DE102016214340A1 - LED module - Google Patents

Abstract

A light-emitting diode module (100) comprises a first substrate (105) with at least one first light-emitting diode (110) which is arranged on a first surface (115) of the first substrate (105) and has a first main light exit surface (120). Furthermore, the light-emitting diode module comprises a second substrate (125) with at least one second light-emitting diode (130) which is arranged on a second surface (135) of the second substrate (125) and has a second main light exit surface (140) and a third substrate (145). with a third surface (155). The first substrate (105) and the second substrate (125) are arranged on the third surface (155) of the third substrate (145) such that the first main light exit surface (120) and the second main light exit surface (140) face each other and the two main light exit surfaces (120, 140) to each other an opening angle (α), in the direction of the main emission (Z) of the LED module form.

Description

The present invention relates to an LED module with a plurality of light emitting diodes and a plurality of substrates.

Many applications of LED modules, for example in projectors, endoscopes of medical technology, headlights of the automotive industry or stage lighting, require a high luminance with high light intensities to keep downstream optical systems as small as possible or even avoided. Also, small light / dark transitions must be realized via the luminance. It is important that the LED module builds despite the high luminance required overall small and yet has a relatively long life.

Although the use of so-called high-power LEDs for LED modules leads to significantly higher luminance, but has the fundamental problem of being able to derive heat to a sufficient extent. The maximum possible electric current for operating an LED is ultimately not limited by the LED chip itself, but by the thermal connection of the LED chip and / or by the thermal capacity of the conversion element on the LED chip. As a result, such LED modules, or their LEDs, often have a reduced life. The higher operating current additionally causes a greater effort in the design of the electrical supply unit, to operate the LEDs or the LED module.

Furthermore, a three-dimensional LED arrangement is known in which there are four LEDs on the side edges of a cube and optionally another LED on the underside. The light is emitted inside the cube-shaped volume and emitted on its top. Hereby, the luminance of up to 5 LEDs is concentrated to approximately the area of one LED, which significantly increases the luminance of the module compared to the luminance of a single LED. The theoretically possible increase in luminance by a factor of 5, however, is far from being achieved in practice, since the light is reflected many times within the cube before emission on the cube top. Since the reflectivity of the surfaces is significantly smaller than 100%, a large part of the light is lost, so that only a little more than an increase to twice the luminance can actually be realized. In addition, the assembly of such a module is very expensive and heat dissipation is almost only possible with a three-dimensional heat sink. Thus, it is hardly possible to place a plurality of such modules close to each other in order to realize a linear LED array, for example for a car headlight.

The present invention is based on the problem to provide an LED module, in a simple way, a high luminance is achieved and the LED module is also easy and inexpensive to produce.

According to the invention, this problem is solved by an LED module according to claim 1. Further developments and advantageous embodiments of the LED module can be found in the dependent claims and the description below.

EMBODIMENTS OF THE LED MODULE

An embodiment of the LED module comprises a first substrate having at least one first light-emitting diode, which is arranged on a first surface of the first substrate and has a first main light exit surface. Furthermore, the LED module comprises a second substrate with at least one second light-emitting diode which is arranged on a second surface of the second substrate and has a second main light exit surface and a third substrate with a third surface. The first substrate and the second substrate are arranged on the third surface of the third substrate such that the first main light exit surface and the second main light exit surface face each other and the two main light exit surfaces form an opening angle to each other in the direction of the main emission direction of the LED module.

In the context of this description, a light-emitting diode can be understood as a component which emits electromagnetic radiation by means of a semiconductor component (LED chip) and an optional conversion element. The formation of electromagnetic radiation of a second wavelength from electromagnetic radiation of a first wavelength (LED chip) is called wavelength conversion. Wavelength conversion is used in light-emitting diodes for color conversion, for example to facilitate the generation of white light. In this case, for example, a blue light (LED chip) is converted into a yellow light. The color mixture of blue light and yellow light forms white light. A conversion element comprises a converter material, also referred to as phosphor. The conversion element can be arranged for wavelength conversion in the light path of a light-emitting diode. For example, a light emitting diode may include an InGaN-based blue or UV emitting chip and a conversion element.

