Lighting assembly with improved thermal behavior and method of manufacturing the same
阅读说明：本技术 具有改进的热行为的照明组件以及制造该照明组件的方法 (Lighting assembly with improved thermal behavior and method of manufacturing the same ) 是由 E.斯塔萨尔 F.H.科尼吉恩 于 2018-06-13 设计创作，主要内容包括：本发明描述了一种具有改进的热行为的照明组件(1),以及制造这种照明组件(1)的方法(100),该照明组件(1)包括：至少一个点状光源(2),具有第一和第二电接触部(21,22)；引线框架(3),包括金属区域(31),以电连接第一和第二电接触部并经由金属区域扩散来自点状光源的热量；以及塑料层(5),至少布置在引线框架之上,并且包括作为至少部分填充有导电材料的过孔(53b)的开口(53),其中一根或多根导电迹线(6)被施加在塑料层的背离引线框架的第一表面(51)上,并且与引线框架的金属区域电绝缘,以能够与引线框架分开地电连接塑料层的第一表面上的附加部件(4)。(The invention describes a lighting assembly (1) with improved thermal behavior, and a method (100) of manufacturing such a lighting assembly (1), the lighting assembly (1) comprising: at least one point-like light source (2) having a first and a second electrical contact (21, 22); a lead frame (3) comprising a metal area (31) to electrically connect the first and second electrical contacts and to spread heat from the point-like light source via the metal area; and a plastic layer (5) arranged at least over the lead frame and comprising openings (53) as vias (53 b) at least partly filled with an electrically conductive material, wherein one or more electrically conductive tracks (6) are applied on a first surface (51) of the plastic layer facing away from the lead frame and are electrically insulated from the metal area of the lead frame to enable electrical connection of an additional component (4) on the first surface of the plastic layer separately from the lead frame.)
1. A lighting assembly (1) comprising
At least one point-like light source (2) having a first and a second electrical contact (21, 22),
a lead frame (3) comprising a suitable metal area (31) to electrically connect the first electrical contact (21) and the second electrical contact (22) of the at least one point-like light source (2) to a power source and to diffuse heat from the at least one point-like light source (2) via the metal area (31), and
a suitably shaped plastic layer (5) arranged at least over the lead frame (3),
wherein the plastic layer (5) comprises an opening (53) arranged above the metal region (31),
wherein the opening (53) is a via (53 b) at least partially filled with a conductive material,
wherein the at least one point-like light source (2) is placed on a first surface (51) of the plastic layer (5) facing away from the leadframe (3) and is in electrical contact with the metal region (31) of the leadframe (3) through the via hole (53 b) and
wherein one or more electrically conductive tracks (6) are applied on the first surface (51) of the plastic layer (5) facing away from the lead frame (3) and are electrically insulated from the metal region (31) of the lead frame (3) to enable electrical connection of an additional component (4) on the first surface of the plastic layer (5) separately from the lead frame (3).
2. The lighting assembly (1) according to claim 1, wherein the material, shape and size of the via (53 b) are adapted so as not to reduce heat spreading compared to heat spreading of point-like light sources (2) directly connected over the lead frame (3).
3. The lighting assembly (1) according to any one of the preceding claims, wherein the plastic layer (5) is provided over the lead frame (3) by overmolding the lead frame (3) with a plastic material as an insulating layer (5).
4. The lighting assembly (1) according to any one of the preceding claims, wherein the electrically conductive tracks (6) on the first surface (51) of the plastic layer (5) are provided by using MID (molded interconnect device) technology.
5. A lighting device (10) comprising one or more lighting assemblies (1) according to claim 1 and at least one driver (7), the driver (7) being connected to the lighting assemblies (1) to drive the one or more lighting assemblies (1).
6. A method (100) of manufacturing a lighting assembly (1) according to claim 1, the lighting assembly (1) having at least one point-like light source (2), the point-like light source (2) having a first and a second electrical contact (21, 22), the method comprising the steps of:
-providing (110) a lead frame (3) comprising a suitable metal area (31) for electrically connecting at least one point-like light source (2) to a power source and diffusing heat from said at least one point-like light source (2) via said metal area (31);
-arranging (120) a suitably shaped plastic layer (5) at least over the lead frame (3) in order to electrically insulate the lead frame (3) from a first surface (51) of the plastic layer (5), wherein the first surface (51) faces away from the lead frame (3);
-providing (125) an opening (53) in the plastic layer (5) at a suitable location, wherein the opening (53) is a via (53 b) at least partially filled with an electrically conductive material,
-providing said at least one point-like light source (2) on said first surface (51) of said plastic layer and electrically connecting said first and second electrical contacts (21, 22) of said at least one point-like light source (2) to said metal area (31) of said lead frame (3) through said via hole (53 b);
-providing (130) electrically conductive tracks (6) on the first surface (51) of the plastic layer (5) facing away from the lead frame (3); and
-connecting (150) at least one additional component (4) to the electrically conductive track (6) on the first surface (51) of the plastic layer (5), the electrically conductive track (6) being electrically insulated from the metal area (31) of the lead frame (3).
