Converter element laminate, method for fixing a converter element on a radiation emitting semiconductor chip, and radiation emitting device

Abstract

A converter element laminate is provided, comprising: a converter element having a top surface and a bottom surface, and an adhesive film on the bottom surface, wherein the adhesive film comprises a B-stage siloxane-based material. Further, a method for fixing a converter element on a radiation emitting semiconductor chip and a radiation emitting device are provided.

Description

[0001]2023PF01797 May 20, 2025P2024,0108 WO N -1 -Description CONVERTER ELEMENT LAMINATE, METHOD FOR FIXING A CONVERTER ELEMENT ON A RADIATION EMITTING SEMICONDUCTOR CHIP, AND RADIATION EMITTING DEVICE A converter element laminate, a method for fixing a converter element on a radiation emitting semiconductor chip, and aradiation emitting device are provided.Embodiments provide a converter element laminate with improved performance, a method for fixing a converter element on a radiation emitting semiconductor chip with improvedperformance and a radiation emitting device with improvedperformance.According to at least one embodiment, a converter elementlaminate is provided. The converter element laminate comprises a converter element having a top surface and a bottom surface, and an adhesive film on the bottom surface. A laminate is to be understood as a sequence of layers or elements that are laminated together. The laminate can be handled as one component but comprises distinguishableregions, in this case the converter element and the adhesivefilm. A converter element is to be understood as an element being able to absorb fully or a part of electromagnetic radiation of a first wavelength range (also called primary radiation) and emit electromagnetic radiation of a second wavelength range (also called secondary radiation). The absorbed2023PF01797 May 20, 2025P2024,0108 WO N -2 -radiation has, in particular, a wavelength maximum that is different from, for example smaller than, the wavelength maximum of the emitted radiation. Such a process is called wavelength conversion. In particular, scattering orabsorption alone is not meant with the term “wavelengthconversion” at present. For example, the wavelength maximum of the absorbed radiation is in the UV or blue spectralrange, i.e., at wavelengths in a range of 400 nm to 500 nm,and the wavelength maximum of the emitted radiation is in theyellow, green or red spectral range, i.e., at longerwavelengths than the absorbed radiation. Such a process is called down-conversion. Responsible for the wavelength conversion is normally a phosphor being included in the converter element. Thus, the phosphor absorbs electromagneticradiation, which is, for example, emitted by a light emittingdiode (LED), converts it by a photoluminescent mechanism, andre-emits it at, for example, longer wavelengths. The converter element may be a ceramic, i.e., consist of the phosphor. Alternatively, the phosphor may be embedded inglass (phosphor-in-glass) or embedded in a matrix material(phosphor-in-polymer) or embedded in a matrix material and being applied on a substrate, for example a glass substrate (phosphor-in-polymer-on-substrate). The converter element may comprise different geometries, for example the shape of a platelet. Thus, the top surface and the bottom surface are according to at least one embodiment parallel to each other. In particular, top and bottom surface of the converter element are parallel to a main extension area of the converter element.2023PF01797 May 20, 2025P2024,0108 WO N -3 -The adhesive film being “on” the bottom surface means theadhesive film is applied on the bottom surface and covers it. In particular, the adhesive film is directly applied on the bottom surface of the converter element, i.e., the converterelement and the adhesive film comprise a common boundary.The adhesive film does not necessarily have to compriseadhesive properties per se but upon a treatment that changesits physical properties. In particular, the adhesive film hasadhesive properties at elevated temperatures. For example,the adhesive film develops adhesive properties when beingheated to a melting temperature and / or a Vicat softeningpoint (Vicat softening temperature) of the material of theadhesive film.When having adhesive properties, the adhesive film can beapplied on a substrate, for example, and being fixed there.Thereby, the converter element is fixed on the substrate bymeans of the adhesive film, the substrate comprising forexample a radiation emitting semiconductor chip. According to at least one embodiment, the adhesive film comprises a B-stage siloxane-based material. A siloxane-based material is to be understood as a material comprising siloxane-groups, in particular as a main component. A siloxane-group can be characterized by having Si atoms being connected to each other by an oxygen atom, i.e., a Si-O-Sigroup, wherein other substituents like alkyl groups, alkoxygroups or hydrogen may be additionally bonded to the Siatoms. The siloxane-based material comprises according to at least one embodiment oligomerized and / or polymerized siloxane-groups.2023PF01797 May 20, 2025P2024,0108 WO N -4 -“B-stage” means that the siloxane-based material is partiallycrosslinked and exists in this state within a range oftemperatures. In the lower end of this range of temperatures, including in particular room temperature, the material isaccording to an embodiment solid and can be handled, e.g.,saw diced. At the upper end of the temperature range, the film is melted, i.e., softened. Within the B-stage temperature range, it is possible to go back and forth between the solid and softened states. However, at a temperature higher than the upper temperature limit of therange, the material is irreversibly cured to a C-stage andloses its B-stage properties. According to at least one embodiment, a converter element laminate is provided, the converter element laminate comprising: a converter element having a top surface and a bottom surface, and an adhesive film on the bottom surface, wherein the adhesive film comprises a B-stage siloxane-based material. In many phosphor-converted radiation emitting devices, like LEDs (light emitting diodes), a converter element comprising a phosphor is glued to an LED chip. As a glue, typically some type of silicone-based glue is widely used. In a first step, the silicone-based glue is usually dispensed onto a substrate, for example, on the LED chip. In a second step, the converter element is