EP3327165A1

EP3327165A1 - Method for creating a conductive track

Info

Publication number: EP3327165A1
Application number: EP16382558.1A
Authority: EP
Inventors: Daniel Teba; Alfonso-Manuel GUZMAN; Francisco Martinez
Original assignee: Valeo Iluminacion SA
Current assignee: Valeo Iluminacion SA
Priority date: 2016-11-24
Filing date: 2016-11-24
Publication date: 2018-05-30

Abstract

Method for manufacturing an electronic assembly (10), the method comprising the steps of providing a plastics substrate (1), applying metal dust (3) within a plasma flow (2) and ejecting a plasma flow (2). The plasma flow (2) is created by an electric power comprised between 500 and 2000 W and at a frequency comprised between 20 and 150 kHz. The metal dust (3) is fed to the plasma flow (2) at a rate comprised between 0.016 and 1.6 g/s. The plasma flow (2) is ejected on the plastics substrate (1) by a plasma nozzle (4), to create a conductive track (5) on the plastics substrate (1). The plasma flow (2) exits the plasma nozzle (4) at a rate comprised between 0.16 and 2.5 I/s, thereby obtaining the electronic assembly (10). The invention also refers to an electronic assembly (10) and a lighting device (11).

Description

TECHNICAL FIELD

This invention belongs to the field of methods which are intended to manufacture electronic assemblies and automotive lighting devices comprising such assemblies.

STATE OF THE ART

Directly depositing a conductive track on a plastics substrate normally supposes substantial cost savings, mainly due to the fact that a dedicated printed circuit board need not be provided. Therefore, other integral parts of the device to be controlled with the electronic assembly can be taken advantage of to play the role of substrate for the conductive track.
Plasma deposition is sometimes used to directly deposit a conductive track on a plastics substrate. This process comprises the step of including in the plasma flow some metal dust particles, usually copper, that are melted by the plasma flow and then deposited on the plastic part, thus creating a conductive track on said plastic part.
One example of this process may be found in document US 2015/174686 A1 .
But when a conductive track is created by this method, it is very common that metal particles are deposited on the plastic part outside the conductive track. These particles may cause problems when two conductive tracks are placed near each other.
Patent EP 2247766 B1 shows a way of solving this problem by the use of masks when creating these tracks. However, these masks need to be specifically designed for each track and plastic part geometry, which make it expensive and non-practical for its use in a field with different and varied shapes and geometries.
In these methods, the border of the conductive track appears as a sharp edge because the process is focused on isolating the conductive track from the masked areas in an abrupt way.
It is then desirable to provide an alternative to these methods which provide for a more versatile way of avoiding contamination of metal particles in the edges of the conductive tracks.

DESCRIPTION OF THE INVENTION

The invention provides a solution for this problem by means of a method for manufacturing an electronic assembly according to claim 1, a method for manufacturing a lighting device for an automotive vehicle according to claim 7, an electronic assembly according to claim 10 and a lighting device according to claim 11. Preferred embodiments of the invention are defined in dependent claims.
In an inventive aspect, the present invention provides a method for manufacturing an electronic assembly, the method comprising the steps of:

providing a plastics substrate;
applying metal dust within a plasma flow created by an electric power, wherein the metal dust is fed to the plasma flow at a rate comprised between 0.016 and 1.6 g/s, the electric power generated to create a plasma flow is comprised between 500 and 2000 W and the electric power is generated at a frequency comprised between 20 and 150 kHz;
ejecting, by means of a plasma nozzle, the plasma flow on the plastics substrate to create a conductive track on the plastics substrate, the plasma flow exiting the plasma nozzle at a rate comprised between 0.16 and 2.5 l/s, thereby obtaining the electronic assembly.

