EP4200458A1

EP4200458A1 - Evaporation boat for evaporation of metals

Info

Publication number: EP4200458A1
Application number: EP21758467.1A
Authority: EP
Inventors: Bernd Ruisinger; Georg P. Victor; Frank A. MESCHKE; Bernd SCHEUTHLE
Original assignee: 3M Innovative Properties Co
Current assignee: 3M Innovative Properties Co
Priority date: 2020-08-19
Filing date: 2021-08-18
Publication date: 2023-06-28
Also published as: CN115885056A; WO2022038548A1

Abstract

The present disclosure relates to an evaporation boat for evaporation of metals and to the use of said evaporation boat for evaporating metals selected from the group consisting of aluminum, copper and silver.

Description

EVAPORATION BOAT FOR EVAPORATION OF METALS

Technical Field

The present disclosure relates to an evaporation boat for evaporation of metals.

Background

The most common method for coating flexible substrates such as polymeric films or papers with metals is the so-called vacuum web coating using physical vapor depositing technology. The coated flexible substrates serve a wide field of applications such as food packaging, for decorative purposes and manufacturing of capacitors.

In vacuum web coaters, the substrate to be coated is passed over a cooled metal drum where it is exposed to metal vapor. Thus, the metal is deposited in a thin layer on the substrate.

To create the required constant metal vapor, a series of ceramic evaporation boats, aligned along the entire width of the film to be coated, are placed in cooled copper clamps and heated up by direct current flow in a vacuum of typically 10'4 mbar to temperatures of 1400 - 1550 °C. Metal wire is continuously fed to the surface of the evaporation boat where it is melted and vaporized. The most common metal used in this process is aluminum. The ceramic evaporation boat typically consists of a mixture of titanium diboride (TiB2) and boron nitride (BN), sometimes aluminum nitride (AIN) is used in addition. Typically, the evaporation boat is a prismatic shaped body with a rectangular cross-sectional area, a length of about 120 to 150 mm, a width of 25 to 40 mm and a height of 8 to 12 mm, with a cavity on the upper side of the evaporation boat which is filled with liquid metal to be evaporated.

The majority of metallized films is used in the packaging industry to extend the lifetime of food. Coating an aluminum layer on plastic films improves barrier properties of the substrate, e.g., impermeability to oxygen, aromatic substances, light, heat or moisture. The barrier properties of coated films are comparable to aluminum foil, but with lower production costs.

Defects in the metallized film, so-called pinholes, affect the barrier properties in an undesired way. It is therefore essential to avoid pinholes as much as possible.

Over the past years the productivity of the metallizing process has gained crucial importance. High web speed in combination with excellent barrier properties are key factors.

DE 10 2008 016 619 B3 discloses an evaporation boat having a plurality of recesses in the vaporizing surface, the opening in each recess having an area/perimeter ratio of greater than or equal to 1.5 mm. The shape of the recesses can be for example circular, rectangular, triangular or elliptical. The main benefit of this evaporation boat is described as improved wetting of aluminum in both longitudinal and cross direction of the vaporizing surface of the evaporation boat. A disadvantage of this evaporation boat is that it does not allow a pinhole free operation, i.e., an operation with little or no pinholes.

EP 1 688 514 A1 discloses an evaporation boat with several grooves in the cavity of the evaporation boat to improve the wetting of liquid aluminum on the upper surface of the evaporation boat from which metal is evaporated. A disadvantage of this evaporation boat is the uneven wetting of liquid aluminum in the cavity if the so-called wire feeding point, i.e., the point where the aluminum wire hits the cavity, is not in the center of the cavity. As a result of the uneven wetting, a pinhole free operation is not possible.

DE 10 2013 211 034 Al discloses an evaporation boat with an inner and an outer cavity on the upper side of the evaporation boat to avoid overflowing of aluminum into the copper clamps. A disadvantage of this design is that it does not allow a pinhole free operation, i.e., an operation with little or no pinholes. In addition, the smaller area of the inner cavity limits the capability to evaporate high amounts of aluminum.

There is still a need to further improve evaporation boats for evaporation of metals with respect to achieve a good fdm quality, i.e., high optical densities and reduced pinholes, in combination with high metal evaporation rates, i.e., high web speeds, when operating the evaporation boats.

As used herein, "a", "an", "the", "at least one" and "one or more" are used interchangeably. Adding an “(s)” to a term means that the term should include the singular and plural form. The term “comprise” shall include also the terms “consist essentially of’ and “consists of’.

Summary

In a first aspect, the present disclosure relates to an evaporation boat for evaporation of metals, wherein the evaporation boat has an upper side, an underside, two lateral surfaces and two clamping surfaces, and wherein metal is evaporated from the upper side of the evaporation boat, and wherein the upper side of the evaporation boat comprises a cavity, and wherein the cavity has an outer contour at the upper side of the evaporation boat, and wherein the outer contour of the cavity has a shortest circumscribing contour, and wherein the outer contour has a circumferential length, and wherein the shortest circumscribing contour has a circumferential length, and wherein the ratio of the circumferential length of the shortest circumscribing contour to the circumferential length of the outer contour is less than 1, preferably at most 0.8.

In another aspect, the present disclosure relates to an evaporation boat for evaporation of metals, wherein the evaporation boat has an upper side, an underside, two lateral surfaces and two clamping surfaces, and wherein metal is evaporated from the upper side of the evaporation boat, and wherein the upper side of the evaporation boat comprises a cavity, and wherein the cavity of the evaporation boat comprises a plurality of recesses in the upper side of the evaporation boat, and wherein each individual recess of the plurality of recesses has an outer contour at the upper side of the evaporation boat, and wherein the outer contour of each individual recess has a shortest circumscribing contour, and wherein the outer contour of each individual recess has a circumferential length, and wherein the shortest circumscribing contour of each individual recess has a circumferential length, and wherein for at least one individual recess, the ratio of the circumferential length of the shortest circumscribing contour to the circumferential length of the outer contour is less than 1, preferably at most 0.8.

In yet a further aspect, the present disclosure relates to the use of an evaporation boat as disclosed herein for evaporating metals selected from the group consisting of aluminum, copper and silver. With the evaporation boat of the present disclosure, the tendency for overflow of liquid metal into the water-cooled copper clamps can be reduced. Furthermore, the area covered by molten metal is maximized, and a smooth melting of the metal wire is enabled. In addition, the thickness of the pool of liquid metal can be kept as thin as possible. As a consequence, the occurrence of pinholes in the metallized film can be prevented largely, even for high evaporation rates. A further advantage of the evaporation boat disclosed herein is a reduced power consumption.

Brief description of the drawings

The present disclosure is explained in more detail on the basis of the drawings, in which:

Figures 1A - ID show various views of a reference evaporation boat;

Figures 2A - 2F show various views of an evaporation boat as disclosed herein;

Figures 3A - 3F show various views of an evaporation boat as disclosed herein;

Figures 4A - 4F show various views of an evaporation boat as disclosed herein;

Figures 4G - 4J show various views of an evaporation boat as disclosed herein;

Figures 5A - 5E show various views of an evaporation boat as disclosed herein;

Figures 6A - 6E show various views of an evaporation boat as disclosed herein;

Figures 7A - 7E show various views of an evaporation boat as disclosed herein;

Figures 8 - 12 show the upper side of an evaporation boat as disclosed herein; and

Figures 13A - 13D show various views of an evaporation boat as disclosed herein.

Detailed Description

The evaporation boat as disclosed herein has an upper side, an underside, two lateral surfaces and two clamping surfaces. Metal is evaporated from the upper side.

The upper side of the evaporation boat disclosed herein comprises a cavity. The cavity comprises a recess in the upper side of the evaporation boat. Under operation of the evaporation boat, the cavity is wetted with liquid metal to be evaporated.

The cavity of the evaporation boat has an outer contour at the upper side of the evaporation boat. The outer contour is in the same plane as the upper side of the evaporation boat outside of the cavity.

The outer contour of the cavity has a shortest circumscribing contour. The shortest circumscribing contour is the shortest contour which circumscribes the outer contour, i.e., the contour having the shortest length and circumscribing the outer contour. In other words, the shortest circumscribing contour is the shortest contour circumscribing the area of the cavity, which may be of any possible shape. The outer contour has a circumferential length, and the shortest circumscribing contour has a circumferential length. For the evaporation boat disclosed herein, the ratio of the circumferential length of the shortest circumscribing contour to the circumferential length of the outer contour is less than 1. This ratio being less than 1 means that the circumferential length of the shortest circumscribing contour of the outer contour of the cavity is smaller than the circumferential length of the outer contour of the cavity. For standard shapes such as a circle or a regular polygon, the shortest circumscribing contour of the outer contour of these standard shapes corresponds to the outer contour of these standard shapes. For a standard evaporation boat with a rectangular cross-sectional area and a cavity with a rectangular outer contour, the ratio of the circumferential length of the shortest circumscribing contour to the circumferential length of the outer contour is 1, as the outer contour corresponds to the shortest circumscribing contour.

The shortest circumscribing contour of the outer contour of the cavity of the evaporation boat disclosed herein may be, e.g., a circle, a polygon, e.g., a rectangle, or a combination of a polygon with one or more curves or portions of a circle. In some embodiments, the shortest circumscribing contour of the outer contour of the cavity of the evaporation boat is a rectangle, or a rectangle with rounded comers, or a combination of a rectangle with two semicircles, i.e., a rectangle with one semicircle replacing each of the two smaller sides of the rectangle.

Preferably, the ratio of the circumferential length of the shortest circumscribing contour to the circumferential length of the outer contour is at most 0.8. In some embodiments, the ratio of the circumferential length of the shortest circumscribing contour to the circumferential length of the outer contour is at most 0.75, or at most 0.70, or at most 0.65, or at most 0.60.

The ratio of the circumferential length of the shortest circumscribing contour to the circumferential length of the outer contour may be at least 0.1. In some embodiments, the ratio of the circumferential length of the shortest circumscribing contour to the circumferential length of the outer contour is at least 0.2, or at least 0.35.

In some embodiments, the ratio of the circumferential length of the shortest circumscribing contour to the circumferential length of the outer contour is at least 0.1 and at most 0.8. In some embodiments, the ratio of the circumferential length of the shortest circumscribing contour to the circumferential length of the outer contour is at least 0.2 and at most 0.8. In some embodiments, the ratio of the circumferential length of the shortest circumscribing contour to the circumferential length of the outer contour is at least 0.35 and at most 0.70.

The ratio of the area enclosed by the outer contour of the cavity to the total surface area of the upper side of the evaporation boat is less than 1, preferably at most 0.95. The ratio of the area enclosed by the outer contour of the cavity to the total surface area of the upper side of the evaporation boat may be at least 0. 15. In some embodiments, the ratio of the area enclosed by the outer contour of the cavity to the total surface area of the upper side of the evaporation boat may be at least 0.15 and at most 0.95.

