CH701972A2 - Method for manufacturing wheel of clock element in clock industry, involves forming unit in lower layer for forming another cavity of another wheel to structure photo resist resin at side of lower layer that forms liner at walls of cavity - Google Patents

Abstract

The method involves providing a substrate that contains an upper layer and a lower layer. The upper layer and the lower layer are joined together by an intermediate layer that is made of silicon dioxide. A unit is formed in the upper layer and the intermediate layer to form a cavity of a wheel (55). Another unit is formed in the lower layer for forming another cavity of another wheel (57) to structure photo resist resin at a side of the lower layer. The former cavity is coated with gold, and the lower layer forms a liner (51) at walls of the latter cavity. An independent claim is also included for a wheel.

Description

Field of the invention

The invention relates to a mobile micro-machinable material mounted crazy on a monobloc axis and its manufacturing method. More specifically, the invention relates to a gear comprising such a mobile.

Background of the invention

It is known to make silicon wheels for a timepiece. However, the handling of such mobile is not easy and it is currently not possible to manufacture a mobile for a timepiece mounted crazy without the risk of damaging or breaking.

Summary of the invention

The object of the present invention is to overcome all or part of the disadvantages mentioned above by proposing a cogwheel with at least one of the movable micro-machinable material is mounted crazy and its manufacturing process.

For this purpose, the invention relates to a train having an axis, a first end is provided with a collar coming form, a first movable micro-machinable material being adjusted on the second end of the axis and a second mobile made of micro-machinable material mounted loosely on said first end of the axis.

According to the invention, it is understood that it is possible to manufacture a wheel whose wheel, for example crystalline silicon, is mounted idle on a one-piece metal axis.

According to other advantageous features of the invention: said second end is provided with a second collar formed integrally with the axis which partially covers said first mobile; said second flange is toothed to form a second level of said first movable; the first mobile comprises at least partially an outer coating; said axis is of a low friction material; the micro-machinable materials are based on silicon.

In addition, the invention relates to a timepiece characterized in that it comprises at least one wheel according to one of the previous variants.

Finally, the invention relates to a method of manufacturing a gear train comprising the following steps: a) providing a substrate comprising an upper layer and a lower layer of micro-machinable material and secured together by an intermediate layer; b) etching at least one pattern in the upper layer and the intermediate layer to expose the lower layer to form at least a first cavity belonging to a first mobile; c) covering at least the bottom of said at least one first cavity of an electrically conductive coating; d) electroforming a material at least in the bottom of said at least one first cavity; e) etching a second pattern in the lower layer to the coating of said electrically conductive material to form at least a second cavity belonging to a second mobile; f) structuring a photoresist on the underside of the lower layer forming a liner on the walls of said at least one second cavity and at least one recess flaring coaxially from said at least one second cavity; g) continuing the electroforming begun in step d) to fill said at least one first cavity and begin electroforming a material in said at least one second cavity and said at least one recess to form an axis; provided with a collar; h) removing the photoresist; i) removing the intermediate layer in order to separate the first and second mobiles; j) release the manufactured wheel of the substrate.

According to the invention, it is understood that it is possible to manufacture very precisely from a single substrate the wheel explained above according to LIGA and DRIE processes that are intertwined.

According to other advantageous features of the invention: step f) also comprises the phase k): covering at least the bottom of said at least one recess of a second electrically conductive coating in order to improve the formation of said collar; the method comprises, before step d), step 1): mounting a piece on the top of the substrate to form at least one other recess flaring coaxially from said at least a first cavity to provide a level electroformed material above the top layer; step c) also makes it possible to cover at least the bottom of said at least one other recess of said electrically conductive coating; the method comprises, after step c), step m): mounting a rod in said at least a first cavity to form a hole in the future train; comprises, before step g), step n): mounting a rod in said at least one second cavity to form a hole in the future train; steps b) and e) comprises the structuring phases of at least one protective mask on the layer to be etched, anisotropic etching of said layer in portions not covered by said at least one protective mask and removal of the protective mask; several wheels are made on the same substrate; each coating comprises at least one layer of gold; the micro-machinable materials are based on silicon.

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 11 <sep> are representations of the successive steps of a method of manufacturing a wheel according to one embodiment of the invention; <tb> fig. 12 <sep> is a perspective representation of a wheel according to one embodiment of the invention; <tb> fig. 13 <sep> is a representation of the last step of a method of manufacturing a gear train according to a variant of the invention; <tb> fig. 14 <sep> is a perspective representation of a gear train according to a variant of the invention; <tb> fig. <Sep> is a block diagram of a method of manufacturing a wheel according to the invention.

