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

Abstract

The printed circuit board (100) for electrical components (5) and / or conductor paths (4) comprises a base (2) extending along a main extension plane (HSE) and an insert (1) which, in the assembled state, is integrated into the base (2). The insert (1) is a metal-ceramic substrate (10) which is at least partially covered, in particular surrounded, by an insulating element (8) on its side (SF) which, in the assembled state, faces the base (2).

Description

[Technical field]

[0001] 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 manufacturing the same. [Background technology]

[0002] Printed circuit boards are well known from the prior art. Such printed circuit boards serve as carriers for electric circuits formed or constituted by conductor paths, electric components and / or connections. The electric circuits are preferably formed on one component side of the printed circuit board. Such circuit boards, also known as PCBs (printed circuit boards), are usually made of plastics, in particular fiber-reinforced plastics, epoxy resins and / or hard paper. The use of such materials has proven to be particularly cost-effective and easy to handle during the manufacturing process. However, the aforementioned materials for printed circuit boards have been shown to have limited thermal conductivity, even though they are necessary to dissipate the heat emanating from certain electric components during operation. The insulating capacity is also limited. Thus, while the performance of electronic components is increasing, printed circuit boards made of conventional materials are not suitable to durably withstand the stresses occurring during operation and to provide good insulating properties.

[0003] On the other hand, printed circuit boards formed as metal-ceramic substrates are characterized by high insulating capabilities and typically have high thermal conductivity compared to that of the materials mentioned above. However, the manufacture of metal-ceramic substrates is more complicated and costly than the manufacture of printed circuit boards made from plastic, epoxy resin, and / or hard paper. Summary of the Invention [Problem to be solved by the invention]

[0004] Based on the prior art, the present invention has the object of providing a printed circuit board which meets the increased requirements for heat dissipation in the area of ​​electrical components, in particular the insulating capacity, and at the same time can be produced at lower costs. [Means for solving the problem]

[0005] This problem is solved 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 example embodiments can be found in the dependent claims and the description.

[0006] According to a first aspect of the invention, there is provided a printed circuit board for electrical components and / or conductor paths, comprising: a base extending along a main extension plane; an insert which, in the assembled state, is integrated into the base, The insert is a metal-ceramic substrate which is at least partially covered, in particular surrounded, by an insulating element on the side which in the assembled state faces the base.

[0007] Compared to the printed circuit boards known from the prior art, it is more preferably provided that the substrate of the printed circuit board is not entirely made of one of the conventional materials such as plastic, hard paper and / or epoxy resin, but that at least a part of the printed circuit board is made of a metal-ceramic substrate. In particular, the metal-ceramic substrate is embedded or inserted into the substrate of the printed circuit board in order to provide a locally increased thermal conductivity. This makes it possible, for example, to insert or embed the metal-ceramic substrate as an insert of the printed circuit board in areas where an increased heat generation is expected. For example, the insert is located in a direction perpendicular to the main extension plane, below the electric or electronic components that are responsible for increasing the heat generation during operation. At the same time, it is possible to manufacture a large part of the substrate from materials such as plastic, in particular fiber-reinforced plastic, epoxy resin or hard paper, which materials are inexpensive and easy to process.

[0008] In particular, it is provided that the insulating element does not surround any component. In other words, if a component is or can be attached to the insert, this component is arranged on at least one side not covered by the insulating element. Preferably, the insulating element is arranged in a direction parallel to the stacking direction below the electrical component (without contacting the component) and / or on the upper side of the ceramic element opposite the ceramic element that is used as a joining or contact surface for the component and is therefore not on a side that is substantially covered by the insulating element. The electrical component is preferably free of the insulating element, i.e. is not in contact with the insulating element on the side of the insert.

[0009] Preferably, the insulating element is separate from the substrate. For example, the substrate differs from the insulating element in terms of its physical properties, for example because it is of a different material. In the inserted state, the substrate, the insert and the insulating element can therefore be distinguished from one another as individual elements. It is further provided that the insulating element preferably has no adhesive or bonding effect. In other words, the insulating element is not suitable for forming an independent material-bonding connection with the substrate. For the fixing, additional, preferably separate adhesive elements or positive and / or frictional locking means are provided.

[0010] Preferably, the metal-ceramic substrate is coated, i.e. coated, with an insulating element. It is furthermore conceivable that the component metallization preferably forms a continuous metal layer essentially free of structures and without electrically insulating discontinuities, and that the insulating elements are arranged only in the area above the pullback, i.e. above the parts of the ceramic element protruding from the component metallization, and, if the component metallization has structures, not between two metal parts of the component metallization separated from each other, for example by an insulating trench.

[0011] In particular, it proves to be particularly advantageous if the side surface of the metal-ceramic substrate is at least partially, preferably completely, surrounded or covered by the insulating element. Due to the lateral arrangement of the insulating element, this insulating element is arranged between the base and the metal-ceramic substrate in the assembled state, supporting or enhancing the insulating effect of the metal-ceramic substrate used, in particular the avoidance of creepage or voids along the surface of the ceramic between the component and the backside metallization. This may make it possible to reduce the first length over which the ceramic element protrudes in order to form a pullback relative to the component metallization, or even to completely eliminate the formation of the pullback. In this case, the insulating element provides the necessary insulation. This is particularly advantageous since the prepreg material (insulator) must fill the cavities formed by the pullback when laminating the printed circuit board. However, the corresponding pullback creates a risk of insulation problems due to creepage or voids on the ceramic surface between the component metallization and the backside metallization. This can be avoided by reducing the pullback. If the conductor paths are formed in the base, the insulating element can also be used for further insulation from the base. In this case, the insulating element can extend over the entire height of the insert or be at least partially interrupted, for example, along a height extension of the insert extending perpendicular to the main extension plane, i.e. along the stacking direction of the metal-ceramic substrate.