7. The method (100) according to claim 6, wherein the step of providing (120) the plastic layer (5) over the lead frame (3) is performed by over molding the lead frame (3) with a plastic material as the plastic layer (5).
8. The method (100) according to claim 6 or 7, wherein the step of providing (130) the electrically conductive track (6) on the first surface (51) of the plastic layer (5) comprises the steps of:
-covering (132) the first surface (51) of the plastic layer (5) with an electrically conductive layer (54);
-partially removing (134) the conductive layer (54) at locations where no conductive tracks (6) should be placed.
9. The method (100) of claim 8, further comprising the step of growing (136) more conductive material (55) over the current conductive material (54) to form a thicker conductive trace (6).
Technical Field
The present invention relates to a lighting assembly with improved thermal behavior, a lighting device comprising such a lighting assembly and a method of manufacturing such a lighting assembly.
Background
Light Emitting Devices (LEDs), which are examples of point-like light sources, have many advantages over incandescent light sources, including lower energy consumption, longer lifetime, improved physical robustness, smaller size and faster switching. LEDs are widely used in applications such as aviation lighting, automobiles, advertising, general lighting, traffic signals, camera flashes, illuminated wallpaper, and the like. To provide more functionality for lighting devices comprising e.g. LEDs, additional electrical components are arranged on the same LED package, which requires separate additional conductive traces to connect the additional components to a power source. When the LED package is kept the same size, these traces will occupy valuable metal area that can no longer be used to spread heat away from the LED. Thermal management of LEDs relies heavily on this available metal area to spread heat and conduct heat away from the LED.
When dealing with lighting assemblies comprising LEDs and additional components, so-called Molded Interconnect Device (MID) technology may be used to provide a substrate comprising structural wiring to separately connect the additional components and LEDs on the same lead frame. With MID technology, the plastic substrate will be plated with a thin metal layer, wherein the metal layer is removed from the substrate at locations where conductive traces are not desired. The remaining conductive traces may be used to contact all components of the lighting assembly, including the LEDs. A disadvantage of MID-prepared substrates is the very poor thermal conductivity of the plastic used, making it useless for high power LEDs.
In the case of a desired small-sized lighting assembly carrying multiple components, a multilayer board can be used to add more functional dielectric layers to provide a complex routing of conductive traces within a very limited volume. A serious drawback of multilayer boards is their poor thermal performance, which becomes even worse with each additional layer of dielectric material.
Lighting assemblies that provide only low or moderate heat spreading away from the LED(s) only allow the application of low power LEDs and/or result in a reduced lifetime of the LEDs used.
Accordingly, there is a need for a lighting assembly with improved thermal management to spread heat away from the LEDs used so as to be able to operate high irradiance LEDs for long lifetimes. It is further desirable that such lighting assemblies can be manufactured with low investment (effort).
Disclosure of Invention
It is an object of the present invention to provide a lighting assembly for point-like light sources, which provides an improved thermal behavior, which can also be manufactured with low production effort.
The invention is defined by the independent claims. The dependent claims define advantageous embodiments.
According to a first aspect, a lighting module is provided. The lighting assembly includes: at least one point-like light source having a first and a second electrical contact; a lead frame comprising a suitable metal area to electrically connect at least a first electrical contact of the at least one point-like light source to a power source and to spread heat from the at least one point-like light source via the metal area; and a suitably shaped plastic layer arranged at least over the lead frame, wherein one or more electrically conductive tracks are applied on the surface of the plastic layer facing away from the lead frame, so that the electrically conductive tracks on the plastic layer are electrically insulated from the metal area of the lead frame, so that an additional component above the plastic layer can be electrically connected separately from the lead frame, or the second electrical contact of the at least one point-like light source is connected with one of the electrically conductive tracks connected to a power source. In an embodiment, a plastic layer may be disposed around the lead frame.
