CH705945B1 - Method of producing a resonator and resonator obtained by such a method - Google Patents

Abstract

The present 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 area of the substrate by a laser in order to make said at least one area more selective; b) etching said at least one area in order to selectively manufacture said resonator. By means of this method, a spiral resonator or a tuning fork for a watch can be obtained.

Description

[0001] The invention relates to a resonator comprising a body used in deformation as a spiral resonator or a tuning fork.

TECHNOLOGICAL BACKGROUND

[0002] It is known from the prior art that certain microtechnology parts made of monocrystalline or polycrystalline materials, such as resonators, are produced by chemical etching. This technique consists of providing the substrate to be etched and depositing a layer of photosensitive resin on it. A mask is placed on this resin and then the whole is exposed to light so that the structure of the photosensitive resin exposed to the light is modified. This modified resin is removed by the action of a chemical element, thus leaving the substrate exposed at the locations where the resin has been removed.

[0003] Subsequently, these exposed areas of the substrate are chemically etched in order to hollow them out. The chemical agent is chosen to attack only the material composing the substrate and not the unmodified photosensitive resin. The duration of this chemical etching step makes it possible to determine the dimensions of the hollows.

[0004] Similarly, it is conceivable that microtechnology parts are produced by machining and/or polishing so that a drill or polisher can be used to shape said parts.

[0005] A first drawback of this chemical etching technique is that it does not allow hollows with straight sides to be produced. Indeed, the hollows obtained have inclined sides. This means that the surface of the hollow varies according to the depth, i.e. this surface increases or decreases as the hollow becomes deeper. Generally this surface decreases with depth. This observation requires adapting the theoretical calculations carried out to obtain hollows with straight sides. In addition, this variation in the profile of the hollows between theory and practice leads to a variation in the characteristics.

SUMMARY OF THE INVENTION

[0006] The invention aims to overcome the drawbacks mentioned above by proposing a manufacturing method making it possible to produce a component comprising hollows whose sides have an easily achievable inclination.

[0007] 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 in order to make said at least one zone more selective; b) etching said at least one zone in order to selectively manufacture said resonator.

[0008] An advantage of the present invention is that it allows recesses to be made that are located below the surface because the material used is chosen to be transparent to the laser. This allows the laser to be able to point at any point on the surface or below the surface of the resonator. The material is then made selective so that the chemical attack that follows only operates on the material that has undergone modification by the laser. This gives a method that allows complex and internal recesses to be made.

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

[0010] In a first advantageous embodiment, the method further comprises the step: c) releasing the component from said substrate.

[0011] 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 a femtosecond.

[0012] In a third advantageous embodiment, the substrate is made of monocrystalline material.

[0013] In another advantageous embodiment, the substrate is made of polycrystalline material.

[0014] In another advantageous embodiment, the substrate is made of an amorphous material such as a ceramic or a glass.

[0015] In another advantageous embodiment, the substrate is made of polymer.

[0016] 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.

[0017] In another advantageous embodiment, said at least one recess is in the form of a groove having at least one of its vertical sides.

[0018] In another advantageous embodiment, said resonator comprises one groove per arm.

[0019] In another advantageous embodiment, said resonator comprises a groove on the upper face of each arm and a groove on the lower face of each arm.

[0020] In another advantageous embodiment, said resonator comprises two grooves per arm.

[0021] In another advantageous embodiment, said resonator comprises two grooves on the upper face of each arm and two grooves on the lower face of each arm.

[0022] 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 group of electrodes located on one of the at least two parallel arms for electrically exciting said at least two parallel arms, characterized in that it comprises at least two straight parallel flanks.

[0023] 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 sides.

[0024] In a second advantageous embodiment, said resonator comprises one groove per arm.

[0025] 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.

[0026] In another advantageous embodiment, said resonator comprises two grooves per arm.

[0027] In another advantageous embodiment, said resonator comprises two grooves on the upper face of each arm and two grooves on the lower face of each arm.

[0028] In another advantageous embodiment, the grooves include a projection which makes it possible to optimize the electric fields, while increasing the alignment tolerances.

[0029] 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 hollow to locally modify the rigidity and thus adjust the frequency of the resonator and/or adjust the isochronism defect.

[0030] In an advantageous embodiment, said at least one hollow comprises at least two parallel blanks.