The area enclosed by the outer contour of the cavity may comprise an area lying in the same plane as the surface area of the upper side of the evaporation boat which is outside of the outer contour of the cavity. Such an area with an upper side lying in the same plane as the surface area of the upper side of the evaporation boat which is outside of the outer contour of the cavity can also be referred to as an “island”. In some embodiments, the area enclosed by the outer contour of the cavity does not comprise an area lying in the same plane as the surface area of the upper side of the evaporation boat which is outside of the outer contour of the cavity. In other words, for these embodiments the area enclosed by the outer contour of the cavity does not comprise an island.

Preferably, the area enclosed by the outer contour of the cavity does not comprise an area lying in the same plane as the surface area of the upper side of the evaporation boat which is outside of the outer contour of the cavity, i.e., the area enclosed by the outer contour of the cavity does not comprise an island.

In some embodiments of the evaporation boat disclosed herein, the cavity comprises one single recess in the upper side of the evaporation boat, and the area enclosed by the outer contour of the cavity is a continuous area. By “one single recess” it is meant that there is only one recess on the upper side of the evaporation boat which is fdled with liquid metal to be evaporated, and there are no other recesses on the upper side of the evaporation boat besides the one single recess. In some embodiments of the evaporation boat disclosed herein, the cavity consists of one single recess in the upper side of the evaporation boat, and the area enclosed by the outer contour of the cavity is a continuous area.

In some embodiments of the evaporation boat disclosed herein, the cavity of the evaporation boat comprises a plurality of recesses in the upper side of the evaporation boat. Each individual recess of the plurality of recesses has an outer contour at the upper side of the evaporation boat. The outer contour of each individual recess has a shortest circumscribing contour. The outer contour of each individual recess has a circumferential length, and the shortest circumscribing contour of each individual recess has a circumferential length. For at least one individual recess, the ratio of the circumferential length of the shortest circumscribing contour to the circumferential length of the outer contour is less than 1, preferably at most 0.8.

As used herein, by “a plurality of recesses” it is meant that at least two recesses are present in the upper side of the evaporation boat. Three, four or five recesses may also be present in the upper side of the evaporation boat. Also more than five recesses may be present in the upper side of the evaporation boat.

For at least one individual recess of the plurality of recesses, the ratio of the circumferential length of the shortest circumscribing contour to the circumferential length of the outer contour is less than 1, preferably at most 0.8. The ratio of the circumferential length of the shortest circumscribing contour to the circumferential length of the outer contour may be less than 1, preferably at most 0.8, also for more than one of the individual recesses of the plurality of recesses. The ratio of the circumferential length of the shortest circumscribing contour to the circumferential length of the outer contour may be less than 1, preferably at most 0.8, also for each individual recess of the plurality of recesses. For example, the cavity of an evaporation boat as disclosed herein may be composed of 4 individual recesses. One of the four individual recesses may be located close to one of the two clamping regions of the evaporation boat, a second one of the four individual recesses may be located close to the other one of the two clamping regions, and the third and the fourth individual recess may be located in the central region of the evaporation boat, i.e., in the region between the two recesses near the clamping regions. The clamping regions of the evaporation boat are located near the clamping surfaces of the evaporation boat. For one of the two individual recesses near one of the clamping regions, the ratio of the circumferential length of the shortest circumscribing contour to the circumferential length of the outer contour may be less than 1. Also for the second recess located close to one of the two clamping regions, the ratio of the circumferential length of the shortest circumscribing contour to the circumferential length of the outer contour may be less than 1, preferably at most 0.8. For the two other recesses, the ratio of the circumferential length of the shortest circumscribing contour to the circumferential length of the outer contour may be 1, or may be also less than 1, preferably at most 0.8.

The evaporation boat has a longitudinal axis. The longitudinal axis is parallel to the lateral surfaces of the evaporation boat. The longitudinal axis is also parallel to the upper side and underside of the evaporation boat. The cavity has a maximal width in a direction perpendicular to the longitudinal axis, and the cavity has a minimal width in a direction perpendicular to the longitudinal axis. The maximal width of the cavity and the minimal width of the cavity are measured in the plane of the upper side of the evaporation boat, i.e., in the plane of the upper side of the evaporation boat outside of the outer contour of the cavity. The minimal width of the cavity typically is smaller than the maximal width of the cavity. For embodiments with the cavity of the evaporation boat comprising one single recess in the upper side of the evaporation boat, the ratio of the minimal width of the cavity to the maximal width of the cavity may be at least 0.15. The ratio of the minimal width of the cavity to the maximal width of the cavity may also be at least 0.2, or at least 0.5.

The minimal width of the cavity in a direction perpendicular to the longitudinal axis is measured by determining the width of the cavity in a direction perpendicular to the longitudinal axis at every position of the cavity in a direction perpendicular to the longitudinal axis, wherein the smallest width of all measured widths is the minimal width of the cavity in a direction perpendicular to the longitudinal axis. “At every position of the cavity in a direction perpendicular to the longitudinal axis” means at every depression or recess of the upper side of the evaporation boat in a direction perpendicular to the longitudinal axis. The maximal width of the cavity in a direction perpendicular to the longitudinal axis is measured by determining the width of the cavity in a direction perpendicular to the longitudinal axis at every position of the cavity in a direction perpendicular to the longitudinal axis, wherein the largest width of all measured widths is the maximal width of the cavity in a direction perpendicular to the longitudinal axis.

The minimal width of the cavity in a direction perpendicular to the longitudinal axis is at least 3 mm, preferably at least 5 mm, more preferably at least 7 mm. In some embodiments, the minimal width of the cavity in a direction perpendicular to the longitudinal axis of the evaporation boat is at least 10 mm. In some embodiments, the minimal width of the cavity in a direction perpendicular to the longitudinal axis of the evaporation boat is half the maximum width of the cavity minus 3 to 7 mm.

For embodiments with the cavity of the evaporation boat comprising a plurality of recesses in the upper side of the evaporation boat, the minimal width of the cavity and the maximal width of the cavity may be measured for each individual recess. The minimal width of the cavity is the smallest width of the individual values for the smallest width of the individual recesses. The minimal width of the individual recesses is measured in a direction perpendicular to the longitudinal axis. The maximal width of the cavity is the largest width of the individual values for the largest width of the individual recesses. The maximal width of the individual recesses is measured in a direction perpendicular to the longitudinal axis. The minimal width of the cavity typically is smaller than the maximal width of the cavity.

The cavity has a minimal width in a direction perpendicular to the longitudinal axis, as described above, and the cavity also has a minimal width in a direction parallel to the longitudinal axis. The minimal width of the cavity in a direction parallel to the longitudinal axis is measured by determining the width of the cavity in a direction parallel to the longitudinal axis at every position of the cavity in a direction parallel to the longitudinal axis, wherein the smallest width of all measured widths is the minimal width of the cavity in a direction parallel to the longitudinal axis.

The minimal width of the cavity in a direction parallel to the longitudinal axis is at least 3 mm, preferably at least 5 mm, more preferably at least 7 mm.

For embodiments with the cavity of the evaporation boat comprising a plurality of recesses in the upper side of the evaporation boat, the minimal width of the cavity and the maximal width of the cavity may be measured for each individual recess. The minimal width of the cavity is the smallest width of the individual values for the smallest width of the individual recesses. The minimal width of the individual recesses is measured in a direction perpendicular to the longitudinal axis, or in a direction parallel to the longitudinal axis, respectively. The maximal width of the cavity is the largest width of the individual values for the largest width of the individual recesses. The maximal width of the individual recesses is measured in a direction perpendicular to the longitudinal axis. The minimal width of the cavity typically is smaller than the maximal width of the cavity.

In some embodiments, the cavity of the evaporation boat comprises one single recess in the upper side of the evaporation boat, and the area enclosed by the outer contour of the cavity is a continuous area, and the area enclosed by the outer contour of the cavity does not comprise an area lying in the same plane as the surface area of the upper side of the evaporation boat which is outside of the outer contour of the cavity, and the evaporation boat has a longitudinal axis, and the cavity has a minimal width in a direction perpendicular to the longitudinal axis, and the minimal width of the cavity in a direction perpendicular to the longitudinal axis is at least 3 mm, preferably at least 5 mm, more preferably at least 7 mm.

The outer contour of the cavity of the evaporation boat disclosed herein comprises a plurality of extensions which are directed inwardly, i.e., towards the area enclosed by the outer contour. The plurality of extensions can also be regarded as extensions of the shortest circumscribing contour of the outer contour of the cavity, i.e., as extensions extending inwardly, i.e., towards the area enclosed by the outer contour, from the shortest circumscribing contour of the outer contour. In other words, the plurality of extensions extending inwardly from the shortest circumscribing contour of the outer contour of the cavity result from extensions of the bulk material of the evaporation boat which is outside of the outer contour of the cavity, the extensions being directed towards the area enclosed by the outer contour. Due to this plurality of extensions of the outer contour, the shortest circumscribing contour of the outer contour has a circumferential length being shorter than the circumferential length of the outer contour. The evaporation boat disclosed herein can also be described as an evaporation boat for evaporation of metals, wherein the evaporation boat has an upper side, an underside, two lateral surfaces and two clamping surfaces, and wherein metal is evaporated from the upper side of the evaporation boat, and wherein the upper side of the evaporation boat comprises a cavity, and wherein the cavity has an outer contour at the upper side of the evaporation boat, and wherein the outer contour of the cavity of the evaporation boat disclosed herein comprises a plurality of extensions which are directed inwardly, i.e., towards the area enclosed by the outer contour. This description of the evaporation boat disclosed herein does not include the shortest circumscribing contour of the outer contour of the cavity. The shortest circumscribing contour is a theoretical contour used for explanatory purposes.

As used herein, “a plurality of extensions” means at least 2 extensions. The outer contour may comprise at least 4, at least 6, at least 8, at least 10, at least 12, at least 20 or at least 50 extensions. Typically, the outer contour comprises at most 100 extensions.

Typically, the extensions are located along the regions of the shortest circumscribing contour of the cavity which are near the two lateral surfaces of the evaporation boat. In some embodiments, the extensions are located also along the regions of the shortest circumscribing contour of the cavity which are near the two clamping surfaces of the evaporation boat.

The extensions may be located along the complete shortest circumscribing contour of the cavity. It is also possible that the extension may only be located along one or more portions of the shortest circumscribing contour.

The outer contour of the cavity may comprise regularly shaped lines, irregularly shaped lines, or combinations thereof. Regularly shaped lines are lines comprising repetitions of a basic pattern. Typically, a regularly shaped line comprises at least three, at least four or at least six repetitions of a basic pattern. The basic pattern of a regularly shaped line may comprise sections of circular lines, sections of polygonal lines, meandric lines, curved lines such as wave-shaped or sinusoidal lines, or combinations thereof. Irregularly shaped lines having no repetitions of a basic pattern and combinations of irregularly shaped lines with regularly shaped lines are also possible.

In some embodiments, the outer contour of the cavity is regularly shaped in the form of a corrugated contour. In some embodiments, the outer contour of the cavity is irregularly shaped with extensions of different shape and size.

