Stable PCB for Solid-State Lighting Applications

Abstract

The present invention provides a lighting device (1000), comprising: (i) a light source (100) configured to generate light source light (101), wherein the light source (100) comprises a solid-state light source; and (ii) a support (200) configured to support the light source (100), wherein the support (200) comprises a metal-based heat-conducting material (201), wherein the lighting device (1000) further comprises: (iii) a layered element (300) configured to be in physical contact with the support (200), wherein the layered element (300) comprises one or more layers (310), wherein the layered element (300) at least comprises an electrically insulating first layer (311), wherein at least a part of the layered element (300) is configured to be between the light source (100) and the support (200) such that, during operation, a part of the light source light (101) irradiates the layered element (300), wherein the layered element (300) comprises light-reflecting particles (410), wherein at least 50 wt.% of the particles have a flaky shape.

Description

Technical Field

[0001] The present invention relates to a lighting device, comprising: (i) a light source configured to generate light source light and (ii) a support configured to support the light source. The present invention also provides a lamp or a lighting fixture comprising such a lighting device. Background Art

[0002] Insulating films that are coated and form protective films in printed wiring boards are known in the art. US2009 / 0141505 states that, in addition to the properties generally required in solder resist films such as solvent resistance, hardness, solder resistance, and electrical insulation, it is also desirable to be able to effectively utilize the excellent light reflectivity emitted by LEDs. US2009 / 0141505 describes, for example, a white thermosetting resin composition including rutile titanium oxide; and a thermosetting resin. Summary of the invention

[0003] Chip scale package (CSP) LEDs are increasingly being used in a variety of applications due to their robust construction and attractive price. Unlike packaged LEDs, CSP LEDs are placed directly on top of a printed circuit board (PCB). In the case of packaged LEDs, the presence of the package may prevent blue light from reaching the PCB. In this case, the CSP high-intensity light from the CSP may reach the surface of the PCB. The PCB, which has high thermal conductivity, has a metal (aluminum) base with an epoxy dielectric layer on top of it, underneath the copper tracks. During CSP LED operation, the (blue) light from the LED falls on the PCB, passes through the solder mask and reaches the dielectric layer. Both the solder mask and, most importantly, the dielectric layer may be degraded by the high-intensity light. As a result of the degradation of the dielectric layer, a short circuit may occur between the metal substrate and the copper traces.

[0004] Therefore, one aspect of the present invention is to provide an alternative lighting system, which preferably also at least partially avoids one or more of the above-mentioned disadvantages.An object of the present invention may be to overcome or ameliorate at least one disadvantage of the prior art, or to provide a useful alternative.

[0005] In a first aspect, the present invention provides an illumination device ("device") comprising: (i) a light source configured to generate light source light and (ii) a support configured to support the light source. Specifically, in an embodiment, the light source and the support are configured so that during operation, a portion of the light source light is directed to the support. In addition, in an embodiment, the support comprises a metal-based thermally conductive material. Specifically, the illumination device further comprises (iii) a layered element configured to be in physical contact with the support. In an embodiment, the layered element comprises one or more layers. Specifically, the layered element may include at least an electrically insulating first layer (also indicated herein as a "dielectric layer"). At least a portion of the layered element may be configured between the light source and the support so that during operation, (the) portion of the light source light can illuminate the layered element. Specifically, the layered element comprises light-reflecting particles. In a particular embodiment, at least 30 wt.% (more specifically at least 50 wt.%, even more specifically at least 70 wt.%) of the particles have a lamellar shape (such as a thin sheet). Thus, in an embodiment, the present invention provides an illumination device comprising: (i) a light source configured to generate light source light and (ii) a support configured to support the light source, wherein the support comprises a metal-based thermally conductive material, wherein the illumination device further comprises (iii) a layered element configured to be in physical contact with the support, wherein the layered element comprises one or more layers, wherein the layered element comprises at least an electrically insulating first layer, wherein at least a portion of the layered element is configured between the light source and the support such that during operation, (the) portion of the light source light illuminates the layered element, wherein the layered element comprises a layer of light-reflecting particles, wherein at least 30 wt.% (more specifically at least 50 wt.%, even more specifically at least 70 wt.%) of the particles have a flake shape and wherein the layer is a substantially closed layer of aligned flake particles, whereby substantially all of the light source light directed to the layered element is reflected back in a direction away from the support. Thus, in an embodiment, the light source and the support may be configured such that during operation, a portion of the light source light is directed to the support.

[0006] Using such an illumination device, the layer on the support can receive light from the light source, but will not be substantially degraded because most of the light is reflected (by the thin sheet). 2 Particles, the above problems may not be easily solved, but the use of flakes, such as alumina flakes, can solve the above problems.

[0007] As described above, the lighting device specifically includes (i) a light source configured to generate light source light; and (ii) a support configured to support the light source.

[0008] The term "light source" may refer to a semiconductor light emitting device, such as a light emitting diode (LED), a resonant cavity light emitting diode (RCLED), a vertical cavity laser diode (VCSEL), an edge emitting laser, etc. The term "light source" may also refer to an organic light emitting diode, such as a passive matrix (ΜMOLED) or an active matrix (AMOLED). In a specific embodiment, the light source includes a solid-state light source (such as an LED or a laser diode). In one embodiment, the light source includes an LED (light emitting diode). The term LED may also refer to a plurality of LEDs. In addition, in an embodiment, the term "light source" may also refer to a so-called chip-on-board (COB) light source. The term "COB" specifically refers to an LED chip in the form of a semiconductor chip, which is neither encapsulated nor connected, but is directly mounted on a substrate (such as a PCB). Therefore, a plurality of semiconductor light sources may be configured on the same substrate. In an embodiment, a COB is a multi-LED chip configured together as a single lighting module. The term "light source" may also refer to a plurality of (substantially the same (or different)) light sources, such as 2-2000 solid-state light sources. The term "light source" may also refer to a chip-scale package (CSP). The CSP may include a single solid-state die on which a layer including a light-emitting material is provided. The term "light source" may also refer to a medium-power package. A medium-power package may include one or more solid-state dies. (Multiple) dies may be covered by a layer including a light-emitting material. The die size may be equal to or less than 2 mm, such as in the range of, for example, 0.2-2 mm. Therefore, in an embodiment, the light source includes a solid-state light source. In addition, in a specific embodiment, the light source includes a chip-scale packaged LED. In this article, the term "light source" may also specifically refer to a small solid-state light source such as a mini size or a micro size. For example, the light source may include one or more of a small LED and a micro LED. Specifically, in an embodiment, the light source includes a micro LED or "microLED" or "μLED". In this article, the term small size or small LED specifically indicates a solid-state light source having a size selected from the range of 100μm-1mm (such as a die size, specifically a length and width). In this article, the term μ size or micro LED specifically indicates a solid-state light source having a size selected from the range of 100μm and smaller (such as a die size, specifically a length and width).

