JP2015179013A - Manufacturing method of balance spring - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a balance spring that manufactures a balance spring for a timepiece made up of silicon with high accuracy.SOLUTION: A manufacturing method of a balance spring is configured to: provide a process of forming a first mask pattern 10 corresponding to a shape of a balance spring composed of a collet, main spring unit, and a spring-holding stud in a top part of an SOI substrate and a second mask pattern 20 having a uniform interval relative to the first mask pattern 10 in a coarse portion of the first mask pattern 10; apply dry etching using a deep digging RIE art to form the main spring under the first mask pattern and form a second active layer shape under the second mask pattern 20; and separate the main spring and the active layer shape through a lift-off process. An interval between the first mask pattern 10 and the second mak pattern 20 is close and uniform, and thereby, side etching is not caused, which in turn obtains the main spring excellent in dimensional accuracy and perpendicularity.

Description

  The present invention relates to a hairspring for a watch, and more particularly to a method for manufacturing a hairspring having silicon as a main component.

  In a conventional mechanical timepiece, a speed governor (balance balance) composed of a hairspring and a balance wheel (with a balance spring) is used in order to keep the operation of the machine regularly at a constant speed. The balance wheel regularly reciprocates by the expansion and contraction of the isochronous balance spring.

  The balance with the escapement composed of escape wheel and ankle is connected to the balance with the balance, and the energy is transmitted from the mainspring to maintain the vibration.

  Known balance springs are often formed by processing metal. For this reason, the shape as designed may not be obtained due to variations in processing accuracy or the influence of internal stress of the metal.

  Since the balance spring needs to regularly vibrate the balance with the balance, if the shape as designed is not obtained, the balance wheel also cannot move isochronously, resulting in a deviation in the rate of the watch. The rate of the watch indicates the degree of advance or delay of the watch per day.

  In recent years, attempts have been made to manufacture timepiece parts by etching a silicon substrate. It is said that it has the advantage that it can be made lighter than the manufacture of watch parts using conventional metal parts, and the advantage that it can be mass-produced at low cost. Thereby, it is expected that a small and lightweight watch can be manufactured.

  When etching a silicon substrate, a reactive ion etching (RIE) technique, which is a dry etching technique, has recently progressed. Among them, deep RIE (Deep RIE) technology has been developed, and etching with a high aspect ratio has become possible.

  According to this technology, since the etching does not go under the part masked with photoresist, the mask pattern can be faithfully reproduced in the vertical depth direction, and the watch part is designed when etching the silicon substrate. It has become possible to manufacture accurately with a street shape (for example, refer to Patent Document 1).

  In the first place, silicon has better temperature characteristics than metal. It has a feature that it is less likely to be deformed with respect to ambient temperature than a metal used as a material for a conventional hairspring. For this reason, it is considered to apply this technique to a speed control mechanism of a timepiece.

Special Table 2011-505003 (6th page, FIG. 1)

It has been found that when silicon is deeply etched and etched using the RIE technique, as represented by the prior art disclosed in Patent Document 1, the shape does not become as designed.

Originally, when silicon is etched using the deep RIE technique, a balance spring is created as designed, that is, according to the mask pattern.
However, when the object to be etched is a hairspring, local over-etching occurs instead. That is, there are a portion etched according to the mask pattern and a portion etched more narrowly than the mask pattern.

The reason is the shape of the hairspring. A hairspring is a shape in which a mainspring arm having one end connected to a whisker and the other end connected to a whisker is wound around the whistleball. In addition, the mainspring arm currently wound is called a mainspring part.
For this reason, when viewed in plan, there are places where there are adjacent parts and places where they are not. Such a state is referred to as having a density of shape.

  For example, in the mainspring portion, the vicinity of the whiskers is spaced in shape, and the shape density is rough. The spirally wound mainspring portion is in a state where the distance between the adjacent mainspring arms is narrow and the shape density is narrow, that is, dense.

  The hairspring that is etched by deep RIE uses a mask pattern according to its shape. The shape density of the hairspring is also the density of the mask pattern.

  For this reason, due to the density of the mask pattern, side etching occurs in the portion where the pattern is rough, and when the hairspring is finished being etched, only the portion where the side etching occurs is processed to be thinner than the mask pattern. It ends up.

