Custom SMD shunt for individual leds

Abstract

The invention relates to printed circuit board, PCB, arrangement comprising a first PCB, a second PCB and a surface mounted device, SMD. The first PCB comprises a first area comprising a first trace layout comprising two first electrical connections electrically coupled to two electrical connections of the second PCB, and a second area, different from the first area, comprising a second trace layout and comprising two second 5 electrical connections identical to the two first electrical connection and electrically coupled to two electrical connections of the SMD.

Description

[0001] 2024PF80394

[0002] 1

[0003] Custom SMD shunt for individual LEDs

[0004] FIELD OF THE INVENTION

[0005] The invention relates to a PCB arrangement. The invention further relates to a lighting system. The invention further relates to a method of providing a PCB arrangement.

[0006] BACKGROUND OF THE INVENTION

[0007] In lighting applications, a large variety of lighting loads may be required. Not all lighting applications require the same light output. Therefore, many designs for light devices are made. This means that there are multiple printed circuit boards, PCBs, that allow all kind of amount of light sources to be mounted. In general, such light sources are LEDs. Depending on the application, more or less LEDs may be used, resulting in multiple PCB designs and also multiple devices to keep in stock. A solution may be to make one PCB design with the option to include or omit an LED so that the number of LEDs can be changed without changing the PCB design. This can be seen in Figure 1. This however requires shunt devices such as shunt resistors that require their own footprint on the PCB. To provide the most design freedom, it may be desired to allow multiple LEDs to be shunted. This also requires multiple footprints on the PCB for shunt devices, resulting in a more complex and larger PCB design. It is desired to provide a PCB design that allows the shunting of the LEDs in a simple way while allowing the PCB to remain simple and also more compact.

[0008] SUMMARY OF THE INVENTION

[0009] It is an objective of the invention to provide a PCB arrangement that allows easier modification of the number of placed components.

[0010] In a first aspect of the invention, a printed circuit board, PCB, arrangement is provided. The PCB arrangement comprises: a PCB, a second PCB and a surface mounted device, SMD, wherein the first PCB comprises:

[0011] - a first area comprising a first trace layout (2) comprising two first electrical connections electrically coupled to two electrical connections of the second PCB (3), and 2024PF80394

[0012] 2

[0013] - a second area, different from the first area, comprising a second trace layout (4) and comprising two second electrical connections identical to the two first electrical connection and electrically coupled to two electrical connections of the SMD.

[0014] A PCB arrangement may have a first PCB on which other components are to be mounted. A second PCB is mounted on this first PCB. The second PCB is mounted at a first area. At this first area, a first trace layout having at least two electrical connections is provided. A surface mounted device, SMD, is mounted on this first PCB. The SMD may be mounted at a second area of the PCB. At this second area, a second trace layout having at least two electrical connections is provided.

[0015] Alternatively to mounting an SMD at the first area, it may be decided that it is not required to mount the SMD at the first area since a specific design would not require it. The first area and second area are on the first PCB to allow a designer to design multiple configurations of SMDs mounted on the first PCB, while requiring only a single PCB arrangement. It may be required that an electric connection that would be made by this SMD would still have to be maintained. For this, the second PCB is used. This second PCB is then mounted at the same location where the SMD would be mounted to the first PCB at the first area. The not to be placed SMD and the second PCB are both arranged to be electrically coupled to the two electrical connections of the first trace layout. By placing the second PCB at the exact location and electrical connections as where the not to be placed SMD would be, no additional trace layout is required saving space on the first PCB, while keeping the design freedom to decide to place or not place an SMD.

[0016] In a further example, the second PCB is arranged to provide a defined impedance between the two electrical connections of the second PCB.

[0017] The second PCB is further arranged to provide a defined impedance between the at least two further electrical connections of the second PCB.

[0018] Preferably, the impedance provided by the second PCB is a defined impedance so that the designer can take this impedance into consideration in the design of the PCB arrangement.

[0019] In a further example, the electrically coupling is done via a solder connection. A solder connection provides a mechanical coupling between the first PCB and the second PCB as well as an electrical coupling between the at least two electrical connections of the first trace layout and the two electrical connections of the second PCB.

[0020] In a further example, the second PCB comprises a copper plane for realizing the defined impedance between the two electrical connections of the second PCB. 2024PF80394

[0021] 3

[0022] A simple copper plane requires no additional process steps during the manufacturing of the second PCB. No additional etching or equivalent process is required for making a track layout. A simple plane of copper also allows the predefined impedance to be as low as possible.

[0023] In a further example, the SMD is a lighting device.

[0024] Preferably, the SMD is a lighting device. Such a lighting device may then be a SMD-based lighting device. A lighting device is preferably a solid-state lighting device. Examples of such solid-state lighting devices are: LED, OLED, laser diodes. The first PCB with second PCB allow the selection of a lighting device to be mounted or not to the first PCB.

