LIGHTING SOURCE FOR A MOTOR VEHICLE HEADLIGHT

Description

[0001] The invention relates to a lighting means for a motor vehicle headlight, the lighting means comprising the following: * an SMD component, comprising a light source for generating light, wherein the SMD component has a light-emitting upper side, on which the light source is arranged, and a lower side facing away from the light-emitting upper side, and * a circuit carrier, wherein the SMD component is connected to the circuit carrier in a thermally conductive and / or electrically conductive manner at a component mounting section of the circuit carrier by means of a solder joint, wherein the solder joint comprises a solder layer having solder material, wherein the solder layer is arranged between the lower side of the SMD component and the component mounting section of the circuit carrier and connects the SMD component to the circuit carrier, wherein the component mounting section of the circuit carrier has a plurality of contact elements arranged in a grid and spaced apart from one another, which extend from a preferably planar base area of ​​the circuit carrier in the direction of the SMD component and contact a side of the solder layer facing away from the SMD component, wherein gas outlet channel sections are formed between adjacent contact elements, wherein the contact elements are arranged relative to one another in such a way that the gas outlet channel sections form a coherent gas outlet channel system, so that each contact element is bordered by a section of the coherent gas outlet channel system, wherein the gas outlet channel sections are delimited by side surfaces of adjacent contact elements, the base area and the side of the solder layer facing away from the SMD component, wherein the gas outlet channel system is designed and configured towhich escape from the solder layer during the soldering process, to escape via the gas outlet channel system from a volume formed between the solder layer and the base area of ​​the circuit carrier, wherein for the heat dissipation of waste heat from the SMD component, the circuit carrier has a plurality of micro-vias configured for heat conduction, wherein the heat conduction takes place substantially along a longitudinal extent of the micro-vias, wherein the micro-vias are arranged in the circuit carrier such that the micro-vias extend at least partially through the circuit carrier towards the component mounting section and penetrate the plurality of contact elements, so that the micro-vias contact the solder layer at a contact region of the solder layer for heat dissipation, wherein the micro-vias have a substantially circular cross-section at the contact region.

[0002] The invention further relates to a motor vehicle headlight comprising a lighting means.

[0003] Illuminants for motor vehicle headlights are known in the prior art. Such illuminants frequently comprise an SMD component with a light source, and the SMD component is attached to a circuit carrier. The circuit carrier is generally also configured, among other things, to cool the SMD component (or the light source). In the prior art, this is frequently achieved via so-called micro-vias, which extend at least partially through the circuit carrier (or from an inner region of the circuit carrier) to the SMD component. The SMD component is typically soldered to the circuit carrier. Cavities can form in the solder layer, particularly in soldered joints with large-area solder layers (i.e., a layer that contains solidified solder or solder material (after the soldering process) to create a bonded connection between components).The cavities are formed by gases that arise during the soldering process (or during the liquefaction of the solder used in the soldering process). These cavities reduce the effective contact area between the SMD component and the circuit board. To reduce the formation of cavities, it must be ensured that the gases can escape from the solder layer, whereby corresponding gas outlet channels are usually formed between the solder layer and the circuit board. Such gas outlet channels reduce the effective contact area between the solder layer and the circuit board, which impairs cooling. The solutions known in the prior art must therefore compromise between effective cooling (high number of micro-vias) and effective gas outlet (high number of gas outlet channels).

[0004] The object of the present invention is to alleviate or eliminate the disadvantages of the prior art. The invention therefore aims, in particular, to create a lighting device in which the soldered connection between components of the lighting device is improved.

[0005] This object is achieved by a lighting device having the features of claim 1. Preferred embodiments are specified in the dependent claims.

[0006] According to the invention, a number of contact elements have a substantially hexagonal base area, wherein the base areas lie in a plane which is oriented substantially parallel to the base area of ​​the circuit carrier, and preferably parallel to the underside of the SMD component, wherein

[0007] the micro-vias are arranged in a two-dimensional hexagonal packing arrangement such that the substantially hexagonal base surfaces of the contact elements are substantially completely penetrated by a plurality of micro-vias, in accordance with the highest area packing density.

