WO2011098071A1

WO2011098071A1 - Method for producing metal-ceramic composite materials, in particular metal-ceramic substrates, and ceramic composite material, in particular metal-ceramic substrate, produced according to said method

Info

Publication number: WO2011098071A1
Application number: PCT/DE2011/000122
Authority: WO
Inventors: Jürgen SCHULZ-HARDER
Original assignee: Curamik Electronics Gmbh
Priority date: 2010-02-12
Filing date: 2011-02-09
Publication date: 2011-08-18
Also published as: EP2534115A1; DE102010007919A1; DE102010007919B4

Abstract

The invention relates to a method for producing metal-ceramic substrates, wherein at least one ceramic substrate, for example at least one plate-shaped ceramic substrate, is connected to an oxidized metal film by direct bonding, specifically by heating under protective gas to a process or bonding temperature that is below the melting temperature of the metal of the metal film but is at least equal to the melting temperature of the eutectic formed by the oxide layer and the metal, wherein the at least one ceramic substrate and the at least one metal film to be connected thereto are accommodated in a reaction chamber formed by an interior of a saggar during the method.

Description

Process for producing metal-ceramic composite materials, in particular metal-ceramic substrates, and ceramic composite material produced by this process, in particular metal-ceramic substrate

The invention relates to a method according to the preamble of claim 1 and to a metal-ceramic composite material according to the preamble 9.

By the term "direct bonding" are meant methods of bonding a metal to ceramics, i. for producing metal-ceramic composite materials, using a surface eutectic layer of the metal, for example metal oxide layer, which is then produced by heating a reactive metal and ceramic components (hereinafter also referred to as "metal oxide layer"). Connection components ") melts to a process or bonding temperature (eutectic temperature) and produces the connection between the connection components while wetting the ceramic as a kind of solder during the subsequent cooling. The bonding temperature is below the melting temperature of the metal. In particular, depending on the metal used, this bonding temperature is in the range between about 714 ° C (copper-phosphorus) and 1820 ° C (chromium-oxygen)

In a known direct-bonding method (DE 23 19 854 / US 3,766,634), the metal is first in an oxygen-containing inert gas atmosphere in a

Temperature is oxidized below the bonding temperature. Subsequently, the metal and the ceramic are heated to the process or bonding temperature. Thereafter, the cooling to room temperature. For the copper-oxygen system, this method specifies an oxygen content of the reactive atmosphere of 0.01-0.5 volume percent (100-5000 ppm).

Also known is an advanced direct-bonding method (DE 26 338 69 / US 3,994,430), in which the metal in a separate, preceding the bonding

CONFIRMATION COPY Process step is treated or oxidized with the reactive gas. After merging the components to be joined metal and ceramic they are heated in an oven to the process or bonding temperature, in one

Inert gas atmosphere with an oxygen content of the order of 0.01-0.5 volume percent (100-5000 ppm).

Also known is a direct-bonding method (DE 30 36 128), in which the

Compound of copper and ceramic in a vacuum oven with an oxygen content between 0.001 - 0.1 mbar (about 1-100 ppm) takes place.

It has also been proposed (DE 32 04 167 / US 4,483,810), the direct-bonding method in a continuous or tunnel furnace under a protective gas atmosphere

in which the oxygen content is adjusted to 20-50 ppm by metered addition of oxygen into the protective gas, at a temperature between 960 ° C and 1072 ° C.

In all the aforementioned known processes, the oxygen content of the

Inert gas atmosphere well above an equilibrium oxygen content or aante!) Of the copper-oxygen system. It is known from the literature that the oxygen content of this system in the temperature range at which the direct bonding or the DCB process is carried out on the order of 2.6-5 ppm.

Thus, in "The Metallurgy of Copper" Incra Series, Vol. II, pages 56, 60 for logK of the reaction Cu + 1 / 2O2 = CU2O at a temperature of 1085 ° C, a value of 2.704 is given. This corresponds to an oxygen partial content of 3.9 x 1 O 2 atm, which is about 3.9 ppm.

