Method for structuring metal-ceramic composite

Abstract

To provide a method for structuring a metal-ceramic composite.SOLUTION: A method for structuring a metal-ceramic composite includes the steps of: providing a metal-ceramic composite including a nitride ceramic substrate containing a front surface and a back surface, a metal coating on the front surface of the nitride ceramic substrate, and a reaction layer located between the metal coating and the ceramic substrate and containing at least one element ERS selected from Ti, Hf, Zr, Nb, V, Ta, and Ce; removing the metal coating to form at least one recessed part in the metal coating, an exposed adhesion acceleration layer remaining in the recessed part; and removing the exposed reaction layer by applying a total fluence of 50 J / cm2 to 650 J / cm2 by a pulse laser beam of a super short laser so that an exposed surface of the ceramic substrate is in the recessed part.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for structuring a metal-ceramic composite. Such a structured metal-ceramic composite can be used as a ceramic circuit carrier in a semiconductor module for power electronics.

[0002] In power electronics, a printed circuit board should be designed for high current as a carrier for power components such as MOSFETs and should be able to dissipate waste heat quickly.

[0003] Ceramic materials such as aluminum oxide, aluminum nitride, and silicon nitride have much higher thermal conductivities than the polymers used to manufacture conventional printed circuit boards, so ceramic circuit carriers are often used in power modules.

[0004] A ceramic circuit carrier includes a ceramic substrate provided with a metal layer at least on the front surface. Conventionally, a metal layer has also been applied to the rear surface of the ceramic substrate. In the final module, semiconductor components are applied to one of these metal layers, while the metal layer on the opposite side of the ceramic substrate is thermally conductively connected to a heat sink. The ceramic substrate electrically insulates the metal layers from each other.

[0005] A metallized ceramic substrate that functions as a ceramic circuit board, known to those skilled in the art, is manufactured, for example, by bringing the front and rear surfaces of a ceramic substrate into contact with a metal film (e.g., a copper or aluminum film) and joining them together.

[0006] In one of these methods known to those skilled in the art, the metal film is joined to the ceramic substrate by eutectic bonding. When the metal film is a copper film, the eutectic bonding is also called 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. A metallized ceramic substrate manufactured using the DCB method may also be called a DCB substrate (or a DBC substrate).

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

[0008] For example, a silicon nitride-based ceramic substrate has very high mechanical strength and high thermal conductivity at the same time, and is therefore very suitable for applications in power electronics.

[0009] Silicon nitride-based ceramic substrates are described, for example, in the following publications: N. Chasserio et al.,”Ceramic Substrates for High-Temperature Electronic Integration,”Journal of Electronic Materials,Volume38(2009),pp.164-174; K. Hirao et al.,”High Thermal Conductivity Silicon Nitride Ceramics,”Journal of the Korean Ceramic Society,Volume49(2012),pp.380-384; Y. Zhou et al.,”Development of high-thermal-conductivity silicon nitride ceramics,”Journal of Asian Ceramic Societies,3(2015),pp.221-229。

[0010] Aluminum nitride-based ceramic substrates have very high thermal conductivity and at the same time have sufficiently high mechanical strength, and thus are also very suitable for applications in power electronics.

[0011] However, silicon nitride substrates are not suitable for metallization using the DCB method, and aluminum nitride substrates should first oxidize the surface, which is complex and may have an adverse effect on the thermal conductivity.

[0012] Therefore, nitride ceramics are often metallized by the active metal brazing method (AMB).

[0013] An active metal brazing filler metal is a brazing filler metal that can wet non-metallic inorganic materials (e.g., ceramics, graphite, glass) depending on its composition. The active metal brazing filler metal contains one or more elements that can react with the ceramic to form an adhesion-promoting reaction layer in addition to a main component such as Cu, Ag, or Au (see, for example, Chapter 8.2.4.3 of Brevier Technische Keramik, Verband der Keramischen Industrie eV, 2003, Fahner Verlag, “Active metal brazing,” pages 203-204). Reactive elements such as hafnium (Hf), titanium (Ti), zirconium (Zr), niobium (Nb), cerium (Ce), tantalum (Ta), and vanadium (V) are used. In the metallization of silicon nitride substrates by the active metal brazing method, the reaction layer contains, for example, nitrides, oxynitrides, and / or silicides of reactive elements (A. Ponicke et al., “Active metal brazing of copper with aluminum nitride and silicon nitride ceramics,” Keramische Zeitschrift, 63(5), 2011, 334-342).

