DE102010062158A1 - Lighting device and method for producing a lighting device - Google Patents

Abstract

The lighting device (L) has a first substrate (1) on which a second substrate (2) equipped with at least one semiconductor light source (9) is applied in a planar manner, the first substrate (1) being integrally bonded to the second substrate (2) without adhesive connected is. The method (S1-S5) is used to produce a lighting device (L), the method comprising at least the following steps: heating a volume region (3) made of plastic of a first substrate (1) above its glass transition temperature (S3); Two-dimensional placement and pressing of a second substrate (2) onto the volume area (3) made of plastic of the first substrate (1) (S4) and cooling of the volume area (3) made of plastic of the first substrate (1) below its glass transition temperature (Tg) when pressed second substrate (2) (S5).

Description

The invention relates to a lighting device which has a first substrate on which a second substrate equipped with at least one semiconductor light source is applied in a planar manner. The invention further relates to a method for producing a lighting device.

There are light devices are known which have a substrate made of ceramic (also called "submount"), which is equipped with a plurality of light-emitting diode chips, wherein the submount is adhered by means of a thermally conductive adhesive on a circuit board. It is disadvantageous that the adhesive is applied only with a non-negligible effort. Thus, a layer thickness of the adhesive for a high heat flux from the second substrate to the first substrate should be as low as possible, but on the other hand a high adhesive strength can be achieved, which in particular withstands thermal cycling and is as insensitive to degradation as possible.

It is the object of the present invention to provide an improved attachment of at least one second substrate equipped with at least one semiconductor light source to a first substrate of a lighting device.

This object is achieved according to the features of the independent claims. Preferred embodiments are in particular the dependent claims.

The object is achieved by a lighting device, comprising a first substrate, on which at least one equipped with at least one semiconductor light source second substrate is applied flat, wherein the first substrate is adhesively bonded cohesively with the at least one second substrate. By dispensing with a dedicated adhesive (such as an adhesive or a solder layer) better heat transfer between the two substrates can be achieved. The cohesive connection also enables a reliable, fixed connection. For example, in contrast to a positive or non-positive connection, for. As by brackets, locking connections, screws, etc., also a simple installation and compact design is possible. Also, a very good land use is achieved.

It is an embodiment that the second substrate with a volume range of plastic of the first substrate is adhesively bonded cohesively. It is exploited that plastic can be particularly easily and versatile cohesively connect, especially at relatively low temperatures.

It is a development that the cohesive connection has been achieved by an "adhesive-free lamination". Adhesive-free lamination may comprise transferring at least one of the contact surfaces of the two substrates to be bonded to a soft (entropy-elastic) state, subsequently compressing the substrates at their common contact surface, and finally cooling to a brittle (entropy-elastic) state. This results in a strong bond in which the substrates are held together by atomic and / or molecular forces.

It is still an embodiment that the plastic has a glass transition temperature Tg between about 100 ° C and about 180 ° C, in particular between about 105 ° C and about 170 ° C. This allows for adhesive-free lamination without damaging the substrates or typically components already disposed thereon (semiconductor light sources, electronic components, etc.).

It is yet another embodiment that the plastic, in particular the plastic volume range of the first substrate, is a thermoplastic or thermosetting plastic. This provides a good and inexpensive ability for adhesive-free lamination.

It is also an embodiment that the second substrate is a ceramic substrate. The ceramic substrate enables excellent thermal heat dissipation from the at least one semiconductor light source. The ceramic advantageously has a thermal conductivity λ of at least about 20 W / (m · K), more preferably at least about 150 W / (m · K), even more preferably at least about 200 W / (m · K) , The ceramic is preferably electrically insulating. The material of the ceramic may comprise, for example, aluminum oxide and / or aluminum nitride. The ceramic, in particular electrically insulating, can have an electrically conductive conductor structure with at least one contact surface and / or at least one conductor track at least on the surface equipped with the at least one semiconductor light source. The conductor structure can be formed for example by means of copper and / or silver, for. B. by means of a printing process. An electrical breakdown strength of the second substrate, in particular the ceramic, is preferably at least 0.5 kV. A layer thickness of the ceramic may in particular be between 0.5 mm and 0.75 mm, in particular between 0.6 mm and 0.7 mm.

It is also an embodiment that the volume range of plastic, in particular the thermoplastic or thermoset volume range, filled epoxy resin has. The filled epoxy can be comparatively simple and inexpensive adapted to different operating requirements, eg. B. to a desired dielectric strength and / or thermal conductivity, for example by the nature and / or concentration of the epoxy resin filled or added admixtures. The filled epoxy resin may in particular be a printed circuit board base material, for example FR4 or FR5.

