CH705945A2 - Method for manufacturing resonator e.g. hairspring resonator, for watch, involves modifying structure of zone of substrate to make zone more selective, and engraving zone to selectively manufacture resonator whose arm is formed with recess - Google Patents

Abstract

The method involves modifying the structure of a zone of a substrate by a laser so as to make the zone more selective, where pulse duration of the laser is from femtosecond to picosecond. The zone is engraved to selectively manufacture a component (101) i.e. resonator (300). The resonator is released from the substrate, where the substrate is made of single-crystal material, polycrystalline material, polymer or amorphous material such as ceramics or glass. A recess i.e. groove (310), is formed on an upper face (314) of an arm (304) of the resonator. An independent claim is also included for a resonator.

Description

The invention relates to a resonator comprising a body used in deformation as a spiral resonator or a tuning fork.

BACKGROUND TECHNOLOGY

It is known from the prior art that certain microtechnical parts made of monocrystalline or polycrystalline type materials, such as resonators, are produced by chemical etching. This technique involves providing the substrate to be etched and depositing a layer of photoresist on it. On this resin is placed a mask then the whole is exposed to light so that the structure of the photosensitive resin exposed to light is modified. This modified resin is removed by action of a chemical element leaving then bare, in places where the resin has been removed, the substrate.

Subsequently, these bare areas of the substrate are chemically etched to dig them. The chemical agent is chosen to attack only the substrate material and not the unmodified light-sensitive resin. The duration of this chemical etching step makes it possible to determine the dimensions of the recesses.

Similarly, it is conceivable that microtechnical parts are made by machining and / or polishing so that a drill or a polisher can be used to shape said parts.

A first disadvantage of this chemical etching technique is that it does not allow to make recesses with straight flanks. Indeed, the hollows obtained have inclined flanks. This means that the surface of the recess varies according to the depth that is to say that this surface grows or shrinks as the recess becomes deep. Generally this surface narrows with depth. This finding makes it necessary to adapt the theoretical calculations made to obtain right-sided hollows. Moreover, this variation of the profile of the recesses between the theory and the practice entails a variation of the characteristics.

SUMMARY OF THE INVENTION

The invention aims to overcome the drawbacks mentioned above by providing a manufacturing method for producing a component comprising recesses whose flanks have an easily achievable inclination.

For this purpose, the invention relates to a method for manufacturing a resonator in a substrate, characterized in that it comprises the following steps: a) modifying the structure of at least one substrate zone to make said at least one zone more selective; b) etching said at least one zone to selectively fabricate said resonator.

An advantage of the present invention is to make it possible to make recesses below the surface because the material used is chosen to be transparent to the laser. This allows the laser to be able to point to any point on the surface or under the surface of the resonator. The material is then made selective so that the subsequent chemical attack only operates on the material that has been modified by the laser. A method is thus obtained which makes it possible to produce complex and internal recesses.

[0009] Advantageous embodiments of the method according to the present invention are the subject of dependent claims.

In a first advantageous embodiment, the method further comprises the step of: c) releasing the component from said substrate.

In a second advantageous embodiment, the structure of said at least one zone is modified by a laser whose pulse duration is of the order of the femtosecond.

In a third advantageous embodiment, the substrate is made of monocrystalline material.

In another advantageous embodiment, the substrate is made of polycrystalline material.

In another advantageous embodiment, the substrate is made of an amorphous material such as a ceramic or a glass.

In another advantageous embodiment, the substrate is made of polymer.

In another advantageous embodiment, the component is a resonator comprising a base from which extend at least two parallel arms each having an upper face and a lower face and further comprising at least one recess made on one of the faces of one of the at least two parallel arms.

In another advantageous embodiment, said at least one recess is in the form of a groove having at least one of its vertical flanks.

In another advantageous embodiment, said resonator comprises a groove per arm.

In another advantageous embodiment, said resonator comprises a groove on the upper face of each arm and a groove on the underside of each arm.

In another advantageous embodiment, said resonator comprises two grooves per arm.

In another advantageous embodiment, said resonator comprises two grooves on the upper face of each arm and two grooves on the underside of each arm.

The present invention relates to a resonator comprising a base from which extend at least two parallel arms each having an upper face and a lower face, and at least one electrode group located on one of the at least two arms. parallel to electrically excite said at least two parallel arms, characterized in that it comprises at least two straight parallel blanks.

In a first advantageous embodiment, one of the faces of one of the at least two parallel arms comprises at least one recess in the form of a groove having vertical flanks.

