Cooling device for electronic components using liquid coolant

Abstract

There is provided a device for cooling a component, including a support configured to receive a component to be cooled, the support including a fluid network configured for liquid circulation therein, the network including a first cavity, a second cavity, and a first channel connecting the first cavity to the second cavity, a first deformable membrane and a second deformable membrane configured to form a mobile wall of the first cavity and a mobile wall of the second cavity respectively, the device further including an actuating device configured to actuate the first membrane and the second membrane, and a thermal conducting element close to the channel or in contact with the channel.

Claims

1. A device for cooling at least one component, comprising: a support having a first face and a second face opposite the first face, the first face being configured to receive at least a component to be cooled, the support comprising a fluid network configured to circulate a liquid therein, the fluid network comprising a first cavity, a second cavity, and at least one first channel connecting the first cavity to the second cavity, a first deformable membrane and a second deformable membrane forming a mobile wall of the first cavity and a mobile wall of the second cavity, respectively, the support further comprising an actuating device configured to actuate the first membrane and the second membrane, the actuating device being provided with actuation electrodes and being configured to enable deformation of the first and/or the second membrane so as to vary a volume of the first cavity and/or a volume of the second cavity and to enable displacement of the liquid in the at least one first channel; and a thermal conducting element extending through the support and being disposed between a wall of the at least one first channel and the second face of the support, the thermal conducting element passing through a first material of the support and being in at least a second material, the first material having a first thermal conductivity, and the second material having a second thermal conductivity greater than the first thermal conductivity.

2. The device according to claim 1, wherein the actuating device is configured to alternately: displace the first membrane so as to reduce the volume of the first cavity, and then displace the second membrane so as to reduce the volume of the second cavity.

3. The device according to claim 2, wherein the actuating device is further configured to: jointly, with displacement of the first membrane so as to reduce the volume of the first cavity, displace the second membrane so as to increase the volume of the second cavity, and then jointly, with displacement of the second membrane so as to reduce the volume of the second cavity, displace the first membrane of the first cavity so as to increase the volume of the first cavity.

4. The device according to claim 1, wherein the actuating device comprises: at least one first electrode located on the first membrane, and at least one second electrode located on the second membrane.

5. The device according to claim 4, wherein the actuating device further comprises at least one fixed electrode located on the support and facing the first electrode in the first cavity and/or facing the second electrode in the second cavity.

6. The device according to claim 5, the fixed electrode being located on one or several protuberances of the support facing the first electrode and/or facing the second electrode.

7. The device according to claim 4, wherein the first membrane or the second membrane comprises a layer of piezoelectric material.

8. The device according to claim 5, wherein the actuating device further comprises biasing means for biasing the first electrode and the second electrode, the biasing means being integrated into the support.

9. The device according to claim 5, wherein the actuating device further comprises biasing means for applying a first potential to the first electrode and a second potential to the second electrode, the second potential being different from the first potential.

10. The device according to claim 1, wherein the thermal conducting element is connected to a heat conducting zone located on said second face of the support.

11. The device according to claim 1, further comprising an electrical connection element passing through the support and connecting the first face of the support and the second face opposite the first face.

12. The device according to claim 1, further comprising m cavities, where m is greater than or equal to 2, and at least n channels where n is greater than or equal to 1, such that the fluid network connects all of the m cavities together.

13. The device according to claim 1, further comprising means for measuring the temperature of the component, and a control means for controlling the actuator as a function of the temperature measured by the measurement means.

14. The device according to claim 1, wherein the thermal conducting element has a first end located at the at least one first channel and a second end located at said second face of the support.

15. The device according to claim 14, wherein the second material is an electrically conducting material or a metal.

16. A device for cooling at least a component, comprising: a support having a first face and a second face opposite the first face, the first face being configured to receive at least a component to be cooled, the support comprising a fluid network configured to circulate a liquid therein, the fluid network comprising a first cavity, a second cavity, and at least a first channel connecting the first cavity to the second cavity, a first deformable membrane and a second deformable membrane forming a mobile wall of the first cavity and a mobile wall of the second cavity, respectively; and a thermal conducting element disposed between a wall of the at least one first channel and said second face of the support, the thermal conducting element extending through a region of the support and being in a material having a thermal conductivity that is greater than a thermal conductivity of the region.

17. The device according to claim 16, wherein the thermal conducting element has a first end located at the at least one first channel and a second end located at the second face of the support.

