Method for producing metal-ceramic substrate, and metal-ceramic substrate produced by such method

Abstract

To reduce the amount of time and / or material required in the production of metal-ceramic substrates, in particular in their structuring.SOLUTION: A method comprises: providing a ceramic element 30 and a metal layer 10 which extend along a main extension plane HSE; and bonding the ceramic element 30 to the metal layer 10 to form a metal-ceramic substrate 1, in particular by means of at least one of a direct metal bonding process, hot isostatic pressing or a soldering process. A structuring part 15 for forming an isolation of metal sections 10' and / or a recess for forming a solder stop is realized in the metal layer 10 by means of a laser process and an etching process. An ultrashort pulse laser is used in the laser process. The recess already created in the laser process is used to flow an etching agent only into the recess or to concentrate the etching agent in the recess in the etching process.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a metal-ceramic substrate and a metal-ceramic substrate manufactured by such a method.

Background Art

[0002] For example, a carrier substrate for electrical components in the form of a metal-ceramic substrate is well known from the prior art, for example Patent Document 1, Patent Document 2, and Patent Document 3, as a printed circuit board or a circuit board. Usually, the connection region between the electrical component and the conductive path is arranged on one component surface of the metal-ceramic substrate, and the electrical component and the conductive path can be interconnected to form an electrical circuit. The essential components of a metal-ceramic substrate are preferably an insulating layer made of ceramic and a metal layer or a structural metallization joined to the insulating layer. The insulating layer made of ceramic has been found to be particularly advantageous in the field of power electronics due to its relatively high insulation strength. Therefore, by structuring the metal layer, conductive paths and / or connection regions for electrical components can be realized.

[0003] In such a carrier substrate, particularly a metal-ceramic substrate, due to the different material selections of one insulating layer and the other metallization, problems caused by different coefficients of thermal expansion, for example, when heat is generated during the operation or manufacture of the carrier substrate, thermal-mechanical stress may be induced or caused, which may lead to bending or damage of the carrier substrate.

[0004] The prior art usually proposes an etching process used to structure or profile at least one metal layer. For this purpose, masking is applied to the side of the metal layer opposite the ceramic element in the form of a resist layer in particular. Next, an etching agent can be used to expose the unmasked areas and structure the metal layer corresponding to the masking. However, such an approach requires a lot of materials and time, especially with regard to the application of the masking and the use of the etching agent.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0006] Based on this, the object of the present invention is to reduce the time and / or the amount of material required in the production of metal-ceramic substrates, especially their structuring.

Means for Solving the Problems

[0007] This problem is solved by the method according to claim 1 and the metal-ceramic substrate according to claim 12. Further developments and further embodiments are described in the dependent claims, the description and the drawings.

[0008] According to a first aspect of the present invention, there is provided a method for manufacturing a metal-ceramic substrate, comprising Providing a ceramic element and at least one metal layer, wherein the ceramic element and the at least one metal layer extend along a main extension plane. Forming a metal-ceramic substrate by joining the ceramic element to the at least one metal layer, in particular by a direct metal bonding process, hot isostatic pressing and / or soldering process. Provided is a method in which preferably a structuring part for forming a separation of the metal part and / or preferably a recess for forming a solder stop is realized in the at least one metal layer by a laser process and a chemical process, in particular etching.

[0009] In contrast to the prior art, the present invention proposes not only the use of an etching agent for structuring, but also the use of a laser beam for removing material so as to form a structuring part and / or a recess. By combining these two methods, it is advantageously possible to omit the formation of masking. In particular, the laser beam is used to define the course of the structuring part, for example, the etching agent used is intended to be used for the uniform removal of the material of the at least one metal layer. Since the laser beam gives the specification of the area where the removal of the material increases, the specification by masking is no longer necessary. For example, since no material is required for the formation of masking, the manufacture of the structuring part is promoted and the material requirement is reduced.

[0010] It is conceivable that the manufacture or removal by the laser beam and / or the etching agent is carried out simultaneously, at least intermittently. That is, the two independent methods for removing the material overlap in time and can further accelerate the manufacturing process. For example, after passing the laser beam a certain number of times, the etching agent is applied to the entire area of the at least one metal layer, and it is conceivable that the laser beam ensures further removal in further passes. More preferably, the treatment by the laser beam and the chemical treatment are carried out continuously.

