WO2021216645A1

WO2021216645A1 - Surface mount device containing a plurality of pixels and sub-pixels

Info

Publication number: WO2021216645A1
Application number: PCT/US2021/028310
Authority: WO
Inventors: Jeremy Hochman
Original assignee: H2VR Holdco Inc
Current assignee: H2VR Holdco Inc
Priority date: 2020-04-21
Filing date: 2021-04-21
Publication date: 2021-10-28
Anticipated expiration: 2022-10-21
Also published as: CN115428146A; JP2023524635A; KR20230002405A; EP4139960A1; KR102949244B1

Abstract

Light-emitting surface mount devices comprised of an array of emitters forming multi-color and white pixels wherein the multi-color pixels have at least substantially the same overall pixel height and width as the white pixels in the array and methods of making same are disclosed. Visual uniformity is enhanced thereby. Pixels comprise emitters such as LEDs surface mounted to a substrate to form micro-arrays. Micro-arrays can be assembled into readily repairable emitter tiles which can be assembled into multi-tile video displays.

Description

SURFACE MOUNT DEVICE CONTAINING A PLURALITY OF PIXELS

AND SUB-PIXELS

RELATED APPLICATION DATA

[0001] This application claims the benefit of priority of U.S. Provisional Patent Application Serial No. 63/012,984, filed April 21, 2020, and titled “Surface Mount Device (SMD)

Containing a Plurality of Pixels and Sub-Pixels of at Least Red, Green, Blue, and White”, which is incorporated by reference herein in its entirety.

FIELD OF THE DISCLOSURE

[0002] The present disclosure generally relates to the field of LED packages. In particular, the present disclosure is directed to embodiments of surface mount devices (SMD) containing a plurality of pixels and sub-pixels of at least red, green, blue, and white.

BACKGROUND

[0003] Video displays that use light-emitting diodes (LEDs) as their light source have significant challenges as resolutions increase and the spacing between pixels is reduced. In addition, not only are there physical challenges because of the reduced spacing, the small spacing also creates an issue when modular tiles are abutted next to one another - there is a high likelihood of physical damage during installation. The robustness and repairability of a display module are important, however these two attributes are often trade-offs for each other.

[0004] In order to make a display ultimately repairable, each circuit board with an array of LEDs is made up of single pixel (or even sub-pixel) SMD LED packages. In one example, in an array of 100 x 100 pixels on a circuit board, 100 x 100 RGB SMD LEDs can be utilized. This allows a single damaged pixel to be replaced without affecting the rest of the array. In an extreme example, assuming each pixel is made of at least one each of red, green, and blue, 300 x 300 individual sub-pixel SMDs can be used for the array. If even a single sub-pixel is damaged, it can be replaced without affecting the others. These two described methodologies have been used for over 20 years in the LED industry.

[0005] In order to make a display as robust as possible, it is typical to see a potting compound user over the top of an LED array. The LED array can be made of individual SMD pixels as in the previous example, or it can be a chip-on-board (COB) process in which the diode chips are bonded directly to a circuit board as shown in FIG. 7. In both of these instances, a self leveling epoxy or silicone can be put over the entire array to make it solid and robust. This achieves a very durable front face to the array capable of withstanding reasonable impact and scratches. The comers and edges of the array, however, are still susceptible to impact, and if impact occurs, the mechanical characteristics of the potting material usually damage a cluster of RGB pixels rather than a single pixel. Further, because of the nature of the potting material being of cured adhesive, it is generally not possible (or not reasonably, commercially possibly) to repair the damaged pixel. Further, if a pixel can in fact be repaired, the potting material cannot be re-applied in a way that is not obviously re-applied (i.e. the repaired surface looks different from the rest of the array). This means that if a single pixel is damaged in the 100 x 100 pixel array, the entire array becomes unusable. This further means that just one damaged pixel requires 9,999 good pixels to be thrown away. This is incredibly inefficient, wasteful, and harmful for the environment. Another downside to these traditional techniques is that when a plurality of arrays are placed together to form a large display, the edges of the abutting arrays can be quite noticeable, similar to grout lines in architectural/building material tiles.

[0006] Another obstacle in creating displays in which the pixels are extremely close together is that the amount of solder junctions to fix the required number of red, green, blue (and possibly white or other sub-pixel colors) sub-pixels to the PCB in an array becomes too time intensive for even the fastest automated machinery. In addition, when screen resolution has a smaller pixel pitch than the acuity of human vision, it can also be unnecessary to have all of the sub-pixel elements in every single pixel location. This can be assimilated to half-tone printing in which sub-pixel colors are spaced in a known pattern to create a perceivable image when viewed from a certain distance. Many LCD or OLED monitors arrange sub-pixels in non-linear arrays, or add another color to help the special arrangement of the pixel or to help with the achievable color gamut of the display.

