FOLDABLE PRINTED CIRCUIT BOARD FOR AN AUTOMOBILE LIGHTING DEVICE

Abstract

The present invention relates to a foldable printed circuit board 200 for a vehicle lighting device. The printed circuit board 200 comprises a substrate 201, one or more electronic components 206 mounted on the substrate 201, and one or more grooves 208 formed at one or more predefined locations on the substrate 201. The substrate 201 is folded at a predefined location, and the electronic component(s) 206 are mounted on an elongated surface 201t or a compressed surface 201c, or both, of the substrate 201. The grooves 208, with a width less than or equal to 0.8 mm, are formed on one or both of the elongated surfaces 201t and compressed surfaces 201c. The configuration of the grooves 208 may be a straight line, a zigzag line, a curved line, or any other suitable geometry. Figure for the abbreviation: Figure 3A

Description

Title of the invention: FOLDABLE PRINTED CIRCUIT BOARD FOR A MOTOR VEHICLE LIGHTING DEVICE TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to a foldable printed circuit board (PCB), and more particularly to a foldable printed circuit board (PCB) for a motor vehicle lighting device.

[0002] CONTEXT OF THE INVENTION

[0003] In automotive light modules, printed circuit boards (PCBs) are used to support electronic components essential to performing the desired functions. Components such as integrated circuits, transistors, diodes, resistors, capacitors, inductors, light sources, transformers, etc. are electrically interconnected on the printed circuit board to form electronic circuits.

[0004] Recently, light modules include pixelated surfaces or illuminated surfaces with a curved design, due to design and style requirements. To meet this requirement, there are solutions such as providing a multitude of small printed circuit boards that follow the desired curvature in a chain. However, connecting these small printed circuit boards requires multiple connectors and wires, which increases the number of components and can affect reliability. This results in increased costs and complex assembly.

[0005] Another solution is to use a flexible printed circuit board (fPCB). However, the flexible printed circuit board is expensive, using expensive polymers (polyimide). In addition, it is not necessarily the first choice, especially when the curvature of the printed circuit board is small, i.e. when the radius of curvature is larger. Therefore, it is preferable to use a rigid and bendable printed circuit board when the required curvature of the printed circuit board is less.

[0006] [Fig.l] illustrates a conventional rigid printed circuit 100 comprising a substrate 101 and an electronic component 106 mounted on a surface of the substrate 101. The electronic component 106 may be mounted on the substrate 101 using connection pins and solders (not shown). The substrate 101 may comprise several layers 102 of a flame-retardant material such as FR4, stacked and bonded together by one or more resin layers 104. In the case of a curved or bendable printed circuit 100, as shown in FIGS. 2A and 2B, mechanical stresses are generated by the bending of the substrate 101, which acts on the component electronic components 106. For example, [Fig. 2A] shows a plurality of electronic components 106 mounted on a surface 101t of the substrate 101. When the substrate 101 is bent or curved as shown in [Fig. 2A], the surface 101t is under tension and therefore exerts mechanical stress on the components 106 mounted at or near the bend location. Similarly, the electronic components 106 may be mounted on a surface 101c that is subjected to compression, as shown in [Fig. 2B]. These mechanical stresses may damage the connection points of the electronic component 106, such as solder and / or connection pins. Furthermore, these mechanical stresses affect the physical integrity of the printed circuit board and impair its reliability during use.

[0007] The prior art and the conventional rigid printed circuit have various drawbacks described above and there is a need for a bendable printed circuit which can overcome the drawbacks of the conventional rigid printed circuit. Summary of the Invention

[0008] The object of the present invention is to solve the above-described disadvantages of known printed circuits. In particular, the object of the present invention is to provide a foldable printed circuit with reduced mechanical stresses around certain specific areas of the folded (bent) printed circuit.

[0009] Another object of the present invention is to provide a bendable printed circuit with improved structural integrity that is not affected by bending or folding.

[0010] Another objective of the present invention is to increase the reliability of electronic components mounted on a foldable printed circuit.

