Manufacturing process for an ultrasonic probe

Abstract

Method for manufacturing an ultrasonic probe This description relates to a method for manufacturing an ultrasonic probe, comprising the following steps: a) attaching, to a flexible interconnect substrate (101), a chip (201) having a plurality of ultrasonic transducers, the chip (201) having a front face having at least one electrical connection pad (203) and a rear face; b) folding a portion of the flexible interconnect substrate (101), so that the flexible interconnect substrate (101) extends over at least a portion of the rear face of the chip and over at least a portion of the front face of the chip, said at least one electrical connection pad (203) of the front face of the chip being connected to at least one corresponding electrical connection pad (205) of the interconnect substrate; and c) cutting the chip (201) into a plurality of elementary chips (103) each having one or more ultrasonic transducers.Figure for the summary: Fig. 2B.

Description

Title of the invention: Method for manufacturing an ul- probe trasonore Technical field

[0001] The present description relates generally to the manufacture of ultrasound probes, and in particular aims at the manufacture of small-sized ultrasound probes intended to be mounted on a catheter, for example for diagnostic applications or intravascular ultrasound treatment. Prior art

[0002] It has already been proposed to integrate small-sized ultrasonic probes into a catheter intended to be introduced into the body of a human or animal patient, for example for diagnostic applications or intravascular ultrasound treatment.

[0003] It would be desirable to have a method for manufacturing such a probe, this method at least partially overcoming some of the drawbacks of the known methods. Summary of the invention

[0004] One embodiment provides a method of manufacturing an ultrasonic probe, comprising the following steps: a) attaching, to a flexible interconnection substrate, a chip comprising a plurality of ultrasonic transducers, the chip comprising a front face comprising at least one electrical connection pad and a rear face; b) folding a portion of the flexible interconnect substrate, so that, at the end of step b), the flexible interconnect substrate extends over at least a portion of the rear face of the chip and over at least a portion of the front face of the chip, said at least one electrical connection pad of the front face of the chip being connected to at least one corresponding electrical connection pad of the interconnect substrate; and c) cutting the chip into a plurality of elementary chips each comprising one or more ultrasonic transducers.

[0005] According to one embodiment, step c) is implemented after step b).

[0006] According to one embodiment, step c) is implemented before step b).

[0007] According to one embodiment, in step a), the chip has its rear face facing the face of the interconnection substrate comprising said at least one electrical connection pad of the interconnection substrate.

[0008] According to one embodiment, in step a), the chip has its front face facing the face of the interconnection substrate comprising said at least one connection pad electrical of the interconnect substrate.

[0009] According to one embodiment, at the end of step c), the elementary chips remain mechanically connected to each other by an uncut strip of the flexible interconnection substrate.

[0010] According to one embodiment, during step b), a cylindrical rod is positioned on the interconnection substrate to control the curvature of the interconnection substrate during bending.

[0011] According to one embodiment, the method comprises, after steps a), b) and c), a step of curving the interconnection substrate according to a desired shape of the probe, for example a cylindrical shape.

[0012] According to one embodiment, the ultrasonic transducers are CMUT or PMUT type transducers.

[0013] According to one embodiment, the chip further comprises at least one electrical connection pad on its rear face.

[0014] Another embodiment provides an ultrasonic probe comprising a flexible interconnection substrate and a plurality of elementary chips attached to the flexible interconnection substrate, each elementary chip comprising one or more ultrasonic transducers, each elementary chip comprising a front face comprising at least one electrical connection pad and a rear face, in which a portion of the flexible interconnection substrate is folded over the elementary chips, such that the flexible interconnection substrate extends over at least a portion of the rear face of each elementary chip and over at least a portion of the front face of each elementary chip, said at least one electrical connection pad of the front face of each elementary chip being connected to a corresponding electrical connection pad of the interconnection substrate. Brief description of the drawings

[0015] These characteristics and advantages, as well as others, will be explained in detail in the following description of particular embodiments given without limitation in relation to the attached figures among which:

[0016] [Fig.l] is a very schematic perspective view of an example of an ultrasonic probe;

[0017] [Fig.2A], [Fig.2B] and [Fig.2C] illustrate steps of an example of a method of manufacturing an ultrasonic probe according to one embodiment; and

[0018] [Fig.3A] and [Fig.3B] illustrate steps of a variant of a method for manufacturing an ultrasonic probe according to one embodiment. Description of the embodiments

[0019] The same elements have been designated by the same references in the different figures. In particular, the structural and / or functional elements common to the different embodiments may have the same references and may have identical structural, dimensional and material properties.

