Abstract
In an embodiment a method for manufacturing at least one electronic component includes providing a second surface area of the component adjacent to a first surface area, wherein the second surface area is repulsive to a first fluid to be applied, applying the first fluid without additional pressurization to the first and/or second surface area, wherein the first surface area is wetted by the first fluid and the first fluid is repelled from the second surface area and applying a second fluid to the first surface area, to the second surface area and/or to a surface area of the solidified first fluid, after solidification of the first fluid applied to the first surface area, wherein applying the second fluid includes applying a positive pressure, a plasma action and/or a compression molding, and wherein the second fluid wets the second surface area.
Claims
1.-25. (canceled)
26. A method for manufacturing at least one electronic component, the method comprising: providing a second surface area of the component adjacent to a first surface area, wherein the second surface area is repulsive to a first fluid to be applied; applying the first fluid without additional pressurization to the first and/or second surface area, wherein the first surface area is wetted by the first fluid and the first fluid is repelled from the second surface area; and applying a second fluid to the first surface area, to the second surface area and/or to a surface area of the solidified first fluid, after solidification of the first fluid applied to the first surface area, wherein applying the second fluid comprises applying a positive pressure, a plasma action and/or a compression molding, and wherein the second fluid wets the second surface area.
27. The method according to claim 26, wherein the second surface area is provided by periodic micro- and/or nano-surface structuring of the second surface area with a periodicity in a range from approximately 600 nm to approximately 1000 nm.
28. The method according to claim 26, wherein the second surface area is provided by using moth eye structures and/or a lotus effect and/or a material or a coating of the second surface area.
29. The method according to claim 26, wherein the first fluid is pasty and/or comprises at least one low-viscosity component.
30. The method according to claim 26, wherein the first fluid comprises a layered adhesive, a solder and/or a potting compound.
31. The method according to claim 26, wherein the second fluid is equal to the first fluid.
32. The method according to claim 26, further comprising wire bonding, wherein the second fluid is an adhesive or a solder applied to the second surface area by additional pressurization.
33. The method according to claim 26, further comprising reducing a wettability of the second surface area by reducing its tackiness and increasing its dirt repellency.
34. The method according to claim 26, further comprising increasing a wettability of the first surface area by an adhesion improvement for a substrate or to wire connections.
35. A device comprising: at least one electronic component comprising: a first surface area; and a second surface area located adjacent to the first surface area, wherein the second surface area is configured to be repellent to a first fluid, wherein the first surface area is wetted by the first fluid and the second surface area is uncovered by the first fluid, and wherein, after solidification of the first fluid applied to the first surface area, a second fluid is applied to the second surface area and to a surface area of the solidified first fluid by additional pressurization.
36. The device according to claim 35, further comprising: a raw chip attached to a substrate; a spray coating applied to the raw chip and to the substrate on its side facing the raw chip; and a covering layer, wherein a main spray-coated surface of the raw chip facing away from the substrate is the second surface area, wherein a remainder of the spray coating with its side facing away from the substrate is the first surface area, wherein the first fluid becomes the covering layer, and wherein the first surface area was wetted and the second surface area remains unwetted.
37. The device according to claim 35, further comprising: a raw chip attached to a substrate, wherein the substrate adjacent to a raw chip mounting surface and/or to a main surface of the raw chip facing away from the substrate forms the second surface area, wherein side surfaces of the raw chip and the main surface of the raw chip facing away from the substrate form the first surface area, wherein the first fluid is applied to the first surface area without additional pressurization and forms a layered adhesive, and wherein the first surface area has been wetted and the second surface area remain unwetted.
38. The device according to claim 37, wherein the second surface area provided at the main surface of the raw chip facing away from the substrate is a contact surface for a wire bonding with the second fluid being a solder for a wire connection.
39. The device according to claim 37, further comprising a third fluid becoming a covering layer.
40. The device according to claim 35, further comprising: a silicone layer attached to a raw chip attached to a substrate on the main surface of the substrate facing away from the substrate, wherein a surface of the silicone layer facing away from the substrate is the second surface area, wherein a side surface of the silicone layer, a side surface of the raw chip and a side of the substrate facing the raw chip form the first surface area, wherein the first fluid is applied to the first surface area as an encapsulation, and wherein the first surface area is wetted and the second surface area remains unwetted.