The present embodiment describes a three-dimensional arrangement of at least two light emitting diodes, wherein the two main light exit surfaces of the light emitting diodes face each other and form, for example, an opening angle of about 60 °. Thus, a cross section through the two main light exit surfaces describes approximately an equilateral triangle. Two sides of the triangle are formed by the two main light-emitting surfaces of the LEDs. The third side of the triangle forms the effective emitting area of the LED module. Ideally, emitted light of the first and second main exit surfaces may pass through the effective emission surface of the LED module directly or after reflection, at the respectively opposite main exit surface. With perfect reflectivity of all surfaces thus a doubling of the luminance could be achieved.

About half of the emitted light of each LED main exit surface passes through the effective emission surface of the LED module without reflection. After the first reflection of the remaining emitted light approximately approximately half of the reflected light again passes through the effective emission area of the LED module. With a reflectivity of 90%, as it is realistic, it is to be expected in this arrangement with a light emission of about 90% of the generated light, which corresponds to an increase in luminance by about 80% compared to a single light emitting diode.

Thus, the system is as efficient as a light emitting diode, which is operated with about twice the current. For all InGaN-based chips, which are operated with higher current density, a reduction in efficiency occurs in the same order of magnitude. The reason for this is the so-called Droop effect.

Because of the halved current density, however, the thermal load of the conversion element is much lower. Likewise, the requirements for the electrical design of the driver electronics, to operate the LED module, lower.

The LED module can be manufactured using standard equipment and standard processes of semiconductor technology. The LED module can be designed with SMT-compatible components. It is possible without any restrictions, a linear LED array of such LED modules by juxtaposing a plurality of LED modules, wherein on the first and second substrate, one or more light-emitting diodes are arranged to produce. Such linear LED arrays are common for example for motor vehicle headlights.

According to a development of the LED module, the third surface of the third substrate has electrical contact surfaces.

The third substrate may comprise an electrically non-conductive base material. In a separate step, the electrical conductors and the electrical contact surfaces are arranged on a surface of the substrate. However, it is also possible that the third substrate is manufactured in a leadframe technology. In this case, a larger metal plate is structured such that many electrical contact structures are predefined by punching out and the spaces generated are filled with a thermoplastic or a silicone as insulating material. Here, the electrical conductors and the electrical contact surfaces are formed directly by the leadframe.

According to a development of the LED module, the first substrate and the second substrate are electrically conductively connected to the electrical contact surfaces of the third substrate.

Thus, the first and the second substrate are supplied with electrical energy centrally via the electrical contact surfaces of the third substrate. In this case, the first and the second substrate are advantageously connected in series, which allows a lower operating current than in a parallel connection. The series connection also ensures that the first and the second substrate are supplied with identical current.

According to a development of the LED module, the first surface of the first substrate and / or the second surface of the second substrate has a reflective surface.

The reflective surface may be formed of the base material of the first or second substrate, for example, metal. It is also possible that the reflective surface comprises a reflective coating, for example, titanium dioxide embedded in a matrix material such as silicone. The reflective surface can contribute to a particularly high efficiency of the LED module, since optical losses in the LED module are minimized.

According to a development of the LED module, the space between the first substrate and the second substrate in the area to the third substrate is at least partially filled with a reflective body. The reflective body does not touch and / or obscure the main exit surfaces of the first and second light emitting diodes.

The reflective body may be formed of a base material having reflective properties and a specially machined surface, such as polished metal. It is about it In addition, it is possible for the reflective body to comprise a reflective coating, for example, titanium dioxide embedded in a matrix material such as silicone. The reflective body can contribute to a particularly high efficiency of the LED module, since optical losses are minimized in the LED module.

According to a further development of the LED module, a heat sink is arranged between the third surface of the third substrate and the rear side of the first substrate opposite the first surface and / or the rear side of the second substrate opposite the second surface.

The heat sink may be formed of a base material of high thermal conductivity, for example metal. The flat contact of the heat sink with the respective substrate surfaces ensures that the heat generated during operation of the LED module can be efficiently dissipated.

It is an embodiment that a thermally conductive agent is arranged to improve the thermal conductivity between the surfaces of the heat sink and the respective substrate surfaces. Preferably, the means for producing the thermal contact is a thermally conductive connecting means, which provides a material connection between the heat sink and the substrates. This may in particular be an adhesive, a TIM film (TIM stands for the technical term: thermal interface material) or a solder.