[0011] Another object of the present invention is to provide a foldable printed circuit that is less expensive than a flexible printed circuit.

[0012] According to the present invention, there is a printed circuit board (PCB) comprising a substrate, at least one electronic component and at least one trench. The substrate is adapted to be folded at a predefined location. At least one electronic component is intended to be mounted on the substrate. The at least one trench is formed on the substrate and has a width of 0.8 mm or less. The width of the trench is preferably less than 0.5 mm, more preferably less than 0.3 mm. The trenches may be made on the substrate at predefined relative positions with respect to the electronic component, based on an analysis of the stresses and strains of the folded substrate. The trenches reduce the mechanical stress acting on the electronic component, thereby improving the structural integrity of the printed circuit board. In this text, the term foldable is understood as a substrate capable of being bent, curved, arched, curved.

[0013] In a non-limiting embodiment of the present invention, the substrate comprises several layers stacked by a resin. Any other suitable adhesive can be used to bond the layers together.

[0014] In a non-limiting embodiment of the present invention, the plurality of layers are made of FR-4 material. FR-4 is a class of material composed of a flame-retardant (FR) epoxy resin and a glass fabric, widely used as a base material for printed circuits.

[0015] In a non-limiting embodiment of the present invention, the substrate is adapted to have an elongated surface and a compressed surface opposite the elongated surface, at the location of the bend. When the substrate is bent, the elongated surface is under tension and the compressed surface is under compression.

[0016] In a non-limiting embodiment of the present invention, the at least one electronic component is adapted to be mounted on the elongated surface. Thus, by bending the substrate, the elongated surface is stretched and the generated tension causes mechanical stresses acting on the electronic component(s), more particularly on the connection means such as the solder and / or the connection pins of the component(s).

[0017] In a non-limiting embodiment of the present invention, the at least one electronic component is adapted to be mounted on the compressed surface. Thus, by bending the substrate, the compressive stress of the compressed surface causes mechanical stresses acting on the electronic component(s), more particularly on the connection means such as the solder and / or the connection pins of the component(s).

[0018] In another non-limiting embodiment of the present invention, the substrate may include a plurality of electronic components mounted on both the elongated surface and the compressed surface.

[0019] In a non-limiting embodiment of the present invention, the at least one trench is adapted to be formed on the elongated surface. The position(s) of the trenches relative to the electronic component may be decided based on an analysis of the stress and strain of the bent substrate. The trenches reduce the mechanical stress acting on the electronic component, thereby improving the structural integrity of the printed circuit.

[0020] In a non-limiting embodiment of the present invention, the at least one trench is adapted to be formed on the compressed surface. The position(s) of the trenches relative to the electronic component may be decided based on an analysis of the stress and strain of the bent substrate. The trenches reduce the mechanical stress acting on the electronic component, thereby improving the structural integrity of the printed circuit.

[0021] In another non-limiting embodiment of the present invention, a plurality of trenches may be provided on both the elongated surface and the compressed surface of the substrate.

[0022] In a non-limiting embodiment of the present invention, the at least one trench is adapted to extend between a first edge of the substrate and a second edge of the substrate. The first edge may be any of the edges of the substrate and the second edge may be any of the remaining edges of the substrate. The trench may be generally perpendicular to the first and second edges, or may be oriented at a predefined angle relative to the edges.

[0023] In a non-limiting embodiment of the present invention, the at least one trench is adapted to extend up to a predefined distance from a first edge of the substrate or a second edge of the substrate. The first edge may be any of the edges of the substrate and the second edge may be any of the remaining edges of the substrate. The trench may be generally perpendicular to the first or second edge of the substrate, or be oriented at a predefined angle relative to the edges.

[0024] In a non-limiting embodiment of the present invention, the at least one trench is adapted to be formed in an intermediate region of the substrate. The trench may be formed at the intermediate region of the substrate without encountering any of the edges.

[0025] In a non-limiting embodiment of the present invention, the at least one trench may be formed in a straight line, zigzag or curved. Any other suitable configuration of the trenches may be adapted depending on the structural requirements.

