Light module for motor vehicle lighting device and method for producing light module

Abstract

The invention relates to a light module (100) for a motor vehicle lighting device, at least comprising an LED lighting means (1), a metallic conductor circuit (2) for electrically contacting the LED lighting means (1), a carrier body (3) on which the LED lighting means (1) and the conductor circuit (2) are arranged, and a metallic heat sink (4), the carrier body (3) is connected to the cooling body (4) in a form-fitting manner. According to the invention, the carrier body (3) has an electrically insulating and thermally conductive composite material (30).

Description

Technical Field

[0001] The present invention relates to a light module for a motor vehicle lighting device, the light module comprising at least an LED lighting device, a metal conductor circuit for electrically contacting and conducting the LED lighting device, a carrier, and a metal cooling body, the LED lighting device and the conductor circuit being arranged on the carrier, the carrier being connected to the cooling body in a form-locking manner. The present invention also relates to a method for manufacturing such a light module. Background Art

[0002] When using high-power LED lighting devices (LED: light-emitting diode) in light modules of motor vehicle lighting devices (especially headlights), thermal management is a particular challenge.

[0003] In the prior art, LED lighting devices are arranged on printed circuit boards, which in turn are arranged on metal cooling bodies. The connection between the LED lighting device and the printed circuit board is usually formed by means of a soldering connection, and the joint gap between the printed circuit board and the cooling body is bridged, for example, by means of a thermally conductive paste. The electrically insulating and thermally insulating carrier of the printed circuit board makes an important contribution to the thermal flow resistance between the LED lighting device and the cooling body. The carrier is composed, for example, of a flame-retardant composite material made of epoxy resin and glass fiber fabric, typically of a FR-4 grade composite material. Alternatively, so-called insulated metal substrates (IMS) for printed circuit boards are known, which are usually constructed as a layer sequence consisting of an aluminum or copper carrier, an electrically insulating and thermally insulating insulating layer, and a copper layer including a conductor circuit. Here, the copper layer is particularly used for lateral heat diffusion. The thermal resistance is mainly dominated by the insulating layer.

[0004] Furthermore, DE 10 2019 129 591 A1 discloses a light module for a motor vehicle lighting device, which has a circuit carrier film made of thermoplastic instead of a printed circuit board, wherein the circuit carrier film is connected to a metallic cooling body in a form-fitting manner. A disadvantage of this embodiment is that the circuit carrier film is susceptible to thermal damage. Due to its small thickness, the circuit carrier film has only a small thermal capacity, so that heat absorption can quickly lead to a critical temperature increase. Summary of the invention

[0005] It is therefore an object of the present invention to provide a light module of the generic type for a motor vehicle lighting device which is distinguished in particular by improved heat management during operation of the LED lighting means.

[0006] This object is achieved starting from a light module according to the preamble of claim 1 in combination with the characterizing features. Advantageous developments of the invention are specified in the dependent claims.

[0007] The present invention includes the following technical teaching: a carrier connected to a heat sink in a form-fitting manner comprises an electrically insulating and thermally conductive composite material, on which at least one LED illuminant and associated conductor tracks are arranged.

[0008] The present invention is based on the idea that the thermal resistance of the carrier is significantly reduced compared to the construction in the prior art, in that the carrier has a functionally integrated composite material, which, in addition to the electrical insulation required for the operation of the LED lighting device, also has outstanding thermal conductivity. Due to this favorable material property, the thermal resistance between the LED lighting device and the metal cooling body can be further reduced compared to the embodiments known from the prior art, so that in the operation of the light module according to the present invention, a particularly efficient heat dissipation of the LED lighting device and other power-consuming devices arranged on the carrier can be achieved. In addition, this is also due to the form-locking connection between the carrier and the cooling body, wherein the associated joint surface is preferably constructed as a large area and determines the heat transfer from the carrier to the cooling body. Therefore, unlike the light module with a printed circuit board in the prior art, there is no joint gap that interrupts the heat flow to the cooling body.

