CH704803A2 - Fabricating electroformed complex part e.g. watch-making part, comprises forming substrate with upper layer attached with lower layer, machining recess in upper layer to form positive geometries, and filling first material in recess - Google Patents

Abstract

The process comprises forming a substrate (1) with an upper layer attached with a lower layer (5), machining a recess in the upper layer for forming positive geometries, filling a first material (7) in the recess for reproducing negative geometries, removing the upper layer by selective chemical etching, depositing a second material (11), by electroplating, over the lower layer, and releasing an electroformed complex part (13) through the second material by removing the substrate and the first material. The recess forms a hole whose cross-section is not constant over its height. The process comprises forming a substrate (1) with an upper layer attached with a lower layer (5), machining a recess in the upper layer for forming positive geometries, filling a first material (7) in the recess for reproducing negative geometries, removing the upper layer by selective chemical etching, depositing a second material (11), by electroplating, over the lower layer, and releasing an electroformed complex part (13) through the second material by removing the substrate and the first material. The recess forms a hole whose cross-section is not constant over its height, where the hole comprises a flared end and an internal thread.

Description

Description

Field of the invention

The invention relates to a method for manufacturing an electroformed part and, more particularly, to such a method for producing complex geometries.

Background of the invention

The electroplating is used and known for a long time. LIGA processes (well-known abbreviation from German "roentgenlthography, Galvanoformung & Abformung") are more recent. They consist in forming a mold by photolithography of a photosensitive resin and then electroplating a metal deposit such as nickel. The accuracy of such LIGA processes is much better than that of a conventional mold obtained, for example, by machining. Such accuracies thus allow the manufacture of micromechanical parts especially for watch movements that were previously unthinkable.

However, such methods are not suitable for complex parts, that is to say, for example, having conical recesses and / or tapped. Indeed, LIGA type electrolytic deposits are formed by successive layers of resin whose cavities are necessarily straight, that is to say of constant section on each thickness of a layer. Therefore, it is currently not possible to manufacture a complex electroformed piece in a single electroplating step, that is to say without machining after electroforming.

Summary of the invention

The object of the present invention is to overcome all or part of the disadvantages mentioned above by proposing a manufacturing process using the advantages of machining, photolithography and electroplating to electroform in a single step electroplating a room complex.

For this purpose, the invention relates to a method for manufacturing an electroformed complex piece characterized in that it comprises the following steps: a) forming a substrate with an upper layer on a lower layer; b) machining at least one recess in the upper layer to positively shape future geometries; c) filling said at least one recess with a first material to negatively reproduce the future geometries; d) removing the top layer; e) depositing a second material by electroplating from the lower layer to form in one step said geometries by overlapping the negative forms of the first material; f) releasing the piece formed by the second material by removing the substrate and the first material.

It is therefore clear that the method, advantageously according to the invention, allows the use of the advantages of machining, photolithography and electroplating to electroform in a single step electroplating a piece mixing simple and complex geometries with very good structural accuracy.

According to other advantageous features of the invention:

said at least one recess forms a hole whose section is not constant over its height;

said hole comprises at least one flared end and / or a tapping;

the machining during step b) is prolonged in a part of the lower layer in order to fix more securely the first material deposited during step c);

the upper layer is formed of copper;

the lower layer is formed of steel;

the first material is formed based on photosensitive resin;

the first material is removed during step f) by dissolution;

the second material is formed on the basis of nickel;

the upper layer is removed in step d) by selective etching;

the lower layer is removed during step f) by selective etching.

Brief description of the drawings

Other features and advantages will become apparent from the description which is given below, for information only and in no way limitative, with reference to the accompanying drawings, in which:

- figs. 1 to 6 are successive representations of manufacturing steps according to the invention;

- figs. 7 to 10 are electroformed pieces obtained from the process according to the invention.

Detailed Description of the Preferred Embodiments

The method according to the invention will be better understood in relation to FIGS. 1 to 6. In a first step a) illustrated in FIG. 1, the method according to the invention consists in forming a substrate 1 with an upper layer 3 secured to a lower layer 5.

Preferably according to the invention, the lower layer 5 is formed based on an electrically conductive material to facilitate the realization of the electroplating step e). Thus, without limitation, layers of steel or nickel are possible.

