DE10355983B4 - Method for soldering ceramic surfaces - Google Patents

Abstract

method for producing a solder joint for metal-ceramic compounds or ceramic-ceramic compounds, wherein at least one of the to be soldered ceramic surfaces (9) before soldering by Introduction of holes (4) is structured, characterized that the holes (4) have a mean diameter greater than 550μm have.

Description

The The present invention relates to a method of soldering ceramic surfaces, in particular a method for producing a solder joint for metal-ceramic compounds or ceramic-ceramic compounds, wherein at least one of the to be soldered ceramic surfaces before soldering through Introduction of drilling is structured.

Out EP 0 476 772 is already a method for producing a solder joint in metal-ceramic composites or ceramic-ceramic composites known, wherein at least one of the ceramic surfaces to be soldered prior to soldering by introducing conical holes with a uniform diameter, uniform depth and uniform spacing between the Holes using a laser is structured. The holes have a mean diameter in the range of 50 microns to 500 microns and a depth in the range of 100 microns to 2 mm. However, this method has certain disadvantages, which will be discussed below.

essential Influence factor on the usability of ceramic-ceramic compounds or Metal-ceramic compounds is a mechanically good, often high-temperature resistant cohesive connection between the individual components. Because the materials to be joined are often strong have different thermal expansion coefficients comes it both after the joining process as well as under stress induced stress states, the affect the strength of the connection zone and in extreme cases even to destroy.

Around the strength of such a joining zone To optimize, in particular, the surface of the ceramic material be enlarged. This can be done by surface structuring, such as the introduction of grooves or grooves by mechanical processing be achieved. This measure but is not always sufficient for a sufficient strength the solder joint to ensure. Also introduced by the introduction of through holes with Grooves on the ceramic surface can not due to the small number of holes and the bore dimensions significant increase in strength observed by enlarging the soldering surface become. An introduction of non-continuous holes in the ceramic material has proved to be more advantageous and can also in particular Framework of the present invention find application.

A disadvantage of the method of EP 0 476 772 On the one hand, that the structuring effort is very high for the dimensions given there and there is the danger that, due to the selected dimensions, sufficient filling of the holes with solder material can not always be guaranteed. Especially for fiber-reinforced ceramics with a two-dimensional layer structure of the fibers, ie with typical laminate structure, there is the further problem that under load the shear stresses in the laminate become too high and the fiber-reinforced ceramic component fails interlaminar. This can be done by the in EP 0 476 772 given design of the holes are only partially prevented.

The DE 33 23 830 A1 describes an arrangement for soldering an electrical circuit board to a base body.

To the soldering a z. B. ceramic substrate existing electrical circuit board on a basic body with the help of a solder foil is the total surface of the the body by capillary-like depressions, z. B. parallel longitudinal grooves, in a uniform manner broken into many small defined partial areas. The wells receive a predictable amount of solder, excess solder flows However, in a groove bottom. As a result, mechanical shear stresses, which cracks and can lead to the destruction of the ceramic substance, considerably reduced. Furthermore becomes during the soldering process a floating of the circuit board on liquid solder and thus a change prevents the position of the circuit board. The invention is for solder joints between circuit boards and their supports in general, for solder joints of ceramic substrates in microwave circuits in particular.

task The object of the present invention is to overcome the disadvantages of the prior art Technique to fix and an improved method of manufacture a solder joint in metal-ceramic compounds or ceramic-ceramic compounds provide.

One The first object of the invention relates to a process for the preparation a solder joint in metal-ceramic compounds or ceramic-ceramic compounds, wherein at least one of the ceramic to be soldered Surfaces before soldering is structured by introducing holes. According to the invention is provided in this first item that the holes a mean diameter greater than 550μm, preferred bigger or equal to 600μm, exhibit. The holes therefore have a much larger diameter as those of the prior art. This allows the Disadvantages of the structuring effort and the filling with Solder material to be corrected.

In a combination with this object of the invention or alternatively to this object of the invention can be provided that at least two classes of drill holes are introduced, where the holes of one class from those of another class at least differ in bore geometry, bore diameter or bore depth. Also, the structuring and filling at least for one Part of the drilling will be simplified, as at least for one class the corresponding parameters can be chosen so that the desired Benefits occur. The other special feature of this item The invention resides in the possibility provide an alternate hole depth so that for the particular Case of a two-dimensional fiber-reinforced ceramic material eventually occurring stresses distributed in different laminate layers become. As a result, the acting deformation energy is effective dissipated. By this technical measure so the coupling of near-surface and remove surfaces Layers in fiber reinforced Ceramic composite are created.

