Copper-ceramic substrate with sinterable top surface

Abstract

The invention relates to a copper-ceramic substrate, to the use of a copper-ceramic substrate and to a method for producing an adhesive connection between a copper-ceramic substrate and an electronic component. The copper-ceramic substrate comprises a) a ceramic body and b) a copper layer connected to the ceramic body in a planar manner, wherein the copper layer has a top surface. Before and after sputtering the top surface for 120 s, the copper-ceramic substrate has an energy spectrum obtained by x-ray photoelectron spectroscopy during analysis of the top surface of the copper layer and which makes the copper-ceramic substrate particularly suitable for bonding to electronic components using a sintered material comprising silver.

Description

[0001] The invention relates to a copper-ceramic substrate, the use of a copper-ceramic substrate and a method for producing an adhesive bond between a copper-ceramic substrate and an electronic component.

[0002] Copper-ceramic substrates play an important role in power electronics. They are key components in the construction of electronic components and ensure the rapid dissipation of large amounts of heat during operation. Copper-ceramic substrates typically consist of a ceramic layer connected to a copper layer.

[0003] Various methods for connecting copper layers to ceramic layers are known from the prior art. In the so-called DCB ("Direct Copper Bonding") method, copper is reacted with a reactive gas (usually oxygen) to provide a copper compound (usually copper oxide) with a lower melting point than copper on the surface of the copper foil. When the copper foil treated in this way is applied to a ceramic body and the composite material is heated, the copper compound melts and wets the surface of the ceramic body, creating a stable adhesive bond between the copper foil and the ceramic body. This method is described, for example, in US Pat. No. 3,744,120 A or DE 2,319,854 C2.

[0004] In an alternative method, copper foil can be bonded to a ceramic body at a temperature of approximately 650°C to 1000°C using an active solder containing a metal (typically silver) with a melting point of at least 700°C and an active metal. The active metal reacts with the ceramic material and thus promotes the bonding of the ceramic material to the remaining solder, forming a reaction layer, while the metal with a melting point of at least 700°C is used to bond the reaction layer to the copper foil. For example, JP4812985 B2 proposes bonding copper foil to a ceramic body using a solder containing 50% to 89% by weight of silver, copper, bismuth, and an active metal. In this way, copper foil can be securely attached to a ceramic body. Alternatively, a silver-free active solder can be used to connect copper foil to a ceramic body. These solders are, for example, based on high-melting-point metals (particularly copper), low-melting-point metals (such as bismuth, indium, or tin), and active metals (such as titanium). This technology is proposed, for example, in DE 102017114893A1. This technology essentially creates a new, independent class of compounds, since the base of the solder used is formed from another metal (copper instead of silver), which leads to changes in the material properties and to adaptations with regard to the other solder components and modified joining conditions.

[0005] In the construction of electronic assemblies, copper-ceramic substrates are often equipped with electronic components. The electronic components need to be firmly bonded to the copper-ceramic substrate. Because electronic assemblies are often exposed to high temperatures during operation, they are often connected to the copper-ceramic substrate using a sintered material containing silver. During the sintering process, the silver forms an adhesive bond with the electronic component and the surface to be connected of the copper-ceramic substrate. Due to the high melting point of silver, the resulting compound is temperature-stable. To achieve high bond strength, the surface to be connected of the copper-ceramic substrate is usually coated with a precious metal, particularly silver or gold, before the sintering process. This facilitates the bonding of the sintered material because the silver contained therein can easily diffuse into the precious metal coating of the copper-ceramic substrate. However, the disadvantage is that coating the copper-ceramic substrate with precious metals is technically complex and requires additional manufacturing steps. Therefore, it is desirable to be able to firmly bond electronic components to the copper-ceramic substrate without providing the surface to be connected of the copper-ceramic substrate with a coating containing precious metal.

[0006] Therefore, it is preferably an object of the present invention to provide a copper-ceramic substrate suitable for adhesive connection to electronic components.

[0007] A further object of the present invention is preferably to provide a copper-ceramic substrate which is suitable for adhesive connection to electronic components without requiring a noble metal-containing coating on the surface of the copper-ceramic substrate to be connected.

[0008] Contributions to these objectives are made by:

[0009] A copper-ceramic substrate comprising

[0010] a) a ceramic body, and

[0011] b) a copper layer, which is connected to the ceramic body in a planar manner, wherein the copper layer has a top surface,

[0012] in

[0013] (A) Spectrum obtained during analysis of the top surface of the copper layer by X-ray photoelectron spectroscopy

[0014] (i) having at least one signal S1 (t=0s), the signal including at least one peak P1 (t=0s) having a maximum value in the range of 526 eV to 538 eV, wherein the at least one peak P1 (t=0s) has an area PF1 (t=0s), wherein the at least one signal S1

[0015] The area PF1(t=0s) of all peaks P1(t=0s) at (t=0s) yields a total area GF1(t=0s), and

[0016] (ii) having at least one signal S2 (t=0s) comprising at least one peak P2 (t=0s) having a maximum value in the range of 0 eV to 1400 eV, wherein at least one peak P2

[0017] (t=0s) has an area PF2(t=0s), where at least one signal S2

[0018] The area PF2(t=0s) of all peaks P2(t=0s) at (t=0s) yields the total area GF2(t=0s),

[0019] where the ratio GF1(t=0s) / GF2(t=0s) has a value V(t=0s),

[0020] (B) Spectrum obtained during analysis of the top surface of the copper layer by X-ray photoelectron spectroscopy after sputtering the top surface of the copper layer for 120 s (sputtering gas: argon, acceleration voltage: 1 kV)

[0021] (i) having at least one signal S1 (t=120 s), the signal comprising at least one peak P1 (t=120 s) having a maximum value in the range of 526 eV to 538 eV, wherein the at least one peak has an area PF1 (t=120 s), wherein the areas PF1 (t=120 s) of all peaks P1 (t=120 s) of the at least one signal S1 (t=120 s) yield a total area GF1

[0022] (t = 120s), and

[0023] (ii) having at least one signal S2 (t=120 s) comprising at least one peak P2 (t=120 s) having a maximum value in the range of 0 eV to 1400 eV, wherein the at least one peak P2 (t=120 s) has an area PF2 (t=120 s), wherein the areas PF2 (t=120 s) of all peaks P2 (t=120 s) of the at least one signal S2 (t=120 s) result in a total area GF2 (t=120 s),

[0024] where the ratio GF1(t=120s) / GF2(t=120s) has a value V(t=120s), and

[0025] The ratio of V(t=120s) / V(t=0s) takes a value within the range of 0.05 to 0.75.

[0026] The invention also provides the use of a copper-ceramic substrate and a method for producing an adhesive connection between a copper-ceramic substrate and an electronic component.

[0027] The copper-ceramic substrate according to the present invention includes a ceramic body.

[0028] The ceramic body is preferably a body formed of ceramic. The body can have any geometric shape, but is preferably designed as a cube. The ceramic body includes boundary surfaces - in the case of a cube, six boundary surfaces. The ceramic body preferably has a main boundary surface. In this document, the main boundary surface preferably refers to the boundary surface with the largest surface area that is connected to the copper layer in a planar manner. The main boundary surface is preferably located in the main extension plane or extends parallel to the main extension plane. Therefore, the main extension plane of the ceramic body is preferably understood to be a plane that extends parallel to the main boundary surface of the ceramic body or encloses the main boundary surface.

[0029] The ceramic of the ceramic body is preferably an insulating ceramic. According to a preferred embodiment, the ceramic is selected from the group consisting of oxide ceramics, nitride ceramics and carbide ceramics. According to another preferred embodiment, the ceramic is selected from the group consisting of metal oxide ceramics, silicon oxide ceramics, metal nitride ceramics, silicon nitride ceramics, boron nitride ceramics and boron carbide ceramics. According to a particularly preferred embodiment, the ceramic is selected from the group consisting of aluminum nitride ceramics, silicon nitride ceramics and aluminum oxide ceramics (such as ZTA ("zirconia toughened alumina") ceramics). According to another very particularly preferred embodiment, the ceramic body consists of: (1) at least one element selected from the group consisting of silicon and aluminum; (2) at least one element selected from the group consisting of oxygen and nitrogen; optionally (3) at least one element selected from the group consisting of (3a) rare earth metals, (3b) metals of the second main group of the periodic table, (3c) zirconium, (3d) copper, (3e) molybdenum and (3f) silicon; and optionally (4) unavoidable impurities. According to yet another very particularly preferred embodiment, the ceramic body is free of bismuth, gallium and zinc.

