WO2020148626A1

WO2020148626A1 - Method for brazing clock-making components

Info

Publication number: WO2020148626A1
Application number: PCT/IB2020/050225
Authority: WO
Inventors: Séverine DOMANGE; Sylvain Jeanneret; Olivier Dubochet; Laurent Guillot
Original assignee: Patek Philippe Sa Geneve
Priority date: 2019-01-16
Filing date: 2020-01-13
Publication date: 2020-07-23
Also published as: CH717141B1

Abstract

The present invention proposes a method for assembling a first clock-making component (1) and a second clock-making component (5). The method comprises the following steps: a) depositing a multilayer metallic coating (7) on at least a first assembly zone of the first clock-making component (1), the multilayer metallic coating (7) comprising a first layer (7a) adjacent to the first clock-making 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; b) alternately depositing, by vapour phase deposition, on at least a second assembly zone of the second clock-making component (5) intended for being assembled with the first assembly zone of the first clock-making component (1), layers of different pure metals, the quantity of pure metals for all of said alternately deposited layers being such that all of said alternately deposited layers constitute a layer of filler metal (8) having a composition corresponding to a eutectic alloy based on said pure metals; c) positioning the first and second clock-making components to enable them to be assembled via the respective first and second assembly zones thereof; and d) heating at least the first and second assembly zones so as to melt the filler metal (8) deposited on the second clock-making component (5) and bonding the first and second clock-making components (1, 5) via the respective first and second assembly zones thereof, 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).

Description

WATCHMAKER COMPONENTS BRAZING PROCESS

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

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

Thanks to their advantageous properties in terms of density, coefficient of friction and insensitivity to magnetic fields, these materials have greatly contributed to improving the precision and efficiency of watch mechanisms. However, these materials do not lend themselves well to certain assembly techniques. Not being able to be driven out due to their fragility, they are generally glued or elastically mounted. Sticking causes pollution problems in the mechanism and long-term poor performance. The elastic mounting, on the other hand, does not allow the transmission of high torques between the two assembled components.

Patent EP 0732635 discloses a method for producing watch components such as an anchor, a wheel, a pinion, a hairspring or a balance, according to which the component is etched in a silicon plate and then its active parts are the case. if necessary covered with a material of predetermined hardness and coefficient of friction. To enable the silicon component to be attached to a metal shaft by brazing, welding or gluing, the wall and the lower and upper edges of an orifice of the silicon component intended to receive the metal axis are coated with a metal deposit.

By "brazing" is meant an assembly operation using a filler metal ("brazing") 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 together, the bonding of the filler metal with each of the parts taking place by atomic diffusion.

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

A solution to this problem has been proposed by patent application EP 3 309 624 filed by the applicant to assemble a non-metallic watch component and a metallic watch component. This solution consists of depositing a multilayer metal coating on a non-metallic watch component, on which is then deposited a filler metal. 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 metallic coating of the first watch component and on the other hand to the metal of the second watch component.

While the method 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 method described in patent EP 0732635, certain difficulties remain, in particular to control the quantity of solder deposited on the non-metallic watch component, and in particular a silicon watch component having previously undergone various treatments, to obtain a robust assembly process. More particularly, since the solder is 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.

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

If the amount of solder deposited is insufficient, the assembly of the components is not strong enough and will not hold.

The present invention aims to provide 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.

The present invention also aims to provide 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.

To this end, the present invention relates to a method for assembling a first watch component and a second watch component.

According to the invention, said method comprises the following steps:

a) depositing a first multilayer metallic coating on at least a first assembly zone of the first watch component, the first multilayer metallic coating comprising at least a first layer adjacent to the first watch component and made of a first metallic material and, above of 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) depositing alternately by vapor deposition, on at least a second assembly area of the second watch component intended to be assembled to 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 constitutes one layer of filler metal with a 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 first and second respective assembly zones,

d) heating at least the first and second assembly areas to melt the filler metal deposited on the second watch component and bind the first and second watch components by their respective first and second assembly areas, by atomic diffusion between said filler metal and the second metallic material of the second layer of the first multilayer metallic coating.

The deposition of the filler metal on one of the watch components by a vapor phase process of several alternating layers of pure metals to form a layer of filler metal in the form of a eutectic alloy comprising said pure metals 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 for producing a stable eutectic.

