

[0029] Thermal coupling of the protective layer to the first side of the LED chip can be achieved by directly contacting the protective layer with the first side of the LED chip. For example, the first surface of the protective layer is in direct contact with the first side of the LED chip. Optionally, there are no gaps between the first side of the LED chip and the first surface of the protective layer. Thus, the radiation source can be free of gaps between the first side of the LED chip and the first surface of the protective layer.

[0030] Optionally, an intermediate layer can be provided between the LED chip and the protective layer. This intermediate layer can thermally couple the protective layer to the LED chip, for example, to facilitate heat transfer between the LED chip and the protective layer.

[0031] The protective layer can be provided to prevent the formation of cavities that could be filled with air or other gases. The protective layer can comprise a transparent adhesive, paste, and / or similar compound. This intermediate layer can be thin, for example, between 0.1 pm and 10 pm or 1 pm and 5 pm. Furthermore, the intermediate layer can be made of a material that is transparent to UV radiation and has good thermal conductivity.

[0032] As mentioned previously, the interlayer serves to thermally couple the LED chip to the protective layer by eliminating cavities or other gaps that would reduce the thermal conductivity between the LED chip and the protective layer. Due to the interlayer's thinness, its material is less critical for thermal conductivity, as thermal conductivity has less of an impact at such a low thickness than the thickness of the interlayer itself. Optionally, the transparent paste can be made of silicone, silicon dioxide (SiO2) slurry, and / or aluminum oxide (AhOsI) gel. The transparent paste can be cured by the ultraviolet radiation emitted by the LED chip.

[0033] Thermal coupling allows heat transfer from the LED chip to the protective layer primarily via conduction. Optionally, thermal coupling excludes heat transfer via convection, such as that which would occur with an air gap between the LED chip and the protective layer. The absence of convection can result in a high heat flow. Thermal coupling can also include heat conduction through mechanical contact, for example, direct mechanical contact between the LED chip and the protective layer, or via an intermediate layer.

[0034] The thermal coupling of the LED chip to the protective layer allows the protective layer to cool the LED chip, with the protective layer in turn being cooled by the liquid. Thus, compared to the prior art, the front side (the first side, i.e., the side from which the UV radiation from the LED chip exits) is also passively cooled.

[0035] Because the liquid to be sterilized is used for cooling, no components are needed to pump a cooling fluid to or from the radiation source. Instead, the inherent movement of the liquid being sterilized is used to dissipate the heat. The flow velocity of the liquid can range from 0.1 m / s to 20 m / s, optionally from 1 m / s to 10 m / s, and optionally from 3 m / s to 7 m / s.

[0036] The radiation source and / or reactor can be free of active cooling. This means that the radiation source and / or reactor has no components that transport and / or pump a coolant to cool the LED chip (for example, no pipes and / or pumps). Furthermore, the radiation source and / or reactor has no components that generate cold (for example, a thermocouple) and / or actively transport heat away from the LED chip (for example, using external energy such as electrical energy). The fluid flowing past the protective layer can provide the only means of heat removal from the LED chip.It is therefore possible that the fluid flowing past the protective layer provides the only active cooling, although the fluid itself cannot be considered active in the strict sense, since no energy is supplied by the radiation source and / or the reactor to move it. Rather, the flow of the fluid can be understood as passive cooling, similar to the dissipation of heat in air.

[0037] Disinfection using UV radiation with the radiation source described here can be used in wastewater treatment plants and / or drinking water supply systems to disinfect (drinking) water. Further applications include process water treatment to support rinsing and cleaning processes in production, the production of ultrapure water for pharmaceutical products, and / or the treatment of ballast water according to IMO standards (International Maritime Organization, IMO). The LED chip can incorporate a known semiconductor structure to generate electromagnetic radiation in the ultraviolet wavelength range. This ultraviolet radiation can cover a wavelength range from 100 nanometers (nm) to 400 nm. The LED chip can generate a radiant density with a lower limit of 50 mW / cm². 2 , 75 mW / cm 2 , 100 mW / cm 2 , 125 mW / cm 2 , 150 mW / cm 2 , 175 mW / cm2 , 200 mW / cm 2 , 225 mW / cm 2 or 250 mW / cm² 2 and an upper limit of 200 mW / cm² 2 , 225 mW / cm 2 , 250 mW / cm 2 , 275 mW / cm 2 , 300 mW / cm 2 , 325 mW / cm 2 , 350 mW / cm 2 , 375 mW / cm 2 or 400 mW / cm² 2 has.