[0009] In an embodiment, the phrase "different light sources" or "a plurality of different light sources" and similar phrases may refer to a plurality of solid-state light sources selected from at least two different bins. Similarly, the phrase "same light source" or "a plurality of same light sources" and similar phrases may refer to a plurality of solid-state light sources selected from the same bin in an embodiment.

[0010] The light source is a type of light source in which a portion of the light source light propagates in a direction away from the support, but a portion of the light source light also reaches the support. For example, a solid-state light source may have a bare die from which a portion of the light source light also escapes from the edge. In another example, the light source may be a solid-state light source having a bare die covered with a luminescent material, wherein the luminescent material light from the luminescent material may also reach the support. Therefore, in an embodiment, the light source and the support are configured such that a portion of the light source light is directed to the support during operation.

[0011] The portion of the light source light directed to the support may be smaller than the portion of the light source light not directed to the support. For example, only a small portion may be directed to the support (and reach the layered element). In an embodiment, the portion of the light source light not directed to the support may be less than 20% of the total power of the light source light escaping from the light source, such as in particular less than 10%. Therefore, during operation, the portion of the light source light illuminating the layered element may be less than 20% of the total power of the light source light escaping from the light source, such as in particular less than 10%. The light source (light) may have an optical axis that is substantially perpendicular to the support. In addition, most of the total power of the light source light escaping from the light source, such as substantially all of the light source light, such as at least about 80%, for example in particular at least 90%, may propagate in a direction away from the light source and the support.

[0012] In the context of at least part of the source light being directed to the support, note that, in particular due to the spatial light distribution of the light source (in particular solid-state light source) and that there may be no (remote) optics. Of course, optics for, for example, beam shaping the source light may be available, however, in embodiments still a part of the source light may be directed to the support. Another (substantial) part may be beam shaped using (remote) optics (and will be directed away from the support).

[0013] The term "remote" specifically indicates that the optical device is not in optical contact, and therefore not in physical contact, with the light emitting surface of the light source. The light emitting surface of the light source may for example be a solid-state die or a surface of a light emitting material on such a solid-state die. The term "remote" may specifically indicate a distance of at least one wavelength of the light source light, such as a distance at a wavelength equal to or greater than the peak maximum of the light source light, such as at least 1.5 times such a value. In an embodiment, the distance is at least 1 μm, such as at least 2 μm, for example at least 5 μm.

[0014] The support is configured to support the light source. Thus, in an embodiment, the light source is functionally coupled to the support. For example, the light source may be welded to the support. Thus, in an embodiment, the support may include one or more conductive tracks to which the light source may be functionally coupled (such as physically and / or conductively coupled). The conductive tracks may include electrodes or may be conductively coupled to electrodes.

[0015] In a particular embodiment, the support comprises a metal-based thermally conductive material. This thermally conductive material may be used in addition to an electrically conductive material such as copper. The electrically conductive material may be particularly useful for providing an electrical circuit of which the light source is a part.

[0016] Such a support with a thermally conductive material may be used to conduct heat energy from the light source via the support to, for example, a heat sink.

[0017] The thermally conductive material may in particular have a thermal conductivity of at least about 20 W / m / K, for example at least about 30 W / m / K, such as at least about 100 W / m / K, in particular for example at least about 200 W / m / K (see also below).

[0018] In an embodiment, the support comprises an aluminum-based thermally conductive material. In an embodiment, the support comprises an aluminum-based thermally conductive material. Alternatively or additionally, in an embodiment, the support comprises a copper-based thermally conductive material. Additionally or alternatively, other metals (solid at room temperature) may also be used.

[0019] As is known in the art, printed circuit boards can mechanically support and electrically connect electronic components using conductive tracks, pads, and other features etched from one or more copper layers laminated onto and / or between layers of a non-conductive substrate (referred to as "tracks" or "conductive tracks" for short).

[0020] Thus, in an embodiment, the PCB may include an insulating layer (or dielectric layer) arranged between the substrate and the conductive layer.

[0021] (Electronic) components (such as solid-state stage light sources) can often be soldered to a PCB to electrically connect and mechanically fasten them to the PCB. For example, a basic PCB can consist of layers of insulating material and copper foil laminated to a substrate. Chemical etching divides the copper into features such as individual wires called tracks or circuit traces, pads for connections, through holes that pass connections between copper layers, and solid conductive areas for EM shielding or other purposes. The tracks act as wires that are fixed in place and are insulated from each other by air and the circuit board substrate material. The surface of the PCB can have a coating that protects the copper from corrosion and reduces the possibility of solder shorts between traces or poor electrical contact with stray bare wires. Because of its function of helping to prevent solder shorts, the coating is called solder resist.

[0022] Therefore, the shape of the PCB may generally be plate-like. Specifically, in an embodiment, the PCB may have a length, a width, and a height, wherein the aspect ratio of the length and the height is at least 5, such as in the range of 5-5000, such as 10-2500, and wherein the aspect ratio of the width and the height is at least 2, such as the aspect ratio is at least 5, such as in the range of 5-5000, such as 10-2500. The terms "length", "width" and "height" may also refer to "maximum length", "maximum width" and "maximum height", respectively. The PCB may specifically have a rectangular cross-section (such as a square cross-section).