[0025] In a further example, the first trace layout and the second trace layout are electrically arranged in a series configuration such that the second PCB are arranged in series with the SMD.

[0026] Especially in a series connection of components, it may be desired that by not placing one of the series components, an electrical bypass is provided. The second PCB provides such bypass and allows the other components in the series connection to receive power or a voltage.

[0027] In a further example, a heigh of the second PCB is smaller than a height of the SMD.

[0028] To prevent the second PCB to change the overall looks of the PCB arrangement too much, it is desired that the height of the second PCB is smaller than the height of the SMD. Especially when the SMD is a lighting device, it is desired to keep the height of the second PCB as low as possible. Preferably, the height of the second PCB is less than 50 % of the height of the SMD. This prevents overall light effects to be disturbed by the placement of the second PCB.

[0029] In a further example, the second PCB has a width and / or length identical to a corresponding width and / or length of the SMD.

[0030] Preferably, the second PCB has the same dimensions as the SMD. This allows a uniform design regardless of the placement of an SMD or a second PCB.

[0031] In a further example, the second PCB comprises a solder mask on a side of the second PCB facing the first PCB.

[0032] A solder mask provided on the further PCB, e.g. at the copper plane, provides a regulator coupling between the further PCB and the PCB. 2024PF80394

[0033] 4

[0034] When soldering is implemented, the solder can be deposited at predefined locations at the second PCB, making the soldering easier.

[0035] In a further example, the second PCB comprises a reflective coating on a side directed away from the first PCB.

[0036] Preferably the second PCB has a side that has a reflective coating. This reflective coating makes the second PCB behave better in lighting implementations. When the second PCB is located close to lighting devices, the light generated by the lighting devices will be reflected by the second PCB, rather than being absorbed.

[0037] In a further example, the defined impedance is a short circuit.

[0038] Preferably, the predefined impedance is a short circuit. This allows the second PCB to directly shunt the location of the not mounted SMD and allow the next device to be directly powered by via the shunt.

[0039] In another example, a lighting system is provided.

[0040] The lighting system comprises the PCB arrangement according to the invention and a driver for driving the lighting device(s).

[0041] BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Examples of the invention will now be described with reference to the accompanying drawings, in which:

[0043] Fig. 1 shows an example of a PCB arrangement.

[0044] Fig. 2 shows another example of a PCB arrangement.

[0045] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0046] The invention will be described with reference to the Figures.

[0047] 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 also 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. 2024PF80394

[0048] 5

[0049] Figure 1 shows an example of a commonly used PCB arrangement. A PCB 1 is provided on which multiple devices are mounted. In this example, LEDs are mounted on the PCB 1. The PCB 1 has a first trace layout 2 on which an LED can be mounted. Two electrical connections are provided between the LED and the first trace layout 2. These may be used to connect the anode and cathode of the LED to the first trace layout 2. An additional electrical connection is provided in between the two electrical connections. This additional electrical connection may be used to electrically and potentially thermally connect the heatsink pad of the LED to the first trace layout 2. Multiple of these LEDs can be placed in a series chain along the PCB 1. If an LED is not used in a design and is not to be placed, a shunt of this LED needs to be provided when the LED is omitted. In this example, additional electrical connections 6 are provided. Between two electrical connections, a shunt device can be provided. This means that for shunting the LED, two shunt devices in series are required. One shunt device may be placed in parallel between anode and heatsink pad of the LED. The other shunt device may be placed between heatsink pad and cathode of the LED. This clearly causes the first trace layout 2 to significantly increase in size. Additionally, two shunt devices, preferably two shunt resistors, are required to shunt a single LED.

[0050] Figure 2 shows an example of a cross section of a printed circuit board, PCB, arrangement. The PCB arrangement has a first PCB 1 that may act as a main PCB board. On the first PCB 1, components such as surface mounted devices, SMD, may be mounted. On the first PCB 1, a first trace layout 2 is provided. The first trace layout 2 is provided in a first area and is used to provide electrically conductive paths on the first PCB 1 between different components. In this example between a second PCB present at the first area and another component located elsewhere. This first trace layout 2 may be made using copper tracks. Alternative materials may also be provided such as silver or carbon when e.g. traces are printed. The first trace layout 2 has at least two electrical connections. In the example provided, three electrical connections are provided but even more electrical connections may also be possible. The electrical connections of the first trace layout 2 can be electrically coupled to electrical connections of the second PCB 3. The second PCB 3 has electrical connections that can be connected to the electrical connections of the first trace layout 2.