41. The device according to claim 35, wherein a substrate adjacent to a raw chip mounting area forms the second surface area, wherein the remaining substrate on a side of the raw chip mounting area forms the first surface area, wherein the first fluid having been applied to the first surface area without additional pressurization forms a layered adhesive, wherein the first surface area was wetted and the second surface area remains unwetted, and wherein a raw chip is attached to the substrate on the first surface area at the raw chip mounting surface.
42. The device according to claim 41, wherein the second fluid becomes an adhesive or a solder, the second fluid having been applied to the second surface area by an additional pressurization.
43. The device according to claim 35, wherein the second surface area is an exit side of a cavity housing.
44. The device according to claim 35, wherein the electronic component is a volume emitter arranged on a substrate, wherein the first surface area includes an area adjacent to the component on a side of the substrate facing the component, wherein the second surface area includes an area at a distance from the component on the side of the substrate facing the component, wherein the first fluid is a reflector material applied to the first surface areas without additional pressurization, wherein the first surface area was wetted and the second surface area remains unwetted.
45. The device according to claim 44, wherein the reflector material is applied with a constant thickness between the volume emitter and the second surface area.
46. The device according to claim 35, wherein a drop of the first fluid is a lens material applied without additional pressurization to the first surface area, wherein the drop is shaped as a circle, and wherein the first surface area was wetted and an outer edge region of the circle as the second surface area remains unwetted.
47. The device according to claim 35, wherein a protective region for electrical contacts is the second surface area, around which the first surface area is arranged, and wherein the second surface area remains unwetted by the first fluid.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0054] The invention is described in more detail with reference to embodiments in conjunction with the figures.
[0055] FIG. 1 shows a first illustration for surface design;
[0056] FIG. 2 shows a second illustration of acting surface designs;
[0057] FIG. 3 shows a third illustration of proposed surface designs;
[0058] FIG. 4 shows an illustration of an effective cancellation of an unwettability;
[0059] FIG. 5 shows a first embodiment of a proposed method with a proposed device;
[0060] FIG. 6 shows an embodiment of a proposed manufacturing method;
[0061] FIG. 7 shows another illustration of a proposed method or a proposed device;
[0062] FIG. 8 shows an embodiment of a conventional device;
[0063] FIG. 9 shows an illustration of a proposed device;
[0064] FIG. 10 shows another embodiment of a proposed device;
[0065] FIG. 11 shows another embodiment of a proposed device;
[0066] FIG. 12 shows another embodiment of a conventional device;
[0067] FIG. 13 shows another embodiment of a proposed device; and
[0068] FIG. 14 shows an embodiment of a proposed manufacturing method.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0069] FIG. 1 shows an illustration of effective surface designs. Reference character 1 indicates a first surface area which can be wetted or covered by means of a first fluid 3. A second surface area 2 is also formed on a substrate 7, which is adjacent and contiguous to the first surface area. Both sur-face areas have a common contact line. All of the aforementioned elements are part of an electronic component B, in particular an optoelectronic component. The second surface area 2 can, for example, use a so-called “lotus blossom effect” for light emitting diode applications. This is based on complex micro- and/or nanostructured surface areas. Such a surface feature can be provided, for example, by means of a DLIP microstructuring process (DLIP=Direct Laser Interference Patterning). In this way, the second surface area 2 is formed as a microstructured area that uses the so-called lotus blossom effect in such a way that the second surface area 2 is a dewetting surface. The first surface area 1 and the second surface area 2 are formed on a substrate which in particular comprises silicone and/or in particular forms LED chip or substrate areas. FIG. 1 shows how a metered volume of liquid material as an embodiment of a first fluid 3 wets the first surface area 1 and does not wet the second surface area 2 due to its microstructured design. FIG. 1 shows a device that can be part of an LED package. The second sur-face area 2 has a structuring, and in particular in the sub-micrometer to micrometer range. Of importance is, for example, a correct aspect ratio.
[0070] In process engineering in particular, the aspect ratio is the ratio of the depth or height of a structure to its smallest lateral dimension. In general, the greater the aspect ratio and the smaller the absolute size of the structure, the more difficult it is to manufacture. The aspect ratio is particularly relevant in microtechnology. For example, a hole 60 millimeters deep can be drilled with a 6-mm drill. Thus, this hole has an aspect ratio of 10(:1). Such structuring can be manufactured by etching processes or anisotropic structuring processes, such as reactive ion etching. Furthermore, wet chemical etching processes can be used. This can be carried out in particular in conjunction with photolithography.