[0023] In an embodiment, the height (or thickness) of the PCB may be selected from the range of 0.2-10 mm, such as 0.5-5 mm, for example 1-2 mm. In an embodiment, the width of the PCB may be selected from the range of 5-200 mm, such as 5-50 mm. In an embodiment, the length of a single printed circuit board area may be selected from the range of 10-50 mm, such as 15-40 mm. In an embodiment, the length of a PCB comprising a plurality of (connected) PCB areas may be selected from the range of 20-2000 mm, such as 20-1500 mm, for example. Other sizes are also possible.

[0024] In a further embodiment, the functional component may comprise an electronic component, in particular an electronic component selected from the group consisting of a solid-state light source, a driver, an electronic module or a sensor. In particular, the electronic component may comprise a solid-state light source.

[0025] In an embodiment, the board may comprise a rigid board or a semi-rigid board, in particular a rigid board. In other embodiments, the board may comprise a semi-rigid board. This may apply to all boards in the board panel arrangement.

[0026] In an embodiment, the plate may comprise a metal, in particular a metal selected from the group comprising copper aluminum, tin, iron, silver and lead, more in particular a metal selected from the group comprising copper and aluminum.

[0027] In further embodiments, the support, such as a (printed circuit) board, may have a thermal conductivity of at least 200 W / (m*K), in particular at least 250 W / (m*K), such as at least 300 W / (m*K).

[0028] In a specific embodiment, the board may include a printed circuit board. Specifically, the board may include one or more of CEM-1PCE, CEM-3PCE, FR-1PCE, FR-2PCB, FR-3PCB, FR-4PCB and aluminum metal core PCB, in particular one or more of CEM-1PCB, CEM-3PCB, FR-1PCB and FR4PCB and aluminum metal core PCB, more in particular one or more of CEM-1PCB, CEM-3PCB, FR-1PCB.

[0029] Specifically, the PCB includes a metal core PCB.

[0030] Therefore, in an embodiment, the printed circuit board comprises a thermally conductive material, such as aluminum.

[0031] In an embodiment, a thin layer of thermally conductive but electrically insulating dielectric may be laminated between the metal base and the copper foil. The copper foil may be etched into the desired circuit pattern, and the metal base contacts the thin dielectric to carry heat away from the circuit. Thus, in an embodiment, the support may be a metal-based PCB (sometimes also indicated as a metal core PCB).

[0032] In particular, the lighting device may (therefore) further comprise (iii) a layered element, the layered element being configured to be in physical contact with the support. The layered element comprises one or more layers. The support may have a support surface associated with the light source. The layered element may be used on at least part of or even substantially the entire support surface. When two or more layers are available, these layers may be stacked in particular. In this way, a stack may be formed by the support and (multiple) layers (stack).

[0033] The layered element comprises at least an electrically insulating first layer. The electrically insulating layer may be configured to insulate an electrical conductor (such as, for example, a copper track) from a thermal conductor, which may also be electrically conductive. The electrically insulating first layer may be thermally conductive. However, the electrically insulating first layer may also comprise a substantially non-thermally conductive material. The electrically insulating layer may also comprise particles that improve thermal conductivity without substantially increasing electrical conductivity.

[0034] The thermal insulator may, for example, have a thermal conductivity equal to or less than 1 W / m / K.

[0035] The electrical insulator may have a value equal to or less than 1·10 -10 S / m, especially equal to or less than 1·10 -13 Conductivity in S / m.

[0036] At least a portion of the layered element may be arranged between the light source and the support. Thus, during operation, a portion of the light source light may illuminate the layered element.

[0037] As described above, the layered element includes light-reflecting particles. In a particular embodiment, at least 30 wt.% (more particularly at least 50 wt.%, even more particularly at least 70 wt.%) of the particles have a flake shape. In a more specific embodiment, at least 90 wt.%, more particularly at least 95 wt.%, even more particularly at least 98 wt.%, even more particularly about 100 wt.% of the particles have a flake shape (such as a thin sheet). The higher the weight percentage of flake-shaped particles, the better the stacking of the flake structure, and therefore the better the protection.

[0038] Using reflective particles, at least part of the light source light will not propagate in the direction of the support, because the light source light is reflected. However, if the light reflective particles are spherical, such as TiO 2 Particles, part of the light source light will still propagate in the direction of the support. In this way, at least part of the layered element may degrade. This may lead to the risk of electrical short circuits. However, with the thin sheets, a substantially closed layer of aligned thin sheets appears to be possible. Therefore, substantially all the light source light directed to the layered element is reflected back in a direction away from the support. Therefore, with the present invention, electrical short circuits caused by light-based degradation of the layered element can be significantly reduced.

[0039] As mentioned above, at least 30 wt.%, such as about at least 50 wt.%, of the particles may have a flake-like shape.

[0040] In an embodiment, the layer comprises at least 70 wt.% light reflecting particles.In an embodiment, the layered element may comprise a layer comprising up to about 98 wt.%, such as up to about 95 wt.%, for example up to about 90 wt.% light reflecting particles.

[0041] In certain embodiments, the layer may have a particle concentration of at least 50 vol.%, such as at least 70 vol.%, more particularly at least 90 vol.% in embodiments. Thus, a portion of the layered element may have a relatively high concentration of plate-like particles. In embodiments, the layer may have a particle concentration of up to about 98 vol.%, such as up to about 95 vol.%, such as up to about 90 vol.%, or even lower.

[0042] For reflection purposes, the higher the content of (plate-like) particles, the better.

[0043] As described above, in an embodiment, the layered element may include an epoxy layer including reflective particles.

[0044] Epoxy resins can include two components, such as molecules with epoxy groups and molecules with amine groups. Molecules with anhydride groups can also be used to obtain crosslinking. Photopolymerizable epoxy resins using photoacid generators can also be used. As an additional or alternative to epoxy resins, other crosslinkable polymers can also be used, such as one or more of acrylates, polyesters and polyurethanes. Alternatively or additionally, organic-inorganic materials can be used, such as sol-gel systems. All of these materials can be used as matrix materials for particles (such as flakes).