[0038] Optionally, the LED chip generates UV-C radiation, i.e., electromagnetic radiation with a wavelength of 280 nm to 100 nm, optionally from 280 nm to 200 nm, and optionally from 250 nm to 280 nm. UV-C radiation is particularly energetic and therefore especially efficient at killing germs in liquids. The absorption of light by DNA (deoxyribonucleic acid), such as that of the germs to be killed, is maximal at a wavelength of 265 nm. Therefore, disinfection can be carried out efficiently at this wavelength.

[0039] The LED chip can be a component of a known UV LED (light-emitting diode) and / or can be the semiconductor component of the known UV LED that emits light when an electric current flows in the forward direction.

[0040] The first side of the LED chip is the side from which the generated ultraviolet radiation is emitted primarily and / or exclusively. The second side of the chip is the side facing away from the first side and / or from which no or only a small proportion of the generated ultraviolet radiation is emitted. For example, a reflective layer can be placed on or near the second side, reflecting light emitted towards the second side back towards the first side.

[0041] The radiation source may include a holder, frame, and / or housing, which can provide additional external surfaces of the radiation source (besides the second surface of the protective layer). The radiation source may also include one or more seals that seal the holder, frame, and / or housing against the protective layer. The second side of the LED chip serves to attach the LED chip to the holder, frame, and / or housing of the radiation source. For example, the LED chip may be directly connected to the holder, frame, and / or housing of the radiation source only via its second side. The second surface of the protective layer may be designed to be the sole component of the radiation source in contact with the liquid.

[0042] The light source can have one, two, or more LED chips. If multiple LED chips are present, they can each be thermally coupled to a single protective layer. In other words, a single protective layer can be used for several LED chips. Each LED chip has electrical contacts, and it is possible for the LED chips to be connected in series via these electrical contacts.

[0043] The reactor for optical disinfection of the liquid can be part of a piping system for transporting the liquid, for example, a section of a pipe or a segment of a piping system. In this case, the vessel can be a pipe, and the pipe can be installed in the piping system with the window. The pipe can, for example, have flanges at opposite ends that allow the pipe to be connected or coupled to other pipes in the piping system.

[0044] The reactor can also serve as a liquid storage container for the liquid to be disinfected. In this case, the container can be a tank. The container can be connected to a piping system for supplying and removing the liquid. The container can have one or more windows, each equipped with the radiation source.

[0045] The window in the container can be a through-opening in an outer wall of the container. An inner surface of the container serves to contain the liquid, so the window forms a connection between the interior and exterior of the container. The radiation source is positioned within this window, so that the second surface of the protective layer forms part or all of the window.

[0046] The radiation source can be designed to seal the window watertight. By positioning the radiation source within the window, the second surface of the protective layer can come into contact with the liquid inside the container. The radiation source can be attached to the container using a holder, frame, and / or housing.

[0047] To increase heat transfer from the LED chip to the liquid, the protective layer is very thin. Even if the protective layer is made of a material with low thermal conductivity, this can be compensated for by using a thin layer. Especially over short distances, the thermal conductivity of the material is less important compared to the distance to be bridged. In this case, the thickness of the protective layer is determined by the distance to be bridged. Therefore, choosing a thin protective layer ensures good heat transfer from the LED chip to the liquid.

[0048] Optionally, the protective layer has a thickness such that at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 95% and a maximum of 80%, 90%, or 100% of the heat energy generated by the LED chip is conducted through the protective layer to be absorbed and carried away by the liquid. Thus, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 95% and a maximum of 80%, 90%, or 100% of the heat generated by the LED chip can be carried away through the protective layer.

[0049] The protective layer can have a thickness of at most 300 pm, 250 pm, 200 pm, 150 pm or 100 pm and / or at least 10 pm, 20 pm, 30 pm, 40 pm or 50 pm. At these thicknesses, the thermal conductivity is still only minimally determined by the material of the protective layer, allowing efficient heat transfer through the protective layer to cool the LED chip.

[0050] The optional system of protective layer and intermediate layer, which can be considered the distance between the first side of the LED chip and the liquid, can have a thickness of at most 300 pm, 250 pm, 200 pm, 150 pm or 100 pm and / or at least 10 pm, 20 pm, 30 pm, 40 pm or 50 pm.

