WO2003030597A2

WO2003030597A2 - Machine and installation for tracing on a support

Info

Publication number: WO2003030597A2
Application number: PCT/FR2002/003388
Authority: WO
Inventors: Régis Nouet
Original assignee: Automa-Tech
Priority date: 2001-10-04
Filing date: 2002-10-04
Publication date: 2003-04-10
Also published as: AU2002347294A1; WO2003030597A3; FR2830719A1

Abstract

The support is coated with a thin layer consisting of a mixture containing a compound capable of absorbing the energy produced by the impact of said laser beam for wavelengths ranging between 400 and 650 nm. The machine comprises: an assembly for supporting and moving said support, a laser radiation source whereof the wavelength ranges between 400 and 650 nm, deflecting means for sweeping across at least part of the surface of said support, and means for modulating said laser beam in accordance with the pattern to be produced on said support.

Description

"Machine and installation for tracing on a support"

The subject of the present invention is an installation for making a trace on a support which uses a thin layer sensitive to laser radiation and a machine capable of being part of the installation for exposing said thin layer with a view to producing the printed circuit. .

The invention relates, in general, the production of printed circuits and more particularly the production of printed circuits by the technique known as direct ablation of a resist layer covering the surface of the support intended to constitute the printed circuit. Even more precisely, the invention relates more particularly to the use of a composition intended to produce the thin layer, this composition being able to be used in relation to a laser having specific characteristics to allow the ablation of the layer. By ablation, it should be understood that, under the effect of the impact of the laser beam, the layer of material is physically removed over its entire thickness.

The printed circuits are constituted by an insulating support on one of the faces or on the two faces of which one carries out conductive traces constituting conductive tracks to connect between them electrical or electronic components fixed on the insulating support.

FIGS. 1A and 1B illustrate a well-known technique for producing a printed circuit. In this so-called light beam exposure technique, the support 110 is constituted by an insulating substrate 112, a conductive layer 114, for example a layer of copper or a copper alloy, and a photosensitive layer 116 called the reserve layer. or in English "resist". Opposite one face of the support 110 thus prepared, there is, in an exposure machine, a plate 118 which comprises transparent zones 120 and zones opaque to light 122 defining the layout of the conductive tracks to be produced on the support insulating. The assembly is subjected to a light beam 124 produced by a light source 126.

As shown in FIG. 1B, after the insolation phase, the zones 116a of the photosensitive layer 116 exposed have a different chemical composition from the zones 116b which are not exposed. This exposure is carried out using an exposure machine. By selective chemical attack, the exposed areas or the non-exposed areas are removed and the remaining part of the photosensitive layer 116 serves as a mask for the subsequent chemical attack on the conductive layer 114. In this way, by chemical attack, the effective trace of the conductive tracks is obtained from the conductive layer 114. The traces of conductive tracks on the printed circuits becoming more and more complex and denser, it has been proposed to insulate the photosensitive layer 116 of the support 110 using a laser beam 130, this laser beam being produced by a laser source 132 emitting the beam 130 which is modulated by the acousto-opic modulator 134 and which scans the surface of the printed circuit to be produced, for example using a polygonal rotary mirror 136. European patent application 1,098,557 in the name of AUTOMA-TECH describes such a machine. In addition, the support 110 is moved in a direction X, X ′ orthogonal to the scanning direction so that the entire surface of the support is scanned by the modulated laser beam 130.

In these two exposure techniques, a photosensitive layer 116 is obtained in fine, some parts of which are maintained and other parts have a modified chemical composition capable of being attacked chemically to cause the removal of either portions with transformed chemical composition, or the portions of the unprocessed photosensitive layer.

It is understood that it would be advantageous to have a technique which allows by scanning to directly remove the portion of the photosensitive layer or more generally of the reserve layer 116 corresponding to the areas of the conductive layer 114 which must not be masked .