  This is because ions and radicals generated in a plasma environment are generated during etching when the distance from the adjacent mask pattern is long (when the density of the pattern shape is rough) during etching by deep RIE. This is because the mask pattern also comes from the lateral direction, and side etching proceeds.

  By the way, when the distance to the adjacent mask pattern is short (when the density of the pattern shape is dense), ions and radicals coming from the lateral direction interfere with the adjacent pattern, and side etching proceeds. There is no end.

  As already described, since the mask pattern is derived from the shape of the hairspring, the density of the mask pattern cannot be freely changed.

  For this reason, in the prior art represented by patent document 1, a balance spring cannot be processed into the shape as designed, and the mechanical timepiece incorporating this causes a rate deviation.

As a proposal for solving this problem, a method is known in which etching is performed twice in a portion where the mask pattern has a high density.
That is, the first etching is performed with a narrower groove width than the design to obtain perpendicularity, and then a mask pattern is formed again, and the second etching is performed with a wide groove width as designed. .

  However, this method requires a work process for performing etching twice, which is very laborious. Further, in the second etching step, accurate alignment with the shape formed in the first time is necessary. For this reason, the defect rate was high and the manufacturing cost was also high.

  This invention is made | formed in view of said subject, and provides the manufacturing method which can manufacture a hairspring accurately.

  As means for solving the above-described problems, the method for manufacturing a hairspring of the present invention is as follows.

  A whisker having a through hole for fitting with the rotating shaft body, a coil-shaped mainspring part connected to the whistle ball and wound around the whisker ball around the through hole, and an end of the mainspring part A method of manufacturing a hairspring having silicon as a main component and having a whiskers to be provided, wherein a base layer having silicon as a main component, a silicon oxide film layer, and an active layer having silicon as a main component are sequentially formed A first mask pattern corresponding to the shape of the hairspring and a second mask pattern arranged on the active layer of the laminated SOI substrate and corresponding to a rough place. A mask pattern forming step for forming the mask pattern, an etching step for etching the active layer into a shape corresponding to each of the first and second mask patterns, and removing the silicon oxide film layer, Is characterized in that it has a, a lift-off process to separate from the base layer to have.

  By adopting such a manufacturing method, a uniform arrangement interval without coarseness can be obtained in the arrangement interval between the first mask pattern and the second mask pattern. As a result, the side etching does not proceed, and a hairspring with good dimensional accuracy can be obtained in the thickness and verticality of the hairspring.

  In the hairspring manufacturing method of the present invention, it is preferable that the portion where the second mask pattern is formed is around the hairball, the outer periphery of the mainspring portion, or the periphery of the hairspring.

  The first mask pattern has a rough distribution around the beard ball, the outer periphery of the mainspring portion, or the periphery of the beard. Therefore, when a second mask pattern is provided in that portion, a mask pattern that is uniformly distributed as a whole is obtained.

  In the hairspring manufacturing method of the present invention, it is preferable that the second mask pattern has a shape having a slit smaller than the distance between the first mask pattern and the second mask pattern.

  By having a small slit in the second mask pattern, the shaped product formed under the second mask pattern is divided into a plurality of slits and separated in the lift-off process. Therefore, it becomes easy to take out a shaped product formed under the second mask pattern. Since the width of the slit is smaller than the distance between the first mask pattern and the second mask pattern, the etching width at the portion where the slit is present is not much different from the etching width at the other portion, and the influence of etching is very much It becomes small and a balance spring with good dimensional accuracy can be obtained.

  Further, in the method for manufacturing a hairspring of the present invention, the mask pattern forming step further includes a step of forming a third mask pattern corresponding to a shape of a frame connected to a part of the hairspring at the connection portion, and a lift-off step After this, it is preferable to have a disconnecting step of disconnecting the frame and the hairspring by destroying the connecting portion.

By forming the third mask pattern corresponding to the shape of the frame, a hairspring connected to a part of the frame is obtained. Then, the hairspring does not fall into the etching solution tank in the lift-off process. Thereafter, if a cutting step for cutting the hairspring is provided at the connection portion with the frame, the hairspring having a beautiful appearance can be obtained without damaging the hairspring when the hairspring is taken out.

  According to the present invention, an accurate quality characteristic can be obtained in the thickness dimension and verticality of the hairspring. And the effect which improves the speed control performance of a hairspring is produced.

