Method for mass production of watch components

Abstract

The invention relates to a method for the mass production of watch components.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a batch of metal watch components using LIGA technology. Background Art

[0002] Methods corresponding to the above definition are known. In particular, the article by A.B. Frazier et al. titled "Metallic Microstuctures Fabricated Using Photosensitive Polyimide Electroplating moulds" published in the Journal of Microelectromechanical Systems (June 1993, Vol. 2, No. 2) describes a method for manufacturing multi-layer metal structures by electroplating growth in a polyimide mould made by lithography of a photosensitive resin layer.

[0003] The method includes the following steps:

[0004] - Creating a sacrificial metal layer and a primer layer on a substrate for subsequent electroplating growth steps,

[0005] - Applying a photosensitive polyimide layer,

[0006] - Irradiating the polyimide layer with UV radiation through a mask corresponding to the profile of the layer of the structure to be obtained,

[0007] - Developing the polyimide layer by dissolving the unirradiated part to obtain a polyimide mould,

[0008] - Filling the mould with nickel by electroplating growth to its height and obtaining a substantially flat upper surface,

[0009] - Depositing a thin chromium layer on the entire upper surface by vacuum spraying,

[0010] - Depositing a new photosensitive resin layer on the chromium layer,

[0011] - Irradiating the resin layer through a new mask corresponding to the profile of the next layer of the structure to be obtained,

[0012] - Developing the polyimide layer to obtain a new mould,

[0013] - Filling the new mould with nickel by electroplating growth to its height,

[0014] - Separating the multi-layer structure and the polyimide mould from the sacrificial layer and the substrate,

[0015] - Separating the multi-layer structure of the polyimide mould.

[0016] It should be understood that, in principle, the method just described can be implemented iteratively to obtain a metal structure having more than two levels.

[0017] A drawback of this method is that many parts are manufactured in batches, which may cause the parts to be damaged due to shock, extrusion, or winding. To overcome this drawback, it is possible to sort these parts, but this method is both costly and time-consuming.

[0018] Another drawback of this method is that when it is necessary to perform one or more finishing steps, complex positioning is required to correctly position the individual parts during the operation. Then, these parts must be rearranged for each finishing stage, which is also costly and time-consuming. Summary of the Invention

[0019] The present invention solves the above drawbacks by providing a solution for keeping parts attached to each other via a grid such that they can be batch processed, machined, and / or decorated.

[0020] The present invention also allows keeping parts attached to a grid like a wafer while cleaning the back side, such that when they are flipped for back-side operations, they can be easily machined and / or decorated without having to implement complex technical means to keep the parts individually positioned. Once the parts have been flipped, accurate positioning is crucial for performing the intended mechanical reprocessing operations.

[0021] To this end, the present invention relates to a method for batch manufacturing watch parts, characterized in that it comprises the following steps:

[0022] a) Providing a substrate covered with a conductive primer layer;

[0023] b) Applying a photosensitive resin layer onto the conductive part of the substrate surface;

[0024] c) Irradiating the resin layer through a mask that defines the outline of a batch of parts, as well as the grid and the material bridges, the material bridges connecting the parts to the grid at non-functional surfaces, the grid, the material bridges, and the watch parts forming a cluster of parts;

[0025] d) Dissolving the unirradiated areas of the photosensitive resin layer to expose the conductive surface of the substrate in place and form a mold;

[0026] e) Conformally electroplating a metal layer from the conductive layer, the metal layer forming the cluster of parts and reaching the level of the upper surface of the photosensitive resin layer;

[0027] f) Removing the photosensitive resin layer and the substrate to release the cluster of parts thus formed;

[0028] g) Releasing the parts from the cluster.

[0029] According to other advantageous variants of the invention:

[0030] - The method includes a step e') between step e) and step f), during which the resin layer and the deposited metal layer are planarized so that the resin layer and the electro-deposited metal layer reach the same level.

[0031] - The method includes:

[0032] - After step d), steps c) and d) are repeated at least once to obtain a mold having

[0033] at least two levels;

[0034] - At least one other metal layer is applied to the at least second level of the mold.