Advantageously, the method of the invention comprises, before step b), a step e) of initial treatment of the second timepiece component, said step e) comprising the formation of a sharp angle on the periphery of the second timepiece component at the junction of its second assembly zone.

In addition, in step a), the first multilayer metallic 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 angle.

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 metallic coating, in order to correspond to the first and second assembly zones, so no bead of solder protrudes from said first and second assembly zones of the first and second watch components respectively which adjoin the sharp angle.

The invention also provides 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 become apparent 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 accompanying drawings in which:

- Figure 1 is a perspective view of an example of a first watch component according to the invention, comprising a silicon balance spring, a ferrule and a member for fixing to a stud;

- Figure 2 shows Figures 2 (a) to 2 (f) which are cross-sectional views of the fastener and the eyebolt, showing different steps of the process according to the invention for assembling the hairspring to the eyebolt;

- Figure 3 is a perspective view of the eyebolt fixing member bearing a first multilayer metal coating;

- Figure 4 is a cross-sectional view, taken along the line A-A of Figure 1, of the eyebolt fixing member, showing the different layers of the first multilayer metal coating;

- Figure 5 is a cross-sectional view of a first variant of eyebolt; - Figure 6 is a partial cross-sectional view of the end of a second variant of eyebolt; and

- Figure 7 is a cross-sectional view of the eyebolt variant of Figure 5 showing the different layers of the second multilayer metal coating.

In the context of the present invention, the term “metal” is understood to mean a metal proper or a metal-based alloy. Likewise, the term “metallic” means entirely consisting of metal / metals or comprising in particular a metal.

FIG. 1 shows an example of a first horological component 1 used in the present invention. In this example, the first horological component 1 comprises a hairspring 2 intended to equip a balance to form with the latter the regulating member 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. By its inner end 2a the hairspring 2 is joined to a ferrule 3 intended to be mounted on the axis of the balance. By its outer end 2b the hairspring 2 is joined to a fastening member 4 intended to be fixed to a stud 5, constituting the second watch component, (visible in FIG. 5 or 6) mounted on a fixed part of the watch movement, to 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-manufacturing technique such as deep reactive ion etching DRIE. 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, of diamond, of ceramic, of glass or of 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 stud 5, can be metallic or be made of a fragile material as defined above. Preferably, the eyebolt 5 is metallic, for example steel.

The present invention relates in particular to a method making it possible to assemble in a robust manner the first component 1, preferably made of silicon, and the stud 5, preferably metallic, that is to say to fix the fixing member 4 to the eyebolt 5. As can be seen, the fixing member 4 comprises a rigid blade 4a which extends the blade of the balance spring 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 pin 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 rooster in a manner known per se. The shoulder 5c is intended to rest on the upper surface 4c (facing the rooster) 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 to the assembly zone facing it on the fixing member 4.

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 may be in the form of a chamfer 5f, for example 45 °, as shown in Figure 5 or in the form of 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 zone assembly 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.

In relation to FIG. 2, an embodiment of the method according to the invention is now described. It consists of the following steps:

a) deposit a first multilayer metal coating 7, which will be described below, on a first assembly area of the fixing member 4 of the first watch component 1,

b) depositing alternately by vapor deposition, on at least the second assembly area of the second watch component 5, namely the pin 5, intended to be assembled to the first assembly area of the fixing member 4 of the first watch component 1 to bind 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 respective assembly zones,

d) heating at least the first and second assembly zones to melt the filler metal 8 deposited on the stud 5 and bind the fixing member 4 of the first watch component 1 and the stud 5 by their first and second zones assembly, by atomic diffusion between said filler metal of the pin 5 and the material of the fixing member 4.

More specifically, the first timepiece component 1 provided for use during step a) is first prepared according to the following steps: i. acquire a stencil 6 ("shadow mask" in English) whose pattern corresponds to the first assembly area of component 1 that is to be metallized, 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 Fig. 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 at most to the base of the shoulder 5c of the pin 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 peg 5 remaining after the sharp angle 5f, 5g has been made in order to avoid the overflow of the filler metal during assembly;

ii. define reference points on component 1;

iii. position stencil 6 on component 1 by 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 according to step a). Due to the choice of the pattern of the stencil, 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, correspondingly at the maximum of the base 5e of the shoulder 5c of the pin 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 with a zone of the second assembly zone of the second watch component. which adjoins the sharp angle.

