CH717141B1 - Process for assembling watch components. - Google Patents

Abstract

The present invention proposes a method of assembling a first watch component and a second watch component (5). The method comprises the following steps: a) depositing a multilayer metal coating (7) on at least a first assembly zone of the first watch component, the multilayer metal coating (7) comprising a first layer adjacent to the first watch component and produced in one first metallic material and, above the first layer, a second layer made of a second metallic material; b) deposit alternately by vapor phase deposition, on at least a second assembly zone of the second watch component (5) intended to be assembled in the first assembly zone of the first watch component, layers of different pure metals, the quantity of pure metals for all of said layers deposited alternately being such that all of said layers deposited alternately constitute a layer of filler metal (8) of composition corresponding to a eutectic alloy based on said pure metals; c) position the first and second watch components to allow their assembly via their respective first and second assembly zones; and d) heating at least the first and second assembly zones to melt the filler metal (8) deposited on the second watch component (5) and bond the first and second watch components via their first and second assembly zones. respective assembly, by atomic diffusion between said filler metal (8) and the second metallic material of the second layer of the first multilayer metallic coating (7).

Description

[0001] The present invention relates to an assembly method between a first watch component and a second watch component. By “watch component” we mean an entire component, for example a hairspring or a pin; we also mean a part of a watch component, for example a hook which is on a barrel shaft, or a pull which is on a winding stem.

[0002] In the watchmaking field, materials such as silicon, diamond, ceramics, glasses or metallic glasses are increasingly used. These materials are considered fragile materials which break without prior plastic deformation at room temperature (25°C),

[0003] Thanks to their advantageous properties in terms of density, coefficient of friction and insensitivity to magnetic fields, these materials have largely contributed to improving the precision and efficiency of watch mechanisms. However, these materials do not lend themselves well to certain assembly techniques. Since they cannot be driven out due to their fragility, they are generally glued or elastically mounted. Sticking causes pollution problems in the mechanism and poor long-term performance. Elastic assembly, for its part, does not allow the transmission of high torques between the two assembled components.

[0004] We know from patent EP 0732635 a process for producing watch components such as an anchor, a wheel, a pinion, a hairspring or a balance wheel, according to which the component is engraved in a silicon plate then its active parts are where appropriate covered with a material of predetermined hardness and coefficient of friction. To enable the silicon component to be fixed to a metal axle by brazing, welding or bonding, the wall and the lower and upper edges of an orifice in the silicon component intended to receive the metal axle are coated with a metal deposit.

[0005] By “brazing” we mean an assembly operation using a filler metal (“solder”) having a melting temperature lower than that of the parts to be joined, the filler metal wetting the surfaces of the parts (brazing zone) to be joined, the connection of the filler metal with each of the parts being done by atomic diffusion.

[0006] The wetting nature of the filler metals varies depending on the materials on which they are deposited. Some materials have poor wettability compared to commercially available filler metals. For brazing a non-metallic part for example, it is therefore appropriate to choose a metallic deposit which has both good adhesion to the non-metallic material and good wettability by the filler metal.

[0007] A solution to this problem was proposed by patent application EP 3 309 624 filed by the applicant for assembling a non-metallic watch component and a metallic watch component. This solution consists of depositing a multilayer metallic coating on a non-metallic watch component on which a filler metal is then deposited. The metallic watch component is then positioned on the non-metallic watch component. Then the assembly is heated to melt the filler metal provided on the first non-metallic watch component so that the two non-metallic and metallic watch components are assembled by means of the molten filler metal which binds on the one hand to the metal coating of the first watch component and on the other hand to the metal of the second watch component.

[0008] If the process proposed by application EP 3 309 624 has made it possible to optimize the strength of the assembly between a non-metallic watch component and a metallic watch component compared to the process described in patent EP 0732635, there remain certain difficulties, in particular in controlling the quantity of solder deposited on the non-metallic watch component, and in particular a silicon watch component having previously undergone different treatments, to obtain a robust assembly process. More particularly, the solder being deposited at several points in the form of drops, the solder may not spread correctly over the entire area to be soldered despite the wettability properties of the multilayer metal coating used.

[0009] If too much solder is deposited, an unsightly bead of solder may appear around the assembled components.

If the quantity of solder deposited is insufficient, the assembly of the components is not sufficiently strong and does not hold together.

[0011] The present invention aims to propose a method of assembling a first watch component and a second watch component making it possible to control the quantity of solder used in order to have a reproducible and reliable assembly process allowing its industrialization .

[0012] The present invention also aims to propose a method of assembling a first watch component and a second watch component making it possible to obtain a clean assembly, without visible traces of solder.

[0013] To this end, the present invention relates to a method of assembling a first watch component and a second watch component.

