WO2007003572A2

WO2007003572A2 - Method for deposition of a material in a hole in an electrically conducting workpiece

Info

Publication number: WO2007003572A2
Application number: PCT/EP2006/063680
Authority: WO
Inventors: Jens Dahl Jensen; Ursus KRÜGER; Ursula Michelsen-Mohammadein; Jan Steinbach; Gabriele Winkler
Original assignee: Siemens Aktiengesellschaft
Priority date: 2005-07-01
Filing date: 2006-06-29
Publication date: 2007-01-11
Also published as: DE102005032019A1; WO2007003572A3

Abstract

The invention relates to a method for deposition of a material in a hole (210), which extends from the surface (6) of an electrically conducting workpiece (200) into or through said workpiece (200) by use of an electric field, comprising the steps: application of an electrically conducting protective layer (8) to the surface (16) of the workpieces, deposition of the material (13) in the hole by means of the electric field and removal of the electrically conducting protective layer (8).

Description

description

A method of depositing a material into a hole in an electrically conductive workpiece

The present invention relates to a method for Abschei ^¬ a material in a hole which extends from the surface of an electrically conductive workpiece of the workpiece into or through it, using an electric field.

For example, in electroplating or sputtering ions are transported rials Mate ^¬ by means of an electric field on the surface, for example, be applied to a surface of a. In both cases, an electric field between an anode and a cathode is constructed, wherein one of the two electrodes is formed by the workpiece to be coated.

During electroplating, the two electrodes are in a galvanic bath containing metal ions. Due to the applied between the electrodes electric field, the positively charged metal ions are transported by the liquid to the cathode, the workpiece, where they deposit into a coating.

When sputtering, however, the electrodes are in a vacuum chamber, and the workpiece usually forms the anode. The cathode is formed by a piece of coating material. In the vacuum chamber, argon is at a pressure of between about 10 ^-3 to 10 ^-2 mbar. Due to a voltage applied between the electrodes high voltage, the argon is ionized and accelerates the positive argon ions towards the cathode be ^¬. There are atoms of the coating material separated by the impinging argon ions, which due to their electrical neutrality can diffuse through the vacuum chamber and deposit on the surface of the workpiece.

Such methods are also used when walls of holes in a workpiece are to be coated or holes are to be filled in a workpiece. Here, when serviceability of the item to be coated, only the walls of the holes, but not the surface, the surface is at ^¬ game may be protected with wax or galvano prior to deposition of the coating material. Such procedural ^¬ is ren z. As described in EP 1 160 352 Al. In the deposition of the coating material inside the holes, layer inhomogeneities occur at the edges of the holes, as shown in FIG.

The FIGURE shows a schematic sectional view of a workpiece 100 having a bore 102 and a galvanol coating protective layer 109 arranged on the surface 104 of the workpiece 100. In addition, the coating 108 can be seen on the inner wall of the bore 102. In the region of the edge between the inner wall 110 and the surface 104, inhomogeneities 112 form, which lead to a narrowing of the opening cross-section of the bore 102. The removal of the inhomogeneities requires a relatively high processing cost.

CH 471 524 and DE 1 199 344 disclose methods for producing printed circuit boards in which holes in the printed circuit boards are galvanically coated. The printed circuit boards consist of an electrically non-conductive base body and are provided with an electrically conductive auxiliary layer and an electrically insulating protective layer. The auxiliary Layers extend over at least one side of the circuit board and over the edges of the holes. On the one hand, they serve as electrodes on the hole walls and, on the other hand, as a supply line for the current during galvanic coating. The auxiliary layers thus enable the galvanic coating of the printed circuit board, which consists of an electrically non-conductive material, in the area of the perforated walls.

The object of the present invention is to provide a method for depositing a material into a hole in an electrically conductive workpiece with the aid of an electric field with which the described layer inhomogeneities in the region of the workpiece surface can be avoided.

This object is achieved by a method according to claim 1. The dependent claims contain advantageous Ausges ^¬ taltungen the method.

In the method according to the invention for depositing a material into a hole which extends into or through the workpiece from the surface of an electrically conductive workpiece, using an electric field, the steps comprise:

- Applying an electrically conductive protective layer on the surface of the workpiece.

- depositing the material to be deposited into the hole using the electric field.