Then the stencil 6 is removed from component 1 to obtain the first horological component 1 resulting from step a), as shown in FIGS. 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 of serigraphy or photolithography type can also be envisaged to define the opening (s) of the stencil.

By definition the first multilayer metal coating 7 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 the like.

In practice, several components are made from a single plate of the material of the first watch component 1. The deposit of the first multilayer metal 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 with respect to reference points on the plate can be used. In the case of a first silicon-based watch component, a silicon or "wafer" wafer will be used, for example, on which the first watch components preferably remain attached during the deposition of the first multilayer metal coating with a stencil.

The stencil 6 makes it possible to deposit the first multilayer metal coating 7 in a localized manner 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 its 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 The invention also does not exclude depositing the first multilayer metal coating 7 in a non-localized manner. For example, one could cover all of component 1 with the first multilayer metallic coating 7 and then remove, for example by laser, said first coating 7 except in the brazing zone corresponding to the first assembly zone.

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

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

The first metal layer 7a is made of a first metal material chosen to have better adhesion to the material of the first component 1 than the second metal material of the second metal layer 7b and possibly better adhesion than the material of a deposited intermediate layer. on the first layer 7a, between the first layer 7a and the second layer 7b. This means that the first material of the first metal layer 7a has, on the material of the first component, a greater adhesion than the adhesion that the second material of the second metal 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, a greater adhesion 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 so as to be able to bond to the filler metal previously deposited on the second watch component 5 by atomic diffusion.

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.

The second metallic material can include 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.

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 outer layer, which will be placed directly in contact with the metal layer. filler 8. Such a layer 7b is preferably made of gold for a layer of filler metal 8 made of an 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 outer layer, typically very thin, deposited on the second layer. metal 7b to protect it from oxidation. In fact, the oxidation of a surface generally degrades the 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 stud 5 during heating (step d)) so that this sacrificial layer will disappear in the metal layer 8. This sacrificial layer has no role of bonding between the metal intake and the first component 1. The metallic material of this optional sacrificial layer can be chosen from the following materials: gold, nickel, platinum, iridium, osmium, palladium, rhodium, ruthenium or molybdenum, or their alloys.

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

This means that the second material of the second metal layer 7b has, vis-à-vis 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 same filler metal.

These adhesion and wettability properties can be measured by conventional tests such as, for the adhesion, a measurement by nanoindentation on a cut (or interfacial), a measurement by nanoscale 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 hanging drop or drop weighing method with a tensiometer.

Thus, the first multilayer metallic coating 7 combines these properties of adhesion and wettability for improved hold of the fixing member 4 on the stud 5. The first metallic layer 7a enables the second metallic layer 7b, wettable by the metal. filler 8 placed on the stud 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 molten, of the second watch component 5 than the first material 7a.

This means that the third material of the third metal layer 7c has, vis-à-vis 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 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.

As an alternative to its function of increasing the wettability of the first multilayer metal coating 7, or in addition to this function, the third metal layer 7c can serve as a diffusion barrier preventing the atoms of the first metal layer 7a (particularly the chromium atoms or titanium) to migrate to the second metal layer 7b and to the filler metal 8 during heating (step d)). Such migration can in fact reduce the adhesion of the first metal layer 7a to component 1 or weaken the solder. Among the materials which can act as a diffusion barrier and thus constitute such a third metal layer 7c, there may be mentioned: 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 metallic layer 7a and the second metallic 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 200 nm and the thickness of the second layer 7b is between 100 nm and 1 miti, 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, which is preferably metallic, is prepared according to step b).

Before the implementation of step b), the second watch component 5 can undergo various preliminary processing steps.

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 component. watchmaker 5 at the junction of its second assembly zone with the shoulder 5c, as shown in FIG. 2 (c). As described above, the sharp angle may be in the form of a chamfer 5f or a groove 5g as shown in Figures 5 and 6 respectively. The base 5e of the pin 5 remaining after the formation of the sharp angle constitutes the area of assembly of the pin with the area of the upper surface 4c of the ring 4b of the fixing member 4 around its hole 4d covered with the first metallic coating 7.