The term "point-like light source" denotes any light source having a small light emitting area (or volume). Such a point-like light source may be an LED or a semiconductor laser, e.g. a quantum well or a quantum dot. The lighting assembly may comprise an array of point-like light sources, such as an array of LEDs. The array of point-like light sources may comprise columns and rows of point-like light sources. The number of point-like light sources arranged in rows and/or columns depends on the specific application of the lighting assembly. The rear side of the point-like light source comprises at least a first electrical contact. In an embodiment, the second electrical contact is also arranged on the rear side of the point-like light source. In another embodiment, the second electrical contact is arranged on the other side of the point light source than the rear side. Here, the second electrical contact may be arranged on a front side (opposite to the rear side) of the point-like light source. At least the first electrical contact should be adapted to be contacted to the lead frame (e.g. directly on the lead frame or on the via), wherein the rear side may be configured to provide a separate contact pad for electrically connecting the point-like light sources. The LEDs are typically small (less than 1 mm)2) And solid state light sources with very high brightness are available in the range of wavelengths, e.g. from IR to visible and ultraviolet. LEDs have many advantages over incandescent light sources, including lower power consumption, longer lifetime, improved physical robustness, smaller size, and faster switching.
The term "lead frame" denotes a metal structure (or metal area) disposed on or within a substrate, such as a chip package, which transmits signals from a specifically connected component (here a point-like light source) to the outside. The connected components may be glued or soldered to the lead frame. The metal structure is suitably shaped to establish an electrically conductive path between the power source and the connected component, here the point-like light source, and to spread heat from the point-like light source to the environment in order to keep the temperature of the point-like light source within a temperature range that does not reduce the lifetime of the point-like light source below a desired threshold. To improve heat spreading, the metal area is preferably shaped as a large area to provide a large surface for transferring heat to the environment. In order to maximize the available metal area for heat spreading, preferably no other parts than the point-like light sources are connected to the lead frame. The preferred material is copper. The size and thickness of the metal area is a trade-off between cost and product size.
An additional electrically operated component means any other component which is not a point-like light source. Additional components may be NTCs, TVS, resistors, ICs, FETs, etc. The required power for these additional components is provided via a separate electrically conductive track which is not part of the lead frame but is instead provided on top of a plastic layer arranged between the lead frame and the electrically conductive track and the additional component. The plastic layer is suitably shaped so that the conductive tracks used to connect the additional parts and the additional parts are electrically insulated from the lead frame. The material of the plastic layer may be epoxy, PPA, LCP, PA or any other suitable non-conductive material having a thickness of at least 30 μm. The electrically conductive tracks applied on the first surface of the plastic layer facing away from the lead frame may be any suitable material that provides sufficient electrical contact between the additional component and an external component, such as a driver or a power source. Preferably, the conductive traces are made of metal (e.g., copper).
The invention improves the heat spreading away from the point-like light sources, since the lead frame mainly comprises electrically conductive paths supplying power to the point-like light sources. Thus, few other traces will occupy valuable metal area that can no longer be used to spread heat away from point-like light sources (e.g., LEDs). Thermal management of the lighting assembly enables to spread the heat and conduct it away from the point-like light sources with almost all available metal area of the lead frame. Additionally, the lead frame is not arranged inside the multilayer board, but on the rear side of the stack of lead frame, plastic layer and additional conductive tracks applied on top of the plastic layer, and thus poor thermal performance of the multilayer board is avoided. For this purpose, it has no influence whether the second electrical contacts of the point-like light sources are connected to the lead frame or to the electrically conductive tracks on top of the plastic layer. Furthermore, in case additional components are supplied, the conductive tracks provided on top of the plastic layer do not have to spread the heat from the point-like light sources, since the lead frame is able to perform this transfer adequately via the metal areas of the lead frame. The disadvantage of very poor thermal conductivity, such as for example the electrically conductive tracks produced by MID technology, does not therefore impair the thermal management of the punctiform light sources.
Thus, the lighting assembly provides an improved thermal behavior and can be manufactured with low production effort. Furthermore, improved thermal management enables operation of such lighting assemblies comprising high irradiance point-like light sources (e.g. high power LEDs) with a long lifetime.
The lighting assembly may be arranged in such a way that the plastic layer comprises at least one opening at a suitable location where the at least one point-like light source should be placed in order to enable at least a first electrical contact of the at least one point-like light source to be connected to the lead frame. The opening provides access to a portion of the metal area of the lead frame for simply placing a point-like light source onto the lead frame for establishing electrical contact to the lead frame, at least for the first electrical contact. The opening enables easy access.
The lighting assembly may be arranged in such a way that the lead frame comprises a suitable number of pads for contacting the first and/or second electrical contact of the at least one light source, wherein the at least one opening is arranged above the pads. A pad is a freely accessible metal area that is large enough to apply a soldering process.
