Method for manufacturing a metal-ceramic substrate and a metal-ceramic substrate manufactured by such a 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, such as Patent Document 1, Patent Document 2, and Patent Document 3, for example, as a printed circuit board or a circuit board. Usually, the connection area 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 the 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 areas 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, such as the possibility of inducing or causing thermo-mechanical stress when heat is generated during the operation or manufacture of the carrier substrate, can lead to bending or damage of the carrier substrate.

[0004] The latest technology proposes an etching process typically used to structure or profile at least one metal layer. For this purpose, a masking agent is applied to the side of the metal layer opposite to the ceramic element, particularly in the form of a resist layer. Then, an etching agent can be used to expose the areas without masking and structure the metal layer corresponding to the masking. However, such an approach requires a lot of materials and time, especially regarding the application of the masking agent and the use of the etching agent. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] German Patent Application Publication No. 102013104739 Specification [Patent Document 2] German Patent No. 19927046 Specification [Patent Document 3] German Patent Application Publication No. 102009033029 Specification [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] Based on this, the present invention aims to reduce the time and / or amount of material required in the manufacture of metal ceramic substrates, particularly in their structuring. [Means for solving the problem]

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

[0008] According to a first aspect of the present invention, a method for manufacturing a metal ceramic substrate, A step of preparing a ceramic element and at least one metal layer, wherein the ceramic element and at least one metal layer extend along a main extending surface, The process includes the step of forming a metal-ceramic substrate by bonding a ceramic element to at least one metal layer, particularly by a direct metal bonding process, a hot isostatic pressing and / or soldering process, A method is provided in which a structured portion for forming separation of a metal portion, and / or a recess for forming a solder joint, is realized in at least one metal layer by a laser process and a chemical process, particularly 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 laser light to remove material to form structured parts and / or recesses. By combining these two methods, it is advantageously possible to omit the formation of masking. In particular, laser light is used to define the course (Verlauf) of the structured parts, and the etching agent used, for example, is intended to be used for the uniform removal of material from at least one metal layer. Since the laser light specifies the areas in which material removal is increased, specification by masking is no longer necessary. For example, since no material is required for the formation of masking, the fabrication of structured parts is facilitated and material requirements are reduced.

[0010] Manufacturing or removal using laser light and / or etching agents can be carried out simultaneously or at least intermittently. That is, two independent methods for removing material can overlap in time and further accelerate the manufacturing process. For example, after passing laser light through a certain number of times, an etching agent can be applied to the entire area of ​​at least one metal layer, and further laser light passes can ensure further removal. More preferably, the laser treatment and chemical treatment are carried out sequentially.

[0011] Another advantage of combining etching and laser removal is that it ensures that the material of the ceramic element is not removed during the laser treatment. This avoids damage to the ceramic element by the laser. For this purpose, it is specifically intended that the removal with the etching agent is not completed before the laser structuring is finished. In particular, laser removal within the scope of the pre- or preparation steps serves to identify the course of the separation grooves and / or recesses, which then obtain their definitive or final depth solely 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 recess is understood to be a profile used, for example, as a solder stop, rather than a profile that separates two adjacent metal parts in at least one metal layer. Such a solder stop prevents unwanted flow of solder material to a specific area, for example, by having the recess function as a groove for receiving solder material and preventing the solder material from flowing any further.

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

[0014] Preferably, the ceramic elements include Al2O3, Si3N4, AIN, HPSX ceramics (i.e., ceramics having 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 (over 90% of theoretical density), and TSZ (tetragonal stabilized zirconium oxide) as the ceramic material. To combine various desired properties, the ceramic elements may also be designed as composite or hybrid ceramics, in which several ceramic layers, each differing in their material composition, are arranged in overlapping positions and joined together to form an insulating element. A metal interlayer may also be placed between two ceramic layers, the metal interlayer preferably thicker than 1.5 mm and / or thicker than the sum of the two ceramic layers. Preferably, ceramics with the highest possible thermal conductivity are used to achieve the lowest possible thermal resistance.

[0015] Those skilled in the art will understand the "DCB process" (direct copper bonding technique) or "DAB process" (direct aluminum bonding technique) as a method for bonding, for example, metal layers or sheets (e.g., copper sheets or foils or aluminum sheets or foils) to each other and / or to ceramics or ceramic layers, using metal or copper sheets or metal or copper foil having a layer or coating (molten layer) on the surface side. For example, in the method described 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 (e.g., copper). Thus, by placing the foil on the ceramic and heating all the layers, they are bonded together. Therefore, it is possible to bond them together by essentially surface melting the metal or copper only in the region of the molten layer or oxide layer.