[0071] In this way, there are numerous parameters that must be taken into account to create an appropriately repellent surface texturing.
[0072] In addition, the material properties of surface areas and fluids are important. If, for example, the first fluid 3 is a silicone containing a phosphor, in particular phosphorus, it is possible to create a clear boundary region between the first surface area 1 and the second surface area 2. Thus, wetting in the second surface area 2 can be specifically prevented. For example, a silicone layer that is adhered tends to wet an adjacent second surface area 2. In particular, embodiments of the present invention relates to the wetting behavior in an edge region of the first surface area 1 to be wetted. A safer method in a global or larger area is to be provided more reliably. A so-called error path is to remain behind a clearly defined line. By an avoidance of undesired wetting, optical decoupling properties can be improved additionally. Specific suitable materials can result from a particular ap-plication.
[0073] FIG. 2 shows an illustration for an effective surface de-sign. Reference sign 2 designates a second surface area 2 which is not to be wetted by a first fluid 3, in particular without additional pressurization, i.e. generally in particular under atmospheric pressure PA/P1. FIG. 2 shows the targeted control of the wettability of polycarbonate substrates for a macromolecular nanotechnology as an example of a second surface area 2 by means of the production of hierarchical structures, in particular using so-called direct laser interference patterning.
[0074] FIG. 3 shows a further illustration of an effective de-vice. Reference character 1 indicates a first surface area which has been covered or wetted by the first fluid 3, for example. According to FIG. 3, a second fluid 4 is now ap-plied to the second surface area 2 under additional pressure. This can be the same optoelectronic component B as shown in FIG. 1. The lower illustration in FIG. 3 shows how the second fluid 4 covers both the first surface area 1 and the second surface area 2, and has solidified thereon. In this case, a high pressure P2/PÜ is to be applied with which the second fluid 4 is pressed into the second surface area 2. A mold press is particularly suitable for this purpose, in which, for example, 50 to 100 KN is applied to an area of approximately 4×4 square inches. This corresponds approximately to a pressure of, in particular, 4 MPa. The required pressure can also be provided for the application of a wirebond. The high pressure in FIG. 4 is marked P2/PÜ. One can see how the second fluid 4 has been pressed into the surface structure of the second surface area. A metered liquid material volume of a second fluid 4 is applied. With a suitable dosage, wetting of the first and second sur-face areas 1 and 2 can be supported in advance. In principle, the second fluid 4 can also be provided by the first fluid 3. Wetting takes place under high pressure, for example during compression molding, which results in subsequent good adhesion due to the mechanical anchoring in the micro-plane or on the microscale in the second surface area 2. In this way, a previous dewetting behavior can be reversed by means of liquid application under high pressure.
[0075] FIG. 5 shows an example of a conventional device or meth-od. FIG. 5 shows a light emitting diode structure, wherein a raw LED chip 9 is formed on a substrate 7, which is covered by a spray coating 11. For example, a phosphor spray coating, for example a phosphorus spray coating, has been carried out. For example, by means of TiO2 jetting or TiO2 spraying, a first fluid 3 has been applied, wherein a sur-face area of the LED raw chip 9 facing away from the substrate 7 is to be uncovered by the first fluid 3. Reference sign D indicates areas in which the TiO2 extends into, for example, the light-emitting area of the light-emitting di-ode. In this case, an optoelectronic component B has defective areas D which obstruct the passage of light.
[0076] According to FIG. 5, a conventional raw chip attach or die attach was carried out, followed by a spray coating on which a TiO2 jetting was carried out. Subsequently, silicone was cured by means of compression molding on a specific element on which no laser structuring was carried out. The defective areas D have tongues or “flashes” or projections which extend into a light-active area of the LED raw chip 9.