[0011] Another advantage obtained from the combination of etching and removal by laser light is to ensure that the material of the ceramic element is not removed during the treatment with laser light. Thereby, damage to the ceramic element by laser light can be avoided. For this purpose, it is particularly intended that the removal by the etchant is not completed before the structuring by laser light is finished. In particular, the removal by laser light within the scope of a preliminary or preparatory step serves to define the course of the separation grooves and / or recesses, and the separation grooves and / or recesses obtain a definitive or final depth only by the etching step.

[0012] Preferably, at least 50%, more preferably at least 75%, and most preferably at least 90% of the material removal is performed by laser light. In particular, the recesses are understood to be profiles, such as those used for soldering, rather than profiles that separate two adjacent metal parts in at least one metal layer. Such soldering, for example, functions as a groove for the solder material to receive the recess, preventing the unnecessary flow of the solder material to a specific area by preventing the solder material from flowing further.

[0013] As materials for at least one metal layer or backside metallization in a metal-ceramic substrate, copper, aluminum, molybdenum and / or their alloys, and laminates such as CuW, CuMo, CuAl, AlCu and / or CuCu are considered, in particular a copper sandwich structure having a first copper layer and a second copper layer, and the particle size of the first copper layer is different from that of the second copper layer. Furthermore, the primary metal layer is preferably surface-modified, in particular as a structural metallization. Possible surface modifications include, for example, noble metals, in particular silver and / or gold, or ENIG ("electroless nickel immersion gold"), sealing with nickel, or edge encapsulation on at least one metal layer, for suppressing crack formation or expansion.

[0014] Preferably, the ceramic element includes Al2O3, Si3N4, AIN, HPSX ceramic (i.e., a ceramic having an Al2O3 matrix containing x percent by composition ratio of ZrO2, such as Al2O3 = HPS9 having 9% ZrO2, or Al2O3 = HPS25 having 25% ZrO2), SiC, BeO, MgO, high-density MgO (more than 90% of the theoretical density), and TSZ (tetragonal stabilized zirconium oxide) as a ceramic material. In order to combine various desired properties, it is also conceivable that the ceramic element is designed as a composite material or hybrid ceramic in which several ceramic layers, each different in terms of its material composition, are arranged overlapping and joined to form an insulating element. It is also conceivable that a metal intermediate layer is arranged between two ceramic layers, and the metal intermediate layer is preferably thicker than 1.5 mm and / or thicker than the sum of the two ceramic layers. Preferably, a ceramic with as high a thermal conductivity as possible is used in order to achieve as low a thermal resistance as possible.

[0015] A person skilled in the art understands the "DCB process" (direct copper bonding technology) or the "DAB process" (direct aluminum bonding technology) as a method, for example, of joining metal layers or sheets (such as copper sheets or foils or aluminum sheets or foils) to each other and / or to ceramics or ceramic layers, which uses a metal or copper sheet or metal or copper foil having a layer or coating (molten layer) on the surface side. In this method described, for example, in U.S. Patent No. 3,744,120 or German Patent Invention No. 2,319,854, this layer or coating (molten layer) forms a eutectic having a melting point below the melting point of the metal (such as copper). Thereby, by placing the foil on the ceramic and heating all the layers, they are joined together. Thus, it is possible to join them together by essentially surface-melting the metal or copper only in the region of the molten layer or oxide layer.

[0016] In particular, next, the DCB process, for example, has the following method steps: a step of oxidizing a copper foil so as to obtain a uniform copper oxide layer; placing a copper foil on a ceramic layer; heating the composite to a process temperature between about 1025 and 1083 °C, for example about 1071 °C; cooling to room temperature.

[0017] An active soldering method for joining a metal layer or metal foil, in particular a copper layer or copper foil, to a ceramic material is understood as a method that is also used in particular for the production of metal-ceramic substrates. The bond between a metal foil, for example a copper foil, and a ceramic substrate, for example an aluminum nitride ceramic, is produced by using a soldering solder containing an active metal in addition to main components such as copper, silver, and / or gold. This active metal is, for example, at least one element of the group of Hf, Ti, Zr, Nb, Ce, and establishes a bond between the soldering solder and the ceramic by a chemical reaction, and the bond between the soldering solder and the metal is a metal soldering bond. Alternatively, joining by thick coating treatment is also conceivable.

