FR3075482A1 - METHOD FOR MANUFACTURING A WAVEGUIDE DEVICE - Google Patents

Abstract

 The invention relates to a method for manufacturing a waveguide device comprising the following steps:  manufacturing a photopolymer core by additive manufacturing, said core comprising side walls with external and internal surfaces, the internal surfaces defining at least one cavity,  - baking the core produced by additive manufacturing by irradiating the core with ultraviolet (UV) radiation so as to harden said core;  the cooking step comprising:  - placing a source of radiation in said cavity so that the ultraviolet radiation propagates from the internal surfaces to the external surfaces of said cavity.  The invention also relates to a device manufactured by said method and a cooking module for cooking a waveguide device.

Description

Method for manufacturing a waveguide device

Technical Field [0001] The present invention relates to a method for manufacturing a waveguide device, a device manufactured by said method and a cooking module for cooking a waveguide device.

State of the art Radiofrequency (RF) signals can propagate either in a space or in waveguide devices. These waveguide devices are used to channel RF signals or to manipulate them in the spatial or frequency domain.

The present invention relates in particular to passive RF devices which make it possible to propagate and manipulate radio frequency signals without using active electronic components. Passive waveguides can be divided into three distinct categories:

• Devices based on waveguiding inside hollow metal channels, commonly called waveguides.

• Devices based on waveguiding inside dielectric substrates.

• Devices based on waveguiding by means of surface waves on metallic substrates such as PCB printed circuits, microstrips, etc.

The present invention relates in particular to the first category above, collectively referred to below as waveguides. Examples of such devices include waveguides as such, filters, antennas, mode converters, etc. They can be used for signal routing, frequency filtering, signal separation or recombination, transmitting or receiving signals in or from free space, etc.

ST012-104en [0005] The waveguides are generally made of a conductive material, for example metal, by extrusion or folding.

There are also known waveguides produced by additive manufacturing, for example by 3D printing, in particular by stereo-lithography (SLA), followed by a step of metallization of the inner walls of the core.

However, after additive manufacturing, the core is not completely "cooked" or "polymerized": there are portions of the core where the polymer is not polymerized or not sufficiently polymerized, which means that these portions are not hard enough. The polymer has not yet reached mechanical properties close to its maximum values or optimal surface properties. It is necessary to carry out an additional stage of polymerization, in other words “cooking” or “post-curing” in order to harden these portions. Generally, the core is placed in an ultraviolet radiation oven to activate the crosslinking of the polymer.

However, this mode of polymerization is not satisfactory because the UV radiation is concentrated on the surfaces exposed to external radiation, in particular the external surfaces of the walls of the core. The radiation propagates from the outside towards the inside of the core, but the surfaces of the hollow or concave zones are only slightly or not irradiated by the radiation because the walls obstruct the propagation of UV radiation, especially during the use of non-transparent polymer resins. Thus, polymerization by UV oven does not make it possible to harden the concave portions which are difficult to expose.

It is possible to increase the power and / or the cooking time in the oven to improve the crosslinking or polymerization of the polymer on the internal surfaces, but this is done to the detriment of the external surfaces which are degraded by the excess radiation, and at the cost of a longer manufacturing time.

Thus, there is a need to improve the manufacture of waveguide devices, in particular with regard to the polymerization step, in other words cooking or hardening of the core which follows the additive manufacturing step. .

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Brief Summary of the Invention An object of the present invention is to provide a method and a module that is free or which minimizes the limitations of known methods and modules.

Another object of the invention is to promote polymerization, in other words cooking, on the internal surfaces of the core.

According to the invention, these aims are achieved in particular by means of a method for manufacturing a waveguide device comprising the following steps:

manufacturing a photopolymer core by additive manufacturing, said core comprising side walls with external and internal surfaces, the internal surfaces defining at least one cavity

- activate the polymerization of the core produced by additive manufacturing by irradiating the core with ultraviolet (UV) radiation so as to harden said core;

- deposit a layer of metal on the internal surfaces;

the polymerization step comprising:

- have a source of UV radiation in said cavity so that the ultraviolet radiation propagates from inside the cavity towards the internal surfaces.

This solution has the particular advantage over the prior art of irradiating the internal surfaces from inside the cavity. This promotes cooking, or polymerization and thus the hardening and polymerization of the internal surfaces of the core. The activation of the polymerization makes it possible to modify its mechanical properties, to "harden" said core, for example to modify its surface properties.

