Patent Application
20170059115
The present disclosure relates to light emitting devices that enhance light cutoff to prevent a significant or otherwise distracting amount of light from being cast into preceding or oncoming cars. More particularly, the present disclosure relates to automotive chip-on-board (COB) light emitting diode (LED) sources on a printed circuit hoard (PCB) that include both reflective and non-reflective darn regions to increase the output of useful light while eliminating or otherwise mitigating the reflection of light that can cause glare.
LED devices including an LED chip that is mounted onto a flat substrate and encapsulated with material, such as silicone, are known. These devices may be generally referred to as “chip on board” (COB) devices.
In the field is known U.S. Pat. No. 8,247,827 (Helbing) disclosing, at col. 4, line 20, a dam 106 whose entire extent around LED 202 is either entirely a reflective dam 206 or a transparent (or “clear”) dam 208, but not both reflective and transparent portions simultaneously. In the case where dam 106 is entirely a reflective dam 206, it is made of a reflective material such as being opaque white formed by titanium dioxide filler in an epoxy or silicone. In the case of dam 106 being entirely a clear or transparent dam 208 it is made of epoxy or silicone without filler. A side-by-side comparison at FIG. 2 shows a dam 106 that is reflective (206) generates a narrow beam pattern 218, in contrast to a dam 102 that is transparent (208) which generates a wider beam 222. While the dam 106 shows a side comparison akin to a “split screen” view which may at first glance misleadingly suggest the dam contains both reflective and transparent portions, one of skill in the art understands from the entirety of Helbing's disclosure in context, e.g. at column 5, lines 20-35 and the overall two different radiation patterns 218, 222, that the entire dam 106 is either opaque reflective in its entirety or transparent in its entirety.
Various dams and encapsulent arrangements for LEDs are known in: U.S. Pat. No. 6,897,490 (Brunner); U.S. Pat. No. 8,044,128 (Sawada); U.S. Pat. No. 8,835,952 (Andrews); U.S. Pat. No. 6,489,637 (Sakamoto); U.S. Pat. No. 7,952,115 (Loh); U.S. Pat. No. 7,834,375 (Andrews); U.S. Pat. No. 7,365,371 (Andrews); U.S. Pat. No. 8,492,790 (Lin); U.S. Pat. No. 8,536,592 (Chang); U.S. Pat. No. 8,536,593 (Lo); and US Pat. Pubs. 2013/0312906 (Shiobara); 2013/0207130 (Reiherzer); 2013/0154130 (Peil); 2003/0062518 (Auch); 2008/0099139 (Miyoshi); 2012/0193647 (Andrews); 2005/0051782 (Negley); and in PCT Intl Application WO 2008/046583 (Schrank). A circuit board is shown in U.S. Pat. No. 7,201,497 (Weaver).
Reference should be made to the following detailed description, read in conjunction with the following figures, wherein like numerals represent like parts:
For a thorough understanding of the present disclosure, reference is made to the following detailed description, including the appended claims, in connection with the above-described drawings. Although the present disclosure is described in connection with exemplary embodiments, the disclosure is not intended to be limited to the specific forms set forth herein. It is understood that various omissions and substitutions of equivalents are contemplated as circumstances may suggest or render expedient. Also, it should be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.
The present disclosure provides a packaged light emitting device that allows enhanced light cutoff in lighting applications that seek to control glare and optimize or otherwise improve lumen output during low-beam generation. To provide the enhanced light cutoff, the packaged device includes both reflective and non-reflective regions to increase the output of useful light while also eliminating or otherwise mitigating the reflection of light that can cause glare. The packaged light emitting device is formed by a single light-emitting diode (LED) or an array of light-emitting diodes (LEDs) disposed on a generally flat substrate, such as a printed circuit board (PCB), and surrounded by a dam to allow the introduction of a sealing material to encapsulate the array of LED devices. This arrangement is generally referred to as chip-on-board (COB), which has seen a steady rise in popularity in a host of applications. For instance, COB is particularly well suited in automotive lighting applications including headlights and fog lights. Thus the packaged device may be used in a host of applications which make use of LED COB devices including, for example, motor vehicles, highway lighting, street lighting, and other applications that benefit from wide-area light emitters.