[0051] The semiconductor layer system of the LED chip can be composed of several semiconductor layers (epitaxy layers). Within this semiconductor layer system, there is at least one active layer. When the LED chip is operating, this active layer generates UV light of a specific wavelength via the voltage (e.g., DC voltage) supplied through the electrical contacts (which will be described in more detail later). This means that the active layer is the layer of the LED chip where electrons and holes recombine to produce the UV radiation. The active layer is therefore also the layer of the LED chip where the heat generated during the production of the ultraviolet radiation is produced.

[0052] The substrate of the LED chip is the component of the LED chip that serves as the base or substrate onto which the semiconductor layer system is deposited (for example, by epitaxy). The substrate can be made of an optically transparent or transmissive material (at least for the wavelength of the radiation generated by the LED chip), such as aluminum oxide (Al₂O₃). Well-known materials and processes can be used to manufacture the LED chip. The LED chip can be a flip chip, in which electrical contacts for supplying the LED chip with electrical power are provided on the semiconductor layer system (optionally its surface). In this case, the substrate can be thermally coupled to the protective layer. In other words, when using a flip chip for the LED chip, the first side of the LED chip can be provided by an outer surface of the substrate.

[0053] When using a flip-chip for the LED chip, the second side serves to supply the LED chip with electricity. For this purpose, electrical contacts for supplying the LED chip with electrical energy are located on this second side and are electrically connected to the semiconductor layer system. These electrical contacts can have a first contact (for example, a positive terminal) and a second contact (for example, a negative terminal). The electrical contacts are connected to the LED chip in such a way that electrical current can flow from the electrical contacts into the LED chip, or vice versa, to generate ultraviolet radiation.

[0054] The electrical contacts can cover a large portion of the surface of the second side of the LED chip. The electrical contacts can be arranged on the LED chip in such a way that they do not touch each other. Solder or other electrically conductive and adhesive materials can be used to electrically connect the contacts to the LED chip. This electrical connection can simultaneously provide a mechanical connection or fixation of the LED chip to the electrical contacts.

[0055] It is possible for the thickness of the semiconductor layer system to be less than the thickness of the substrate, where the thickness can be measured in the direction of extension from the first side to the second side. In this case, the active layer can be located closer to the second side. Nevertheless, sufficient heat transfer from the active layer through the substrate and the protective layer, and into the liquid, is possible so that the LED chip can be cooled by the liquid.

[0056] In the radiation source described here, the heat transfer distance can be reduced because the active layer is located close to the cooling element (i.e., the liquid) and / or there is no thermal barrier between the active layer and the liquid. In the prior art, this thermal barrier is an air gap between the LED chip and a glass cover. The protective layer can be made of glass, such as silicon dioxide (SiCh) or aluminum oxide (Al₂O₃). These exemplary protective layer materials exhibit a high degree of UV radiation transmission while also being liquid-tight. When using a flip chip for the LED chip, the refractive indices of the substrate and the protective layer can be similar or the same (for example, when using aluminum oxide for both the substrate and the protective layer).It is also possible that a refractive index difference exists, for example, if the protective layer is made of SiÜ2 with a refractive index of 1.5 and the LED chip is made of aluminum gallium nitride (AIGaN) with a refractive index of 2.5. However, this refractive index difference is smaller than that of known LED chips where AIGaN is in air (refractive index 1). The smaller or non-existent refractive index difference between the protective layer and the substrate results in little or no light being reflected at the interface between the substrate and the protective layer; for example, total internal reflection at the interface is reduced. This can increase the radiative power of the LED chip by improving the extraction of the generated radiation, especially compared to known radiation sources where the LED chip is in contact with air.

[0057] Furthermore, the aforementioned exemplary materials for the protective layer can be applied flexibly at the thicknesses used here, so that they can be placed around the LED chip, i.e. bent, to at least partially adapt to the shape of the LED chip.

[0058] In one example, the electrical contacts are planar, meaning they extend in a single plane, so the LED chip protrudes from the electrical contacts. The protective layer can be positioned on the electrical contacts and the LED chip such that it extends under a curve from the front side of the LED chip to the front of the electrical contacts. The protective layer can have an S-shaped cross-section. In this example, the protective layer can protrude from the electrical contacts to accommodate the LED chip.

