EP1852002A1

EP1852002A1 - Method for producing electrically conductive patterns on a non-developable surface of an insulating substrate, and resulting device

Info

Publication number: EP1852002A1
Application number: EP06709341A
Authority: EP
Inventors: Christian Desagulier; Alain Lacombe; Bruno Esmiller
Original assignee: Astrium SAS
Current assignee: ArianeGroup SAS
Priority date: 2005-02-23
Filing date: 2006-02-20
Publication date: 2007-11-07
Also published as: US7721426B2; FR2882490B1; US20080210456A1; WO2006090050A1; FR2882490A1

Abstract

The invention concerns a method for producing electrically conductive patterns on a non-developable surface of an insulating substrate, and the resulting device. The invention is characterized in that it consists in: coating the non-developable surface (6) uniformly with a layer of electrically conductive material (9), which is in turn coated with a layer of protective material (10), and then, using a mobile laser head, eliminating by laser ablation the portions of said protective substance layer (10) which do not cover said electrically conductive patterns, then eliminating the portions of said electrically conductive material (9) exposed by the elimination of said portions of said protective material layer (10)

Description

Process for producing electrically conductive patterns on a non-developable surface of an insulating substrate, and device obtained

The present invention relates to a method for producing electrically conductive patterns on a non-developable three-dimensional surface of an insulating substrate. Although not exclusively, it is particularly suitable for producing, on a surface at least approximately in the form of a paraboloid, a hyperboloid, etc., a polarization grid (frequency reuse antenna) or a series of resonant patterns (dichroic antennas). The invention also relates to devices comprising such a substrate, said non-developable surface carrying said electrically conductive patterns, made according to the method.

It is known that, in order to produce a printed circuit on a plane face of an electrically insulating substrate, it is first of all uniformly covering said surface with a layer of a metal, such as copper or aluminum, after which this metal layer is itself uniformly covered with a photosensitive product. Then, the photosensitive product is exposed to a light beam, through a mask corresponding to the printed circuit to obtain. Such exposure renders chemically resistant the portions of the photosensitive material directly above the portions of the metal layer to form the printed circuit, so that appropriate etching can then selectively remove the portions of the photosensitive product. which have not been made chemically resistant by exposure, as well as the portions of metal layer under them.

As a result of said chemical attack, the desired printed circuit is thus obtained. In the case where it is desired to apply this method to the production of printed circuits on a surface which is no longer flat, but can not be developed in three dimensions, difficulties would be encountered when the mask is applied to said surface. . Indeed, for obvious reasons of convenience and accuracy, such a mask is flat. Also, it would be necessary to cut said mask into pieces of reduced areas and apply by juxtaposing said parts on said non-developable surface, or to make said mask of a flexible material that can be applied by deformation thereon. In both cases, the printed circuit obtained would be imprecise, both as regards the shape and the position of the patterns which compose it.

It will be noted moreover that if, in a variant, said printed circuit is made on a plane auxiliary substrate intended to be subsequently applied to the non-developable surface, the same difficulties as those mentioned above with regard to the masks are encountered.

In order to overcome these drawbacks and to make it possible to produce precise printed circuits directly on non-developable three-dimensional surfaces, the method described in US Pat. No. 4,738,746 can be implemented; EP-0 241 331 and FR-2 596 230. In this process, as in the one mentioned above, one begins by uniformly covering said surface, then undevelopable three-dimensional, a layer of a material. electrically conductive, which is in turn covered with a layer of a protective material. After forming said layers of conductive material and protective material, the outline of said patterns is mechanically traced thereon by means of a tool that digs grooves whose depth is at least equal to the thickness of said layer of protection, and then said layers are subjected to the action of a chemical agent capable of selectively attacking said electrically conductive material without attacking said material. protection, this etching operation being continued for a time sufficient for said electrically conductive material to be removed over its entire thickness above said grooves, after which the parts of said layer are peeled off from the substrate; electrically conductive material exterior to said patterns.

Thus, by virtue of this latter method, electrically conductive patterns can be made directly on non-developable three-dimensional surfaces without resorting to a mask or an auxiliary substrate with which, moreover, it would be technically difficult to obtain optical characteristics. They are as precise in their shape as in their position on the said surfaces.

In such an earlier method, for the tracing of the contours of said electrically conductive patterns, a tool provided with at least one etching tip or at least one cutting blade is used, said tool being mounted in a machine (eg controlled digital and five axes of rotation) responsible for moving relative to the non-developable surface.

It is thus possible to produce non-developable surface devices carrying electrically conductive patterns in an easy and precise manner. For example, the implementation of this known method allows the realization of high quality grid reflectors, able to work in the Ku band (from 1 1 to 18 GHz) and formed of at least one network of parallel conductive wires, these conductors son having a width of 0.25 mm, a thickness of 35 micrometers and being distributed in a pitch of 1 mm on an area at least approximately in the form of paraboloid, whose opening diameter can reach 2300 mm.