[0031] In another advantageous embodiment, said body is made of quartz or ceramic or glass and in that it comprises locally parallel sides over the entire length of said body.

BRIEF DESCRIPTION OF THE FIGURES

[0032] The aims, 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 non-limiting example and illustrated by the appended drawings in which: – Figure 1 schematically represents a front view of a resonator according to the prior art; – Figures 2a to 2e schematically represent the steps of the method according to the present invention; – Figures 3 and 4 schematically represent a first embodiment of the resonator according to the present invention; – Figure 5 schematically represents a variant of the first embodiment of the resonator according to the present invention; – Figure 6 schematically represents a second embodiment of the resonator according to the present invention; – Figures 7 and 8 schematically represent a first variant of the second embodiment of the resonator according to the present invention; – Figure 9 schematically represents a second variant of the second embodiment of the resonator according to the present invention; – Figure 10 schematically represents a third embodiment of the resonator according to the present invention; and – Figure 11 schematically represents the spiral part of the balance-spring resonator according to the present invention.

DETAILED DESCRIPTION

[0033] Figures 3 and 4 schematically represent a component according to the present invention.

[0034] 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 at least two parallel arms 304 extend. These two parallel arms 304 carry metallizations which form, on these branches, two groups of electrodes 308 which allow them to be subjected to electric fields to make them vibrate. The resonator 300 further comprises, on the base 302, connection pads 309 connected respectively to the groups of electrodes 308 as visible 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.

[0035] In order to improve the characteristics of the resonator 300, it is known to produce 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 reduction in electrical consumption. This reduction in consumption is a consequence of the reduction in electrical resistance representing the losses in the equivalent diagram of the resonator 300.

[0036] To produce the grooves 310 of the component 101, the present invention proposes to provide a manufacturing method. In the present case, the emphasis will be placed on the production of the grooves 310 or recesses 200.

[0037] In a first step shown in FIG. 2a, the component 101 is provided, here the resonator 300, without the grooves 310 being made. It is then understood that this resonator 300 is made beforehand. This resonator 300 is made according to the most appropriate method depending on the material constituting it, here called the first material, such as for example machining or chemical etching.

[0038] A second step consists in providing a laser (L) whose pulse duration is here of the order of the femtosecond, i.e. 10<-15>second (typically 100 fs). The pulse duration can range from the femtosecond to the picosecond (10<-12>second). This laser (L) is then used to modify the structure of said arm 304 as visible 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 focal point (P) of the laser (L), a point (P) which can be located on or under the surface of the arm 304. For the laser (L) whose pulse duration is here of the order of the femto-second, the first material can 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 a ceramic. The focal point (P) is then pointed towards the resonator 300 at areas located on or under the surface of the resonator 300. All this is done according to a predetermined or desired sequence in order to locally cause a modification of the structure by multi-photon absorption. Indeed, the modification of the structure of the material 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 a femtosecond or a picosecond. These lasers are, in fact, capable of providing this energy density at the focal point, that is to say where the energy density is the greatest. The structure of a first arm 304 is then modified as visible in FIG. 2c and the other arm 304 is taken care of. The resonator 300 is then obtained as visible in FIG. 2d.

[0039] The third step consists of providing a chemical agent. This chemical agent is chosen to allow the zones Z1 whose structure is modified to be dissolved more quickly than the zones Z2 whose structure has not been modified. This means that the attack speed of the zones Z1 whose structure has been modified by the focal point (P) of the laser (L) is greater than the attack speed of the zones Z2 whose structure has not been modified by the laser (L). Indeed, the local modification of the structure by the focal 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 immersing, for a determined time, said resonator in a bath composed of the chemical agent, it is ensured that all the zones Z1 whose structure has been modified by the focal 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 areas and thus not to excessively dissolve the areas whose structure is not modified. We then obtain the resonator 300 visible in Figure 2e.

[0040] Furthermore, it will be noted that for the dissolution of the Z1 zones whose structure has been modified to take place, it is necessary for the Z1 zones to be accessible to the chemical agent. It is therefore understood that at least one surface or at least one Z1 zone close to the surface is modified. Indeed, the present method makes it possible to produce internal structures but requires that the chemical agent can have access to the Z1 zones whose structure is modified. With a Z1 zone whose structure is modified on the surface, said chemical agent is allowed to directly dissolve the modified Z1 zones. Nevertheless, it is conceivable that the Z1 zones whose structure has been modified are not located on the surface but just below the surface. The chemical agent then dissolves the few unmodified Z2 zones separating said chemical agent from the modified Z1 zones to then allow the dissolution of the latter. Of course, each recess 200 of the resonator 300 must be configured in this way or must be joined. Once all the modified Z1 zones have been dissolved, the said resonator is removed from the bath.