[0014] According to the invention, said method comprises the following steps: a) depositing a first multilayer metallic coating on at least one first assembly zone of the first watch component, the first multilayer metallic coating comprising at least one first layer adjacent to the first watch component and made of a first metallic material and, above the first layer, a second layer made of a second metallic material different from the first metallic material, and intended to bond to the second watch component by atomic diffusion, b) deposit alternately by vapor phase deposition, on at least a second assembly zone of the second watch component intended to be assembled in the first assembly zone of the first watch component, layers of different pure metals, the quantity of pure metals for all of said layers deposited alternately being such that all of said layers deposited alternately constitute a layer of filler metal of composition corresponding to a eutectic alloy based on said pure metals, c) positioning the first and second watch components to allow their assembly by their respective first and second assembly zones, d) heating at least the first and second assembly zones to melt the filler metal deposited on the second watch component and bond the first and second watch components by their respective first and second assembly zones, by atomic diffusion between said filler metal and the second metallic material of the second layer of the first multilayer metallic coating.

[0015] Deposition of the filler metal on one of the watch components by a vapor phase process of several alternating layers of pure metals to constitute a layer of filler metal in the form of a eutectic alloy comprising said metals pure materials makes it possible to precisely control the quantity of solder deposited as well as the quality of the deposit, the quantity of each metal deposited being able to be precisely controlled in order to obtain the ideal proportions to produce a stable eutectic.

[0016] Advantageously, the method of the invention comprises, before step b), a step e) of initial treatment of the second watch component, said step e) comprising the formation of a sharp angle on the periphery of the second component watchmaker at the junction of its second assembly area.

[0017] Furthermore, in step a), the first multilayer metal coating is preferably deposited on the first watch component on the first assembly zone at least so as not to protrude from a zone intended to be assembled to a zone of the second assembly zone of the second watch component which adjoins the sharp corner.

[0018] Such a sharp angle makes it possible to precisely delimit the zone of spreading of the filler metal on the first watch component, and more precisely on the second layer of its metal coating, in order to correspond to the first and second assembly zones , so that no solder bead protrudes from said first and second assembly zones of the first and second watch components respectively which adjoin the sharp corner.

[0019] The invention also proposes a watch mechanism comprising an assembly of a first watch component and a second watch component obtained by the assembly process as defined above.

Other characteristics and advantages of the present invention will appear on reading the following detailed description of several embodiments of the invention, given by way of non-limiting examples, and made with reference to the appended drawings in which : – Figure 1 is a perspective view of an example of a first watch component according to the invention, comprising a silicon hairspring, a ferrule and a member for fixing to a pin; – Figure 2 represents Figures 2(a) to 2(f) which are cross-sectional views of the fixing member and the eyebolt, showing different stages of the method according to the invention for assembling the hairspring to the eyebolt; – Figure 3 is a perspective view of the fixing member to the eyebolt carrying a first multilayer metal coating; – Figure 4 is a cross-sectional view, along the line A-A of Figure 1, of the fixing member to the eyebolt, showing the different layers of the first multilayer metal covering; – Figure 5 is a cross-sectional view of a first alternative piton; – Figure 6 is a partial cross-sectional view of the end of a second alternative piton; and – Figure 7 is a cross-sectional view of the piton variant of Figure 5 showing the different layers of the second multilayer metal covering.

[0021] In the context of the present invention, the term “metal” means a metal itself or a metal-based alloy. Likewise, the term “metallic” means entirely made of metal/metals or including in particular a metal.

Figure 1 shows an example of a first watch component 1 used in the present invention. In this example, the first watch component 1 comprises a hairspring 2 intended to equip a balance wheel to form with the latter the regulating organ of a watch movement. The hairspring 2 consists of an elastic blade wound in a spiral between an inner end 2a and an outer end 2b. Through its inner end 2a, the balance spring 2 is joined to a ferrule 3 intended to be mounted on the axis of the balance wheel. Through its outer end 2b, the hairspring 2 is joined to a fixing member 4 intended to be fixed to a pin 5, constituting the second watch component, (visible in Figure 5 or 6) mounted on a fixed part of the watch movement, at know the rooster. Typically the first component 1, comprising the hairspring 2, the ferrule 3 and the fixing member 4, is in a single piece obtained by a micro-fabrication technique such as DRIE deep reactive ion etching. The first component 1 can be made of a fragile material as defined above. The first component 1 may for example be made of silicon (monocrystalline or polycrystalline, doped or not) or other semiconductor material, diamond, ceramic, glass or metallic glass. The material of component 1 can also be composite and include a core covered by a coating. A typical example of a composite material is a silicon core covered by a coating of silicon oxide present naturally or formed on silicon for example by thermal oxidation as described in patent EP 1422436.

Preferably, the material of the first watch component is silicon or silicon covered with a layer of silicon oxide.

The second watch component, here the pin 5, can be metallic or made of a fragile material as defined above. Preferably, the pin 5 is metallic, steel for example.

[0025] The present invention relates in particular to a method making it possible to robustly assemble the first component 1, preferably made of silicon, and the stud 5, preferably metallic, that is to say, to fix the fixing member. fixing 4 to the pin 5. As can be seen, the fixing member 4 comprises a rigid blade 4a which extends the blade of the hairspring 2 and which is interrupted (as shown) or terminated by a ring 4b.

As shown in Figure 5 and also partially in Figure 6, the eyebolt 5 successively comprises a head 5a, a first cylindrical part 5b, a shoulder 5c and a second cylindrical part 5d. The head 5a and the first cylindrical part 5b are intended respectively to rest on and to pass through the cock in a manner known per se. The shoulder 5c is intended to rest on the upper surface 4c (facing towards the cock) of the ring 4b. The second cylindrical part 5d is intended to engage in the hole 4d of the ring 4b so that the base 5e of the shoulder 5c extended by at least one zone of the second cylindrical part 5d constitutes the assembly zone of the eyebolt 5 intended to be assembled in the assembly zone facing it on the fixing member 4.