[0077] FIG. 6 shows an improved device compared to FIG. 5. The steps die attach, layer attach and film assisted molding are carried out. A raw LED chip 9 is applied to a substrate 7, which is covered by means of a spray coating 11, for example by spray coating a conversion material, in particular a phosphor, for example phosphorus. Once again, a TiO2 layer is to be applied. To improve the device according to FIG. 5, a clear edge region R to the remaining spray coating 11 is now created by means of providing a second surface area 2. The second surface area 2 is microstructured, for example, by means of microstructuring, in particular by means of DLIP (Direct Laser Interference Patterning). In this way, the remaining area of the spray coating 11 is created as a first surface area 1 remaining. The second surface area 2 is the surface area of the LED raw chip 9 facing away from the substrate 7, via which light is transmitted. In this way, a direct edge region R to the remaining spray coating 11 is created. After the spray coating, a so-called “jetting” (spraying) of a corresponding material, which can be TiO2, for example, then takes place. This now provides the first fluid 3, which is to cover a first surface area 1 but is not to wet the second surface area 2. Such an application takes place without additional pressurization, in particular under atmospheric pressure PA or pressure P1. According to a pro-posed device or a proposed manufacturing method of a device, a clearly defined edge or boundary region between the first surface area 1 and the second surface area 2 has now been created for the first fluid 3. Due to the surface properties of the second surface area 2, the second surface area 2 re-mains unwetted by the first fluid 3. In addition, the amount of the first fluid 3 to be applied can be specifically determined and metered in such a way that it is just sufficient for the first surface area 1. As a result, no tongues of the first fluid 3 or of the TiO2 are pushed onto the second surface area 2. Thus, the tongues shown in FIG. 5 are no longer present.
[0078] FIG. 7 shows a continuation of a method according to FIG. 6. According to FIG. 7, a further embodiment of an electronic component B is created by applying a second fluid 4 to the second surface area 2 and in the cured first fluid 3 to produce a covering layer 13. The application of the second fluid 4 is performed while removing the non-wettability of the second surface area 2, for example, in a “compression molding” or molding press. Optionally, a supporting plasma may be created. In further product variants, the covering layer 13 can in principle also be applied with-out additional compression molding of the covering layer 13.
[0079] By means of such a proposed device and by means of such a proposed method, so-called TiO2 tongues can be prevented from entering the optically acting surface area of the LED raw chip 9. In this way, a gain in brightness is producible.
[0080] FIG. 8 shows a further example of a conventional device. According to FIG. 8, a raw chip 9, in particular an LED raw chip, is arranged on a substrate 7. On a light-acting surface side of the raw chip 9, an element is attached by means of an adhesive, which also covers areas of the substrate 7 as well as bonding areas. These defective areas D are marked in FIG. 8. According to FIG. 8, the raw chip 9 is bonded to a contact wire 15 and encapsulated by a covering layer 13. The device according to FIG. 8 was created, for example, by means of the steps “Die-Attach” (DA), “Layer-Attach” (LA) and “Film Assisted Molding” (FAM). Disadvantageously, the adhesive on the raw chip 9 is addition-ally pressed out onto the substrate 7 and on the bonding surfaces. In this way, a light path of the optoelectronic component B is impaired. Adversely, light absorption occurs in a bonding area and/or in the substrate. The covering layer 13 is produced by means of FAM, for example from TiO2.
[0081] FIG. 9 shows an illustration of an improved device com-pared to FIG. 8. In an advantageous method, second surface areas 2 are provided on the substrate 7 adjacent to a raw chip mounting surface and/or on a main surface of the raw chip 9 facing away from the substrate. In this way, a first surface area 1 is provided as the side surfaces and as the main surface of the raw chip 9 facing away from the substrate. In a further process step, a first fluid 3 created as a layered adhesive is applied to the first surface areas 1 without applying additional pressure, wherein the first surface areas 1 are wetted and the second surface 2 remains unwetted. In this way, leakage of an adhesive can be con-trolled and in this way, subsequent optical losses can be avoided. In this way a brightness gain can be provided. Ac-cording to FIG. 9, a raw LED chip 9 with locally de-wetting surface areas 2 can be provided. In addition to un-covered substrate areas, pure bonding areas can also be left uncovered, for example on the raw chip 9. On these small bonding areas (bond pads), contact wires 15 can be electrically connected by means of a solder, as an example of a second fluid 4. Finally, a further second fluid 4a can be applied by means of FAM under high pressure PÜ or P2 in such a way that a covering layer 13 is formed which finally cures. According to the device and the method shown in FIG. 9, optical losses caused by an interfering adhesive can be avoided. Furthermore, reflective material can be prevent-ed from covering bond pads. It can also be avoided that adhesive runs onto a substrate 7 on the left and right side of a raw chip 9 in FIG. 9. By means of bonding, in particular with additional application of FAM, a layer comprising silicone and TiO2, for example, can also be applied under high pressure to the surface-structured areas and the two second surface areas 2, respectively.
