Metallized film, apparatus for manufacturing a metallized film, method for manufacturing a metallized film and film capacitor comprising the metallized film.

The invention relates to a method for manufacturing a

metallized film, which can be used to produce a film

capacitor, and an apparatus for manufacturing the metallized film. Furthermore, the invention relates to a metallized film manufactured by the method and a film capacitor comprising the metallized film.

Film capacitors are widespread devices for energy storage in a variety of electronic applications. Typically, a film capacitor comprises a substrate which is sandwiched between two electrodes which are deposited on surfaces of the

substrate. The lifetime of the film capacitor strongly depends on the quality of the electrodes. The electrodes are commonly metal layers deposited on top of a plastic film substrate. In particular, the adhesion of the electrodes on the surfaces of the substrate is a key feature of the

electrodes. Also the resistivity of the electrodes towards environmental influences, such as temperature and humidity, has a huge influence on the lifetime of the film capacitor. The aforementioned issues are strongly related to the method which is used to manufacture the film capacitor.

Accordingly, the present invention provides an improved method for manufacturing a metallized film which can be used to produce a film capacitor. Moreover, the present invention provides an apparatus for manufacturing the metallized film , a metallized film which is manufactured by the method and a film capacitor comprising the metallized film.

Here and in the following, a metallized film is a polymer based substrate comprising at least one main surface, wherein at least one metal layer is deposited on top of the main surface. In particular, the polymer based substrate may be a thin and flexible substrate, which can be used in a roll-to- roll process.

Here and in the following, a main surface of the polymer based substrate is a surface whose size is independent from the thickness of the substrate. Typically the polymer based substrate comprises two main surfaces which are located on opposite surfaces of the substrate.

A method for manufacturing a metallized film is given by claim 1. Further embodiments of the method, an apparatus for manufacturing the metallized film , a metallized film and a film capacitor comprising the metallized film are given by further claims.

The present invention provides a method for manufacturing a metallized film comprising the steps:

a) Deposition of at least one pre-nucleation layer on at least one main surface of a polymer based substrate by magnetron sputtering,

b) Deposition of at least one metallization layer on top of the pre-nucleation layer by a layer deposition method, which can be different from magnetron sputtering. In other words, the pre-nucleation layer is sandwiched between the polymer based substrate and the metallization layer .

Here and in the following a pre-nucleation layer is a layer, which is deposited on the main surface of the polymer based substrate promoting the nucleation of the metallization layer. This effect of the pre-nucleation layer improves the adhesion of the metallization layer on the substrate compared to a metallization layer, which is deposited on a substrate without a pre-nucleation layer.

Here and in the following a metallization layer is a layer which represents the actual electrode layer of a film

capacitor .

In a second aspect of the invention, the method for

manufacturing the metallized film comprises the steps:

a) Deposition of at least one metallization layer, wherein the metallization layer is deposited on at least one main surface of a polymer based substrate or on top of a pre- nucleation layer, which is deposited on the main surface of the polymer based substrate,

b) Deposition of at least one surface layer on top of the metallization layer by magnetron sputtering, wherein the metallization layer and/or the pre-nucleation layer are deposited by a layer deposition method, which can be

different from magnetron sputtering.

Here and in the following a surface layer, is a layer which is deposited on top of the metallization layer protecting the metallization layer from negative environmental influences, such as temperature and humidity. The utilization of magnetron sputtering enables the deposition of thin and uniform pre-nucleation layers. It is also possible to provide a plurality of pre-nucleation layers, which are stacked one upon the other. Each of the pre-nucleation layers comprises a different composition, can be conducted by magnetron sputtering with less effort than with other deposition techniques. Furthermore, stoichiometric compounds or alloys may be deposited as pre-nucleation layers by magnetron sputtering. The aforementioned characteristics of the magnetron sputtering are also applicable for the surface layer relating to the second aspect of the invention. Due to the aforementioned features, it is possible to form pre-nucleation layers by magnetron sputtering, which

excellently promote the nucleation of the metallization layer on the polymer based substrate. Moreover, magnetron

sputtering enables forming surface layers, which effectively protect the metallization layer from environmental

influences. So, the deposition of the pre-nucleation layer and/or the surface layer by magnetron sputtering has

beneficial effects on the overall lifetime of a film

capacitor comprising the metallized film.