[0020] For the sake of clarity, only the steps and elements useful for understanding the described embodiments have been shown and are detailed. In particular, the production of the ultrasonic transducers of the described probes has not been detailed, the described embodiments being compatible with all or most of the known structures of ultrasonic transducers. Furthermore, the production of the control circuits of the ultrasonic transducers has not been detailed, the described embodiments being compatible with the usual control circuits of ultrasonic transducers or the production of the control circuits being within the scope of the person skilled in the art from the indications of the present description.

[0021] Unless otherwise specified, when referring to two elements connected to each other, this means directly connected without intermediate elements other than conductors, and when referring to two elements connected (in English "coupled") to each other, this means that these two elements can be connected or be connected by means of one or more other elements.

[0022] In the following description, when reference is made to absolute position qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or relative position qualifiers, such as the terms "above", "below", "upper", "lower", etc., or to orientation qualifiers, such as the terms "horizontal", "vertical", etc., reference is made unless otherwise specified to the orientation of the figures.

[0023] Unless otherwise specified, the expressions "about", "approximately", "substantially", and "of the order of" mean to within 10%, preferably to within 5%.

[0024] [Fig.l] is a very schematic perspective view of an example of an ultrasonic probe 100.

[0025] The probe 100 comprises a flexible interconnection substrate 101 on which are fixed a plurality of elementary chips 103 each comprising one or more ultrasonic transducers, not detailed in the figures. By way of example, each elementary chip 103 is an ultrasonic wave emission / reception chip, also called an "ultrasonic array", composed of one or more elementary ultrasonic transducers, for example aligned along an axis parallel to a longitudinal axis of the probe or arranged in a matrix on the plane of the array.

[0026] The flexible interconnection substrate 101 is wound around a cylinder (not visible in the figure), for example with a circular section, so as to obtain a probe of generally cylindrical shape, for example of small dimensions, for example with a diameter of between 1 and 5 mm. The elementary chips form facets adapted to emit ultrasound towards the outside of the cylinder, in directions radial. In this example, the elementary chips have the shape of parallel rectangular strips, extending parallel to the central axis of the cylinder. By way of example, the probe comprises at least two, preferably at least four, preferably at least eight, elementary chips 103, for example regularly distributed around the cylinder.

[0027] Each chip comprises electrical connection pads (not visible in [Fig.l]) connected to corresponding electrical connection elements (not visible in [Fig.l]) of the interconnect substrate 101.

[0028] The interconnection substrate 101 is for example a flexible printed circuit, comprising electrically conductive interconnection elements, for example metal tracks and pads, for example made of copper, formed on a flexible dielectric support, for example made of a polymer material, for example a polyimide. One or more electrically conductive wires, not detailed in the figure, can electrically connect the interconnection substrate 101 to electronic circuits external to the probe, to control the elementary chips 103.

[0029] To produce such a probe, one possibility consists of fixing and electrically connecting to a connection face of the interconnection substrate 101, a single monolithic chip comprising all of the ultrasonic transducers of the probe, then cutting the chip into a plurality of elementary chips 103 each comprising one or more ultrasonic transducers. At the end of the cutting step, each elementary chip 103 remains fixed and electrically connected to the interconnection substrate 101. The substrate 101 can then be wound around a cylinder, to give the desired shape to the probe.

[0030] The electrical connection between the monolithic chip and the interconnection substrate 101 can be made by means of conductive wires connecting the connection face of the interconnection substrate to the front face of the chip, opposite the interconnection substrate. An encapsulation resin, for example an epoxy resin, can be provided to protect the connection wires. This method of connection by conductive wires, also called "wire bonding" in English, however has certain drawbacks. In particular, the conductive wires and, where appropriate, the encapsulation resin, lead to an increase in the diameter of the probe. Furthermore, there is a risk of damaging the conductive wires during the step of cutting the monolithic chip into elementary chips 103.

[0031] Alternatively, the monolithic chip and the interconnection substrate 101 can be assembled by a method called surface mounting (“flip chip” in English). In this case, the chip comprises electrical connection pads on its rear face, i.e. its face opposite the face for transmitting / receiving the ultrasonic waves. These pads are positioned directly on and in contact with pads of corresponding electrical connection located on the connection face of the interconnect substrate 101. Thus, the size is reduced compared to a connection by conductive wires, and the risks of damaging the electrical connections during the cutting step of the monolithic chip are reduced. However, a disadvantage of this solution is that the manufacturing cost of the transducer chip is relatively high, due to the need to integrate conductive vias crossing the chip substrate to connect the ultrasonic transducers to the electrical connection pads on the rear face of the chip. This is particularly true in the case of transducers in MEMS technology (from the English "Micro Electro Mechanical System" - micro electromechanical system).

