SUBSTRATE WITH INTEGRATED SURGE PROTECTION

Description

[0001] The present invention relates to a substrate comprising a ceramic base body.

[0002] Substrates are widely used components in industrial manufacturing for mounting and connecting microelectronic components, such as integrated circuits, and power semiconductors, such as LEDs. These mounted microelectronic components and power semiconductors can then be easily integrated into other electronic components.

[0003] Examples of such substrates are disclosed in US 5396034 A or US 2005 / 263867 A1.

[0004] Due to the ever-increasing demands for miniaturization and performance of electronic components, it is necessary to increase the number of microelectronic components and power semiconductors that can be mounted on a given substrate area. This results in higher demands on the substrate itself, specifically regarding the number of cross-connections within that area and the thermal conductivity of the substrate materials. The thermal conductivity of the substrate material is a particularly important factor. As the number of microelectronic components and power semiconductors that need to be mounted on the substrate increases, the heat generated by these components must be dissipated more efficiently to prevent overheating.

[0005] Conventional substrates often consist of polymer-based composite materials that, while allowing for a sufficiently high number of rewires, exhibit very low thermal conductivity. This limits the number of microelectronic components and power semiconductors that can be mounted on the substrate, despite the high number of rewires, and hinders further miniaturization.

[0006] A sufficiently high number of rewirings is defined here and in the following as a number of rewirings that makes it possible to increase the number of microelectronic components and power semiconductors that can be installed on the given area of ​​the substrate to such an extent that miniaturization and / or performance improvement of the other components can be achieved.

[0007] To improve thermal conductivity, substrates with metallic inlays are conventionally used. Due to their design, such substrates do not allow through-holes or rewiring within the metallic inlays, which reduces the number of microelectronic components and power semiconductors that can be integrated into the given substrate area. This hinders further miniaturization. Furthermore, the thermal conductivity of such substrates is limited to 7 to 8 W / m·K, which also impedes further miniaturization and performance improvements.

[0008] The object of the present invention is therefore to provide a substrate that has a thermal conductivity greater than 8 W / m·K and that enables a sufficiently high number of rewiring operations to be provided.

[0009] These problems are solved according to the invention by a substrate according to claim 1. Further embodiments of the substrate can be found in further claims.

[0010] According to the invention, a substrate is provided that has a ceramic base body and an organic surface structure on at least one first outer surface of the ceramic base body. External wiring is integrated into the organic surface structure. The combination of a ceramic base body with an organic surface structure allows the advantages of both materials to be combined. For example, the ceramic base body exhibits a thermal conductivity that is significantly higher than that of a conventional polymer-based substrate. On the other hand, the organic surface structure allows for the production of a sufficiently high number of external wiring elements, which enables further miniaturization and an increase in performance.

[0011] Furthermore, the organic surface structure of the substrate according to the invention can comprise a plurality of organic layers. A multilayered structure of the organic surface allows, compared to a single-layer structure, a further increase in the number of external cross-connections on a given area of ​​the substrate according to the invention. This allows the number of integrated microelectronic components and power semiconductors on the given area of ​​the substrate according to the invention to be further increased, thereby enabling further miniaturization. Moreover, the higher number of microelectronic components and power semiconductors integrated on the given area of ​​the substrate according to the invention also improves the performance of other components that comprise the substrate according to the invention with the microelectronic components and power semiconductors integrated thereon.For example, the number of LEDs in an LED module with a given area can be increased, thereby improving the properties of the LED module.

[0012] Furthermore, the organic layers of the organic surface structure of the substrate according to the invention can each contain different organic materials as their main component. In other words, each organic layer can have a different composition. This allows the properties of the organic layers, such as thermal expansion, optical absorption, and reflection, to be tailored to meet the desired requirements.

[0013] In particular, the main component of the organic surface structure of the substrate according to the invention can be selected from a group comprising photoresists and filled polymers.

[0014] A filled polymer is a polymer that contains a filler which improves the polymer's properties. In one embodiment of the substrate according to the invention, the main component of the organic surface structure can comprise a filled polymer that is filled with ceramic particles to increase its thermal conductivity. This allows the microelectronic components and power semiconductors mounted on the substrate according to the invention to be even better protected against overheating.

[0015] By using a photoresist, the organic surface structure of the substrate according to the invention can be formed very simply and precisely. This allows the distances between individual rewiring connections to be made so small that further miniaturization and / or performance improvements are possible.