From "electrochemical equilibrium investigations on system copper-oxygen between 1065 and 1 300 ° C", habilitation thesis J. Osterwald, Berlin, 1965 the following formula is known for the temperature dependence of the oxygen partial content: Iog (po2) = - (20970/7) + 10, 166.

Here are po2 the oxygen partial content in ppm and

T is the temperature in ° C.

From this, the following oxygen content levels can be determined depending on the temperature:

In another reference (Neumann et al Metal Process, 1 985, page 85), the oxygen content of the copper-oxygen system at a eutectic temperature of 1065 ° C is 2.69 x 10 ^-6 , which corresponds to about 2.69 ppm ,

It can therefore be taken for granted that the equilibrium oxygen content in direct bonding of copper and ceramic (DCB process) is in the range between 2 and 6 ppm.

The above-mentioned known methods therefore have u. a. the disadvantage that a post-oxidation of the copper takes place due to the significantly greater oxygen content in the protective gas atmosphere in which the DCB process is carried out.

A regulation of the oxygen content in a protective gas atmosphere (for example of nitrogen and / or argon) in the range of less than 10 ppm, in particular also in a factory production of metal-ceramic composite materials or substrates, is compatible with the

required accuracy not, possibly only with an extremely high technical effort possible. Furthermore, an oxygen partial pressure or oxygen content in the Inert gas atmosphere of the DCB process less than the equilibrium pressure of the system metal (copper) oxygen to a reduction of the adhesion of the metal (copper) to the ceramic, while at a high oxygen partial pressure or oxygen content in the inert gas atmosphere comes to a strong post-oxidation which in extreme cases, a melting of the entire metal, for example, the entire metal or copper foil result.

For this reason, it has already been proposed (DE 101 48 550), in the manufacture of metal-ceramic composite materials, each consisting of at least one preferably plate-shaped ceramic substrate and at least one metal foil, these

During the direct-bonding process, bonding components are accommodated in a reaction chamber formed by a capsule with an inner protective gas atmosphere which is separated by the capsule from an outer protective gas atmosphere surrounding this capsule and in which direct bonding of the oxidized metal foil to the ceramic substrate by heating under protective gas to the process or bonding temperature which is below the melting point of the metal of the metal foil, but at least equal to the melting temperature of the eutectic formed by the oxide film and the metal of the metal foil.

For the purposes of the invention, "inner protective gas atmosphere" is to be understood as meaning the atmosphere or protective gas atmosphere within the encapsulated interior or reaction space of a capsule. "Outer protective gas atmosphere" means the protective gas atmosphere surrounding the respective capsule during direct bonding, i. the

Inert gas atmosphere in an oven.

The object of the invention is to further improve the known method and

in particular to enable a simplified and rational production of metal-ceramic composite materials, in particular metal-ceramic substrates and especially those for electrical or electronic circuits of the highest quality. To solve this problem, a method according to claim 1 and a metal-ceramic composite material according to claim 9 are formed.

Further developments, advantages and applications of the invention will become apparent from the following description of exemplary embodiments and from the figures. In this case, all described and / or illustrated features alone or in any combination are fundamentally the subject of the invention, regardless of their summary in the claims or their dependency. Also, the content of the claims is made an integral part of the description.

In the inventive method, which is also in particular for

Manufacture of metal-ceramic substrates and thereby particularly suitable for the production of copper-ceramic substrates for use as circuit boards for electrical circuits and circuits, at least one ceramic substrate and an oxidized metal foil are arranged in the encapsulated space or reaction space formed in the capsule in that the metal foil with an oxidized surface side is flat against a

Surface side of the plate-shaped ceramic substrate is applied.

