An LED filament

Abstract

An LED filament, comprising a pin and at least one LED arrangement. The pin is configured to connect to an output terminal of a power supply for the LED filament. The pin connects to the LED arrangement by a first wire and a second wire. The ends of the first wire and second wire that are connected to the pin are distanced from one to another, but connected via the pin. The ends of the first wire and second wire that are connected to the LED arrangement are positioned to overlap one another.

Description

[0001] An LED filament

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to the field of LED lighting, and in particular, to LED filaments.

[0004] BACKGROUND OF THE INVENTION

[0005] There is an increasing use of and interest in LED lamps (e.g., light bulbs) for lighting applications in a wide variety of environments. One form of LED lamp makes use of one or more LED filaments for the light source. A typical LED filament will comprise one or more LED arrangements connected in series to a pin or between two pins. The or each pin is itself connected to a power supply for the LED lamp.

[0006] There is an ongoing interest in reducing a risk of an LED lamp failing, e.g., due to a broken wire within the LED lamp. In other words, there is a desire to maintain or improve a reliability of an LED lamp that makes use of one or more LED filaments.

[0007] EP 2535640A1 discloses a LED light bulb, comprising: a LED light bulb shell; a core column with an exhaust tube and a bracket; at least one LED light emitting strip with LED chips therein emitting 4K light; a driver; and an electrical connector.

[0008] WO 2017202456A1 discloses a filament for a lamp comprising at least two light emitting semiconductor chips, wherein at least three lead frames are embedded in a carrier body, wherein a first light emitting semiconductor chip and a second light emitting semiconductor chip are arranged on the lead frames.

[0009] SUMMARY OF THE INVENTION

[0010] The invention is defined by the claims.

[0011] According to examples in accordance with an aspect of the invention, there is provided an LED filament for an LED lamp.

[0012] The LED filament comprises: a pin for connection to an output terminal of a power supply; an LED arrangement connecting to the pin, the LED arrangement comprising a wire connection element for connecting to a conductive wire; a first wire connecting a first pin connection point of the pin to a first LED connection point of the wire connecting element of the LED arrangement; and a second wire separate to the first wire, connecting a second pin connection point of the pin to a second LED connection point of the wire connecting element of the LED arrangement.

[0013] Preferably, the first pin connection point and the second pin connection point are distanced from one another; and the first LED connection point and the second LED connection point overlap one another.

[0014] The present disclosure thereby provides an LED filament with a redundant wire connecting a pin of the filament to an LED arrangement of the filament. Thus, two separate wires connect the pin of the filament to the LED arrangement. This significantly improves a reliability of the LED filament, particularly to heating of the LED filament.

[0015] It has been recognized that during manufacture of an LED lamp using the LED, there is commonly a need to seal a bulb (covering the LED filament) to a stem. This sealing procedure typically involves a heating to create the interface between the bulb and the stem. As the pin of the LED filament will typically be connected to an output terminal located in / on the stem, this can cause a localized heating near the pin. By providing two wires that connect the pin to the LED arrangement, redundancy can be created at a location most susceptible to this form of heating, thereby reducing a risk of the LED lamp failing by improving a robustness of the LED filament.

[0016] It will be appreciated that the pin and the wire connection element are both formed of an electrically conductive material (e.g., a metal). As such, the first pin connection point and the second pin connection point are electrically connected to one another via the material of the pin. Similarly, the first LED connection point and the second LED connection point are electrically connected to one another via the material of the wire connection element.

[0017] The LED filament may further comprise a substrate mounting the pin and the LED arrangement. In such examples, a first wire position, being a position on the first wire that is most distant from the substrate, may be more proximate to the pin than the LED arrangement; and a second wire position, being a position on the second wire that is most distant from the substrate, may be more proximate to the LED arrangement than the pin.

[0018] This embodiment recognizes that manufacturing techniques and limitations means that, for a typical wire that connects two parts of an LED filament together, the weakest bond or connection between the wire and either part of the LED filament will be located closer to the highest (i.e., most distant from the substrate) part of the wire. By positioning the two highest points of the first and second wires closer to different parts of the LED filament, then a localized heating near one of the parts of the LED filament is less likely to damage or break both the first and second wires. Thus, the LED filament is made more robust.

[0019] A localized heating may, for instance, occur during a manufacture of an LED lamp using the LED filament (e.g., during a sealing procedure or the like) and / or during use of the LED filament after manufacture of the LED lamp (e.g., due to waste heat generated by the LED arrangement).

[0020] In some examples, the pin lies between the first wire position and the substrate; and the LED arrangement lies between the second wire position and the substrate.

