Printed circuit board, metal-ceramic substrate as an insert, and method for manufacturing a printed circuit board

Abstract

The invention relates to a printed circuit board (100) for electrical components (5) and / or conductor tracks (4), comprising - a base body (2) which extends along a main extension plane (HSE), and - an insert (1) which, in a mounted state, is integrated into the base body (2), wherein the insert (1) is a metal-ceramic substrate (10), wherein the metal-ceramic substrate (1) is at least in some sections covered, in particular surrounded, by an insulation element (8) on a side surface (SF) facing the main body (2) in the mounted state.

Description

[0001] Printed circuit board, metal-ceramic substrate as an insert and method for producing a printed circuit board

[0002] The present invention relates to a printed circuit board, a metal-ceramic substrate as an insert for such a printed circuit board and a method for producing a printed circuit board.

[0003] Printed circuit boards are well known in the art. Such printed circuit boards serve as carriers for electrical circuits that are formed or composed of conductor tracks, electrical components, and / or connections. The electrical circuits are preferably formed on one component side of the printed circuit board. Such printed circuit boards, also called PCBs (printed circuit boards), are usually made of a plastic, in particular a fiber-reinforced plastic, an epoxy resin, and / or a laminated paper. The use of such materials has proven particularly cost-effective and easy to handle during the manufacturing process. However, it has been found that the materials mentioned for printed circuit boards have limited thermal conductivity, which is necessary to dissipate heat generated by certain electrical components during operation. This insulation capacity is also limited.With the increasing performance of electronic components, circuit boards made of conventional materials are therefore unsuitable for permanently withstanding the stresses arising during operation and for providing good insulation properties.

[0004] On the other hand, circuit boards constructed as metal-ceramic substrates are characterized by high insulation properties and typically exhibit higher thermal conductivities than those of the aforementioned materials. However, the production of metal-ceramic substrates is more complex and cost-intensive than the production of circuit boards made of plastic, epoxy resin, and / or laminated paper.

[0005] Based on the prior art, the present invention aims to provide printed circuit boards that meet the high demands for heat dissipation and, in particular, insulation capacity in the area of ​​the electrical component and, at the same time, can be produced at a lower cost.

[0006] This object is achieved by a printed circuit board according to claim 1, a metal-ceramic substrate according to claim 9 and a method according to claim 10. Further embodiments can be found in the subclaims and the description.

[0007] According to a first aspect of the present invention, a printed circuit board for electrical components and / or conductor tracks is provided, comprising

[0008] - a base body extending along a main extension plane, and

[0009] - an insert which is integrated into the base body in an assembled state, wherein the insert is a metal-ceramic substrate and wherein the metal-ceramic substrate is at least partially covered, in particular surrounded, by an insulating element on a side surface facing the base body in the assembled state.

[0010] Compared to the circuit boards known from the prior art, it is preferably provided that the base body of the circuit board is not made entirely of one of the common materials, such as plastic, laminated paper and / or epoxy resin, but rather a section of the circuit board is formed from at least a metal-ceramic substrate. In particular, the metal-ceramic substrate is embedded or inserted into the base body of the circuit board in order to specifically ensure increased thermal conductivity locally. This makes it possible, for example, to insert or embed metal-ceramic substrates as inserts in the circuit board in areas where increased heat generation is to be expected. For example, the insert is arranged in a direction running perpendicular to the main extension plane below the electrical or electronic component that is responsible for increased heat generation during operation.At the same time, it is possible to manufacture the majority of the base body from a material such as a plastic, in particular a fiber-reinforced plastic, epoxy resin or hard paper, which is cost-effective and easy to process.

[0011] In particular, it is provided that the insulating element does not surround any component. In other words: if a component is mounted or can be mounted on the insert, this component is arranged at least on one side surface which is free of coverage by the insulating element. The insulating element is preferably arranged below the electrical component in a direction parallel to the stacking direction (without being in contact with the component) and / or on an upper side of the ceramic element facing away from the ceramic element, which is used as a connection or contact surface for the component and thus not on the side surface which is substantially covered by the insulating element. The electrical component is preferably free of an insulating element, i.e. is not in contact with the insulating element of the side surface of the insert.

[0012] The insulation element is preferably to be distinguished from the base body. For example, the base body differs from the insulation element with regard to their physical properties, for example because they are made of different materials. In the inserted state, the base body, the insert and the insulation element can therefore be distinguished from one another as individual components. Furthermore, it is preferably provided that the insulation element does not exert any adhesive or bonding effect. In other words: the insulation element is unsuitable for forming an independent material-to-material connection with the base body. An additional, preferably separate, adhesive element or a form-fitting and / or frictional connection means is provided for fixing. The metal-ceramic substrate is preferably coated with the insulation element, i.e. a coating is formed.

[0013] Furthermore, it is preferably conceivable for the component metallization to be substantially free of patterning and to form a continuous metal layer without any electrically insulating interruption. Furthermore, it is provided that the insulation element is arranged exclusively in the region above the pullback, i.e., above the portion of the ceramic element protruding from the component metallization, and not between two metal portions of the component metallization separated from each other, for example, by an insulation trench, provided the component metallization is patterned.

[0014] In particular, it proves to be particularly advantageous if the metal-ceramic substrate is surrounded or encased on its side surface, at least in sections, preferably completely, by an insulating element. By arranging the insulating element laterally, this insulating element is arranged between the base body and the metal-ceramic substrate in the assembled state and supports or reinforces the insulating effect of the metal-ceramic substrate used, in particular the avoidance of creepage or air gaps along the surface of the ceramic between the component and rear-side metallization. This sometimes makes it possible to reduce the initial length by which the ceramic element protrudes from the component metallization to form a pullback, or even to completely dispense with the formation of a pullback. In this case, the insulating element provides the required insulation.This is particularly advantageous because a prepreg material (insulator) has to fill the cavities formed by the pullback when the circuit board is laminated. However, such pullback creates the risk of insulation problems due to creepage or air gaps on the ceramic surface between the component metallization and the backside metallization. This can be avoided with a reduced pullback. If conductive tracks are formed in the base body, the insulation element can also be used to further insulate the base body. The insulation element can extend over the entire height of the insert or, for example, it can be interrupted at least in sections along a vertical extension of the insert that runs perpendicular to the main extension plane, i.e. along a stacking direction of the metal-ceramic substrate.