[0035] - The mold has several levels;

[0036] - The material bridge has the same thickness as the thickness of the component;

[0037] - The material bridge is thinner than the component;

[0038] - The method includes a step g) of finishing the front, back, and / or sides of the wafer finishing table component, and the finishing step includes depositing layers, such as structured and / or decorative layers;

[0039] - The cluster of watch components includes a batch of identical components selected from: wheels, cams, pointers, levers, scroll wheels, pendulums, hands, or lettering blocks;

[0040] - The cluster of watch components includes a batch of different components, such as wheels, cams, pointers, levers, pendulums, scroll wheels, hands, or lettering blocks.

[0041] The invention also relates to a batch of watch components or a cluster of watch components obtained by implementing the manufacturing method according to the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] With reference to the accompanying drawings, other features and advantages of the invention will become apparent from the following detailed description given by way of non-limiting example, in which:

[0043] Figure 1 The manufacturing process according to the invention is schematically shown;

[0044] Figure 2 An example of a cluster of components obtained using the method according to the invention is illustrated. DETAILED DESCRIPTION

[0045] The invention relates to a method for manufacturing watch components.

[0046] In terms of the functional outer contour, it should be understood as a watch component whose external shape forms a functional surface designed to cooperate with other watch parts and / or components.

[0047] The substrate 1 used in step a) of the method according to the invention is formed, for example, by a silicon substrate. During the first step a) of the method, a conductive layer 2, i.e., a layer capable of initiating metal deposition by electroplating means, is deposited, for example, by physical vapor deposition (PVD). Typically, the conductive layer 2 is of the type Au, Ti, Pt, Ag, Cr or Pd, or a stack of at least two of these materials, and has a thickness included between 50 nm and 500 nm. For example, the conductive layer 2 can be formed by a chromium or titanium sublayer covered by a gold or copper layer.

[0048] The photosensitive resin 3 used in this method is preferably a negative resin based on an octafunctional epoxy resin, which is designed to polymerize under the action of UV radiation.

[0049] According to a particular embodiment of the invention, the resin is in the form of a dry film, and the resin is then applied to the substrate 1 by lamination.

[0050] Alternatively, the photosensitive resin can be a positive photoresist, which is designed to decompose under the action of UV radiation. It should be understood that the invention is not limited to several specific types of photosensitive resins. A person skilled in the art will be able to select the photosensitive resin suitable for his or her needs from all known resins applicable to UV lithography.

[0051] During step b), the resin layer 3 is deposited on the substrate 1 to a desired thickness by any suitable means, by centrifugal coating, spin coating or spraying. Typically, the resin thickness is between 10 μm and 1000 μm, and preferably between 30 μm and 300 μm. Depending on the desired thickness and the deposition technique used, the first resin layer 3 will be deposited in one or more layers.

[0052] After that, the first resin layer 3 is heated, usually to between 90 and 120 °C, for a period depending on the deposition thickness, to remove the solvent (pre-baking stage). This heating dries and hardens the resin.

[0053] Figure 1 The next step c) illustrated in the figure includes irradiating the first resin layer 3 with UV radiation through a mask 4, which defines the component to be formed and thus the mold for the photopolymerized region 3a and the non-photopolymerized region 3b.

[0054] According to the invention, during step c), the mask allows defining the outer shape of a batch of components 5, as well as the outer shapes of the grid 7 and the material bridges 6. The material bridges allow connecting the components to the grid at non-functional surfaces.

[0055] Thus, the grid, the material bridges, and the table parts form a cluster of parts at the end of the process.

[0056] As required by those skilled in the art, the grid and / or the material bridges are thinner than the parts.

[0057] Advantageously, the material bridges connect the parts to the grid at the non-functional outer contour of the parts. This means such table parts where the outer shape of the part forms a functional surface designed to cooperate with other table parts and / or components, and thus, by analogy, the non-functional outer contour (or surface) is a contour unlikely to cooperate with another part.