[0021] In some examples, a first hypothetical straight line connects between the first pin connection and the first LED connection point; a second hypothetical straight line connects between the second pin connection and the second LED connection point; an angle between the first hypothetical straight line and the first wire at the first pin connection point is greater than an angle between the first hypothetical straight line and the first wire at the first LED connection point; and an angle between the second hypothetical straight line and the second wire at the second LED connection point is greater than an angle between the second hypothetical straight line and the second wire at the second pin connection point.

[0022] It is recognized that in a typical structure for a wire connecting two parts of an LED filament together, the angle between a hypothetical line connecting the two parts together and the wire will be greater at a weaker (wire) bond than at a stronger (wire) bond. By positioning the greatest angle for each wire at different locations, then a localized heating is less likely to damage or break both the first and second wires. Thus, the LED filament is made more robust.

[0023] In some examples, the angle between the first hypothetical straight line and the first wire at the first pin connection point is greater than the angle between the first hypothetical straight line and the first wire at the first LED connection point; and the angle between the second hypothetical straight line and the second wire at the second LED connection point is more than 25° greater than the angle between the second hypothetical straight line and the second wire at the second pin connection point.

[0024] In some examples, the angle between the first hypothetical straight line and the first wire at the first LED connection point is less than 15°; and / or the angle between the second hypothetical straight line and the second wire at the second pin connection point is less than 15°.

[0025] These approaches introduce slackness into each wire, increasing the toughness and resilience of the wire to thereby further increase the reliability of the LED filament. In some examples, the majority of the first wire is more proximate to the first pin connection point than the first wire connection point; and the majority of the second wire is more proximate to the second wire connection point than the first pin connection point.

[0026] The LED filament may further comprise one or more further LED arrangements, wherein each further LED arrangement is connected in series with the LED arrangement to form a sequence of LED arrangements.

[0027] In some examples, the first wire and the second wire are formed using a ball bonding technique.

[0028] In some examples, the first wire comprises a first ball bond directly connected to the first pin connection point; a first tail bond directly connected to the first LED connection point; and a first loop connecting the first ball bond to the first tail bond; and the second wire comprises a second ball bond directly connected to the second LED connection point; a second tail bond directly connected to the second pin connection point; and a second loop connecting the second ball bond to the second tail bond.

[0029] It is herein recognized that wires created using ball bonding techniques exhibit a vulnerability at the junction where the ball bond meets the wire loop. This juncture, often referred to as necking, is particularly susceptible to breakage or failure when subjected to heat, e.g., during bulb sealing. The proposed approach helps to mitigate this risk by placing the ball bonds of the first and second wires on separate sections of the LED filament. This configuration substantially decreases the likelihood of simultaneous connection failure at both wire sections in the event of localized heating.

[0030] The LED filament may further comprise a wavelength conversion layer configured to encapsulate at least the first wire and the second wire. In some examples, the substrate is optically transmissive; and the wavelength conversion layer is configured to encapsulate the substrate.

[0031] The described approaches as above may also be implemented in a Chip-on- Board (CoB) LED configuration, which is similar to the LED filament, i.e., two separate wires connect the electrode / pin of the CoB package to the LED arrangement on the substrate of CoB. This significantly improves a reliability of the CoB against heating.

[0032] There is also proposed an LED lamp comprising one or more LED filaments, or CoB LED light source, as herein proposed.

[0033] In some examples, the lamp is designed for retrofitting in an HID lighting arrangement and is capable of emitting light having a luminous flux of no less than 2,000 lumens. In some examples, the LED lamp further comprises a stem; a bulb sealed to the stem, wherein the stem and bulb together enclose the one or more LED filaments.

[0034] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment s) described hereinafter.

[0035] BRIEF DESCRIPTION OF THE DRAWINGS

[0036] For a better understanding of the invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, in which:

[0037] Figure 1 illustrates an existing LED filament;

[0038] Figure 2 illustrates a proposed LED filament;

[0039] Figure 3 illustrates the proposed LED filament;

[0040] Figure 4 illustrates the proposed LED filament;

[0041] Figure 5 illustrates a wire for use in a proposed LED filament;

[0042] Figure 6 illustrates a portion of the proposed LED filament;

[0043] Figure 7 illustrates a further proposed LED filament;

[0044] Figure 8 illustrates yet another proposed LED filament; and

[0045] Figure 9 illustrates a proposed LED lamp.

[0046] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0047] The invention will be described with reference to the Figures.

[0048] It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the apparatus, systems and methods, are intended for purposes of illustration only and are not intended to limit the scope of the invention. These and other features, aspects, and advantages of the apparatus, systems and methods of the present invention will become better understood from the following description, appended claims, and accompanying drawings. It should be understood that the Figures are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the Figures to indicate the same or similar parts.