[0059] In addition to its first and second sides, the LED chip can have a side surface that connects the first and second sides. The protective layer may be designed in such a way that it does not completely adhere to the side surface (for example, only to the first side), allowing a gap to form between the protective layer and the side surface. This is due to the limited deformability or flexibility of the protective layer. Furthermore, if the protective layer is in direct contact with the side of the LED chip, this can lead to a higher extraction efficiency of UV light from the chip (refractive index matching).

[0060] The LED chip can essentially be cuboid-shaped, such that its side face extends orthogonally to the first and / or second face. Because the protective layer can only be bent to a certain degree, a cavity is created when the protective layer extends from the first face to the electrical contacts.

[0061] In an alternative embodiment, the protective layer is flat or straight, extending in a single plane. In this case, the LED chip protrudes from the liquid at the first surface of the protective layer. The electrical contacts can be bent or curved, extending from the second side of the LED chip towards the first surface of the protective layer. The electrical contacts can have an S-shaped curvature in cross-section.

[0062] The electrical contacts can be made of an electrically conductive material, such as metal. Similar to the protective layer described previously, the material of the electrical contacts can be curved to a certain extent, so that in this embodiment as well, cavities form between the curved electrical contacts and the side surface of the LED chip.

[0063] These cavities can be unfilled, i.e., filled with air. In this case, a thermal barrier is provided on the side surface of the LED chip, through which heat dissipation is lower compared to the front side.

[0064] To increase heat dissipation via the side surface, the cavity can be filled with a thermally conductive material and / or a (transparent) paste. The thermally conductive material or paste can be cured by the electromagnetic radiation generated by the LED chip. The transparent paste can—as described above—comprise, for example, silicone, silicon dioxide (SiO2) slurry, and / or aluminum oxide (Al2O3) gel.

[0065] The thermally conductive material and / or paste increase the thermal coupling from the side surface of the LED chip to the protective layer or the electrical contacts. In this way, heat dissipation from the side surface of the LED chip to the electrical contacts or the protective layer can be improved.

[0066] In another alternative embodiment, the protective layer can be a coating of the LED chip, and optionally also of a portion of the electrical contacts. For example, the protective layer can be sprayed onto the LED chip and parts of the electrical contacts. The protective layer, as a coating, can be applied by spraying, sputtering, PVD (physical vapor deposition), CVD (chemical vapor deposition), and / or a sol-gel process, or similar methods. Thus, the process step of "applying a protective layer" can be achieved by coating the LED chip.

[0067] In this case, no cavities form between the side surface of the LED chip and the protective layer, thus ensuring good thermal coupling between the protective layer and the LED chip, even at the side surface of the LED chip. The area of ​​the protective layer that covers the side surfaces of the LED chip can also be in contact with the liquid, thereby providing efficient heat dissipation at the side surface of the LED chip as well.

[0068] Analogous considerations apply if the protective layer curves along the side surface of the LED chip and the cavity is filled with a thermally conductive material and / or a paste.

[0069] As an alternative to the flip-chip LED chip, a conventional LED chip can be used, in which the semiconductor layer system is supplied with electrical energy via wires or other electrical conductors. The surface of the semiconductor layer system can represent the first side of the LED chip, and the substrate the second side.

[0070] In this case, for example, the electrical contacts make contact with parts of the semiconductor layer system on the side face and / or the first side. The intermediate layer can be provided to fill voids that occur between the electrical contacts on the first side and the protective layer, in order to provide good thermal coupling.

[0071] Because the active layer is located on or near the first side (for example, closer to the first side than to a second side of the LED chip), the distance for heat transfer from the active layer to the liquid is short. This increases the efficiency of heat transfer through the protective layer and thus the efficiency of the cooling. This is particularly evident when compared to the cooling of conventional LED chips, because with the same active layer arrangement as in the radiation source described here, the heat must first be transported through air located between the first side and a glass cover before it can be dissipated into the liquid. In the radiation source described here, the distance for heat transfer can be reduced because the active layer is located close to the cooling element (i.e.,is arranged in the liquid) and / or there is no thermal barrier between the active layer and the liquid.

[0072] To provide heat dissipation on the second surface of the LED chip, a heat sink can be provided on that side. This heat sink can be made of a material with high thermal conductivity, such as a metal. The heat sink can then transfer the heat to cooling fins and / or liquid cooling, similar to conventional radiation sources.

