CH707562A2 - Method for manufacturing e.g. escapement wheels of clock, involves selectively machining portion of metal parts to form escapement wheels and forks with two different levels, and releasing wheels and forks with substrate and photoresist - Google Patents

Abstract

The method involves forming a silicon substrate (2) with an electrically conductive upper surface (4). A mold is structured from a photoresist (6) to make cavities, which include bottoms formed by the electrically conductive upper surface. The cavities of the mold are filled by electroplating to form metal parts (21, 51, 81). A portion of the metal parts is selectively machined to form escapement wheels and forks with two different levels. The wheels and the forks with the substrate and the photoresist are released. An independent claim is also included for a clock.

Description

Field of the invention

The invention relates to a method of manufacturing a piece of micromechanical monoblock comprising at least two distinct levels.

Background of the invention

It is known to form metal parts at several different levels using successive LIGA type process, that is to say from stacked layers comprising a structured mold resin and a metal in the hollow of the mold deposited by electroplating.

However, these successive processes to form several levels are difficult to implement because it is necessary to properly reference the levels between them. In addition, it appeared that this difficulty generated much higher costs compared to two galvanic deposits at a single level.

Summary of the invention

The object of the present invention is to overcome all or part of the disadvantages mentioned above by proposing an alternative method of manufacturing a piece of micromechanical monoblock comprising at least two distinct levels, less expensive to implement.

For this purpose, the invention relates to a method for manufacturing a monobloc micromechanical component comprising at least two distinct levels, characterized in that it comprises the following steps: a) forming a silicon substrate whose upper surface is electrically conductive; b) structuring a mold from a photosensitive resin to make cavities whose bottom is formed by said electrically conductive upper face; c) filling the cavities of the mold by electroplating to form a metal part; d) selectively machining a portion of the metal part to form a one-piece micromechanical part at at least two distinct levels; e) releasing the micromechanical part of the substrate and the photoresist.

[0006] It is advantageously understood according to the invention that each one-piece micromechanical part comprising at least two distinct levels is formed from a metal part in a single pattern formed by a LIGA process which is then machined directly on the substrate in order to benefit from the precise positioning of each metal part on the substrate.

Therefore, the external and possibly internal dimensions remain at the high precision induced by the LIGA process and the rest of the monobloc micromechanical part benefits from the precision of machining, less advantageous compared to the LIGA process, to preserve the manufacturing costs. A piece of micromechanical monobloc having at least two distinct levels is thus obtained which is much less difficult to manufacture by keeping the external and, possibly, internal parts of a very high precision.

According to other advantageous features of the invention: The upper surface is made electrically conductive by doping the silicon substrate and / or by depositing an electrically conductive layer on the silicon substrate; The silicon substrate has a thickness of between 0.3 and 1 mm; Step b) comprises the phases f): depositing a layer of photosensitive resin on the electrically conductive top surface of the substrate, g): selectively illuminating a portion of the photosensitive resin and h): developing the photosensitive resin in order to structure the photosensitive resin; mold; The metal part is formed based on nickel-phosphorus such as NiP or NiP12; - The method further comprises between step c) and step d), step i): leveling, by running in, the mold and the metal part; In step e), the process comprises phases j): removing the photoresist and k): removing the substrate; - between phase j) and phase k), the method further comprises phase I): depositing a coating on the micromechanical part-substrate assembly; Phase I) is carried out by physical or chemical vapor deposition or by electroplating; Several micromechanical parts are formed on the same substrate.

In addition, the invention relates to a timepiece characterized in that it comprises a piece of micromechanical monobloc at least two distinct levels obtained according to one of the previous variants.

