COPPER-CERAMIC COMPOSITE

Abstract

The present invention relates to a copper-ceramic composite comprisinga ceramic substrate which contains aluminum oxide, the aluminum oxide having particle sizes in the range of 0.01 m to 25 m and a quantity distribution of the particle sizes with a median value d.sub.50 and an arithmetic mean value d.sub.arith, and the ratio of d.sub.50 to d.sub.arith being in the range of 0.75 to 1.10, a coating made of copper or a copper alloy provided on the ceramic substrate.

Claims

1. A copper-ceramic composite comprising a ceramic substrate containing aluminum oxide, wherein the aluminum oxide has grain sizes in the range from 0.01 m to 25 m and has a number distribution of the grain sizes with a median value d.sub.50 and an arithmetic mean d.sub.arith, and the ratio of d.sub.50 to d.sub.arith is in the range from 0.75 to 1.10, and a coating composed of copper or a copper alloy present on the ceramic substrate.

2. The copper-ceramic composite of claim 1, wherein the ratio of d.sub.50 to d.sub.arith is in the range from 0.78 to 1.05, more preferably in the range from 0.80 to 1.00.

3. The copper-ceramic composite of claim 1, wherein the aluminum oxide has a number distribution of the grain sizes with a d.sub.5 value and a d.sub.95 value, and the ratio d.sub.5 to d.sub.95 is in the range from 0.1 to 0.4, more preferably in the range from 0.11 to 0.35, even more preferably in the range from 0.12 to 0.30.

4. The copper-ceramic composite of claim 1, wherein the grain sizes of the aluminum oxide are in the range of 0.3 m to 23 m, more preferably in the range of 0.5 m to 20 m.

5. The copper-ceramic composite of claim 1, wherein the ceramic substrate contains the aluminum oxide in an amount of at least 65% by weight.

6. The copper-ceramic composite of claim 1, wherein the coating composed of copper or a copper alloy is applied by a DCB process to the ceramic substrate.

7. The copper-ceramic composite of claim 1, wherein the coating composed of copper or a copper alloy at least partly has structuring to form electrical contact areas.

8. The copper-ceramic composite of claim 1, wherein the coating composed of copper or a copper alloy has a thickness in the range of 0.2-1.2 mm over at least 70% of its area; and/or the ceramic substrate has a thickness in the range of 0.2-1.2 mm over at least 70% of its area.

9. A module containing at least one copper-ceramic composite according to claim 1 and one or more bond wires.

Description

EXAMPLES

[0113] The following examples show how the grain structure of the aluminum oxide in the ceramic substrate influences the mechanical strength and the thermal conductivity of a copper-ceramic composite.

[0114] Five copper-ceramic specimens were produced by a DCB process and differed in their grain size distributions of the aluminum oxide in the ceramic substrate:

Copper-ceramic composite 1, hereinafter K-K-V 1 (according to the invention)
Copper-ceramic composite 2, hereinafter K-K-V 2 (comparative specimen)
Copper-ceramic composite 3, hereinafter K-K-V 3 (comparative specimen)
Copper-ceramic composite 4, hereinafter K-K-V 4 (comparative specimen)
Copper-ceramic composite 5, hereinafter K-K-V 5 (comparative specimen)

[0115] In each of these five copper-ceramic composites, both the upper side and also the underside of the ceramic substrate were provided with a copper coating. The copper coating was firstly bonded by means of the SLB process to one side of the ceramic substrate. The opposite side of the ceramic substrate was subsequently provided by means of the SLB process with a further copper coating so as to form a copper-ceramic substrate in which a copper foil is bonded to each of the two sides of the ceramic. One of the two copper coatings on each of the specimens was subsequently structured by an etching process (same structuring for all specimens). In all three examples, the substrates comprised 96% by weight of Al.sub.2O.sub.3, but differed in their grain structure.

[0116] In each of these five copper-ceramic composites, the ceramic substrate had the following dimensions:

Thickness of the ceramic substrate: 0.38 mm;
Lengthwidth of the ceramic substrate: 190140 mm.sup.2

[0117] The copper coating in each case had a thickness of 0.3 mm.

[0118] FIG. 5 shows an SEM image of the surface of the ceramic substrate of K-K-V 1, by means of which the Al.sub.2O.sub.3 grain sizes of the working example K-K-V 1 were determined.

[0119] Grain size ranges and symmetry values of the grain size distributions of the Al.sub.2O.sub.3 in the specimens K-k-V-1 to K-K-V 5 are listed in table 1.

[0120] For each of these five specimens, determinations were made both of the flexural fracture strength and of the thermal conductivity of the ceramic substrate in the copper-ceramic composite.

[0121] In the determination of the flexural fracture strength the force resulting in fracture was determined via three-point bending. The measurement was based on DIN EN 843-1 (2008), with the specimen geometry differing from the DIN EN 843-1 (2008) in that the specimens had dimensions of 20400.38 mm.sup.3 or 20400.63 mm.sup.3.

[0122] The results are summarized in table 1 below:

TABLE-US-00001 TABLE 1 Mechanical strength and thermal conductivity of the ceramic substrate of the copper-ceramic composite Mechan- Thermal ical conduc- strength tivity Specimen K-K-V Grain size range: 0.63-13.3 m ++ ++ 1 (according to Symmetry value d.sub.50/d.sub.arith: 0.86 the invention) Specimen K-K-V Grain size range: 0.74-15.1 m ++ 2 (comparison) Symmetry value d.sub.50/d.sub.arith: 0.66 Specimen K-K-V Grain size range: 0.58-9.7 m ++ 3 (comparison) Symmetry value d.sub.50/d.sub.arith: 1.31 Specimen K-K-V Grain size range: 3.1-28.4 m + + 4 (comparison) Symmetry value d.sub.50/d.sub.arith: 0.84 Specimen K-K-V Grain size range: 0.003-1.49 m +++ 5 (comparison) Symmetry value d.sub.50/d.sub.arith: 0.85

[0123] Additionally, the effect of the breadth of the grain size distribution of the aluminum oxide on mechanical strength and thermal conductivity was investigated. The results are shown by table 2.

TABLE-US-00002 TABLE 2 Effect of the breadth of the Al.sub.2O.sub.3 grain size distribution Breadth of Al.sub.2O.sub.3 Distribution d.sub.5/d.sub.95 Mechanical strength Thermal conductivity 0.24 + + 0.03 + 0.61 +

[0124] As table 2 shows, a further optimization of mechanical strength and thermal conductivity on the part of the ceramic substrate can be achieved if the breadth of the grain size distribution is within the range according to the invention.