[0015] For example, it is also conceivable for the insulating element to extend over a first height in a direction perpendicular to the main extension plane, wherein the ratio of the first height to a total height of the insert, measured in the same direction, assumes a value between 0.4 and 1, preferably between 0.6 and 1, and particularly preferably between 0.7 and 1. This creates, for example, an annular, circumferential insulating element which can be used in specific areas to provide insulation protection between the component metallization and the back-side metallization. For example, it is conceivable for the insulating element to extend as an annular sheath at the level of the ceramic element of the metal-ceramic substrate and to provide insulation protection between the component metallization and the back-side metallization in this area.Furthermore, it is conceivable that the first height in this case assumes a value by which the ratio of a first thickness of the ceramic element, measured perpendicular to the main extension plane, to the first height of the insulating element assumes a value between 0.5 and 2, preferably between 0.8 and 1.5, and particularly preferably between 1.1 and 1.5. It is preferably provided that the insulating element is part of the insert.

[0016] Furthermore, it is preferably provided that the insulation element is a coating on the side surface and / or forms a cladding body or encapsulation body, which is produced, for example, within the framework of a casting, injection molding, spraying, dipping, or injection molding process. Preferably, the material used for the insulation element is free of ceramic and / or comprises ceramic particles incorporated into a corresponding plastic matrix. It is particularly preferably provided that the insulation element is formed substantially from a plastic, an epoxy resin, and / or a hard paper, which particularly preferably corresponds to that from which the base body is formed.It is preferably provided that the metal-ceramic substrate has a ceramic element, a component metallization and preferably a back-side metallization, wherein the insulating element surrounds the component metallization and / or the ceramic element at least in sections, preferably completely, on the side facing the base body in the assembled state. It is conceivable for the insulating element to surround only the component metallization and / or the ceramic element and / or the back-side metallization, i.e. the insulating element surrounds only a specific partial area which is predetermined by one or more components of the metal-ceramic substrate. It is also conceivable for the insulating element to encase or surround only the component metallization and the ceramic element and / or only the ceramic element and the back-side metallization.In particular, it is possible to increase the insulation between the insert and the base body by arranging the insulation element appropriately on the circumference or on the side surface of the metal-ceramic substrate, depending on the application. Furthermore, it is conceivable for the insulation element to extend from the component metallization area into the ceramic element area and / or into the rear-side metallization area without completely covering the component metallization, the ceramic element, and / or the rear-side metallization on their side surfaces.

[0017] When surrounding or encasing, the metal-ceramic substrate is preferably surrounded by a closed curve of the insulation element in a plane running parallel to the main extension plane.

[0018] Preferably, the ceramic element is formed between the component metallization and the rear-side metallization. The component metallization, the ceramic element, and the rear-side metallization are arranged one above the other along a stacking direction perpendicular to the main extension plane. In particular, the metal-ceramic substrate is composed of component metallization, ceramic element, and rear-side metallization. Essential components of the metal-ceramic substrates are an insulating layer, which is preferably made entirely of a ceramic, and at least one metal layer bonded to the insulating layer. Due to their comparatively high insulation strengths, insulating layers made of ceramic have proven particularly advantageous in power electronics.By structuring the metal layer, conductor tracks and / or connection surfaces for the electrical components can then be created. Preferably, the component metallization of the metal-ceramic substrate intended as an insert is not structured, but forms a closed surface. A prerequisite for providing such a metal-ceramic substrate is a permanent bond between the metal layer and the ceramic layer. In addition to a so-called direct metal bonding process, i.e., a DCB or DAB process, bonding via an active solder process, a thick-film layer process, diffusion bonding, and / or hot isostatic bonding is also conceivable.

[0019] Possible materials for the metal layer or metallization include copper, aluminum, molybdenum, tungsten, and / or their alloys, such as CuZr, AlSi, or AlMgSi, as well as laminates such as CuW, CuMo, CuAl, and / or AlCu, or MMC (metal matrix composite), such as CuW, CuMo, or AlSiC. Furthermore, it is preferably provided that the metal layer or metallization on the manufactured metal-ceramic substrate, in particular as component metallization, is surface-modified. Possible surface modifications include, for example, sealing with a precious metal, in particular silver and / or gold, or (electroless) nickel or ENIG (electroless nickel immersion gold), or edge encapsulation of the metallization to suppress crack formation or crack widening. For example, the metal of the component metallization differs from the metal of the backside metallization.

[0020] The ceramic element preferably comprises Al2O3, SiSn4, AlN, an HPSX ceramic (i.e., a ceramic with an Al2O3 matrix containing an x-percent ZrO2 content, for example Al2O3 with 9% ZrO2 = HPS9 or Al2O3 with 25% ZrO2 = HPS25), SiC, BeO, MgO, high-density MgO (> 90% of the theoretical density), TSZ (tetragonally stabilized zirconium oxide) as the ceramic material. It is also conceivable for the ceramic element to be designed as a composite or hybrid ceramic, in which, in order to combine various desired properties, several ceramic layers, each differing in terms of their material composition, are arranged one above the other and joined together to form a ceramic element.

[0021] In particular, it is provided or preferably provided that, when encasing the component metallization or its side surface, the insulating element is flush with the ceramic element in a direction parallel to the main extension plane and / or protrudes from the ceramic element. Alternatively, it is also conceivable for the ceramic element to protrude from the insulating element in a direction parallel to the main extension plane.

