Metal-ceramic substrate, method for its production and module

Abstract

The invention relates to a metal-ceramic substrate. The problem addressed is to provide a metal-ceramic substrate having a highly stable bonding between the metal layer and the ceramic body, as well as a high thermal and electrical conductivity. The metal-ceramic substrate comprises (a) a ceramic body, (b) a metal layer and (c) a bonding layer between the ceramic body and the metal layer. The bonding layer comprises (i) a metal M1 having a melting point of at least 700°C, (ii) a metal M2 having a melting point of less than 700°C, (iii) a metal M3 selected from the group of active metals, and (iv) a metal M4 selected from the group consisting of bismuth, gallium, zinc, indium, germanium, aluminum and magnesium. The bonding layer has the following characteristics: (c1) M(M2) EDX = 10 to 20 wt.-%, (c2) 15 wt.-% ≤ [M(M4) / M(M2)] ICP * 1000 wt.-% + M(M2) EDX ≤ 100 wt.-% and (c3) M(Ag) EDX < 10 wt.-%.

Description

[0001] This invention relates to metal-ceramic substrates, methods for producing metal-ceramic substrates, and modules having metal-ceramic substrates.

[0002] Metal-ceramic substrates play a crucial role in power electronics. They are key components when building electronic parts and ensure the rapid dissipation of large amounts of heat during operation. Metal-ceramic substrates typically consist of a ceramic layer and a metal layer bonded to the ceramic layer.

[0003] Several methods for bonding metal layers to ceramic layers are known from the prior art. In the so-called DCB (“Direct Copper Bonding”) method, a copper compound (typically copper oxide) with a melting point lower than copper is provided on the surface of a copper foil by reacting copper with a reactive gas (usually oxygen). When the copper foil treated in this manner is applied to a ceramic body and the composite is fired, the copper compound melts and wets the surface of the ceramic body, resulting in a stable adhesive bond between the copper foil and the ceramic body. This method is described, for example, in US 3744120 A or DE 2319854 C2.

[0004] Despite its obvious advantages, the DCB method has two main drawbacks. First, the method must be carried out at relatively high temperatures (i.e., slightly below the melting point of copper). Second, the method can only be used for oxide-based ceramics such as alumina or surface-oxidized aluminum nitride. Therefore, an alternative method for producing metal-ceramic substrates under less stringent conditions is needed. In one alternative method, a metal foil can be bonded to a ceramic body at a temperature of approximately 650°C to 1000°C, using a special solder containing a metal (typically silver) with a melting point of at least 700°C and an active metal. The active metal acts to react with the ceramic material and thus promote the adhesion of the ceramic material to the remaining solder, forming a reactive layer, while the metal with a melting point of at least 700°C is used to bond said reactive layer to the metal foil. For example, JP4812985 B2 proposes using a solder containing 50% to 89% by weight of silver, along with copper, bismuth, and an active metal, to bond copper foil to a ceramic body. Using this method, the copper foil can be stably attached to the ceramic body.

[0005] To avoid problems associated with silver migration, it may be advantageous to use silver-free solder to bond the metal foil to the 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 technique is proposed, for example, in DE 102017114893A1. This technique essentially produces a new, independent class of compounds because the base material of the solder used is formed from another metal (copper instead of silver), which leads to changes in material properties and creates adaptations to other solder compositions and improved bonding conditions. Therefore, the metal-ceramic substrate produced in this way includes, in addition to the metal layer and the ceramic body, an adhesive layer containing an active metal between the metal layer and the ceramic body.

[0006] The increasing demands in power electronics have led to higher requirements for the stability of the bond between the metal layer and the ceramic body in metal-ceramic substrates, as well as for the thermal and electrical conductivity of the metal-ceramic substrates. It has been found that the stability of the bond between the metal layer and the ceramic body increases with the increase of the low-melting-point metal content in the adhesive layer. However, increasing the low-melting-point metal content in the adhesive layer leads to increased diffusion of the low-melting-point metal into the metal layer of the metal-ceramic substrate. This effect results in a decrease in the thermal and electrical conductivity of the metal-ceramic substrate.

[0007] Therefore, a metal-ceramic substrate is needed that, on the one hand, includes a highly stable bond between the metal layer and the ceramic body, and on the other hand, possesses high thermal and electrical conductivity. Furthermore, such a metal-ceramic substrate also needs to be at least largely free of silver to avoid problems associated with silver migration.

[0008] Therefore, an object of the present invention is to provide a metal-ceramic substrate that, on the one hand, includes a highly stable bond between the metal layer and the ceramic body, and on the other hand, has high thermal conductivity and electrical conductivity. Therefore, another object of the present invention is to provide a metal-ceramic substrate that does not have problems related to silver migration.

[0009] These objectives are achieved using the metal-ceramic substrate of claim 1. Therefore, the present invention provides...

[0010] A metal-ceramic substrate comprising

[0011] (a) Ceramic body,

[0012] (b) Metal layer, and

[0013] (c) An adhesive layer located between the ceramic body and the metal layer, wherein the adhesive layer comprises

[0014] (i) Metal M1 with a melting point of at least 700°C,

[0015] (ii) Metal M2 with a melting point less than 700°C,

[0016] (iii) Metal M3 selected from the group of active metals, and

[0017] (iv) Select metal M4 from the group consisting of bismuth, gallium, zinc, indium, germanium, aluminum, and magnesium.

[0018] The adhesive layer is characterized by having the following features:

[0019] (c1)M(M2) EDX =10% to 20% by weight

[0020] (c2) 15% by weight ≤ [M(M4) / M(M2)] ICP *1000% by weight + M (M2) EDX ≤100% by weight, and

[0021] (c3)M(Ag) EDX <10% by weight

[0022] in:

[0023] M(M2) EDX The content of metal M2 in the adhesive layer was determined using EDX.

[0024] [M(M4) / M(M2)] ICP It is the ratio of the content of metal M4 in the adhesive layer to the content of metal M2 in the adhesive layer, determined by ICP, and

[0025] M(Ag) EDX The silver content in the adhesive layer was determined using EDX.

[0026] Furthermore, the present invention provides a method for producing a metal-ceramic substrate and a module having a metal-ceramic substrate.

[0027] The metal-ceramic substrate according to the present invention comprises a ceramic body, a metal layer, and an adhesive layer.

[0028] In a metal-ceramic substrate, an adhesive layer is located between the ceramic body and the metal layer. Therefore, the adhesive layer preferably contacts both the ceramic body and the metal layer. According to a preferred embodiment, the metal-ceramic substrate includes a ceramic body, a (first) metal layer, a (first) adhesive layer in contact with the ceramic body and the first metal layer, a second metal layer, and a second adhesive layer in contact with both the ceramic body and the second metal layer. According to this embodiment, the (first) adhesive layer is preferably located between the ceramic body and the (first metal) layer, and the second adhesive layer is preferably located between the ceramic body and the second metal layer. Furthermore, according to this embodiment, the composition of the first adhesive layer preferably corresponds to the composition of the second adhesive layer.

