Heat transfer through the catheter tip

Abstract

To provide ablation catheters.SOLUTION: Described embodiments include an apparatus that includes a flexible electrically insulating substrate, including an inner surface and an outer surface and shaped to define (i) multiple narrower channels passing between the inner surface and the outer surface and (ii) one or more wider channels passing between the inner surface and the outer surface. The apparatus further includes an outer layer of an electrically conducting metal covering at least a part of the outer surface, an inner layer of the electrically conducting metal covering at least a part of the inner surface, a plating layer of the electrically conducting metal with which the wider channels are plated to connect the outer layer to the inner layer, and respective columns of the electrically conducting metal that fill the narrower channels to connect the outer layer to the inner layer. Other embodiments are also described.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an ablation catheter and its use in an ablation procedure. [Background technology]

[0002] In some ablation procedures, an electrode disposed at the tip of an ablation catheter is brought into contact with tissue, and radio frequency (RF) energy is then passed from the electrode into the tissue, causing an increase in the temperature of the tissue and thus causing damage within the tissue.

[0003] U.S. Patent Application Publication No. 2018 / 0110562, the disclosure of which is incorporated herein by reference, describes a catheter including an insertion tube, a flexible substrate, and one or more electrical devices. The insertion tube is configured for insertion into a patient's body. The flexible substrate is configured to encase a distal end of the insertion tube and includes an electrical interconnect. The electrical devices are coupled to the flexible substrate and connected to the electrical interconnect. Summary of the Invention [Means for solving the problem]

[0004] According to some embodiments of the present invention, there is provided a device comprising a flexible, electrically insulating substrate having an inner surface and an outer surface and shaped to define (i) a plurality of narrow channels passing between the inner and outer surfaces and (ii) one or more wider channels passing between the inner and outer surfaces, The device further comprises an outer layer of conductive metal covering at least a portion of the outer surface, an inner layer of conductive metal covering at least a portion of the inner surface, a plated layer of conductive metal plating the wider channels so as to connect the outer layer to the inner layer, and respective columns of conductive metal filling the narrow channels so as to connect the outer layer to the inner layer.

[0005] In some embodiments, the substrate is shaped to define at least 1,000 narrow channels.

[0006] In some embodiments, the total area of ​​the outer openings of each of the narrow channels is at least 10% of the area of ​​the outer surface.

[0007] In some embodiments, the conductive metal comprises gold.

[0008] In some embodiments, the device further comprises at least one constantan trace disposed on the inner surface and electrically insulated from the inner layer, and at least one gold trace disposed on the inner surface and electrically insulated from the inner layer, covering the constantan trace at the thermocouple junction.

[0009] In some embodiments, the device further comprises a support structure coupled to the inner layer, the substrate and support structure being shaped to define an inner lumen.

[0010] In some embodiments, the substrate and support structure are shaped to define a thimble that includes an internal lumen.

[0011] In some embodiments, the apparatus further comprises a catheter configured for insertion into the body of the subject, the support structure being coupled to a distal end of the catheter.

[0012] In some embodiments, the distal end of the catheter includes a flow diverter configured to redirect fluid received from the proximal end of the catheter, and the support structure is coupled to the flow diverter such that the flow diverter is disposed within the inner lumen.

[0013] In some embodiments, the narrow channels each have an average diameter of 5 to 50 micrometers.

[0014] In some embodiments, the average narrow channel diameter of each of the narrow channels is less than 50% of the average wide channel diameter of each of the wide channels.

[0015] In some embodiments, the thickness of the substrate is between 5 and 75 micrometers.

[0016] In some embodiments, the device further comprises one or more conductive traces disposed on the inner surface and electrically insulated from the inner layer, the substrate being shaped to define respective holes opposite the traces, and the outer layer comprising a main portion and one or more islands electrically insulated from the main portion and each contacting the trace by at least partially filling the holes.

[0017] According to some embodiments of the present invention, there is further provided a method comprising inserting into a subject's body a distal end of a catheter comprising a substrate, the substrate having an inner surface at least partially coated by an inner metal layer and an outer surface at least partially coated by an outer metal layer, the substrate shaped to define (i) a plurality of narrow channels passing between the inner and outer surfaces and filled with metal columns, and (ii) one or more wide plated channels passing between the inner and outer surfaces. The method further comprises, following insertion of the distal end of the catheter into the subject's body, contacting tissue of the subject with the outer metal layer. While in contact with the tissue, the method further comprises passing an electric current through the outer metal layer to generate heat in the tissue and transfer it to the inner metal layer via the metal columns. The method further comprises discharging heat from the inner metal layer into the subject's blood by passing irrigation fluid through the wide plated channels.

[0018] In some embodiments, the tissue comprises cardiac tissue of the subject.

[0019] In some embodiments, the method includes the outer metal layer including a main portion and one or more islands electrically isolated from the main portion, and the method further includes using the islands to sense electrogram signals from the cardiac tissue.

