WO2013091751A2

WO2013091751A2 - Electrically conductive component and method for producing such a component

Info

Publication number: WO2013091751A2
Application number: PCT/EP2012/004540
Authority: WO
Inventors: Wolfgang Winkelmann; Wolfgang Weinhold
Original assignee: Schoeller-Electronics Gmbh
Priority date: 2011-12-23
Filing date: 2012-10-30
Publication date: 2013-06-27
Also published as: WO2013091751A3; DE102011122283A1

Abstract

The invention relates to a method for producing an electrically conductive component (1), in particular a circuit board, wherein a metal layer is applied to a conductive surface of the component (1) by galvanic deposition from a metal salt solution (2) and carbon nanoparticles (5) are admixed with the metal salt solution (2). The component (1), having the metal layer deposited thereon, has an improved predetermined mechanical characteristic and/or a predetermined electrical characteristic.

Description

Electrically conductive component, and

Method for producing such a component

The invention relates to a method for producing an electrically conductive component according to the preamble of claim 1, an electrically conductive component according to the preamble of claim 8 and an arrangement according to claim 13. For the production of printed circuit boards, the consideration of micro- or nanoparticles is known z. From WO 2007/128015 A2. In the method according to this document, first a mixture is provided which consists of nanoparticles, eg. As metallic particles of copper, and a salt solution containing a conductive metal. Subsequently, the mixture is applied to a circuit board and heat-treated under a reducing atmosphere to form a continuous conductive member on the circuit board. This coating technique can be carried out at comparatively low temperatures, in which damage to a material used for circuit boards is not to be feared. However, the application of the mixture to the circuit board is a separate process step and is therefore disadvantageous.

The coating of surfaces by electroplating has been known for a long time. In connection with the production of printed circuit boards, WO 2008/015168 A1 discloses a method for applying a metal layer to a substrate by electrodeposition of a metal from a metal salt solution. The surface of the substrate to be coated has carbon nanotubes which bring about improved electrical conductivity and thus support the galvanic metal deposition process. A disadvantage of this method is that prior to the actual performance of the electroplating process, the surface of the substrate must already have carbon nanotubes, or that carbon nanotubes in the form of an adhesive polymer coating or a lacquer are to be applied to the substrate.

The invention has for its object to provide an electrically conductive component with improved mechanical and / or electrical properties and a

CONFIRMATION COPY to create speaking process for its production, which can be produced or carried out in a simple manner.

This object is achieved by a method having the features of claim 1 by a component having the features of claim 8, and by an arrangement having the features of claim 13. Advantageous developments of the invention are defined in the dependent claims.

Essential for the invention is the fundamental consideration that in the production of an electrically conductive component in a metal salt solution, from which a metal layer is applied or deposited on a conductive surface of the component by electrodeposition, carbon nanoparticles are included. This means that the metal layer on the surface of the device is deposited in the presence of these carbon nanoparticles. As a result, the electrically conductive device with the metal layer deposited thereon acquires a predetermined mechanical property and / or a predetermined electrical characteristic which is improved over conventionally manufactured circuit boards. In this case, it may be found that carbon nanoparticles are deposited on the metal layer, preferably that carbon nanoparticles are at least partially embedded in the molecular structure of the metal layer.

In an advantageous development of the invention, the carbon nanoparticles consist of spherical molecules of carbon atoms, also known as fullerenes. Additionally or alternatively, it is also possible that the carbon nanoparticles in the form of nanotubes (CNT) are present. The carbon nanotubes may have a diameter of 0.005 to 0.08 μπι and a length of 0.5 to 1000 μιη. In an advantageous development of the invention, the metal layer deposited on the surface of the component may at least partially consist of copper, and preferably consist entirely of copper. In correspondence with this, the metal salt solution also contains proportions of copper. The use of copper is particularly advantageous for the production of printed circuit boards and in the metallic coating of their surface. For the electrodeposition of a copper layer on the surface of the substrate, an acidic electroplating bath is preferably used. Alternatively, a basic or cyanidic electroplating bath is possible.

In addition to the use of copper, the metals chromium, nickel, gold and silver are also suitable for the electrodeposition of a metal layer on the surface of the substrate, for example. It is also possible for a plurality of metal layers, either of the same metal or using different types of metal, to be deposited successively galvanically on the surface of the substrate, for example by B. the substrate is immersed with a metallizable surface in each case under application of a current in different electroplating baths with solutions of different metals.

