Method for structuring metal-ceramic composite material

Abstract

The invention relates to a method for structuring a metal-ceramic composite material, comprising the following steps: providing a metal-ceramic composite material containing a nitride ceramic substrate, a metal coating and a reaction layer. A semiconductor device includes a nitride ceramic substrate including a front surface and a back surface, a metal coating layer on the front surface of the nitride ceramic substrate, and a reaction layer between the metal coating layer and the ceramic substrate and containing one or more element ERS selected from Ti, Hf, Zr, Nb, V, Ta, and Ce; removing the metal coating such that at least one recess is created in the metal coating and an exposed adhesion promoting layer is present in the recess; the exposed reaction layer is removed using a pulsed laser beam of an ultra-short pulsed laser such that the exposed surface of the ceramic substrate is present in the recess, where the pulsed laser beam applies a total flux of 50 J / cm2 to 650 J / cm2.

Description

[0001] The present invention relates to a method for structured metal-ceramic composites. Such structured metal-ceramic composites can be used as ceramic circuit carriers in semiconductor modules of power electronic devices.

[0002] In power electronic devices, printed circuit boards must be designed for high currents, serve as carriers for power components (such as MOSFETs), and be able to dissipate waste heat quickly.

[0003] Since ceramic materials (such as alumina, aluminum nitride, and silicon nitride) have a much higher thermal conductivity than the polymers used to produce conventional printed circuit boards, ceramic circuit carriers are often used in power modules.

[0004] The ceramic circuit carrier contains a ceramic substrate that is provided with a metal layer at least on its front side. Conventionally, a metal layer is also applied to the back side of the ceramic substrate. In the final module, semiconductor components are applied to one of these metal layers, and the metal layer on the opposite side of the ceramic substrate is thermally connected to a heat sink. The ceramic substrate electrically insulates the metal layers from each other.

[0005] It is known to those skilled in the art that metallized ceramic substrates serving as ceramic circuit boards are produced, for example, by bringing the front and back sides of the ceramic substrate into contact with a metal film (such as a copper film or an aluminum film) and bonding them together.

[0006] In one of the methods known to those skilled in the art, the metal film is bonded to the ceramic substrate by eutectic bonding. If the metal film is a copper film, the eutectic bonding is also referred to as the DCB method or the DBC method (DCB: "direct copper bonding"; DBC: "direct bonded copper"). In the case of an aluminum film, the term "DAB" ("direct aluminum bonding") is also used for eutectic bonding. Metallized ceramic substrates produced using the DCB method are sometimes also referred to as DCB substrates (alternatively: DBC substrates).

[0007] Ceramic substrates based on nitrides (such as aluminum nitride or silicon nitride) (nitride ceramic substrates) are used as ceramic circuit carriers due to their advantageous properties.

[0008] For example, ceramic substrates based on silicon nitride have very high mechanical strength while having high thermal conductivity and are therefore very suitable for applications in power electronic devices.

[0009] Ceramic substrates based on silicon nitride are described, for example, in the following publications:

[0010] N. Chasserio et al., "Ceramic Substrates for High-Temperature Electronic Integration", Journal of Electronic Materials, Vol. 38 (2009), pp. 164-174;

[0011] K. Hirao et al., "High Thermal Conductivity Silicon Nitride Ceramics", Journal of the Korean Ceramic Society, Volume, Vol. 49 (2012), pp. 380-384;

[0012] Y. Zhou et al., "Development of high-thermal-conductivity silicon nitride ceramics", Journal of Asian Ceramic Societies, 3 (2015), pp. 221-229.

[0013] Aluminum nitride-based ceramic substrates have very high thermal conductivity, sufficient mechanical strength, and are thus also very suitable for applications in power electronic devices.

[0014] However, silicon nitride substrates are not suitable for metallization using the DCB method, and aluminum nitride substrates must first be oxidized on the surface, which is complex and may have a negative impact on thermal conductivity.