Furthermore the present invention provides an apparatus for manufacturing a metallized film wherein the apparatus

comprises one or more magnetron sputtering units and one or more layer deposition units which utilize layer deposition methods which can be different from magnetron sputtering. The magnetron sputtering units can easily be incorporated in a commercial metallization apparatus, which utilizes a layer deposition method, which can be different from magnetron sputtering . Accordingly, the costs for fabricating the aforementioned apparatus, which comprises one or more magnetron sputtering units and one or more layer deposition units, which utilize deposition methods which can be different from magnetron sputtering, can be kept low. This keeps the total costs of the metallized film low.

The type of magnetron sputtering utilized by the magnetron sputtering units is not limited. In particular, the type of the magnetron sputtering can be selected from a group of magnetron sputtering types comprising at least direct current pulsed sputtering, mid-frequency alternating current

sputtering, radio frequency sputtering and reactive magnetron sputtering .

Moreover, also the type of magnetron sputtering cathodes is not limited to a specific type. For example, the type of the cathode may be planar or rotatable. Also the number of the cathodes in a magnetron sputtering unit is not limited. For example, the magnetron sputtering units can comprise single or double cathodes. Also the number of magnetron sputtering units is not limited. For example, the magnetron sputtering units can be single or multiples.

Targets utilized in the magnetron sputtering units may comprise single elements or multiple elements. Targets comprising multiple elements can be utilized for the

deposition of layers comprising stoichiometric compounds or alloys .

The present invention also provides a metallized film which is manufactured by the method for manufacturing a metallized film of the present invention, wherein the metallized film comprises at least one pre-nucleation layer, which is

deposited on a main surface of a polymer based substrate and at least one metallization layer, which is deposited on top of the pre-nucleation layer. Furthermore, the metallized film comprises a surface layer which is deposited on top of the metallization layer, wherein the surface layer comprises at least one material selected from a group comprising AlOx,

SiC, SiOx, TiOx, A1 and Mg.

The polymer based substrate which is utilized for the

metallized film typically comprises a dielectric polymer. The dielectric polymer is selected from a group of dielectric polymers comprising at least polypropylene, polyphenylene sulfide, polyethylene terephthalate, polyimide and polyureas.

Moreover the invention provides a film capacitor comprising a metallized film, wherein the metallized film is manufactured by the method for manufacturing a metallized film of the present invention.

In a further embodiment of the method for manufacturing a metallized film, the surface layer may be deposited on top of the metallization layer by magnetron sputtering wherein the pre-nucleation layer is deposited on the main surface of the polymer substrate by magnetron sputtering and the

metallization layer is deposited on top of the pre-nucleation layer by a layer deposition method which can be different from magnetron sputtering.

A variety of different layer deposition methods, which can be different from magnetron sputtering, can be used for layer deposition. For example, such layer deposition methods can be atomic layer deposition, chemical vapor deposition and further physical vapor deposition techniques, such as thermal evaporation, electron beam evaporation and pulsed laser deposition .

In a further embodiment of the method for manufacturing a metallized film , the polymer based substrate may be

subjected to a pre-treatment which activates the main surface of the polymer based substrate before any film is deposited on the main surface of the polymer based substrate. The pre treatment is conducted to improve the adhesion of the layers deposited on the main surface of the polymer based substrate. In particular, the pre-treatment makes the main surface of the substrate more hydrophilic. In a further embodiment of the pre-treatment, the main surface of the polymer based substrate is functionalized by the pre-treatment . For the pre-treatment a variety of techniques can be utilized. The utilized technique can be selected from a group comprising at least corona treatment, flame treatment and plasma treatment.

In a further embodiment of the method for manufacturing a metallized film, all aforementioned steps to manufacture the metallized film may be implemented in a roll-to-roll process. The roll-to-roll process is a very common high throughput production method which enables the production of a large number of devices in a short time span. Accordingly, the production costs of the metallized film can be kept low.