[0008] This advantageously maximizes the number of micro-vias per contact element area, which in turn improves the cooling of the SMD component. At the same time, gases can escape through the gas outlet channel system from the solder material liquefied during the soldering process, during the production of a solid (or rigid) solder layer. The solder layer can thus be designed to be essentially free of gas bubbles. In this context, a hexagonal base area is understood to be a polygon with six corners and six sides. Preferably, the base areas of the number of contact elements form an equilateral hexagon (all six sides are of equal length); more preferably, the base areas of the number of contact elements form a regular or regular hexagon (all six sides are of equal length, and furthermore, all angles at the six corners are of equal size).The number of contact elements with a substantially hexagonal base area can comprise all contact elements or fewer, for example at least 90%, 80%, 70%, 60%, or 50% of all contact elements of the total number of contact elements. The higher the number of contact elements with a substantially hexagonal base area, the more efficiently the cooling of the SMD component can be achieved, since the substantially hexagonal base area can be interspersed with micro-vias according to the highest packing density. The micro-vias (preferably the heat-conducting (metal) core of the micro-vias) can, in particular, start from an interior region of the circuit carrier (for example a metal inlay) and open at the solder layer or contact this for heat conduction. The light source can comprise a pixel LED light source. The solder connection can be produced using a soldering process, which is preferably a reflow soldering process.

[0009] It can be provided that adjacent microvias on the hexagonal base surface of a contact element are arranged essentially directly adjacent to one another, wherein the plurality of microvias preferably have a substantially equal diameter at the contact area. The contact area is understood to mean the area where the microvias or the contact element contact the solder layer.

[0010] It can be provided that the microvias in the contact area have an inner hole diameter that is preferably <0.5 mm, preferably <0.25 mm, particularly preferably <0.15 mm. The microvias preferably have a diameter of 0.1 to 0.2 mm. The distance between adjacent microvias is preferably 0.1 to 0.35 mm.

[0011] It can be provided that the micro-vias are designed substantially conically or truncated conically along their longitudinal extent, wherein the micro-vias are preferably designed such that a cone diameter or a truncated cone diameter decreases towards the solder layer, wherein in particular an angle between a cone axis or a truncated cone axis and a lateral surface of the cone or the truncated cone is 6° to 15°.

[0012] It can be provided that the microvias are arranged in the circuit carrier in such a way that those areas of the component assembly section containing the gas outlet channel system are free of microvias. In particular, only the contact elements are interspersed with microvias.

[0013] It can be provided that the circuit carrier has an outer surface facing the SMD component, on which the assembly section is formed, wherein the circuit carrier has a solder resist layer which is arranged at least partially, preferably completely, around the assembly section on the outer surface.

[0014] It can be provided that the contact elements are coated with a thermally conductive and / or electrically conductive material, in particular with a metal, for example copper, or are formed from a thermally conductive and / or electrically conductive material.

[0015] The circuit carrier may be designed as a multilayer printed circuit board having a metal inlay, preferably a copper inlay, with the microvias being thermally connected to the metal inlay. Preferably, the microvias are filled with metal, in particular copper, and thermally connected to the metal inlay via this metal filling. The thermally conductive filling material of the microvias is preferably the same material as the metal inlay of the circuit carrier.

[0016] It can be provided that the hexagonal contact elements form polyhedra, which have a substantially equal hexagonal base area. The gas outlet channel system is formed, in particular, between the polyhedra. The contact elements can, in particular, have a first number of edge elements and a second number of central elements, wherein the edge elements are arranged at the edge of the component section and wherein the central elements are surrounded by the edge elements. Preferably, at least the central elements, and preferably also the edge elements, have a hexagonal base area.

[0017] It can be provided that the base surfaces of the hexagonal contact elements each form a regular hexagon.