Especially can be provided that at least one bore of a first Class and at least one hole of a second class in shape a geometric group are introduced. So it will not be only holes evenly distributed and at a uniform distance arranged one another, but it is always a geometric Grouping a certain number of holes, then this Groupings over the surface to be structured Repeat distributed. It can all geometric groups have an identical geometric structure can or can also several geometric groups of different geometrical Structure over the surface Repeat distributed. In particular, it may be provided that the spacing of the holes within a geometric group is lower is the distance of the geometrical centers of two geometric ones Groups. The distance between the holes is always the distance the bore centers understood from each other.

Especially may be a method according to the invention for producing a solder joint to a ceramic material with laminate structure of several layers be used. According to the invention is provided that the holes with a hole depth be introduced, which is larger as the thickness of the outermost Laminate layer. This can be achieved that after soldering the occurring loads distributed over more than one layer of laminate and an introduction of force into deeper layers of the ceramic material he follows. This is particularly advantageous for absorbing shear forces the ceramic material. In particular, with such a method a delamination of the utmost Laminate layer avoided by external forces become.

This Method may, for example, for producing a solder joint to a fiber-reinforced ceramic material used, which is a laminate structure of several layers with different, periodically repeating fiber orientation having. According to the invention is provided here that the holes with a hole depth be introduced, which is equal to or greater than the distance from the surface of the ceramic material up to that layer of the laminate structure, the same fiber orientation as the top layer of the laminate structure having. Since the fibers according to their Orientation in the fiber longitudinal direction a particularly high ability for power absorption or load absorption within the ceramic material have, by this measure me achieved that a load absorption in all orientation directions the fibers and thus in as possible largely optimized in two dimensions. The external loads or forces are in turn by the filled with solder holes transferred to the corresponding laminate layers.

A method according to the invention can also be used for producing a soldered connection to a fiber-reinforced ceramic material such that the spacing of the holes is at least the bore diameter plus 5 times, in particular plus at least 10 times, preferably plus at least 25 times the diameter of a fiber of the fiber-reinforced ceramic material , Here again, the distance between the bore centers is understood as the distance between holes. The distance between adjacent edges of the holes is therefore only 5 times, 10 times or 25 times the diameter of a fiber. By this measure, it is guaranteed that a relatively large number of intact fibers always remain between two holes, so that the laminate structure has a relatively high strength due to the remaining number intact Has fibers.

Especially can be provided that the number of holes, bore diameter and Hole geometry selected be that through the holes the surface area of the ceramic Surface and / or each cross-sectional area by the ceramic material by a maximum of 50%, in particular by a maximum 25% compared an identical body is reduced without drilling. The holes cause a reduction of the material-filled Volume of the ceramic material and thus a structural weakening of the Material. By this measure can guarantee a continued good stability of the ceramic material become.

A especially cheap embodiment The invention provides that the distance between the holes between 50% and 150%, in particular between 75% and 125% of one the hole depths is. In this case, so the distance between the holes in the area of Magnitude one of the bore depths or substantially equal to one of the bore depths.

In principle, after the structuring of the surface to be soldered, a solder material can be applied directly to the corresponding surface according to one of the known methods of the prior art. A development of the invention provides that, after the structuring of the surface to be soldered, a flexible shaped body which contains at least solder material is applied to the structured surface. Such flexible moldings are basically known from the prior art, for example DE 38 01 958 , With such moldings, on the one hand larger structural distances between the elements to be soldered can be bridged, on the other hand causes the shaped body after soldering and a certain balance of different thermo-mechanical properties of the soldered materials.

One Another object of the invention is a process for the preparation a rocket engine made of ceramic elements or ceramic elements and metal elements, wherein at least some of the elements after a method described above for producing a solder joint get connected. It can basically any elements of the rocket engine according to such a method connected, such as elements of a rocket combustion chamber with each other, elements of a rocket nozzle with each other or elements an injection head with each other. There can also be connections between Injection head and rocket combustion chamber or rocket combustion chamber and rocket, or between corresponding elements of these components, after one be created in such proceedings.

Specific embodiments of the present invention will be described below with reference to FIGS 1 to 8th described.