[0030] The ceramic body preferably has a thickness in the range of 0.05 mm to 10 mm, more preferably in the range of 0.1 mm to 5 mm, particularly preferably in the range of 0.15 mm to 3 mm.

[0031] The copper-ceramic substrate according to the present invention comprises a copper layer connected in a planar manner to a ceramic body, wherein the copper layer has a top surface.

[0032] The copper layer comprises copper. In addition to copper, the copper layer preferably also contains oxygen, which is present as copper oxide, in particular as copper (I) oxide (Cu2O) and / or copper (II) oxide (CuO). According to a preferred embodiment, the copper layer therefore contains copper, oxygen and unavoidable impurities. According to another preferred embodiment, the proportion of copper is at least 90% by weight, more preferably at least 95% by weight, even more preferably at least 99% by weight and particularly preferably at least 99.9% by weight, based on the total weight of the copper layer. According to another particularly preferred embodiment, the copper layer consists of copper, oxygen and unavoidable impurities.

[0033] The thickness of the copper layer is preferably in the range of 0.01 mm to 10 mm, particularly preferably in the range of 0.03 mm to 5 mm, and very particularly preferably in the range of 0.05 mm to 3 mm.

[0034] The copper layer is preferably adhesively connected to the ceramic body.According to a preferred embodiment, the copper layer is connected to the ceramic body by a method selected from the group consisting of a DCB (Direct Copper Bonding) method and an active soldering method, in particular an AMB (Active Metal Brazing) method.

[0035] When the copper layer is connected to the ceramic body by the DCB method, the copper foil is preferably connected to the ceramic body, wherein a melt layer containing a chemical compound containing copper and a reactive gas (preferably oxygen) is generated on the surface of the copper foil by heating to a temperature in the range of 1025° C. to 1083° C., in particular to 1071° C. This melt layer forms a eutectic with a melting temperature lower than that of copper, so that by placing the copper foil on the ceramic body and heating it, a positive connection is generated between the copper foil and the ceramic body. Such a method is disclosed, for example, in German patent application DE 2319854 A1.

[0036] When the AMB method is used to connect the copper layer to the ceramic body, the copper foil is preferably connected to the ceramic body using an active solder. For this purpose, the active solder is preferably positioned between the ceramic body and the copper foil and melted (particularly preferably at a temperature in the range of 800°C to 1000°C). When the active solder solidifies, a positive connection is formed between the ceramic body and the copper foil. Thus, the copper layer can also be connected to the ceramic body in a planar manner via the connecting layer. The connecting layer can be, for example, an active solder layer or a diffusion layer. Such a method is disclosed, for example, in European Patent Application EP153618A2.

[0037] The copper layer is connected to the ceramic body in a planar manner. Accordingly, the copper layer is preferably connected to the main boundary surface of the ceramic body in a planar manner. The copper layer is preferably not connected to the entire main boundary surface of the ceramic body. In particular, it can be provided that the main boundary surface of the ceramic body is larger than the surface of the copper layer connected to the ceramic body. In these cases, the main boundary surface of the ceramic body protrudes. In addition, it can be provided that the copper layer is structured. The structured portion is preferably understood to mean a recessed portion in the copper layer, which separates the individual parts of the copper layer from each other and thus electrically isolates these parts from each other. Such a structured portion is often created by an etching technique.

[0038] The copper layer has a top surface. The top surface of the copper layer is preferably the surface of the copper layer facing away from the ceramic body, in particular the main boundary surface of the ceramic body. Therefore, the top surface of the copper layer is preferably the surface of the copper layer provided for bonding connection with the electronic component.

[0039] The top surface of the copper layer is preferably designed so that it can be firmly bonded to the electronic component using a sintering material containing silver. The top surface of the copper layer is such that A) during analysis of the top surface of the copper layer by X-ray photoelectron spectroscopy, the spectrum obtained (i) has at least one signal S1 (t = 0s) including at least one peak P1 (t = 0s) having a maximum value in the range of 526 eV to 538 eV, wherein the at least one peak P1 (t = 0s) has an area PF1 (t = 0s), wherein the areas PF1 (t = 0s) of all peaks P1 (t = 0s) of the at least one signal S1 (t = 0s) yield a total area GF1 (t = 0s), and (ii) has at least one signal S2 (t = 0s) having a maximum value in the range of 526 eV to 538 eV. comprising at least one peak P2 (t=0s) having a maximum value in the range of 0 eV to 1400 eV, wherein the at least one peak P2 (t=0s) has an area PF2 (t=0s), wherein the areas PF2 (t=0s) of all peaks P2 (t=0s) of the at least one signal S2 (t=0s) yield a total area GF2 (t=0s), wherein the ratio GF1 (t=0s) / GF2 (t=0s) has a value V (t=0s), (B) after sputtering the top surface of the copper layer for 120 s (sputtering gas: argon, accelerating voltage: 1 kV), after The energy spectrum obtained during the analysis of the top surface of the copper layer by the method of claim 1 (i) has at least one signal S1 (t=120s), the signal including at least one peak P1 (t=120s) having a maximum value in the range of 526 eV to 538 eV, wherein the at least one peak P1 has an area PF1 (t=120s), wherein the areas PF1 (t=120s) of all peaks P1 (t=120s) of the at least one signal S1 (t=120s) yield a total area GF1 (t=120s), and (ii) has at least one signal S2 (t=120s), the signal including a maximum value in the range of 0 eV to at least one peak P2 (t=120s) in the range of 1400eV, wherein the at least one peak P2 (t=120s) has an area PF2 (t=120s), wherein the areas PF2 (t=120s) of all peaks P2 (t=120s) of the at least one signal S2 (t=120s) yield a total area GF2 (t=120s), wherein the ratio GF1 (t=120s) / GF2 (t=120s) has a value V (t=120s), and wherein the ratio V (t=120s) / V (t=0s) takes a value in the range of 0.05 to 0.75.

[0040] The energy spectrum preferably includes the range of 0 eV to 1400 eV.

[0041] Before sputtering the top surface of the copper layer, an energy spectrum was recorded using X-ray photoelectron spectroscopy. Here, signals S1 and S2, peaks P1 and P2, areas PF1 and PF2 and total areas GF1 and GF2 and a ratio V were obtained, which are described by addition (t=0s).

[0042] Furthermore, after sputtering the top surface of the copper layer for 120 s (sputtering gas: argon, accelerating voltage: 1 kV), an energy spectrum was recorded by X-ray photoelectron spectroscopy. Here, signals S1 and S2, peaks P1 and P2, areas PF1 and PF2, and total areas GF1 and GF2, as well as the ratio V, were obtained and described by addition (t = 120 s).

[0043] According to a preferred embodiment, after sputtering the top surface of the copper layer for 240 s (sputtering gas: argon, accelerating voltage: 1 kV), the spectrum is also recorded by X-ray photoelectron spectroscopy. Here, the signals S1 and S2, the peaks P1 and P2, the areas PF1 and PF2 and the total areas GF1 and GF2 and the ratio V are obtained, which are described by adding (t = 240 s).

[0044] The energy spectrum has at least one signal S1. Therefore, it may also have a plurality of signals S1.

[0045] The at least one signal S1 comprises at least one peak P1 having a maximum value in the range of 526 eV to 538 eV. Thus, the peak P1 is characterized by having a maximum value in the range of 526 eV to 538 eV.

[0046] Thus, the energy spectrum may, for example, have a signal S1 comprising one or more peaks P1. On the other hand, the energy spectrum may also have a plurality of signals S1, each signal comprising one or more peaks P1.

[0047] At least one peak P1 has an area PF1, wherein the areas PF1 of all peaks P1 of at least one signal S1 generate a total area GF1. For example, if the energy spectrum has multiple signals S1, each signal having multiple peaks P1, the total area GF1 is generated by the sum of the areas PF1 of all peaks P1.