In a second advantageous embodiment, said resonator comprises a groove per arm.

In a third advantageous embodiment, said resonator comprises a groove on the upper face of each arm and a groove on the lower face of each arm.

In another advantageous embodiment, said resonator comprises two grooves per arm. I

In another advantageous embodiment, said resonator comprises two grooves on the upper face of each arm and two grooves on the underside of each arm.

In another advantageous embodiment, the grooves comprise a projection that optimizes the electric fields, while increasing the alignment tolerances.

The invention also relates to a resonator comprising a flywheel coupled to a body formed of a bar wound on itself to form a hairspring characterized in that said body comprises at least one recess for locally modifying the rigidity. and thus adjust the frequency of the resonator and / or adjust the isochronism defect.

In an advantageous embodiment, said at least one recess comprises at least two parallel blanks.

In another advantageous embodiment, said body is made of quartz or ceramic or glass and in that it comprises locally parallel flanks along the entire length of said body.

BRIEF DESCRIPTION OF THE FIGURES

The objects, advantages and characteristics of the method according to the present invention will appear more clearly in the following detailed description of embodiments of the invention given solely by way of nonlimiting example and illustrated by the appended drawings in which: <tb> Fig. 1 <sep> schematically represents a front view of a resonator according to the prior art; <tb> Figs. 2a to 2e <sep> schematically represent the steps of the process according to the present invention; <tb> Figs. 3 and 4 <sep> schematically represent a first embodiment of the resonator according to the present invention; <tb> Fig. <Sep> schematically represents a variation of the first embodiment of the resonator according to the present invention; <tb> Fig. 6 <sep> schematically represents a second embodiment of the resonator according to the present invention; <tb> Figs. 7 and 8 <sep> schematically represent a first variant of the second embodiment of the resonator according to the present invention; <tb> Fig. 9 <sep> schematically represents a second variant of the second embodiment of the resonator according to the present invention; <tb> Fig. <Sep> schematically represents a third embodiment of the resonator according to the present invention; and <tb> Fig. 11 <sep> schematically represents the spiral portion of the balance-spring resonator according to the present invention.

DETAILED DESCRIPTION

Figs. 3 and 4 schematically represent a component according to the present invention.

The component 101 manufactured with the method according to the present invention is a resonator 300. A conventional resonator visible in FIG. 1 comprises a body 100 used in deformation. This body 100 takes the form of a base 302 placed on a base 306 and from which extend at least two parallel arms 304. These two parallel arms 304 carry metallizations which form, on these branches, two groups of 308 electrodes that allow to subject them to electric fields to make them vibrate. The resonator 300 further comprises, on the base 302, connection pads 309 respectively connected to the electrode groups 308 as shown in FIG. 4. Each arm 304 comprises an upper face 314 and a lower face 316. The dimensions of such a resonator 300 are a length of 1 mm, a width of 0.1 mm and a thickness of 0.1 mm.

To improve the characteristics of the resonator 300, it is known to make recesses 200 in the form of grooves 310 or grooves and located on these arms 304. These grooves 310 increase the piezoelectric coupling, which allows a decrease in electricity consumption. This reduction in consumption is a consequence of the reduction of the electrical resistance representing the losses in the equivalent circuit of the resonator 300.

To achieve the grooves 310 of the component 101, the present invention proposes to provide a manufacturing method. In this case, the focus will be on the realization of grooves 310 or recesses 200.

In a first step shown in FIG. 2a, the component 101, here the resonator 300, is equipped without the grooves 310 being made. It will be understood that this resonator 300 is previously produced. This resonator 300 is made according to the most appropriate method depending on the material constituting it, called here first material, such as machining or chemical etching.

A second step is to provide a laser (L) whose pulse duration is here of the order of femto-second that is to say 10 "15 seconds (typically 100 fs). Pulse duration can range from femtosecond to picosecond (10-12 seconds). This laser (L) is then used to modify the structure of said arm 304 as shown in FIG. 2b, for this purpose, the first material is chosen to be transparent to the laser. This makes it possible to point, with the focusing point (P) of the laser (L), a point (P) which can be on or under the surface of the arm 304. For the laser (L) whose pulse duration is here of the order of femto-second, the first material may be a monocrystalline material such as quartz, sapphire or synthetic ruby, or a polycrystalline material such as polycrystalline ruby or an amorphous material such as a glass such as silica or ceramic. The focusing point (P) is then pointed towards the resonator 300 at zones on or below the surface of the resonator 300. All of this is done in a predetermined or desired sequence to locally cause a modification of the absorption structure. multi-photon. Indeed, the modification of the material structure by multi-photon absorption requires a very high energy density. However, obtaining such a necessary energy density is currently only possible with lasers whose pulse duration is very low, that is to say, of the order of femto-second or pico. -second. These lasers are, in fact, capable of providing this energy density at the point of focus, that is to say where the energy density is the most important. The structure of a first arm 304 is then modified as shown in FIG. 2cet we take care of the other arm 304. We then obtain the resonator 300 as visible in FIG. 2d.