[0018] Hot isostatic pressing is known, for example, from European Patent No. 3080055, the content of which is hereby expressly incorporated by reference with respect to hot isostatic pressing. Preferably, the structuring by a chemical process ends, in particular after the end of the preparation step by a laser beam. Thereby, it is ensured that the final removal is carried out only with an etchant, and it is ensured that the ceramic element is not damaged by the laser beam.

[0019] In particular, it is intended that masking during etching be avoided in the manufacture of the structuring part. This is possible especially since the structuring is defined by removal by laser light and the etching having an isotropic effect is used to uniformly remove the entire upper surface of at least one metal layer. Alternatively, it is also conceivable that masking is intended. In a pre-step before etching, it is also conceivable that recesses are formed having a depth smaller than the thickness of at least one metal layer. Next, for example, using the already formed recesses, the etchant can be made to flow only into this recess or the etchant can be concentrated in this recess. For example, it is conceivable that the etchant is applied and as a result of the tilting and rotational movement on the upper surface of at least one metal layer, the excess etchant flows out of the metal-ceramic substrate or flows into the recess.

[0020] Preferably, a chemical process, in particular a chemical process alone, is intended to remove the metal and expose the region of the outer surface of the ceramic element. In other words, the chemical process that starts or continues after the laser treatment ensures that the residual amount of the metal layer is removed to form the separation groove.

[0021] In principle, it is also conceivable that masking is at least partially intended, for example, to realize a stepped course or to maintain the thickness in the region outside the planned separation groove. In this case, it can be seen that the pre-structuring by laser light, i.e., the formation of the recesses during the pre-step, is advantageous because it enables the masking to be applied in a more flexible and simplified manner, for example, by a corresponding printing process onto the region where the material has not been removed during the pre-step.

[0022] Furthermore, the masking is at least partially intentional and is removed partially by the laser light, and it is conceivable that no material is removed from the upper surface of at least one metal layer during etching. In this way, the thickness of the original metal layer can be retained at least in the selected regions. In these regions, it is further conceivable to structure at least one metal layer using laser light in combination with an etching process, similar to the further embodiments described above.

[0023] Preferably, the chemical process and the laser process are intended to be carried out at least intermittently simultaneously. It can be seen that this is advantageous for the speed and duration required to achieve the desired structured parts and / or recesses.

[0024] Preferably, the laser process is used at least partially to define the shape of the side surface of at least one metal layer that is not parallel to the main extension plane. In particular, this relates to the side surface that joins the upper edge of at least one metal layer to the lower edge of at least one metal layer. This side surface that substantially bounds at least one metal layer laterally can be appropriately shaped to have a particularly advantageous effect on thermal shock resistance. For example, it has been shown that the thermal shock resistance can be increased by forming local maxima and / or local minima between the upper edge and the lower edge.

[0025] Preferably, the manufactured side surface extends obliquely and / or curvedly and / or stepwise and / or dividedly. The corresponding geometric shape can induce additional preferred properties of the metal-ceramic substrate, particularly with respect to thermal shock resistance and the peelability of at least one metal layer from the ceramic element. Furthermore, thermal diffusion can be considered in the formation of the corresponding shape of at least one metal layer or its side surface.

[0026] In particular, the space between two mutually insulated adjacent metal parts is intended to have an aspect ratio (height of the space to width) greater than 1, more preferably greater than 1.5, and most preferably greater than 2. This allows for the provision of narrow separation grooves, enabling a very compact arrangement of the metal parts, especially when the metal layer is relatively thick, for example, exceeding 1.5 mm. In particular, the fact that the material can be removed not only by isotropic etching (the theoretical aspect ratio can only be at most 1) but also by directed laser light is utilized. This first enables the corresponding aspect ratio.

[0027] Preferably, it is intended that an ultrashort pulse laser is used for removal by laser light. The light used may be, for example, continuously emitted light or pulsed light. Preferably, it is ultrashort pulse laser light having a light pulse with a pulse length or pulse duration shorter than nanoseconds. Preferably, the UKP laser is a laser source that provides light pulses having a pulse duration of 0.1 - 800 ps, more preferably 1 - 500 ps, and most preferably 10 - 50 ps.