[0022] It is preferably provided that on the component side, an upper side of the component metallization facing away from the ceramic element is arranged below an upper side of the base body in the assembled state, viewed in the stacking direction. In other words: on the component side, the upper side of the component metallization is designed to be recessed relative to the upper side of the base body when the insert is integrated into the circuit board. For example, in the embedded state of the insert, the upper side of the component metallization has a recess depth of 10 pm to 200 pm, preferably between 10 pm and 150 pm, and particularly preferably between 10 pm and 100 pm, relative to the upper side of the base body. Alternatively or additionally, it is provided that on the rear side, an underside of the rear-side metallization facing away from the ceramic element has a recessed profile relative to the underside of the base body, preferably with one of the recess depths mentioned above.The insert is therefore smaller than the thickness of the base body when viewed in the stacking direction, and moreover, it is preferably provided that the top and bottom of the insert are both not flush with the top and bottom of the base body. It is conceivable that on the rear side of the circuit board, only the bottom side of the insert is flush with the bottom of the base body. It is preferably provided that the insulating element covers, at least in sections, a side of the component metallization facing away from the ceramic element. In other words, the top side of the metal-ceramic substrate is also covered, at least in sections, with the insulating element. For example, it is conceivable that an edge section or edge region, i.e. an outer edge region in a plane running parallel to the main extension plane, of the component metallization orthe top side of the component metallization is additionally covered with the insulation element in order to further insulate the component metallization from the base body of the circuit board. The edge region is preferably understood to be the area formed on the outer edge, which forms up to 15%, preferably up to 10% and particularly preferably up to 5% of the total surface on the outside of the component metallization facing away from the ceramic element. It is also conceivable for the component metallization to cover more than 10%, preferably more than 30% and particularly preferably more than 50% of the top side of the component metallization, even outside the edge region, and to only allow access to the component metallization in certain areas in order to further insulate the component metallization from the base body and at the same time ensure sufficient access for connecting a component metallization.It is also conceivable that conductor tracks run over the insulation element in order to create an electrical connection between a section of the base body and the component metallization.

[0023] Preferably, the ceramic element of the metal-ceramic substrate protrudes by a first length relative to the component metallization of the metal-ceramic substrate in a direction parallel to the main extension plane. A corresponding protruding region, also known as a pullback, serves in particular to electrically insulate the component metallization and the rear-side metallization and can preferably also be used as a form-locking means when inserting or securing the insert into or on the base body of the circuit board.It is conceivable that the component metallization and / or the ceramic element and / or the backside metallization is covered with an insulating element of essentially constant width, so that the metal-ceramic substrate insert encased in the insulating element also has a corresponding projection at the level of the ceramic element, which is due to the ceramic element projecting by a certain length. The width of the insulating element is measured in a direction parallel to the main extension plane.

[0024] Preferably, the insert and / or the insulating element interacts with the base body in a form-fitting manner in a direction perpendicular to the main extension plane and is preferably integrally connected to the base body. This creates a particularly stable and permanent connection between the base body and the insert, which is particularly advantageous because, due to the different thermal expansion coefficients for metal, ceramic, and epoxy resin, a connection via a frictional connection generally does not result in a permanent bond. Accordingly, a corresponding modulation depth of the side surface creates a desired form-fitting connection, which prevents the metal-ceramic substrate from changing its geometric shape under the influence of temperature and thereby impairing the circuit board.

[0025] If desired, this can also create an additional frictional connection between the insert and the base body.

[0026] Preferably, the positive connection acts in both possible directions, which run perpendicular to the main extension plane of the base body. Furthermore, it is conceivable that, in addition to the insert, further inserts are arranged in the base body. It is also conceivable that the insert is only flush with the base body on the component side, and the back of the metal-ceramic substrate is enclosed by the base body. In other words: the metal-ceramic substrate or the insert is embedded or inserted into a recess in the base body of the circuit board. This also results in a positive connection parallel to the main extension plane. In particular, it is provided that the metal-ceramic substrate and the base body are designed such that their thermal expansion coefficients are as similar as possible. In other words: any difference between the thermal expansion coefficients of the insert and the base body is kept as small as possible.For this purpose, for example, an appropriate thickness of the ceramic element is set in the metal-ceramic substrate. It is also conceivable that a stabilizing layer is provided to adjust the thermomechanical expansion coefficient, or that multiple metal layers and / or different metallizations (e.g., component metallizations and back metallizations are made of different metals or materials) are used to ensure the desired adaptation. This can ensure that expansions occurring during operation do not cause significant mechanical stresses between the base plate and the metal-ceramic substrate, which could, for example, lead to cracking. It is also preferably conceivable that different ceramic layers are used in a metal-ceramic substrate with multiple ceramic layers.

[0027] It has proven advantageous if, in addition to the form fit, a material bond is realized between the side surface of the insert and the base body.

[0028] Preferably, for example, the component metallization or the insulating element and / or the ceramic element provide a corresponding lateral profiling, in particular with a corresponding modulation depth. The lateral surface of the insulating element and / or the component metallization and / or the ceramic element and / or the metal-ceramic substrate can be curved, slanted, stepped, nose-shaped, and / or otherwise shaped to ensure the positive connection in a direction perpendicular to the main extension plane.

[0029] To achieve the positive engagement, the insulation element is preferably profiled on a side surface that does not run parallel to the main extension plane. In particular, the profiling occurs on a side that, in the assembled state, faces the base body and is in contact with the base body.

[0030] Preferably, the insulation element has a width in a direction parallel to the main extension plane that assumes a value between 10 pm and 800 pm, preferably between 150 pm and 500 pm, and particularly preferably between 250 pm and 350 pm. This provides a comparatively thin insulation layer, which has proven sufficient to ensure additional significant insulation protection between the component metallization and the rear-side metallization, in particular when the first length is less than 80 pm, preferably less than 50 pm, and preferably less than 25 pm.

[0031] In particular, it is provided that the insulation element has a width, averaged along the first height of the insulation element, in a direction parallel to the main extension plane, which assumes a value that is greater than 250 pm, preferably greater than 350 pm, and particularly preferably greater than 500 pm. It has been found that such wide insulation elements are suitable for forming an effective and additional insulation layer. In particular, such a wide insulation element also allows the realization of thinner ceramic elements, preferably with thicker component metallizations and rear-side metallizations.

[0032] Preferably, the component metallization and / or the backside metallization are thicker than the thickness of the insulating element. This places greater demands on the insulating element, particularly with regard to the electrical insulation strength between the component metallization and the backside metallization.

[0033] Preferably, it is provided that, measured in a direction running perpendicular to the main extension plane, the ceramic element has a first thickness, the base body a second thickness and the component metallization a third thickness, wherein a ratio between the first thickness and the second thickness and / or a ratio between the first thickness and the third thickness assumes a value between 0.01 and 0.3, preferably between 0.01 and 0.2 and particularly preferably between 0.01 and 0.15. As a result, a comparatively thin ceramic is advantageously used. Here, it proves to be particularly advantageous if the insulating element surrounds the side surfaces of the metal-ceramic substrate to increase the insulation.