[0058] The annealing step (post-baking step) of the first resin layer 3 may be necessary to complete the photopolymerization induced by UV radiation. This annealing step is preferably carried out between 90 °C and 95 °C. The photopolymerized region 3a becomes insensitive to most solvents. However, the unpolymerized regions can subsequently be dissolved by solvents.

[0059] Thereafter, the unpolymerized regions 3b of the first photosensitive resin layer 3 are dissolved to expose the conductive layer 2 of the substrate 1 in place. This operation is carried out by dissolving the unpolymerized regions 3b using a suitable solvent (such as PGMEA (propylene glycol methyl ethyl acetate)). Thus, a mold of the photopolymerized photosensitive resin 3a defining the first layer of the part is made.

[0060] Figure 1 The next step d) illustrated in the figure includes depositing a layer of metal from the conductive layer 2 into the mold by electroforming or electroplating until a block is formed with a height preferably reaching less than the height of the mold, which allows for better mechanical strength during subsequent machining. The term metal herein naturally includes metal alloys. Typically, the metal will be selected from the group consisting of: nickel, copper, gold, or silver, and gold-copper, nickel-cobalt, nickel-iron, nickel-phosphorus, or nickel-tungsten as alloys.

[0061] Optionally, the process includes step e’) after step e), which includes machining the metal layer forming the part 5 and, if necessary, the photopolymerized resin layer 3a to a thickness pre-defined by the thickness of the part to be made by a mechanical process.

[0062] Step f) includes releasing the cluster of parts by removing the substrate, the conductive layer, and the resin layer in a series of wet or dry etching steps, which operations are familiar to those skilled in the art.

[0063] For example, the conductive layer 2 and the substrate 1 are removed by wet etching, which allows the release of the cluster of parts from the substrate 1 without damaging the substrate. It is noted that in the example of a silicon substrate, this can be etched with a potassium hydroxide (KOH) solution.

[0064] After completion of this first sequence, as shown in step g), a cluster of components embedded in a resin layer is obtained.

[0065] The second sequence consists of removing the first resin layer 3 and the second resin layer 6 by means of O2 plasma etching, spaced from the wet etching of the intermediate metal layer.

[0066] Thereafter, the method may include a step that includes performing a machining operation, such as chamfering the edges of the visible faces of the components, for example, or tapping or countersinking the components. These operations will obviously depend on the geometry of the final components to be obtained.

[0067] After completion of this step, the obtained cluster of components can be cleaned, and the components still fixed to the cluster can be subjected to various decorative and / or functional treatments, usually physical or chemical depositions.

[0068] The components can undergo various surface finishing operations while still being accurately and easily held to the cluster by means of a fixture. Thus, the front, back, and / or sides of the watch components can be machined while the components are still held to the wafer. The finishing step can include depositing layers, structural layers, or decorative layers on different faces of the watch components. These operations can be functional (strengthening, friction, etc.) or aesthetic (coloring, patterning) using PVD or CVD.

[0069] Finally, the last step consists of releasing the components from the formed cluster. Different methods, such as laser cutting, stamping, or mechanical fracture, can be used to separate the components from the cluster.

[0070] According to an optional step, after step b), the resin layer 3 is machined to a certain thickness. Advantageously, this operation allows for fine control of the geometry of the parts according to the scale of the substrate 1. Once the resin has thickened, a heat treatment is carried out to eliminate the machining marks.

[0071] The above example is written for single-layer components. The method can also be applied to components having several layers or levels.

[0072] To this end, in step c), a multi-layer mold is made by depositing at least one second conductive layer on the photopolymerized region 3a. The second conductive layer can have the same characteristics as the first conductive layer 2, that is, it is of the Au, Ti, Pt, Ag, Cr, Pd type or a stack of at least two of these materials, and has a thickness included between 50 nm and 500 nm.

[0073] Then, a new photosensitive resin layer is deposited on the second conductive layer in order to cover the second conductive layer and fill the openings in the previously developed resin layer.

[0074] Alternatively, it is also possible to apply a photoresist of the second resin layer so as to cover the first resin layer, and the photoresist does not penetrate the opening formed at the beginning of the process. To obtain such a result, a "solid" resin can be used, for example, which can be adhered by lamination.