[0073] The heat sink can simultaneously provide the electrical contacts, giving them a dual function: supplying power to the LED chip and cooling the other side of the LED chip. Alternatively, the heat sink can be thermally coupled to the electrical contacts, with the electrical contacts positioned between the heat sink and the other side of the LED chip.

[0074] In another variant, the heat sink can be located directly on the second side of the LED chip, for example, on those areas of the second side where the electrical contacts do not touch each other. In this case, the heat sink and the electrical contacts can completely cover the second side of the LED chip.

[0075] It is also possible that the heat sink touches the side surfaces of the LED chip, for example, filling part of the cavity. The heat sink can consist of one or more copper foils.

[0076] Example of implementation

[0077] The disclosure is explained in more detail below with reference to exemplary embodiments and drawings. Specifically, the following is shown schematically:

[0078] FIG. 1 shows a section of a first embodiment of a radiation source in a cross-sectional view;

[0079] FIG. 2 shows a section of a second embodiment of the radiation source in a cross-sectional view;

[0080] FIG. 3 shows a section of a third embodiment of the radiation source in a cross-sectional view; FIG. 4 shows a reactor with the radiation source in a side view;

[0081] FIG. 5 is a block diagram illustrating a method for producing the radiation source according to Fig. 3;

[0082] FIG. 6 shows a section of a third embodiment of the radiation source in a cross-sectional view; and

[0083] FIG. 7 shows a simulation of the temperatures for different variants of the radiation source.

[0084] FIG. 1 schematically shows a cross-sectional section of a radiation source 10. The representation is not to scale; in particular, the thicknesses of the components and layers may be shown as thicker than they actually are for the sake of clarity.

[0085] The radiation source 10 serves to disinfect a liquid 12, such as drinking water, which flows past the radiation source 10. The radiation source 10 generates UV radiation, optionally UV-C radiation, which kills microorganisms such as viruses, bacteria, fungi and / or protozoa.

[0086] The radiation source 10 comprises an LED chip 14, a protective layer 16, a first electrical contact 18a, and a second electrical contact 18b. The LED chip 14 is configured to generate ultraviolet radiation. The LED chip 14 includes a substrate 20a and a semiconductor layer system 20b, which is composed of several semiconductor layers (epitaxy layer). The semiconductor layer system 20b can provide an active layer 20 in which the ultraviolet radiation is generated by the recombination of electrons and holes. The semiconductor layer system 20b can be applied to the substrate 20a by epitaxy. The substrate 20a can be made of aluminum oxide and form the first side 14a.

[0087] The LED chip 14 has a first side 14a and a second side 14b, which is opposite the first side 14a. The LED chip 14 is essentially cuboidal in shape, such that the first side 14a is opposite the second side 14b. The first electrical contact 18a and the second electrical contact 18b are connected to the second side 14b of the LED chip 14 to supply the LED chip 14 with electrical energy. The first electrical contact 18a can be a positive terminal of the power supply, and the second electrical contact 18b can be a negative terminal of the power supply. The first electrical contact 18a and the second electrical contact 18b can be made of a metal and serve to electrically connect the LED chip 14 to an electrical power source.For example, the first electrical contact 18a and the second electrical contact 18b can be electrically connected to respective plugs of the radiation source 10, by means of which the radiation source 10 can be connected to a power supply.

[0088] The LED chip 14 according to Fig. 1 has a flip-chip design. This means that the first electrical contact 18a and the second electrical contact 18b are directly electrically and / or mechanically connected to the semiconductor layer system 20b on the second side 14b, for example by soldering or other adhesive and electrically conductive materials. The protective layer 16 can be made of glass, such as silicon dioxide or aluminum oxide. The protective layer 16 has a first surface 16a and a second surface 16b, which can come into contact with the liquid 12. The protective layer 16 is transparent to the UV radiation generated by the LED chip 14, so that the UV radiation can penetrate the liquid 12 to kill germs there (this is symbolized by the arrow).

[0089] In the embodiment according to Fig. 1, the protective layer 16 is planar, i.e., it extends in a non-curved plane. The protective layer 16, with its first surface 16a, is in direct contact with the first side 14a of the LED chip 14 (here, an outer surface of the substrate 20a), so that the protective layer 16 is thermally coupled to the LED chip 14. Optionally, no cavities are provided between the protective layer 16 and the LED chip 14, which could reduce or diminish heat flow from the LED chip 14 to the protective layer 16.