[0015] Therefore, nitride ceramics are usually metallized by active metal brazing (AMB).

[0016] Active metal solders are metal solders that, due to their composition, are capable of wetting non-metallic inorganic materials (e.g., ceramics, graphite, glass). Active metal solders contain, in addition to the main components (such as Cu, Ag, or Au), one or more elements that can react with the ceramic to form an adhesion-promoting reaction layer (see, for example, Brevier Technische Keramik, Chapter 8.2.4.3 in the Ceramic Industry Association, “Active metal brazing,” pp. 203 - 204, 2003, Verlag Fahner). Reactive elements such as hafnium (Hf), titanium (Ti), zirconium (Zr), niobium (Nb), cerium (Ce), tantalum (Ta), and vanadium (V) are used. When metallizing a silicon nitride substrate by active metal brazing, the reaction layer contains, for example, nitrides, oxynitrides, and / or silicides of one reactive element (A. et al., “Active metal brazing of copper with aluminum nitride and silicon nitride ceramics”

[0017] Keramische Zeitschrift, 63(5), 2011, 334 - 342).

[0018] The metal coating of a metal - ceramic composite carrying semiconductor components is structured (e.g., by etching using an etching mask). Thus, the structured metal coating has one or more recesses that separate the regions of the metal coating that remain after structuring from each other. Structuring of the AMB substrate is typically carried out in a two - step process. For example, in the first step, a first etching solution optimized for the removal of the metal coating is used. Using this first etching solution, the metal coating is removed in defined (e.g., unmasked) regions, and the reaction layer formed during active metal brazing is exposed. In another step, a second etching solution optimized for the removal of the reaction layer is used to expose the surface of the ceramic substrate.

[0019] For later use as a power electronic device module, it is important that adjacent conductor tracks formed by structuring are electrically insulated from each other. This in turn requires that no residues of the reaction layer remain between adjacent conductor tracks. Therefore, the etchant solution used in the second etching step should completely remove the exposed reaction layer. However, this often results in underetching of the metal coating, i.e., the etchant solution in the second etching step not only removes the reaction layer exposed after the first etching step, but also removes the reaction layer on the side of the metal coating that is still covered and is thus required for the bonding between the metal coating and the ceramic substrate. This can cause the metal coating to detach from the ceramic substrate under thermal cycling stress.

[0020] For the etching process of the reaction layer produced by the active metal soldering method, aggressive chemicals are required, which can leave undesirable (e.g., corrosive) residues on the ceramic even after the final washing step. When using an etching medium containing fluoride, fluoride residues may remain on the exposed ceramic surface. Such etchant residues can have a corrosive effect in a power electronic device module.

[0021] When trying to remove as completely as possible the reaction layer exposed after the first removal step in a further removal step, there is always a risk of damaging the ceramic substrate. This in turn can lead to impairment of the mechanical properties of the ceramic substrate, such as flexural strength.

[0022] An object of the present invention is to structure a metal-ceramic composite produced by active metal soldering by means of a method that allows the effective exposure of the ceramic surface in defined areas without achieving this at the expense of the thermal shock resistance of the metal-ceramic composite and / or the mechanical properties of the ceramic substrate, such as flexural strength. The effective exposure of the ceramic surface particularly includes that substantially no conductive material and / or corrosive material remains on the surface of the exposed ceramic substrate.

[0023] This object is achieved by a method for structuring a metal-ceramic composite, the method comprising the following steps:

[0024] - Providing a metal-ceramic composite, the metal-ceramic composite comprising:

[0025] - A nitride ceramic substrate, the nitride ceramic substrate comprising a front side and a back side,

[0026] - A metal coating, the metal coating being located on the front side of the nitride ceramic substrate,

[0027] - A reaction layer, the reaction layer being present between the metal coating and the ceramic substrate,

[0028] And containing one or

[0029] Multiple elements E RS ,

[0030] - Remove the metal coating to create at least one recess in the metal coating and an exposed adhesion-promoting layer in the recess.

