CH712599B1 - Method for manufacturing a ceramic watch component. - Google Patents

Abstract

The invention relates to the manufacture of a ceramic timepiece component obtained by filling a mold (3) structured by photolithography with a precursor material (5 2) of the desired ceramic. The mold (3) is removed before the precursor material (5 2) is transformed into ceramic.

Description

Field of the invention

The invention relates to a method for manufacturing a ceramic timepiece component and more specifically based on polycrystalline ceramic.

Background of the invention

In the field of watchmaking, it is known to form cladding parts in polycrystalline ceramic using injection molding (also known by the abbreviation "CIM"). Thus, a material, generally called "feedstock", is injected into a mold under pressure, then debinding and sintering steps are carried out to obtain the polycrystalline ceramic part with a high rate.

However, the injection step generates lines of junctions of the fronts of the injected material which requires a touch-up step as well as mechanical fragility localized at these junctions. It is also necessary to remove excess material from the injection areas.

Finally, injection molding is difficult to apply to the manufacture of parts of thinness typically less than 1 millimeter because of the difficulty in injecting the material through fine channels, but also by the difficulty of demolding and rectifying the parts without breakage.

Summary of the invention

The object of the present invention is to overcome all or part of the drawbacks mentioned above by proposing a manufacturing process capable of forming without retouching a horological component in polycrystalline ceramic of small thickness, without flatness defect and with high precision. dimensional.

To this end, according to a first embodiment, the invention relates to a method of manufacturing a ceramic watch component comprising the following steps: forming, by photolithography on a substrate, a mold provided with at least one cavity; filling said at least one mold cavity with a ceramic precursor material; remove the mold to release a blank of precursor material; transform the blank into a precursor material by making a ceramic watch component; releasing the ceramic watch component from the substrate.

In addition, according to a second embodiment, the invention relates to a method for manufacturing a ceramic watch component comprising the following steps: forming, by photolithography on a substrate, a mold provided with at least one cavity; filling said at least one mold cavity with a ceramic precursor material; remove the mold to release a blank of precursor material; releasing the precursor material blank from the substrate; transform the blank into a precursor material by making a ceramic watch component.

[0008] In accordance with other advantageous variants of the invention: the mold is formed from a photosensitive resin of the positive or negative type; said at least one mold cavity comprises at least one non-vertical wall; the mold has several cavities; two cavities of different patterns are formed, one above the other concentrically to form a watch component on several levels; at least two adjacent cavities are connected by a channel to form a plate with several watch components connected together; the substrate is formed based on silicon or ceramic; the filling step is carried out by liquid; the filling step includes the following phases; pouring a slip into the mold and drying the slip to obtain the precursor material of a ceramic in the mold; the slip comprises a liquid material, ceramic powder and at least one adjuvant intended to facilitate the process; the liquid material comprises water or a solvent; the ceramic powder has a grain size of less than 10 μm; the ceramic powder comprises boron to improve the tribology of the watch component; said at least one adjuvant comprises a binder allowing the preform in precursor material to form a homogeneous mass at the end of the drying phase; said at least one adjuvant comprises a dispersant allowing the slip to form a homogeneous suspension during the casting phase; the mold removal step includes a dry attack, a wet attack or a heat treatment; the method further comprises, before the mold filling step, a step of depositing a non-stick layer making it possible to more easily remove the substrate; the method further comprises, after the step of forming the mold, a step of thickening the mold in order to homogenize its thickness; the method further comprises, before the step of removing the mold, a step of thickening the mold and the blank in precursor material in order to adjust the surface condition and the thickness of the blank in material precursor; the watch component forms all or part of a cladding part or of a movement member of a timepiece.

Brief description of the drawings

Other features and advantages will emerge clearly from the description given below, by way of indication and in no way limitative, with reference to the appended drawings, in which: <tb> fig. 1 to 4 <SEP> are representations of successive stages of the process according to the invention; <tb> fig. 5 to 10 <SEP> are representations of watch components according to the invention; <tb> fig. 11 and 12 <SEP> are representations of successive stages of the method according to an alternative of the invention; <tb> fig. 13 and 14 <SEP> are representations of watch components according to an alternative of the invention.