[0045] In certain embodiments in which the layered element may include an electrically insulating first layer and a solder resist having a second layer, the insulating layer may be disposed between the support and the second layer including the solder resist. In such embodiments, the second layer including the solder resist may include light reflecting particles. The solder resist layer may, for example, include an epoxy resin filled with reflective particles, such as the particles described herein (and / or, for example, TiO 2 particles).

[0046] Alternatively or additionally, the electrically insulating first layer may comprise light reflecting particles.

[0047] As known to those skilled in the art, the material compositions of the insulating layer and the solder resist layer are specifically different.

[0048] The insulating layer and / or the solder resist layer may each include a thermosetting resin composition, wherein in particular one or both of them include the flake particles described herein.

[0049] Thus, in an embodiment, the first layer of electrical insulation may include at least a portion of the total number of light reflective particles. Alternatively or additionally, the second layer comprising solder resist may include at least a portion of the total number of light reflective particles. More specifically, in an embodiment, the first layer of electrical insulation includes light reflective particles. Alternatively, in an embodiment, the second layer comprising solder resist includes light reflective particles. When light reflective particles are available in different layers, these particles may be substantially the same, or may be different (in terms of particle size and / or particle material).

[0050] The aspect of reflectivity may be particularly relevant in the area around the light source. Thus, in an embodiment, the layered element comprises a layered element portion arranged adjacent to the light source, wherein the layered element portion comprises at least a portion of the total number of particles, such as at least a portion (at least 30 wt.%) of the total number of particles having a flake-like shape. Such an element portion may, for example, have a thickness of at least 4 mm. 2 , for example at least 25 mm 2 For example, at 100mm 2 Therefore, in an embodiment, the light reflective particles may be arranged adjacent to the light source.

[0051] In embodiments, i.e., embodiments in which there is space between at least a portion of the light source and a layer physically connected to the light source, the aspect of reflectivity may also be relevant in the region below the light source. For example, the light source may be physically connected to an insulating layer (particularly an electrically insulating first layer). The physical coupling may be, for example, via two (or more) electrode contacts from a light source having two (or more) electrode contacts, respectively. This may provide space, which is, for example, (substantially) defined in embodiments by the light source and the layered element and the electrodes (and electrode contacts). Therefore, the lighting device may also include two or more electrodes. The light source and the two or more electrodes may be functionally coupled. There is space between the two or more electrodes, in particular comprising a substantially non-conductive material. Therefore, in embodiments, at least a portion of the one or more layers occupies at least a portion of the space. This portion of the one or more layers may (also) comprise light-reflecting particles. Therefore, in embodiments, the lighting device may also include two or more electrodes, wherein the light source and the two or more electrodes are functionally coupled, wherein there is space between the two or more electrodes, wherein at least a portion of the one or more layers occupies at least a portion of the space, wherein at least a portion of the one or more layers occupying at least a portion of the space comprises at least a portion of the total number of light-reflecting particles.

[0052] Thus, in an embodiment, an insulating first layer (such as, for example, a layer between an electrode and a support) may comprise light reflecting particles. Alternatively or additionally, the solder resist layer may comprise light reflecting particles. Alternatively or additionally, a layer with light reflecting particles may be applied on top of the electrode (part) around the solid-state light source and / or applied as an underfill; such a layer may, for example, be an insulating first layer.

[0053] As mentioned above, the particles are indicated as light reflecting particles. Specifically, the particles are reflective for at least a portion of the light source. Thus, one or more wavelengths of the light source can be reflected by the sheet.

[0054] The light source can be configured to generate (at least) visible light and / or UV light source light. The term "UV" or "UV light" and similar terms may refer to a wavelength selected from the range of 100-380 nm in this article. Instead of the term "UV light" and similar terms, the term "UV radiation" may also be applied. The terms "light" and "radiation" may refer to the same in this article. The terms "visible", "visible light" or "visible light emission" and similar terms refer to light with one or more wavelengths in the range of about 380-780 nm.

[0055] Therefore, in an embodiment, the light source may be configured to generate light source light having a wavelength selected from the range of 100-780nm, such as from the range of 200-7800nm, in particular having a wavelength selected from the range of 100-500nm, such as from the range of 200-500nm, for example from the range of 230-500nm.

[0056] In an embodiment, the particles are reflective for at least a portion of visible light and / or UV light. Thus, in an embodiment, the particles may reflect light having one or more wavelengths selected from the range of 100-780 nm, such as 200-780 nm. In an embodiment, the particles reflect at least a portion of infrared light, in particular at least a portion of light having one or more wavelengths selected from the range of 780-1400 nm (essentially near infrared). In an embodiment, the particles reflect one or more wavelengths of light of the light source.

[0057] In an embodiment, the term "reflection" may indicate that at least 25%, in particular at least 40%, for example at least 50%, such as at least 60% of the light is reflected. For example, for an average of each wavelength (i.e., average wavelength), the reflection may be at least 25%, such as at least 40%, for example at least 50%, such as at least 60%, or even higher.

[0058] Since the particles have a platelet-like shape and can be aligned, the reflection can be at least partial, or even substantially specular.

[0059] Particles having a platelet-like shape are also indicated herein as platelet-like particles.Particles having a platelet-like shape may be substantially platelet-like.

[0060] In an embodiment, a particle may have a particle length (L1), a particle height (L2), and a particle width (L3).

[0061] At least 30 wt.% (more particularly at least 50 wt.%, even more particularly at least 70 wt.%, even at least 90 wt.%) of the particles (having a plate-like shape) may particularly have a first aspect ratio AR1, the first aspect ratio AR1 being defined as the ratio of the particle length (L1) to the particle height (L2), wherein AR1 ≥ 50, such as AR1 ≥ 100, even AR1 ≥ 200. For example, in an embodiment, AR1 ≥ 250, for example even AR1 ≥ 500. In an embodiment, AR1 ≤ 10,000. The larger the ratio, the better the alignment and / or formation of the closed layer having specular reflective properties may be.