[0014] The metal coating of the metal-ceramic composite carrying the semiconductor component is structured (for example, by etching using an etching mask). Thus, the structured metal coating has one or more recesses in which the areas of the metal coating remaining after structuring are separated from each other. The structuring of the AMB substrate is usually 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 (for example, unmasked) areas, exposing the reaction layer formed during active metal soldering. In a further step, the surface of the ceramic substrate is exposed using a second etching solution optimized for the removal of the reaction layer.

[0015] For later use as a power electronics module, it is essential that the adjacent conductor tracks formed by structuring are electrically insulated from each other. For this purpose, it is necessary that no residue of the reaction layer remains between the adjacent conductor tracks. Therefore, the etching solution used in the second etching step should completely remove the exposed reaction layer. However, this often results in under-etching of the metal coating, i.e., the etching solution in the second etching step not only removes the reaction layer exposed after the first etching step but also the reaction layer on the side surface of the metal coating that is still covered and thus required for the bonding between the metal coating and the ceramic substrate. This can cause the metal coating to peel off from the ceramic substrate under thermal cycle stress.

[0016] For the etching process of the reaction layer obtained from the active metal soldering method, highly reactive chemicals are required that can leave undesirable (for example, corrosive) residues on the ceramic even after the final cleaning step. When using an etching medium containing fluoride, fluoride residues may remain on the exposed ceramic surface. Residues of such etching agents can have a corrosive effect in power electronics modules.

[0017] When attempting to completely remove, to the extent 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. As a result, it can lead to a decrease in mechanical properties such as the bending strength of the ceramic substrate.

[0018] An object of the present invention is to enable efficient exposure of the ceramic surface in a defined area, but without achieving this at the expense of the thermal shock resistance of the metal-ceramic composite and / or mechanical properties such as the bending strength of the ceramic substrate. Structuring a metal-ceramic composite produced by an active metal brazing method by a method that does not. Efficient exposure of the ceramic surface particularly includes substantially no conductive and / or corrosive material remaining on the exposed ceramic substrate surface.

[0019] This object is achieved by a method for structuring a metal-ceramic composite, the method comprising the following steps: Providing a metal-ceramic composite, wherein the metal-ceramic composite comprises A nitride ceramic substrate including a front surface and a rear surface, A metal coating on the front surface of the nitride ceramic substrate, A reaction layer present between the metal coating and the ceramic substrate and containing one or more elements E selected from Ti, Hf, Zr, Nb, V, Ta, and Ce RS And providing, Removing the metal coating, as a result of which at least one recess is formed in the metal coating and an exposed adhesion promotion layer is present in the recess, Removing the exposed reaction layer using a pulsed laser beam of an ultrashort pulsed laser such that the exposed surface of the ceramic substrate is present in the recess, the pulsed laser beam having a total fluence of 50 J / cm 2 ~650 J / cm 2 Is applied, the step of removing,

[0020] By exposing the ceramic surface in a defined area, the metal-ceramic composite structured by the method according to the invention is a metal-ceramic composite produced by the active metal brazing method, and the ceramic is a nitride ceramic. Such metal-ceramic composites are known to those skilled in the art and are commercially available or can be produced by known methods. The removal of the metal coating for exposing the reaction layer obtained from the active metal brazing process can also be carried out using conventional removal methods (e.g., etching), as will be described in more detail below.

[0021] In the present invention, removal is carried out using an ultrashort pulse laser, and the total fluence applied by the ultrashort pulse laser to expose the ceramic substrate is 50 J / cm 2 ~650 J / cm 2 It has been found that when this is the case, 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 can still be maintained at a high level.