[0090] The protective layer 16 has a thickness of 200 pm, optionally a maximum of 150 pm, and optionally 100 pm. A minimum thickness of the protective layer can be 10 pm, 20 pm, 30 pm, 40 pm, or 50 pm. Due to this small thickness of the protective layer 16, efficient heat transfer from the LED chip 14 during the generation of UV radiation to the liquid 12 is possible. In this way, the LED chip 14 can be cooled by the liquid 12. The liquid 12 provides efficient cooling of the LED chip 14 because it is a good thermal conductor and / or is passed by the radiation source 10 for sterilization, thus ensuring good heat dissipation. The heat transfer corresponds to the direction of the arrow in Fig. 1. The LED chip 14 has a side surface 14c that connects the first side 14a with the second side 14b.The side surface 14c can connect the first side 14a with the second side 14b and be perpendicular to them.

[0091] The first electrical contact 18a and the second electrical contact 18b can extend from the second side 14b of the LED chip 14 of the first surface 16a of the protective layer 16. The first electrical contact 18a and the second electrical contact 18b can be curved, for example, in an S-shape in a cross-sectional view. A cavity 22 can be formed between the side surface 14c and the first and second electrical contacts 18a, 18b. This cavity 22 can be filled with air, a thermally conductive material, and / or a transparent paste.

[0092] The thermally conductive material and / or the transparent paste can increase the thermal conductivity from side surface 14c to the first and second electrical contacts 18a, 18b. Thus, the first and second electrical contacts 18a, 18b on the second side 14b and side surface 14c can contribute to heat dissipation from the LED chip 14. The electrical contacts can be thermally coupled to a heat sink 24 (not shown in Fig. 1) to dissipate the heat absorbed by the first and second electrical contacts 18a, 18b. Therefore, the second side 14b and / or side surface 14c can also contribute to cooling the LED chip 14.

[0093] The radiation source 10 according to the example of Fig. 2 is identical to the radiation source 10 according to the example of Fig. 1 with respect to its optional features, properties and / or characteristics, except for the differences described below.

[0094] In the radiation source 10 according to the example in Fig. 2, the first electrical contact 18a and the second electrical contact 18b are planar. Furthermore, the first electrical contact 18a and the second electrical contact 18b form the heat sink 24 by being thicker than in the example in Fig. 2. This allows for the absorption of more heat from the LED chip 14.

[0095] In the radiation source 10 according to the example in Fig. 2, the protective layer 16 is curved. The protective layer 16 can extend from the first side 14a to the flat first and second electrical contacts 18a, 18b, for example, by means of an S-shape in cross-section. This is also possible with a protective layer 16 made of glass, since the protective layer 16 has a small thickness and is therefore sufficiently flexible to achieve the described curvature.

[0096] In the example shown in Fig. 2, the cavity 22 is formed between the first surface 16a of the protective layer 16 and the side surface 14c of the LED chip 14. This allows heat energy to be dissipated from the side surface 14c of the protective layer 16 into the liquid 12.

[0097] The radiation source 10 according to the example of Fig. 3 is identical to the radiation source 10 according to the example of Fig. 1 or Fig. 2 with respect to its optional features, properties and / or characteristics, except for the differences described below.

[0098] The protective layer 16 in the example shown in Fig. 3 is not designed as curved glass as in the examples shown in Fig. 1 and Fig. 2. Rather, the protective layer 16 is a coating applied to the LED chip 14 and parts of the first and second electrical contacts 18a, 18b. Thus, there is no cavity 22. Instead, the protective layer 16 is in direct contact with the side surface 14c, allowing for good heat dissipation from the side surface 14c into the liquid 12 through the protective layer 16. The protective layer 16 can be applied, for example, by spraying or sputtering.

[0099] Fig. 4 shows a reactor 26 in a top view. The reactor 26 can be part of a piping system (for example, a pipe section) through which, for example, drinking water can be pumped. The reactor 26 has a container 28 (a pipe in Fig. 4) with a window 30. The window 30 can be a through-opening extending from an outside of the container 28 to an inside of the container 28. The window 30 is closed by the radiation source 10, which is why the window 30 is shown with a dashed line in Fig. 4.

[0100] The container 28 is designed to transport and / or store the liquid 12. The radiation source 10 seals the window 30 in a liquid-tight manner. For this purpose, the protective layer 16 can be in contact with the outside of the container 28, for example, with an interposed seal. Furthermore, the tube 28 and the radiation source 10 can have means by which the radiation source 10 can be mechanically and / or adhesively attached to the container 28.