It is a preferred embodiment for achieving a sufficiently high electrical breakdown strength and a sufficiently low thermal resistance that the plastic volume range comprises a layer having a layer thickness between 0.025 mm and 0.3 mm, in particular between 0.05 mm and 0.2 mm, forms. The dielectric strength is preferably at least 0.5 kV.

The first substrate may in particular be a printed circuit board. A base material of the printed circuit board may in particular be plastic, ie the base layer or core of the printed circuit board may be the volume region made of plastic. The circuit board may be a metal core board for improved heat dissipation.

The volume region of plastic may generally be formed as a plastic layer or plastic layer. If the first substrate is a printed circuit board or board, the plastic layer may be a base layer or base layer.

It is an embodiment which is advantageous for achieving a high luminance or light intensity in a compact space, that the at least one semiconductor light source is configured in each case as a naked light-emitting diode chip (LED (nude) chip). The LED chip is not housed individually, but applied as a bare chip ("bare die") on the second substrate. Alternatively, packaged semiconductor light sources may also be mounted on the second substrate.

In general, the at least one semiconductor light source z. B. have at least one diode laser and / or a (packaged or unhoused) light emitting diode.

If several LEDs are present, they can be lit in the same color or in different colors. A color can be monochrome (eg red, green, blue, etc.) or multichrome (eg, white). The light emitted by the at least one light-emitting diode can also be an infrared light (IR LED) or an ultraviolet light (UV LED). Several light emitting diodes can produce a mixed light; z. B. a white mixed light. The at least one light-emitting diode may contain at least one wavelength-converting phosphor (conversion LED). The at least one light emitting diode may be equipped with at least one own and / or common optics for beam guidance, z. At least one Fresnel lens, collimator, and so on. Instead of or in addition to inorganic light emitting diodes, z. Based on InGaN or AlInGaP, organic LEDs (OLEDs, eg polymer OLEDs) can generally also be used.

The object is also achieved by a method for producing a lighting device, the method having at least the following steps: (a) heating a volume region of plastic of a first substrate above its glass transition temperature Tg; (b) laminating and pressing at least one second substrate onto the plastic volume region of the first substrate, and (c) cooling the plastic volume region of the first substrate below its glass transition temperature Tg when the second substrate is pressed on. By this "adhesive-free lamination" the same advantages can be achieved as for the above-described lighting device. The method can generally be configured analogously to the lighting device.

The heating can be done in particular to a temperature between 105 ° C and 170 ° C.

It is an embodiment that the step of heating is preceded by a step of exposing the plastic volume region of the first substrate to a conductor layer. Thus, the lighting device can be used in a simple manner with conventional printed circuit boards as the first substrate. The exposure can be performed by etching, for example.

The conductor layer can be, for example, a structured or non-structured copper layer. The structured conductor layer serves to conduct current and may, inter alia, have conductor tracks, contact fields, electrical connection elements, etc.

It is yet another embodiment that, prior to the step of heating, a step of loading a conductor layer covering the plastic volume region of the first substrate is performed. This protects the semiconductor light sources in the manufacture of the lighting device. Alternatively, the first substrate can be equipped even after an application of the second substrate, for. B. with at least one driver block.

The steps of exposing the volume area and heating may be performed in any order, but preferably such that the step of exposing is performed before the loading step.

In the following figures, the invention will be described schematically with reference to an embodiment schematically.

1 shows in plan view a first substrate of a lighting device in a not yet prepared for receiving a second substrate, unpopulated state;

2 shows in plan view a first substrate of a lighting device in a partially prepared for receiving a second substrate, unpopulated state;

3 shows in plan view the first substrate in a prepared state for receiving the second substrate;

4 shows in plan view the first substrate in the prepared for receiving the second substrate state on a heating means;

5 shows in plan view the first substrate in the prepared state for receiving the second substrate on the heating means with an attached second substrate; and

6 shows a flowchart for producing a lighting device.

1 shows in plan view a first substrate 1 a lighting device L in a for receiving or fixing a second substrate 2 (also called submount, see 4 ) not yet prepared state. The first substrate 1 may be, for example, a commercially available circuit board.

The substrate 1 is present as a rectangular in plan view printed circuit board, which is a substrate or base material 3 made of thermosetting plastic in the form of filled epoxy resin, in particular FR4, as having a volume range of plastic.

On a front side 4 the first substrate 1 there is a conductor layer 5 , z. B. a copper layer. The conductor situation 5 can be unstructured (full-surface) or preferably structured. The structured conductor layer 5 can have at least one conductor track and / or a contact surface (not shown). The conductor situation 5 is not yet equipped in this state.