[0027] In a particularly preferred manner, the shoulder 5c has a sharp angle on its outer periphery at the junction with its base 5e as will be detailed below. The sharp angle can be formed by a chamfer 5f, for example at 45°, as shown in Figure 5 or formed by a groove 5g as shown in Figure 6. The ends of the chamfer 5f or the groove 5g can be softened by a fillet or a rounding. The second assembly zone then corresponds to the surface of the base 5e remaining after the realization of the sharp angle and to the zone of the second cylindrical part 5d in the extension of the base 5e.

[0028] In relation to Figure 2, an embodiment of the method according to the invention is now described. It comprises the following steps: a) deposit a first multilayer metallic coating 7, which will be described below, on a first assembly zone of the fixing member 4 of the first watch component 1, b) deposit alternately by deposition in the vapor phase, on at least the second assembly zone of the second watch component 5, namely the pin 5, intended to be assembled with the first assembly zone of the fixing member 4 of the first watch component 1 to connect said first watch component to the second watch component, layers of different pure metals, the quantity of pure metals for all of said layers deposited alternately being such that all of said layers deposited alternately constitute a layer of filler metal 8 of composition corresponding to a eutectic alloy based on said pure metals, as described below, c) position the fixing member 4 of the first watch component 1 and the pin 5 to allow their assembly by their first and second assembly zones respective, d) heating at least the first and second assembly zones to melt the filler metal 8 deposited on the pin 5 and connect the fixing member 4 of the first watch component 1 and the pin 5 by their first and second respective assembly zones, by atomic diffusion between said filler metal of the stud 5 and the material of the fixing member 4.

More specifically, the first watch component 1 supplied for implementation during step a) is first prepared according to the following steps: i. equip yourself with a stencil 6 (“shadow mask” in English) whose pattern corresponds to the first assembly zone of component 1 that you wish to metallize, that is to say an area of the wall of the hole 4d and an area of the upper surface 4c of the ring 4b around the hole 4d, as shown in Figure 2(a); the pattern is defined so that, on the upper surface 4c of the ring 4b around the hole 4d, the exposed area corresponds maximum to the base of the shoulder 5c of the piton 5 remaining after the realization of the sharp angle 5f , 5g. The exposed area is preferably smaller than the base of the shoulder 5c of the eyebolt 5 remaining after the realization of the sharp angle 5f, 5g in order to avoid overflow of the filler metal during assembly; ii. define landmarks on component 1; iii. position stencil 6 on component 1 following the reference points; iv. attach stencil 6 to component 1.

Then, the first multilayer metal coating 7 is deposited on the stencil assembly 6 - component 1 in accordance with step a). Due to the choice of the stencil pattern, the first coating 7 is present on the component 1 only on an area of the wall of the hole 4d and on the area of the upper surface 4c of the ring 4b around the hole 4d, in correspondence at the maximum of the base 5e of the shoulder 5c of the peak 5 remaining after the realization of the sharp angle 5f, 5g. Thus the first multilayer metal coating 7 is deposited on the first watch component 1 on the first assembly zone so as not to protrude from a zone intended to be assembled to a zone of the second assembly zone of the second watch component which adjoins the sharp corner.

[0031] Then we remove the stencil 6 from component 1 to obtain the first watch component 1 from step a), as shown in Figures 2(b) and 3.

The stencil 6 is for example made of metal, silicon, ceramic or plastic. Depending on the material chosen, the stencil 6 can be obtained by mechanical or chemical machining, laser cutting, physical or chemical engraving or stamping of a plate, for example. A method such as screen printing or photolithography can also be considered to define the opening(s) of the stencil.

[0033] By definition the first multilayer metal coating 7 is solid, that is to say that all its layers are in the solid state. It can be deposited as thin films by PVD (physical vapor deposition), including vacuum evaporation or sputtering, or by CVD (chemical vapor deposition), including ALD (atomic layer deposition) and MVD. (molecular vapor deposition). It can also be deposited in the form of thick layers by projection, galvanic growth or otherwise.

[0034] In practice, several components are made from the same plate of the material of the first watch component 1. The deposition of the first multilayer metallic coating 7 can be carried out on each component after the latter has been separated from said plate, or simultaneously on all components while they are still attached to the plate. In the latter case, a single stencil covering all the components of the plate and positioned in relation to reference points on the plate can be used. In the case of a first watch component based on silicon, we will for example use a silicon plate or “wafer” to which the first watch components preferably remain attached during the deposition of the first multilayer metallic coating using a stencil.

The stencil 6 allows the first multilayer metal coating 7 to be deposited locally on the component 1, as described above. In the present invention the use of a stencil is preferred to the implementation of a photolithography process because of its simplicity and low cost. The present invention does not, however, exclude the implementation of a photolithography process, with a resin mask formed on component 1. The present invention also does not exclude depositing the first multilayer metallic coating 7 in a non-localized manner. . For example, we could cover the entire component 1 with the first multilayer metal coating 7 then remove, for example by laser, said first coating 7 except in the brazing zone corresponding to the first assembly zone.