[0101] A method for manufacturing the radiation source 10 according to Fig. 3 is described with reference to the block diagram of Fig. 5. In step S1, the LED chip 14 is provided. This step S1 can include arranging the LED chip on the electrical contacts 18a, 18b. The LED chip 14 can be mechanically attached to the electrical contacts 18a, 18b, for example by soldering. For this purpose, solder can be heated and applied to the second side 14b or to the electrical contacts 18a, 18b, and then the LED chip 14 can be attached to the electrical contacts 18a, 18b. This mechanical attachment simultaneously establishes an electrical connection to the semiconductor layer system 20b.

[0102] In step S2, the protective layer 16 is applied to the first side 14a, the side surface 14c, and one top surface of the electrical contacts 18a, 18b using a spraying process. Applying the protective layer 16 by spraying ensures that there are no voids between the first side 14a and the protective layer 16, thus providing good thermal coupling between the first side 14a and the protective layer 16.

[0103] Alternatively, in step S2 (for the fabrication of the radiation source 10 according to Fig. 1 or Fig. 2), the protective glass layer 16 can be pressed onto the first side 14a. The protective layer 16 can be attached using a transparent paste applied to the first side 14a. Furthermore, it is alternatively or additionally possible to apply a (non-transparent) adhesive to the electrical contacts 18a, 18b and / or the holder to secure the protective glass layer 16 and seal it against the ingress of liquid to the LED chip 14. The radiation source 10 according to the example in Fig. 6 is identical to the radiation source 10 according to the example in Fig. 1 with respect to its optional features, properties, and / or characteristics, except for the differences described below.

[0104] The LED chip 14 used in the embodiment of Fig. 6 is not a flip chip, unlike the one in Fig. 1. This means that the first side 14a is provided by the semiconductor layer system 20b and the second side 14b by the substrate 20a. Furthermore, the electrical contacts 18a, 18b are not located on the second side 14b, but are electrically connected to the first side 14a and / or the side surface 14c of the semiconductor layer system 20b.

[0105] An intermediate layer of a transparent paste can be provided between the first side 14a and the protective layer 16 to compensate for irregularities in the semiconductor layer system 20b on the first side 14a, thus preventing voids between the protective layer 16 and the first side. In the embodiment shown in Fig. 1, the intermediate layer can be omitted because the substrate 20a provides a substantially smooth first side 14a. The substrate 20a is mechanically attached to the heat sink 20. This also establishes thermal coupling between the substrate 20a and the heat sink 24.

[0106] Fig. 7 shows three different simulations of heat propagation from the LED chip 14 as used in the radiation source 10. In all three simulations, three LED chips 14 are arranged in a copper bed. The LED chip 14 has a cuboid shape, such that the second side 14b and the four sides of the face 14c are in contact with the copper bed. The only exception is the third, lower simulation, in which a thermal resistor (see arrow) is provided on all sides of the face 14c to simulate the effect of the cavity 22.

[0107] In the first, upper simulation, no protective layer 16 is included; in the second, middle simulation and in the third, lower simulation, a protective layer 16 made of quartz with a thickness of 100 pm is included. The active layer 20 produces a power density of 200 mW / cm². 2 The flow velocity of liquid 12 is 5 m / s.

[0108] The copper bed provides a heat sink 24. The first, upper simulation thus represents an ideal situation, since the first side 14a of the LED chip 14 is not covered by the protective layer, and therefore the heat from the LED chip 14 can transfer directly into the liquid 12. Furthermore, all other sides of the LED chip 14 are thermally coupled to the heat sink 24 (the copper bed) to dissipate the heat directly. The simulation shows that a temperature increase occurs only in the area of ​​the active layer 20. The maximum temperature is approximately 42°C. The temperature on the second side 14b of the LED chip 14 is approximately 31°C.

[0109] In the second, middle simulation, which, unlike the first, upper simulation, includes a protective layer 16 made of quartz glass with a thickness of 100 pm, the maximum temperature in the area of ​​the active layer 20 increases to approximately 53 °C. The temperature on the second side 14b of the LED chip 14 is approximately 40 °C. Furthermore, the simulation also showed an increase in the temperature in the copper bed between the LED chips 14. The comparison of the first, upper simulation with the second, middle simulation demonstrates the influence of the protective layer 16 on the heat generation.