[0062] Alternatively or additionally, at least 30 wt.% (more particularly at least 50 wt.%, even more particularly at least 70 wt.%) of the particles (having a plate-like shape) may particularly have a second aspect ratio AR2 of particle length (L1) and particle width (L3), wherein 1≤AR2≤5, such as 1≤AR2≤3, or even 1≤AR2≤2. Thus, the length and width of the particles may be in the same range, or even substantially the same, while the height is much smaller than the length or width.

[0063] In an embodiment, for at least 30 wt. %, more particularly at least 50 wt. %, more particularly at least 70 wt. %, the length (L1) and width (L3) may be respectively selected from the range of 10-1000 μm, for example the range of 30-500 μm, particularly 40-400 μm, more particularly 50-500 μm.

[0064] Alternatively or additionally, in an embodiment, for at least 30 wt.%, more particularly at least 50 wt.%, and even more particularly at least 70 wt.%, the particle height (L2) can be selected from the range of 20-500 nm, particularly 40-300 nm, even more particularly 50-200 nm, such as 60-150 nm in a specific embodiment.

[0065] In an embodiment, for at least 30 wt.% of the particles, in particular at least 30 wt.% of the flake-like particles, AR1 ≥ 50. In an embodiment, for at least 30 wt.% of the particles, in particular at least 30 wt.% of the flake-like particles, 1 ≤ AR2 ≤ 5. In an embodiment, for at least 30 wt.% of the particles, in particular at least 30 wt.% of the flake-like particles, the length (L1) and the width (L3) may be individually selected from the range of 10-1000 μm. In an embodiment, for at least 30 wt.% of the particles, in particular at least 30 wt.% of the flake-like particles, the particle height (L2) may be selected from the range of 20-500 nm.

[0066] The phrase "individually selected" and similar phrases in this context indicate that the length and width can be the same, but can also be different, but can still be selected from the same (indicated) range. In particular, using these dimensions, relatively dense layers can be obtained. In addition, especially with these dimensions, the particles can be packed in a desired manner ("leaf-like").

[0067] In an embodiment, the particles, in particular the flakes, may have a thickness selected from the range of about 50-200 nm, a length selected from the range of about 50-500 μm, and a width selected from the range of about 50-500 μm.

[0068] In certain embodiments, the particles have a shape selected from one or more of a coin shape and a flake shape. Specifically, flake-shaped particles can provide better floatation than coin-shaped particles.

[0069] Good results were obtained using aluminum particles with an outer oxide layer. The layer reduces or prevents the conductivity of such flakes and also provides reflectivity. Therefore, in an embodiment, at least 30 wt.% (more particularly at least 50 wt.%, even more particularly at least 70 wt.%) of the particles comprise aluminum particles with an outer aluminum oxide layer.

[0070] In an embodiment, at least 30 wt. % of the particles comprise aluminum particles having an outer layer of aluminum oxide, in particular at least 30 wt. % of the plate-like particles comprise aluminum particles having an outer layer of aluminum oxide.

[0071] As mentioned above, the term "light source" may also refer to a plurality of light sources. Thus, in an embodiment, the lighting device may further comprise a support having a plurality of light sources, each of which is functionally coupled to the support. Substantially identical substantially continuous layered elements may be on the support arranged between the light emitting surface of the (multiple) light sources and the support.

[0072] In yet another aspect, the present invention provides a lamp comprising a lighting device or a lamp fixture comprising a lighting device. Such a lamp or lamp fixture may include multiple light sources. Such a lamp or lamp fixture may include multiple lighting devices.

[0073] The lighting device can be or can be applied to, for example, an office lighting system, a home application system, a store lighting system, a home lighting system, an accent lighting system, a spotlight system, a theater lighting system, a fiber optic application system, a projection system, a self-luminous display system, a pixelated display system, a segmented display system, a warning sign system, a medical lighting application system, an indicator sign system, a decorative lighting system, a portable system, an automotive application, a (outdoor) road lighting system, a city lighting system, a greenhouse lighting system, a horticultural lighting or an LCD backlight.

[0074] In an alternative embodiment, instead of a support comprising a metal-based thermally conductive material, the support may comprise (the PCB comprises) FR-2, phenolic paper or phenolic cotton paper, paper impregnated with phenolic resin FR-4, woven glass fiber cloth impregnated with epoxy resin, Kapton, UPILEX or polyimide foil. In yet another alternative embodiment, instead of a support comprising a metal-based thermally conductive material, the support may comprise (the PCB comprises) a ceramic body, such as alumina or garnet (e.g. Y 3 Al 5 O 12 ). BRIEF DESCRIPTION OF THE DRAWINGS

[0075] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which corresponding reference numerals indicate corresponding parts, and in which:

[0076] Figure 1 Some aspects of the invention and the described problems are schematically depicted;

[0077] 2a-2f schematically depict aspects of embodiments of particles, with some shapes depicted for reference;

[0078] Figure 3 Some aspects of the invention are schematically depicted;

[0079] Figures 4a-4d schematically depict some aspects; and

[0080] Figure 5 The lamp or luminaire is depicted schematically. The schematic diagram is not necessarily drawn to scale. DETAILED DESCRIPTION

[0081] Figure 1 The effect that light from a light source may have on layers adjacent to the light source is schematically depicted. Figure 1 The description is made with respect to chip scale package (CSP) LEDs. However, the invention is not limited to CSP light sources.

[0082] Chip scale package (CSP) LEDs are increasingly being used in various applications due to their robust construction and attractive price. Unlike packaged LEDs, CSP LEDs are placed directly on top of a printed circuit board (PCB). In the case of packaged LEDs, the presence of the package prevents blue light from reaching the PCB. In this case, the CSP high-intensity light from the CSP reaches the surface of the PCB. The PCB, which has high thermal conductivity, has a metal (aluminum) base with an epoxy dielectric layer located below the copper tracks on top of the metal base. In addition to the area reserved for soldering the LED, a reflective solder resist layer containing reflective particles is present on the surface of the PCB. During CSP LED operation, blue light from the LED falls on the PCB, the light passes through the solder resist layer and reaches the dielectric layer. By the high-intensity light, the solder resist layer but most importantly the dielectric layer degrades. As a result of the degradation of the dielectric layer, a short circuit occurs between the metal substrate and the copper traces.