[0049] The invention provides an LED filament, comprising a pin and at least one LED arrangement. The pin is configured to connect to an output terminal of a power supply for the LED filament. The pin connects to the LED arrangement by a first wire and a second wire. The ends of the first wire and second wire that are connected to the pin are distanced from one to another, but connected via the pin. The ends of the first wire and second wire that are connected to the LED arrangement are positioned to overlap one another.

[0050] In the context of the present disclosure, a filament is an elongate element that emits light when powered. An LED filament comprises a linear string of LED arrangements, e.g., connected in series. In particular, an LED filament may be formed from a string of LEDs covered or encapsulated with a covering or protective portion. The covering portion may be continuously formed along the LED filament. The covering portion may be formed from a wavelength conversion layer, e.g., a phosphor blended resin or plastics.

[0051] Figure 1 illustrates an example of an existing LED filament 100 for improved contextual understanding. The LED filament 100 comprises a pin 110, a set of one or more LED arrangements 121, 122, 123 and a substrate 130.

[0052] The pin 110 is designed for connection to an output terminal of a power supply (not visible in Figure 1). The set of one or more LED arrangements are connected, in series to one another, to the pin 110 via respective wires. For instance, a first wire 131 connects the pin 110 to a first LED arrangement 121, a second wire 132 connects the first LED arrangement to a second LED arrangement 122.

[0053] The pin 110 is located at one end of the elongate shape of the LED filament 100. Although not illustrated, the LED filament may comprise a second pin at the opposite end of the elongate shape of the LED filament. The set of one or more LED arrangements 121, 122, 123 may be connected between the pin 110 and the second pin (not visible in Figure 1).

[0054] Each LED arrangement may, for instance, be or comprise a separate LED chip configured to emit light when powered. Suitable examples of LED chips for use in LED filaments are well known and established in the art.

[0055] The operation and light emission control of LED arrangements are well known in the art, and are not described in detail for the sake of conciseness. The precise configuration and / or design of the LED arrangements is largely immaterial to the proposed approach.

[0056] The present disclosure provides a mechanism for improving the reliability of an LED filament. In particular, the present disclosure proposes to use a pair of wires to connect the pin to a (first) LED arrangement, rather than a single wire (as illustrated in the existing LED filament 100).

[0057] It has been recognized that during manufacture of an LED lamp, there is commonly a need to seal a stem of the lamp to a bulb of the lamp. The bulb encloses the LED filament, and is typically more proximate to the LED filament at a location near the pin of the LED filament. This is because the pin will be close to the stem, which usually houses or is proximate to the output terminal(s) of the power supply. It has been recognized that the heat sealing of the stem to the bulb will result in an increased risk of damage to the connection between the pin and the first LED arrangement. Thus, there is a specific risk of damage between the pin and the LED arrangement, which is mitigated through use of the proposed technique.

[0058] Figure 2 provides a first view of a proposed LED filament 200.

[0059] The LED filament comprises a pin 210 for connection to an output terminal of a power supply. The LED filament also comprises an LED arrangement 220 connecting to the pin 210. The LED filament 200 may also comprise a substrate 250 on which the pin 210 and LED arrangement 220 are mounted.

[0060] The LED filament may further comprise one or more further LED arrangements 241, 242, wherein each further LED arrangement is connected in series with the LED arrangement to form a sequence of LED arrangements.

[0061] The LED arrangement 220 comprises a wire connection element 225 for connecting to a conductive wire. The wire connection element 225 may, for instance, define a conductive pad or patch electrically connected to a power line of the LED arrangement 220. Thus, the LED arrangement 220 may be designed to draw power provided to the wire connection element 225 for powering or driving other components of the LED arrangement (e.g., LEDs or the like).

[0062] The LED filament further comprises a first wire 231 and a second wire 232, both of which connect the pin 210 to the wire connecting element 225 of the LED arrangement 220. This provides redundancy in the connection between the pin 210 and the LED arrangement 220 to reduce a risk of a connection failure or a disconnection between the pin 210 and the LED arrangement 220.

[0063] Each wire may be formed using a wire bonding technique, such as wedge bonding or ball bonding, which are widely known in the art. In the context of the present disclosure, a wire bonding technique is a method or process that used to create electrical interconnections between two electrical components using a (thin) metal wire and a combination of heat, pressure and / or ultrasonic energy to form bonds between the metal wire and the electrical components. Example wire bonding techniques include wedge bonding and ball bonding. In wedge bonding, ultrasonic energy is applied to create a bond between the wire and the bonding surface without melting the wire. Ball bonding typically uses a combination of heat and pressure (and optionally ultrasonic energy) to form a ball at the end of the wire which is then bonded to the surface. A more complete descriptive example of a ball bonding technique is provided later in this disclosure. Harman, George G. 2010. Wire Bonding in Microelectronics (version 3rd ed). 3rd ed. New York: McGraw-Hill provides more detailed examples and explanations for how to perform wire bonding. Prasad, Shankara K. Advanced wirebond interconnection technology. Springer Science & Business Media, 2004 also provides a number of example techniques for performing wire bonding.