placed onto the uncured glue droplet(s). After the converter element is placed, the silicone-based glue layer is cured. However, if too littleglue is dispensed, then there is insufficient glue coverageon the LED chip and the converter element, leaving behind air voids between the LED chip and the converter element. If too much glue is dispensed, then the excess glue squeezes out2023PF01797 May 20, 2025P2024,0108 WO N -5 -from between the LED chip and converter element. Both caseslead to a loss of device brightness and yield, and dependingon the severity could impact other device properties. Variations in the glue dispensing and surface roughness of the converter element often result in the deliberate use of too much glue as a compromise between performance, i.e., brightness, and yield loss. Additionally, conventionally used silicone-based glues degrade when exposed to temperatures greater than about 150°C, possibly leading to a delamination of the converterelement from the LED chip. In order to overcome this problem,so far a thin glue layer as possible is used. With a converter element laminate as described here the need to dispense a liquid glue on a substrate like an LED chip canbe eliminated. Instead, an adhesive film is applied to aconverter element prior to the attachment of the converterelement to a substrate, for example an LED chip. Thus, theconverter element laminate is attached to the substrate, forexample the LED chip. The lateral dimension of the adhesivefilm may be exactly chosen, so that neither air voids nor squeezed out material arise during the attachment of the converter element. Therefore, the problem of too little ortoo much glue can be solved with the converter elementlaminate. Additionally, the adhesive film as described here is more thermally stable than traditional silicone-gluesreducing the risk of delamination even at high temperatureapplications.2023PF01797 May 20, 2025P2024,0108 WO N -6 -Therefore, when using the converter element laminate, radiation emitting devices may be provided having high yields and a high stability even at temperatures greater than 150°C. According to at least one embodiment, the bottom surface of the converter element has a lateral dimension that corresponds to a lateral dimension of the adhesive film. In other words, the bottom surface of the converter element has the same length and width as the adhesive film. Thus, the converter element laminate has smooth side surfaces, wherein the side surfaces of the converter element and the side surfaces of the adhesive film are laterally equidimensional. A side surface is the surface perpendicular to the top andbottom surface. When attaching such a converter elementlaminate to a LED chip, for example, a squeezing out of adhesive material or the formation of air voids can be avoided. According to at least one embodiment, the B-stage siloxane-based material has a melting temperature and / or Vicatsoftening point in the range of 50°C inclusive to 150°Cinclusive, in particular in the range of 50°C inclusive to 100°C inclusive, for example in the range of 60°C inclusive to 80°C inclusive. Accordingly, the B-stage siloxane-based material is solid or at least semi-solid at room temperature allowing for a good handling of the converter element laminate. In particular, the B-stage siloxane-based material reveals its adhesive properties in the melted state. According to at least one embodiment, the B-stage siloxane- based material is semi-cured. This means, the B-stage siloxane-based material is neither a monomer nor a fullycured polymer, but a partially polymerized and / or crosslinked2023PF01797 May 20, 2025P2024,0108 WO N -7 -material. In contrast, a fully cured siloxane-based materialwould be fully polymerized and crosslinked and not polymerizeanymore, even at elevated temperatures. According to at least one embodiment, the B-stage siloxane- based material comprises a content of T-unit siloxane groups in the range of at least 50%, in particular of at least 60%,for example of at least 80%. The content refers to thecontent of all siloxane-groups in the material. A siloxane-based material generally has Si-O-groups and may comprise M-units (R3SiO-), D-units (-OR2SiO-), T-units (-ORSiO2-) and / or Q-units (-OSiO3-). R may be independently chosen from organic groups like saturated or unsaturated hydrocarbons, for example, methyl, ethyl or phenyl groups.If the content of T-units in the B-stage siloxane-basedmaterial is at least 50%, it may cure into a stable, inparticular thermally stable film containing a crosslinkednetwork of polysiloxane. According to at least one embodiment, the B-stage siloxane- based material comprises a content of D-unit siloxane groups of up to 50%, in particular up to 40%, for example up to 20%. The content refers to the content of all siloxane-groups in the material. D-unit siloxane-groups make the material more flexible and, thus, improve the handling of the material. According to at least one embodiment, the B-stage siloxane- based material comprises reactive groups chosen from silanol, alkoxy, and mixtures thereof. Reactive groups enhance a crosslinking of the siloxane-based material when it is heated to a curing temperature. Exemplary alkoxy groups are methoxy and ethoxy.2023PF01797 May 20, 2025P2024,0108 WO N -8 -According to at least one embodiment, the B-stage siloxane- based material comprises silanol as a reactive group. Acontent of silanol-groups with respect to the B-stagesiloxane-based material is, for example, in the range of 3%to 5% inclusive. Silanol-groups are at one hand reactive groups for crosslinking when the adhesive film is heated to a curing temperature. On the other hand, the silanol-groups may form hydrogen bonds making the B-stage siloxane-based material solid at temperatures below the melting temperature and / or Vicat softening point. According to at least one embodiment, the B-stage siloxane- based material comprises non-reactive side groups. Non- reactive side-groups may adapt the refractive index of the B-stage siloxane-based material and also of the cured material. Exemplary non-reactive side groups are methyl, phenyl and mixtures thereof. According to at least one embodiment, the B-stage siloxane- based material has a Vicat softening point of 50°C or higher, for example in the range of 50°C inclusive to 150°C inclusive. According to at least one embodiment, the B-stage siloxane- based material has a curing temperature in a range of 100°C inclusive to 250°C inclusive. When curing, the B-stage siloxane-based material