As shown in Figure 4, the first multilayer metal coating 7 comprises at least a first metal layer 7a adjacent to the first component 1 and a second metal layer 7b deposited above the first metal layer 7a.

The first metal layer 7a is preferably deposited in contact with the first component 1.

The first metallic layer 7a is made of a first metallic material chosen to have better adhesion to the material of the first component 1 than the second metallic material of the second metallic layer 7b and possibly better adhesion than the material of a intermediate layer deposited on the first layer 7a, between the first layer 7a and the second layer 7b. This means that the first material of the first metallic layer 7a has, on the material of the first component, an adhesion greater than the adhesion that the second material of the second metallic layer 7b would have on the same material of the first component, when there is no middle layer. Likewise, this means that the first material of the first metallic layer 7a has, on the material of the first component, an adhesion greater than the adhesion that the material of an intermediate layer would have on the same material of the first component, when this intermediate layer is present.

The first metallic material of the first metallic layer 7a is chosen for example from chromium, titanium, tantalum, or a compound based on one or more of these metals, and preferably titanium.

The second metallic layer 7b is made of a second metallic material different from the first metallic material and chosen to be able to bind to the filler metal previously deposited on the second watch component 5 by atomic diffusion.

[0041] Preferably, the second metallic material of the second layer 7b is one of the metals used in the composition of the filler metal 8. More preferably, the second metallic material of the second layer 7b is the same metal as that chosen to constitute the last layer of the multilayer assembly constituting the filler metal 8.

[0042] The second metallic material may comprise at least one of the following materials: gold, platinum, palladium, silver, copper, nickel, molybdenum, rhodium, tungsten, tin, cobalt, iridium, tantalum, vanadium, hafnium, zirconium, ruthenium, niobium, osmium, and their alloys.

[0043] According to a first particularly preferred embodiment, the second layer 7b of the first multilayer metal coating 7 is made of a non-oxidizable material, so that the second layer 7b is an external layer, which will be placed directly in contact with the layer of filler metal 8. Such a layer 7b is preferably made of gold for a layer of filler metal 8 made of Au/Sn alloy.

According to another embodiment in which the second metallic material constituting the second layer 7b is oxidizable, for example copper or silver, the metallic coating 7 may comprise an additional sacrificial external layer, typically very thin, deposited on the second metallic layer 7b to protect it from oxidation. Indeed, the oxidation of a surface generally degrades wettability. This sacrificial layer is made of a metallic material different from the second metallic material and chosen to mix with the filler metal 8 deposited on the pin 5 during heating (step d)) so that this sacrificial layer will disappear in the metal layer filler 8. This sacrificial layer has no connecting role between the filler metal and the first component 1. The metallic material of this possible sacrificial layer can be chosen from the following materials: gold, nickel, platinum, iridium , osmium, palladium, rhodium, ruthenium or molybdenum, or their alloys.

[0045] Furthermore, the second material of the second metallic layer 7b is chosen to have better wettability by the heated filler metal 8, preferably molten, deposited on the pin 5, than the first metallic material of the first metallic layer 7a.

[0046] This means that the second material of the second metal layer 7b has, with respect to the filler metal, a wettability greater than the wettability that the first material of the first metal layer 7a would have with respect to the filler metal. screw of the same filler metal.

[0047] These adhesion and wettability properties can be measured by conventional tests such as, for adhesion, a measurement by nanoindentation on a cut (or interfacial), a measurement by nanoscratch or a measurement by micro scratch test, and for wettability, a measurement of the contact angle between the surface of a drop and the surface of the sample or a method of hanging drop or drop weighing with a tensiometer.

[0048] Thus, the first multilayer metal coating 7 combines these adhesion and wettability properties for improved holding of the fixing member 4 on the stud 5. The first metal layer 7a allows the second metal layer 7b to be wettable by the filler metal 8 deposited on the pin 5, to adhere firmly to component 1. These two layers 7a, 7b remain in the solid state during heating (step d)).

The first multilayer metallic coating 7 may further comprise, between the first layer 7a and the second layer 7b, a third layer 7c made of a third metallic material different from the first metallic material, and from the second metallic material, and also chosen to have better wettability by the heated filler metal 8, preferably melted, of the second watch component 5 than the first material 7a.

[0050] This means that the third material of the third metallic layer 7c has, with respect to the filler metal, a wettability greater than the wettability that the first material of the first metallic layer 7a would have with respect to the filler metal. screw of the same filler metal.

The third metallic material comprises at least one of the following materials: platinum, palladium, tungsten, cobalt, iridium, tantalum, vanadium, hafnium, ruthenium, niobium, osmium, and their alloys, and preferably platinum or palladium .

[0052] As an alternative to its function of increasing the wettability of the first multilayer metallic coating 7, or in addition to this function, the third metallic layer 7c can serve as a diffusion barrier preventing the atoms of the first metallic layer 7a (particularly the chromium or titanium atoms) to migrate towards the second metal layer 7b and towards the filler metal 8 during heating (step d)). Such migration can in fact reduce the adhesion of the first metal layer 7a on component 1 or weaken the solder. Among the materials which can act as a diffusion barrier and thus constitute such a third metallic layer 7c, we can cite: nickel, tantalum, platinum, palladium, vanadium, iridium, tungsten, cobalt, hafnium, zirconium, ruthenium or niobium, or alloy based on one or more of these metals.