[0064] Examples of suitable materials for forming a wire include any suitable conductive metal, such as aluminum, copper, silver, gold, or any alloy including the aforementioned materials. Other examples are also known in the industry.

[0065] During manufacture, the first wire 231 may be formed before the second wire 232. In one working example, during manufacture, connections between each LED arrangement (if more than one LED arrangement is present) are formed first, before the first wire 231 is formed, after which the second wire 232 may be formed.

[0066] Figure 3 provides a second view of the proposed LED filament 200.

[0067] As illustrated in Figure 3, the first wire 231 connects a first pin connection point 311 (of the pin 210) to a first LED connection point 321 of the wire connecting element 225. Similarly, the second wire 232 connects a second pin connection point 312 (of the pin 210) to a second LED connection point 322 of the wire connecting element 225.

[0068] The first pin connection point 311 and the second pin connection point 312 are distanced from one another. In other words, there is a non-zero spacing between the first wire and the second wire at the respective points at which they connect to the pin. More particularly, the first pin connection point 311 may be no less than 0.5 mm, e.g., no less than 1 mm away from the second pin connection point 312. The distance may be a distance measured along a surface of the pin. This approach reduces a risk of damaging the pin connection points during manufacture of the first and second wires.

[0069] It will be appreciated that the first pin connection point 311 is electrically connected to the second pin connection point 312More specifically, the first wire 231 and the second wire 232 are directly electrically connected together via the (material of the) pin 210. In other words, the power or voltage at the first pin connection point 311 is identical or nearidentical to the power or voltage at the second pin connection point 312.

[0070] Similarly, the first LED connection point 321 and the second LED connection point 322 overlap one another, e.g., are directly physically connected together. In this way, the first wire 231 and the second wire 232 are directly connected together at or via the wire connection element. In other words, the power or voltage at the first wire connection point 321 is identical or near-identical to the power or voltage at the second wire connection point 322. In the context of the present disclosure, near-identical indicates a same or similar value within an acceptable margin of error, e.g., ±5% or ±1%.

[0071] Figure 4 provides a third view of the proposed LED filament 200. In some approaches, it is possible to define a first wire position 411 and a second wire position 412.

[0072] The first wire position 411 is a position on the first wire that is most distant from the substrate 250. For instance, where the first wire is produced using a ball bonding technique, the first wire position 411 may represent a position of a most distant part of the loop of the first wire that is formed during the ball bonding technique.

[0073] Ball bonding is a widely used wire bonding technique to form a wire-based electrical connection between two electrical components. In this process, a fine wire, typically made of gold, copper, or aluminum, is bonded between two points to form an electrical connection.

[0074] One approach for performing a ball bonding technique is as follows. Firstly, a wire is fed through a capillary tool. The end of the wire is melted (typically using an electric spark in a process known as electronic flame-off) to form a small ball. The capillary tool then presses the ball formed at the end of the wire onto a bonding location of a first electronic component to create a first bond (the ball bond). The capillary tool then moves to a bonding location on a second electronic component, creating a wire loop as it moves (e.g., by effectively spooling out the capillary tool). The wire is then pressed, by the capillary tool, onto the bonding location of the second electronic component, creating a wedge-shaped bond (the tail bond). The wire is then cut (e.g., by a clamping and pulling procedure) to create the electrical connection between the two electronic components. More specific and detailed examples of ball bonding techniques (e.g., thermosonic ball bonding and thermocompression ball bonding) are known in the art, such as those set out in Prasad, Shankara K. Advanced wirebond interconnection technology. Springer Science & Business Media, 2004.

[0075] Similarly, the second wire position 412 is a position on the second wire that is most distant from the substrate 250. For instance, where the second wire is produced using a ball bonding technique, the second wire position may represent a position of a most distant part of the loop of the second wire that is formed during the ball bonding technique.

[0076] Preferably, the first wire position 231 is more proximate to the pin 210 than the LED arrangement 220 and the second wire position 232 is more proximate to the LED arrangement 220 than the first wire position. More particularly, the pin 210 may lie between the first wire position 411 and the substrate; and the LED arrangement may lie between the second wire position 412 and the substrate. These approaches reduce a risk of a localized heating resulting in a failure of both the first and second wire, and therefore the connection between the pin 210 and the LED arrangement 220, as the majority of each wire are located in different positions.