According to a development of the LED module, the opening angle is between 40 ° and 100 °.

The opening angle formed by the main light exit surfaces of the first and second light emitting diodes defines the size of the effective emission area of the LED module. As the opening angle increases, the effective emitting area of the LED module increases, and consequently, the luminance of the module decreases. In order to provide an LED module with optimized luminance, the opening angle is preferably in the following order in the following ranges: 40 ° to 100 °, 40 ° to 80 ° and 40 ° to 60 °.

According to a development of the LED module, the first light-emitting diode and the second light-emitting diode are designed as surface-emitting light-emitting diodes.

Surface-emitting light-emitting diodes typically have an electrical contact on their upper side and an electrical contact on their underside. The radiation generated in the LED is emitted only via the main light exit surface. In the case of volume-emitting light-emitting diodes, a small proportion of the radiation generated is also emitted via the side surfaces of the light-emitting diode. Thus, surface emitting LEDs have a higher luminance by design than volume emitting LEDs.

According to a development of the LED module, an at least partially translucent disk is arranged in the direction of the main emission direction, above the first and the second light emitting diode.

The disk may be made of diffused (i.e., designed for light scattering) or transparent (i.e., clear) material. When laying down on a clear material, the luminance of the LED module can be optimized, while in the determination of a diffused material, the property of a uniform radiation characteristic is improved.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the solution according to the invention are explained in more detail below with reference to the drawings. In the figures, the first digit (s) of a reference numeral indicate the figure in which the reference numeral is used first. The same reference numerals are used for similar or equivalent elements or properties in all figures.

Show it

1 a schematic representation of an LED module 100 according to a first embodiment in a sectional view;

2 a schematic representation of a sub-module 200 according to a first embodiment in a three-dimensional representation;

3 a schematic representation of the electrical contacting of the sub-modules with the carrier substrate according to a first embodiment in a plan view;

4 a schematic representation of an LED module 400 according to a second embodiment in a sectional view;

5 a schematic representation of an LED module 500 according to a third embodiment in a plan view.

EMBODIMENTS OF THE LED MODULE

1 shows a schematic representation of an LED module 100 according to a first Embodiment in a sectional view. The LED module is composed of two sub-modules (see description 2 ). Each sub-module comprises a substrate 105 . 125 with at least one light emitting diode 110 . 130 , At the light emitting diode 110 . 130 it is preferably a surface emitting light emitting diode. The two sub-modules are on a substrate 145 applied electrically conductive. Optionally, they are mechanical through wedge-shaped heat sinks 180 supports the thermal connection of the LEDs 110 . 120 to the substrate 145 improve. The two submodules 200 can be identical.

To reduce absorption losses, the space X is between the first substrate 105 and the second substrate 125 in the area to the third substrate 145 with a reflective body 165 , at least partially, completed. This prevents light from entering and being absorbed in this space X.

In addition, it is possible to attach a side cover, ideally made of a highly reflective material, to reduce radiation losses.

2 shows a schematic representation of a sub-module 200 according to a first embodiment in a three-dimensional representation. The light-emitting diode 110 is on a large metal body 205 applied, for example by soldering, gluing or sintering. The surface emitting LED 110 is about their backside contact with the metal body 205 electrically connected.

The substrate 105 of the submodule 200 includes another, usually smaller metal body 210 which represents the second electrical contact. The metal body 210 is over a bonding wire 215 with the corresponding front side contact of the surface emitting LED 110 connected.

Further elements and contact surfaces, for example for the additional integration of an ESD chip, are possible, but can also be used in the substrate (FIG. 145 , in 2 not shown) of the LED module to be integrated.

The substrate 105 is cut off at one side at an angle of about 60 °, with both contact surfaces 220 . 225 the metal body 205 . 210 lie on the cutting edge. For thermal reasons, it is advantageous if the large-area metal surface extends over as large a portion of the oblique side surface as possible, since this surface is in direct thermal contact with the substrate (FIG. 145 , in 2 not shown).