[0029] The ceramic body preferably includes a first surface and a second surface. The metal layer preferably includes the first surface. The second metal layer (if present) preferably includes the first surface. According to a preferred embodiment, the (first) adhesive layer is located in a metal-ceramic substrate between the first surface of the ceramic body and the first surface of the (first) metal layer. According to another preferred embodiment, the metal-ceramic substrate contains a second adhesive layer in contact with the second surface of the ceramic body and the first surface of the second metal layer. According to this embodiment, the (first) adhesive layer is preferably located in a metal-ceramic substrate between the first surface of the ceramic body and the first surface of the (first) metal layer, and the second adhesive layer is preferably located between the second surface of the ceramic body and the first surface of the second metal layer. According to another preferred embodiment, no other layer is located between the ceramic body and the (first) metal layer except for the adhesive layer according to the invention. According to yet another embodiment, no other layer is located between the ceramic body and the second metal layer (if present) except for the adhesive layer according to the invention.

[0030] 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, silver nitride ceramics, and alumina ceramics (such as ZTA (“zirconium oxide toughened alumina”) ceramics). According to yet another very particularly preferred embodiment, the ceramic body comprises (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 (3a) rare earth metals, (3b) metals of Group 2 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.

[0031] The ceramic body preferably has a thickness of 0.05 mm to 10 mm, more preferably in the range of 0.1 mm to 5 mm, and particularly preferably in the range of 0.15 mm to 3 mm.

[0032] The metal of the metal layer is preferably selected from the group consisting of copper, aluminum, and molybdenum. According to a particularly preferred embodiment, the metal of the metal layer is selected from the group consisting of copper and molybdenum. According to a very particularly preferred embodiment, the metal of the metal layer is copper. According to another very particularly preferred embodiment, the metal layer consists of copper and unavoidable impurities.

[0033] The metal layer preferably has a thickness 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 adhesive layer comprises (i) a metal M1 having a melting point of at least 700°C, (ii) a metal M2 having a melting point of less than 700°C, (iii) a metal M3 selected from the group consisting of active metals, and (iv) a metal M4 selected from the group consisting of bismuth, gallium, zinc, indium, germanium, aluminum and magnesium.

[0035] The adhesive layer is preferably understood to refer to the region of the metal-ceramic substrate located between the ceramic body and the metal layer.

[0036] The adhesive layer comprises (i) a metal M1 with a melting point of at least 700°C. The metal M1 with a melting point of at least 700°C preferably has a melting point of at least 850°C, and particularly preferably at least 1000°C. According to a preferred embodiment, the metal M1 with a melting point of at least 700°C is selected from the group consisting of copper, nickel, tungsten, and molybdenum. According to a particularly preferred embodiment, the metal M1 with a melting point of at least 700°C is copper.

[0037] The adhesive layer (ii) comprises a metal M2 with a melting point less than 700°C. The metal M2 with a melting point less than 700°C preferably has a melting point less than 600°C and particularly preferably has a melting point less than 550°C. According to a particularly preferred embodiment, the metal M2 with a melting point less than 700°C is tin.

[0038] The adhesive layer comprises (iii) metal M3 selected from the group consisting of active metals. Therefore, metal M3 is preferably a metal that bonds to the ceramic through a chemical reaction. According to a preferred embodiment, metal M3 is selected from the group consisting of hafnium, titanium, zirconium, niobium, cerium, tantalum, and vanadium. According to a more preferred embodiment, metal M3 is selected from the group consisting of hafnium, titanium, zirconium, niobium, and cerium. According to a particularly preferred embodiment, metal M3 is selected from the group consisting of hafnium, titanium, and zirconium. According to a very particularly preferred embodiment, metal M3 is titanium.

[0039] The adhesive layer comprises (iv) metal M4. Metal M4 is a metal selected from the group consisting of bismuth, gallium, zinc, indium, germanium, aluminum, and magnesium. According to a particularly preferred embodiment, metal M4 is selected from the group consisting of bismuth, gallium, and zinc. According to a very particularly preferred embodiment, metal M4 is bismuth.

[0040] Metals M1, M2, M3, and M4 are different metals. Therefore, the adhesive layer between the ceramic body and the metal layer comprises each of metals M1, M2, M3, and M4. Thus, the adhesive layer between the ceramic body and the metal layer comprises (i) metal M1 with a melting point of at least 700°C, (ii) metal M2 with a melting point less than 700°C, (iii) metal M3 selected from the group consisting of active metals, and (iv) metal M4 selected from the group consisting of bismuth, gallium, zinc, indium, germanium, aluminum, and magnesium, wherein metals M1, M2, M3, and M4 are different. Therefore, metal M2 with a melting point less than 700°C is not selected from the group consisting of bismuth, gallium, zinc, indium, aluminum, and magnesium. Furthermore, metal M2 is not an active metal. Similarly, metal M1 with a melting point of at least 700°C is not germanium. Furthermore, metal M1 with a melting point of at least 700°C is not an active metal.

[0041] According to the present invention, the adhesive layer has the following characteristics:

[0042] (c1)M(M2) EDX =10% to 20% by weight

[0043] (c2) 15% by weight ≤ [M(M4) / M(M2)] ICP *1000% by weight + M (M2) EDX ≤100% by weight, and

[0044] (c3)M(Ag) EDX <10% by weight

[0045] in:

[0046] M(M2) EDX It is the content of metal M2 in the adhesive layer determined by EDX [in weight %];

[0047] [M(Bi) / M(M2)] ICP It is the ratio of the content of metal M4 in the adhesive layer to the content of metal M2 in the adhesive layer, determined by ICP.

[0048] M(Ag) EDX The silver content in the adhesive layer is determined by means of EDX [in weight %].

[0049] According to feature (c1), the content of metal M2 in the adhesive layer, as determined by EDX, is 10% to 20% by weight. According to a preferred embodiment, the adhesive layer has the following characteristics:

[0050] (c1′)M(M2) EDX =10% to 18% by weight.

[0051] According to a particularly preferred embodiment, the adhesive layer has the following characteristics:

[0052] (c1″)M(M2) EDX =10% to 15% by weight.