[0083] To solve this problem, we propose to use high aspect ratio metal flakes (aluminum, silver, copper, etc.) in epoxy resin. 2 In contrast to materials such as TiOx, aluminum flakes can completely shield light when overlapped, preventing it from reaching the underlying dielectric layer. In this way, reliable metal core PCBs can be produced for use in conjunction with CSP LEDs. Aluminum flakes also exhibit better reflectivity than TiOx thin layers.

[0084] Figure 1 In the upper part an embodiment of a construct such as a metal core PCB with soldered CSPs is schematically shown. Figure 1 The lower portion shows the locations of resist and dielectric degradation.

[0085] Figure 1 Schematically depicted is an embodiment of a lighting device 1000 comprising a light source 100 configured to generate light source light 101 and a support 200 configured to support the light source 100. In an embodiment, the light source 100 may comprise a solid state light source.

[0086] As schematically depicted, the light source 100 and the support 200 are configured such that during operation, a portion of the light source light 101 may be directed to the support 200 .

[0087] In certain embodiments, the support 200 may include a metal-based thermally conductive material 201 .

[0088] Specifically, the lighting device 1000 may further include a layered element 300. The layered element 300 is configured to be in physical contact with the support 200. The layered element 300 includes one or more layers 310. When two or more layers 310 are available, the layers may be stacked.

[0089] The layered element 300 may include at least an electrically insulating first layer 311, in particular for electrically isolating the light source from the support 200. At least a portion of the layered element 300 may be arranged between the light source 100 and the support 200, such that during operation, a portion of the light source light 101 illuminates the layered element 300.

[0090] Reference numeral 222 indicates an electrode, and reference numeral 221 indicates an electrode contact of the light source 100. Therefore, the lighting device 1000 may also include two or more electrodes 222, wherein the light source 100 and the two or more electrodes 222 are functionally coupled (via the electrode contact 221). As schematically indicated, there is a space 223 between the two or more electrodes 222.

[0091] Reference numeral 312 denotes a second layer, such as, for example, a second layer including a solder resist.

[0092] Reference numeral 111 indicates, for example, the surface of a solid-state light source die (e.g., an LED die). The solid-state light source light can escape from the die. Optionally, a luminescent material can be provided, which is available between at least a portion of the surface 111 of the solid-state light source die and a surface 112 of the luminescent material. From the latter surface 112, the light source light can escape and the luminescent material light can escape, or substantially only the luminescent material light can escape. The luminescent material can convert the light of a solid-state light source such as an LED into luminescent material light. Therefore, reference numeral 112 actually indicates the luminescent surface (of the light source 100). If the luminescent material is not available, reference numeral 111 would be the luminescent surface of the light source 100.

[0093] Therefore, it is proposed herein to use light reflecting particles, in particular flakes, in a layer on the support 200. In the following, some aspects of the particles are first discussed.

[0094] For the sake of understanding, Figure 2a schematically depicts a particle and some aspects thereof. Note, see for example Figures 2c and 2e, that the particles used in the present invention are particularly relatively flat.

[0095] The particle includes material 411, or may consist essentially of such material 411. The particle 410 has a first dimension or length L1. In the example on the left, L1 is substantially the diameter of a spherical particle. A particle having a non-spherical shape, such as an elongated particle 410, is depicted on the right. Here, as an example, L1 is the particle length. L2 and L3 can be viewed as width and height. Of course, the particle may include a combination of particles of different shapes.

[0096] 2b-2f schematically depict some aspects of the particles 410. Some particles 410 have a longest dimension A1 of a longest dimension length L1 and a shortest dimension A2 of a shortest dimension length L2. As can be seen from the figure, the longest dimension length L1 and the shortest dimension length L2 have a first aspect ratio greater than 1.

[0097] Figure 2b schematically depicts a particle 410 in 3D, wherein the particle 410 has a length, a height and a width, the particle (or flake) having essentially an elongated shape. Thus, the particle may have an additional axis (minor axis or major axis), indicated herein as an additional dimension A3.

[0098] In essence, the particles 410 are fine particles, ie, L2<L1, in particular, L2<<L1 and L2<<L3.

[0099] Figure 2c schematically depicts a particle with a more irregular shape, where in practice the smallest cuboid surrounds the particle.

[0100] Note that the symbols L1, L2 and L3 and A1, A2 and A3 are used only to indicate the axes and their lengths, and that the numbers are used only to distinguish the axes. In addition, note that the particles are not substantially elliptical or cuboid. The particles may have any shape in which at least the longest dimension is significantly longer than the shortest dimension or minor axis, and they may be substantially flat. In particular, relatively regularly formed particles are used, i.e., the remaining volume of an imaginary smallest cuboid enclosing the particle is small, e.g., less than 50% of the total volume, e.g., less than 25%.

[0101] FIG2 d schematically depicts a particle 410 including a coating 412 in cross-section. The coating may include a light-reflecting material. For example, the coating may include a (white) metal oxide. In other embodiments, the coating may consist essentially of a metal, such as an Ag coating. In other embodiments, the coating may be only on one or two of the large surfaces and not on the thin side surfaces of the particle.

[0102] In an embodiment, the particles 410 may be aluminum particles having an outer layer 412 of aluminum oxide. Thus, in an embodiment, at least 30 wt. %, such as at least 50 wt. %, of the particles 410 comprise aluminum particles having an outer layer 412 of aluminum oxide.

[0103] As mentioned above, the particles 410 may be reflective for at least a portion of visible light and / or UV light. Specifically, the particles may be reflective for one or more wavelengths selected from the range of 100-780 nm, preferably 200-780 nm.

[0104] Figure 2e schematically depicts particles with relatively irregular shapes.

[0105] The particulate material may comprise a wide distribution of particle sizes.

[0106] A cuboid may be used to define the (orthogonal) dimensions of length L1 , L2 and L3.

[0107] Figure 2f schematically depicts cylindrical, spherical and irregularly shaped particles, which are not generally used herein (see also above).

