WO2002037511A1

WO2002037511A1 - Method for making a sealed feedthrough with integrated capacitor and resulting element

Info

Publication number: WO2002037511A1
Application number: PCT/FR2001/003387
Authority: WO
Inventors: Yvan Paquin
Original assignee: Saint-Gobain Ceramiques Avancees Desmarquest
Priority date: 2000-11-03
Filing date: 2001-10-31
Publication date: 2002-05-10
Also published as: AU2002223727A1; FR2816443A1

Abstract

The invention concerns a method for making a closing and electrically connecting element adapted to be mounted sealed in a housing of an implantable medical equipment, and the resulting closing and electrically connecting element. Such a closing and electrically connecting element is sometimes designated, by the term sealed feedthrough It is used in particular in cardiac assistance appliances, such as pacemakers or defibrillators. The process for producing the capacitor comprises a step which consists in depositing, on a support plate made of insulating material (20), metallised zones (25, 26) forming first and second electrodes and, on one surface of said support plate, at least a surface of electrically conductive layers (30, 31) separated by a dielectric material (32), and the integration of the electrodes with the conductor and with the cross-piece is carried out by soldering.

Description

Method for manufacturing a sealed bushing with integrated capacitor and element thus obtained

The invention relates to a method for manufacturing an electrical closure and connection element adapted to be mounted, in a sealed manner, in a hole in an implantable medical equipment case, and a closure and connection element electric thus obtained.

Such a shutter and electrical connection element is sometimes designated, for short, under the name of "watertight crossing". They are used in particular in cardiac assistance devices, such as pacemakers or defibrillators.

This sealed passage is used in particular to ensure the connection between the internal electronics of the cardiac equipment and a probe connected to the heart muscle.

The equipment housing generally forms a FARADAY cage, so that it is the watertight crossing which constitutes the weak point of the equipment from the point of view of electromagnetic disturbances. It is clear, in fact, that it is useful to protect implantable equipment, such as a pacemaker or a defibrillator, from electromagnetic disturbances which may be generated with the patient, for example due to the use a mobile phone or when crossing a security gate at an airport, for example.

This is why it has been proposed to provide watertight bushings with an electromagnetic filtering capacitor, designed so as to be able to filter a range of frequencies liable to interfere with the operation of the equipment, and to protect the internal electronics of the last. Such protection is now demanded by American official bodies, and could even become compulsory in the short term.

Various solutions have already been proposed, in particular by the following documents:

- EP - A1 - 0 331 959

- EP - A1 - 0 776 016

- EP - A1 - 0 916 364

- WO - A1 - 97/20332 - WO - A1 - 97/41923

- WO - A1 - 98/30281

- US - A - 4,424,551

- US - A - 5,333,095

- US - A - 5,620,476 - US - A - 5,825,608

- US - A - 5,836,992.

As a general rule, the solutions proposed use solid capacitors, which are then attached, most often by gluing, either on the bushing ensuring the functions of obturation and electrical connection, or on the wall of the housing, the contents of which are to protect.

However, the massive nature of certain capacitors makes it costly to manufacture and sometimes leads to a space requirement (all the more so since the crossing with which the capacitor is associated is often shaped so as to contain this capacitor. Furthermore, fixing by gluing, which is very widely used in the field, has certain drawbacks in that its application is not always easy to control, especially in the range of sizes imposed on implantable equipment, and that it is necessary, to avoid any contamination in service, proceed with specific degassing operations. The object of the invention is to overcome the aforementioned drawbacks, by means of a manufacturing process and a structure of such shutter and electrical connection equipment which lead to a moderate cost (thanks to of the inexpensive technologies well mastered and easy to implement), small footprint and high reliability.

To this end, it proposes a method of manufacturing an obturation and electrical connection element adapted to be mounted in an orifice of an implantable medical equipment case, comprising steps according to which:

a crossing is made, at least part of which is electrically conductive and which is adapted to be fixed to the housing, this crossing comprising at least one space for the passage of an electrical conductor,

a capacitor is produced having at least a first electrode, at least a second electrode and at least one passage orifice for the electrical conductor,

this electrical conductor is engaged in the space defined in the crossing and in the orifice for the passage of the capacitor,

- the capacitor is secured to the bushing and this first electrode is electrically connected to the electrical conductor and this second electrode to the electrically conductive part of the ferrule, characterized in that the step of producing the capacitor includes a deposition step, on a support plate of insulating material in which this passage orifice is formed, of metallized zones forming the first and second electrodes and, on one face of this support plate, of at least one pair of electrically conductive layers separated by a layer of dielectric material, these layers being respectively connected to these first and second electrodes, and the joining and connection step includes a step of soldering the first electrode to the electrical conductor of the second electrode at the crossing.

