WO2003097557A1

WO2003097557A1 - Method for producing a ceramic-copper composite substrate

Info

Publication number: WO2003097557A1
Application number: PCT/DE2003/001420
Authority: WO
Inventors: Jürgen SCHULZ-HARDER
Original assignee: Schulz-Harder Juergen
Priority date: 2002-05-15
Filing date: 2003-05-03
Publication date: 2003-11-27
Also published as: AU2003229282A1; JP2005525288A; CN1653016A; JP4368789B2; CN1323054C

Abstract

The invention relates to a method for producing a copper-ceramic composite substrate. According to said method, film blanks are oxidised on at least one surface, the oxidised film blanks are subsequently tempered in a protective gas atmosphere and then bonded with the ceramic by means of a DCB stage.

Description

Method of manufacturing a ceramic-copper composite substrate

The invention relates to the production of a ceramic-copper composite substrate which can be used, for example, as a printed circuit board for electrical circuits, in particular for electrical power circuits.

A plate-shaped ceramic material (ceramic layer or ceramic substrate) as well as from e.g. rolled copper foil used by cutting or punching, which are then connected to the ceramic layer using DCB technology. In this method, for example known from US Pat. No. 37 44 120 or from DE-PS 23 19 854, the film blanks are each provided with a layer of copper oxide on their surface sides. This layer forms a eutectic with a melting temperature below the melting temperature of the copper, so that by placing the foil on the ceramic and by heating all the layers, these can be connected to one another, specifically by melting the copper only in the area of the oxide layer.

This DCB method then has e.g. the following procedural steps:

• Oxidizing a copper foil so that there is a uniform copper oxide layer;

• placing the copper foil on the ceramic layer;

Heating the composite to a process temperature between about 1065 to 1083 ° C, e.g. to about 1071 ° C;

• Cool down to room temperature. A method for producing a ceramic-copper composite substrate (EP 0 335 679 B1) is known in particular, in which, as the starting material for the DCB process, foil blanks made of copper with the greatest possible hardness, namely with a Vickers hardness in the range from 100 to 150 kg / mm can be used. This is to ensure that the hardness of the copper metallizations produced is still sufficiently high even after the DCB process.

The object of the invention is to demonstrate a method which ensures an improved quality of the DCB connection between the copper and the ceramic, in particular also without defects in the flat connection between these materials and with a sufficiently high tear-off strength between the copper and the ceramic , A method according to claim 1 is designed to achieve this object.

The invention is based on the finding that a quality of the DCB connection which is significantly improved over the known methods can be achieved in that, in contrast to known methods, the hardness of the material of the film blanks at the beginning of the actual DCB process is less than 70 kg / mm ² is set and this can be reliably achieved by a tempering step preceding the DCB process.

Developments of the invention are the subject of the dependent claims. The invention is explained in more detail below with reference to the figures using exemplary embodiments. Show it:

Figure 1 in a simplified representation and in section a copper-ceramic composite substrate, produced by the method according to the invention. 2 to 5 the process steps in different processes according to the

Invention; Fig. 6 shows the process steps for only one-sided oxidation of the film blanks.

In the figures, 1 generally designates a copper-ceramic composite substrate which was produced using the DCB process and has a ceramic layer 2 (for example made of aluminum nitride ceramic), each of which has a metallization formed by a copper foil on its two surface sides 3 or 4 is provided.

In the method shown in FIG. 2, the ceramic layer 2 and foil cuts 3 'and 4' made from a copper foil 5 are used to produce the substrate 1. The latter is produced by rolling and therefore has a Vickers hardness greater than 70 kg / mm. The blanks 3 'and 4' are obtained, for example, from the copper foil 5 by punching.

In a process step denoted by A1 in FIG. 2, the film blanks 3 'and 4' are oxidized, in particular also on their surface sides, for example using a suitable chemical oxidation process, so that as a result of this process step the film blanks 3 'and 4' on their surface sides in each case are provided with a copper oxide layer 6, which forms the eutectic melting layer in the later DCB process.