Such a technique has already been proposed in particular in US Pat. No. 4,114,059. This document describes a technique for ablation of a resist layer or "resist" layer constituted by a polymer and which is subjected to a laser beam, emitting in the ultraviolet, whose wavelength is less than 220 nm. However, this technique has certain disadvantages insofar as, to effectively obtain the localized ablation of the entire thickness of the resist or resist layer, it is necessary to carry out several laser impacts at the same point of the layer. reserve. In addition, the impacts of laser beam are defined by a mask interposed between the laser beam and the reserve layer.

There is therefore a real need to have a machine and an installation which actually allow the ablation of a reserve layer using a laser beam to produce in particular a printed circuit.

A first object of the invention is to provide an installation for making a layout on a support.

According to the invention, the installation is characterized in that it comprises:

- Means for producing on at least one face of said support a layer consisting of a mixture of a first compound capable of being deposited in a thin layer and of seeing its chemical composition modified under the effect of the impact of radiation without removing said layer at the point of impact, said modified or unmodified chemical composition being capable of being selectively removed by a chemical agent, and a second compound capable of absorbing the energy produced by impact said laser beam for wavelengths between 400 and 650 nm and capable of triggering the removal of said first compound at the point of impact, said second compound representing less than 5% of said composition by weight; and

- an exposure machine comprising:

.. a support and displacement assembly for said support; .. at least one source of laser beam whose wavelength is between 400 and 650 nm; and

.. means for moving at least one laser beam produced by said source on the surface of said layer of material and for modulating said beam, whereby said layer of material is completely removed over its entire thickness at the points of impact of said modulated beam .

It is understood that, on the one hand, thanks to the addition to a standard material usually used to produce the reserve layer for the production of a printed circuit of a second compound capable of absorbing the energy produced by the impact of the laser beam whose wavelength is between 400 and 650 nm, it is possible, at using a single impact of the laser beam, to obtain the complete ablation of the entire thickness of the layer and therefore the production of a mask having a high quality definition. Thanks to the direct ablation of the portions of the thin layer having been struck by the laser beam, the conventional steps of removing the portions of exposed surfaces are dispensed with.

In addition, the use of a laser beam with a wavelength of 532 nm makes it possible to achieve significant power levels which allow the circuits to be produced with an industrial rate. This is not the case with current laser emitting in the UV.

A second object of the invention is to provide an exposure machine capable of being used in the installation defined above.

According to the invention, the exposure machine for producing a printed circuit from a support is characterized in that said support is coated with a thin layer constituted by a mixture of a first compound capable of being deposited in thin layer and to see its chemical composition modified under the effect of the impact of radiation without there being removal of said layer at the point of impact, said modified or unmodified chemical composition being capable of being selectively removed by a chemical agent, and a second compound capable of absorbing the energy produced by the impact of said laser beam for wavelengths between 400 and 650 nm and capable of triggering the removal of said first compound at the point impact, said second compound representing less than 5% of said composition by weight and in that it comprises:

. a support and displacement assembly for said support; . a source of laser radiation whose wavelength is between 400 and 650 nm;

. deflector means for scanning at least a part of the surface of said support using at least one laser beam produced by said source; and

. means for modulating said laser beam as a function of the design to be produced on said support, whereby said layer is completely removed over its entire thickness at the points of impact of said beam. Other characteristics and advantages of the invention will appear better on reading the following description of several embodiments of the invention given by way of nonlimiting examples. The description refers to the appended figures, in which:

- Figures 1A and 1B, already described, show in a simplified manner a sunshine technique using a conventional light source;

- Figure 2 shows, in a simplified way, the exposure of a reserve layer using a laser beam;

- Figures 3a and 3b illustrate the use of the composition in a direct ablation process; - Figure 4a is a simplified elevational view of an exposure machine with direct laser ablation;

- Figure 4b is a view of the optical system of the exposure machine of Figure 4a; and

- Figure 5 is an overall diagram, seen from above of the installation of direct ablation by laser beam.

As already indicated briefly, the invention is based in particular on the use of a particular composition making it possible to produce a thin layer on a support subjected to laser radiation of well-defined wavelength which makes it possible to obtain the ablation of this layer under the effect of the impact of the laser beam on it and therefore of defining a trace on the surface of this support in the layer, as a function of the scanning of the laser beam.