- Remove the electrically conductive protective layer. Optionally, an electrically insulating mask is applied ^¬ the additionally to the electrically conductive protective layer to ^¬.

The method according to the invention can be used both in the ^deposition of material by means of electroplating methods and by means of sputtering methods.

The method according to the invention is based on the knowledge that the inhomogeneities in the region of the hole edge are a consequence of the increased field line density in the edge region. The increased field line density leads to a particularly intensive material deposition in the edge area.

By means of the electrically conductive protective layer which it is carried away ^¬ creased field line concentration of the workpiece surface, namely, in the edge region of the protective layer. The inhomogeneity therefore arises, instead of in the region of the edge between the inner side of the hole and the workpiece surface, in the edge region of the electrically conductive protective layer. Reductions in the cross-sectional area of the hole therefore also take place in the edge region of the electrically conductive protective layer. After removing the protective layer and possible after removal of the protective layer over the workpiece surface standing coating residues upstream is a uniform loading coating on the inside of the holes in front of which in the region of the edge between the hole inner wall and the workpiece surface no inhomogeneity and no narrowing of the opening ^¬ has cross-section of the hole, which goes beyond the predetermined due to the layer thickness reduction.

In particular, an electrically insulating masking material may be used as the electrically conductive protective layer, in which electrically conductive particles, for example metallic Particles or graphite particles are incorporated. A derar ^¬ term material can be applied to the workpiece surface as an ordinary mask material.

The removal of the electrically conductive protective layer after the deposition of the material in the hole in the workpiece can be done mechanically or chemically-mechanically. The same applies to the removal of residues of the material deposited in the hole, which after removal of the electrically conductive protective layer optionally also over the surface of the

Projecting workpiece. The mechanical or chemical-mechanical ^¬ African ablation of the electrically conductive protective layer and / or the mechanical or chemical-mechanical removal of the residues can take place for instance by means of a blasting process or by means of chemical polishing (CMP). In particular, the removal of the electrically conductive protective layer and the removal of any residues of deposited material can take place in the same work step.

If, in addition, an electrically insulating mask material has been attached to the protective layer, the latter can un ^¬ ter use of a solvent or be removed using oxygen plasma. The protective layer itself can be removed if it is made of a Maskenma ^¬ material including embedded conductive particles by using the solvent or of the sow erstoffplasmas.

The inventive method is particularly suitable as a method for depositing a coating on the wall of the hole. Alternatively, however, the method can also be used to completely fill the hole, as in ^¬ playing manner for the filling of vias (electrically conductive feedthroughs by a material) is required. Both the coating of the wall of the hole and the fuel ^¬ len of the hole may be either electrically or by means of a sputtering process.

Further features, properties and advantages of the present invention will become apparent from the following description of an embodiment with reference to the accompanying ^¬ the figures.

Fig. 1 shows a workpiece with a coated hole which has been coated by a prior art method.

Fig. 2 shows a workpiece with a hole at the beginning of the method according to the invention.

FIG. 3 shows the workpiece from FIG. 2 with an electrically conductive protective layer applied thereon.

Fig. 4 shows the workpiece of Fig. 3 after the application of a coating on the wall of the hole in the workpiece.

Fig. 5 shows the workpiece of Fig. 4 after removal of the mask and the protective layer.

Fig. 6 shows the finished workpiece at the end of the process.

7 shows a schematic representation of a section of a turbine blade.

The method according to the invention is described below using the example of coating the wall of a cooling-air bore in a turbine engine. illustrated bucket. Therefore, before explaining the method, the structure of a turbine blade will be described briefly with reference to FIG.

The turbine blade 200 has a leading edge 202 and a trailing edge 204. The leading edge 202 and the outflow ^¬ edge 204 are connected to each other via a convex curved suction side 206 and a concave curved or substantially straight pressure side 208.

The turbine blade 200 is hollow inside and has cooling air holes 210, 212, 214 extending from the outside of the turbine blade 200 to hollow inner portions 203, 205, 207 and blowing out through the hollow portions 203, 205, 207 Allow supplied cooling air.

In operation, the turbine blade flows around exhaust gases voltage 200 hot Burn ^¬. This rotates a rotor (not shown) to which the turbine blade is attached. In order to increase the resistance of the surface of the turbine blade 200 against the hot combustion exhaust gases, cooling air is blown through the cooling air holes 210, 212, 214, which lays over its surface in the manner of a film and thus provides for cooling.