In a further embodiment of the method for manufacturing a metallized film, the deposition methods for the deposition of the pre-nucleation layer and for the deposition of the metallization layer may be configured in such a way that each of the said layers comprises one or more metals selected from a group of metals comprising at least Al, Zn, Ag, Au, Cu, Cr, Li, Pt, Mg, Sn, Fe, Ni and any of their alloys. In a

preferred embodiment the pre-nucleation layer comprises at least one metal selected from a group comprising at least Au, Ag, Al, Pt, Cr, Ni, Fe, Cu and any of their alloys, and the metallization layer comprises at least one metal which is selected from a group comprising at least Zn, Mg, Sn, Li and any of their alloys.

In a further embodiment of the method for manufacturing a metallized film, at least one raw material may be utilized for the deposition of the surface layer, wherein the raw material is selected in such a way that said layer comprises at least one material selected from a group of materials comprising at least A10 _x , SiC, SiO _x , TiO _x , Al and Mg. As the surface layer is deposited by a separate layer deposition step, a metal which is contained in the surface layer can be selected independently from a metal which is contained in the metallization layer. For example, the metallization layer comprises Zn as a main component, wherein the surface layer comprises A10 _x as a main component.

In a further embodiment of the apparatus for manufacturing the metallized film, the magnetron sputtering units and the layer deposition units may be arranged in such a way that in a first manufacturing step the pre-nucleation layer is deposited on the main surface of a polymer based substrate by the magnetron sputtering units and in a second manufacturing step the metallization layer is deposited on top of the pre- nucleation layer by the layer deposition units.

In other words, the pre-nucleation layer is deposited by magnetron sputtering on the main surface of the substrate before the metallization layer is deposited on top of the pre-nucleation layer by a layer deposition method which can be different from magnetron sputtering.

In a further embodiment of the apparatus for manufacturing the metallized film, the apparatus may comprise magnetron sputtering units, layer deposition units, which utilize layer deposition methods, which can be different from magnetron sputtering, and one or more additional magnetron sputtering units. The magnetron sputtering units, the additional magnetron sputtering units and the layer deposition units are arranged in such a way that in a first manufacturing step the pre-nucleation layer is deposited by the magnetron sputtering units, in a second film deposition step the metallization layer is deposited on top of the pre-nucleation layer by the layer deposition units and in a third deposition step the surface layer is deposited by the additional magnetron sputtering units.

With other words the metallization layer is sandwiched between the pre-nucleation layer and the surface layer, wherein the pre-nucleation layer and the surface layer are deposited by magnetron sputtering and the metallization layer is deposited by a layer deposition method, which can be different from magnetron sputtering.

In a further embodiment of the apparatus for manufacturing the metallized film, the magnetron sputtering units and the layer deposition units may be arranged in such a way that in a first manufacturing step the metallization layer is deposited directly on the main surface of the polymer based substrate by the layer deposition units and in a second manufacturing step, the surface layer is deposited on top of the metallization layer by the magnetron sputtering units. In other words, the metallization layer is deposited on the main surface of the substrate without a previous deposition of a pre-nucleation layer.

In a further embodiment of the apparatus for manufacturing the metallized film, the apparatus may comprise magnetron sputtering units, layer deposition units and additional layer deposition units, wherein the layer deposition units and the additional layer deposition units utilize layer deposition techniques which can be different from magnetron sputtering. The magnetron sputtering units, the layer deposition units and the additional layer deposition units are arranged in such a way that in a first manufacturing step the pre- nucleation layer is deposited on the main surface of the polymer based substrate by the additional layer deposition units and in a second manufacturing step the metallization layer is deposited on top of the pre-nucleation layer by the layer deposition units and in a third manufacturing step the surface layer is deposited on top of the metallization layer by the magnetron sputtering units. In other words, the pre- nucleation layer and the metallization layer are deposited by layer deposition methods which can be different from

magnetron sputtering.

In a further embodiment of the apparatus for manufacturing the metallized film, the apparatus may comprise in addition to the magnetron sputtering units and the layer deposition units at least one pre-treatment unit. The pre-treatment unit is arranged in such a way that the polymer based substrate is subjected to a pre-treatment, which activates the main surface of the polymer based substrate, before any film is deposited on the main surface of the polymer based substrate. In other words, the pre-treatment is applied to a polymer based substrate which does not feature any film on its main surface. This step improves the adhesion of the films

deposited on the main surface leading to an improved lifetime of the film capacitor comprising the metallized film.

