ELECTRICAL CONNECTION TO MINIATURE SENSORS

Abstract

A conductor arrangement is provided for connection to a miniature sensor. First and second conductor wires are spaced by a spacer. The maximum lateral dimension of the conductor arrangement, perpendicular to the wire length direction, is less than 500 m. The spacing means that wire bending processes do not need to be carried out in order to make connection to the miniature sensor.

Claims

1. A conductor arrangement for connection to a miniature sensor, comprising: a first conductor wire; a second conductor wire; a dummy wire forming an insulating spacer between and bonded to the first and second conductor wires, wherein the first and second conductor wires and the dummy wire form a flat conductor array, wherein the maximum lateral dimension (w) of the conductor arrangement, perpendicular to the wire length direction, is less than 500 m.

2. A conductor arrangement as claimed in claim 1, wherein the first and second conductor wires each comprise a metal core and an insulating shroud.

3. A conductor arrangement as claimed in claim 2, wherein each metal core has a diameter of less than 100 m, for example less than 50 m.

4. A conductor arrangement as claimed in claim 2, wherein each insulating shroud has thickness of less than 40 m, for example less than 20 m.

5. A conductor arrangement as claimed in claim 2, wherein the spacer comprises an insulating cylinder.

6. A conductor arrangement as claimed in claim 5, wherein the spacer has an outer diameter equal to the outer diameter of each conductor wire.

7. A conductor arrangement as claimed in claim 1, wherein there are exactly two conductor wires.

8. A sensor arrangement comprising: a sensor module, having first and second connection pads; and a conductor arrangement as claimed in claim 1, wherein the first and second conductor wires each comprise a bare end portion which is connected to a respective one of the connection pads.

9. A sensor module as claimed in claim 8, wherein the bare end portions are straight.

10. A sensor arrangement as claimed in claim 8, wherein each bare end portion is connected to the respective connection pad by soldering or welding.

11. A sensor arrangement as claimed in claim 8, wherein the pitch of the first and second conductor wires is equal to a pitch of the first and second connection pads, wherein for example the pitch is between 30 and 200 m.

12. A sensor arrangement as claimed in claim 8, wherein the sensor module comprises a pressure sensor and/or a flow sensor and/or a temperature sensor and/or an ultrasound transducer.

13. A sensor arrangement as claimed in claim 8, comprising a guidewire sensor arrangement.

14. A guidewire comprising a sensor arrangement as claimed in claim 8.

15. A catheter or stent system, comprising: a guidewire as claimed in claim 14; and a catheter or stent which is adapted to be guided over the guidewire.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Examples of the invention will now be described in detail with reference to the accompanying drawings, in which:

[0039] FIG. 1 shows a conventional connection between a conductor arrangement and a sensor;

[0040] FIG. 2 shows a connection between a conductor arrangement in accordance with an example of the invention and a sensor to form a sensor arrangement;

[0041] FIG. 3 shows the conductor arrangement of FIG. 2 in cross section;

[0042] FIG. 4 shows the guidewire in cross section; and

[0043] FIG. 5 shows a guidewire and catheter system using the sensor arrangement of FIG. 2.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0044] The invention provides a conductor arrangement for connection to a miniature sensor. First and second conductor wires are spaced by a spacer. The maximum lateral dimension of the conductor arrangement, perpendicular to the wire length direction, is less than 500 m. The spacing means that wire bending processes do not need to be carried out in order to make connection to the miniature sensor.

[0045] The invention is of particular interest for guidewire sensors.

[0046] Bifilar and multifilar wires are used in guidewires for connecting the sensor at the tip of the guidewire to the back (proximal) side of the guidewire where signal processing and analysis takes place.

[0047] These extremely small wires are typically made by bonding insulated conductors in pairs, triplets or even multiple wire bundles. The gap between the conductors is determined by the insulation thickness of the individual conductors and is for example only a few micrometers.

[0048] Typical pitches of bond pads on sensors are in the range of 30 to 200 micrometers, for example 30 to 60 micrometers. This means that the conductors in a wire have to be brought to the desired pitch by a bending process. This bending process is complicated and can decrease the wire and product quality.

[0049] FIG. 1 shows a sensor 1 connected to a conventional conductor arrangement 2 having two conductor wires, each having a conducting core 4 and an insulating shroud 6. The conductor arrangement 2 is formed as a pair of bonded wires, connected by the insulating shroud 6 around each wire.

[0050] As shown in the left image, the insulating shroud 6 is removed from an end region to form bare wire end portions.

[0051] The bare wire portions are then bent apart at bends 8 as shown in the middle image, so that the wire spacing corresponds to a bond pad pitch.

[0052] The right image shows the bare end portions connected to bond pads 10 of the sensor module 1. This connection may be by soldering or welding.

[0053] FIG. 2 shows a similar sensor connection to a conductor arrangement 20 in accordance with the invention. The same components are given the same reference numerals as in FIG. 1.

