EP0780858A1 - Miniature device to execute a predetermined function, in particular a microrelay - Google Patents

Abstract

The microminiature relay mechanism includes a swinging arm mechanism (19) which is flexible and mounted on a central bridge (28). The two arm ends have magnetic material end strips (20,21). The substrate has a lower magnetic layer (6a,6b) and side protruding magnetic contacts (9) matching the magnetic arm ends. Magnetic coils (10,10a,10b,11,11a,11b) are provided by photoetching magnetic strips on the substrate surface. The magnetic circuit at either end can selectively close the arm.

Description

The present invention relates to miniaturized devices intended to provide a predetermined function and obtained by techniques usually used for the manufacture of integrated circuits. Such devices can in particular be used in the field of microrelays.

It has long been known to manufacture miniaturized relays composed of separate spare parts such as the magnetic circuit, the excitation coil, the contacts, the springs and possibly the permanent magnet. These parts are assembled using high-performance robots, which allows the manufacturer to provide a relay, the cost of which is very low.

However, with the ever increasing development of the use of integrated circuits, the need has arisen to further reduce the dimensions of these electromagnetic relays in order to give them a size similar to that of these circuits and thus to associate them directly. to their integrated control circuit. However, the conventional manufacturing techniques mentioned above oppose such advanced miniaturization.

Various proposals have therefore been made to achieve such an objective. For example, in an article in the "Journal of Microelectromechanical Systems", Vol. 2, No. 1, March 1993, Chong H. Ahn and Mark G. Allen describe a micro-machined miniaturized relay comprising a substrate in which a magnetic circuit is integrated, coils "wound" on this magnetic circuit, a fixed contact and a mobile contact. The latter is provided at the free end of an elastically deformable lever so as to be able to apply the movable contact to the fixed contact by excitation of the coil. The "winding" of the latter is carried out by conduction paths extending over several levels of integration.

Another similar proposition was made by B. Roger et al. in an article published in "Transducers '95 -Eurosensors IX", pages 320 to 323.

In general, microrelays must meet a certain number of mechanical and electrical criteria in order to be used in practice, for example in telecommunications and in many other fields. Table 1 below sets out and situates some values that must be respected by relay manufacturers in order for their product to pass, for example, the standards imposed for automatic test equipment (ATE-SECURITY) and in telecommunications. TABLE 1 Characteristics ATE TELECOM Insulation between coils and contacts (kV) 0.5 to 1.5 1.5 to 2.5 Insulation between contacts (kV) 0.5 to 1.5 1.0 to 1.5 Distance between contacts (µm) 40 to 210 210 to 440 Contact force (g) ≤4.5 ≥4.5 Contact resistance (Ω) 10 to 0.1 0.02 to 0.05 10mA to 1A 1A Control power (W) ≤ 0.1 ≤ 0.1 Number of cycles 10 ⁷ to 10 ⁶ 10 ⁶ Switching time (ms) ≤ 2 ≤ 2

It can be seen that these constraints are extremely severe and a priori seem to fall outside the orders of magnitude compatible with the usual dimensions of integrated circuits.

Among these constraints, those concerning the insulation between contacts and the contact force are particularly difficult to satisfy.

On the one hand, the required value of the insulation requires a large distance between contacts and on the other hand, the contact force requires the creation in the air gap between armature and magnetic circuit of a very strong magnetic induction B ₀ , as can be seen from Table 2 below: TABLE 2 B ₀ (T) 0.2 0.3 0.4 0.5 p ₀ (g / mm ² ) 1.6 3.6 6.4 9.9 Ni / d ₀ (A-turns / µm) 0.16 0.24 0.32 0.40

In this table, p ₀ is the force generated per unit area of the air gap.

This table shows that the number of ampere-turns Ni of the control coil must be very high for an air gap d ₀ of only 10 micrometers and that hundreds, even thousands of turns are necessary, if we want to limit the power of control below 100 mW and that the coil can be kept energized for long periods. Such a constraint does not currently enter into the technological possibilities available in microtechnology.

The object of the invention is to provide a miniaturized device manufactured by micro-machining which is compatible both with the above requirements and with its association with a nearby integrated control circuit.

The subject of the invention is therefore a miniature device for carrying out a predetermined function, this device being obtained by micro-machining on a substrate using electroplating, photolithography and / or similar techniques, in particular for carrying out of miniature microrelays, and comprising means forming a magnetic circuit, at least one excitation coil and means for ensuring the execution of said function under the action of said magnetic circuit, all of these elements being obtained on said substrate by integration operations similar to those used for the manufacture of integrated circuits, said means for ensuring the execution of said function being carried at least partially by a lever elastically deformable and attached in overhang to said substrate, characterized in that said lever forms a tilt and is attached approximately in its middle to the substrate by means of a deformable connection and in that at each free end said lever is provided with a magnetic armature forming part of said magnetic circuit means, the latter defining a seat against which said armature can be applied with a first magnetic force generated by said magnetic circuit and opposite to that generated by the elastic deformation of said lever, the coil, associated with each magnetic circuit being excitable sel ectively and capable of generating a second magnetic force opposite to that of the magnetic circuit for, when the armature associated with this coil is applied to its seat, release this armature and apply the other armature to its seat by tilting said lever.