[0018] It can be provided that each gas outlet channel section of the gas outlet channel system has a channel width defined as a normal distance between parallel side edges of two adjacent contact elements, wherein the gas outlet channel system is configured such that all gas outlet channel sections have substantially the same channel width. The channel width of a gas outlet channel section is preferably 150-250 µm.

[0019] It can be provided that each gas outlet channel section of the gas outlet channel system has a channel height corresponding to a standard distance between the base area of ​​the circuit carrier and the side of the solder layer facing away from the SMD component. Preferably, the channel height of the gas outlet channel system is constant across the entire assembly section, preferably ranging from 100 to 200 µm. The channel height can, in particular, correspond to the vertical height of the contact elements (preferably the vertical height of the contact elements between the base area and the solder layer). The channel height can thus be understood as the layer thickness of the contact elements.

[0020] It can be provided that the component mounting section of the circuit carrier has a larger surface area than the underside of the SMD component. The component mounting section is preferably a region (or surface section) formed on the circuit carrier that is wettable with solder material and is designed to accommodate, and subsequently for electrical, thermal, or mechanical contact with, an SMD component.

[0021] It can be provided that the connection between the SMD component and the assembly section of the circuit carrier is designed by the solder layer in such a way that the underside of the SMD component, the base area of ​​the circuit carrier and the base areas of the hexagonal contact elements lie in planes which are oriented substantially parallel to one another.

[0022] It can be provided that of the plurality of contact elements arranged in a grid, at least 50%, preferably more than 75%, preferably more than 85%, particularly preferably more than 95% of the contact elements have a hexagonal base area.

[0023] A motor vehicle headlight can be provided which has a lighting means according to the invention.

[0024] US 2013 / 087813 A1 discloses a lighting device according to the prior art.

[0025] The invention is explained in more detail below with reference to an exemplary and non-limiting embodiment, which is illustrated in the figures. Figure 1 a schematic sectional view of a lighting means according to the invention; Figure 2 a schematic representation of a circuit carrier according to a first embodiment of a lighting means according to the invention; Figure 3a schematic representation of a circuit carrier according to a second embodiment of a lighting means according to the invention;

[0026] In the following figures, unless otherwise stated, the same reference symbols denote the same features.

[0027] Figure 1 shows a schematic sectional view of a lighting device 1 according to the invention for a motor vehicle headlight. The lighting device 1 comprises an SMD component 2 with a light source 3 for generating light. The SMD component 2 has a top side 2a on which the light source 3 is arranged, whereby the top side 2a is designed to be light-emitting. The SMD component 2 further has a bottom side 2b facing away from the light-emitting top side 2a. The light source 3 can be a pixel LED light source.

[0028] The lighting device 1 comprises a circuit carrier 4, wherein the SMD component 2 is connected to the circuit carrier 4 in a thermally and electrically conductive manner by means of a soldered connection. The soldered connection is in the form of a solder layer 9 which has soldering material. The basic principle for producing such a solder connection is known to a person skilled in the art and will therefore not be discussed in detail here. The solder layer 9 is arranged between the underside 2b of the SMD component 2 and a mounting section 4a of the circuit carrier 4 and connects the SMD component 2 to the circuit carrier 4. The solder connection is produced by a soldering process. The soldering process can be a reflow soldering process. In order to enable a uniform application (or a uniform layer thickness) of solder material, it can be used, particularly in the case of large-area solder connections (orAssembly sections 4a), it may be advantageous not to apply the soldering material continuously (during the soldering process), but rather to divide the soldering material into soldering material segments using a stencil. The resulting solder layer 9 (cured after its manufacturing process) is continuous (in particular essentially across the entire assembly section 4a).

[0029] The circuit carrier 4 is in the Figure 1 In the embodiment shown, the printed circuit board is designed as a multilayer circuit board having a metal inlay 8, preferably a copper inlay. The microvias 7 are thermally conductively connected to the metal inlay 8. The microvias 7 are in particular filled with metal, preferably copper, and connected to the metal inlay 8.

