This application claims priority of European patent application No. N° N° EP17205320.9 filed Dec. 5, 2017, which is hereby incorporated by reference herein in its entirety.
The present invention relates to a method of manufacturing a clock or watch component carried out starting from a micro-machinable material.
Manufacture of clock and watch components starting from a micro-machinable material such as silicon and by micromachining techniques, notably by dry etching, for example by deep reactive ion etching (DRIE) or by chemical wet etching, is known.
A method of manufacture of this kind from the prior art, shown in
The method of manufacture then comprises a step consisting of adding a mask on the visible face of the wafer 1, by depositing (step E2,
The mask formed in the preceding step then allows the formation of at least one clock or watch component, by etching (step E4,
Finally, the remaining resin is removed (step E5,
One aim of the present invention is to propose a method of manufacturing a clock or watch component that improves the method of the prior art.
More particularly, the aim of the present invention is to propose a simplified method of manufacturing a clock or watch component.
For this purpose, the invention is based on a method of manufacturing a clock or watch component, characterized in that it comprises the following steps:
The step consisting of providing a wafer may comprise a step consisting of providing a wafer with thickness approximately equal to the maximum thickness of the clock or watch component to be manufactured.
The method may comprise a step of etching the material of the component in the full thickness of the whole of the material of the component present in the wafer and/or in the full thickness of the single slice comprising the material of the component of the wafer.
The invention is defined more precisely by the claims.
These aims, features and advantages of the present invention will be presented in detail in the following description of particular nonlimiting embodiments in relation to the appended figures, where:
Each of
Each of
Each of
According to the embodiments of the invention, the method of manufacturing a clock or watch component is improved in that it greatly simplifies the end of the method of the prior art, by simplifying or even by eliminating the release step E6 described above. By convention, as mentioned above, the adjective upper shall be used to denote a surface of the side of the face of a wafer that will undergo the first etching, and the adjective lower for a surface of an opposite side.
Like the method of the prior art described above, a method of manufacture of this kind comprises a first step E11 (
The method of manufacture then comprises a step consisting of adding a mask on the upper surface of the wafer 11, by depositing (step E12,
The mask formed in the preceding step then allows formation of at least one clock or watch component, by etching (step E14,
Finally, the resin that remains is removed by dissolution, in a development step (step E15,
Steps E12 to E15 correspond approximately to steps E2 to E5 of the solution of the prior art, and therefore are not described in detail. Notably, the etching is carried out conventionally, by photolithography and DRIE. The great advantage of this first embodiment of the invention is that the second supporting slice of the wafer has been eliminated, making it possible to eliminate the tedious release step E6 of the prior art by dissolution of the intermediate layer 3.
As a variant, the wafer 11 made of micro-machinable material could be in the form of several superposed layers, and/or made of several materials. The important feature of the embodiment is that the wafer does not comprise any layer the function of which is limited to forming a support and that it is etched in its whole thickness. In other words, the clock or watch component obtained has a maximum final thickness approximately equal to the thickness of the wafer 11 used, i.e. to the thickness of the slice 12.
Thus, the embodiment described above certainly allows considerable simplification of the method of manufacturing a clock or watch component. It is mainly based on eliminating any support in a wafer 11 made of micro-machinable material, and on the unexpected finding that it is possible to manufacture a clock or watch component starting from a slice that does not comprise a support.
A method of manufacture of this kind comprises a first step E21 (
Thus, this second embodiment comprises a preliminary step, not shown, consisting of depositing or assembling a metallic lower layer 24 on a slice 22 made of micro-machinable material, to form the wafer 21. According to a first embodiment, this preliminary step consists of coating a surface of a slice made of micro-machinable material with a layer of metal deposited by a technique of physical vapor deposition (PVD). As an example, a metallic lower layer of this kind may be a layer of pure aluminum of 2 microns. As a variant, said lower layer may have any other thickness, preferably between 0.5 and 5 microns inclusive. Alternatively, any technique for depositing a pure metal and/or an alloy may be used for coating the lower surface of the slice made of micro-machinable material with a metallic layer. Preferably, the metal deposited is aluminum, gold or platinum. Additionally, it is possible to deposit a keying coat beforehand on the slice made of micro-machinable material, for example of titanium or of chromium, to improve the adhesion of the metallic lower layer. As a variant, any other technique of deposition or of assembly of a metallic lower layer forming a coating on the surface of the slice made of micro-machinable material may be used (e.g. electrolytic growth, chemical vapor deposition, gluing a sheet, etc.).
The method of manufacture then comprises a step consisting of adding a mask on the upper surface of the wafer 21, by depositing (step E22,
The mask formed in the preceding step then allows formation of at least one clock or watch component, by etching (step E24,
Finally, the resin that remains is removed by dissolution, in a development step (step E25,
The method according to this second embodiment then comprises a release step E26 (
Thus, this second embodiment is still very simple, since the final separation of the clock or watch component 29, by eliminating the manufacturing residues such as the resin and the lower layer, which is in the form of a metallic supporting layer according to one embodiment, comprises a release step E26 that is greatly simplified relative to the method of the prior art, which uses a support consisting of two parts, one of which corresponds to the material of the component, and which cannot thereby be dissolved chemically without first protecting the components etched in the first slice with an additional layer.