It is a top view explaining the shape of a hairspring. It is a top view explaining the mask pattern of the hairspring of the present invention. It is sectional drawing explaining the manufacturing method of the hairspring of this invention. It is a top view explaining the mask pattern of the hairspring of this invention, Comprising: It is a figure explaining a 3rd mask pattern. It is a top view explaining the manufacturing method of the hairspring of the present invention, and is a figure showing the state after a lift-off process. It is a top view explaining the slit provided in a 2nd mask pattern. It is a top view explaining the slit provided in a 2nd mask pattern.

The hairspring manufacturing method of the present invention is characterized in that a second mask pattern is provided in order to eliminate the density of the first mask pattern corresponding to the shape of the hairspring used when manufacturing the hairspring. It is a feature.
Thereby, side etching does not occur even in a place where the pattern density of the first mask pattern is rough, and the hairspring can be etched according to the mask pattern.

  Further, by providing a third mask pattern in the shape of a frame around the hairspring, it is possible to prevent the hairspring from dropping into the etching solution tank in the lift-off process and improve workability.

  Hereinafter, the method for manufacturing a hairspring of the present invention will be described with reference to FIGS. The drawings used in the description are schematic diagrams, and portions not related to the invention are omitted or simplified. The same number is assigned to the same configuration, and detailed description is omitted.

[Shape description of hairspring: Fig. 1]
First, the shape of the hairspring 11 will be described with reference to FIG.
The hairspring 11 is processed by a method described later from a substrate containing silicon as a main component. The shape has a whisker ball 11a having a through hole 11a1 for fitting a rotating shaft body (not shown) in the center. One end is connected to the whistle ball 11a, and a mainspring part 11b is formed of a coil-shaped mainspring arm that is wound a plurality of times around the center of the through hole 11a1 of the whistle ball 11a. And it is comprised with the whisk 11c connected to the other end of the mainspring part 11b. The whiskers 11a, the mainspring portion 11b, and the whiskers 11c are integrally formed.

[Description of mask pattern of hairspring: FIGS. 1 and 2]
Next, a mask pattern for manufacturing the hairspring 11 will be described with reference to FIGS. 1 and 2.
FIG. 2 shows a mask pattern for forming the hairspring 11 shown in FIG. The mask pattern shown in FIG. 2 includes a first mask pattern 10 corresponding to the shape of the hairspring and a second mask pattern 20 having a shape that eliminates the density of the arrangement of the first mask pattern 10. doing.

  As already described, the shape of the hairspring 11 includes a wide portion and a narrow portion in a plan view, and the shape is coarse and dense. Since the shape of the first mask pattern 10 shown in FIG. 2 is the same as that of the hairspring 11 shown in FIG. 1, the shape of the first mask pattern 10 shown in FIG.

  In the hairspring 11 shown in FIG. 1, the portions having a coarse shape density (a wide gap in a plane) are the inner peripheral portion 12a1 of the through hole 11a1 of the whistle ball 11a, the outer peripheral portion 12a of the whistle ball 11a and the mainspring portion 11b. It is the outer peripheral part 12c. In particular, the outer peripheral part 12c is widely open between the mainspring part 11b and the whiskers 11c. On the other hand, a portion having a dense shape (a portion having a narrow gap in a plane) is a winding portion 12b around which the mainspring arm constituting the mainspring portion 11b is wound in an orderly manner.

  As shown in FIG. 2, it corresponds to the mask pattern corresponding to the inner peripheral portion 12a1 of the through hole 11a1 of the whistle ball 11a, the mask pattern corresponding to the outer peripheral portion 12a of the whistle ball 11a, and the outer peripheral portion 12c of the mainspring portion 11b. A second mask pattern 20 is provided for each mask pattern to be performed.

  The second mask pattern 20 is given the reference numerals of the second mask pattern 20a1, the second mask pattern 20a, and the second mask pattern 20c, respectively, in FIG.

By having the second mask pattern 20, there is no rough portion in the shape of the first mask pattern 10, and the distance between adjacent portions is constant.
As already explained, when the adjacent mask pattern is close (when the mask pattern is dense), the adjacent mask pattern becomes a shield for ions and radicals coming from the lateral direction, and side etching can be prevented. It can be done. Then, the hairspring 11 having the shape of the first mask pattern 10 can be made.