The device according to the invention has side walls delimited by external and internal surfaces. The external surfaces constitute the external envelope of the device. The internal surfaces define at least one cavity, for example a channel for guiding the waves or waveguide channel. For example, when the opening of the cavity has a rectangular section, the cavity has four internal surfaces, opposite two by two. In one embodiment, said cavity comprises a waveguide channel for guiding

ST012-104en radiofrequency electromagnetic waves; or in another embodiment a filter channel or filter for filtering these waves.

In the present invention, the radiation source is in the cavity, in the sense that the source is included in the volume delimited by the internal surfaces of the cavity. UV radiation during cooking propagates from the source towards the internal surface towards the external surface. Thus, the propagation takes place in the opposite direction to that of UV oven where the radiation propagates from the UV lamps of the oven towards the external surface in the direction of the internal surface.

The source, for example an optical fiber, a nanostructured optical fiber, or an activated plasma, is housed within a cavity: for example, the source can be maintained in the middle of the cavity at a determined distance from the internal surface. walls. Alternatively, the source can rest on one of the internal walls or be inserted by endoscopic or fibro-scopic means.

In particular, the wavelength of UV radiation corresponds to the activation wavelength of the photopolymer. For example, this wavelength is between 250 nm and 500 nm.

In one embodiment, said cavity comprises a waveguide channel for guiding electromagnetic radiofrequency waves.

In one embodiment, said cavity comprises a channel for filtering radiofrequency electromagnetic waves.

The channel is a channel for guiding waves, and whose section is determined according to the frequency of the electromagnetic signal to be transmitted. The dimensions a, b of this channel (see FIG. 1) and its shape are determined as a function of the operating frequency of the device, that is to say the frequency of the electromagnetic signal for which the device is manufactured and for which a mode stable transmission and optionally with minimum attenuation is obtained.

According to one embodiment, the cooking step comprises:

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- Insert an optical fiber into said cavity, said fiber being capable of emitting UV radiation in an axial and / or radial direction of the fiber relative to the longitudinal axis.

Fiber can emit:

- Axially, through the free end of the fiber introduced into the cavity; this can be advantageous when the user wishes a precise irradiation of a surface portion, in an axial direction relative to the fiber; and or

- Radially; this makes it possible to optimize the radiation time since the radiation takes place simultaneously over the entire length of the fiber capable of emitting radially, for example the portion introduced into the cavity. This type of radial irradiation can be achieved for example by a nanostructured optical fiber.

The optical fiber can emit radially over its entire length, or only over a portion of its length, for example the portion intended to be introduced into the cavity.

The optical fiber can emit radially with an intensity which varies along its length.

The optical fiber can emit radially with an intensity which varies along its periphery.

According to one embodiment, the cooking step comprises:

- Moving said fiber in the cavity axially and / or radially so as to irradiate a selected portion of the internal surface of the cavity.

The fiber can be coupled to means for moving the fiber in the cavity; for example to insert or remove the fiber or radiation source from the cavity. For example, these means include an articulated arm to control the movement of the fiber. Fiber can also be attached to the end of a pistol. The operator operates the fiber to choose the areas to be irradiated to harden the core.

In one embodiment, the fiber is chosen according to the cavity to be hardened.

ST012-104en In one embodiment, the fiber is articulated on an articulated arm to control the axial and / or radial movement of said fiber. In one embodiment, the optical fiber is an axial emission fiber, UV radiation in fact from the exit of the fiber, in an axial direction, that is to say parallel to the longitudinal axis of the fiber. The arm allows to control the orientation of the fiber to irradiate in different directions. This makes it possible to control the orientation of the fiber and to selectively choose the portion of surface to be irradiated. This irradiates a portion of the inner surface or the outer surface.

In one embodiment, the fiber is fixed to a robot which controls the movement of said fiber. Alternatively, the fiber can be coupled to a laying or other support.

In one embodiment, the cooking step comprises:

- disposing said core made by additive manufacturing in a sealed chamber;

- Introducing a plasma into the cavity, said plasma being activatable by electric pulse to generate ultraviolet radiation;

- Activate the plasma in the cavity by electrical impulse so that the activated plasma in the cavity emits ultraviolet radiation which propagates from inside the cavity towards the internal surfaces.

The activated plasma is at least introduced into the cavity so that after activation, the radiation reaches the internal surfaces of the cavity. Alternatively, the plasma can be introduced into the cavity but also around the core, the core then being in an activatable plasma bath, so that after electrical impulse, the UV radiation reaches the external and internal surfaces of the 'soul. Advantageously, in this embodiment, this makes it possible to irradiate the internal and external surfaces of the core, to minimize or replace the use of a UV oven.

