WO2001063634A2

WO2001063634A2 - Microswitch and process for its production

Info

Publication number: WO2001063634A2
Application number: PCT/IB2001/000236
Authority: WO
Inventors: Michael Schwab; Kay Krupka
Original assignee: Tyco Electronics Amp Gmbh
Priority date: 2000-02-23
Filing date: 2001-02-23
Publication date: 2001-08-30
Also published as: AU2001266244A1; WO2001063634A3

Abstract

The invention relates to a microswitch with a substrate (1) and a spring (2). The spring (2) consists of an intrinsically biased material. Therefore, deposition of an additional layer producing the curvature of the spring (2) can be dispensed with. As a result, temperature dependence on contact spacing, contact resistance and contact force is largely avoided. Adhesion problems of the additional layer are also avoided. The invention further relates to the production of the microswitch by surface micromechanical methods and sacrificial layer technology.

Description

MICROS ITCH AND PROCESS FOR ITS PRODUCTION

The invention relates to a microswitch which has a planar substrate and a spring bent away from the substrate with electrodes arranged on the substrate and on the spring which electrodes can be connected to a direct voltage source and in the closed state of the microswitch are separated from one another by a dielectric. In addition, the invention relates to a process for producing the microswitch.

Such microswitches are known as micromechanical relays from DE 197 36 674 Cl where a moving contact is arranged on the spring and a fixed contact is arranged on the substrate. The moving contact acts as a bridge across spaced apart fixed contacts. With the known microswitches, the curvature of the spring is achieved by applying additional layers to the spring. These additional layers exert a compressive or tensile stress on the spring. The known microswitches have the disadvantage that the layer applied to the spring generally consists of a material which is different to that of the spring itself. These two materials generally have different coefficients of thermal expansion. As a result, there is thermal mismatching between layer and spring which, like the bimetallic effect, leads to temperature-dependent spring curvature. Consequently, there is the problem that important design parameters of the microswitch, such as the contact spacing, the overtravel, the contact force and the contact resistance are subject to temperature-dependent fluctuation. A further disadvantage relates to the adhesion of the layer to the spring. With frequent actuation of the microswitch in particular, the adhesion point between layer and spring is stressed to such an extent that the layer detaches from the spring over time. Furthermore, the problem often occurs that the layer itself is also not resistant to changing loads, in other words, with frequent change in curvature it becomes brittle and tears due to material fatigue. A further disadvantage in applying layers to the spring consists in that with a micromechanical relay which is produced by a sequence of layer application and layer removal processes, the layer has to be adjusted on the spring. The aim of the present invention is therefore to provide a microswitch in which the spring is bent without application of an additional layer.

This aim is achieved according to the invention by a microswitch according to claim 1. Advantageous developments of the invention and examples of processes for producing the invention can be inferred from the further claims .

The invention describes a microswitch having an opened and closed states. The microswitch has a planar substrate and a spring with a fixed and a spring arm portion. The fixed portion is rigidly connected to the substrate while the spring arm portion is bent away from the substrate at least at its free end in the opened state of the microswitch, and in the closed state rests substantially flat on the substrate. The microswitch has two electrodes located opposite one another which can be connected to a direct voltage source, the upper electrode of which is arranged on the side of the spring arm portion facing the substrate and the lower electrode of which is arranged on the side of the substrate facing the spring. The two electrodes are separated from one another in the closed state of the microswitch by a dielectric. Furthermore, the spring arm portion of the microswitch consists at least partially of an intrinsically biased spring material. By using an intrinsically biased spring material according to the invention, a bent spring arm portion can be achieved without an additional layer on the spring. Furthermore, a microswitch can be produced by the moving wedge principle, in other words, a microswitch with a wedge-shaped air gap between spring arm portion and substrate, wherein when the microswitch is switched from the opened to the closed state, the spring arm portion uncoils on the plane substrate, so that the wedge-shaped air gap moves in the direction of the free end of the spring arm portion. Due to the very small electrode spacing in the narrow region of the wedge, the wedge-shaped air gap has the advantage that it can be actuated with a very low direct voltage. The microswitch according to the invention can be designed particularly advantageously in that a moving contact is arranged on the spring arm portion and a fixed contact is arranged on the substrate in such a way that the contacts contact one another in a bridging manner in the closed state. As a result, an electrical switch or a microrelay can be produced in a particularly simple manner.