It demonstrate:

1 : Textured ceramic surface with two classes of holes

2 : Textured ceramic surface with a geometric group of holes

3 : Textured ceramic surface with a first alternative geometric group of holes

4 : Textured ceramic surface with a second alternative geometric group of holes

5 : Schematic representation of the preparation of a solder joint using a soldering mat

6 : Schematic representation of the introduction of the holes by means of laser

7 Schematic cross section through a fiber-reinforced ceramic with laminate structure and holes

8th as 7 , wherein the distance of the bores is substantially equal to the bore depth.

Ceramic components, in particular of fiber-reinforced ceramic, gain due to their herausra technical properties are becoming increasingly interesting and finding ever-growing areas of application. The advantage, in particular of fiber-reinforced high-performance ceramics, is their excellent wear resistance, high temperature resistance, good resistance to corrosion and low specific weight.

Metal-ceramic compounds enable the combination of the advantages of metallic and ceramic materials. This requires suitable joining methods. A possibility of joining of metal and ceramics represents soldering dar. This cohesive joining process allows Vacuum-tight and high-temperature resistant connections with high Strength. It is also characterized by its suitability for mass production also for Components with many, difficult to access joints out.

there There is the problem that ceramics are due to conventional solders the different atomic bond of ceramic and solder not wetted become. Only through the use of active elements (eg Ti, Hf, Zr) can be over a Reaction zone at the interface transition Metal / ceramic realize a connection.

• • Löten metallisierter Keramik und
• • Aktivlöten.

For brazing metal with ceramic and ceramic with ceramic, there are two principles of operation

• • Soldering metallized ceramics and
• • Active soldering.

At the Solder metallized monolithic ceramics will be the joining surface of the ceramic component coated with a metal, so that subsequently in the Soldering the wetting of the ceramic joining partner allows conventional solders becomes. This is a big one Selection of solders and soldering methods to disposal, which can be adapted to the application. It is possible the item to be soldered with as possible low soldering temperature ductile to the soldering of metal and ceramic inevitably resulting thermal stresses to minimize.

But also high temperature resistant solder connections are by soldering metallized ceramic possible. Since the active element already at the beginning of the soldering process on the surface of the Ceramic is the formation of strength-reducing brittle phases in the soldered structure reduced. Compared to the active soldering is a significant better flow and gap filling capacity.

The active soldering is a direct soldering process, in which the active element is added directly to the solder. The advantage across from the soldering metallized ceramic is that on the complex metallization the ceramic is dispensed with. However, the solder must be applied directly to the joint surface because active solders have only a low fluidity. Both the active soldering as also the soldering metallized ceramic can done in vacuum or inert gas.

At the Solder of ceramics with metals is basically the problem that conventional solders can not connect to ceramics. The cause lies in the different atomic bond of the ceramics with their predominantly ionic or covalent bonds, those of solders with their metallic ones Atomic bond can not be wetted.

By the use of an active element, e.g. Titanium is possible, the ceramic surfaces so that they can be wetted by the solder. The Main problems in the production of solder joints between ceramics and metal such as e.g. Steel consists in the wetting of the ceramic through the lot as a basic requirement for creating a connection and in the tensions that arise in the solder joint due to the different thermal expansion the joint partners involved form and thus in addition to the brittle phase the strength interfere with the connection.

The Formation of the solder joint is essentially due to diffusion-controlled reaction mechanisms affected. On the one hand, the surface of the ceramic is converted in this way, that they can be wetted by the solder, on the other hand, can while of soldering brittle phases form, which leads to a reduction in the strength of the solder joint to lead.

In the production of metal-fiber composites and ceramic-reinforced-ceramic (CMC) composites, the difference in thermal expansions of the different materials is the major problem. Especially for 2D-reinforced CMC components, ie components made from a CMC composite two-dimensional fiber structure is present, produced for example via a laminating technology, the danger is great that under thermal stress, the shear stresses are too high and the kerami interlaminar, ie intermediate in its weakest point, fails.

The aforementioned problems can be resolved by the present invention. All the above technical measures are basically also applicable in the context of the present invention.