[0026] In a non-limiting embodiment of the present invention, the at least one trench is formed on the substrate using a laser or a drilling or V-grooving process. Preferably, the trench may be formed as a blind via or micro via using a laser ablation process. The laser ablation process provides a trench or blind via with a width of less than or equal to 0.8 mm. Furthermore, a trench with a width preferably less than 0.5 mm, more preferably less than 0.3 mm, may be obtained by the laser ablation process. It is also possible to use any other suitable material removal method to form the trench on the substrate.

[0027] In a non-limiting embodiment of the present invention, the dimensions of the trench, i.e. the length, width and depth, depend on the radius of curvature applied to the substrate and / or the voltage generated on the electronic components. The width of the trench is less than or equal to 0.8 mm, preferably less than 0.5 mm, more preferably less than 0.3 mm. The depth of the trench may be such that the trench extends partially in a single layer or in several layers of the substrate. The radius of curvature of the substrate can be 200 mm or more.

[0028] The present invention also relates to a vehicle lighting device comprising the printed circuit board (PCB) described above, wherein at least one light source is adapted to be mounted on the substrate. The printed circuit may comprise the components necessary for the operation of the lighting device and the printed circuit may be adapted to provide the desired curved shape(s) to create a predefined lighting effect / style. Brief description of the drawings

[0029] To complete the description and allow a better understanding of the invention, a set of drawings is provided. These drawings are an integral part of the description and illustrate an embodiment of the invention, which should not be interpreted as limiting the scope of the invention, but only as an example of how the invention can be carried out. The drawings include the following features: • [Fig.l] illustrates a schematic diagram of a printed circuit, according to the prior art; • [Fig.2A] and [Fig.2B] illustrate schematic diagrams of a foldable printed circuit, according to the prior art; • [Fig.3A] and [Fig.3B] illustrate schematic diagrams of a foldable printed circuit, according to an embodiment of the present invention; • [Fig.4] illustrates a schematic top view of the foldable printed circuit, according to an embodiment of the present invention; and • [Fig.5A], [Fig.5B] and [Fig.5C] illustrate possible configurations of the trench on a substrate of the printed circuit board, according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0030] Embodiments of the present invention are described below with reference to the accompanying drawings. Unless otherwise indicated, the technical features described in detail for a given embodiment may be combined with the technical features described in the context of other embodiments described by way of example and not in a limiting manner.

[0031] The elements shown in the drawings are not to scale and are simplified in order to improve the clarity of the disclosure.

[0032] In the following description, the expression "elongated surface" means a surface subjected to tension, and the expression "compressed surface" means a surface subjected to compression. Thus, when a substrate having two surfaces is When bent, the surface facing the center of curvature is under compression ("compressed surface") and the surface opposite the center of curvature is under tension ("elongated surface"). In the case of an unbent substrate, i.e., before stressing and bending, both surfaces are flat and the expressions "elongated surface" and "compressed surface" must be deduced as their respective configurations intended when the substrate is bent.

[0033] [Fig.3A] and [Fig.3B] show a bendable printed circuit board (PCB) 200. The printed circuit comprises an electronic component 206 mounted on a substrate 201. The substrate 201 is bent / curved with a predefined radius of curvature. Thus, the substrate 201 has an elongated surface 201t and a compressed surface 201c. The substrate 201 can be manufactured by stacking several layers 202 bonded together by a layer(s) of resin 204 or any other suitable adhesive material.

[0034] In one embodiment of the present invention, the radius of curvature of the substrate is 200 mm or more.

[0035] In one embodiment of the present invention, the layers 202 of the substrate 201 may be made from a flame retardant material such as FR-4. FR-4 is a composite material composed of a woven fiberglass fabric and a flame resistant epoxy resin binder.