To make the connection by direct bonding, the at least one

Ceramic substrate and the at least one oxidized metal foil (preferably copper foil) as components to be connected or compound components introduced into the reaction space formed by the interior of the capsule. In a pretreatment phase, for example in a heating phase, the reaction space which is widely opened via at least one rinsing or treatment opening to a surrounding outer protective gas atmosphere is then rinsed with the protective gas (eg nitrogen and / or argon) to remove ambient oxygen, so that a protective gas atmosphere is formed in the reaction space with low oxygen content sets. The rinsing of the reaction space can be carried out during a pretreatment phase with the capsule open not only in a short time, but also very intensively with a reduced consumption of protective gas (eg argon or nitrogen). At the end of the pretreatment phase, the at least one treatment opening is closed and the connection components, ie the at least one ceramic substrate and the at least one oxidized metal foil, in a treatment or bonding phase in the reaction space formed by the interior of the capsule in an inner protective gas atmosphere Bonding temperature heated under the

Melting temperature of the metal is, but at least equal to the melting temperature of the eutectic of the metal (eg, Cu) and the metal oxide (eg., CU2O). In a subsequent process step (cooling phase), the cooling of the capsule and of the components accommodated in the reaction space then takes place, and in fact continues

closed treatment opening and in the outer under inert gas atmosphere.

The capsule used is e.g. Also, for example, is not completely closed to the outside during the treatment or bonding phase and during the cooling phase, but has at least one gas exchange opening, which is for example an additional opening and / or generated by not completely closing the at least one treatment opening is and can take place through the gas exchange between the inner and outer inert gas atmosphere. However, the encapsulation of the reaction space achieved with the capsule is at least 60%. For the purposes of the invention, "encapsulation" means the percentage of the closed surface portion of the total area surrounding the encapsulated interior space (total area minus the area of the surface)

Gas exchange openings) based on this total area to understand. A 95% encapsulation thus means that 95% of the area surrounding the capsule interior is closed and only 5% of this total area is formed by one or more gas exchange openings.

The inventive method is thus characterized by the fact that during the bonding phase and the cooling phase at least a substantial separation of the inert gas atmosphere in the furnace chamber ("outer inert gas atmosphere"), which surrounds the at least one capsule of the inert gas atmosphere in the interior or reaction space of the Capsule ("inner inert gas atmosphere") is in which (reaction space), the direct bonding takes place and in which the connection components of metal and ceramic are accommodated at least with the region at which the connection is to take place.

Preferably, the cross section of the at least one gas exchange opening or the total cross section of a plurality of gas exchange openings is selected so that this cross section or total cross section account for less than 40% of the total, the reaction space bounding inner surface of the capsule, the capsulation achieved by the enclosure so larger than 60%.

The oxygen content in the outer protective gas atmosphere has no or substantially no influence on the quality of the produced metal-ceramic composite or the produced metal-ceramic substrate, even if the outer protective gas atmosphere has an oxygen content far below or far above the equilibrium oxygen content. This far-reaching independence of the results achieved by the method according to the invention of the oxygen content of the outer protective gas atmosphere is due to the fact that at the relatively high process temperature (960 - 1072 ° C), at which the direct bonding takes place, the diffusion of oxygen from the outer, surrounding the respective _^ capsule protective gas atmosphere is very low in the inner protective gas atmosphere inside the capsule or in the reaction space. This effect can be further enhanced by a targeted current conduction of the outer protective gas atmosphere, namely by the fact that the flow is initially directed to the gas exchange openings of the respective capsule for rinsing. In actual bonding at process temperature, the flow is then directed to the closed area of the capsule.

In a preferred embodiment of the method according to the invention, however, the oxygen content is controlled in the protective gas atmosphere surrounding the capsule, but at least limited by a regulation, but not too great accuracy for the control or adjustment is required. As a result, gross fluctuations in the Oxygen content compensated (fluctuations) either by the entry of oxygen at the furnace openings or by an oxygen consumption due to oxidation of metallic furnace components.