[0048] Peak P1 having a maximum value in the range of 526 to 538 eV indicates the presence of oxygen species. The oxygen species may be, for example, a species selected from the group consisting of copper oxides (eg, copper (I) oxide, copper (II) oxide), copper hydroxides, and organic compounds.

[0049] Therefore, the total area GF1 is related to the proportion of oxygen species on the top surface of the copper layer of the copper-ceramic substrate.

[0050] The energy spectrum has at least one signal S2. Therefore, it may also have a plurality of signals S2.

[0051] At least one signal S2 includes at least one peak P2 with a maximum value in the range of 0 eV to 1400 eV. Thus, peak P2 is characterized by having a maximum value in the range of 0 eV to 1400 eV. At least one signal S2 may specifically also include at least one signal S2 as described herein as signal S1 (e.g., a signal including at least one peak with a maximum value in the range of 526 eV to 538 eV). Thus, signal S2 also includes signal S1.

[0052] Thus, the energy spectrum may, for example, have a signal S2 comprising one or more peaks P2. On the other hand, the energy spectrum may also have a plurality of signals S2, each signal comprising one or more peaks P2.

[0053] At least one peak P2 has an area PF2, wherein the areas PF2 of all peaks P2 of at least one signal S2 generate a total area GF2. For example, if the energy spectrum has multiple signals S2, each signal having multiple peaks P2, then the total area GF2 is generated by the sum of the areas PF2 of all peaks P2.

[0054] Typically, the energy spectrum has multiple signals S2.

[0055] The energy spectrum has a signal S2 as described herein as signal S1 (e.g., a signal including at least one peak with a maximum value in the range of 526 eV to 538 eV). Therefore, signal S2 includes at least one peak P2 with a maximum value in the range of 526 eV to 538 eV, which indicates the presence of an oxygen species. The oxygen species can be, for example, a species selected from the group consisting of copper oxides, copper hydroxides, and organic compounds.

[0056] Furthermore, the energy spectrum preferably has a further signal S2 comprising at least one further peak P2.

[0057] The further signal S2 may for example be indicative of the Cu2p region of the energy spectrum and thus comprise at least one peak P2 indicative of the presence of a copper species. The copper species may for example be copper(I) oxide, copper(II) oxide, metallic copper or copper hydroxide.

[0058] The further signal S2 may for example comprise a peak P2 indicating the presence of carbon species. The carbon species may for example be an adsorbate for copper or common organic impurities (eg carbon dioxide from ambient air).

[0059] The further signal S2 may for example comprise a peak P2 indicating the presence of a further species. The further species may for example be a nitrogen species accumulated on the top surface of the copper layer during the production of the copper-ceramic substrate.

[0060] Therefore, the total area GF2 is related to the proportion of copper species on the top surface of the copper layer of the copper-ceramic substrate.

[0061] According to a preferred embodiment, the ratio V(t=120s) / V(t=0s) takes a value in the range of 0.10 to 0.75.

[0062] According to a particularly preferred embodiment, the ratio V(t=120 s) / V(t=0 s) takes a value in the range of 0.25 to 0.75.

[0063] According to a very particularly preferred embodiment, the ratio V(t=120 s) / V(t=0 s) assumes a value in the range from 0.30 to 0.75.

[0064] According to a further preferred embodiment, after the top surface of the copper layer has been sputtered for 240 s (sputtering gas: argon, acceleration voltage: 1 kV), the spectrum obtained during analysis of the top surface of the copper layer by X-ray photoelectron spectroscopy is

[0065] (i) having at least one signal S1 (t=240s) comprising at least one peak P1 (t=240s) having a maximum value in the range of 526 eV to 538 eV, wherein at least one peak P1

[0066] (t=240s) has an area PF1(t=240s), where at least one signal S1

[0067] The area PF1 (t=240s) of all peaks P1 (t=240s) at (t=240s) yields a total area GF1 (t=240s), and

[0068] (ii) having at least one signal S2 (t=240s) comprising at least one peak P2 (t=240s) having a maximum value in the range of 0 eV to 1400 eV, wherein at least one peak P2

[0069] (t=240s) has an area PF2(t=240s), where at least one signal S2

[0070] The area PF2(t=240s) of all peaks P2(t=240s) at (t=240s) yields the total area GF2(t=240s),

[0071] where the ratio GF1(t=240s) / GF2(t=240s) has a value V(t=240s), and

[0072] The ratio of V(t=240s) / V(t=0s) takes a value within the range of 0.04 to 0.40.

[0073] According to a preferred embodiment, the ratio V(t=240s) / V(t=0s) has a value in the range of 0.05 to 0.35.

[0074] According to a particularly preferred embodiment, the ratio V(t=240 s) / V(t=0 s) takes a value in the range of 0.05 to 0.30.

[0075] According to a very particularly preferred embodiment, the ratio V(t=240 s) / V(t=0 s) assumes a value in the range from 0.05 to 0.20.

[0076] Surprisingly, it has been found that a copper-ceramic substrate can be firmly bonded to an electronic component using a sintered material containing silver, such that A) the spectrum (i) obtained during the analysis of the top surface of the copper layer by X-ray photoelectron spectroscopy has at least one signal S1 (t=0s) comprising at least one peak P1 (t=0s) having a maximum value in the range of 526 eV to 538 eV, wherein the at least one peak P1 (t=0s) has an area PF1 (t=0s), wherein the areas PF1 (t=0s) of all peaks P1 (t=0s) of the at least one signal S1 (t=0s) result in a total area GF1 (t=0s), and (ii) having at least one signal S2(t=0s) comprising at least one peak P2(t=0s) having a maximum value in the range of 0 eV to 1400 eV, wherein the at least one peak P2(t=0s) has an area PF2(t=0s), wherein the areas PF2(t=0s) of all peaks P2(t=0s) of the at least one signal S2(t=0s) yield a total area GF2(t=0s), wherein the ratio GF1(t=0s) / GF2(t=0s) has a value V(t=0s), (B) after sputtering the top surface of the copper layer for 120 s (sputtering gas: argon, accelerating current The invention relates to a method for analyzing a top surface of the copper layer by X-ray photoelectron spectroscopy, wherein the energy spectrum obtained during the analysis of the top surface of the copper layer by X-ray photoelectron spectroscopy (i) has at least one signal S1 (t=120s), the signal including at least one peak P1 (t=120s) having a maximum value in the range of 526 eV to 538 eV, wherein the at least one peak P1 has an area PF1 (t=120s), wherein the areas PF1 (t=120s) of all peaks P1 (t=120s) of the at least one signal S1 (t=120s) result in a total area GF1 (t=0s), and (ii) has at least one signal S2 (t=120s), the signal including at least one peak P2 (t=120s) having a maximum value in the range of 0eV to 1400eV, wherein the at least one peak P2 (t=120s) has an area PF2 (t=120s), wherein the areas PF2 (t=120s) of all peaks P2 (t=120s) of at least one signal S2 (t=120s) yield a total area GF2 (t=120s), wherein the ratio GF1 (t=120s) / GF2 (t=120s) has a value V (t=120s), and wherein the ratio V (t=120s) / V (t=0s) takes a value in the range of 0.05 to 0.75.