[0016] According to the invention, a passivation layer is applied to the first outer surface of the ceramic substrate. The organic surface structure is applied to this passivation layer. In other words, the passivation layer is located between the first outer surface of the ceramic substrate and the organic surface structure. The arrangement of the passivation layer and the organic surface structure described above can be applied analogously to more than one outer surface of the ceramic substrate.

[0017] The passivation layer protects the ceramic substrate from potential corrosion that can occur during the production of the organic surface structure, for example, due to the solvents used. The passivation layer primarily consists of an inorganic material selected from a group including SiO₂, SiN, and AlN.

[0018] Furthermore, the organic surface structure of the substrate according to the invention can have a coefficient of thermal expansion that corresponds to that of the ceramic base body. The deviation of the coefficient of thermal expansion of the organic surface structure relative to the coefficient of thermal expansion of the ceramic base body is a maximum of ± 1 ppm / K. In particular, the organic surface structure can have a coefficient of thermal expansion in the range between 2 ppm / K and 12 ppm / K. Due to the very similar coefficients of thermal expansion of the organic surface structure and the ceramic base body of the substrate according to the invention, stresses between the organic surface structure and the ceramic base body during thermal stress, for example from the heat emitted by a power semiconductor, are largely avoided.This results in a longer service life of the substrate according to the invention.

[0019] Furthermore, the ceramic substrate of the inventive substrate can have a thermal conductivity of more than 8 W / m·K. In more advantageous embodiments of the inventive substrate, the ceramic substrate can have a thermal conductivity of more than 20 W / m·K, in particular more than 100 W / m·K. Such high thermal conductivity makes it possible to efficiently dissipate the heat generated by the microelectronic components and power semiconductors mounted on the substrate. This virtually eliminates overheating of the components mounted on the substrate, thereby enabling further miniaturization and / or increased performance.

[0020] In order to enable such a high thermal conductivity of the ceramic base body of the substrate according to the invention, the main component of the ceramic base body can be selected from a group comprising ZnO-Bi, ZnO-Pr, Al 2 O 3 and AlN.

[0021] Furthermore, the ceramic base body of the substrate according to the invention can contain a thermally conductive functional ceramic as its main component. Functional ceramics are ceramics whose properties have been optimized for an application in a specific technical field. For example, a functional ceramic can exhibit electrical conductivity that increases with rising temperature. The ceramic base body of the substrate according to the invention can comprise a functional ceramic as its main component, selected from the group consisting of ceramics with negative temperature coefficients (NTC ceramics), positive temperature coefficients (PTC ceramics), and varistor ceramics.

[0022] In particular, the use of a varistor ceramic makes it possible to implement overvoltage protection within the ceramic base body of the substrate according to the invention. This eliminates the need for a discrete component mounted on the substrate to provide overvoltage protection. As a result, the substrate according to the invention, including the microelectronic components and power semiconductors mounted on it, can be designed more compactly.

[0023] Furthermore, the ceramic substrate body according to the invention can have internal rewiring and vias. In particular, the presence of internal rewiring makes it possible to integrate highly stressed conductors, such as power lines to the power semiconductors or integrated circuits, into the ceramic substrate body according to the invention. Since the ceramic substrate body according to the invention has a higher thermal conductivity than conventional polymer-based substrates, the heat emitted by such conductors can be dissipated even more efficiently, and overheating of the microelectronic components and power semiconductors mounted on the substrate according to the invention can be effectively prevented.

[0024] In order to realize the internal rewiring and the surge protection integrated into the ceramic base body, the ceramic base body of the substrate according to the invention can comprise a plurality of ceramic layers.

[0025] Furthermore, the ceramic base body of the substrate according to the invention can be wholly or partially embedded in an organic printed circuit board. In particular, the main component of the organic printed circuit board can, for example, comprise a composite material of epoxy resin and glass fibers.

[0026] In particular, the coefficient of thermal expansion of the organic printed circuit board can be adapted to the coefficient of thermal expansion of the ceramic substrate such that the coefficient of thermal expansion of the printed circuit board deviates from the coefficient of thermal expansion of the ceramic substrate by a maximum of ± 1 ppm / K. This largely prevents stresses that arise between the substrate according to the invention and the organic printed circuit board due to thermal loads, for example from an LED. This extends the service life of the substrate according to the invention, which is wholly or partially embedded in the organic printed circuit board.

[0027] Furthermore, the organic circuit board can also have an organic surface structure and external and internal rewiring. The ceramic base body of the substrate according to the invention and the organic circuit board can be conductively connected to each other by means of internal and external rewiring.