The cavity of the evaporation boat as disclosed herein has a bottom surface and a lateral surface along the outer contour of the cavity. Typically, the bottom surface of the cavity is parallel to the upper side of the evaporation boat. The lateral surface of the cavity is extending from the outer contour of the cavity at the upper side of the evaporation boat to the bottom surface of the cavity. Typically, the lateral surface of the cavity is flat. The angle which is enclosed by the surface area of the upper side of the evaporation boat which is outside of the outer contour of the cavity and the lateral surface of the cavity may be from 45 to 135°. In some embodiments, the angle which is enclosed by the surface area of the upper side of the evaporation boat which is outside of the cavity and the lateral surface is 90°. At the lower end of the lateral surface of the cavity which is adjacent to the bottom surface of the cavity, the transition from the lateral surface to the bottom surface of the cavity may be rounded, for example due to machining by milling. At the upper end of the lateral surface of the cavity, there may be a bevel appropriately designed for the ceramic material of the evaporation boat.

In some embodiments, the lateral surface of the cavity is sloping upwards from the bottom surface of the cavity to the outer contour of the cavity. The lateral surface of the cavity may be sloping upwards with a curvature or in an irregular manner. The lateral surface of the cavity may be sloping upwards only near the clamping regions, or also in other regions of the cavity.

The cavity of the evaporation boat as disclosed herein has a depth. The depth of the cavity is the depth from the plane of the upper side of the evaporation boat outside of the outer contour of the cavity to the bottom surface of the cavity, measured perpendicularly to the plane of the upper side of the evaporation boat outside of the outer contour of the cavity. The depth of the cavity typically is from 0.5 mm to 5 mm, preferably from 1 to 3 mm. The ratio of the depth of the cavity to the height of the evaporation boat may be from 0.03 to 0.65 and preferably is from 0.05 to 0.3. The height of the evaporation boat is measured in the region outside of the outer contour of the cavity.

The lateral surface of the cavity has a height. The height of the lateral surface of the cavity is measured perpendicularly to the plane of the upper side of the evaporation boat outside of the outer contour of the cavity. The height of the lateral surface of the cavity corresponds to the depth of the cavity and typically is from 0.5 mm to 5 mm, preferably from 1 to 3 mm.

Due to the plurality of extensions of the outer contour directed inwardly, also the lateral surface of the cavity comprises extensions of the lateral surface of the cavity.

In some embodiments of the evaporation boat disclosed herein, the bottom surface of the cavity is not parallel to the upper side of the evaporation boat, and the depth of the cavity may be different at different positions of the bottom surface of the cavity. For example, the depth of the cavity may be larger near the outer contour of the cavity and may be smaller in the central region of the cavity, i.e., at positions more distant from the outer contour. It is possible that the depth of the cavity is 3 mm, for example, near the outer contour of the cavity, and the depth of the cavity is 1 mm or even 0 mm, for example, in the central region of the cavity. The bottom surface of the cavity may also have several peaks and depressions. For example, the cavity may have a wave-shaped bottom surface. The bottom surface of the cavity may also have peaks and depressions distributed in other regular patterns. The bottom surface of the cavity may also be a freeform surface, having irregularly distributed peaks and depressions.

If the bottom surface is not parallel to the upper side of the evaporation boat, and the depth of the cavity is different at different positions of the bottom surface of the cavity, the depth of the cavity is measured at a position having the largest depth, i.e., the depth of the cavity is to be understood as the maximum depth of the cavity. The depth of the cavity typically is from 0.5 mm to 5 mm, preferably from 1 to 3 mm, also for embodiments with the bottom surface of the cavity not being parallel to the upper side of the evaporation boat.

In some embodiments of the evaporation boat disclosed herein, the cavity comprises a recess in the upper side of the evaporation boat and a central region. The recess is located along the outer contour of the cavity, and the central region is enclosed by the recess. The depth of the cavity measured at positions of the recess may be from 0.5 to 5 mm and is different from the depth of the cavity measured at positions of the central region. The depth of the cavity measured at positions of the central region may be from 0 to 5 mm. If the depth of the cavity measured at positions of the recess is different at different positions of the recess, the depth of the cavity measured at positions of the recess is measured at a position having the largest depth, i.e., the depth of the cavity measured at positions of the recess is to be understood as the maximum depth of the recess of the cavity. If the depth of the cavity measured at positions of the central region is different at different positions of the central region, the depth of the cavity measured at positions of the central region is measured at a position having the largest depth, i.e., the depth of the cavity measured at positions of the central region is to be understood as the maximum depth of the central region of the cavity.

In some embodiments of the evaporation boat disclosed herein, the cavity has a meander-shaped form. Preferably, the meander-shaped form has rounded comers. The outer contour of the meandershaped cavity may be formed by sections of circular lines connected by straight lines. The outer contour of the meander-shaped cavity has the form of a meander-shaped line, preferably with rounded comers. Preferably, the meander-shaped line is along the two lateral surfaces of the evaporation boat.

In some embodiments, the cavity has a meander-shaped form, preferably a meander-shaped form having rounded comers, and the evaporation boat has a longitudinal axis, and the cavity has a minimal width in a direction perpendicular to the longitudinal axis, and the minimal width of the cavity in a direction perpendicular to the longitudinal axis is at least 3 mm, preferably at least 5 mm, more preferably at least 7 mm.

The outer contour of the cavity of the evaporation boat disclosed herein comprises a plurality of extensions which are directed inwardly. The plurality of extensions are extensions extending inwardly from the shortest circumscribing contour of the outer contour. Typically, the extensions are located along the regions of the shortest circumscribing contour of the cavity which are near the two lateral surfaces of the evaporation boat. The outer contour of the cavity may comprise at least four, preferably at least six, more preferably at least eight extensions which are directed inwardly. Half of the number of the extensions may be located along each of the two lateral surfaces of the evaporation boat.

The width of the extensions in a direction parallel to the longitudinal axis of the evaporation boat is at least 1 mm. The width of the extensions in a direction parallel to the longitudinal axis of the evaporation boat is at most 10 mm. The distance of two adjacent extensions may be at least 2 mm, preferably at least 5 mm, more preferably at least 7 mm, in a direction parallel to the longitudinal axis of the evaporation boat. The distance of two adjacent extensions may be constant in a direction parallel to the longitudinal axis of the evaporation boat.

The length of the extensions in a direction perpendicular to the longitudinal axis of the evaporation boat is at least 1 mm, preferably at least 5 mm, more preferably at least 10 mm. The length of the extensions in a direction perpendicular to the longitudinal axis of the evaporation boat is at most the maximal width of the cavity minus 3 mm, preferably minus 5 mm, more preferably minus 10 mm. The length of the extensions in a direction perpendicular to the longitudinal axis of the evaporation boat is measured from the shortest circumscribing contour of the outer contour of the cavity to the end of the extension in a direction perpendicular to the longitudinal axis of the evaporation boat. The lengths of the individual extensions of the plurality of extensions may be identical for all extensions of the outer contour of the cavity, or may be different for the individual extensions of the outer contour of the cavity. The average length of the extensions, i.e., the arithmetic mean value of the length of the individual extensions, in a direction perpendicular to the longitudinal axis of the evaporation boat may be from 10 to 90%, or from 20 to 80%, or from 30 to 70%, or from 40 to 60% of the maximum width of the cavity. Preferably, the average length of the extensions in a direction perpendicular to the longitudinal axis of the evaporation boat is from 30 to 70%, more preferably from 40 to 60% of the maximum width of the cavity. In a preferred example, the average length of the extensions in a direction perpendicular to the longitudinal axis of the evaporation boat is half of the maximum width of the cavity.

The individual extensions of the plurality of extensions may have two or three or more different lengths. At least one, preferably at least two, of the extensions have a length in a direction perpendicular to the longitudinal axis of the evaporation boat of at least 50%, preferably of at least 60%, of the maximum width of the cavity.

Preferably, there are three different lengths of the individual extensions of the outer contour of the cavity. The first of the three different lengths of the extensions in a direction perpendicular to the longitudinal axis of the evaporation boat corresponds to from 10 to 90% of the maximum width of the cavity. The second of the three different lengths of the extensions in a direction perpendicular to the longitudinal axis of the evaporation boat corresponds to the first of the three lengths minus 0. 1 to 10 mm, preferably minus 3 to 7 mm. The third of the three different lengths of the extensions in a direction perpendicular to the longitudinal axis of the evaporation boat corresponds to the first of the three lengths plus 0.1 to 10 mm, preferably plus 3 to 7 mm. Preferably, the difference in length between the first and second of the three lengths is identical to the difference in length between the first and third of the three lengths. Preferably, the first, second and third of the three different lengths of the extensions in a direction perpendicular to the longitudinal axis of the evaporation boat are from 12 to 22 mm, 7 to 17 mm, and 17 to 27 mm, respectively.

The individual extensions of the outer contour of the cavity may be arranged in an alternating manner along the two lateral surfaces of the evaporation boat.

In some embodiments, the cavity of the evaporation boat comprises one single recess in the upper side of the evaporation boat, and the area enclosed by the outer contour of the cavity is a continuous area, and the area enclosed by the outer contour of the cavity does not comprise an area lying in the same plane as the surface area of the upper side of the evaporation boat which is outside of the outer contour of the cavity, and the evaporation boat has a longitudinal axis, and the cavity has a minimal width in a direction perpendicular to the longitudinal axis, and the minimal width of the cavity in a direction perpendicular to the longitudinal axis is at least 3 mm, preferably at least 5 mm, more preferably at least 7 mm, and the outer contour of the cavity comprises at least four extensions which are directed inwardly, the at least four extensions being extensions extending inwardly from the shortest circumscribing contour of the outer contour, and the width of the extensions in a direction parallel to the longitudinal axis of the evaporation boat is at least 1 mm and at most 10 mm, and the length of the extensions in a direction perpendicular to the longitudinal axis of the evaporation boat is at least 1 mm and at most the maximal width of the cavity minus 3 mm.

In some embodiments, the cavity of the evaporation boat has a meander-shaped form, preferably a meander-shaped form having rounded comers, and the cavity of the evaporation boat comprises one single recess in the upper side of the evaporation boat, and the area enclosed by the outer contour of the cavity is a continuous area, and the area enclosed by the outer contour of the cavity does not comprise an area lying in the same plane as the surface area of the upper side of the evaporation boat which is outside of the outer contour of the cavity, and the evaporation boat has a longitudinal axis, and the cavity has a minimal width in a direction perpendicular to the longitudinal axis, and the minimal width of the cavity in a direction perpendicular to the longitudinal axis is at least 3 mm, preferably at least 5 mm, more preferably at least 7 mm, and the outer contour of the cavity comprises at least four extensions which are directed inwardly, the at least four extensions being extensions extending inwardly from the shortest circumscribing contour of the outer contour, and the width of the extensions in a direction parallel to the longitudinal axis of the evaporation boat is at least 1 mm and at most 10 mm, and the length of the extensions in a direction perpendicular to the longitudinal axis of the evaporation boat is at least 1 mm and at most the maximal width of the cavity minus 3 mm.