[0077] Without wishing to be bound by any theory, this may be due to the presence of a certain concentration of oxygen species in the region on the top surface of the copper layer. Conventional prior art copper-ceramic substrates are easily passivated on the surface by contact with an oxygen-containing atmosphere. The presence of this surface passivation layer appears to be sufficient to form a sintered bond between the copper layer of the copper-ceramic substrate and the electronic component. The copper-ceramic substrate according to the present invention is such that A) during the analysis of the top surface of the copper layer by X-ray photoelectron spectroscopy, the energy spectrum obtained (i) has at least one signal S1 (t=0s), which includes at least one peak P1 (t=0s) with a maximum value in the range of 526 eV to 538 eV, wherein the at least one peak P1 (t=0s) has an area PF1 (t=0s), wherein the areas PF1 (t=0s) of all peaks P1 (t=0s) of the at least one signal S1 (t=0s) produce a total area GF1 (t=0s), and (ii) has at least one signal S2 (t=0s). s), the signal comprising at least one peak P2 (t=0s) having a maximum value in the range of 0 eV to 1400 eV, wherein the at least one peak P2 (t=0s) has an area PF2 (t=0s), wherein the areas PF2 (t=0s) of all peaks P2 (t=0s) of the at least one signal S2 (t=0s) yield a total area GF2 (t=0s), wherein the ratio GF1 (t=0s) / GF2 (t=0s) has a value V (t=0s), (B) after sputtering the top surface of the copper layer for 120 s (sputtering gas: argon, accelerating voltage: 1 kV), after X-ray The energy spectrum obtained during the electron spectroscopy analysis of the top surface of the copper layer (i) has at least one signal S1 (t=120s), the signal including at least one peak P1 (t=120s) having a maximum value in the range of 526 eV to 538 eV, wherein the at least one peak P1 has an area PF1 (t=120s), wherein the areas PF1 (t=120s) of all peaks P1 (t=120s) of the at least one signal S1 (t=120s) yield a total area GF1 (t=120s), and (ii) has at least one signal S2 (t=120s), the signal including a maximum value at 0eV. at least one peak P2 (t=120s) in the range of V to 1400eV, wherein the at least one peak P2 (t=120s) has an area PF2 (t=120s), wherein the areas PF2 (t=120s) of all peaks P2 (t=120s) of the at least one signal S2 (t=120s) yield a total area GF2 (t=120s), wherein the ratio GF1 (t=120s) / GF2 (t=120s) has a value V (t=120s), and wherein the ratio V (t=120s) / V (t=0s) takes a value in the range of 0.05 to 0.75.

[0078] A copper-ceramic substrate comprising a copper layer contains a defined proportion of oxygen species, the top surface of the copper layer having an energy spectrum. The oxygen species are present not only directly on the top surface of the copper layer, but also in deeper regions of the top surface of the copper layer. Quite surprisingly, the defined proportion of oxygen species also present in the deeper regions of the top surface of the copper layer appears to promote the formation of a sintered bond between the copper layer of the copper-ceramic substrate and the electronic component, compared to a smaller proportion of oxygen species or a certain proportion of oxygen species present directly on the top surface of the copper layer (as is the case on the top surface of the copper layer of a copper-ceramic substrate that has been conventionally passivated or thermally passivated in a manner customary in the art).

[0079] According to a further preferred embodiment, the spectrum obtained during the analysis of the top surface of the copper layer by X-ray photoelectron spectroscopy has at least one signal S2 comprising at least one peak P2a with a maximum value in the range of 933.2 eV to 934.0 eV.

[0080] The signal S2 including the peak P2a having a maximum value in the range of 933.2 eV to 934.0 eV indicates the presence of copper (II) oxide (CuO) on the top surface of the copper layer.

[0081] According to a preferred embodiment, the top surface of the copper layer is designed so that the energy spectrum obtained during the analysis of the top surface of the copper layer by X-ray photoelectron spectroscopy has at least one signal S2, which includes at least one peak P2b having a maximum value in the range of 932.2 eV to 932.8 eV, wherein the peak P2a occupies an area F2a and the peak P2b occupies an area F2b, and the ratio of the area F2a to the area F2b is at least 0.4.

[0082] The signal S2 including at least one peak P2b having a maximum value in the range of 932.2 eV to 932.8 eV indicates the presence of copper (I) oxide (Cu2O) and / or metallic copper (II) (Cu(0)) on the top surface of the copper layer. Therefore, the signal S2 may also have multiple peaks P2b, for example, a peak P2b indicating the presence of copper (I) oxide (Cu2O) and a peak P2b indicating the presence of metallic copper (II) (Cu(0)). The area F2b preferably includes the areas of all peaks P2b having a maximum value in the range of 932.2 eV to 932.8 eV. Therefore, the area F2b is preferably the sum of the areas of all peaks P2b having a maximum value in the range of 932.2 eV to 932.8 eV.

[0083] Thus, the area F2a of peak P2a is related to the proportion of copper (II) oxide (CuO) on the top surface of the copper layer. In contrast, the area F2b of at least one peak P2b is related to the proportion of copper (I) oxide (Cu2O) and / or metallic copper (Cu(0)) on the top surface of the copper layer.

[0084] According to a preferred embodiment, the ratio of area F2a to area F2b is at least 0.5, particularly preferably at least 5.0 and very particularly preferably at least 8.0.

[0085] According to a further preferred embodiment, the ratio of area F2a to area F2b is not greater than 1000, more preferably not greater than 500, particularly preferably not greater than 100, very particularly preferably not greater than 50, and in particular not greater than 30.

[0086] According to a preferred embodiment, the ratio of area F2a to area F2b is in the range of 0.4 to 1000, more preferably in the range of 0.5 to 500, particularly preferably in the range of 5.0 to 100, very particularly preferably in the range of 8.0 to 30.

[0087] Surprisingly, it has been found that a copper-ceramic substrate can be firmly bonded to an electronic component using a sintered material containing silver, the copper-ceramic substrate being designed so that the spectrum obtained during analysis of the top surface of the copper layer by X-ray photoelectron spectroscopy has a signal including at least one peak P2a having a maximum value in the range of 933.2 eV to 934.0 eV.

[0088] Without wishing to be bound by any theory, this may be due to the presence of copper (II) oxide (CuO) on the top surface of the copper layer. Conventional prior art copper-ceramic substrates are easily passivated by contact with an oxygen-containing atmosphere. It has been found that copper (I) oxide (Cu2O) is mainly formed on the top surface of the copper layer. The presence of copper (I) oxide (Cu2O) seems to be detrimental to the formation of sintered bonds between the copper layer of the copper-ceramic substrate and the electronic components. According to a preferred embodiment, the copper-ceramic substrate makes the energy spectrum obtained during the top surface analysis of the copper layer by X-ray photoelectron spectroscopy have at least one signal, the signal including at least one peak P2a with a maximum value within the range of 933.2 eV to 934.0 eV. This peak P2a indicates the presence of copper (II) oxide (CuO). Compared with copper (I) oxide (Cu2O), copper (II) oxide (CuO) surprisingly seems to promote the formation of sintered bonds between the copper layer of the copper-ceramic substrate and the electronic components.

[0089] Furthermore, it was surprisingly found that a particularly strong adhesive connection of a copper-ceramic substrate to an electronic component can be achieved using a sintered material if the top surface of the copper layer is designed such that the spectrum obtained during analysis of the top surface of the copper layer by X-ray photoelectron spectroscopy has at least one signal including at least one peak P2b with a maximum value in the range of 932.2 eV to 932.8 eV, wherein peak P2a occupies area F2a and peak P2b occupies area F2b, and the ratio of area F2a to area F2b is at least 0.4.

[0090] Without wishing to be bound by any theory, this may be due to the fact that in this case, the ratio of copper (II) oxide (CuO) to copper (I) oxide (Cu2O) and metallic copper (Cu(0)) on the top surface of the copper layer is increased. While the peak P2a with a maximum value at 933.2 eV to 934.0 eV indicates the presence of copper (II) oxide (CuO), at least one peak P2b with a maximum value in the range of 932.2 eV to 932.8 eV indicates the presence of copper (I) oxide (Cu2O) and metallic copper (Cu(0)). Since the presence of copper (II) oxide (CuO) has a favorable effect on the formation of an adhesive connection between the top surface of the copper-ceramic substrate and the electronic component using the sintered material, this effect appears to be greater the higher the ratio of copper (II) oxide (CuO) to copper (I) oxide (Cu2O) and metallic copper (Cu(0)) on the top surface of the copper layer. A particularly high bond strength is ultimately achieved when a specific ratio of copper (II) oxide (CuO) to copper (I) oxide (Cu2O) and metallic copper (Cu(0)) is not exceeded, such that the ratio of area F2a to area F2b is in the range of 0.4 to 1000.

[0091] According to a preferred embodiment, the copper-ceramic substrate comprises an additional (second) copper layer which is connected to the ceramic body in a planar manner. The additional copper layer is preferably connected in a planar manner to the boundary surface facing away from the main boundary surface of the ceramic (and preferably extends parallel to this main boundary surface). The additional (second) copper layer can have the same properties as the (first) copper layer or can differ from the (first) copper layer in its properties. With regard to the properties of the additional (second) copper layer, reference is made to the above explanations.