[0028] Furthermore, the substrate according to the invention and / or the organic printed circuit board can have external over-wiring made of a first metal and internal over-wiring made of a second metal, wherein the first metal differs from the second metal. The first metal and the second metal can be selected from a group of metals including copper and silver. The use of different metals makes it possible to optimally match the coefficients of thermal expansion of the internal and external over-wiring to the material in which they are integrated. This reduces mechanical stresses in the substrate according to the invention and improves its service life.

[0029] The substrate according to the invention can be produced by conventional methods. Such a method may, for example, comprise the following steps: Providing a ceramic substrate, applying a passivation layer to a first outer surface of the ceramic substrate, applying a first organic layer to the passivation layer, leaving areas on the passivation layer that are to become part of external rewiring uncoated or having the coating removed there, applying a first metal layer to the first organic layer and the areas of the passivation layer that are to become part of the external rewiring, applying a second organic layer to the first metal layer, leaving areas on the passivation layer that are to become part of the external rewiring and areas on the first organic layer that are also to become part of the external rewiring uncoated, applying a second metal layer to the areas on the passivation layer and the first organic layer.The outer wiring is formed by removing the second organic layer and the first metal layer, whereby the first metal layer is only removed in those areas that do not form the outer wiring. Furthermore, the areas on the passivation layer and the first organic layer that form the outer wiring are designed such that an electrically conductive contact exists between the respective areas.

[0030] By repeating the process steps listed above, it is possible to produce a second level or further levels with structured metallizations for rewiring.

[0031] The invention will now be described in more detail with reference to exemplary embodiments and accompanying figures. Figure 1 shows a schematic cross-section of an embodiment of the substrate according to the invention. Figure 2shows a schematic cross-section of an embodiment of the substrate according to the invention with internal rewiring. Figure 3 shows a schematic cross-section of an embodiment of the substrate according to the invention with internal rewiring and integrated overvoltage protection. Figure 4 shows a schematic cross-section of an embodiment of the substrate according to the invention, wherein the substrate according to the invention is embedded in an organic printed circuit board.

[0032] Identical, similar, or seemingly identical elements are marked with the same reference symbols in the figures. The figures and their proportions are not to scale.

[0033] Figure 1 The schematic cross-section shows an embodiment of a substrate according to the invention, comprising a ceramic base body 1, a passivation layer 12 on a first outer surface 9 and on a second outer surface 10of the ceramic base body 1. Furthermore, organic surface structures 2 on the passivation layers 12 formed. The passivation layers 12 They are, for example, 100 nm thick and contain, for example, SiN. The passivation layers 12 protect the ceramic base body 1 against corrosion, for example by aggressive solvents used during the production of the organic surface structure 2 can be used. Furthermore, external rewiring is required. 3 into organic surface structures 2 integrated. Due to the organic surface structures 2 on the first outdoor area 9 and the second outdoor area 10 Is it possible to use the first outdoor surface? 9 installed microelectronic components and power semiconductors (not shown) via vias 4 through contacts 5,the second outer surface 10 are designed to contact. This type of contacting allows, for example, the transition from a contact plane with relatively large contact distances to a contact plane with relatively small contact distances. Furthermore, the ceramic substrate primarily comprises AlN, which has a thermal conductivity of more than 100 W / m·K. This enables highly efficient heat dissipation from microelectronic components and power semiconductors (not shown) mounted on the substrate. This effectively prevents overheating. In combination with the organic surface structure 2, which have a sufficiently high number of external rewiring connections 3 This makes it possible to reduce the distances between components mounted on the substrate, thus enabling further miniaturization and performance improvements.

[0034] Figure 2 The schematic cross-section shows another embodiment of a substrate. In addition to the embodiment according to... Figure 1 the ceramic base body 1 internal rewiring 6 on. Through the internal rewiring 6 Is it possible to integrate heavily stressed cables into the ceramic base body? 1, to integrate a material with better thermal conductivity than conventional polymer-based substrates. This provides additional protection for the microelectronic components and power semiconductors (not shown) mounted on the substrate against overheating. This makes it possible to increase the number of microelectronic components and power semiconductors mounted on the substrate within a given area, effectively preventing overheating and enabling a more compact substrate design.