[0075] The second resin layer is irradiated through the opening of the mask, and the mask defines the profile of the second layer of the desired microstructure. This step requires aligning the mask with the opening of the first layer.

[0076] Those skilled in the art can also implement 3D printing to deposit the second conductive layer 5.

[0077] This solution enables selective and more accurate deposition of the second conductive layer, and thus there is no deposit on the sidewalls of the photopolymerizable resin 3a.

[0078] The next step shown includes depositing a second photosensitive resin layer, which covers the structure obtained in the previous step. The same resin is used during this step, and the thickness can be greater than the thickness deposited in step a). Generally, the thickness varies according to the geometry of the component to be obtained.

[0079] The next step includes irradiating the second resin layer through a mask, which defines the second layer of the component and dissolves the unirradiated area of the second photosensitive resin layer. At the end of this stage, a mold including the first and second layers with the first conductive layer 2 and the second conductive layer exposed in place is obtained.

[0080] The method of the present invention has a particularly advantageous application in manufacturing components for timepieces (such as springs, anchors, wheels, etc.). Due to this method, it is possible to obtain a cluster of robust and geometrically reliable components.

[0081] This method can be used to fabricate entire clusters on the "wafer" scale or sub-assemblies of small clusters on the same wafer. By "wafer", it should be understood as the substrate for forming the cluster.

[0082] This method also allows the use of clusters of components in a manner similar to manufacturing components on silicon wafers.

[0083] Of course, the present invention is not limited to the example shown, i.e., the fabrication of cams, but can have various variations and modifications, which will be apparent to those skilled in the art.

Claims

1. A method for batch manufacturing of watch components, characterized in that: The method comprises the following steps: a) providing a substrate (1) covered with a conductive primer layer (2); b) applying a photosensitive resin layer (3) on the conductive layer (2) on the surface of the substrate (1); c) irradiating the resin layer (3) through a mask (4), the mask defining the outline of a collection of components (5) and a grid (7) and material bridges (6), the material bridges (6) connecting the components (5) to the grid (7) at the non-functional surface, the grid, material bridges and surface components forming a cluster of components; d) dissolving the un-irradiated area (3b) of the photosensitive resin layer (3) to expose the conductive layer (2) of the substrate at an appropriate position and form a mold; e) conformally depositing a metal layer from the conductive layer (2), the metal layer forming a cluster of components and reaching the level of the upper surface of the photosensitive resin layer; f) removing the photosensitive resin layer and substrate to release the cluster of components formed thereby; g) releasing the batch of components from the cluster.

2. The method according to claim 1, characterized in that: The method comprises a step e') between step e) and step f), during which the resin layer and the deposited metal layer are planarized so as to bring the resin layer and the electrodeposited metal layer to the same level.

3. The method according to any one of claims 1 or 2, characterized in that The method comprises: - after step d), repeating steps c) and d) at least once to obtain a mold having at least two layers; - applying at least one further metal layer to said at least second face of said mould.

4. The method according to any one of claims 1 to 3, wherein: The mold has several levels.

5. The method according to any one of claims 1 to 4, wherein: The material bridge (6) has the same thickness as the component (5).

6. The method according to any one of claims 1 to 4, characterized in that The material bridge (6) has a thickness which is less than the thickness of the component (5).

7. The manufacturing method according to any one of claims 1 to 6, characterized in that: The method comprises a step g) of wafer finishing of the front, back and / or side faces of the watch component (1), said finishing step comprising depositing a layer, for example a structured layer and / or a decorative layer.

8. The method according to any one of claims 1 to 7, wherein: The cluster of watch parts comprises a group of identical parts selected from the group consisting of: a wheel, a cam, a pointer, a lever, a snail, an oscillating weight, a speed indicator or an inlay.

9. The method according to any one of claims 1 to 7, wherein: Said cluster of watch parts comprises a number of different parts, such as wheels, cams, hands, levers, pendulums, snails, hands or inlays.

10. A batch of watch parts (1) obtained by implementing the method for manufacturing a batch of watch parts (1) according to any one of claims 1 to 9.

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