[0077] Moreover, it is recognized that in a typical structure for a wire connecting two parts of an LED filament together, the bond (between wire and any other part of the LED filament) closest to the highest point of the wire (i.e., the first / second wire position) will be weaker than the bond furthest from the highest point of the wire. By configuring the first and second wire to have their highest positions (i.e., first / second wire position) closest to different parts of the LED filament, a localized heating (e.g., at the pin or at the LED arrangement) will have a reduced effect at the weakest bond of one of the wires, thereby improving a robustness of the LED filament.

[0078] In preferred examples, the majority of the first wire is more proximate to the first pin connection point than the first wire connection point; and the majority of the second wire is more proximate to the second wire connection point than the first pin connection point.

[0079] This approach reduces a risk of a localized heating resulting in a failure of both the first and second wire, as the majority of each wire are located in different regions.

[0080] Figure 5 illustrates an example of a wire 231, 232 for use in proposed embodiments, e.g., for use as the first wire or the second wire.

[0081] The wire 231, 232 may be produced between a first location and a second location using a ball bonding technique. As is well known, a ball bonding technique creates the wire by first using a nozzle to deposit a ball of conductive material at the first location before moving the nozzle over to the second location whilst extruding the conductive material. The nozzle is then pressed into the second location to form the wire between the first location and the second location.

[0082] Typically, in the ball bonding technique, after moving downward to deposit the ball of conductive material, the nozzle will then move vertically away from the first location before moving across to the second location.

[0083] It is therefore possible to define a wire 231, 232 produced in this way as comprising a ball bond 510 (at the first location), a loop 520 (between the first location and the second location) and a tail bond 530 (at the second location).

[0084] In preferred variants in which each of the first wire and the second wire is produced using a ball bonding technique, the ball bond of the first wire 231 is directly connected to (i.e., in direct contact with) the first pin connection point and the ball bond of the second wire 232 is directly connected to (i.e., in direct contact with) the second LED connection point. In this context, directly connected means connected without going via the tail bond.

[0085] It is herein recognized that a common point of weakness of a wire produced by a ball bonding technique is at the ball bond (specifically, the interface between the ball bond and the loop), which results in so-called necking. This point of weakness has a higher risk of breaking or failing when the wire is heated (e.g., during a bulb sealing procedure) than other locations or positions on the wire.

[0086] By positioning the ball bonds of the first and second wires against different parts of the LED filament, a risk of failure of a connection between the two parts of the LED filament is significantly reduced. In particular, a localized heating at only one of the parts is less likely to cause a failure in both wires, as might otherwise happen if the ball bonds are positioned at a same part of the LED filament.

[0087] In such examples, it will be appreciated that the ball bond of the first wire is distanced from the tail bond of the second wire. Thus, the ball bond between the first wire and the pin is distanced from the tail bond between the second wire and the pin. In other words, there is a non-zero distance between the ball bond of the first wire and the tail bond of the second wire. As previously mentioned, this approach reduces a risk of damaging the pin connection points during manufacture of the first and second wires (particularly reducing a risk of unintentionally melting the ball bond).

[0088] In preferred variants in which of the first wire and the second wire is produced using a ball bonding technique, the ball bond of the second wire 232 is directly physically connected to (i.e., in direct contact with) the tail end of the first wire 231. In particular, the ball bond of the second wire 232 may cover or lie on top of the tail end of the first wire. Thus, during manufacture, the ball bond of the second wire may be formed on top of a tail bond of the first wire. Thus, the first wire may be produced before the second wire. This improves an ease of manufacture and a reliability of an electrical connection between the first LED connection point and the second LED connection point.

[0089] Figure 6 illustrates a portion of the proposed LED filament 200, to illustrate a preferred configuration for the first and second wires. Reference is also made to Figure 3.

[0090] In particular, it is possible to define a first hypothetical straight line xi that connects between the first pin connection point 311 and the first LED connection point 321 and a second hypothetical straight line X2 that connects between the second pin connection point 312 and the second LED connection point 322. Due to the viewing angle of Figure 6, the first hypothetical straight line xi overlaps the second hypothetical straight line X2 (such t In a preferred example, an angle 0i between the first hypothetical straight line xi and the first wire 231 at the first pin connection point 311 is greater than an angle 02 between the first hypothetical straight line and the first wire 231 at the first LED connection point 321. Similarly, an angle 03 between the second hypothetical straight line and the second wire 232 at the second LED connection point 322 is preferably greater than an angle 04 between the second hypothetical straight line and the second wire 232 at the second pin connection point 312.

[0091] It is recognized that in a typical structure for a wire connecting two parts of an LED filament together, the angle between a hypothetical line connecting the two parts together and the wire will be greater at a weaker bond than at a stronger bond. This is due to natural manufacturing restrictions. Accordingly, the above configuration for the first and second wire positions the weakest bond (for each wire) at different relative locations - one connected to the LED arrangement and one directly connected to the pin. This improves a robustness of the LED filament. In particular, a localized heating at only one of the parts is less likely to cause a failure in both wires, as might otherwise happen if the weakest bonds are positioned at a same part of the LED filament.

