Classifications

• • G—PHYSICS
  • G04—HOROLOGY
  • G04B—MECHANICALLY-DRIVEN CLOCKS OR WATCHES; MECHANICAL PARTS OF CLOCKS OR WATCHES IN GENERAL; TIME PIECES USING THE POSITION OF THE SUN, MOON OR STARS
  • G04B15/00—Escapements
  • G04B15/14—Component parts or constructional details, e.g. construction of the lever or the escape wheel
• • G—PHYSICS
  • G04—HOROLOGY
  • G04B—MECHANICALLY-DRIVEN CLOCKS OR WATCHES; MECHANICAL PARTS OF CLOCKS OR WATCHES IN GENERAL; TIME PIECES USING THE POSITION OF THE SUN, MOON OR STARS
  • G04B15/00—Escapements
  • G04B15/06—Free escapements
  • G04B15/08—Lever escapements
• • G—PHYSICS
  • G04—HOROLOGY
  • G04B—MECHANICALLY-DRIVEN CLOCKS OR WATCHES; MECHANICAL PARTS OF CLOCKS OR WATCHES IN GENERAL; TIME PIECES USING THE POSITION OF THE SUN, MOON OR STARS
  • G04B31/00—Bearings; Point suspensions or counter-point suspensions; Pivot bearings; Single parts therefor
  • G04B31/08—Lubrication
• • G—PHYSICS
  • G04—HOROLOGY
  • G04D—APPARATUS OR TOOLS SPECIALLY DESIGNED FOR MAKING OR MAINTAINING CLOCKS OR WATCHES
  • G04D3/00—Watchmakers' or watch-repairers' machines or tools for working materials
  • G04D3/0069—Watchmakers' or watch-repairers' machines or tools for working materials for working with non-mechanical means, e.g. chemical, electrochemical, metallising, vapourising; with electron beams, laser beams
• • G—PHYSICS
  • G04—HOROLOGY
  • G04D—APPARATUS OR TOOLS SPECIALLY DESIGNED FOR MAKING OR MAINTAINING CLOCKS OR WATCHES
  • G04D3/00—Watchmakers' or watch-repairers' machines or tools for working materials
  • G04D3/0074—Watchmakers' or watch-repairers' machines or tools for working materials for treatment of the material, e.g. surface treatment
  • G04D3/0087—Watchmakers' or watch-repairers' machines or tools for working materials for treatment of the material, e.g. surface treatment for components of the escapement mechanism, e.g. lever escapement, escape wheel

Definitions

• the present invention relates, in a first aspect, to a micromechanical watchmaking piece cut from a plate-shaped silicon substrate and whose cut edges comprise portions intended to serve as contact surfaces arranged to slide against corresponding contact zones of the invention. Another micromechanical part in a timepiece, the cut edges of the piece having a ribbed surface comprising an alternation of ribs and grooves, these ribs and these grooves being rectilinear.
• This first aspect of the invention relates in particular to a micromechanical watchmaking piece which conforms to the above definition and which forms part of an anchor escapement.
• the present invention relates to a method for manufacturing a watchmaking micromechanical component which is in accordance with the first aspect of the invention, the method comprising the steps of:
• the sequence formed of an etching step followed by a deposition step of a passivation layer is repeated a large number of times. For example, between 100 and 1000 times to etch a groove that passes vertically through a substrate whose thickness is 500 microns.
• Flanks produced by the alternating succession of deposition steps and etching steps do not produce flanks perfectly straight, but finely waved flanks that exhibit alternation of reliefs and hollows regularly spaced.
• the amplitude of the ripple is a function of the frequency with which the deposition and etching steps alternate.
• micromechanical watchmaking parts by micromachining a silicon wafer using DRIE technology gives good results.
• vertical flanks of a micromechanical part it is not uncommon for the vertical flanks of a micromechanical part to be intended to serve as contact surfaces intended to slide against at least one contact zone of another micromechanical part. It turns out that these vertical contact surfaces are not entirely satisfactory from a tribological point of view.
• An object of the present invention is to overcome the disadvantages of the prior art which have just been explained.
• the present invention achieves this and other objects by providing a watchmaking micromechanical component according to the appended claim 1 and two manufacturing processes according to the appended claims 12 and 13 respectively.
• the ribs and grooves form a staggered pattern, with first intervals in which the spacing separating the ribs from each other is equal to a first distance, and at least a second interval in which the spacing between the ribs is equal to a second distance different from the first distance.
• the ribs and the grooves are each contained in a plane parallel to the plate.
• the ribs and the grooves are perpendicular to the main faces of the plate.
• the grooves belonging to the first intervals preferably all have the same first depth. This depth is between 10 nm and 2 pm.
• the second distance is preferably greater than the first distance.