Thanks to these characteristics, and more particularly when this device is used in its application to a microrelay, it can satisfy the severe operating conditions set out above, while being able to be manufactured by integrated circuit technology.

Thus, according to a particularly advantageous application of the invention, the device forms a microrelay comprising at least one fixed contact provided on said substrate and at least one movable contact carried by said lever forming rocker, this movable contact being intended to be applied to said fixed contact when said armature is applied to its seat.

Thus, by its own elasticity, the lever can keep the movable contact sufficiently distant from the fixed contact in the event of opening of these contacts to ensure the necessary insulation. Furthermore, the permanent magnetic flux applies the movable contact to the fixed contact in the event of the closure of these contacts with sufficient pressure to ensure a contact resistance corresponding to the requirements of use. Therefore, the coils do not have to remain permanently energized in any of the stable positions of the device.

• la figure 1 est une vue partielle en coupe d'un substrat dans lequel est usiné un dispositif selon l'invention dans son application à un microrelais;
• la figure 2 est une vue en plan du microrelais;
• la figure 3 est une vue en coupe transversale et à une échelle légèrement plus grande du microrelais prise selon la ligne III-III de la figure 2 et montrant notamment un double jeu de contacts;
• les figures 4 et 5 sont des diagrammes illustrant le comportement magnétique du microrelais;
• la figure 6 est un schéma illustrant le comportement mécanique du microrelais selon l'invention.
• la figure 7 est une vue en coupe d'un microrelais selon un autre mode de réalisation de l'invention;
• la figure 8 est une vue en plan du microrelais de la figure 7;
• la figure 9 est une vue en coupe du microrelais des figures 7 et 8, prise selon la ligne IX-IX de la figure 8;
• la figure 10 est une vue en coupe d'un autre mode de réalisation de l'invention;
• la figure 11 est une vue en plan du microrelais de la figure 10;
• la figure 11 représente une vue en coupe verticale d'un microrelais conforme à l'invention et construit selon un autre mode de réalisation, et
• les figures 12 et 13 montrent un autre mode de réalisation du dispositif selon l'invention, en illustrant notamment une application particulière.

Other characteristics and advantages of the invention will appear during the description which follows, given solely by way of example and made with reference to the appended drawings in which:

• Figure 1 is a partial sectional view of a substrate in which is machined a device according to the invention in its application to a microrelay;
• Figure 2 is a plan view of the microrelay;
• Figure 3 is a cross-sectional view on a slightly larger scale of the microrelay taken along line III-III of Figure 2 and showing in particular a double set of contacts;
• Figures 4 and 5 are diagrams illustrating the magnetic behavior of the microrelay;
• FIG. 6 is a diagram illustrating the mechanical behavior of the microrelay according to the invention.
• Figure 7 is a sectional view of a microrelay according to another embodiment of the invention;
• Figure 8 is a plan view of the microrelay of Figure 7;
• Figure 9 is a sectional view of the microrelay of Figures 7 and 8, taken along the line IX-IX of Figure 8;
• Figure 10 is a sectional view of another embodiment of the invention;
• Figure 11 is a plan view of the microrelay of Figure 10;
• FIG. 11 shows a view in vertical section of a microrelay according to the invention and constructed according to another embodiment, and
• Figures 12 and 13 show another embodiment of the device according to the invention, in particular illustrating a particular application.

The devices according to the invention which will be described are manufactured by a technique called "above chip" ("above the chip") by which it is therefore produced above a substrate 1 preferably produced by silicon (Figure 1 to 3).

Face 2 of this substrate is arbitrarily called "upper face" in the following description. Furthermore, for clarity of the figures, certain dimensions have been greatly exaggerated.

It will be noted that the photoengraving and photolithography techniques used to machine the microrelay are known to those skilled in the art who will be able to implement the succession of process steps necessary for this machining.

To fix the ideas, the longitudinal dimension of the device can be chosen between 2 and 3 mm, approximately.

The underside 3 of the substrate 1 has two cavities 4 and 5 which, if the substrate is made of silicon, can be machined by an anisotropic attack. These cavities are each intended to receive a permanent magnet, 6a and 6b respectively. These magnets 6a and 6b can be pellets fixed in the respective cavities or can also be obtained by depositing suitable substances. Each of them has a North pole and a South pole near the upper surface 2. In the case shown, these magnets extend along the longitudinal dimension of the device (that is to say in the plane of the figure 1). The bottom of each cavity is formed by a layer 7 of material of the substrate 1 remaining after the formation of the cavity.

The upper face 2 is covered with a multi-layer of insulator 8, for example made of silicon oxide. This multi-layer 8 is composed of three layers (not drawn individually) which isolate a configuration of coils so that each turn of this configuration is isolated from what surrounds it. In the center of these coils, openings 9 are formed in the substrate 1 from the face 2 and they extend into the multi-layer of insulator 8.