Brief description of the drawings

Other features and advantages will become apparent from the description which is given below, for information only and not limiting, with reference to the accompanying drawings, in which: <tb> figs. 1 to 5 <SEP> are representations of successive steps of a method according to a first embodiment of the invention; <tb> figs. 6 and 7 <SEP> are representations of final steps of a method according to a second embodiment of the invention; <tb> figs. 8 to 10 <SEP> are representations of an electroformed metal part and then machined using a method according to a first variant of the invention; <tb> figs. 11 to 13 <SEP> are representations of an electroformed metal part and then machined using a method according to a second variant of the invention and then assembled; <tb> figs. 14 to 16 <SEP> are representations of electroformed metal part then machined using a method according to a third variant of the invention and then assembled; <tb> fig. <SEP> is a block diagram of a method according to the invention.

Detailed Description of the Preferred Embodiments

The object of the present invention is to provide a method of manufacturing a piece of micromechanical monoblock comprising at least two different levels that is cheaper to implement. The present invention also aims to manufacture all or part of a micromechanical part from this process. The micromechanical part is intended to be mounted preferentially in a timepiece. Of course, it is also conceivable to apply the present invention in other fields such as, in particular, aeronautics or automobiles.

As illustrated in FIG. 17, the invention relates to a method 1 for manufacturing a one-piece micromechanical part 31, 41, 61, 91 comprising at least two distinct levels.

According to the method 1, a first step 3, as illustrated in FIG. 1, is intended to form a silicon substrate 2 whose upper surface 4 is electrically conductive. Preferably, the upper surface 4 is electrically conductive by doping the silicon substrate 2 and / or by depositing an electrically conductive layer on the silicon substrate 2.

In all cases, it is very important that the adhesion of the future galvanic deposit against the substrate 2 is as strong as possible. Indeed, it is essential for step 9 that the metal part 21, 51, 81 is very strongly fixed against the upper surface 4 and, incidentally, against the substrate 2.

Preferably according to the invention, the silicon substrate 2 has a thickness of between 0.3 and 1 mm. In addition, in the case where an electrically conductive layer would be used, the latter would preferably be based on gold, that is to say in pure gold or one of its alloys. Finally, it could be, for example, deposited by physical or chemical vapor deposition or any other method of deposition.

The process 1 continues, as illustrated in FIG. 2, with a second step 5 for structuring a mold from a photosensitive resin 6 to produce cavities 8 whose bottom is formed by the electrically conductive upper face 4 of the substrate 2.

Of course, FIG. 2 is only a simplified representation and very complex shapes can be structured. Thus, several cavities 8, not necessarily of identical shapes, can be structured in the resin 6 during step 5 so that several micromechanical parts 31, 41, 61, 91 can be formed on the same substrate 2.

Step 5 preferably comprises the three phases. Step 5 comprises a first phase intended to deposit a photoresist layer 6 on the electrically conductive upper surface 4 of the substrate 2. Such a phase can be obtained by centrifugal coating or by ultrasonic spraying. The second phase is intended to selectively illuminate a portion of the photosensitive resin. It is therefore understood that depending on the nature of the photosensitive resin, that is to say if the resin is of the positive or negative type, the illumination will be focused on the desired future cavities 8 or on the parts other than the future cavities 8 desired.

Finally, the step 5 ends with a third phase for developing the selectively illuminated photosensitive resin 6 in order to structure the mold, that is to say harden the photosensitive resin 6 remaining between the cavities 8. This third phase is generally obtained by etching to form the cavities 8 followed by a heat treatment to harden the resin still present.

The process 1 continues, as illustrated in FIG. 3, with a third step 7 for filling the cavities 8 of the mold by electroplating to form a metal part 21, 51, 81. As explained above, the metal part 21, 51, 81 has the same pattern in projection. It is therefore understandable that the LIGA process does not involve additional difficulties in implementing it, such as, for example, other patterns on higher levels.

Advantageously according to the invention, the method 1 allows, thanks to the very precise photolithography step 5, to obtain a metal part 21, 51, 81 with external and possibly internal dimensions of high accuracy. to meet the very high tolerances of a micromechanical component in the field of watchmaking. By internal dimensions, it should be understood that from any part of structured resin 6 which is enclosed in cavities 8, perforations and / or holes in the metal part 21, 51, 81 can be directly formed during Step 7.