[0030] As in Figure 2 and Figure 3As can be seen, the assembly section 4a is formed from a plurality of contact elements 5a arranged in a grid and spaced from one another, forming a contact element grid 5. Gas outlet channel sections 6a are formed between adjacent contact elements 5a. The contact elements 5a are arranged relative to one another in such a way that the gas outlet channel sections 6a form a coherent gas outlet channel system 6 through (or in) the assembly section 4a. Each contact element 5a is bordered by a section of the coherent gas outlet channel system 6. The gas outlet channel system 6 is designed and configured to allow gases which, during the soldering process, escape from the liquefied solder volume which forms after cooling to form the solder layer 9, to escape via the gas outlet channel system 6 from a volume formed between the underside 2b of the SMD component 2 and the assembly section 4a of the circuit carrier 4.

[0031] In other words, the gas outlet channel system 6 divides the assembly section 4a into sub-regions separated from one another by gas outlet channel sections 6a. The gas outlet channel system 6 is configured in the assembly section 4a such that the sub-regions (or contact elements 5a) of the assembly section 4a have a hexagonal footprint. The assembly section 4a is thus formed as a segmented assembly section 4a by the gas outlet channel system 6 penetrating the assembly section 4a, with the individual segments being configured as hexagonal contact elements 5a (or contact elements 5a with a hexagonal footprint).

[0032] To dissipate waste heat from the SMD component 2, the circuit carrier 4 has a plurality of micro-vias 7 configured for heat conduction, which micro-vias have a substantially circular cross-section and a longitudinal extension. Heat conduction occurs substantially along the longitudinal extension of the micro-vias. The micro-vias 7 are arranged in the circuit carrier 4 such that the micro-vias 7 extend at least partially through the circuit carrier 4 toward the component mounting section 4a and penetrate this at least partially or open at the solder layer 9. As a result, the micro-vias 7 penetrate the component mounting section 4a at a contact region of the solder layer 9 for heat dissipation. The contact region is formed, in particular, exclusively on the contact elements 5a of the component mounting section 4a.

[0033] As in the Figures 2 and 3As shown, a number of contact elements 5a have a substantially hexagonal base surface 5b. The base surfaces 5b lie in a plane that is oriented substantially parallel to the underside 2b of the SMD component 2.

[0034] The micro-vias 7 are arranged in a two-dimensional hexagonal packing arrangement such that the essentially hexagonal base areas 5b of the contact elements 5a are essentially completely penetrated by a plurality of micro-vias 7, according to the highest area packing density, wherein a minimum distance is preferably present between adjacent micro-vias 7. The hexagonal base area 5b of the number of contact elements 5a is thus essentially filled with the micro-vias 7, which have an essentially circular base area. Adjacent micro-vias 7 are arranged essentially directly adjacent to one another within the hexagonal base area 5b of the contact elements 5a. The plurality of micro-vias 7 can have an essentially equal diameter.The microvias 7 have a, in particular maximum, hole diameter d at the contact area of ​​the solder layer 9, which is preferably <0.5 mm, preferably <0.25 mm, particularly preferably <0.15 mm. The microvias 7 are arranged in the assembly section 4a of the circuit carrier 4 such that those areas of the assembly section 4a that have the gas outlet channel system 6 are free of microvias 7.

[0035] The hexagonal contact elements 5a each have a substantially equal hexagonal base area 5b. The base areas 5b of the hexagonal contact elements 5a each form a regular hexagon.

[0036] In the Figure 2In the embodiment shown, the contact element surface has five central hexagonal contact elements 5a. These are surrounded by further contact elements, which have different shapes (further polygons) and are also interspersed with microvias 7. The SMD component 2 is schematically indicated around the assembly section 4a.