Furthermore, a microswitch which is produced according to the invention by repeated deposition of layers on the substrate and by structured etching of the layers is particularly advantageous. Owing to this procedure which is conventional in surface micromechanics, a miniaturised microswitch can in particular be produced without two micromechanical components, such as spring and substrate, having to be joined together.

Furthermore, a microswitch according to the invention, in which a partial spring arm portion towards the free end of the spring arm portion is coated with a reversal layer, is particularly advantageous. This reversal layer consists at least partially of a reversal material which is intrinsically biased in such a way that biasing of the spring arm portion material is overcompensated and as a result, the partial spring arm portion is bent towards the substrate. Owing to this counter-curvature of the spring arm portion in the partial spring arm portion, an overtravel can be achieved for the microswitch or for the microrelay. This overtravel means that reliable switching is still possible even after wear of the electrical contacts.

It is particularly advantageous in this case to arrange the reversal layer on the side of the spring arm portion remote from the substrate because, as a result, operation of the capacitor formed by the two electrodes is the least restricted.

An intrinsically biased spring arm portion can be achieved in a particularly advantageous manner in that according to the invention the atoms are arranged in the spring arm portion in such a way that their mean bond length decreases continuously or in stages over the thickness of the spring with distance from the substrate. This variation in the bond length of the atoms is transmitted to the external structure of the spring arm portion, so that it bends without any additional layers having been present.

Overcompensation of biasing of the spring arm portion material can also advantageously be achieved in that, according to the invention, a reversal layer made of a material which is different to that of the spring arm portion is provided. This other material must be selected in such a way that the side of the spring arm portion remote from the substrate has a compressive stress in the region of the partial spring arm portion.

An alloy in particular can be considered as material for the spring arm portion and/or as reversal material. With an alloy, intrinsic biasing can be adjusted in that, according to the invention, the content by weight of an alloy component in the spring arm portion decreases continuously or in stages over the thickness of the spring with distance from the substrate. By varying the content by weight of an alloy component, the lattice structure in the spring arm portion changes and therefore the mean spacing between the atoms forming the spring, resulting in biasing of the spring arm portion.

When using an alloy as material for the spring arm portion and/or as reversal material it is particularly advantageous to adjust the intrinsic biasing in such a way that, according to the invention, the alloy has a matrix of crystallites of a matrix metal into which the crystallites of an interstitial metal are intercalated. In this case, the crystallites of the matrix metal are distributed with regard to their size in such a way that, in the closed state of the spring arm portion, the crystallite size of the matrix metal decreases continuously or in stages with distance from the substrate. At the same time, the crystallites of the interstitial metal are such that the crystallite size and/or the crystallite density of the interstitial metal increases continuously or in stages with distance from the substrate. To this end, a matrix metal made of nickel and an interstitial metal made of iron are considered particularly advantageous as both these metals have resilient properties. Such a microswitch can be produced particularly easily and cost effectively in that the alloy is deposited from an electrolyte by electroplating, the size of the crystallites of the matrix and interstitial metal and the density of the crystallites of the interstitial metal being controlled by adjusting temperature and/or pH of the electrolyte, by the electrolytic current density I or by electrolyte additives .

In the event that spring arm portion and reversal layer consist of the same alloy, the reversal layer can be produced particularly easily as a layer in which the same alloy component, which has a decreasing content by weight in the spring, has a content by weight in the reversal layer which increases in stages or continuously with distance from the substrate. Such a construction of spring arm portion and reversal layer using the same material can also be produced particularly easily and cost-effectively.

