Flexible LED Light Engine Interconnects

Systems and methods disclosed herein include a light engine circuit board including a flexible substrate having a first interconnect region located at a first end of the flexible substrate and a second interconnect region located at a second end of the flexible substrate, in which the first interconnect region and the second interconnect region each comprise one or more solder strips, and one or more LEDs on the flexible substrate.

FIELD OF THE DISCLOSURE

This disclosure relates to light engines, and specifically to systems and methods for interconnecting flexible light emitting diode (LED) light engine printed circuit boards (PCBs).

BACKGROUND

LEDs or other solid-state light sources may be placed on a variety of different surfaces, objects, or spaces depending on the application. Some of these surfaces or objects may be non-planar (e.g., curved). With the advent of flexible substrates, LEDs and LED light engines may be placed on a flexible PCB in order to attach to non-planar surfaces. However, given the large number of applications for flexible LED light engines it is difficult to custom design a flexible LED light engine to satisfy the size, length, and bend specifications for every particular application. What is needed are flexible LED light engines that are easily adapted to different size and bend constraints without losing reliability of operation.

SUMMARY

Various implementations disclosed herein include a light engine circuit board that includes a flexible substrate, one or more LEDs on the flexible substrate, and one or more interconnect regions, each including one or more solder strips. Adjacent light engine circuit boards may be connected by overlapping an interconnect region of one circuit board with an interconnect region of the other circuit board so that the solder strips of the overlapping interconnect regions conduct electricity. The interconnect regions may allow angular bending (e.g., bending at right angles) or circular bending with a tight bending radius.

Further implementations disclosed herein include a light engine circuit board, including a flexible substrate having a first interconnect region located at a first end of the flexible substrate and a second interconnect region located at a second end of the flexible substrate, in which the first interconnect region and the second interconnect region each comprise one or more solder strips, and a plurality of light emitting diodes (LEDs) on the flexible substrate.

In some implementations, the first interconnect region is located on a top surface of the flexible substrate and the second interconnect region is located on a bottom surface of the flexible substrate. In some implementations, the one or more solder strips include two solder strips. In some implementations, the one or more solder strips are line shaped, T-shaped, or I-shaped. In some implementations, the one or more solder strips on the first interconnect region and the one or more solder strips on the second interconnect region are shaped and positioned in such a way as to overlap each other when the first end is placed on top of the second end. In some implementations, the first interconnect region and the second interconnect region are shaped to overlap each other when the first end is placed on top of the second end. In some implementations, the one or more solder strips are electrically coupled to the plurality of LEDs via one or more traces. In some implementations, the circuit board further includes an adhesive tape layer. In some implementations, the plurality of LEDs are electrically coupled to a power source, and when a portion of the light engine circuit board is cut, a remaining plurality of LEDs on the light engine circuit board are still electrically coupled to the power source.

Further implementations disclosed herein include a system, the system including a first light engine circuit board that includes a first flexible substrate having a first interconnect region located at a first end of the first flexible substrate, in which the first interconnect region comprises one or more solder strips and a plurality of light emitting diodes (LEDs) on the first flexible substrate, and a second light engine circuit board that includes a second flexible substrate having a second interconnect region located at a second end of the second flexible substrate, in which the second interconnect region comprises one or more solder strips and a plurality of LEDs on the second flexible substrate, in which the first interconnect region of the first light engine circuit board overlaps with the second interconnect region of the second light engine circuit board to provide an electrical connection between the first light engine circuit board and the second light engine circuit board.