The upper side of the evaporation boat may be point-symmetrical to the center point of the upper side of the evaporation boat. In some embodiments, the upper side of the evaporation boat is point- symmetrical to the center point of the upper side of the evaporation boat, and the upper side of the evaporation boat is not mirror-symmetrical to the middle axis of the upper side of the evaporation boat.

In a preferred embodiment, the outer contour of the cavity has eight extensions having three different lengths in a direction perpendicular to the longitudinal axis of the evaporation boat, and the eight extensions are arranged in an alternating manner along the two lateral surfaces of the evaporation boat, and the upper side of the evaporation boat is point-symmetrical to the center point of the upper side of the evaporation boat, and one extension having the second of the three different lengths of the extensions is arranged next to the center point of the upper side of the evaporation boat, and one extension having the third of the three different lengths of the extensions is arranged adjacent to the extension next to the center point, and two extensions having the first of the three different lengths of the extensions are arranged at the end of the cavity near the clamping regions.

For a standard evaporation boat known in the art having a standard cavity, i.e., a cavity with a circumferential length of the shortest circumscribing contour of the cavity being as long as the circumferential length of the outer contour of the cavity, the lateral surface of the cavity is a boundary for the molten metal. The molten metal does not overflow the lateral surfaces of the cavity to the upper side of the evaporation boat at the two longer sides of the cavity. For higher evaporation rates, there is a risk that molten metal will overflow the lateral surfaces of the cavity at the two smaller sides of the cavity near the clamping regions.

For the evaporation boat as disclosed herein, the surface area of the lateral surface of the cavity is larger than the lateral surface of the cavity for a standard evaporation boat. The increased surface area of the lateral surface of the cavity compared to a standard evaporation boat is due to the extensions of the outer contour of the cavity, i.e., due to the increased circumferential length of the outer contour of the cavity compared to a standard evaporation boat. The increased lateral surface area of the cavity of the evaporation boat as disclosed herein is an additional surface area from which molten metal can be evaporated. Therefore, the evaporation rate per area unit, for example per mny, is locally increased at the outer contour of the cavity, due to the increased lateral surface of the cavity. The locally increased evaporation rate helps to guide or suction the molten metal from the wire feeding point, i.e., the point where the aluminum wire hits the cavity, to the lateral surface of the cavity and beyond the outer contour of the cavity, to the upper side of the evaporation boat outside of the outer contour of the cavity. The lateral surface of the cavity is no boundary for the molten metal, but instead the molten metal can overflow the outer contour of the cavity and can wet also the upper surface of the evaporation boat outside of the outer contour of the cavity. This can also be described as a kind of “suction effect” which leads to a wider area wetted by molten metal. For the evaporation boat as disclosed herein, the wetted surface area is wider than for a standard evaporation boat, i.e., the wetted surface area is broader in a direction perpendicular to the longitudinal axis. The suction effect caused by the increased surface area of the lateral surface of the cavity leads to a wider area wetted by molten metal even if the bottom surface of the cavity is smaller than for a standard cavity. The suction effect caused by the increased surface area of the lateral surface of the cavity also helps to improve the distribution of molten metal within the cavity, whereas for standard evaporation boats fluid displacement is the main mechanism for spreading the molten metal across the cavity. As an effect of that, the pool of molten metal is thinner for the evaporation boat disclosed herein, compared to a standard evaporation boat with a standard cavity, when the same feeding rate of metal wire and the same total evaporation rate is used. Due to the thinner pool of molten metal, the evaporation boat as disclosed herein has less tendency for overheating and pin-hole formation. A further advantage is that the thinner pool of molten metal improves the energy efficiency and reduces the power consumption of the evaporation boat, as the parallel resistance of the pool of molten metal is increased.

The evaporation boat as disclosed herein has an additional surface area at the upper side of the evaporation boat that can be used for evaporation, as a result of the longer circumferential length of the outer contour of the cavity compared to the circumferential length of the shortest circumscribing contour of the cavity. The additional surface area of the upper side of the evaporation boat that can be used for evaporation is equal to the difference in circumferential length of the outer contour of the cavity and circumferential length of the shortest circumscribing contour of the cavity multiplied by the depth of the cavity. The evaporation boat as disclosed herein may have a cross-sectional area with a rectangular shape. The rectangular cross-sectional area is perpendicular to the longitudinal axis of the evaporation boat. Other cross-sectional areas are also possible.

The two clamping surfaces of the evaporation boat disclosed herein typically are parallel to each other, and the longitudinal axis is perpendicular to the two clamping surfaces of the evaporation boat. The rectangular cross-sectional area typically is parallel to the clamping surfaces.

In some embodiments, at least one part of the evaporation boat has a cross-sectional area with a trapezoidal shape. The trapezoidal-shaped cross-sectional area is perpendicular to the longitudinal axis of the evaporation boat, which means typically parallel to the clamping surfaces. For these embodiments, the upper side of the evaporation boat is parallel to the underside of the evaporation boat, and each of the two lateral surfaces of the evaporation boat may be inclined at an angle of from 30 to less than 90 degrees against the upper side of the evaporation boat in the at least one part of the evaporation boat having a cross-sectional area with a trapezoidal shape.

In some embodiments, at least one part of the evaporation boat has a cross-sectional area with a triangular shape. The triangular cross-sectional area is perpendicular to the longitudinal axis of the evaporation boat, i.e., typically parallel to the clamping surfaces. In this case, the underside of the evaporation boat corresponds to the two lateral surfaces of the evaporation boat which are inclined against the upper side of the evaporation boat.

In some embodiments, at least one part of the evaporation boat has a cross-sectional area having the form of a halved ellipse. In this case, the underside of the evaporation boat has the form of a halved ellipse. The two lateral surfaces of the evaporation boat correspond to a right and a left part of the halved ellipse of the underside of the evaporation boat.

The evaporation boat as disclosed herein may have a length of from 90 to 170 mm, a width at the upper side of from 15 to 50 mm, and a height of from 6 to 12 mm.

The evaporation boat as disclosed herein is heated up by direct current flow.

Also disclosed herein is a process for evaporating metal using an evaporation boat as disclosed herein, comprising providing a continuous supply of metal in solid form to the upper side of the evaporation boat, heating an evaporation boat as disclosed herein by direct current, melting the metal in the cavity of the evaporation boat, and evaporating the metal from the upper side of the evaporation boat.

Various embodiments of the evaporation boat according to the present disclosure are shown in the drawings.

Figure 1A shows a plan view of the upper side 2 of a reference evaporation boat 1. Figure IB shows a 3D view of the evaporation boat 1 of Figure 1A. Figure 1C shows a cross-sectional view of the evaporation boat 1 of Figures 1A - IB at the sectional line denoted in Figures 1A and IB by “1C”. Metal is evaporated from the upper side 2 of the evaporation boat 1. The upper side 2 has a rectangular shape. The underside 3 of the evaporation boat 1 also has a rectangular shape. In Figure IB, one of the two lateral surfaces 14 and one of the two clamping surfaces 15 of the reference evaporation boat 1 are also shown.

The upper side 2 of the evaporation boat 1 of Figure 1A comprises a cavity 4. The cavity 4 is a recess in the upper side of the evaporation boat. Under operation of the evaporation boat, the cavity is wetted with liquid metal to be evaporated. The cavity 4 has an outer contour 5 at the upper side 2 of the evaporation boat 1. The cavity 4 has a bottom surface 11 and a lateral surface 12 along the outer contour 5 of the cavity 4. The lateral surface 12 of the cavity 4 is extending from the outer contour 5 of the cavity 4 at the upper side 2 of the evaporation boat 1 to the bottom surface 11 of the cavity 4. The bottom surface 11 is parallel to the underside 3 of the evaporation boat 1. The angle which is enclosed by the surface area of the upper side 2 of the evaporation boat 1 which is outside of the outer contour 5 of the cavity 4 and the lateral surface 12 of the cavity 4 is 90°. The outer contour 5 of the cavity 4 corresponds to the shortest circumscribing contour 6 of the outer contour 5 of the cavity 4. The shortest circumscribing contour 6 is the shortest contour which circumscribes the outer contour 5. The circumferential length of the shortest circumscribing contour 6 corresponds to the circumferential length of the outer contour 5, and the ratio of the circumferential length of the shortest circumscribing contour 6 to the circumferential length of the outer contour 5 is 1.0.

Figure ID schematically shows a plan view of the upper side 2 of the evaporation boat 1 of Figure IB under operation. The upper side 2 of the evaporation boat has been wetted by molten aluminum. The area 13 which is wetted by molten aluminum is schematically shown as a hatched area.

Figure 2A shows a plan view of the upper side 2 of an evaporation boat 1 as disclosed herein. Figure 2B shows a 3D view of the evaporation boat 1 of Figure 2A. Figure 2C shows a cross-sectional view of the evaporation boat 1 of Figures 2A - 2B at the sectional line denoted in Figures 2A and 2B by “2C” Figure 2D shows a cross-sectional view of the evaporation boat of Figures 2A - 2B at the sectional line denoted in Figures 2A and 2B by “2D”. Metal is evaporated from the upper side 2 of the evaporation boat 1. The upper side 2 has a rectangular shape. The underside 3 of the evaporation boat 1 also has a rectangular shape. In Figure 2B, one of the two lateral surfaces 14 and one of the two clamping surfaces 15 of the evaporation boat 1 are also shown. The upper side 2 of the evaporation boat comprises a cavity 4. The cavity 4 is a recess in the upper side of the evaporation boat. The cavity 4 of the evaporation boat 1 of Figures 2A - 2D comprises one single recess 20. Under operation of the evaporation boat, the cavity is wetted with liquid metal to be evaporated. The cavity 4 has an outer contour 5 at the upper side 2 of the evaporation boat 1. The outer contour 5 is formed by sections of circular lines. The cavity 4 has a bottom surface 11 and a lateral surface 12 along the outer contour 5 of the cavity 4. The lateral surface 12 of the cavity 4 is extending from the outer contour 5 of the cavity 4 at the upper side 2 of the evaporation boat 1 to the bottom surface 11 of the cavity 4. The bottom surface 11 is parallel to the underside 3 of the evaporation boat 1. The angle which is enclosed by the surface area of the upper side 2 of the evaporation boat 1 which is outside of the outer contour 5 of the cavity 4 and the lateral surface 12 of the cavity 4 is 90°.

Figure 2E shows the plan view of the upper side 2 of the evaporation boat of Figure 2B. In addition to the plan view of Figure 2A, the shortest circumscribing contour 6 of the outer contour 5 of the cavity 4 is also shown in Figure 2E. The shortest circumscribing contour 6 is the shortest contour which circumscribes the outer contour 5. The shortest circumscribing contour is of course not a real contour present at the upper side 2 of the evaporation boat 1, it is instead a theoretical contour which is used for explanatory purposes. In Figure 2E, the shortest circumscribing contour 6 is shown as a dotted line. As can be seen in Figure 2E, the circumferential length of the shortest circumscribing contour 6 is shorter than the circumferential length of the outer contour 5. The ratio of the circumferential length of the shortest circumscribing contour 6 to the circumferential length of the outer contour 5 is 0.93. The outer contour 5 of the cavity 4 comprises eight extensions 10 which are directed inwardly. Four of these extensions are located along each of the two lateral surfaces of the evaporation boat. The eight extensions of the outer contour directed inwardly can be regarded as extensions of the shortest circumscribing contour 6 of the outer contour 5. Due to these extensions, the circumferential length of the shortest circumscribing contour 6 is shorter than the circumferential length of the outer contour 5. The eight extensions of the outer contour directed inwardly can also be regarded as extensions of the lateral surface of the cavity.