The method of the invention can also comprise, 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 metallic coating 10 on at least the second second watch component assembly area 5.

Preferably, step f) is carried out between step e) and step b).

The second multilayer metal coating 10 is solid, that is, 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 deposition vapor phase), 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 the like.

With reference to FIG. 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 optionally, 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 on the second metallic watch component 5, respectively on the fourth layer, better adhesion than the fifth metallic material, respectively the sixth metallic material if it is present or the metal d 'bring.

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

Likewise, this means that the fifth material of the fifth metallic layer 10b has, on the fourth layer 10a, a greater adhesion than the adhesion that the sixth material of the sixth layer 10c would have if it is present, or that would have. the filler metal, 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 molten, than the fifth metallic material. This means that the sixth material of the sixth metallic layer 10c has, with respect to the filler metal, a wettability greater than the wettability that the fifth material of the fifth metallic layer 10b would have with respect to the same. filler metal.

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

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 / cobalt alloy.

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

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

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

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

The thickness of each layer of the second multilayer metal coating 10 is typically less than 10 miti, preferably less than 5 miti. In particular, the fourth metal layer 10a can have a thickness less than 1 miti, the possible intermediate layer between the fourth metal layer 10a and the fifth metal layer 10b can have a thickness less than 2 miti, the fifth metal layer 10b can have a thickness. 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.

After having been prepared in accordance with steps e) and f), the peak 5 is treated according to step b) of the method of the invention by depositing the filler metal 8 on the second metallic coating 10, as shown in FIG. 2 (d).

Said second metallic coating 10 as well as the filler metal 8 are deposited at least on the base 5e of the peg 5 remaining after the realization of the sharp angle 5f, 5g constituting the area of assembly of the peg with the area of the surface top 4c covered with the first metal coating 7 as well as on the area of the second cylindrical part 5d in the extension of the base 5e constituting the area of assembly of the eyebolt with the area of the wall of the hole 4d of the fixing member 4 covered with the first metallic coating 7. As will be seen below, it is not a problem that at least the deposit of the filler metal 8 rises around the periphery of the shoulder 5c beyond the sharp angle . The filler metal 8 can also be deposited under the cylindrical part 5d. The filler metal 8 is deposited on the second metallic coating 10 by a vapor deposition process. The eyebolts are arranged in a setting making it possible to deposit the filler metal 8 only on the desired parts of the eyebolt and not on the entire piton. The positioning of the eyebolts in the fitting can also be used beforehand for the deposition of the second metallic coating 10 when it is produced by PVD.

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

According to the invention, the layer of filler metal 8 is obtained by depositing alternately, in vapor phase, on at least a second assembly zone of the second watch component 5 intended to be assembled with the first zone of assembly of the first watch component 1, layers of different pure metals, the amount 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 deposited successively one on top of the other on the second metal coating 10 on the pin 5 by vacuum evaporation, by controlling their thickness and their number, until the eutectic composition of the alloy is obtained. base of said corresponding metals. The thickness of the layers of pure metal deposited alternately is less than 1.5 miti, preferably less than 1 miti, and more preferably less than 800 nm, and preferably between 5 nm and 1 miti, and preferably between 10 nm and 800 nm, and more preferably between 100 nm and 800 nm, the ratio between the thicknesses of the layers 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.

This type of deposit 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 various layers of pure metals deposited. alternately. By controlling the exact and very low thickness (less than 1 μm) of each layer of pure metal deposited alternately, it is possible to guarantee that the ratio of the chemical composition of the alloy of the filler metal obtained to the composition of the initial alloy corresponding to the layers of pure metal and that this composition corresponds exactly to the ideal proportions for producing a stable eutectic based on said metals. In addition, the localized deposition of the filler metal on the metal component and not on the silicon component is easier to implement and is compatible with industrial production.