This composition consists of a mixture of a first compound usually called resist or photoresist, that is to say a compound capable of being deposited in a thin layer on the support and of having its chemical composition modified under the effect of the impact of radiation without removing the layer at the point of impact. The modified chemical composition can be removed subsequently by a selective chemical agent while the unmodified composition part is not attacked by this agent. Alternatively, for certain resists, it is the unmodified layer which can be removed by a selective chemical agent.

Such compounds are commonly found in commerce, for example under the following brands: - the compound called XV750 from the company Coates;

- compound P2000 from the company Vantico; or - Compounds SP22 and SP24 from the company Shippley.

The material also consists of a second compound which is capable of absorbing the energy produced by the impact of the laser beam for the given wavelengths which are between 400 and 650 nm and capable of triggering the removal of the first material formed by the resist at the point of impact.

There are several materials capable of being activated by a laser beam, the wavelength of which is between 400 and 650 nm. Mention may in particular be made of eosin. Mention may also be made of rhodamine.

The material intended to form the thin layer is obtained by mixing the first compound of the photoresist type and the second compound of the eosin type, so that the second compound represents less than 5% of the composition by weight and preferably less than 2 %.

In FIGS. 3A and 3B, the use of an exposure layer according to the invention has been illustrated for producing a trace on a printed circuit. In FIG. 3A, the support 140 is shown, consisting of a plate of insulating material 142 on which a conductive layer 144. is produced. The support 140 is covered by a layer 144 of the resist material described above. The production of the layer of material 144 can be obtained by electrolytic deposition or by coating depending on the nature of the compound. Preferably, the thickness of the layer 146 of material is less than 12 μm and preferably equal to 8 μm. As shown in FIG. 3B, the support 140 coated with its reserve layer 146 is subjected to the impact of a laser beam symbolized by 148. According to the invention, the laser beam has a wavelength between 400 and 650 nm and, preferably, equal to 532 nm. Preferably, the laser is of the pulsed type. Its illumination per unit area and per pulse received by the support is preferably between 10 ιτύ / cm ² / pulse and 200 mJ / cm ² / pulse. The tests carried out with the composition described above using a laser beam whose wavelength is equal to 532 nm make it possible to obtain in the reserve layer 146 areas such as 150, 152 in which the reserve layer 146 is completely removed over its entire thickness under the effect of the laser beam 148. In addition, the tests performed have shown that the sides, for example the sides 150a, 150b of the removed area 150, have an excellent definition compatible with the definition required for the production of printed circuits.

Referring first to Figure 4a, we will describe the entire exposure machine according to the invention. This comprises a frame comprising a lower part 12 and an upper part 14, this frame being of course fixed. The lower part 12 of the frame supports a movable plate 16 to receive a panel 20. The plate 16 can move in a direction X, that is to say in a direction orthogonal to the plane of the figure. For this, there is shown schematically ball screw systems 18, 19 driven by motors. The support plate 16 is intended to receive the printed circuit panel 20 which must be subjected to the laser beam in order to define the conductive tracks to be produced on the printed circuit panel. The panel is previously coated with a thin layer made with the composition described above. The upper part 14 of the frame supports optical units which have been represented schematically by rectangles 22ι, 22 ₆ . Each optical unit 22 delivers a laser beam at its output, this laser beam having a direction orthogonal to the plane of the panel 20, that is to say a vertical direction. The scanning zones of each laser beam are represented symbolically by the dotted lines 24, the scanning being carried out in the direction Y orthogonal to the direction X.

The optical assembly comprises a laser 40 of wavelength preferably equal to 532 nm. The beam F delivered by the laser 40 is applied to the input of a beam splitter 42 which divides this beam into 6 divided beams FD1, FD2, FD3, FD4, FD5, FD6. Preferably, all of the divided beams FD have powers of the same order of magnitude and comprise a limited number of wavelengths which are moreover very close to one another.