[0012] For example, it is also conceivable that the insulating element extends by a first height in a direction perpendicular to the main extension plane, the ratio of the first height to the total height of the insert measured in the same direction having a value of 0.4 to 1, preferably 0.6 to 1, more preferably 0.7 to 1. In this way, for example, an annular peripheral insulating element is formed, which can be used in a specific area for insulating protection between the component metallization and the back metallization. For example, it is conceivable that the insulating element extends as an annular coating at the height of the ceramic element of the metal-ceramic substrate, providing insulating protection between the component metallization and the back metallization in this area. Furthermore, it is conceivable that the first height has a value in which the ratio of the first thickness of the ceramic element, measured perpendicular to the main extension plane, to the first height of the insulating element has a value of 0.5 to 2, preferably 0.8 to 1.5, more preferably 1.1 to 1.5. Preferably, it is provided that the insulating element is part of the insert.

[0013] It is further provided that the insulating element is preferably a coating on the side and / or forms a cover or encapsulation, for example manufactured by a casting, injection, spraying, dipping or injection moulding process. Preferably, the material used for the insulating element is free of ceramic and / or comprises ceramic particles embedded in a corresponding plastic matrix. It is preferably provided that the insulating element is essentially formed from plastic, epoxy resin and / or hard paper, more preferably corresponds to that from which the substrate is formed.

[0014] Preferably, it is provided that the metal-ceramic substrate has a ceramic element, a component metallization and preferably a backside metallization, the insulating element at least partially, preferably completely, surrounding the component metallization and / or the ceramic element on the side facing the substrate in the assembled state. It is conceivable that the insulating element only surrounds the component metallization and / or the ceramic element and / or the backside metallization, i.e. that the insulating element only surrounds a specific sub-area defined in each case by one or more components of the metal-ceramic substrate. It is also conceivable that the insulating element envelops or surrounds only the component metallization and the ceramic element and / or only the ceramic element and the backside metallization. In particular, by arranging the insulating element around or on the side of the metal-ceramic substrate depending on the application, it is possible to increase the insulation between the insert and the substrate. It is also conceivable that the insulating element extends from an area of ​​the component metallization to an area of ​​the ceramic element and / or an area of ​​the backside metallization on the side of the component metallization, the ceramic element and / or the backside metallization without completely covering the component metallization, the ceramic element and / or the backside metallization.

[0015] When surrounded or covered, the metal-ceramic substrate is preferably surrounded by the enveloping curve of the insulating element in a plane extending parallel to its main extension plane. It is preferably provided that the ceramic element is formed between the component metallization and the backside metallization. The component metallization, the ceramic element and the backside metallization are arranged on top of one another along a stacking direction perpendicular to the main extension surface. In particular, it is provided that the metal-ceramic substrate consists of the component metallization, the ceramic element and the backside metallization. The essential components of the metal-ceramic substrate are an insulating layer, more preferably made entirely of ceramic, and at least one metal layer bonded to the insulating layer. Due to their relatively high insulating strength, insulating layers made of ceramic have proven to be particularly advantageous in power electronics. By structuring the metal layer, conductor paths and / or connection areas for electrical components can be realized. It is preferably provided that the component metallization is not structured, but forms a closing surface when the metal-ceramic substrate is provided as an insert. A prerequisite for providing such a metal-ceramic substrate is a permanent bonding of the metal layer to the ceramic layer. In addition to the so-called direct metallurgical bonding methods, ie the DCB or DAB methods, bonding by active soldering processes, thick film layer methods, diffusion bonding and / or hot isostatic bonding are also conceivable.

[0016] Copper, aluminum, molybdenum, tungsten and / or their alloys such as CuZr, AlSi, AlMgSi, as well as laminates such as CuW, CuMo, CuAl and / or AlCu, or MMCs (metal matrix composites) such as CuW, CuMo, AlSiC, are considered as materials for the metal layers or metallizations. It is further provided that the metal layers or metallizations on the produced metal-ceramic substrates are preferably surface-modified, in particular as component metallizations. Surface modifications include, for example, sealing with noble metals, in particular silver and / or gold, or (electroless) nickel or ENIG ("electroless nickel immersion gold"), or edge encapsulation on the metallizations to suppress crack formation or expansion. For example, the metal of the component metallization is also different from the metal of the backside metallization.

[0017] Preferably, the ceramic element comprises as ceramic materials Al2O3, Si3N4, AlN, HPSX ceramics (i.e. ceramics with an Al2O3 matrix containing x percent ZrO2, e.g. Al2O3=HPS9 with 9% ZrO2 or Al2O3=HPS25 with 25% ZrO2), SiC, BeO, MgO, high density MgO (>90% of theoretical density), TSZ (tetragonal stabilized zirconium oxide). The ceramic element may also be formed as a compound ceramic or hybrid ceramic, in which several ceramic layers, each differing in their material composition, are placed on top of each other and joined together to form the ceramic element in order to combine various desired properties.

[0018] In particular, it is provided, or preferably provided, that when the component metallization or its side surface is coated, the insulating element terminates flush with the ceramic element in a direction parallel to the main extension surface and / or protrudes relative to the ceramic element. Alternatively, it is also conceivable that the ceramic element protrudes relative to the insulating element in a direction parallel to the main extension surface.

[0019] Preferably, on the component side, the upper side of the component metallization, facing away from the ceramic element, is arranged below the upper surface of the base in the assembled state, viewed in the stacking direction. In other words, on the component side, the upper surface of the component metallization is formed in such a way that it is recessed into a channel in the upper surface of the base when the insert is integrated into the printed circuit board. For example, in the embedded state of the insert, the upper surface of the component metallization has a recess depth of 10 μm to 200 μm, preferably 10 μm to 150 μm, more preferably 10 μm to 100 μm, relative to the upper surface of the base. Alternatively or additionally, it is provided that on the back side, the lower surface of the back metallization, facing away from the ceramic element, has a recessed channel relative to the lower surface of the base, preferably having one of the abovementioned recess depths. It is thus also provided that the insert is smaller than the thickness of the base when viewed in the stacking direction, and preferably that neither the upper nor the lower surface of the insert terminates flush with the upper and lower surfaces of the base. It is contemplated that the insert will simply terminate flush with the underside of the base on the backside of the printed circuit board.