• the scaled pattern comprises a plurality of second intervals, and the second distance is between 200 nm and 50 miti, and preferably between 800 nm and 10 pm.
• the grooves belonging to the second intervals all have the same depth. This depth is between 10 nm and 10 pm.
• the staggered pattern comprises a single second slot comprising a single groove
• the second distance is between 200 nm and 2/3 of the total height of the piece, and preferably between between 1/3 and 1/2 of the total height of the room.
• the depth of the single groove of the second gap is preferably between 0 nm and 50 ⁇ m.
• Figure 1 is a schematic plan view showing a Swiss lever escapement of the prior art
• Figures 2A, 2B 2C are schematic sectional views showing the ribbed surfaces that have the cut edges of three watch micromechanical parts which respectively correspond to three variants of a first particular embodiment of the invention
• Figure 3 is a schematic sectional view showing the ribbed surface that has the cut edges of a micromechanical watch part according to a second particular embodiment of the invention.
• FIG. 4 is a double graph showing the evolution of the flow of the reactive gas and the flow of the passivation gas during six consecutive steps of a particular implementation of one of the two processes of the invention
• FIG. 5 is a schematic plan view of a tooth of an escape wheel which conforms to a third embodiment of FIG. the invention, the ribs and furrows formed that presents the pulse plane of the tooth being perpendicular to the main plane of the escape wheel.
• Figure 1 is a schematic plan view showing a Swiss lever escapement of the prior art.
• the mechanism shown comprises in particular an escape wheel 3, an anchor 5 and a large plate 7 through whose center the axis of the balance 9 passes.
• the two arms of the anchor each end with a pallet 11, 13.
• the vanes are arranged to cooperate with the teeth 15 of the escape wheel 3.
• the escape wheel is connected to the cylinder (not shown) via a gear train (not shown) which engages with the pinion exhaust (referenced 17).
• the escape wheel is thus urged continuously forward (that is, clockwise as shown in Figure 1). It will be noted that at the moment shown, one of the teeth 15 of the escape wheel 3 is immobilized against the rest face of the entry pallet 11 of the anchor 5.
• the anchor 5 starts a pivoting movement around the axis 19 in the clockwise direction. Pivoting the anchor clockwise causes the entry pallet to slide upward (in the drawing) against the leading edge of tooth 15. This release phase will end when the rest of the pallet will have ceased to hinder the advance of the front flank of the tooth 15. Then it will be the flattened top of the same tooth (called tooth impulse plane) which will have to slide against the face lower palette 1 1 (the pulse plane of the pallet). The angled contact between the two impulse planes will also have the effect of pushing the pallet 1 1 upwards, so that the pivoting movement of the anchor 5 in the clockwise direction will be accentuated.
• tooth impulse plane the flattened top of the same tooth
• This pulse phase will end when the input pallet January 1 has been pushed far enough to provide a completely clear passage to the tooth 15.
• FIGS. 2A, 2B and 2C are diagrammatic cross-sectional views showing the ribbed surfaces presented by the cut edges of three watchmaking micromechanical parts 1, 10 and 20 which respectively correspond to three variants of a first particular embodiment of the invention. invention.
• the ribs 21a and the grooves 23a that the cut edges of the piece 1 present form a staggered or stepped pattern, with first intervals 25a in which the ribs are separated from each other by narrow furrows whose width is equal to a first distance, and second intervals 27a in which the ribs are separated from each other by a wide groove whose width is equal to a second distance greater than the first distance.
• the first gaps 25a and the second intervals 27a alternate cyclically so that a second gap is always interspersed between two first intervals and vice versa.
• the ribbed surface of the cut edge of the workpiece 1 has a pattern which repeats periodically over the entire height of the workpiece. In the variant shown, this pattern is formed of two narrow grooves followed by a single wide groove. It may further be pointed out that, in this variant, the narrow grooves may have, for example, a width of 2 ⁇ m and a depth of between 10 nm and 2 ⁇ m.
• the broad grooves may have a width of 8 ⁇ m and a depth of between 10 nm and 10 ⁇ m.
• the pattern of the ribbed surface of the cut edge of the piece shown in Fig. 2B is quite similar to the pattern of Fig. 2A. It can be seen in fact that the ribs 21b and the grooves 23b that have the cut edges of the piece 10 form a staggered pattern, or in other words staggered, with first intervals 25b in which the grooves 23b are narrow, and second intervals 27b in which the grooves 23b are wide.
• the ribbed surface of the cut edge of the workpiece 10 has a pattern that repeats periodically over the entire height of the workpiece.
• this pattern is formed of a single narrow groove followed by a wide groove.
• the narrow grooves may have, for example, a width of 1 ⁇ m and a depth of between 10 nm and 2 ⁇ m.
• the broad grooves may have a width of 9 ⁇ m and a depth of between 10 nm and 10 ⁇ m.