In a further process step, designated B1 in FIG. 2, the film blanks provided with the oxide layer 6 are then tempered, specifically in a protective gas atmosphere and at a temperature in the range between 200 and 400 ° C., specifically over a period of 2 to 20 minutes so that the Vickers hardness of the film blanks 3 'and 4' as a result of the tempering then is well below 70 kg / mm. For the purposes of the invention, “protective gas atmosphere” is to be understood as an atmosphere which contains no oxygen or in which the oxygen content is negligible.

Method step B1 Tensions which arise, for example, from the rolling of the copper foil 5 and / or from the punching of the foil blanks 3 'and 4' removed from the copper material. Furthermore, it has been shown that the greatly reduced hardness of the film blanks 3 'and 4' achieved with process step B enables a DCB connection with significantly improved quality to be achieved in the subsequent DCB process.

In a subsequent process step C1, the oxidized and tempered film blank 3 'and the ceramic layer 2 (ceramic substrate) are brought together, so that in a further process step D1 to form the metallization 3, the film blank 3' using the DCB process with the ceramic substrate 2 is flat can be connected (first DCB step).

In a further process step E1, the ceramic substrate 3, which had hitherto been provided with the metallization 3 only on one side, is brought together with the oxidized and tempered film blank 4 ', so that in a further process step F1 for forming the metallization 4, the film blank 4' is also used using the DCB -Process (second DCB step) can be connected to the ceramic layer 2 and so the desired copper-ceramic composite substrate 1 is obtained.

In the process described, film cuts 3 'and 4' with a very low Vickers hardness of less than 70 kg / mm ² are deliberately used as the starting material for the DCB process (process steps D1 and F1). As a result, the quality of the DCB connection between the ceramic and the respective metallization 3 or 4 made of copper significantly improved. This is apparently due to the fact that the copper material is stress-free due to the tempering and because of the reduced hardness of the foil blanks, the foil blank is optimally clinging to the surface of the ceramic layer 2 at the beginning of the respective DCB process.

FIG. 3 shows the individual method steps in a further possible embodiment of the method according to the invention for producing the copper-ceramic composite substrate 1. The following method steps are used in this method: A2 oxidizing B2 tempering

C2 merging the ceramic layer 2 with film blank 3 'D2 first DCB step E2 merging the ceramic layer 2 metallized on one side with

Foil cut 4 'F2 second DCB step

The method shown in FIG. 3 differs from the method in FIG. 2 essentially in that the foil blanks 3 'and 4' obtained from the copper foil 5 are first annealed in method step B2, again in a protective gas atmosphere at a temperature in the range between 200 and 400 ° C over a period of two to twenty minutes, so that the Vickers hardness of the film blanks 3 'and 4' as a result of this tempering is clearly below 70 kg / mm ² (process step B2). It is only in the next process step A2 that the tempered film blanks 3 'and 4' are oxidized, ie the sequence of process steps A2 and B2 in the process shown in FIG. 3 is interchanged with the process in FIG. By the annealing preceding the oxidation, the oxidation or the formation of the Oxide layers 6 significantly simplified. The further method steps in the method in FIG. 3 correspond to the method steps in FIG. 2.

FIG. 4 shows a further embodiment of the method according to the invention. The following process steps are used in this process:

A3 Oxidize

B3 tempering

B3 'tempering

C3 merging the ceramic layer 2 with the film blank 3 '

D3 first DCB step

E3 merging the one-sided metallized ceramic layer 2 with

Foil cut 4 'F3 second DCB step

In this embodiment, once the foil blanks 3 'and 4' have been produced, the foil blanks 3 'and 4' are oxidized to form the oxide layers 6, for example by punching them out of the copper foil 5 in method step A3.