[0053] According to feature (c2), there is a relationship between the content of metal M4 and the content of metal M2, which gives the adhesive layer the following characteristics:

[0054] (c2) 15% by weight ≤ [M(M4) / M(M2)] ICP *1000% by weight + M (M2) EDX ≤100% by weight

[0055] According to a preferred embodiment, the adhesive layer has the following characteristics:

[0056] (c2′): 15% by weight ≤ [M(M4) / M(M2)] ICP *1000% by weight + M (M2) EDX ≤80% by weight

[0057] According to a particularly preferred embodiment, the adhesive layer has the following characteristics:

[0058] (c2″): 15% by weight ≤ [M(M4) / M(M2)] ICP *1000% by weight + M (M2) EDX ≤70% by weight.

[0059] Surprisingly, it has been found that the amount of metal M2 with a melting point below 700°C required for a particularly stable bond between the ceramic body and the metal layer can be reduced by adding a small amount of metal M4, so that the electrical and thermal conductivity of the metal-ceramic substrate is not impaired due to the diffusion of metal M2 into the metal layer. Furthermore, it has been surprisingly found that a particularly stable bond is achieved if the content of metal M2 in the adhesive layer is within a defined region. The relationship between the ratio of metal M2 to M4 in the adhesive layer required for this effect is represented by features (c1) and (c2). Therefore, surprisingly, by adjusting the content of metal M2 with a melting point below 700°C and the content of metal M4 selected from the group consisting of bismuth, gallium, zinc, indium, germanium, aluminum, and magnesium, a metal-ceramic substrate is provided that, on the one hand, exhibits a particularly stable bond between the ceramic body and the metal layer, and on the other hand, possesses high electrical and thermal conductivity.

[0060] According to feature (c3), the silver content in the adhesive layer, as determined by EDX, does not exceed 10% by weight. Therefore, the present invention also includes embodiments in which the adhesive layer is silver-free, i.e., the silver content in the adhesive layer, as determined by EDX, is 0% by weight.

[0061] According to a particularly preferred embodiment, the adhesive layer has the following characteristics:

[0062] (c3′)M(Ag) EDX <5% by weight

[0063] According to a very particularly preferred embodiment, the adhesive layer has the following characteristics:

[0064] (c3″)M(Ag) EDX <1% by weight.

[0065] The absence of silver or the presence of only a small amount of silver means that unwanted migration of silver at the edges of the adhesive layer in the metal-ceramic substrate can be avoided or reduced.

[0066] According to a preferred embodiment, the content of metal M1 in the adhesive layer (M(M1)) is determined using EDX. EDX The content of metal M1 in the adhesive layer is in the range of 65% to 89% by weight. According to a particularly preferred embodiment, the content of metal M1 in the adhesive layer (M(M1)) is determined by means of EDX. EDX The content of metal M1 in the adhesive layer is in the range of 67% to 88% by weight. According to a very particularly preferred embodiment, the content of metal M1 in the adhesive layer (M(M1)) is determined by means of EDX. EDX It is in the range of 70% to 88% by weight.

[0067] According to a preferred embodiment, the content of metal M3 in the adhesive layer (M(M3)) is determined using EDX. EDX The content of metal M3 in the adhesive layer is in the range of 0.5% to 15% by weight. According to a particularly preferred embodiment, the content of metal M3 in the adhesive layer (M(M3)) is determined by means of EDX. EDX The content of metal M3 in the adhesive layer is in the range of 0.5% to 14% by weight. According to a very particularly preferred embodiment, the content of metal M3 in the adhesive layer (M(M3)) is determined by means of EDX. EDX It is in the range of 1% to 14% by weight.

[0068] According to a preferred embodiment, the content of metal M4 in the adhesive layer (M(M4)) is determined by ICP. ICP The content of metal M4 in the adhesive layer is in the range of 0.01% by weight to 2% by weight. According to a particularly preferred embodiment, the content of metal M4 in the adhesive layer (M(M4)) is determined by means of ICP. ICP The content of metal M4 in the adhesive layer is in the range of 0.01% to 1.5% by weight. According to a very particularly preferred embodiment, the content of metal M4 in the adhesive layer (M(M4)) is determined by means of ICP. ICP It is in the range of 0.1% by weight to 1% by weight.

[0069] The metal-ceramic substrate according to the present invention can be produced in a manner that constitutes standard practice in the art.

[0070] According to a preferred embodiment, a method for producing a metal-ceramic substrate according to the present invention includes the following steps:

[0071] a) Provide a stack, the stack containing

[0072] a1) Ceramic body,

[0073] a2) Metal foil, and

[0074] a3) Solder material, which is in contact with the ceramic body and the metal foil, wherein the solder material comprises:

[0075] (i) Metal M1 with a melting point of at least 700°C,

[0076] (ii) Metal M2 with a melting point less than 700°C,

[0077] (iii) Metal M3 selected from the group of active metals, and

[0078] (iv) Metal M4 selected from the group consisting of bismuth, gallium, zinc, indium, germanium, aluminum, and magnesium, and

[0079] b) Heat the stack to obtain a metal-ceramic substrate.

[0080] Therefore, it is preferable that a stack is initially provided, which contains a ceramic body, a metal foil, and solder material in contact with the ceramic body and the metal foil.

[0081] In the stack, the solder material is therefore preferably located between the ceramic body and the metal foil. According to a preferred embodiment, the stack includes a ceramic body, a (first) metal foil, a (first) solder material in contact with the ceramic body and the first metal foil, a second metal foil, and a second solder material in contact with the ceramic body and the second metal foil. According to this embodiment, the (first) solder material is preferably located between the ceramic body and the (first) metal foil, and the second solder material is preferably located between the ceramic body and the second metal foil. Furthermore, according to this embodiment, the first solder material preferably corresponds to the second solder material.

[0082] The ceramic body, metal foil, and solder material are preferably designed such that the metal-ceramic substrate according to the invention is produced upon heating.

[0083] Therefore, regarding the ceramic body and metal layer of the metal-ceramic substrate, the ceramic body and metal foil are preferably designed as described above.

[0084] The solder material preferably comprises (i) a metal M1 with a melting point of at least 700°C, (ii) a metal M2 with a melting point of less than 700°C, (iii) a metal M3 selected from the group consisting of active metals, and (iv) a metal M4 selected from the group consisting of bismuth, gallium, zinc, indium, germanium, aluminum, and magnesium. Metals M1, M2, M3, and M4 are preferably designed as described above with respect to the adhesive layer of the metal-ceramic substrate.

[0085] Therefore, metals M1, M2, M3, and M4 are different metals. Therefore, the solder material in contact with the ceramic body and the metal layer comprises each of metals M1, M2, M3, and M4. Therefore, the solder material in contact with the ceramic body and the metal layer comprises (i) metal M1 with a melting point of at least 700°C, (ii) metal M2 with a melting point less than 700°C, (iii) metal M3 selected from the group consisting of active metals, and (iv) metal M4 selected from the group consisting of bismuth, gallium, zinc, indium, germanium, aluminum, and magnesium, wherein metals M1, M2, M3, and M4 are different. Therefore, metal M2 with a melting point less than 700°C is not selected from the group consisting of bismuth, gallium, zinc, indium, aluminum, and magnesium. Furthermore, metal M2 is not an active metal. Similarly, metal M1 with a melting point of at least 700°C is not germanium. Furthermore, metal M1 with a melting point of at least 700°C is not an active metal.