18. The device according to claim 17, wherein the material is an electrically conducting material or a metal.

19. A device for cooling at least a component, comprising: a support having a first face and a second face opposite the first face, the first face being configured to receive at least a component to be cooled, the support comprising a fluid network configured to circulate a liquid therein, the fluid network comprising a first cavity, a second cavity, and at least a first channel connecting the first cavity to the second cavity, a first deformable membrane and a second deformable membrane forming a mobile wall of the first cavity and a mobile wall of the second cavity, respectively; and a thermal conducting via extending through a region of the support and having a first end located at the channel and a second end located at a second face of the support, the thermal conducting via being in at least a given material having a thermal conductivity that is greater than a thermal conductivity of the region of the support, the given material being an electrically conducting material or a metallic material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) This invention will be better understood after reading the following description of example embodiments given purely for information and in no way limitative, with reference to the appended drawings on which:

(2) FIG. 1A shows a first example of a device comprising a fluid network located close to a component to be cooled and in which a liquid is circulated by actuation of deformable membranes;

(3) FIGS. 1B-1C show a particular example actuation of membranes so as to apply a to and fro movement on the cooling liquid in the fluid network;

(4) FIG. 2 shows an embodiment wherein a thermal conducting element is placed in contact with the fluid network to improve heat dissipation;

(5) FIG. 3A shows a variant layout of the fluid network provided with one additional fluid channel facing the component;

(6) FIG. 3B shows a variant layout of the fluid network provided with two convergent channels connected to a third channel;

(7) FIGS. 4 and 5 show variant layouts of fluid networks provided with several channels intersecting each other facing the component to be cooled;

(8) FIG. 6 shows an example embodiment of electrostatic actuation means of the mobile membranes;

(9) FIG. 7 shows a particular example configuration of electrostatic actuation means comprising electrodes located under the deformable membranes;

(10) FIG. 8 shows a variant embodiment with an additional conducting zone to improve distribution of heat dissipation;

(11) FIGS. 9A-9B show an example embodiment in which a connecting element is arranged to enable contact to be made on the component to be cooled;

(12) FIGS. 10 and 11 show various example configurations of actuation electrodes in the form of protuberance(s) to improve the deformation of membranes;

(13) FIG. 12 shows an example embodiment of piezoelectric actuation means of deformable membranes;

(14) FIGS. 13A-13F show a first example of a method of making a fluid network device provided with membranes deformable by electrostatic actuation;

(15) FIGS. 14A-14C show a second example of a method of making a fluid network device with piezoelectric actuation;

(16) FIGS. 15A-15B show a first example of a method of filling the fluid network;

(17) FIGS. 16A-16C show a second example of a method of filling the fluid network;

(18) FIGS. 17A-17C show a third example of a method of filling the fluid network;

(19) Identical, similar or equivalent parts of the different figures have the same numeric references to facilitate comparison between the different figures.

(20) The different parts shown in the figures are not necessarily all at the same scale to make the figures more easily understandable.

(21) Furthermore, in the following description, terms that depend on the orientation such as under, on, above, upper, lower etc. of a structure should be understood assuming that the structure is oriented as shown in the figures.

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

(22) An example of a device provided with a fluid network suitable for cooling an electronic or electromechanical component is shown in FIGS. 1A-1B (FIG. 1A showing a top view while FIGS. 1B and 1C show a cross-sectional view of a first and second position of the device respectively).

(23) The fluid network is formed in a support 1 on which a component 2 will be located. The support 1 may be in the form of a substrate, for example based on silicon. The fluid network is located close to the component 2 and includes a channel 3 through which a liquid passes to cool the component. The channel 3 connects a first cavity 6 and a second cavity 7 between which the liquid can circulate. In the particular example in FIGS. 1A and 1B, a wall of the channel 3 is arranged under and in contact with the component 2 in order to provide better cooling. The channel 3 extends in one direction, called main direction between the first cavity 6 and the second cavity 7. The main direction of the channel is a direction taken parallel to the x-axis of an orthogonal reference [O; x; y; z] shown in some figures.

(24) The cooling liquid is chosen so as to have good thermal conductivity and low viscosity. For example, it may be water or oil or glycol or even a metal in liquid form. A mix of liquids may also be provided. The liquid may also comprise conducting particles, for example of the metal nanoparticles type, so as to improve heat exchanges between the component and the support.