Due to its flat shape, the substrate can 105 be manufactured in leadframe technology. In this case, a larger metal plate is structured such that many contact structures are predefined, which are connected, for example, in the area of the later oblique edge. The insulating areas in between are produced by injection molding, for example with a thermoplastic or a silicone as insulating material 230 , After the LED assembly and the Drahtbondprozess the components, for example, by sawing, isolated. The oblique saw edge can be generated by tilting the saw or by using a saw blade with wedge-shaped cross-section. For a later connection to the substrate ( 145 , in 2 not shown) may be the resulting sawing surface 220 . 225 to coat with a metallization. For example, the metal plate from which the leadframe is made may be made of copper whose sawn surface 220 . 225 coated with silver or gold.

Alternatively, the inclined surface can already be defined and metallised during leadframe production. During further processing, the components then hang together at another, for example, at the opposite edge of the oblique edge.

Alternatively, the substrate 105 of the submodules 200 be made of partially metallized ceramic. In this case, the inclined surface can already be predefined and pre-metallized.

The in 1 shown heatsink 180 can also be made using leadframe technology. The wedge-shaped heat sink 180 can be made from the same material as the leadframe technology substrate 105 exist and also be coated. The heat sink 180 has a similar width as the large-area metal body 205 of the substrate 105 , The heat sink 180 is during assembly with the back of the large-area metal body 205 connected so that a good thermal contact is made.

3 shows a schematic representation of the electrical contacting of the sub-modules 200 with the carrier substrate 145 according to a first embodiment in a plan view.

The carrier substrate 145 The LED module, which can also be made in leadframe technology or ceramic, has contact surfaces 305 . 310 . 315 on top of which are the sloping side surfaces 220 . 225 of the submodules 200 be applied electrically and thermally conductive, for example by soldering, sintering or gluing. The two submodules become 200 advantageously connected in series, which allows a lower operating current than in a parallel connection. The series connection also ensures that the sub-modules 200 be supplied with identical current.

The contacts 305 . 310 . 315 are designed as large as possible and when using a leadframe technology in addition to the back of the substrate 145 performed to allow a good thermal connection. By suitable choice of metallization, it is possible to provide SMT-capable components.

About the contact surfaces 305 . 310 becomes the LED module 100 , with its submodules 200 and the associated contact surfaces 220 . 225 , supplied with electrical energy. By on the submodules 200 arranged light-emitting diodes 110 . 130 , in 3 not shown and the contact surface 315 of the carrier substrate 145 , becomes an electrically conductive connection from the contact surface 305 to the contact surface 310 provided.

The assembly of the LED module 100 takes place in the following steps. First, the heatsink 180 on the carrier substrate 145 applied with a pick-and-place technology, for example by a soldering, gluing or sintering process. They are preferred on the larger contact surfaces 310 . 315 arranged and are slightly narrower than the sub-modules 200 , This will cause an electrical short between the contact surfaces 305 and 315 respectively. 310 and 315 prevented. Subsequently, the two sub-modules 200 mounted in mutually rotated by 180 ° orientation, with both their back to the heat sink 180 as well as with its oblique edge directly on the contact areas 305 . 310 . 315 of the carrier substrate 145 be soldered, glued or sintered. The heat sinks 180 serve to solidify the connection as a mechanical support and leadership, then they serve the heat dissipation.

4 shows a schematic representation of an LED module 400 according to a second embodiment in a sectional view.

For the purpose of mechanical protection or for homogenization of the light emission is in the direction of the main emission Z, on the first and the second light-emitting diode 110 . 130 , an at least partially translucent disc 410 arranged. For fixing the disc 410 become the heat sinks 180 be used, which are designed for sufficient height.

If the module is used for a car headlight, is on / in the disc 410 an absorbent or reflective edge 420 integrated. Such a shading edge 420 is required for light sources in vehicle headlights to produce a sufficiently high contrast ratio for the low beam function.

In addition, it is possible to attach a side cover, ideally made of a highly reflective material, to reduce radiation losses. In principle, when using a leadframe technology for the substrate 145 This sidewall will be integrated as a leadframe package wall.

5 shows a schematic representation of an LED module 500 according to a third embodiment in a plan view.

The LED module 500 is designed as a linear LED array. The LED module is of the basic principle as the described LED module 100 built up. On the first substrate 105 and the second substrate 125 are several light emitting diodes 510 . 520 arranged. On the sides of the linear LED array are side covers 530 arranged.