More precisely, the configuration of the coils comprises two sets 10 and 11 of two flat coils 10a, 10b, 11a, 11b produced by metallic deposits, of aluminum for example, of suitable shape and embedded in the insulating layer 8. The figures 1 to 3 show their location with bold lines. In the embodiment shown, each coil has a generally rectangular shape in plan.

Sets 12 and 13 of pole pieces 12a, 12b and 13a, 13b consist of FeNi deposits of rectangular shape which fill the openings 9 and which slightly exceed the multi-layer of insulation 8. Each pole piece is surrounded by its coil corresponding.

We see in Figures 1 and 2 that the assemblies formed by a magnet, a set of coils and a set of pole pieces are spaced from each other by a certain distance according to the longitudinal dimension of the device. These assemblies are arranged symmetrically with respect to a plane perpendicular to this longitudinal dimension, with respect to a support device 14 formed from two mesas 15 and 16. On the sides which face each other, these mesas are provided with arms of respective torsion 17, 18 forming deformable links with a double lever 19 which extends over practically the entire length of the device. It is made of an elastically deformable material, FeNi or silicon oxide may be suitable for this purpose, and it has a generally rectangular shape.

Flow closing pieces or frames 20 and 21 are respectively provided at the free ends of this lever 19. They are preferably made of FeNi and have a dimension such that they can cover the set of corresponding pole pieces when they are applied on these.

Figure 3 shows a cross-sectional view of one end of the lever 19 and shows in particular the construction of the means for performing the function for which the device according to the invention is designed. In the case described herein, these means include electrical contact devices, so that this is a microrelay here. Two double contacts 22 and 23 are thus provided respectively at each end of the lever 19, which electrically can make a reversing contactor of this microrelay.

Returning to FIG. 3, the preferred embodiment of the microrelay provides for two fixed double contacts 22 and 23, FIG. 3 showing the double contact 22, the contact 23 being exactly identical. The lever 19 carries the movable contacts of the reverser thus formed.

At the end of the lever 19, each frame 20, 21 comprises lateral extensions 24 and 25 elastically deformable which have come from forming. Pavers 26 made of a metal that is a good conductor of electricity such as gold are provided at the end of each of these extensions, and intended to cooperate respectively with fixed contacts 27 deposited on either side of the one of the pole pieces, 12a, 13b in this case, in order to minimize the contact resistance. In Figure 1 one of its fixed contacts 27 is visible behind the pole piece 13b.

According to a variant, the lateral extensions 24 and 25 can be made of a material other than that of the associated reinforcement. It will however be observed that an elasticity of these extensions is essential so that the contact blocks 26 and the contacts 27 can be applied to each other under mechanical stress and that possible wear can be compensated for. The elastic deformation of these extensions stores the forces applied to the contacts in the form of potential mechanical energies which generate dynamic forces opposite to those applied to the contacts when they open. These dynamic forces are used to overcome the adhesion forces of the contacts.

The coils 10a, 10b, 11a, 11b are preferably of the flat type and can comprise a few tens of turns each.

The magnetic properties of the magnets 6a and 6b are of decisive importance for the functioning of the microrelay according to the invention. We will first describe a first mode of operation which involves the use of magnets in a "very hard" material such as samarium-cobalt, platinum-cobalt, ferrite-strontium and other similar materials. The term “very hard materials” is understood to mean those which are pre-magnetized during manufacture and have linear curves, with a slope close to μ ₀ (see the line B (H) in FIG. 4).

A_a

surface de l'aimant,

l_a

longueur de l'aimant,

A_p

surface d'une pièce polaire 12a, 12b, 13a ou 13b (FeNi),

l_p1

entrefer composé de la somme des intervalles entre les pièces polaires 12a et 12b, ou 13a et 13b et l'armature 20 ou 21, lorsque celle-ci est appliquée sur les contacts correspondants par l'intermédiaire des extensions élastiques 24 et 25,

l_p0

le même entrefer lorsque l'armature est éloignée des pièces polaires après basculement du dispositif:

$$\mathit{\text{<figure-callout id="1" label="tg α" filenames="imgf0001.png" state="{{state}}">tg</figure-callout>}}{\text{α}}_{}{}_{\text{1}}{\text{= -µ}}_{\text{0}}\frac{{\mathit{\text{A}}}_{\mathit{\text{<figure-callout id="1" label="p l p" filenames="imgf0001.png" state="{{state}}">p</figure-callout>}}}}{{\mathit{\text{l}}}_{\mathit{\text{p}}}}\text{∗}\frac{{\mathit{\text{l}}}_{\mathit{\text{a}}}}{{\mathit{\text{A}}}_{\mathit{\text{a}}}}{\text{= -Λ}}_{\text{1}}\frac{{\mathit{\text{l}}}_{\mathit{\text{a}}}}{{\mathit{\text{A}}}_{\mathit{\text{a}}}}$$