[0041] A fourth step consists of cleaning said resonator so that all chemical agent residues are eliminated. This allows the chemical reaction to be definitively stopped.

[0042] The advantage of the method 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 on the surface or under the surface of the component can be structurally modified. It is therefore possible to structurally modify the resonator 300 according to complex shapes which will be chemically etched precisely.

[0043] This possibility of complex shapes is then used to produce recesses having straight and vertical sides 312. Indeed, the modified zones Z2 are arranged to provide these straight sides 312 and since the chemical etching step only acts on the modified zones, the verticality of the sides 312 is maintained. 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 straight and vertical sides 312 makes it possible to improve the piezoelectric coupling. Indeed, these sides 312 lead to an increase in the motional capacity of the resonator 300. Now, this motional capacity represents the efficiency of the piezoelectric coupling. For the resonator 300 shown in FIG. 3, the increase in the gain in piezoelectric coupling is 30%.

[0044] In a first embodiment visible in FIGS. 3 and 4, the resonator takes up the model of the resonator 300 of the prior art, that is to say that 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 in a centered manner as visible in FIG. 4.

[0045] In a variant of this first embodiment of the invention, each face 314, 316 of each arm 304 comprises a groove 310. It is 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 relative to the plane A-A' visible in FIG. 5.

[0046] In a second embodiment, it is provided to have at least two grooves 310 on one of the faces 314, 316 of each arm 304 as visible 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.

[0047] This second embodiment may have a variant in that each face 314, 316 of each arm 304 comprises at least two grooves 310 as visible in FIG. 7.

[0048] This variant may consist of having two grooves each comprising a straight flank 312b and an inclined flank 312a, these two grooves 310 being separated by a central element 313 as visible in FIG. 6. These grooves are arranged so that the central element 313 is formed by the inclined flanks 312a of the two grooves 310. These flanks 312a are inclined so that the surface area of the groove 310 decreases when the depth increases. This arrangement makes it possible to take advantage of the straight flanks 312b of the grooves 310 to increase the coupling. In addition, 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 less.

[0049] This second embodiment and its variant also have the advantage of making it possible to shorten the duration of the process because there is less material to remove and therefore less material to modify with the laser (L).

[0050] 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 pulse duration is of the order of a femtosecond to modify areas 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 removed. The chemical etching step is then carried out and this makes it possible to dissolve the contours of the area to be removed. As the contours of the latter are dissolved by the action of the chemical agent, the area to be removed detaches 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 make the grooves 310, without modifying the structure of this entire part. The time saving is therefore significant.

[0051] 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 towards 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 tolerances necessary when aligning the masks used when producing the electrodes 308.

[0052] In a third embodiment visible in FIG. 10, it is possible for the resonator 300 to comprise 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 to modify 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 acts as a central arm 304 makes it possible to center the center of gravity and to have a better balance of the resonator 300.

[0053] Advantageously, the method according to the present invention may not only be used to produce the grooves 310 of the arms 304 of the resonator 300. Indeed, since the method according to the present invention is precise and makes it possible to produce complex shapes, its use to produce the entire resonator 300 from a substrate is conceivable. This possibility of producing 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 method. 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 only used to produce a resonator 300 with two or three arms 304 not having grooves 310 on one and/or the other of the arms 304.

[0054] It is also possible to imagine that the resonator according to the invention is in the form of a balance-spring resonator. This balance spring comprises a flywheel called a balance on which a spiral spring is coaxially mounted. The balance comprises an annular mass called a rim 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 visible in FIG. 11. Such a spiral 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 a femtosecond or picosecond. The chemical etching step then makes it possible to separate the spiral 400 from the rest of the substrate.

[0055] The advantage of the method according to the present invention is to make it possible to precisely produce the desired shape for the hairspring 400. This method also makes it possible to obtain a hairspring having straight flanks over its entire length, i.e. to have locally parallel flanks. This thus avoids the presence of overhangs according to certain crystallographic orientations present after a conventional chemical etching technique, and thus allows a better balance of the hairspring resonator.