[0082] According to FIG. 9, a lotus blossom effect can be used to set light-absorbing chip and substrate areas for a layered adhesive. Controlled wetting is achieved by means of an adhesive layer on a bond pad area or on a substrate. Second surface areas 2 enable dewetting or a stop function. No “floating layers” result, since an adhesive distribution can be specifically controlled. Wire bonding under pressure is then possible on the microstructured second surface areas 2, whereby the second fluid 4 can then be a solder. Thereafter, there is an additionally increased adhesive force during wire bonding as a result of a surface enlargement by means of a micromechanical anchoring. The lotus blossom effect can be cancelled for the second surface areas 2 in a TiO2 application under high pressure PÜ in a FAM process.
[0083] FIG. 10 shows a further example of a proposed device. FIG. 10 shows a raw chip 9 arranged on a substrate 7, on whose surface facing away from the substrate 7 a silicone layer has been applied. Conventionally, the disadvantage is that the applied silicone layer has an insufficient stopping effect in contrast to ceramic layers for TiO2 encapsulation.
[0084] According to further embodiments, the surface of the silicone layer can be microstructured in such a way that, in contrast to a first wettable surface area 1, a second surface area 2 is created which repels or allows a first fluid 3 to bead off. Thus, the silicone layer in the second sur-face area 2 is set to be wettable for, for example, a TiO2 encapsulation. For the manufacture of a corresponding optoelectronic component B, the cancellation of a so-called lotus blossom effect is not necessary. However, a film-assisted molding (FAM) can be carried out by means of a compression molding step or in the case of strong under-casting. In a device according to FIG. 10, tongues of the first fluid 3 penetrating into the second surface area 2 can be effectively avoided. This can be achieved by structuring the silicone layer over a large area. The TiO2 material remains on a top edge. The silicone layer can be bonded and surface-structured in a simple manner. In this way, a TiO2 undercast up to a defined line is made possible for silicone layers, which was conventionally only possible when creating ceramic layers with sharp edges. In this way, a gain in brightness can be achieved. In addition, new design options arise. By providing the silicone layer with a dewetting surface to avoid tongues or “flash”, respectively, a TiO2 cast can be performed in a simple way.
[0085] FIG. 11 shows another example of a proposed device. A raw chip 9 is attached on a substrate 1 by means of an adhesive layer. In order to hold the adhesive in the area of a raw chip mounting surface 17, a second surface area 2 has been created in a bond pad area. This stops the adhesive applied to the first surface area 1 as the first fluid 3 in the direction toward the bond pad. By means of a solder as the second fluid 4, a contact wire 15 can be pressed onto the second surface area 2 under high pressure PÜ and thus be contacted. In the first surface area 1 on the surface of the substrate 7, the adhesive has also been applied as the first fluid 3.
[0086] According to this proposed embodiment, wetting by a die at-tach adhesive on subsequent bonding areas can be avoided. The lotus blossom effect or the non-wettability in the second surface area 2 can be eliminated by wire bonding under high pressure. This results in better adhesion of a wire bond, since there is no adhesive contamination and there is also a micromechanical anchoring for the solder. FIG. 11 shows an embodiment for a general manufacture of dewetting surface areas 2, in particular on light emitting diode pack-ages. For example, top surfaces of cavity housings can be micro- and/or nanostructured to prevent overflow of, for ex-ample, a silver conductive adhesive. According to FIG. 11, the substrate 7 may have been pre-treated. According to FIG. 11, pressure holding can be performed until, for example, the adhesive material or the bonding material hardens. Microstructuring can be carried out especially when very high pressure can be applied. According to the embodiment shown in FIG. 11, this results in increased robustness for wire bond connections. FIG. 11 shows a substrate 7 with a dewetting area created as a second surface area 2. This can also be used for wire bonding under high pressure PÜ.