A method for manufacturing an electronic assembly using these parameters ensures that the borders of the conductive tracks of the electronic assembly can be defined without falling back on masks or other elements that would normally suppose an increase of the production cost and reduce the versatility of the method -in other words, these value ranges limits the dispersion of the metal particles outside the borders of the conductive track. The electronic assembly obtained by this method differs from those obtained by prior art methods in that the borders of the conductive tracks are of irregular, random shape (i.e. they do not follow a given pattern, such as that of a mask).
In some particular embodiments, the metal dust is fed to the plasma flow at a rate comprised between 0.016 and 0.16 g/s, preferably between 0.03 and 0.035 g/s.
This flow rate is advantageous to achieve a good density of the conductive track.
In some particular embodiments, the plasma flow exits the plasma nozzle at a rate comprised between 0.58 and 1.33 l/s, preferably between 0.80 and 0.85 l/s.
This flow rate provides a good environment for the metal dust particles being deposited on the plastic substrate.
In some particular embodiments, the electric power generated to create a plasma flow is comprised between 800 and 1200 W, preferably between 950 and 1050 W.
This power is suitable for create a plasma flow with energy enough to melt conductive metals.
In some particular embodiments, the microwave frequency is comprised between 50 and 100 kHz, preferably between 60 and 65 kHz.
This frequency is suitable for creating a plasma flow which optimizes the metal melting and its deposition in the plastic substrate.
The suitable combination of these parameters improves the metal transfer coefficient, which should be understood in this specification as the ratio between the metal actually deposited on the plastic substrate and the metal dust which is fed into the plasma flow. The metal transfer coefficient should be improved but without excessively increasing temperature, as this would cause the plastic substrate deformation.
In some particular embodiments, the plasma flow comprises at least one of nitrogen, helium, neon, argon, krypton or xenon.
Inert gases as nitrogen or noble gases are preferred to avoid chemical reactions between melted metal and activated gases at plasma high temperatures where activated species are generated, obtaining non electrical conductive oxides.
It has been surprisingly found that the use of inert gases in the plasma deposition improves the final outcome, due to high temperatures, which would make other fluids react with melted metal.
In another inventive aspect, the invention provides a method for manufacturing a lighting device for an automotive vehicle, the method comprising the steps of:

manufacturing an electronic assembly by a method according to any one of preceding claims;
providing a light source in electric connection with the electronic assembly,
providing an optical element suitable for receiving light emitted by the light source and for shaping the light into a light pattern projected outside the lighting device.

An optical element is an element that has some optical properties to receive a light beam and emit it in a certain direction and/or shape, as a person skilled in automotive lighting would construe without any additional burden. Reflectors, collimators, light guides, projection lenses, etc., or the combination thereof are some examples of these optical elements.
This method achieves the manufacturing of a lighting device for its use in an automotive vehicle, wherein the conductive tracks may be directly formed on a plastics substrate. This saves costs and space, as no printed circuit board is needed to be arranged on the lighting device structure.
In some particular embodiments, the light source is a semiconductor light source. These kind of light sources, such as LEDs or laser devices, offer efficiency advantages over standard light sources.
In another inventive aspect, the invention provides an electronic assembly obtained by the method of the previous inventive aspect, the electronic assembly comprising a conductive track with sides comprising discontinuities in the track material. The electronic assembly obtained by this method differs from those obtained by prior art methods in that they are easier to obtain, as they do not require the use of external devices to limit the plasma flow. Further, they do not depend on the way a mask is placed during the track formation, so the final result is much less influenced by human skills than parts obtained by prior art methods.
In another inventive aspect, the invention provides for a lighting device for automotive vehicle comprising an electronic assembly according to the previous inventive aspect.
Lighting devices for automotive vehicles can benefit from the use of electronic assemblies comprising conductive tracks directly deposited on a plastics substrate. In the first place, a wide range of the lighting device's parts can be used either as plastics substrate or as base for the plastics substrate (in which case the plastics substrate may for instance coat the base), taking into account that even three-dimensional plastics substrates are suitable for direct deposition of conductive tracks. Therefore, a dedicated printed board circuit is not required, which leads to reducing the cost and the weight of the lighting device. As was stated above, cost savings are even more significant due to the fact that direct deposition does not normally want removing conductive material to shape the conductive tracks.

BRIEF DESCRIPTION OF THE DRAWINGS

To complete the description and in order to provide for a better understanding of the invention, a set of drawings is provided. Said drawings form an integral part of the description and illustrate an embodiment of the invention, which should not be interpreted as restricting the scope of the invention, but just as an example of how the invention can be carried out. The drawings comprise the following figures:

Figure 1 shows one of the steps of a method for manufacturing an electronic assembly according to the invention.
Figure 2 shows the manufacturing of a lighting device out of the electronic assembly of figure 1.
Figure 3 shows a lighting device which comprises such an electronic assembly being installed in an automotive vehicle.