Furthermore, a microswitch in which the spring material and/or the reversal material is a nickel/iron alloy is particularly advantageous. Nickel is known as material for spring arms. The disadvantage of pure nickel is, however, that nickel is very brittle and as a result, the spring arms produced from nickel would not withstand a large number of changes in curvature. Only mixing of iron with nickel produces a spring arm which can be stressed in this regard. The content by weight of iron in the alloy is preferably between 5 and 20%, wherein a content by weight between 10 and 17% has proved to be particularly advantageous.

With the aid of a nickel/iron alloy, the intrinsically biased spring arm portion can be produced in that, according to the invention, the content by weight of iron decreases continuously or in stages over the thickness of the spring arm portion with distance from the substrate. As a result, a curvature of the spring arm portion can be produced in a particularly simple and cost-effective manner. When using a spring arm portion made of a nickel/iron alloy, a reversal layer made of pure nickel with a stress-regulating additive, such as saccharine, can be used in addition to a reversal layer made of a nickel/iron alloy. With the aid of this mixture it has proved particularly easy to achieve overcompensation of the spring arm portion curvature in the region of the partial spring portion.

A spring arm portion or a reversal layer made of a nickel/iron alloy can be particularly advantageously produced by electroplating in a surface micromechanical process. In this case, the spring arm portion or the reversal layer is deposited from a mixture of a nickel sulphate and an iron sulphate solution. In order to obtain a microswitch which is suitably dimensioned for current applications, it is particularly advantageous to design the free end of the spring arm portion of the spring arm portion so as to be between 5 and 10 μm thick and between 500 and 2000 μm long. With a microswitch dimensioned in such a way an upward bend of the spring of 15 μm can be achieved with the aid of a direct voltage of 20 volts and by using a nickel/iron alloy for example.

Furthermore, the invention describes a process for producing the spring arm portion and/or the reversal layer of a microswitch in which the following steps are carried out: a) optionally applying a sacrificial layer to the substrate b) continuously depositing the spring material or reversal material on the sacrificial layer and the substrate or on the spring with an electrolytic current density which increases or decreases continuously or in stages with increasing layer thickness c) optionally wet-chemical etching of the sacrificial layer (25) . Due to deposition according to the invention of the spring or reversal material by a varying electrolytic current density, for example in the case of a nickel/iron spring arm portion, an iron content which varies over the thickness of the layer can be incorporated into the layer. As a result, an effect is used which is usually undesirable in layer electroplating as the layers are applied as smooth layers which are not bent away from the substrate. By varying the iron content in the spring arm or in the reversal layer, appropriate intrinsic biasing can be achieved.

A process for producing the spring of a microswitch in which a sacrificial layer of copper is used and in which an electrolytic current density is used to which: 1 A/dm² < I < 10 A/dm² applies is particularly advantageous. These values for the electrolytic current density have proved to be particularly suitable in experiments. Copper is particularly advantageous as sacrificial layer as it is a material which can be easily selectively etched to a nickel/iron alloy. Other materials can also be considered as sacrificial layer, however, such as Fe, Zn, Al or even polybenzoxazoles or polyimides . The invention will be described in more detail below with the aid of embodiments and the associated drawings :

Figure 1 shows a side view of a microswitch according to the invention in schematic cross-section; Figure 2 shows a side view of a microswitch according to the invention with reversal layer;

Figure 3 shows the mean spacing of the atoms in a bent spring (in schematic cross-section); Figure 4 shows the production of the spring by means of a sacrificial layer in schematic cross-section; and

Figure 5 shows the detailed layer construction of a microswitch according to the invention in schematic cross-section.