[0031] - Use a pulsed laser beam from an ultrashort pulse laser to remove the exposed reaction layer such that

[0032] the exposed surface of the ceramic substrate is present in the recess, where the pulsed laser beam is applied

[0033] with a total fluence of 50 J / cm 2 to 650 J / cm 2 .

[0034] The metal-ceramic composite material structured by exposing the ceramic surface in a defined area in the method according to the invention is a metal-ceramic composite material produced by active metal brazing, where the ceramic is a nitride ceramic. Such metal-ceramic composite materials are known to those skilled in the art and are commercially available or can be produced by known methods. Removing the metal coating to expose the reaction layer produced by the active metal brazing process can also be carried out using conventional removal methods (e.g., etching), as explained in more detail below.

[0035] In the present invention, it has been found that if removal is carried out using an ultrashort pulse laser and the total fluence applied by the ultrashort pulse laser for exposing the ceramic substrate is 50 J / cm 2 to 650 J / cm 2 , then the exposed reaction layer can be completely removed from the surface of the ceramic substrate, and the flexural strength of the ceramic substrate and the thermal shock resistance of the metal-ceramic composite material can still be maintained at a high level.

[0036] An ultrashort pulse laser is a laser that can emit laser pulses with a pulse duration in the picosecond ("picosecond laser") or femtosecond ("femtosecond laser") range. As known to those skilled in the art, the fluence (or energy density) of a laser refers to the energy applied per unit area. For a pulsed laser beam, the fluence can refer to the energy of a single laser pulse or the sum of all laser pulses emitted during material processing. The latter is called the total fluence or cumulative fluence and refers to the total energy per unit area applied by the pulsed laser beam to the irradiated area of the metal-ceramic composite material.

[0037] The total fluence F 总 is generated by the following relationship:

[0038] F 总 = E 总 / A L

[0039] Among them

[0040] E 总 is the total energy applied by the pulsed laser beam, and

[0041] A L is the total area irradiated by the laser beam.

[0042] If each laser pulse of the pulsed laser beam has the same pulse energy EP, the total flux F 总 is generated by the following relationship:

[0043] F 总 = N P × E P / A L

[0044] Among them

[0045] N P is the total number of laser pulses applied by the pulsed laser beam,

[0046] E P is the energy of the laser pulse,

[0047] A L is the total area irradiated by the laser beam.

[0048] As described in more detail below, if the total flux applied by the pulsed laser beam of the ultrashort pulse laser is less than 50 J / cm 2 , the exposed reaction layer is not removed or is only insufficiently removed, while if the applied total flux is greater than 650 J / cm 2 , the exposed reaction layer is completely removed, but the flexural strength of the ceramic substrate is significantly deteriorated.

[0049] The metal-ceramic composite material to be structured in the method according to the invention comprises:

[0050] - A nitride ceramic substrate, which comprises a front side and a back side,

[0051] - A metal coating, which is located on the front side of the nitride ceramic substrate, and

[0052] - A reaction layer, which exists between the metal coating and the ceramic substrate and contains one or more elements E selected from Ti, Hf, Zr, Nb, V, Ta, and Ce RS .

[0053] The nitride ceramic substrate contains, for example, silicon nitride or aluminum nitride. In a preferred embodiment, the nitride ceramic substrate contains silicon nitride.

[0054] For example, the nitride ceramic substrate contains silicon nitride or aluminum nitride in a proportion of at least 70% by weight, more preferably at least 80% by weight.

[0055] Optionally, the nitride ceramic substrate may contain one or more metal oxides. These oxides are added, for example, as sintering aids during the production of the ceramic substrate. For example, the nitride ceramic substrate contains one or more of the following oxides: one or more alkaline earth metal oxides such as magnesium oxide; one or more transition metal oxides (e.g., one or more rare earth oxides such as yttrium oxide); silicon oxide (e.g., SiO 2 ) or silicate.