As referred to herein, the term reflective generally refers to a surface that reflects at least a portion of incident visible light. On the other hand, a non-reflective surface generally refers to a surface that reflects relatively less incident visible light than the reflective surface through, for example, absorption, diffraction, or other properties that mitigate reflection of light. These terms are intended to include common, ordinary meaning, but should not be construed as necessarily an exact reflectivity. In any event, and for the purpose of providing some specific examples, the minimum reflectivity of a “reflective” surface includes a reflectivity value of at least 80% for visible wavelengths, if not more. In contrast, the maximum reflectivity value of a “non-reflective” surface is 10%, with a preference towards the reflectivity being between 1% and 9%.
It should be appreciated that a non-transparent surface is functionally different than a transparent surface in the context of light beam optics. That is, non-transparent surfaces can absorb photons and generally do not spread a light beam. In contrast, a transparent surface does spread a light beam. To this end, while reference is made to a black (non-transparent) and transparent surface, the resulting light beams produced therefrom, respectively, have different beam patterns.
In any event, the packaged device disclosed herein includes part of its surface being non-reflective (e.g., black or transparent), and the remaining portion being reflective (e.g., white). This is to maximize or otherwise increase the output of useful light and to minimize or otherwise decrease the reflection of the light that otherwise causes glare. The white area, while capturing photons that would otherwise be wasted, produces light at a lower intensity than the main image of a light beam. In order to effectively produce a low beam, high intensity is desirable close to the light/dark cutoff with little or no spillover of lower intensity. To provide this balance, there is a non-reflective (e.g., black or transparent) region along a top or bottom portion along the long-side of the packaged device that produces the light/dark cutoff, and a reflective (e.g., white) area on the opposite side to recover photons that would otherwise be wasted. In some cases, the line of demarcation between reflective and. non-reflective areas is at the base, or top, as the case may be, of the LED devices fixedly attached to an upper surface of the packaged device. Thus the ratio of surface area that is reflective versus non-reflective is configurable, depending on a desired beam configuration.
In more detail, dam material of the packaged device is used to form a desired lens in the LED COB process. Aspects and embodiments disclosed herein manifest an appreciation that an entirely reflective dam, such as a white dam, produces high luminous intensity in a produced beam. In addition, an entirely non-reflective dam, such as a black or transparent dam, reduces glare. Thus, an embodiment disclosed herein includes a darn having both a reflective region and a non-reflective region to provide enhanced light cutoff (e.g., to reduce glare) and optimize or otherwise improve lumen output during low-beam generation.
Turning now to
In one aspect, the packaged device 100 includes a circuit board 1 comprising, for example, a printed circuit board (PCB) or other suitable substrate. For instance, the circuit board 1 can include a dielectric material such as, for example, glass fiber reinforced (fiberglass) resin, or a metal-core printed circuit board (MCPCB) or a ceramic substrate or ceramic heatsink, just to name a few. As shown, the circuit board 1 includes a circuit board upper surface 2, and a circuit board bottom surface (not shown) opposing the circuit board upper surface 2.
The circuit board 1 includes a plurality of solid-state light-emitting sources, such as light-emitting diodes (LEDs) 3, fixedly coupled to the circuit board upper surface 2, and forming an array 4, preferably a linear array of LEDs 4. The LEDs 3 may be attached via a feature of the circuit board 1, such as a ceramic sub-mount, or other suitable feature integrated or otherwise attached to the circuit board 1. The LEDs 3 are adjacent one another, and optionally and preferably arranged in a linear array 4. The LED linear array 4 is disposed along a first (forward) major long axis 6 that extends tangent to a long side of the linear array of LEDs 4 on a laterally forward direction 14 of the array. If the arrangement of LEDs 3 diverges from being a linear array 4, first long axis 6 is considered constructed tangent the forewardmost LED(s) in direction 14. In addition, the linear array of LEDs 4 also further define a rear major long axis 5 that also extends tangent to a long side of the linear array of LEDs 4 that is in parallel with the first major long axis 6. The linear array of LEDs 4 further defines two opposed lateral sides 8 and 10, respectively.
The packaged device 100 is not necessarily limited to four LEDs 3, as shown. For example, the packaged device 100 can include three (3), or more than four (4), LEDs 3, depending on a desired configuration. Moreover, while the linear array of LEDs 4 is shown in a generally center position of the packaged device 100, other locations will be apparent in light of this disclosure. The linear array of LEDs 4 can include uniform spacing between LEDs 3, or non-uniform spacing. Such spacing can include, for example, 1 millimeter or more or less, typically 0.1 mm in automotive lamps. The length L of the linear array of LEDs 4 can vary depending on, for instance, the size of each of the LEDs 3, the particular number of LEDs 3 within the linear array of LEDs 4, and desired component spacing configuration (e.g., uniform spacing, or non-uniform spacing). Likewise, the width W of the linear array of LEDs 4 can vary depending on similar factors, including the number of rows of LEDs 4, for example.