[0092] The method for producing the copper-ceramic substrate according to the present invention is not further limited.

[0093] Preferably, the method for producing the copper-ceramic substrate according to the present invention comprises the following steps:

[0094] (a) providing a copper-ceramic substrate, the copper-ceramic substrate comprising

[0095] (i) a ceramic body, and

[0096] (ii) a copper layer connected to the ceramic body in a planar manner, wherein the copper layer has a top surface, and

[0097] (b) The top surface of the copper layer of the copper-ceramic substrate is treated so that

[0098] (A) Spectrum obtained during analysis of the top surface of the copper layer by X-ray photoelectron spectroscopy

[0099] (i) having at least one signal S1 (t=0s), the signal including at least one peak P1 (t=0s) having a maximum value in the range of 526 eV to 538 eV, wherein the at least one peak P1 (t=0s) has an area PF1 (t=0s), wherein the area PF1 of all peaks P1 (t=0s) of the at least one signal S1 (t=0s) is equal to or greater than PF1.

[0100] (t=0s) yields a total area GF1(t=0s), and

[0101] (ii) having at least one signal S2 (t=0s), the signal including at least one peak P2 (t=0s) having a maximum value in the range of 0 eV to 1400 eV, wherein the at least one peak P2 (t=0s) has an area PF2 (t=0s), wherein the area PF2 of all peaks P2 (t=0s) of the at least one signal S2 (t=0s) is equal to or greater than PF2 (t=0s).

[0102] (t=0s) produces a total area GF2(t=0s),

[0103] where the ratio GF1(t=0s) / GF2(t=0s) has a value V(t=0s),

[0104] (B) Spectrum obtained during analysis of the top surface of the copper layer by X-ray photoelectron spectroscopy after sputtering the top surface of the copper layer for 120 s (sputtering gas: argon, acceleration voltage: 1 kV)

[0105] (i) having at least one signal S1 (t=120s), the signal including at least one peak P1 (t=120s) having a maximum value in the range of 526 eV to 538 eV, wherein the at least one peak has an area PF1 (t=120s), wherein the area PF1 of all peaks P1 (t=120s) of the at least one signal S1 (t=120s) is

[0106] (t=120s) yields a total area GF1(t=120s), and

[0107] (ii) having at least one signal S2 (t=120 s) comprising at least one peak P2 (t=120 s) having a maximum value in the range of 0 eV to 1400 eV, wherein the at least one peak P2 (t=120 s) has an area PF2 (t=120 s), wherein the areas PF2 (t=120 s) of all peaks P2 (t=120 s) of the at least one signal S2 (t=120 s) result in a total area GF2 (t=120 s),

[0108] The ratio of GF1(t=120s) / GF2(t=120s) has a value of V

[0109] (t = 120s), and

[0110] The ratio of V(t=120s) / V(t=0s) takes a value within the range of 0.05 to 0.75.

[0111] The method for producing a copper-ceramic substrate according to the present invention preferably comprises providing a copper-ceramic substrate comprising (i) a ceramic body and (ii) a copper layer connected to the ceramic body in a planar manner, wherein the copper layer has a top surface.

[0112] The copper-ceramic substrate may be a standard copper-ceramic substrate. Therefore, the copper-ceramic substrate preferably comprises a ceramic body and a copper layer connected to the ceramic body in a planar manner, wherein the copper layer has a top surface. For the properties of the copper-ceramic substrate and its components, reference may be made to the above information. However, the top surface of the copper layer is preferably not such that A) the energy spectrum obtained during the analysis of the top surface of the copper layer by X-ray photoelectron spectroscopy (i) has at least one signal S1 (t=0s), which includes at least one peak P1 (t=0s) with a maximum value in the range of 526 eV to 538 eV, wherein at least one peak P1 (t=0s) has an area PF1 (t=0s), wherein the areas PF1 (t=0s) of all peaks P1 (t=0s) of at least one signal S1 (t=0s) produce a total area GF1 (t=0s), and (ii) has at least one signal S2 (t=0s). s), the signal comprising at least one peak P2 (t=0s) having a maximum value in the range of 0 eV to 1400 eV, wherein the at least one peak P2 (t=0s) has an area PF2 (t=0s), wherein the areas PF2 (t=0s) of all peaks P2 (t=0s) of the at least one signal S2 (t=0s) yield a total area GF2 (t=0s), wherein the ratio GF1 (t=0s) / GF2 (t=0s) has a value V (t=0s), (B) after sputtering the top surface of the copper layer for 120 s (sputtering gas: argon, accelerating voltage: 1 kV), after X-ray The energy spectrum obtained during the electron spectroscopy analysis of the top surface of the copper layer (i) has at least one signal S1 (t=120s), the signal including at least one peak P1 (t=120s) having a maximum value in the range of 526 eV to 538 eV, wherein the at least one peak P1 has an area PF1 (t=120s), wherein the areas PF1 (t=120s) of all peaks P1 (t=120s) of the at least one signal S1 (t=120s) yield a total area GF1 (t=120s), and (ii) has at least one signal S2 (t=120s), the signal including a maximum value at 0eV. at least one peak P2 (t=120s) in the range of V to 1400eV, wherein the at least one peak P2 (t=120s) has an area PF2 (t=120s), wherein the areas PF2 (t=120s) of all peaks P2 (t=120s) of the at least one signal S2 (t=120s) yield a total area GF2 (t=120s), wherein the ratio GF1 (t=120s) / GF2 (t=120s) has a value V (t=120s), and wherein the ratio V (t=120s) / V (t=0s) takes a value in the range of 0.05 to 0.75.

[0113] The method for producing a copper-ceramic substrate according to the present invention preferably includes cleaning the top surface of the copper layer of the copper-ceramic substrate.

[0114] For example, the cleaning is performed by exposing the top surface of the copper layer of the copper-ceramic substrate to a reducing organic compound. The reducing organic compound may be, for example, formic acid.

[0115] The method for producing a copper-ceramic substrate according to the present invention preferably comprises processing the top surface of the copper layer of the copper-ceramic substrate so that A) the spectrum (i) obtained during the analysis of the top surface of the copper layer by X-ray photoelectron spectroscopy has at least one signal S1 (t=0s) comprising at least one peak P1 (t=0s) having a maximum value in the range of 526 eV to 538 eV, wherein the at least one peak P1 (t=0s) has an area PF1 (t=0s), wherein the areas PF1 (t=0s) of all peaks P1 (t=0s) of the at least one signal S1 (t=0s) result in a total area GF1 (t=0s), and (ii) having at least one signal S2(t=0s) comprising at least one peak P2(t=0s) having a maximum value in the range of 0 eV to 1400 eV, wherein the at least one peak P2(t=0s) has an area PF2(t=0s), wherein the areas PF2(t=0s) of all peaks P2(t=0s) of the at least one signal S2(t=0s) yield a total area GF2(t=0s), wherein the ratio GF1(t=0s) / GF2(t=0s) has a value V(t=0s), (B) after sputtering the top surface of the copper layer for 120 s (sputtering gas: argon, accelerating voltage : 1 kV), the energy spectrum obtained during the analysis of the top surface of the copper layer by X-ray photoelectron spectroscopy (i) has at least one signal S1 (t=120 s), the signal including at least one peak P1 (t=120 s) having a maximum value in the range of 526 eV to 538 eV, wherein the at least one peak P1 has an area PF1 (t=120 s), wherein the areas PF1 (t=120 s) of all peaks P1 (t=120 s) of the at least one signal S1 (t=120 s) result in a total area GF1 (t=120 s), and (ii) has at least one signal S2 (t=120 s) including The invention further comprises at least one peak P2 (t=120s) having a maximum value in the range of 0 eV to 1400 eV, wherein the at least one peak P2 (t=120s) has an area PF2 (t=120s), wherein the areas PF2 (t=120s) of all peaks P2 (t=120s) of at least one signal S2 (t=120s) produce a total area GF2 (t=120s), wherein the ratio GF1 (t=120s) / GF2 (t=120s) has a value V (t=120s), and wherein the ratio V (t=120s) / V (t=0s) takes a value in the range of 0.05 to 0.75.