[0056] The nitride ceramic substrate has, for example, a thickness in the range of 0.1 mm to 1.0 mm.

[0057] A metal coating is present on the front surface of the nitride ceramic substrate. Optionally, the metal coating can also be used on the back surface of the ceramic substrate.

[0058] The metal coating present on the front surface and optionally on the back surface of the nitride ceramic substrate is, for example, a copper coating or an aluminum coating. The metal coating has, for example, a thickness in the range of 0.05 mm to 1.5 mm, more preferably 0.2 mm to 0.8 mm.

[0059] If the metal coating is a copper coating, it has, for example, a copper content of at least 97% by weight, more preferably at least 99% by weight.

[0060] If the metal coating is an aluminum coating, it has, for example, an aluminum content of at least 97% by weight, more preferably at least 99% by weight.

[0061] The metal coating is, for example, a copper film or an aluminum film, which is applied to the nitride ceramic substrate by active metal brazing.

[0062] The reaction layer contains one or more elements E RS , selected from Hf, Ti, Zr, Nb, V, Ta, and Ce, preferably selected from Hf, Ti, Zr, Nb, and Ce, more preferably selected from Hf, Ti, and Zr. Particularly preferred element E in the reaction layer RS is titanium. For example, element E RS is present in the reaction layer in the form of nitride, oxynitride, and / or silicide. For example, the reaction layer contains a total amount of element E of at least 50% by weight RS . For example, the reaction layer contains a total amount of element E of at least 70% by weight, more preferably at least 85% by weight SR of nitride, oxynitride, and silicide. In a semiconductor module for power electronics devices, the migration of silver may cause problems. Therefore, it may be preferred that the reaction layer contains silver in a proportion of not more than 5% by weight, more preferably not more than 1% by weight, or even does not contain silver.

[0063] In the method according to the invention, the metal coating of the provided metal-ceramic composite is removed in a defined area (e.g., considering a specific desired conductor track arrangement), such that at least one recess is produced in the metal coating and an exposed reaction layer is present in the recess.

[0064] Removing the metal coating to form one or more recesses in the metal coating can be carried out by methods known to those skilled in the art.

[0065] For example, the metal coating is removed by etching (e.g., using an etching mask such that the metal coating is in contact with the etching medium and removed only in the unmasked area) or by laser ablation.

[0066] In a preferred embodiment, the metal coating is removed by etching. Suitable etching media and etching conditions for removing the metal coating (e.g., a copper coating or an aluminum coating) are known to those skilled in the art. For example, etching is carried out using an aqueous metal chloride solution (e.g., an aqueous ferric chloride solution or an aqueous copper chloride solution). However, other etching solutions known to those skilled in the art can also be used. If necessary, the etching can be carried out in several steps using different etching solutions. The etching is continued until the reaction layer is exposed. Regarding the composition of the exposed reaction layer, reference can be made to the above statements.

[0067] The exposed reaction layer present in the recess is irradiated with a pulsed laser beam of an ultrashort pulse laser and removed, such that the surface of the ceramic substrate in the recess is exposed. The surface of the ceramic substrate is exposed to a total fluence of 50 J / cm 2 to 650 J / cm 2 applied by the pulsed laser beam. Through this applied total fluence, the exposed reaction layer can be completely removed from the surface of the ceramic substrate without affecting the flexural strength of the ceramic substrate or the thermal shock resistance of the metal-ceramic composite.

[0068] In an exemplary embodiment, the total fluence applied by the pulsed laser beam is 100 J / cm 2 to 320 J / cm 2 .

[0069] The pulsed laser beam of the ultrashort pulse laser has, for example, laser pulses with a pulse duration in the picosecond (“picosecond laser”) or femtosecond (“femtosecond laser”) range. For example, the pulse duration is from 1 fs to 100 ps, more preferably from 100 fs to 50 ps (e.g., from 1 ps to 100 ps, more preferably from 1 ps to 50 ps, or from 1 fs to 1000 fs, more preferably from 100 fs to 1000 fs).

