HK1189871B - Method for producing a complex smooth micromechanical part - Google Patents

Description

Method for producing complex smooth micromechanical parts

Technical Field

The present invention relates to a complex micromechanical part made of any material, for example a carbon-based material, and to a method for manufacturing such a part.

Background

The manufacture of micromechanical parts purely from synthetic diamond or DLC (diamond-like carbon) is very expensive and is tribologically disadvantageous due to the disadvantageous roughness produced by thick layer deposition processes or etching methods in the substrate. Therefore, it is currently preferred to coat micromechanical parts with a thin layer of synthetic diamond or DLC, although this does not enable all shapes to be obtained.

Disclosure of Invention

The aim of the present invention is to overcome all or part of the aforementioned drawbacks by proposing a micromechanical part with a complex geometry, using a minimum amount of material and having a greatly improved roughness and a very favourable rejection rate and production costs.

The invention therefore relates to a method for manufacturing a micromechanical part made of a single piece of material, characterized in that it comprises the following steps:

a) forming a substrate comprising a negative cavity for fabricating the micromechanical part.

b) Coating the negative cavity of the substrate with a layer of material.

c) A thickness greater than the thickness of the deposited layer is removed from the substrate, leaving a limited thickness of the layer in the negative cavity.

d) The substrate is removed to release the micromechanical part formed in the negative cavity.

It is therefore evident that this method allows to manufacture a one-piece micromechanical part, i.e. without interruption of the material, having a "skin" of material, i.e. a small amount of material, the external surface of which reproduces the very advantageous roughness of the base material, which greatly reduces the cost of the material required on the skin and improves the overall roughness, in particular on the external surface, so as to perfect its tribological properties.

According to other advantageous features of the invention:

-the negative cavity comprises walls forming teeth;

-said material is crystalline or amorphous carbon-based;

between step b) and step c), the method comprises a step e): filling the cavity coated with the first material with a second material, so as to obtain, after steps c) and d), a micromechanical part made of the first material and reinforced and/or decorated with the second material;

-between step c) and step d), the method comprises a step f): filling the cavity coated with the first material with a second material, so as to obtain, after step d), a micromechanical part made of the first material and reinforced and/or decorated with the second material;

-in step f), the second material is formed projecting from the cavity, so as to form an additional functional element of the micromechanical part;

-the second material comprises a metal or metal alloy;

-said micromechanical part forming an external part of the timepiece, a balance spring, a balance, a pallet, a bridge, a train of wheels or an escape wheel.

Drawings

Other characteristics and advantages of the invention will appear more clearly from the following description, given by way of non-limiting illustration, with reference to the accompanying drawings, in which:

figures 1 to 5 are views of successive steps of a manufacturing method according to a first embodiment of the invention;

figures 6 to 10 are views of an exemplary micromechanical part produced according to a first embodiment of the present invention;

figures 11 to 13 are views of successive steps of a manufacturing method according to a second embodiment of the invention;

figure 14 is a view of an example micromechanical part produced according to a second embodiment of the present invention;

figures 15 and 16 are views of successive steps of a manufacturing method according to a third embodiment of the invention;

figure 17 is a view of an example micromechanical part produced according to a third embodiment of the present invention.

Detailed Description

As described above, the present invention relates first to a one-piece micromachine component made of, for example, a carbon-based material. "carbon-based" refers to a crystalline form, a synthetic carbon allotrope, such as diamond or one or several layers of graphene, or an amorphous form, a synthetic carbon allotrope, such as diamond-like carbon (DLC).

Of course, other types of materials that can be deposited in layers and have tribological advantages may be used instead of synthetic carbon allotropes, advantageously according to the invention. Such alternative materials may be, for example, silicon-based compounds, i.e. for example silicon nitride, silicon oxide or silicon carbide.

Such micromechanical parts are designed for applications in the field of timepieces. However, other fields, in particular, such as the aeronautical, jewelry or automotive industries, are also conceivable.

In the timepiece field, such micromechanical parts may for example form the external part of the watch, a balance spring, a balance, a pallet, a bridge or even a train of wheels, such as an escape wheel, which is formed wholly or partly of synthetic carbon allotropes or of the above-mentioned alternative material bases.