Detailed description of preferred embodiments

The component according to the invention has been devised for applications in the watchmaking field and is made necessary by the increasing proportion held by fragile materials such as those based on ceramics. Watch components have the characteristic of having a very small thickness compared to their main surface in projection. Thus, a main projected surface can typically have a point length or a diameter between 2 and 6 millimeters which is high with regard to the thickness between 10 to 400 μm.

This is why, the invention relates to a manufacturing process capable of forming without retouching a horological component of polycrystalline ceramic of small thickness, without defect in flatness and with high dimensional precision. Indeed, retouching on such a small thickness of ceramic is very difficult to achieve without causing breakage or scratching on the ceramic.

It is therefore understood that the timepiece component can form all or part of a cladding piece or a movement member of a timepiece. One can, for example, consider forming the hairspring, the pendulum, the anchor, the bridges, the oscillating mass or even the mobiles such as the escapement wheels totally or partially ceramic-based. It is also possible to form a case, a dial, a display, a decoration, an index, a wall lamp, a flange, a bezel, a push-button, a crown, a case back, a needle or a bracelet totally or partially at ceramic base according to the invention.

In order to guarantee flatness and dimensional accuracy, the invention relates to a manufacturing process using the filling of a structured mold by photolithography of a precursor material of the desired ceramic. Indeed, as explained below, the use of photolithography provides very high dimensional precision to the ceramic watch component.

The method of manufacturing the ceramic watch component comprises a first step intended to form, by photolithography on a substrate 1, a mold 3 provided with at least one cavity 21, 22 as illustrated in FIG. 1. Photolithography being a known process in itself, it will not be further explained below.

The mold 3 can be formed indifferently from a photosensitive resin of the positive or negative type. As part of the development, a negative photosensitive resin of the SU-8 type was used for its ease of structuring, its low cost and its capacity to form layers up to 500 μm.

As shown in FIG. 1, one or more cavities 21, 22 can be structured on the surface of the substrate 1. If several cavities 21, 22 are structured, they can be of identical or different patterns. We can also see, as an example in fig. 1, cavities 21, 22 each of annular shape with a distal wall 61, 62 which is substantially vertical and toothed and a proximal wall 41, 42 which is substantially vertical. It is therefore understood that the timepiece component 21 which will be formed will be a toothed wheel 23 provided with a central recess 25 as illustrated in FIG. 4.

Obviously, the process of this first step can be adapted according to the forms of component desired. Thus, in a nonlimiting manner, the photolithography can be of the stereolithography type (also known under the English abbreviation "SLA"), of the maskless type (also known under the English abbreviation "MLA") or of the variation mask type transmittance (also known as "gray scale lithography").

Indeed, by way of example, a photolithography of the mask type with variation in transmittance allows said at least one cavity 21, 22 of the mold 3 to include at least one non-vertical wall to obtain, for example, a component of the type of fig. 13 as explained below.

In addition, the first step cannot be limited to a mold 3 with a single pattern per cavity 21, 22. The first step could also form a mold on several levels, that is to say that at least two cavities of different patterns are formed concentrically one above the other to form a watch component on several levels.

According to an alternative illustrated in FIG. 11, we can see a mold 13 with an imprint 11 comprising a lower cavity 121 of annular shape with a distal wall 161 substantially vertical and toothed and a proximal wall 141 substantially vertical, and an upper cavity 122, wider and concentric with respect to the lower cavity 121, annular in shape with a substantially vertical and toothed distal wall 162 and a substantially vertical proximal wall 142. It is therefore understood that the timepiece component 31 which will be formed will be a double toothed wheel 33, 37 in one piece which is provided with a central recess 35 as illustrated in FIG. 12. By way of example, such a mold 13 can be obtained by several successive photolithographies during the first step.