One or more other intermediate layers can also be provided between the first metal layer 7a and the second metal layer 7b if necessary.

The thickness of each layer of the first multilayer metal coating 7 is typically less than 1 µm, preferably less than 0.5 µm. Preferably, the thickness of the first layer 7a is between 5 nm and 100 nm, preferably between 10 nm and 50 nm, the thickness of the third layer 7c is between 20 nm and 300 nm, preferably between 50 nm and 50 nm. nm and 200 nm and the thickness of the second layer 7b is between 100 nm and 1 µm, preferably between 200 nm and 500 nm. The possible sacrificial layer in the case of a second oxidizable layer 7b may have a thickness of less than 50 nm.

In parallel with the preparation of the first watch component 1 according to step a), the second watch component 5 is prepared, which is preferably metallic, according to step b).

[0056] Before the implementation of step b), the second watch component 5 can undergo different preliminary processing steps.

[0057] More particularly, the method of the invention may comprise, before step b), a step e) of initial treatment of the second watch component 5, said step e) comprising the formation of a sharp angle on the periphery of the second watch component 5 at the junction of its second assembly zone with the shoulder 5c, as shown in Figure 2(c). As described above, the sharp corner can be formed by a chamfer 5f or formed by a groove 5g as shown in Figures 5 and 6 respectively. The base 5e of the peg 5 remaining after the formation of the sharp angle constitutes the assembly zone of the peg with the area of the upper surface 4c of the ring 4b of the fixing member 4 around its hole 4d covered with first metal coating 7.

[0058] The method of the invention may also comprise, before step b), a step f) of intermediate processing of the second watch component 5, said step f) comprising the deposition of a second multilayer metallic coating 10 on at minus the second assembly zone of the second watch component 5.

Preferably, step f) is implemented between step e) and step b).

The second multilayer metal coating 10 is solid, that is to say that all of its layers are in the solid state. It can be deposited as thin films by PVD (physical vapor deposition), including vacuum evaporation or sputtering, or by CVD (chemical vapor deposition), including ALD (atomic layer deposition) and MVD. (molecular vapor deposition). It can also be deposited in the form of thick layers by projection, galvanic growth or otherwise.

[0061] With reference to Figure 7, the second multilayer metallic coating 10 may comprise at least a fourth layer 10a in contact with the second watch component 5 and made of a fourth metallic material, on the fourth layer 10a, at least a fifth intermediate layer 10b made of a fifth metallic material different from the fourth metallic material and possibly, on the fifth layer 10b, a sixth layer 10c made of a sixth metallic material different from the fifth metallic material and different from the filler metal 8.

The fourth, respectively the fifth metallic material, is chosen to have better adhesion on the second metallic watch component 5, respectively on the fourth layer, than the fifth metallic material, respectively the sixth metallic material if it is present or the filler metal.

[0063] This means that the fourth material of the fourth metallic layer 10a has, on the second metallic watch component 5, an adhesion greater than the adhesion that the fifth material of the fifth metallic layer 10b would have on the same watch component 5 .

[0064] Likewise, this means that the fifth material of the fifth metallic layer 10b has, on the fourth layer 10a, an adhesion greater than the adhesion that the sixth material of the sixth layer 10c would have if it is present, or that the filler metal would have, on the same material of the fourth layer 10a.

The sixth metallic material is chosen to have better wettability by the filler metal 8, in particular when it is heated, preferably melted, than the fifth metallic material.

[0066] This means that the sixth material of the sixth metal layer 10c has, with respect to the filler metal, a wettability greater than the wettability that the fifth material of the fifth metal layer 10b would have with respect to the filler metal. screw of the same filler metal.

[0067] Thus, the second multilayer metal coating 10 combines these adhesion and wettability properties for improved holding of the filler metal 8 on the pin 5. The fourth metal layer 10a allows the fifth metal layer 10b to adhere better to the peg 5. The fourth metallic material can also be chosen so that the fourth metal layer 10a also makes it possible to protect the metal surface of the peg 5, for example against corrosion. The fifth metal layer 10b allows the sixth metal layer 10c, wettable by the filler metal 8 subsequently deposited, to adhere firmly to the pin 5. These three layers 10a, 10b, 10c remain in the solid state during heating ( step d)).

[0068] The fourth metallic material of the fourth metallic layer 10a is chosen for example from nickel, gold, cobalt, or an alloy based on one or more of these metals, and preferably nickel or a gold alloy. /cobalt.

It is possible to provide between the fourth metal layer 10a and the fifth metal layer 10b another intermediate layer, for example a metal layer of gold/cobalt alloy, particularly if the fourth metal layer 10a is made of nickel.

The fourth layer 10a as well as the intermediate layer can be deposited galvanically. A layer of gold deposited galvanically can advantageously replace the fourth layer 10a in nickel as well as the intermediate layer in gold/cobalt.