However, this prior process has technical and economic limits. For example, if instead of a grid reflector for working in the Ku-band, it is desired to make such a reflector for the Ka band (from 20 to 30 GHz), the width, the thickness and the distribution pitch of the conducting wires become smaller (for example 0.15 mm, 18 micrometers and 0.5 mm respectively) and This results in difficulties due to the smallest width and the smallest thickness of the conductive wires and the zones between wires:

- The trace parameters of the conductive patterns (pressure and arrangement of the tips or etching blades) and the etching parameters (duration) become more sensitive, so that geometric defects and embrittlement of the conductive threads result. when peeling;

when tracing the conducting wires, the edge effects become significant, the tips or blades pushing, in the manner of a plow, the conductive material of reduced thickness and reducing the adhesion of the conductive wires to the substrate; and - the zones between wires are fragile and are therefore liable to break during peeling.

As a result, care must be taken to ensure that the tool always performs perfect tracing and that the process flow must be slowed down, which increases the manufacturing costs of such a reflector. The present invention aims to overcome these disadvantages.

To this end, according to the invention, the method for producing electrically conductive patterns on a non-developable three-dimensional surface of an electrically insulating substrate, the method according to which one begins by uniformly covering said non-developable surface with a layer of an electrically conductive material, which is in turn covered with a layer of a protective material, after which portions of said layer of protective material which do not cover areas of said layer of electrically conductors trice to form said patterns, and then removing portions of said layer of electrically conductive material discovered by the removal of said portions of said layer of protective material, is remarkable in that the removal of portions of the layer of protective material , which do not cover said zones of said layer of electrically conductive material to form said patterns, is made by laser ablation using a laser head that is moved, with respect to said non-developable surface covered with said layer of electrically conductive material and said layer of protective material, to cover all portions of said layer of protective material which do not cover said areas of said layer of electrically conductive material to form said electrically conductive patterns.

Thus, thanks to the present invention, it eliminates any mechanical contact with the layer of protective material and with the layer of electrically conductive material during the production of said electrically conductive patterns, which avoids the disadvantages mentioned herein. above with regard to the process according to US Pat. No. 4,738,746. It will be noted that the document US Pat. No. 5,364,493 already describes a method for producing electrically conductive patterns on a substrate by laser ablation. However, in this document, there is provided a fixed laser beam passing through a plane mask, so that the method described can not be suitable for producing electrically conductive patterns on a non-developable three-dimensional surface.

For the movement of the laser head provided by the process according to the present invention, it is advantageous to use a machine similar to that mentioned above, provided for the implementation of the previous method of US-4,738,746. In an advantageous embodiment, the portions of the layer of electrically conductive material, discovered by laser ablation of said portions of the layer of protective material, are removed by the action of a chemical agent capable of attacking the material electrically conductive without attacking said protective material.

Preferably, said chemical agent may be iron perchloride, when said layer is copper.

Moreover, said protective material, insensitive to the action of said chemical agent, may be an organic varnish. After removal of the portions of said layer of electrically conductive material discovered by laser ablation of said portions of said layer of protective material, it is possible either to eliminate or leave the remains of said layer of protective material covering said electrically conductive patterns. The invention also relates to a device, such as a reflector for example, comprising an electrically insulating substrate carrying electrically conductive patterns on one of its non-developable surfaces with three dimensions and remarkable in that said electrically conductive patterns are realized by the implementation of the method according to the invention specified above.

The figures of the appended drawing will make it clear how the invention can be realized. In these figures, identical references designate similar elements.

FIG. 1 schematically represents an antenna device, whose reflector is provided with electrically conductive patterns produced by the implementation of the method according to the present invention.

Figure 2 is an enlarged schematic front view of a portion of the reflector of Figure 1, illustrating the shape and arrangement of said electrically conductive patterns. FIGS. 3A to 3D schematically illustrate, in section, steps of the method according to the present invention, applied to the production of the electrically conductive patterns of FIGS. 1 and 2.

In FIGS. 2 and 3A to 3D, the surface of the reflector carrying the said electrically conductive patterns, although concave and non-developable, is shown flat for ease of drawing. FIG. 1 diagrammatically shows a device antenna 1 provided with an antenna reflector 2 (shown in diametral section), supported by a bearing surface 3, via a support 4.

The reflector 2 comprises an electrically insulating substrate 5 (for example made of composite material), the surface 6 opposite the support 4 is concave and has a non-developable shape, for example the at least approximate shape of a paraboloid, a hyperboloïde, etc ... On this surface 6 non-developable three-dimensional, the reflector 2 carries electrically conductive patterns, formed in the example shown by conductors 7 parallel to each other and equidistant. Each conductor 7 has a rectangular section of width et and thickness e and the distribution pitch of the parallel conductors 7 is designated p. Thus, between two adjacent conductors 7 is formed a separation zone 8, band-shaped having a width equal to p (see also Figure 2).