Alternatively, the linear LED array may consist of several sub-modules placed side by side in series on a large carrier substrate 145 are arranged to be constructed. This makes it possible to produce flexible and modularly different sized LED arrays from identical submodules. Such linear arrays are common, for example, for motor vehicle headlights.

FINAL FINDING

The lighting device has been described to illustrate the underlying idea using some embodiments. The embodiments are not limited to specific feature combinations. Although some features and configurations have been described only in connection with a particular embodiment or individual embodiments, they may each be combined with other features from other embodiments. It is also possible to omit or add in individual embodiments illustrated features or particular embodiments, as far as the general technical teaching is realized.

LIST OF REFERENCE NUMBERS

100

light emitting diode module

105

first substrate

110

first light-emitting diode

115

first surface

120

first main light exit surface

125

second substrate

130

second light-emitting diode

135

second surface

140

second main light exit surface

145

third substrate, carrier substrate

155

third surface

160

reflective surface

165

reflective body

170

back

175

back

180

heatsink

185

effective emission area

200

sub-module

205

metal surface

210

metal surface

215

bonding wire

220

electrical contact surface

225

electrical contact surface

230

insulating area

305

Contact surface, N-contact

310

Contact surface, P-contact

315

contact area

400

light emitting diode module

410

 cover disc

420

absorbent or reflective edge

500

light emitting diode module

510

led

520

led

530

lateral cover

α

opening angle

X

room

Z

Main emission direction electrical contact surfaces

Claims (9)

Light emitting diode module ( 100 ), comprising - a first substrate ( 105 ) with at least one first light-emitting diode ( 110 ) on a first surface ( 115 ) of the first substrate ( 105 ) is arranged and a first main light exit surface ( 120 ), - a second substrate ( 125 ) with at least one second light-emitting diode ( 130 ) on a second surface ( 135 ) of the second substrate ( 125 ) is arranged and a second main light exit surface ( 140 ), - a third substrate ( 145 ) with a third surface ( 155 ), wherein - the first substrate ( 105 ) and the second substrate ( 125 ) on the third surface ( 155 ) of the third substrate ( 145 ), and - the first main light exit surface ( 120 ) and the second main light exit surface ( 140 ) are arranged opposite one another and the main light exit surfaces ( 120 . 140 ) form an opening angle (α) relative to one another in the direction of the main emission direction (Z) of the light-emitting diode module. Light emitting diode module ( 105 ) according to claim 1, wherein the third surface ( 155 ) of the third substrate ( 145 ) has electrical contact surfaces (x). Light emitting diode module ( 105 ) according to one of the preceding claims, wherein the first substrate ( 105 ) and the second substrate ( 125 ) with the electrical contact surfaces (x) of the third substrate ( 145 ) are electrically connected. Light emitting diode module ( 100 ) according to any one of the preceding claims, wherein the first surface ( 115 ) of the first substrate and / or the second surface ( 125 ) of the second substrate has a reflective surface ( 160 ) exhibit. Light emitting diode module ( 100 ) according to one of the preceding claims, wherein the space (X) between the first substrate ( 105 ) and the second substrate ( 125 ) in the area to the third substrate ( 145 ) with a reflective body ( 165 ) is at least partially filled and the reflective body ( 165 ) the main exit surfaces ( 120 . 140 ) of the first and the second light emitting diode ( 110 . 130 ) not touched and / or obscured. Light emitting diode module ( 100 ) according to any one of the preceding claims, wherein between the third surface ( 155 ) of the third substrate ( 145 ) and the first surface ( 115 ) opposite back ( 170 ) of the first substrate ( 105 ) and / or the second surface ( 135 ) opposite back ( 175 ) of the second substrate ( 125 ) a heat sink ( 180 ) is arranged. Light emitting diode module ( 100 ) according to one of the preceding claims, wherein the opening angle (α) is between 40 ° and 100 °. Light emitting diode module ( 100 ) according to one of the preceding claims, wherein the first light-emitting diode ( 110 ) and the second LED ( 130 ) are formed as surface emitting light-emitting diodes. Light emitting diode module ( 400 ) according to one of the preceding claims, wherein in the direction of the main emission direction (Z), above the first and the second light-emitting diode ( 110 . 130 ), an at least partially translucent disc ( 410 ) is arranged.

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