[0028] Preferably, the realization of the structured part and / or the recess is intended to be further assisted by mechanical processing, especially within the scope of pre - or preparatory steps. For example, the removal of material from a large area of at least one metal layer is carried out by mechanical processing, such as machining, especially milling. In particular, in a later step, predetermined breaking points are embedded, and in, for example, a master card, in areas where breaking occurs between individual metal - ceramic substrates along these breaking points, it is conceivable that this is carried out.

[0029] Preferably, it is intended that a recess having a depth measured perpendicular to the main extension plane is manufactured by a laser beam, and the ratio of the maximum depth of the recess to the thickness of at least one metal layer is a ratio of 0.7 to 0.99, preferably 0.8 to 0.98, more preferably 0.9 to 0.95. The maximum depth particularly means the maximum depth to be determined, measured in a direction perpendicular to the main extension plane from the upper surface of at least one metal layer. As long as the depth of the recess is adjusted, the maximum depth also particularly means its arithmetic mean, and is determined, for example, by determining the depth of the recess at 100 different positions and then averaging them.

[0030] Preferably, it is intended that at least one metal layer has a thickness greater than 1 mm, more preferably greater than 1.5 mm, and most preferably greater than 2.5 mm. The use of a laser beam or pre-structuring has been found to be particularly advantageous for such thick metal layers because it can particularly reduce the distance between two adjacent metal parts, which is impossible to achieve when the material is removed only by an etching agent. This enables the printed circuit board to be designed so that metal parts can be realized and formed on the upper surface of the ceramic element with maximum space savings.

[0031] Another object of the present invention is a method for manufacturing a metal-ceramic substrate, comprising: providing a ceramic element and at least one metal layer, the ceramic element and the at least one metal layer extending along a main extension plane; forming a metal-ceramic substrate by joining the ceramic element to the at least one metal layer, particularly by a direct metal bonding process, hot isostatic pressing and / or soldering process; Preferably, the structuring for forming the separation of the metal part and / or the recess for forming the soldering stop are realized in at least one metal layer by a mechanical process, such as milling or turning, and a chemical process, in particular etching. All the advantages and characteristics described for the method for manufacturing a metal-ceramic element using a laser beam are equally applicable to the method for manufacturing a metal-ceramic element using a mechanical process.

[0032] Preferably, the treatment by the chemical process is completed after the mechanical process, and / or the treatment by the mechanical process is intended to be carried out as a pre-step that is temporally before the chemical process or partially overlaps with the chemical process. Thereby, advantageously, it is possible to avoid damaging the outer side of the ceramic element during removal by a mechanical tool. Instead, the remaining metal residues are gently removed from the outer side of the ceramic element in a material-friendly manner, and the ceramic element is exposed again in specific regions. Thereby, a structuring or a desired separation groove is finally formed between two adjacent metal parts.

[0033] A further object of the present invention is a metal-ceramic substrate manufactured by the method according to the present invention. All the characteristics and advantages described with respect to the method can equally be transferred to the metal-ceramic substrate, and vice versa. In particular, the metal-ceramic substrate is a component of a power module and functions as a carrier for electrical or electronic components.

[0034] Further advantages and features will become apparent from the following description of the preferred embodiments of the subject matter of the present invention with reference to the accompanying drawings. The individual features of the individual embodiments can be combined with each other within the scope of the present invention.

Brief Description of the Drawings

[0035]

Figure 1

Figure 2

Figure 3

[0036] FIG. 1 schematically shows a metal-ceramic substrate according to a first preferred embodiment of the present invention. Such a metal-ceramic substrate 1 is preferably a carrier for electrical components (not shown). In particular, the metal-ceramic substrate 1 comprises a ceramic element 30 and at least one metal layer 10, and the ceramic element 30 and the at least one metal layer 10 are intended to extend along a main extension plane HSE. In this case, the at least one metal layer 10 is joined to the ceramic element 30, and the at least one metal layer 10 and the ceramic element 30 are arranged one above the other in a stacking direction S extending perpendicular to the main extension plane HSE. In this connection, it is particularly intended that the at least one metal layer 10 has a plurality of metal parts 10', and these metal parts 10' are electrically insulated from each other and arranged adjacent to each other, for example, along a direction extending parallel to the main extension plane HSE.