In an advantageous development of the invention, the desired predetermined mechanical and / or electrical property of the metal layer can be achieved by adding carbon nanoparticles containing the amount of copper contained in the metal salt solution, which amounts to 0.02-0.05% by weight with respect to the amount of copper. preferably 0.03 - 0.04 weight percent, and more preferably 0.0315 - 0.0339 weight percent. Such a proportion by weight of carbon nanoparticles with respect to the amount of copper contained in the electroplating bath may conveniently be achieved by a suspension in which the carbon nanoparticles are contained, this suspension being admixed with the electroplating bath or metal salt solution prior to commencement of the galvanic process ,

According to another teaching according to claim 8, which has independent significance, an electrically conductive component, in particular in the form of a printed circuit board, is claimed in which a metal layer is electrodeposited on a conductive surface of the component. In such a device, carbon nanoparticles are at least attached to the metal layer, so that the device has a predetermined mechanical and / or electrical property. The carbon nanoparticles may also be embedded at least partially, or preferably completely, in the molecular structure of the metal layer. In an advantageous development of the invention, the predetermined mechanical property of the electrically conductive component with the metal layer deposited on it can be greater than in comparison with a metal layer which has been galvanically deposited on a component made from a metal salt solution without the use of carbon nanoparticles. In this way, the predetermined mechanical property, for example a surface roughness, a brittleness or hardness, or else a thermal conductivity of the component with the metal layer deposited on it can be purposefully increased.

Increased brittleness and / or increased surface roughness are advantageous, for example, in the case of printed circuit boards, in order to thereby realize wear-resistant plug contacts with low contact resistance. Increased surface roughness may also be advantageous for adhesion of adhesive, solder resist, or the like.

In the same way as a predetermined mechanical property, the presence of the carbon nanoparticles in the metal salt solution during the electrodeposition of the metal layer can also be used to specifically improve an electrical conductivity of the metal layer or of the component. This can e.g. be useful for optimizing the strip conductor architecture on the surface of an electrically conductive component in the form of a printed circuit board.

In an advantageous embodiment of the invention, the predetermined mechanical property of the metal layer may be formed from a coefficient of thermal expansion, which is adapted to a thermal expansion coefficient of another component, which may be mounted on the surface of the electrically conductive component or its metal layer. This further component may preferably be a semiconductor die. This ensures that no stress cracks occur in the operating state of a printed circuit board.

According to another teaching according to claim 13, which has independent significance, an arrangement is claimed which consists of an electrically conductive component and of another component. The electrically conductive device may be manufactured by the above explained method. The The tere component, in particular a semiconductor die, is mounted on a surface of the component. An essential feature of this arrangement is that the thermal expansion coefficient of the metal layer of the electrically conductive component is adapted to the thermal expansion coefficient of the other component. If the Baulemenent example is formed of a printed circuit board, stress cracks in the operation of the circuit board can be effectively prevented by the explained adaptation of the respective thermal expansion coefficient. In this arrangement, the electrically conductive component may also have further predetermined mechanical and / or electrical properties, which have already been explained in detail above.

In the following the invention will be explained in more detail with reference to a drawing showing only one exemplary embodiment. In the drawing shows:

1 shows a principle greatly simplified electroplating bath for carrying out a proposed method for producing an electrically conductive component, and

2 shows cross-sectional sectional views of a) a metal layer that has been conventionally electrodeposited onto the surface of a device, and b) a metal layer that has been electrodeposited with the electroplating bath of FIG. 1 onto the surface of a device.

In principle, FIG. 1 shows in simplified form a galvanic bath in a cross-sectional view. The electroplating bath is used to coat an electrically conductive component 1 with a metal layer 2 (see illustration b of FIG. 2) and contains a metal salt solution 3 in the form of a commercially available acidic copper sulphate bath, which u. a. Having copper sulfate.

For the electroplating bath a DC voltage source is provided in a known manner, with an anode A at the positive pole and a cathode K at the negative pole. The device 1 originally consists of a substrate with a conductive surface, wherein the substrate is connected to the cathode and immersed in the copper sulfate 3. The anode consists at least partially of copper and is designed as a consumption electrode. When an electrical current is applied, copper metal ions are released from the anode. By means of the electroplating bath of FIG. 1, a metal layer 2 is electrodeposited on a surface of the substrate or of the component 1. Of particular importance for the invention is the fact that the copper sulfate bath 3 carbon nanoparticles 4 are mixed, which are symbolized in Fig. 1 non-scale by points within the copper sulfate 3. Preferably, these carbon nanoparticles 4 are formed from fullerenes. By applying a current, a copper layer is electrodeposited on a surface of the substrate by depositing copper ions by reduction. The building element 1 is thus formed from the substrate, on the surface of which the metal layer 2 is electrodeposited.

The following table gives some parameters for carrying out the galvanic process with the electroplating bath of FIG. 1:

The electroplating bath preferably contains sulfuric acid as the conductive acid, and is thus-as already explained in the general part of the description-an acidic electroplating bath. The concentration of sulfuric acid is chosen so that the electroplating bath or the acid have a maximum conductivity.

The performance of the galvanic process in the presence of the carbon nanoparticles leads to the electrically conductive component 1 with the metal layer 2 deposited thereon receiving predetermined mechanical properties which have already been explained in the general part of the description. If fullerenes are embedded in the molecular structure of the copper layer 2, an increased surface roughness or an increased brittleness of the component with the metal layer deposited thereon is due to the fact that the diameter of the fullerenes (D = 0.7 nm) is significantly larger than the lattice con - constant of copper (a = 0.36 nm). As a result, there is an uneven embedding of the fullerenes in the molecular structure of copper.