[0007] In light of these challenges, there remains a need in the art for readily configurable and repairable modular solutions to creation of LED tiles for creation of tiled LED displays and large video wall-type LED displays, in particular. SUMMARY OF THE DISCLOSURE

[0008] To address challenges presented by prior art designs, in some embodiments a light- emitting surface mount device includes a micro-array of self-emitting pixels with at least one white emitter sized substantially equal in height and width to a set of multi-color emitters of a neighboring pixel. The micro-array comprises at least two horizontal and two vertical pixels. At least two of the pixels each preferably comprise one white emitter and at least two pixels each preferably comprise said multi-color emitter, which may be red/green/blue emitters forming a set of sub-pixels. In some alternatives, the device may comprise a micro-array substrate with each emitter surface mounted on the micro-array substrate. In other alternatives, the device may comprise a micro-array substrate with each multi-color emitter directly bonded thereto and a white emitter substrate with the white emitter directly bonded to the white emitter substrate. In such latter embodiments, the white emitter substrate may be directly bonded to the micro-array substrate.

[0009] In other embodiments, a light-emitting surface mount device includes a 2x2 pixel micro-array with one row consisting of a first pixel formed of one each of a red LED, green LED and blue LED and a second pixel formed of a single white LED and with another row consisting of a first pixel formed of a single white LED and a second pixel formed of one each of a red LED, green LED and blue LED. Each of the pixels has the same total height and width. Alternatively, other emitter types, such as OLED, PLED, AMOLED, LCD, or LEC are used.

[0010] Further aspects and features of disclosed devices include optional configuration as one of a BGA package, a QFN package or a PLCC package. In some embodiments, a light transmissive encapsulation layer is disposed over emitters. In one preferred embodiment, the individual light-emitting surface mount devices as described are no larger than 5 mm x 5 mm.

[0011] In further embodiments, the disclosed light-emitting surface mount devices are configured in an array on a tile substrate to form a light-emitting tile. Such light-emitting tiles may be assembled as an array to form an video display wall in other disclosed embodiments.

[0012] Challenges presented by prior art designs are also met by disclosed methods of making light-emitting micro-arrays, which may comprise steps of configuring plural multi-color pixels made up of sets of multi-color emitters and having an overall combined height and width r, surface mounting the multi-color pixels to a micro-array substrate, configuring plural white emitters having an overall height and width substantially the same as the height and width of each multi-color pixel, and surface mounting the white emitters to the micro-array substrate adjacent the multi-color pixels to form a micro-array of alternating multi-color pixels and white pixels. In some embodiments, the method of making light-emitting micro-arrays may further comprise first surface mounting the white emitter to individual substrates and subsequently surface mounting the individual substrates with the white emitters separately on the micro-array substrate. In other embodiments, the method of making light-emitting micro-arrays may further comprise encapsulating the emitters in a light transmissive protective layer after surface mounting to the micro-array substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] For the purpose of illustrating the disclosure, the drawings show aspects of one or more embodiments of the disclosure. However, it should be understood that the present disclosure is not limited to the precise arrangements and instrumentalities shown in the drawings, wherein:

FIG. l is a partial schematic plan view of an LED tile according to an embodiment of the present disclosure.

FIG. 2 is a schematic plan view of a micro-array according to an embodiment of the present disclosure.

FIG. 3 is a schematic cross-sectional view of a micro-array according to an embodiment of the present disclosure.

FIG. 4 is a schematic cross-sectional view of a micro-array according to another embodiment of the present disclosure.

FIG. 5 is a diagram illustrating visual acuity in average adults as applied in embodiments of the present disclosure.

FIG. 6 is a front view of an LED display according to the present disclosure utilizing tiles made up of micro-arrays as disclosed herein.