A first embodiment of a method for producing such a micromechanical part is shown in fig. 1 to 5. In step a, the method comprises forming a negative cavity 3 in the substrate 1 for forming the future micromechanical part 11, 21, 31, 41. A variety of substrates 1 are possible. Preferably, the material of the substrate 1 is chosen to have a very low roughness, i.e. to have the natural characteristic of a smooth surface.

By way of example, fig. 1 and 2 show a step a of forming from a silicon substrate 1, which makes it possible to obtain a very good roughness, i.e. an arithmetic mean deviation Ra substantially less than 10 nm. Thus, in the first stage shown in fig. 1, the substrate 1 is covered by a mask 2 having holes 4 that expose the top of the substrate 1. In the second stage, etching is performed in the holes 4. This may be a wet or dry etch. Finally, in a third stage, shown in fig. 2, the cover 2 is removed, leaving only the negative cavity 3 made in the substrate 1.

The second step b consists in making the material of thickness e necessary for future micromechanical parts₁Coating at least the negative cavity 3. In the example shown in fig. 3, the substrate 1 is completely coated with a layer 5, i.e. at least the layer 5 is coated in the cavities 3 etched in step a. Similar to the deposition material, the type of deposition may be varied. Step b may include, in a non-limiting manner, chemical vapor deposition, physical vapor deposition, or electrodeposition.

In a third step c, the method comprises removing a portion of substrate 1 coated with layer 5 so as to leave a limited thickness of said layer 5 in said negative cavity 3. Preferably according to the invention, the thickness e of the specific layer 5 is removed from the substrate 1₁Greater thickness e₂As shown in fig. 4. It can thus be seen that the layer 5 present in the cavity 3 of the substrate 1 is thus free-standing, i.e. not joined to the rest of the layer 5 deposited in step b.

In a fourth and final step d of the first embodiment, the method comprises removing the substrate 1, thereby releasing the micromechanical part formed in the cavity 3. Thus, in the above example where the substrate 1 is made of silicon, step d may comprise a selective etching of silicon. This can be obtained, for example, by chemical etching using a bath comprising tetramethylammonium hydroxide (TMAH and TMAOH).

At the end of step d, as shown in fig. 5, a micromechanical part formed only by layer 5 is obtained, the geometry of which matches cavity 3 present in substrate 1. Advantageously, the outer surface (i.e. the surface in direct contact with the substrate 1) has a very good roughness, i.e. comparable to the roughness of the substrate 1, and is preferably used as a mechanical contact surface. Finally, the height e for micromechanical parts between 10 μm and 500 μm₃Depositing only a thickness e₁Layer 5 of 0.2 μm to 20 μm. It is therefore evident that material and production costs are saved due to the shortened time in step b.

It is thus seen that a micromechanical part is obtained whose base section is formed by at least two intersecting and non-aligned sections, such that one of the at least two sections forms the height e of the micromechanical part₃. Said height e₃Greater than the thickness e of each section₁. Naturally, depending on the complexity of the cavity 3, the base section may be a relatively simple, substantially U-shaped section, i.e. comprising three sections.

Thus, depending on the complexity of the cavity 3, the micromechanical part is formed by projection/projection (including rotation) of at least one base section with two or three sections on a rectilinear or non-rectilinear directrix. Furthermore, it is not difficult to form a very complex or variable section, for example to form a tooth on the wall of the cavity 3, which tooth will form a corresponding tooth for one of the sections of this section.

By way of non-limiting example, the micromechanical part 11, 21, 31, 41 that can be produced according to the first embodiment is shown in fig. 6 to 10. Fig. 6 therefore shows a micromechanical part 11 whose basic U-shaped cross section is projected on a straight alignment. Fig. 7 shows a micromechanical part 21 with a base cross section similar to micromechanical part 11, but with the base cross section projected on a sinusoidal, i.e. non-linear, directrix. It can also be seen that it is possible to produce micromechanical parts, half of which is formed by part 11 and the other half of which is formed by part 21, both in the transverse direction and in the longitudinal direction in one piece, without complicating the method.

Fig. 8 and 9 show an exemplary base section that can have two sections, which is projected rotationally to obtain a micromechanical part 31 in the form of a cap. Such micromechanical parts may, for example, be fixed to an element to improve its tribological relationship with another component. By way of example, the micromechanical part 31 may be fixed on the end of the pivot 32 of the shaft 33, so that the pivot 32 cooperates with the bearing via the micromechanical part 31.