  The second mask pattern 20 shown in FIG. 2 may be an elongated shape having the same thickness as that of the mask pattern constituting the first mask pattern 10, for example, the mask pattern portion corresponding to the mainspring arm. The second mask pattern 20 can be freely changed in view of the shape of the hairspring.

[Description of Manufacturing Method: FIGS. 2 to 5]
Next, a method of manufacturing the hairspring 11 having the above shape will be described with reference to FIGS.
FIG. 3 is a cross-sectional view schematically showing a part of the plan view of FIG. 2 in order to explain the manufacturing process, in which the whisker ball 11a at the center of the hairspring 11 and the spring part connected thereto It is the figure which took out and extracted the partial area | region of 11b.

  As shown in FIG. 3A, an SOI (Silicon on Insulator) substrate is prepared. The SOI substrate 1 includes a silicon oxide film layer (SiO 2 layer) 3 having a thickness of 1 to 3 μm formed on a base layer 2 having a thickness of, for example, 400 to 500 μm, which is mainly composed of silicon (Si). It has a three-layer structure in which an active layer 4 mainly composed of silicon (Si) is formed on the oxide film layer 3.

  Since the active layer 4 is a layer constituting the hairspring 11, its thickness is determined by the hairspring to be manufactured. If the productivity of the hairspring 11 is taken into consideration, it is preferable that the SOI substrate 1 has such a size that a large number of hairsprings 11 can be taken out.

Next, as shown in FIG. 3B, a resist film 5 having a predetermined thickness is formed on the active layer 4 of the SOI substrate 1 by a known method such as a spin coating method.
Resist liquids for forming the resist film 5 include a positive type and a negative type, and are appropriately selected together with a mask film to be used. In the embodiment of the present invention, an example using a positive resist solution will be described.

  After applying the resist film 5, for example, a pre-bake process is performed at a temperature of 80 to 100 ° C. to evaporate the organic solvent contained in the resist solution, and the resist film 5 is adhered to the active layer 4.

  Next, as shown in FIG. 3C, a first mask pattern 10 and a second mask pattern 20 are formed using a known technique.

For example, the following method is used to form the mask pattern on the resist film 5.
First, on a predetermined glass surface (not shown), a first chromium pattern corresponding to a first mask pattern mainly composed of chromium (Cr) or the like and a second chromium pattern corresponding to a second mask pattern are provided. A glass mask is prepared.

  Next, a glass mask is placed on a known exposure apparatus, and the resist film 5 on the surface of the SOI substrate 1 is irradiated with ultraviolet rays of a predetermined wavelength through the glass mask to expose the resist film 5. A portion exposed later is developed to transfer the first mask pattern 10 and the second mask pattern 20.

  Next, as shown in FIG. 3D, the active layer 4 is etched according to the shapes of the first mask pattern 10 and the second mask pattern 20 shown in FIG. The active layer 4 is etched by dry etching using a deep RIE technique.

  During etching by deep RIE, ions and radicals that are about to enter from the lateral direction of the first mask pattern 10 are shielded by the second mask pattern 20, so that the first mask pattern 10 Side etching is suppressed in the lower active layer, and the active layer is etched according to the shape of the first mask pattern 10.

  By the way, the second mask pattern 20 serves as a barrier against side etching with respect to the first mask pattern 10, but side etching partially occurs in the active layer under the second mask pattern 20 itself. However, since the active layer etched by the second mask pattern 20 is not related to the shape of the hairspring in the first place, there is no problem.

  Here, a name is given to each of the etched active layers for easy explanation. The active layer corresponding to the first mask pattern 10, that is, the active layer constituting the hairspring is assumed to be the first active layer shapes 10a and 10b. The active layer corresponding to the second mask pattern 20, that is, the active layer serving as a barrier for preventing side etching, is assumed to be second active layer shapes 20a and 20b.

Next, as shown in FIG. 3E, the first mask pattern 10 and the second mask pattern 20 which are resist layers are peeled using an organic solvent such as acetone.
As a result, the first active layer shapes 10a and 10b and the second active layer shapes 20a and 20b are exposed.

Next, as shown in FIG. 3 (f), the first active layer shapes 10 a and 10 b and the second active layer shapes 20 a and 20 b are separated from the base layer 2. This process is performed using a known technique called lift-off. In the lift-off process, a liquid tank containing a chemical that is resistant to the silicon layer and in which the silicon oxide film dissolves, for example, hydrofluoric acid (hydrofluoric acid), is prepared.
Soaked.