The adjustment of the oxygen content in the outer protective gas atmosphere is preferably carried out as a function of the encapsulation. Depending on the encapsulation of the

Oxygen content in the outer inert gas atmosphere, for example, set as follows:

- Encapsulation of 60 to 80% with an oxygen content in the outer

Inert gas atmosphere between 2 - 20 ppm,

- Encapsulation 80 - 95% with an oxygen content in the outer protective gas atmosphere between 50 and 200 ppm or 1 - 20 ppm

- Encapsulation above 95% with an oxygen content in the outer inert gas atmosphere greater than 200 ppm or less than 20 ppm

The following table reproduces the results of tests carried out with the method according to the invention when joining a plate-shaped ceramic

(Aluminum-oxide-ceramic) were obtained with a copper foil formed by a copper foil layer, with different oxygen content of the outer

Inert gas atmosphere and different encapsulation, each with a

Process temperature of 1068 ° C. The strength of the bond between the ceramic and the copper layer or copper foil (tear resistance in N / cm) as well as the surface quality of the exposed copper surfaces were investigated

(Copper surface appearance). o ₂ encapsulation tear resistance copper surface ppm% N / cm look

<2 95> 60 blank

<2 80 50 blank

<2 60 40 blank

<2 50 30 blank

10 95> 60 blank

10 60> 60 blank

10 50> 60 slightly oxidized

20 95> 60 blank

20 80> 60 blank

20 50> 60 slightly oxidized

50 95> 60 blank

50 80> 60 blank

50 60> 60 blank

50 50> 60 oxidized

100 95> 60 blank

100 80> 60 blank

100 60> 60 slightly oxidized

100 40> 60 strongly oxidized

200 95> 60 blank

200 80> 60 oxidized

In the above table, therefore, the influence of the oxygen content in the outer atmosphere and the encapsulation on the tear resistance and the nature of the copper surfaces are reproduced. It was assumed above that during the bonding phase and during the cooling phase, the encapsulation of the reaction space is not one hundred percent, but the reaction space communicates with the outer protective gas atmosphere via a gas exchange opening, thus introducing the connection components into the encapsulated one Reaction space in a normal atmosphere and at the beginning of the actual process to allow displacement of the normal atmosphere, in particular the air from the reaction space by the inert gas.

The at least one ceramic substrate and the at least one metal foil can be inserted one after the other into the respective capsule, or else as a stack prepared outside the capsule.

The metal foil is, for example, before introduction into the capsule in a

previously oxidized process step, for example by treatment with a suitable reactive gas, for. B. oxygen. In the method according to the invention, however, it is also possible to use an already preoxidized metal foil.

Oxygen as a reactive gas is particularly suitable for metal foils made of copper.

The heating of the respective capsule and the components accommodated in this capsule to the direct-bonding temperature takes place in an oven, preferably in a continuous or tunnel oven, wherein the oven compartment contains the outer protective gas atmosphere with a regulated oxygen content. The setting of the

Oxygen content in the outer protective gas atmosphere is effected by metering oxygen into the protective gas.

In principle, however, there is also the possibility of a one hundred percent encapsulation of the reaction space, in which case a protective gas atmosphere containing a certain proportion of oxygen is then introduced into this reaction space in the preparation phase through the at least one treatment or scavenging opening. However, it is also possible to work with an oxygen-free shielding gas, specifically when a free volume in the interior of the capsule correspondingly high oxide content is provided on the metal foil. Dissociation of the oxide then sets up the necessary equilibrium oxygen content.

The encapsulated space preferably contains a buffer substance, at least in the case of a 100% encapsulation, with which (buffer substance) the oxygen partial pressure in the interior

Inert gas atmosphere, i. is adjusted and / or maintained in the encapsulated reaction space at the reaction or bonding temperature to ensure optimum DCB bonding between the metal (copper) and the ceramic, while preventing at least disturbing post-oxidation. This set by the buffer substance oxygen partial pressure is then preferably between 3 - 10 ppm. The buffer substance contains, for example, CuO in the form of powder, optionally mixed with copper powder.