[0036] [Fig. 3A] shows an exemplary embodiment of the present invention. The electronic component 206 is mounted on the compressed surface 201c. One or more trenches 208 are provided on at least one of the elongated surface 201t and the compressed surface 201c. The trenches 208 may be formed at predefined locations / positions on the curved surfaces 201t, 201c of the substrate 201. The trenches 208 may be provided at suitable locations on the elongated surface 201t, i.e., the surface of the substrate 201 opposite the surface on which the electronic component 206 is mounted. Alternatively, the trenches 208 may be provided at suitable locations on the compressed surface 201c, i.e., the surface of the substrate 201 on which the electronic component 206 is mounted. The trenches 208 may be located at suitable locations on both the elongated surface 201t and the compressed surface 201c.

[0037] [Fig. 3B] shows another exemplary embodiment of the present invention. The electronic component 206 is mounted on the elongated surface 201t of the substrate 201. One or more trenches 208 are provided on at least one of the elongated surface 201t and the compressed surface 201c. The trenches 208 may be formed at predefined locations on the curved surfaces 201t, 201c of the substrate 201. The trenches 208 may be provided at suitable locations on the compressed surface 201c, i.e., the surface of the substrate 201 opposite the surface on which the electronic component 206 is mounted. Alternatively, the trenches 208 may be provided at suitable locations on the elongated surface 201t, i.e., the surface of the substrate 201 on which the electronic component 206 is mounted. The trenches 208 may be located at suitable locations on the elongated surface 201t and on the compressed surface 201c.

[0038] In one embodiment of the present invention, a plurality of electronic components 206 may be mounted on the elongated surface 201t or the compressed surface 201c or both curved surfaces 201t, 201c. Further, a plurality of trenches 208 may be provided on the elongated surface 201t or the compressed surface 201c or both curved surfaces 201t, 201c, at predefined relative positions with respect to the electronic component 206.

[0039] In one embodiment of the present invention, trench 208 may be formed on substrate 201 using a laser or a drilling or V-grooving process. Any other material removal process capable of forming a cut with a width of 0.8 mm or less may be used.

[0040] In one embodiment of the present invention, the trench 208 has a width preferably less than 0.5 mm, more preferably less than 0.3 mm.

[0041] In a preferred embodiment of the present invention, the trenches 208 may be formed as blind vias or microvias using a laser ablation process. The laser ablation process may result in the trench 208 or blind via being 0.8 mm or less in width. Further, a trench 208 with a width preferably less than 0.5 mm, more preferably less than 0.3 mm, may be obtained by the laser ablation process. Furthermore, any other suitable material removal method may be used to form the trench 208 in the substrate 201.

[0042] In one embodiment of the present invention, the geometry and location of the trenches 208 on the substrate 201 may be selected based on a stress-strain analysis of the bent / curved printed circuit board 200. The trench 208 has a width of 0.8 mm or less to sufficiently relieve the mechanical stress generated by bending without affecting the structural integrity of the printed circuit board 200.

[0043] [Fig. 4] illustrates a schematic top view of the printed circuit showing the possible locations of the trenches 208 on the substrate 201. The trench 208a may extend from a first edge 201a to a second edge 201b of the substrate 201. Alternatively, the trench 208b may extend up to a predefined distance from the first edge 201a of the substrate 201, or from the second edge 201b of the substrate 201. Although, in [Fig. 4], the trenches 208a, 208b are shown generally perpendicular to the respective edges 201a, 201b, the trenches 208a, 208b may have an angular configuration / orientation relative to the edges 201a, 201b. Furthermore, the first edge 201a and the second surface 201b illustrated in [Fig.4] are only for example. The substrate 201 may have a predefined number of edges. In this case, the first edge 201a may be made as any edge of the substrate 201 and the second edge 201b may be made as any remaining edge of the substrate 201.

[0044] In one embodiment of the present invention, the trench 208c may be provided in an intermediate region of the substrate 201, such that the trench 208 does not encounter any of the edges of the substrate 201, as illustrated in [Fig. 4]. The trench 208 may have any predefined geometry.

[0045] [Fig.5A], [Fig.5B] and [Fig.5C] illustrate different configurations of the trench 208 on the substrate 201. The trench 208 may be formed in a straight line as shown in [Fig.5A]. Alternatively, the trench 208 may be formed in a zigzag pattern, as shown in [Fig.5B]. The trench 208 may also be formed along a curved line, as shown in [Fig.5C]. It is understood that the trench 208 may have any other configuration depending on the structural requirements.