[0022] An ultrashort pulse laser is a laser that can emit laser pulses having a pulse duration in the picosecond ( "picosecond laser") or femtosecond ( "femtosecond laser") range. As is known to those skilled in the art, the fluence (or energy density) of a laser refers to the energy applied per unit area. In the case of a pulsed laser beam, the fluence can refer to a single laser pulse emitted during the processing of the material or the entirety of all laser pulses. The latter is called the total fluence or cumulative fluence and refers to the total energy per unit area applied to the irradiated area of the metal-ceramic composite by the pulsed laser beam.

[0023] The total fluence F total is obtained from the following relationship: F total = E total / A L (where Etotal is the total energy applied by the pulsed laser beam, and A L is the total area irradiated by the laser beam).

[0024] When the laser pulses of the pulsed laser beam each have the same pulse energy EP, the total fluence Ftotal is obtained from the following relationship: F total = N P × E P / A L (wherein, N P is the total number of laser pulses applied by the pulsed laser beam, E P is the energy of the laser pulse, A L is the total area irradiated by the laser beam).

[0025] As will be described in more detail below, when the total fluence applied by the pulsed laser beam of the ultrashort pulsed laser is less than 50 J / cm 2 , the exposed reaction layer is not removed or is removed only insufficiently, while when the total fluence applied exceeds 650 J / cm 2 , the exposed reaction layer is completely removed, but the flexural strength of the ceramic substrate is significantly reduced.

[0026] The metal-ceramic composite structured by the method according to the invention comprises a nitride ceramic substrate including a front surface and a rear surface, a metal coating on the front surface of the nitride ceramic substrate, a reaction layer present between the metal coating and the ceramic substrate and containing one or more elements E RS selected from Ti, Hf, Zr, Nb, V, Ta and Ce.

[0027] The nitride ceramic substrate contains, for example, silicon nitride or aluminum nitride. In a preferred embodiment, the nitride ceramic substrate contains silicon nitride.

[0028] For example, the nitride ceramic substrate contains silicon nitride or aluminum nitride at a ratio of 70% by weight or more, more preferably 80% by weight or more.

[0029] Optionally, the nitride ceramic substrate may contain one or more metal oxides. These are added, for example, as sintering aids during the manufacture 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 (for example, one or more rare earth oxides such as yttrium oxide), silicon oxide (for example, SiO 2 ), or one or more of silicates.

[0030] The nitride ceramic substrate has a thickness in the range of, for example, 0.1 mm to 1.0 mm.

[0031] There is a metal coating 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.

[0032] The metal coating present on the front surface and optionally the back surface of the nitride ceramic substrate is, for example, a copper coating or an aluminum coating. The metal coating has a thickness in the range of, for example, 0.05 mm to 1.5 mm, more preferably 0.2 mm to 0.8 mm.

[0033] When the metal coating is a copper coating, it has a copper content of, for example, at least 97% by weight, more preferably at least 99% by weight.

[0034] When the metal coating is an aluminum coating, it has an aluminum content of, for example, at least 97% by weight, more preferably at least 99% by weight.

[0035] The metal coating is, for example, a copper film or an aluminum film applied to a nitride ceramic substrate by an active metal brazing method.

[0036] The reaction layer contains one or more elements E 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. RS In the reaction layer, a particularly preferred element E RS is titanium. For example, the element E RS is present in the reaction layer in the form of nitrides, oxynitrides, and / or silicides. For example, the reaction layer contains the element E RS in a total amount of at least 50% by weight. For example, the reaction layer contains nitrides, oxynitrides, and silicides of the element E SR in a total amount of at least 70% by weight, more preferably at least 85% by weight. In a power electronics semiconductor module, the migration of silver can cause problems. Therefore, the reaction layer preferably contains silver in a proportion of 5% by weight or less, more preferably 1% by weight or less, or even preferably does not contain silver.

[0037] In the method according to the invention, the metal coating of the provided metal-ceramic composite is removed in a defined region (for example, taking into account a specific desired conductor track arrangement), as a result, at least one recess is formed in the metal coating, and the exposed reaction layer is present in the recess.