The present invention overcomes the mentioned disadvantages by providing a sufficient enlargement of the interface surface and the coupling of surface-distant layers in the ceramic material, in particular in applications in fiber-reinforced materials. To achieve this, the ceramic material is structured on its surface with a defined number of holes. 6 shows an example of the production of holes 4 in a ceramic material 2 , For example, a laser can do this 5 , eg a Nd: YAG laser. However, it is also possible to use suitable mechanical or other drilling means, such as, for example, spark erosion agents. The one with a laser 5 generated laser beam 9 can via an X-scanner 6 and a Y-scanner 7 be deflected in two spatial directions X, Y and with a suitable optics 8th , For example, a planar field optics, on the surface to be structured of the ceramic material 2 be focused. The laser has the advantage that it can be used independently of geometry, economically and automatically.

It is now preferably provided that two classes A, B are provided by bores which have at least one alternating drilling depth. That is, a first class of holes has a - except for usual manufacturing tolerances - uniform first depth, a second class of holes a second depth, which is different from the first depth (see also 5 ). Preferably, the two classes A, B also each have a different bore diameter a, b, wherein the bore diameter within the class - is - except for usual manufacturing tolerances - uniform. As a result of this measure, any stresses which may occur in the case of ceramic materials with a laminar structure can be distributed in different laminate layers, so that the applied energy is dissipated. Example:

One such example is in 1 shown. Thus, the average bore diameter is well above 550 microns. In this example, the holes of class A and the holes of class B are each alternating in the surface 9 a ceramic material structured. The geometry of the holes of class A and B is identical in this example: The holes have a cross-sectional area that corresponds to a square with rounded corners, and the holes are tapered into the material, so are cone-shaped (see also 5 and 6 ). But there are also fundamentally different hole geometries possible. The above values may be used for the following embodiments.

2 shows an alternative embodiment, a structured ceramic surface 9 that just like the example after 1 has two classes A, B of bores of average diameter a, b. In each case a hole of class A and a hole of class B form a geometric group 10 namely, a pair of holes as the simplest possibility of a geometric group. This geometric group 10 Repeats over the ceramic surface 9 time. The distance of the holes x within the geometric group 10 is less than the distance d of the geometric centers of two adjacent geometric groups 10 ,

3 shows an embodiment with an alternative geometric group form 11 , where respectively 5 Holes class A and 4 Class B holes into a square geometric group 11 are summarized, in turn, over the surface 9 repeated. Again, the distance of the holes x is within the geometric group 11 less than the distance d of the geometric centers of two adjacent geometric groups 11 ,

4 shows an embodiment with a further alternative geometric group form 12 , whereby in each case a drilling of the class A and 8th B holes of class B annular around the hole of class A to a geometric group 12 are summarized, in turn, over the surface 9 repeated. The distance of the holes x within the geometric group is in 4 for reasons of simplicity not shown, but is clearly less than the distance d of the geometric centers of two adjacent geometric groups 12 ,

In a subsequent process step can be provided either that the perforated surface 9 is metallized by means of active soldering. Here, the metal coating is also in the holes 4 deposited. The result is an interface between the ceramic material, such as C / SiC, and metal, by penetrating metallic needles with a defined depth in the ceramic material. For soldering with the metal element to be joined, for example, solder foils can be used.

For soldering larger gaps between ceramic and metal and for bridging large differences in the thermo-mechanical properties of the materials (differences in the coefficient of thermal expansion TAK) of the respective materials can flexible moldings 3 used, which contain at least one solder material, as in 5 shown. The moldings may be formed, for example, as solder mats. Such flexible solder mats can also contain materials for activating the ceramic surface in addition to the solder - such as in particular the above-mentioned active elements. Thus, such solder mats offer an advantageous combination of compensation for thermo-mechanical differences, surface activation and a simple and inexpensive solder application.

As 5a) shows, first a soldering mat 3 on a textured surface 9 a ceramic element 2 applied. The ceramic surface 9 has conical holes 4 with alternating hole depth on. Subsequently, a metallic element 1 on the soldering mat 3 applied and it will be the two elements 1 . 2 with the help of the soldering mat 3 soldered. After soldering, the soldering mat remains 3 with a certain flexibility between the soldered elements 1 . 2 where the holes 4 filled with solder material, as in 5b) shown.

7 shows a schematic cross section through a fiber-reinforced ceramic element 2 with a laminate structure of several layers 21 . 22 . 23 . 24 wherein the layers each have a different, periodically repeating fiber orientation. In shift 21 and 23 the fibers lie in the plane of the drawing, in layer 22 and 24 the fibers are perpendicular to the plane of the drawing, as shown schematically in 7 shown. The thickness of the laminate layer 21 is denoted by d _S , the distance from the surface 9 of the ceramic material up to the layer 23 the laminate structure, which has the same fiber orientation as the top layer 21 has the laminate structure is denoted by d _P. The diameter of the fibers is typically a few micrometers, for example between 1 and 5 .mu.m, in particular between 2 and 4 .mu.m.