Detailed Description of the Preferred Embodiments

As shown in FIG. 15, the invention relates to a manufacturing method 1 of a gear train 51, 51 for example for a timepiece. The manufacturing method 1 comprises successive steps intended to prepare a substrate 29 made of micro-machinable materials, such as, for example, silicon-based materials. In the explanatory below, the respective quantities are not on the same scale. Indeed, some thicknesses have been increased as those of the coatings 37 and 47 to make more understandable said explanatory.

A first step 2 of the method 1 is to provide a substrate 9 having an upper layer 31 and a lower layer 33 of micro-machinable materials secured together by an intermediate layer 32 as shown in FIG. 1.

Preferably, the substrate 29 is a S.O.I. (Well known abbreviation from the English term "Silicon On Isulator"). Thus, the intermediate layer 32 is preferably made of silicon dioxide. In addition, the upper 31 and lower 33 layers are crystalline silicon.

According to the invention, the method 1 comprises a second step 3, intended to burn at least one pattern 34 in the upper layer 31 and the intermediate layer 32 to partially discover the top of the lower layer 33.

The second step 3 consists initially of structuring at least one mask 36 of protection on the upper layer 31 as illustrated in FIG. 1. As can also be seen in fig. 1, the mask 36 comprises at least one pattern 34 which does not cover the upper layer 31. Such a mask 36 may, for example, be obtained by photolithography using a positive or negative type photoresist.

In a second step, the upper layer 31 is etched until discovering the intermediate layer 32 as shown in FIG. 2. According to the invention, the etching preferably comprises an anisotropic dry attack of the deep reactive ion etching (RRE) type. The anisotropic etching is carried out in the upper layer 31 according to the pattern 34 of the mask 36.

In a third step, the pattern 34 is extended in the intermediate layer 32 by etching to partially discover the top of the lower layer 33. According to the invention, the etching may comprise a chemical attack or a directional etching of exposed parts of layer 32.

In a fourth step, the mask 36 is removed. Of course, depending on the resistance of the mask 36 to the etching mode of the intermediate layer 32, the mask 36 can be removed before or after this etching.

Thus, as shown in FIG. 3, at the end of the second step 3, the upper layers 31 and 32 are etched in their respective thickness of at least one cavity 35, forming a first mobile 55, 55 of the future wheel 51, 51 .

In a third step 5, an electrically conductive coating 37 is deposited by covering at least the bottom of each of said at least one cavity 35. In the example illustrated in FIG. 4, it can be seen that it is the upper assembly of the substrate 29 which is coated. As will be explained below, the walls of said at least one cavity 35 need not be coated, while the presence of the coating on the top of the top layer 31 may be necessary for the embodiment of the gear train 51 provided below.

Preferably, the coating 37 is obtained by a vapor deposition. However, other types of deposit are possible as a chemical deposit. Preferably, the coating 37 comprises at least one layer of gold, optionally deposited on a chromium tie layer.

Preferably, in order to limit the areas of the future electroforming, the method 1 may comprise a step 6 of mounting a workpiece 38 on the top of the substrate 29. This step 6 may consist, for example, in structuring by photolithography a resin photosensitive type positive or negative.

Advantageously, this step 6 may also allow the formation of at least one recess 39 flaring coaxially from said at least one cavity 35 to achieve said embodiment of the gear train 51 as shown in FIG. 5.

Preferably, the method 1 may comprise at the same time, before or after step 6, a step 7 of mounting a rod 40, as shown in FIG. 5, from the bottom of said at least one cavity 35 to directly form a shaft hole 54, 54 of the gear 51, 51 during the future electroforming. This has the advantage not only of avoiding having to machine the gear 51, 51 after the electroforming is completed, but also of being able to carry out any shape of inner section, uniformly or otherwise, over the entire height of the future hole 54, 54. This step 7 may also consist, for example, of structuring by photolithography a photosensitive resin of the positive or negative type.

The method 1 then continues with the electroforming step 9 for growing an electrolytic deposit 41 at least in the bottom of said at least one cavity 35. In the example illustrated in FIG. 6, representing the variant embodiment of the gear train 51, it can be seen that the deposit 41 grows in both said at least one cavity 35 and in said at least one recess 39 around the rod 40.

Preferably, step 9 is stopped before the deposit protrudes from above the substrate 29. In the case of the first variant of the gear train 51, the top of the substrate 29 is the top of said at least one cavity 35. In the case of the second variant of the gear train 51, the top of the substrate 29 is the top of said at least one recess 39 as illustrated in FIG. 6. It is understood why, in this second variant, it may be necessary that the top of the upper layer 31, that is to say the bottom of said at least one recess 39, also comprises the coating 37 formed during the step 5.

According to the invention, the method 1 continues with the step 13 for engraving at least one pattern 44 in the lower layer 33 to discover the coating 37 and, optionally, the deposit 41.