Finally, fig. 10 shows a last example of a more complex micromechanical part 41, which does not make the method more difficult to implement. The micromechanical part 41 comprises a substantially disc-shaped plate 43 from whose peripheral edge orthogonally project teeth 45, and the centre of the plate 43 comprises a duct 47 formed with a hole 48, the hole 48 being intended to cooperate with, for example, a pivot pin. Fig. 10 thus shows that the thickness of the teeth 45 and of the plate 43 is determined by the thickness e of the layer 5 deposited in step b of the method₁And (4) forming.

A second embodiment, which is different from the first embodiment described above, is shown in fig. 11 to 13. Steps a to d remain the same as in the first embodiment. However, as shown in fig. 11, step e is performed between step b and step c, which comprises filling the hollow 6 in the cavity 3 coated with the first material 5 with the second material 7. Thus, after steps c and d similar to the first embodiment, as shown in fig. 12 and 13, respectively, a micromechanical part made of first material 5, reinforced and/or decorated with second material 7, is obtained.

Preferably, the filling of the hollow 6 is achieved by electrodeposition or thermal deformation. The second material is preferably a metal or metal alloy, which may or may not be amorphous. However, in an alternative, there is no means by which the type of deposition and/or the natural characteristics of the deposited material can be prevented from changing.

Subsequently, in a fourth step c, not only the thickness of said layer 5 is confined within said negative cavity 3, but also the deposit 7 of the second material is leveled and preferably flush with said confined portion of layer 5. Finally, in a fifth and final step d of the second embodiment, the method comprises the removal of the substrate 1, thus releasing the micromechanical part formed in the cavity 3, with the same variants and advantages as in the first embodiment.

At the end of step d, as shown in fig. 13, a micromechanical part formed by layer 5 is obtained, the geometry of which matches cavity 3 present in substrate 1 and is reinforced and/or decorated by deposition 7. Advantageously, the outer surface formed by the layer 5, i.e. the surface in direct contact with the substrate 1, has a very good roughness, i.e. a roughness comparable to that of the substrate 1, and preferably serves as a contact surface.

According to a further advantage of the invention, it is thus possible to coat parts with thin layers, which was previously impossible to achieve, since the thin layer deposition requires special conditions, such as pressure, temperature or the compounds used. By way of non-limiting example, it is thus advantageously possible according to the invention to form a predominantly metallic part from the deposit 7, the deposit 7 being diamond-coated 5, while it is currently difficult, as far as the applicant is aware, to diamond-coat metallic parts.

Finally, a height e for the micromechanical part of between 10 μm and 500 μm₃The deposited thickness e of the layer 5₁Between 0.2 μm and 20 μm, the remainder being made of deposit 7. It is evident that material costs and production costs are saved due to the reduced time of step b of depositing layer 5, the rest of the part being formed by the cheaper deposit 7.

It can thus be seen that a micromechanical part can be obtained using the same basic cross-section as in the first embodiment. By way of non-limiting example, fig. 14 shows a micromechanical part 51 that can be manufactured according to the second embodiment. The micromechanical part 51 comprises a substantially disc-shaped plate 53, corresponding to the plate 43 of fig. 10, from the periphery of which plate 53 orthogonally project teeth 55, the centre of the plate 53 comprising a duct 57 formed with a hole 58, the hole 58 being intended to cooperate with, for example, a pivot pin. Fig. 14 thus shows that the thickness of the teeth 55 and of the ducts 57 is determined by the thickness e of the layer 5 deposited in step b of the method₁The rest is formed by passing through in step eThe portion 52 formed by the deposit 7.

Fig. 15 to 16 show a third alternative embodiment to the first embodiment described above. Steps a to d remain the same as in the first embodiment. However, as shown in fig. 15, a fourth step f is performed between step c and step d, which comprises filling the hollow 6 in the cavity 3 coated with the first material 5 with the second material 17. Thus, after step d, similar to the first embodiment, a micromechanical part made of first material 5, reinforced and/or decorated with second material 7, is obtained, as shown in fig. 16.

Step f serves to fill the hollow 6 of the cavity 3, and may also advantageously be formed with a thickness e, compared to step e of the second embodiment₃Thereby forming an additional functional element of the micromechanical part, as shown in fig. 15.

Step f preferably comprises a phase of building up a mould 18 on the substrate 1 after step c, followed by a phase of filling the recesses formed jointly by the hollows 6 of the cavities 3 and the perforations in the mould 18. Finally, step f comprises a stage of removing the mold 18 from the surface of the substrate 1.