The lighting assembly may be arranged such that the at least one opening is a via hole at least partially filled with an electrically conductive material, and such that the first electrical contact of the at least one point-like light source placed above the plastic layer is in electrical contact with the lead frame through the via hole. Furthermore, the groove can guide the placement of the point-like light source and can stabilize the position of the point-like light source during a contacting process (e.g., a welding process).
The term "via" refers to a vertical interconnect channel, which is an electrical connection between layers in an electronic circuit. In order not to reduce the thermal conductivity away from the point-like light sources, the vias are provided with a sufficiently large cross-section, depending on the specific application of the lighting assembly. The use of vias enables the application of more or less unstructured plastic layers over the lead frame, which makes the manufacturing process of the plastic layers easier.
The lighting assembly may be arranged in such a way that the material, shape and size of the vias are adapted so as not to reduce the heat spreading compared to the heat spreading of point-like light sources directly connected over the lead frame. The conductive material within the vias may have a higher thermal conductivity than the conductive material used in the leadframe, and/or the cross-section of the vias is large enough (suitable shape and size) not to reduce heat spreading.
The lighting assembly may be arranged in such a way that a plastic layer is provided over the lead frame by over-molding the lead frame with the plastic material as an insulating layer. Here, the plastic layer may be applied directly onto the lead frame without the need for a separate production step of manufacturing and providing the plastic layer for subsequent attachment to the lead frame. In particular over-molding avoids additional logic and manufacturing steps for providing plastic layers of the correct shape and size. Furthermore, a firm connection between the lead frame and the plastic layer is established.
The lighting assembly may be arranged in such a way that the conductive tracks on the first surface of the plastic layer are provided by using MID technology. MID techniques involve at least partially covering a first surface of a plastic layer with a conductive layer, typically followed by partial removal of the conductive layer at locations where conductive traces should not be placed, in order to provide remaining conductive traces. Finally, the conductive traces are thickened by growing more conductive material over the current conductive material. Thicker conductive traces are more stable and provide better conductivity.
According to a second aspect, a lighting device is provided. The lighting device comprises one or more lighting assemblies according to the invention and at least one driver connected to the lighting assemblies for driving the one or more lighting assemblies. The driver is used for operating the lighting assembly, in particular the point-like light source and the additional components. Finally, the other optical elements are arranged in the optical path of the light emitted from the point-like light source. The term "optical element" means any element that acts on light passing through the element. The optical element is an at least partially transparent body that is suitably shaped to act on light in a desired manner resulting in refraction, diffraction, reflection or blocking of portions of the light beam passing through the optical element. The collimator as an optical element narrows the light beam in a particular direction, for example, focuses the light beam on a focal point having a focal length with the collimator or an optical element including the collimator. Hence, the lighting device comprises one or more lighting assemblies having an improved thermal behavior and which can be manufactured with low production effort. Furthermore, improved thermal management enables to operate such lighting devices comprising high irradiance point-like light sources (e.g. high power LEDs) with a long lifetime.
According to a third aspect, a method of manufacturing a lighting assembly is provided, the lighting assembly having at least one point-like light source according to the invention, the point-like light source having a first and a second electrical contact. The method comprises the following steps:
-providing a lead frame comprising suitable metal areas to electrically connect the at least one point-like light source to a power source and to spread heat from the at least one point-like light source via the metal areas;
-arranging a suitably shaped plastic layer at least over the lead frame in order to electrically insulate the lead frame from the first surface of the plastic layer;
-providing electrically conductive tracks on a first surface of the plastic layer facing away from the lead frame;
-connecting at least a first electrical contact of at least one point-like light source to a lead frame; and is
-connecting the at least one additional component to the electrically conductive tracks on the first surface of the plastic layer separately from the lead frame, and/or connecting the second electrical contact of the at least one point-like light source with one of the electrically conductive tracks connected to the power source.
Thus, the method provides a lighting assembly with improved thermal behavior and how to manufacture the lighting assembly with reduced investment. Furthermore, improved thermal management enables operation of such lighting assemblies comprising high irradiance point-like light sources (e.g. high power LEDs) with a long lifetime.
The method may be arranged in such a way that it further comprises the step of providing at least one opening in the plastic layer at a suitable location where at least one point-like light source should be placed in order to connect at least the first electrical contact to the lead frame. As an example, the point-like light sources may be soldered onto the lead frame.
The method may be arranged in such a way that the openings are provided as grooves or vias.
