Method for manufacturing a three-dimensional printed circuit board, and three-dimensional printed circuit board and vehicle lighting device

Abstract

The invention relates to a method for manufacturing a printed circuit board. The method comprises the following steps: - providing (401) at least one metal plug in an injection mould, the mould having a shape that defines a substrate of the printed circuit board, the plug being in contact at two of its ends with the mould so as to project from each side of the substrate; - injection-moulding (402) by injecting plastic into the mould; - printing (403) an electrical circuit on one face of the substrate; - positioning (405) electronic components on the printed face of the substrate in at least one planar region; - connecting the components (406). The invention also relates to the printed circuit board obtained in this manner and to its use in a vehicle lighting device.

Description

Method of manufacturing a relief printed circuit, relief printed circuit and vehicle lighting device.

[0001] The invention relates to a method of manufacturing a relief printed circuit, to the relief printed circuit and to a vehicle lighting device.

[0002] Light-emitting diode (LED) vehicle lighting devices are currently composed of a housing comprising light focusing optics and enclosing one or more printed circuits or PCBs (Printed Circuit Boards) comprising LEDs as well as a printed circuit supporting a microcontroller communicating with a CAN bus (Controller Area Network) allowing to receive commands for switching on lights or functions, such as high beams, dipped beams, or reverse lights, or brake lights, etc. Such a structure requires the manufacture of several elements which must be assembled and electrically connected to each other by electrical wires. The manufacture and recycling of these vehicle lighting devices requires a reduction in the number of elements and the materials used.

[0003] The invention aims to reduce the number of elements constituting a vehicle lighting device by producing a single printed circuit whose substrate also serves as part of the housing of the vehicle lighting device. Such a printed circuit reduces the number of elements to be assembled and materials used, in addition the internal connection of the vehicle lighting device is eliminated. Furthermore, an external connection element is directly integrated into the substrate of the printed circuit.

[0004] More particularly, the invention is a method for manufacturing a relief printed circuit. The method comprises the following steps: - providing at least one metal plug in an injection mold, the mold having a shape defining the substrate, said plug being in contact at two of its ends with the mold so as to protrude from each side of said substrate, - injection molding of plastic in said mold, - printing an electrical circuit on one face of the substrate, - placing electronic components on the printed face of the substrate at least in one flat area, - connecting the components.

[0005] To provide improved pull-out resistance, the metal plug may include a retaining flange projecting from said plug, said flange being placed on an area of ​​the plug which is fully covered with plastic during molding.

[0006] To provide better resistance to rotation, one end of the metal plug may have a flattened head that is flush with the printed face of the substrate, with the electrical circuit print covering said flattened head.

[0007] Depending on the various choices of a person skilled in the art, printing can be carried out by depositing a metallic ink or paint, or by electrostatic or thermal metallic spraying.

[0008] Alternatively, after molding, the printing face of the substrate may be completely flat upon exiting the mold, with printing being done by screen printing using a metallic paint, and the substrate being deformed by hot stamping after printing.

[0009] According to another point of view, the invention is a relief printed circuit comprising a substrate having a face on which an electrical circuit is printed. The printed circuit comprises at least one metal plug passing through said substrate, said substrate having been obtained by molding a plastic with said plug placed as an insert. The substrate is of any shape and the printed face comprises at least one flat area on which at least one electronic component is placed.

[0010] And finally, the invention also relates to a vehicle lighting device comprising a housing enclosing at least one electronic circuit comprising at least one light source of the light-emitting diode type and optical means. Said housing comprises at least first and second external parts, the first part being intended to be turned towards the vehicle, and the second part being intended to be turned towards the outside of the vehicle and being at least partially transparent or translucent to allow light emission. The first part constitutes the substrate of a printed circuit according to the invention, the printed face of which is placed inside said housing, the end of the metal plug protruding outside the housing forming a connection element.

[0011] Preferably, the substrate may comprise, on the face opposite the printed face, a projection around the at least one metal plug, said projection and the at least one metal plug forming a connector.

[0012] According to one embodiment, the printed circuit may comprise a plurality of flat surfaces located opposite optical focusing means, each flat surface receiving at least one light source such as a light-emitting diode.

[0013] locates the invention on a vehicle,

[0014] shows an example of a lighting device according to the invention,

[0015] shows a detail of the

[0016] shows a flowchart for manufacturing a printed circuit according to the invention,

[0017] shows a variant of the,

[0018] shows a variant of manufacturing a printed circuit according to the invention. Detailed description

[0019] For the sake of clarity and understanding, the attached figures are not drawn to scale. Indeed, the existing dimensional relationships between certain elements do not allow for the creation of comprehensible diagrams if these are produced while maintaining a dimensional relationship close to reality. In addition, certain elements not relating to the core of the invention have also been omitted in order to avoid unnecessary overload of details on the drawings.