The third step is to provide a chemical agent. This chemical agent is chosen to allow zones Z1 whose structure is modified to be dissolved more quickly than zones Z2 whose structure has not been modified. By this is meant that the attack velocity of the zones Z1 whose structure has been modified by the focusing point (P) of the laser (L) is greater than the attack speed of the zones Z2 whose structure has not has been modified by the laser (L). Indeed, the local modification of the structure by the focusing point (P) of the femtosecond laser (L) makes it possible to choose a chemical agent that is more reactive to the modified zones Z1 than to the unmodified zones Z2. Consequently, by dipping, during a predetermined time, said resonator in a bath composed of the chemical agent, it is made sure that all zones Z1 whose structure has been modified by the focusing point (P) of the laser (L ) are dissolved. Of course, the dimensions of the resonator 300 are calculated to take into account the chemical attack of the chemical agent on the unmodified zones and | thus do not excessively dissolve areas whose structure is not modified. The resonator 300 visible in FIG. 2nd.

Furthermore, it will be noted that in order for the dissolution of zones Z1 whose structure has been modified to take place, it is necessary for zones Z1 to be accessible for the chemical agent. It is therefore understood that at least one surface or at least one zone Z1 close to the surface is modified. Indeed, the present method makes it possible to produce internal structures but requires that the chemical agent be able to access zones Z1 whose structure is modified. With a zone Z1 whose structure is modified on the surface, said chemical agent is allowed to directly dissolve the modified zones Z1. Nevertheless, it is conceivable that zones Z1 whose structure has been modified are not located on the surface but just below the surface. The chemical agent then dissolves the few unmodified zones Z2 separating said chemical agent from the modified zones Z1 in order subsequently to allow them to dissolve. Of course, each recess 200 of the resonator 300 will have to be configured in this way or must be joined. Once all the Z1 modified zones are dissolved, said resonator is out of the bath.

A fourth step is to clean said resonator so that all chemical agent residues are removed. This allows the chemical reaction to be permanently stopped.

The advantage of the process according to the present invention is twofold. Indeed, this method makes it possible to locally modify the structure of the material of the component so that each location at the surface or under the surface of the component can be structurally modified. It is therefore possible to structurally modify the resonator 300 into complex shapes that will be chemically etched in a precise manner.

This possibility of complex shapes is then used to make recesses with right flanks 312 and vertical. Indeed, the modified zones Z2 are arranged to provide these flanks 312 rights and as the chemical etching step acts only on the modified areas, the verticality of the flanks 312 is kept. It can be generalized by saying that the advantage of the present method is to preserve the original shapes of the recesses 200. The presence of the right and vertical flanks 312 makes it possible to improve the piezoelectric coupling. Indeed, these flanks 312 cause an increase in the emotional capacity of the resonator 300. Now, this emotional ability represents the effectiveness of the piezoelectric coupling. For the resonator 300 shown in FIG. 3, the increase in the piezoelectric coupling gain is 30%.

In a first embodiment shown in FIGS. 3 and 4, the resonator resumes the model of the resonator 300 of the prior art, that is to say it comprises two grooves 310. These two grooves 310 are each located on the upper face 314 of one of the arms 304. Each arm 304 then comprises a groove 310. Preferably, the groove 310 of each arm 304 is placed centrally as shown in FIG. 4.

In a variant of this first embodiment of the invention, each face 314, 316 of each arm 304 has a groove 310. It will be understood that for a resonator 300 having two arms 304, said resonator 300 comprises four grooves. 310. There is then a groove 310 on the upper face 314 of each arm 304 and a groove 310 on the lower face 316 of each arm 304. In this variant, the grooves 310 of each arm 304 are opposite to the plane A- A 'visible in fig. 5.

In a second embodiment, it is expected to have at least two grooves 310 on one of the faces 314, 316 of each arm 304 as shown in FIG. 6. Preferably, the at least two grooves 310 of an arm 304 are placed on the same face 314, 316 as the at least two grooves 310 of the other arm 304. This arrangement makes it possible to optimize the electric fields in the resonator 300.