Plasma is a composition capable of emitting UV radiation after excitation. The plasma can comprise any component, atom or molecule having this property. For example, the plasma may include Hg mercury derivatives.

According to one embodiment, it is possible to combine several sources of radiation, in one or more sequences as required: for example, the user can start with an irradiation of the cavity or cavities using an activated plasma. Then, if there are portions left to harden, it uses a fiber which emits axially and chooses irradiation in particular on these portions.

In one embodiment, the chamber is evacuated before introducing the plasma. This facilitates the introduction of the plasma into the chamber.

According to one embodiment, the cooking step comprises:

- Insert the core in a UV oven so as to irradiate the external surfaces of the core.

In one embodiment, additive manufacturing is preferably chosen from stereo lithography (SLA), or else by ink jets ("binder jetting"), DED ("Direct Energy Deposition"), EBFF ( "Electron Beam Freeform Manufacturing"), FDM ("Fused Deposition Modeling"), PFF ("Plastic Freeforming"), by aerosols, BPM ("Ballistic Particle Manufacturing"), powder bed, SLS ("Selective Laser Sintering"), ALM ("Additive Layer Manufacturing"), polyjet, EBM ("Electron Beam Melting)", preferably by stereo-lithography (SLA).

In one embodiment, the additive manufacturing is carried out by stereo-lithography. This manufacturing method allows extremely precise manufacturing with excellent surface conditions.

According to one embodiment, the photopolymer is comprising epoxy derivatives, acrylates, antimony, or a mixture of these derivatives.

According to one embodiment, the metal layer is deposited by electrodeposition or electroplating. Metallization makes it possible to cover the internal surfaces of non-conductive photopolymer with a conductive layer.

According to one embodiment, the metal layer comprises a metal chosen from copper and its alloys, gold, silver, nickel, aluminum, rhodium.

ST012-104en According to one embodiment, the radiation source, for example the fiber, emits at any wavelength between 250 nm and 500 nm.

According to one embodiment, the duration of the irradiation is between a few seconds and a day.

The invention also relates to a waveguide device manufactured by the method according to the invention. In a device manufactured by the method according to the invention, a homogeneous or almost homogeneous polymerization is observed between the internal and external surfaces of the device, which is not the case when using only a UV oven for example.

The invention also relates to a cooking module for cooking a waveguide device, said device comprising a core of photopolymer by additive manufacturing, said core comprising side walls with external and internal surfaces, internal surfaces defining at least one cavity, characterized in that said cooking module comprises a source of ultraviolet radiation intended to be arranged in said cavity so that the ultraviolet radiation which propagates from inside the cavity towards the internal surfaces .

According to one embodiment, the radiation source comprises a plasma activated by electric pulse to generate said UV radiation.

In one embodiment, the cooking module comprises a UV oven. Advantageously, it is possible to combine two cooking modes: on the one hand a UV oven for particularly cooking the external surfaces, and on the other hand a source of radiation in the cavity for particularly cooking the internal surfaces.

In one embodiment, the cooking module comprises:

- A sealed chamber intended to receive said core produced by additive manufacturing;

- a plasma source for introducing a plasma at least into the cavity, said plasma being activatable by electrical pulse to generate ultraviolet radiation;

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- an electric pulse generator to activate the plasma in the cavity.

According to one embodiment, the plasma source introduces plasma throughout the chamber so that the core is in a plasma bath.

In one embodiment, the cooking module can cooperate with an additive manufacturing module to manufacture the photopolymer core. The manufacturing module comprises, for example, the elements for manufacturing by stereo lithography (SLA), this type of module being known from the prior art.

The manufacturing module can cooperate with a metallization module to metallize the internal surfaces of the core.

"Axially radiated radiation" means radiation emitted in a direction parallel to the longitudinal axis of the fiber. The so-called conventional optical fibers emit from one end, the beam being cone-shaped from said end, with a radial but not significant component, the radiation is mainly axial.

By "radial radiation emission" means radiation emitted in a transverse direction relative to the longitudinal axis of the fiber, that is to say from the circumference of the fiber or circumferential or lateral emission. The transverse direction can be perpendicular or substantially perpendicular to the axial direction, for example with an angle between 70 ° and 120 °. Radial emission can take place from the end of the fiber. Alternatively, the radial emission can also take place over a portion of the fiber remote from the end or over the entire length of the fiber. The emission can be done on a part of the circumference like a pierced pipe, or on the whole circumference. Preferably, the portion of the fiber which is in the cavity emits over its entire length. It is also possible to use a fiber which emits radially along a gradient, with an emission which evolves as a function of the portion of the fiber considered. For example, fibers known as nanoactive or nano-structured radial emission are known.