[0071] The fifth metallic material of the fifth metallic layer 10b is chosen for example from chromium, titanium, tantalum, or a compound based on one or more of these metals, and preferably titanium.

[0072] The sixth metallic material of the sixth metallic layer 10c is chosen for example from the following materials: copper, platinum, palladium, silver, gold, molybdenum, rhodium, tungsten, iridium, vanadium, hafnium, osmium, or an alloy with base of one or more of these metals, and preferably platinum.

The fifth and sixth metal layers 10b and 10c are preferably deposited by PVD.

[0074] The thickness of each layer of the second multilayer metal coating 10 is typically less than 10 µm, preferably less than 5 µm. In particular, the fourth metal layer 10a may have a thickness less than 1 µm, the possible intermediate layer between the fourth metal layer 10a and the fifth metal layer 10b may have a thickness less than 2 µm, the fifth metal layer 10b may have a thickness of less than 2 µm. thickness less than 100 nm and the sixth metal layer 10c may have a thickness less than 200 nm. Each of these layers preferably has a minimum thickness of between 5 nm and 10 nm.

[0075] After having been prepared in accordance with steps e) and f), the eyebolt 5 is treated according to step b) of the process of the invention by depositing the filler metal 8 on the second metal coating 10, as shown in Figure 2(d).

[0076] Said second metal covering 10 as well as the filler metal 8 are deposited at least on the base 5e of the eyebolt 5 remaining after the realization of the sharp angle 5f, 5g constituting the assembly zone of the eyebolt with the zone of the upper surface 4c covered with the first metallic coating 7 as well as on the zone of the second cylindrical part 5d in the extension of the base 5e constituting the assembly zone of the eyebolt with the zone of the wall of the hole 4d of the member fixing 4 covered with the first metal coating 7. As will be seen below, it is not a problem for at least the deposit of the filler metal 8 to rise around the perimeter of the shoulder 5c beyond the 'sharp corner. The filler metal 8 can also be deposited under the cylindrical part 5d.

The filler metal 8 is deposited on the second metal coating 10 by a vapor phase deposition process. The pitons are arranged in a position allowing the filler metal 8 to be deposited only on the desired parts of the piton and not on the entire piton. The installation of the eyebolts in the installation can also be used beforehand for the deposition of the second metallic coating 10 when it is produced by PVD.

[0078] The vapor deposition process can be for example a PVD physical vapor deposition process, and preferably a vacuum evaporation deposition process, or cathode sputtering, or a CVD chemical vapor deposition process. . A vacuum evaporation deposition process is particularly preferred.

[0079] In accordance with the invention, the layer of filler metal 8 is obtained by depositing alternately, in the vapor phase, on at least a second assembly zone of the second watch component 5 intended to be assembled with the first assembly zone of the first watch component 1, layers of different pure metals, the quantity of pure metals for all of said layers deposited alternately being such that all of said layers deposited alternately constitutes a layer of filler metal 8 of composition corresponding to a eutectic alloy based on said pure metals. Thus, the layers of pure metal are successively deposited one on top of the other on the second metal coating 10 on the pin 5 by evaporation under vacuum, controlling their thickness and their number, until obtaining the eutectic composition of the alloy to be base of said corresponding metals. The thickness of the layers of pure metal deposited alternately is less than 1.5 µm, preferably less than 1 µm, and more preferably less than 800 nm, and preferably between 5 nm and 1 µm, and preferably between 10 nm and 800 nm, and more preferably between 100 nm and 800 nm, the ratio between the layer thicknesses being adapted to the eutectic composition of the alloy to be achieved. The layers at the ends may have a thickness greater than that of the other layers.

[0080] This type of deposition has the advantage of perfectly controlling the quantity of filler metal deposited since it is determined by the thickness of the layer of filler metal deposited, and therefore by the thicknesses of the different layers of filler metal. pure metals deposited alternately. By controlling the exact and very low thickness (less than 1 µm) of each layer of pure metal deposited alternately, we can guarantee conservation of the ratio of the chemical composition of the filler metal alloy obtained in relation to the composition of the initial alloy corresponding to the layers of pure metal and that this composition corresponds exactly to the ideal proportions to produce a stable eutectic based on said metals. In addition, the localized deposition of the filler metal on the metallic component and not on the silicon component is easier to implement and is compatible with industrial production.

[0081] During heating according to step d), the filler metal melts at the melting temperature of the eutectic to create a metallic interface between component 1 and pin 5. Examples of materials which can constitute the metal of contribution 8 are: – for soft soldering (temperature lower than 450°C): alloy based on gold, tin, indium, lead, bismuth, germanium or antimony like the alloys tin/bismuth, gold/tin, silver/tin, indium/tin, lead/tin, indium/lead, tin/antimony, tin/copper/silver, indium/silver, tin/indium/germanium; – for hard brazing (temperature above 450°C): alloy based on copper, nickel, silver, aluminum or zinc, for example copper/silver alloy, copper/silver/nickel, copper/silver /phosphorus, aluminum/silicon.