[0020] According to some embodiments of the present invention, there is further provided a method comprising drilling a plurality of narrow channels and one or more wide channels through a flexible, electrically insulating substrate to pass between an inner surface of the substrate and an outer surface of the substrate, the method further comprising at least partially coating the inner and outer surfaces with a conductive metal to completely fill the narrow channels and to plate the wide channels.

[0021] In some embodiments, at least partially coating the inner and outer surfaces, completely filling the narrow channels, and plating the wide channels comprises depositing the conductive metal on the inner and outer surfaces of the substrate and into the narrow and wide channels; subsequent to depositing the conductive metal on the inner surface of the substrate, plating the substrate in a plating bath of the conductive metal for a first time interval while the outer surface of the substrate is coated; subsequent to plating the substrate for the first time interval, at least partially stripping the coating from the outer surface of the substrate; and subsequent to stripping the coating from the outer surface of the substrate, plating the substrate in the plating bath for a second time interval, thereby at least partially coating the inner and outer surfaces, completely filling the narrow channels, and plating the wide channels.

[0022] In some embodiments, the method further includes bonding the conductive metal coating on the interior surface to a support structure, and shaping the substrate and support structure to define an interior lumen.

[0023] In some embodiments, molding the substrate and support structure includes molding the substrate and support structure to define a thimble including an internal lumen.

[0024] In some embodiments, the method further comprises etching one or more conductive traces on the inner surface of the substrate, wherein depositing a conductive metal on the inner surface of the substrate comprises depositing the conductive metal on the inner surface of the substrate such that the conductive traces remain electrically insulated from the conductive metal, and further comprising forming respective holes in the substrate opposite the traces, and depositing the conductive metal on the outer surface of the substrate comprises depositing the conductive metal on the outer surface of the substrate to form (i) a main portion and (ii) one or more islands electrically insulated from the main portion and each contacting the trace by at least partially filling the holes.

[0025] The present invention will be more fully understood from the following detailed description of the embodiments thereof, taken in conjunction with the drawings in which: [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a schematic diagram illustrating a system for ablating tissue of a subject, according to some embodiments of the present invention. [Figure 2A] 1 is a schematic diagram illustrating a distal tip of a catheter, according to some embodiments of the present invention. [Figure 2B] 1A-1C schematically illustrate cross sections through a portion of a tip electrode according to some embodiments of the present invention. [Figure 3] 2B schematically illustrates a longitudinal cross section through the distal tip shown in FIG. 2A, according to some embodiments of the present invention. [Figure 4] 1 is a flowchart of a method for manufacturing a tip electrode according to some embodiments of the present invention. [Figure 5] 1A-1C are schematic diagrams illustrating tip electrodes before deformation, according to some embodiments of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0027] Overview Embodiments of the present invention include ablation electrodes comprising at least one flexible printed circuit board (PCB) bonded to a metallic support sheet by an adhesive. The flexible PCB includes a flexible, electrically insulating substrate having an outer surface coated with an outer layer of a conductive (and biocompatible) metal, such as gold, palladium, or platinum, and an inner surface coated with an inner layer of the same (and / or another) conductive metal. The inner surface may further support one or more electrical components, such as sensors (e.g., thermocouples) and traces, electrically insulated from the inner metal layer. Following deposition of the electrical components, coating of the substrate, and bonding of the PCB to the support sheet, the flexible PCB (together with the support sheet) can be transformed into any suitable shape. For example, in some embodiments, the flexible PCB is transformed into a thimble-shaped electrode, hereinafter referred to as the "tip electrode." The electrode is coupled to the distal end of a catheter.

[0028] During the ablation procedure, the outer metal layer is brought into contact with the tissue to be ablated, and then an ablation current is passed through the outer metal layer into the tissue. While the ablation current is applied to the tissue, a sensor may acquire any relevant physiological indices from the tissue. Typically, plated open vias that penetrate the electrode provide an electrical connection between the inner and outer metal layers, so that the ablation current can pass outward through the plated vias and potential signals from the tissue can pass inward through the plated vias. Electrical connection can also be provided by blind vias, each formed by removing a portion of the substrate so that the outer metal layer directly contacts the underlying trace.

[0029] The plated vias also provide fluid communication between the inner and outer surfaces of the electrode, allowing irrigation fluid (e.g., saline) to pass through the plated vias and into the surrounding blood. The irrigation fluid dissipates heat from the interior of the electrode into the blood and also dilutes the blood at the tissue-electrode interface, reducing the likelihood of clot formation or scorching. Due to the fact that the plated vias provide for the passage of irrigation fluid through their interior, the plated vias are also sometimes referred to as "irrigation channels" or "irrigation holes."

[0030] A problem with using electrodes of the type described above is that the substrate can provide significant thermal resistance, limiting the amount of heat that can be transferred from the tissue-electrode interface to the interior of the electrode, which in turn limits the amount of heat that can be removed by the irrigation fluid.