polymerizes and crosslinks into a C-stage material. According to at least one embodiment, the adhesive film has athickness of at least 0.5 µm and of at most -40% to +20% of apeak area roughness of the converter element, in particular2023PF01797 May 20, 2025P2024,0108 WO N -9 -of at least 0.8 µm and of at most -30% to +10% of a peak arearoughness of the converter element. Thus, the thickness of the adhesive film depends on the camber and roughness of the conversion element material being present on the bottomsurface. For example, if the material of the converterelement is smooth, without any camber, the thickness of theadhesive film should be less than 3 μm, preferably less than2 μm. However, if the material of the converter element hascamber or a rough surface, a thicker adhesive film is needed.For example, if the average area roughness (Sa) and peak arearoughness (Sp) of the material of the converter element areabout 1 μm and about 5 μm respectively, then the thickness ofthe adhesive film should be on the order of about 4 μm toabout 6 μm to accommodate that roughness. Such a thickness ofthe adhesive film leads to a homogeneous bondline between the adhesive film and the substrate on which the converter element will be fixed, for example a radiation emitting semiconductor chip. Further, a method for fixing a converter element on a radiation emitting semiconductor chip is provided. The method is suitable for producing and for processing a converter element laminate as described here. Thus, all features and embodiments described with respect to the converter element laminate are also valid for the method and vice versa. According to at least one embodiment, the method for fixing a converter element on a radiation emitting semiconductor chip comprises applying an adhesive film on a bottom surface of a converter element sheet to form a laminate. A converter element sheet is to be understood as a sheet made of converter material that can be singulated to converter2023PF01797 May 20, 2025P2024,0108 WO N -10 -elements in a desired size. For example, the converter element sheet has a size of about 100 cm2, a singulated converter element has a size in a range of about 0.5 mm2to 2,0 mm2, for example 1 mm2. The converter element sheet comprises a top surface and a bottom surface, the singulated converter elements accordingly each comprise a top surface and a bottom surface, both being portions of the top and the bottom surface of the converter element sheet. Applying an adhesive film on the bottom surface of the converter element sheet means in particular on the whole bottom surface of the converter element sheet. Thus, the whole bottom surface of the converter element sheet is covered with an adhesive film after this method step. The properties and characteristics of the adhesive film correspond to the properties and characteristics of the adhesive film discussed with respect to the converter element laminate and apply here accordingly. According to at least one embodiment, the method further comprises singulating the laminate into converter element laminates, wherein each converter element laminate comprises a converter element having a top surface and a bottom surface and an adhesive film on the bottom surface, wherein the adhesive film comprises a B-stage siloxane-based material.Thus, a plurality of converter element laminates as describedabove is produced with this method. As the adhesive film isapplied before singulating the laminate into a plurality ofconverter element laminates, it is possible to produce a converter element laminate wherein the adhesive film and the converter element, at least the bottom surface of the converter element, have the same lateral dimension.2023PF01797 May 20, 2025P2024,0108 WO N -11 -Accordingly, the side surfaces of the adhesive film and theconverter element are matching, i.e., have a smoothtransition. According to least one embodiment, the method further comprises pressing a converter element laminate with the adhesive film on a main emission area of a radiation emittingsemiconductor chip. The radiation emitting semiconductor chipmay be a light emitting diode chip or a laser diode chip. With this step, the converter element is arranged on the main emission area of the radiation emitting semiconductor chip, wherein the adhesive film is arranged between the radiation emitting semiconductor chip and the converter element. According to at least one embodiment, the method for fixing a converter element on a radiation emitting semiconductor chip comprises applying an adhesive film on a bottom surface of a converter element sheet to form a laminate, singulating the laminate into converter element laminates, wherein each converter element laminate comprises a converter element having a top surface and a bottom surface and an adhesive film on the bottom surface, wherein the adhesive film comprises a B-stage siloxane-based material, and pressing a converter element laminate with the adhesive filmon a main emission area of a radiation emitting semiconductorchip. Due to the converter element laminate wherein the adhesive film and at least the bottom surface of the converter element have the same lateral dimensions, the pressing step can be performed without the formation of air voids and without a squeezing out of the adhesive film over the side surfaces of the semiconductor chip and the converter element. Thus, with2023PF01797 May 20, 2025P2024,0108 WO N -12 -this method, a radiation emitting device can be produced, which has a high yield and a high brightness. Additionally, due to the material of the adhesive film, a radiation emitting device with high thermal stability can be produced with this method. According to at least one embodiment, applying the adhesive film on the bottom surface of the converter element sheet comprises applying a solution of the B-stage siloxane-based material on the bottom surface of the converter element sheet and drying the solution to form the adhesive film. Thus, the B-stage siloxane-based material is dissolved in an appropriate solvent before being applied on the bottomsurface. The solvent can be chosen from polar solvents.Exemplary solvents are alcohols like ethanol or isopropanol,hydrocarbons like hexane, octane, isododecane, or toluene, ketones like acetone, methyl ethyl ketone, or dibutyl ketone, esters like ethyl acetate, propyl propionate, butyl acetate, butoxyethyl acetate, or propylene glycol methyl etheracetate, and silanes like dimethyldimethoxysilane,dimethyldiethoxysilane, or