[0016] In particular, the DCB process then follows, for example, the following method steps: The steps include: oxidizing the copper foil to obtain a uniform copper oxide layer, The steps include placing copper foil on a ceramic layer, The steps include heating the composite to a process temperature between approximately 1025 and 1083°C, for example, approximately 1071°C, The method includes the step of cooling to room temperature.

[0017] Active soldering, a method for joining metal layers or metal foils, particularly copper layers or copper foils, to ceramic materials, is understood to be a method also used in the manufacture of metal-ceramic substrates. The bond between a metal foil, such as copper foil, and a ceramic substrate, such as aluminum nitride ceramic, is achieved by using a soldering compound containing an active metal in addition to its main components, such as copper, silver, and / or gold. This active metal is, for example, at least one element from the group Hf, Ti, Zr, Nb, and Ce, which establishes the bond between the soldering compound and the ceramic through a chemical reaction, and the bond between the soldering compound and the metal is a metal-solder bond. Alternatively, joining by thick coating treatment is also possible.

[0018] Hot isostatic pressurization is known, for example, from European Patent No. 3080055, the details of which are expressly included herein by reference with respect to hot isostatic pressurization. Preferably, the chemical structuring process is completed, in particular, after the preparation step using laser light. This ensures that the final removal is performed solely by an etching agent and that the ceramic element is not damaged by the laser light.

[0019] In particular, it is intended that masking during etching is avoided in the manufacture of the structured 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 recesses already formed, the etching agent can be made to flow only into this recess or the etching agent can be concentrated in this recess. For example, the etching agent is applied and as a result of the tilting and rotational movement on the upper surface of at least one metal layer, it is conceivable that the excess etching agent flows out of the metal ceramic substrate or flows into the recesses.

[0020] Preferably, a chemical process, particularly a chemical process alone, is intended to remove the metal and expose the area 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 area outside the planned separation groove. In this case, the pre-structuring by laser light, i.e., the formation of the recesses during the pre-step, is advantageous as it enables the masking to be applied in a more flexible and simplified manner, for example, by a corresponding printing process onto the areas where no material has 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 material is not removed from the upper surface of at least one metal layer during etching. Thus, 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 surface. 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 in the lateral direction 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 divided. 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 taken into account 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 to width of the space) greater than 1, more preferably greater than 1.5, and most preferably greater than 2. This allows for the creation of a narrow separation groove, 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 (theoretically, an aspect ratio of at most 1 is possible) but also by directional laser light is utilized. This, firstly, enables the corresponding aspect ratio.

[0027] Preferably, an ultrashort pulse laser is intended to be used for laser light removal. The light used may be, for example, continuously emitted light or pulsed light. Preferably, it is an ultrashort pulse laser light having light pulses 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 to 800 ps, ​​more preferably 1 to 500 ps, ​​and most preferably 10 to 50 ps.

[0028] Preferably, the realization of structured portions and / or recesses is intended to be further assisted by mechanical processing, particularly within the scope of pre- or preparation steps. For example, the removal of material from a large area of ​​at least one metal layer may be carried out by mechanical processing, e.g., processing, particularly milling, in particular in areas where predetermined fracture points are embedded in a later process, and in a master card, for example, fractures occur between individual metal-ceramic substrates along these fracture points.

[0029] Preferably, a recess having a depth measured perpendicular to the main extending surface is intended to be manufactured by laser light, and the ratio of the maximum depth of the recess to the thickness of at least one metal layer is 0.7 to 0.99, preferably 0.8 to 0.98, and more preferably 0.9 to 0.95. The maximum depth means, in particular, the maximum depth to be determined, measured perpendicular to the main extending surface from the top surface of at least one metal layer. Insofar as the depth of the recess is adjusted, the maximum depth also means its arithmetic mean, which is determined, for example, by determining the depth of the recess at 100 different locations and then averaging them.

[0030] Preferably, at least one metal layer is intended to have a thickness greater than 1 mm, more preferably greater than 1.5 mm, and most preferably greater than 2.5 mm. Laser utilization or pre-structuring has proven particularly advantageous for such thick metal layers because it can significantly reduce the distance between two adjacent metal portions, which is not possible if the material is removed solely by etching. This allows printed circuit boards to be designed to realize and form metal portions on the surface of ceramic elements with maximum space savings.

[0031] Another object of the present invention is a method for manufacturing a metal-ceramic substrate, A step of preparing a ceramic element and at least one metal layer, wherein the ceramic element and at least one metal layer extend along a main extending surface, The process includes the step of forming a metal-ceramic substrate by bonding a ceramic element to at least one metal layer, particularly by a direct metal bonding process, a hot isostatic pressing and / or soldering process, Preferably, structural portions for forming separation of metal parts, and / or preferably recesses for forming solder joints, are realized in at least one metal layer by mechanical processes, such as milling or turning, and chemical processes, particularly etching. All the advantages and properties described for the method of manufacturing metal-ceramic elements using laser light also apply to the method of manufacturing metal-ceramic elements using mechanical processes.