As shown in
The circuit board 1 further includes an encapsulation-receiving region 32 on the circuit board upper surface 2, with the encapsulation-receiving region 32 surrounding the linear array of LEDs 4. The encapsulation-receiving region 32 on the circuit board upper surface 2 is configured to receive an encapsulent, such as silicone. A dam 30 is disposed on the circuit board upper surface 2, with the dam 30 surrounding, in spaced relation, the linear array of LEDs 4, and on an inner-region thereof, the encapsulation-receiving region 32. As discussed below, the dam 30 can be fixedly attached via a sealant or other suitable fastener that provides adhesion between the dam 30 and the circuit board upper surface 2. The dam 30 is configured to advantageously prevent the encapsulant (not shown) from flowing in regions of the circuit board upper surface 2 outside of the encapsulation-receiving region 32 while the encapsulant solidifies.
The dam 30 can have a thickness of at least 0.1 millimeters, although other thicknesses are also within the scope of this disclosure. Likewise, and as discussed below with regard to
Within the encapsulation-receiving region 32, the circuit board upper surface 2 further includes a first circuit board portion 20, with the first circuit board portion 20 located in a forward region 12 disposed in the laterally forward direction 14 of the first major long axis 6. As discussed below in greater detail, the first circuit board portion 20 is a non-reflective surface. The non-reflective first circuit board portion 20 can be generally flat, or it can be a raised surface. The first circuit board portion 20 can include a surface that is generally a black hue. Some such example materials providing such a non-reflective surface are discussed further below.
Also within the encapsulation-receiving region 32, the circuit board further includes a second circuit board portion 22 of the circuit board upper surface 2, with the second circuit board portion 22 located in a rear region 13 disposed in the laterally rearward direction 16. The second circuit board portion 22 of the circuit board upper surface 2 occupies an area of region 32 less the space occupied by the first circuit board portion 20 of the encapsulation-receiving region 32. As also discussed in greater detail below, the second circuit board portion 22 is a reflective surface. The reflective second circuit board portion 22 can be generally flat, or it can be a raised surface. Some such example materials providing such a reflective surface are discussed further below.
Now referring to
As shown, the non-reflective dam portion 36 is a region of the dam 30 disposed in the laterally forward direction 14 forward of an intersection of the first major long axis 6 and the darn 30. The non-reflective dam portion 36 and reflective dam portion 34 thus collectively define the entire dam 30. The reflective dam portion 34 occupies a remaining region of the dam 30 and is disposed in a rearward direction 16 behind the first major long axis 6. The reflective dam portion 34 surrounds the two opposed lateral sides 8, 10 and the rear long axis 5 of the linear array of LEDs 4. The forward region 12 of the circuit board upper surface 2 also includes non-reflective qualities, as indicated by shading thereon (
Thus the first circuit board portion 20 can include a surface with a reflectivity that is less than or equal to the reflectivity of the non-reflective dam portion 36, and vice-versa. In some cases, this can include the first circuit board portion 20 comprising a surface with a black hue, and the non-reflective dam portion 36 having a transparent surface. Alternatively, non-reflective dam portion 36 can have a black hue. Similarly, the second circuit board portion 22 can include a surface with a reflectivity that is less than or equal to the reflectivity of the reflective dam portion 36, and vice-versa. However, the reflectivity of the surfaces of the first circuit board portion 20 and the non-reflective dam portion 36 are less than the reflectivity of the surfaces of the second circuit board portion 22 and the reflective dam portion 34.
The reflective dam portion 34 and non-reflective dam portion 36 can include a silicone damming material such as methyl rubber, phenyl rubber, other suitable material formed into desired dam geometries. For example, the non-reflective dam portion 36 can include silicone such as ShinEtsu X-35-396B or ShinEtsu Ker-6075-F, offered by Shin-Etsu Chemical Co., Ltd., mixed with carbon black pigments to form a black hue, or unmixed (e.g., transparent). On the other hand, the reflective dam portion 34 can include methyl rubber such as ShinEtsu Ker-2000Dam, also offered by Shin-Etsu Chemical Co., Ltd. A suitable material for a white reflective dam portion 36 is a silicone damming material with titanium oxide filler. In any such cases, the selected damming material may have a high viscosity to ensure the dam 30 does not flatten during curing. The exact material selection for reflective and non-reflective dam portions 34 and 36, respectively, is not particularly relevant to the present disclosure, but is important to the extent that the dam 30 have both reflective and non-reflective portions to achieve a desired light cutoff during operation of the packaged device 100.