methyltrimethoxysilane. Furtherexemplary solvents are acetates, like n-butyl acetate orPGMEA (1-methoxy-2-propylacetate). When drying the solution, the solvent dissipates, and the adhesive film remains on the bottom surface. According to at least one embodiment, the solution further comprises a curing agent. An exemplary curing agent is a mixture of 3-aminopropyltriethoxysilane andtetramethylguanidine. Further exemplary curing agents areselected from the group of Titanium alkoxides (such as Ti butoxide, Ti isopropoxide), Aluminum alkoxides (such as Aluminum s-butoxide bis(ethylacetoacetate)), organic salts of2023PF01797 May 20, 2025P2024,0108 WO N -13 -Tin (such as Bis(2-ethylhexanoate)tin, dibutyltin dilaurate), organic bases (amines, oyridines, guanidines), or acids such as phosphoric acid or p-toluenesulfonic acid. The amount of curing agent in the solution is according to at least oneembodiment in the range of 0 wt% inclusive to 1 wt%inclusive. According to at least one embodiment, applying the adhesive film on the bottom surface of the converter element sheet comprises applying a solution of the B-stage siloxane-based material on a temporary substrate and drying the solution to form the adhesive film. Thus, a solution as described above may be applied on a temporary substrate in order to form an adhesive film on the temporary substrate. Then, according to at least one embodiment, the adhesive film is laminated on the bottom surface of the converter element sheet. In particular, the temporary substrate is removed from the adhesive film before or while laminating. Laminating may be performed at an elevated temperature, for example above theVicat softening temperature of the B-stage siloxane-basedmaterial, but below the curing temperature. According to at least one embodiment, the solution is applied by a method chosen from spraying, slot-die-casting, tape-casting or spin-coating. With these methods, the solution canbe applied on the bottom surface of the converter element sheet or on the temporary substrate, depending on the embodiment. In an alternative embodiment, the B-stage siloxane-based material is applied on the bottom surface of the converter element sheet by molding. Thus, the material is not dissolved but directly applied on the bottom surface to form an2023PF01797 May 20, 2025P2024,0108 WO N -14 -adhesive film there. Molding takes place, for example, at a melting and / or Vicat softening temperature of the B-stage siloxane-based material. According to at least one embodiment, the adhesive film is laminated on the bottom surface of the converter element at atemperature chosen from the range of 50°C inclusive to 150°Cinclusive, in particular from the range of 50°C inclusive to 100°C inclusive, for example from the range of 60°C inclusiveto 80°C inclusive. This means, the adhesive film, that hasbeen formed on the temporary substrate is laminated on the bottom surface at a melting and / or Vicat softening temperature of the B-stage siloxane-based material. According to at least one embodiment, the laminate is singulated at a temperature chosen from the range of room temperature inclusive to below 50°C. Thus, in case of elevated temperatures in the method steps before, the laminate is cooled down, at least to a temperature below the melting and / or Vicat softening temperature range of the B-stage siloxane-based material, in particular cooled down to room temperature. At temperatures below the melting and / or Vicat softening temperature the B-stage siloxane-based material is solid or almost solid and singulating isfacilitated. Singulating may be performed by saw dicing orlaser dicing, for example. Any other method for machiningdown the laminate into individual converter element laminates is suitable as well. According to at least one embodiment, the converter element laminate is pressed on the main emission area of the radiation emitting semiconductor chip at a temperature chosenfrom the range of 50°C inclusive to 150°C inclusive, in2023PF01797 May 20, 2025P2024,0108 WO N -15 -particular from the range of 50°C inclusive to 100°C inclusive, for example from the range of 60°C inclusive to80°C inclusive, for example to 75°C. Thus, the pressing takesplace at a melting and / or Vicat softening temperature rangeof the B-stage siloxane-based material. This means, the adhesive film starts to melt and soften and, thus, to conform to the main emission surface of the radiation emitting semiconductor chip. Exemplary pressures are in the range of 10 g / mm2inclusive to 325 g / mm2inclusive, in particular10 g / mm2 inclusive to 100 g / mm2 inclusive. In this step thefixing of the converter element to the radiation emitting semiconductor chip takes place. According to at least one embodiment, the method further comprises curing the adhesive film after pressing it on the main emission area of the radiation emitting semiconductor chip. In this step the B-stage siloxane-based material crosslinks to a C-stage siloxane-based material which cannot convert to a B-stage material anymore. The cured material issolid and forms a cured adhesive film between thesemiconductor chip and the converter element. According to at least one embodiment, the adhesive film is cured at a temperature chosen from the range of 100°Cinclusive to 250°C inclusive. The curing can take place formore than one hour, for example for two hours. Further, a radiation emitting device is provided. The method for fixing a converter element on a radiation emitting semiconductor chip as described here is suitable to produce a radiation emitting device as described here. Thus, all features and embodiments described with respect to the2023PF01797 May 20, 2025P2024,0108 WO N -16 -converter element laminate and with respect to the method arealso valid for the radiation emitting device and vice versa.According to at least one embodiment, the radiation emitting device comprises a radiation emitting semiconductor chip having a main emission area, and a converter element on the main emission area,wherein a cured adhesive film is arranged completely betweenthe main emission area of the radiation emitting semiconductor chip and the converter element, wherein the cured adhesive film comprises a content of T-unit siloxane groups in the range of at least 50%. The radiation emitting semiconductor chip may be a light emitting diode chip or a laser diode chip. According to at least one embodiment the light emitting device is a light emitting diode (LED). In particular, the radiation emitting semiconductor chip comprises an epitaxial