In order to implement the method for manufacturing micromechanical parts 31, 41, 61, 91 for the watch industry, it is preferred to use a material which is tribologically advantageous for contacts with ruby pieces , steel or brass. In addition, a low sensitivity to magnetic fields is sought. Finally, in order to facilitate step 9, it is also preferable that the material is not too hard. Thus, in view of the above constraints, it appeared particularly suitable to fill the cavities 8 during step 7 with an alloy formed of nickel and phosphorus (NiP) and in particular such an alloy whose proportion of phosphorus is substantially equal to 12% (NiP12).

The process 1 continues, as shown in FIG. 4, with a step 9 for selectively machining a portion of the metal part 21, 51, 81 to form a micromechanical part 31, 41, 61, 91 at at least two distinct levels. As explained above, the metal part 21, 51, 81 having the same pattern in projection is then modified in its thickness to form at least two patterns on several levels. The desired micromechanical part 31, 41, 61, 91 is thus obtained without having to form several stacked levels from successive LIGA processes.

It is understood the importance of the strong adhesion of each metal part 21, 51, 81 against the upper surface 4 of the substrate 2. In fact, during the machining of step 9, each metal part 21, 51, 81 will be subject to strong constraints. Therefore, if the adhesion is not sufficient, the method 1 loses the benefit of the precise positioning of each metal part 21, 51, 81 on the substrate 2, or even risk of shearing the metal parts 21, 51, 81 to the point to dissociate them from the substrate 2.

On the contrary, with this strong adhesion, because of the precise positioning of each metal part 21, 51, 81 on the substrate 2, it is possible, during step 9, to machine each metal part 21, 51 , 81 still on the substrate 2 with a programmable automaton according to precise dimensions. Note that, even if step 9 is intended to machine each metal part 21, 51, 81, part of the structured resin 6 can however also be machined by the stresses induced by the tools used or the volumes to be removed as illustrated. by the clearances visible in fig. 4.

Finally, the method 1 ends, as shown in FIG. 5, with step 11 for releasing the micromechanical part 31, 41, 61, 91 of the substrate 2 and the photosensitive resin 6. Thus, in a first phase 12, the step 11 is intended to remove the photoresist 6 and then in a second phase 14, intended to remove the substrate 2. The phase 12 can be obtained, for example, by a plasma etching while the phase 14 is, preferably, obtained by etching. Preferably, in the case where an electrically conductive layer would be used to form the electrically conductive upper surface 4, the latter would, also during phase 14, be removed and, optionally, recovered using a selective chemical attack. .

Of course, the present invention is not limited to the example shown but is susceptible to various variations and modifications that will occur to those skilled in the art. In particular, the method 1 may comprise an optional step 10, between step 7 and step 9, intended to level by grounding the mold formed of photosensitive resin 6 and the metal part 21, 51, 81. This step optional may be desired to ensure the dimensions of the micromechanical part 31, 41, 61, 91, that is to say, be sure that the mold is completely filled.

It is also conceivable to take advantage of the presence of several metal parts 21, 51, 81 on the same substrate 2 to coat them with a predetermined layer. Thus, the method 1 can, as illustrated in FIG. 6, comprise an optional phase 16, between the phase 12 and the phase 14, for depositing a coating 13 on the micromechanical part micromechanical part assembly 31, 41, 61, 91 - substrate 2. Such a phase 16 can be obtained, for example, by a physical or chemical vapor deposition, an electroplating or any other type of deposit.

At the end of the phase 14, a micromechanical part 31, 41, 61, 91 partially coated with a layer 13 is obtained. Preferably, the layer 13 is intended to improve the tribology of the micromechanical part. 31, 41, 61, 91 as, for example, formed from an allotrope of carbon such as graphene or carbon in diamond form. However, the layer 13 can also be used for another function such as changing the color or the hardness of the micromechanical part 31, 41, 61, 91.