This second embodiment may have a variant in that each face 314, 316 of each arm 304 comprises at least two grooves 310 as shown in FIG. 7.

This variant may consist of having two grooves each comprising a right flank 312b and an inclined flank 312a, these two grooves 310 being separated by a central member 313 as shown in FIG. 6. These grooves are arranged so that the central member 313 is formed by the inclined flanks 312a of the two grooves 310. These flanks 312a have inclined so that the surface of the groove 310 decreases as the depth increases. This arrangement makes it possible to take advantage of the right flanks 312b of the grooves 310 to increase the coupling. In addition, the fact of having two small grooves 310 instead of a very wide groove 310 makes it possible not to remove too much material from the resonator 300 and thus to weaken it.

This second embodiment and its variant also have the advantage of shortening the duration of the process because there is less material to remove and therefore less material to modify with the Iaser (L).

However, to achieve this second embodiment, it is possible to use the method according to the invention in another way. Indeed, it has been described that the method uses a laser (L) whose duration of the pulses is of the order of femto-second to modify zones of the resonator 300 and dissolve them by chemical action. However, it is also possible to use the laser (L) to cut the resonator 300. The laser (L) is used to modify the contours of an area to be deleted. The chemical etching step is then performed and this makes it possible to dissolve the contours of the zone to be removed. As the contours of the latter are dissolved by the action of the chemical agent, the zone to be removed is detached from the resonator 300. It is then possible to sculpt the surface of the resonator 300 and remove a part of it, for example to the grooves 310, without modifying the structure of all this part. The saving of time is, therefore, significant.

In a second variant visible in FIG. 9, each groove 310 comprises a relatively large surface portion 314. These surface portions 314 are in the form of a projection 315 located on the surface of the resonator 300. This projection 315 has a rectangular profile and extends in the direction from the center of the arms. This arrangement makes it possible, in addition to the advantages of having an optimized electric field, to improve the alignment of the masks. Indeed, in the case of this second embodiment, the surface portions 314 are used to increase the necessary tolerances during the alignment of the masks employed during the production of the electrodes 308.

In a third embodiment shown in FIG. 10, it is possible that the resonator 300 includes a third arm 304 so that the resonator 300 has a shape similar to that of a trident. This third arm 304 is used for fixing the resonator 300 and more particularly for modifying its center of gravity. Indeed, this third arm 304 is used as a fixing point so that it is in contact with the base 306 supporting the resonator 300. This arrangement of the third arm 304 which serves as a central arm 304 allows to center the center of gravity and to have a better balance of the 300 resonator.

Advantageously, the method according to the present invention may not be used to achieve the grooves 310 of the arm 304 of the resonator 300. Indeed, as the method according to the present invention is accurate and allows for complex shapes, its use to realize the entire resonator 300 from a substrate is possible. This possibility of making the entire resonator 300 with the method according to the present invention is advantageous because it makes it possible to shorten the duration of the process. The use of this method makes it possible to carry out, in a single step, the step of producing the contours and the step of producing the grooves 310 of the resonator 300. Of course, it will be understood that this way of doing things can also be used for the case of a standard resonator 300 with two arms 304. Furthermore, it is conceivable that the method according to the present invention is used only to produce a resonator 300 with two or three arms 304 having no grooves 310 on one and / or the other of the arms 304.

It can also be imagined that the resonator according to the invention is in the form of a balance-spring resonator. This balance spring comprises a flywheel called pendulum on which is mounted co-axially a spiral spring. The balance comprises an annular mass called serge held by at least two arms and the spiral spring comprises a body 100 which is in the form of a bar 5 wound on itself to form a spiral 400 as shown in FIG. 11. Such a hairspring 400 can be manufactured using the method according to the invention. For this, the contours of the spiral 400 are drawn on a substrate using the laser (L) whose pulse duration is of the order of femto-second or picosecond. The chemical etching step then makes it possible to separate the hairspring 400 from the rest of the substrate.

The advantage of the method according to the present invention is to achieve precisely the desired shape for the hairspring 400. This method also allows to obtain a hairspring having straight flanks over its entire length, that is to say to have locally parallel flanks. This thus avoids the presence of overhangs according to certain crystallographic orientations present after a conventional technique of chemical etching, and thus allows a better balance of the spiral resonator.