It is also perfectly conceivable that at least two adjacent cavities are connected by a channel to form a wafer with several watch components connected together. This would allow manipulation in a wafer in the manner of a silicon wafer after etching of components.

In the examples of Figs. 1 and 11, the substrate 1 forms the bottom of the cavities 21, 22, 121. Consequently, the substrate 1 can be formed on the basis of silicon or ceramic according to the embodiment explained below. However, the bottom could alternatively be formed by a layer of the mold 3, 13.

Whatever the manner of forming the bottom of the cavities, it immediately appears that its surface condition can be advantageously chosen in order to define the appearance of the corresponding face of the horological component. For example, the bottom of the cavities could have a surface structure arranged to form a decoration on the corresponding face of the watch component or, on the contrary, a polished surface giving a mirror-polished appearance to the corresponding face of the watch component.

Optionally, the method may include after the first step of forming the mold 3 or between each photolithography of the mold 13, a step of thickening the mold 3, 13 in order to homogenize the thickness of the mold 3 or at least one of the thicknesses of the mold 13.

In addition, before the start of the second step explained below, the method can, optionally, include a step of depositing a non-stick layer making it possible to more easily release the blank of precursor material and / or the ceramic watch component at the end of the process. Such a layer could be deposited on the entire upper surface of the mold 3, 13 or only on a part of the mold 3, 13, for example only in the cavities 21, 22, 121, 122 or only on the bottom of the cavities 21, 22, 121. Such a non-stick layer could, for example, be a thin layer of boron nitride powder. Advantageously according to the invention, such a layer allows easier release but also compensation for shrinking the ceramic during the sintering step explained below.

The second step of the process is intended to fill said at least one cavity 21, 22, 121, 122 of the mold 3, 13 using a precursor material of a ceramic. Preferably according to the invention, the filling step is carried out by the liquid route.

Thus, according to a preferred example, the filling step comprises a first phase intended to pour a slip in the mold 3, 13 followed, optionally, by a scraping intended to remove the surplus slip. According to the invention, the slip may include a liquid material, ceramic powder and at least one adjuvant intended to facilitate the process. The liquid material can comprise preferably deionized water or a solvent.

The ceramic powder can include a wide variety of materials thanks to the chosen liquid route. A metal oxide, carbide or nitride such as, for example, a zirconia or an alumina can be used. Of course, the mixture of several powders of different natures can also be envisaged. It also appeared that a grain size of less than 10 μm was desirable in relation to the final dimensions desired and in particular the small thickness indicated above.

In particular for the purpose of manufacturing watch components capable of transmitting forces and having a low coefficient of friction, it has appeared that a boron-based ceramic powder, such as, for example, boron carbide (B4C) or titanium diboride (TiB2), was particularly interesting.

For example, said at least one additive to the slip may include a dispersant allowing the slip to form a homogeneous suspension especially during the casting phase.

Thus, according to the preferred example, the filling step can continue with a second phase intended to dry the slip in order to obtain the precursor material 51, 52 of the ceramic as illustrated in FIG. 2. It is understood that the purpose of this second phase is mainly to remove the liquid material from the slip, that is to say the water or the solvent mentioned above.

In order to allow the precursor material 51, 52 to form a homogeneous mass at the end of the drying phase, said at least one slip additive may comprise a binder such as, for example, an organic binder.

Optionally, the method may include, before the third step explained below, a step of thickening the mold 3, 13 and the precursor material 51, 52 in order to adjust the surface condition and the thickness of the blank 71, 72 in precursor material.

The process continues with a third step intended to remove the mold 3, 13 to release a blank 71, 72 in precursor material 51, 52. In the example of FIG. 3, it can be seen that the blanks 71, 72 of precursor material 51, 52 thus form toothed wheels with a central recess 81, 82.