The stage of building up the mold 18 may be formed by photolithography, for example, using a negative or positive photosensitive resin. Furthermore, the filling phase may be formed, for example, using electrodeposition. The second material is preferably a metal or metal alloy, which may or may not be amorphous. However, there is no means by which the type of deposition and/or the natural properties of the deposited material can be prevented from changing.

Step f may also include a final step of grinding and/or polishing the top portion of the deposit 17. Therefore, in the fifth and final step d of the third embodiment, the method comprises removing the substrate 1, thus releasing the micromechanical part formed in the cavity 3, with the same advantages as the first embodiment.

At the end of step d, as shown in fig. 16, a micromechanical part formed by layer 5 is obtained, the geometry of which matches cavity 3 present in substrate 1 and is reinforced and/or decorated with deposit 17. Advantageously, the outer bottom surface formed by the layer 5, i.e. the surface in direct contact with the substrate 1, has a very good roughness, i.e. a roughness comparable to that of the substrate 1 and preferably serves as a contact surface.

According to a further advantage of the invention, it is thus possible to coat parts with thin layers, which was previously impossible to achieve, since the thin layer deposition requires special conditions, such as pressure, temperature or the compounds used. By way of non-limiting example, it is therefore advantageously possible according to the invention to form a predominantly metallic part from the deposit 17, the deposit 17 being partially diamond-coated 5, while it is currently difficult to diamond-coat metallic parts, as far as the applicant is aware.

Furthermore, in the third embodiment, the micromechanical part also comprises a second top layer, which is formed entirely by the deposit 17, i.e. without the layer 5, thus forming an additional functional element of the micromechanical part. In a non-limiting manner, the functional element may be a tooth 12, a hole 14 and/or a shoulder 16 for cooperating, for example, with another component.

As described in the first two embodiments, it is evident that material and production costs are saved due to the shortened deposition step of the layer 5, while the remaining part of the part is formed with a cheaper deposition 17 and can provide very complex geometries.

It can thus be seen that the micromechanical part can be obtained with the same base section as the first two embodiments. By way of non-limiting example, fig. 17 shows a micromechanical part 61 that can be manufactured according to a third embodiment. The micromechanical part 61 comprises a substantially disc-shaped plate 63, corresponding to the plate 43 of fig. 10, from the periphery of which plate 63 orthogonally projects teeth 65, the centre of the plate 63 comprising a duct 67 formed with a hole 68, the remainder being filled in step f by the deposit 17. At a second level, formed only by deposit 17, micromechanical part 61 has a wheel 62 whose periphery comprises teeth 64 and whose centre comprises a hole with a preferably smaller cross section than hole 68, hole 68 being intended to cooperate, for example, with a pivot pin.

The invention is of course not limited to the examples shown, but can have many variants and alternatives obvious to a person skilled in the art. In particular, several micromechanical parts, which may or may not have the same design, may be manufactured simultaneously on the same substrate. Furthermore, in the example of fig. 4 or 12, it can be seen that the removal of the substrate 1 also forms a substantially U-shaped cross-section portion, which is formed by the layer 5 on the periphery and bottom of the substrate 1.

Thus, not only several cavities 3, which may be identical or different, may be formed on the substrate 1, but also cavities may be formed on several faces of the substrate 1, i.e. steps a and c and possibly e or f may be performed on several faces of the substrate 1. Thus, in the case of the second and third embodiments, it is possible to envisage obtaining a one-piece part formed by the layer 5 on the periphery and/or bottom of the substrate 1 and a reinforced and/or decorated part formed by the layer 5 and the deposits 7, 17 on top of the substrate 1.

Furthermore, the embodiments may be combined with each other. Thus, by way of non-limiting example, the piece 51 can be produced by means of the third modified embodiment. In fact, it is possible to replace the deposit 7 of the second embodiment by a similar deposit 17 (i.e. not projecting from the cavity 3) by step f after carrying out steps a to c. Obviously, step f of the modification of the third embodiment is similar to step e of the second embodiment, but step f is carried out after step c, rather than after step b.

Finally, although the figures show substantially perpendicular sections, it is clear that these sections may also form acute or obtuse angles with respect to each other.