$$\mathit{\text{tg}}{\text{α}}_{\text{0}}{\text{= -µ}}_{\text{0}}\frac{{\mathit{\text{A}}}_{\mathit{\text{p}}}}{{\mathit{\text{l}}}_{\mathit{\text{p}}}{}_{\text{0}}}\text{∗}\frac{{\mathit{\text{l}}}_{\mathit{\text{a}}}}{{\mathit{\text{A}}}_{\mathit{\text{a}}}}{\text{= -Λ}}_{\text{0}}\frac{{\mathit{\text{l}}}_{\mathit{\text{a}}}}{{\mathit{\text{A}}}_{\mathit{\text{0}}}}$$

$${\mathit{\text{tgα}}}_{\mathit{\text{σ}}}{\text{= -Λ}}_{\text{σ}}\frac{{\mathit{\text{l}}}_{\mathit{\text{a}}}}{{\mathit{\text{A}}}_{\mathit{\text{a}}}}$$

Λ₁, Λ₀ e Λ_σ étant respectivement la perméance en l'état appliqué et non appliqué de l'armature et la perméance de fuite.Using the following notations, we can write the values of the permeance Λ of the magnetic circuit:

A _a

magnet surface,

_has the

magnet length,

A _p

surface of a pole piece 12a, 12b, 13a or 13b (FeNi),

l _p1

air gap composed of the sum of the intervals between the pole pieces 12a and 12b, or 13a and 13b and the armature 20 or 21, when the latter is applied to the corresponding contacts by through elastic extensions 24 and 25,

l _p0

the same air gap when the armature is distant from the pole pieces after tilting the device:

$$\mathit{\text{<figure-callout id="1" label="tg α" filenames="imgf0001.png" state="{{state}}">tg </figure-callout>}}{\text{α}}_{}{}_{\text{1}}{\text{= -µ}}_{\text{0}}\frac{{\mathit{\text{AT}}}_{\mathit{\text{<figure-callout id="1" label="p l p" filenames="imgf0001.png" state="{{state}}">p </figure-callout>}}}}{{\mathit{\text{l}}}_{\mathit{\text{p}}}}\text{∗}\frac{{\mathit{\text{l}}}_{\mathit{\text{at}}}}{{\mathit{\text{AT}}}_{\mathit{\text{at}}}}{\text{= -Λ}}_{\text{1}}\frac{{\mathit{\text{l}}}_{\mathit{\text{at}}}}{{\mathit{\text{AT}}}_{\mathit{\text{at}}}}$$

$$\mathit{\text{tg}}{\text{α}}_{\text{0}}{\text{= -µ}}_{\text{0}}\frac{{\mathit{\text{AT}}}_{\mathit{\text{p}}}}{{\mathit{\text{l}}}_{\mathit{\text{p}}}{}_{\text{0}}}\text{∗}\frac{{\mathit{\text{l}}}_{\mathit{\text{at}}}}{{\mathit{\text{AT}}}_{\mathit{\text{at}}}}{\text{= -Λ}}_{\text{0}}\frac{{\mathit{\text{l}}}_{\mathit{\text{at}}}}{{\mathit{\text{AT}}}_{\mathit{\text{0}}}}$$

$${\mathit{\text{tgα}}}_{\mathit{\text{σ}}}{\text{= -Λ}}_{\text{σ}}\frac{{\mathit{\text{l}}}_{\mathit{\text{at}}}}{{\mathit{\text{AT}}}_{\mathit{\text{at}}}}$$

Λ ₁ , Λ ₀ e Λ _σ being respectively the permeance in the applied and non-applied state of the reinforcement and the leakage permeance.

et le point de travail sur la courbe (figure 4) sera P₁.Under these conditions, when the armature is applied, the application force produced by the two poles of the magnet will be: $${\mathit{\text{<figure-callout id="1" label="F" filenames="imgf0001.png" state="{{state}}">F</figure-callout>}}}_{\text{1}}\text{= 2 ∗}\frac{{\left({\mathit{\text{B}}}_{\text{1}}\text{-}{\mathit{\text{<figure-callout id="2" label="B σ" filenames="imgf0001.png,imgf0002.png" state="{{state}}">B </figure-callout>}}}_{\text{σ}}\right)}^2}{{\text{2µ}}_{\text{0}}}\text{∗}{\mathit{\text{AT}}}_{\mathit{\text{p}}}\text{=}\frac{{\left(\mathit{\text{B}}{}_{\text{1}}\text{-}\mathit{\text{<figure-callout id="2" label="B σ" filenames="imgf0001.png,imgf0002.png" state="{{state}}">B </figure-callout>}}{}_{\text{σ}}{}_{}\right)}^{\text{2}}}{{\text{µ}}_{\text{0}}}\text{∗}{\mathit{\text{AT}}}_{\mathit{\text{p}}}$$

and the working point on the curve (figure 4) will be P ₁ .