Each divided beam FD is applied to the input of an electro-optical modulator 46 associated with a control circuit 47. As is well known, the modulator can take a passing state or a non-passing state interrupting the transmission of the laser beam . Each beam leaving a modulator is applied to the input of an optical unit 22. The optical unit comprises an input optic 44 and a optical system 48 intended to direct the beam towards a rotary polygonal mirror 50. As is well known, the polygonal mirror 50 is constituted by a plurality of reflecting faces 52. In the particular case of FIG. 2, there are six reflecting faces . In other embodiments, the mirror could have ten faces. The mirror 50 is rotated by a motor 54 associated with a control circuit 56 and with position sensors.

Such a laser beam generator is described in detail in EP 1 098 403 in the name of AUTOMA-TECH As is well known, the laser beam leaving the optical system 48 strikes a facet 52 of the polygonal mirror at an incidence which varies so continuous according to the rotation of the mirror allowing the angle of the emerging beam to be deflected continuously. A continuous deflection of the beam reflected by the face is thus obtained. The angle in which the reflected beam is deflected by the rotation of the facet of the polygonal mirror is symbolically represented by 58. The deflection of the beam by a facet of the rotating mirror corresponds to the scanning of a segment S of the panel. The definition of the start of the scanning and the end of the scanning by the laser beam is carried out by synchronizing the control of the on or not on state of the modulator with the rotation of the polygonal mirror. The modulator is of course non-passing during the periods of time when the incident laser beam should have passed from one facet of the mirror to the next. Each facet thus defines a scanning period corresponding to a segment. The beam is applied to the input of a objective 60. The object 60 has the dual function of focusing the laser beam so that its diameter is, in the particular case considered, equal to 20 μm, that is to say say greater than the pixel and direct the laser beam in the direction X'X 'of the optical axis of the optical unit. Such a deflection and modulation system for laser beams is described in EP 1 098 557 in the name of AUTOMA-TECH.

The optical unit 22 finally comprises, for its essential elements, a deflector mirror 62 which is orthogonal to the optical axis X'-X 'of the optical unit. The mirror 62 which reflects the deflected laser beam in a vertical direction, that is to say towards the panel support 16 and therefore towards the panel itself and orthogonally to it. The deviation of the beam is such that the deflected beam strikes the mirror 62 at points which extend over a length 11 centered on the optical axis X'X '. The optical components are produced in such a way that the length 11 is greater than the length corresponding to the scanning zone Z of the panel associated with the laser beam considered.

Referring now to Figure 5, we will describe the entire display installation of printed circuit boards.

This assembly includes a station A for preparing the support intended to constitute the printed circuit. At this station, the thin layer of the composition described above is produced on one side or on both sides of the support. Depending on the nature of the composition, the thin layer can be produced by coating or by electrolytic deposition. This layer has a thickness of the order of 8 μm. After a possible drying step, a conveyor C makes it possible to transfer the prepared supports to the exposure machine M which has already been described in connection with FIGS. 4a and 4b.

In a preferred example of implementation of the invention, the material is obtained by mixing resist of the brand XV 750 from the company Coates with eosin, the eosin representing 1% by weight of the mixture. This composition is spread on the support so that a layer of uniform thickness equal to 8 microns is obtained.

In this example, for the exposure machine, a diode pumped solid-state laser is used, preferably in "locked mode" or in "Q-switched" mode. This laser is of the Neodyme-Yag or Neodyme-YV0 ₄ or Neodyme-YLf type. It delivers a laser beam with a wavelength of 1064 nm. It is associated with a frequency doubling crystal to finally obtain a laser beam having a wavelength of 532 nm. This laser is adjusted to produce an illumination per unit area and per pulse of 100 mJ / cm ² / pulse, at the output of the optical system described above, that is to say an illumination applied to the panel.