grown semiconductor layer sequence with an active region being able to generateelectromagnetic radiation. For example, the active regioncomprises a pn-junction or a quantum well structure. The converter element is applied on the main emission area of the radiation emitting semiconductor chip such that radiation emitted from the semiconductor chip reaches at least partially the converter element. The converter element can be a type chosen from ceramic, phosphor-in-glass, phosphor-in-polymer, phosphor-in-polymer- on-substrate or any hybrid combination thereof. Furthermore, the converter element can have any geometrical form, for example a platelet. In particular, the converter element comprises a top surface and a bottom surface, wherein the2023PF01797 May 20, 2025P2024,0108 WO N -17 -bottom surface faces the semiconductor chip and the top surface faces away from the semiconductor chip. A phosphor being contained in the converter element is according to at least one embodiment chosen from a groupconsisting of (RE1-xCex)3(Al1-yA´y)5O12 with 0 < x ≤ 0.1 and 0 ≤y ≤ 1, (RE1-xCex)3(Al5-2yMgySiy)O12 with 0 < x ≤ 0.1 and 0 ≤ y ≤2, (RE1-xCex)3Al5-ySiyO12-yNy with 0 < x ≤ 0.1 and 0 ≤ y ≤ 0.5,(RE Ce ) C 3+1-x x 2 aMg2Si3O12:Ce with 0 < x ≤ 0.1, (AE1-xEux)2Si5N8 with0 < x ≤ 0.1, (AE1-xEux)AlSiN3 with 0 < x ≤ 0.1, (AE1-xEux)2Al2Si2N6 with 0 < x ≤ 0.1, (Sr1-xEux)LiAl3N4 with 0 < x ≤0.1, (AE1-xEux)3Ga3N5 with 0 < x ≤ 0.1, (AE1-xEux)Si2O2N2 with 0< x ≤ 0.1, (AExEuy)Si12-2x-3yAl2x+3yOyN16-y with 0.2 ≤ x ≤ 2.2 and0 < y ≤ 0.1, (AE1-xEux)2SiO4 with 0 < x ≤ 0.1, (AE1-xEux)3Si2O5with 0 < x ≤ 0.1, K2(Si1-x-yTiyMnx)F6 with 0 < x ≤ 0.2 and 0 < y≤ 1-x, (AE1-xEux)5(PO4)3Cl with 0 < x ≤ 0.2, (AE1-xEux)Al10O17with 0 < x ≤ 0.2, wherein RE is one or more of Y, Lu, Tb andGd, AE is one or more of Mg, Ca, Sr, Ba, A´ is one or more of Sc and Ga, Eu (II)-doped ^-SiAlON and combinations thereof. Other luminescent materials having dopants like Cr3+, Ni2+, Co2+, Cu2+or other optically active dopants are possible materials as well. These phosphors are able to absorb in the near-UV to blue region of the electromagnetic spectrum and emit in the visible to near-IR region of the electromagnetic spectrum. The phosphor can be chosen depending on the desiredcolor point, and other spectral properties.A complete arrangement of the cured adhesive film between the main emission area of the radiation emitting semiconductor chip and the converter element means, that there are at least no air voids between the semiconductor chip and the converterelement, but the bondline is completely filled with the cured2023PF01797 May 20, 2025P2024,0108 WO N -18 -adhesive film. This serves for a high reliability and highyields of a radiation emitting device as described here. The cured adhesive film is according to at least one embodiment a cured siloxane-based film resulting from curing a B-stage siloxane-based material as described here. Thus, the cured adhesive film has a close-meshed network of siloxane-groups and a lower oxygen content than, for example,traditional silicone glues. Additionally, such a curedsiloxane-based film has a high thermal stability. Therefore, the radiation emitting device as described here is suitable for applications at high temperatures, in particular at temperatures higher than 200°C, for example at 250°C. According to at least one embodiment, the radiation emitting semiconductor chip, the cured adhesive film and the converterelement comprise laterally equidimensional side surfaces.Thus, the cured adhesive film does neither go beyond withrespect to the semiconductor chip and the converter element nor is it set back with respect to the semiconductor chip and the converter element. Thus, if neither any additionalmaterial of the radiation emitting device, such as, forexample, a reflector material being applied around the radiation emitting semiconductor chip and the converterelement, nor air can fill in between the radiation emittingsemiconductor chip and the converter element, a loss of yieldby blocking radiation or undesired color-over-spaceproperties can be avoided. Additionally, due to the conciseside surfaces of the radiation emitting semiconductor chip, the cured adhesive film and the converter element, there is no adhesive material going beyond the side surfaces and forming an undesired optical path for the primary radiation that would then be absorbed and not converted anymore.2023PF01797 May 20, 2025P2024,0108 WO N -19 -Therefore, a radiation emitting device as describe here, has a high reliability and a high yield. According to at least one embodiment, the radiation emittingsemiconductor chip comprises a micro-LED. In particular, theradiation emitting semiconductor chip is a micro-LED. Micro-LEDs may have a length, a width, a thickness and / or a cross section being smaller than or equal to 100 µm, in particular smaller than or equal to 70 µm, for example, smaller than or equal to 50 µm. In particular, micro-LEDs, for example rectangular micro-LEDs, comprise an edge length of an emission area, in particular in plan view of the layersof the layer sequence, smaller than or equal to 70 µm, forexample smaller than or equal to 50 µm. A micro-LED is, for example, a light emitting diode wherein the growing substrate is removed, so that a thickness of the micro-LED is for example in a range of 1.5 µm inclusive to 10 µm inclusive. Advantageous embodiments and developments of the converter element, the method for producing the converter element, and the radiation emitting device will become apparent from the exemplary embodiments described below in conjunction with the figures.Figure 1 shows a schematic cross section of a converterelement before being fixed on a radiation emitting semiconductor chip.Figure 2a shows a schematic cross section of a radiationemitting device according to a reference example.2023PF01797 May 20, 2025P2024,0108 WO N -20 -Figure 2b shows a schematic cross section of a radiationemitting device according to a reference example.Figure 3 shows a schematic cross section of a radiationemitting device according to an embodiment. Figures 4a to 4d show schematic cross sections of method steps for fixing a converter element on a radiation emittingsemiconductor chip according to various embodiments.In the exemplary embodiments and figures, similar or similarly acting constituent parts are provided with the same reference symbols. The elements illustrated in the figures and their size relationships among one another should not be regarded as being true to scale. Rather, individual