During the 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 the peak 5. Examples of materials that can constitute the filler metal 8 are:

- for soft brazing (temperature below 450 ° C): alloy based on gold, tin, indium, lead, bismuth, germanium or antimony such as 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 pure tin. The layers of gold and tin are deposited successively on top of each other at least on the second metallic coating 10 on the pin 5 by vacuum evaporation or by cathodic 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 an appropriate number and with an appropriate thickness, until a layer of filler metal 8 can be formed in the form of an Au7sSn25 alloy. The total number of pairs of Au / Sn layers can for example be between 5 and 20, and preferably between 7 and 15, with an additional gold layer preferably being added on the last layer of tin so that the metal layer filler 8 begins and ends with a layer of pure gold. The thickness of the pure gold layers can be between 100 nm and 1 miti, and preferably between 200 nm and 800 nm, and the thickness of the pure tin layers can be between 20 nm and 1 miti, and preferably between 50 nm and 800 nm, the ratio between the thicknesses of the layers being adapted to the eutectic composition Au75Sn25 to be achieved. The layers at the ends can have a thickness greater than that of the other layers.

Preferably, the thickness of the layer of input metal is between 1 µm and 10 µm, and more preferably between 3 µm and 7 µm.

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

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

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 the modification of the chemical composition of the steel constituting the piton. .

The first multilayer metal coating 7 on component 1 as well as the second multilayer metal coating 10 on the stud 5 each have a high wettability and thus delimit a brazing zone between the component 1 and the stud 5 in which the filler metal 8 fade may spread out during heating.

In addition, the sharp angle provided on the pin 5, at the junction of the second assembly area, allows the molten filler metal possibly deposited on the periphery of the shoulder 5c and on the sharp angle of the pin 5 to be brought back towards the inside of the component assembly 1 - stud 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 stud 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.

Therefore, after assembly of 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 opposite the base. 5th remaining after forming the sharp angle, without overflowing around this 5th base, 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 masks the filler metal 8 as well as the first metallic coating 7. Thus, no bead of filler metal 8 is not visible, the aesthetic appearance of the assembly component 1 - hook 5 being greatly improved. In addition, with the process according to the invention, the deposit 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 reliability. 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 method of the invention are all assembled in a homogeneous and very strong manner. Indeed, thanks in particular to the second metal coating provided on the stud to improve in particular the adhesion of the filler metal on the stud, the assembly has a very strong hold, the silicon breaking before the solder in the event of very high stress. during manufacture or when worn.

The present invention is not limited to the attachment of 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 escape anchor, a balance, a rocker, a jumper, a component with flexible or flamed blades, or a lever to its axis of rotation, to the fixing of metal weights on a balance to increase its inertia or more generally to the assembly of two watch components.

Claims

1. A method of assembling a first watch component (1) and a second watch component (5), comprising the following steps:

a) depositing a first multilayer metallic coating (7) on at least a first assembly zone of the first watch component (1), the first multilayer metallic 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) depositing by vapor deposition, on at least a second assembly area of the second watch component (5) intended to be assembled to the first assembly area of the first watch component (1), a layer of metal of contribution (8),

c) position the first and second watch components to allow their assembly by their first and second respective assembly areas,

d) heating at least the first and second assembly zones to melt the filler metal (8) deposited on the second watch component (5) and bind 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 amount of pure metals for all of said layers deposited alternately being such that the filler metal layer (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 outer 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 on the first watch component (1) better adhesion 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 metal 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 processing of the second watch component (5), said step e) comprising the formation of a sharp angle (5f, 5g) around the periphery 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 processing of the second watch component (5), said step f) comprising the deposit of a second multilayer metallic coating (10) on at least the second assembly zone of the second watch component (5), the second multilayer metallic 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 a fifth intermediate layer (10b) made of a fifth metallic material different from the fourth metallic material.

1 1. The method of claim 10, characterized in that the fourth, respectively the fifth metallic material, is chosen to have on the second watch component (5), respectively on the fourth layer (10a), better adhesion than the fifth metallic material, respectively the filler metal (8).

12. Method according to one of claims 10-1 1, 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. The method of 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 metal coating (7) is deposited on the first watch component (1) on the first assembly zone at the less so as not to protrude from a zone intended to be assembled with a zone of the second assembly zone of the second metal watch component (5) which adjoins the sharp angle.

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: hairspring (2) or other spring, wheel, pinion, escapement anchor, balance , rocker, lever, jumper, component with flexible or flamed 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 piton.

21. Method according to one of the preceding claims, characterized in that the thickness of the layers of pure metal deposited in alternation is less than 1.5 miti, preferably less than 1 miti, and more preferably less than 800 nm, l the thickness of the filler metal layer (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 evaporative deposition process.

23. A 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.