[0051] Preferably, the electrically connection between the first trace layout 2 and the second PCB 3 are made using a solder connection. A solder mask may be used on the second PCB 3 to allow e.g. the solder connection to be applied in a regulated way. The solder mask may then be applied on the side of the second PCB 3 facing the first PCB 1. Preferably, the second PCB 3 is designed in a very simple fashion to make it as cheap as possible. The 2024PF80394

[0052] 6 second PCB 3 may have a single layer of copper 10, or any other electrically conductive material, that provides a short circuit between the electrical connections of the second SMD 3 and therefore also between the electrical connections present at the first PCB 1. Alternatively, when the first trace layout 2 has very small features it may be preferred to pattern the copper layer 10 in a way that will make the connection between the copper layer 10 on the second PCB 3 to the first trace layout 2 in a more reliable way.

[0053] In another example, the second PCB 3 may have a reflective coating 11 on one side of the second PCB 3. This side is the side of the second PCB 3 facing away from the first PCB 1. The optical behavior of the further PCB 3 may then be improved, which may especially be interesting when placed nearby lighting devices such as LEDs.

[0054] A second trace layout 4 is provided on the first PCB 1. The second trace layout 4 is provided in a second area and is used to provide electrically conductive paths on the first PCB 1 between different components. In this example between an SMD, present at the second area, and another component located elsewhere. Such other component may be the second PCB 3 located at the first area. The second trace layout 4 has at least two electrical connections. In the example provided, three electrical connections are provided but even more electrical connections may also be possible. The SMD has electrical connections that can be connected to the electrical connections of the second trace layout 4.

[0055] This results in that the second PCB and the SMD have a similar electrical layout allowing them to be placed at the same location of the first trace layout 2 or the second trace layout 4. In other words, the second PCB and the SMD are interchangeable without any further modifications in the PCB arrangement.

[0056] Preferably, the height of the second PCB 3 is smaller than the height of the SMD. Preferably, the height of the second PCB 3 is less than half of the height of the SMD.

[0057] Preferably, the second PCB 3 has a width and / or length identical to a corresponding width and / or length of the SMD.

[0058] Preferably, the PCB arrangement is provided in a lighting system. The lighting system further has a driver for providing power to the PCB arrangement and therefore also the components on the first PCB 1. In this example, power may be provided to the lighting load.

[0059] In the examples provided, the second PCB 3 provides a short circuit between the electric connections. Instead of a short circuit, any other predefined impedance can be provided. This can be realized by resistors, inductors and capacitors. 2024PF80394

[0060] 7

[0061] In the examples provided, the lighting device may be any kind of semiconductor lighting device. Examples of such lighting devices are LEDs, laser diodes or vertical cavity surface emitting lasers, VCELs.

[0062] In the examples provided, the two first electrical connections of the first trace layout 2 are identical to the two second electrical connections of the second trace layout 4. It may be desired to also have the entire first trace layout 2 to be identical to the second trace layout 4.

[0063] Other 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. 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. Any reference signs in the claims should not be construed as limiting the scope.

Claims

2024PF803948CLAIMS:

1. A printed circuit board, PCB, arrangement comprising: a first PCB (1), a second PCB (3) and a surface mounted device, SMD, wherein the first PCB (1) comprises:- a first area comprising a first trace layout (2) comprising two first electrical connections electrically coupled to two electrical connections of the second PCB (3), and- a second area, different from the first area, comprising a second trace layout (4) and comprising two second electrical connections identical to the two first electrical connection and electrically coupled to two electrical connections of the SMD.

2. The PCB arrangement of claim 1, wherein the second PCB (3) is arranged to provide a defined impedance between the two electrical connections of the second PCB (3).

3. The PCB arrangement according to any of the preceding claims, wherein the electrically coupling is done via a solder connection.

4. The PCB arrangement according to any of the preceding claims, wherein the second PCB (3) comprises a copper plane for realizing the defined impedance between the two electrical connections of the second PCB (3).

5. The PCB arrangement according to any of the preceding claims, wherein the SMD is a lighting device.

6. The PCB arrangement according to any of the preceding claims, wherein the first trace layout (2) and the second trace layout (4) are electrically arranged in a series configuration such that the SMD and the second PCB (3) are arranged in series.

7. The PCB arrangement according to any of the preceding claims, wherein a height of the second PCB (3) is smaller than a height of the SMD.2024PF8039498. The PCB arrangement according to any of the claims 1 to 6, wherein the second PCB (3) has a width and / or length identical to a corresponding width and / or length of the SMD.

9. The PCB arrangement according to any of the preceding claims, wherein the further PCB (3) comprises a solder mask on a side of the second PCB (3) facing the first PCB (1).

10. The PCB arrangement according to any of the preceding claims, wherein the second PCB (3) comprises a reflective coating on a side directed away from the first PCB (1).

11. The PCB arrangement according to any of the preceding claims, wherein the defined impedance is a short circuit.

12. A lighting system comprising a PCB arrangement according to claim 5 and a driver for driving the lighting device.

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