[0116] The treatment of the top surface of the copper layer of the copper-ceramic substrate is not further limited. The treatment of the top surface of the copper layer of the copper-ceramic substrate preferably includes plasma treatment of the top surface of the copper layer or deposition of copper oxide on the top surface of the copper layer.

[0117] According to a preferred embodiment, the treatment of the top surface of the copper layer of the copper-ceramic substrate comprises a plasma treatment.

[0118] Plasma is preferably understood to mean a partially ionized gas, which particularly preferably contains highly excited particles and free radicals. The plasma is preferably capable of causing oxidation on the top surface of the copper layer of the copper-ceramic substrate. Copper (II) oxide is preferably formed in the process.

[0119] According to a particularly preferred embodiment, the plasma treatment is carried out with an oxygen plasma. The oxygen plasma can be generated in a manner customary in the art. For this purpose, for example, an AP-600 plasma system (Nordson-March) can be used.

[0120] The plasma treatment is preferably performed at a high-frequency electric power of 200 W to 1000 W, and particularly preferably performed at a high-frequency electric power of 500 W to 700 W, for example, at 600 W.

[0121] The plasma treatment is preferably carried out at a frequency in the range of 10 MHz to 15 MHz and particularly preferably at a frequency in the range of 13 MHz to 14 MHz, for example at a frequency of 13.56 MHz.

[0122] According to a preferred embodiment, the plasma treatment is carried out at a base pressure of 0.1 mbar to 0.5 mbar, and particularly preferably at a base pressure of 0.2 mbar to 0.4 mbar.

[0123] According to a preferred embodiment, the plasma treatment is carried out at a process pressure of 0.5 mbar to 1.5 mbar, and particularly preferably at a process pressure of 0.7 mbar to 1.0 mbar.

[0124] According to a preferred embodiment, the oxygen flow rate after reaching the base pressure is in the range of 50 SCCM / min to 150 SCCM / min, such as 100 SCCM / min to 150 SCCM / min.

[0125] The plasma treatment is preferably performed for a time period in the range of 100 s to 1000 s, and particularly preferably for a time period in the range of 150 s to 900 s.

[0126] According to another preferred embodiment, the treatment of the top surface of the copper layer of the copper-ceramic substrate comprises depositing copper oxide on the top surface of the copper layer. The copper oxide may preferably be copper (II) oxide. Preferably, the copper oxide is deposited on the top surface of the copper layer of the copper-ceramic substrate by methods conventional in the art, such as by sputtering.

[0127] The copper-ceramic substrate according to the invention is preferably used for adhesive bonding to electronic components.

[0128] An electronic component is preferably understood to mean an electronic or electrical part. The electronic component is preferably selected from the group consisting of semiconductor components. The semiconductor component is preferably selected from the group consisting of transistors, diodes and integrated circuits.

[0129] According to a preferred embodiment, the electronic component includes a metal coating. The metal coating can be used to facilitate easier bonding of the electronic component to the copper-ceramic substrate via the sintered material. The metal coating may preferably include different layers. The metal coating of the electronic component preferably includes a noble metal. The noble metal may be part of an alloy containing the noble metal. The noble metal preferably contains at least one element selected from the group consisting of gold, silver, and palladium. According to a preferred embodiment, the metal coating of the electronic component contains silver or an alloy containing at least one element selected from the group consisting of nickel, palladium, and gold.

[0130] According to a preferred embodiment, the copper-ceramic substrate is also suitable for adhesive connection with electronic components. Therefore, the top surface of the copper-ceramic substrate is preferably not in contact with the connecting layer, which has already formed an adhesive connection with another part (particularly preferably an electronic component).

[0131] The present invention provides a method for producing an adhesive connection between a copper-ceramic substrate and an electronic component, wherein:

[0132] a) providing a copper-ceramic substrate comprising (a) a ceramic body and (b) a copper layer connected to the ceramic body in a planar manner, wherein the copper layer has a top surface, wherein A) an energy spectrum obtained during analysis of the top surface of the copper layer by X-ray photoelectron spectroscopy (i) has at least one signal S1 (t=0s), the signal comprising at least one peak P1 (t=0s) having a maximum value in the range of 526 eV to 538 eV, wherein the at least one peak P1 (t=0s) has an area PF1 (t=0s), wherein the areas PF1 (t=0s) of all peaks P1 (t=0s) of the at least one signal S1 (t=0s) yield a total area GF1 (t=0s), and (ii) has at least one signal S2 (t=0s), the signal comprising at least one peak P2 (t=0s) having a maximum value in the range of 0 eV to 1400 eV, wherein the at least one peak P2 (t=0s) has an area PF2

[0133] (t=0s), wherein the area PF2(t=0s) of all peaks P2(t=0s) of at least one signal S2(t=0s) yields a total area GF2(t=0s), wherein GF1(t=0s) / GF2

[0134] (t=0s) has a value V(t=0s), (B) after the top surface of the copper layer is sputtered for 120s (sputtering gas: argon, acceleration voltage: 1 kV), the spectrum (i) obtained during the analysis of the top surface of the copper layer by X-ray photoelectron spectroscopy has at least one signal S1

[0135] (t=120s), the signal includes at least one peak P1 (t=120s) having a maximum value in the range of 526 eV to 538 eV, wherein the at least one peak P1 has an area PF1 (t=120s), wherein the area PF1 of all peaks P1 (t=120s) of at least one signal S1 (t=120s) is

[0136] (t=120s) produces a total area GF1 (t=120s), and (ii) has at least one signal S2 (t=120s) including at least one peak P2 (t=120s) having a maximum value in the range of 0 eV to 1400 eV, wherein the at least one peak P2 (t=120s) has an area PF2

[0137] (t=120s), where all peaks P2 of at least one signal S2 (t=120s)

[0138] The area PF2(t=120s) of (t=120s) yields the total area GF2(t=120s), where

[0139] the ratio of GF1(t=120s) / GF2(t=120s) has a value of V(t=120s), and wherein the ratio of V(t=120s) / V(t=0s) takes a value in the range of 0.05 to 0.75,

[0140] b) providing electronic components,

[0141] c) providing a sintered material comprising silver,

[0142] d) positioning the electronic component, the copper-ceramic substrate, and the sintered material to create an arrangement in which the electronic component is in contact with the top surface of the copper layer of the copper-ceramic substrate via the sintered material, and

[0143] e) Subjecting the arrangement to a treatment that produces a sintered bond between the electronic component and the copper-ceramic substrate.

[0144] In the method, a copper-ceramic substrate is provided.

[0145] The copper-ceramic substrate is a copper-ceramic substrate as described herein.

[0146] Thus, the copper-ceramic substrate comprises a) a ceramic body, and b) a copper layer connected to the ceramic body in a planar manner, wherein the copper layer has a top surface, wherein (A) the spectrum obtained during analysis of the top surface of the copper layer by X-ray photoelectron spectroscopy

[0147] (i) having at least one signal S1 (t=0s), the signal including at least one peak P1 (t=0s) having a maximum value in the range of 526 eV to 538 eV, wherein the at least one peak P1 (t=0s) has an area PF1 (t=0s), wherein the at least one signal S1

[0148] The area PF1(t=0s) of all peaks P1(t=0s) at (t=0s) yields a total area GF1(t=0s), and

[0149] (ii) having at least one signal S2 (t=0s) comprising at least one peak P2 (t=0s) having a maximum value in the range of 0 eV to 1400 eV, wherein at least one peak P2

[0150] (t=0s) has an area PF2(t=0s), where at least one signal S2

[0151] The area PF2(t=0s) of all peaks P2(t=0s) at (t=0s) yields the total area GF2(t=0s),

[0152] where the ratio GF1(t=0s) / GF2(t=0s) has a value V(t=0s),

[0153] (B) Spectrum obtained during analysis of the top surface of the copper layer by X-ray photoelectron spectroscopy after sputtering the top surface of the copper layer for 120 s (sputtering gas: argon, acceleration voltage: 1 kV)

[0154] (i) having at least one signal S1 (t=120s), the signal including at least one peak P1 (t=120s) having a maximum value in the range of 526eV to 538eV, wherein the at least one peak has an area PF1 (t=120s), wherein the at least one signal S1

[0155] The area PF1 (t=120s) of all peaks P1 (t=120s) at (t=120s) yields a total area GF1 (t=120s), and

[0156] (ii) having at least one signal S2 (t=120 s) comprising at least one peak P2 (t=120 s) having a maximum value in the range of 0 eV to 1400 eV, wherein the at least one peak P2 (t=120 s) has an area PF2 (t=120 s), wherein the areas PF2 (t=120 s) of all peaks P2 (t=120 s) of the at least one signal S2 (t=120 s) result in a total area GF2 (t=120 s),

[0157] where the ratio GF1(t=120s) / GF2(t=120s) has a value V(t=120s), and

[0158] The ratio of V(t=120s) / V(t=0s) takes a value within the range of 0.05 to 0.75.