It should be noted that, conventionally, the layers of the capacitors constitute the main part of the thickness thereof, whereas, according to the invention, although one seeks to reduce the bulk, a plate is used, the main function is to support diapers. However, the space required remains very moderate, especially since this capacitor has a generally planar shape, which can be much less annoying than a massive shape. On the other hand, the use of such a support makes it possible to take advantage of techniques for depositing well known and controlled layers, therefore inexpensive and reliable. This is in particular the case of metallization techniques, on the one hand, and, preferably, of deposition in thick layers or screen printing (technique well known for the production of hybrids, in electronics).

In addition, the use of capacitors of generally planar shape, produced in the form of layers on a support, lends itself very well to a method of fixing having undeniable advantages with regard to bonding, namely brazing, c '' is to say a fixing of welding by addition of material. Indeed, this technique is precise and does not then lead, in service, to any degassing, this being completely carried out during brazing: it therefore does not lead to any contamination and ensures better adhesion than bonding; in addition it and has greater reliability during the subsequent operation of welding the bushing on the stimulator housing. For these brazing operations, it is possible in particular to use alloys making it possible to resist the subsequent operation of welding the bushing on the housing without altering the connection of the bushing, for example Ag / Cu. The choice of the material of the support plate depends on the temperature at which the brazing is carried out (depending on the nature of the added material). It is advantageously a ceramic, all the more economical to produce since the general shape is generally flat; furthermore its high melting temperature leaves the user with a large choice for soldering temperatures. Among the ceramics which can be used, there may be mentioned alumina, because of its low cost price.

Insofar as the choice of material (or materials, where there are several) of the support plate allows, the brazing steps are advantageously carried out simultaneously. The crossing may comprise several parts assembled by brazing, with gold for example. In this case, the capacitor brazing operations are carried out with materials corresponding to temperatures of lower brazing, for example Ag / Cu, Ag / Cu / Pd, Gold / Cu etc .. corresponding to temperatures of 780 ° to 960 ° C while gold corresponds to a brazing temperature of 1063 ° C.

Preferably, the first electrode is produced, namely that intended to be connected to the electrical conductor, by metallization of the interior of the passage orifice in which this conductor is engaged. This facilitates good electrical contact without interfering with the soldering operation in the immediate vicinity.

In an equally preferred manner, the second electrode is produced by metallization of a portion of the rear face of the support plate (if “front face” designates the face of this support plate on which the various layers are produced electrically conductive or dielectric). Two means, in particular, can be used to connect this second electrode to those layers of the capacitor that we want to connect to it: a particularly simple way consists in metallizing at least part of the edge of the plate, between the second electrode and the layers concerned; or provide holes in the plate and metallize the internal surface (at least in part), which is a little more complex than the first solution, but has the advantage of reducing the areas to be metallized and minimizing the mechanical stresses on layers.

A layer protection is advantageously provided on the layers, for example consisting of a layer of dielectric material.

The invention also covers an element obtained according to the method, that is to say adapted to be mounted in an orifice of an implantable medical equipment case, comprising:

- at least one electrical conductor,

a bushing, at least part of which is electrically conductive and adapted to be fixed to the housing, this bushing comprising at least one orifice for the passage of this electrical conductor,

- a capacitor integral with this ferrule, having at least a first electrode electrically connected to the conductor electric and at least a second electrode electrically connected to the electrically conductive part of the ferrule, characterized in that the capacitor is formed of at least a pair of two electrically conductive layers respectively connected to metallization zones forming the first and second electrodes and separated by a dielectric layer, these layers being deposited on one face of a support plate made of insulating material, and these first and second electrodes are respectively connected by brazing to the electrical conductor and to the electrically conductive part of the bushing. This element lends itself to the same comments as the process defined above.