FIG. 7 is a partial schematic plan view of an example of a prior art LED tile. DETAILED DESCRIPTION

[0014] Embodiments disclosed herein utilize micro-arrays of RGB(N)+W (red/green/blue/(other possible color) + white) pixels in order to alleviate a need for more RGB pixel sets than commercially practicable using conventional techniques, and to provide a more robust and durable array that facilitates light-emitting diode (LED) array and circuit board repair as may be necessitated by component failure or physical damage. While RGB and White LED pixels are a common construct and thus used herein for illustration purposes, the principles of the present disclosure are equally applicable to any type of emitter using multi-color pixels, whether RGB LED type emitters, other emitter types ( e.g ., organic light-emitting diodes (OLED), polymer light-emitting diodes (PLED), active-matrix light-emitting diodes (AMOLED), liquid crystal displays (LCD) or light-emitting electrochemical cells (LEC) as non-limiting examples), or other multi-color pixel combinations (e.g„ multi-primary color pixels with four or five colors such as RGBY, RGBM, RGBC or RGBYC as non-limiting examples). The scope of the present disclosure and appended claims is therefore not limited to the illustrative RGB LED examples.

[0015] FIG. 1 illustrates a portion of tile 100 according to one embodiment of the present disclosure, comprising an array of micro-arrays 102 mounted on an appropriate primary tile substrate 104, which may be, for example, a printed circuit board (PCB) or other appropriate substrate. Examples of suitable substrates for primary tile substrate 104 include standard PCB material such as FR4, flexible circuit material or foil, conductive fabric, conductive glass, or metal circuit boards. As indicated by arrows X and Y along the edges of tile substrate 104, tile 100 may extend in each X, Y direction as needed to form a desired tile size for a particular application. For example, the tile size may comprise a 10x10 array of micro-arrays 102, or a 100x100 array, or any size in-between, smaller or larger. Note that for micro-arrays 102 positioned on the edge of the larger tile array 100, the spacing to the edge of tile substrate 104 will be half of the spacing between adjacent micro-arrays 102 so as to provide a visually continuous appearance when multiple tiles 100 are abutted to form a video panel. Further spacing considerations are discussed below.

[0016] Details of an embodiment of an individual micro-array 102 are shown in FIGS. 2, 3 and 4. As shown FIG. 2, micro-array substrate 106 has mounted thereon eight LEDs forming four pixels, in other words forming a 2x2 pixel array making up a single micro-array 102. In this example, two pixels comprise one each of red LED 110, green LED 112, blue LED 114, and two pixels comprise a single white LED 116. In one embodiment, each of LEDs 110, 112, 114 and 116 are direct bonded to substrate 106 as shown in FIG. 3. In another embodiment, RGB LEDs 110, 112 and 114 are direct bonded to substrate 106, but W LED 116 is formed on a separate substrate 120 and then bonded to substrate 106 as shown in FIG. 4. For example, W LED 116 may be formed itself as an SMD package with a small blue emitter (die) to excite an illuminating substance, such as phosphor, which covers the entire or virtually the entire designated area of LED 116 in order to provide an appropriately sized white illumination area as discussed below.

In yet another embodiment, RGB LEDs 110, 112 and 114 are themselves surface mounted to a separate substrate, which is then bonded to substrate 106. Substrate 106 may comprise a standard PCB itself made from FR4 material or similar, or may be a wafer substrate material such as sapphire, silicon, silicon carbide, or gallium nitride. As is generally known in the art, substrate 106 may comprise multiple layers, including for example ceramic layer 122, metal interconnect layer 124 and a lower layer 126 comprising elements such as a thermal pad and cathode.

[0017] In another advantage of embodiments disclosed herein, the micro-arrays may be individually encapsulated with a light transmissive protective encapsulation layer 128 over the LEDs, as shown in FIG. 3. Examples of materials for encapsulation layer 128 include silicone or epoxy resin/potting compounds or conformal coatings such as parylene, paraxylene, acrylic, silicone, polyurethane or lacquer. Additionally, lenses 130, for example epoxy or silicone lenses, may be optionally disposed over the entire micro-array or over individual or groups of emitters as shown in FIG. 4. In some embodiments, encapsulation layer 128 may be used together with lenses 130.

[0018] Embodiments described herein easily lend themselves to different types of surface- mount packaging as may be best suited to particular applications. For example, embodiments disclosed herein may be provided as ball grid array (BGA) packages, various types of flat no leads packages such as quad-flat no-leads (QFN) packages, or various chip carrier packages such as plastic-leaded chip carrier (PLCC) packages. [0019] One feature of embodiments disclosed herein is that the size, i.e. overall profile (height and width) dimensions of white LED 116 are at least substantially the same as the combined size (combined height and width) of RGB LEDs 110, 112 and 114 together so as to provide a smooth and consistent visual appearance in all illumination conditions. This means that in various embodiments the combined height and combined width of the multi-color pixel and the height and width of the white pixel, if not identical, vary from one another by not more than about 1% to about 20%. (Within plus/minus 0% would be identical in size). In some embodiments, the combined height and combined width of the multi-color pixel is within about 5% to about 10% of the height and width of the white pixel.