[0159] In the method, an electronic component is provided.

[0160] For the properties of electronic components, you can refer to the above information.

[0161] In the method, a sintered material comprising silver is provided,

[0162] The sintering material containing silver is preferably selected from the group consisting of a sintering paste, a sintering film and a sintering preform.

[0163] The sintered material preferably comprises silver.

[0164] According to a preferred embodiment, the sintering material comprises a sintering paste. The sintering paste is preferably a sintering paste conventionally used in the art. Preferably, the sintering paste comprises silver and an organic compound. Preferably, the silver in the sintering paste is present as silver particles. The silver particles can take any shape and can therefore be present, for example, as spherical silver particles, silver flakes or irregularly shaped silver particles. The organic compound is preferably selected from the group consisting of a dispersant, a binder, a fatty acid and mixtures thereof. The dispersant can be selected from dispersants conventionally used in the art. An exemplary dispersant is terpineol. The binder can be selected from polymers conventionally used in the art. Examples include cellulose derivatives such as methylcellulose, ethylcellulose, ethylmethylcellulose, carboxycellulose and hydroxypropylcellulose. The fatty acid can be selected from fatty acids conventionally used in the art. The fatty acid is preferably selected from the group consisting of lanoic acid (octanoic acid), capric acid (decanoic acid), lauric acid (dodecanoic acid), myristic acid (tetradecanoic acid), palmitic acid (hexadecanoic acid), margaric acid (heptadecanoic acid), stearic acid (octadecanoic acid), arachidic acid (eicosanoic acid), behenic acid (docosanoic acid) and lignoceric acid (lignoceric acid).

[0165] According to another preferred embodiment, the sintered material comprises a sintered film. Preferably, the sintered film is a sintered film conventionally used in the art, such as disclosed, for example, in European Patent Application EP 3154729 A1. Thus, the sintered film may, for example, comprise a sintering paste comprising metal particles (particularly silver particles) and a binder, the binder being pre-dried on a carrier substrate. The sintered film may, for example, have a thickness in the range of 5 μm to 300 μm.

[0166] According to a further preferred embodiment, the sintered material comprises a sintered preform.Preferably, the sintered preform is a conventional sintered preform such as disclosed in European patent application EP2428293 A2.

[0167] According to a preferred embodiment, in this respect, a sintering material is applied to the top surface of the copper layer of the copper-ceramic substrate. The sintering material can be applied to the top surface of the copper layer of the copper-ceramic substrate using conventional methods in the art. Preferably, in the case of a sintering paste, the sintering material is applied by spraying, dispensing, spraying, brushing, rubbing, dipping or printing, in particular by screen printing or stencil printing, and in the case of a sintered film or sintered preform, the sintering material is applied by simply placing it on the sintering material. Thereafter, the electronic component can be positioned so that the top surface to be connected is on the sintering material, so as to produce an arrangement in which the electronic component is in contact with the top surface of the copper layer of the copper-ceramic substrate via the sintering material.

[0168] According to an alternative preferred embodiment, a sintering material is applied to the top surface of the electronic component to be connected. The sintering material can be applied to the top surface of the electronic component to be connected using conventional methods in the art. Preferably, in the case of a sintering paste, the sintering material is applied by spraying, dispensing, spraying, brushing, rubbing, dipping or printing, in particular screen printing or stencil printing, and in the case of a sintered film or sintered preform, the sintering material is applied by simply placing it on the sintering material. Thereafter, the copper-ceramic substrate can be positioned so that the top surface of the copper layer is on the sintering material, so as to produce an arrangement in which the electronic component is in contact with the top surface of the copper layer of the copper-ceramic substrate via the sintering material.

[0169] In this method, the arrangement is subjected to a treatment that produces a sintered bond between the electronic component and the copper-ceramic substrate.

[0170] According to a preferred embodiment, the treatment is performed by applying temperature and / or pressure.

[0171] In case of temperature application, the arrangement is preferably exposed to a temperature in the range of 150°C to 350°C, more preferably to a temperature in the range of 180°C to 280°C and particularly preferably to a temperature in the range of 200°C to 250°C.

[0172] In the case of pressure application, the arrangement is preferably exposed to a pressure in the range of >0 bar to 300 bar, particularly preferably in the range of 0.1 bar to 30 bar and very particularly preferably in the range of 0.2 bar to 10 bar.

[0173] This method produces a sintered bond and thus an adhesive connection between the electronic component and the copper-ceramic substrate.

[0174] Description of the method :

[0175] Analyzing the top surface of the copper layer by X-ray photoelectron spectroscopy, recording the spectrum and evaluating the spectrum are preferably performed according to the following method:

[0176] In preparation for X-ray photoelectron spectroscopy measurements, the copper-ceramic substrate was cut into sample pieces with an edge length of 0.9 (+ / - 0.1) cm × 1.4 (+ / - 0.1) cm using a side cutter. Striations on the trimmed edges were removed using a scalpel to ensure a straight support surface. Dust was removed from the specimens using nitrogen gas. The specimens were bonded to the sample holder using non-conductive adhesive tape.

[0177] X-ray photoelectron spectroscopy was recorded on a PHIVersaProbe 4 from Physical Electronics with an Al anode (monochromatic Kα = 1.487 keV) as the source. First, the overall spectrum of the specimen was recorded (range 0 eV to 1400 eV). Conclusions were drawn from the overall spectrum regarding the elements present on the examined top surface of the specimen. A detailed spectrum of the specimen was then recorded within the energy range in which the signal could be identified in the overall spectrum. To record the detailed spectrum, an X-ray beam (200 μm diameter; 50 W, 15 kV; measuring time: 25 to 40 minutes (e.g., 30 minutes); 20 ms integration time / measuring point) was used, the peak-to-noise setting was activated, and a neutralizer (a combination of Ar+ and e- with low kinetic energy) was used.

[0178] After recording all detail spectra, sputtering treatment was performed at the same position. Argon was used as the sputtering gas and the acceleration voltage was 1 kV (sputtering gas: Argon, acceleration voltage: 1 kV, sputtering area: 4 mm 2 ) Ar+ ions were used to bombard the 4 mm thick layer on the top surface of the copper foil of the copper-ceramic substrate. 2 Sputtering was performed on a sputtering area (e.g., 2 mm × 2 mm) with a sputtering time of 2 × 120 s. After each sputtering step, X-ray photoelectron spectra were recorded. Thus, three measurements were performed on each sample.

[0179] Spectra were evaluated using analysis software CasaXPS (version 2.3.224PR1.0, Casa Software Ltd.). The CC / CH component of the C 1s signal (ubiquitous) was normalized to 284.8 eV as a reference, and the binding energy of the detailed spectrum was shifted accordingly. Background correction was performed using the Shirley function. Peaks were generated from the obtained signals using analysis software. The number of peaks was adjusted based on the fitting model from the literature (XPS-NIST database), and the peaks were assigned to elements or compounds. Analysis software was used to calculate the peak areas of the generated peaks, taking into account the relative sensitivity factor.

[0180] Exemplary embodiments :

[0181] The invention is described in more detail below with the aid of exemplary embodiments, which, however, are not to be understood as restrictive.

[0182] Example 1 :

[0183] For this example, a copper-ceramic substrate measuring 27×38 mm was used, wherein a ceramic body made of silicon nitride ceramic was connected on both sides to a copper layer with a thickness of 0.3 mm using the AMB (Active Metal Brazing) method.

[0184] The copper-ceramic substrate was first cleaned. For this purpose, it was first exposed to vacuum in the chamber of a soldering system (PINKVadu 200), then to formic acid at an atmospheric pressure of 500 mbar and a temperature of 180° C., and then to nitrogen.