Objects, characteristics and advantages of the invention appear from the description which follows, given by way of nonlimiting illustrative example, with reference to the appended drawings in which: - Figure 1 is a block diagram of implantable medical equipment provided with an element according to the invention,

FIG. 2 is an elevation view of an element according to the invention, according to a first embodiment,

FIG. 3 is a sectional view along the line III-III of FIG. 2,

FIG. 4 is an enlarged view, in section, of the only capacitor of the element in FIGS. 2 and 3,

FIG. 5 is a view from below, along arrow V of FIG. 4, - FIG. 6 is a sectional view along the line VI-VI of FIG. 4,

FIG. 7 is an enlarged view of the lower part of the element in FIGS. 2 and 3,

FIG. 8 is a view similar to FIG. 4, showing another capacitor according to the invention according to a second embodiment, FIG. 9 is a bottom view thereof, along arrow IX of FIG. 8,

- Figure 10 is a top view, along arrow X of Figure 8, and - Figure 11 is a simplified flow diagram of a method of manufacturing an element according to the invention.

FIG. 1 schematically represents implantable medical equipment 10, which mainly comprises an electronic circuit 11 disposed inside a housing 12 comprising an outlet orifice allowing the connection of the circuit 11 to an external probe (not shown) through 'A shutter and electrical connection element 13 according to the invention.

The housing 12 is in practice made of a metallic material and consequently forms a FARADAY cage. Electromagnetic interference

(denoted R) are therefore mainly likely to affect this equipment at the location of the obturation element. This is why this element comprises, in a manner known per se, a filtering capacitor shown diagrammatically at 14.

Such a closure element 13, shown in Figures 2 and 3, comprises a sealed passage 15 and the capacitor 14; this crossing comprises at least one space 16 for the passage of an electrical conductor 17 (there are in practice two or more); this conductor also passes through the capacitor by means of a passage orifice 18 provided for this purpose. The capacitor 14 has a very flat shape attached to a flat face of the bushing; it is electrically mounted between this electrical conductor and an electrically conductive portion of the bushing, itself connected in practice to an electrical ground, for example to the housing.

The crossing here consists of a central part 15A and a peripheral part 15B. At least one of them is electrically conductive; it is here the peripheral part which is for example made of a material similar to that of the case (titanium alloy in particular) while the other part is insulating, advantageously made of a ceramic material, for example alumina. The combination of these two parts alone ensures the closure of the orifice of the housing (its shape in FIG. 2 is only shown by way of example, different from that of the diagram in the figure).

The form of the bushing and its method of attachment to the housing not being part of the invention, they will not be described in more detail.

The structure of the capacitor 14 is shown on a larger scale in FIG. 4, in combination with FIGS. 5 and 6.

This capacitor comprises a support plate 20 of insulating material, therefore simple in shape, with planar faces 21 and 22 and a peripheral edge 23.

In this plate are provided as many passage orifices 18 as there are electrical conductors to be passed through this capacitor (there is preferably only one capacitor per element 13, but it should be understood that in a variant , provision may be made to attach several capacitors to the bushing, side by side, in this plate are further provided, in the example under consideration, bores 24 whose function will appear later.

This support plate made of insulating material is advantageously made of at least one ceramic material, for example alumina. When, as shown, the bushing has an insulating part, the material constituting this insulating part and this plate is advantageously the same.

On this plate are metallized zones forming first and second electrodes 25 and 26; the first electrode 25 is here formed by a coating of the internal surface of the passage opening (s) 18, while the second electrode 26 is here formed by four portions of an annular track formed on the face 22 of the support plate; this track intercepts the aforementioned bores 24.

On the face 21, that is to say on the opposite face of the support plate, are formed at least a pair of electrically conductive layers 30 and 31 separated by a layer 32 of dielectric material.

These layers are advantageously produced by the layer technology thick, already known in particular in the production of printed circuits or hybrid circuits in electronics.

In the example considered, there is only one pair of such layers, but it should be understood that the explanations which follow are generalized without difficulty for the skilled person in case, to obtain the necessary capacity, it would be necessary to have several pairs layers (multilayer).

The capacitor 14 thus comprises an electrically conductive layer 30, here directly deposited on the face 21 of the support plate. As shown in Figure 6, this layer 30 is forming a ground electrode is in the example considered, separated into two right and left parts, respectively associated with the right and left conductors which pass through the capacitor: these parts stop at distance from the orifices of passage of these conductors to be properly insulated therefrom. However, since it is a ground electrode, this layer could be in one piece.

On the other hand, these parts extend radially at least as far as the bores 24, therefore perpendicular to the portions of the annular track.

Insofar as the internal surface of these bores is metallized

(reference 24A in FIG. 4), the ground electrode 30 is electrically connected to the right and left portions of the annular track formed on the face 22, the bores 24 serving for the electrical connection through the support plate.