Figure 1 shows a microswitch in opened state with a substrate 1 and a spring 2. The spring 2 has a fixed portion 3 and a spring arm portion 4. The fixed portion 3 is rigidly connected to the substrate 1, while the spring arm 4 is bent away from the substrate 1. A lower electrode 8 is arranged on the substrate 1. An upper electrode 7 is arranged on the lower side of the spring arm portion 4. In the closed state of the microswitch the two electrodes 7, 8 are separated from one another by a dielectric 6. The two electrodes 7, 8 can be connected to a direct voltage source 5, whereby there is an electrostatic attraction between the two electrodes 7, 8 which moves the spring arm portion 4 in the direction of the substrate 1, whereby finally, the closed state of the microswitch is attained.

Figure 2 shows a microswitch according to the invention in a state between the opened and closed state, with a substrate 1 and a spring 2. The spring 2 has a fixed portion 3 and a free spring portion 4. The fixed portion 3 is rigidly connected to the substrate 1. The spring arm portion 4 is bent away from the substrate 1 in the open state. Furthermore, the spring arm portion 4 has a partial spring portion 11 which is covered by a reversal layer 12. The reversal layer 12 is intrinsically biased in such a way that the curvature of the spring arm portion 4 is overcompensated, whereby the partial spring portion 11 is bent towards the substrate 1. An insulating layer 14 is arranged on the substrate 1. This insulating layer 14 electrically separates a fixed contact 10 arranged on the substrate 1 from a lower electrode 8 arranged on the substrate 1. An upper electrode 7 is arranged on the spring arm portion 4 remote from the lower electrode 8. The two electrodes 7, 8 are separated from one another in the closed state of the microswitch by a dielectric 6. The two electrodes 7, 8 can be connected with a direct voltage source 5, whereby an electrostatic attraction is exerted between the electrodes 7, 8 and therefore between the spring arm portion 4 and the substrate 1 for switching the microswitch. A moving contact 9 is arranged on the free end of spring arm portion 4 remote from the fixed contact 10, which cooperates with the fixed contact 10 in the closed state of the microswitch. A further insulating layer 23 is arranged between the moving contact 9 and the spring arm portion 4 which decouples the contact system 9, 10 from the direct voltage source 5.

The moving wedge principle can be seen by looking at Figure 1 and Figure 2. The wedge-shaped air gap between the spring arm portion 4 and the substrate 1 moves in the opened state of Figure 1 in the direction of the fixed contact 10 in Figure 2 when a direct voltage is applied from the left-hand end of the lower electrode 8.

Figure 3 shows a detail of the spring arm portion 4" constructed from schematically illustrated atoms 13. These atoms 13 have a spacing "d" from one another which decreases from the side of the spring arm portion 4 facing the substrate (not shown in the figure) to the side of the spring arm portion 4 remote from the substrate. As a result, intrinsic biasing of the spring arm portion 4 is achieved, whereby the latter is bent away from the substrate. Figure 4 shows the production of the spring 2 of a microswitch, wherein a sacrificial layer 25 is applied to the substrate 1. This sacrificial layer 25 can consist of copper for example. Any other sacrificial layer which can be removed wet-chemically or physically is, however, also conceivable. The spring 2 with its fixed spring portion 3 and its spring arm portion 4 is then deposited on the sacrificial layer 25 or on the substrate 1. This depositing process can, for example, take place by electrolytic application of a nickel/iron alloy with varying electrolytic current density. Due to the varying electrolytic current density, the spring portion 4 is intrinsically biased, whereby the latter is bent away from the substrate 1 after etching away the sacrificial layer 25.