(25) Liquid circulation in the channel 3 is achieved by displacement of one or several deformable membranes 4, 5 attached to the support 1 and forming a mobile wall of the first cavity 6 and a mobile wall of the second cavity 7 respectively. The cavities 6, 7 are also provided with fixed walls 8, 9 formed in the support 1.

(26) Deformation of the membranes 4, 5 and their displacement between several positions can thus alternately reduce or increase the volume of cavities 6, 7 in order to alternately tend to expel liquid from the cavities 6, 7 or draw liquid into them. Modulation of the volume of cavities 6, 7 can thus generate liquid displacements. Actuation of membranes 4, 5 can be arranged such that the deformation applied to one membrane is different from the deformation applied to the other membrane.

(27) In the particular example embodiment in FIG. 1, the membranes 4, 5 are in the form of a disk with a radius R for example between 1 and 10 mm. The height or depth H of the cavities 6, 7 may for example be between 50 and 500 m.

(28) FIGS. 1B and 1C show a particular actuation example of membranes 4, 5, in which the volume of the cavities 6 and 7 is varied alternately.

(29) FIG. 1B shows a first position of the device in which the first cavity 6 has a given volume that may be maximum and corresponds to a first position of the first membrane 4, while the second cavity 7 has another volume that may be minimum and corresponds to a first position of the second membrane 5.

(30) FIG. 1C shows a second position of the device, the first cavity 6 then having a minimum volume corresponding to a second position of the first membrane 4, while the second cavity 7 has a maximum volume corresponding to a second position of the second membrane 5.

(31) Actuation means of membranes 4, 5 can thus be configured so that the device can be moved from the first to the second position and vice versa according to a predetermined sequence. The result is that a to and fro movement of liquid is created in the channel 3 in order to improve cooling of the component 2 located above it.

(32) A variant embodiment of the device described above also includes a thermal conducting element 26 passing through the support 1 and arranged close to the fluid channel 3 or in contact with it. Close to in this case means that the element 26 is located at a distance of less than 100 m from the channel. This facilitates heat dissipation to the outside when the liquid that is in channel 3 is heated due to heating of component 2.

(33) In the example embodiment shown in FIG. 2, the thermal conducting element 26 extends from the channel 3 as far as face 1b of the support 1, called the back face in other words a face opposite the face called the front face and denoted 1a, on which the component 2 is located. The thermal conducting element 26 may be based on a material with a thermal conductivity higher than the thermal conductivity of the material from which the support 1 is made. The thermal conducting element 26 may be metallic, for example based on Cu, and may be made using a technology similar to that used for a TSV (Through Silicon Via) type electrical connection element.

(34) The thermal conducting element 26 may be coated with a barrier layer to metal diffusion, for example made of titanium nitride. This barrier layer to diffusion may itself be coated with a layer of dielectric material for example such as SiO.sub.2, particularly when the support 1 is based on a semiconductor or conductor.

(35) The thermal conductive member 26 may also be coated and in contact with a thermal insulation layer. This will favour the diffusion of heat by the thermal conductive element 26 without loss on the sides. As an example, the thermal insulation layer may be SiO.sub.2.

(36) The device is not limited to a single thermal conducting element passing through the support 1 and it may include one or several additional thermal conducting elements, the dimensions and distribution of which are adapted as a function of an estimate of the position of heating points of the component 2.

(37) The device is not limited to a fluid network provided with a single channel and two cavities. The device may be provided with n fluid channels (where n1) and m cavities (where m2) to form the fluid network.

(38) In this case, a matrix layout of membranes or flexible walls may be made, some membranes possibly following different movement or deformation sequences relative to each other.

(39) Another example embodiment, shown in FIG. 3A, includes a fluid network provided with a plurality of fluid channels 3, 30 under the component 2, and particularly a second channel 30 comprising two additional cavities 36, 37 at its ends, between which a liquid will circulate. Displacement of membranes 34, 35 forming the mobile walls of these additional cavities located at the ends of the second channel 30 provides a means of moving a liquid in this second channel 30. The channels 3, 30 may be arranged to communicate with each other. The fluid network is not necessarily limited to two channels. On the layout of the fluid network in FIG. 3A, the channel 3 follows a first direction (the direction of the x axis in FIG. 3A) while the other channel 30 follows a second direction (the direction of the y axis in the orthogonal coordinate system [O; x; y; z] in FIG. 3A) different from the first direction and that may be orthogonal to the first direction.