• the pattern of the ribbed surface of the cut edge of the piece shown in FIG. 2C is quite similar to the patterns of FIGS. 2A and 2B. It can be seen indeed that the ribbed surface of the cut edge of the piece 20 has a pattern that repeats periodically over the entire height of the piece. It can be seen that in the variant of Figure 2C, this pattern is formed of five narrow grooves followed by a single wide groove. It may further be pointed out that, in this variant, the narrow grooves may have, for example, a width of 1 ⁇ m and a depth of between 10 nm and 2 ⁇ m. In addition, the broad grooves may have a width of 9 ⁇ m and a depth of between 10 nm and 10 ⁇ m.
• Figure 3 is a schematic sectional view showing the ribbed surface that has the cut edges of a micromechanical watch part 100 according to a second particular embodiment of the invention. It can be seen in FIG. 3 that the ribs 121 and furrows 123 that the cut edge of the workpiece 100 form form a stepped or staggered pattern, with first gaps 125 in which the spacing separating the ribs 121 from other is equal to a first distance, and a second interval 127 in which the spacing between the ribs is equal to a second distance different from the first distance.
• the only second gap 127 is itself formed of a single groove 123 whose width is equal to said second distance.
• this second distance is greater than a quarter of the total thickness of the workpiece 100.
• the workpiece 100 could have a thickness of between 80 ⁇ m and 500 ⁇ m, and said second distance could be between 20 pm and 150 pm.
• the first intervals 125 are two in number.
• the two gaps 125 each extend between one of the two main surfaces of the workpiece 100 and the second interval 127.
• the two intervals 125 comprise the same number of grooves 123, and that they therefore have the same width.
• the two slots 125 may not include the same number of grooves.
• the grooves which form the first gaps 125 are narrow grooves which may have, for example, a width of 1 ⁇ m and a depth of between 10 nm and 2 ⁇ m.
• the present invention also relates to a method for manufacturing watch micromechanical parts such as those which are the subject of appended figures 2A, 2B, 2C and 3. A particular mode of implementation of the method of the invention will now be described. .
• the method of the invention comprises a first step of providing a plate-shaped silicon substrate.
• the substrate may not be entirely made of silicon or be constituted by doped silicon.
• the substrate could be formed of silicon on insulator (SOI according to its abbreviation).
• SOI silicon on insulator
• such a sandwich structure substrate comprises two layers of silicon connected by a layer intermediate silicon oxide.
• the substrate could alternatively consist of a silicon layer attached to another type of base such as metal.
• the next step of the method consists in depositing and structuring a perforated etching mask on a horizontal surface of the substrate.
• the etching mask is formed on one of the two main faces of the plate-shaped substrate. Referring to FIGS. 2A, 2B, 2C and 3, it will be understood that in the illustrated examples the etching mask is formed on the upper horizontal face of the substrate.
• the mask is formed from a material capable of withstanding subsequent etching steps. According to the present example, the etching mask is made of silicon oxide.
• the process continues with a step of etching the exposed surface of the substrate through the apertures of the mask by reactive ion etching so as to dig into the substrate at a depth equal to a first distance.
• Reactive ion etching is known to those skilled in the art as such.
• the most used gas for the etching step is SF6, and the main parameters for optimizing the etching are the SF6 flux which is advantageously between 200 and 780 sccm, and preferably between 350 and 600 sccm; the power of the radio frequency for exciting the plasma which is advantageously between 1000 and 3000 Watts at 2.45 GHz, and preferably between 1500 and 2600 Watts at 2.45 GHz; and the duration of an etching step which is advantageously between 0.8 seconds and 35 seconds and preferably between 1.5 and 7 seconds.
• the parameters are chosen so that, at the end of the step, the ion etching has dug the silicon substrate to a depth equal to a first predetermined distance (for example 2 microns with respect to the example of the Figure 2A).
• the next step of the process consists in depositing a chemically inert passivation layer on the surfaces exposed by etching during the preceding step.
• the most used gas for the passivation step is C4F8, and the main parameters for optimizing the deposition of the passivation layer are the flow of C4F8 which is advantageously between 10 and 780 sccm, and preferably between 50 and 400 sccm; the power of the radio frequency for exciting the plasma which is advantageously between 1000 and 3000 Watts at 2.45 GHz, and preferably between 1500 and 2600 Watts at 2.45
• GHz GHz
• duration of a passivation step which is advantageously between 0.8 seconds and 20 seconds and preferably between 1 and 4 seconds.
• the process sequence comprising the etching step and the passivation step which have just been described is then repeated.
• This first iterative sequence is executed consecutively a first number (n) predetermined times, or equivalently, the first iterative sequence is performed as many times as there are furrows in a first interval (ie 2 times in the example which is the object of Figure 2A, 1 time according to Figure 2B and 5 times according to Figure 2C).