[0020] Spacing and sizing of micro-arrays 102 can be based on visual acuity of an observer. Typical visual acuity for adults is 1 arc-minute in size, or approximately 2 pixels per degree as illustrated in FIG. 5. In general, a micro-array size should be selected such that a viewer would not perceive the boundaries of the micro-array. Parameters to be considered in sizing micro array 102 include an array size which is large enough to yield improvements in durability and robustness, yet small enough for repairability to the array on a PCB.

[0021] As reflected in FIG. 5, the distance a viewer is to the screen will have a direct correlation to an ideal array size, however generally the pixel pitch is also chosen based on this distance. In one example, a 100 x 100 pixel array may be formed according to the present disclosure using an array of micro-arrays 102 with sub-pixels and pixels in as small as a 2x2 array and large as a 16x16 array such that the micro-array size need not exceed 5mm x 5mm. In the case of a 2x2 micro-array, the footprint of the SMD is four times more robust than a single RGB SMD pixel, yet it is small enough such that it can be replaced to repair the array without being commercially unreasonable. And it is also small enough to be within visual acuity such that an observer will not be able to see a physical pattern or break-up in a very large array (in other words, the “texture” of the front of a very large display will appear uniform).

[0022] In one example, the dimensions of micro-array 102 may be approximately 5 mm or less by 5 mm or less. With a 5x5mm micro-array, individual pixel size may be in the range of about 2x2mm to about 2.4x2.4mm in some embodiments. As illustrative examples, white LED 116 may comprise a 6504 Kelvin or 2700 Kelvin LED. A further feature of embodiments disclosed herein, is that each micro-array 102 may be individually encapsulated as shown in FIG. 3. Thus, when an LED fails on one micro-array, only that specific micro-array need be replaced. The replacement micro-array then provides a more uniform appearance with the existing micro arrays because any variations in encapsulation layers fall within each of the micro-arrays. Also, a single LED failure only requires replacement of a single micro-array, for example just eight LEDs in one embodiment, thus providing much more efficiency and less waste compared to prior designs.

[0023] FIG. 6 illustrates an example of a video display or portion of a video display comprised of micro-arrays 102 as disclosed herein. In this embodiment video display 140 comprises an array of tiles 100, with each tile made up of an array of micro-arrays 102. In this example, for illustration purposes only, six tiles 100 each including sixteen micro-arrays 102 are shown. Typical real-world installations will comprise far larger arrays as will be understood by persons skilled in the art.

[0024] Further to the array size above, as explained above, embodiments disclosed herein do not utilize simple RGB sets for a pixel. White pixel 116 is added in at least one color temperature in place of an RGB set. In other words, instead of adding another sub-pixel color and attempting to decrease the sub-pixel spacing even more, embodiments of the present disclosure replace three sub-pixels with less components but in a different color. This helps achieve efficiency and also can yield a uniform flat-field white point for a video display.

[0025] Embodiments disclosed herein include:

• Surface mount devices comprising a micro-array of self-emitting pixels including at least one white emitter sized substantially equal in area to a set of red/green/blue emitters of a neighboring pixel, wherein the array has at least 2 horizontal and 2 vertical pixels.

• Surface mount devices containing a plurality of pixels and sub-pixels of at least red, green, blue, and white.

• Surface mount devices wherein the device is configured for use with surface mount technology processes.

• Surface mount devices wherein the device comprises a micro-array of RGB+W emitters such that the micro-array is no larger than 5 mm x 5 mm. [0026] The foregoing has been a detailed description of illustrative embodiments of the disclosure. It is noted that in the present specification and claims appended hereto, conjunctive language such as is used in the phrases “at least one of X, Y and Z” and “one or more of X, Y, and Z,” unless specifically stated or indicated otherwise, shall be taken to mean that each item in the conjunctive list can be present in any number exclusive of every other item in the list or in any number in combination with any or all other item(s) in the conjunctive list, each of which may also be present in any number. Applying this general rule, the conjunctive phrases in the foregoing examples in which the conjunctive list consists of X, Y, and Z shall each encompass: one or more of X; one or more of Y; one or more of Z; one or more of X and one or more of Y; one or more of Y and one or more of Z; one or more of X and one or more of Z; and one or more of X, one or more of Y and one or more of Z.