[0020] Before describing the invention, it should be put into context. The figure shows the rear of a vehicle 1. Such a vehicle 1 comprises two lighting devices 10 intended to perform signaling functions such as position lights, brake lights, turn signals, possibly at least one reversing light and fog lights. In the lighting device with an LED type light source, such a lighting device has a connector for being connected to the CAN bus of the vehicle and receiving messages containing switching on and off commands. Each lighting device 10 comprises a microcontroller connected to the connector for interpreting the commands received by the CAN bus and sending specific commands to one or more LED control circuits for switching on or off LEDs placed opposite optical focusing and diffusion devices.

[0021] La represents a lighting device 10 in section along the axis AA shown in the. The lighting device 10 comprises a housing having first and second external parts 100 and 200. The first external part 100 faces towards the inside of the vehicle and is provided with fixing means (not shown) intended to fix the lighting device 10 to the vehicle. The second external part 200 faces towards the outside of the vehicle and is at least partially transparent or translucent to allow light emission therethrough. The first and second parts 100 and 200 are fixed together, for example using screws (not shown) and form a closed housing. The housing can be sealed using a seal (not shown) placed at the junction between the first and second parts 100 and 200.The number of parts constituting the housing may be greater, the first and second parts both being able to be fixed on a third intermediate part. The important thing for the invention is that the first part 100 constitutes a printed circuit substrate 100 of any shape but comprising flat areas 110 for receiving electronic components, such as a microcontroller 120 and LEDs 130.

[0022] The LEDs being directly placed on the first part 100 of the housing, this also makes it possible to have a more compact lighting device 10. A set 300 of reflectors can be held between the first and second parts 100 and 200. Each reflector of the set is placed opposite the flat surfaces and in particular each LED in order to focus the light emitted by the LEDs on Fresnel lenses 210 etched on an internal surface of the second part 200 which diffuse the light more widely outside the housing. Many variants are possible and the number of optical elements can be different as well as their shapes.

[0023] The housing being closed, the connection of the lighting device 10 with the CAN bus is made by at least one metal plug 140 passing through the first part and protruding outside the housing in order to form an external connection element. For this purpose, the metal plug is elongated, of circular or rectangular section depending on the type of female connector that one wishes to use to cooperate with the latter. The first part 100 may also comprise a projection 150 surrounding the plug(s) 140 to form a connector.

[0024] In order to provide a little more detail on the production of the printed circuit board constituting the first part, thedetails the circled area B on thelimiting itself to the first part 100 of the case. Thealso aiming to detail the production of the printed circuit board, the lasera detailed in conjunction with the flowchart of thewhich details the sequence of production steps.

[0025] The first manufacturing step 401 consists of providing the metal plug(s) 140 in an injection mold. For example, the mold may have the final shape of the first part of the housing 100. Although the shape of the first part 100 may be arbitrary, flat areas 110 should be made at the locations that will receive the electronic components. Each flat area 110 must be at least slightly larger than the component that will be placed there to ensure correct placement and to perform welding or soldering. In order for the metal plug 140 to be electrically usable, its two ends must be in contact with the mold in order to protrude on either side of the first part 100. Since the metal plug 140 is intended to receive a female connector, the latter receives an axial force that risks causing it to slide inside the first part if too much force is exerted.In order to prevent slippage, it is appropriate either to have a thickness of the first part 100 sufficiently large to ensure good adhesion, or to use a metal plug 140 which comprises a retaining collar 160 projecting relative to said plug. The retaining collar 160 is placed on an area of ​​the body of the metal plug 140 which is entirely covered with material during molding and prevents any slippage of said plug 140.

[0026] Once the metal plugs 140 are placed in the mold, the material forming the body of the first part 100 and also forming the substrate 100 for the printed circuit is injected into the mold. The material injected into the mold is a plastic having dielectric characteristics allowing it to ensure the substrate function of a printed circuit while having mechanical characteristics compatible with the housing function. In addition, the plastic must have a melting temperature high enough to withstand the following manufacturing steps. For example, for certain choices of the following steps, a melting temperature above 120°C may be sufficient. Preferably but not limitingly, the plastic may be chosen from: polylactic acid, polycarbonate, polyethylene terephthalate, polymethyl methacrylate, polyetheretherketone.

[0027] Polylactic acid, known by the acronym PLA (from the English PolyLactic Acid), has the advantage of being an industrially biodegradable material. The mechanical and dielectric characteristics of PLA allow it to serve as a printed circuit board substrate and housing, and its melting temperature is 185°C in its crystalline form.