[0087] FIG. 12 shows an illustration of a conventional device. A raw chip 9 is applied to a substrate 7. Here, the raw chip 9 is a volume emitter. It has reflector material on the left and right. Disadvantageously, a small thickness of the reflector material results on an upper side, which is marked as defective region D. The reflector material here is for example TiO2. In this way, a brightness of the volume emitter is impaired.
[0088] FIG. 13 shows an improvement of the device according to FIG. 12. According to FIG. 13, the shaping of the reflector material, here in the case of volume emitters, can be improved by means of weeding areas or by providing a second surface area 2 as opposed to a first surface area 1.
[0089] According to FIG. 13, second surface areas 2 of the side of the substrate 7 facing the volume emitter are provided at a distance from the volume emitter or from the raw chip 9. As a result, two first surface areas 1 are simultaneously created between the volume emitter and the generated second surface areas 2 on the left and right of the volume emitter. If a metered amount of reflector material is now applied to the first surface areas 1 on the left and right of the volume emitter as the first fluid 3, a stronger reflector thickness can now be formed on the upper side of the volume emitter. Due to the stopping effect caused by the second surface area 2 provided in a wetting manner, a modified “meniscus” of the reflector material can be created in the cross-section shown. It changes in the illustrated cross-section the surface course of the reflector thickness from concave to convex, since a thicker reflector thickness can be created at the upper side of the volume emitter compared to the prior art. In principle, the boundary lines between the first surface area 1 and the second surface area 2 can be varied in such a way that alternative advantageous sur-face gradients can be provided. Due to the thicker reflector material above, an increased brightness can be generated. Shaping of the reflector material in the case of volume emitters can be provided in a targeted manner.
[0090] Further advantageous embodiments result from a general manufacture of dewetting areas on light-emitting diode packages, whereby, for example, tops of cavity housings can be provided in a dewetting manner in order to avoid overflow. This results in increased process stability. Overflow during volume casting can be avoided. If necessary, greater stability can also be achieved in the case of metered lenses or over-casting, since leakage is prevented. This can also result in lower color location scattering. In this way, package sur-faces with dewetting properties can be advantageously provided, for example a top surface to avoid tongues or “flash” in volume casting.
[0091] According to another embodiment, the transition area between the second surface area 2 and the first surface area 1 can be used as a stick edge. For example, metered lenses in the form of silicone drops can be created. For this purpose, ring-shaped structuring can be created, for example. For ex-ample, protection of electrical contact areas can be provided. This results in new design options as well as increased process stability.
[0092] According to a further embodiment, a reduction of a stickiness of surfaces can be created. Similarly, dirt-repellent surfaces can be provided. This can be used for processing such as during sawing or singulation or in subsequent applications.
[0093] According to a further embodiment, an improvement in adhesion of mold compound to substrate or of wire bond connections can be created when the lotus blossom effect is eliminated. This can be used to provide generally better adhesion as well as reduced risk of delamination.
[0094] For example, a direct laser interference patterning (DLIP) system can be used to create second surface areas (not shown). Such a system can produce a desired micrometer or submicrometer pattern on a large surface area.
[0095] Different lasers can be integrated into the DLIP system so that high process speeds, flexible structural geometries and/or the processing of 3D components are possible.
[0096] In an exemplary DLIP process, two laser beams are superimposed. By superimposing the laser beams, a structure size in the micrometer or submicrometer range can be set. In addition, the superposition results in an interference pattern depth in the millimeter to centimeter range. The superposition of both laser beams defines a superposition volume or interference volume. The structure size is determined by the width of the transition area to the surface area to be pro-cessed.
[0097] For example, a periodic hexagonally oriented structure can be generated on polyethylene (PET) or a periodic line structure on stainless steel (not shown).
[0098] FIG. 14 shows an example of a method according to embodiments of the invention. According to a first step S1, a second surface area of the component adjacent to a first surface area is provided, the second surface area being made repulsive for a first fluid to be applied. In a second step S2, the first fluid is applied, in particular a metered amount, to the first and/or second surface area, in particular only to the first surface area, without applying additional pressure, the first sur-face area being wetted by the first fluid and the first flu-id being rejected by the second surface area in such a way that the latter remains uncovered.
[0099] Although the invention has been illustrated and described in detail by means of the preferred embodiment examples, the present invention is not restricted by the disclosed examples and other variations may be derived by the skilled person without exceeding the scope of protection of the invention.