It should be noted that although with Be ^¬ train to FIG. 7 a connected to the rotor blade ei ^¬ ner turbine has been described what is said can be mutatis mutandis trans- ferred to a connected to the turbine housing vane.

During the manufacturing process and / or during the reprocessing of a turbine blade 200, metallic coatings are applied to the inner walls of the cooling-air bores. As it is to other coatings than the coatings that are applied to the outside of the turbine blade, to prevent the coating is applied to the outside ^¬ side of the turbine blade is to be prevented. This is achieved by means of a protective layer applied to the outer surface of the turbine blade.

The method according to the invention, with which the coating is applied to the inside of the cooling-air bores, will be described below with reference to FIGS. 2 to 6.

2 shows, as an example of a workpiece with a hole whose inner wall is to be coated, a section of a turbine blade 200 with a cooling air hole 210 arranged therein. Shown is a section of the metallic base body 2 of the turbine blade 200, through which the Cooling air hole 210 extends therethrough. The cooling air bore 210 is limited to the main body 2 by a wall 4 which is to be provided with a metallic coating. In FIG. 2, also the surface to be protected free upper ^¬ 6 of the base body, so the outer side of the ^turbine blade 200 is to recognize.

In a first method step, an electrically conducting tend protective layer is applied to the free surface 6 of the ^turbine blade 200. 8 In the present exemplary embodiment, the electrically conductive layer 8 consists of a lacquer suitable for galvanic baths, for example etching and galvanoresist SD2155A1 from Lackwerke Peters GmbH and Co KG, into which small metal particles are introduced as conductive particles. In addition or instead of the metal Parti ^¬ kel other conductive particles, for example Gra ^¬ phitpartikel be introduced can. The turbine blade 200 after the application of the electrically conductive protective layer 8 is shown in Fig. 3.

After the electrically conductive protective layer 8 has been applied, an electrically insulating lacquer or wax mask can optionally also be applied to the surface 10 of the electrically conductive protective layer 8. In the present embodiment, however, such a mask is dispensed with.

After the electrically conductive protective layer 8 has been applied, the coating of the wall 4 of the cooling air bore 210 can take place. In the present embodiment, the wall 4 is galvanically coated. For this purpose, the turbine blade 200 is placed in a galvanic bath, which contains an electrically conductive liquid with dissolved ions of the coating material. The coating material may be a metal which is also contained in the base body 2, for example cobalt or nickel. To the turbine blade 200, a negative voltage is applied, so that it acts as Ka ^¬ method. The bath also contains an anode, al ^¬ such an electrode to which a positive voltage is applied. The positively charged metal ions in the electroplating bath are portable due to the between the turbine blade 200 and the anode Toggle lying electric field to the turbine blade 200 trans ^¬ and are deposited there against the inner wall 4 of the cooling ^¬ air bore 210 and on the surface 10 of the electrically conductive protective layer 8 off. A deposit on the Oberflä ^¬ che 6 of the base body 2 is prevented by the electrically conductive protective layer 8. If an optional insulating varnish or wax mask has been applied to the surface 10 of the electrically conductive protective layer 8, the deposition of the metal ions takes place only on the wall 4 of the hole 210. The field lines of the electric field have a particularly high density in the region of the edge 11 between the surface 10 of the electrically conductive protective layer 8 and the inner wall of the electrically conductive protective layer 8, which continues the inner wall 4 of the bore. Due to the increased field line density, an increased number of ions of the coating material in the region of the edge 11 compared to the inner wall of the bore or the electrically conductive protective layer 8. In the region of this edge 11, therefore, a layer inhomogeneity 15 in the form of a bead is formed, which is undesirable, while the hole wall 4 of the hole 210 has a uniform coating 13 (cf., FIG. 4). In contrast to the method according to the invention, the bead forms in the prior art at the edge between the inner wall 4 and the surface 6 of the body and leads to the disadvantages described above.