[0034] A further aspect of the present invention is a metal-ceramic substrate used as an insert for a printed circuit board according to the present invention, wherein the insert is at least partially surrounded by an insulating element on a side surface that does not run parallel to the main extension plane. All properties and advantages described for the printed circuit board apply analogously to the metal-ceramic substrate used as an insert, and vice versa.

[0035] In particular, it is completely unusual in the prior art to cover the side surfaces of the metal-ceramic element, especially at the level of the ceramic element, with an insulating element. Preferably, the insert is completely surrounded by an insulating element on the non-parallel side surfaces. Such an insert can be safely inserted into any base body of suitable size. In particular, the insulating element is not self-adhesive. This simplifies the handling of the insert, especially when inserting it into the base body.

[0036] Furthermore, it is provided that the metal-ceramic substrate is provided as an insert together with the insulating element and is installed together with the insulating element connected to the metal-ceramic substrate. It is conceivable that the insulating element itself is adhesive and that a protective covering is provided, which is preferably only removed when the insert is to be inserted into the base plate. In particular, it is provided that the insulating element surrounds the metal-ceramic substrate in a closed manner, at least in a vertical section of the metal-ceramic substrate. For example, the insulating element surrounds the component metallization, the ceramic element and / or the back-side metallization in strip form. It is also conceivable that only a partial section or a vertical section of the component metallization, the ceramic element and / or the back-side metallization is surrounded or covered by the insulating element.The strip-shaped course of the insulation element is preferably closed in a plane parallel to the main extension plane.

[0037] Another object of the present invention is a method for producing an insert which is intended for a printed circuit board according to the invention comprising:

[0038] - Providing a metal-ceramic substrate with a main extension plane,

[0039] - at least partially covering the metal-ceramic substrate with an insulating element and

[0040] - Inserting the insert with the insulation element into the base body. All the advantages and properties described for the printed circuit board apply analogously to the process, and vice versa.

[0041] Preferably, the base body is made of a different material than the insert. In particular, the base body is substantially free of ceramic or does not contain a ceramic element as an insulating layer or stabilizing layer. Preferably, the base body contains less than 10 wt.%, preferably less than 5 wt.%, and particularly preferably less than 3 wt.% ceramic.

[0042] In particular, it is provided that the proportion of the metal-ceramic substrate in the proportion of the circuit board is less than 50%, preferably less than 30% and particularly preferably less than 15%. Furthermore, it is provided that the insert extends from the component side of the base plate to the rear of the main body of the circuit board. In other words, the insert is flush with the main body in a direction running perpendicular to the main extension plane on both sides, i.e., essentially flush with the component side and the rear. The positive connection between the main body and the metal-ceramic substrate serving as the insert particularly creates a permanent bond between the metal-ceramic substrate and the main body, which prevents the insert from becoming detached from the circuit board.

[0043] According to a preferred embodiment, it is provided that in order to form the positive interaction

[0044] - the metal-ceramic substrate is profiled on a side surface that is not parallel to the main extension plane and / or

[0045] - a ceramic element of the metal-ceramic substrate protrudes by a first length relative to a component metallization and / or the rear-side metallization of the metal-ceramic substrate in a direction parallel to the main extension plane, wherein the metal-ceramic substrate is surrounded by an insulating element. The lateral profiling can be supported by the insulating element or maintained with an insulating element that has a constant width across the entire height of the insert.

[0046] For example, it is provided that a side surface, in particular a side surface of the component metallization and / or rear-side metallization and / or of the insulating element, is concavely and / or convexly curved. Alternatively, it is also conceivable for the component metallization and / or the insulating element to be stepped. In particular, it is provided that the base body engages in the recessed or projecting profiles on the side surfaces of the insulating element, the component metallization and / or rear-side metallization in order to bring about the positive connection in one direction or both directions that run perpendicular to the main extension plane. For example, it is conceivable for the outermost edge of the component metallization and / or of the insulating element to be stepped, in particular stepped in such a way that the open region of the step is formed on the side facing the component side and / or the rear side.In a corresponding manner, a component can be arranged on the component metallization in such a way that, while taking isotropic heat transfer into account, the heat spread is fully captured by the component metallization. The sections of the component metallization that do not contribute to heat transfer anyway are removed in this stepped pattern and replaced by the base body. Preferably, a protruding section of the ceramic element is used to create the form fit. In particular, this is the section known as the pullback, which ensures sufficient insulation between the component metallization and the backside metallization.

[0047] Preferably, the first length assumes a value between 1 pm and 200 pm, preferably between 20 pm and 100 pm, and particularly preferably between 25 pm and 60 pm. The first length preferably relates to a projection by which the ceramic element protrudes relative to the insulation element, which surrounds, for example, the component metallization, in a direction parallel to the main extension plane.

[0048] It has been found that an effective form fit can be achieved simply by appropriate dimensioning, and the additional insulating effect of the material from which the base body of the circuit board is formed also ensures electrical insulation between the component metallization and the rear-side metallization. This comparatively very small protruding section of the ceramic element, i.e. this comparatively small so-called pullback, enables the insert, i.e. the metal-ceramic substrate, to be integrated into the base body of the circuit board in the most space-saving way possible. Preferably, the metal-ceramic substrate, in particular with the insulating element, has a maximum extension in a plane dimensioned parallel to the main extension plane, which maximum extension assumes a value of between 1 mm and 200 mm, preferably between 4 mm and 60 mm, and particularly preferably between 6 mm and 30 mm.This provides comparatively small inserts that can be used as needed to locally increase thermal conductivity in the circuit board. In particular, a comparatively large number of individual inserts can be provided from a large-scale board. Such a large-scale board is determined by the format immediately after the component metallization is bonded to the backside metallization, which is achieved using a corresponding bonding process.

[0049] It is also conceivable for the first length to take a negative value. In this case, the component metallization and / or the backside metallization and / or the insulating element surrounding the component metallization and / or backside metallization protrudes from the ceramic element in a direction parallel to the main extension plane. The absolute value of the first length can take the values ​​mentioned above.