[0020] It is preferably provided that the insulating element at least partially covers the side of the component metallization opposite the ceramic element. In other words, the top surface of the metal-ceramic substrate is also at least partially covered with the insulating element. For example, in order to further insulate the component metallization from the substrate of the printed circuit board, it is conceivable that the peripheral part or peripheral area of ​​the component metallization or the top surface of the component metallization, i.e. the outer peripheral area in a plane parallel to the main extension plane, is further covered with the insulating element. The peripheral area is preferably understood to be a surface formed on the outer edge, which forms up to 15%, preferably up to 10%, more preferably up to 5% of the total outer surface area of ​​the component metallization opposite the ceramic element. It is also conceivable that the component metallization covers more than 10%, preferably more than 30%, more preferably more than 50% of the top surface of the component metallization, also outside the peripheral area, further isolating the component metallization from the substrate and at the same time allowing access to the component metallization only in certain areas in order to ensure sufficient access for the connection of the component metallization. In this way, it is also conceivable that the conductor paths extend through the insulating element to achieve an electrical connection between the substrate subsection and the component metallization.

[0021] Preferably, it is provided that the ceramic elements of the metal-ceramic substrate protrude by a first length relative to the component metallization of the metal-ceramic substrate in a direction parallel to the main extension surface. The corresponding protruding areas, also known as pullbacks, serve in particular for electrical insulation of the component metallization and the backside metallization and can preferably also be used as form-fitting means when inserting or fixing the insert in or on the substrate of the printed circuit board. It is conceivable that the component metallization and / or the ceramic elements and / or the backside metallization are covered with an insulating element having an essentially constant width, so that the metal-ceramic substrate insert covered with the insulating element also has a protrusion corresponding to the height of the ceramic element, which is due to the ceramic element protrusion by a first length. The width of the insulating element is dimensioned in a direction parallel to the main extension surface.

[0022] It is preferably provided that the insert and / or insulating element interacts with the substrate in a form-fitting manner in a direction extending perpendicular to the main extension plane, and is preferably material-bonded to the substrate. This creates a particularly stable and permanent connection between the substrate and the insert, which is particularly advantageous since bonding by friction methods generally does not result in a permanent bond due to the different thermal expansion coefficients of metals, ceramics and epoxy resins. The desired form-fit is thus achieved by a corresponding modulation depth of the side surface, which prevents the metal-ceramic substrate from changing its geometry under the influence of temperature and thus damaging the printed circuit board.

[0023] If desired, a frictional connection between the insert and the base body can also be achieved. Preferably, the form-fitting acts in both possible directions perpendicular to the main extension plane of the base. It is also conceivable that in addition to the insert, further inserts are arranged in the base. It is also conceivable that the inserts terminate flush with the base only on the component side, the back side of the metal-ceramic substrate being sealed by the base. In other words, the metal-ceramic substrate or the insert is embedded or inserted into a recess in the base of the printed circuit board. This also results in a form-fitting parallel to the main extension plane.

[0024] In particular, it is provided that the metal-ceramic substrate and the base are designed such that the thermal expansion coefficients of the metal-ceramic substrate and the base are as similar as possible. In other words, the difference in the thermal expansion coefficients of the insert and the base is kept as small as possible. For this purpose, for example, a corresponding thickness of the ceramic elements in the metal-ceramic substrate is set. It is also conceivable that stabilization layers are provided to adjust the thermomechanical expansion coefficients or that several metal layers and / or different metallizations (for example, the component metallization and the back metallization are made of different metals or materials) are used to ensure the desired adjustment in an appropriate manner. In this way, it can be ensured that due to expansion during operation, no significant mechanical stresses arise between the substrate and the metal-ceramic substrate, which may for example lead to crack formation. It is also conceivable that different ceramic layers are preferably used for metal-ceramic substrates with several ceramic layers.

[0025] It has proven to be advantageous if, in addition to the form-fit, a material bond is created between the side surface of the insert and the basic body. It is preferably provided, for example, that the component metallization and / or the insulating element and / or the ceramic element provide a corresponding side profile, in particular with a corresponding modulation depth. The side surfaces of the insulating element and / or the component metallization and / or the ceramic element and / or the metal-ceramic substrate may be curved, inclined, stepped, nose-shaped and / or otherwise shaped in order to produce a form-fit in a direction perpendicular to the main extension plane.

[0026] Preferably, in order to form a form-fitting cooperation, it is provided that the insulating element is contoured on a side surface which does not extend parallel to the main extension surface, in particular the contouring being performed on the side surface which faces and is in contact with the substrate in the assembled state.

[0027] Preferably, it is provided that the insulating element has a width, in a direction parallel to the main extension plane, having a value between 10 μm and 800 μm, preferably between 150 μm and 500 μm, more preferably between 250 μm and 350 μm, thereby providing a relatively thin insulating layer that has been found to be sufficient to provide additional significant insulating protection between the component metallization and the backside metallization, especially when the first length is less than 80 μm, preferably less than 50 μm, more preferably less than 25 μm.

[0028] In particular, it is provided that the insulating element has a width averaged along its first height in a direction parallel to its main extension plane, said width having a value greater than 250 μm, preferably greater than 350 μm, more preferably greater than 500 μm. Such wide insulating elements have been shown to be suitable for forming an effective additional insulating layer. In particular, such wide insulating elements also allow thinner ceramic elements to be realized, preferably with thicker component and backside metallizations.

[0029] Preferably, it is provided that the component metallization and / or the backside metallization is thicker than the thickness of the insulating element, which places higher demands on the insulating element, in particular with regard to the electrical insulation strength between the component metallization and the backside metallization.