The ratio of the area enclosed by the outer contour 5 of the cavity 4 to the total surface area of the upper side 2 of the evaporation boat 1 as shown in Figures 2B and 2E is 0.28. The area enclosed by the outer contour 5 of the cavity 4 may also be larger than shown in Figures 2B and 2E, and the ratio of the area enclosed by the outer contour 5 of the cavity 4 to the total surface area of the upper side 2 of the evaporation boat 1 may also be up to 0.7 or up to 0.95. For example, the width of the area which is outside of the shortest circumscribing contour and along the lateral surfaces of the evaporation boat may be as small as 1 mm, and the width of the area which is outside of the shortest circumscribing contour and near the clamping regions of the evaporation boat may be only 5 mm. The ratio of the minimal width of the cavity 4 to the maximal width of the cavity 4 is 0.75 for the evaporation boat shown in Figures 2 A - 2E.

Figure 2F schematically shows a plan view of the upper side 2 of the evaporation boat 1 of Figure 2B under operation. The upper side 2 of the evaporation boat has been wetted by molten aluminum. The area 13 which is wetted by molten aluminum is schematically shown as a hatched area.

For the reference evaporation boat with a standard cavity as shown in Figure ID, the lateral surface of the cavity is a boundary for the molten metal. The molten metal does not overflow the lateral surfaces of the cavity to the upper side of the evaporation boat at the two longer sides of the cavity. For higher evaporation rates, there is a risk that molten metal will overflow the lateral surfaces of the cavity at the two smaller sides of the cavity near the clamping regions.

For the evaporation boat disclosed herein as shown in Figures 2A - 2F, the surface area of the lateral surface of the cavity is larger than the lateral surface of the cavity for the reference evaporation boat of Figures 1A - ID. The increased surface area of the lateral surface of the cavity compared to the reference evaporation boat of Figures 1A - ID is due to the eight extensions 10 of the outer contour 5 of the cavity 4, i.e., due to the increased circumferential length of the outer contour of the cavity compared to the reference evaporation boat of Figures 1A - ID. The increased lateral surface area of the cavity of the evaporation boat of Figures 2 A - 2F is an additional surface area from which molten metal can be evaporated. Therefore, the evaporation rate per area unit, for example per mm², is locally increased at the outer contour 5 of the cavity 4, due to the increased lateral surface of the cavity. The locally increased evaporation rate helps to guide or suction the molten metal from the wire feeding point, i.e., the point where the aluminum wire hits the cavity, to the lateral surface of the cavity and beyond the outer contour of the cavity, to the upper side of the evaporation boat outside of the outer contour of the cavity. Due to the increased surface area of the lateral surface of the cavity, the lateral surface of the cavity is no boundary for the molten metal, but instead the molten metal can overflow the outer contour of the cavity and can wet also the upper surface of the evaporation boat outside of the outer contour of the cavity. This can also be described as a kind of “suction effect” which leads to a wider area wetted by molten metal. For the evaporation boat disclosed herein as shown in Figures 2A - 2F, the wetted surface area is wider than for the reference evaporation boat of Figures 1A - ID, i.e., the wetted surface area is broader in a direction perpendicular to the longitudinal axis. This can be seen in Figure 2F as compared to Figure ID. The suction effect caused by the increased surface area of the lateral surface of the cavity also helps to improve the distribution of molten metal within the cavity, whereas for the reference evaporation boat fluid displacement is the main mechanism for spreading the molten metal across the cavity. As an effect of that, the pool of molten metal is thinner for the evaporation boat of Figure 2F compared to the reference boat of Figure ID, when the same feeding rate of metal wire and the same total evaporation rate is used. Due to the thinner pool of molten metal, the evaporation boat as disclosed herein has less tendency for overheating and pin-hole formation. The thinner pool of molten metal improves the energy efficiency and reduces the power consumption of the evaporation boat, as the parallel resistance of the pool of molten metal is increased.

Figure 3A shows a plan view of the upper side 2 of a further embodiment of an evaporation boat 1 as disclosed herein. Figure 3B shows a 3D view of the evaporation boat 1 of Figure 3A. Figure 3C shows a cross-sectional view of the evaporation boat 1 of Figures 3 A - 3B at the sectional line denoted in Figures 3A and 3B by “3C”. Figure 3D shows a cross-sectional view of the evaporation boat of Figures 3A - 3B at the sectional line denoted in Figures 3A and 3B by “3D”. Metal is evaporated from the upper side 2 of the evaporation boat 1. The upper side 2 has a rectangular shape. The underside 3 of the evaporation boat 1 also has a rectangular shape. In Figure 3B, one of the two lateral surfaces 14 and one of the two clamping surfaces 15 of the evaporation boat 1 are also shown. The upper side 2 of the evaporation boat comprises a cavity 4. The cavity 4 is a recess in the upper side of the evaporation boat. The cavity 4 of the evaporation boat 1 of Figures 3A - 3D comprises one single recess 20. Under operation of the evaporation boat, the cavity is wetted with liquid metal to be evaporated. The cavity 4 has an outer contour 5 at the upper side 2 of the evaporation boat 1. The outer contour 5 is formed by sections of circular lines which are connected by straight lines parallel to the lateral surfaces 14 of the evaporation boat. The cavity 4 has a bottom surface 11 and a lateral surface 12 along the outer contour 5 of the cavity 4. The lateral surface 12 of the cavity 4 is extending from the outer contour 5 of the cavity 4 at the upper side 2 of the evaporation boat 1 to the bottom surface 11 of the cavity 4. The bottom surface 11 is parallel to the underside 3 of the evaporation boat 1. The angle which is enclosed by the surface area of the upper side 2 of the evaporation boat 1 which is outside of the outer contour 5 of the cavity 4 and the lateral surface 12 of the cavity 4 is 90°.

Figure 3E shows the plan view of the upper side 2 of the evaporation boat of Figure 3B. In addition to the plan view of Figure 3 A, the shortest circumscribing contour 6 of the outer contour 5 of the cavity 4 is also shown in Figure 3E. The shortest circumscribing contour 6 is the shortest contour which circumscribes the outer contour 5. The shortest circumscribing contour is of course not a real contour present at the upper side 2 of the evaporation boat 1, it is instead a theoretical contour which is used for explanatory purposes. In Figure 3E, the shortest circumscribing contour 6 is shown as a dotted line. As can be seen in Figure 3E, the circumferential length of the shortest circumscribing contour 6 is shorter than the circumferential length of the outer contour 5. The ratio of the circumferential length of the shortest circumscribing contour 6 to the circumferential length of the outer contour 5 is 0.96. The outer contour 5 of the cavity 4 comprises six extensions 10 which are directed inwardly. Three of these extensions are located along each of the two lateral surfaces of the evaporation boat. The six extensions of the outer contour directed inwardly can be regarded as extensions of the shortest circumscribing contour 6 of the outer contour 5. Due to these extensions, the circumferential length of the shortest circumscribing contour 6 is shorter than the circumferential length of the outer contour 5. The six extensions of the outer contour directed inwardly can also be regarded as extensions of the lateral surface of the cavity.

The ratio of the area enclosed by the outer contour 5 of the cavity 4 to the total surface area of the upper side 2 of the evaporation boat 1 as shown in Figures 3B and 3E is 0.29. The area enclosed by the outer contour 5 of the cavity 4 may also be larger than shown in Figures 3B and 3E, and the ratio of the area enclosed by the outer contour 5 of the cavity 4 to the total surface area of the upper side 2 of the evaporation boat 1 may also be up to 0.7 or up to 0.95. The ratio of the minimal width of the cavity 4 to the maximal width of the cavity 4 is 0.65 for the evaporation boat shown in Figures 3A - 3E.

Figure 3F schematically shows a plan view of the upper side 2 of the evaporation boat 1 of Figure 3B under operation. The upper side 2 of the evaporation boat has been wetted by molten aluminum. The area 13 which is wetted by molten aluminum is schematically shown as a hatched area. For the evaporation boat disclosed herein as shown in Figure 3F, the wetted surface area is wider than for the reference boat of Figure ID. This can be explained by the additional surface area of the upper side of the evaporation boat that can be used for evaporation and which is generated by the increased surface area of the lateral surface of the cavity which is larger than the lateral surface of the cavity for the reference boat of Figure ID. The increased surface area of the lateral surface of the cavity compared to the reference boat of Figure ID is due to the six extensions of the outer contour of the cavity. The further effects which are caused by the increased surface area of the lateral surface of the cavity have been explained above for the evaporation boat of Figures 2A - 2F.

Figure 4A shows a plan view of the upper side 2 of a further embodiment of an evaporation boat

I as disclosed herein. Figure 4B shows a 3D view of the evaporation boat 1 of Figure 4A. Figure 4C shows a cross-sectional view of the evaporation boat 1 of Figures 4A - 4B at the sectional line denoted in Figures 4A and 4B by “4C”. Figure 4D shows a cross-sectional view of the evaporation boat of Figures 4A - 4B at the sectional line denoted in Figures 4A and 4B by “4D”. Metal is evaporated from the upper side 2 of the evaporation boat 1. The upper side 2 has a rectangular shape. The underside 3 of the evaporation boat 1 also has a rectangular shape. In Figure 4B, one of the two lateral surfaces 14 and one of the two clamping surfaces 15 of the evaporation boat 1 are also shown. The upper side 2 of the evaporation boat comprises a cavity 4. The cavity 4 is a recess in the upper side of the evaporation boat. The cavity 4 of the evaporation boat 1 of Figures 4A - 4D comprises one single recess 20. Under operation of the evaporation boat, the cavity is wetted with liquid metal to be evaporated. The cavity 4 has an outer contour 5 at the upper side 2 of the evaporation boat 1. The outer contour 5 is formed by sections of circular lines which are connected by straight lines parallel to the lateral surfaces 14 of the evaporation boat. The cavity 4 has a bottom surface 11 and a lateral surface 12 along the outer contour 5 of the cavity 4. The lateral surface 12 of the cavity 4 is extending from the outer contour 5 of the cavity 4 at the upper side 2 of the evaporation boat 1 to the bottom surface 11 of the cavity 4. The bottom surface

I I is parallel to the underside 3 of the evaporation boat 1. The angle which is enclosed by the surface area of the upper side 2 of the evaporation boat 1 which is outside of the outer contour 5 of the cavity 4 and the lateral surface 12 of the cavity 4 is 90°.