[0050] In particular, it is provided that the side surface is profiled in such a way, i.e. has such a side profiling that a modulation depth or height is established which assumes a value between 1 pm and 200 pm, preferably between 20 pm and 100 pm and particularly preferably between 25 pm and 60 pm. The modulation depth or height is to be understood as a deviation measured in a direction parallel to the main extension plane from an imaginary, cylindrical outer profile that is assigned to a narrowest point of the metal-ceramic substrate (measured in planes parallel to the main extension plane). The imaginary cylindrical outer profile extends perpendicular to the main extension plane. If the modulation depth is formed by a ceramic element protruding from the component metallization and / or backside metallization and / or the insulation element, the modulation depth can correspond to the first length.It is also conceivable that the modulation depth is caused by the component metallization and / or the ceramic element protruding relative to the backside metallization in a direction parallel to the main extension plane. For example, it is also conceivable that the side surface in the region of the ceramic element has an oblique profile relative to the stacking direction (in other words: the top and bottom of the ceramic element have different diameters or dimensions). In particular, the above applies analogously to the modulation depth of the side profiling of the insulation element.

[0051] For example, it is conceivable for the profile of the side surface or sides in the region of the component metallization and / or back-side metallization to extend parallel to the stacking direction (i.e. the cross-section of the component metallization and / or back-side metallization is essentially constant in the region of the component metallization or back-side metallization when viewed in the stacking direction). The modulation depth is then preferably realized by a step at the level of the ceramic element and / or by a corresponding geometry of the insulation element. The modulation depth can be generated by profiling or modulation in the region of the ceramic element and / or the insulation element, wherein the profiling can occur continuously in the stacking direction across the thickness of the ceramic element or the insulation element, or discretely or abruptly at the level of the ceramic element.

[0052] Furthermore, it is conceivable for the insert to have one or more projections that protrude in a direction parallel to the main extension plane relative to the general shape of the outer circumference of the insert. This, preferably nose-shaped, projection can advantageously cause an additional positive connection in the circumferential direction along the outer circumference, which supports a rotationally fixed arrangement in the base body. It has been found that such a projection is advantageously created by separating the metal-ceramic substrates from a large card using laser light and / or water cutting. Due to a constant width of the insulation element, this projection is then also formed on the insert with the insulation element.

[0053] Preferably, the metal-ceramic substrate has a rounded profile or a rounded corner in the main plane of extension. A corresponding design of the insert's cross-section in a plane that runs parallel to the main plane of extension proves particularly advantageous because it can reduce the stress concentration on the base body of the circuit board. This, in turn, can extend the service life of the circuit board with the insert.

[0054] Preferably, it is provided that the metal-ceramic substrate comprises a ceramic element, wherein a component metallization is bonded to the ceramic element, wherein

[0055] -- a stabilising layer, for example in the form of a further ceramic element, is provided or formed, wherein a metallic intermediate layer is arranged between the ceramic element and the stabilising layer, and / or

[0056] -- the component metallization and / or the backside metallization comprises a first metal layer and / or a second metal layer, wherein the first metal layer and the second metal layer are arranged one above the other.

[0057] In particular, it is possible to influence the thermal expansion coefficient of the insert through the appropriate design of the metal-ceramic substrate in order to adapt it to the thermal expansion coefficient of the base body. For example, it is conceivable to design the stabilizing layer from a different material or to dimension it accordingly. The thickness of the ceramic element can also be used to optimize the thermomechanical expansion coefficient of the insert such that mechanical stresses between the base body and the insert are reduced. The first metal layer preferably differs from a second metal layer with regard to its grain size, wherein preferably a grain size in the first metal layer is smaller than a grain size in the second metal layer and / or particularly preferably a thickness of the first metal layer is thinner than a second metal layer.Furthermore, it is conceivable for the thickness of the component metallization to differ from the thickness of the backside metallization. This advantageously makes it possible to influence the height of the ceramic element within the base body of the circuit board and, in particular, to ensure that the insulating ceramic element is arranged offset in the base body toward the back side and away from the component side, or vice versa.

[0058] Furthermore, it is provided that profiling of a side surface that does not run parallel to the main extension plane and / or the realization of a ceramic element on the metal-ceramic substrate that protrudes relative to the component metallization and / or the rear-side metallization in a direction parallel to the main extension plane is provided. In particular, it is conceivable that profiling and / or exposure is carried out, for example, by etching, by mechanical processing, for example by milling, by processing with laser light, and / or by a water jet.

[0059] Preferably, a component side and / or rear side extending substantially parallel to the main extension plane is covered with a protective layer or resist layer, and subsequently, the side surface is profiled and / or the ceramic element is partially exposed using an etching medium. This allows a desired profiling of the side surface and the exposure of a laterally protruding portion of the ceramic element to be easily achieved using a simple etching process. Subsequently, the side surfaces are covered, at least in sections, preferably completely, with an insulating element. In particular, it is provided that the insert is cut out of a metal-ceramic substrate provided as a large card.

[0060] Furthermore, it is conceivable that the side surfaces of the inserts are ground or polished before being inserted into the base body.

[0061] Further advantages and features will become apparent from the following description of preferred embodiments of the subject matter of the invention with reference to the accompanying figures. Individual features of the individual embodiments can be combined with one another within the scope of the invention. It shows:

[0062] Fig.1: schematic representation of a printed circuit board according to a first preferred embodiment of the present invention in a plan view (top) and a sectional view (bottom)

[0063] Fig. 2: Insert according to a first preferred embodiment of the present invention

[0064] Fig. 3 Insert according to a second preferred embodiment of the present invention

[0065] Fig. 4 Insert according to a third preferred embodiment of the present invention

[0066] Fig. 5. Insert according to a fourth preferred embodiment of the present invention and

[0067] Fig. 6 Insert according to a fifth preferred embodiment of the present invention

[0068] Figure 1 shows a printed circuit board 100 according to a first preferred embodiment of the present invention in a plan view (top) and a sectional view (bottom). Such printed circuit boards 100 serve, in particular, as carriers for circuits formed from electrical or electronic components 5, terminals 7, and / or conductor tracks 4. The electrical or electronic components 5, the conductor tracks 4, and / or the terminals 7, for example in the form of soldering pads (pats) or soldering eyes, are preferably arranged or connected to a component side BS of the printed circuit board 100.For a particularly cost-effective production of such printed circuit boards 100, it has been established to use plastics, in particular fiber-reinforced plastics, epoxy resin and / or hard paper as materials for a base body 2, which extends essentially along a main extension plane HSE and on whose component side BS the connections 7, electronic components 5 and / or conductor tracks 4 are formed or connected.