While the first major long axis 6 shown in
To this end, the reflective and non-reflective regions (including corresponding dam 30 portions) may occupy a generally equal area (e.g., 50/50) of the circuit board upper surface 2 bounded by dam 30, or be split unevenly between the two. For example, the first circuit board portion 20 may occupy 51% to 80%, or more, of the circuit board upper surface 2 bounded by dam 30. In other examples, the opposite may be true such that the second circuit board portion 22 occupies 51% to 80%, or more, of the circuit board upper surface 2 bounded by dam 30. In any event, during processing of the packaged device 100, the formation of reflective and non-reflective regions of both of the circuit board upper surface 2 and the dam 30, and the extent of surface space of circuit board 1 consumed thereby, can be configurable depending on a desired configuration.
Referring now to
Referring now to
Referring now to
As should be appreciated in light of this disclosure, the shape of the dam 30, and dimensions thereof, are not limited to the particular embodiments illustrated herein, as previously discussed.
Referring now to
Also shown in the embodiment of
In any event, the wire bond 41 may include or otherwise couple to electrical terminals (not shown) for forming such an electrical connection between a lighting system/assembly and the packaged device 100. These terminals may be located on the backside surface 11 of the circuit board 1, or at a position outside of the encapsulation-receiving region 32 adjacent the dam 30. Note that in some cases the wire bond 41 is routed through reflective regions, or alternatively, below the non-reflective regions, to reduce the potential of the wire bond 41 reflecting light incident to its surface in those areas of the packaged device 100 that are provided with a non-reflective surface. Stated more generally, the wire bond 41 is routed in such a way that it does not introduce a reflective surface in an otherwise non-reflective region of the packaged device 100. To this end, numerous routing options for wire bond 41 will be apparent in light of this disclosure.
Now referring to
Also as shown, the encapsulation-receiving region 32 includes the second circuit board portion 22 being a reflective region, as indicated by an absence of shading thereon, and is bounded by the reflective dam portion 34. The second circuit board portion 22 can be white, or include a mirrored finish such as an aluminized surface. In any event, this reflective region allows the packaged device 100′ to recover photons that would otherwise be wasted, as previously discussed.
Referring now to
Also shown is an optional raised reflective surface 37 adjacent the reflective dam portion 34. The implementation of wall 35 at reflective dam portion 34 as a sloping wall (
Referring to
Referring to
In some cases processing of the packaged device 100 is as follows. First, a die is attached and the wire bond 41 is formed on the circuit board 1. Next, a liquid silicone white material (e.g., TiO2 loaded) is poured as a first dam material to form the reflective dam portion 34, then a second black (or transparent, as the case may be) silicone dam material, for instance, is poured to form the non-reflective dam portion 36. During this stage, the first and second materials remain in a semi-liquid state and are suitably viscous such that they do not generally intermix but instead retain the shape of the dam, as governed by the die. In some cases the packaged device 100 is placed into an oven to aid in curing the dam materials. Note that it may be desirable to have a small width for dam 30 to maintain a comparatively large height/pitch, at a constant height, in order to create a mechanically small package. The transparent dam material benefits from having a high viscosity, so it doesn't flatten out during process.
While several embodiments of the present disclosure have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the functions and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications is deemed to be within the scope of the present disclosure. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the teachings of the present disclosure is/are used.
Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the disclosure described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, the disclosure may be practiced otherwise than as specifically described and claimed. The present disclosure is directed to each individual feature, system, article, material, kit, and/or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and/or methods, if such features, systems, articles, materials, kits, and/or methods are not mutually inconsistent, is included within the scope of the present disclosure.
All definitions, as defined and used herein, should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and/or ordinary meanings of the defined terms.
The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, are understood to mean “at least one.”
The phrase “and/or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Other elements may optionally be present other than the elements specifically identified by the “and/or” clause, whether related or unrelated to those elements specifically identified, unless clearly indicated to the contrary.
The phrase “comprising” in the claims hereinbelow, or in describing features of an embodiment in the written description hereinabove, includes the case of only the features recited in the claim or described in an exemplary embodiment, as well as the case of features in addition to those recited in the claim or described in an embodiment.
An abstract is submitted herewith. It is pointed out that this abstract is being provided to comply with the rule requiring an abstract that will allow examiners and other searchers to quickly ascertain the general subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims, as set forth in the rules of the U.S. Patent and Trademark Office.
The following non-limiting reference numerals are used in the specification:
