HK1113948B - Micro-mechanical part made of insulating material and method of manufacturing the same - Google Patents

Description

Micromechanical component made of insulating material and method for producing same

Technical Field

The present invention relates to a micromechanical part made of insulating material, and more particularly a fixed or movable part of a timepiece movement close to other parts, without interfering directly or indirectly with the operation of the movable part due to attracting particles.

Background

Insulating materials, such as silicon and its composites, quartz, diamond, glass, ceramics or other materials, are increasingly used to manufacture micromechanical components for the horological manufacturing industry, whether fixed components, such as plates or splints, or mobile components forming parts of the drive train or regulation system, such as balance springs, balances or escape wheels.

In particular in balance springs that are completely isolated from the other components, for example by pinning on pins and by adhesion by non-conductive adhesive, it has been observed that the use of silicon has a drawback. In fact, after a certain operating time, a certain number of coils, located between the outer end curve and the inner end curve of the balance spring, tend to adhere to the balance-cock, which entails a compromise of the isochronism of the regulating system. The same phenomenon is observed also in other parts made of silicon or other insulating materials, which will gradually have an adverse effect on the isochronism.

Disclosure of Invention

The aim of the present invention is to provide a solution to the problems described by means of fixed or movable micromechanical parts made of insulating material and whose surface is treated so as to avoid the risk of adhesion.

The invention therefore relates to a micromechanical part made of insulating material, such as silicon and its composites, diamond, glass, ceramic or other materials, all or part of whose surface is coated with a thin deposit of conductive material, such as metallic or non-metallic conductive material. The conductive deposit preferably has a thickness of less than 50 nm. This very thin deposit is not visible to the naked eye but can be detected via current analytical devices, eliminating the risk of attraction and adhesion by adjacent components due to friction or tension creating electrostatic charges in the components.

This deposition can be carried out on a single or composite part made of insulating material, i.e. wherein at least the outer surface is made of insulating material.

From the materials that can achieve the stated object, non-oxidizing and non-magnetic metals such as gold, platinum, rhodium, palladium are preferably selected.

From the group of non-metallic conductive materials, graphite, carbon, doped silicon and conductive polymers are preferably selected.

These metals can be deposited by known methods, so that the thickness can be controlled by adjusting the operating conditions, for example by sputtering, PVD, doping, ion implantation or by electrolytic methods. The same technique can be used to deposit the non-conductive metallic material.

In a preferred mode of application, said micromechanical part is a part in the drive train of the timepiece movement, such as a balance spring, a pallet fork, an escape wheel or a toothed wheel, or any other fixed part, such as an arbour bearing forming a movable part. In the following detailed description, the invention will be explained more particularly by means of a balance spring, which is the most sensitive component of a timepiece movement.

The invention also relates to a timepiece incorporating a micromechanical part of this type.

Drawings

Further features and advantages of the invention will become more clearly apparent in the description of the following exemplary embodiments, given by way of non-limiting description, with reference to the accompanying drawings, in which:

figure 1 shows a top view, partly broken away, of a balance with a balance spring provided with a balance spring treated according to the invention;

FIG. 2 is a sectional view taken along line II-II of FIG. 1, with a view taken partially away

Detailed Description

The invention is more particularly described by means of a sprung balance regulating device shown in fig. 1, in which balance spring 1 is made of silicon, by way of example, by adapting a micro-machining technique or an accelerometer used in the manufacture of integrated circuits, from a sheet of silicon or any other amorphous or crystalline insulating material. For example, wet etching, dry plasma processing, or Reactive Ion Etching (RIE) may be performed using a mask that is appropriate for the desired profile of the balance spring.

Given the small dimensions, the same silicon plate allows to mass-produce balance springs, whose characteristics are determined by the thickness of the plate and the shape of the mask, which characteristics can be calculated for the operation of the balance spring in one plane.

Although reference is now made to fig. 2, in which the section is limited to balance spring 1 and balance-cock 9, the performance of coil 11 after a certain operating time is represented on the left when coil 1 is not processed. As shown, the coils 11 move away from the normal position shown in dotted lines, attracted by the balance-cock 9, and they are even glued to the latter, which obviously interferes with normal operation, i.e. with operation with extension/retraction movement in only one plane.