[0038] The removal of 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.

[0039] For example, the metal coating is removed by etching (for example, using an etching mask so that the metal coating is removed by contacting the etching medium only in the unmasked regions) or by laser ablation.

[0040] In a preferred embodiment, the metal coating is removed by etching. Suitable etching media and etching conditions for removing the metal coating (e.g., copper or aluminum coating) are known to those skilled in the art. For example, etching is performed using an aqueous metal chloride solution (e.g., an aqueous iron chloride solution, an aqueous copper chloride solution). However, other etching solutions known to those skilled in the art can also be used. The etching can be performed in several steps using different etching solutions if necessary. The etching continues until the reaction layer is exposed. Regarding the composition of the exposed reaction layer, reference can be made to the above description.

[0041] The exposed reaction layer present in the recess is irradiated with a pulsed laser beam of an ultrashort pulsed laser to remove the reaction layer, and as a result, the surface of the ceramic substrate within the recess is exposed. The surface of the ceramic substrate is exposed with a total fluence of 50 J / cm 2 ~650 J / cm 2 applied by the pulsed laser beam. At 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.

[0042] In an exemplary embodiment, the total fluence applied by the pulsed laser beam is 100 J / cm 2 ~320 J / cm 2 is.

[0043] The pulsed laser beam of the ultrashort pulsed laser has a laser pulse having a pulse duration in the range of, for example, picoseconds ("picosecond laser") or femtoseconds ("femtosecond laser"). For example, the pulse duration is 1 fs to 100 ps, more preferably 100 fs to 50 ps (e.g., 1 to 100 ps, more preferably 1 to 50 ps, or less than 1 to 1000 fs, more preferably less than 100 to 1000 fs).

[0044] Appropriate laser operating parameters that can adjust the total fluence to be imprinted are known to those skilled in the art.

[0045] As described above, the total fluence applied by the pulsed laser beam is obtained from the total energy applied by the pulsed laser beam per unit area.

[0046] For example, the total fluence applied by the pulsed laser beam can be adjusted by one or more of the following parameters: The energy of the laser pulse, The pulse frequency (i.e., the number of laser pulses per unit time), The diameter of the laser beam hitting the surface of the material to be removed, The range of spatial overlap of the laser pulses (e.g., the spatial overlap of consecutive laser pulses along a scan line, or the spatial overlap between laser pulses of adjacent scan lines), The number of lasers passing over the material to be removed, The scan speed (i.e., the speed at which the pulsed laser beam scans over the material to be removed).

[0047] These parameters can be adjusted and changed with commercially available ultrashort pulsed lasers by means known to those skilled in the art.

[0048] For example, each pulse of the pulsed laser beam has a pulse energy of at least 15 μJ, more preferably at least 20 μJ, for example, 15 μJ to 300 μJ, more preferably 20 μJ to 200 μJ.

[0049] For example, the pulsed laser beam has a pulse frequency of 100 kHz to 50 MHz, more preferably 500 kHz to 20 MHz.

[0050] The pulsed laser beam hitting the exposed adhesion promoting layer has a diameter of, for example, 3 μm to 200 μm, more preferably 10 μm to 100 μm.

[0051] The diameter of the pulsed laser beam hitting the exposed reaction layer can be adjusted through the focal spot diameter of the laser beam. For example, the pulsed laser beam has a focal spot diameter of 3 μm to 200 μm, more preferably 10 μm to 100 μm, and the metal-ceramic composite is arranged such that the exposed reaction layer is within the focus of the pulsed laser beam.

[0052] The pulsed laser beam is induced, for example, along one or more scanning lines (also called processing lines or processing paths) on the exposed adhesion promoting layer to be removed.

[0053] Preferably, the pulse frequency and 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).

[0054] The pulse overlap PO is usually expressed in %, and can be calculated, for example, using the following formula: PO=(1 - v scan / (D L ×f L ))×100% (where v scan is the scanning speed of the pulsed laser beam (i.e., the speed at which the pulsed laser beam is induced on the exposed adhesion promoting layer), D L is the diameter of the pulsed laser beam hitting the exposed adhesion promoting layer, f L is the pulse frequency of the pulsed laser beam).