This layer 30 is covered by the dielectric layer 32, which extends to the immediate vicinity of the passage openings for the conductors (it constitutes the dielectric of the capacitor).

And above this dielectric layer is arranged layer 31 which is dissociated into as many parts as there are conductors, here two. The outline of the parts of this layer is shown in dashed lines in FIG. 6: it has the shape of a disc of diameter a little smaller than that of the layer 30 and its two parts are separated by a vertical diametral space in the figure. 6, substantially equal to that which separates the two parts of the layer 30. The layer 31 extends to the passage openings until they are connected electrically with the internal coating of these constituting the first electrode 25.

It will be appreciated that thus are formed side by side on the support plate as many elementary capacitors as there are electrical conductors which pass through the closure element 13.

Advantageously, all of the layers are covered by a protective layer 33 of any suitable material, for example dielectric material, which increases the insulation between the electrodes.

For example, the layers 30 and 31 and the metallization layers are made of Ag / Pd or Ag / Pt.

The capacitor 14 has a flat shape given by that of the support plate. It is attached to the bushing on one side of it, preferably the one which is intended to be inside the housing.

This capacitor is secured to this crossing so that the second electrode 26 is earthed by electrical connection with the metal part of this crossing, at its part 15B (ferrule) in the example considered. This connection is made by brazing, in the area shown diagrammatically at 35 in FIG. 7.

This capacitor is also secured to the conductors so as to be able to effectively filter the disturbances applied to this conductor. This connection is made by brazing, in the area shown diagrammatically at 36 in FIG. 7.

The brazing zones 35 and 36 are for example produced by Ag / Cu brazing. Figures 8 to 10 show another capacitor, adapted to be mounted on a ferrule such as that of the previous example.

Its general structure is the same as that of the capacitor 14, and the constituent elements similar to those of FIGS. 4 to 7 are designated by reference signs which are deduced therefrom by addition of the “prime” index. Thus, this capacitor 14 'has a support plate 20' in which as many passage orifices 18 'are formed as there are conductors. On a face 21 'of this plate are deposited layers 30', 31 'and 32', respectively connected to electrodes 25 'and 26', the first electrode being produced by metallization of the internal surface of the orifices 18 'and the second electrode being made on the face 22 'opposite to that carrying the layers 30' to 32 '.

A protective layer 33 'partially covers the stack of layers.

The shape of the support plate is not strictly circular due to the flats 50 (see below), which in particular allow, if it is useful, a rigorous angular positioning of the capacitor (this can result from the manufacturing process of the capacitor ).

Unlike the capacitor 14, that of FIGS. 8 to 10 does not have bores 24, and the electrical connection 24A 'between the layer 30' and the right-to-left portions of the track 26 'forming the second electrode is made by a metallization layer produced on the peripheral edge of the support plate. As before, the track 26 ′ is advantageously made in four portions and the metallization layer preferably only covers the cylindrical portion of the edge of the support plate; thus, if the support plate is made from a disc, it is possible to metallize the whole of this section before making the flats, locally removing the metallization layer: this results in a particularly simple manufacture.

FIG. 11 summarizes the main steps making it possible to produce a closure element 14 or 14 ′ according to the invention: - a crossing is made and, (at least in part, since completion stages are possible, for example to define flats) a support plate,

- Alternating conductive and dielectric layers are deposited on the support plate, preferably by thick layer technology;

- metallized zones adapted to form first and second capacitor electrodes are produced on this plate, at least one electrical conductor is engaged in a passage orifice formed in the support plate,

- The first electrode is preferably fixed by soldering, simultaneously to the electrical conductor and the second electrode to the ferrule.

As indicated above, there may be several elementary capacitors on the support plate, for each electrical conductor.

For example: - the support plate of the capacitor 14 has a diameter of 4.2 mm,

- its thickness is 0.4 mm,

- the passage openings have a diameter of 0.5 mm,

- the bores have a diameter of 0.25 mm, - the spacing between the right and left halves of the layers is 0.5 mm,

- the thickness of the conductive layers is 15 microns,

- the thickness of the dielectric layer between them, is about 40-50 microns. - the thickness of the protective layer is 25 microns.