Of course, alternatively to a single layer of an electrically conductive material, it is also possible to use a layer formed by any material coated with an electrically conductive layer.

Preferably according to the invention, the upper layer 3 is formed based on a malleable material to facilitate the realization of the step b) machining. Thus, in a nonlimiting manner, layers of copper or aluminum are possible.

The type of connection between the lower layer 5 and the upper layer 3 is not important for the present invention. The bonding may, for example, be obtained by electroplating one layer on the other indifferently between the lower layer and the upper layer, by bonding or by rolling.

As illustrated in FIG. 2, the second step b) of the method consists in machining at least one recess 2, 4 in the upper layer 3 to positively shape the future geometries. As explained above, the geometries that are particularly targeted, are, for example, a hole whose section is not constant over its height, that is to say having at least one flared portion and / or tapping . At least one flared portion is understood as, for example, a hole completely conical, and / or provided with a countersink and / or a recess and / or a countersink.

It is thus understood that the advantageous precision of a machining before the actual manufacture of the electroformed piece is used, that is to say that a machining is performed on a substrate 1 chosen to obtain the best accuracy possible and not undergoing its constraints a posteriori on the piece electroformed.

According to a variant of the invention, the machining during step b) is extended in a portion of the lower layer 5 as illustrated in FIG. 2 to fix more securely the first material to be deposited in step c).

As illustrated in FIG. 3, the third step c) of the method comprises filling with a first material 7 said at least one recess 2, 4 to negatively reproduce the future geometries. Preferably, the first material 7 is a positive or negative photosensitive resin in order to obtain a very good reproduction accuracy.

Step c) thus consists, preferably, in depositing the photoresist 7 by spin coating (also known as "spin coating") and then selectively illuminating said resin, for example through a partially open mask, to leave the resin 7 cured only at said recesses 2, 4.

As an alternative to the preferred embodiment, it is also possible to completely cover the upper layer 3 of resin 7 and then machine the top of the substrate 1 to make its upper part perfectly flat.

As illustrated in FIG. 4, the fourth step d) of the method consists in removing the upper layer 3 to leave only the first material 7 protrude from the lower layer 5. It is better understood at this step d), the interest of the variant of the step b) for fixing more securely the first material 7.

Preferably, step d) is carried out by a selective etching, that is to say an attack that does not alter the first material 7 nor the lower layer 5.

In addition, alternatively, as shown in FIG. 4, at least one other material 9 can be deposited after step d) in order to form simpler geometries and / or to limit the deposit of the future electroplating of step e). Preferably, said at least one other material 9 is a positive or negative photosensitive resin in order to obtain a very good manufacturing accuracy.

As illustrated in FIG. 5, the fifth step e) of the method consists in depositing a second material 11 by electroplating from the electrically conductive lower layer 5 in order to form in a single step the part 13 with said complex geometries by covering the negative shapes in first material 7 and, optionally, the simplest geometries by covering said at least one material 9.

Preferably according to the invention, the part 13 is formed based on a 1 1 electrically conductive material necessary for the realization of the electroplating step e). However, preferably, the second material 1 1 will be different from that used for the lower layer 5 to facilitate step f) of release of the part 13. Thus, without limitation, gold or nickel-based layers as nickel-phosphorus are conceivable.

As illustrated in FIG. 6, the sixth and last step f) of the method consists in releasing the piece 13 formed by the second material 11 by removing the substrate 1, the first material 7 and, optionally, the at least one other material 9.

Preferably, the first material 7 and, optionally, said at least one other material 9 are removed during step f) by dissolving the photosensitive resin. In addition, preferably in step f), a selective chemical etching of the lower layer 5 is carried out, that is to say an attack which only disintegrates the lower layer 5.