Alternatively or additionally, the metal layer 2 on the surface of the component 1 may also have a predetermined electrical property.

Fig. 2 respectively shows cross-sectional sectional views of a metal layer which has been electrodeposited on a printed circuit board. In detail, the representation b) of FIG. 2 shows in section a copper layer 2, which was galvanically deposited with the electroplating bath of FIG. 1 on a printed circuit board 1. In the illustration of FIG. 2b), the free surface of the copper layer 2 is located at the lower edge of the sectional image.

On the other hand, the illustration a) of Fig. 2 shows a copper layer 2a which has been conventionally electrodeposited onto a printed circuit board, i. without the use of carbon nanoparticles in the metal salt solution. The free surface of the copper layer 2a is located in the representation a) of FIG. 2 at the upper edge of the sectional image.

A comparison of the two representations of Fig. 2 illustrates that the surface of the copper layer 2, which was deposited on the printed circuit board 1 with the galvanic bath according to Fig. 1 (see illustration b), has a greater surface roughness than the copper layer 2a (cf. Illustration a), which was deposited on a printed circuit board without the use of carbon nanoparticles. As already explained above, this larger surface roughness can be based on the fact that fullerenes are embedded in the copper layer 2. The surface roughness of the copper layer 2 can be compared with the copper layer 2a, e.g. be larger by a factor of 5.

According to the invention, the electrically conductive component 1 may in particular be a printed circuit board which, as explained above, has predetermined mechanical and / or electrical properties. Alternatively, the electrically conductive component can also be an RFID antenna, a transponder antenna, a sensor or the like.

Claims

claims

1. A method for producing an electrically conductive component (1), in particular a printed circuit board, with improved mechanical and / or electrical properties, wherein a metal layer (2) by electrodeposition of a metal salt solution (3) on a conductive surface of the device (1 ) is applied,

characterized,

in that the metal salt solution (3) has carbon nanoparticles (4), so that the electrodeposition of the metal layer (2) takes place in the presence of the carbon nanoparticles (4).

2. The method according to claim 1, characterized in that carbon nanoparticles (4) are deposited on the metal layer (2), preferably that carbon nanoparticles (4) are at least partially embedded in the molecular structure of the metal layer (2).

3. The method according to any one of the preceding claims, characterized in that the carbon nanoparticles are fullerenes (4) and / or nanotubes (CNT).

4. The method according to any one of the preceding claims, characterized in that on the surface of the component (1) deposited metal layer (2) consists at least partially of copper.

5. The method according to claim 4, characterized in that in the metal salt solution (3) contained amount of copper with carbon nanoparticles (4) is added, wherein the carbon nanoparticles (4) with respect to the amount of copper 0.02 - 0.05 weight percent, preferably 0.03-0.04 weight percent, more preferably 0.0315-0.0339 weight percent.

6. The method according to any one of the preceding claims, characterized in that the carbon nanoparticles (5) in the metal salt solution (3) are suspended.

7. The method according to any one of the preceding claims, characterized in that the step of a galvanic deposition of a metal layer on the surface of the device is repeatedly performed, preferably that in this case a layer of the same metal or a different metal is deposited on the surface of the device galvanically ,

8. Electrically conductive component (1) with improved mechanical and / or electrical properties, in particular a printed circuit board, in which a metal layer (2) is electrodeposited on a conductive surface of the component (1),

characterized,

in that carbon nanoparticles (4) are deposited on the metal layer (2), preferably in that carbon nanoparticles (4) are at least partially embedded in the molecular structure of the metal layer (2).

9. Method or component (1) according to any one of the preceding claims, characterized in that the predetermined mechanical property and / or electrical property compared to a metal layer (2) on a metal salt solution component conventionally and without the use of carbon Nanoparticles is or is, each having a greater value.

10. A method or device (1) according to any one of the preceding claims, characterized in that the predetermined mechanical property is a surface roughness, a brittleness or a thermal conductivity.

1 1. A method or device (1) according to any one of the preceding claims, characterized in that the predetermined mechanical property of the metal layer (2) is a coefficient of thermal expansion, which corresponds to a coefficient of thermal expansion of a further component on the surface of the electrically conductive component ( 1) is attachable, is adapted, preferably, that the further component is a semiconductor Die.

12. Method or component (1) according to one of the preceding claims, characterized in that the predetermined electrical property of the metal layer (2) is an electrical conductivity.

13. Arrangement consisting of an electrically conductive component (1), which is produced by a method according to one of claims 1 to 7 or by a method according to one of claims 9 to 12, and a further component, in particular a semiconductor die, which is mounted on a surface of the electrically conductive component (1), wherein the thermal expansion coefficient of the metal layer (2) of the electrically conductive component (1) is adapted to the thermal expansion coefficient of the further component.