[0092] In some examples, the angle 0i between the first hypothetical straight line and the first wire at the first pin connection point is greater than the angle 02 between the first hypothetical straight line and the first wire at the first LED connection point; and the angle 03 between the second hypothetical straight line and the second wire at the second LED connection point is more than 25° greater than the angle 04 between the second hypothetical straight line and the second wire at the second pin connection point.

[0093] In particular, the angle 02 between the first hypothetical straight line and the first wire at the first LED connection point may be less than 15°; and / or the angle 04 between the second hypothetical straight line and the second wire at the second pin connection point is less than 15°.

[0094] These approaches make each wire slacker, increasing the toughness and resilience of the wire to increase the reliability of the LED filament.

[0095] Although not illustrated in the preceding embodiments, in some further examples, the LED filament further comprises a second pin for connection to a second output terminal of a power supply (e.g., a ground or reference terminal). The second pin may be located on an opposite end of the LED filament to the pin, e.g., an opposite end of the elongate shape of the LED filament. For the sake of clarity, the previously described pin may be referred to as a first pin. In such examples, the LED filament may further comprise a first pin connecting wire and a second pin connecting wire connecting the second pin to an LED arrangement (which may be the most proximate LED arrangement to the second pin). The LED arrangement connecting to the second pin is not necessarily the same as the one connected to the first pin, but rather may be the last LED arrangement in a series of LED filaments connected between the first pin and the second pin. Of course, if the LED filament comprises only a single LED arrangement, then the first pin and the second pin connect (via respective wires) to the same LED arrangement.

[0096] The ends of the first pin connecting wire and second pin connecting wire that are connected to the LED arrangement pin are directly connected to one another. Similarly, the ends of the first pin connecting wire and second pin connecting wire that are connected to the second pin are directly connected to one another. In other words, the power or voltage at the point of connection between the first LED connecting wire and the second pin is identical or near-identical to the power or voltage at the point of connection between the second LED connecting wire and the LED arrangement.

[0097] The first and second pin connecting wires may be embodied similarly to the first 231 and second 232 wire respectively (connecting the pin to the LED arrangement 220).

[0098] Thus, for instance: the majority of the first pin connecting wire may be more proximate to the LED arrangement than the second pin; and the majority of the second pin connecting wire may be more proximate to the second pin than the LED arrangement.

[0099] In variants in which the first pin connecting wire and the second pin connecting wire is produced using a ball bonding technique, the ball bond of the first pin connecting wire may be directly connected to (i.e., in direct contact with) the LED arrangement and the ball bond of the second pin connecting wire may be directly connected to (i.e., in direct contact with) the second pin. In this context, directly connected means connected without going via the tail bond.

[0100] It is further possible to define a first pin connecting wire position, being a position on the first pin connecting wire that is most distant from the substrate, and a second pin connecting wire position, being a position on the second pin connecting wire that is most distant from the substrate.

[0101] In some such examples the first pin connecting wire position is more proximate to the LED arrangement than the second pin and the second pin connecting wire position is more proximate to the second pin than the LED arrangement. More particularly, the LED arrangement may lie between the first pin connecting wire position and the substrate; and the second pin may lie between the second pin connecting wire position and the substrate.

[0102] Figures 7 and 8 illustrate a further optional feature for any herein disclosed LED filament, namely a wavelength conversion layer.

[0103] Figure 7 illustrates a first example of an LED filament 700 comprising a wavelength conversion layer 710 that is configured to encapsulate at least the first wire and the second wire. The wavelength conversion layer is also configured to cover each LED arrangement.

[0104] The wavelength conversion layer is configured to convert at least some of the light emitted by each LED arrangement from a first predetermined wavelength band to one or more second predetermined wavelength bands.

[0105] Put another way, the wavelength conversion layer is excitable by light emitted by the LED arrangement(s) (i.e., causes the excitation of an electron within the wavelength conversion layer from a lower energy level to a higher energy level) where said excitation subsequently causes the wavelength conversion layer to emit light in the one or more second predetermined wavelength bands (e.g., due to relaxation of the excited electron). In other words, the wavelength conversion layer is configured to absorb at least some of the light passing through it and emit light in the one or more second predetermined wavelength bands.

[0106] Suitable examples of wavelength conversion layers are well known in the art.