After the oxidation (process step A3), in this embodiment the invention takes place in a process step C3, the merging of the oxidized film cut 3 'with the ceramic layer 2. Subsequently, the process step B3 is used for the annealing of the oxidized film cut 3', the tempering of the Ceramic layer 2 serves as a support for the oxidized film blank 3 '. The tempering is again carried out at a temperature between 200 to 400 ° C in a protective gas atmosphere and with a duration between 2 and 20 minutes so that the film blank 3 'has a Vickers hardness significantly less than 70 kg / mm ² as a result of process step B3 has, with which, among other things, all tensions are removed from the material of the film blank 3 '. In a subsequent process step D3, the pre-oxidized and tempered film blank 3 'is then connected to the ceramic layer 2 by means of the DCB process to form the metallization 3. In a further process step E3, the pre-oxidized film blank 4' is applied to the surface side of the metal coating 3 facing away Ceramic layer 2 placed. In a subsequent process step B3 ', the oxidized film blank 4' is then again tempered at a temperature of 200 to 400 ° C and in a protective gas atmosphere for a period of 2 to 20 minutes, so that the Vickers hardness of the film blank 4 'after completion this process step is definitely well below 70 kg / mm ² .

In a further process step F3, the oxidized and tempered film blank 4 'is connected to the ceramic layer 2 using the DCB process in order to produce the metallization 4, so that the desired ceramic-copper composite substrate 1 is finally obtained.

FIG. 5 shows, in a representation similar to FIG. 4, the individual method steps in a modified embodiment of the method according to the invention

Manufacture of the copper-ceramic composite substrate 1.

The following process steps are used in this process:

A4 oxidize

A4 'Oxidize

B4 tempering

C4 bringing the ceramic layer 2 together with the film blank 3 '

D4 first DCB step

E4 Merging the ceramic layer 2 metallized on one side with

Foil cut 4 'F4 second DCB step G4 turning the film cut 3 'G4' turning the film cut 4 '

In the process shown in FIG. 5, similar to the process in FIG. 3, the film blanks 3 'and 4' obtained from the copper foil 5 are first annealed in a process step B4, again in a protective gas atmosphere at a temperature in the range between 200 and 400 ° C and over a period of two to twenty minutes, so that as a result of this treatment, the film cuts 3 'and 4' have a Vickers hardness of less than 70 kg / mm ² . In a subsequent method step C4, the ceramic layer 2 and the tempered film blank 3 'are brought together. Then, in a method step A4, the film blank 3 'resting on the ceramic layer 2 is oxidized, ie the copper oxide layer 6 is formed at least on the surface side of the film blank 3' facing away from the ceramic layer 2. In an additional process step G4, the film blank 3 'is turned so that this cut then lies with its copper oxide layer 6 on the ceramic layer 2 and so in process step D4 the film blank 3' for forming the metallization 3 using the DCB -Process can be connected to the ceramic substrate 2 (first DCB step).

In a further method step E4, the tempered film blank 4 'is brought together with the ceramic layer 2 metallized on one side, so that in a method step A4' the foil blank 4 'resting on the ceramic layer 2' is oxidized at least on its surface side facing away from the ceramic layer 2. The film blank 4 'is then turned in a method step G4', so that it rests with its oxide layer 6 on the ceramic layer 2 and then in the method step F4 the foil blank 4 'by means of the DCB Process (2nd DCB step) to form the metallization 4 with the ceramic layer 2 is connected.

The oxidation of the film cut 3 '(process step A4) or the film cut 4' (process step A4 ') takes place, for example, in each case by thermal oxidation.

It was assumed above that, at least in the method of FIGS. 2-4, the film blanks 3 'and 4' are oxidized on their two surface sides, i. H. be provided with the oxide layer 6. FIG. 6 shows a method in which the film blanks 3 ′ and 4 ′ are each provided only on one surface side of the oxide layer 6. The starting material is again the copper foil 5, from which the foil blanks 3 'and 4' are produced by cutting or punching. In a method step H, the film blank 3 is first placed with a surface side on an auxiliary body 7, which is made in the form of a plate from a rubber-elastic material. In a further method step I, the film blank 4 'is placed on the other surface side of the auxiliary body 7. By evacuating cavities 8 formed in the auxiliary body, the film cuts 3 'and 4' are each detachable again by vacuum, but are fixed flat and close to the auxiliary body 7, so that only a single surface side of each film cut 3 'or 4' is exposed and this surface side is then provided with the copper oxide layer 6, for example by chemical oxidation.