[0037] In the Figure 3 In the embodiment shown, the assembly section 4a has twelve central hexagonal contact elements 5a. These are surrounded by further contact elements, which have different shapes (further polygons) and are also interspersed with microvias 7. The SMD component 2 is again schematically indicated around the assembly section 4a.

[0038] The number of hexagonal contact elements 5a is essentially determined by their size and the size and shape of the assembly section 4a.

[0039] Each gas outlet channel section 6a of the gas outlet channel system 6 has a channel width defined as a normal distance between parallel side edges of two adjacent contact elements 5a. The gas outlet channel system 6 is preferably designed such that all gas outlet channel sections 6a have the same channel width.

[0040] Each gas outlet channel section 6a of the gas outlet channel system 6 has a channel height corresponding to a standard distance between the base area 4b of the circuit carrier 4 and the side of the solder layer 9 facing away from the SMD component 2. Preferably, the channel height of the gas outlet channel system 6 is constant over the entire assembly section 4a, with the channel height preferably being 100-200 µm.

[0041] Of the total number of contact elements 5a arranged in a grid, at least 50%, preferably more than 75%, preferably more than 85%, particularly preferably more than 95% have a hexagonal base area 5b.

[0042] The invention is not limited to the embodiments shown, but is defined by the entire scope of the claims.

[0043] Any reference signs in the claims are exemplary and serve only to facilitate the readability of the claims without limiting them.

Claims

1. Illuminant (1) for a motor vehicle headlight, the illuminant (1) comprising the following: * an SMD component (2), comprising a light source (3) for generating light, the SMD component (2) having a light-emitting top side (2a), on which the light source (3) is arranged, and an underside (2b) facing away from the light-emitting top side (2a), and * a circuit carrier (4), wherein the SMD component (2) is connected to the circuit carrier (4) in a thermally conductive and / or electrically conductive manner at a mounting section (4a) of the circuit carrier (4) by means of a solder connection, wherein the solder connection comprises a solder layer (9), which has solder, the solder layer (9) being arranged between the underside (2b) of the SMD component (2) and the mounting section (4a) of the circuit carrier (4) and connecting the SMD component (2) to the circuit carrier (4), wherein the mounting section (4a) of the circuit carrier (4) has a plurality of contact elements (5a) arranged in a grid and spaced apart from one another, which extend from a, preferably flat, base surface (4b) of the circuit carrier (4) in the direction of the SMD component (2) and contact a side of the solder layer (9) facing away from the SMD component (2), wherein gas outlet channel sections (6a) are formed between adjacent contact elements (5a), wherein the contact elements (5a) are arranged relative to one another in such a way that the gas outlet channel sections (6a) form a continuous gas outlet channel system (6), so that each contact element (5a) is surrounded by a section of the continuous gas outlet channel system (6), wherein the gas outlet channel sections (6a) are bounded by side surfaces of neighboring contact elements (5a), the base surface (4b) and the side of the solder layer (9) facing away from the SMD component (2), wherein the gas outlet channel system (6) is designed and set up to allow gases which escape from the solder layer (9) during the soldering process to escape via the gas outlet channel system (6), from a volume formed between the solder layer (9) and the base surface (4a) of the circuit carrier (4) via the gas outlet channel system (6), wherein for heat dissipation of waste heat from the SMD component (2), the circuit carrier (4) has a plurality of micro-vias (7) set up for heat conduction, wherein the heat conduction takes place essentially along a longitudinal extension of the micro-vias (7), wherein the micro-vias (7) are arranged in the circuit carrier (4) in such a way that the micro-vias (7) extend at least in sections through the circuit carrier (4) towards the mounting section (4a) and pass through the plurality of contact elements (5a), so that the micro-vias contact the solder layer (9) at a contact region of the solder layer (9) for heat dissipation, wherein the micro-vias (7) have a substantially circular cross-section at the contact region, wherein a number of contact elements (5a) have a substantially hexagonal base area (5b), wherein the base areas (5b) lie in a plane which is oriented substantially parallel to the base surface (4b) of the circuit carrier and preferably parallel to the underside (2b) of the SMD component (2), wherein the micro-vias (7) are arranged in a two-dimensional hexagonal packing arrangement in such a way that the substantially hexagonal base areas (5b) of the contact elements (5a) are substantially completely interspersed by a plurality of micro-vias (7) in accordance with the highest surface packing density.