[0028] Polycarbonate, known by the acronym PC, is already widely used in the automotive industry and has dielectric characteristics compatible with the function of printed circuit substrate and its melting temperature is 230°C. The same is true for polyethylene terephthalate or PET whose melting temperature is 255°C, polymethyl methacrylate or PMMA whose melting temperature is 180°C. Polyetheretherketone or PEEK, more expensive than the other plastics mentioned, has a melting temperature above 340°C with good mechanical and dielectric characteristics.

[0029] After the plastic injection, the mold is cooled and the first part 100, provided with the metal pins 140, is removed from the mold in a step 403. Next comes a step 404 of printing conductive tracks to form an electrical circuit 170 on the face of the substrate 100 corresponding to the interior of the housing. Several printing techniques can be used for step 404 depending on the plastics chosen and the more or less significant currents which must circulate in the electrical circuit 170.

[0030] Conductive inkjet printing or localized spraying of metallic paint allows for low-temperature printing. However, the low conductivity of inks and paints requires relatively thick tracks. Thickening the tracks requires several successive prints of the conductive tracks, with the ink or paint having to dry between each print. Achieving sufficient thickness for a high current of the order of an ampere can take a relatively long time.

[0031] Printing can also be achieved using electrostatic or thermal spraying of fine metal particles. However, these metal spraying processes require the use of a plastic whose melting temperature is higher than the spraying temperature. Spraying can reach temperatures of around 200°C. Spraying can be done through a mask that defines the conductive tracks of the printed circuit. However, it is preferable to use a fine nozzle allowing deposition on a surface corresponding to a conductive track width.

[0032] Once the conductive tracks have been printed, a step 405 of placing the components is then carried out. The step 405 of placing the components can be carried out automatically using a movable plate to support the first part 100 during placement so as to place each flat area horizontally to receive an electronic component 120 or 130 to be placed. To hold the component 120 or 130 while waiting for it to be soldered, a drop of glue 180 can be deposited before the placement of the component 120 or 130 by a placement machine.

[0033] After the placement of the components, a step 406 of connecting the components is carried out by soldering or brazing. Depending on the soldering or brazing technique used, step 406 is carried out after the placement of all the components or after the placement of each component.

[0034] A soldering or brazing technique consists of placing dots of silver-based conductive glue. Drops of conductive glue can be deposited using a hollow needle at the contacts of each of the components 120 and 130 to form a weld or braze 190 with one of the conductive tracks of an electrical circuit 170. Such a technique can be carried out when placing each component 120 or 130. It should be noted that the use of conductive glue ensuring the welds or brazes 190 can make it unnecessary to use the drops of glue 180 which ensure the holding in position of the components 120 and 130 if the conductive glue has a rapid drying time and does not need to be polymerized.

[0035] Another welding or brazing technique is laser welding. This technique uses a very fine welding wire, the laser providing very localized heating that can exceed the melting temperature of the substrate 100 but on an extremely small surface area and for a very short time, which does not damage the substrate 100.

[0036] A person skilled in the art will be able to adapt the different steps of the method thus described depending on the material chosen for the substrate 100.

[0037] The person skilled in the art will notice that the electrical contact between the metal plug 140 and the conductive track is relatively weak on the. To reinforce the conduction, it is possible to perform a weld or solder at the conductive track. However, it is also possible to use a metal plug 140 comprising a flattened head 145 on the end opening on the side of the printed face of the substrate 100, as shown on the. Thus, the flattened head 145 is placed so as to be flush, or even slightly protruding relative to the substrate 100 and can be entirely covered by a conductive track of the electrical circuit 170, which makes it possible to have a contact surface equal to the surface of the flattened head 145. The shape of the flattened head 145 can be round, however a rectangular or star shape makes it possible to reinforce a rotational blocking of the plug when the latter is of circular section.

[0038] In the method described using the, the molding of the first part 100 is carried out with its final shape, and the face to be printed is found to have any shape during the printing step 404. The any shape of the surface to be printed requires the use of printing processes by projection of ink, paint or metallic particles.

[0039] A variant of the manufacturing method is illustrated in which comprise the same steps as with some differences indicated below. In this variant, the molding of the first part 100 is done in a mold whose shape does not correspond to the final shape but whose face to be printed is entirely flat. During the printing step 404, it is then possible to print the electrical circuit 170 by screen printing, which makes it possible to quickly deposit a thick layer of conductive paint using a mask. The conductive paint being polymerized, a hot stamping step 407 is then carried out. Hot stamping consists of pressing the first part 100 between two dies while heating the two dies to a softening temperature of the material to give it its final shape.The pressing also has the effect of pushing the conductive tracks into the substrate material 100, which increases the adhesion of the conductive paint. The steps 405 and 406 of placing the components and connecting the components can then be carried out as previously described. Such a variant makes it possible to have a paint deposit of significant thickness and therefore very good conduction without resorting to metallic spraying.