In some implementations, the one or more solder strips on the first interconnect region and the one or more solder strips on the second interconnect region overlap when the first interconnect region overlaps the second interconnect region in order to provide the electrical connection. In some implementations, the first interconnect region is located on a top surface of the first flexible substrate and the second interconnect region is located on a bottom surface of the second flexible substrate. In some implementations, the first light engine circuit board may be angularly bent with respect to the second light engine circuit board at the location where the first interconnect region overlaps the second interconnect engine. In some implementations, the first light engine circuit board may be bent at a 90° angle with respect to the second light engine circuit board. In some implementations, the first light engine circuit board may be bent at an acute angle with respect to the second light engine circuit board. In some implementations, the first light engine circuit board and the second light engine circuit board are bent in an arc shape. In some implementations, the arc shape has a radius of curvature of 1 inch or greater. In some implementations, the arc shape has a radius of curvature between 1 inch and 6 inches. In some implementations, the arc shape has a radius of curvature that depends on at least one of a physical dimension of the plurality of LEDs, a number of LEDs per unit length of the first and second light engine circuit boards, and a thickness of one or more materials comprising the first and second light engine circuit boards.

These and other features of the present implementations will be understood better by reading the following detailed description, taken together with the figures herein described. The accompanying drawings are not intended to be drawn to scale. For purposes of clarity, not every component may be labeled in every drawing.

DETAILED DESCRIPTION

FIG. 1is a block diagram illustrating a flexible LED light engine PCB100with interconnects in accordance with various implementations. The PCB100may include a flexible substrate102. The flexible substrate102may be composed of, for example, a polyimide material. The flexible substrate102may include multiple layers, such as top and bottom conducting layers and a middle insulating layer. The PCB100may also include an adhesive layer (not shown inFIG. 1) that allows the PCB100to be attached to a particular surface. The PCB100may also include a number of LEDs104, or other solid-state light sources. The number of LEDs in PCB100may vary depending on the length of the PCB100. In some implementations, the PCB100may be cut to a particular length for a certain application without affecting the operability of the PCB100.

The PCB100may also include interconnect regions106a,106b(jointly,106). The interconnect regions106are used to connect multiple PCBs100together, to increase the length of the light engine to suit a particular application. The interconnection regions106each include one or more solder strips108a,108b(jointly,108). The solder strips108provide conduction points so that power is conducted through the interconnect regions106to connected PCBs100. In some implementations, the current carrying traces are located on the bottom layer of the PCB100. In this case, the solder strips of the interconnect region on the bottom layer may be directly connected to the traces. The solder strips of the interconnect region on the top layer may be connected to the traces using a via from the bottom layer to the top layer.

For a given PCB100, the interconnect region on one end of the PCB (e.g.,106a) is located on the top layer of the PCB100while the interconnect region on the other end of the PCB (e.g.,106b) is located on the bottom layer of the PCB100. Thus, when the interconnect regions of adjacent PCBs are joined together, the top layer interconnect region of one PCB overlaps the bottom layer interconnect region of the other PCB. The solder strips108of overlapping interconnect regions also overlap such that when solder strips108are soldered together, they provide conduction points for traces connected to the solder strips108. For example, the solder strips108may allow power to flow from one PCB to another PCB.

The interconnect regions106may be shaped to allow not only circular bending of multiple joined PCBs, but angular bending as well with less stress on the connection points so that PCB operation is not affect. For example, the interconnect regions106may be bent at a right angle, or an acute angle without losing conduction capability. The interconnect regions106may also enable circular bending at very high degrees (e.g., bends with a radius of curvature of 1-3 inches).

In the solder joining process, the interconnect regions of adjacent PCBs100may be soldered together through either an automated or manual solder process. Uniform heat is applied at top and bottom solder strips of adjacent PCBs to form a strong and reliable connection joint. The solder strips108may comprise copper pads that provide a path for conduction through the electrically insulating substrate to pads or traces on the other side of the PCB100. The copper pads may be connected to copper conductors that carry current to components on the PCB100. The copper conductors may function as a bus bar and may be thick enough to carry high currents. Copper conductors may be run on or under the insulating substrate for isolation, current carrying capacity, and protection. This method of attachment is highly effective in joining printed circuit strips into larger strips, arrays, and flex reels to be used in a variety of lighting applications.