On the other hand, when the armature is distant from the pole pieces, the force produced by the two poles will be: $${\mathit{\text{F}}}_{\text{0}}\text{= 2 ∗}\frac{\left({\mathit{\text{B}}}_{\text{0}}\text{-}{\mathit{\text{B}}}_{\text{σ}}\right)}{{\text{2µ}}_{\text{0}}}\text{∗}{\mathit{\text{AT}}}_{\mathit{\text{p}}}\text{=}\frac{\left({\mathit{\text{B}}}_{\text{0}}\text{-}{\mathit{\text{B}}}_{\text{σ}}\right)}{{\text{µ}}_{\text{0}}}\text{∗}{\mathit{\text{AT}}}_{\mathit{\text{p}}}$$

As F ₁ >> F _o + F _m where F _m is the sum of the mechanical forces (forces exerted on the lever 19 by its by the elastic deformation), the reinforcement which was applied at the time considered on the pole pieces will remain so until an intervention on the corresponding coils is not carried out.

ce qui fait basculer le levier 19 et le microrelais prend la position opposée.In order for the microrelay to switch, a current i must be sent to the coils on the side where the armature is applied to the pole pieces. This current produces a demagnetization field equal to Ni / l _a (N being the number of turns of the coils considered), which displaces the working point from P ₁ to P ₁ '. Under these conditions, in P ₁ ' $${\text{F}}_{\text{1}}{\text{'<F}}_{\text{0}}{\text{+ F}}_{\text{m}}$$

which switches lever 19 and the microrelay takes the opposite position.

The demagnetization field must however remain limited to a value such that the magnet will not be demagnetized (In other words P ₁ 'can move on the demagnetization line beyond the point P _o without going too far).

It should be observed, however, that very hard magnetic materials require a relatively high number of ampere-turns Ni to obtain sufficient excursions of induction B and allow the necessary forces to be generated on the contacts.

It is known that the less hard magnetic materials demagnetize in the presence of an inverse magnetic field by following non-linear induction curves B (H). It is therefore preferable to choose these materials to obtain more convenient values of Ni at the cost, however, of a slightly more complicated command of the coils 10a, 10b and 11a, 11b, since this command must then produce magnetization pulses. and demagnetization.

Hard and semi-hard magnetic materials are also advantageous due to the fact that they can be deposited better by the galvanic processes currently known. In furthermore, they do not have to be magnetized during manufacture. It should be noted that among other materials, cobalt-tungsten, cobalt-iron and cobalt-nickel-phosphorus are well suited for this use.

In the application envisaged for the present invention, materials with fairly weak coercive fields are preferred, for example of the order of 10 kA / m, or approximately 125 Oersteds. They can thus be magnetized or demagnetized by choosing the direction of the current in the relevant coils of the microrelay. In the context of the invention, an appropriate induction value of the magnetization field can be 2 to 3 times the coercive field.

FIG. 5 represents the magnetization / demagnetization curve used in this case. In the example shown, it is assumed that there is practically no air gap, which makes it possible to reduce leaks as much as possible. This is technologically possible and the influence of the air gaps can thus become negligible (tgα _σ = 0).

It is also arbitrarily assumed that the reinforcement 20 situated on the left side in FIGS. 1 and 2 has been applied beforehand to the corresponding pole pieces 12a and 12b. For this, it was necessary to impose a magnetization field Ni / l _a on the magnet 6a by sending a current of corresponding direction in the coils 10a and 10b. It may be a current pulse lasting a few milliseconds. As a result, the working point of this magnet is at P ₁ of the curve in FIG. 5.

The application force produced is then that defined in equation (4) above. Unlike in the case of FIG. 4, the force F ₀ , on the right side of the device, is nonexistent, because the magnet 6b is only weakly magnetized. Consequently, like F1 >> Fm, after the magnetization on the left side, the armature 20 on the left remains applied to its pole pieces 12a and 12b.

To tilt the device, it is then necessary to send a demagnetization current of a predetermined amplitude and duration in the left coils 10a and 10b and simultaneously to send a magnetization current in the right coils 11a and 11b of a double or triple amplitude, but of the same duration as the demagnetization current.

• que le point de travail de l'aimant se déplace du point P1 de la courbe vers le point P1' où F1'=Fm;
• que le ou les contacts de gauche s'ouvrent sous l'action simultanée de Fm et de la libération des énergies potentielles mécaniques emmagasinées dans les extensions latérales 24 et 25;
• que l'entrefer entre l'armature 20 et les pièces polaires 12a et 12b augmente considérablement, ce qui réduit fortement la pente de la droite de travail dans le diagramme de la figure 5 (tgα₀);
• que le point P₁' se déplace vers le point P₀, puis, lorsque le nombre d'ampère-tours Ni=0, le point P₀ se déplace vers le point P₀';
     et à droite:
• que le point P₀' se déplace vers le point P_µ, puis, lorsque le nombre d'ampère-tours Ni=0, le point P_µ se déplace vers le point P₁.