[0185] The copper-ceramic substrate was then plasma treated with oxygen plasma. For this purpose, the copper-ceramic substrate was centrally placed on the upper sample carrier of a plasma system (AP-600 (Nordson-March)). The plasma treatment was carried out for a process time of 90 seconds at a power of 600 W, a frequency of 13.56 Hz, a base pressure of 0.3 mbar, and a process pressure of 0.9 mbar. After the plasma treatment, the copper-ceramic substrate was removed from the plasma system.

[0186] The top surface of the copper layer of the copper-ceramic substrate was analyzed by X-ray photoelectron spectroscopy according to the above method. The results are shown in Table 1.

[0187] The copper-ceramic substrate was then equipped with a silicon chip. For this purpose, a 150 μm thick printing template and a scraper were used to print the copper-ceramic substrate with a sintering paste (ASP 338-28, Heraeus). The sintering paste was pre-dried for 20 minutes at 140°C in a nitrogen atmosphere with a residual oxygen content of 50 ppm in a convection oven and then cooled. A silicon chip measuring 4 × 4 mm (thickness = 250 μm) with bottom metallization (100 nm aluminum, 50 nm titanium, 100 nm nickel, and finally 700 nm silver) was positioned on the pre-dried sintering paste. Sintering was carried out in a PINK sintering press (Pink, Wertheim) in a nitrogen atmosphere at a pressure of 20 MPa and a temperature of 250°C for a period of 3 minutes.

[0188] Example 2 :

[0189] Example 2 was carried out in the same manner as Example 1, but in contrast to Example 1, the plasma treatment was carried out for 180 s instead of 90 s.

[0190] Example 3 :

[0191] Example 3 was carried out in the same manner as Example 1, but compared with Example 1, the plasma treatment was carried out for 300 s instead of 90 s.

[0192] Example 4 :

[0193] Example 4 was carried out in the same manner as Example 1, but in contrast to Example 1, the plasma treatment was carried out for 420 s instead of 90 s.

[0194] Example 5 :

[0195] Example 5 was carried out in the same manner as Example 1, but in contrast to Example 1, the plasma treatment was carried out for 600 s instead of 90 s.

[0196] Comparative Example 1 :

[0197] Comparative Example 1 was carried out in the same manner as Example 1, but, in contrast to Example 1, cleaning with formic acid and plasma treatment were omitted.

[0198] Comparative Example 2 :

[0199] Comparative Example 1 was performed in the same manner as Example 1, but compared with Example 1, the plasma treatment was omitted.

[0200] Comparative Example 3 :

[0201] Comparative Example 1 was performed in the same manner as Example 1, but in contrast to Example 1, the plasma treatment was performed for 900 s instead of 90 s.

[0202] evaluate :

[0203] The components obtained in Examples 1 to 5 and Comparative Examples 1 to 3 were examined for the mechanical bonding strength of the silicon chip on the copper-ceramic substrate. For this purpose, a shear test was performed using a bonding tester Nordson Dage 4000 Plus (Nordson, USA). For this purpose, the components were first clamped into a fixture. For the test, a 6 mm wide steel shear chisel was used, which acted on the component with increasing force until the silicon chip was separated from the copper-ceramic substrate. The force that separated the silicon chip is called the shear strength and is specified in N mm 2 The bond strength was evaluated in units of 16 values. For the evaluation, 16 values ​​were generated in each case and the average value of the shear strength was calculated. The results are shown in Table 1.

[0204]

[0205]

[0206] Table 1: Results of bond strength tests.

[0207] The results show that the copper-ceramic substrates according to Examples 1 to 5 of the present invention are significantly superior to the copper-ceramic substrates of Comparative Examples 1 to 3 in their suitability for producing strong adhesive connections to electronic components.

Claims

1. A copper-ceramic substrate, comprising a) a ceramic body, and b) a copper layer connected to the ceramic body in a planar manner, wherein the copper layer has a top surface, It is characterized by: (A) Energy spectrum obtained during analysis of the top surface of the copper layer by X-ray photoelectron spectroscopy (i) having at least one signal S1 (t=0s), said signal comprising at least one peak P1 (t=0s) having a maximum value in the range of 526 eV to 538 eV, wherein said at least one peak P1 (t=0s) has an area PF1 (t=0s), wherein said areas PF1 (t=0s) of all peaks P1 (t=0s) of said at least one signal S1 (t=0s) yield a total area GF1 (t=0s), and (ii) having at least one signal S2 (t=0s), said signal comprising at least one peak P2 (t=0s) having a maximum value in the range of 0 eV to 1400 eV, wherein said at least one peak P2 (t=0s) has an area PF2 (t=0s), wherein said areas PF2 (t=0s) of all peaks P2 (t=0s) of said at least one signal S2 (t=0s) result in a total area GF2 (t=0s), where the ratio GF1(t=0s) / GF2(t=0s) has a value V(t=0s), (B) Spectrum obtained during analysis of the top surface of the copper layer by X-ray photoelectron spectroscopy after the top surface of the copper layer was sputtered for 120 s (sputtering gas: argon, acceleration voltage: 1 kV) (i) having at least one signal S1 (t=120 s), said signal comprising at least one peak P1 (t=120 s) having a maximum value in the range of 526 eV to 538 eV, wherein said at least one peak has an area PF1 (t=120 s), wherein said areas PF1 (t=120 s) of all peaks P1 (t=120 s) of said at least one signal S1 (t=120 s) yield a total area GF1 (t=120 s), and (ii) having at least one signal S2 (t=120 s), said signal comprising at least one peak P2 (t=120 s) having a maximum value in the range of 0 eV to 1400 eV, wherein said at least one peak P2 (t=120 s) has an area PF2 (t=120 s), wherein said areas PF2 (t=120 s) of all peaks P2 (t=120 s) of said at least one signal S2 (t=120 s) result in a total area GF2 (t=120 s), where the ratio GF1(t=120s) / GF2(t=120s) has a value V(t=120s), and The ratio of V(t=120s) / V(t=0s) takes a value within the range of 0.05 to 0.

75.

2. The copper-ceramic substrate according to claim 1, characterized in that (C) Spectrum obtained during analysis of the top surface of the copper layer by X-ray photoelectron spectroscopy after the top surface of the copper layer was sputtered for 240 s (sputtering gas: argon, acceleration voltage: 1 kV) (iii) having at least one signal S1 (t=240s), said signal comprising at least one peak P1 (t=240s) having a maximum value in the range of 526 eV to 538 eV, wherein said at least one peak P1 (t=240s) has an area PF1 (t=240s), wherein said areas PF1 (t=240s) of all peaks P1 (t=240s) of said at least one signal S1 (t=240s) yield a total area GF1 (t=240s), and (iv) having at least one signal S2 (t=240 s), said signal comprising at least one peak P2 (t=240 s) having a maximum value in the range of 0 eV to 1400 eV, wherein said at least one peak P2 (t=240 s) has an area PF2 (t=240 s), wherein said areas PF2 (t=240 s) of all peaks P2 (t=240 s) of said at least one signal S2 (t=240 s) result in a total area GF2 (t=240 s), where the ratio GF1(t=240s) / GF2(t=240s) has a value V(t=240s), and The ratio of V(t=240s) / V(t=0s) takes a value within the range of 0.04 to 0.

40.

3. The copper-ceramic substrate according to claim 1 or 2, characterized in that The ceramic of the ceramic body is selected from the group consisting of aluminum nitride ceramics, silicon nitride ceramics, and aluminum oxide ceramics. 4 . Use of the copper-ceramic substrate according to claim 1 for adhesive connection to electronic components.

5. A method for producing an adhesive bond between a copper-ceramic substrate and an electronic component, wherein: a) providing the copper-ceramic substrate according to claim 1, b) providing electronic components, c) providing a sintered material comprising silver, d) positioning the electronic component, the copper-ceramic substrate, and the sintered material to produce an arrangement in which the electronic component is in contact with the top surface of the copper layer of the copper-ceramic substrate via the sintered material, and e) subjecting the arrangement to a treatment that produces a sintered bond between the electronic component and the copper-ceramic substrate.

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