DETAILED DESCRIPTION OF THE INVENTION

Figure 1 shows one of the steps of a method for manufacturing an electronic assembly according to the invention.
In this figure, a plastics substrate 1 has been provided, and a plasma flow 2 containing metal dust 3 is ejected by means of a plasma nozzle 4 on the plastics substrate 1 to create a conductive track 5.
The plasma flow 2 has been generated by an electric power comprised between 800 and 1200 W, generated at a frequency comprised between 50 and 100 kHz. Metal dust 3 has been fed to said plasma flow 2 at a rate comprised between 0.016 and 0.16 g/s.
The resulting plasma flow 2 with the metal dust 3 is made exit the plasma nozzle 4 at a rate comprised between 0.58 and 1.33 l/s.
When this plasma flow 2 with metal dust 3 impacts the plastics substrate 1, a conductive track 5 is formed on it. The electronic assembly 10 is therefore manufactured.
Figure 2 shows the manufacturing of a lighting device 11 out of this electronic assembly 10. In this figure, an electronic assembly 10 which has been manufactured according to a method partially shown in figure 1 is provided, and a semiconductor light source 6 has been added to this electronic assembly 10.
The final step includes the provision of some optical elements 71, 72 suitable for receiving light from the semiconductor light source 6 and projecting it in the shape of a pattern light in a forward direction.
The forward direction should be understood as the advance direction of an automotive vehicle where the lighting device is intended to be installed.
In the particular embodiment shown in this figure, the optical elements include a reflector 71 and a projection lens 72. The reflector 71 is placed in the electronic assembly 10, arranged to reflect the light emitted by the semiconductor light source 6. The projection lens is in turn located in a forward position with respect to the lighting device 11, and receives the light from the semiconductor light source 6 which has been reflected by the reflector 71. The projection lens 72 orientates this received light according to the vehicle advancing direction.
These optical elements 71, 72 makes the lighting device 11 suitable for being installed in an automotive vehicle 100 and able to perform lighting functions, such as high-beam and low-beam. Figure 3 shows a lighting device 11 which comprises such an electronic assembly 10 being installed in an automotive vehicle 100.
This lighting device 11 occupies a smaller volume than the lighting devices of the state of the art, and that makes that the lighting device may be smaller or house more elements without the need of increasing its size.
This lighting device 11 may be incorporated in an automotive vehicle 100, saving space and weight, because its manufacturing requires less time and a lower number of elements.

Claims

Method for manufacturing an electronic assembly (10), the method comprising the steps of:
- providing a plastics substrate (1);

- applying metal dust (3) within a plasma flow (2) created by an electric power, wherein the metal dust (3) is fed to the plasma flow (2) at a rate comprised between 0.016 and 1.6 g/s, the electric power generated to create a plasma flow (2) is comprised between 500 and 2000 W and the electric power is generated at a frequency comprised between 20 and 150 kHz;

- ejecting, by means of a plasma nozzle (4), the plasma flow (2) on the plastics substrate (1) to create a conductive track (5) on the plastics substrate (1), the plasma flow (2) exiting the plasma nozzle (4) at a rate comprised between 0.16 and 2.5 l/s, thereby obtaining the electronic assembly (10).
Method according to claim 1, wherein the metal dust (3) is fed to the plasma flow (2) at a rate comprised between 0.016 and 0.16 g/s, preferably between 0.03 and 0.035 g/s.
Method according to any of claims 1 or 2, wherein the plasma flow (2) exits the plasma nozzle (4) at a rate comprised between 0.58 and 1.33 l/s, preferably between 0.80 and 0.85 l/s.
Method according to any of preceding claims, wherein the electric power generated to create a plasma flow (2) is comprised between 800 and 1200 W, preferably between 950 and 1050 W.
Method according to any of preceding claims, wherein the frequency at which electric power is generated is comprised between 50 and 100 kHz, preferably between 60 and 65 kHz.
Method according to any of preceding claims, wherein the plasma flow (2) comprises at least one of nitrogen, helium, neon, argon, krypton or xenon.
Method for manufacturing a lighting device (11) for an automotive vehicle, the method comprising the steps of:
- manufacturing an electronic assembly (10) by a method according to any one of preceding claims;

- providing a light source (6) in electric connection with the electronic assembly (10),

- providing an optical element (71, 72) suitable for receiving light emitted by the light source (6) and for shaping the light into a light pattern projected outside the lighting device (11); and

- providing a housing (12) accommodating the electronic assembly (10) and the optical element (71, 72).
Method for manufacturing a lighting device according to claim 7, wherein the light source (6) is a semiconductor light source.
Method for manufacturing a lighting device according to any of claims 7 or 8, wherein the optical element is one of a reflector (71), a projector lens (72), a collimator, a light guide or a combination thereof.
Electronic assembly obtained by the method of any one of claims 1-6, the electronic assembly (10) comprising a conductive track (5) with sides comprising discontinuities in the track material.
Lighting device (11) for automotive vehicle (100) comprising an electronic assembly (10) according to claim 10.