This has the effect, on the left:

• that the working point of the magnet moves from point P1 of the curve to point P1 'where F1' = Fm;
• that the left contact (s) open under the simultaneous action of Fm and the release of potential mechanical energies stored in the lateral extensions 24 and 25;
• that the air gap between the armature 20 and the pole pieces 12a and 12b increases considerably, which greatly reduces the slope of the working line in the diagram of Figure 5 (tgα ₀ );
• that the point P ₁ 'moves towards the point P ₀ , then, when the number of ampere-turns Ni = 0, the point P ₀ moves towards the point P ₀ ';
  and on the right:
• that the point P ₀ 'moves towards the point P _µ , then, when the number of ampere-turns Ni = 0, the point P _µ moves towards the point P ₁ .

It will be observed in FIG. 1 that the lever 19 has two very thick zones forming the frames 20 and 21 and a thin blade 28 which connects these two frames together. The torsion arms 17 and 18 are attached to this blade 28 approximately in the middle.

The thickness of the frames 20 and 21 is determined by the magnetic flux which must be able to pass through them. As shown in Figure 1, this thickness is relatively important compared to that of the blade 28. As a result, the frames 20 and 21 are relatively rigid.

Furthermore, it has already been observed that when the contacts are open, a certain distance between them (> 100 µm) must be respected to guarantee the required electrical insulation. The reinforcements being almost rigid, it is therefore necessary for the zone 28 to be flexible, which moreover brings another advantage, that of creating an amplification of movement between the torsion arms 17 and 18 and the outer ends of the reinforcements 20 and 21.

Referring to Figure 6, we can theoretically describe this amplification as follows.

avec I = ( $\frac{{\mathit{\text{h}}}^{\text{3}}\mathit{\text{b}}}{\text{12}}$

) qui est le moment d'inertie de la lame flexible, b et h en étant respectivement la largeur et l'épaisseur. E est le module d'élasticité de cette lame. On notera que P_a<<F_1p qui est la force d'un seul pôle magnétique, F_1p=F₁/2.To deform the blade 28, the torsion arms 17 and 18 installed at a height h _s must support a force P _a = 3 EI $\frac{{\mathit{\text{h}}}_{\mathit{\text{s}}}}{{\mathit{\text{<figure-callout id="3" label="l" filenames="imgf0004.png" state="{{state}}">l</figure-callout>}}}^{\text{3}}}$

with I = ( $\frac{{\mathit{\text{h}}}^{\text{3}}\mathit{\text{b}}}{\text{12}}$

) which is the moment of inertia of the flexible blade, b and h being the width and the thickness respectively. E is the modulus of elasticity of this blade. Note that P _has << F _1p which is the force of a single magnetic pole, F _1p = F _1/2 .

$${\mathit{\text{h}}}_{\mathit{\text{c}}}\text{=}\left(\text{5 + 3}\frac{{\mathit{\text{l}}}_{\mathit{\text{R}}}}{\mathit{\text{l}}}\right)\frac{{\mathit{\text{h}}}_{\mathit{\text{s}}}}{\text{2}}$$

Si a titre d'exemple on choisit l_R=l, alors h_c=4h_s, ce qui est une valeur praticable pour respecter les exigences d'isolation.When contacts are open, their distance h _c can be determined by $${\mathit{\text{h}}}_{\mathit{\text{vs}}}{\mathit{\text{= h}}}_{\mathit{\text{s}}}{\mathit{\text{+ tgα}}}_{\mathit{\text{s}}}{\mathit{\text{(l + l}}}_{\mathit{\text{R}}}{\mathit{\text{) where tgα}}}_{\mathit{\text{s}}}\text{=}\frac{\text{3}}{\text{2}}\frac{{\mathit{\text{h}}}_{\mathit{\text{s}}}}{\mathit{\text{l}}}\text{is:}$$

$${\mathit{\text{h}}}_{\mathit{\text{vs}}}\text{=}\left(\text{5 + 3}\frac{{\mathit{\text{l}}}_{\mathit{\text{R}}}}{\mathit{\text{l}}}\right)\frac{{\mathit{\text{h}}}_{\mathit{\text{s}}}}{\text{2}}$$

If by way of example we choose l _R = l, then h _c = 4h _s , which is a practicable value to meet the insulation requirements.

Figures 7 to 9 show another embodiment of a microrelay according to the invention which differs from that of Figures 1 to 3 by the arrangement of the contacts. Indeed, here each crosspiece 24 and 25 has at its free end a support bridge 29 which is fixed thereto by means of an insulating layer 30. The support bridge 29 is made of FeNi, for example and carries two contact blocks 31, 32 intended to cooperate with two contacts 33, resp. 34 formed in the insulating layer 8 of the substrate 1 which they project over a certain distance.

Thus, this embodiment ensures closure resp. the opening of four electrical circuits at a time which will be isolated from the double lever 19 by the presence of the insulating layers 30.