By waveguide device is meant in the present application any device comprising a hollow channel delimited by conductive walls and intended for guiding RF electromagnetic waves in the channel, for example

ST012-104en for the remote transmission of an electromagnetic signal, filtering, reception and emission in ether (antennas), mode conversion, signal separation, signal recombination, etc.

By radiation source is meant an element which emits radiation. In the case of a fiber, the fiber is connected to a generator which is outside the cavity, the source is the end of the fiber for an axial emission fiber or a portion upstream of the end for a radial fiber . In the case of a source which would be a plasma, the source consists of the plasma activated in the cavity.

The embodiments described for the method according to the invention apply mutatis mutandis to the device and to the module according to the present invention and vice versa.

Brief description of the figures [0057] Examples of implementation of the invention are indicated in the description illustrated by the appended figures in which:

Figure 1 illustrates a method according to the invention according to a first embodiment.

FIG. 2 illustrates a method according to the invention according to a second embodiment.

FIG. 3 illustrates a method according to the invention according to a third embodiment.

Example (s) of embodiment of the invention The invention shown in Figures 1 to 3 illustrates three embodiments of the invention, but the invention is not limited to the embodiments shown.

Figures 1 and 2 show a device 1, 100 comprising a core 2, 102. The core 2, 102 is delimited by walls 3, 103 which include

ST012-104en external surfaces 4, 104 and internal 5, 105. The internal surfaces 5, 105 define a cavity 6, 106 here a waveguide channel 7, 107.

The core 2, 102 shown in Figures 1 to 3 was manufactured by stereolithography by photo-polymerization of a photosensitive polymer material according to a process known to those skilled in the art (not shown). After manufacturing by stereo lithography, the core 2, 102 is cooked in two stages:

the core 2, 102 is first introduced into a UV oven to harden the external surfaces 4, 104; then

- An irradiation source 8, 108 is arranged in the channel 7, 107 for baking and hardening the internal surfaces 5, 105 of the channel 7, 107;

In the first embodiment illustrated in Figure 1, the radiation source 8 comprises an optical fiber 9 which emits UV light in a substantially axial direction from its end introduced into the cavity.

In the second embodiment, the radiation source 108 is a side emission fiber 109, which radiates radially and axially.

In this example, the emission frequency is between: 250,500nm; it is possible to use any wavelength or range in this value range. The source can be an LED, a laser or a UV lamp.

In the first and second embodiments, the fiber 9, 109 may be secured to an articulated arm 10, 110. The arm 10, 110 belongs to a machine tool (not shown in Figures 1 and 2) which controls the movement of the arm 10. Thanks to the articulated arm 10, 110 the user can insert the fiber 9, 109 into the channel 7, 107, choose the portion of the channel 7, 107 to be irradiated as required, for example if one portion needs to be cured more than another.

FIG. 3 represents a cooking or polymerization module for

200 for baking or polymerizing a device 201 according to a third embodiment of the invention.

ST012-104en The baking or polymerization module 200 makes it possible to bake or polymerize the core 202 manufactured by SLA. The cooking module 200 comprises a sealed chamber 203 in which the core 202. The chamber 203 is placed under vacuum by a vacuum pump 204. A plasma is injected into the chamber 203 by an injector 205. In this mode embodiment, the plasma is advantageously based on mercury Hg which has the advantage of emitting adequate light.

The chamber includes an electric pulse generator 206 which supplies filaments 207 fixed in the chamber 203 to activate the plasma by electric pulse.

In this embodiment, the core is in a plasma bath so that after activation of the plasma, UV radiation from the activated plasma irradiates the external and internal surfaces of the core.

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Reference numbers used in the figures