[0030] Preferably, it is provided that the ceramic element has a first thickness, the substrate has a second thickness and the component metallization has a third thickness, measured in a direction perpendicular to the main extension plane, the ratio between the first and second thickness and / or the ratio between the first and third thickness having a value between 0.01 and 0.3, more preferably between 0.01 and 0.2, most preferably between 0.01 and 0.15. This makes it advantageous to use relatively thin ceramics. In this case, it proves to be particularly advantageous if the insulating element surrounds the side surface of the metal-ceramic substrate in order to increase the insulation.

[0031] A further aspect of the invention is a metal-ceramic substrate used as an insert for a printed circuit board according to the invention, the insert being at least partially surrounded by an insulating element on a side that does not extend parallel to the main extension plane. All the properties and advantages described for the printed circuit board are likewise obtained for the metal-ceramic substrate used as an insert and vice versa.

[0032] In particular, covering the side surfaces of a metal-ceramic substrate with insulating elements, especially at the height of the ceramic elements, is quite unusual in the prior art. Preferably, it is provided that the insert is completely surrounded by insulating elements on the non-parallel sides. In particular, such an insert can be inserted without difficulty into any substrate of suitable size. In particular, the insulating elements are not self-adhesive. This simplifies the handling of the insert, especially when inserting it into the substrate.

[0033] It is further provided that the metal-ceramic substrate is provided as an insert together with the insulating element, which is bonded and placed on the metal-ceramic substrate together with the insulating element, whereby it is envisaged that the insulating element itself is adhesive, providing a protective cover which is preferably removed only when the insert is inserted into the substrate.

[0034] In particular, it is provided that the insulating element surrounds the metal-ceramic substrate in a surrounding manner at least in a height portion of the metal-ceramic substrate. For example, the insulating element surrounds the component metallization, the ceramic element and / or the backside metallization in the form of a strip. It is also conceivable that only a small section or a height portion of the component metallization, the ceramic element and / or the backside metallization is surrounded or covered by the insulating element. In this case, the strip-shaped course of the insulating element preferably lies in a plane parallel to the main extension plane in a surrounding manner.

[0035] A further object of the invention is to provide a method for the manufacture of an insert for a printed circuit board according to the invention, comprising the steps of: providing a metal-ceramic substrate having a main extension surface; at least partially covering the metal-ceramic substrate with an insulating element; - Inserting an insert having an insulating element into the base.

[0036] All advantages and properties discussed with respect to the printed circuit board are equally applicable to the present method and vice versa. Preferably, it is provided that the substrate is made of a different material than the insert. In particular, it is provided that the substrate is essentially free of ceramic or does not provide ceramic elements as insulating or stabilizing layers. Preferably, the substrate comprises less than 10% by weight of ceramic, more preferably less than 5% by weight, most preferably less than 3% by weight.

[0037] In particular, it is thereby provided that the proportion of the metal-ceramic substrate in the proportion of the printed circuit board is less than 50%, more preferably less than 30%, most preferably less than 15%. It is further provided that the insert extends from the component side of the base of the printed circuit board to the back side of the base. In other words, the insert terminates substantially flush with the base in a direction perpendicular to the main extension plane on both sides, i.e. on the component side and on the back side. In particular, a permanent bond between the metal-ceramic substrate and the base is formed by a form fit between the base and the metal-ceramic substrate, which prevents the insert from coming off the printed circuit board.

[0038] According to a preferred embodiment, in order to form a cooperation via form fit: the metal-ceramic substrate is contoured on a side that does not extend parallel to the main extension surface, and / or - the ceramic elements of the metal-ceramic substrate protrude by a first length in a direction parallel to the main extension surface relative to the component metallization and / or the backside metallization of the metal-ceramic substrate, The metal-ceramic substrate is surrounded by an insulating element, in which case the side profile can be supported by the insulating element or maintained by an insulating element having a constant width through the entire height of the insert.

[0039] For example, it is provided that the side surfaces, in particular the side surfaces of the component metallization and / or the back metallization and / or the insulating element, are concavely and / or convexly curved. Alternatively, it is also conceivable that the component metallization and / or the insulating element are stepped. In particular, it is provided that the substrate engages with recessed or protruding paths on the side surfaces of the insulating element, the component metallization and / or the back metallization so as to create a form-fit in one or both directions extending perpendicularly to the main extension surface. For example, it is conceivable that the outermost edges of the component metallization and / or the insulating element are stepped, in particular stepped in such a way that the open areas of the steps are formed on the side surfaces facing the component face and / or the back face. In a corresponding manner, taking into account the isotropic transport of heat, the component can be placed on the component metallization in such a way that the heat diffusion is completely absorbed by the component metallization. Here, the parts of the component metallization that do not contribute in any way to the heat transport are removed in this stepped path and replaced by the substrate. Preferably, the protruding portion of the ceramic element is used to form a form fit, in particular what is known as the pullback, to provide sufficient insulation between the component metallization and the backside metallization.

[0040] Preferably, the first length is defined to have a value between 1 μm and 200 μm, preferably between 20 μm and 100 μm, more preferably between 25 μm and 60 μm. More preferably, the first length relates to a protrusion of the ceramic element in a direction parallel to its main extension plane, for example relative to an insulating element surrounding the component metallization.

[0041] It has been shown that an effective form fit can already be achieved by suitable dimensioning, and that the additional insulating effect of the material from which the substrate of the printed circuit board is made also ensures electrical insulation between the component metallization and the backside metallization. This relatively very small protruding portion of the ceramic element, i.e. this relatively small so-called pullback, allows the insert, i.e. the metal-ceramic substrate, to be integrated into the substrate of the printed circuit board in the most space-saving manner possible. It is preferably provided that the metal-ceramic substrate, in particular the one with the insulating element, has a maximum expansion in a plane parallel to the main extension plane, the value of which has a value between 1 mm and 200 mm, more preferably between 4 mm and 60 mm, most preferably between 6 mm and 30 mm. This provides an insert of relatively small dimensions, which can be used to locally increase the thermal conductivity in the printed circuit board if necessary. In particular, a relatively large number of individual inserts can be provided from a master card. Such a master card is defined by the format immediately after the bonding of the component metallization to the backside metallization, which is carried out via the component bonding process.