Examples of horological applications are presented using three variants illustrated in FIGS. 8 to 16. In a first variant illustrated in FIGS. 8 to 10, there is shown a metal part 21 obtained during step 7 of method 1. It is generally in the form of a double-toothed star 22, 24 having a central hole 26. At the end of Step 11 of method 1, it is thus possible to obtain a micromechanical part in the form of an escape wheel 31 illustrated in FIG. 9 or an escape wheel 41 illustrated in FIG. 10, one and the other being monobloc and having at least two distinct levels coated or not with a layer 13.

Thus, in the case of FIG. 9, the metal part 21 has been machined at the eight arms 33, each end of which forms the toothing 22 in a lower level. The remainder of the metal part 21 remained unchanged, in particular at the hole 26 and the eight arms 35, each end of which forms the second toothing 22 in the lower level and in a higher level.

[0032] Alternatively, in the case of FIG. 10, the metal part 21 has been machined at the eight arms 43, each end of which forms the toothing 22 in a lower level. Similarly, the surrounding hole 26 has been machined to leave the hole 26 present in the lower level. Finally, the eight arms 45 and part of the upper level have been machined so that only the ends of the arms 45 remain, keeping the second toothing 22 in the lower level and in the upper level.

In a second variant illustrated in FIGS. 11 to 13, is presented a metal piece 51 obtained in step 7 of method 1. It is generally in the form of a H-shaped part comprising two parallel portions 53, 55 interconnected by a transverse portion 57. As shown in fig. 11, the transverse portion 57 has a central portion 56 whose section is more flared than the rest of the portion.

At the end of step 11 of the method 1, one can thus obtain a micromechanical part in the form of a fork 61 shown in FIG. 12 and comprising at least two distinct levels coated or not with a layer 13. Thus, the metal part 51 has been machined at the two parts 53, 55 parallel to two depths, that is to say, forming three levels, and at the level of the non-flared portion of the transverse portion 57 in a single depth.

In the example of FIG. 12, the fork 61 thus comprises all the portions 53, 55 parallel only to the lower level by forming two horns 62, 64. An intermediate level only partially comprises the parallel portions 53, 55 and the non-flared portion of the transverse portion 57 in FIG. forming only shoulders 63 and 65. Finally only the central portion 56 of the transverse portion 57 is retained from the metal piece 51 forming only in the upper level a tenon.

As shown in FIG. 13, the fork 61 can then be mounted, by driving the central portion 56 forming tenon, in the hole 76 of a rod 73 to form an anchor 71. The rod 73 can itself be obtained by a LIGA method with a dart 78 in one piece. In addition, from the fork 61, the rod 73 can be equipped with vanes 75, 77 at its arms 72, 74 and with a pivot axis 79. Of course, advantageously according to the invention, all or part of the Anchor 71 can also be obtained using method 1 according to the invention. For example, the pallets 75, 77, the rod 73, the dart 78, the hole 76 could be monoblock and obtained from the method 1 according to the invention.

In a third variant illustrated in FIGS. 14 to 16, is presented a metal part 81 obtained in step 7 of method 1. It is generally in the form of a U-shaped part comprising two parallel portions 83, 85 interconnected by a base 87. visible in fig. 14, the base is thicker than the portion 83, 85 parallel to allow the formation of an ajoint 86 substantially cross-shaped.

At the end of step 11 of method 1, one can thus obtain a micromechanical part in the form of a fork 91 shown in FIG. The metal part 81 has been machined at the two parallel portions 83, 85 at one depth and at the base 87 at two depths. , that is to say by forming three levels,

In the example of FIG. 15, the fork 61 thus comprises all the parts 83, 85 parallel only to the lower level forming two horns 92, 94. An intermediate level only partially comprises the base 87 forming a cylinder 93 tapering by a shoulder 95 to form the higher level. Finally, the narrowing is used to release the openwork 86 in the upper level and form four pins 96, 97, 98, 99.