2 shows in plan view the first substrate 1 in a for receiving the second substrate 2 partially prepared condition. For this purpose, the volume range of plastic or the base material 3 been uncovered centrally or freed, as well as in the 6 illustrated flowchart described in step S1. The exposure can be carried out in particular by an etching process. A free space created in this way 7 is also rectangular in plan view, in particular square.

3 shows in plan view the first substrate 1 similar to the partially prepared state, but now the structured conductor layer 5 with at least one electronic component 6 , in particular a driver component (resistor, capacitor, integrated circuit, etc.) is equipped, as well as in 6 shown in step S2.

4 shows in plan view the first substrate 1 with the vacated area 7 wherein the second substrate 1 to a heating means in the form of a heating plate 8th has been applied to the base material 3 to heat up to or above its glass transition temperature Tg, as well as step S3 in FIG 6 shown. This will be the base material 3 converted into a soft state.

5 shows in plan view the first substrate 1 on the heating plate 8th with the on the base material 3 in the cleared area 7 attached second substrate 2 , The second substrate 2 contacts with its back the soft base material 3 flat under pressure (eg on the base material 3 pressed on), while its front with several LED nude chips 9 is equipped. This is also in 5 , Step S4, indicated.

The following is the base material 3 again cooled below its glass transition temperature Tg, z. B. by deactivating the hot plate 8th , At least until reaching or falling below the glass transition temperature Tg, the second substrate 2 further pressed, as in step S5 in 6 described.

After that, the first substrate 1 and the now solid and two-dimensional cohesively associated second substrate 2 having lighting device L from the heating plate 8th be removed.

Among other things, it may be a step of electrically connecting the conductor layer 5 the first substrate 1 with the second substrate, in particular an electrically conductive structure thereof, connect, for. B. by wire bonding.

Of course, the present invention is not limited to the embodiment shown.

Thus, two or more second substrates may also be attached to the first substrate in the manner described.

Also, a shape of the substrates may differ, for example by a circular in plan view form.

LIST OF REFERENCE NUMBERS

1

first substrate

2

second substrate

3

base material

4

Front side of the first substrate

5

conductor layer

6

electronic component

7

free-space area

8th

heating plate

9

LED bare chip

L

lighting device

S1-S5

steps

Claims (10)

Lighting device (L) comprising a first substrate ( 1 ), on which at least one with at least one semiconductor light source ( 9 ) equipped second substrate ( 2 ) is applied flat, wherein the first substrate ( 1 ) with the at least one second substrate ( 2 ) is adhesively bonded cohesively. Lighting device (L) according to claim 1, wherein the at least one second substrate ( 2 ) with a volume range ( 3 ) made of plastic of the first substrate ( 1 ) is adhesively bonded cohesively. Lighting device (L) according to claim 2, wherein the plastic ( 3 ) has a glass transition temperature (Tg) between 100 ° C and 180 ° C, in particular between 105 ° C and 170 ° C. Lighting device (L) according to one of claims 2 or 3, wherein the volume range ( 3 ) made of plastic of the first substrate ( 1 ) a thermoplastic or thermoset volume range ( 3 ) and the second substrate ( 2 ) is a ceramic substrate. Lighting device (L) according to one of claims 2 to 4, wherein the thermoplastic or thermoset volume range ( 3 ) filled epoxy resin. Lighting device (L) according to one of claims 2 to 5, wherein the volume range ( 3 ) of plastic forms a layer with a layer thickness between 0.025 mm and 0.3 mm, in particular between 0.05 mm and 0.2 mm. Lighting device (L) according to one of the preceding claims, wherein the at least one semiconductor light source ( 9 ) is configured in each case as a naked LED chip. Method (S1-S5) for producing a lighting device (L), the method comprising at least the following steps: - Heating a volume range ( 3 ) made of plastic of a first substrate ( 1 ) above its glass transition temperature (S3); Surface contact with and pressing on at least one second substrate ( 2 ) to the volume range ( 3 ) made of plastic of the first substrate ( 1 ) (S4) and - cooling the volume range ( 3 ) made of plastic of the first substrate ( 1 ) below its glass transition temperature (Tg) with at least one second substrate pressed on ( 2 ) (S5). Method (S1-S5) according to claim 8, wherein before the step of heating a step: - exposure of the volume area ( 3 ) made of plastic of the first substrate ( 1 ) is performed from a conductor layer (S1). Method (S1-S5) according to one of claims 8 or 9, wherein prior to the step of heating, a step: - loading a volume range ( 3 ) made of plastic of the first substrate ( 1 ) covering conductor layer ( 5 ) (S2).

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