[0070] Suitable laser operating parameters for adjusting the total flux applied thereby are known to those skilled in the art.

[0071] As described above, the total flux applied by the pulsed laser beam is generated by the total energy applied by the pulsed laser beam per unit area.

[0072] For example, the total flux applied by the pulsed laser beam can be adjusted by one or more of the following parameters:

[0073] - The energy of the laser pulse,

[0074] - The pulse frequency (i.e., the number of laser pulses per unit time)

[0075] - The diameter of the laser beam impinging on the surface of the material to be removed,

[0076] - The extent of spatial overlap of the laser pulses (e.g., spatial overlap of consecutive laser pulses along a scan line or spatial overlap between laser pulses of adjacent scan lines),

[0077] - The number of passes of the laser over the material to be removed,

[0078] - The scan speed (i.e., the speed at which the pulsed laser beam scans over the material to be removed).

[0079] These parameters can be adjusted and varied on commercially available ultrafast pulsed lasers by measures known to those skilled in the art.

[0080] For example, the pulses of the pulsed laser beam each have a pulse energy of at least 15 μJ, more preferably at least 20 μJ, such as 15 μJ to 300 μJ, more preferably 20 μJ to 200 μJ.

[0081] For example, the pulsed laser beam has a pulse frequency of 100 kHz to 50 MHz, more preferably 500 kHz to 20 MHz.

[0082] The pulsed laser beam impinging on the exposed adhesion-promoting layer has a diameter of, for example, 3 μm to 200 μm, more preferably 10 μm to 100 μm.

[0083] The diameter of the pulsed laser beam impinging on the exposed reaction layer can be adjusted via the focused diameter of the laser beam. For example, the pulsed laser beam has a focused diameter of 3 μm to 200 μm, more preferably 10 μm to 100 μm, and the metal-ceramic composite is positioned such that the exposed reaction layer is located at the focus of the pulsed laser beam.

[0084] The pulsed laser beam is guided, for example, along one or more scan lines (also referred to as processing lines or processing paths) over the exposed adhesion-promoting layer to be removed.

[0085] Preferably, the pulse frequency and the scanning speed of the pulsed laser beam are selected such that immediately consecutive laser pulses spatially overlap (i.e., the impact surfaces of immediately consecutive laser pulses on the exposed adhesion-promoting layer overlap each other).

[0086] The pulse overlap PO is usually given in % and can be calculated, for example, using the following equation:

[0087] PO = (1 - v 扫描 / (D L × f L )) × 100%

[0088] where

[0089] v 扫描 is the scanning speed of the pulsed laser beam (i.e., the speed at which the pulsed laser beam is guided over the exposed adhesion-promoting layer),

[0090] D L is the diameter of the pulsed laser beam impinging on the exposed adhesion-promoting layer,

[0091] f L is the pulse frequency of the pulsed laser beam.

[0092] The pulse overlap PO can be adjusted by the pulse frequency and the scanning speed of the pulsed laser beam for a specific laser beam diameter.

[0093] For example, in the method of the present invention, a pulse overlap of at least 60%, more preferably at least 80%, is selected.

[0094] For example, the following relationship applies:

[0095] PO = (1 - v 扫描 / (D L × f L )) × 100% ≥ 60%

[0096] More preferably, the following applies:

[0097] PO = (1 - v 扫描 / (D L × f L )) × 100% ≥ 80%

[0098] After the front side of the ceramic substrate has been exposed in at least one recess, if desired, the structured metal-ceramic composite can be subjected to further processing steps. For example, semiconductor components and / or metal bonding wires can be applied to the structured metal coating.

[0099] Measurement method

[0100] Composition of the reaction layer

[0101] The composition of the adhesion-promoting layer was determined by combining energy-dispersive X-ray spectroscopy (EDX) with scanning electron microscopy (SEM-EDX).