The step of removing the mold 3, 13 may include a dry attack, a wet attack or a heat treatment. Typically, in the case cited above of a photosensitive resin of the SU-8 type, a plasma attack or a heat treatment of a few hundred degrees Celsius can be envisaged to carry out the third step.

According to a first embodiment, the method continues with a fourth step intended to transform the blank 71, 72 into precursor material 5i, 52 into timepiece component 21 into ceramic then, in a fifth step, to release the timepiece component 21 ceramic substrate 1.

According to a second embodiment, the method continues with a fourth step intended to release the blank 71, 72 in precursor material 51, 52 from the substrate 1 then, in a fifth step, to transform the blank 71, 72 into material precursor 51, 52 by timepiece component 21 made of ceramic.

Whatever the embodiment, the ceramic transformation step may, for example, include a first debinding phase intended to remove precursor material 51, 52, any adjuvant provided during the process, then a second phase of sintering. Each phase is mainly characterized by the temperature applied to the precursor material 51, 52. Thus, the temperature during the first phase can be between 300 and 700 ° C while the temperature, during the second phase, can be between 1400 and 1700 ° C.

It is therefore understood that if the step of removing the mold 3, 13 is carried out by heat treatment, the first debinding phase can be carried out at the same time.

At the end of the process, one obtains, advantageously according to the invention, a timepiece component 21, 31 at at least one level, completely integral in polycrystalline ceramic whose dimensional precision is of the order of a few microns and of which the form can be very varied.

Thus, without limitation, it is possible to manufacture a timepiece component at a level such as, for example, a toothed wheel 23 illustrated in FIG. 4 provided with a central recess 25, a hairspring 41 illustrated in FIG. 5 provided with a ferrule 43 and with a monobloc blade 45, all or part of an anchor 51 illustrated in FIG. 6 like the strip 53 and / or the pallets 55, a pad 61 illustrated in FIG. 7 provided with a hole 65 and an oil tank 63, a window 71 illustrated in FIG. 8 provided with a curved upper surface, needles 81 illustrated in FIG. 9, a middle part 99 or a link 92 of the bracelet 94 illustrated in FIG. 10.

In addition, without limitation, it is possible to manufacture a timepiece component on several levels such as, for example, a mobile 31 illustrated in FIG. 12 provided with two toothed wheels 33, 37 in one piece and with a central recess 35, all or part of an anchor 51 illustrated in FIG. 6 like the rod 53 and / or the pallets 55 and / or the stinger 57, a pinion 101 illustrated in FIG. 13 provided with a toothing 103, a dial 111 illustrated in FIG. 14 provided with a window 113, a decoration 115 and a revolution of hours 117 or horns 97 provided with recesses for the bracelet bar 94, a crown 93 or a pusher 95 illustrated in FIG. 10.

Of course, the present invention is not limited to the illustrated example but is capable of various variants and modifications which will appear to those skilled in the art while remaining within the scope of the claims. The process could be used for the manufacture of objects in the field of tableware, jewelry or fine jewelry.

Claims (21)