[0069] Due to the constant advancements in the field of electronics, particularly with regard to the performance of electrical components 5, it has become apparent that the materials used for the base body 2 cannot permanently withstand the new challenges, particularly with regard to the heat generated during operation. This is due in particular to the fact that the materials used for the base body 2 of a printed circuit board 100 have a comparatively low thermal conductivity, which means that the heat generated by the electrical components during operation cannot be dissipated to a sufficient extent.

[0070] Printed circuit boards 100 which are designed as metal-ceramic substrates, on the other hand, can dissipate the heat generated to a sufficient extent due to their increased thermal conductivity, in particular compared to printed circuit boards made of base bodies 2 made of the above-mentioned materials, ie plastics, in particular fibre-reinforced plastics, epoxy resin and / or hard paper, but are more complex to produce and cost-intensive in terms of manufacturing technology.

[0071] In order to utilize the positive properties of a printed circuit board 100 made of a plastic, an epoxy resin, or a laminated paper and the positive properties of a metal-ceramic substrate, in particular its thermal conductivity, it is preferably provided that the printed circuit board 100 according to the embodiment shown in Figure 1 has a base body 2 that extends along the main extension plane HSE and into which an insert 1 is integrated, wherein the insert 1 is provided as a metal-ceramic substrate. It is preferably provided that the metal-ceramic substrate used as insert 1 is arranged in the printed circuit board 100 at locations where increased heat generation is to be expected.For example, it is provided that the insert 1 is arranged in a stacking direction S running perpendicular to the main extension plane HSE below one or more electrical components 5 in order to dissipate the heat generated during operation. It is preferably provided that an extension A of the insert 1 is greater than an extension of the electrical component measured parallel to the main extension plane HSE in order to ensure effective heat dissipation.

[0072] Preferably, it is provided that at least one insert 1, preferably a plurality of inserts 1 are integrated into the base body 2 of the printed circuit board 100. A component side BS of the insert 1 is essentially flush with a component side BS of the base body 2 and / or a rear side RS of the insert 1 is flush with the rear side RS of the base body 2. Furthermore, it is preferably provided that a proportion of a volume of the insert 1 or a plurality of inserts 1 in the volume of the base body 2 or of the entire printed circuit board 100 is less than 50%, preferably less than 30%, and particularly preferably less than 15%. It has been found that with such low proportions it is already possible to effectively improve the thermal properties of the printed circuit board 100 and at the same time to work predominantly with materials for the base body 2 that are easy to process and less cost-intensive than metal-ceramic substrates.

[0073] It is preferably provided that the insert 1, which in particular on the component side BS and the rear side RS is flush with the component side BS and rear side RS of the base body 2 in a stacking direction S running perpendicular to the main extension direction HSE, interacts positively with the base body 2 in a direction running perpendicular to the main extension direction HSE. This enables or supports a secure hold of the insert 1 in the circuit board 100. It is preferably provided that the selection of materials, be it a material of the base body 2 on the one hand or one of the materials or several materials of the ceramic element 30, is made such that the differences in the thermal expansion coefficients are kept as small as possible in order to prevent thermomechanical stresses from leading to cracks and / or damage to the circuit board 100 and / or the metal-ceramic substrate.Preferably, the thermal expansion coefficient of the insert 1 does not deviate from the thermal expansion coefficient of the base body 2 by more than 30%, preferably not more than 15%, and particularly preferably not more than 10% of the thermal expansion coefficient of the insert 1. To select the inserts in question, the person skilled in the art uses, for example, simulations for the respective compositions of the inserts and compares these with the values ​​for the base body 2. In particular, it is provided that the insert 1 is cylindrical and / or has a substantially rectangular, in particular square, cross-section, wherein the corners are rounded.

[0074] Figure 2 illustrates an insert 1 as a first exemplary embodiment of the present invention. To form an insert, essentially formed from a metal-ceramic substrate, it is provided in particular that, in a first step, a component metallization 20 is bonded to a ceramic element 30. The component metallization 20 and / or the rear-side metallization 20' is preferably bonded using a direct metal bonding method, such as a DCB or DAB method, a soldering method, in particular an active solder metal method, a diffusion bonding process, and / or hot isostatic pressing. Bonding using a thick-film technique is also conceivable. The inserts 1 are preferably cut out of a large card, i.e., singulated.

[0075] In particular, it is provided that the insert 1 has a ceramic element 30, a component metallization 20, and a rear-side metallization 20'. In the assembled state, in which the insert 1 is integrated into the circuit board 100 or into the base body 2, the component metallization 20 faces the component side BS of the circuit board 100, while the rear-side metallization 20' faces the rear side RS. It is further provided that the ceramic element 30 has a first thickness D1, the component metallization 20 has a third thickness D3, and the rear-side metallization 20' has a fourth thickness D4. Preferably, the third thickness D3 is the same as the fourth thickness D4.However, it is also conceivable that, for example, the third thickness D3 is greater than the fourth thickness D4, or vice versa, whereby the ceramic element 30 can advantageously be positioned differently within the insert 1 along the stacking direction S running perpendicular to the main extension plane HSE. For example, this makes it possible to provide a thicker component metallization 20, which, due to the increased third thickness, provides high thermal conductivity in the region facing the component 5. This can prove advantageous for heat dissipation.

[0076] Furthermore, it is preferably provided that the ceramic element 30 with the first thickness D1 is dimensioned such that a ratio between the first thickness D1 and the component metallization 20 and / or a ratio of the first thickness D1 to the second thickness D2 of the base body 2 assumes a ratio that lies between 0.01 and 0.3, preferably between 0.01 and 0.2, and particularly preferably between 0.01 and 0.15. As a result, a thin ceramic element 30 is used compared to the component metallization 20 and the base body 2 in order to ensure both good heat dissipation and the desired insulation strength.

[0077] Furthermore, it is provided that the ceramic element 30 protrudes by a first length L1 relative to the component metallization 20 and / or the rear-side metallization 20' in a direction running parallel to the main extension plane HSE. This forms a so-called pullback on the outer circumference of the metal-ceramic substrate 1. The upper side of the insert 1 facing the component side BS and the underside of the insert 1 facing the rear side RS are connected to one another via side surfaces SF that do not run parallel to the main extension plane HSE. The side surfaces SF of the metal-ceramic substrate face the base body 2 of the printed circuit board 100 in the assembled state. In particular, the side surface SF of the metal-ceramic substrate comprises partial sections of the component metallization 20, the ceramic element 30 and the rear-side metallization 20'.