[0027] Various modifications and additions can be made without departing from the spirit and scope of this disclosure. Features of each of the various embodiments described above may be combined with features of other described embodiments as appropriate in order to provide a multiplicity of feature combinations in associated new embodiments. Furthermore, while the foregoing describes a number of separate embodiments, what has been described herein is merely illustrative of the application of the principles of the present disclosure. Additionally, although particular methods herein may be illustrated and/or described as being performed in a specific order, the ordering is highly variable within ordinary skill to achieve aspects of the present disclosure. Accordingly, this description is meant to be taken only by way of example, and not to otherwise limit the scope of this disclosure.

[0028] Exemplary embodiments have been disclosed above and illustrated in the accompanying drawings. It will be understood by those skilled in the art that various changes, omissions and additions may be made to that which is specifically disclosed herein without departing from the spirit and scope of the present disclosure.

Claims

What is claimed is:

1. A light-emitting surface mount device comprising a micro-array of self-emitting pixels including at least one white emitter with a height and width sized at least substantially equal to a combined height and width of a multi-color set of emitters of a neighboring pixel, wherein the micro-array comprises at least 2 horizontal and 2 vertical pixels.

2. The light-emitting surface mount device of claim 1, wherein at least two said pixels each comprise said one white emitter and at least two said pixels each comprise said multi-color emitters forming a set of sub-pixels.

3. The light-emitting surface mount device of claim 1 or claim 2, further comprising a micro array substrate with each said emitter surface mounted on the micro-array substrate.

4. The light-emitting surface mount device of claim 1 or claim 2, further comprising a micro array substrate with each said multi-color emitters directly bonded thereto and a white emitter substrate with the white emitter directly bonded to the white emitter substrate, and wherein the white emitter substrate is directly bonded to the micro-array substrate.

5. The light-emitting surface mount device of any preceding claim, wherein the white emitters comprise a white LED and the multi-color emitters comprise a combination of red, green and blue LEDs.

6. A light-emitting surface mount device comprising a 2x2 pixel micro-array with one row consisting of a first pixel formed of one each of a red LED, green LED and blue LED and a second pixel formed of a single white LED and with another row consisting of a first pixel formed of a single white LED and a second pixel formed of one each of a red LED, green LED and blue LED.

7. The light-emitting surface mount device of claim 6, wherein each said pixel has at least substantially equal total height and width.

8. The light-emitting surface mount device of any of claims 1-5 and 7, wherein the total height and width of each pixel varies by not more than about 1% - 20% of the total height and width of each other pixel in said micro-array.

9. The light-emitting surface mount device of claim 8, wherein the total height and width of each pixel varies by not more than about 5% - 10% of the total height and width of each other pixel in said micro-array.

10. The light-emitting surface mount device of any preceding claim, wherein the device is configured as one of a BGA package, a QFN package or a PLCC package.

11. The light-emitting surface mount device of any preceding claim, wherein the device is no larger than 5 mm x 5 mm.

12. The light-emitting surface mount device of any preceding claim, further comprising a light transmissive encapsulation layer over emitters or LEDs on the micro-array substrate.

13. A light-emitting tile comprising an array of light-emitting surface mount devices according to any preceding claim.

14. A video display wall comprising an array of light-emitting tiles according to claim 13.

15. A method of making a light-emitting micro-array, comprising: configuring plural multi-color pixels, each pixel comprising plural different color emitters and having an overall height and width; surface mounting the multi-color pixels to a micro-array substrate; configuring plural white emitters, each said white emitter having an overall height and width substantially the same as the height and width of each said multi-color pixel; and surface mounting the white emitters to the micro-array substrate adjacent the multi-color pixels to form a micro-array of alternating multi-color pixels and white pixels.

16. The method of making a light-emitting micro-array according to claim 15, wherein said surface mounting the white emitters comprise first surface mounting the white emitters to individual substrates and subsequently surface mounting the individual substrates with the white emitters separately on the micro-array substrate.

17. The method of making a light-emitting micro-array according to claim 15 or claim 16, further comprising encapsulating the emitters in a light transmissive protective layer after surface mounting the emitters to the micro-array substrate.

18. The method of making a light-emitting micro-array according to any of claims 15, 16 or 17, wherein the emitters are configured such that the micro-array is no larger than 5 mm x 5 mm.

19. The light-emitting surface mount devices or method of making a light-emitting micro-array according to any preceding claim, wherein said emitters comprise at least one of LEDs, OLEDs, PLEDs, AMOLEDs, LCDs, or LECs.