[0032] Figures 2A, 2B and 2C illustrate successive steps of an example of a method for manufacturing an ultrasonic probe according to one embodiment.

[0033] [Fig.2A] illustrates the assembly obtained at the end of a step of transferring a monolithic chip 201 onto a connection face of a flexible interconnection substrate 101.

[0034] [Fig.2A] comprises a front view (a) of the assembly, and a sectional view (b) along plane bb of view (a).

[0035] At this stage of the process, the flexible interconnection substrate is unrolled and positioned, for example, on a flat support, not shown.

[0036] The chip 201 has, for example, a rectangular shape. The chip 201 comprises a plurality of ultrasonic transducers corresponding to all the transducers of the probe. The transducers (not detailed in the figures) are, for example, CMUT type transducers (capacitive membrane transducers) or PMUT type transducers (piezoelectric membrane transducers). The embodiments described are, however, not limited to this particular case and apply more generally to all types of ultrasonic transducers. The production of the chip 201 has not been detailed, the embodiments described being compatible with all or most of the known methods for manufacturing an ultrasonic transducer chip, or the production of such a chip being within the scope of the person skilled in the art from the indications of the present description.The chip 201 comprises a front face corresponding to the emission / reception face of the ultrasonic waves, and a rear face opposite its front face. The chip 201 comprises electrical connection pads 203 arranged on the side of its front face.

[0037] The interconnection substrate 101 comprises a connection face comprising electrical connection pads 205 intended to be connected respectively to the electrical connection pads 203 of the chip 201.

[0038] In this example, when transferring the chip 201, the rear face of the chip 201 is turned towards the connection face of the interconnection substrate 101. The rear face of the chip 201 is for example fixed to the connection face of the interconnection substrate 101 by an adhesive layer, not visible in the figure. A portion of the interconnection substrate 101 comprising the electrical connection pads 205 is not covered by the chip 201. In the example shown, the interconnection substrate 101 covers the entire rear face of the chip. Thus, in this example, the surface area of ​​the interconnection substrate 101 is greater than the surface area of ​​the chip 201. The embodiments described are however not limited to this particular case. As a variant, the interconnection substrate 101 may cover only a portion of the rear face of the chip 201.

[0039] The electrical connection pads 205 of the interconnection substrate 101 are arranged in an arrangement substantially identical to that of the electrical connection pads 203 of the chip 201. The electrical connection pads 205 are arranged in a part of the interconnection substrate 101 intended to be folded onto the front face of the chip 201, so as to place the pads 203 and 205 facing each other respectively.

[0040] In the example shown, a rod 207 of generally cylindrical shape, for example with a circular section, is arranged on the connection face of the interconnection substrate 101, for example attached to an edge of the chip 201. The rod 207 is arranged, in top view, between an edge of the chip 201 and the part of the interconnection substrate 101 comprising the connection pads 205, along the folding axis of the substrate 101. The rod 207, optional, advantageously makes it possible to control the radius of curvature of the interconnection substrate 101 when the latter is folded onto the front face of the chip 201, limiting the risk of breaking the metal tracks of the substrate 101 during folding. The rod 207 is for example a wire, for example made of nylon.

[0041] [Fig.2B] illustrates the assembly obtained at the end of a step of folding the part of the interconnection substrate 101 comprising the connection pads 205 onto the front face of the chip 201, so as to position the connection pads 205 of the substrate opposite the connection pads 203 of the chip.

[0042] [Fig.2B] comprises a front view (a) of the assembly, and a sectional view (b) along plane bb of view (a).

[0043] In this example, the substrate is wound around the rod 207 during the bending step. A tool with a shape complementary to the rod 207, optional and not shown in [Fig. 2A] and 2B, can be used to press and hold the substrate 101 in position around the rod 207 during this step and the following steps.

[0044] During this step, the connection pads 205 of the substrate are fixed and electrically connected respectively to the corresponding connection pads 203 of the chip 201. The fixing and electrical connection of the pads 203 to the pads 205 can be carried out by any suitable method, for example by welding, soldering, bonding using a conductive paste or glue, or by means of a conductive adhesive film. anisotropic (ACF), etc.