The method according to the present invention also makes it possible to facilitate the adjustment of the resonator 300. Indeed, the two main characteristics of a balance-spring resonator are the frequency and the isochronism, that is to say the capacity of the resonator. a resonator 300 to have a duration of oscillations independent of the amplitude of these and the position of the watch. To adjust the frequency and isochronism of a sprung balance resonator, the local modification of the rigidity of the hairspring is a solution. To do this, the accuracy of the method according to the invention is useful because it allows for recesses 310 or grooves or baths along the turns of the spiral resonator. These recesses or gorges or baths are made locally so that! locally reduce the rigidity of the resonator and benefit from the advantages of precision of the process. These recesses 310 have at least two straight flanks, parallel but it is possible that the flanks are parallel in pairs. The flanks of the recesses may also be locally parallel.

It will be understood that various modifications and / or improvements and / or combinations obvious to those skilled in the art can be made to the various embodiments of the invention described above without departing from the scope of the invention defined by the appended claims.

Claims (25)

1. A method of manufacturing a resonator in a substrate (101, 300), characterized in that it comprises the following steps: a) modifying the structure of at least one zone of the substrate in order to make said at least one zone more selective; b) etching said at least one zone to selectively fabricate said resonator. 2. The manufacturing method according to claim 1, characterized in that it further comprises the step: c) releasing the component from said substrate. 3. The manufacturing method according to claims 1 or 2, characterized in that the structure of said at least one area is modified by a laser (L). 4. Manufacturing method according to one of the preceding claims, characterized in that the substrate is made of transparent material at the wavelength of the laser. 5. Manufacturing process according to claims J or 4, characterized in that the duration of the pulses of the laser (L) range from femtosecond to picosecond. 6. Manufacturing process according to claim 4, characterized in that the substrate is made of monocrystalline material. 7. Manufacturing process according to claim 4, characterized in that the substrate is made of polycrystalline material. 8. Manufacturing process according to claim 4, characterized in that the substrate is made of polymer. 9. The manufacturing method according to claim 4, characterized in that the substrate is made of an amorphous material such as a ceramic or a glass. 10. Method according to one of claims 1 to 9, characterized in that the component is a resonator (300) comprising a base (302) from which extend at least two parallel arms (304) each having a face upper (314) and a lower face (316) and further comprising at least one recess (310) formed on one of the faces of one of the at least two parallel arms (304). 11. The method of claim 10, characterized in that said at least one recess (310) is in the form of a groove having at least one of its flanks (312) vertical. 12. The method of claim 10 or 11, characterized in that said resonator comprises a groove (310) per arm. 13. The method of claim 10 or 11, characterized in that said resonator comprises a groove (310) on the upper face (314) of each arm and a groove (310) on the lower face (316) of each arm (304). ). 14. The method of claim 10 or 11, (characterized in that said resonator comprises two grooves (310) per arm. 15. The method of claim 10 or 11, characterized in that said resonator comprises two grooves (310) on the upper face of each arm and two grooves (310) on the underside of each arm. 16. Resonator (300) comprising a base (302) from which extend at least two parallel arms (304) each having an upper face (314) and a lower face (316) and at least one group of electrodes located on one of the at least two parallel arms (304) to electrically excite said at least two parallel arms (304), characterized in that it comprises at least two flanks (312) parallel right and vertical. 17. Resonator according to claim 16, characterized in that one of the faces of one of the at least two parallel arms (304) comprises at least one recess (310) in the form of a groove having flanks. (312) verticals. 18. Resonator according to claim 17, characterized in that said resonator comprises a groove (310) per arm. 19. Resonator according to claim 17, characterized in that said resonator comprises a groove (310) on the upper face of each arm and a groove (310) on the lower face of each arm. 20. Resonator according to claim 17, characterized in that said resonator comprises two grooves (310) per arm. 21. Resonator according to claim 17, characterized in that said resonator comprises two grooves (310) on the upper face of each arm and two grooves (310) on the lower face of each arm. 22. Resonator according to one of claims 17 to 21, characterized in that the grooves comprise a projection (315) which optimizes the electric fields, while increasing the alignment tolerances. 23. Resonator (300) comprising a flywheel coupled to a body (100) formed a bar wound on itself to form a hairspring characterized in that said body comprises at least one recess (310) for locally modifying the rigidity and thus adjust the frequency of the resonator and / or adjust the isochronism defect. 24. Resonator (300) according to claim 23, characterized in that said at least one recess comprises at least two parallel and vertical blanks. 25. Resonator according to claim 23 or 24, characterized in that said body is made of quartz or ceramic or glass and in that it comprises locally parallel and vertical flanks along the entire length of said body.