[0078] In order to increase the insulation strength of the inserted insert 1, in particular with respect to the base body 2 of the printed circuit board 100, it is preferably provided that an insulation element 8 covers the side surface SF of the metal-ceramic substrate at least in sections. By covering the side walls or side surfaces SF of the metal-ceramic substrate, the insulation element 8 is arranged between the base body 2 and the metal-ceramic substrate in the assembled state. For example, the insulation element 8 can be a coating with a corresponding insulation layer which, for example, has a width B of between 10 pm and 800 pm, preferably between 150 pm and 500 pm and particularly preferably between 250 pm and 350 pm in a direction parallel to the main extension plane HSE. In the exemplary embodiment shown in Figure 2, the insulation element 8 covers orThe insulating element 8 completely surrounds the component metallization 20 and the rear-side metallization 20'. In particular, in the exemplary embodiment of Figure 2, the side surface of the ceramic element 30 is free of the insulating element 8, and the insulating element 8 extends above and below the ceramic element 30. For example, the cladding element 8 is an encapsulation with a filler material, which, for example, in the exemplary embodiment of Figure 2, is flush with the outer circumference of the ceramic element 30. The corresponding filler material is and / or contains, for example, a plastic, in particular a fiber-reinforced plastic, an epoxy resin, and / or a hard paper, and is particularly preferably made of the same material as the base body 2 of the printed circuit board 100.It is particularly preferred if the filling material for the insulating element 8 has additional insulating components, such as ceramic particles, which are distributed in the filling material of the insulating element 8.

[0079] Figure 3 shows an insert 1 according to a second exemplary embodiment of the present invention. In the exemplary embodiment shown here in Figure 3, the insulating element 8 is designed such that it exclusively surrounds the component metallization 20, in particular over the entire height of the component metallization 20. Alternatively, it is conceivable that only the rear-side metallization 20' is enclosed by an insulating element 8. In the exemplary embodiment shown in Figure 3, the partial section of the side surface SF of the metal-ceramic substrate in which the ceramic element 30 and the rear-side metallization 20' are arranged remains essentially free of an insulating element 8.

[0080] It is preferably provided that the insulation element 8 extends along a first height H1 measured perpendicular to the main extension plane HSE, wherein a ratio of the first height H1 to a total height H2 of the entire insert 1 assumes a value between 0.4 and 1, preferably between 0.5 and 1 and particularly preferably between 0.7 and 1.

[0081] Figure 4 shows an insert 1 according to a third exemplary embodiment of the present invention. In the embodiment shown in Figure 4, the insulating element 8 completely surrounds the metal-ceramic substrate on its side surfaces SF. In the exemplary embodiment shown, the top and bottom, i.e. the outer side of the metal-ceramic substrate facing the component side BS and the outer side facing the rear side RS, are free of an insulating element 8. Alternatively, it is also conceivable for the insulating element 8 to additionally cover the component side BS and / or rear side RS at least partially and / or completely. In this case, at least a partial area on the component side BS is preferably left free in order to allow corresponding connection options of a component 5 to the component metallization 20.

[0082] In particular, in the exemplary embodiment of Figure 4, it is provided that the side surfaces SF of the ceramic element 30 are also surrounded by the insulating element 8, and thus the side surfaces SF of the metal-ceramic substrate are completely enclosed. For example, it is provided here that a first length L1 of the projecting section of the ceramic element 30, relative to a second length L2 of the component metallization 20 and / or rear-side metallization 20', measured parallel to the main extension plane HSE, assumes a value between 0.01 and 0.3, preferably between 0.01 and 0.2, and particularly preferably between 0.01 and 0.1. Furthermore, it is conceivable that the second length L2 of the component metallization 20 differs from the second length L2 of the rear-side metallization 20' (not shown).

[0083] Preferably, the component side BS and / or rear side RS of the metal-ceramic substrate remain free of an insulating element 8 or a part of the insulating element 8 in order to provide corresponding connection surfaces to the component side BS or to allow direct access of the cooling element to the rear side metallization 20'.

[0084] Figure 5 shows a fourth exemplary embodiment of the present invention. The embodiment in Figure 5 essentially corresponds to that of Figure 4, with the insulating element 8 having a side profile on the side surface SF. Such a side profile advantageously makes it possible to create a positive connection between the base body 2 and the insert 1, which fixes and permanently holds the insert 1 in the base body 2 of the printed circuit board 100. Preferably, a material connection between the insert and the base body is additionally created.

[0085] Furthermore, it is conceivable that in all other exemplary embodiments, the side surface SF of the insert 1 with the insulating element 8 has a side profile in order to thereby form a positive connection with the base body 2 in a direction perpendicular to the main extension plane HSE. For example, it is conceivable that only the insulating element 8 in the region of the component metallization 20 and / or rear-side metallization 20' or the component metallization 20 and / or rear-side metallization 20' has a corresponding side surface profile that is suitable for a corresponding side profile for a positive connection.It is also conceivable for the ceramic element 30 to protrude relative to the metal layer and / or component metallization 20 and / or relative to the insulating element 8 in a direction running parallel to the main extension plane HSE, in order to thereby bring about a corresponding positive connection in a direction running perpendicular to the main extension plane HSE. For example, the side profiling is a concave and / or convex shaped section which can, for example, also extend over the entire second height of the insert 1. It is conceivable for the side profiling to be predetermined, for example, by the insulating element 8. It is conceivable for the side profiling to arise during the formation of the insulating element 8, for example by means of a corresponding casting mold, or by subsequent processing, for example by machining.Furthermore, it is conceivable that the side profiling is formed by an at least partially stepped, oblique, curved, or tapered profile of the insulating element 8. It is also conceivable that the side surface SF of the insert 1 and / or the insulating element 8 is wave-shaped or forms several local maximums and minimums in the width B in order to be designed for the desired form fit.