Figure 4E shows the plan view of the upper side 2 of the evaporation boat of Figure 4B. In addition to the plan view of Figure 4A, the shortest circumscribing contour 6 of the outer contour 5 of the cavity 4 is also shown in Figure 4E. The shortest circumscribing contour 6 is the shortest contour which circumscribes the outer contour 5. The shortest circumscribing contour is of course not a real contour present at the upper side 2 of the evaporation boat 1, it is instead a theoretical contour which is used for explanatory purposes. In Figure 4E, the shortest circumscribing contour 6 is shown as a dotted line. As can be seen in Figure 4E, the circumferential length of the shortest circumscribing contour 6 is shorter than the circumferential length of the outer contour 5. The ratio of the circumferential length of the shortest circumscribing contour 6 to the circumferential length of the outer contour 5 is 0.74. The outer contour 5 of the cavity 4 comprises fourteen extensions 10 which are directed inwardly. Seven of these extensions are located along each of the two lateral surfaces of the evaporation boat. The fourteen extensions of the outer contour directed inwardly can be regarded as extensions of the shortest circumscribing contour 6 of the outer contour 5. Due to these extensions, the circumferential length of the shortest circumscribing contour 6 is shorter than the circumferential length of the outer contour 5. The fourteen extensions of the outer contour directed inwardly can also be regarded as extensions of the lateral surface of the cavity. The ratio of the area enclosed by the outer contour 5 of the cavity 4 to the total surface area of the upper side 2 of the evaporation boat 1 as shown in Figures 4B and 4E is 0.29. The area enclosed by the outer contour 5 of the cavity 4 may also be larger than shown in Figures 4B and 4E, and the ratio of the area enclosed by the outer contour 5 of the cavity 4 to the total surface area of the upper side 2 of the evaporation boat 1 may also be up to 0.7 or up to 0.95. The ratio of the minimal width of the cavity 4 to the maximal width of the cavity 4 is 0.60 for the evaporation boat shown in Figures 4A - 4E.

Figure 4F schematically shows a plan view of the upper side 2 of the evaporation boat 1 of Figure 4B under operation. The upper side 2 of the evaporation boat has been wetted by molten aluminum. The area 13 which is wetted by molten aluminum is schematically shown as a hatched area. For the evaporation boat disclosed herein as shown in Figure 4F, the wetted surface area is wider than for the reference boat of Figure ID. This can be explained by the additional surface area of the upper side of the evaporation boat that can be used for evaporation and which is generated by the increased surface area of the lateral surface of the cavity which is larger than the lateral surface of the cavity for the reference boat of Figure ID. The increased surface area of the lateral surface of the cavity compared to the reference boat of Figure ID is due to the fourteen extensions of the outer contour of the cavity. The further effects which are caused by the increased surface area of the lateral surface of the cavity have been explained above for the evaporation boat of Figures 2A - 2F.

Figure 4G shows a plan view of the upper side 2 of a further embodiment of an evaporation boat 1 as disclosed herein. Figure 4H shows a 3D view of the evaporation boat 1 of Figure 4G. Figure 41 shows a cross-sectional view of the evaporation boat 1 of Figures 4G - 4H at the sectional line denoted in Figures 4G and 4H by “41”. Figure 4J shows a cross-sectional view of the evaporation boat of Figures 4G - 4H at the sectional line denoted in Figures 4G and 4H by “4J”. The upper side 2 of the evaporation boat of Figures 4G - 4J shown in Figure 4G corresponds to Figure 4A. As can be seen from Figures 4H - 4J, the cross-sectional area of the evaporation boat of this embodiment has a trapezoidal shape. The shortest circumscribing contour 6 of the outer contour 5 of the cavity 4 corresponds to the shortest circumscribing contour 6 of the evaporation boat of Figures 4A - 4E, as shown in Figure 4E. Under operation, the plan view of the evaporation boat corresponds to the plan view of the evaporation boat of Figures 4A - 4E, as shown in Figure 4F.

Figure 5A shows a plan view of the upper side 2 of a further embodiment of an evaporation boat 1 as disclosed herein. Figure 5B shows a 3D view of the evaporation boat 1 of Figure 5A. Figure 5C shows a cross-sectional view of the evaporation boat 1 of Figures 5 A - 5B at the sectional line denoted in Figures 5A and 5B by “5C”. Figure 5D shows a cross-sectional view of the evaporation boat of Figures 5A - 5B at the sectional line denoted in Figures 5A and 5B by “5D” Metal is evaporated from the upper side 2 of the evaporation boat 1. The upper side 2 has a rectangular shape. The underside 3 of the evaporation boat 1 also has a rectangular shape. In Figure 5B, one of the two lateral surfaces 14 and one of the two clamping surfaces 15 of the evaporation boat 1 are also shown. The upper side 2 of the evaporation boat comprises a cavity 4. The cavity 4 is a recess in the upper side of the evaporation boat. The cavity 4 of the evaporation boat 1 of Figures 5A - 5D comprises one single recess 20. Under operation of the evaporation boat, the cavity is wetted with liquid metal to be evaporated. The cavity 4 has an outer contour 5 at the upper side 2 of the evaporation boat 1. The outer contour 5 is formed by wave-shaped lines along the lateral surfaces 14 of the evaporation boat. The cavity 4 has a bottom surface 11 and a lateral surface 12 along the outer contour 5 of the cavity 4. The lateral surface 12 of the cavity 4 is extending from the outer contour 5 of the cavity 4 at the upper side 2 of the evaporation boat 1 to the bottom surface 11 of the cavity 4. The bottom surface 11 is parallel to the underside 3 of the evaporation boat 1. The angle which is enclosed by the surface area of the upper side 2 of the evaporation boat 1 which is outside of the outer contour 5 of the cavity 4 and the lateral surface 12 of the cavity 4 is 90°.

Figure 5E shows the plan view of the upper side 2 of the evaporation boat of Figure 5B. In addition to the plan view of Figure 5 A, the shortest circumscribing contour 6 of the outer contour 5 of the cavity 4 is also shown in Figure 5E. The shortest circumscribing contour 6 is the shortest contour which circumscribes the outer contour 5. The shortest circumscribing contour is of course not a real contour present at the upper side 2 of the evaporation boat 1, it is instead a theoretical contour which is used for explanatory purposes. In Figure 5E, the shortest circumscribing contour 6 is shown as a dotted line. As can be seen in Figure 5E, the circumferential length of the shortest circumscribing contour 6 is shorter than the circumferential length of the outer contour 5. The ratio of the circumferential length of the shortest circumscribing contour 6 to the circumferential length of the outer contour 5 is 0.52. The outer contour 5 of the cavity 4 comprises sixteen extensions 10 which are directed inwardly. Eight of these extensions are located along each of the two lateral surfaces of the evaporation boat. The sixteen extensions of the outer contour directed inwardly can also be regarded as extensions of the shortest circumscribing contour 6 of the outer contour 5. Due to these extensions, the circumferential length of the shortest circumscribing contour 6 is shorter than the circumferential length of the outer contour 5. The sixteen extensions of the outer contour directed inwardly can also be regarded as extensions of the lateral surface of the cavity.

Figure 6A shows a plan view of the upper side 2 of a further embodiment of an evaporation boat 1 as disclosed herein. Figure 6B shows a 3D view of the evaporation boat 1 of Figure 6A. Figure 6C shows a cross-sectional view of the evaporation boat 1 of Figures 6A - 6B at the sectional line denoted in Figures 6A and 6B by “6C”. Figure 6D shows a cross-sectional view of the evaporation boat of Figures 6A - 6B at the sectional line denoted in Figures 6A and 6B by “6D”. Metal is evaporated from the upper side 2 of the evaporation boat 1. The upper side 2 has a rectangular shape. The underside 3 of the evaporation boat 1 also has a rectangular shape. In Figure 6B, one of the two lateral surfaces 14 and one of the two clamping surfaces 15 of the evaporation boat 1 are also shown. The upper side 2 of the evaporation boat comprises a cavity 4. The cavity 4 comprises a recess 16 in the upper side 2 of the evaporation boat and the region 17 which is enclosed by the recess 16. The region 17 which is enclosed by the recess 16 is the central region of the cavity 4. The recess 16 is located along the outer contour 5 of the cavity 4 Under operation of the evaporation boat, the cavity is wetted with liquid metal to be evaporated. The cavity 4 has an outer contour 5 at the upper side 2 of the evaporation boat 1. The outer contour 5 is formed by sections of circular lines. The depth of the cavity of the evaporation boat of Figures 6A - 6D is larger near the outer contour of the cavity and is smaller in the central region of the cavity, i.e., at positions more distant from the outer contour. The depth of the cavity may be 0.5 to 5 mm, for example 3 mm, at positions 16 near the outer contour of the cavity. The depth of the cavity is 0 mm in the central region 17 of the cavity in the embodiment shown in Figures 6A - 6D. The depth of the cavity may also be larger, for example 1 - 2 mm, in the central region 17 of the cavity.

The cavity 4 has a bottom surface 11 and a lateral surface 12 along the outer contour 5 of the cavity 4. The lateral surface 12 of the cavity 4 is extending from the outer contour 5 of the cavity 4 at the upper side 2 of the evaporation boat 1 to the bottom surface 11 of the cavity 4. The central region 17 of the cavity is also the central region of the bottom surface 11 of the cavity 4 and lies in the same plane as the upper side 2 of the evaporation boat in regions outside of the outer contour 4. The angle which is enclosed by the surface area of the upper side 2 of the evaporation boat 1 which is outside of the outer contour 5 of the cavity 4 and the lateral surface 12 of the cavity 4 is 90°.

The outer contour 5 of the cavity corresponds to the outer contour of the recess 16. The recess 16 has an inner contour 18. The depth of the cavity 5 is different at positions outside of the inner contour 18 from the depth of the cavity 5 at positions inside of the inner contour 18. The depth of the cavity at positions of the recess 16, i.e., outside of the inner contour 18, may be 0.5 to 5 mm and is larger than the depth of the cavity at positions of the central region 17 of the cavity, i.e., at positions inside of the inner contour 18.

The area enclosed by the outer contour 5 of the cavity comprises an area 17 lying in the same plane as the surface area of the upper side 2 of the evaporation boat which is outside of the outer contour 5 of the cavity 4, in other words the area 17 can also be referred to as an “island”.