[0040] Other variants and improvements may be made without departing from the scope defined by the claims. Furthermore, the invention has been described in relation to a rear lighting device of a vehicle. Those skilled in the art will readily understand that the invention can be transposed to front lighting devices of a vehicle. The invention may be used in other application contexts. Indeed, the production of a printed circuit that can be used as a housing element is not limited to vehicle lights but may be applied to any type of device in which one would wish to eliminate one or more printed circuits, thus making it possible to reduce the number of elements to be assembled and / or reduce the number of materials for recycling.

Claims

Method for manufacturing a relief printed circuit characterized in that it comprises the following steps:- providing (401) at least one metal plug (140) in an injection mold, the mold having a shape defining a substrate (100) of said printed circuit, said plug (140) being in contact at two of its ends with the mold so as to protrude from each side of said substrate (100),- injection molding (402) of plastic in said mold,- printing (403) of an electrical circuit (170) on one face of the substrate (100),- placing (405) of electronic components (120, 130) on the printed face of the substrate (100) at at least one flat area (110),- connecting the components (406). The method of claim 1, wherein the metal plug (140) comprises a retaining flange (160) projecting from said plug (140), said flange (160) being placed on an area of ​​the plug which is entirely covered with plastic during molding. Method according to one of claims 1 or 2, in which one of the ends of the metal plug (140) comprises a flattened head (145) which is flush with the printed face of the substrate (100), the printing of the electrical circuit (170) covering said flattened head (145). Method according to one of claims 1 to 3, in which the plastic is chosen from: polylactic acid, polycarbonate, polyethylene terephthalate, polymethyl methacrylate, polyetheretherketone. Method according to one of claims 1 to 4, in which the printing (404) is carried out by depositing a metallic ink or paint, or by electrostatic or thermal metallic spraying. Method according to one of claims 1 to 4, in which, after molding (402), the printing face of the substrate (100) is entirely flat when leaving the mold, in which the printing (404) is done by screen printing using a metallic paint, and in which the substrate (100) is deformed by hot stamping (407) after printing. Method according to one of claims 1 to 6, in which the connection of the components (406) is carried out using a conductive glue. Method according to one of claims 1 to 6, in which the connection of the components (406) is carried out by laser. Relief printed circuit comprising a substrate (100) having a face on which an electrical circuit (170) is printed, characterized in that it comprises at least one metal plug (140) passing through said substrate (100), and in which said substrate (100) has been obtained by molding a plastic with said plug (140) placed as an insert, and in which the substrate (100) is of any shape and the printed face comprises at least one flat area (110) on which at least one electronic component (120, 130) is placed. A printed circuit board according to claim 9, wherein the metal plug (140) comprises a retaining flange (160) projecting from said plug (140), said flange (160) being placed within said substrate (100). Printed circuit according to one of claims 9 or 10, in which one of the ends of the plug (140) comprises a flattened head (145) which is flush with the printed face of the substrate (100), the printing of the printed circuit covering said flattened head (145). Printed circuit according to one of claims 9 to 11, in which the plastic is chosen from: polylactic acid, polycarbonate, polyethylene terephthalate, polymethyl methacrylate, polyetheretherketone. Lighting device (10) for a vehicle (1) comprising a housing enclosing at least one electronic circuit comprising at least one light source (120) of the light-emitting diode type and optical means (130, 210), said housing comprising at least first and second external parts (100, 200), the first part (100) being intended to be turned towards the vehicle (1), and the second part (200) being intended to be turned towards the outside of the vehicle (1) and being at least partially transparent or translucent to allow light emission, characterized in that the first part (100) constitutes the substrate (100) of a printed circuit according to one of claims 9 to 12, the printed face of which is placed inside said housing, the end of the metal plug (140) protruding outside the housing forming a connection element. Lighting device (10) for a vehicle (1) according to claim 13, wherein the substrate (100) comprises, on the face opposite the printed face, a projection (150) around the at least one metal plug (140), said projection (150) and the at least one metal plug (140) forming a connector. Vehicle lighting device (10) according to one of claims 13 or 14, in which the printed circuit comprises a plurality of flat surfaces (110) located opposite optical focusing means (130), each flat surface receiving at least one light source, such as a light-emitting diode (130).

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