Depending on the materials used, it is possible to vary the thickness of the layer of ablation material. We understand that the thinner the layer, the more precise the line. However, the layer that has not been removed must constitute an effective mask for attacking the layer. conductive by a chemical agent. It appears that this thickness cannot be attrrea i innfféόrriieoui irreo à à 2? o nuu 3 ^ m miicrrronnnsc

Claims

1. Installation for making a layout on a support, characterized in that it comprises: - means for producing on at least one face of said support a layer consisting of a mixture of a first compound capable of being deposited in a layer thin and to see its chemical composition modified under the effect of the impact of radiation without there being removal of said layer at the point of impact, said modified or unmodified chemical composition being capable of being selectively removed by a chemical agent, and a second compound capable of absorbing the energy produced by the impact of said laser beam for wavelengths between 400 and 650 nm and capable of triggering the removal of said first material at the point d impact, said second compound representing less than 5% of said composition by weight; and

- an exposure machine comprising:

.. a support and displacement assembly for said support;

.. at least one source of laser beam whose wavelength is between 400 and 650 nm; and

2. Installation according to claim 1, characterized in that the thickness of said layer is less than 20 microns.

3. Installation according to claim 2, characterized in that the thickness of said thin layer is between 2 and 12 microns.

4. Installation according to any one of claims 1 to 3, characterized in that said laser beam is produced by a pulsed laser of the solid type Neodyme-Yag, Neodyme-YV04 or Neodyme-YLf.

5. Installation according to claim 4, characterized in that said pulsed laser has a wavelength equal to 1064 nm and in that the laser is preferably associated with a doubler to obtain a wavelength of 532 nm.

6. Installation according to any one of claims 1 to 5, characterized in that the illumination produced by the laser beam received by the panel is between 10 mJ / cm ² / pulse and 200 mJ / cm ² / pulse.

7. Installation according to any one of claims 1 to 6, characterized in that the weight content in the second compound is at most equal to 2%.

8. Installation according to any one of claims 1 to 7, characterized in that the wavelength of the laser beam is of the order of 532 nm.

9. Installation according to any one of claims 1 to 8, characterized in that said second compound is chosen from the group comprising eosin and rhodamine.

10. Exposure machine for producing a printed circuit from a support, characterized in that said support is coated with a thin layer consisting of a mixture of a first compound capable of being deposited in a thin layer and of see its chemical composition modified under the effect of the radiation without removing said layer or point of impact, said modified or unmodified chemical composition being capable of being selectively removed by a chemical agent , and a second compound capable of absorbing the energy produced by the impact of said laser beam for wavelengths between 400 and 650 nm and capable of triggering the removal of said first material at the point of impact, said second compound representing less than 5% of said composition by weight; and in that said machine comprises:

. a support and displacement assembly for said support;

. a source of laser radiation whose wavelength is between 400 and 650 nm;

. means for modulating said laser beam as a function of the design to be produced on said support, whereby said layer is completely removed over its entire thickness at the points of impact of said beam.

11. Exposure machine according to claim 10, characterized in that said laser beam is produced by a pulsed laser of the solid type Neodyme-Yag, Neodyme-YV04 or Neodyme-YLF.

12. Exposure machine according to claim 10 or 11, characterized in that said pulsed laser has a wavelength equal to

1064 nm and in that the laser is associated with a frequency doubler to obtain a wavelength of 532 nm.

13. An exposure machine according to any one of claims 10 to 12, characterized in that the illumination produced by the laser beam received by the panel is between 10 mJ / cm ² / pulse and 200 mJ / cm ² / impulse.

14. Machine according to any one of claims 10 to 13, characterized in that said thickness of the layer is between 2 and 12 microns.

15. Machine according to claim 14, characterized in that said thickness of the thin layer is of the order of 8 microns.

16. Machine according to any one of claims 10 to 15, characterized in that said second compound is chosen from the group comprising eosin and rhodamine.

17. Machine according to any one of claims 10 to 16, characterized in that said deflector means comprise at least one rotary polygonal mirror.

18. Machine according to any one of claims 10 to 17, characterized in that said laser radiation source comprises a laser radiation generator and means for dividing said beam emitted by said generator into a plurality of divided laser beams.