For the realization of the reflector 2 schematically illustrated in Figures 1 and 2, it begins by uniformly covering the non-developable surface 6 of the substrate 5 by a layer 9 of an electrically conductive material (see Figure 3A) of thickness equal to e . Such a layer 9 may, for example, be deposited under vacuum on the surface 6 or be attached thereto by gluing. It may be metallic and for example constituted by copper or aluminum. Then, by any known means, said layer of electrically conductive material 9 is covered by a layer 10 of a protective material, for example an organic varnish.

In accordance with the present invention and as illustrated in FIG. 3B, the laser protective ablation portions of the protective material layer 10 are then laser-ablated by means of a moving laser head. Placing the separation zones 8, that is to say which do not cover the zones of the layer 9 to form the conductors 7. After this laser ablation, it does not remain on the layer of electrically conductive material anymore. 9 lines 10.7 protective material, above the future conductors 7 and having the width I.

After the operation illustrated in FIG. 3B, the protective lines 10.7 and the conductive layer 9 are subjected to the action of a chemical agent, for example applied by spraying or dipping. This chemical agent attacks, between the lines 10.7, the layer of electrically conductive material 9, without attacking said lines 10.7 of protective material. The chemical agent, then selectively eliminating the conductive layer 9, is for example iron perchloride, when the layer 9 is copper. The action of the chemical agent on the conductive layer 9 is continued until it is removed over its entire thickness in line with the separation zones 8 (Figure 3C). This results in driver training 7.

Then, rinsing is performed on the entire substrate 5 and said layers 9 and 10 partially cut.

Optionally, the removal of the lines 10.7 covering the conductors 7 (FIG. 3D) is also carried out. However, the protective material of the layer 10 (for example an organic varnish) is chosen to possess characteristics that make it compatible with the environment. (eg spatial) in which the reflector will be called to work. Also, the lines 10.7 can then remain on the conductors 7 and serve as protection therefor, for example against corrosion.

From the foregoing, it will be appreciated that the method according to the present invention is:

- Economical and fast, especially since the laser ablation speed can be very fast (for example 0.3 m / s) and that one can use multiple ablation laser sources simultaneously;

- Reversible, since a programming error of the machine or an ablation anomaly can be corrected, the ablation can resume after partial reconstitution of the layer 10 of protective material, without alteration of the substrate 5 and the conductive layer 9 ;

- robust, since it frees itself from the mechanical cutting of very fine patterns; and - versatile, since it allows the realization of conductive patterns of various shapes.

By way of example, it is mentioned hereinafter that the implementation of the method according to the invention made it possible to manufacture a reflector such as that represented in FIGS. 1 and 2 with = = 0.125 mm, p = 0.5 mm. and e = 18 micrometers, the diameter D of the aperture of said reflector being equal to

2300 mm.

Claims

1. A method for producing electrically conductive patterns (7) on a non-developable three-dimensional surface (6) of an electrically insulating substrate (5), wherein first uniformly covering said non-developable surface (6) with a layer of an electrically conductive material (9), which is in turn covered with a layer of a protective material (10), after which portions of said layer of protective material (10) which do not cover areas of said layer of electrically conductive material (9) to form said patterns (7), then remove portions of said layer of electrically conductive material (9) discovered by removal of said portions of said layer of protective material (10), characterized in that the removal of the portions of the layer of protective material (10), which do not cover said areas of said layer of electrically conductor (9) to form said patterns (7), is performed by laser ablation with the aid of a moving laser head that is moved, with respect to said non-developable surface (6) covered with said layer of electrically conductor (9) and said layer of protective material (10), to cover all portions of said layer of protective material which do not cover said areas of said layer of electrically conductive material to form said electrically conductive patterns (7) .

2. Method according to claim 1, characterized in that the portions of the layer of electrically conductive material (9), discovered by laser ablation of said portions of the layer of protective material (10), are removed by the action a chemical agent capable of attacking the electrically conductive material without attacking said protective material.

3. Method according to claim 2, characterized in that the chemical agent removing said layer of conductive material (9) is iron perchloride, when said layer (9) is copper.

4. Method according to one of claims 2 or 3, characterized in that said protective material (10), insensitive to the action of said chemical agent, is an organic varnish.

5. Method according to one of claims 1 to 4, characterized in that, after removal of the portions of said layer of electrically conductive material (9) discovered by laser ablation said portions of said layer of protective material (10) the remnants (10.7) of said layer of protective material (10) covering said electrically conductive patterns (7) are eliminated.

6. Method according to one of claims 1 to 4, characterized in that, after removal of the portions of said layer of electrically conductive material (9) discovered by laser ablation said portions of said layer of protective material (10) leaving the remainders (10.7) of said layer of protective material (10) covering said electrically conductive patterns (7).

7. Device comprising an electrically insulating substrate (5) carrying electrically conductive patterns (7) on one of its non-developable three-dimensional surfaces (6), characterized in that said electrically conductive patterns (7) are realized by the implementation of the process specified in one of claims 1 to 6.