3

Claims (12)

It is therefore understood that the method, advantageously according to the invention, allows the use of the advantages of machining, photolithography and electroplating to electroform in a single step electroplating a piece mixing simple and complex geometries with a very good structural accuracy, that is to say between 1 and 5 // m, not only of each geometry but also of the referencing between the geometries. As shown in FIG. 6, the piece 13 thus comprises geometries that are not possible to be obtained currently by electroforming such as, for example, a hole whose section is not constant over its height. It is thus possible to see a hole 12 having a countersink 14 and a tapping 15, a simple hole 16 or a hole 18 having a countersink or a recess 17. It is therefore understood that a wide variety of parts is able to be obtained using the method according to the invention. Four embodiments of electroformed parts are shown in a nonlimiting manner in FIGS. 7 to 10. In a first embodiment illustrated in FIG. 7, the electroformed part 23 forms a wheel. It comprises a peripheral toothing 21, a central hole 26 substantially conical, that is to say that its section is continuously variable, and three holes 22, 22 <'> 22 "distributed around the central hole 26 with a countersink 24 , 24 <'>, 24 "and a thread 25, 25 <'>, 25 <">. In a second embodiment illustrated in FIG. 8, the electroformed part 33 forms a bridge. It has a central ajoration! 36 non-symmetrical, three holes 32, 32 <'>, 32 <"> for receiving pins and two holes 38, 38 <'> having a recess 37, 37 <'> and a tapping 35, 35 <'>. In addition, it can be seen in FIG 8 that the piece 33 does not have a constant thickness, since the thickness of the piece 33 is thinner, especially at the hole 31 intended to receive the bearing 39. In a fourth embodiment illustrated in FIG. 9, the electroformed piece 43 forms a wheel. It has a set of teeth 41 on its upper part and a central hole 46 to form a substantially annular piece. In a first embodiment illustrated in FIG. 10, the electroformed piece 53 forms a column wheel. It comprises a peripheral toothing 51, a central hole 56 substantially conical, that is to say that its section is continuously variable, and six columns 59 distributed around the central hole 56 whose section according to their height is not constant. Of course, the present invention is not limited to the example shown but is susceptible to various variations and modifications that will occur to those skilled in the art. In particular, the embodiments presented below can be combined with each other and do not represent exhaustively the possibilities of possible embodiments by the method according to the invention. In addition, the preferred modes or variants of the method according to the invention are only used to give an embodiment of the invention without being limited thereto. Thus, other materials or other methods of material removal or structuring can be envisaged. Finally, the examples given above relate to parts of timepieces. It goes without saying that the invention can not be circumscribed in the field of timepieces and could, for example, be applied to other technical fields. claims 1. A method of manufacturing an electroformed complex piece (13, 23, 33, 43, 53) characterized in that it comprises the following steps: a) forming a substrate (1) with an upper layer (3) secured to a lower layer (5); b) machining at least one recess (2, 4) in the upper layer (3) to positively shape the future geometries; c) filling said at least one recess (2, 4) with a first material (7) to negatively reproduce future geometries; d) removing the upper layer (3); e) depositing a second material (1 1) by electroplating from the lower layer (5) to form in a single step said geometries by covering the negative forms of first material (7); f) releasing the formed piece (13, 23, 33, 43, 53) by the second material (1 1) by removing the substrate (1) and the first material (7). 2. Method according to the preceding claim, characterized in that said at least one recess (2, 4) forms a hole (12, 18, 22, 22 <'>, 22 <">, 26, 36, 38, 38 < '>, 56) whose section is not constant over its height. 3. Method according to the preceding claim, characterized in that said hole (12, 18, 22, 22 <'>, 22 <">, 38, 38 <'>) comprises at least one flared end (14, 17, 24 , 24 <'>, 24 <">, 37, 37 <'>). 4. Method according to claim 2 or 3, characterized in that said hole (12, 22, 22 <'>, 22 ", 38, 38 <'>) comprises a tapping (15, 25, 25 <'>, 25 <">, 35, 35 <'>). 4 5. Method according to one of the preceding claims, characterized in that the machining in step b) is extended in a portion of the lower layer (5) to fix more firmly the first material (7) deposited in step c). 6. Method according to one of the preceding claims, characterized in that the upper layer (3) is formed of copper. 7. Method according to one of the preceding claims, characterized in that the lower layer (5) is formed of steel. 8. Method according to one of the preceding claims, characterized in that the first material (7) is formed based on photoresist. 9. Method according to the preceding claim, characterized in that the first material (7) is removed in step f) by dissolution. 10. Method according to one of the preceding claims, characterized in that the second material (11) is formed based on nickel. 11. Method according to one of the preceding claims, characterized in that the upper layer (3) is removed in step d) by selective etching. 12. Method according to one of the preceding claims, characterized in that the lower layer (5) is removed in step f) by selective etching. 5