[0009] Suitable composite materials have, in particular, a matrix made of plastic, preferably polyamide or other partially crystalline plastics, and metallic, ceramic and / or graphite fillers, wherein the fillers preferably have a spherical configuration and are uniformly distributed in the matrix. Such composite materials are known from DE 10 2015 015 276 A1 and DE 10 2017 001 013 A1. In particular, the electrical and thermal properties of such composite materials can be "customized" by changing the filling density of the fillers. The material properties "electrically insulating" and "thermally conductive" expressed in claim 1 of the present application are configured so that suitable values ​​of electrical resistance and thermal conductivity exist for a specific embodiment of the light module according to the present invention. The design of these values ​​is determined, in particular, by the current flowing through the conductor path during operation of the light module and by the heat to be dissipated. In particular, the desired electrical and thermal properties should exist isotropically, and for example, the spherical configuration of the fillers and the uniform distribution within the formed carrier help to achieve this.

[0010] For example, the carrier has at least 10 7 Ω (10 megohms) electrical insulation resistance, and / or the composite material has a thermal conductivity of at least 4 W / mK, preferably at least 10 W / mK. In order to achieve the desired insulation resistance with suitable carrier dimensions, the composite material has, for example, at least 10 9 Volume resistance in Ωm (at a test voltage of 500 V in accordance with DIN EN 61340-2-3).

[0011] The carrier has, for example, a thickness of 0.5 mm to 5 mm, preferably 1 mm to 3 mm. Such a thickness enables lateral heat diffusion within the carrier, so that in particular the formation of undesirable hot spots can be suppressed. In addition, a sufficient thickness is critical in order to ensure a reliable production process of the thermal body by means of injection molding.

[0012] Preferably, the carrier and the cooling body form a comprehensive joint area, wherein the cooling body has a joint surface with micron-level and / or nanometer-level cavities in the joint area, and the composite material of the carrier fills these cavities when forming a positive connection, preferably when forming a side recess. The lateral size of the joint area is preferably substantially equal to the lateral size of the carrier, that is, the entire cross section of the carrier contributes to the heat transfer in the cooling body. The micron-level and / or nanometer-level cavities introduced into the joint surface cause a further increase in the effective surface for heat transfer. The cavity can exist, for example, in a nest-like manner or as a groove-shaped recess in a straight or zigzag shape, or have a more complex morphology, and for example, there can also be a combination of a cavity and a surface protrusion. Here, the size of the surface structure is preferably adapted to the plasticity of the specific composite material of the carrier. For example, the micron-level cavity has a characteristic structure size of 1 micron to 100 microns. Nanostructuring can especially cause a targeted change in surface energy, and thus utilize the matrix material softened during manufacturing to affect the wettability of the metal surface. In this case, the cavity and the geometric undercut produce a positive connection both perpendicularly and parallel to the plane normal of the joining surface. The undercut can be formed, for example, by a step or a bulge of the cavity.

[0013] In another embodiment, the heat sink has at least one metallic heat dissipation element for the at least one LED illuminant, wherein the heat dissipation element protrudes from the joint surface of the heat sink and is laterally surrounded by the carrier, so that a direct heat bridge is formed between the LED illuminant and the heat sink by means of the heat dissipation element. Such a heat dissipation element is preferably constructed as one piece with the heat sink and of the same material, and contacts the LED illuminant, for example, by means of a solder connection or heat conducting paste, so that particularly efficient heat dissipation from the operating LED illuminant can be achieved.

[0014] Furthermore, the light module according to the invention can include at least one metallic heat diffusion element, which is at least partially surrounded by the composite material of the carrier. The heat diffusion element can be designed, for example, in the form of a metal plate and oriented parallel to the joining surface of the cooling body and the carrier, thereby enabling lateral heat diffusion.

[0015] The invention also relates to various methods for producing a light module according to one of the preceding embodiments.