Polyimide film is the most common insulating material used in flex circuitry. For example, thin board substrate polyimide adds flexibility to the connection, reducing stress at the solder joint associated with the use of solder strips. Staggered overlapping attachments of solder strips may prevent tearing of the solder strips on the PCB100when bending stresses are introduced. The thin board substrate materials and thicknesses also assist in handling solder melt temperatures without delamination or mutilation. The interconnect regions106and solder strips108of adjacent PCBs100may designed to match each other in shape, spacing, area, thermal features, and other attributes.

The interconnect regions106and the copper conductor/bus bar may be further protected from moisture by adding a thermal conductive insulating tape, which also helps in better thermal management. Commercially available adhesive transfer tapes suitable for use with PCB100may include models 3M 8810, 3M 468MPF and 9495MP. The interconnect regions106may also include a conformal coating on one side of the PCB to strengthen the joint and protect the solder strips108from exposure to outside elements. Thermal vias around the LEDs104may also be used to improve thermal management in the case of high-power LEDs.

FIGS. 2A-2Fshow illustrative examples of various interconnect region shapes in accordance with various implementations, each of which enable the circular or angular bending qualities as described above. With respect to each ofFIGS. 2A-2F, the left interconnect region is on one side (e.g., bottom layer) of a first PCB while the right interconnect region is on the other side (e.g., top layer) of a second, adjacent PCB such that the solder strips overlap when placed on top of each other. In some implementations, paired interconnect regions may be designed to fit only with each other, i.e., they are complementary shaped. For example, PCBs100that do not have paired or keyed interconnect regions may not be attached to each other. The shape and configuration of interconnect regions is not limited to those shown inFIGS. 1-2F, but may encompass any other suitable shape and configuration known to persons of ordinary skill in the art.

FIGS. 3A-3Cshow illustrative examples of various solder strip shapes in accordance with various implementations, each of which enable the circular or angular bending qualities as described above. For example,FIG. 3Aillustrates a line-shaped solder strip,FIG. 3Billustrates a T-shaped solder strip, andFIG. 3Cillustrates an I-shaped solder strip. The shape and configuration of solder strips is not limited to those shown inFIGS. 3A-3C, but may encompass any other suitable shape and configuration known to persons of ordinary skill in the art.

FIGS. 4A-4Bshow the dimensions of an example PCB interconnect design in accordance with various implementations. This interconnect design combines the interconnect region shape illustrated inFIG. 2Fwith the solder strip shape illustrated inFIG. 3C. Such a design may be advantageous for manual or semi-automated soldering processes as it allows easy alignment of the solder strips. For example, a long strip with cross-beams at both ends provide attachment strength in both the longitudinal and lateral axes of the PCB, and provide a singular orientation for attachment.

FIGS. 5A-5Care examples of possible bend configurations of a flexible LED light engine with interconnects in accordance with various implementations. For example,FIG. 5Ashows that multiple LED light engines jointed using the disclosed interconnect design may achieve small bend radiuses when bent in an arc shape, for example up to bend radiuses of 1 inch. In general, the bend radius may be dependent on a number of factors, including but not limited to the physical dimension of LED, the number of LEDs per unit length of the light engine, and the thickness of various materials in the light engine (e.g., thermal adhesive tape, PCB copper thickness, polyimide material, glue used in construction of PCB stackup and PCB (single layer vs. multi-layer)). FIG.5B shows that multiple LED light engines jointed using the disclosed interconnect design may be bent at right angles (i.e., 90 degrees) at the interconnect region106without affecting current conduction.FIG. 5Cshows that multiple LED light engines jointed using the disclosed interconnect design may be bent at acute angles at the interconnect region106without affecting current conduction.

Throughout the entirety of the present disclosure, use of the articles “a” and/or “an” and/or “the” to modify a noun may be understood to be used for convenience and to include one, or more than one, of the modified noun, unless otherwise specifically stated. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.