[0110] In the third, lower simulation, where, unlike the second, middle simulation, thermal resistance is provided on all four sides of the surface 14c, the maximum temperature in the area of ​​the active layer 20 increases to approximately 60 °C. The temperature on the second side 14b of the LED chip 14 is approximately 41 °C. Furthermore, the simulation also shows an increase in the temperature in the copper bed between the LED chips 14. The third, lower simulation most closely approximates the temperature behavior of the radiation source 10 described here and shows that the temperature of the active layer 20 can be maintained at approximately 60 °C, which is beneficial for the continuous operation of the radiation source 10.

Claims

1. PATENT CLAIMS 1. Radiation source for the optical sterilization of a liquid (12), comprising an LED chip (14) for generating ultraviolet radiation, wherein the LED chip (14) has a first side (14a) and a second side (14b) opposite the first side (14a), and a protective layer (16) which is transparent to the ultraviolet radiation and liquid-tight and has a first surface (16a) and a second surface (16b), wherein the first side of the LED chip (14) is in contact with the first surface (16a) of the protective layer (16) such that the protective layer (16) is thermally coupled to the LED chip (14), and wherein the second surface (16b) of the protective layer (16) is designed to come into contact with the liquid (12).

2. Radiation source according to claim 1, wherein the protective layer (16) has a thickness such that at least 10%, optionally at least 30%, of the heat energy generated by the LED chip (14) is conducted through the protective layer (16), and / or the thickness of the protective layer (16) is at most 200 pm, optionally at most 150 pm, further optionally 100 pm, and / or the protective layer (16) comprises silicon oxide or aluminum oxide.

3. Radiation source according to claim 1 or 2, wherein the LED chip (14) comprises a substrate (20a) and a semiconductor layer system (20b) which is applied to the substrate (20a) and in which the ultraviolet radiation is generated, and wherein the substrate (20a) provides the first side (14a).

4. Radiation source according to claim 3, further comprising electrical contacts (18a, 18b) for supplying the LED chip (14) with electrical energy, wherein the electrical contacts (18a, 18b) are arranged on the second side (14b) of the LED chip (14).

5. Radiation source according to claim 4, wherein the protective layer (16) is planar, the electrical contacts (18a, 18b) optionally extend from the second side (14b) to the first surface (16a), forming a cavity (22) between a side surface of the LED chip (14) and the electrical contacts (18a, 18b).

6. Radiation source according to claim 4, wherein the protective layer (16) is curved, wherein optionally the electrical contacts (18a, 18b) are flat and the The protective layer (16) extends from the first side (14a) forming a cavity (22) between a side surface of the LED chip (14) and the protective layer to the electrical contacts (18a, 18b).

7. Radiation source according to claim 5 or 6, wherein the cavity (22) is filled with air or a thermally conductive material, optionally a transparent paste.

8. Radiation source according to claim 4, wherein the protective layer (16) is a coating of the first side (14a) and a side surface of the LED chip (14) and at least a part of the electrical contacts (18a, 18b), wherein optionally the electrical contacts (18a, 18b) are planar.

9. Radiation source according to claim 1 or 2, wherein the LED chip (14) comprises a substrate (20a) and a semiconductor layer system (20b) which is applied to the substrate (20a) and in which the ultraviolet radiation is generated, and wherein the substrate (20a) provides the second side (14b).

10. Radiation source according to one of the preceding claims, further comprising a heat sink (24) which is thermally coupled to the second side (14b) of the LED chip (14), is in contact with the electrical contacts (18a, 18b) or is formed by the electrical contacts (18a, 18b).

11. Reactor for the optical disinfection of a liquid (12), comprising a container (28) with a window (30) and a radiation source (10) according to one of the preceding claims for irradiating an interior of the container, wherein the window (30) is at least partially closed by the radiation source (10).

12. Method for producing a radiation source (10) for the optical disinfection of a liquid (12), Providing an LED chip (14) for generating ultraviolet radiation, wherein the LED chip (14) has a first side (14a) and a second side (14b) opposite the first side (14a), Applying a protective layer (16) that is transparent to ultraviolet radiation and liquid-tight and has a first surface (16a) and a second surface (16b) to the first side (14a) of the LED chip (14) such that the protective layer (16) is thermally coupled to the LED chip (14) and the second surface (16b) of the protective layer (16) is formed, which came into contact with the liquid (12).

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