[0016] The first manufacturing method comprises at least the following steps:

[0017] - provide a metallic cooling body,

[0018] - introducing micro- and / or nano-scale cavities into the joining surface of the cooling body,

[0019] - injection molding of a carrier body made of an electrically insulating and thermally conductive composite material, wherein the composite material of the carrier body fills the cavities in the joining surface of the heat sink while forming a positive connection,

[0020] - applying metallic conductor tracks to the carrier, and

[0021] - Applying the at least one LED lighting device.

[0022] For example, micrometer- and / or nanometer-scale cavities can be introduced into the joining surfaces of the cooling body by means of electrochemical methods, by means of laser material processing methods or by means of mechanical methods. For example, electrochemical removal methods are suitable for introducing complex surface structures into conductive metal workpieces with precision in the micrometer range. For higher production precision up to the nanometer range, modern methods of photonics and laser material processing can be used. Mechanical methods are a cost-effective alternative, wherein structures with undercuts can also be realized, for example, by means of a combination of milling and hammering.

[0023] The carrier is preferably manufactured together with the conductor track as a so-called molded interconnect device (MID), for which MID manufacturing processes known from the prior art can be used, such as two-component injection molding, hot embossing, laser structuring or mask exposure methods. The LED lighting device is applied and electrically contacted, for example, by means of a suitable soldering method or by means of thermally conductive bonding.

[0024] In the case of an embodiment of manufacturing a light module with heat spreading elements protruding from the joint surface of the heat sink, these heat spreading elements are laterally encapsulated by the composite material during the injection molding of the carrier. Additional heat spreading elements can be embedded and encapsulated by the composite material during the injection molding of the carrier and thus integrated into the carrier.

[0025] A second method for producing a light module according to the invention comprises at least the following steps in a non-fixed order:

[0026] - provide a metallic cooling body,

[0027] - introducing micro- and / or nano-scale cavities into the joining surface of the cooling body,

[0028] - providing a carrier,

[0029] - direct thermal joining of the carrier to the heat sink, wherein the composite material of the carrier fills the cavities in the joining surface of the heat sink while forming a positive connection,

[0030] - applying metallic conductor tracks to the carrier, and

[0031] - Applying the at least one LED lighting device.

[0032] A third method for producing a light module according to the invention comprises at least the following steps in a non-fixed order:

[0033] - provide a metallic cooling body,

[0034] - introducing micro- and / or nano-scale cavities into the joining surface of the cooling body,

[0035] - providing a carrier film made of an electrically insulating and thermally conductive composite material,

[0036] - direct thermal bonding of the carrier film to the cooling body, wherein the composite material of the carrier film fills the cavities in the bonding surface of the cooling body while forming a positive connection,

[0037] - providing a carrier,

[0038] - direct thermal bonding of the carrier body to the carrier film, and

[0039] The at least one LED illuminant and the metallic conductor paths are applied to the carrier.

[0040] In the second method and the third method, the carrier is respectively provided as a separate component, wherein the application of the at least one LED illuminant and the metallic conductor path can be selectively carried out before or after the carrier is connected to the heat sink.

[0041] Unlike the second method, in the third method, a carrier film is first applied to the joining surface of the cooling body. The carrier film preferably has the same composite material as the carrier, so that a body of consistent material is formed when the carrier is joined to the carrier film. The advantage of using a carrier film is, for example, that when establishing a form-locking connection with the cooling body, a high pressing pressure can be applied to the carrier film without having to worry about damage to the LED lighting device or conductor circuit that may have been arranged on the carrier. The carrier film connected to the cooling body then forms a smooth joining surface for the carrier.

[0042] Direct thermal joining is carried out by heating the carrier or the carrier film in the joining zone, for example by means of laser radiation, by means of infrared radiation, by means of convection heating and / or by means of inductive heating or contact heating of the cooling body. The heating converts the matrix material of the composite material into a softened, flowable state, so that in particular the cavities in the joining surface of the cooling body can be filled to form a positive fit.