[0055] The pulse overlap PO can be adjusted for a specific laser beam diameter according to the pulse frequency and scanning speed of the pulsed laser beam.

[0056] For example, in the method of the present invention, a pulse overlap of at least 60%, more preferably at least 80% is selected.

[0057] For example, the following relationship applies: PO = (1 - v scan / (D L × f L )) × 100% ≥ 60%

[0058] More preferably, the following applies: PO = (1 - v scan / (D L × f L )) × 100% ≥ 80%

[0059] After exposing the front surface of the ceramic substrate with at least one recess, the structured metal-ceramic composite can be subjected to further processing steps, if necessary. For example, semiconductor components and / or metal bonding wires can be applied to the structured metal coating.

[0060] Measurement method Composition of the reaction layer The composition of the adhesion promoting layer is determined by energy dispersive X-ray spectroscopy (EDX) combined with a scanning electron microscope (SEM-EDX).

[0061] In SEM-EDX, a focused primary electron beam is induced (screened) point by point on the sample surface. Scattered electrons are detected using a detector, and the number of electrons per pixel results in a grayscale microscopic image of the sample surface. Furthermore, 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 inspection, for example, a scanning electron microscope (JSM-6060 SEM, JEOL Ltd) equipped with a silicon drift EDX detector (NORAN, Thermo Scientific Inc) and analysis software (Pathfinder Mountaineer EDS System, for example version 2.8, Thermo Scientific Inc) are used. In the case of the scanning electron microscope, the following settings are used: magnification: 1000 times, acceleration voltage = 15 kV, working distance = 10 mm, spot size (50 - 60) (set to reach 25% + / - 5% of the dead time of the EDX detector). The following settings of the EDX detector are used to detect the EDX spectrum: live time = 30 seconds, speed = automatic, low energy cut-off = 100 keV, high energy cut-off = automatic (following the SEM acceleration voltage).

[0062] The composition of the reaction layer can be determined both qualitatively (detection of specific elements and phases, for example, metal nitride phases present in the adhesion promotion layer) and quantitatively by SEM-EDX. For example, measurements are taken at at least 10 points on the reaction layer.

Example

[0063] In the example described below, a compatible silicon nitride substrate was first metallized under the same conditions by an active metal brazing method using a copper film to obtain a copper-silicon nitride composite.

[0064] The metallization of the silicon nitride substrate by the active metal brazing method was performed as follows.

[0065] On one side of the ceramic substrate, an active metal brazing paste was applied by screen printing to an area of 168 mm × 130 mm and pre-dried at 125 °C for 15 minutes. The active metal brazing paste consisted of 67 wt% copper powder, 19.8 wt% tin powder, 3.7 wt% titanium hydride, and 9.5 wt% organic vehicle. The thickness of the paste after pre-drying was 25 ± 5 μm. Subsequently, an oxygen-free highly conductive copper film with a purity of 99.99% and dimensions of 170 mm × 132 mm × 0.3 mm was placed on the pre-dried paste. Next, the obtained arrangement was turned over, the paste was similarly applied to the opposite side of the ceramic substrate by screen printing, pre-dried, and the copper film was attached to obtain a sandwich arrangement. A load of 1 kg was applied to the sandwich arrangement and fired at a maximum temperature of 910 °C for 20 minutes, and then cooled to room temperature to obtain an unstructured metal-ceramic composite. By manufacturing using the active metal brazing method, an adhesion promoting reaction layer exists between the metal coating and the ceramic substrate. This contains titanium (for example, in the form of a nitride).

[0066] Subsequently, in each of the provided metal-ceramic composites, the metal coating was removed in a region defined under the same conditions, and as a result, in each of the metal-ceramic composites, at least one recess was formed in the metal coating and the exposed reaction layer was present in the recess. The copper coating was removed using an etching solution containing CuCl 2 containing.

[0067] The exposed reaction layer remaining on the ceramic substrate after etching was subsequently removed under different conditions.