elements may be represented with an exaggerated size for the sake of better representability and / or for the sake of better understanding.Figure 1 shows a schematic cross section of a converterelement 30 before being fixed on a radiation emitting semiconductor chip 20. The semiconductor chip 20 is applied on a substrate 10 and has on its surface facing away from the substrate 10 its main emission area 22 which is surrounded bya metallization 21. The converter element 30 can be in theform of a ceramic, a phosphor-in-glass, a phosphor-in- polymer, a phosphor-in-polymer-on-substrate or any hybrid combination thereof. For example, the converter element 30 is of the phosphor-in- polymer-on-substrate type. In this specific example, the converter element 20 comprises a two-layer system, wherein the top layer is a borosilicate glass, and the bottom layer2023PF01797 May 20, 2025P2024,0108 WO N -21 -is a composite of phosphor powder, and optional silica fillers, dispersed in a polysiloxane matrix. The phosphor powder can be chosen from a group consisting of (RE1-xCex)3(Al1-yA´y)5O12 with 0 < x ≤ 0.1 and 0 ≤ y ≤ 1, (RE1-xCex)3(Al5-2yMgySiy)O12 with 0 < x ≤ 0.1 and 0 ≤ y ≤ 2, (RE1-xCex)3Al5-ySiyO12-yNy with 0 < x ≤ 0.1 and 0 ≤ y ≤ 0.5, (RE1-xCex)2CaMg2Si3O12:Ce3+ with 0 < x ≤ 0.1, (AE1-xEux)2Si5N8 with 0 <x ≤ 0.1, (AE1-xEux)AlSiN3 with 0 < x ≤ 0.1, (AE1-xEux)2Al2Si2N6with 0 < x ≤ 0.1, (Sr1-xEux)LiAl3N4 with 0 < x ≤ 0.1, (AE1-xEux)3Ga3N5 with 0 < x ≤ 0.1, (AE1-xEux)Si2O2N2 with 0 < x ≤ 0.1,(AExEuy)Si12-2x-3yAl2x+3yOyN16-y with 0.2 ≤ x ≤ 2.2 and 0 < y ≤0.1, (AE1-xEux)2SiO4 with 0 < x ≤ 0.1, (AE1-xEux)3Si2O5 with 0 <x ≤ 0.1, K2(Si1-x-yTiyMnx)F6 with 0 < x ≤ 0.2 and 0 < y ≤ 1-x,(AE1-xEux)5(PO4)3Cl with 0 < x ≤ 0.2, (AE1-xEux)Al10O17 with 0 < x≤ 0.2, wherein RE is one or more of Y, Lu, Tb and Gd, AE isone or more of Mg, Ca, Sr, Ba, A´ is one or more of Sc and Ga, Eu (II)-doped ^-SiAlON and combinations thereof. Other luminescent materials having dopants like Cr3+, Ni2+, Co2+, Cu2+or other optically active dopants are possible materials as well. The radiation emitting semiconductor chip 20 comprises anepitaxially grown semiconductor layer sequence with an activeregion. The active region can emit electromagnetic radiation, the primary radiation. The primary radiation has wavelengths, for example, from the UV or blue spectral range. The electromagnetic radiation produced in the active region leaves the radiation emitting semiconductor chip 20 throughthe main emission area 22. In a completed radiation emittingdevice, the primary radiation is at least partly absorbed by the phosphor in the converter element 30 and converted into secondary radiation, i.e., radiation of another wavelength.2023PF01797 May 20, 2025P2024,0108 WO N -22 -Figures 2a and 2b show reference examples of radiationemitting devices 250, wherein the converter element 30 is fixed to the radiation emitting semiconductor chip 20 with a conventional silicone glue 60. For fixing the converter element 30 to the radiation emitting semiconductor chip 20, the glue 60 is dispensed onto the radiation emitting semiconductor chip 20. Then the converter element 30 is placed onto the uncured glue droplet(s). After the converter element 30 is placed, the glue 60 is cured. Figure 2a shows the case of too little glue 60. After the fixation of the converter element 30 a reflector 50, forexample a white reflector 50, can be placed around thesequence of radiation emitting semiconductor chip 20 and converter element 30. As there is too little glue 60 between the radiation emitting semiconductor chip 20 and theconverter element 30, and, thus, air voids between them, thesurrounding material of the reflector 50 fills in the area between the radiation emitting semiconductor chip 20 and the converter element 30. However, the material of the reflector 50 blocks the radiation and leads to undesired color-over- space properties, typically resulting in yield loss. Such a device has to be discarded.Figure 2b shows the case of too much glue 60. During theprocedure of fixing the converter element 30 on the radiation emitting semiconductor chip 20, the glue 60 has squeezed out from between the radiation emitting semiconductor chip 20 and the converter element 30. The squeezed-out glue provides an optical path for radiation emitted by the radiation emitting semiconductor chip 20 to propagate to the metal 21 surrounding the radiation emitting semiconductor chip 20 and be absorbed by those metals 21, for example.2023PF01797 May 20, 2025P2024,0108 WO N -23 -Figure 3 shows a cross section of a radiation emitting device200 according to an exemplary embodiment, wherein theconverter element 30 is fixed to the radiation emittingsemiconductor chip 20 with a cured adhesive film 40. Thecured adhesive film 40 covers the entire main emission area22, and proceeds to the edge of the main emission area 22, but not beyond. Additionally, there are no voids between radiation emitting semiconductor chip 20 and converterelement 30. Thus, neither material of a reflector 50 nor airor other material in case of no reflector (not shown here)may fill in between the radiation emitting semiconductor chip20 and the converter element 30 and lead to a loss of yield by blocking radiation or leading to undesired color-over- space properties. Additionally, due to the concise side surfaces of the radiation emitting semiconductor chip 20, the cured adhesive film 40 and the converter element 30, there is no adhesive material going beyond the side surfaces and forming an undesired optical path for light that would then be absorbed by metals 21 as shown here, or in case of no metals 21 (not shown here) by any other environments. Thus, with a cured adhesive film 40 the disadvantages of conventional silicone glue can be overcome. As the cured adhesive film 40 is based on a siloxane-based material with a content of T-unit siloxane groups in the range of at least 50%, the cured adhesive film 40 is additionally thermally stable, such that the radiation emitting device 200 has a high reliability also in high temperature applications at temperatures of, for example, 250°C or more. Figures 4a to 4d show schematic cross sections of methodsteps for fixing a converter element 30 to a radiation2023PF01797 May 20, 2025P2024,0108 WO N -24 -emitting semiconductor chip 20 in order to produce a radiation emitting device 200. Figure 4a shows a first step, wherein a converter elementsheet 31 and an adhesive film 41 are provided and laminatedtogether. The adhesive film 41 comprises a B-stage