[0086] According to a preferred embodiment, (i) metal M1, (ii) metal M2, (iii) metal M3, and (iv) metal M4 are present as components of at least one metal component. Therefore, the solder material preferably includes at least one metal component comprising (i) metal M1, (ii) metal M2, (iii) metal M3, and (iv) metal M4. For example, it is preferable that the solder material comprises: a metal component (i) containing metal M1, a metal component (ii) containing metal M2, a metal component (iii) containing metal M3, and a metal component (iv) containing metal M4. Furthermore, it is also preferable that the solder material comprises: a metal component (i) containing members from the group consisting of (i) metal M1, (ii) metal M2, (iii) metal M3, and (iv) metal M4; and at least one additional metal component (ii) comprising members from the group consisting of (i) metal M1, (ii) metal M2, (iii) metal M3, and (iv) metal M4, which is not included in metal component (i). The term "metal component" is not further limited. In addition to metals and metal alloys, it also includes metal compounds such as intermetallic phases and other compounds (such as, for example, metal hydrides). According to a preferred embodiment, the metal component is therefore selected from the group consisting of metals, metal alloys, and metal compounds.

[0087] The solder material preferably comprises (i) a metal M1 with a melting point of at least 700°C. According to a preferred embodiment, the solder material comprises a metal component (i) containing a metal M1 with a melting point of at least 700°C. According to a particularly preferred embodiment, the solder material comprises a metal component (i) containing copper. According to another preferred embodiment, the metal component (i) is copper.

[0088] The solder material preferably comprises (ii) a metal M2 with a melting point less than 700°C. According to a preferred embodiment, the solder material comprises a metal component (ii) containing a metal M2 with a melting point less than 700°C. According to a particularly preferred embodiment, the metal component (ii) is an alloy of the metal M2 with a melting point less than 700°C and another metal. The other metal may be selected, for example, from the group consisting of a metal M1 with a melting point less than 700°C, a metal M2 with a melting point of at least 700°C, a metal M3 selected from the group consisting of active metals, and a metal M4 selected from the group consisting of bismuth, indium, germanium, gallium, and zinc. According to another preferred embodiment, the metal component (ii) containing the metal M2 with a melting point less than 700°C is selected from the group consisting of tin, tin-copper alloys, tin-bismuth alloys, tin-antimony alloys, tin-zinc-bismuth alloys, and indium-tin alloys.

[0089] The solder material preferably comprises a metal M3 selected from the group of active metals. According to a preferred embodiment, the solder material comprises a metal component (iii) containing a metal M3 selected from the group of active metals. According to a particularly preferred embodiment, the metal component (iii) is an active metal alloy or active metal compound, particularly preferably an active metal hydride. The metal component (iii) is preferably selected from the group consisting of titanium hydride, titanium-zirconium-copper alloy, zirconium hydride, and hafnium hydride. According to a particularly preferred embodiment, the metal component (iii) is titanium hydride.

[0090] The solder material preferably comprises metal M4. According to a preferred embodiment, the solder material comprises a metal component (iv) containing metal M4 selected from the group consisting of bismuth, gallium, zinc, indium, germanium, aluminum, and magnesium. According to a particularly preferred embodiment, the solder material comprises a bismuth-containing metal component (iv). According to another preferred embodiment, the metal component (iv) is bismuth.

[0091] According to a preferred embodiment, based on the total metal weight of the solder material, the proportion of metal M1 with a melting point of at least 700°C is 65% to 89% by weight, particularly preferably 67% to 88% by weight, and very particularly preferably 70% to 88% by weight. According to another preferred embodiment, based on the total metal weight of the solder material, the proportion of metal M2 with a melting point less than 700°C is 10% to 20% by weight, particularly preferably 10% to 18% by weight, and very particularly preferably 10% to 15% by weight. According to yet another preferred embodiment, based on the total metal weight of the solder material, the proportion of metal M3 selected from the group consisting of active metals is 0.5% to 15% by weight, particularly preferably 0.5% to 14% by weight, and very particularly preferably 1% to 14% by weight. According to another preferred embodiment, based on the total metal weight of the solder material, the proportion of metal M4, selected from the group consisting of bismuth, gallium, zinc, indium, germanium, aluminum, and magnesium, is from 0.01 wt% to 2 wt%, particularly preferably from 0.01 wt% to 1.5 wt%, and very particularly preferably from 0.1 wt% to 1 wt%. The solder material preferably contains no silver or a small amount of silver. Therefore, based on the total metal weight of the solder material, the proportion of silver is preferably less than 10 wt%, particularly preferably less than 5 wt%, and very particularly preferably less than 1 wt%.

[0092] The solder material is in contact with both the ceramic body and the metal foil. Therefore, the solder material is preferably located between the ceramic body and the metal foil. For example, the solder material can be provided on the ceramic body, and then the metal foil can be applied to the solder material. The solder material is preferably at least one material selected from the group consisting of pastes, foils, and deposits, comprising a metal M1 with a melting point of at least 700°C, a metal M2 with a melting point less than 700°C, a metal M3 selected from the group consisting of active metals, and a metal M4 selected from the group consisting of bismuth, gallium, zinc, indium, germanium, aluminum, and magnesium.

[0093] The solder material can be a paste. The paste preferably includes (a) at least one metallic component, including a metal M1 with a melting point of at least 700°C, a metal M2 with a melting point of less than 700°C, a metal M3 selected from the group consisting of active metals, and a metal M4 selected from the group consisting of bismuth, gallium, zinc, indium, germanium, aluminum and magnesium, and (b) an organic dielectric.

[0094] The organic medium is preferably an organic medium commonly used in related technical fields. The organic medium preferably contains an organic binder, an organic dispersant, or a mixture thereof.

[0095] Preferably, the organic binder is removed from the solder material during the heating process. The organic binder is preferably a thermoplastic or thermosetting plastic. Examples of organic binders include cellulose derivatives (such as ethyl cellulose, butyl cellulose, and cellulose acetate), polyethers (such as polyoxymethylene), and acrylic resins (such as polymethyl methacrylate and polybutylene methacrylate).