In a development of the invention, the method is designed, for example, in such a way that

during direct bonding, the reaction space is sealed against the outer protective gas atmosphere surrounding the capsule or the encapsulation is greater than 60%,

and or

that in the process maximum allowable oxygen content in the outer

Protective gas atmosphere increases with increasing encapsulation,

and or

that the outer protective gas atmosphere at an encapsulation between 60 and 80% about

Contains 50 to 100 ppm oxygen,

and or

Contains 2 to 20 ppm oxygen,

and or that the outer protective gas atmosphere at an encapsulation of 80-95% contains 50 to 200 ppm oxygen,

and or

that the outer protective gas atmosphere with an encapsulation of 80 - 95% 1 to 20 ppm

Contains oxygen,

and or

that the outer protective gas atmosphere at an encapsulation greater than 95% contains oxygen in a proportion of less than 20 ppm or greater than 200 ppm,

and or

that the respective capsule is designed in the form of a frame enclosing the reaction space,

and or

that the respective capsule is formed like a dish with a lid,

and or

the respective capsule with at least one support or intermediate layer for the

Connection components is executed,

and or

that a buffer substance is accommodated in the reaction space to create an oxygen equilibrium potential in the reaction space during direct bonding,

and or

that the buffer substance such on the basis of copper oxide, preferably on the

Base is copper oxide / copper,

and or

that the encapsulation is chosen in the range of 99 to 65%,

und7oder

that a tunnel or continuous furnace is used, in which the capsules on a

Transporter are arranged,

and or that several capsules or individual capsules are stacked and / or arranged side by side in a plurality of rows on a conveyor of the continuous or tunnel kiln,

wherein the aforementioned features can be used individually or in any combination.

The invention will be explained in more detail below with reference to the figures of exemplary embodiments. Show it:

Fig. 1 in a simplified representation and in section a according to the invention

Method produced metal-ceramic composite material;

Fig. 2 in a simplified representation of a trained as a tunnel furnace system for

Producing the metal-ceramic substrates of Figure 1;

Fig. 3 u. 4 is a simplified sectional view of one of the system of Figure 2

used capsules in the open state and in the closed state; Fig. 5-9 in representations similar to Figures 3 and 4 show further embodiments of the capsules used in the invention.

The metal-ceramic substrate (copper-ceramic substrate) generally designated 1 in FIG. 1 consists, in a known manner, of the flat ceramic layer 2 and of two metal layers in the form of copper layers or foils applied on one surface side by DCB bonding 3 and 4.

The production of the substrates 1 takes place in a plant 5 shown schematically in Figure 2 with a tunnel oven 7. The forming the respective substrate

Connection components (ceramic layer 2 and pre-oxidized copper foils 3 and 4) are each introduced into a, for example, flat, rectangular or square, shaft-like or shell-like capsule 7, for example as

Layer sequence 1 .1 with the copper layer 4 lying down on a separating layer 8, which separates the copper layer 4 from the inner surface of the bottom of the capsule 7 and an bonding of the Copper layer 4 prevented at this bottom, with the ceramic layer 2 on top of the copper foil 4 resting and with the copper foil 3 on the copper foil. 4

facing away upper side of the ceramic layer 2 resting. The separation layer 8 is

For example, a porous layer of fine particles or of a powder of a high temperature resistant material, such as mullite, Al2O3, T1O2, ZrÜ2, MgO, CaO, CaCO2 and with a grain size, for example, less than 30 μιη.