Figure 5 shows a microswitch according to the invention with a substrate 1. The illustration is not to scale, on the contrary the width of the microswitch has been shortened by a factor of approximately 1000. The substrate 1 can, for example, consist of silicon or ceramic. Due to the low electric conductance, a substrate 1 made of ceramic is particularly suitable for high frequency lines. A first insulating layer 14 is arranged on the substrate 1. This insulating layer 14 serves to electrically separate fixed contact 10 and electrode 8. A first adhesive layer 15 is arranged in sections on the first insulating layer 14. A conductor layer is arranged on the first adhesive layer 15 which forms a supply line 16 to the spring 2, the lower electrode 8 and a supply line 17 to the fixed contact 10. The conductor layers 16, 8, 17 preferably consist of metal. It is particularly advantageous to produce the conductor layers 16, 8, 17 from gold because gold is a particularly good electrical conductor. The conductor layers 16, 8, 17 can advantageously be deposited by sputtering or vapour deposition. A second adhesive layer 18 is arranged in each case on the supply line 17 to the fixed contact 10 and on the supply line 16 to the spring 2. A fifth adhesive layer 27 and a second insulating layer 19 thereabove is arranged on the lower electrode 8. The second insulating layer 19 forms the dielectric which separates the two electrodes 7, 8 from one another. The upper electrode 7 is formed in this case on the lower side of the spring portion 4. A first starting layer 20 suitable for electroplating is arranged in each case on the two adhesive layers 18. The material of the spring 2 and the material of the fixed contact 10 can be deposited by electroplating onto these starting layers 20. A second adhesive layer 18 is also arranged at the right-hand end of the microswitch above the supply line 17 to the fixed contact 10. A first starting layer 20 suitable for electroplating is also arranged above this second adhesive layer 18. A bonding pad 26 suitable for contacting the microswitch can be deposited, for example by electroplating, above this starting layer 20. The fixed contact 10 is arranged on the first starting layer 20 pertaining to the supply line 17 to the fixed contact 10 and the spring 2 is arranged on the first starting layer 20 pertaining to the supply line 16 to the spring 2. The spring 2 and the fixed contact 10 are deposited by electroplating for example. A stack of layers comprising a third adhesive layer 21, a third insulating layer 22 and a second starting layer 24 suitable for electroplating is located between the moving contact 9 arranged on the spring 2 and the spring 2. This stack of layers is required because the moving contact 9 is applied to the substrate 1 upstream of the spring 2 in the surface micromechanical production process. Finally, a reversal layer 12 is arranged on the free spring portion 4 which produces a curvature of the spring 2 towards the substrate 1. The supply line to the fixed contact 17 is protectively covered between the bonding pad 26 and the fixed contact 10 by the second insulating layer 19. The insulating layers 14, 19, 22 can preferably consist of silicon dioxide or silicon nitride. The insulating layers 14, 19, 22 made of silicon dioxide can be deposited particularly advantageously and simply by moist oxidation of silicon. The adhesive layers, which also impart the adhesion between the conductor layers 16, 8, 17 and the substrate 1 and the adhesion of the starting layers for the electroplating 20, 24 to the insulating layers 14, 19, 22, can preferably consist of chromium, titanium or titanium/tungsten. Such adhesive layers 15, 18, 21, 23 can preferably be deposited by sputtering or vapour deposition. The fixed contact 10 and/or the moving contact 9 consist particularly advantageously of a gold/cobalt alloy. While pure gold would have the better electric conductance it is too soft and would therefore have increased mechanical abrasion. The fixed contact 10 and the moving contact 9 can, for example, be deposited by electroplating. The starting layers 20, 24 for depositing a gold/cobalt alloy by electroplating preferably consist of copper. The starting layers 20, 24 can in turn also be deposited by electroplating. They can, however, also be deposited by sputtering or vapour deposition .

The invention is not limited to the embodiments shown by way of example but is defined in its most general form by claim 1 and claim 41.

Claims

1. A microswitch comprising an opened and a closed state and having a planar substrate (1) and a spring (2) with a fixed portion (3) and a spring arm portion (4), wherein the fixed portion (3) is rigidly connected to the substrate (1) and the spring arm portion (4) is bent away from the substrate (1), at least at an end opposite the fixed portion (3), in the opened state, and in the closed state rests on the substrate (1), which has two mutually opposed upper and lower electrodes (7, 8) which can be connected to a direct voltage source (5) and in the closed state are separated by a dielectric (6), in which the upper electrode (7) is arranged on the side of the free spring portion (4) facing the substrate (1), in which the lower electrode (8) is arranged on the side of the substrate (1) facing the spring (2) and in which the spring (2) consists at least partially of an intrinsically biased spring material.