[0068] In Examples EB-1.1, EB-1.2, EB-1.3, EB-1.4 and EB-1.5, and Comparative Examples VB-1.1, VB-1.2 and VB-1.3 according to the present invention, the exposed reaction layer was removed using an IR ultrashort pulse laser (TruMicro Series 2000, Trumpf). These Examples EB-1.1 to EB-1.5 and VB-1.1 to VB-1.3 were identical in the following parameters. Pulse duration: 3 ps Focal diameter of the pulsed laser beam: 55 μm Scanning speed: 5500 mm / s Pulse frequency: 1 MHz Pulse overlap: 90% Distance between adjacent scanning lines: 25 μm

[0069] However, the pulse energy and the number of passes through the scanning line (i.e., the number of times the specified scanning line is passed through by the pulsed laser beam) were varied to apply a total fluence in the range of 50 - 650 J / cm in Examples EB-1.1 to EB-1.5 according to the present invention. In Comparative Example VB-1.1, a lower total fluence was applied, and in Comparative Example VB-1.2, a higher total fluence was applied. 2 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 was also removed using an IR ultrashort pulse laser (TruMicro Series 2000, Trumpf). Examples EB-2.1 to EB-2.5 and VB-2.1 to VB-2.2 were identical in the following parameters.

[0070] 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 was also removed using an IR ultrashort pulse laser (TruMicro Series 2000, Trumpf). Examples EB-2.1 to EB-2.5 and VB-2.1 to VB-2.2 were identical in the following parameters. Pulse duration: 850 fs Focal diameter of the pulsed laser beam: 55 μm Scanning speed: 1100 mm / s Pulse frequency: 5 MHz Pulse overlap: 90% Distance between adjacent scanning lines: 15 μm

[0071] Here too, the pulse energy and the number of passes of the scanning line by the pulsed laser beam were varied to apply a total fluence in the range of 50 - 650 J / cm in Examples EB-2.1 to EB-2.5 according to the present invention. In Comparative Example VB-2.1, a lower total fluence was applied, and in Comparative Example VB-2.2, a higher total fluence was applied. 2 In Examples EB-2.1 to EB-2.5 according to the present invention, and Comparative Examples VB-2.1 and VB-2.2, the exposed reaction layer was also removed using an IR ultrashort pulse laser (TruMicro Series 2000, Trumpf). Examples EB-2.1 to EB-2.5 and VB-2.1 to VB-2.2 were identical in the following parameters.

[0072] In Comparative Example VB3, the exposed reaction layer was removed using an etching solution containing ammonium fluoride, fluoroboric acid, and hydrogen peroxide.

[0073] Each of the structured metal-ceramic composites obtained after removal of the reaction layer was examined with respect to the following properties: Possible residues of the exposed reaction layer on the ceramic substrate, The flexural strength of the ceramic substrate, The thermal shock resistance of the metal-ceramic composite.

[0074] The thermal shock resistance was evaluated using the following test method.

[0075] In preparation for the thermal shock resistance test, ultrasonic microscopy (PVA Tepla SAM300) was first used to check whether the metal-ceramic composite was in a complete state. For the test, only metal-ceramic composites were used that did not show delamination between the ceramic body and the metal layer, or other deformations that could cause delamination of the metal layer from the ceramic body (e.g., cracks). To test the thermal shock resistance, the metal-ceramic composite was repeatedly exposed to a cryogenic liquid (temperature -65 °C, Galden Do2TS) and a hot liquid (temperature +150 °C, Galden Do2TS) for 5 minutes each in a cycle chamber (ESPEC TSB-2151). The metal-ceramic composite was rechecked for delamination and other deformations every 1000 cycles using ultrasonic microscopy (PVA Tepla SAM300). The test was terminated after 3000 cycles. Next, the metal-ceramic composite was retested for delamination and other deformations using ultrasonic microscopy (PVA Tepla SAM300). The state of each metal-ceramic composite after the thermal shock resistance test was compared with the state of the metal-ceramic composite before the thermal shock resistance test with respect to delamination and other deformations. Delamination and other deformations (e.g., cracks) appeared as white discoloration in the ultrasonic images. The results were classified as follows: Very good: No delamination was observed Insufficient: Delamination was observed at the corners of the metal-ceramic substrate.