[0042] It is also conceivable that the first length has 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 the backside metallization protrudes relative to the ceramic element in a direction parallel to the main extension plane. The absolute value of the first length can have the above-mentioned values.

[0043] In particular, it is provided that the side surface is profiled, i.e. has such a side surface profile, such that a modulation depth or height is set with a value between 1 μm and 200 μm, preferably between 20 μm and 100 μm, more preferably between 25 μm and 60 μm. The modulation depth or height is to be understood as the deviation, measured in a direction parallel to the main extension surface, from an imaginary cylindrical outer path assigned to the narrowest point of the metal-ceramic substrate (measured in a plane parallel to the main extension surface). The imaginary cylindrical outer path runs perpendicular to the main extension surface. If the modulation depth is formed by ceramic elements protruding from the component metallization and / or the back metallization and / or the insulating element, the modulation depth can correspond to the first length. It is also conceivable that the modulation depth results from the component metallization and / or the ceramic elements protruding in a direction parallel to the main extension surface relative to the back metallization. For example, it is also conceivable that the side surface in the region of the ceramic element has a path that is inclined with respect to the stacking direction (in other words, the upper and lower faces of the ceramic element have different diameters or dimensions). In particular, the above applies equally to the modulation depth of the lateral profile of the insulating element.

[0044] For example, it is conceivable that the lateral surface or the paths of the lateral surfaces in the area of ​​the component metallization and / or the backside metallization run parallel to the stacking direction (i.e. the cross section of the component metallization and / or the backside metallization is essentially constant in the area of ​​the component metallization or the backside metallization when viewed in the stacking direction). The modulation depth is then preferably realized by a step in the height of the ceramic element and / or by a corresponding geometric shape of the insulating element. The modulation depth can be created by a contouring or modulation in the area of ​​the ceramic element and / or the insulating element, which contouring may be continuous in the stacking direction through the thickness of the ceramic or insulating element or may be discrete or abrupt in the height of the ceramic element.

[0045] It is further conceivable that the insert has one or more protrusions that protrude in a direction parallel to the main extension plane relative to the overall path of the insert's periphery. This, preferably nose-shaped, protrusion can advantageously provide an additional form fit in the circumferential direction along the periphery, thereby supporting a rotationally fixed arrangement in the base. Advantageously, it has been shown that such a protrusion is produced by cutting the metal-ceramic substrate from the master card using laser light and / or water cutting. Since the width of the insulating element is constant, this protrusion is then also formed on the insert with the insulating element.

[0046] It is preferably provided that the metal-ceramic substrate has a rounded contour or rounded corners in the main extension plane. A corresponding design of the cross section of the insert in a plane running parallel to the main extension plane proves to be advantageous, since it makes it possible to reduce notch effects, especially on the substrate of the printed circuit board, which in turn makes it possible to extend the service life of the printed circuit board with the insert.

[0047] Preferably, the metal-ceramic substrate is provided with a ceramic element, the component metallization being bonded to the ceramic element; a stabilization layer, for example in the form of a further ceramic element, is provided or formed, the metal intermediate layer being arranged between the ceramic element and the stabilization layer, and / or The component metallization and / or the backside metallization comprises a first metal layer and / or a second metal layer, the first metal layer and the second metal layer being arranged on top of each other.

[0048] In particular, it is possible to influence the thermal expansion coefficient of the insert by designing the metal-ceramic substrate accordingly, in order to match it to the thermal expansion coefficient of the base. For example, it is conceivable to design the stabilization 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, so that the mechanical stresses between the base and the insert are reduced. Preferably, the first metal layer differs from the second metal layer in terms of graining, more preferably, the graining in the first metal layer is smaller than that in the second metal layer and / or most preferably, the thickness of the first metal layer is smaller than that of the second metal layer. Furthermore, it is conceivable that the thickness of the component metallization differs from the thickness of the back metallization. This makes it possible to advantageously influence the height position of the ceramic element in the base of the printed circuit board, in particular to ensure that the insulating ceramic element is positioned in the base offset towards the back side and away from the component side, or vice versa.

[0049] It is further envisaged that a contouring of the side surfaces not extending parallel to the main extension surface and / or the realisation of ceramic elements on the metal-ceramic substrate which protrude in a direction parallel to the main extension surface relative to the component metallisation and / or the rear metallisation is provided. In particular, it is envisaged that the contouring and / or the exposure is carried out, for example, by etching, by machining, for example by milling, by machining with laser light and / or by a water jet.

[0050] Preferably, the component face extending substantially parallel to the main extension face and / or the back face are covered with a protective or resist layer, after which the side faces are contoured and / or the ceramic elements are partially exposed using an etching medium. In this way, the desired contouring of the side faces and the exposure of the laterally protruding parts of the ceramic elements are easily achieved by a simple etching process. The side faces are then at least partially, preferably completely, covered with insulating elements. In particular, it is provided that the insert is cut out from a metal-ceramic substrate provided as a master card.

[0051] It is further contemplated that the sides of the insert may be polished or ground prior to insertion into the substrate. Further advantages and features emerge from the following description of preferred embodiments of the object according to the invention, with reference to the attached drawings, in which: The individual features of the individual embodiments can be combined with one another within the scope of the invention. [Brief description of the drawings]

[0052] [Figure 1] 1 shows a schematic diagram of a plan view (top) and a cross-sectional view (bottom) of a printed circuit board according to a first more preferred embodiment of the present invention. [Diagram 2] 1 shows an insert according to a first preferred embodiment of the present invention. [Diagram 3] 3 shows an insert according to a second preferred embodiment of the present invention. [Figure 4] 4 shows an insert according to a third preferred embodiment of the present invention. [Diagram 5] 1 shows an insert according to a fourth preferred embodiment of the present invention. [Figure 6] 13 shows an insert according to a fifth preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0053] In Fig. 1 a printed circuit board 100 according to a first preferred embodiment of the invention is shown in top view (above) and in cross section (below). Such a printed circuit board 100 serves in particular as a carrier for a circuit formed by electric or electronic components 5, connections 7 and / or conductor paths 4. The electric or electronic components 5, the conductor paths 4 and / or the connections 7, for example in the form of soldering surfaces (pads) or soldering eyes, are preferably arranged or bonded to a component side BS of the printed circuit board 100. For a particularly cost-effective production of such a printed circuit board 100, it is established to use plastics, in particular fiber-reinforced plastics, epoxy resins and / or hard paper, as materials for the substrate 2, which essentially extends along the main extension surface HSE and on whose component side BS the connections 7, the electronic components 5 and / or the conductor paths 4 are formed or bonded.