In a further embodiment the apparatus for manufacturing the metallized film may be adapted to perform a roll-to-roll process. The roll-to-roll process enables a high throughput production of the metallized film leading to a reduction of the production costs of the metallized film.

In a further embodiment of the apparatus for manufacturing the metallized film, the apparatus may be utilized to

manufacture film capacitors comprising the metallized film, which is manufactured by the method for manufacturing a metallized film of the present invention

We note that the thickness of the layers which are deposited by magnetron sputtering can be influenced by the number of magnetron sputtering units which are incorporated in the apparatus for manufacturing the metallized film. So, the thickness of the layer which is deposited by the magnetron sputtering units can be increased by increasing the number of consecutively arranged magnetron sputtering units which are utilized to deposit the layer. So, an increased number of magnetron sputtering units results in an increased layer deposition rate leading to a thicker layer, which is

deposited by the magnetron sputtering units.

Moreover, it is also possible to incorporate a number of consecutively arranged magnetron sputtering units in the apparatus for manufacturing the metallized film to deposit a plurality of pre-nucleation layers, which are stacked one upon the other, wherein each of the pre-nucleation layers comprises a different composition. The same is also

applicable for surface layers.

In the following a metallized film and different embodiments of an apparatus for manufacturing a metallized film are explained in more detail with the aid of the drawings.

Components of the drawings which are similar to each other feature the same reference signs

Figure 1 illustrates a cross sectional view of a metallized film;

Figure 2 illustrates an apparatus for manufacturing a

metallized film;

Figure 3 illustrates another embodiment of the apparatus for manufacturing a metallized film;

Figure 4 illustrates another embodiment of the apparatus for manufacturing a metallized film; and

Figure 5 illustrates another embodiment of the apparatus for manufacturing a metallized film.

Figure 1 illustrates in a cross sectional view a cut-out of a metallized film comprising a pre-nucleation layer 1 which is deposited on a main surface 2' of a polymer based substrate 2, a metallization layer 3 which is deposited on top of the pre-nucleation 1 layer and a surface layer 4 which is deposited on top of the metallization layer. The substrate 2 comprises a commonly used dielectric polymer, such as polypropylene. On the main surface of the substrate 2, a metal containing pre-nucleation layer 1 is deposited by magnetron sputtering. The metal which is contained in the pre-nucleation layer 1 can be selected from a group

comprising at least Ag, Au, Al, Pt, Cr, Ni, Fe, Cu or any combinations thereof.

The metallization layer 3 is deposited by a deposition method, which can be different from magnetron sputtering, on top of the pre-nucleation layer 1. Thus, the metallization layer 3 is, for example, deposited by a layer deposition method such as atomic layer deposition, chemical vapor deposition, sputtering, thermal evaporation, pulse layer deposition or electron beam evaporation. After deposition of the metallization layer 3 the surface layer 4 is deposited by magnetron sputtering. The surface layer 4 contains a

material, which can be selected from a group comprising at least A10 _x , SiO _x , SiC, Mg and Al . The deposition of the pre- nucleation layer 1 by magnetron sputtering results in a good adhesion of the metallization layer 3 to the polymer based substrate 2, wherein the metallization layer 3 is protected from environmental influences by a surface layer 4.

Figure 2 illustrates an apparatus for manufacturing a

metallized film. The apparatus is adopted to perform a roll- to-roll process. Thus, the apparatus comprises an unwinder 100 wherein the polymer based substrate 2 is inserted as a roll, which is steadily unwound during the process. The apparatus further comprises a re-winder 300 winding a first metallized film 213, which comprises the polymer based substrate 2, the pre-nucleation layer 1 and the metallization layer 3, to a roll. A coating drum 200 is located between the unwinder 100 and the re-winder 300. The curved arrows indicate the rotating direction of the unwinder, the re- winder and coating drum. The straight arrows indicate the moving direction of the polymer based substrate 2 and the first metallized film 213.