(40) FIG. 3B shows another fluid network layout, with two first convergent channels 3.sub.2, 3.sub.3 connected through one end to a third channel 3.sub.1. The first two channels 3.sub.2, 3.sub.3 are each provided with another end, this other end opening up into a cavity. The cavities to which the channels 3.sub.2, 3.sub.3 are connected are advantageously similar in size to each other and membranes 34, 35 are installed on top of them. The third channel 3.sub.1 opens up in a cavity above which there is another membranes 5 and has a volume greater than or equal to the sum of the volumes of the cavities located at the ends of the channels 3.sub.2, 3.sub.3. The cross-section of the third channel 3.sub.1 is advantageously equal to the sum of the cross-sections of the first two channels 3.sub.2, 3.sub.3. In this case, the first two channels 3.sub.2, 3.sub.3 advantageously have the same cross-section. The deformable membranes 34, 35 may be actuated at the same time and they may have the same displacement or the same deformation so as to cause a to and fro movement of the liquid between the cavity with the largest volume and the other cavities with a smaller volume.

(41) FIG. 4 shows another example configuration of the cooling fluid network, with channels or segments of channels intersecting and communicating with each other. The channel 3 forms a main portion communicating with other secondary portions 3, 3 that may be parallel to each other and connected to this main portion through segments orthogonal to the main portion.

(42) The variant embodiment in FIG. 5 further includes a channel 30 orthogonal to the main channel 3.

(43) In order to limit head pressure drops in the fluid network, the channels 3, 3, 3 may be provided with a cross-section with a rounded shape, or possibly an ovoid or circular shape. The cross-section in this description refers to a cross-section taken parallel to the z axis in the orthogonal coordinate system in FIGS. 4 and 5 or orthogonal to the main plane of the support (the main plane of the support being a plane passing through the support and parallel to the [O; x; y] plane in FIG. 3). Pressure drops may further be limited at channel intersections by assuring that angles at intersections between the channels are less than 90.

(44) In each of the other example embodiments described above, the movement of the membranes 4, 5 forming the mobile walls of cavities 6, 7 from one position to the other position to enable expansion or contraction of the volume of these cavities 6, 7 and displacement of the liquid in the channel(s) of the fluid network, is controlled through actuation means.

(45) FIG. 6 shows one example embodiment of the actuation means 60 of the electrostatic type. The liquid is moved in a channel 3 connecting cavities 6, 7 in this case by varying the electrostatic attraction forces applied on the membranes 4, 5.

(46) The membranes 4, 5 are provided with separate electrodes 67, 68 for this purpose, facing a fixed electrode 69 integrated into the support 1.

(47) An independent control of the mobile electrodes 67, 68 relative to each other may be provided to modulate the volume of the cavity 6, for example by increasing it, while modulating the volume of the cavity 7 differently, for example by reducing it. In this example embodiment, the electrodes 67, 68 are not connected to each other and they may be thus biased independently of each other. The result is that one membrane can be deformed while the other membrane is deformed in a different manner depending on the potentials applied to each of them.

(48) The electrodes 67, 68 fixed to membranes 4, 5 are free to move and move towards or away from the fixed electrode 69 depending on the potential applied to them. In this example embodiment, the shape of a membrane 4, 5 is varied by modulating the attraction between a mobile membrane electrode 67, 68 and a fixed support electrode 69. The potentials applied to the electrodes may for example be of the order of ten volts.

(49) The actuation means may include control means 65 configured to control the biasing of electrodes and adapted to place the electrodes 67, 68 in a biasing state in which at least one first electrode 67 is brought to a first potential V1, and at least one other electrode 68 is brought to a second potential V2, where V2V1. Thus, the electrodes 67, 68 may be controlled independently of each other by the biasing control means 65. The electrode biasing control means 65 may be in the form of a circuit comprising an addressing circuit of the electrodes 67, 68. The control means 65 in FIG. 6 are integrated into the support 1.

(50) In the example embodiment shown in FIG. 6, the fixed electrode 69 is advantageously connected to the thermal conducting element 26 that then is also an electricity conducting element and can make a contact. The fixed electrode 69 may be a common electrode and arranged facing a set of several electrodes 67, 68.