The thus loaded with the connection components or with the consisting of the copper foils 3 and 4 and the ceramic layer 2 layer sequence 1 .1 capsule 7 with a transport system or conveyor (transport chain) of the tunnel kiln 6 in a

Transport direction TR moves through different zones of this furnace, first through a heating zone A, in which the temperature rises inside the tunnel oven 6 from room temperature, for example, to a temperature in the range between 120 ° C and 300 ° C, then by a treatment or Bonding zone B, in which the temperature in the tunnel kiln from the final temperature of the heating zone A to the

Bonding temperature of the DCB process, i. at a temperature in the range between

1065 ° C and 1085 ° C, for example, to a temperature of 1083 ° C increases, and then through a cooling zone C, in which the temperature inside the tunnel kiln 6 from the bonding temperature drops back to the ambient temperature.

The interior of the tunnel kiln 6 is acted upon by a protective gas atmosphere. The protective gas of this atmosphere, which is introduced in particular in the region of the heating zone A and in the region of the cooling zone C into the interior of the tunnel kiln 6, is for example nitrogen and / or argon. The inert gas atmosphere also contains a small proportion of oxygen. The oxygen content of the protective gas atmosphere within the tunnel kiln 6 is, for example, 0.2 ppm - 1000 ppm.

Each capsule 7 consists for example of a trough-like base body 9, in the interior of which the layer sequence 1 .1 is received, as well as a lid 10 which closes the base body 9 at its upper side. A special feature is that through corresponding guide and / or actuating elements within the heating zone of the cover 10 of the respective capsule 7 is lifted from the base body 9, so that the respective capsule 7 is opened over a relatively large area and thus an intensive rinsing of the

Capsule interior can be done with the gas of the inert gas atmosphere or with the protective gas, by the formed between the raised lid 10 and the upper edge of the cup-shaped or bowl-shaped base body 9 rinse or treatment opening 1 first

After leaving the heating zone A1, the cover 10 is deposited by the guiding or actuating means on the base body 10, so that the interior of the respective capsule 7 is closed on the capsule top and in the interior or in

Reaction space of the capsule enclosed "inner inert gas atmosphere" at 100% encapsulation is completely separated from the "outer inert gas atmosphere" inside the tunnel kiln 6 or at an encapsulation of less than 100%, for example between 40% and 100% via at least one gas exchange opening 9.1 or 10.1, which is provided in the base body 9 and / or cover 10 and whose opening cross section corresponds to the respective encapsulation, is in communication with the outer atmosphere in the tunnel interior.

The oxygen content of the outer protective gas atmosphere in the tunnel interior is chosen as a function of the respective encapsulation, for example

according to the table below

The closed state or the encapsulation of the respective capsule 7 is also maintained within the cooling zone C.

The opening of the respective capsule 7 in the heating zone has u.a. the advantage of intensive flushing of the capsule interior with inert gas or with the

Inert gas atmosphere of the tunnel kiln 6 in a short time at reduced

Schutzgasverbraucht. The closing of the respective capsule 7 and the thereby achieved encapsulation of the capsule interior have the advantage that within the

Capsule interior during the DCB bonding in the manner described above, an equilibrium oxygen content by post-oxidation of the copper of the copper layers 3 and 4 and / or by release of oxygen from these

Copper layers to the inner or encapsulated inert gas atmosphere sets an oxygen content, which is less than 10 ppm, preferably in the range between 2 and 6 ppm and thus ensures optimal DCB bonding.

Another significant advantage of the encapsulation in zones B and C is that subsequent oxidation of the copper layers 3 and 4 after DCB bonding and during cooling to ambient temperature is prevented, or at least greatly reduced. Furthermore, encapsulation also prevents impairment of the DCB bonding due to external influences, for example due to oxygen removal by the transport element of the tunnel kiln 6, which is of great advantage, in particular after renewal of the transport element.

After leaving the tunnel kiln 6 at the cooling zone C and after removing the respective substrate 1, the relevant capsule 7 is available for reuse.

It has been assumed above that the opening of the respective capsule 7 for rinsing takes place by lifting the lid 10. Of course, there are other possibilities for opening and closing the respective capsule, so that the Capsule interior or the inner protective gas atmosphere in the bonding and cooling zone B and C is not or only in accordance with the respective desired encapsulation with the outer protective gas atmosphere in combination.