[0054] Continual further developments in the field of electronics, in particular with regard to the performance of the electronic components 5, have shown that the materials used for the substrate 2 are not able to durably withstand new challenges, in particular with regard to the heat generated during operation. This is due in particular to the fact that the aforementioned materials for the substrate 2 of the printed circuit board 100 have a relatively low thermal conductivity and therefore cannot dissipate to a sufficient extent the heat generated by the electrical components during operation.

[0055] On the other hand, printed circuit boards 100 formed as metal-ceramic substrates are able to dissipate the generated heat to a sufficient extent due to their high thermal conductivity, in particular in comparison with printed circuit boards made of the above-mentioned materials, i.e. substrates 2 made of plastic, in particular fiber-reinforced plastic, epoxy resin and / or hard paper, but are more complex and costly to produce in terms of manufacturing techniques.

[0056] In order to take advantage of the positive properties of the printed circuit board 100 made of plastic, epoxy resin or hard paper and of the metal-ceramic substrate, in particular its thermal conductivity, it is preferably provided that the printed circuit board 100 according to the embodiment shown in FIG. 1 has a base 2 extending along a main extension plane HSE and with which an insert 1 is integrated, the insert 1 comprising a metal-ceramic substrate. It is preferably provided that the metal-ceramic substrate used as the insert 1 is arranged in the printed circuit board 100 in a position where an increase in heat generation is expected. For example, it is provided that the insert 1 is arranged below one or more electrical components 5 in a stacking direction S perpendicular to the main extension plane HSE so as to be able to dissipate the heat generated during operation. Preferably, in order to ensure an effective heat dissipation, the expansion A of the insert 1 is greater than the expansion of the electrical components dimensioned parallel to the main extension plane HSE.

[0057] It is preferably provided that at least one insert 1, preferably several inserts 1, are integrated into the base 2 of the printed circuit board 100. The component side BS of the insert 1 preferably ends substantially flush with the component side BS of the base 2 and / or the back side RS of the insert 1 ends flush with the back side RS of the base 2. Furthermore, it is preferably provided that the volumetric proportion of the insert 1 or inserts 1 in the volume of the base 2 or the entire printed circuit board 100 is less than 50%, more preferably less than 30%, more preferably less than 15%. It has been shown 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 mainly with materials for the base 2 that are easier to process and less costly than metal-ceramic substrates.

[0058] Preferably, it is provided that the insert 1 terminates flush with the component face BS and the rear face RS of the base 2, in particular in the stacking direction S extending perpendicular to the main extension direction HSE, and interacts with the base 2 via a form-fitting in a direction extending perpendicular to the main extension direction HSE. This allows or supports a secure retention of the insert 1 in the printed circuit board 100. Preferably, it is provided that the selection of the materials, whether the material of the base 2 on the one hand, or one or several of the materials of the ceramic element 30, is made in such a way that the difference in thermal expansion coefficients is kept as low as possible to prevent thermomechanical stresses from causing cracks and / or damage of the printed circuit board 100 and / or the metal-ceramic substrate. Preferably, the thermal expansion coefficient of the insert 1 does not deviate from that of the base 2 by more than 30%, preferably not more than 15%, more preferably not more than 10%. To select the insert in question, the skilled person uses, for example, simulations for the respective composition of the insert and compares these simulations with the values ​​for the base 2. In particular, it is provided that the insert 1 is cylindrical and / or has an essentially rectangular, in particular square, cross section with rounded corners.

[0059] 2 shows an insert 1 as a first exemplary embodiment of the invention. To form an insert essentially made of a metal-ceramic substrate, it is provided that in a first step, in particular, the bonding of the component metallization 20 to the ceramic element 30 takes place. The bonding of the component metallization 20 and / or the backside metallization 20' is preferably carried out by a direct metal bonding method such as the DCB or DAB method, by a soldering method, in particular an active soldering metal method, by a diffusion bonding process and / or by hot isostatic pressing. Bonding by thick-film techniques is also conceivable. Preferably, the insert 1 is separated from the master card, i.e. singulated.

[0060] In particular, it is provided that the insert 1 comprises a ceramic element 30, a component metallization 20 and a backside metallization 20'. In the assembled state in which the insert 1 is integrated into the printed circuit board 100 or into the substrate 2, the component metallization 20 faces the component side BS of the printed circuit board 100 and the backside metallization 20' faces the backside RS. Furthermore, the ceramic element 30 has a first thickness D1, the component metallization 20 has a third thickness D3 and the backside metallization 20' has a fourth thickness D4. The third thickness D3 is preferably of the same size as the fourth thickness D4. However, it is also conceivable, for example, that the third thickness D3 is greater than the fourth thickness D4 or vice versa, thus advantageously allowing the ceramic element 30 to be positioned differently in the insert 1 along a stacking direction S that runs perpendicular to the main extension plane HSE. For example, this allows to provide a thicker component metallization 20, which due to the increased third thickness provides a higher thermal conductivity in the area facing the component 5, which proves to be advantageous when dissipating heat.

[0061] Furthermore, it is preferably provided that the ceramic element 30 having the first thickness D1 is dimensioned such that the ratio between the first thickness D1 and the component metallization 20 and / or the ratio of the first thickness D1 to the second thickness D2 of the substrate 2 is between 0.01 and 0.3, preferably between 0.01 and 0.2, more 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 substrate 2 in order to ensure both good heat dissipation and the desired dielectric strength.