Figure 6E shows the plan view of the upper side 2 of the evaporation boat of Figure 6B. In addition to the plan view of Figure 6A, the shortest circumscribing contour 6 of the outer contour 5 of the cavity 4 is also shown in Figure 6E. The shortest circumscribing contour 6 is the shortest contour which circumscribes the outer contour 5. The shortest circumscribing contour is of course not a real contour present at the upper side 2 of the evaporation boat 1, it is instead a theoretical contour which is used for explanatory purposes. In Figure 6E, the shortest circumscribing contour 6 is shown as a dotted line. As can be seen in Figure 6E, the circumferential length of the shortest circumscribing contour 6 is shorter than the circumferential length of the outer contour 5. The ratio of the circumferential length of the shortest circumscribing contour 6 to the circumferential length of the outer contour 5 is 0.93. The outer contour 5 of the cavity 4 comprises eight extensions 10 which are directed inwardly. Four of these extensions are located along each of the two lateral surfaces of the evaporation boat. The eight extensions of the outer contour directed inwardly can be regarded as extensions of the shortest circumscribing contour 6 of the outer contour 5. Due to these extensions, the circumferential length of the shortest circumscribing contour 6 is shorter than the circumferential length of the outer contour 5. The eight extensions of the outer contour directed inwardly can also be regarded as extensions of the lateral surface of the cavity. Figure 7A shows a plan view of the upper side 2 of a further embodiment of an evaporation boat 1 as disclosed herein. Figure 7B shows a 3D view of the evaporation boat 1 of Figure 7A. Figure 7C shows a cross-sectional view of the evaporation boat 1 of Figures 7A - 7B at the sectional line denoted in Figures 7A and 7B by “7C”. Figure 7D shows a cross-sectional view of the evaporation boat of Figures 7A - 7B at the sectional line denoted in Figures 7A and 7B by “7D”. Metal is evaporated from the upper side 2 of the evaporation boat 1. The upper side 2 has a rectangular shape. The underside 3 of the evaporation boat 1 also has a rectangular shape. The upper side 2 of the evaporation boat comprises a cavity 4. The cavity 4 is composed of three recesses 7 in the upper side 2 of the evaporation boat. Each of the three recesses 7 has an outer contour 8 at the upper side 2 of the evaporation boat 1. The outer contour 5 of the cavity 4 of the evaporation boat 1 is composed of the outer contours 8 of the three individual recesses 7.

Figure 7E shows the plan view of the upper side 2 of the evaporation boat of Figure 7B. In addition to the plan view of Figure 7A, the shortest circumscribing contour 9 of the outer contour 8 of each of the three individual recesses 7 is also shown in Figure 7E. The shortest circumscribing contour 9 is the shortest contour which circumscribes the outer contour 8. The shortest circumscribing contour is of course not a real contour present at the upper side 2 of the evaporation boat 1, it is instead a theoretical contour which is used for explanatory purposes. In Figure 7E, the shortest circumscribing contour 6 is shown as a dotted line. The shortest circumscribing contour 9 has a circular shape, i.e., it is a circumscribing circle. As can be seen in Figure 7E, the circumferential length of the shortest circumscribing contour 9 is shorter than the circumferential length of the outer contour 8 for each of the three recesses 7. The sum of the circumferential lengths of the outer contour 8 of the individual recesses 7 is the circumferential length of the outer contour 5 of the cavity 4 of the evaporation boat 1. The sum of the circumferential lengths of the shortest circumscribing contour 9 of the individual recesses 7 is the circumferential length of the shortest circumscribing contour 6 of the cavity 4 of the evaporation boat 1.

The outer contour 8 of the three recesses 7 each comprises twelve extensions 10 which are directed inwardly, towards the center of the circumscribing circle. The twelve extensions directed inwardly can be regarded as extensions of the shortest circumscribing contour 9 of the outer contour 8. It is also possible that the recesses 7 have more or less extensions than twelve, for example three to twenty extensions. The extensions 10 have a rounded shape near the circumscribing circle and at the innermost portions of the extensions which are closest to the center of the circumscribing circle. Due to these extensions, the circumferential length of the shortest circumscribing contour 9 is shorter than the circumferential length of the outer contour 8.

Figures 8 and 9 each show a plan view of the upper side 2 of a further embodiment of an evaporation boat 1 as disclosed herein. These embodiments are similar to the embodiment of Figure 7B, with the cavity 4 being composed of three individual recesses 7. The extensions 10 of Figure 9 have a non-rounded shape near the circumscribing circle and at the innermost portions of the extensions which are closest to the center of the circumscribing circle. The extensions 10 of Figure 8 have a triangular shape. Figures 10 to 12 each show a plan view of the upper side 2 of a further embodiment of an evaporation boat 1 as disclosed herein. These embodiments have a cavity 4 consisting of one single recess in the upper side 2 of the evaporation boat 1. The outer contour 5 of the cavity 4 of the embodiment of Figure 10 comprises a meandric line, the outer contour 5 of the cavity 4 of the embodiment of Figure 11 comprises extensions 10 directed inwardly with a rounded shape and with different lengths of the extensions in a direction parallel to the clamping surfaces of the evaporation boat, i.e., in a direction perpendicular to the longitudinal axis of the evaporation boat, and the outer contour 5 of the cavity 4 of the embodiment of Figure 12 comprises extensions 10 also extending from the shortest circumscribing contour 6 at the two smaller sides of the cavity 4 near the clamping regions. The minimal width of the cavity in a direction perpendicular to the longitudinal axis of the evaporation boat and the maximal width of the cavity in a direction perpendicular to the longitudinal axis of the evaporation boat are measured at positions outside of the extensions 19 near the clamping regions.

Figure 13A shows a plan view of the upper side 2 of a further embodiment of an evaporation boat 1 as disclosed herein. Figure 13B shows a 3D view of the evaporation boat 1 of Figure 13A. Figure 13C shows a cross-sectional view of the evaporation boat 1 of Figures 13A - 13B at the sectional line denoted in Figure 13A by “13C” Metal is evaporated from the upper side 2 of the evaporation boat 1. The upper side 2 has a rectangular shape. The underside 3 of the evaporation boat 1 also has a rectangular shape. In Figure 13B, one of the two lateral surfaces 14 and one of the two clamping surfaces 15 of the evaporation boat 1 are also shown. The upper side 2 of the evaporation boat comprises a cavity 4. The cavity 4 is a recess in the upper side of the evaporation boat. The cavity 4 of the evaporation boat 1 of Figures 13A - 13C comprises one single recess 20. Under operation of the evaporation boat, the cavity is wetted with liquid metal to be evaporated. The cavity 4 has an outer contour 5 at the upper side 2 of the evaporation boat 1. The outer contour 5 is formed by sections of circular lines connected by straight lines. Along the two lateral surfaces 14 of the evaporation boat, the outer contour 5 has the form of a meander-shaped line with rounded comers. Also, the cavity 4 has a meander-shaped form with rounded comers.

The cavity 4 has a bottom surface 11 and a lateral surface 12 along the outer contour 5 of the cavity 4. The lateral surface 12 of the cavity 4 is extending from the outer contour 5 of the cavity 4 at the upper side 2 of the evaporation boat 1 to the bottom surface 11 of the cavity 4. The bottom surface 11 is parallel to the underside 3 of the evaporation boat 1. The angle which is enclosed by the surface area of the upper side 2 of the evaporation boat 1 which is outside of the outer contour 5 of the cavity 4 and the lateral surface 12 of the cavity 4 is 90°.

Figure 13D shows the plan view of the upper side 2 of the evaporation boat of Figure 13B. In addition to the plan view of Figure 13 A, the shortest circumscribing contour 6 of the outer contour 5 of the cavity 4 is also shown in Figure 13D. The shortest circumscribing contour 6 is the shortest contour which circumscribes the outer contour 5. The shortest circumscribing contour is of course not a real contour present at the upper side 2 of the evaporation boat 1, it is instead a theoretical contour which is used for explanatory purposes. In Figure 13D, the shortest circumscribing contour 6 is shown as a dotted line. As can be seen in Figure 13D, the circumferential length of the shortest circumscribing contour 6 is shorter than the circumferential length of the outer contour 5. The ratio of the circumferential length of the shortest circumscribing contour 6 to the circumferential length of the outer contour 5 is 0.57. The outer contour 5 of the cavity 4 comprises eight extensions 10 which are directed inwardly. The eight extensions are extensions extending inwardly from the shortest circumscribing contour 6 of the outer contour 5. Four of these extensions are located along each of the two lateral surfaces of the evaporation boat. The eight extensions of the outer contour directed inwardly can also be regarded as extensions of the shortest circumscribing contour 6 of the outer contour 5. Due to these extensions, the circumferential length of the shortest circumscribing contour 6 is shorter than the circumferential length of the outer contour 5. The eight extensions of the outer contour directed inwardly can also be regarded as extensions of the lateral surface of the cavity.

The width of the extensions in a direction parallel to the longitudinal axis of the evaporation boat is 3 mm. The length of the extensions in a direction perpendicular to the longitudinal axis of the evaporation boat is 12, 17 and 22 mm, respectively. The width of the evaporation boat is 38 mm, the maximal width of the cavity in a direction perpendicular to the longitudinal axis of the evaporation boat is 34 mm. The minimal width of the cavity in a direction perpendicular to the longitudinal axis is 12 mm, and the minimal width of the cavity in a direction parallel to the longitudinal axis is 8 mm.

The material from which the evaporation boat disclosed herein is made may comprise titanium diboride and boron nitride. In some embodiments, the material from which the evaporation boat is made comprises titanium diboride, boron nitride and aluminum nitride. The titanium diboride content of the material from which the evaporation boat is made typically ranges from 25 to 40 vol.-%.

The volume of the evaporation boat disclosed herein typically ranges from about 25 cnf to 85 cn

The evaporation boats disclosed herein can be produced by conventional methods such as hot- pressing a powder mixture comprising titanium diboride and boron nitride into a hot-pressed body and machining the evaporation boats from the hot-pressed bodies. The evaporation boats with the rectangular, trapezoidal or other cross-sectional areas can be produced by machining, such as sawing. The upper side of the evaporation boat where metal is evaporated from can be produced by machining, such as grinding and milling and the like. The cavity of the evaporation boat can be produced by machining, such as grinding and milling and the like.

The edges of the evaporation boat as disclosed herein may be chamfered, i.e., rounded, according to common practice for ceramic materials.

The evaporation boat as disclosed herein can be used for evaporating metals selected from the group consisting of aluminum, copper and silver. In some embodiments of the present disclosure, the evaporation boat is used for evaporating aluminum for transparent aluminum oxide (A1O_X) coatings.

Examples Examples 1 - 3 (EXI - EX3) and Comparative Example (CEX)

Evaporation boats according to the present disclosure as shown in Figures 2A - 2E (Example 1), 3A - 3E (Example 2) and 4A - 4E (Example 3) were prepared and tested in a lab coater under the typical conditions of a standard web coating process.

For comparison, a reference evaporation boat having a cavity according to Figures 1A - 1C was also tested (Comparative Example). The dimensions of all tested evaporation boats were 9 x 38 x 130 mm. All evaporation boats were produced from one lot from a powder mixture comprising titanium diboride and boron nitride, with a titanium diboride content of 47.0 wt.-%.

The aluminum feeding rate, which is the amount of aluminum which is fed to the boat in one minute, was increased stepwise to a maximum rate of 11 g/min.

The results achieved for power consumption are shown in Table 1. Power consumption for the Comparative Example is set to 100% as a reference. Power consumption for Examples 1 to 3 is expressed as percentage of power consumption of the Comparative Example. The values in Table 1 for power consumption for a specific aluminum feeding rate are the mean values for three evaporation boats over the whole time when this specific aluminum feeding rate was run (e.g., 4. 1 g/min, as indicated in Table 1).