Preferably, the filler metal 8 comprises at least one alloy based on gold and tin obtained by alternating layers of pure gold and layers of pure tin. The layers of gold and tin are deposited successively one on top of the other at least on the second metal coating 10 on the pin 5 by vacuum evaporation or by cathode sputtering until the eutectic composition of the alloy is obtained. It is also possible to use as alloys in the form of alternating layers of pure metals alternating layers of tin/silver, tin/copper/silver, germanium/gold. Preferably, the layers of gold and tin are deposited successively on top of each other, in appropriate number and thickness until it is possible to form a layer of filler metal 8 in the form of an Au75Sn25 alloy. The total number of Au/Sn layer pairs can for example be between 5 and 20, and preferably between 7 and 15, an additional gold layer preferably being added to the last tin layer so that the metal layer of contribution 8 begins and ends with a layer of pure gold. The thickness of the layers of pure gold can be between 100 nm and 1 µm, and preferably between 200 nm and 800 nm, and the thickness of the layers of pure tin can be between 20 nm and 1 µm, and preferably between 50 nm and 800 nm, the ratio between the layer thicknesses being adapted to the Au75Sn25 eutectic composition to be achieved. The layers at the ends may have a thickness greater than that of the other layers.

[0083] Preferably, the thickness of the layer of filler metal is between 1 µm and 10 µm, and more preferably between 3 µm and 7 µm.

[0084] The method according to the invention continues with step c) consisting of positioning the pin 5 such that the second cylindrical part 5d is engaged in the hole 4d and that the base 5e of the shoulder 5c is in support on the upper surface 4c of the fixing member 4 (more precisely the filler metal 8 is supported on the first multilayer metal coating 7), and apply a predefined pressure, as shown in Figure 2(e).

[0085] Then in accordance with step d), the component 1 - stud 5 assembly is heated to a predefined temperature to melt the filler metal 8 and bind the component 1 and the stud 5. Depending on the temperature chosen the Brazing will be soft (low temperature) or hard (high temperature).

[0086] Advantageously, step d) is carried out under hydrogen, argon and/or nitrogen in order to protect the watch components from any degradation, and in particular to prevent modification of the chemical composition of the steel. constituting the peak.

[0087] The first multilayer metal coating 7 on component 1 as well as the second multilayer metal coating 10 on the peg 5 each have high wettability and thus delimit a brazing zone between the component 1 and the peg 5 in which the metal d The molten contribution 8 may spread during heating.

[0088] In addition, the sharp angle provided on the pin 5, at the junction of the second assembly zone, allows the molten filler metal possibly deposited on the periphery of the shoulder 5c and on the sharp angle of the eyebolt 5 to be brought towards the interior of the component assembly 1 - eyebolt 5, on the first and second assembly zones between the upper surface 4c of the fixing member 4 and the chamfered base 5e of the eyebolt 5 This phenomenon is favored by the high wettability of the first coating 7 deposited on the upper surface 4c of the fixing member 4 exactly at the level of the first and second assembly zones.

[0089] As a result, after assembling the two components 1 and 5, the filler metal 8, at the level of the upper surface 4c of the fixing member, only covers the first multilayer metal coating 7 positioned exactly facing each other. of the base 5e remaining after the formation of the sharp angle, without overflowing around this base 5e, as shown in Figure 2(f). In addition, the rest of the shoulder 5c wider than the base 5e remaining after the formation of the sharp angle hides the filler metal 8 as well as the first metal coating 7. Thus, no bead of filler metal 8 is visible, the aesthetic appearance of the assembly component 1-piton 5 being greatly improved.

[0090] Furthermore, with the process according to the invention, the deposition of filler metal is improved compared to the process described in application EP 3 309 624, both in terms of quality and in terms of precision. and reproducibility with regard to the quantity of filler metal deposited on the pin 5, making it possible to industrialize the deposition of the filler metal. Thus, the watch components assembled according to the process of the invention are all assembled in a homogeneous and very resistant manner. Indeed, thanks in particular to the second metal coating provided on the pin to improve in particular the adhesion of the filler metal on the pin, the assembly has very strong strength, the silicon breaking before brazing in the event of very significant stress. during manufacturing or when wearing.

[0091] The present invention is not limited to fixing a hairspring to the eyebolt. It can in fact also be applied, for example, to the fixing of a hairspring to the balance axis, to the fixing of a wheel, a pinion, an escapement anchor, a balance, a rocker, a jumper, a component with flexible or buckled blades, or a lever at its axis of rotation, the fixing of metal weights on a balance to increase its inertia or more generally the assembly of two watch components.

Claims (23)