[0076] The evaluation of how completely the exposed reaction layer was removed was performed by scanning electron microscopy and EDX.

[0077] To measure the flexural strength, a three-point flexural strength tool was installed in the testing machine and the corresponding test recipe according to DIN EN 843-1:2008-08 was used. The following test parameters were set: preload 0.5 N, preload rate 0.5 mm / min, test rate 10 mm / min (position control).

[0078] Due to the shape of the flat substrate, the sample dimensions presented here deviate from the dimensions described in the standard. Nevertheless, these parameters enable fracture within the time specified by the standard after loading (5 - 15 s) so that the requirements of the standard are met. From the measured fracture force and sample dimensions, the fracture stress σf was determined for each sample according to Equation 1.

Equation

[0079] The flexural strength was classified as follows. High: Above 630 MPa Medium: 600 - 630 MPa Low: Below 600 MPa.

[0080] The results are summarized in Table 1 below.

[0081]

Table 1

[0082] Examples are shown below.

[0083] When the exposed reaction layer was removed using an ultrashort pulse laser, the obtained metal-ceramic composite showed very good thermal shock resistance. However, completely removing the exposed reaction layer while maintaining high flexural strength could be achieved only when the total fluence applied by the ultrashort pulse laser was within the scope of the present invention (50 - 650 J / cm 2 ). When the total fluence exceeded 650 J / cm 2 , it led to a loss of flexural strength. On the other hand, when the total fluence was less than 50 J / cm 2 , the exposed reaction layer was not removed or was only insufficiently removed.

[0084] When the exposed reaction layer was removed by etching, the reaction layer could be completely removed without affecting the flexural strength, but the obtained metal-ceramic composite showed a significant decrease in thermal shock resistance.

Claims

1. A method for structuring a metal-ceramic composite comprising the steps of: Providing a metal-ceramic composite, the metal-ceramic composite comprising: a nitride ceramic substrate including a front surface and a rear surface; a metal coating on a front surface of the nitride ceramic substrate; Between the metal coating and the ceramic substrate, one or more elements E selected from Ti, Hf, Zr, Nb, V, Ta, and Ce are present. ＲＳ providing a reactive layer containing removing the metal coating such that at least one recess is formed in the metal coating and an exposed reaction layer is present in the recess; removing the exposed reaction layer using a pulsed laser beam of an ultrashort pulsed laser such that an exposed surface of the ceramic substrate is in the recess, the pulsed laser beam having a pulsed laser beam strength of 50 J / cm ２ ~650 J / cm ２ and applying and removing a total fluence of.

2. The method of claim 1 , wherein the nitride ceramic substrate comprises silicon nitride or aluminum nitride and the metal coating is a copper coating or an aluminum coating.

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

4. The total fluence applied by the pulsed laser beam is 100 J / cm ２ ~320 J / cm ２ The method according to any one of claims 1 to 3, wherein

5. The method of any one of claims 1 to 4, wherein the pulsed laser beam comprises pulses having a pulse duration of from 1 femtosecond to 100 picoseconds.

6. The method of any one of claims 1 to 5, wherein the pulsed laser beam comprises pulses each having a pulse energy of at least 15 μJ.

7. The pulsed laser beam has a pulse frequency f of 100 kHz to 50 MHz. Ｌ The method according to any one of claims 1 to 6, comprising:

8. The pulsed laser beam impinging on the exposed adhesion-promoting layer has a diameter D Ｌ The method according to any one of claims 1 to 7, comprising:

9. The pulsed laser beam is irradiated under the following conditions: (1-v ｓｃａｎ / (D Ｌ ×f Ｌ ))×100%≧60% (In the formula, v ｓｃａｎ is the scanning speed of the pulsed laser beam, D Ｌ is the diameter of the pulsed laser beam impinging on the exposed adhesion-promoting layer, f Ｌ The method according to any one of claims 1 to 8, wherein:

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