The right side shows balance spring 1 after treatment, and the dotted line shows the position occupied by coil 11 when it is not treated. As shown, the balance spring remains perfectly in one plane, it can be observed, in fact, surprisingly, that by carrying out a treatment of very thin deposition of conductive material on all or part of the surface of the coil, said adverse effects are eliminated without altering the intrinsic mechanical properties of the balance spring. By "very thin deposition" is meant a deposition having a thickness of less than 50nm, preferably between 10 and 20 nm. At deposition less than 50nm, the intrinsic mechanical properties of the part are not altered, and the deposits are not visible to the naked eye, but can be perceived via current analytical techniques. When a conductive metal material is used, the material used is preferably a non-oxidizing and non-magnetic metal, such as gold, platinum, rhodium, palladium. Such deposition may be carried out by a variety of well-known methods, such as sputtering, PVD, ion implantation, or electrolytic deposition.

By way of example, 15nm gold deposition was carried out by sputtering by applying a current of 60mA for 15 seconds.

In depositing the non-metallic conductive material, it is preferred to select from the group consisting of graphite, carbon, doped silicon, and conductive polymers, and to use the deposition techniques and thicknesses described.

We have just described a silicon balance spring, but other amorphous or crystalline non-conductive materials, such as those mentioned, can also be used and treated by surface metallization to avoid the risks of attraction and adhesion.

It is also possible to use synthetic materials in order to manufacture a balance spring having a thin deposit of silicon on which the conductive material is to be manufactured, a core of insulating silicon and a thick coating of silicon oxide.

The "composite material" may also include a metal core embedded within an insulating material.

Likewise, the invention is not limited to a balance spring and can be applied to other moving parts, such as pallets, escape wheels or toothed wheels, and other fixed or moving parts of a timepiece movement.

Claims (16)

1. Timepiece comprising a balance spring made of at least one insulating material and incorporated in the drive train of a timepiece movement, characterized in that all or part of the surface of said at least one insulating material is coated with a deposit of conductive material.

2. Timepiece comprising an escapement mechanism including a pallet and an escape wheel incorporated in a drive train of a timepiece movement, the pallet and/or escape wheel being made of at least one insulating material, characterized in that all or part of the surface of said at least one insulating material is coated with a deposit of a conductive material.

3. The timepiece of claim 1 or 2, wherein the deposit of conductive material has a thickness of less than 50 nm.

4. The timepiece of claim 3, wherein the deposit of conductive material has a thickness of between 10 and 20 nm.

5. The timepiece of claim 1 or 2, wherein the insulating material is selected from the group consisting of silicon and silicon composites, diamond, glass and ceramics.

6. The timepiece of claim 5 including a silicon oxide coating thereon forming silicon cores of greater than 50nm thickness.

7. The timepiece of claim 1 or 2, wherein the conductive material is a metallic material.

8. The timepiece of claim 7, wherein the metal used for deposition is a non-oxidized and non-magnetic material.

9. The timepiece of claim 8, wherein the metal is selected from the group consisting of gold, platinum, rhodium and palladium.

10. The timepiece of claim 1 or 2, wherein the conductive material is a non-metallic conductive material.

11. The timepiece of claim 10, wherein the non-metallic conductive material used for deposition is selected from the group consisting of carbon, doped silicon, and conductive polymers.

12. The timepiece of claim 11, wherein the non-metallic conductive material used for deposition is made of graphite.

13. A method of manufacturing a timepiece according to any one of the preceding claims, including the steps of:

processing a part or a batch of parts in a sheet of insulating material, and

the deposition of the layer of conductive material is carried out on all or part of the surface of the component, while the operating conditions are adjusted so as to obtain the desired thickness.

14. The method of claim 13, wherein the depositing step comprises depositing a metallic material or a conductive non-metallic material.

15. The method of claim 14, wherein the conductive deposition is performed by sputtering, PVD, doping, ion implantation, by electrolytic methods, or any other method to achieve such deposition.

16. The method of claim 13, wherein the insulating material is silicon coated with silicon oxide and the conductive material is gold.