siloxane- based material with a content of T-unit siloxane groups in the range of at least 50%. This material is solid at room temperature, has a Vicat softening point at 50°C or higher, for example in the range of 50°C inclusive to 150°Cinclusive, and / or a melting temperature in the range of 50°Cinclusive to 150°C inclusive. A curing temperature of thismaterial is in the range of 100°C inclusive to 250°Cinclusive. Table 1 shows possible compositions of such a B-stage material: Group Type(s) Relative Range WithinGroup T-unit 50% to 100% Siloxane D-unit 0% to 50% Silanol 0% to 100% Reactive side group Methoxy 0% to 100% for cross-linking Ethoxy 0% to 100% Non-reactive side Methyl 0% to 100% group Phenyl 0% to 100% Table 1 In the exemplary embodiment described here, the B-stage siloxane-based material of the adhesive film 41 is composed of a T-unit methyl siloxane with about 3% to 5% silanol groups. This material is solid at room temperature and has a melting and / or Vicat softening temperature in the range of 65°C to 75°C.2023PF01797 May 20, 2025P2024,0108 WO N -25 -To produce an adhesive film 41 a solution of the siloxane-based material in an appropriate solvent like n-butyl acetateand optionally a small amount of a curing agent is prepared. As a curing agent a mixture of 3-aminopropyltriethoxysilane and tetramethylguanidine in an amount of less than 1 wt% is used in this exemplary embodiment. The solution is eitherapplied directly to the bottom surface 311 of the converterelement sheet 31, or on a temporary substrate. Theapplication of the solution is performed by slot-die coating, tape casting, spraying, spin coating, or any other method suitable for making a thin polymer film. After drying thesolution, the adhesive film 41 remains on the bottom surface311 of the converter element sheet 31 or on the temporarysubstrate. In figure 4a, the adhesive film 41 is prepared on a temporary substrate, delaminated from the temporary substrate andlaminated on the bottom surface 311 of the converter elementsheet 31. The lamination on the bottom surface 311 of theconverter element sheet 31 is performed at the melting and / orVicat softening temperature T1, in order to fix the adhesivefilm 41 to the bottom surface 311 of the converter elementsheet 31. At such a temperature T1, the adhesive film 41 alsoconforms to the bottom surface 311 of the converter elementsheet 31 leading to a smooth bondline between converterelement sheet 31 and adhesive film 41.The thickness of the adhesive film 41 is chosen in dependence of the surface properties of the converter element sheet 31. In case of cambers and roughness the thickness of the adhesive film 41 is chosen higher than in case of a smooth surface of the converter element sheet 31. The thickness isfor example at least 0.5 µm and at most -40% to +20% of the2023PF01797 May 20, 2025P2024,0108 WO N -26 -peak roughness of the material of the converter element sheet 31. In a next step, as shown in figure 4b, the laminate of converter element sheet 31 and adhesive film 41 is singulated to form converter element laminates 100. The singulation is performed at room temperature which is marked as T0. At T0 the adhesive film 41 is solid and can be easily singulated, for example by saw dicing or laser dicing. While the laminate of converter element sheet 31 and adhesive film 41 haslengths and widths of about 10 cm, the lengths and widths ofthe converter element laminate 100 are in the order of 0.5 mm to 2.0 mm. Due to the common dicing of converter element sheet 31 and adhesive film 41, converter element laminates 100 are resulting, that have concise side surfaces of the singulated converter element 30 and the laminated adhesivefilms 41 on the bottom surface 301 of the converter element30. Figure 4c shows the next step. The converter element laminate 100 is moved with the aid of a carrier 70 to and above a radiation emitting semiconductor chip 20 which is arranged ona substrate 10. The temperature is raised again to T1, i.e.,the melting and / or Vicat softening temperature of the B-stagesiloxane-based material of the adhesive film 41. In thisexample, T1 is 75°C. At T1 the adhesive film 41 starts to melt and soften. When pressing the adhesive film 41 on the main emission area 22 of the radiation emitting semiconductor chip 20, the adhesive film 41 conforms to the main emission area 22. Thus, no voids arise between the converter element 30 and the radiation emitting semiconductor chip 20. Additionally, as the amount of adhesive film 41 is chosen so that the adhesive film 41 fully covers the bottom surface of2023PF01797 May 20, 2025P2024,0108 WO N -27 -the converter element 30 but does not go beyond, there is nosqueeze out of adhesive film 41 while pressing.Figure 4d shows an additional step, where the adhesive film 41 is cured at its curing temperature T2. In this example, the curing temperature is equal to or greater than 100°C. T2is hold for two hours in this example. At T2, the B-stageproperties of the siloxane-based material are lost, and acured adhesive film 40, i.e., a C-stage material results.The features and exemplary embodiments described in connection with the figures can be combined with each other according to further exemplary embodiments, even if not all combinations are explicitly described. Furthermore, the exemplary embodiments described in connection with the figures may have alternative or additional features as described in the general part. The invention is not restricted to the exemplary embodiments by the description on the basis of said exemplary embodiments. Rather, the invention encompasses any new feature and also any combination of features, which in particular comprises any combination of features in the patent claims and any combination of features in the exemplary embodiments, even if this feature or this combination itself is not explicitly specified in the patent claims or exemplary embodiments.This patent application claims the priority of US patentapplication 63 / 651,237, the disclosure content of which ishereby incorporated by reference.2023PF01797 May 20, 2025P2024,0108 WO N -28 -References10 substrate20 radiation emitting semiconductor chip21 metal22 main emission area30 converter element301 bottom surface31 converter element sheet311 bottom surface40 cured adhesive film41 adhesive film50 reflector60 glue70 carrier100 converter element laminate200 radiation emitting device250 reference radiation emitting deviceT0 room temperatureT1 melting and / or Vicat softening temperatureT2 curing temperature