[0102] In SEM-EDX, a focused primary electron beam is rastered (scanned) point by point over the sample surface. Scattered electrons are detected using a detector, and the number of electrons per pixel results in a microscopic image of the sample surface displayed in gray scale. In addition, the primary electron beam excites the sample to emit characteristic X-ray radiation, and the elements in the sample and their weight ratios can be determined by analyzing the energy spectrum using an EDX detector. For the examination, for example, a scanning electron microscope (JSM-6060SEM, JEOL Ltd) with a silicon drift EDX detector (NORAN, Thermo Scientific Inc) and analysis software (Pathfinder Mountaineer EDS System, version 2.8, for example, Thermo Scientific Inc) was used. For the scanning electron microscopy, the following settings were used: magnification: 1000x, acceleration voltage = 15 kV, working distance = 10 mm, spot size (50 - 60) (set to achieve a dwell time at the EDX detector of 25% + / - 5%). The following settings of the EDX detector were used to detect the EDX spectrum: live time = 30 s, rate = automatic, low energy cut-off = 100 keV, high energy cut-off = automatic (per SEM acceleration voltage).

[0103] By means of SEM-EDX, the composition of the reaction layer can be determined both qualitatively (detecting certain elements and phases, such as the metal nitride phase present in the adhesion-promoting layer) and quantitatively. For example, the measurements were carried out at at least 10 points on the reaction layer. Examples

[0104] In the examples described below, first, a matching silicon nitride substrate was metallized by active metal brazing using a copper film under the same conditions to obtain a copper-silicon nitride composite.

[0105] The metallization of the silicon nitride substrate by active metal brazing was carried out as follows:

[0106] On one of the side surfaces of the ceramic substrate, an active metal brazing paste is applied by screen printing over an area measured at 168 mm × 130 mm and pre-dried at 125 °C for 15 minutes. The active metal brazing paste consists of 67 wt% copper powder, 19.8 wt% tin powder, 3.7 wt% titanium hydride, and 9.5 wt% organic carrier. The thickness of the paste after pre-drying is 25 μm + / - 5 μm. Subsequently, a copper film made of oxygen-free high-conductive copper with a purity of 99.99% and dimensions of 170 mm × 132 mm × 0.3 mm is placed on the pre-dried paste. Then the resulting arrangement is flipped, and the paste is similarly applied to the opposite side of the ceramic substrate by screen printing, pre-dried, and assembled using the copper film to obtain a sandwich arrangement. The sandwich arrangement is weighted with a 1 kg weight, fired at a maximum temperature of 910 °C for 20 minutes, and then cooled to room temperature to obtain an unstructured metal-ceramic composite. Due to production by active metal brazing, an adhesion-promoting reaction layer exists between the metal coating and the ceramic substrate. It contains titanium (e.g., in the form of a nitride).

[0107] Subsequently, in each of the provided metal-ceramic composites, the metal coating is removed in a defined area under the same conditions such that at least one recess is created in the metal coating in each metal-ceramic composite, and the exposed reaction layer is present in the recess. The copper coating is removed using an etching solution containing CuCl 2 .

[0108] Subsequently, the exposed reaction layer remaining on the ceramic substrate after etching is removed under different conditions.

[0109] In Examples EB-1.1, EB-1.2, EB-1.3, EB-1.4, and EB-1.5 according to the present invention and Comparative Examples VB-1.1, VB-1.2, and VB-1.3, the exposed reaction layer is removed using an IR ultra-short pulse laser (TruMicro Series 2000, Trumpf). These Examples EB-1.1 to EB-1.5 and VB-1.1 to VB-1.3 are matched in the following parameters:

[0110] Pulse duration: 3 ps

[0111] Focus diameter of the pulsed laser beam: 55 μm

[0112] Scanning speed: 5500 mm / s

[0113] Pulse frequency: 1 MHz

[0114] Pulse overlap: 90%

[0115] Distance between adjacent scan lines: 25 μm

[0116] However, the pulse energy and the number of passes through the scan lines (i.e., the frequency at which the pulsed laser beam passes through a specific scan line) vary such that in Examples EB-1.1 to EB-1.5 according to the present invention, a total flux in the range of 50 J / cm 2 to 650 J / cm 2 is applied, while in Comparative Example VB-1.1, a lower total flux is applied, and in Comparative Example VB-1.2, a higher total flux is applied.