Step 13 consists in a first step to structure at least one mask 46 of protection on the lower layer 33 as shown in FIG. 7. As can also be seen in fig. 7, the mask 46 comprises at least one pattern 44 which does not cover the lower layer 33. Such a mask 46 may, for example, be obtained by photolithography using a positive or negative type of photosensitive resin.

In a second step, the lower layer 33 is etched until the coating 37 and, optionally, the deposit 41. According to the invention, the etching preferably comprises an anisotropic dry attack of the ion etching type. deep reagent (DRE). The anisotropic etching is carried out in the lower layer 33 according to the pattern 44 of the mask 46.

In a third step, the mask 46 is removed. Thus, at the end of step 13, the lower layer 33 is etched throughout its thickness with at least a second cavity 45, making it possible to form a second mobile 57, 57 of the future wheel 51, 51.

The method 1 then comprises a step 16 consisting in structuring a photosensitive resin 43 on the underside of the lower layer 33 by forming a lining 51 on the walls of said at least one second cavity 45.

Preferably, in a next step 15, an electrically conductive coating 47 is deposited by covering the top of the structured resin 43. By analogy with the walls of said at least one cavity 35, the lining 51 of said at least one second cavity 45 also does not need to be coated.

Preferably, the coating 47 is obtained by a vapor deposition. However, other types of deposit are possible as a chemical deposit. Preferably, the coating 47 comprises at least one layer of gold, optionally deposited on a chromium tie layer.

Preferably, in order to form at least a second recess 49 flaring coaxially from said at least one second cavity 45, the method 1 comprises a step 17 of mounting a part 48 on the underside of the substrate 29. This step 17 For example, it may consist in structuring by photolithography a photosensitive resin of the positive or negative type.

Preferably, step 17 of method 1 may also consist of mounting a rod 42, as shown in FIG. 8, from the bottom of said at least one second cavity 45 in order to directly form an axle hole 54, 54 of the gear 51, 51 during the future electroforming according to the same advantages as those explained for the rod 40. Preferably if the rods 40 and 42 are respectively formed in the cavities 35 and 45, they are aligned.

The method 1 then continues with a new electroforming step 19 for continuing the deposition begun during step 9 in order to fill said at least one cavity 35 (and, optionally, said at least one recess 39). and starting electroforming a material in said at least one second cavity 45 and said at least one second recess 49 to form an axis 53, 53 provided with a flange 52, 52 and, optionally, a second collar 54.

Preferably, at the end of step 19, the electrolytic deposition 41 protrudes from above and below the substrate 29. A break-in is then performed in order to put the deposit 41 at the same level as that of the substrate 29 as illustrated in FIG. fig. 9.

The method 1 continues with the step 21 of removing the resin 43, the workpiece 48 and, optionally, the workpiece 38 as illustrated in FIG. 10. The next step 23 is to remove the intermediate layer 32 to separate the first 55, 55 and second 57, 57 mobile formed respectively in the upper layer 31 and the lower layer 33. According to the invention, the withdrawal is produced by etching which may consist, for example, in a chemical etching. Finally, in the final step 25, the gear train 51, 51 thus formed is released from the substrate 29.

Thus, according to the first variant of the method 1 illustrated in FIGS. 13 and 14, the invention allows the realization of a composite wheel 51 having an axis 53 whose one end is provided with a flange 52 formed in shape, a first mobile 55 of micro-machinable material being fitted on the second end of the axis 53 and a second mobile 57 of micro-machinable material being mounted loosely on said first end of the shaft 53. As illustrated in these FIGS. 13 and 14, we see that the axis 53 has a hole 54 allowing the gear train 51 to be driven against a shaft or a pivot.

According to the second variant of the method 1 illustrated in FIGS. 11 and 12, the invention allows the realization of a composite gear train 51 having an axis 53 whose first and second ends are provided with a flange 52, 56 come form. In addition, the gear train 51 comprises a first wheel, a first wheel 55 of micro-machinable material is fitted on the second end of the shaft 53, secured and partial overlap of a second wheel 56 of electroformed material . A second mobile 57 of micro-machinable material is mounted loosely on said first end of the axis 53. As illustrated in these FIGS. 11 and 12, we see that the axis 53 has a hole 54 allowing the gear train 51 to be driven against a shaft or a pivot.

As visible in FIGS. 11 and 13, the first mobile 55, 55 may comprise at least partially an outer coating corresponding to the thin layer of coating 37 for improving the tribology of said first mobile 55, 55. In addition, preferably, the axis 53, 53 electroformed is a low friction material.

Of course, the present invention is not limited to the example shown but is susceptible of various variations and modifications that will occur to those skilled in the art. Thus, a plurality of gear trains 51, 51 can be manufactured on the same substrate 29 in order to produce a series production of gear trains 51, 51 which are not necessarily identical to each other.