2. The microswitch according to claim 1, wherein a moving contact (9) is arranged on the spring (2) and a fixed contact (10) is arranged on the substrate (1) in such a way that the contacts (9, 10) contact one another in the closed state.

3. The microswitch according to claims 1 or 2, which is produced by repeated deposition of layers on the substrate (1) and structured etching of the layers.

4. The microswitch according to claims 1 to 3, wherein a partial spring portion (11) of the free spring portion (4) is coated with a reversal layer (12) which consists at least partially of a reversal material which is intrinsically biased in such a way that biasing of the spring material is over-compensated and the partial spring portion (11) is bent towards the substrate.

5. The microswitch according to claim 4, wherein the reversal layer (12) is arranged on the side of the spring arm (4) remote from the substrate (1) .

6. The microswitch according to claim 1 to 5, wherein, in the opened state, the mean bond length (d) between the atoms (13) in the spring arm (4) decreases continuously or in stages over the thickness of the spring arm (4) with distance from the substrate (1) .

7. the microswitch according to claim 4 to 6, wherein, in the closed state, the mean bond length between the atoms (13) in the reversal layer (12) increases continuously or in stages over the thickness of the reversal layer (12) with distance from the substrate

(1) •

8. The microswitch according to claim 3, wherein the reversal layer (12) consists of a material which is different to that of the spring arm (4) .

9. The microswitch according to claims 1 to 8, wherein the spring material and/or the reversal material is an alloy .

10. The microswitch according to claim 9, wherein, in the closed state, the content by weight of an alloy component in the spring (2) decreases continuously or in stages over the thickness of the spring arm (4) with distance from the substrate (1) .

11. The microswitch according to claim 10, wherein, in the closed state, the content by weight of the same alloy component in the reversal layer (12) increases continuously or in stages over the thickness of the reversal layer (12) with distance from the substrate (1) •

12. The microswitch according to claims 1 to 11, wherein the spring material and/or the reversal material is a nickel/iron alloy.

13. The microswitch according to claim 12, wherein the content by weight of iron in the alloy is between 5 and 20%.

14. The microswitch according to claim 13, wherein the content by weight of iron in the alloy is between 10 and 17%.

15. The microswitch according to claim 14, wherein, in the closed state, the content by weight of iron in the spring (2) decreases continuously or in stages over the thickness of the spring (2) with distance from the substrate ( 1 ) .

16. The microswitch according to claims 4 to 15, wherein the reversal layer (12) comprises a mixture of nickel and saccharine.

17. The microswitch according to claims 1 to 16, wherein the spring material and/or the reversal material is produced by electroplating.

18. The microswitch according to claims 1 to 17, wherein the free spring portion (4) of the spring (2) is between 5 and 10 μm thick and between 500 μm and 2000 μm long .

19. The microswitch according to claims 1 to 18, wherein the substrate (1) consists of silicon.

20. The microswitch according to claims 1 to 18, wherein the substrate (1) consists of ceramic.

21. The microswitch according to claims 1 to 20, wherein a first insulating layer (14) is arranged on the substrate ( 1 ) .

22. The microswitch according to claims 21, wherein a first adhesive layer (15) is arranged on the first insulating layer (14) .

23. The microswitch according to claim 22, wherein a first conductor layer forming a supply line (16) to the spring (2), a second conductor layer forming the lower electrode (8) and a third conductor layer forming a supply line (17) to the fixed contact (10) is arranged on the first adhesive layer (15) .