[0117] In Examples EB-2.1, EB-2.2, EB-2.3, EB-2.4, and EB-2.5 according to the present invention and Comparative Examples VB-2.1 and VB-2.2, the exposed reaction layer is also removed using an IR ultrashort pulse laser (TruMicro Series 2000, Trumpf Group). These Examples EB-2.1 to EB-2.5 and VB-2.1 to VB-2.2 are matched in the following parameters:

[0118] Pulse duration: 850 fs

[0119] Focused diameter of the pulsed laser beam: 55 μm

[0120] Scanning speed: 1100 mm / s

[0121] Pulse frequency: 5 MHz

[0122] Pulse overlap: 90%

[0123] Distance between adjacent scan lines: 15 μm

[0124] Again, the pulse energy and the number of passes through the scan lines of the pulsed laser beam vary such that in Examples EB-2.1 to EB-2.5 according to the present invention, a total flux in the range of 50 J / cm 2 to 650 J / cm 2 is applied, while in Comparative Example VB-2.1, a lower total flux is applied, and in Comparative Example VB-2.2, a higher total flux is applied.

[0125] In Comparative Example VB3, an etchant containing ammonium fluoride, fluoboric acid, and hydrogen peroxide is used to remove the exposed reaction layer.

[0126] Each of the obtained structured metal-ceramic composites after removing the reaction layer is studied with respect to the following characteristics:

[0127] - Possible residues of the reaction layer exposed on the ceramic substrate,

[0128] - Flexural strength of the ceramic substrate,

[0129] - Thermal shock resistance of the metal-ceramic composite material.

[0130] The thermal shock resistance was evaluated using the following test method:

[0131] In the preparation for the thermal shock resistance test, first, ultrasonic microscopy (PVA Tepla SAM300) was used to check whether the metal-ceramic composite material was in perfect condition. For this test, only metal-ceramic composite materials were used that did not show delamination between the ceramic body and the metal layer or other deformations (e.g., cracks) that could cause delamination of the metal layer from the ceramic body. To test the thermal shock resistance, the metal-ceramic composite material was repeatedly exposed in a cycling chamber (ESPEC TSB-21 51) to cold liquid (temperature -65 °C, Galden Do2TS) and hot liquid (temperature +150 °C, Galden Do2TS) for respective 5-minute periods. Every 1000 cycles, the metal-ceramic composite material was checked again for delamination and other deformations using ultrasonic microscopy (PVA Tepla SAM300). The test was terminated after 3000 cycles. Then, the metal-ceramic composite material was checked again for delamination and other deformations using ultrasonic microscopy (PVA Tepla SAM300). The state of the corresponding metal-ceramic composite material after the thermal shock resistance test was compared with the state of the metal-ceramic composite material before the thermal shock resistance test in terms of delamination and other deformations. Delamination and other deformations (e.g., cracks) were visible as white discolorations in the ultrasonic images. The results were classified as follows:

[0132] Very good: No visible delamination

[0133] Poor: Delamination was visible at the corners of the metal-ceramic substrate

[0134] The degree to which the exposed reaction layer was completely removed was evaluated by scanning electron microscopy and EDX.

[0135] To measure the flexural strength, a 3-point flexural strength tool was installed in the testing machine, and the corresponding test recipe according to DIN EN843-1:2008-08 was used. The following test parameters were set: preload 0.5 N, preload speed 0.5 mm / min, test speed 10 mm / min (position control).