  Since only the silicon oxide film layer 3 is dissolved by this lift-off process, the first active layer shapes 10 a and 10 b and the second active layer shapes 20 a and 20 b are separated from the base layer 2.

  In the lift-off process, the first active layer shapes 10a and 10b and the second active layer shapes 20a and 20b fall while drifting toward the bottom of the hydrofluoric acid liquid tank. If a net-like filter is provided, it is possible to prevent the liquid tank from dropping to the bottom. Then, only the first active layer shapes 10a and 10b, that is, the hairspring can be obtained.

  At this time, if the filter has a mesh or a hole size that allows the second active layer shapes 20a and 20b to pass but not the hairspring 11 only, the shape of the hairspring 11 and the second active layer shape. 20a and 20b can be easily selected.

  Of course, it is possible to prevent the hairspring 11 from dropping into the hydrofluoric acid bath in the lift-off process. Hereinafter, a description will be given with reference to FIGS. 4 and 5.

[Description of Third Mask Pattern: FIGS. 4 and 5]
FIG. 4 is a plan view showing the mask pattern corresponding to FIG. 2, and is a diagram for explaining the third mask pattern 30. FIG.
As shown in FIG. 4, the third mask pattern 30 surrounds the periphery of the first mask pattern 10 and the second mask pattern 20 in the shape of a frame, and a part of the hairspring 11, for example, the whisker 11 c Are connected to the end portions of the two at the connection portion 35. The third mask pattern 30 is not in contact with the second mask pattern 20.

  As shown in FIG. 3C, after the first mask pattern 10 and the second mask pattern 20 are formed, the third mask pattern 30 is formed by using a technique similar to these mask patterns. A mask pattern 30 is provided on the resist film 5.

Alternatively, a third chromium pattern corresponding to the third mask pattern 30 may be formed in advance on a glass mask (not shown) already described.
Then, when the mask pattern is transferred to the resist film 5 of the first mask pattern 10 and the second mask pattern 20, the third mask pattern 30 can also be transferred. This is convenient because the mask pattern can be transferred to the resist film 5 only once.

After forming the resist film 5 in the shape of the first to third mask patterns in this way, the active layer is etched using the deep RIE technique. Then, the resist film 5 is peeled off.
Thereafter, when the active layer is separated from the base layer 2 through a lift-off process, the active layer has a shape as shown in FIG. Here, the active layer corresponding to the third mask pattern 30, that is, the frame-shaped active layer surrounding the balance spring is defined as the third active layer shape 30a.

As already described, since the part of the whisker 11c of the first mask pattern 10 is connected to the connection part 35 of the third mask pattern 30, the second mask pattern 20 is removed by the lift-off process. Although it falls, the first mask pattern 10 is connected at the connection portion 35a of the third active layer shape 30a corresponding to the connection portion 35 and remains as it is.
Thereby, the first mask pattern 10 corresponding to the hairspring 11 and the second mask pattern 20 having the second active layer shape can be selected.

Thereafter, in order to take out the hairspring 11 shown in FIG. 1 from the state shown in FIG.
This is done by breaking the portion 5a.
For example, manual breakage by tweezers or breakage by a machine such as a dicing saw can be used for the breakage.

  In consideration of the productivity of the hairspring 11, when the SOI substrate 1 having a size capable of extracting a large number of hairsprings 11 is used, the third mask patterns 30 provided around the plurality of hairsprings are connected to each other. In this case, if the third active layer shape 35a is gripped after the dry etching by the deep RIE technique, it is convenient that a plurality of hairsprings can be conveyed at one time.

As described above, the hairspring 11 shown in FIG. 1 is formed by such a manufacturing process.
What is important is that the space between the first mask pattern 10 and the second mask pattern 20 is substantially uniform, as shown in FIGS.

In the example described above, the second mask pattern 20 has a pattern thickness suitable for the location in order to eliminate the density of the first mask pattern 10, but the present invention is not limited to this.
Although depending on the shape of the hairspring 11, if the density of the first mask pattern 10 is uniform, the second mask pattern 20 may have the same thickness as the first mask pattern 11. is there.