[0096] Organic dispersants are preferably organic compounds that impart a suitable viscosity to the paste and are discharged during the drying or heating of the paste. Organic dispersants can be selected from, for example, aliphatic alcohols, terpene alcohols, alicyclic alcohols, aromatic cyclic carboxylic acid esters, alicyclic esters, carbitol, and aliphatic polyols. Examples of organic dispersants include octanol, decanol, terpineol (e.g., dihydroterpineol), cyclohexanol, dibutyl phthalate, carbitol, ethyl carbitol, ethylene glycol, butanediol, and glycerol.

[0097] The paste may also contain additives used in standard practice in the art. Examples of such additives include inorganic binders (such as glass frit), stabilizers, surfactants, dispersants, rheology modifiers, wetting agents, defoamers, fillers, and curing agents.

[0098] According to a preferred embodiment, the proportion of at least one metal component, comprising a metal M1 with a melting point of at least 700°C, a metal M2 with a melting point less than 700°C, a metal M3 selected from the group consisting of active metals, and a metal M4 selected from the group consisting of bismuth, gallium, zinc, indium, germanium, aluminum, and magnesium, is 20% to 95% by weight, more preferably 30% to 95% by weight, and particularly preferably 75% to 95% by weight, relative to the total weight of the paste. According to another preferred embodiment, the proportion of the organic medium is 5% to 80% by weight, more preferably 5% to 70% by weight, and particularly preferably 5% to 25% by weight, relative to the total weight of the paste.

[0099] According to another preferred embodiment, the weight ratio of (a) the total weight of at least one metal component comprising a metal M1 with a melting point of at least 700°C, a metal M2 with a melting point of less than 700°C, a metal M3 selected from the group of active metals, and a metal M4 selected from the group of bismuth, gallium, zinc, indium, germanium, aluminum, and magnesium, to the weight of (b) the organic medium is at least 5:1, particularly preferably at least 7:1, and very particularly preferably at least 8:1. According to a preferred embodiment, the weight ratio of (a) the total weight of at least one metal component comprising a metal M1 with a melting point of at least 700°C, a metal M2 with a melting point of less than 700°C, a metal M3 selected from the group of active metals, and a metal M4 selected from the group of bismuth, gallium, zinc, indium, germanium, aluminum, and magnesium, to the weight of (b) the organic medium is in the range of 1:1 to 20:1, particularly preferably in the range of 2:1 to 20:1, and particularly preferably in the range of 5:1 to 15:1.

[0100] To provide a stacking effect, the paste is preferably applied to the surface of the ceramic body. The paste can be applied, for example, by a dispersion method or a printing method. Suitable printing methods include, for example, screen printing, inkjet printing, and offset printing. Preferably, the paste is applied to the surface of the ceramic body by screen printing.

[0101] After the paste is applied, it may be pre-dried if necessary. Pre-drying can be carried out at room temperature or high temperature. The pre-drying conditions can vary depending on the organic medium contained in the paste. The pre-drying temperature may be, for example, in the range of 50°C to 180°C, and preferably in the range of 80°C to 150°C. Pre-drying typically takes place over a period of 2 minutes to 2 hours, and preferably over a period of 5 minutes to 1 hour.

[0102] Subsequently, the metal foil can be applied to its surface with a pre-dried paste to obtain a stack.

[0103] Solder material can be a film.

[0104] The membrane comprises a metal M1 with a melting point of at least 700°C, a metal M2 with a melting point of less than 700°C, a metal M3 selected from the group consisting of active metals, and a metal M4 selected from the group consisting of bismuth, gallium, zinc, indium, germanium, aluminum, and magnesium. Furthermore, the membrane may contain other components, such as, for example, a suitable binder.

[0105] The film can be obtained, for example, by using at least one metal component comprising a metal M1 with a melting point of at least 700°C, a metal M2 with a melting point less than 700°C, a metal M3 selected from the group consisting of active metals, and a metal M4 selected from the group consisting of bismuth, gallium, zinc, indium, germanium, aluminum, and magnesium, and optionally by homogenizing other components and heating them to a temperature below the melting temperature of the metal M1 with a melting point of at least 700°C, the metal M2 with a melting point less than 700°C, the active metal M3, and the metal M4 selected from the group consisting of bismuth, gallium, zinc, indium, germanium, aluminum, and magnesium, but sufficient to form a bond between the metals. This temperature can be, for example, at least 200°C.

[0106] Alternatively, the film can be obtained, for example, by mixing at least one metal component with a binder and by shaping and heating the mixture to form a green body. The metal component includes a metal M1 with a melting point of at least 700°C, a metal M2 with a melting point less than 700°C, a metal M3 selected from the group consisting of active metals, and a metal M4 selected from the group consisting of bismuth, gallium, zinc, indium, germanium, aluminum, and magnesium. During heating, the binder can solidify and form a matrix in which the metal is distributed.

[0107] To provide a stack, the film can be placed, for example, on ceramic. Subsequently, the surface of a metal foil can be applied to the film located on the ceramic to obtain a stack.

[0108] According to another embodiment, the solder material can be a deposit. The deposition of the solder material can be achieved, for example, by electrodeposition or vapor deposition. Preferably, the solder material is deposited on a ceramic body. Subsequently, a metal foil can be applied to the solder material deposited on the ceramic to obtain a stack.

[0109] The stack is heated to obtain a metal-ceramic substrate. According to a preferred embodiment, heating is performed to obtain the metal-ceramic substrate using a solder material that forms an adhesive bond between the ceramic body and the metal foil. The adhesive bond is preferably formed by bonding metal M3 to the ceramic body during heating and bonding metals M1 (with a melting point of at least 700°C), metal M2 (with a melting point less than 700°C), metal M4 (selected from the group consisting of bismuth, gallium, zinc, indium, germanium, aluminum, and magnesium), and the metal foil to form an alloy. During subsequent solidification, the adhesive bond is then formed between the ceramic body and the metal foil via the active metal M3 bonded to the ceramic body and the resulting alloy.

[0110] During the heating process, the stack is heated to a peak temperature. The peak temperature is not further limited, but is preferably less than or equal to the melting point of metal M1, which has a melting point of at least 700°C, and lower than the melting point of the metal in the metal foil. According to a preferred embodiment, the peak temperature is at least 10°C lower, particularly preferably at least 50°C lower than the melting point of the metal in the metal foil. According to another preferred embodiment, the peak temperature is at least 700°C. The peak temperature is preferably in the range of 700°C to 1100°C, particularly preferably in the range of 750°C to 1050°C, and very particularly preferably in the range of 800°C to 1000°C. The peak temperature used herein refers to the temperature measured at the stack using a thermocouple. The peak temperature is the maximum temperature measured at the stack. To prevent adverse effects due to excessive fluidity of the molten metal, such as excessive contraction or expansion of the molten metal, those skilled in the art will endeavor to avoid excessively high peak temperatures.