[0032] Preferably, the chemical process is completed after the mechanical process is finished, and / or the mechanical process is intended to be performed as a preliminary step that chronologically precedes or partially overlaps with the chemical process. This advantageously avoids damaging the outside of the ceramic element during removal with mechanical tools. Instead, any remaining metal residue is gently removed from the outside of the ceramic element in a material-friendly manner, and the ceramic element is re-exposed in the specified area. This ultimately forms a structural portion or desired separation groove between the two adjacent metal portions.

[0033] A further object of the present invention is a metal-ceramic substrate manufactured by the method according to the present invention. All the properties and advantages described with respect to this method can be similarly applied to metal-ceramic substrates, and vice versa. In particular, metal-ceramic substrates are components of power modules and function as carriers for electrical or electronic components.

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

[0035] [Figure 1] This figure shows a metal-ceramic substrate according to a first preferred embodiment of the present invention. [Figure 2]This figure shows a metal-ceramic substrate according to a second preferred embodiment of the present invention. [Figure 3] This figure shows a metal-ceramic substrate according to a third preferred embodiment of the present invention. [Modes for carrying out the invention]

[0036] Figure 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 an electrical component (not shown). In particular, the metal-ceramic substrate 1 comprises a ceramic element 30 and at least one metal layer 10, the ceramic element 30 and at least one metal layer 10 are intended to extend along a main extending plane HSE. In this case, at least one metal layer 10 is bonded to the ceramic element 30, and the at least one metal layer 10 and the ceramic element 30 are arranged vertically in a stacking direction S that extends perpendicular to the main extending plane HSE. In this regard, the at least one metal layer 10 is particularly intended to have a plurality of metal portions 10', which are electrically insulated from each other and arranged adjacent to each other, for example, along a direction that extends parallel to the main extending plane HSE.

[0037] Furthermore, it is most preferable that the back surface metallization 20 be provided on the side of the ceramic element 30 opposite to at least one metal layer 10 when viewed in the stacking direction S. The back surface metallization 20 is intended to counteract deformations that normally occur during operation, particularly those caused by thermomechanical stress resulting from the different coefficients of thermal expansion in at least one metal layer 10 and the ceramic element 30. At the same time, the back surface metallization 20 is intended to provide sufficient heat capacity, which is particularly desirable to provide adequate buffering in overload conditions.

[0038] For example, to realize a structured portion 15 that separates two adjacent metal portions 10' from each other, the prior art typically involves applying a masking or resist layer to at least one bonded metal layer 10, and then removing the areas within the at least one metal layer 10 that are not covered by the resist layer or masking through an etching process. Advantageously, this enables a structured portion 15 of the at least one metal layer 10, resulting in, for example, two metal portions 10' of the at least one metal layer 10 being electrically insulated from each other. However, the application and manufacture of masking is expensive and consumes a relatively large amount of etching agent.

[0039] Figure 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 structured portion 15, and especially for the formation of a space between two adjacent metal portions, i.e., a so-called separation groove, the removal of material in at least one metal layer 10 is intended to be achieved by both the use of laser light and etching.

[0040] Preferably, in a preliminary step, a recess 18 is formed in at least one metal layer 10 by laser light, and the recess 18 has a maximum depth T that is less than the thickness D of the at least one metal layer 10. This ensures that no material is completely removed from the at least one metal layer 10 during the laser treatment of the at least one metal layer 10. This ensures that the laser light does not remove any components of the bonded ceramic element at the end of the treatment of the at least one metal layer 10. In particular, the ratio of the maximum depth T of the recess to the thickness D of the at least one metal layer 10 is intended to be 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 the at least one metal layer 10 by laser light.

[0041] This may be a continuously operating CW laser or ultrashort pulse laser, for example, used to remove or ablate the material of at least one metal layer 10 in a preliminary step. Alternatively, in addition to laser treatment, mechanical treatment may be used to ensure that recesses 18 have a maximum depth T less than the thickness D of at least one metal layer 10 within the scope of the preliminary step. This is useful, for example, in cases where a relatively large area is exposed or in areas where predetermined fracture points will be introduced later, such as in the case of a Mastercard, where the metal-ceramic substrate is separated into several individual metal-ceramic substrates along these fracture points.