[0062] Furthermore, it is provided that the ceramic element 30 protrudes by a first length L1 in a direction parallel to the main extension plane HSE relative to the component metallization 20 and / or the back metallization 20'. As a result, a so-called pullback is formed on the outer periphery of the metal-ceramic substrate 1. The upper side of the insert 1 facing the component side BS and the lower side of the insert 1 facing the back side RS are joined to each other by a side surface SF that does not extend parallel to the main extension plane HSE. In the assembled state, the side surface SF of the metal-ceramic substrate faces the base 2 of the printed circuit board 100. In particular, the side surface SF of the metal-ceramic substrate includes a subsection of the component metallization 20, the ceramic element 30 and the back metallization 20'.

[0063] In order to increase the insulating strength of the inserted insert 1, in particular with respect to the substrate 2 of the printed circuit board 100, it is preferably provided that the insulating element 8 at least partially covers the side surface SF of the metal-ceramic substrate. By covering the side wall or side surface SF of the metal-ceramic substrate, the insulating element 8 is arranged in the assembled state between the substrate 2 and the metal-ceramic substrate. For example, the insulating element 8 may be a coating with a corresponding insulating layer having a width B in the direction parallel to the main extension plane HSE, for example, of 10 μm to 800 μm, preferably 150 μm to 500 μm, more preferably 250 μm to 350 μm. In the embodiment example shown in FIG. 2, the insulating element 8 completely covers or surrounds the component metallization 20 and the back metallization 20′. In particular, in the embodiment example of FIG. 2, the side surface of the ceramic element 30 is devoid of the insulating element 8, which in each case extends above and below the ceramic element 30. For example, the covering element 8 is an encapsulant with a filling material, which terminates flush with the outer periphery of the ceramic element 30, for example in the embodiment example of Fig. 2. The corresponding filling material is for example and / or comprises a plastic, in particular a fibre-reinforced plastic, an epoxy resin and / or a hard paper, and is particularly preferably made of the same material as the substrate 2 of the printed circuit board 100. More preferably, provisions are made for the case where the filling material for the insulating element 8 has additional insulating components, such as ceramic particles dispersed in the filling material of the insulating element 8.

[0064] 3 shows an insert 1 according to a second exemplary embodiment of the invention. In the example embodiment shown here in FIG. 3, the insulating element 8 is formed to exclusively surround the component metallization 20, in particular over the entire height of the component metallization 20. Alternatively, it is conceivable that only the backside metallization 20' is surrounded by the insulating element 8. In the example embodiment shown in FIG. 3, a subsection of the side surface SF of the metal-ceramic substrate, on which the ceramic element 30 and the backside metallization 20' are arranged, remains essentially free of the insulating element 8.

[0065] Preferably, the insulating element 8 extends along a first height H1 dimensioned perpendicular to the main extension plane HSE, the ratio of the first height H1 to the overall height H2 of the entire insert 1 having a value of 0.4 to 1, preferably 0.5 to 1, more preferably 0.7 to 1.

[0066] 4 shows an insert 1 according to a third exemplary embodiment of the invention. In the embodiment shown in FIG. 4, the insulating element 8 completely surrounds the metal-ceramic substrate on the side surface SF of the metal-ceramic substrate. In the illustrated embodiment example, the insulating element 8 is absent on the top and bottom surfaces, i.e. on the outside of the metal-ceramic substrate facing the component side BS and on the outside facing the back surface RS. Alternatively, it is also conceivable that the insulating element 8 further covers the component side BS and / or the back surface RS at least partially and / or completely. In this case, it is preferable that at least a small area on the component side BS is free in order to allow a corresponding connection option of the component 5 for the component metallization 20.

[0067] In particular, in the embodiment example of figure 4, the side surface SF of the ceramic element 30 is also surrounded by the insulating element 8, thus completely surrounding the side surface SF of the metal-ceramic substrate. For example, it is provided here that the first length L1 of the protruding part of the ceramic element 30 relative to the second length L2 of the component metallization 20 and / or the backside metallization 20', dimensioned parallel to the main extension surface HSE, has a value between 0.01 and 0.3, preferably between 0.01 and 0.2, more preferably between 0.01 and 0.1.

[0068] It is further contemplated that the second length L2 of the component metallization 20 may differ from the second length L2 of the backside metallization 20' (not shown). Preferably, the component side BS and / or the back side RS of the metal-ceramic substrate remain free of the insulating element 8 or part of the insulating element 8 in order to provide a corresponding connection area to the component side BS or to allow direct access of a cooling element to the back side metallization 20'.

[0069] Fig. 5 shows a fourth exemplary embodiment of the invention, where the embodiment of Fig. 5 essentially corresponds to the embodiment of Fig. 4, with the insulating element 8 having a side profile formation on the side surface SF. By such a side profile formation it is advantageously possible to achieve a form fit between the base body 2 and the insert 1, which form fit fixes and permanently holds the insert 1 in the base body 2 of the printed circuit board 100. Preferably, a material bonded connection is also achieved between the insert and the base body.

[0070] Furthermore, in all other exemplary embodiments shown, it is conceivable that the side surface SF of the insert 1 with the insulating element 8 has a side profile in order to form a form-fit with the base body 2 in a direction extending perpendicular to the main extension surface HSE. For example, it is conceivable that only the insulating element 8 in the region of the component metallization 20 and / or the back metallization 20' or only the component metallization 20 and / or the back metallization 20' has a corresponding side profile suitable for a corresponding side profile for form-fitting. It is also conceivable that the ceramic element 30 protrudes in a direction parallel to the main extension surface HSE with respect to the metal layer and / or the component metallization 20 and / or with respect to the insulating element 8, thereby creating a corresponding form-fit in a direction perpendicular to the main extension surface HSE.