Claims

1. Method for manufacturing an obturation and electrical connection element adapted to be mounted in an orifice of an implantable medical equipment case (10), comprising steps according to which:

- a bushing (15) is made of which at least part (15B) is electrically conductive and which is adapted to be fixed to the housing, this bushing comprising at least one space for the passage of an electrical conductor (17), - realizes a capacitor (14, 14 ') having at least a first electrode (25, 25') and at least a second electrode (26, 26 ') and at least one passage orifice (18, 18') for the electrical conductor ,

- the capacitor is secured to the bushing and this first electrode is electrically connected to the electrical conductor and this second electrode to the electrically conductive part of the ferrule, characterized in that the step of producing the capacitor includes a deposition step, on a support plate of insulating material (20, 20 ′) in which this passage orifice is formed, of metallized zones (25, 26, 25 ′, 26 ′) forming the first and second electrodes and, on one face of this plate support, of at least a pair of electrically conductive layers (30, 31, 30 ', 31') separated by a layer of dielectric material (32, 32 '), these layers being respectively connected to these first and second electrodes, and the joining and connection step includes a brazing step (36) of the first electrode to the electrical conductor and the second electrode to the crossing.

2. Method according to claim 1, characterized in that said at least one pair of electrically conductive layers and the layer are produced. dielectric material disposed therebetween by the thick layer technique.

3. Method according to claim 1 or claim 2, characterized in that the support plate on which is deposited said at least one pair of electrically conductive layers and the layer of dielectric material disposed between them is made of a ceramic material.

4. Method according to claim 3, characterized in that the ceramic material of the capacitor comprises alumina.

5. Method according to any one of claims 1 to 4, characterized in that the brazing steps are carried out simultaneously.

6. Method according to any one of claims 1 to 5, characterized in that the zone forming the first electrode is produced by metallization of the passage orifice intended to receive the electrical conductor.

7. Method according to any one of claims 1 to 6, characterized in that the area forming the second electrode is produced by metallization of at least one area of the face of the support plate which is opposite to the face of this support plate on which said at least one pair of electrical layers are produced separated by a layer of dielectric material.

8. Method according to claim 7, characterized in that the second electrode is connected to a layer of said at least one pair of electrical layers by a metallized area of the edge of the support plate.

9. Method according to claim 7 or claim 8, characterized in that the second electrode is connected to a layer of said at least one pair of electrical layers by a metallized zone of at least one bore passing through the support plate.

10. Method according to any one of claims 1 to 9, characterized in that said at least one pair of electrical layers is covered by a layer of dielectric material.

11. Sealing and electrical connection element (13) adapted to be mounted in an orifice of an implantable medical equipment case (10), comprising:

- at least one electrical conductor (17), - a bushing (15) at least part of which (15B) is electrically conductive and suitable for being fixed to the housing, this bushing comprising at least one orifice for the passage of this electrical conductor,

- a capacitor (14, 14 ') integral with this ferrule, having at least a first electrode (25, 25') electrically connected to the electrical conductor and at least a second electrode (26,

26 ') electrically connected to the electrically conductive part of the shell, characterized in that the capacitor is formed from at least a pair of two electrically conductive layers (30, 31, 30', 31 ') respectively connected to zones of metallization forming the first and second electrodes and separated by a dielectric layer (32, 32 '), these layers being deposited on one face of a support plate made of insulating material, and these first and second electrodes are respectively connected by soldering ( 35, 36, 35 ', 36') to the electrical conductor and to the electrically conductive part of the bushing.

12. Element according to claim 11, characterized in that said at least one pair of electrically conductive layers and the layer of dielectric material disposed between them is produced by the technique of thick layers.

13. Element according to claim 11 or claim 12, characterized in that the support plate on which is disposed said at least one pair of electrically conductive layers and the layer of dielectric material disposed between them is made of a ceramic material.

14. Element according to claim 13, characterized in that the ceramic material of the capacitor comprises alumina.

15. Element according to any one of claims 11 to 14, characterized in that the zone forming the first electrode is a metallized zone of the passage orifice intended to receive the electrical conductor.

16. Element according to any one of claims 1 to 15, characterized in that the zone forming the second electrode comprises at least one metallized zone of the face of the support plate which is opposite to the face of this support plate on which are made of said at least one pair of electrical layers separated by a layer of dielectric material.

17. Element according to claim 16, characterized in that the second electrode is connected to a layer of said at least one pair of electric layers by a metallized zone (24A ′) of the edge of the support plate.

18. Element according to claim 16 or claim 17, characterized in that the second electrode is connected to a layer of said at least one pair of electric layers by a metallized zone (24A) of at least one through bore (24) the support plate.

19. Element according to any one of claims 11 to 18, characterized in that said at least one pair of electrical layers is covered by a layer of dielectric material (33, 33 ').