[0043] With regard to the introduction of the cavity into the joining surface of the heat sink and with regard to the application of the at least one LED illuminant and the metallic conductor paths to the carrier, reference is made explicitly to the embodiments explained above in conjunction with the description of the first method according to the invention.

[0044] In particular, the carrier can be provided prefabricated, ie it has metallic conductor tracks and at least one LED illuminant already applied thereon. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Other measures for improving the present invention will be described in more detail below together with the description of preferred embodiments of the present invention with the aid of the accompanying drawings. Among them:

[0046] Figure 1 A first embodiment of the optical module according to the invention is shown, and

[0047] Figure 2 A second embodiment is shown. DETAILED DESCRIPTION

[0048] The accompanying drawings show a schematic cross-sectional view of an embodiment of a light module 100 for a motor vehicle lighting device according to the present invention, respectively showing an LED lighting device 1, a metallic conductor track 2 for electrically contacting and conducting the LED lighting device 1, a carrier 3, and a metallic heat sink 4, on which the LED lighting device 1 and the conductor track 2 are arranged, and the carrier 3 is connected in a form-fitting manner to the heat sink 4. According to the present invention, the carrier 3 has an electrically insulating and thermally conductive composite material 30.

[0049] Due to the outstanding thermal conductivity of the composite material 30 (the thermal conductivity is, for example, at least 4 W / mK, in particular greater than 10 W / mK), extremely efficient heat dissipation through the carrier 3 to the cooling body 4 is achieved during operation of the LED lighting device 1. The thickness D of the carrier 3 is preferably 1 mm to 3 mm, so that the carrier 3 has a sufficiently high heat capacity to disperse and conduct the accumulated heat flow without suffering thermal damage.

[0050] Figure 1The inset of FIG. 4 shows an enlarged cross-sectional view of the entire joining region 34 between the heat sink 4 and the carrier 3. The heat sink 4 has a joining surface with micro- and / or nano-scale cavities 41 in the joining region 34, which are filled by the composite material 30 of the carrier 3 when a positive connection is formed. Due to the raised shape of the cavities 41, the penetrated composite material 30 forms an undercut of the carrier 3.

[0051] exist Figure 2 In the embodiment of , the cooling body 4 has a metal heat dissipation element 5, to which the LED lighting device 1 is soldered exemplarily. The heat dissipation element 5 is constructed to be integral with the cooling body 4 and of the same material and is laterally surrounded by the carrier 3, so that a direct metal heat bridge is formed between the LED lighting device 1 and the cooling body 4 by means of the heat dissipation element 5, and the heat bridge can achieve particularly rapid heat dissipation.

[0052] Furthermore, the light module 100 comprises a metallic heat spreading element 6 which is surrounded by the composite material 30 of the carrier 3 and contributes to improving lateral heat spreading within the carrier 3 .

[0053] The invention is not limited to the preferred exemplary embodiments given above in terms of its embodiment. On the contrary, a large number of variants are conceivable, which also use the solution shown in essentially different types of embodiments. All features and / or advantages (including structural details, spatial arrangements and method steps) derived from the claims, the description or the drawings can be important to the invention both individually and in different combinations.

[0054] Reference numerals list

[0055] 100 optical modules

[0056] 1LED lighting devices

[0057] 2-conductor circuit

[0058] 3 Carrier

[0059] 30 Composite Materials

[0060] 34 Junction area

[0061] 4 cooling bodies

[0062] 41 Cavity

[0063] 5. Cooling components

[0064] 6Heat diffusion element

[0065] D The thickness of the carrier

Claims

1. A light module (100) for a motor vehicle lighting device, the light module comprising at least an LED lighting device (1), a metal conductor path (2) for electrically contacting the LED lighting device (1), a carrier (3) and a metal cooling body (4), the LED lighting device (1) and the conductor path (2) being arranged on the carrier, the carrier (3) being connected to the cooling body (4) in a form-fitting manner, It is characterized in that The carrier (3) comprises an electrically insulating and thermally conductive composite material (30).