24. The microswitch according to claim 23, wherein the conductor layers (16, 8, 17) consist of metal.

25. The microswitch according to claim 24, wherein the conductor layers (16, 8, 17) consist of gold.

26. The microswitch according to claims 23 to 25, wherein the conductor layers (16, 8, 17) are deposited by sputtering or vapour deposition.

27. The microswitch according to claims 23 to 26, wherein a second adhesive layer (18) is arranged in each case on the supply line (17) to the fixed contact (10) and on the supply line (16) to the spring (2) .

28. The microswitch according to claims 23 to 27, wherein a second insulating layer (19) is arranged on the lower electrode (8).

29. The microswitch according to claims 27 or 28, wherein a first starting layer (20) suitable for electroplating is arranged on the second adhesive layers (18) .

30. The microswitch according to claims 23 to 29, wherein the spring (2) is arranged on the first starting layer (20) of the fixed contact (10) pertaining to the supply line (17) to the fixed contact (10) and on the first starting layer (20) pertaining to the supply line (16) to the spring (2) .

31. The microswitch according to claims 2 to 30, wherein a stack of layers made of a third adhesive layer

(21), a third insulating layer (22), a fourth adhesive layer (23) and a second starting layer suitable for electroplating (24) is arranged between the moving contact (9) and the spring (2) .

32. The microswitch according to claims 21 to 31, wherein the insulating layers (14, 19, 22) consist of silicon dioxide or silicon nitride.

33. The microswitch according to claim 32, wherein the insulating layers (14, 19, 22) are deposited by moist oxidation of silicon.

34. The microswitch according to claims 22 to 33, wherein the adhesive layers (15, 18, 21, 23) consist of chromium, titanium or titanium/tungsten.

35. The microswitch according to claims 22 to 34, wherein the adhesive layers (15, 18, 21, 23) are deposited by sputtering or vapour deposition.

36. The microswitch according to claims 2 to 35, wherein the fixed contact (10) and/or the moving contact (9) consist of a gold/cobalt alloy.

37. The microswitch according to claims 2 to 36, wherein the fixed contact (10) and/or the moving contact

(9) are deposited by electroplating.

38. The microswitch according to claims 29 to 38, wherein the starting layers (20, 24) consist of copper.

39. The microswitch according to claims 29 to 38, wherein the starting layers (20, 24) are deposited by electroplating.

40. The microswitch according to claims 29 to 38, wherein the starting layers (20, 24) are deposited by sputtering or vapour deposition.

41. A process for producing the spring (2) and/or the reversal layer (12) of a microswitch according to claim 6 with the following steps :

a) optionally applying a sacrificial layer (25) to the substrate (1) b) continuously depositing the spring material or reversal material on the sacrificial layer (25) and the substrate (1) or on the spring (2) by electroplating with an electrolytic current density (I) which increases or decreases continuously or in stages with increasing layer thickness c) optionally wet-chemical etching of the sacrificial layer (25) .

42. The process for producing the spring (2) of a microswitch according to claim 15, wherein a sacrificial layer (25) made of copper is used and wherein an electrolytic current density (I) is used to which: 1 A/dm² < I < 10 A/dm² applies.

43. The microswitch according to claim 10, wherein the alloy has a matrix of crystallites of a matrix metal into which the crystallites of a interstitial metal are intercalated, wherein, in the closed state of the spring, the crystallite size of the matrix metal decreases continuously or in stages with distance from the substrate and wherein the crystallite size and/or crystallite density of the interstitial metal increases continuously or in stages with distance from the substrate.

44. The microswitch according to claim 43, wherein the matrix metal is nickel and the interstitial metal is iron .

45. The process for producing a microswitch according to claim 43, wherein the alloy is deposited from an electrolyte by electroplating and wherein the size of the crystallites of the matrix metal and interstitial metal and the density of the crystallites of the interstitial metal are controlled by adjusting temperature and/or pH of the electrolyte, by the electrolytic current density (I) or by electrolyte additives .