(51) In the particular example shown in FIG. 6 in which the electrode 69 acts as a common fixed electrode, it may also be used to facilitate assembly between an upper part of the device comprising the mobile electrodes 67, 68 and a lower part comprising the fixed electrode 69. This is the case, for example, when the electrode 69 is based on a metal such as Cu or Au and the assembly is made by metal/metal bonding, for example Copper to Copper or gold to gold. The distance between the mobile electrode 67 or 68 and the fixed electrode 69 may be such that the volume of the cavities 4, 5 may be varied by between 5 and 50%.

(52) Actuation of the membranes 4, 5 by means of the control means 65 may be slaved to or triggered by temperature measurements made locally in component 2. Thus, the control means may be adapted to detect a signal showing a temperature rise of the component 2. Temperature measurement means, for example in the form of a built-in thermometer made from at least one transistor, may be integrated and may measure the temperature locally and control another logical circuit controlling the control means.

(53) In the example in FIG. 6, the electrodes 67, 68 are arranged on the membranes 4, 5.

(54) It would also be possible to position the electrodes 67, 68 under the membranes 4, 5, for example such that they are located in the cavities 6, 7 (FIG. 7). In this case, the mobile electrodes 67, 68 are brought closer to the fixed electrode 69 that makes it easier to actuate the electrodes with lower voltages.

(55) The fixed electrode 69 may be in contact with the thermal conductive member 26, thereby making it possible to place the fixed electrode 69 at a given potential applied to the thermal conductive member 26, when the latter is also electrically conductive.

(56) A variant embodiment shown in FIG. 8 shows that the conducting zone 86 may be integrated on the back face 1b of the support 1. This conducting zone 86 is connected to a thermal conducting element 26 passing through the support 1, that distributes heat on the back face 1b of the support 1. This conducting zone 86 may be made of metal, for example such as copper, and it may have a thickness of between several micrometers and several tens of micrometers. The conductive zone 86 may be intended to receive a radiator or heat sink structure in order to dissipate the heat conveyed by the thermal conductive element 26 and the conductive zone 86. The radiator or sink structure may be fixed e.g. by direct bonding or be formed by 3D printing.

(57) Another variant embodiment shown in FIGS. 9A-9B, includes a connecting element 90 configured to make electrical contact on the component 2 that is to be cooled. This connecting element 90 may be in the form of a via passing through the support 1 that extends between the front face 1a and the back face 1b of the support 1. It is thus possible to electrically connect the component 2 to be cooled through the back face of the support 1. The connecting element 90 may be arranged so as to pass through the support 1 without being in contact with the fixed electrode 69.

(58) FIGS. 10 and 11 show different variant layouts of the fixed electrode 69 facing a membrane 4.

(59) The support 1 may comprise a relief pattern 102 also called a protuberance, that is arranged in a cavity 6 and on which the fixed electrode 69 is arranged. This can bring the mobile electrode 67 closer and provides better control over deformation of the membrane 4 on which the mobile electrode 68 is located (FIG. 10).

(60) Several other protuberances 112, 114 may be provided with different heights, to facilitate deformation of the membrane and make it have a different profile. FIG. 11 shows a particular example embodiment in which the peripheral protuberances 112, 114 with height H.sub.2 are formed around a central protuberance 102 with height H.sub.1, where H.sub.1<H.sub.2.

(61) The geometries of the peripheral protuberances 112, 114 in a plane parallel to the main plane of the support 1 may be different.

(62) The addition of peripheral protuberances 102, 112, 114 can also reduce biasing voltages necessary to deform the membrane 4.

(63) Another example embodiment of the device with piezoelectric type actuation means is shown in FIG. 12. Membranes 4, 5 are provided with electrode pairs 67, 127 and 68, 128 respectively located on each side of a layer 125 or a stack comprising at least one sub-layer based on a piezoelectric material such as for example PZT (Lead Zirconate Titanium) so as to enable deformation of the membranes. The first membrane 4 is deformed by applying a first pair of potentials to electrodes 67, 127, while a second pair of potentials is applied to electrodes 68, 128, in order to deform the second membrane 5.

(64) A fluid network device like that described above is suitable for cooling microelectronic devices or chips or microsystems that can release heat that has to be dissipated to assure that the components will work correctly and have a reasonable life. In particular, chips of integrated circuits made using a 3D technology can be cooled, in other words made with elements such as transistors, distributed on several levels of superposed semiconducting layers.