[0046] In one embodiment of the present invention, a vehicle lighting device (not shown) may be provided with the printed circuit board (PCB) 200 described above. At least one light source (not shown) may be mounted on the substrate 201 of the printed circuit board 200. The printed circuit board 200 may have a plurality of electronic components 206 mounted on the substrate 201 and electrically interconnected to achieve the desired lighting function. The substrate 201 of the printed circuit board 200 is bent at one or more predefined locations with one or more predefined radii of curvature to achieve the desired curved lighting effect, in accordance with stylistic and functional requirements.

[0047] Those skilled in the art will appreciate that the present invention is in no way limited to the preferred embodiments described above. On the contrary, numerous modifications and variations are possible within the scope of the appended claims. Furthermore, those skilled in the art will appreciate that the various embodiments described herein may be freely combined to obtain new combinations.

[0048] Furthermore, variations of the disclosed embodiments may be understood and made by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to obtain advantages. List of reference signs

[0049] 100, 200: Printed circuit board (PCB)

[0050] 101, 201: Substrate

[0051] 10It, 20It: Elongated surface

[0052] 101c, 201c: Compressed surface

[0053] 102, 202: Substrate layers

[0054] 201a: First edge of the substrate

[0055] 201b: Second edge of the substrate

[0056] 104, 204: Resin

[0057] 106, 206: Electronic components

[0058] 208, 208a, 208b, 208c: Trenches

Claims

Claims

1. A printed circuit board (200), comprising: a. a substrate (201) configured to be bent at a predefined location; b. at least one electronic component (206) configured to be mounted on the substrate (201); and c. at least one trench (208) formed on the substrate (201), wherein the width of the at least one trench (208) is less than or equal to 0.8 mm.

2. The printed circuit board (200) according to claim 1, wherein the substrate (201) comprises several layers (202) stacked by a resin (204).

3. The printed circuit board (200) of claim 2, wherein the plurality of layers (202) are fabricated from FR-4 material.

4. The printed circuit board (200) according to claim 1, 2 or 3, wherein the substrate (201) is configured to have an elongated surface (201t) and a compressed surface (201c) opposite the elongated surface (201t), at the location of the bend.

5. The printed circuit board (200) of claim 4, wherein the at least one electronic component (206) is configured to be mounted on the elongated surface (201t).

6. The printed circuit board (200) of claim 4, wherein the at least one electronic component (206) is configured to be mounted on the compressed surface (201c).

7. The printed circuit board (200) of claim 5 or 6, wherein the at least one trench (208) is configured to be formed on the elongated surface (20 It).

8. The printed circuit board (200) of claim 5 or 6, wherein the at least one trench (208) is configured to be formed on the compressed surface (201c).

9. The printed circuit board (200) according to one of the preceding claims, wherein the at least one trench (208a) is configured to extend between a first edge (201a) of the substrate (201) and a second edge (201b) of the substrate (201).

10. The printed circuit board (200) according to one of claims 1 to 8, wherein the at least one trench (208b) is configured to extend a predefined distance from a first edge (201a) of the substrate (201), or from a second edge (201b) of the substrate (201).

11. The printed circuit board (200) according to one of claims 1 to 8, wherein the at least one trench (208c) is configured to be formed in an intermediate region on the substrate (201).

12. The printed circuit board (200) of claim 9, 10 or 11, wherein the at least one trench (208) is configured to be formed in a straight line, a zigzag line or a curved line.

13. The printed circuit board (200) according to one of the preceding claims, wherein the at least one trench (208) is formed on the substrate (201) using a laser or a drilling or V-grooving method.

14. The printed circuit board (200) according to one of the preceding claims, wherein the length, width and depth of the trench (208) depend on the radius of curvature applied to the substrate and / or the stresses generated on the electronic components (206).

15. A vehicle lighting device comprising a printed circuit board (200) according to any preceding claim, wherein at least one light source is configured to be mounted on the substrate (201).

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