1. Method for manufacturing at least one timepiece component (21, 31, 41, 51, 61, 71, 81, 93, 95, 94, 97, 99, 101, 111) made of ceramic comprising the following steps: - forming, by photolithography on a substrate (1), a mold (3, 13) provided with at least one cavity (21, 22, 121, 122); - filling said at least one cavity (21, 22, 121, 122) with the mold (3, 13) using a precursor material (51, 52) of a ceramic; - remove the mold (3, 13) to release a blank (71, 72) of precursor material; - transform the blank (71, 72) into a precursor material (51, 52) by a watch component (21, 31, 41, 51, 61, 71, 81, 93, 95, 94, 97, 99, 101, 111) into ceramic ; - releasing the timepiece component (21, 31, 41, 51, 61, 71, 81, 93, 95, 94, 97, 99, 101, 111) in ceramic from the substrate (1). 2. Method for manufacturing a timepiece component (21, 31, 41, 51, 61, 71, 81, 93, 95, 94, 97, 99, 101, 111) made of ceramic comprising the following steps: - forming, by photolithography on a substrate (1), a mold (3, 13) provided with at least one cavity (21, 22, 121, 122); - filling said at least one cavity (21, 22, 121, 122) with the mold (3, 13) using a precursor material (51, 52) of a ceramic; - remove the mold (3, 13) to release a blank (71, 72) of precursor material (51, 52); - releasing the blank (71, 72) of precursor material (51, 52) from the substrate (1); - transform the blank (71, 72) into a precursor material (51, 52) by a watch component (21, 31, 41, 51, 61, 71, 81, 93, 95, 94, 97, 99, 101, 111) into ceramic . 3. Method according to claim 1 or 2, characterized in that the mold (3, 13) is formed from a photosensitive resin of the positive or negative type. 4. Method according to one of the preceding claims, characterized in that said at least one cavity (21, 22, 121, 122) of the mold (3.13) comprises at least one non-vertical wall. 5. Method according to one of the preceding claims, characterized in that the mold (3, 13) has several cavities (21, 22, 121, 122). 6. Method according to the preceding claim, characterized in that two cavities (121, 122) of different patterns are formed one above the other concentrically to form a timepiece component (31, 41, 51, 61, 71 , 81, 93, 95, 94, 97, 99, 101, 111) on several levels. 7. Method according to claim 5 or 6, characterized in that at least two adjacent cavities (21, 22, 121, 122) are connected by a channel to form a wafer with several watch components (21, 31, 41, 51, 61, 71, 81, 93, 95, 94, 97, 99, 101, 111) interconnected. 8. Method according to one of the preceding claims, characterized in that the substrate (1) is formed based on silicon or ceramic. 9. Method according to one of the preceding claims, characterized in that the filling step is carried out by the liquid route. 10. Method according to the preceding claim, characterized in that the filling step comprises the following phases: - pour a slip in the mold (3, 13); - dry the slip in order to obtain the precursor material (51, 52) of a ceramic in the mold (3, 13). 11. Method according to the preceding claim, characterized in that the slip comprises a liquid material, ceramic powder and at least one adjuvant intended to facilitate the process. 12. Method according to the preceding claim, characterized in that the liquid material comprises water or a solvent. 13. Method according to claim 11 or 12, characterized in that the ceramic powder has a grain size less than 10 µm. 14. Method according to one of claims 11 to 13, characterized in that the ceramic powder comprises boron to improve the tribology of the timepiece component (21, 31, 41, 51, 61, 71, 81, 93, 95, 94, 97, 99, 101, 111). 15. Method according to one of claims 11 to 14, characterized in that said at least one adjuvant comprises a binder allowing the blank (71, 72) of precursor material (51, 52) to form a mass homogeneous to the 'after the drying phase. 16. Method according to one of claims 11 to 15, characterized in that said at least one adjuvant comprises a dispersant allowing the slip to form a homogeneous suspension during the casting phase. 17. Method according to one of the preceding claims, characterized in that the step of removing the mold (3, 13) comprises a dry attack, a wet attack or a heat treatment. 18. Method according to one of the preceding claims, characterized in that the method further comprises, before the step of filling the mold (3, 13), a step of depositing a non-stick layer making it possible to remove more easily the substrate (1). 19. Method according to one of the preceding claims, characterized in that the method further comprises, after the step of forming the mold (3, 13), a step of thickening the mold (3, 13) in order to '' homogenize its thickness. 20. Method according to one of the preceding claims, characterized in that the method further comprises, before the step of removing the mold (3, 13), a step of thickening the mold (3, 13) and the blank (71, 72) of precursor material (51, 52) in order to adjust the surface condition and the thickness of the blank (71, 72) of precursor material (51, 52). 21. Method according to one of the preceding claims, characterized in that the timepiece component (21, 31, 41, 51, 61, 71, 81, 93, 95, 94, 97, 99, 101, 111) forms all or part of a covering piece or of a movement member of a timepiece.