Claims

2023PF01797 May 20, 2025P2024,0108 WO N -29 -Claims1. A converter element laminate (100), comprising:a converter element (30) having a top surface and a bottomsurface (301),and an adhesive film (41) on the bottom surface (301),wherein the adhesive film (41) comprises a B-stage siloxane-based material.

2. The converter element laminate (100) according to claim 1,wherein the bottom surface (301) of the converter element(30) has a lateral dimension that corresponds to a lateraldimension of the adhesive film (41).

3. The converter element laminate (100) according to any of the preceding claims, wherein the B-stage siloxane-basedmaterial has a melting temperature and / or Vicat softeningpoint in the range of 50°C inclusive to 150°C inclusive.

4. The converter element laminate (100) according to any of the preceding claims, wherein the B-stage siloxane-based material is semi-cured.

5. The converter element laminate (100) according to any ofthe preceding claims, wherein the B-stage siloxane-based material comprises a content of T-unit siloxane groups in the range of at least 50%.

6. The converter element laminate (100) according to any ofthe preceding claims, wherein the adhesive film (41) has athickness of at least 0.5 µm and of at most -40% to +20% of apeak area roughness of the converter element (30).2023PF01797 May 20, 2025P2024,0108 WO N -30 -7. A method for fixing a converter element (30) on aradiation emitting semiconductor chip (20), the methodcomprising:applying an adhesive film (41) on a bottom surface (311) of aconverter element sheet (31) to form a laminate,singulating the laminate into converter element laminates(100), wherein each converter element laminate (100)comprises a converter element (30) having a top surface and abottom surface (301) and an adhesive film (41) on the bottomsurface (301), wherein the adhesive film (41) comprises a B-stage siloxane-based material, andpressing a converter element laminate (100) with the adhesivefilm (41) on a main emission area (22) of a radiationemitting semiconductor chip (20).

8. The method according to claim 7, wherein applying theadhesive film (41) on the bottom surface (311) of theconverter element sheet (31) comprises applying a solution ofthe B-stage siloxane-based material on the bottom surface(311) of the converter element sheet (31) and drying thesolution to form the adhesive film (41).

9. The method according to claim 7, wherein applying theadhesive film (41) on the bottom surface (311) of theconverter element sheet (31) comprises applying a solution ofthe B-stage siloxane-based material on a temporary substrateand drying the solution to form the adhesive film (41).

10. The method according to claim 9, wherein the adhesivefilm (41) is laminated on the bottom surface (311) of theconverter element sheet (31).2023PF01797 May 20, 2025P2024,0108 WO N -<sub>31 -11. The method according to any one of claims 8 to 10,wherein the solution is applied by a method chosen fromspraying, slot-die-casting, tape-casting or spin-coating.

12. The method according to claim 10, wherein the adhesivefilm (41) is laminated on the bottom surface (301) of theconverter element (30) at a temperature chosen from the rangeof 50°C inclusive to 150°C inclusive.

13. The method according to any of claims 7 to 12, whereinthe laminate is singulated at a temperature chosen from therange of room temperature inclusive to below 50°C.

14. The method according to any of claims 7 to 13, whereinthe converter element laminate (100) is pressed on the mainemission area (22) of the radiation emitting semiconductorchip (20) at temperature chosen from the range of 50°Cinclusive to 150°C inclusive.

15. The method according to any of claims 7 to 14, furthercomprising curing the adhesive film (41) after pressing it onthe main emission area (22) of the radiation emittingsemiconductor chip (20).

16. The method according to claim 15, wherein the adhesivefilm (41) is cured at a temperature chosen from the range of100°C inclusive to 250°C inclusive.

17. A radiation emitting device (200), comprisinga radiation emitting semiconductor chip (20) having a mainemission area (22), anda converter element (30) on the main emission area (22),2023PF01797 May 20, 2025P2024,0108 WO N -32 -wherein a cured adhesive film (40) is arranged completelybetween the main emission area (22) of the radiation emittingsemiconductor chip (20) and the converter element (30),wherein the cured adhesive film (40) comprises a content ofT-unit siloxane groups in the range of at least 50%.

18. The radiation emitting device (200) according to claim17, wherein the radiation emitting semiconductor chip (20),the cured adhesive film (40) and the converter element (30)comprise laterally equidimensional side surfaces.

19. The radiation emitting device (200) according to any ofclaims 17 and 18, wherein the radiation emittingsemiconductor chip (20) comprises a micro-LED.

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