1. Method for assembling a first watch component (1) and a second watch component (5), comprising the following steps: a) deposit a first multilayer metallic coating (7) on at least a first assembly zone of the first watch component (1), the first multilayer metal coating (7) comprising at least a first layer (7a) adjacent to the first watch component (1) and made of a first metallic material, and above the first layer (7a), a second layer (7b) made of a second metallic material different from the first metallic material, b) deposit by vapor deposition, on at least a second assembly zone of the second watch component (5) intended to be assembled with the first assembly zone of the first watch component (1), a layer of metal of intake (8), c) position the first and second watch components to allow their assembly via their respective first and second assembly zones, d) heating at least the first and second assembly zones to melt the filler metal (8) deposited on the second watch component (5) and connect the first and second watch components (1, 5) by their first and second respective assembly zones, by atomic diffusion between said filler metal (8) and the second metallic material of the second layer (7b) of the first multilayer metallic coating (7), characterized in that the layer of filler metal (8) consists of a set of layers of different pure metals deposited alternately, the quantity of pure metals for all of said layers deposited alternately being such that the layer of filler metal (8) has a composition corresponding to a eutectic alloy based on said pure metals. 2. Method according to claim 1, characterized in that the second metallic material of the second layer (7b) of the first multilayer metallic coating (7) is one of the metals used in the composition of the filler metal (8). 3. Method according to one of the preceding claims, characterized in that the second layer (7b) of the first multilayer metal coating (7) is an external layer. 4. Method according to one of the preceding claims, characterized in that the second metallic material of the second layer (7b) comprises at least one of the following materials: gold, platinum, palladium, silver, copper, nickel, molybdenum, rhodium, tungsten, tin, cobalt, iridium, tantalum, vanadium, hafnium, zirconium, ruthenium, niobium, osmium, and their alloys. 5. Method according to one of the preceding claims, characterized in that the first metallic material of the first layer (7a) is chosen to have better adhesion to the first watch component (1) than the second metallic material of the second layer (7b). 6. Method according to one of the preceding claims, characterized in that the first metallic material of the first layer (7a) comprises at least one of the following materials: chromium, titanium, tantalum, and a compound based on a or more of these metals. 7. Method according to one of the preceding claims, characterized in that the first multilayer metallic coating (7) further comprises, between the first layer (7a) and the second layer (7b), a third layer (7c) made of a third metallic material different from the first metallic material and chosen to have better wettability by the heated filler metal (8) of the second watch component (5) than the first material of the first layer (7a). 8. Method according to claim 7, characterized in that the third metallic material comprises at least one of the following materials: platinum, palladium, tungsten, cobalt, iridium, tantalum, vanadium, hafnium, ruthenium, niobium, osmium, and their alloys. 9. Method according to one of the preceding claims, characterized in that it comprises, before step b), a step e) of initial treatment of the second watch component (5), said step e) comprising the formation of a sharp angle (5f, 5g) around the perimeter of the second watch component (5) at the junction of its second assembly zone. 10. Method according to one of the preceding claims, characterized in that it comprises, before step b), a step f) of intermediate treatment of the second watch component (5), said step f) comprising the deposition of a second multilayer metal coating (10) on at least the second assembly zone of the second watch component (5), the second multilayer metal coating (10) comprising at least a fourth layer (10a) in contact with the second watch component ( 5) and made of a fourth metallic material, and at least one fifth intermediate layer (10b) made of a fifth metallic material different from the fourth metallic material. 11. Method according to claim 10, characterized in that the fourth, respectively the fifth metallic material, is chosen to have better adhesion on the second watch component (5), respectively on the fourth layer (10a) than the fifth material metallic, respectively the filler metal (8). 12. Method according to one of claims 10 to 11, characterized in that the fourth metallic material comprises at least one of the following materials: nickel, gold, cobalt. 13. Method according to one of claims 10 to 12, characterized in that the fifth metallic material comprises at least one of the following materials: chromium, titanium, tantalum, and a compound based on one or more of these metals . 14. Method according to one of the preceding claims, characterized in that the first watch component (1) is made of at least one of the following materials: silicon or other semiconductor material, glass, ceramic, diamond, metallic glass . 15. Method according to one of the preceding claims, characterized in that the second watch component (5) is metallic. 16. Method according to one of the preceding claims, characterized in that the filler metal (8) comprises at least one alloy based on gold, tin, indium, copper, nickel, silver, aluminum, lead, bismuth, antimony, germanium or zinc. 17. Method according to claim 16, characterized in that the filler metal (8) comprises at least one alloy based on gold and tin obtained by alternating layers of pure gold and layers of pure tin . 18. Method according to one of claims 9 to 17, characterized in that in step a), the multilayer metallic coating (7) is deposited on the first watch component (1) on the first assembly zone at less so as not to protrude from an area intended to be assembled to an area of the second assembly area of the second metal watch component (5) which adjoins the sharp corner. 19. Method according to one of the preceding claims, characterized in that the first watch component (1) comprises at least one of the following components: balance spring (2) or other spring, wheel, pinion, escapement anchor, balance wheel , rocker, lever, jumper, component with flexible or flared blades. 20. Method according to one of the preceding claims, characterized in that the first watch component (1) comprises a hairspring (2) and a fixing member (4) joined to the outer end (2b) of the hairspring (2) , in that the second watch component (5) comprises a stud and in that the first multilayer coating (7) is deposited at least on the fixing member (4), said filler metal (8) being deposited on the peak. 21. Method according to one of the preceding claims, characterized in that the thickness of the layers of pure metal deposited alternately is less than 1.5 µm, preferably less than 1 µm, and more preferably less than 800 nm, l The thickness of the layer of filler metal (8) being between 1 µm and 10 µm, and preferably between 3 µm and 7 µm. 22. Method according to one of the preceding claims, characterized in that the vapor deposition process is a vacuum evaporation deposition process. 23. Watch mechanism comprising an assembly of a first watch component (1) and a second watch component (5) obtained by the assembly process according to one of claims 1 to 22.