Device

Soul

Wall

External surface

Internal surface

Cavity

Channel

Radiation source

Optical fiber

Articulated arm

100 Device

102 Soul

103 wall

104 External surface

105 Internal surface

106 Cavity

107 Channel

108 radiation source

109 Fiber optics

110 Articulated arm

200 Cooking module

202 Soul

203 Room

204 Vacuum pump

205 Plasma injector

206 Electric generator

207 Filament

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Claims (16)

claims 1. Method for manufacturing a waveguide device (1, 100) comprising the following steps: - manufacturing a core (2, 102, 202) in photopolymer by additive manufacturing, said core (2, 102, 202) comprising lateral walls (3, 203) with external (4, 204) and internal (5, 205) surfaces ), the internal surfaces (5, 205) defining at least one cavity (6, 206), - Activate the polymerization of the core (2, 102, 202) produced by additive manufacturing by irradiating the core (2, 102, 202) with ultraviolet (UV) radiation so as to harden said core (2, 102, 202 ); - deposit a layer of metal on the internal surfaces; characterized in that the polymerization step comprises: - placing a source of UV radiation (8, 108) in said cavity (6, 206) so that the ultraviolet radiation propagates from the radiation source (8, 108) towards the internal surfaces (4, 104) then the external surfaces (5, 105) of said cavity (6, 106). 2. Method according to claim 1, said cavity (6, 106) comprising a waveguide channel or a filter channel (7, 107) for guiding electromagnetic radiofrequency waves. 3. Method according to one of claims 1 or 2, in which the polymerization step comprises: - Insert an optical fiber (9, 109) in said cavity (6, 106), said fiber (9, 109) being capable of emitting UV radiation in an axial and / or radial direction of the fiber relative to the longitudinal axis (9, 109). 4. Method according to one of claims 1 to 3, the polymerization step comprising: - Moving said fiber (9, 109) in the cavity axially and / or radially so as to irradiate a selected portion of the internal surface (4, 104) of the cavity. 5. Method according to claims 1 or 2, in which the polymerization step comprises: ST012-104fr - disposing said core (2, 102, 202) manufactured by additive manufacturing in a sealed chamber (204); - Introducing a plasma at least into the cavity (6, 106), said plasma being activatable by electric pulse to generate ultraviolet radiation; - activating the plasma in the cavity (6, 106) by electrical impulse so that the activated plasma in the cavity (6, 106) emits ultraviolet radiation which propagates from inside the cavity (6, 106) towards the internal surfaces (5, 105). 6. Method according to claim 5, the method comprising: - Vacuum the chamber (204) before introducing the plasma. 7. Method according to one of claims 5 to 6, the plasma comprising mercury 8. Method according to one of claims 1 to 7, the polymerization step comprising: - Insert the core (2, 102, 202) in a UV oven so as to irradiate the external surfaces (4, 104) of the core (2, 102, 202). 9. Method according to one of claims 1 to 8, in which the additive manufacturing is chosen from stereo-lithography ("SLA"), manufacturing by ink jets ("binder jetting"), DED ("Direct Energy Déposition "), EBFF (" Electron Beam Freeform Manufacturing "), FDM (" Fused Déposition Modeling "), PFF (" Plastic Freeforming "), by aerosols, BPM (" Ballistic Particle Manufacturing "), powder bed, SLS (" Selective Laser Sintering ”), ALM (“ Additive Layer Manufacturing ”), polyjet, EBM (“ Electron Beam Melting ”), preferably by stereo-lithography (“ SLA ”). 10. Method according to one of claims 1 to 9, the photopolymer comprising epoxy derivatives, acrylates or antimony. 11. waveguide device (1, 100) manufactured according to one of claims 1 to 10. ST012-104fr 12. Polymerization module (200) for hardening a waveguide device (1, 101), said device comprising a core (2, 102, 202) made of photopolymer by additive manufacturing, said core (2, 102, 202) comprising side walls (3, 103) with external (4, 104) and internal (5, 105) surfaces, the internal surfaces (5, 105) defining at least one cavity (6, 106), characterized in that said module (200) comprises a source of ultraviolet radiation (8, 108) intended to be disposed in said cavity (6, 106) so that the ultraviolet radiation which propagates from inside the cavity (6, 106) towards the internal surfaces (5, 105). 13. Module (200) according to claim 12, in which the radiation source (8, 108) is an optical fiber (9, 109), said fiber (9, 109) being articulated on an articulated arm (10, 110) to control the axial and / or radial movement of said fiber (9, 109). 14. Module (200) according to claim 12, wherein the radiation source (8, 108) comprises a plasma activated by electric pulse to generate said UV radiation. 15. Module (200) according to claim 14, in which said module (200) comprises: - A sealed chamber (204) intended to receive said core (2, 102, 202) manufactured by additive manufacturing; - a plasma source for introducing a plasma at least into the cavity (6, 106), said plasma being activatable by electric pulse to generate ultraviolet radiation; - an electric pulse generator (206) to activate the plasma in the cavity (6, 106). 16. Module (200) according to claim 15, wherein the plasma source introduces plasma into the chamber (203) so that the core (2, 102, 202) is in a plasma bath.