• the flow of the reactive gas and the duration of an etching step can be varied simultaneously.
• the flow of active gas by increasing the flow of active gas, the etching is accelerated.
• the density of the reactive gas molecules which makes the etching more isotropic, and thus makes the furrows deeper.
• the gas flow factor is therefore greater than the duration of the etching step.
• the next step of the method involves reactively etching the exposed surface of the substrate through the openings of the mask, so as to dig into the substrate on the substrate. a depth equal to a second distance different from the first distance.
• the etch parameters are chosen so that, at the end of the step, the ion etching has hollowed out the substrate in silicon to a depth equal to the second predefined distance (for example 8 microns with respect to the example of Figure 2A).
• the next step of the process consists in depositing a chemically inert passivation layer on the surfaces exposed by etching during the preceding step.
• the process sequence comprising the etching step and the passivation step which have just been described is then repeated.
• This second iterative sequence is consecutively executed a second predetermined number (m) of times, or equivalently, the second iterative sequence is performed as many times as there are furrows in a second interval (ie, once in each examples illustrated in Figures 2A, 2B, 2C and 3).
• m predetermined number
• the flow of the process returns to the beginning of the first iterative sequence so as to start writing a new first interval.
• the process sequence of first etching a first interval and then a second interval may itself be repeated.
• This third iterative sequence is executed a third number (v) determined from time to time, or equivalently, the third iterative sequence is performed once for each second interval that has the ribbed surface of the cut edge of the piece.
• micromechanical watchmaking piece is then freed from its mask before being preferably covered with a layer of silicon oxide before it is finally released from the substrate.
• FIG. 4 is a double graph showing the evolution of the flow of the reactive gas and of the flow of the passivation gas during six consecutive steps of a particular implementation of the process of the invention used to produce the watch micromechanical parts which make FIG. 2A, 2B, 2C and 3.
• the embodiment of FIG. 4 more specifically makes it possible to produce the micromechanical part of the example of FIG. 2A.
• the graph shows a first iterative sequence comprising a step of etching G1 followed by a step of passivation P1.
• the SF6 flux is 400 sccm for 5 seconds.
• the flow of C4F8 is 200 sccm for 2 seconds.
• the first iterative sequence is then repeated once to complete a first interval formed of two grooves.
• the process proceeds to a second sequence consisting of an etching step G2 followed by a passivation step P2.
• the flow of SF6 is 400 sccm for 35 seconds.
• the flow of C4F8 is 200 sccm for 15 seconds.
• the surface of the cut edges of the micromechanical watchmaking piece is ribbed and comprises an alternation of ribs and rectilinear furrows.
• these ribs and grooves were horizontal, or in other words, each contained in a plane parallel to the plate.
• the schematic partial plan view of FIG. 5 illustrates a third exemplary embodiment of the invention, the micromechanical part being constituted by an escape wheel.
• the ribs and the grooves are oriented perpendicularly to the main plane of the escape wheel.
• the partial view of Figure 5 shows only one of the teeth (referenced 200) of the escape wheel.
• the pulse plane of the tooth 200 has an alternation of ribs 221 and grooves 223 which are rectilinear and vertical. It can be seen that the ribs 221 and the grooves 223 form a staggered pattern, with first gaps 225 in which the grooves 223 are narrow, and second intervals 227 in which the grooves are wide. In addition, the ribs 221 and grooves 223 have a pattern that repeats periodically over the entire width of the pulse plane of the tooth 200.
• a method of manufacturing a micromechanical component made of mono- or poly-crystalline silicon comprising the following steps:
• step (e) repeating the execution of a sequence of steps comprising step (c) followed by step (d) until the sequence has been carried out a specified number of times, or that the reactive ion etching dug through the entire thickness of the substrate;
• the etching mask is structured so that the edges of the openings of the openwork mask are not smooth, but instead have a scalloped profile consisting of an alternation of prominences and depressions which form a staggered pattern with a plurality of first intervals in which the spacing separating the prominences from each other is equal to a first distance, and second intervals in which the spacing between the prominences is equal to a second distance distance different from the first distance, the first distance being between 200 nm and 5 miti, and preferably between 200 nm and 2 pm.

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• Engineering & Computer Science (AREA)
• Optics & Photonics (AREA)
• Plasma & Fusion (AREA)
• Micromachines (AREA)

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• 2019
  • 2019-02-04 JP JP2020542404A patent/JP7204761B2/ja active Active
  • 2019-02-04 US US16/968,056 patent/US11829107B2/en active Active
  • 2019-02-04 WO PCT/IB2019/050875 patent/WO2019155347A1/fr not_active Ceased
  • 2019-02-04 EP EP19707492.5A patent/EP3750010B1/de active Active
  • 2019-02-04 CN CN201980012512.0A patent/CN111684364B/zh active Active

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