[0042] Following a preliminary step in which a recess 18 having a maximum depth T less than the thickness D of at least one metal layer 10 is formed, the material of at least one metal layer 10 is removed 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 necessary for separating adjacent metal portions 10' is performed, for example, in the area of ​​a planned separation groove. In this case, the remaining portion 13 also extends over the metal portion 13 that is held on the manufactured metal-ceramic substrate 1 after the structured portion or recess is formed, for example.

[0043] In connection with this, more preferably, a masking or resist layer is intended to be omitted during the etching process or etching step. This allows for uniform material removal, particularly in at least one metal layer 10, preferably on the side opposite to the ceramic element 30. Due to the profile or contour of a recess 18 predetermined by a laser beam having a maximum depth T less than the thickness D of at least one metal layer 10, the remaining portion 13 of the material of at least one metal layer 10 can be removed, particularly in the region of this recess 18, in order to achieve electrical insulation between two adjacent metal sections 10' in at least one metal layer 10.

[0044] Therefore, the described procedure advantageously allows for the omission of the costly formation of a masking or resist layer on the upper surface of at least one metal layer 10. Furthermore, since the etching process is intended to remove only a small or small amount of material, particularly to ensure that the ceramic element 30 is not damaged during manufacturing by laser light and / or mechanical processes, the etching agent can be advantageously saved, and preferably the method can be facilitated. The method is particularly facilitated when the formation of a masking or resist layer that predetermines the position of the structured portion 15 is omitted.

[0045] Preferably, in this case, the shape of the side surface 17 of at least one metal layer 10 that does not extend parallel to the main extending surface is to be determined at least partially by laser light. Thus, it is advantageous to use laser light to determine how the outer region of at least one metal layer 10 or metal portion 10' is configured. This is determined for thermal shock resistance and has proven advantageous to realize a shape on the side surface 17 that joins the upper edge of at least one metal layer 10 to the lower edge of at least one metal layer 10, which is particularly advantageous as the lower edge limits the at least one metal layer on the side facing the ceramic element 30 and the upper edge limits the metal layer 10 on the side opposite to the ceramic element 30.

[0046] Figure 3 shows top views of two different manufactured metal-ceramic substrates 1, which were manufactured using an exemplary method for manufacturing a metal-ceramic substrate 1 according to the present invention. In particular, the upper embodiment of Figure 3 shows island-shaped square metal portions 10', while the lower embodiment shows substantially circular spaces for structuring portions 15 realized in at least one metal layer 10. [Explanation of symbols]

[0047] 1. Metal-ceramic substrate 10 metal layer 10' metal part 13 The remaining part 14 recess 15 Structuring part 17 Side view 18 recesses 20. Backside metallization 30 ceramic elements S stacking direction D Thickness T depth HSE main extension plane

Claims

1. A method for manufacturing a metal ceramic substrate (1), A step of preparing 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 extending surface (HSE), The step of forming a metal-ceramic substrate (1) by bonding the ceramic element (30) to the at least one metal layer (10) by at least one of a direct metal bonding process, a hot isostatic pressing process and a soldering process, includes the step of bonding the ceramic element (30) to the at least one metal layer (10), At least one of the structural portion (15) for forming separation of the metal portion (10') and the recess (14) for forming solder joints is realized in the at least one metal layer (10) by a laser process and an etching process. In the aforementioned laser process, an ultrashort pulse laser is used, Using the recesses (18) already formed by the laser process, in the etching process, either the etching agent is allowed to flow only into the recesses (18), or the etching agent is concentrated in the recesses (18). The shape of the side surface (17) of the at least one metal layer (10) that is not parallel to the main extending surface (HSE) is determined at least partially by the laser process. The manufactured side (17) is slanted, curved, stepped, and / or divided, in this manner.

2. The method according to claim 1, wherein the etching process is terminated after the laser process is completed.

3. The method according to claim 1 or 2, wherein the laser process is performed as a preliminary step prior to the etching process in terms of time.

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

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

6. The method according to any one of claims 1 to 5, wherein the space between two mutually insulated adjacent metal parts has an aspect ratio greater than 1.

7. The method according to any one of claims 1 to 6, wherein the formation of at least one of the structured portion (15) and the recess (14) is further assisted by mechanical processing.

8. The method according to any one of claims 1 to 7, wherein a recess (18) having a depth (T) dimensioned perpendicular to the main extending surface (HSE) is manufactured by laser light, and the ratio of the maximum depth (T) of the recess (18) to the thickness (D) of the at least one metal layer (10) is 0.7 to 0.

99.

9. The method according to any one of claims 1 to 8, wherein the at least one metal layer (10) has a thickness (D) greater than 1 mm.

10. A metal-ceramic substrate (1) manufactured by the method described in any one of claims 1 to 9.

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