2. Illuminant (1) according to claim 1, wherein adjacent micro-vias (7) on the hexagonal base area (5b) of a contact element (5a) are arranged substantially directly adjacent to each other, wherein preferably the plurality of micro-vias (7) at the contact area have a substantially equal diameter.

3. Illuminant (1) according to any of the preceding claims, wherein the micro-vias (7) at the contact area have an inner hole diameter (d) which is preferably < 0.5 mm, preferably < 0.25 mm, particularly preferably < 0.15 mm.

4. Illuminant (1) according to any of the preceding claims, wherein the micro-vias (7) are essentially conical or frustoconical along their longitudinal extension, wherein preferably the micro-vias (7) are designed in such a way that a cone diameter or a frustoconical diameter decreases towards the solder layer (9), wherein in particular an angle between a cone axis or a frustoconical axis and a lateral surface of the cone or the frustoconical axis is 6° to 15°.

5. Illuminant (1) according to any of the preceding claims, wherein the micro-vias (7) are arranged in the circuit carrier (4) in such a way that those regions of the mounting section (4a) which have the gas outlet channel system (6) are free of micro-vias (7).

6. Illuminant (1) according to any of the preceding claims, wherein the circuit carrier (4) has an outer surface facing the SMD component (2), on which the mounting section (4a) is formed, wherein the circuit carrier (4) has a solder resist layer which is arranged at least partially, preferably completely, around the mounting section (4a) on the outer surface.

7. Illuminant (1) according to any of the preceding claims, wherein the contact elements (5a) are coated with a thermally conductive and / or electrically conductive material, in particular with a metal, for example copper, or are formed from a thermally conductive and / or electrically conductive material.

8. Illuminant (1) according to any of the preceding claims, wherein the circuit carrier (4) is designed as a multilayer printed circuit board which has a metal inlay (8), preferably a copper inlay, wherein the micro vias (7) are connected to the metal inlay (8) in a thermally conductive manner.

9. Illuminant (1) according to any of the preceding claims, wherein the hexagonal contact elements (5a) form polyhedra which have a hexagonal base area (5b) of substantially the same size.

10. Illuminant (1) according to any of the preceding claims, wherein the base areas (5b) of the hexagonal contact elements (5a) each form a regular hexagon.

11. Illuminant (1) according to any of the preceding claims, wherein each gas outlet channel section (6a) of the gas outlet channel system (6) has a channel width which is defined as a normal distance between parallel side edges of two adjacent contact elements (5a), wherein the gas outlet channel system (6) is designed in such a way that all gas outlet channel sections (6a) have substantially the same channel width.

12. Illuminant (1) according to any of the preceding claims, wherein each gas outlet channel section (6a) of the gas outlet channel system (6) has a channel height which corresponds to a normal distance between the base surface (4b) of the circuit carrier (4) and the side of the solder layer (9) facing away from the SMD component (2), wherein preferably the channel height of the gas outlet channel system (6) is constant over the entire mounting section (4a), wherein preferably the channel height is 100-200 µm.

13. Illuminant (1) according to any of the preceding claims, wherein the mounting section (4a) of the circuit carrier (4) has a larger area than the underside (2b) of the SMD component.

14. Illuminant (1) according to any of the preceding claims, wherein of the plurality of contact elements (5a) arranged in a grid, at least 50%, preferably more than 75%, preferably more than 85%, particularly preferably more than 95% of the contact elements (5a) have a hexagonal base area (5b).

15. Motor vehicle headlamp, comprising an illuminant (1) according to any of the preceding claims.