[0111] During heating, the stack is heated for a sustained high-temperature heating period. The high-temperature heating period herein preferably refers to the time during which the stack is exposed to a temperature at least equal to the peak temperature - 250°C. Therefore, at an exemplary peak temperature of 900°C, the high-temperature heating period corresponds to the time during which the stack is exposed to a temperature of at least 650°C during heating. According to a preferred embodiment, the high-temperature heating period does not exceed 60 minutes, more preferably not more than 50 minutes, particularly preferably not more than 45 minutes, and very particularly preferably not more than 40 minutes. The high-temperature heating period is preferably in the range of 2 minutes to 60 minutes, more preferably in the range of 3 minutes to 50 minutes, particularly preferably in the range of 5 minutes to 45 minutes, and very particularly preferably in the range of 10 minutes to 40 minutes.

[0112] The stack is preferably heated by the energy input required for heating along the direction of the stack (starting from the heating zone). The adhesive bond is preferably formed by bonding metal M3 to the ceramic body and bonding metals M1 (with a melting point of at least 700°C), metal M2 (with a melting point less than 700°C), metal M4 (with a melting point less than 700°C selected from the group consisting of bismuth, gallium, zinc, indium, germanium, aluminum, and magnesium), and a metal foil to form an alloy. During subsequent solidification, an adhesive bond is then formed between the ceramic body and the metal foil via the active metal M3 bonded to the ceramic body and the alloy.

[0113] According to a particularly preferred embodiment, the stacks are heated in an oven, preferably in a continuous heating furnace or in a chamber furnace.

[0114] A non-oxidizing atmosphere is preferably present in the heating zone. The non-oxidizing atmosphere is preferably an inert gas atmosphere. A nitrogen, helium, or argon atmosphere is preferably present in the heating zone. According to a particularly preferred embodiment, a nitrogen atmosphere is present in the heating zone. The proportion of reactive gases (especially oxygen) in the non-oxidizing atmosphere is preferably less than 1000 ppm, more preferably less than 500 ppm, and particularly preferably less than 40 ppm.

[0115] When heated and stacked, an adhesive bond is preferably formed between the ceramic body and the metal foil via a solder material to obtain a metal-ceramic substrate comprising a ceramic body, a metal layer, and an adhesive layer located between the ceramic body and the metal layer. If desired, the metal-ceramic substrate can be subjected to further processing steps. For example, the exposed surfaces of the metal-ceramic substrate, preferably the metal layer of the metal-ceramic substrate, can be polished. Preferably, the surface of the metal layer of the metal-ceramic substrate is physically or chemically polished. Furthermore, the metal-ceramic substrate can be constructed. For example, the metal-ceramic substrate may be provided with conductive traces. These conductive traces are preferably formed by etching.

[0116] The metal-ceramic substrate according to the present invention can be particularly used in electronic applications, especially in the field of power electronics.

[0117] Therefore, the present invention also provides a module having the above-described metal-ceramic substrate.

[0118] According to a preferred embodiment, such a module includes a base plate. The base plate is preferably extensively bonded to a metal layer of a metal-ceramic substrate. According to another preferred embodiment, the module includes at least one chip. The at least one chip is preferably extensively bonded to at least one metal layer of a metal-ceramic substrate. According to yet another preferred embodiment, the module includes a metal-ceramic substrate having a first metal layer and a second metal layer (wherein the first metal layer is preferably opposite the second metal layer), a base plate, and at least one chip, wherein the at least one chip is bonded to the first metal layer of the metal-ceramic substrate and the base plate is bonded to the second metal layer of the metal-ceramic substrate.

[0119] The characteristics of the adhesive layer on the metal-ceramic substrate are preferably determined using the following measurement method:

[0120] Measurement methods :

[0121] (i) Method for determining the content of metals M1, M2, M3 and silver in the adhesive layer (characteristic M(M1)) EDX M(M2) EDX M (M3) EDX and M(Ag) EDX ) :

[0122] The contents of metals M1, M2, M3 and silver in the adhesive layer are preferably determined as follows:

[0123] In the first step, a cut of 100mm is made from the metal-ceramic substrate to be inspected by first sawing perpendicularly to the plane spanned by the metal layer of the metal-ceramic substrate at a low rotational speed using a diamond saw blade and with an oil-based lubricant (Buehler). 2 Up to 400mm 2 A cubic sample blank with a rectangular base is used within the specified range. The sample blank thus has a sample surface supplied for study. This sample surface extends perpendicularly to the plane traversed by the metal layer of the metal-ceramic substrate before sawing. Therefore, it has multiple sections on the ceramic body, the metal layer, and the bonding layer between them. First, the sample blank is embedded in a mold with low-shrinkage epoxy resin (Epo-Fix, Struers), with the sample surface oriented perpendicular to the mold wall. The epoxy resin is then cured at room temperature. After curing, the sample surface of the sample blank is mechanically polished using an automated polishing device (Tegrapole, Struers) to obtain a roughness of 1 μm or less.

[0124] In the second step, the polished sample surface is conductively coated with iridium at a thickness of 1 nm to 5 nm using a metal sputtering device (Q150T, Quorum Technologies).

[0125] In the third step, the analytical area on the sample surface is examined using scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX). In SEM-EDX, a primary electron beam is guided (shielded) and focused point-by-point on the sample surface. The scattered electrons are detected using a detector, and the number of electrons per pixel results in a microscopic image of the sample surface displayed in grayscale. Furthermore, the primary electron beam excites the sample to emit characteristic X-ray radiation, where the elements in the sample and their weight proportions can be determined by analyzing the energy spectrum using an EDX detector. For this examination, a scanning electron microscope (JSM-6060SEM, JEOL Ltd.) with a silicon-drifted EDX detector (NORAN, Thermo Scientific Inc.) and analysis software (Pathfinder Mountaineer EDS System, e.g., version 2.8, Thermo Scientific Inc.) is used. For scanning electron microscopy, use the following settings: magnification: 1000x, accelerating voltage = 15kV, working distance = 10mm, spot size (50-60) (set to reach 25% + / - 5% of the EDX detector's dwell time).

[0126] In the fourth step, the sample surface is examined using EDX software and displayed as an electron micrograph (backscattered electron micrograph). A rectangular field of view of at least 125 μm (horizontal) × 90 μm (vertical) is obtained, with the analysis area defined using the point analysis function of the EDX software. The analysis area can be referenced. Figure 1 The description is as follows:

[0127] a) The sample surface is oriented such that, in electron micrograph 100, the cutout of the ceramic body 120 is at the bottom, and the cutout of the metal layer 110 is at the top. In electron micrograph 100, the transition 5 between the ceramic body (dark) 120 and the adhesive layer or metal layer (light) 110 is visible. The lower boundary line 10 of the rectangle of the analysis region 130 is described by a line parallel to the transition 5, which extends directly through the ceramic body 120 at the transition 5.

