Patent ID: 12211964

Elements that are identical, similar or have the same effect are given the same reference signs in the figures. The figures and the proportions of the elements shown in the figures are not to be regarded as true to scale. Rather, individual elements, in particular layer thicknesses, may be shown exaggeratedly large for better representability and/or understanding.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

FIG.1shows a schematic sectional view of a radiation emitting device1comprising a semiconductor chip2which, in operation, emits electromagnetic radiation of a first wavelength range from a radiation exit surface3. Further, the radiation emitting device1comprises a potting4comprising a matrix material5and a plurality of nanoparticles6. The semiconductor chip2is surrounded by the potting4. The surface of the semiconductor chip2opposite to the radiation exit surface3is disposed on a carrier element22for stabilization and is not surrounded by the potting4. The concentration of the nanoparticles6in the matrix material5decreases starting from the radiation exit surface3of the semiconductor chip2, so that a refractive index of the potting4decreases continuously starting from the radiation exit surface3of the semiconductor chip2. That is, a portion of the potting4adjacent to the radiation exit surface3of the semiconductor chip2has a larger refractive index than a portion of the potting4located farther away from the semiconductor chip2.

The matrix material5is selected from the group of polysiloxanes. Polysiloxanes are organosilicon compounds in which two silicon atoms are bonded to one another via an oxygen atom. Preferably, polysiloxanes have an organic group on the silicon atom. For example, the organic group is a methoxy, methyl, phenyl, or phenoxy group. The organic group of the polysiloxanes affects the refractive index of the matrix material. The polysiloxanes exhibit a high thermal stability and stability to the electromagnetic radiation of the semiconductor chip2.

The nanoparticles6comprise a material or consist of a material selected from the group of metal oxides. The diameter of the nanoparticles6is not greater than 10 nanometers.

The radiation emitting device1according to the exemplary embodiment ofFIG.2comprises a semiconductor chip2, a carrier element22, a conversion layer9and a particle layer10. In operation, the semiconductor chip2emits electromagnetic radiation of a first wavelength range from a radiation exit surface3. The semiconductor chip2is embedded in the conversion layer9. The conversion layer9comprises phosphor particles8and a matrix material5. The particle layer10is in direct contact with the conversion layer9. The particle layer10comprises a matrix material5and nanoparticles6. The particle layer10and the conversion layer9together form the potting4. The conversion layer may also comprise nanoparticles6and the particle layer10may comprise phosphor particles8.

The concentration of the nanoparticles6and the phosphor particles8in the matrix material5of the potting4decreases starting from the radiation exit surface3of the semiconductor chip2, so that a refractive index of the potting4decreases starting from the radiation exit surface3of the semiconductor chip2.

In the conversion layer9, phosphor particles8are embedded in the matrix material5. These convert electromagnetic radiation of the first wavelength range into electromagnetic radiation of a second wavelength range. In other words, the phosphor particles8impart wavelength-converting properties to the potting4. The phosphor particles8comprise or are formed from a garnet phosphor and/or a nitride phosphor. Furthermore, the phosphor particles8have a larger diameter than the nanoparticles6. In the present case, the phosphor particles8have a diameter between 1 micrometer inclusive and 30 micrometers inclusive.

FIG.3shows a schematic sectional view of a nanoparticle6according to an exemplary embodiment. The nanoparticle6is coated with a shell7. The shell7comprises a silicone and/or silicon dioxide or consists of a silicone and/or silicon dioxide. Preferably, the shell7is formed thin. “Thin” in this context means that the shell has a thickness between at least 1 nanometer and at most 5 nanometers. Advantageously, the shell7leads to a reduction in the agglomeration of nanoparticles6in the matrix material5. A homogeneous distribution of the nanoparticles6in the matrix material5is consequently improved.

In the method according to the exemplary embodiment ofFIGS.4to8, a cavity11is provided in a first step (FIG.4). The semiconductor chip2, which in operation emits electromagnetic radiation of a first wavelength range from a radiation exit surface3, is introduced into the cavity11. The surface of the semiconductor chip2opposite the radiation exit surface3is arranged on a carrier element22for mechanical stabilization and is not surrounded by the potting4.

In a next step, a first liquid potting material12comprising nanoparticles6, phosphor particles8and a first matrix material14is introduced into the cavity11. Here, the semiconductor chip2is surrounded by the first liquid potting material12. The first liquid potting material12may be introduced into the cavity11by spray coating or by casting.

In a further step, a second liquid potting material13is introduced into the cavity11by casting or spray coating (FIG.6). The second liquid potting material13comprises a second matrix material15and is presently free of nanoparticles6and free of phosphor particles8. The matrix materials14and15may be the same. The first liquid potting material is not cured while the second liquid potting material is applied.

In a next step, the first liquid potting material12mixes with the second liquid potting material13so that the concentration of the nanoparticles6and the phosphor particles8in the matrix material5, starting from the radiation exit surface3of the semiconductor chip2, decreases. As a result, a refractive index of the potting4, starting from the radiation exit surface3of the semiconductor chip, decreases (FIG.7). Simultaneously or alternatively, the nanoparticles6and the phosphor particles8sediment in the matrix material5due to the gravitational force acting on them. Due to the generally larger diameter and a larger weight of the phosphor particles8in relation to the diameter and a weight of the nanoparticles6, the sedimentation of the phosphor particles8here leads to an arrangement in which the phosphor particles8are arranged closer to the radiation exit surface3of the semiconductor chip2than the nanoparticles6. The first matrix material14and the second matrix material15have a low viscosity in the liquid state.

As shown inFIG.8, in a final step of the method, the liquid potting material12and13is cured after sedimentation and/or mixing. For example, the liquid potting material12and13is cured at about 150° C. to form a potting4. In this method, the potting4is formed.

In the conventional method shown inFIG.9, a centrifuge16is used. A plurality of devices1are arranged on a flat carrier17. The plurality of devices1are rotated on the carrier17about a pivot point19. The distances20between a pivot point19and a center point of each device18are different from each other. A centrifugal force direction21of the centrifugal force acting on the devices1is indicated by arrows. The centrifuge16is capable of conveying the nanoparticles6to the vicinity of the radiation exit surface3of the semiconductor chip2by a centrifugal force due to a uniform circular motion of the carrier around the pivot point19.

FIG.10shows a section marked A inFIG.9, in which a base surface of the device1is perpendicular to the centrifugal force direction21and thus feels an almost homogeneous centrifugal force over an entire base surface. This arrangement leads to an almost homogeneous sedimentation of the nanoparticles in the liquid potting material.

FIG.11shows a section marked B inFIG.9, which is different from section A. The base surface of the device1according toFIG.11is not perpendicular to the centrifugal force direction21, but encloses an acute angle with the centrifugal force direction21. Thus, the device1according toFIG.9feels an inhomogeneous centrifugal force over its entire base surface. This arrangement leads to inhomogeneous sedimentation of the nanoparticles in the liquid potting material.

In the method according to the exemplary embodiment ofFIG.12, a plurality of devices1are arranged on a curved carrier17. A center point18of each device1to the pivot point19of the centrifuge16has the same distance20to the pivot point19of the centrifuge16. In this case, a shorter distance20between the pivot point19and the center point of each device18can be selected with advantage, which results in a high centrifugal force. Thus, the nanoparticles6can be sedimented more easily and more quickly, which leads to a uniform layer formation during the sedimentation.

The invention is not limited to these by the description based on the exemplary embodiments. Rather, the invention encompasses any new feature as well as any combination of features, which in particular includes any combination of features in the patent claims, even if this feature or combination itself is not explicitly stated in the patent claims or exemplary embodiments.