[0108] 2b-2f, the term "first dimension" or "longest dimension" specifically refers to the length L1 of the smallest rectangular cuboid (cuboid) enclosing the irregular shape. When the particle is substantially spherical, the longest dimension L1, the shortest dimension L2 and the diameter are substantially the same.

[0109] As described above, the particles 410 have a particle length L1, a particle height L2, and a particle width L3. At least 30 wt.% of the particles may have a plate-like shape, the plate-like shape having a first aspect ratio AR1 and a second aspect ratio AR2, the first aspect ratio AR1 being defined as the ratio of the particle length L1 to the particle height L2, and the second aspect ratio AR2 being the ratio of the particle length L1 to the particle width L3. In an embodiment, AR1 ≥ 50 and / or 1 ≤ AR2 ≤ 5.

[0110] In an embodiment, for at least 30 wt.%, such as at least 50 wt.%, the length L1 and the width L3 are individually selected from the range 10-1000 μm. Furthermore, in an embodiment, the particle height L2 is selected from the range 20-500 nm.

[0111] As described above, specifically, the shape of the particle 410 is selected from one or more of a coin shape and a flake shape, more specifically a flake shape.

[0112] Figure 3 An embodiment of a layered element 300 with plate-like particles 410 is schematically depicted, which are included in a layer 315. Here, the layered element 300 includes a layer 315, which may include at least 30 wt.%, in particular at least 50 wt.%, for example at least 70 wt.% of light-reflecting particles 410. For example, the layer 315 may have a particle concentration of at least 50 vol.%, such as at least 70 vol.%.

[0113] In an embodiment, the layer 315 includes a layer containing a polymeric bonding agent, and the layer containing a polymeric bonding agent includes the reflective particles 410. Specifically, the layer 315 includes an epoxy layer, and the epoxy layer includes the reflective particles 410.

[0114] Figure 4a-4d (actually there are Figure 1 ) schematically depicts an embodiment of a lighting device 1000, which includes a light source 100 configured to generate light source light 101. The light source 100 includes a solid-state light source. As described above, the light source 100 may include a chip-scale packaged LED. In addition, the lighting device 1000 includes a support 200 configured to support the light source 100. Specifically, the support 200 includes an aluminum-based thermally conductive material 201. For example, the support 200 may include a (metal-based) printed circuit board. Therefore, in an embodiment, the support 200 may include a metal-based thermally conductive material 201.

[0115] The light source 100 and the support 200 are configured such that during operation, a portion of the light source light 101 may be directed to the support 200 .

[0116] Furthermore, the lighting device 1000 comprises a layered element 300 which is configured to be in physical contact with the support 200. The layered element 300 comprises one or more layers 310.

[0117] In an embodiment, the layered element 300 comprises at least an electrically insulating first layer 311, wherein at least a portion of the layered element 300 is arranged between the light source 100 and the support 200. Thus, during operation, a portion of the light source light 101 may illuminate the layered element 300. As schematically depicted (see FIGS. 4a-4c ), the layered element 300 may comprise light reflective particles 410, wherein at least 30 wt.%, such as at least 70 wt.%, for example at least 90 wt.% of the particles have a flake-like shape.

[0118] As shown in Figures 4b-4d (and Figure 1 ), the layered component 300 may include an electrically insulating first layer 311 and a second layer 312 including a solder resist, wherein the insulating layer 311 is arranged between the support 200 and the second layer 312 including the solder resist.

[0119] In an embodiment, the second layer 312 comprising solder resist comprises light reflecting particles 410, see Fig. 4b. However, in other embodiments, the electrically insulating first layer 311 comprises light reflecting particles 410. In further embodiments, both layers may comprise light reflecting particles.

[0120] As schematically depicted in Fig. 4a, the layered element 300 may include a layered element portion 320 configured adjacent to the light source 100. The layered element portion 320 includes at least a portion of the total number of particles having a flake shape. Reference numeral d1 indicates the (equivalent circular) diameter of the light source 100, and reference numeral d2 indicates the circular equivalent diameter of the layered element portion 320. For the values ​​of d1 and d2, d2>d1 may be particularly applied. Typically, a layer may include reflective particles throughout the entire layer.

[0121] 4d, an embodiment is schematically depicted, wherein at least a portion of the one or more layers 310 occupies at least a portion of the space 223, and wherein this portion of the one or more layers 310 comprises at least a portion of the total number of light reflective particles 410. Here, the space 223 may comprise a portion of the second layer 312 comprising solder resist, but other variations are possible.

[0122] Figure 5 A light emitting element 50, such as a lamp or a luminaire, is schematically depicted, wherein the lamp or luminaire comprises a lighting device 1000. Here, as an example, the light emitting element 50 comprises a plurality of lighting devices 100. The light emitting element is configured to generate light emitting element light 51, which may mainly consist of light source light.

[0123] In an embodiment, the solder resist layer including the plate-like particles may be patterned, such as by a screen printing method. Alternatively or additionally, it may also be patterned using a photolithography method (using a photomask).

[0124] The term "plurality" refers to two or more.

[0125] Those skilled in the art will understand the terms "substantially" or "approximately" and similar terms herein. The terms "substantially" or "approximately" may also include embodiments with "all", "completely", "all", etc. Therefore, in embodiments, the adjectives substantially or approximately may also be removed. Where applicable, the term "substantially" or the term "approximately" may also relate to 90% or higher, such as 95% or higher, in particular 99% or higher, even more in particular 99.5% or higher, including 100%.

[0126] The term "comprising" also includes embodiments wherein the term "comprising" means "consisting of.

[0127] The term "and / or" specifically refers to one or more items mentioned before and after "and / or". For example, the phrase "item 1 and / or item 2" and similar phrases may refer to one or more of item 1 and item 2. The term "comprising" may refer to "consisting of" in one embodiment, but may also refer to "comprising at least the defined substances and optionally one or more other substances" in another embodiment.

[0128] In addition, the terms first, second, third, etc. in the specification and claims are used to distinguish similar elements and not necessarily to describe a sequential or chronological order. It should be understood that the terms so used are interchangeable under appropriate circumstances, and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

[0129] An apparatus, device or system may be described herein during operation. It will be clear to one skilled in the art that the present invention is not limited to methods of operation, or apparatus, devices or systems in operation.