[0035] Figure 3The schematic cross-section shows another embodiment of a substrate. In addition to the one shown in Figure 2 The ceramic base body described above features surge protection. 7 for this purpose, the ceramic base body comprises 1 A varistor ceramic, whose main component is, for example, ZnO-Pr. Through the integration of overvoltage protection. 7 into the ceramic base body 1 can be applied to the training of surge protection 7 The need for a discrete component on the substrate's outer surface is eliminated. This creates more space for microelectronic components and power semiconductors that can be mounted on the substrate.

[0036] Figure 4 The schematic cross-section shows an embodiment of a substrate, which is similar to that in Figure 3 It can be formed, but this is in a recess of a surface. 11 an organic printed circuit board 8is embedded. The passivation layer 12, the first outdoor surface 9 the ceramic base body is applied flush with the surface 11 the circuit board 8 ab. The main component of the organic printed circuit board 8 It can, for example, include fiberglass and epoxy resin. The substrate, which is similar to the one in Figure 3 described, and the organic printed circuit board 8 Both exhibit an organic surface structure. 2 with integrated external rewiring 3 on. The substrate, which is similar to that in Figure 3 described, and the organic printed circuit board 8 are via internal rewiring 6 and external rewiring 3 conductively connected to each other. By embedding the substrate in the organic circuit board, it is particularly possible to use standard sizes for ceramic substrates. 1and for organic printed circuit boards 8 to resort to standard sizes, which simplifies manufacturing and thus reduces costs, as no special sizes are required, for example for the ceramic base body. 1, must be made. Reference symbol list

[0037] 1 ceramic base 2 organic surface structure 3 external rewiring 4 Via 5 contact 6 internal rewiring 7 Surge protection 8 organic printed circuit board 9 first outdoor area 10 second outdoor area 11 Surface of the organic printed circuit board 12 passivation layer

Claims

1. A substrate, comprising a ceramic base body (1) and an organic surface structure (2) on at least one first outer surface (9) of the ceramic base body (1), wherein external rewiring structures (3) are integrated into the organic surface structure (2) and wherein the ceramic base body (1) has an integrated overvoltage protection element (7), wherein a passivation layer (12) is applied at least to the first outer surface (9) of the ceramic base body (1), wherein the passivation layer (12) is located between the first outer surface (9) of the ceramic base body (1) and the organic surface structure (2) and contains as its main component an inorganic material selected from a group comprising SiO2, AlN, and SiN.

2. The substrate according to claim 1, wherein the organic surface structure (2) comprises a plurality of organic layers.

3. The substrate according to any one of claims 1 or 2, wherein the organic layers of the organic surface structure (2) each contain as their main component different organic materials selected from a group comprising photoresists and filled polymers.

4. The substrate according to any one of claims 1 to 3, wherein the ceramic base body (1) has a thermal conductivity of more than 8 W / m·K.

5. The substrate according to any one of claims 1 to 4, wherein the main component of the ceramic base body (1) is selected from a group comprising ZnO-Bi, ZnO-Pr, Al2O3, and AlN.

6. The substrate according to any one of claims 1 to 5, wherein the ceramic base body (1) contains a functional ceramic selected from a group comprising varistor ceramics, NTC ceramics, and PTC ceramics.

7. The substrate according to any one of claims 1 to 6, wherein the ceramic base body has internal rewiring structures (6) and vias (4).

8. The substrate according to any one of claims 1 to 7, wherein the organic surface structure (2) has a thermal expansion coefficient that corresponds to that of the ceramic base body (1) with a deviation of at most ± 1 ppm / K.

9. The substrate according to any one of claims 1 to 8, wherein the ceramic base body (1) comprises a plurality of ceramic layers.

10. The substrate according to any one of claims 1 to 9, wherein the ceramic base body (1) is wholly or partially embedded in an organic printed circuit board (8), wherein the thermal expansion coefficient of the organic printed circuit board (8) corresponds to that of the ceramic base body (1) with a deviation of at most ± 1 ppm / K.

11. The substrate according to claim 10, wherein the ceramic base body (1) and the organic printed circuit board (8) have an organic surface structure (2) with integrated external rewiring structures (3) on at least one outer surface (11).

12. The substrate according to claim 10 or 11, wherein the organic base body (1) and the organic circuit board (8) are conductively connected to each other by means of external rewiring structures (3) and / or internal rewiring structures (6).

13. The substrate according to any one of claims 1 to 12, wherein the external rewiring structures (2) consist of a first metal and the internal rewiring structures (6) consist of a second metal, wherein the first metal differs from the second metal.

14. The substrate according to any one of claims 1 to 13, wherein the first metal and the second metal are selected from a group of metals comprising copper and silver.