[0107] For instance, the wavelength conversion layer may comprise a fluorescent material for conversion of light from the first predetermined wavelength band to the one or more second predetermined wavelength bands. For example, the wavelength conversion layer may comprise phosphor particles configured to emit light in the one or more second predetermined wavelength bands when excited by the excitation light. Furthermore, the material composition of the phosphor particles may be adjusted to tune / select the one or more second predetermined wavelengths.

[0108] Wavelength conversion layers comprising phosphor particles can be alternatively labelled phosphor layers.

[0109] Figure 8 illustrates a second example of an LED filament 800 comprising a wavelength conversion layer 810 that is configured to (further) encapsulate the substrate. For this embodiment, the substrate is formed from an optically transmissive material, e.g., one that transmits no less than 80% of light incident thereon. Thus, the substrate may be formed from a transmissive and / or dispersive material, such as glass, plastic, TiCL, AI2O3 and so on. There is also proposed an LED lamp comprising one or more LED filaments as herein proposed.

[0110] Figure 9 illustrates an example of a proposed LED lamp 900. The LED lamp comprises one or more LED filaments 200, 700, 700, 800, a stem 910 and a bulb 920. Each LED filament is as any herein proposed LED filament.

[0111] The stem 910 and the bulb 920 are sealed to one another, e.g., by way of a heat sealing process known in the art. Together, the stem 910 and the bulb 920 enclose or house the LED filament(s).

[0112] The stem 910 may provide wires for electrical connection for powering the LED filament(s). In particular, the stem 910 may house or mount an output terminal of a power supply to the LED filament(s). Thus, the pin of the / each LED filament may be connected to an output terminal provided at or in the stem 910. Approaches for providing such electrical connections are well known in the art.

[0113] The bulb 920 may, for instance, be formed of a transparent or translucent material that ensures illumination from the LED filament(s) is capable of dissipating or being transmitted to the surroundings. Thus, the bulb may be formed from a transmissive and / or dispersive material. For example, the material of the bulb 920 may be glass or plastic.

[0114] In the depicted embodiment, the bulb 920 has a bulged cross section. More specifically, under the IEC / TR 60887:2010 standard, the bulb 920 has a shape corresponding to the letter symbol “B”. However, in alternative embodiments the bulb 920 may have a candle flame shaped cross-section, a spherical shaped cross-section, a mushroom shaped cross section, or any shaped cross-section appropriate to house at least the plurality of filaments.

[0115] Thus, the shape of the bulb 920 may be appropriately modified or changed to match the desired standard for the lamp. The shape of the bulb for a given bulb type (e.g., A60, G95 or ST64) is defined by the letter prefix in the bulb type, as set out in the IEC / TR 60887:2010 standard. The numbers in the bulb type define the diameter / width of the bulb, as also set out in the IEC / TR 60887:2010 standard.

[0116] The LED lamp 900 may further comprise a cap or base 930, connected to the stem 920.

[0117] The base 930 may provide a means for mounting the LED lamp 900 to a socket (not shown) on a wall, ceiling or any other surface. In some embodiments, the base may comprise a screw cap (as illustrated in Figure 9), a pin and push cap or a bayonet cap. However, embodiments are not restricted to these, and the base 930 may be any means suitable for fitting the LED lamp to a lamp receiving socket. The base 930 may be appropriately configured to facilitate external powering of the (wires in the) stem. Thus, the base may comprise one or more conductors for providing a path for power from outside of the lamp 900 to the stem 910.

[0118] Of course, the LED lamp may comprise one or more other features or elements.

[0119] By way of example, the LED lamp may comprise a mount (not visible in Figure 9) that provides structural support to other elements of the LED lamp.

[0120] As another example, the LED lamp may comprise a central pillar 940 configured to provide structural support to the LED filament(s). The central pillar 940 may also comprise one or more conductors for forming an electrical circuit for the plurality of filaments, e.g., providing a return path for current flow through the plurality of filaments. The central pillar 940 may be positioned to align with, e.g., be centered around, a central axis of the LED lamp 900. More particularly, the central axis may extend in the direction of the lamp and intersect a centroid of the lamp 900.

[0121] In some examples, the LED lamp is designed for retrofitting in an HID lighting arrangement (e.g., a Son-T lighting arrangement) and is capable of emitting light having a luminous flux of no less than 2,000 lumens, e.g., no less than 3,000 lumens. This can be achieved, for instance, through appropriate design of the cap of base, the shape of the bulb 920, and / or the design of the LED arrangements in the LED filaments.

[0122] The illustrated LED lamp takes the form of an upright filament lamp. In this way, each LED filament is positioned vertically with respect to the lamp, so that they lie perpendicularly to a socket into which the lamp is connected.