[0037] Furthermore, it is most preferred that a backside metallization 20 is provided on the side of the ceramic element 30 opposite to the at least one metal layer 10 when viewed in the stacking direction S. The backside metallization 20 is intended, in particular, to counteract deformations that usually occur during operation, which are caused by thermomechanical stresses resulting from different coefficients of expansion in the at least one metal layer 10 and the ceramic element 30. At the same time, the backside metallization 20 is intended to provide sufficient heat capacity, which is particularly desirable for providing an appropriate buffer in overload situations.

[0038] For example, in order to realize a structuring part 15 that separates two adjacent metal parts 10' from each other, the prior art usually applies a masking or resist layer to at least one joined metal layer 10 and intends to remove the regions within at least one metal layer 10 that are not covered by the resist layer or masking by an etching process. Advantageously, this enables the structuring part 15 of at least one metal layer 10, so that, for example, two metal parts 10' of at least one metal layer 10 are electrically insulated from each other. However, the application and manufacture of masking are expensive and consume a relatively large amount of etching agent.

[0039] FIG. 2 schematically shows a cross-sectional view of a metal-ceramic substrate 1 manufactured by a method according to an exemplary embodiment of the present invention. In particular, for the manufacture of the structuring part 15, especially for the formation of the space between two adjacent metal parts, i.e., the so-called separation groove, it is intended that the removal of the material in at least one metal layer 10 is realized by both the use of laser light and etching.

[0040] Preferably, first, in a preliminary step, recesses 18 are formed in at least one metal layer 10 by laser light, and the recesses 18 have a maximum depth T that is smaller than the thickness D of at least one metal layer 10. Thereby, it is ensured that during the treatment of at least one metal layer 10 by laser light, the material is not completely removed from at least one metal layer 10. This ensures that the laser light does not remove any component of the joined ceramic element at the end of the treatment of at least one metal layer 10. In particular, here, the ratio of the maximum depth T of the recess to the thickness D of at least one metal layer 10 is intended to have a ratio between 0.7 and 0.99, more preferably between 0.8 and 0.98, and most preferably between 0.9 and 0.95. In other words, a considerable amount of material is removed from at least one metal layer 10 by laser light.

[0041] This may be a continuously operating cw laser or an ultrashort pulse laser used, for example, to remove or ablate the material of at least one metal layer 10 in a pre-step. Alternatively, in addition to the treatment with laser light, mechanical treatment may also be used to ensure a recess 18 having a maximum depth T smaller than the thickness D of at least one metal layer 10 within the scope of the pre-step. This is useful, for example, in cases where a relatively large area is to be exposed, or in areas where predetermined breaking points are to be made later, such as in the case of a master card, in areas where the metal ceramic substrate is to be separated into several individual metal ceramic substrates along these breaking points.

[0042] Following the pre-step in which a recess 18 having a maximum depth T smaller than the thickness D of at least one metal layer 10 is formed, the removal of the material of at least one metal layer 10 is carried out by an etching process. In particular, the remaining portion 13 of at least one metal layer 10 that remains after the material of at least one metal layer 10 has been removed by laser light and is to be removed by the etching process is intended to be removed by the etching process. In other words, by using the etching process, the removal of the remaining portion 13 required for the separation of adjacent metal portions 10' is carried out, for example, in the area of a planned separation groove. In this case, the remaining portion 13 also extends, for example, over the metal portion 13 held on the manufactured metal ceramic substrate 1 after the formation of the structured part or the recess.

[0043] In this context, more preferably, it is intended that the masking or resist layer is omitted during the etching process or etching step. Thereby, in particular in at least one metal layer 10, preferably on the side opposite to the ceramic element 30, uniform material removal is performed. Due to the profile or contour of the recess 18 predetermined by the laser beam having a maximum depth T smaller than the thickness D of the at least one metal layer 10, in particular in the region of this recess 18, the remaining part 13 of the material of the at least one metal layer 10 can be removed to achieve electrical insulation of two adjacent metal sections 10' in the at least one metal layer 10.