Thus, the second embodiment described above certainly allows considerable simplification of the method of manufacturing a clock or watch component. It is based on the use of a metallic support for a slice consisting of a micro-machinable material, and on the unexpected finding that it is possible to manufacture a clock or watch component starting from a wafer comprising a single slice of micro-machinable material and a thin metallic lower layer, much thinner than the support in the prior art, which is also made of micro-machinable material. A person skilled in the art would have had a negative prejudice to such a solution, notably considering that the metal would diffuse in the micro-machinable material, altering its properties. A person skilled in the art would also have a negative prejudice regarding the feasibility of this method of manufacture, as the treatment equipment is generally designed for wafers of a certain rigidity to ensure precision and robustness.
Note that relative to the first embodiment, the metallic lower layer used in this second embodiment also offers the following additional advantages:
This second embodiment has been described on the basis of a lower layer of metal. As a variant, it is also possible to deposit or grow a layer of silicon oxide SiO2 or of polymer, for example a polymer film of poly-p-xylylene, better known by the name Parylene, on the lower face of the slice made of micro-machinable material, which notably fulfils the same stiffening function as a metallic layer. The release step E26 will simply consist of dissolution of the layer of SiO2 or of polymer by means of acids such as mixtures based on hydrofluoric acid or by plasma oxygen treatment.
Finally, the concept implemented in the two embodiments of the invention described above consists of proposing a method of manufacturing a clock or watch component that does away with the step of release of a support made of micro-machinable material, which is complex and time-consuming, by avoiding the use of a micro-machinable material as a support. In other words, the whole of the thickness of the micro-machinable material present in the wafer is used for forming the clock or watch component, without any supporting function. Therefore it does not comprise a slice of micro-machinable material used only for the function of support: the single slice of micro-machinable material present in the wafer 11, 21 is intended to form at least one clock or watch component by etching. Thus, in the preceding embodiments, the method does not comprise etching of micro-machinable material on the lower face of the wafer to facilitate the release step E6, but only etching on the upper face. The clock or watch component obtained preferably has a maximum thickness corresponding approximately to the thickness of the whole micro-machinable material (corresponding to the sum of the thickness of all the layers made of micro-machinable material in the case of a multilayer slice) initially present in the wafer serving for its manufacture.
As a variant, the method of manufacturing a clock or watch component may also comprise additional treatment steps, carried out before or after release of the component from the resin and/or from the metallic support, such as thinning of the slice of micro-machinable material or of the component, mechanical or laser-beam reworking, coating, thermal treatment of oxidation, cleaning/degreasing, etc.
Quite obviously, the method of the invention applies to the manufacture of a great many clock or watch components. The clock or watch component may be an entity ready to be mounted in a movement (for example a lever, a spring, etc.) or a component intended to be assembled on one or more other components of the movement (for example a balance spring on the balance staff, a wheel plate on its spindle, a pallet on the pallet staff (or spindle), a balance wheel on the balance staff, etc.). Alternatively, the clock or watch component may be an external component, such as a hand. This method is particularly suitable for manufacturing simple clock or watch components 2.5 D (two-and-a-half dimensions), with thickness greater than or equal to 100 μm. The second embodiment will be preferred for the more fragile components that have thin structures, which risk being broken, or the more flexible components, which risk being deformed during the etching step, such as spiral springs, or the thinnest components, notably with a thickness of less than 100 microns. The first embodiment will be preferred for components that are less fragile, notably more massive, such as wheels, as well as for components with a thickness strictly greater than 100 μm. However, both embodiments are still suitable for manufacturing all these clock or watch components.
In the embodiment examples described above, the deposited layer that serves as a mask for etching is made of a light-sensitive resin. This layer of light-sensitive resin may be replaced with any other layer that can serve as a mask against etching of the DRIE type, for example a layer of silicon oxide, silicon nitride, a metallic layer, etc. A person skilled in the art will select the layer that is suitable for his/her needs.
In the embodiments of the invention described above, “micro-machinable material” means any material suitable for micromachining, notably including any material that can be etched directionally through a mask. Moreover, micromachining means all of the techniques allowing structures of micrometric size to be produced in a material through a mask, for example such as chemical etching or photolithography. The micro-machinable material used in the embodiment examples described above is silicon, but doped silicon, porous silicon, etc. may be used instead. Other micro-machinable materials could of course be used, for example diamond, quartz, sapphire and ceramics. It may also be a hybrid material. The micro-machinable material may also be any microstructurable material, sufficiently rigid to be manipulated. Thus, the invention is suitable more generally for manufacturing a clock or watch component consisting of or comprising a material called “material of the component” that can be cut through a mask. Advantageously, this material of the component will be worked starting from a slice of thickness greater than or equal to 100 μm, arranged within a wafer, as explained in the embodiments described, or more generally in a wafer comprising a layer comprising one or more material(s) of the component of which the whole thickness, preferably greater than or equal to 100 μm, will be etched to form the component. Moreover, a wafer of this kind may optionally comprise a support in another material, notably a metal or a metal alloy, called material of the support, different than the material of the component and compatible with it, i.e. not affected during etching of the material of the component, such as execution of the etching steps E14, E24 described above. Advantageously, the thickness of the optional support is very small, less than or equal to 10 μm, or even less than or equal to 5 μm, or even less than or equal to 3 μm. Moreover, this thickness is preferably greater than or equal to 0.5 μm. This thickness is therefore regarded as negligible relative to the thickness of the slice of material of the component, of the wafer, and of the clock or watch component manufactured.
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