[0123] However, other forms of LED (filament) lamps comprising filaments are known in the art, and could be employed for use with the present disclosure. For instance, a spiral LED filament lamp usually comprises a bundle of one or more LED filaments that is / are arranged to form a spiral or a helix, i.e., to form a spiral or helical structure. A crossing LED filament lamp comprises a plurality of LED filaments that are inclined within the LED lamp, so that they are inclined with respect to a socket into which the lamp is connected.

[0124] Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality.

[0125] The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. If the term "adapted to" is used in the claims or description, it is noted the term "adapted to" is intended to be equivalent to the term "configured to". If the term "arrangement" is used in the claims or description, it is noted the term "arrangement" is intended to be equivalent to the term "system", and vice versa. Any reference signs in the claims should not be construed as limiting the scope.

Claims

CLAIMS:

1. An LED filament (200, 700, 800) for an LED lamp (900), the LED filament comprising: a pin (210) for connection to an output terminal of a power supply; an LED arrangement (220) connecting to the pin, the LED arrangement comprising a wire connection element for connecting to a conductive wire; a first wire (231) connecting a first pin connection point (311) of the pin to a first LED connection point (321) of the wire connecting element of the LED arrangement; a second wire (232), separate to the first wire, connecting a second LED connection point (322) of the wire connecting element of the LED arrangement to a second pin connection point (312) of the pin; and a substrate (250) mounting the pin and the LED arrangement, wherein a first wire position (411), being a position on the first wire (231) that is most distant from the substrate, is more proximate to the pin than the LED arrangement; and a second wire position (412), being a position on the second wire (232) that is most distant from the substrate, is more proximate to the LED arrangement than the pin.

2. The LED filament of claim 1, wherein: the first LED connection point (321) and the second LED connection point (322) overlap one another; and the first pin connection point (311) and the second pin connection point (312) are distanced from one another.

3. The LED filament of claim 1, wherein the: the pin lies between the first wire position (411) and the substrate; and the LED arrangement lies between the second wire position (412) and the substrate.

4. The LED filament of any one of claims 1 to 3, wherein:a first hypothetical straight line (xi) connects between the first pin connection and the first LED connection point; a second hypothetical straight line (X2) connects between the second pin connection and the second LED connection point; an angle (0i) between the first hypothetical straight line and the first wire at the first pin connection point is greater than an angle (02) between the first hypothetical straight line and the first wire at the first LED connection point; and an angle (0s) between the second hypothetical straight line and the second wire at the second LED connection point is greater than an angle (04) between the second hypothetical straight line and the second wire at the second pin connection point.

5. The LED filament of claim 4, wherein: the angle (0i) between the first hypothetical straight line and the first wire at the first pin connection point is greater than the angle (02) between the first hypothetical straight line and the first wire at the first LED connection point; and the angle (0s) between the second hypothetical straight line and the second wire at the second LED connection point is more than 25° greater than the angle (04) between the second hypothetical straight line and the second wire at the second pin connection point.

6. The LED filament of any one of claims 4 or 5, wherein: the angle (02) between the first hypothetical straight line and the first wire at the first LED connection point is less than 15°; and / or the angle (04) between the second hypothetical straight line and the second wire at the second pin connection point is less than 15°.

7. The LED filament of any one of claims 1 to 6, wherein: the majority of the first wire is more proximate to the first pin connection point than the first wire connection point; and the majority of the second wire is more proximate to the second wire connection point than the first pin connection point.

8. The LED filament of any one of claims 1 to 7, further comprising one or more further LED arrangements (241, 242), wherein each further LED arrangement is connected in series with the LED arrangement to form a sequence of LED arrangements (220, 241, 242).

9. The LED filament (700, 800) of any one of claims 1 to 8, further comprising a wavelength conversion layer (710, 810) configured to encapsulate at least the first wire and the second wire.

10. The LED filament (800) of claim 9, when dependent upon claim 3, wherein: the substrate (250) is optically transmissive; and the wavelength conversion layer (810) is configured to encapsulate the substrate.

11. The LED filament of any one of claims 1 to 10, wherein: the first wire comprises a first ball bond (510) directly connected to the first pin connection point; a first tail bond (530) directly connected to the first LED connection point; and a first loop (520) connecting the first ball bond to the first tail bond; and the second wire comprises a second ball bond directly connected to the second LED connection point; a second tail bond directly connected to the second pin connection point; and a second loop connecting the second ball bond to the second tail bond.

12. An LED lamp (900) comprising one or more LED filaments as claimed in any one of claims 1 to 11.

13. The LED lamp of claim 12, wherein the lamp is designed for retrofitting in an HID lighting arrangement and is capable of emitting light having a luminous flux of no less than 2,000 lumens.

14. The LED lamp (900) of any one of claims 12 or 13, comprising: a stem (910); and a bulb (920) sealed to the stem, wherein the stem and bulb together enclose the one or more LED filaments.

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