(65) A fluid network device like that described above may be compact along the z direction, so that it can be integrated into devices requiring a small dimension along z, for example such as portable telephones or tablets.

(66) One example embodiment of a fluid network device like that described above will now be described with reference to FIGS. 13A-13F.

(67) FIG. 13A shows a step of manufacturing a fixed electrode 69 by deposition of a metal layer 132 on a front face of a first substrate 131 that will form a lower part of support 1. The first substrate 131 may be semiconducting and for example based on Si. The metal layer 132 may be made of copper and its thickness may for example be of the order of one micron. When it is required to make a fixed electrode 69 covering one or several relief patterns or protuberances such as in the example in FIGS. 10, 11, the substrate 131 is formed before the metal deposit, for example by etching.

(68) A thermal conducting element 26 that comes into contact with the metal layer 132, may be made by the formation of a hole passing through the first substrate 131. The hole may be made for example by photolithography and then for example by DRIE (Deep Reactive Ion Etching) type etching stopping on the metal layer 132. The width of the conducting element 26 may be between 10 and several hundred microns.

(69) When this width is smaller, the substrate 131 could be thinned through its back face beforehand. The hole is then coated with an electrical insulating layer, for example based on SiO.sub.2, and for example with a thickness of the order of several hundred nanometers.

(70) A barrier layer to metal diffusion could then possibly be deposited in the hole. This barrier layer may be for example based on TiN, and its thickness may for example be several tens of nanometers. These insulating barrier layers are then etched at the bottom of the hole before the hole is filled with a metal material.

(71) The metal filling material may for example be copper. Filling may be done by physical vapour deposition (PVD) or for example by chemical vapour deposition (CVD), and then by electro-chemical deposition.

(72) As a variant, the thermal conducting element 26 may be made before the fixed electrode 69 is formed.

(73) A lower conducting portion 133a of the connecting element 90 as shown in the FIGS. 9A-9B can also be made during the formation of the thermal conducting element 26. This portion 133a can thus be made at the same time as the element 26 by the formation of a hole in the substrate 131 then filling of the hole with the metal material.

(74) In order to make an upper part of the support 1 on which the membranes 4, 5 and mobile electrodes 67, 68 will be fixed, a second substrate 134 may be provided on which metal zones 135 are formed (FIG. 13B). The metal zones 135 may for example be based on copper and their thickness may for example be of the order of one micron. These metal zones 135 are designed to allow assembly between the two substrates 131 and 134. In the case in which the planned assembly method is direct bonding, and particularly copper to copper bonding, a surface preparation of the zones 135 and the surface of the layer 132 may be made by chemical-mechanical polishing (CMP).

(75) An upper conducting portion 133b of a connecting element 90 (like that shown in FIGS. 9A-9B) may also be made in the second substrate 134. This upper conducting portion 133b is formed in contact with a region of the second substrate on which a component to be cooled will be placed.

(76) In the second substrate 134, a fluid network is then formed comprising at least one channel and cavities at the ends of the channel.

(77) The next step is to assemble a first substrate 131 and a second substrate 134 (FIG. 13C).

(78) The assembly may be made according to a direct bonding method, advantageously metal/metal (Cu/Cu or Au/Au) or by fuse brazing using a eutectic alloy for example such as AuSn (with a melting temperature of the order of 280 C.), or for example based on AuSi (with a melting temperature of the order of 363 C.) or AIGe (with a melting temperature of the order of 419 C.). Direct oxide/oxide (SiO.sub.2/SiO.sub.2) bonding is possible as a variant.

(79) The assembly between the two substrates 131, 134 is designed so that a support provided with a sealed fluid network is formed. During this step, assembly of the lower conducting portion 133a made in the first substrate 131 and the upper conducting portion 133b made in the second substrate 134 may also be made by direct bonding so as to form the connecting element 90.

(80) The next step is to thin the back face of the second substrate 134, in order to make openings 136, 137 exposing cavities 6, 7 respectively (FIG. 13D).

(81) The next step is to fill the cavities and channels by dispensing an appropriate liquid L through the openings 136, 137 (FIG. 13E). The liquid L may for example be dispensed by inkjet.