[0136] Due to the shape of the flat substrate, the sample sizes shown here deviated from the sizes described in the standard. However, these parameters allowed for fracture within the time specified in the standard (5 s to 15 s) after loading, such that the requirements of the standard were met. From the measured fracture force and the sample size, the fracture stress σf of each sample was determined using Equation 1:

[0137]

[0138] Formula 1: Equation for calculating the fracture stress σf

[0139] wherein

[0140] σf is the fracture stress (in N×mm-2, equal to MPa)

[0141] F is the maximum force at fracture (in N)

[0142] b is the width of the specimen (in mm)

[0143] h is the height of the specimen (in mm)

[0144] l is the distance between the centers of the support rollers (in mm)

[0145] The flexural strength is classified as follows:

[0146] High: >630 MPa

[0147] Medium: 600 MPa to 630 MPa

[0148] Low: <600 MPa

[0149] The results are summarized in Table 1 below.

[0150] Table 1: Total flux and properties of the structured metal-ceramic composite applied in the examples

[0151]

[0152]

[0153] Examples are shown below :

[0154] When the exposed reaction layer is removed using an ultrashort pulse laser, the resulting metal-ceramic composite shows very good thermal shock resistance. However, complete removal of the exposed reaction layer while maintaining high flexural strength is only achieved when the total fluence applied by the ultrashort pulse laser is within the range according to the present invention (50 J / cm 2 to 650 J / cm 2 ). If the total fluence is greater than 650 J / cm 2 , this results in impairment of the flexural strength, while in the case where the total fluence is less than 50 J / cm 2 , the exposed reaction layer is not removed or is only inadequately removed.

[0155] If the exposed reaction layer is removed by etching, the reaction layer can be completely removed without affecting the flexural strength, but the resulting metal-ceramic composite shows a significant reduction in thermal shock resistance.

Claims

1. A method for structuring a metal-ceramic composite material, the method comprising the following steps: - Provide a metal-ceramic composite material, the metal-ceramic composite material comprising - a nitride ceramic substrate, the nitride ceramic substrate comprising a front side and a back side, - a metal coating, said metal coating being located on said front side of said nitride ceramic substrate, - a reaction layer, said reaction layer being present between said metal coating and said ceramic substrate and containing one or more elements E selected from the group consisting of Ti, Hf, Zr, Nb, V, Ta and Ce RS , - removing the metal coating so that at least one recess is produced in the metal coating, and there is an exposed reaction layer in the recess, - removing the exposed reaction layer using a pulsed laser beam of an ultrashort pulse laser so that the exposed surface of the ceramic substrate is present in the recessed portion, wherein the pulsed laser beam applies 50 J / cm 2 Up to 650J / cm 2 The total flux. 2 . The method according to claim 1 , wherein the nitride ceramic substrate contains silicon nitride or aluminum nitride, and the metal coating is a copper coating or an aluminum coating.

3. A method according to claim 1 or claim 2, wherein the metal coating is removed by etching or laser ablation, preferably by etching.

4. The method according to any one of the preceding claims, wherein the total fluence applied by the pulsed laser beam is 100 J / cm 2 Up to 320J / cm 2 .

5. The method according to any one of the preceding claims, wherein the pulsed laser beam comprises pulses having a pulse duration of 1 femtosecond to 100 picoseconds.

6. The method of any one of the preceding claims, wherein the pulsed laser beam comprises pulses each having a pulse energy of at least 15 μJ.

7. The method according to any one of the preceding claims, wherein the pulsed laser beam has a pulse frequency f of 100 kHz to 50 MHz. L .

8. The method according to any one of the preceding claims, wherein the pulsed laser beam impinging on the exposed adhesion promoting layer has a radius D of 3 μm to 200 μm. L .

9. The method according to any one of the preceding claims, wherein the pulsed laser beam satisfies the following conditions: (1-v 扫描 / (D L ×f L ))×100%≥60% in v 扫描 is the scanning speed of the pulsed laser beam, D L is the diameter of the pulsed laser beam striking the exposed adhesion promoting layer, f L is the pulse frequency of the pulsed laser beam.

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