[0130] It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims.

[0131] In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim.

[0132] The use of the verb "comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. Unless the context clearly requires otherwise, throughout the specification and claims, the words "comprises," "comprising," etc. should be interpreted in an inclusive sense, rather than an exclusive or exhaustive sense; that is, in the sense of "including but not limited to."

[0133] The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

[0134] The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In a device claim, or an apparatus claim or a system claim, several means are enumerated, several of which may be embodied by one and the same item of hardware. The 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.

[0135] The present invention also provides a control system that can control a device, apparatus or system, or can perform a method or process described herein. In addition, the present invention also provides a computer program product that, when functionally coupled to a device, apparatus or system or run on a computer included in the device, apparatus or system, controls one or more controllable elements of such a device, apparatus or system.

[0136] The present invention also applies to an apparatus, device or system comprising one or more features described in the specification and / or shown in the drawings. The present invention also relates to a method or process comprising one or more features described in the specification and / or shown in the drawings.

[0137] The various aspects discussed in this patent can be combined to provide additional advantages. In addition, those skilled in the art will appreciate that embodiments can be combined, and more than two embodiments can also be combined. In addition, certain features can form the basis of one or more divisional applications.

Claims

1. A lighting device (1000) comprising (i) a light source (100) and (ii) a support (200), the light source (100) being configured to generate source light (101), wherein the light source (100) comprises a solid-state light source, the support (200) being configured to support the light source (100), wherein the support (200) comprises a metal-based heat-conductive material, and wherein the lighting device (1000) further comprises (iii) a layered element (300), the layered element (300) being configured to be in physical contact with the support (200), wherein the layered element (300) comprises one or more layers, wherein the layered element (300) at least comprises an electrically insulating first layer (311), and wherein at least a portion of the layered element (300) is configured to be between the light source (100) and the support (200) such that during operation of the lighting device, a portion of the source light (101) irradiates the layered element (300), and wherein the layered element (300) further comprises a layer of light-reflecting particles (410). wherein at least 30 wt.% of the light-reflecting particles have a flake shape, and wherein the layer of light-reflecting particles is a closed layer of aligned flake-shaped light-reflecting particles, whereby all of the source light (101) directed to the layered element (300) is reflected back in a direction away from the support (200); wherein each light-reflecting particle has a particle length (L1), a particle height (L2), and a particle width (L3), and wherein for at least 30 wt.% of the light-reflecting particles, the length (L1) and the width (L3) are each selected from the range of 10 μm - 1000 μm, and the particle height (L2) is selected from the range of 20 nm - 500 nm.

2. The lighting device (1000) according to claim 1, wherein the light source (100) comprises a chip-scale packaged LED.

3. The lighting device (1000) according to any one of claims 1 and 2, wherein the layer of light-reflecting particles comprises at least 80 wt.% of the light-reflecting particles (410), and wherein the layer of light-reflecting particles has a particle concentration of at least 50 vol.%.

4. The lighting device (1000) according to any one of claims 1 and 2, wherein the layer of light-reflecting particles comprises a layer containing a polymeric binder, the layer containing a polymeric binder comprising the light-reflecting particles (410).

5. The lighting device (1000) according to any one of claims 1 and 2, wherein the layered element (300) comprises the electrically insulating first layer (311) and a second layer (312) comprising a solder resist, wherein the first layer (311) is configured to be between the support (200) and the second layer (312) comprising a solder resist, and wherein the second layer (312) comprising a solder resist comprises the light-reflecting particles (410).

6. The lighting device (1000) according to any one of claims 1 and 2, wherein the first electrically insulating layer (311) comprises the light-reflecting particles (410).

7. The lighting device (1000) according to any one of claims 1 and 2, further comprising two or more electrodes (222), wherein the light source (100) and the two or more electrodes (222) are functionally coupled, wherein there is a space (223) between the two or more electrodes (222), wherein at least a portion of the one or more layers occupies at least a portion of the space (223), and wherein at least a portion of the one or more layers that occupies at least a portion of the space (223) comprises at least a portion of the total number of the light-reflecting particles (410).

8. The lighting device (1000) according to any one of claims 1 and 2, wherein the light-reflecting particles (410) are reflective for at least a portion of visible light and / or UV light, and wherein at least 50 wt.% of the light-reflecting particles have a first aspect ratio AR1 and a second aspect ratio AR2, the first aspect ratio AR1 being defined as the ratio of the particle length (L1) and the particle height (L2), wherein AR1 ≥ 50, and the second aspect ratio AR2 being defined as the ratio of the particle length (L1) and the particle width (L3), wherein 1 ≤ AR2 ≤ 5.

9. The lighting device (1000) according to any one of claims 1 and 2, wherein for at least 50 wt.% of the light-reflecting particles, the length (L1) and the width (L3) are each selected from the range of 10 μm - 1000 μm, and wherein the particle height (L2) is selected from the range of 20 nm - 500 nm.

10. The lighting device (1000) according to any one of claims 1 and 2, wherein the light-reflecting particles (410) have a coin shape.

11. The lighting device (1000) according to any one of claims 1 and 2, wherein the light-reflecting particles (410) have a flake shape.

12. The lighting device (1000) according to any one of claims 1 and 2, wherein at least 50 wt.% of the light-reflecting particles (410) comprise aluminum particles having an alumina outer layer (412).

13. The lighting device (1000) according to any one of claims 1 and 2, wherein the support (200) comprises an aluminum-based heat-conductive material.

14. The lighting device (1000) according to any one of claims 1 and 2, wherein the support (200) comprises a printed circuit board.

15. The lighting device (1000) according to any one of claims 1 and 2, wherein the layered element (300) comprises a layered element portion (320) disposed adjacent to the light source (100), and wherein the layered element portion (320) comprises at least a portion of the total number of the light-reflecting particles (410) having a flake shape.

16. A lamp, comprising the lighting device (1000) according to any one of claims 1 to 15.

17. A luminaire, comprising the lighting device (1000) according to any one of claims 1 to 15.

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