The tempering of the film cuts 3 'and 4' in the protective gas atmosphere at a temperature between 200 and 400 ° C for a period of two to twenty minutes to achieve the Vickers hardness well below 70 kg / mm is then carried out either before process step H or but following process step A5. The further processing of the tempered and oxidized film blanks 3 'and 4' then takes place, for example, in accordance with the method in FIG. 2, although the film blanks are of course placed on the ceramic layer 2 with their surface side formed by the oxide layer.

The invention has been described above using exemplary embodiments. It goes without saying that changes and modifications are possible without thereby departing from the inventive idea on which the invention is based.

LIST OF REFERENCE NUMBERS

Ceramic-copper composite substrate ceramic layer, 4 metallization from copper ', 4' cut from copper foil copper foil oxide layer auxiliary body

Claims

claims

1 . Process for producing a copper-ceramic composite substrate with the following process steps:

(a) Production of foil blanks (3 ', 4') from a copper foil;

(b) oxidizing the film blanks (3 ', 4') on at least one of their surface sides to form a copper oxide layer (6) on this surface side;

(c) annealing the oxidized film blanks (3 ', 4') in a protective gas atmosphere at a temperature in the range between 200 and 400 ° C and for a period of 2 to 20 minutes to achieve a Vickers hardness for the film material less than 70 kg / mm ² ;

(d) producing the ceramic-copper composite substrate by connecting at least one oxidized and tempered film blank (3 ', 4') lying on at least one surface side of a ceramic layer (2) to the ceramic layer by heating in a protective gas atmosphere to a DCB temperature below the Melting point of copper, but above the eutectic temperature of the copper / oxygen system; and

(e) cooling the obtained ceramic-copper composite substrate to room temperature.

2. Method for producing a copper-ceramic composite substrate with the following method steps:

(a) Production of foil blanks (3 ', 4') from a copper foil;

(b) tempering the oxidized film blanks (3 ', 4') in a protective gas atmosphere at a temperature in the range between 200 and 400 ° C and for a period of 2 to 20 minutes to achieve a Vickers hardness for the film material less than 70 kg / mm ² ;

(c) oxidizing the film blanks (3 ', 4') on at least one of them Surface side to form a copper oxide layer (6) on this surface side;

3. The method according to claim 1 or 2, characterized in that the film blanks are each oxidized on their two surface sides to form an oxide layer (6).

4. The method according to claim 1 or 2, characterized in that the film blanks (3 ', 4') are each oxidized on one surface side to form an oxide layer (6).

5. The method according to any one of the preceding claims, characterized in that at least one oxidized and annealed film blank (3 ', 4') is applied to both surface sides of the ceramic layer (2) by means of the DCB process.

6. The method according to claim 5, characterized in that the annealing of the film blanks (3 ', 4') takes place before the oxidation.

7. The method according to claim 5, characterized in that the annealing of the film blanks (3 ', 4') takes place after the oxidation.

8. The method according to any one of the preceding claims, characterized in that the annealing of the film blanks (3 ', 4') is carried out in each case on the ceramic layer (2) resting blanks.

9. The method according to any one of the preceding claims, characterized in that the oxidation of the film blanks is carried out by wet chemical oxidation.

10 Method according to one of the preceding claims, characterized in that the film blanks (3 ', 4') are oxidized by thermal oxidation.

1 1 .Method according to one of the preceding claims, characterized in that the oxidation of the film blanks (3 ', 4') is carried out using oxygen or in a protective gas atmosphere containing oxygen, for example in a nitrogen atmosphere with an oxygen content of up to 20%.

12 Method according to one of the preceding claims, characterized in that the film blanks (3 ', 4') are tempered during the oxidation.

13 Method according to one of the preceding claims, characterized in that the film blanks (3 ', 4') are oxidized with the film blank (3 ', 4') resting on the ceramic layer (2).

Process according to one of the preceding claims, characterized in that, in the case of only one-sided oxidation, the film blanks (3 ', 4') before the DCB process be turned.