2. The optical module (100) according to claim 1, characterized in that The carrier (3) has at least 10 7 The composite material (30) has an electrical insulation resistance of at least Ω, and / or the composite material (30) has a thermal conductivity of at least 4 W / mK, preferably at least 10 W / mK.

3. The optical module (100) according to claim 1 or 2, characterized in that: The composite material (30) has a matrix of plastic, preferably polyamide or another partially crystalline plastic, and metallic, ceramic and / or graphite fillers, which preferably have a spherical shape and are uniformly distributed in the matrix.

4. The light module (100) according to one of the preceding claims, characterized in that The carrier ( 3 ) has a thickness (D) of 0.5 mm to 5 mm, preferably 1 mm to 3 mm.

5. The light module (100) according to one of the preceding claims, characterized in that The cooling body (4) has at least one metal heat dissipation element (5) for contacting the at least one LED illuminating device (1); the heat dissipation element (5) protrudes from a joint surface of the cooling body (4) and is laterally surrounded by the carrier (3), so that a heat bridge is formed between the LED illuminating device (1) and the cooling body (4) by means of the heat dissipation element (5).

6. The light module (100) according to one of the preceding claims, characterized in that The light module (100) comprises at least one metallic heat diffusion element (6), which is at least partially surrounded by the composite material (30) of the carrier (3).

7. The light module (100) according to one of the preceding claims, characterized in that The carrier (3) and the heat sink (4) form a joining region (34), in which the heat sink (4) has a joining surface with micrometer- and / or nanometer-scale cavities (41), which the composite material (30) of the carrier (3) fills up while forming a positive connection, preferably while forming undercuts.

8. Method for producing a light module (100) for a motor vehicle lighting device according to one of the preceding claims, the method comprising at least the following steps: - providing a metallic cooling body (100), - introducing micrometer-scale and / or nanometer-scale cavities (41) into the joining surface of the cooling body (4), - injection molding of a carrier (3) made of an electrically insulating and thermally conductive composite material (30), the composite material (30) of the carrier (3) filling the cavity (41) in the joining surface of the heat sink (4) while forming a positive connection, - applying the metallic conductor track (2) to the carrier (3), and - Applying the at least one LED lighting device (1).

9. A method for producing a light module (100) for a motor vehicle lighting device according to any one of claims 1 to 5, the method comprising at least the following steps in a non-fixed order: - providing a metallic cooling body (4), - introducing micrometer-scale and / or nanometer-scale cavities (41) into the joining surface of the cooling body (4), - providing a carrier (3), - directly thermally joining the carrier (3) to the cooling body (4), the composite material (30) of the carrier (3) filling the cavity (41) in the joining surface of the cooling body (4) while forming a positive connection, - applying the metallic conductor track (2) to the carrier (3), and - Applying the at least one LED lighting device (1).

10. A method for producing a light module (100) for a motor vehicle lighting device according to any one of claims 1 to 5, the method comprising at least the following steps in a non-fixed order: - providing a metallic cooling body (4), - introducing micrometer-scale and / or nanometer-scale cavities (41) into the joining surface of the cooling body (4), - providing a carrier film made of an electrically insulating and thermally conductive composite material, - directly thermally joining the carrier film to the cooling body (4), the composite material of the carrier film filling the cavity (41) in the joining surface of the cooling body (4) while forming a positive connection, - providing a carrier (3), - directly thermally bonding the carrier body (3) to the carrier film, and - Applying the at least one LED illuminant (1) and the metallic conductor path (2) to a carrier (3).

11. The method according to claim 9 or 10, characterized in that: Direct thermal bonding is carried out by heating the carrier (3) and / or the carrier film in the bonding zone (34) by means of laser radiation, by means of infrared radiation, by means of convection heating and / or by means of inductive or contact heating of a cooling body (4).

12. The method according to any one of claims 9 to 11, characterized in that A carrier (3) is provided, which has a metallic conductor track (2) applied thereon and at least one LED illuminant (1).

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