[0045] Preferably, the flexible interconnection substrate 101 does not cover the entire front face of the chip 201. In particular, the ultrasound emission / reception surface of the chip is preferably not covered by the substrate 101, so as not to disturb the propagation of the ultrasonic waves. As a variant, the front face of the chip 201 is entirely covered by the interconnection substrate 101 at the end of the folding step.

[0046] [Fig.2C] is a front view illustrating the assembly obtained at the end of a step of cutting the chip into a plurality of elementary chips 103 each comprising one or more ultrasonic transducers. Each elementary chip 103 comprises at least one electrical connection pad 203 connected to a corresponding electrical connection pad 205 of the flexible interconnection substrate 101.

[0047] The cutting can be carried out by any known method of cutting a chip into a plurality of elementary chips, for example using a saw or by laser cutting.

[0048] In this example, the elementary chips 103 are distinguished along cutting lines parallel to the central axis of the final cylindrical ultrasonic probe.

[0049] At least one strip 209 of the flexible interconnect substrate 101 is not cut during this step. At the end of the cutting step, the elementary chips 103 remain mechanically connected to each other by said strip 209.

[0050] In the example shown, the chip 201, the rod 207 (optional) and the interconnection substrate 101 are entirely cut along the cutting paths. Thus, the uncut strip 209 is located outside the face of the chip 201. As a variant (not shown), only the part of the interconnection substrate 101 covering the front face of the chip 201, the rod 207 (optional) and the chip 201 are cut. In other words, the part of the interconnection substrate arranged on the side of the rear face of the chip 201 is not cut and forms the mechanical holding strip of the elementary chips 103.

[0051] At the end of the cutting step, the substrate 101 can be rolled up to form a cylindrical probe of the type described in relation to [Fig.l].

[0052] Figures 3A and 3B illustrate successive steps of another example of a method for manufacturing an ultrasonic probe according to one embodiment.

[0053] [Fig.3A] illustrates the assembly obtained at the end of a step of transferring a monolithic chip 201 onto a connection face of a flexible interconnection substrate 101.

[0054] [Fig.3A] comprises a front view (a) of the assembly, and a sectional view (b) along plane bb of view (a).

[0055] The step of [Fig.3A] differs from the step of [Fig.2A] essentially in that, in the example of [Fig.3A], during the transfer, the chip 201 has its front face facing the connection face of the flexible interconnect substrate 101.

[0056] Thus, the electrical connection pads 203 of the chip are directly placed opposite the electrical connection pads 205 of the substrate 101 and electrically connected to the pads 205.

[0057] An advantage of this variant is that the connection of the pads 203 and 205 is easier to achieve when the flexible substrate 101 is fully unrolled and flat, than after folding the substrate 101 as described in the previous example. This makes it easier in particular to apply pressure to the pads during fixing.

[0058] In the example shown, the front face of the chip 201 is entirely covered by the substrate 101. In this example (non-limiting), a part 101S of the substrate 101 covering the ultrasonic emission / reception zone of the chip 201, called the sacrificial part, is pre-cut along a cutting line 303, so as to allow its removal during a subsequent step.

[0059] Furthermore, in the example shown (non-limiting), the substrate 101 comprises, for example in its sacrificial part 101S, an extra thickness 305 projecting towards the chip 201. The extra thickness 305 has for example a height substantially equal to the cumulative height of the projecting parts of the connection pads 203 and 205. During the step of fixing the pads 203 of the chip on the pads 205 of the substrate, the chip 201 rests, by its front face on the extra thickness 305. This makes it possible to compensate for the height of the pads and to keep the chip 201 substantially parallel to the substrate 101 during this step.

[0060] [Fig.3B] illustrates the assembly obtained at the end of a step of folding the interconnection substrate 101 onto the rear face of the chip 201.

[0061] In this example, the substrate is wrapped around the rod 207 (optional) during the folding step.

[0062] The rear face of the chip 201 is for example fixed to the connection face of the interconnection substrate 101 by an adhesive layer, not visible in the figure.

[0063] At the end of this step, the sacrificial part 101S of the interconnection substrate 101, and, where appropriate, the excess thickness 305, can be removed from the side of the front face of the chip.

[0064] The rest of the process is for example identical or similar to what was described previously.

[0065] Various embodiments and variations have been described. Those skilled in the art will understand that certain features of these various embodiments and variations could be combined, and other variations will occur to those skilled in the art. In particular, the described embodiments are not limited to the particular example described above of application to a cylindrical ultrasonic probe, but can be applied to other non-planar probe shapes, subject to possible adaptations within the scope of the person skilled in the art.