[0054] The conductor arrangement 20 has a spacer 22 between the two conductor wires. The spacer may be formed of the same material as the insulating shroud 6 of the two wires so that they may all be bonded together. The spacer may have the shape of a dummy (i.e. non-conducting) wire between the two conductor wires. In this way, the standard process for forming a wire triplet or wire bundle may be applied to the conductor wires and spacer(s). This design avoids the need for the bending process (the middle image in FIG. 1) of forming the conductor wires with the same pitch as the pitch of the bond pads 10 on the sensor.

[0055] During the removal of the insulation 6 from the conductor wires, the spacer is also removed. This stripping process is for example performed by a laser with a wavelength which removes the organic insulation but does not attack the metal core of the conductor wires. An excimer laser with a wavelength of 248 nm is one option.

[0056] FIG. 3 shows a cross section of the conductor arrangement. There are two conductor wires 30, 32, each with a metal core 4 and an insulating shroud 6. The spacer 22 is bonded with the shrouds 6. The spacer is shown as a cylinder in this example, and it therefore functions as a dummy wire between the conductor wires. The bonding with the shrouds creates an integrated structure.

[0057] By way of example, the total width w of the conductor arrangement may be 125 m. The core 4 of each conductor wire may have a diameter of 30 m and a shroud thickness of 5 m. The central spacer has the same total diameter of 40 m as each conductor wire. This gives the example shown a pitch of 75 m.

[0058] A cylindrical spacer design is preferred because the spacing provided is then independent of the orientation of the spacer. It also means that the collection of conductor wires and spacers may be bonded in the same way as a conventional set of conductor wires. The diameter of the central spacer cylinder is thus preferably the same as for the conductor wires, so that they may more easily be formed into a one-dimensional (flat) array before being bonded together. If more space is needed between the conductor wires a second dummy wire may for example be provided. The conductor wire diameter may be chosen so that one or more spacers of the same diameter results in the required bond pad spacing.

[0059] The individual electrical conductors are for example insulated with polyamide or polyimide by applying these materials as a liquid (in a solvent) followed by a curing step.

[0060] A bifilar structure is for example made by feeding two insulated wires and the dummy spacer wire into a process which bonds the wires for example using an epoxy. The spacer thus preferably has the form of a dummy wire so that it can be processed as if it was a conventional wire when forming the bonded overall structure. This means that standard bonding processes for an array of multifilar wires of the desired small dimensions may be used.

[0061] However, the spacer may in theory have any suitable shape for maintaining a desired spacing between the conductor wires. It may have a bar form, of a width equal to or less than the outer diameter of each wire 30, 32. In such a case, the spacer may be formed integrally with the insulating shrouds of the conductor wires as part of the process of providing an insulating shroud around the cores of the individual conductor wires. The example shown has two conductor wires. However, there may be more than two conductor wires. The multiple conductor wires are preferably formed as a flat array so that the conductor wires may be attached to a planar array of bond pads without the need to deform the conductor arrangement.

[0062] The invention may be used in any application where there is a benefit in having conductor wires having a pitch equal to the pitch of the pads of a sensor. As explained above, the invention is of particular interest for miniature sensors and conductor wires. One example of a set of dimensions has been given above.

[0063] More generally, each metal core may have a diameter of less than 100 m for example less than 50 m, and each insulating shroud may have a thickness of less than 40 m for example less than 20 m. The total width w is typically less than 500 m.

[0064] One area of particular interest is for guidewire sensors for use as part of a guidewire of a catheter or stent delivery system.

[0065] FIG. 4 shows a cross section of a guidewire, comprising an outer sheath 40 within which the electrical conductor arrangement 42 passes. There may also be optical fibers 44 for optical signals, for example from optical sensors.

[0066] FIG. 5 shows a catheter system comprising a guidewire 50 with a sensor 1 at the tip, in a region 52 of interest. A catheter 54 is guided around the guidewire 50. A signal processing system 56 receives signals from the sensor 1 which may have optical as well as electrical sensor elements. There may also be sensor elements distributed along the length of the guidewire.

[0067] A stent system may function in the same way, with the stent delivered along the guidewire.

[0068] Some examples of sensor type have been given above. There are various MEMS sensor devices which may be provided as part of a guidewire system, such as pressure sensing MEMS, flow sensing MEMS, barometer MEMS. Electrical connections may also be made in the same way to an antenna or to electronic imaging arrangements. The wire connection solution explained above may be applied to all of these possible sensors.

[0069] The example above places the sensor at the tip of the guidewire. The sensor may instead be located set back from the end of the guidewire, for example recessed into a side wall of the guide wire.

[0070] The way the guidewire is used and the details of the catheter system will not be described in detail since the conventional methods and systems may be used.

[0071] The invention may be applied to any miniaturized sensor system, for example for a sensor directly at the tip of a catheter (without needing a guidewire), or a needle or other small diameter inspection probe. There are medical as well as non-medical applications for such sensing.

[0072] Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word comprising does not exclude other elements or steps, and the indefinite article a or an does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.