[0044] Thus, in the described procedure, advantageously, it is possible to omit the formation of an expensive masking or resist layer on the upper surface of the at least one metal layer 10. Further, the etching process is intended to remove only a small or a small amount of material, in particular to ensure that the ceramic element 30 is not damaged during production by the laser beam and / or mechanical process, so that the etching agent can be advantageously saved and preferably the method can also be promoted. In particular, the method is promoted even when the formation of a masking layer or resist layer for predetermining the position of the structuring part 15 is omitted.

[0045] Preferably, in this case, it is intended that the shape of the side surface 17 of the at least one metal layer 10, which does not extend parallel to the main extension surface, is at least partially determined by the laser beam. In this way, advantageously, it is possible to use the laser beam to specify how the outer region of the at least one metal layer 10 or metal part 10' is configured. It has been found that this is determined for thermal shock resistance and it is advantageous to realize on the side surface 17 a shape that joins the upper edge of the at least one metal layer 10 to the lower edge of the at least one metal layer 10, the lower edge delimiting at least one metal layer on the side facing the ceramic element 30 and the upper edge delimiting the metal layer 10 on the side opposite to the ceramic element 30, which is particularly advantageous.

[0046] Figure 3 shows a top view of two differently manufactured metal-ceramic substrates 1, which were manufactured using an exemplary method for manufacturing the metal-ceramic substrate 1 according to the present invention. In particular, the upper embodiment in FIG. 3 shows an island-shaped square metal part 10', and in the lower embodiment, a substantially circular space for the structuring part 15 is realized in at least one metal layer 10.

Explanation of reference numerals

[0047] 1 Metal-ceramic substrate 10 Metal layer 10’ Metal part 13 Remaining part 14 Recess 15 Structuring part 17 Side surface 18 Recess 20 Backside metallization 30 Ceramic element S Laminating direction D Thickness T Depth HSE Main extension surface

Claims

1. A method for manufacturing a metal-ceramic substrate (1), comprising: providing a ceramic element (30) and at least one metal layer (10), wherein the ceramic element (30) and the at least one metal layer (10) extend along a main extension plane (HSE); forming the metal-ceramic substrate (1) by joining the ceramic element (30) to the at least one metal layer (10) by at least one of a direct metal joining process, a hot isostatic pressing process, and a soldering process; at least one of a structuring part (15) for forming a separation of a metal part (10') and a recess (14) for forming a solder stop is realized in the at least one metal layer (10) by a laser process and an etching process; an ultrashort pulse laser is used in the laser process; a method in which, in the etching process, an etching agent is caused to flow only into the recess (18) or concentrated in the recess (18) by using the recess (18) already formed by the laser process.

2. The method according to claim 1, wherein the treatment by the etching process ends after the end of the laser process.

3. The method according to claim 1 or 2, wherein the treatment by the laser process is performed as a pre-step temporally before the etching process.

4. The method according to any one of claims 1 to 3, wherein the etching process removes metal such that an outer region of the ceramic element (30) is exposed.

5. The method according to any one of claims 1 to 4, wherein the etching process and the laser process are performed at least intermittently simultaneously.

6. The method according to any one of claims 1 to 5, wherein the shape of a side surface (17) of the at least one metal layer (10) that is not parallel to the main extension plane (HSE) is at least partially determined by the laser process.

7. The method according to claim 6, wherein the manufactured side surface (17) is oblique, curved, stepped, and / or divided.

8. The method according to any one of claims 1 to 7, wherein a space between two adjacent metal parts insulated from each other has an aspect ratio greater than 1.

9. The method according to any one of claims 1 to 8, wherein the formation of at least one of the structured portion (15) and the recess (14) is further assisted by mechanical processing.

10. A recess (18) having a depth (T) dimensioned perpendicular to the main extension plane (HSE) is produced by a laser beam, and the ratio of the maximum depth (T) of the recess (18) to the thickness (D) of the at least one metal layer (10) has a ratio of 0.7 to 0.

99. The method according to any one of claims 1 to 9.

11. The method according to any one of claims 1 to 10, wherein the at least one metal layer (10) has a thickness (D) greater than 1 mm.

12. A metal-ceramic substrate (1) produced by the method according to any one of claims 1 to 11.

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