[0128] b) In this orientation, the presence of metal M2 (with a melting point less than 700°C) and active metal M3 on the sample surface is examined. Grayscale images of electron micrographs 100 within the adhesive or metal layer 110 are studied, with metal M2 having the brightest pixels and metal M3 having the darkest pixels (except for ceramic bodies). A line parallel to the lower boundary 10 of the rectangle of the analysis region 130 in electron micrograph 100 forms the upper boundary 20 of the rectangle of the analysis region 130, extending through the farthest point where metal M2 or metal M3 with a melting point less than 700°C was detected.

[0129] c) The left boundary line 30 and the right boundary line 40 of the rectangle of the analysis area 130 extend parallel to each other at a distance corresponding to the distance (preferably 125 μm) of the boundary line of the field of view on the sample surface, and are perpendicular to the lower boundary line 10 and the upper boundary line 20.

[0130] In the fifth step, the EDX spectrum is detected using the following settings for the EDX detector: real-time = 30s, rate = auto, low energy cutoff = 100keV, high energy cutoff = auto (acceleration voltage per SEM).

[0131] In the sixth step, the spectrum is analyzed. For this purpose, elements to be examined are selected and elements contained in the ceramic body (their presence can optionally be determined in advance by conventional testing methods), iridium, and epoxy resin are deselected. The amount of each element to be examined is expressed as a percentage by weight, where the total corresponds to 100%.

[0132] Steps three through six are repeated nine times at different points. The average value is then determined from the total of ten individual measurements.

[0133] (ii) A method for determining the ratio of the content of element M4 in the adhesive layer to the content of metal M2 in the adhesive layer. (Features [M(M4) / M(M2))) ICP :

[0134] The ratio [M(M4) / M(M2)] in the adhesive layer of the metal-ceramic substrate ICP Preferably, it is determined as follows:

[0135] The metal-ceramic substrate to be examined is transferred to a plastic beaker made of HDPE (high-density polyethylene) and mixed with hydrochloric acid (concentration = 30%) and nitric acid (concentration = 65%) under low heat. Hydrofluoric acid (concentration = 40%) is added to the digestion solution to dissolve any other insoluble components. For metal-ceramic substrates of standard size, the following amounts of acid have been found to be advantageous: 30 ml hydrochloric acid (concentration = 30%), 20 ml nitric acid (concentration = 65%), and 50 μl hydrofluoric acid (concentration = 40%).

[0136] The resulting sample solution was transferred to a balanced polyethylene bottle. The sample solution was then diluted with water according to the expected value related to the content of the element to be tested. Aliquots of the sample solution were transferred to 100 mL volumetric flasks containing 10 mL of hydrochloric acid (30 wt%), 10 mL of buffered saline (10 g / L sodium chloride), and a calibration standard (e.g., 1 g / L yttrium solution). The correlation ratio [M(M4) / M(M2)] of the resulting test solution relative to the calibration standard was measured using ICP-OES (Inductively Coupled Plasma Optical Emission Spectrometry). ICPFor this purpose, an iCAP 6500Duo ICP emission spectrometer (Thermo Scientific) was used, with the following plasma settings configured for the measurement: purge pump rate (rpm): 35; analysis pump rate (rpm): 35; pump tube type: Tygon orange / white; HF power: 1150W; nebulizer gas: 0.60 L / min; auxiliary gas: 0.5 L / min.

[0137] The present invention is illustrated by the following exemplary embodiments, which should not be construed as limiting.

[0138] Exemplary Implementation :

[0139] Production of metal-ceramic substrates (Examples 1-8 and Comparative Examples 1-7) :

[0140] In Examples 1-8 and Comparative Examples 1-7, metal-ceramic substrates with different compositions in terms of the adhesive layer were produced. Therefore, in each case, a stack containing a ceramic body, a metal foil, and solder material in contact with the ceramic body and the metal foil was provided, and then heated. The resulting metal-ceramic substrates were then tested for their respective bond strength, thermal conductivity, and electrical conductivity.

[0141] In order to produce the metal-ceramic substrates 1-8 and comparative examples 1-7 according to the present invention, pastes according to the compositions shown in Table 1 were first prepared.

[0142] Table 1 :

[0143]

[0144] For this purpose, tin, titanium hydride, and bismuth, as powders, were continuously introduced into the specified amount of a texanol-containing organic carrier and mixed in a static mixing apparatus at 35 Hz for 20 minutes until a homogeneous paste was obtained in each case. Subsequently, copper powder was added incrementally. The resulting mixture was stirred until a homogeneous paste was obtained.

[0145] Using the paste produced in this manner, the opposing surfaces of the ceramic body are bonded to both sides of the copper foil. For this purpose, a ceramic body with dimensions of 177.8mm × 139.7mm × 0.32mm (available from Toshiba Materials) is used, with identical front and rear sides. The corresponding paste is screen-printed onto the rear side of this type of ceramic body using a 165-mesh screen, with a dimension of 137mm. 2 ×175mm 2The area was pre-dried at 125°C for 15 minutes. The thickness of the pre-dried paste was 35 μm ± 5 μm. The resulting arrangement was then rotated to uniformly print and pre-dry the paste onto the front side of the ceramic body. Subsequently, copper foil made of oxygen-free, highly conductive copper with a purity of 99.99% and dimensions of 174 mm × 137 mm × 0.3 mm was provided on both sides of the ceramic body with the paste on both sides to obtain a stack with the following structure: copper foil - pre-dried paste - ceramic - pre-dried paste - copper foil.

[0146] The stack was then heated in a continuous heating furnace. For this purpose, silicon carbide plates with graphite foil were first placed on the conveyor chain of the continuous heating furnace. The stack was placed on the graphite foil, and then covered with another graphite foil and weighted with another silicon carbide plate (weight = 600g). The structure was then transported on the conveyor chain through the heating zone of the continuous heating furnace and heated from 50°C to a peak temperature of 935°C (measured at the stack using a K-type thermocouple from Temperatur MesselementeHettstedt GmbH) for 2 minutes over 25 minutes. The temperature of the structure was then cooled back to 50°C over 25 minutes.

[0147] The resulting metal-ceramic substrate is then cooled to room temperature to obtain a metal-ceramic substrate, each containing a ceramic layer bonded to a copper layer on both sides via an adhesive layer.

[0148] evaluate :

[0149] For the metal-ceramic substrates of Examples 1-8 and Comparative Examples 1-7, the values ​​were determined according to Table 2:

[0150] Table 2 :

[0151]

[0152] In addition, the bond strength on the metal-ceramic substrates of Examples 1-8 and Comparative Examples 1-7 was determined by peel strength test, and the electrical conductivity and thermal conductivity were also determined.

[0153] The results are listed in Table 3.