After the desired coating thickness on the inner wall 4 of the cooling air hole 210 is reached, the electroplating process is terminated and the electrically conductive

Protective layer 8 removed. To remove the protective layer 8, inorganic and / or organic solvents or oxygen plasma can be used. In the present exemplary embodiment, however, the electrically conductive protective layer 8 is removed by chemical-mechanical polishing in order to expose the surface 6 of the main body 2 again. In this case, remaining coating residues 14 can remain over the free surface 6. The turbine blade 210 with coating residues 14 is shown in FIG. 5.

The removal of the coating residues 14 takes place in the present ^¬ embodiment by means of a sand blasting process, with which the residues 14 are removed over a large area. Alternatively, however, it is possible to remove the coating to use a chemical mechanical polishing process. Likewise, it is also possible to use the sand blasting method for removing the electrically conductive protective layer instead of the chemical mechanical polishing method.

After the coating residues 14 have been removed, the process is completed. The result is the turbine blade 200 shown in FIG. 6, in which the inner wall 4 of the cooling air bore 210 is provided with a coating 13. As can be seen in Fig. 6, in the region of the edge between the free surface 6 of the workpiece and the ^¬ be coated wall 4 of the cooling air hole 210 is no inhomogeneity of the coating 13 is present. This is it lead zurückzu ^¬ that the inhomogeneity of the cooling air hole 210 of the electrically conductive protective layer was transferred 8 by means of the electric conductibility ELIGIBLE protective layer from the region of the edge between the free surface 6 of the base body 2 and the wall 4 in the region of the edge 11 , With the ^{removal of} the electrically conductive protective layer 8, therefore, the inhomogeneity 15 is also completely removed, so that only the homogeneous coating remains in the region of the inner wall 4 of the cooling air bore 210.

The method according to the invention has been described with reference to the coating of the cooling air bore of a turbine blade. The

However, the method can also be used for coating other holes and holes, provided that they are coated with the aid of an electric field. In addition to electroplating, sputtering also represents a process in which the coating takes place with the aid of an electric field. The method according to the invention can therefore also be carried out with a sputtering process instead of the electroplating process. Finally, it is also possible to use the process instead of coating the inner wall of a hole and for filling the Lo ^¬ ches as vias, for example, for the filling of feed-throughs, so-called, in the semiconductor technology is the case.

Claims

claims

A method of depositing a material (13) into a hole (210) extending into or through the workpiece (200) from the surface (6) of an electrically conductive workpiece (200) using an electrical device Field with the steps:

- Applying an electrically conductive protective layer (8) on the surface (6) of the workpiece (200); - deposition of the material (13) into the hole (210) under Ver ^¬ application of the electric field;

- Remove the electrically conductive protective layer (8).

2. The method of claim 1, in which is used as the electrically conductive protective layer (8) an electrically insulating Maskenma ^¬ material, in which electrically conductive Par ^¬ particles are incorporated.

3. The method according to claim 2, in which find metal particles as electrically conductive particles.

4. The method of claim 2, in which are used as electrically conductive particles of graphite particles.

5. The method according to any one of the preceding claims, in which the removal of the electrically conductive protective layer (8) by mechanical or chemical-mechanical ablation he follows ^¬ .

A method according to any one of the preceding claims, wherein any portions (14) of the deposited material (13) projecting beyond the surface (6) of the workpiece (200) after removal of the electrically conductive protective layer (8) are mechanical or chemical mechanical be removed.

7. The method according to claim 5 or 6, in which the mechanical or chemical-mechanical removal and / or the mechanical or chemical-mechanical removal by means of a beam method or by means of chemical-mechanical polishing takes place.

8. The method according to any one of claims 5 to 7, in which the electrically conductive protective layer (8) and any residues (14) deposited material (13) are removed in the same step.

A method according to any one of the preceding claims, wherein removal of the electrically conductive protective layer (8) is carried out using a solvent or oxygen plasma.

10. The method according to any one of the preceding claims, in which the deposition is designed as applying a coating (13) on the wall (4) of the hole (210).

11. The method according to any one of claims 1 to 9, in which the hole (210) is filled by means of the deposition.

12. The method according to any one of the preceding claims, in which the deposition of the material (13) takes place galvanically.

13. The method according to any one of claims 1 to 11, in which the deposition of the material by means of a sputtering process he follows ^¬ .

14. A method according to any one of the preceding claims, wherein deposition of a material into a hole (210) in a turbine blade (200) occurs.