In 7 For the sake of simplicity, it is a cross section through the ceramic material 2 shown, in which only the same size holes. The holes 4 have a distance x (distance of the bore centers) and a diameter a. The distance x is greater than the bore diameter a plus 5 times the diameter of a fiber, in particular based on the layer 22 is recognizable. It's in the layer 22 So at least five intact fibers between two holes 4 ,

The holes 4 in 7 have a hole depth L that is greater than the thickness d _{S of} the outermost laminate layer 21 , namely a depth L equal to the distance d _P from the surface 9 is. The corresponding advantages have already been described at the beginning.

8th shows essentially the same arrangement as 7 , wherein the distance x of the bores is substantially equal to the bore depth L. The hole depth L is less than the distance d _P from the surface this time 9 but still larger than the thickness d _{S of} the outermost laminate layer 21 , Again, the corresponding benefits have already been described at the outset.

Example:

at a hole depth L of 1.1 mm for class A holes such as already described may preferably a bore distance x be chosen in the range of 1.0 to 1.3 mm.

Claims (11)

Process for producing a solder joint in metal-ceramic compounds or ceramic-ceramic compounds, wherein at least one of the ceramic surfaces to be soldered ( 9 ) before soldering by introducing holes ( 4 ), characterized in that the holes ( 4 ) have a mean diameter greater than 550μm. Method according to claim 1, characterized in that at least two classes (A, B) of bores ( 4 ), whereby the bores ( 4 ) of one class (A) differ from those of another class (B) at least in bore geometry, bore diameter (a, b) or hole depth (L). Method according to one of claims 1 or 2, characterized in that at least one bore ( 4 ) of a first class (A) and at least one bore ( 4 ) of a second class (b) in the form of a geometric group ( 10 . 11 . 12 ) are introduced. Method according to claim 3 , characterized in that the distance (x) of the holes ( 4 ) within a geometric group ( 10 . 11 . 12 ) is less than the distance (d) of the geometric centers of two geometric groups ( 10 . 11 . 12 ). Method according to one of claims 1 to 4 for producing a solder joint to a ceramic material ( 2 ) with a multilayer laminate structure ( 2i . 22 . 23 . 24 ), characterized in that the bores ( 4 ) having a hole depth (L) greater than the thickness (d _S ) of the outermost laminate layer ( 21 ). Process according to claim 5 for producing a solder joint to a fiber-reinforced ceramic material ( 2 ) with a multilayer laminate structure ( 21 . 22 . 23 . 24 ) with different, periodically repeating fiber orientation, characterized in that the holes ( 4 ) having a bore depth (L) which is equal to or greater than the distance (d _P ) from the surface ( 9 ) of the ceramic material ( 2 ) up to the layer ( 23 ) of the laminate structure having the same fiber orientation as the topmost layer ( 21 ) of the laminate structure. Method according to one of claims 1 to 6 for the production a solder joint to a fiber reinforced Ceramic material, characterized in that the distance (x) between the holes at least the bore diameter (a, b) plus the 5 times, in particular plus at least 10 times, preferably plus at least 25 times the diameter of a fiber of the fiber reinforced ceramic material is. Method according to one of claims 1 to 7, characterized in that the number of holes, bore diameter (a, b) and bore geometry are selected so that through the holes ( 4 ) the surface area of the ceramic surface ( 9 ) and / or each cross-sectional area through the ceramic material ( 2 ) is reduced by a maximum of 50% compared to an identical body without holes. Method according to one of claims 1 to 8, characterized in that the distance (x) between the holes ( 4 ) is between 50% and 150%, in particular between 75% and 125% of one of the bore depths (L). Method according to one of claims 1 to 9, characterized in that after the structuring of the surface to be soldered ( 9 ) a flexible molded body 3 , which at least contains solder material, on the structured surface ( 9 ) is applied. Method for producing a rocket engine from ceramic elements or ceramic elements ( 2 ) and metal elements ( 1 ), wherein at least some of the elements are connected by a method for producing a solder joint according to one of the claims 1 to 10.