[0071] For example, the side profile is a concave and / or convex portion, which may extend, for example, over the entire second height of the insert 1. It is conceivable that the side profile is predetermined, for example, by the insulating element 8. It is conceivable that the side profile is created when the insulating element 8 is formed, for example, by a corresponding mold or by a subsequent process, for example machining. It is also conceivable that the side profile is formed, at least in part, by a stepped, inclined, curved or tapered path 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 designed wavy or forms several local maxima and minima in the width B in order to be formed for the desired form fit.

[0072] FIG. 6 shows a fifth exemplary embodiment of the invention. This embodiment differs in that the component metallization 20 projects relative to the backside metallization 20' in order to realize a lateral path of the insert 1 that creates a form-fit between the insert 1 and the substrate 2. The modulation depth M is determined by the component metallization 20 projecting in a direction parallel to the main extension plane HSE. It can further be seen that the side surface SF of the insert 1 in the region of the ceramic element 30 has a path that is inclined relative to the stacking direction S. This results in a projecting path of the side surface SF in the region of the component metallization 20. Alternatively, it is also conceivable that the backside metallization 20' projects relative to the ceramic element 30. In the example shown in FIG. 6, the path of the side surface SF in the region of the component metallization 20 and the backside metallization 20' is parallel to the stacking direction S. It is also conceivable that the path of the side surface SF in the region of the backside metallization 20 and / or the component metallization 20' contributes to the formation of the modulation depth or height. In principle, it is also conceivable that the flank SF has several maxima and / or minima in the modulation depth or height M of the flank SF.

[0073] In particular, the embodiment of Fig. 6 provides that the side surface SF of the metal-ceramic substrate 1 is preferably completely covered with the insulating element 8. In this case, the insulating element 8 has a substantially constant width B along its entire height. The insert 1 of Fig. 6 has a corresponding side surface contouring, 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 easy to manufacture, since only the entire side surface SF needs to be covered with an insulating layer 8 of constant width in order to provide the desired additional insulating protection. [Explanation of symbols]

[0074] 1 Insert 2 Base 4 Conductor Path 5 parts 7 Connection 8. Insulating Elements 20 Component Metallization Department 20' Backside metallization 30 Ceramic Elements 100 Printed Circuit Board HSE main extension surface S Stacking direction D1 First thickness D2 Second thickness D3 Third thickness L1 First length L2 Second length M modulation depth science fiction aspect RS Back BS parts side B Width H1 First height H2 Overall height

Claims

1. A printed circuit board (100) for electrical components (5) and / or conductor paths (4), comprising: - a substrate (2) extending along a main extension plane (HSE); - an insert (1) which, in the assembled state, is integrated into said base body (2), The insert (1) is a metal-ceramic substrate (10), A printed circuit board (100) in which, in the assembled state, said metal-ceramic substrate (1) is at least partially covered, in particular surrounded, by an insulating element (8) on the side (SF) facing said base (2).

2. 2. The printed circuit board (100) of claim 1, wherein the metal-ceramic substrate (1) comprises a ceramic element (30), a component metallization (20) and preferably a backside metallization (20'), and the insulating element (9) partially, preferably completely, surrounds the ceramic element (30) on the side facing the base (2) in the assembled state.

3. 3. The 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'), and the insulating element (9) at least partially, preferably completely, surrounds the component metallization (20) on the side facing the base (2) in the assembled state.

4. 4. The printed circuit board (100) of claim 2 or 3, wherein the insulating element (8) at least partially covers a top surface of the component metallization (20) opposite the ceramic element (30).

5. The printed circuit board (100) according to any one of claims 1 to 4, wherein the ceramic element (30) of the metal-ceramic substrate (10) protrudes by a first length (L1) in a direction parallel to the main extension plane (HSE) relative to a component metallization portion (20) of the metal-ceramic substrate (10).

6. The printed circuit board (100) according to any one of claims 1 to 5, wherein the insert (1) and / or the insulating element (8) cooperate with the base (2) via form-fitting in a direction perpendicular to the main extension plane (HSE).

7. 6. The printed circuit board (100) according to claim 5, wherein the insert (1) and / or the insulating element (8) are material-bonded to the substrate (2).

8. The printed circuit board (100) according to any one of claims 1 to 7, wherein the insulating element (8) is contoured on a side surface (SF) that does not extend parallel to the main extension surface (HSE) in order to form a cooperation via form fitting.

9. The printed circuit board (100) according to any one of claims 1 to 8, 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 plane of extension (HSE), the width (B) having a value between 10 μm and 800 μm, preferably between 150 μm and 500 μm, more preferably between 250 μm and 350 μm.

10. The printed circuit board (100) according to any one of claims 1 to 9, 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), the width (B) having a value greater than 250 μm, preferably greater than 350 μm, more preferably greater than 500 μm.

11. When measured in a direction perpendicular to the main extension plane (HSE), the ceramic element (30) has a first thickness (D1), the substrate (2) has a second thickness (D2), and the component metallization (20) has a third thickness (D3); the ratio between said first thickness (D1) and said second thickness (D2), and / or the ratio between said first thickness (D1) and said third thickness (D3) is The printed circuit board (100) according to any one of the preceding claims, having a value of 0.01 to 0.3, preferably 0.01 to 0.2, most preferably 0.01 to 0.

15.

12. A metal-ceramic substrate (10) suitable as an insert (1) for a printed circuit board (100) according to any one of claims 1 to 11, said insert (1) being at least partially surrounded by an insulating element (8) on said non-parallel running side faces (SF).

13. 13. The metal-ceramic substrate (10) according to claim 12, wherein the insert (1) is completely surrounded by an insulating element (8) on the side faces (SF) which do not run parallel.

14. 14. The metal-ceramic substrate (10) according to claim 12 or 13, wherein the insulating element (8) surrounds the metal-ceramic substrate (10) at least in a height portion of the metal-ceramic substrate (10).

15. A method for manufacturing a printed circuit board (100) according to any one of claims 1 to 11, comprising the steps of: - providing a metal-ceramic substrate (10) having a main extension surface (HSE); - at least partially covering said metal-ceramic substrate (1) with an insulating element (8); - inserting said insert with said insulating element into said base body (2).

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