Similarly, it is also possible to change silicon-based materials with crystallized alumina or crystalline silica or silicon carbide.

It is also conceivable that the coatings 37 and / or 47 are of different natures and / or that they are each deposited according to different methods than those described above. It is also conceivable that these coatings 37 and / or 47 are useless by using an electrically conductive micro-machining material such as doped silicon and / or that the resin 43 is electrically conductive.

Finally, the flange 52, 52 as well as the flange 54, 54 may also include a toothing. In addition, the application of gear train 51, 51 is not limited to a timepiece.

Claims (17)

A method of manufacturing (1) a gear train (51, 51) comprising the steps of: a) providing (2) a substrate (29) comprising an upper layer (31) and a lower layer (33) of micro-machinable material and secured together by an intermediate layer (32); b) etching (3) at least one pattern (34) in the upper layer (31) and the intermediate layer (32) until the bottom layer (33) is exposed to form at least a first cavity (35) belonging to a first mobile (55, 55); c) covering (5) at least the bottom of said at least one first cavity (35) of an electrically conductive coating (37); d) electroforming (9) at least one material in the bottom of said at least one first cavity (35); e) etching (13) a second pattern (44) in the lower layer (33) to the coating (37) of said electrically conductive material to form at least a second cavity (45) belonging to a second mobile (57, 57 ); f) structuring (16) a photosensitive resin (42, 43, 48) on the underside of the lower layer (33) forming a liner (51) on the walls of said at least one second cavity (45) and at least one recess (49) flaring coaxially from said at least one second cavity (45); g) continuing (19) electroforming started in step d) to fill said at least one first cavity (35) and start electroforming (19) of a material in said at least one second cavity (45); ) and said at least one recess (49) to form an axle (53, 53) with a flange (52, 52); h) removing (21) the photoresist (38, 40, 42, 43, 48); i) removing (23) the intermediate layer (32) to separate the first (55, 55) and second (57, 57) mobile; j) releasing (25) the wheel train (51, 51) manufactured from the substrate (29). 2. Method (1) according to the preceding claim, characterized in that step f) also comprises the following phase: k) covering (15) at least the bottom of said at least one recess (49) of a second coating (47) electrically conductive to improve the formation of said flange. 3. Method (1) according to claim 1 or 2, characterized in that it comprises, before step d), the following step: I) mounting a workpiece (38) on top of the substrate (29) to form at least one further recess (39) flaring coaxially from said at least one first cavity (35) to provide a level of electroformed material above the upper layer (31). 4. Method (1) according to the preceding claim, characterized in that step c) also covers at least the bottom of said at least one other recess (39) of said coating (37) electrically conductive. 5. Method (1) according to one of the preceding claims, characterized in that it comprises, after step c), the following step: m) mounting (7) a rod (40) in said at least one first cavity (35) to form a hole (54, 54) in the future train (51, 51). 6. Method (1) according to one of the preceding claims, characterized in that it comprises, before step g), the following step: n) mounting (17) a rod (42) in said at least one second cavity (45) to form a hole (54, 54) in the future train (51, 51). 7. Method (1) according to one of the preceding claims, characterized in that steps b) and e) comprises the following phases: structuring at least one mask (36, 46) for protection on the layer to be etched (31, 33); - Perform an anisotropic attack of said layer according to the parts not covered by said at least one protective mask; - remove the protective mask. 8. Method (1) according to one of the preceding claims, characterized in that several wheels (51, 51) are manufactured on the same substrate (29). 9. Method (1) according to one of the preceding claims, characterized in that each coating (37, 47) comprises at least one layer of gold. 10. Method (1) according to one of the preceding claims, characterized in that the micro-machinable materials are based on silicon. 11. Gear (51, 51) having an axis (53, 53) whose first end is provided with a flange (52, 52) shaped, a first mobile (55, 55) of micro material -usinable being adjusted on the second end of the shaft (53, 53) and a second mobile (57, 57) of micro-machinable material mounted crazy on said first end of the axis. 12. Gear according to the preceding claim, characterized in that said second end is provided with a second flange (56) formed in shape with the axis (53) which partially covers said first mobile (55). 13. Gear according to the preceding claim, characterized in that said second flange (56) is toothed to form a second level of said first movable (55). 14. Gear according to one of claims 11 to 13, characterized in that the first mobile (55, 55) comprises at least partially an outer coating (37). 15. Gear according to one of claims 11 to 14, characterized in that said axis (53, 53) is of a low friction material. 16. Gear according to one of the preceding claims, characterized in that the micro-machinable materials are based on silicon. 17. Timepiece characterized in that it comprises at least one wheel according to one of claims 11 to 16.