Table 1:

It can be seen from Table 1 that at higher aluminum feeding rates the overall power consumption for Examples 1, 2 and 3 was lower than that for the reference evaporation boat (Comparative Example). This shows that the thickness of the liquid aluminum in the cavity of the evaporation boats of Examples 1, 2 and 3 was lower than for the reference evaporation boat. By that effect, so-called pinholes in the metallized fdm can be minimized. In addition, the upper side of the tested evaporation boats with the liquid metal pool were drawn schematically. In Figures ID, 2F, 3F and 4F, the area 13 which is wetted by molten aluminum is schematically shown as a hatched area. It can be seen from these drawings that for Examples 1, 2 and 3 there is a much wider wetted area across the boat width than for the reference evaporation boat of the Comparative Example, whereas for the reference evaporation boat of the Comparative Example, there is a much higher tendency for aluminum flow towards the copper clamps, compared to Examples 1, 2 and 3.

Claims

1. Evaporation boat for (1) evaporation of metals, wherein the evaporation boat (1) has an upper side (2), an underside (3), two lateral surfaces (14) and two clamping surfaces (15), and wherein metal is evaporated from the upper side (2) of the evaporation boat, and wherein the upper side (2) of the evaporation boat comprises a cavity (4), and wherein the cavity (4) has an outer contour (5) at the upper side (2) of the evaporation boat, and wherein the outer contour (5) of the cavity (4) has a shortest circumscribing contour (6), and wherein the outer contour (5) has a circumferential length, and wherein the shortest circumscribing contour (6) has a circumferential length, and wherein the ratio of the circumferential length of the shortest circumscribing contour (6) to the circumferential length of the outer contour (5) is at most 0.8.

2. Evaporation boat (1) for evaporation of metals, wherein the evaporation boat (1) has an upper side (2), an underside (3), two lateral surfaces (14) and two clamping surfaces (15), and wherein metal is evaporated from the upper side (2) of the evaporation boat, and wherein the upper side (2) of the evaporation boat comprises a cavity (4), and wherein the cavity (4) of the evaporation boat (1) comprises a plurality of recesses (7) in the upper side (2) of the evaporation boat, and wherein each individual recess (7) of the plurality of recesses has an outer contour (8) at the upper side (2) of the evaporation boat (1), and wherein the outer contour (8) of each individual recess (7) has a shortest circumscribing contour (9), and wherein the outer contour (8) of each individual recess (7) has a circumferential length, and wherein the shortest circumscribing contour (9) of each individual recess (7) has a circumferential length, and wherein for at least one individual recess (7), the ratio of the circumferential length of the shortest circumscribing contour (9) to the circumferential length of the outer contour (8) is at most 0.8.

3. The evaporation boat of claim 1 or 2, wherein the shortest circumscribing contour (6, 9) is a circle, a polygon, or a combination of a polygon with one or more curves or portions of a circle.

4. The evaporation boat of any of claims 1 to 3, wherein the area enclosed by the outer contour (5, 8) of the cavity does not comprise an area lying in the same plane as the surface area of the upper side of the evaporation boat which is outside of the outer contour of the cavity.

5. The evaporation boat of any of claims 1 to 4, wherein the ratio of the circumferential length of the shortest circumscribing contour (6, 9) to the circumferential length of the outer contour (5, 8) is at most 0.75, or at most 0.70, or at most 0.65, or at most 0.60.

6. The evaporation boat of any of claims 1 to 5, wherein the ratio of the circumferential length of the shortest circumscribing contour (6, 9) to the circumferential length of the outer contour (5, 8) is at least 0.1, or at least 0.2, or at least 0.35.

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7. The evaporation boat of any of claims 1 to 6, wherein the ratio of the circumferential length of the shortest circumscribing contour (6, 9) to the circumferential length of the outer contour (5, 8) is at least 0.1 and at most 0.8.

8. The evaporation boat of any of claims 1 to 7, wherein the ratio of the area enclosed by the outer contour (5, 8) of the cavity (4) to the total surface area of the upper side (2) of the evaporation boat (1) is at most 0.95.

9. The evaporation boat of any of claims 1 to 8, wherein the cavity (4) comprises one single recess (20) in the upper side (2) of the evaporation boat (1), and wherein the area enclosed by the outer contour (5) of the cavity (4) is a continuous area.

10. The evaporation boat (1) of any of claims 1 to 9, wherein the evaporation boat has a longitudinal axis, and wherein the cavity (4) has a maximal width in a direction perpendicular to the longitudinal axis, and wherein the cavity (4) has a minimal width in a direction perpendicular to the longitudinal axis, and wherein the minimal width of the cavity (4) is smaller than the maximal width of the cavity, and wherein the ratio of the minimal width of the cavity (4) to the maximal width of the cavity (4) is at least 0.15.

11. The evaporation boat of any of claims 1 to 10, wherein the evaporation boat (1) has a longitudinal axis, and wherein the cavity (4) has a minimal width in a direction perpendicular to the longitudinal axis, and wherein the minimal width of the cavity in a direction perpendicular to the longitudinal axis is at least 3 mm, preferably at least 5 mm, more preferably at least 7 mm.

12. The evaporation boat of any of claims 1 to 11, wherein the cavity (4) comprises one single recess (20) in the upper side (2) of the evaporation boat (1), and wherein the area enclosed by the outer contour (5) of the cavity (4) is a continuous area, and wherein the area enclosed by the outer contour (5, 8) of the cavity does not comprise an area lying in the same plane as the surface area of the upper side of the evaporation boat which is outside of the outer contour of the cavity, and wherein the evaporation boat (1) has a longitudinal axis, and wherein the cavity (4) has a minimal width in a direction perpendicular to the longitudinal axis, and wherein the minimal width of the cavity in a direction perpendicular to the longitudinal axis is at least 3 mm, preferably at least 5 mm, more preferably at least 7 mm.

13. The evaporation boat (1) of any of claims 1 to 12, wherein the outer contour (5, 8) of the cavity (4) comprises a plurality of extensions (10) which are directed inwardly, and wherein the plurality of extensions are extensions extending inwardly from the shortest circumscribing contour of the outer contour.

14. The evaporation boat of any of claims 1 to 13, wherein the cavity (4) has a meander-shaped form, and wherein the meander-shaped form preferably has rounded comers.

15. The evaporation boat of claim 14, wherein the evaporation boat (1) has a longitudinal axis, and wherein the cavity (4) has a minimal width in a direction perpendicular to the longitudinal axis, and wherein the minimal width of the cavity in a direction perpendicular to the longitudinal axis is at least 3 mm, preferably at least 5 mm, more preferably at least 7 mm.

16. The evaporation boat of any of claims 1 to 15, wherein the outer contour (5) of the cavity (4) comprises a plurality of, preferably at least four, extensions (10) which are directed inwardly, and wherein the plurality of extensions are extensions extending inwardly from the shortest circumscribing contour of the outer contour, and wherein the width of the extensions in a direction parallel to the longitudinal axis of the evaporation boat is at least 1 mm and at most 10 mm, and wherein the length of the extensions in a direction perpendicular to the longitudinal axis of the evaporation boat is at least 1 mm and at most the maximal width of the cavity minus 3 mm.

17. The evaporation boat of claim 16, wherein the individual extensions (10) of the outer contour (5) of the cavity (4) have three different lengths, and wherein the average length of the extensions in a direction perpendicular to the longitudinal axis of the evaporation boat is from 10 to 90% of the maximum width of the cavity, and wherein the first of the three different lengths of the extensions in a direction perpendicular to the longitudinal axis of the evaporation boat corresponds to from 10 to 90% of the maximum width of the cavity, and wherein the second of the three different lengths of the extensions in a direction perpendicular to the longitudinal axis of the evaporation boat corresponds to the first of the three lengths minus 0. 1 to 10 mm, and wherein the third of the three different lengths of the extensions in a direction perpendicular to the longitudinal axis of the evaporation boat corresponds to the first of the three lengths plus 0.1 to 10 mm.

18. The evaporation boat of claim 16 or 17, wherein the individual extensions (10) of the outer contour (5) of the cavity (4) are arranged in an alternating manner along the two lateral surfaces (14) of the evaporation boat (1).

19. The evaporation boat of any of claims 1 to 18, wherein the cavity (4) comprises one single recess (20) in the upper side (2) of the evaporation boat (1), and wherein the area enclosed by the outer contour (5) of the cavity (4) is a continuous area, and wherein the area enclosed by the outer contour (5, 8) of the cavity does not comprise an area lying in the same plane as the surface area of the upper side of the evaporation boat which is outside of the outer contour of the cavity, and wherein the evaporation boat (1) has a longitudinal axis, and wherein the cavity (4) has a minimal width in a direction perpendicular to the longitudinal axis, and wherein the minimal width of the cavity in a direction perpendicular to the longitudinal axis is at least 3 mm, preferably at least 5 mm, more preferably at least 7 mm, and wherein the outer contour (5) of the cavity (4) comprises at least four extensions which are directed inwardly, and wherein the at least four extensions are extensions extending inwardly from the shortest circumscribing contour of the outer contour, and wherein the width of the extensions in a direction parallel to the longitudinal axis of the evaporation boat is at least 1 mm and at most 10 mm, and wherein the length of the extensions in a direction perpendicular to the longitudinal axis of the evaporation boat is at least 1 mm and at most the maximal width of the cavity minus 3 mm.

20. The evaporation boat (1) of any of claims 1 to 19, wherein the cavity (4) has a bottom surface (11), and wherein the cavity (4) has a lateral surface (12) along the outer contour (5) of the cavity (4), and wherein the lateral surface (12) of the cavity (4) is extending from the outer contour (5) of the cavity (4) at the upper side (2) of the evaporation boat (1) to the bottom surface (11) of the cavity (4), and wherein the angle which is enclosed by the surface area of the upper side (2) of the evaporation boat (1) which is outside of the outer contour (5) of the cavity (4) and the lateral surface (12) of the cavity (4) is from 45 to 135°.

21. The evaporation boat (1) according to any of claims 1 to 20, wherein the ratio of the depth of the cavity (4) to the height of the evaporation boat (1) is from 0.03 to 0.65, preferably from 0.05 to 0.3.

22. The evaporation boat (1) of any of claims 1 to 21, wherein the cavity (4) comprises a recess (16) in the upper side (2) of the evaporation boat (1) and a central region (17), and wherein the recess (16) is located along the outer contour (5) of the cavity (4), and wherein the central region (17) is enclosed by the recess (16), and wherein the depth of the cavity (4) measured at positions of the recess (16) is different from the depth of the cavity (4) measured at positions of the central region (17), and wherein the depth of the cavity (4) measured at positions of the recess (16) is from 0.5 to 5 mm, and wherein the depth of the cavity (4) measured at positions of the central region (17) is from 0 to 5 mm.

23. The evaporation boat (1) according to any of claims 1 to 22, wherein the material from which the evaporation boat (1) is made comprises titanium diboride and boron nitride.

24. Use of the evaporation boat (1) according to any of claims 1 to 23 for evaporating metals selected from the group consisting of aluminum, copper and silver.