The coating drum 200 is in charge of compensating thermal stress on the film during the evaporation by maintaining a temperature between 5 °C and -40 °C. The deposition of the metallization layer 3 occurs at the coating drum 200. For the deposition of the metallization layer 3, a layer deposition method which can be different from magnetron sputtering is utilized. Accordingly, a layer deposition unit 20, which utilizes layer deposition methods which can be different from magnetron sputtering, is arranged in such a way that the deposition of the metallization layer 3 takes place at the coating drum 200. Moreover, the apparatus comprises a pre treatment unit 30 and a magnetron sputtering 10 unit which are arranged in such a way that the pre-treatment and the magnetron sputtering occur before the deposition of the metallization layer 3.

Moreover, the magnetron sputtering unit 10 and the pre treatment unit 30 are arranged in such a way that the pre treatment occurs before the magnetron sputtering. The pre treatment is utilized to activate the main surface 2' of the polymer based substrate 2 to enhance the adhesion of the layers which are deposited on the main surface 2 'of the polymer based substrate 2. The pre-treatment unit 30 utilizes a technique, which is selected from a group comprising at least corona treatment, plasma treatment or flame treatment.

After the pre-treatment, the pre-nucleation layer 1 is deposited on the main surface 2' of the polymer based

substrate 2 by the magnetron sputtering unit 10. The metallization layer 3 is deposited on top of the pre- nucleation layer 1 by the layer deposition unit 20 at the coating drum 200 after deposition of the pre-nucleation layer 1. Subsequently, the first metallized film 213 is wound to a roll at the re-winder 300.

Figure 3 shows a further embodiment of the apparatus for manufacturing a metallized film. The apparatus is similar to that illustrated in Figure 2 except that an additional magnetron sputtering unit 10' is arranged in such a way that a surface layer 4 is deposited on top of the metallization layer 3 by the additional magnetron sputtering unit.

Accordingly, the apparatus is configured to deposit the pre- nucleation layer 1 and a surface layer 4 by magnetron

sputtering and the metallization layer by a layer deposition method which can be different from magnetron sputtering.

Finally, a second metallized film 2134, which comprises the polymer based substrate 2, the pre-nucleation layer 1, the metallization layer 3 and the surface layer 4, is wound to a roll at a re-winder 300.

Figure 4 illustrates a further embodiment of the apparatus for manufacturing a metallized film. The apparatus is similar to that illustrated in Figure 2 except that the magnetron sputtering unit 10 is now arranged in such way that the surface layer 4 is deposited on top of the metallization layer by the magnetron sputtering unit 10 after the

metallization layer was deposited on the main surface 2 'of the polymer based substrate 2 by the layer deposition unit 20. In other words, in contrast to Figure 2, the magnetron sputtering unit 10 is now utilized to deposit the surface layer 4 and not to deposit the pre-nucleation layer 1. Moreover, in an apparatus which is assembled like this, the metallization layer 3 is deposited directly on the main surface 2' of the polymer based substrate 2 without a

previous deposition of the pre-nucleation layer 1. Finally, a third metallized film 234, which comprises the polymer based substrate 2, the metallization layer 3 and the surface layer 4, is wound to a roll at a re-winder 300.

Figure 5 illustrates a further embodiment of the apparatus for manufacturing a metallized film. The apparatus is similar to that depicted in Figure 4, except that an additional layer deposition unit 20", which utilizes a layer deposition method, which can be different from magnetron sputtering, is arranged subsequent to the pre-treatment unit 30 and previous to the layer deposition unit 20. Accordingly, the pre- nucleation layer 1 and the metallization layer 3 are

deposited by layer deposition methods which can be different from magnetron sputtering. The surface layer 4 is deposited by magnetron sputtering. Subsequently, the second metallized film 2134, which comprises the polymer based substrate 2, the pre-nucleation layer 1, the metallization layer 3 and the surface layer 4, is wound to a roll at a re-winder 300.

The present invention is not restricted to the embodiments illustrated in the drawings. In particular the number of layers which are deposited on the main surface of the

substrate may vary. Moreover also the number of magnetron sputtering units and layer deposition units may vary. List of Reference Signs

1 pre-nucleation layer

2 polymer based substrate

2 main surface of the polymer based substrate

3 metallization layer

4 surface layer

10 magnetron sputtering unit

10 additional magnetron sputtering unit

20 layer deposition unit

20 additional layer deposition unit

30 pre-treatment unit

100 unwinder

200 coating drum

213 first metallized film

234 second metallized film

300 re-winder

2134 third metallized film