[0056] The method according to the present invention also makes it easier to adjust the resonator 300. Indeed, the two major characteristics of a balance-spring resonator are the frequency and the isochronism, that is to say the capacity of a resonator 300 to have a duration of oscillations independent of the amplitude of these and of the position of the watch. To adjust the frequency and the isochronism of a balance-spring resonator, the local modification of the rigidity of the balance spring is a solution. To do this, the precision of the method according to the invention is useful because it makes it possible to produce recesses 310 or grooves or baths along the turns of the balance spring resonator. These recesses or grooves or baths are produced locally so as to locally reduce the rigidity of the resonator and benefit from the precision advantages of the method. These recesses 310 have at least two straight, parallel sides, but it is possible for the sides to be parallel two by two. The sides of the recesses can also be locally parallel.

[0057] 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 different embodiments of the invention set out above without departing from the scope of the invention defined by the appended claims.

Claims (23)

1. Method for manufacturing a resonator in a substrate (101, 300) made of material transparent to the wavelength of a laser, characterized in that it comprises the following steps: a) modifying the structure of at least one zone of the substrate by the laser (L), in order to make said at least one zone more selective; b) etching said at least one zone in order to selectively manufacture said resonator. 2. Manufacturing method according to claim 1, characterized in that it further comprises the step: c) releasing the resonator from said substrate. 3. Manufacturing method according to claim 1 or 2, characterized in that the duration of the laser pulses (L) ranges from femtosecond to picosecond. 4. Manufacturing method according to one of claims 1 to 3, characterized in that the substrate is made of monocrystalline material. 5. Manufacturing method according to one of claims 1 to 3, characterized in that the substrate is made of polycrystalline material. 6. Manufacturing method according to one of claims 1 to 3, characterized in that the substrate is made of polymer. 7. Manufacturing method according to one of claims 1 to 3, characterized in that the substrate is made of an amorphous material such as a ceramic or a glass. 8. Method according to one of claims 1 to 7, characterized in that the resonator (300) comprises a base (302) from which extend at least two parallel arms (304) each having an upper face (314) and a lower face (316) and further comprising at least one recess (310) made on one of the faces of one of the at least two parallel arms (304). 9. Method according to claim 8, characterized in that said at least one recess (310) is in the form of a groove having at least one of its sides (312) vertical. 10. Method according to claims 8 or 9, characterized in that said resonator comprises a recess (310) per arm. 11. Method according to claims 8 or 9, characterized in that said resonator comprises a recess (310) on the upper face (314) of each arm and a recess (310) on the lower face (316) of each arm (304). 12. Method according to claims 8 or 9, characterized in that said resonator comprises two recesses (310) per arm. 13. Method according to claims 8 or 9, characterized in that said resonator comprises two recesses (310) on the upper face of each arm and two recesses (310) on the lower face of each arm. 14. Resonator (300) obtained by the method according to claim 1, 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 straight and vertical parallel flanks (312). 15. Resonator according to claim 14, 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 vertical sides (312). 16. Resonator according to claim 15, characterized in that said resonator comprises a recess (310) per arm. 17. Resonator according to claim 15, characterized in that said resonator comprises a recess (310) on the upper face of each arm and a recess (310) on the lower face of each arm. 18. Resonator according to claim 15, characterized in that said resonator comprises two recesses (310) per arm. 19. Resonator according to claim 15, characterized in that said resonator comprises two recesses (310) on the upper face of each arm and two recesses (310) on the lower face of each arm. 20. Resonator according to one of claims 15 to 19, characterized in that the recesses comprise a projection (315) which makes it possible to optimize the electric fields, while increasing the alignment tolerances. 21. Resonator (300) obtained by the method according to claim 1, comprising a flywheel coupled to a body (100) forming a bar wound on itself to form a spiral characterized in that said body comprises at least one recess (310) to locally modify the rigidity and thus adjust the frequency of the resonator and/or adjust the isochronism defect. 22. Resonator (300) according to claim 21, characterized in that said at least one recess comprises at least two parallel and vertical sides. 23. Resonator according to claim 21 or 22, characterized in that said body is made of quartz or ceramic or glass and in that it comprises locally parallel and vertical sides over the entire length of said body.