The method may be arranged in such a way that the step of providing a plastic layer over the lead frame is performed by over-moulding the lead frame with a plastic material as the plastic layer. Here, the plastic layer may be applied directly onto the lead frame without the need for a separate production step of manufacturing and providing the plastic layer for subsequent attachment to the lead frame. In particular over-molding, avoids the additional logic and manufacturing steps for providing a plastic layer with the correct shape and dimensions. Furthermore, a firm connection between the lead frame and the plastic layer is established.
The method may be arranged in such a way that the step of providing an electrically conductive track on the first surface of the plastic layer comprises the steps of:
-covering a first surface of the plastic layer with an electrically conductive layer;
-partially removing the conductive layer at locations where no conductive tracks should be placed.
The method may be arranged in such a way that the step of growing more conductive material over the current conductive material to form a thicker conductive trace. Thus, MID technology may be applied to provide structured conductive traces to supply operating power to additional components.
It shall be understood that preferred embodiments of the invention may also be any combination of the dependent claims and the respective independent claims.
Further advantageous embodiments are defined below.
Drawings
These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.
The invention will now be described by way of example based on embodiments with reference to the accompanying drawings.
In the drawings:
fig. 1 shows a main sketch of an embodiment of a lighting assembly according to the invention: (a) in a perspective top view without point-like light sources, (b) in a perspective rear view, and (c) in a top view with attached point-like light sources and additional components in the groove.
Fig. 2 shows in a side view another embodiment of the lighting assembly according to the invention, wherein the point-like light sources are connected to the lead frame by vias.
Fig. 3 shows a main schematic view of a lighting device comprising a lamp assembly and a driver according to the invention.
Fig. 4 shows a main sketch of another embodiment of a lighting assembly according to the invention: (a) in a perspective top view without point-like light sources, (b) in a perspective rear view, and (c) in a top view with attached point-like light sources in a groove, wherein the second electrical contact is connected to an electrically conductive track on top of the plastic layer.
Fig. 5 shows an embodiment of a method of manufacturing a lighting assembly according to the invention.
In the drawings, like numbers refer to like objects throughout. Objects in the drawings are not necessarily drawn to scale.
Detailed Description
Various embodiments of the invention will now be described with the aid of the accompanying drawings.
Fig. 1 shows a main sketch of an embodiment of a lighting assembly according to the invention: (a) in a perspective top view without point-like light sources, (b) in a perspective rear view, and (c) in a top view with attached point-like light sources and additional components in the groove. The
Fig. 2 shows in a side view another embodiment of the
Fig. 3 shows a main sketch of a lighting device according to the invention, comprising two
Fig. 4 shows a main sketch of another embodiment of a lighting assembly (1) according to the invention: (a) in a perspective top view without point-like light sources (2), (b) in a perspective rear view, and (c) in a top view with attached point-like light sources (2) in a groove (53 a), wherein the second electrical contact (22) is connected to the electrically conductive track (6) above the plastic layer (5). For fig. 4a and 4b we refer to the drawings description of fig. 1a, 1 b. In fig. 4c, two point-
Fig. 5 shows an embodiment of the method according to the invention for manufacturing a
While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive.
Other modifications will be apparent to persons skilled in the art upon reading this disclosure. Such modifications may involve other features which are already known in the art and which may be used instead of or in addition to features already described herein.
Variations to the disclosed embodiments can be understood and effected by those skilled in the art, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality of elements or steps. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.
Any reference signs in the claims shall not be construed as limiting the scope.
List of reference numerals:
1 Lighting Assembly according to the invention
2 point-like light sources, e.g. LEDs
First electric contact of 21 point-like light source
Second electrical contact of 22 point-like light sources
3 lead frame
31 metal region of lead frame
32 bonding pad
4 additional electric operating parts
5 Plastic layer
51 first surface of plastic layer
52 lower surface of plastic layer (facing the lead frame)
53 openings in the plastic layer
53a as the opening of the groove
53b as openings for vias
54 conductive layer on plastic layer
55 more conductive material grown over the current
6 conductive trace
7 driver
10 Lighting device according to the invention
100 method of manufacturing a lighting assembly according to the invention
110 provide a lead frame
120 providing a suitably shaped plastic layer over the lead frame
125 providing at least one opening in the plastic layer
130 provide conductive traces on a first surface of the plastic layer
132 covering the first surface of the plastic layer with a conductive layer
134 partially removing the conductive layer where the conductive traces should not be placed
136 growing more conductive material over the current conductive material
140 connecting at least one point-like light source to the lead frame
150 connect one or more additional components to the electrically conductive tracks and/or connect the second electrical contact of the at least one point-like light source with one of the electrically conductive tracks connected to the power source.