FIG. 5 shows a schematic representation of a capsule 7a whose main body 9a which can be closed by the cover 10a on the circumference, preferably on two opposite peripheral sides, has large flushing openings 12, each of which can be closed by a cover 13. The openings 12 and the associated cover 1 3 are located, for example, on the transverse to the transport direction TR oriented sides of the respective capsule. The at least one gas exchange opening is e.g. in the

Base body 9a and / or provided in the lid 10a, as indicated by 9a.1 or 10a.1.

FIG. 6 shows, in a simplified sectional view, two capsules 7b following one another in the transport direction TR, which are each provided with a large-sized flushing opening 14 at their circumferential sides oriented perpendicular to the transport direction, namely, for example, at the shell-like base body 9b, which is provided at its upper side by means of a cover 10b is closable. The capsules 7b are moved through the tunnel kiln 6 in such a way that consecutive capsules 7b within the zone A are spaced apart from one another in the transport direction TR so that flushing of the respective capsule interior with protective gas (nitrogen and / or argon) is possible via the openings 14. By

corresponding means are the capsule 7b at least after reaching the

Braking treatment zone B so that, according to the figure 7 in the transport direction TR consecutive capsules 7b at the scavenging ports 14 having

Connect end faces close to each other and thus these openings are at least closed so far that the inner inert gas atmosphere in the interior or

Reaction space of each capsule 7b is separated from the outer protective gas atmosphere of the tunnel kiln 6 at least according to the desired encapsulation. Figures 8 and 9 show as another embodiment, a capsule 7c, which consists of a plurality of stacked individual capsules 1 5, which in the illustrated

Embodiment each shell-like with a bottom and a peripheral wall

are formed and each for receiving a layer sequence 1 .1 consisting of the copper foils 3 and 4 and the intermediate ceramic layer 2 serve, in the manner as described above in connection with Figures 3 and 4.

In the heating zone A, the individual capsules 1 5 by there leadership and / or

Actuating means in the form shown in Figure 8 spaced from each other and also a lid 16 for the uppermost single capsule 1 5 is spaced therefrom, so that the interior of the individual capsules 1 5 can be flushed over large flushing openings with inert gas (nitrogen and / or argon). At the latest when reaching the treatment zone B, the individual capsules 1 5 stacked on each other, so that the interior or reaction chamber of the lower individual capsules is closed by the overlying individual capsule 1 5 and the interior or reaction chamber of the uppermost single capsule 1 5 are closed by the lid 16 , By gas exchange openings, not shown, for example, in the peripheral wall of the individual capsules 1 5 or by the

Opening cross section of these gas exchange openings is set the required encapsulation.

The invention has been described above by means of exemplary embodiments. It is understood that numerous other changes or modifications are possible without thereby departing from the inventive concept underlying the invention.

Thus, it has heretofore been assumed that the production of the substrates 1 using the tunnel kiln 6, i. continuously in a continuous process.

Basically there is also the possibility of bonding at stationary in a

Furnace interior arranged, preferably stacked and each loaded with at least one layer sequence 1 .1 capsules in a protective gas atmosphere, for example again from nitrogen and / or argon with the low oxygen content in the range between 0.2 ppm - 1000 ppm perform, in a heating phase, the capsules are opened to flush the respective capsule interior with the protective gas over a large area and then closed during the DCB bonding as far that the required encapsulation is obtained.

Furthermore, it is also possible in particular with the use of separating elements to arrange one after another in each capsule 7, 7a-7d a plurality of layer sequences 1 .1, specifically for the simultaneous production of a plurality of substrates 1. There is also the possibility of the

Produce substrates 1 in two operations, by bonding

For example, first a metal layer on one surface side of the ceramic layer and then in a further operation by bonding the other metal layer on the other surface side of the ceramic layer.