[0066] Furthermore, the embodiments described are not limited to the example of application indicated above to the production of intravascular ultrasound probes, but apply more generally to the production of all types of ultrasound probes of non-planar shapes, for example of small dimensions, for medical or non-medical applications.

[0067] Furthermore, although exemplary embodiments have been described above in which the flexible substrate 101 is folded onto the front face or the rear face of the monolithic chip 201 before cutting the chip 201 into elementary chips 103, the described embodiments are not limited to this particular case. As a variant, the cutting of the monolithic chip 201 can be carried out after the latter has been fixed to the flexible interconnect substrate 101 but before the step of folding a portion of the substrate 101 onto the face of the chip opposite its transfer face. In particular, the person skilled in the art will know how to adapt the example of FIGS. 2A to 2C by implementing the cutting of the chip 201 between the transfer step of [Fig. 2A] and the folding step of [Fig. 2B]. Similarly, the person skilled in the art will know how to adapt the example of figures 3A and 3B by implementing the cutting of the chip 201 between the transfer step of [Fig.3A] and the folding step of [Fig.3B]. .

[0068] Furthermore, in the two implementation examples described in relation to the figures, connections have been described only on the front face (ground and hot point of each chip). It is however possible to provide electrical connections on the two main faces of each chip.

[0069] For example, a ground connection may be provided on the front face, and transferred to the folded part of the flexible substrate. Electrodes for connection to the ultrasonic transducers may be provided on the rear face, connected respectively to corresponding pads of the flexible substrate.

[0070] According to another example, a ground connection may be provided on the rear face, connected to a metal plane, for example copper on the flexible interconnect substrate. Electrodes for connection to the ultrasonic transducers may be provided on the front face, connected to the folded part of the flexible interconnect substrate.

Claims

Claims

1. A method of manufacturing an ultrasonic probe, comprising the following steps: a) attaching, on one face of a flexible interconnection substrate (101), a chip (201) comprising a plurality of ultrasonic transducers, the chip (201) comprising a front face comprising at least one electrical connection pad (203) and a rear face; b) folding a portion of the flexible interconnection substrate (101), so that, at the end of step b), said face of the flexible interconnection substrate (101) extends and is fixed on at least a portion of the rear face of the chip and on at least a portion of the front face of the chip, said at least one electrical connection pad (203) of the front face of the chip being connected to at least one corresponding electrical connection pad (205) of said face of the interconnection substrate (101);and c) cutting the chip (201) into a plurality of elementary chips (103) each comprising one or more ultrasonic transducers.;

2. The method of claim 1, wherein step c) is carried out after step b).

3. The method of claim 1, wherein step c) is performed before step b).

4. Method according to any one of claims 1 to 3, wherein, in step a), the chip (201) has its rear face facing the face of the interconnection substrate (101) comprising said at least one electrical connection pad (205) of the interconnection substrate (101).

5. Method according to any one of claims 1 to 3, in which, in step a), the chip (201) has its front face facing the face of the interconnection substrate (101) comprising said at least one electrical connection pad (205) of the interconnection substrate (101).

6. Method according to any one of claims 1 to 5, in which, at the end of step c), the elementary chips (103) remain mechanically connected to each other by an uncut strip (209) of the flexible interconnection substrate (101).

7. A method according to any one of claims 1 to 6, wherein, in step b), a cylindrical rod (207) is positioned on the interconnect substrate (101) to control the curvature of the interconnect substrate (101) during bending.

8. Method according to any one of claims 1 to 7, comprising, after steps a), b) and c), a step of curving the interconnection substrate (101) into a desired shape of the probe, for example a cylindrical shape.

9. A method according to any one of claims 1 to 8, wherein the ultrasonic transducers are CMUT or PMUT type transducers.

10. Method according to any one of claims 1 to 9, in which the chip (201) further comprises at least one electrical connection pad on its rear face side.

11. An ultrasonic probe comprising a flexible interconnection substrate (101) and a plurality of elementary chips (103) fixed to one face of the flexible interconnection substrate (101), each elementary chip (103) comprising one or more ultrasonic transducers, each elementary chip (103) comprising a front face comprising at least one electrical connection pad (203) and a rear face, in which a portion of the flexible interconnection substrate (101) is folded over the elementary chips (103), so that said face of the flexible interconnection substrate (101) extends and is fixed to at least a portion of the rear face of each elementary chip (103) and to at least a portion of the front face of each elementary chip (103),said at least one electrical connection pad (203) of the front face of each elementary chip (101) being connected to a corresponding electrical connection pad (205) of said face of the interconnection substrate (101).,

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