As shown in FIG. 15, the fork 91 can then be mounted, by driving the pins 96, 97, 98, 99, into the holes 106 of a rod 103 to form an anchor 101. The rod 103 can itself be obtained by a LIGA method with a 108 dart in one piece. In addition, the fork 91, the rod 103 may be equipped, similarly to the second variant, pallets at its arms 102, 104 and a pivot axis. Of course, advantageously according to the invention, all or part of the anchor 101 can also be obtained using the method 1 according to the invention. For example, the pallets, the rod 103, the dart 108, the holes 106 could be monoblock and obtained from the method 1 according to the invention.

Therefore, advantageously according to the invention, the external dimensions 22, 24, 53, 55, 56, 83, 85 and possibly internal 26, 86 remain at the high precision induced by the LIGA process and the rest of the the one-piece micromechanical part 31, 41, 61, 91 benefits from the precision of machining in order to preserve manufacturing costs. Thus, a micromechanical part 31, 41, 61, 91 comprising one piece with at least two distinct levels is obtained which is much less difficult to manufacture by keeping the external parts 22, 24, 53, 55, 56, 83, 85 and possibly internal 26, 86 very precise.

Of course, the present invention is not limited to the example shown but is susceptible to various variations and modifications that will occur to those skilled in the art. In particular, in the field of watchmaking, the micromechanical parts 31, 41, 61, 91 can not be limited to an entire or part of a mobile or an anchor. Other watch parts can be considered as, in particular, bridges, plates or pendulums.

In addition, as explained above, it is also conceivable to apply the present invention in other areas that the watch industry, such as aeronautics or automotive.

Claims (11)

1. Method (1) for manufacturing a micromechanical component (31, 41, 61, 91) comprising at least two distinct levels, characterized in that it comprises the following steps: a) forming (3) a silicon substrate (2) whose upper surface (4) is electrically conductive; b) structuring (5) a mold from a photosensitive resin (6) to make cavities (8) whose bottom is formed by said electrically conductive upper face (4); c) filling (7) the cavities (8) of the mold by electroplating to form a metal part (21, 51, 81); d) selectively machining (9) a portion of the metal piece (21, 51, 81) to form a one-piece micromechanical piece (31, 41, 61, 91) at at least two distinct levels; e) releasing (11) the micromechanical part (31, 41, 61, 91) of the substrate (2) and the photoresist (6). 2. Method (1) according to the preceding claim, characterized in that the upper surface (4) is made electrically conductive by the doping of the substrate (2) of silicon and / or by the deposition of an electrically conductive layer on the substrate (2) silicon. 3. Method (1) according to claim 1 or 2, characterized in that the substrate (2) of silicon has a thickness of between 0.3 and 1 mm. 4. Method (1) according to one of the preceding claims, characterized in that step b) comprises the following phases: f) depositing a photoresist layer (6) on the electrically conductive upper surface (4) of the substrate (2); g) selectively illuminating a portion of the photoresist (6); h) developing the photosensitive resin (6) to structure the mold. 5. Method (1) according to one of the preceding claims, characterized in that the metal part (21, 51, 81) is formed based on nickel-phosphorus (NiP, NiP12). 6. Method (1) according to one of the preceding claims, characterized in that it further comprises between step c) and step d), the following step: i) leveling (10), by running-in, the mold and the metal part (21, 51, 81). 7. Method (1) according to one of the preceding claims, characterized in that, in step e), the method (1) comprises the following phases: j) removing (12) the photoresist; k) removing (14) the substrate; and in that between the phase j) and the phase k), the method (1) further comprises the following phase: I) depositing (16) a coating (13) on the micromechanical part assembly (31, 41, 61, 91) - substrate (2). 8. Process (1) according to the preceding claim, characterized in that the phase I) is carried out by physical or chemical vapor deposition. 9. Method (1) according to claim 7, characterized in that the phase I) is carried out by electroplating. 10. Method (1) according to one of the preceding claims, characterized in that a plurality of micromechanical parts (31, 41, 61, 91) are formed on the same substrate (2). 11. Timepiece characterized in that it comprises a micromechanical part (31, 41, 61, 73, 91, 103) monobloc at least two distinct levels obtained according to one of the preceding claims.