[0086] Figure 6 shows a fifth exemplary embodiment of the present invention. This embodiment differs in that the component metallization 20 protrudes relative to the rear-side metallization 20' in order to realize a lateral surface profile of the insert 1, which causes a positive connection between the insert 1 and the base body 2. A modulation depth M is defined by the component metallization 20 protruding in a direction parallel to the main extension plane HSE. It can also be seen that the lateral surface SF of the insert 1 in the region of the ceramic element 30 has an oblique profile relative to the stacking direction S. This causes the protruding profile of the lateral surface SF in the region of the component metallization 20. Alternatively, it is also conceivable for the rear-side metallization 20' to protrude relative to the ceramic element 30.In the example shown in Figure 6, the profiles of the side surface SF in the region of the component metallization 20 and the rear-side metallization 20' are parallel to the stacking direction S. It is also conceivable that the profile of the side surface SF in the region of the rear-side metallization 20 and / or component metallization 20' contributes to the formation of the modulation depth or height. In principle, it is also conceivable that the side surfaces SF have several local maxima and / or minima in their modulation depth / height M.

[0087] In particular, in the exemplary embodiment of Figure 6, it is provided that the side surface SF of the metal-ceramic substrate 1 is preferably completely covered with an insulating element 8. The insulating element 8 has a substantially constant width B essentially over its entire height. The insert 1 from Figure 6 is to be attributed a corresponding side surface profiling, since due to the constant thickness or constant width of the insulating element 8, the contour of the side surface SF of the metal-ceramic substrate is also present on the outside of the insulating element 8. In particular, this embodiment proves to be particularly simple to manufacture, since the entire side surface SF only needs to be covered with a constant-width insulating layer 8 to ensure the desired additional insulation protection.

[0088] Reference symbol:

[0089] 1 mission

[0090] 2 basic bodies

[0091] 4 conductor track

[0092] 5 Component

[0093] 7 Connection

[0094] 8 Insulation element

[0095] 20 Component metallization

[0096] 20' backside metallization

[0097] 30 ceramic elements

[0098] 100 circuit boards

[0099] HSE main extension level

[0100] S Stacking direction

[0101] D1 first thickness

[0102] D2 second thickness D3 third thickness

[0103] L1 first length

[0104] L2 second length

[0105] M Modulation depth SF side surface

[0106] RS back

[0107] BS component side

[0108] B Width

[0109] H1 first height H2 total height

Claims

Claims for a printed circuit board (100) for electrical components (5) and / or conductor tracks (4), comprising - a basic body (2) extending along a principal extension plane (HSE), and - an insert (1) which is integrated into the base body (2) in an assembled state, wherein the insert (1) is a metal-ceramic substrate (10) and wherein the metal-ceramic substrate (1) is at least partially covered, and in particular surrounded, by an insulating element (8) on a side surface (SF) facing the base body (2) in the assembled state. Printed circuit board (100) according to claim 1, wherein the metal-ceramic substrate (1) comprises a ceramic element (30), a component metallization (20) and preferably a backside metallization (20'), wherein the insulating element (9) surrounds the ceramic element (30) at least partially, and preferably completely, on the side facing the base body (2) in the assembled state.Printed circuit board (100) according to claim 1 or 2, wherein the metal-ceramic substrate (1) comprises a ceramic element (30), a component metallization (20), and preferably a backside metallization (20'), wherein the insulating element (9) surrounds the component metallization (20) at least partially, preferably completely, on the side facing the base body (2) in the assembled state. Printed circuit board (100) according to claim 2 or 3, wherein the insulating element (8) covers at least partially a top side of the component metallization (20) facing away from the ceramic element (30).

5. Printed circuit board (100) according to one of the preceding claims, wherein the ceramic element (30) of the metal-ceramic substrate (10) projects in a direction parallel to the main extension plane (HSE) relative to a component metallization (20) of the metal-ceramic substrate (10) by a first length (L1 ).

6. Printed circuit board (100) according to one of the preceding claims, wherein the insert (1 ) and / or the insulating element (8) interacts with the base body (2) in a form-fitting manner in a direction perpendicular to the main extension plane (HSE).

7. Printed circuit board (100) according to claim 5, wherein the insert (1 ) and / or the insulating element (8) is materially bonded to the base body (2).

8. Printed circuit board (100) according to one of the preceding claims, wherein the insulating element (8) is profiled on a side surface (SF) which is not parallel to the main extension plane (HSE) in order to form the positive locking interaction.

9. Printed circuit board (100) according to one of the preceding claims, wherein the insulating element (8) has a width (B) averaged along the first height of the insulating element in a direction measured parallel to the main extension plane (HSE), which assumes a value between 10 pm and 800 pm, preferably between 150 pm and 500 pm and particularly preferably between 250 pm and 350 pm.

10. Printed circuit board (100) according to one of the preceding claims, wherein the insulating element (8) has a width (B) averaged along the first height of the insulating element (8) in a direction measured parallel to the main extension plane (HSE), which takes on a value greater than 250 pm, preferably greater than 350 pm and particularly preferably greater than 500 pm. Printed circuit board (100) according to one of the preceding claims, wherein, measured in a direction perpendicular to the principal extension plane (HSE), the ceramic element (30) has a first thickness (D1), the base body (2) has a second thickness (D2), and the component metallization (20) has a third thickness (D3), wherein -- a ratio between the first thickness (D1 ) to the second thickness (D2) and / or -- a ratio between the first thickness (D1) and the third thickness (D3) assumes a value between 0.01 and 0.3, preferably between 0.01 and 0.2, and preferably between 0.01 and 0.

15. Metal ceramic substrate (10) suitable as an insert (1) for a printed circuit board (100) according to one of the preceding claims, wherein the insert (1) is at least partially surrounded by an insulating element (8) on a non-parallel side surface (SF). Metal ceramic substrate (10) according to claim 12, wherein the insert (1) is completely surrounded by an insulating element (8) on the non-parallel side surface (SF). Metal-ceramic substrate (10) according to claim 12 or 13, wherein the insulating element (8) completely surrounds the metal-ceramic substrate (10) at least in a vertical section. Method for manufacturing a printed circuit board (100) according to any one of claims 1 to 11, comprising: - Providing a metal-ceramic substrate (10) with a main extent plane (HSE), - at least partially cladding the metal-ceramic element (1 ) with an insulating element (8) and - Inserting the insert with the insulating element into the base body

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