Figures 10 and 11 show another embodiment of the microrelay according to the invention in which there is provided a double lever 35 itself formed by two blades 36 and 37 extending parallel to each other.

These blades are carried by the two mesas 15 and 16, by means of the torsion arms 17 and 18. They are secured to one another by means of three connecting blocks 38, 39 and 40 provided respectively at the level torsion arms 17 and 18 and at the two ends of the parallel blades 36 and 37. These blocks are produced for example from FeNi and they are isolated from the blades by means of respective layers of insulation 41, 42 and 43.

Furthermore, the blades carry at each end a separate frame 44 resp. 45 cooperating with the respective pole pieces 12a, 12b, 13a and 13b. In addition, each blade carries two crosspieces 46, 47 which are in turn integral with support bridges 48 for blocks 49, 50 cooperating with contacts 51, 52 fixed in the insulating layer 8. The circuits that these assemblies can establishing or interrupting can thus be galvanically separated from each other.

Figures 12 and 13 show another embodiment of the microrelay according to the invention.

In this case, a substrate 60 is covered with an insulating layer 61 on one of its faces and has a cavity 62 opening on the other face.

This microrelay also comprises two mesas 63, 64 from which extend torsion arms 65 and 66 supporting a blade 67 in the form of a double fork, only one 67A of its forks being shown in the drawings.

A magnet 68 is placed in the cavity 62 and cooperates with two pole pieces 69 and 70 passing through openings 70 made in the substrate 60 and the insulating layer 61. Each of these pole pieces is surrounded by a coil 71 resp. 72 embedded in the insulating layer 61.

The free ends of the branches of the fork 67A carry a support bridge 73 fitted with contact blocks 74, 75 provided at its ends. These blocks cooperate with fixed contacts 76, 77.

The support bridge 73 is made in one piece with the fork-shaped blade 67 and also with three connecting lugs 78 which extend from the support bridge 73 inwards between the branches of the fork 67A. Mechanically, these connection tabs extend these branches so that it can be considered that, in the present embodiment, the blade 67 is folded back on itself, while fulfilling exactly the same functions as the blades described in conjunction with the previous embodiments. The main advantage of this folded configuration of the blade is that the device as a whole takes up less space on the substrate than those described above.

The connection tabs are attached to a frame plate 79 which, when the corresponding side of the contacts 76 and 77 is closed, is applied to the pole pieces 69 and 70 by means of the support bridge 73. On note that in this closed position, the connection tabs 78 are under elastic stress by acting in the same direction as the fork 67A, which is clearly visible in FIG. 12. Consequently, the elastic forces with which the fork 67A and the legs 78 are put under stress add up to improve the operation of the assembly when the armature 79 is repelled by the magnetic field generated for the opening of the contacts.

FIG. 12 also illustrates that the invention is not limited to its application to a microrelay.

Indeed, in an example of a different application which is not given by way of limitation and which could be envisaged in all the variants described above in place of the fixed contacts and the movable contacts or jointly with the use of these contacts, the moving element of the magnetic circuit could be coated with a reflective layer CR (drawn in phantom) capable of intercepting a light beam FL and of returning it selectively to a target (not shown) depending on the position of the tilting lever. Of course, the same mobile element could also simply intercept the beam without returning it, whereby the reflective layer would not be necessary.

According to another variant of the invention applying more particularly to the microrelay, it can be provided only a single double contact (see Figure 1), the relay then being only a simple switch. According to yet another variant, the electrical contact (s) could be simple without lining on either side of the lever 19.

Still in the context of application to a microrelay, it would also be possible to provide on one side or on either side of the lever 19, a pair of insulated contacts which would then be bridged in the corresponding position of the relay.

Finally, in all of the embodiments described above, the substrate can itself be produced in a magnetic material, the regions below the coils then being locally magnetized by replacing the permanent magnets.

From the above description, it can therefore be seen that the invention provides a device for achieving a predetermined function and in particular a microrelay whose dimensions are close to those of current integrated circuit chips and which in particular makes it possible to comply with the stringent requirements imposed on relays currently used in advanced technologies.

Claims (20)