[Description of the configuration in which slits are provided in the second mask pattern: FIGS. 6 and 7]
Next, an example in which a slit is provided in the second mask pattern 20 will be described.
FIG. 6 is a plan view for explaining the slits 22 provided in the second mask pattern 20. The relationship between the size of the slit 22 and the distance between the first mask pattern 10 is shown. FIG. 7 is a plan view for explaining a different shape of the slit 22.

  As already explained, the second active layer shape 20a, which is the shape of the second mask pattern 20 as well as the first active layer shape 10a, 10b, which is the shape of the active layer balance spring 11, by the lift-off process. 20b is separated from the base layer 2. At this time, the second active layer shapes 20a and 20b are preferably separated without interfering with the first active layer shapes 10a and 10b. Therefore, the slits 22 are provided in the second mask pattern 20 in order to make the second active layer shapes 20a and 20b small.

  As shown in FIG. 6, the width m of the slit 22 provided in the second mask pattern 20 is preferably smaller than the distance w between the second mask pattern 20 and the first mask pattern 10. This is because when the width m of the slit 22 is greater than the distance w, side etching occurs in the portion of the first mask pattern 10 that is planarly opposed to the slit 22 as in the case where the second mask pattern 20 is not provided. It is because it ends up.

  The slit 22 provided in the second mask pattern 20 is not limited to the shape shown in FIG. For example, as shown in FIG. Moreover, you may combine a some straight line as shown in FIG.7 (b).

  Moreover, although the slit 22 demonstrated using FIG.6 and FIG.7 is an example provided in the 2nd mask pattern 20, in order to make the 2nd active layer shape 20a, 20b into a small shape, the slit 22 is small. Since it is provided, it is preferable to provide a plurality at predetermined intervals.

Of course, the method of manufacturing the hairspring described above is not limited to this, and can be modified without departing from the spirit of the invention.
For example, although the connection part between the first mask pattern 10 and the third mask pattern 30 is exemplified by the hairspring holding part of the hairspring, it is of course not limited to this part. In addition, a mask pattern may be provided in which a plurality of connection portions are provided or adjacent hairsprings and connection portions are arranged in a straight line in order to facilitate breakage by a machine such as a dicing saw.

  According to the present invention, since the hairspring having silicon as a main component can be formed according to the mask pattern, it is suitable for a mechanical timepiece having a high accuracy in which the rate does not shift.

DESCRIPTION OF SYMBOLS 1 SOI substrate 2 Base layer 3 Silicon oxide film layer 4 Active layer 5 Resist film 10 1st mask pattern 10a, 10b 1st active layer shape 11 Hairspring 11a Hairball 11a1 Through-hole 11b Mainspring part 11c Beard 20 Second Mask pattern 20a, 20b Second active layer shape 22 Slit 30 Third mask pattern 30a Third active layer shape 35 Connection portion 35a Connection portion in third active layer shape 30a

Claims (4)

A hair ball having a through hole for fitting with a rotating shaft body, a coil-shaped mainspring portion connected to the whisker ball and wound around the hair ball around the through hole, and A method for producing a hairspring having a main component of silicon having a beard provided at an end portion,
Above the active layer of the SOI substrate formed by sequentially laminating a base layer mainly composed of silicon, a silicon oxide film layer, and an active layer mainly composed of silicon,
A first mask pattern corresponding to the shape of the hairspring;
A second mask pattern arranged corresponding to a rough arrangement of the first mask pattern;
Forming a mask pattern, and
An etching step of etching the active layer into a shape corresponding to each of the first and second mask patterns;
A lift-off step of removing the silicon oxide film layer and separating the hairspring from the base layer;
A method of manufacturing a hairspring. The method of manufacturing a hairspring according to claim 1, wherein the portion where the second mask pattern is formed is around the hairball, the outer periphery of the mainspring portion, or the circumference of the hairspring. The hairspring according to claim 1 or 2, wherein the second mask pattern has a shape having a slit smaller than a distance between the first mask pattern and the second mask pattern. Method. The mask pattern forming step includes
Forming a third mask pattern corresponding to a shape of a frame connected to a part of the hairspring at a connection portion;
After the lift-off process, a disconnecting process of disconnecting the frame and the balance spring by destroying the connection portion;
The method for manufacturing a hairspring according to any one of claims 1 to 3, wherein:

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