Claims (17)

1. A method of manufacturing a one-piece micromechanical part (11, 21, 31, 41, 51, 61) made of synthetic carbon allotropes, characterized in that it comprises the following steps:

a) forming a substrate (1) comprising a negative cavity (3) for manufacturing a micromechanical part;

b) coating the negative cavity (3) of a substrate (1) with a layer (5) of a synthetic carbon allotrope, the thickness (e) of said layer₁) Is less than the depth of the negative cavity (3);

c) removing from the substrate (1) a thickness (e) greater than that of the layer (5) deposited₁) Greater thickness (e)₂) So as to leave a limited thickness of the deposited layer (5) in the negative cavity (3);

d) the substrate (1) is removed, releasing a one-piece micromechanical part (11, 21, 31, 41, 51, 61) formed in the negative cavity (3), said micromechanical part comprising an outer surface having a roughness comparable to the roughness of the substrate (1).

2. Method according to claim 1, characterized in that the negative cavity (3) comprises walls forming teeth (45, 55, 65).

3. The method according to claim 1, wherein the synthetic carbon allotrope (5) is in crystalline form.

4. The method according to claim 1, wherein the synthetic carbon allotrope (5) is in a non-crystalline form.

5. Method according to claim 1, characterized in that, between step b) and step c), the method comprises the following steps:

e) filling the cavity (3) coated by said synthetic carbon allotrope (5) with a second material (7), so as to obtain, after steps c) and d), a micromechanical part (51) made of synthetic carbon allotrope (5) and reinforced and/or decorated with the second material (7).

6. A method according to claim 5, characterized in that the second material (7, 17) comprises a metal or a metal alloy.

7. Method according to claim 1, characterized in that, between step c) and step d), the method comprises the following steps:

f) filling the cavity (3) coated by said synthetic carbon allotrope (5) with a second material (7, 17), so as to obtain, after step d), a micromechanical part (51, 61) made of synthetic carbon allotrope (5) and reinforced and/or decorated with the second material (7, 17).

8. Method according to claim 7, characterized in that in step f) the second material (17) is formed protruding from the negative cavity (3) to form an additional functional element (12, 14, 16, 62) of the micromechanical part.

9. The method according to claim 7, wherein the second material (7, 17) comprises a metal or a metal alloy.

10. The method according to claim 1, characterized in that said micromechanical part forms an external part of a timepiece, a balance spring, a balance, a pallet fork, a bridge or a train of wheels.

11. Hollow micromechanical part (11, 21, 31, 41, 51, 61) produced by a method according to claim 1, formed from a single piece made of synthetic carbon allotrope in the form of a layer (5) having a thickness (e)₁) Between 0.2 μm and 20 μm, said micromechanical part comprising a height (e)₃) Greater than the thickness (e) of the layer (5) made of synthetic carbon allotropes₁) Of the height (e) of the outer surface₃) Between 10 μm and 500 μm, and the roughness of the outer surface has an arithmetic mean deviation (Ra) substantially lower than 10 nm.

12. A part according to claim 11, characterized in that the outer surface forms teeth (45, 55, 65).

13. Micromechanical part (11, 21, 31, 41, 51, 61) produced by a method according to claim 5, formed from a single piece made of synthetic carbon allotrope in the form of a layer (5) having a thickness (e)₁) Between 0.2 μm and 20 μm, said micromechanical part comprising a height (e)₃) Greater than the thickness (e) of the layer (5) made of synthetic carbon allotropes₁) Of the height (e) of the outer surface₃) Between 10 μm and 500 μm, and the roughness of the outer surface has an arithmetic mean deviation (Ra) substantially lower than 10nm, characterized in that the hollow of the synthetic carbon allotrope-based micromechanical part is filled with a second material (7, 17) in order to produce a synthetic carbon allotrope-based micromechanical part (51, 61) reinforced and/or decorated with the second material (7, 17).

14. Micromechanical part according to claim 13, characterized in that the second material is formed from the height (e) of the outer surface₃) To form additional functional elements (12, 14, 16, 62) of the micromechanical part.

15. Micromechanical part according to claim 13, characterized in that the second material (7, 17) comprises a metal or a metal alloy.

16. Timepiece, characterized in that it comprises a micromechanical part (11, 21, 31, 41, 51, 61) according to any one of claims 11 to 15.

17. The timepiece of claim 16 wherein said micromechanical part forms all or part of an external part, a balance spring, a balance, a pallet fork, a bridge or a train of wheels.