Miniature device for carrying out a predetermined function, this device being obtained by micromachining on a substrate (1) using electroplating, photolithography and / or similar techniques, in particular for making miniature microrelays, and comprising means (6a, 6b, 12a, 12b, 13a, 13b, 20, 21, 44, 45, 68, 69, 70, 79) forming a magnetic circuit, at least one excitation coil (10a, 10b, 11a, 11b, 71, 72) and means (25, 26, 27, 29, 31 to 34, 46 to 51, 74 to 77, CR) for ensuring the execution of said function under the action of said magnetic circuit, all of these elements being obtained on said substrate (1) by integration operations similar to those used for the manufacture of integrated circuits, said means for ensuring the execution of said function being carried at least partially by an elastically deformable lever (19, 35 , 67) and attached in overhang to said substrate (1), characterized in that e said lever (19, 35, 67) forms a tilt and is attached approximately in the middle to the substrate (1) by means of a deformable connection (17, 18, 65, 66) and in that at each free end of said lever (19, 35, 67) is provided with a magnetic armature (20, 21, 44, 45, 79) forming part of said magnetic circuit means (6a, 6b, 12a, 12b, 13a, 13b, 20, 21, 44, 45, 68, 69, 70, 79), the latter defining a seat against which said armature can be applied with a first magnetic force generated by said magnetic circuit and opposite to that generated by the elastic deformation of said lever (19 , 35, 67), the coil (10a, 10b, 11a, 11b, 71, 72) associated with each magnetic circuit being selectively excitable and capable of generating a second magnetic force opposite to that of the magnetic circuit for, when the armature (20, 21, 44, 45, 79) associated with this coil is applied to its seat, release this frame and apply the other frame to its seat by tilting said lever (19, 35, 67). Device according to claim 1, characterized in that it forms a microrelay and in that said means for performing said function comprise at least one fixed contact (27, 33, 34, 51, 52, 76, 77) provided on said substrate and at least one movable contact (26, 31, 32, 49, 50, 74, 75) carried by said lever forming rocker (19, 35, 67), this movable contact being intended to be applied on said fixed contact when said armature (20, 21, 44, 45, 79) is applied to its seat. Device according to either of Claims 1 and 2, characterized in that each magnetic circuit comprises a permanent magnet (6a, 6b, 68) made of a very hard magnetic material. Device according to either of Claims 1 and 2, characterized in that each magnetic circuit comprises a magnet (6a, 6b, 68) made of hard or semi-hard magnetic material. Device according to either of Claims 3 and 4, characterized in that the said magnet has the form of a patch attached to the said substrate. Device according to either of Claims 3 and 4, characterized in that the said substrate is made of a magnetic material and in that the said magnet is formed by a magnetized region of the said substrate. Device according to any one of claims 4 to 6, characterized in that said coils (10a, 10b, 11a, 11b, 71, 72) are arranged to be further excited in order to generate said first magnetic force. Device according to any one of Claims 2 to 7, characterized in that at least one movable electrical contact (26, 31, 32, 49, 50, 74, 75) is provided at each end of said lever (19, 35 , 67). Device according to any one of claims 2 to 8, characterized in that each of said movable electrical contacts (26, 31, 32, 49, 50, 74, 75) is carried by a connecting element (24, 25, 46, 47, 73) integral with said lever and extending transversely relative to the latter. Device according to claim 9, characterized in that said connecting element (24, 25, 46, 47) is elastically deformable and put under elastic stress when said movable contact (26, 31, 32, 49, 50) is applied to said fixed contact (27, 33, 34, 51) under the action of said first force. Device according to either of Claims 9 and 10, characterized in that the said connecting element (24, 25) is electrically insulated with respect to the said lever. Device according to any one of Claims 8 to 10, characterized in that at least two movable contacts (31, 32) are provided at at least one of the ends of said lever (35) located on either side of this, and in that the lever (35) is made in two elongated parts extending parallel one next to the other and electrically isolated from each other. Device according to any one of Claims 8 to 12, characterized in that the said lever (35) is electrically isolated from the said substrate. Device according to any one of the preceding claims, characterized in that the said lever (67) is folded back on itself on either side of its point of attachment to the said substrate (1). Device according to any one of the preceding claims, characterized in that the said magnetic circuit comprises pole pieces (12a, 12b, 13a, 13b, 69, 70) forming the seat for applying the corresponding armature (20, 21, 44, 45, 79). Device according to claim 15, characterized in that each of the said pole pieces (12a, 12b, 13a, 13b, 69, 70) is surrounded by an excitation coil (10a, 10b, 11a, 11b, 71, 72). Device according to any one of the preceding claims, characterized in that the said lever (19, 35, 67) is attached to the said substrate (1) by means of at least one torsion arm (17, 18, 65, 66 ). Device according to Claim 5, characterized in that the said magnetic circuit comprises pole pieces (12a, 12b, 13a, 13b, 69, 70) forming the seat for applying the corresponding armature (20, 21, 44, 45, 79), in that each of said pole pieces (12a, 12b, 13a, 13b, 69, 70) is surrounded by an excitation coil (10a, 10b, 11a, 11b, 71, 72) and in that said substrate (1) has on one of its faces (3) cavities (4, 62) intended to accommodate said magnets (6a, 6b, 68) and in that the remainder of each magnetic circuit is disposed on the opposite face (2) of said substrate (1). Device according to claim 18, characterized in that on said opposite face (2) of said substrate (1) is provided an insulating layer (8) in which said coils (10a, 10b, 11a, 11b, 71 are embedded), 72) and said pole pieces (12a, 12b, 13a, 13b, 69). Device according to any one of Claims 1, 5 to 7 and 14 to 18, characterized in that said function consists in acting on a beam of light rays (FL) and in that said magnetic circuit comprises a movable armature (79) capable of intercepting said beam to interrupt and / or reflect it as a function of the position of said lever (67).

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