[0154] Table 3 :

[0155]

[0156] legend:

[0157] +++: Adhesive strength in peel strength test >100N / cm.

[0158] ++: Adhesive strength in peel strength test = 75 < 100 N / cm.

[0159] +: Adhesive strength in peel strength test = 40 < 75 N / cm.

[0160] -: Adhesive strength in peel strength test <40N / cm.

[0161] Exemplary implementations show that the metal-ceramic substrate meets the following conditions:

[0162] (c1)M(M2) EDX =10% to 20% by weight

[0163] (c2) 15% by weight ≤ [M(M4) / M(M2)] ICP *1000% by weight + M (M2) EDX ≤100% by weight, and

[0164] (c3)M(Ag) EDX =0% by weight to 10% by weight

[0165] Compared to the adhesive layer, this metal-ceramic substrate exhibits stable adhesion between the metal layer and the ceramic body, along with high thermal and electrical conductivity. Since these metal-ceramic substrates are silver-free, there are no issues related to silver migration. In contrast, metal-ceramic substrates that do not meet conditions (c1) and (c2) result in less stable adhesion between the metal layer and the ceramic body, or the obtained metal-ceramic substrate has lower thermal and electrical conductivity compared to the former.

[0166] Preparation of metal-ceramic substrates (Examples 9 and 10 and Comparative Example 8) :

[0167] In Examples 9 and 10 and Comparative Example 8, metal-ceramic substrates were produced similarly to those in Examples 1-8 and Comparative Examples 1-7, but with different compositions of the adhesive layers, and their associated adhesive strengths, thermal conductivity, and electrical conductivity were then verified.

[0168] The paste composition shown in Table 4 is used to produce metal-ceramic substrates.

[0169] Table 4 :

[0170] evaluate :

[0171] For the metal-ceramic substrates of Examples 9 and 10 and Comparative Example 8, the values ​​according to Table 2 were determined. Furthermore, the bond strength on the metal-ceramic substrates of Examples 9 and 10 and Comparative Example 8 was determined by peel strength testing, and the electrical and thermal conductivity were also determined.

[0172]

[0173] The results are shown in Table 5.

[0174] Table 5 :

[0175]

[0176] legend:

[0177] +++: Adhesive strength in peel strength test >100N / cm.

[0178] ++: Adhesive strength in peel strength test = 75 < 100 N / cm.

[0179] +: Adhesive strength in peel strength test = 40 < 75 N / cm.

[0180] -: Adhesive strength in peel strength test <40N / cm.

[0181] Exemplary embodiments 9 and 10 confirm that the metal-ceramic substrate meets the following conditions:

[0182] (c1)M(M2) EDX =10% to 20% by weight

[0183] (c2) 15% by weight ≤ [M(M4) / M(M2)] ICP *1000% by weight + M (M2) EDX ≤100% by weight, and

[0184] (c3)M(Ag) EDX =0% by weight to 10% by weight

[0185] Compared to the adhesive layer, this metal-ceramic substrate exhibits stable adhesion between the metal layer and the ceramic body, along with high thermal and electrical conductivity. Since these metal-ceramic substrates are silver-free, there are no issues related to silver migration. In contrast, metal-ceramic substrates that do not meet conditions (c1) and (c2) result in less stable adhesion between the metal layer and the ceramic body, or the obtained metal-ceramic substrate has lower thermal and electrical conductivity compared to the former.

Claims

1. A metal-ceramic substrate, the metal-ceramic substrate comprising: (a) Ceramic body, (b) Metal layer, and (c) an adhesive layer located between the ceramic body and the metal layer, wherein the adhesive layer comprises (i) A metal M1 having a melting point of at least 700°C, wherein the metal M1 is copper. (ii) A metal M2 with a melting point less than 700°C, wherein the metal M2 is tin. (iii) A metal M3 selected from the group consisting of active metals, wherein the metal M3 is selected from the group consisting of titanium and zirconium, wherein the content M(M3) of the metal M3 in the adhesive layer is determined by means of EDX. EDX Within the range of 0.5% to 15% by weight, and (iv) Metal M4, wherein metal M4 is selected from the group consisting of bismuth and germanium. The metal-ceramic substrate is characterized in that the adhesive layer has the following features: (c1)M(M2) EDX =10% to 20% by weight (c2)15% by weight ≤ [M(M4) / M(M2)] ICP * 1000% by weight + M (m2) EDX ≤100% by weight, and (c3)M(Ag) EDX <10% by weight in: M(M2) EDX The content of metal M2 in the adhesive layer, determined by EDX, is expressed as [in weight %]. [M(M4) / M(M2)] ICP It is the ratio of the content of metal M4 in the adhesive layer to the content of metal M2 in the adhesive layer, determined by ICP. M(Ag) EDX The silver content in the adhesive layer is determined by EDX (in weight %).

2. The metal-ceramic substrate according to claim 1, wherein the ceramic used to form the ceramic body is selected from the group consisting of aluminum nitride ceramic, silicon nitride ceramic and alumina ceramic.

3. The metal-ceramic substrate according to claim 1 or 2, wherein the metal used to form the metal layer is copper.

4. The metal-ceramic substrate according to claim 1 or 2, wherein the metal M4 is bismuth.

5. The metal-ceramic substrate according to claim 1 or 2, wherein the adhesive layer has the following characteristics: (c1´)M(M2) EDX =10% to 15% by weight.

6. The metal-ceramic substrate according to claim 1 or 2, wherein the adhesive layer has the following characteristics: (c2´)15% weight ≤ [M(M4) / M(M2)] ICP * 1000% by weight + M (m2) EDX ≤70% by weight.

7. The metal-ceramic substrate according to claim 1 or 2, wherein the adhesive layer has the following characteristics: (c3´)M(Ag) EDX <1% by weight.

8. A method for producing a metal-ceramic substrate, the method comprising the following steps: a) Provide a stack, the stack containing a1) Ceramic body, a2) Metal foil, and a3) Solder material, wherein the solder material is in contact with the ceramic body and the metal foil, wherein the solder material comprises: (i) A metal M1 having a melting point of at least 700°C, wherein the metal M1 is copper. (ii) A metal M2 with a melting point less than 700°C, wherein the metal M2 is tin. (iii) A metal M3 selected from the group consisting of active metals, wherein the metal M3 is selected from the group consisting of titanium and zirconium, wherein the content M(M3) of the metal M3 in the adhesive layer is determined by means of EDX. EDX Within the range of 0.5% to 15% by weight, and (iv) Metal M4, wherein metal M4 is selected from the group consisting of bismuth and germanium, and b) Heat the stack to obtain a metal-ceramic substrate.

9. A module comprising a metal-ceramic substrate according to any one of claims 1 to 7.

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