LIST OF REFERENCE NUMBERS

1 substrate

2 ceramic layer

3, 4 copper layer or copper foil

5 attachment

6 tunnel kiln

7, 7a, 7b, 7c capsule

8 separating layer

9, 9a, 9b basic body

10, 10a, 10b cover

1 1, 12 opening

1 3 lid

14 opening

1 5 single caps

16 lids

A heating zone

B treatment or bonding zone

C cooling zone

TR transport direction

Claims

claims

1 . A method for producing metal-ceramic substrates, wherein at least one

Ceramic substrate, for example, at least one plate-shaped ceramic substrate is bonded to an oxidized metal foil by direct bonding, by heating under inert gas to a process or bonding temperature, which is below the melting point of the metal of the metal foil (3, 4), but at least equal Melting temperature of the eutectic formed by the oxide layer and the metal, wherein the at least one ceramic substrate and to be connected thereto at least one metal foil (3, 4) during the process in one of a

Inside a capsule (7, 7a - 7d) formed reaction space are housed, wherein during the direct bonding formed in the interior of the reaction chamber inner protective gas atmosphere of an outer surrounding the capsule

Protective gas atmosphere is separated or via a first opening cross section with the outer protective gas atmosphere in communication, wherein the first

Aperture cross-section is selected so that an encapsulation of the reaction space, the (encapsulation) is defined as a percentage of the closed part of the reaction space enclosing the total area relative to this total area is greater than 60%, characterized in that the reaction space of the capsule (7, 7a-7d) during a pretreatment phase preceding direct bonding,

for example, during a heating phase (A), with the outer protective gas atmosphere via a second of at least one flushing opening (1 1, 12, 14) formed

Opening cross-section is connected, which is greater than the encapsulation

determining opening cross-section.

2. The method according to claim 1, characterized in that in the

Pre-treatment phase over the at least one purge gas from the outer inert gas atmosphere and / or inert gas for purging in the reaction chamber of the capsule (7, 7a - 7d) is initiated.

3. The method according to claim 1 or 2, characterized in that at the end of

Pre-treatment phase and / or before direct bonding, the at least one

Flushing (1 1, 12, 14) is closed or at least closed so far that only the required for the encapsulation first opening cross-section remains.

4. The method according to any one of the preceding claims, characterized in that the opening and closing of the at least one flushing opening by raising and lowering a lid (10, 16) of or on the capsule (7, 7d) or of or on a base body (9, 9d) of the capsule and / or by opening and closing at least one lid or flap (1 3) takes place.

5. The method according to any one of the preceding claims, characterized in that when using capsules (7b) with at least one provided on at least one capsule wall rinsing opening and closing of the rinsing done by the fact that with open rinsing openings (14) the capsules (7b) are arranged such that the flushing openings (14) are exposed, and in the case of closed flushing openings (14), the capsules (7b) are arranged in such a way that they close close to one another in the region of the flushing openings (14).

6. The method according to any one of the preceding claims, characterized in that the at least one flushing opening of the capsules (7, 7a - 7d) is closed during a subsequent to the direct bonding cooling phase (C).

7. The method according to any one of the preceding claims,

and or

that in the process maximum allowable oxygen content in the outer Protective gas atmosphere increases with increasing encapsulation.

8. The method according to any one of the preceding claims, characterized in that the outer protective gas atmosphere at an encapsulation between 60 and 80% contains about 50 to 100 ppm oxygen,

and or

Contains 2 to 20 ppm oxygen,

and or

that the outer protective gas atmosphere at an encapsulation of 80-95% contains 50 to 200 ppm oxygen,

and or

Contains oxygen,

and or

that the outer protective gas atmosphere at an encapsulation greater than 95% oxygen in a proportion of less than 20 ppm or greater than 200, ppm contains.

9. metal-ceramic composite material, in particular metal-ceramic substrate (1), produced by the method according to one of the preceding claims.