(82) The next step is to close the cavities 6, 7 by forming the membranes 4, 5. This is done by rolling a film 138 that can be flexible, for example based on a photosensitive resin or Polyethylene Terephthalate (PET), or silicone. This film 138 is suitable for bonding to the second substrate 134 and it may be etched so as to form several distinct membranes. It would also be possible to make a prior glue deposit for example a UV setting glue on the second substrate 134 to enable bonding of the flexible film 138. In this case, the film 138 is bonded onto the substrate 134 by the glue setting after the film 138 has been transferred onto the substrate 134. The film 138 may be between several microns and several hundred microns thick.

(83) The next step is to deposit mobile electrode patterns by photolithography and etching. The metal deposit may be preceded firstly by a bonding layer to the metal material. The bonding layer may for example be based on Cr or Ti and it may be several tens of nm thick. The metal electrode material may for example be copper, with a thickness of between several ten and several hundred nm (FIG. 13F).

(84) The next step may be to assemble a component on a region 139 of the second substrate 134 located between the membranes 4, 5, and exposing a connecting element 90 formed by bonding of conducting portions 133a and 133b.

(85) As a variant of the previously described method, when it is required to make a device like that shown in FIG. 7 with electrodes located under the membranes, these electrodes are formed on the film 138 before the film is transferred on the support.

(86) Another variant method for the use of a piezoelectric actuation device, is shown in FIGS. 14A-14C.

(87) In this example, the steps in a method such as that described previously with reference to FIGS. 13A-13C may be performed, except for formation of a fixed electrode 69 that is not compulsory in this case. The result is that two substrates 131, 134 are assembled to form a support in which a fluid channel 3 and cavities 6, 7 are provided (FIG. 14A).

(88) Then (FIG. 14B), the back face 134a of the second substrate 134 is thinned so as to keep a thickness for example of the order of several microns. The membranes are formed from thinned zones 141, 142 of the second substrate 134 and located facing cavities 6, 7.

(89) Zones based on the insulating material 144 are then formed on thinned zones 141, 142. An electrical insulating material 144 for example such as SiO.sub.2, for example several hundred nm thick to several micrometers thick, may be deposited for this purpose and shaped by photolithography and etching.

(90) The next step is to form lower electrodes on zones made from the insulating material 144. This is done by using deposition and then formation steps of a layer based on a metal material 145, for example such as platinum or ruthenium and, for example with a thickness of the order of several hundred nanometers.

(91) Zones made from piezoelectric material 146 are then formed on the lower electrodes. This is done by deposition and formation steps of a layer of piezoelectric material 146. The piezoelectric material 146 may for example be based on PZT and its thickness may be between several micrometers and several tens of micrometers.

(92) The next step is to form upper electrodes on zones of piezoelectric material 146 (FIG. 14C). This may be done by depositing and forming a layer based on a metal material 147 for example such as gold and for example with a thickness of the order of several hundred nanometers.

(93) A first example method of filling the fluid network is shown in FIGS. 15A-15B.

(94) Filling may then be done by dispensing through one or several holes or vents 151, 152 formed in the support and advantageously placed around the periphery of membranes 4, 5, the vents 151, 152 opening up into the fluid channel 3 (FIG. 15A).

(95) In this case, the vents 151, 152 are closed after the fluid network has been filled with a liquid L. This may be done for example by rolling a layer of flexible material 154, for example based on PET, or a silicone layer (FIG. 15B).

(96) As a variant of the method described above, holes or vents 161, 162 may be made in the membranes, for example by drilling (FIG. 16A). This drilling may be done after having formed the lower electrodes, the piezoelectric material layer 146 and the upper electrodes. In this case, an appropriate design will be chosen for the electrodes, for example perforations in the part common to the lower and upper electrodes. The fluid circuit is then filled with a liquid L dispensed using vents 161, 162 (FIG. 16B).

(97) The vents 161, 162 are then closed off by means of a film 164. The film 164 may be formed by rolling and be based on polymer (FIG. 16C).

(98) As a third variant of the two manufacturing methods described above, vents 171, 172 are made through the back face of the substrate 131 (FIG. 17A). It is possible to take advantage of the step described above to make the thermal conductor 26 passing through the thickness of the substrate to excavate vents 171, 172. Thus, the vents 171, 172 can be made in the same etching step as the step in which a hole is made in which the heat conductor 26 is housed.

(99) Then, after the fluid network has been filled with liquid L through vents 171, 172 (FIG. 17B), the vents 171, 172 are closed off for example by rolling a layer of flexible material 174 (FIG. 17C) as described in the previous two variants.