[0031] To address this issue, embodiments described herein provide a large number (e.g., tens of thousands) of small closed vias (hereinafter referred to as "thermal vias") to increase the thermal connectivity between the two surfaces of the electrode. Such thermal vias may include, for example, columns of conductive metal, such as gold, connecting the outer metal layer to the inner metal layer. Typically, the thermal vias are distributed across the entire surface of the electrode. The thermal vias increase the amount of heat transferred to the interior of the electrode, thus facilitating its removal by the irrigation fluid.

[0032]

[0006] Embodiments of the present invention also include a process for manufacturing an electrode. Typically, both sides of a substrate are first coated with copper, and therefore, electrode manufacturing typically begins by etching this copper except where copper traces are required on the inner surface of the substrate. Next, constantan traces used for thermocouples are deposited on the inner surface. Subsequently, one or more wide channels, multiple relatively narrow channels, and optionally, one or more blind vias are drilled through the substrate.

[0033] Then, on the inner surface of the substrate, a mask is applied over the traces and over the exclusion zones around the traces that insulate them from the inner metal layer (except that a mask is not applied over the portions of the constantan traces designated as thermocouple junctions). Similarly, on the outer surface, another mask is applied over the exclusion zones that insulate the microelectrode "islands" from the remainder of the outer metal layer.

[0034] A thin layer of metal (typically gold) is then sputtered into the channels and onto both sides of the substrate. The metal sputtered onto the interior surfaces includes traces that intersect with the constantan traces, thus forming thermocouple junctions. Following sputtering of the metal, the mask is removed, and the interior traces and exclusion zones are covered with another mask, and the entire exterior surface is also masked.

[0035] The substrate is then placed in a plating bath for a period of time to (i) coat any remaining exposed portions of the substrate's interior surface with metal, i.e., extend the metal layer laterally over the interior surface, (ii) increase the thickness of the inner layer, (iii) seal narrow channels to thermal bias, and (iv) narrow wide channels to plated irrigation channels. The interior and exterior masks are then removed. The internal traces and exclusion zones are then covered with at least one coverlay.

[0036] The substrate is then returned to the plating bath for an additional period of time, increasing the thickness of both the outer and inner layers and narrowing the plated irrigation channels. Typically, the total time the substrate is in the plating bath is set to allow the thickness of the inner layer to reach that of the coverlay. (Typically, the thickness of the outer layer is not increased significantly to reduce the risk of cracking the outer layer when the substrate is folded into its final shape.)

[0037] Next, openings having a diameter equal to or greater than the diameter of the irrigation holes are drilled into a metal support sheet, for example, a cobalt-chromium alloy. The support sheet is then bonded to the inner metal layer and coverlay so that the openings in the support sheet are aligned with the irrigation channels in the substrate. The plated substrate and support sheet are then deformed into their desired shapes. Finally, wires associated with the electrodes are connected, and the electrodes are then coupled to the catheter.

[0038] System Description Reference is now made first to FIG. 1, which is a schematic illustration of a system 20 for ablating tissue in a subject 26, according to some embodiments of the present invention.

[0039] 1 illustrates a physician 28 using an ablation catheter 22 to perform a unipolar ablation procedure on a subject 26. In this procedure, the physician 28 first inserts a distal tip 32 of the catheter 22 into the subject and then guides the distal tip 32 to the tissue to be ablated. For example, the physician may advance the distal tip through the subject's vasculature until it contacts cardiac tissue belonging to the subject's heart 24. Next, while the distal tip 32 is in contact with the tissue, the physician passes a radio frequency (RF) current between the distal tip 32 and a neutral polarity patch 30 connected external to the subject, for example, to the subject's back.

[0040] To facilitate catheter guidance, catheter 22 may include one or more electromagnetic position sensors that, in the presence of an external magnetic field, generate a signal that varies with the position of the sensor. Alternatively or additionally, any other suitable tracking system, such as an impedance-based tracking system, may be used. For example, both electromagnetic tracking and impedance-based tracking may be used, as described, for example, in U.S. Pat. No. 8,456,182, the disclosure of which is incorporated herein by reference.

[0041] The catheter 22 is connected proximally to a console 34, which includes, for example, a processor (PROC) 23, a pump 25, and a signal generator (GEN) 27. (The electrode patches 30 are also typically connected to the console 34 via wires 42.) During an ablation procedure, the signal generator 27 generates the ablation currents described above. These currents are carried through the catheter 22 via one or more wires to the distal tip 32. In addition, the pump 25 supplies irrigation fluid, such as saline, to the distal tip of the catheter, as further described below with reference to FIGS. 2A and 2B and 3.

[0042] Console 34 further includes control knobs 35 that can be used by a physician to control parameters of the ablation current. In particular, in response to manipulation of control knob 35 by physician 28, processor 23 can adjust the parameters of the ablation current by outputting appropriate commands to signal generator 27 via any suitable wired or wireless communication interface. Processor 23 can also control pump 25 via any suitable wired or wireless interface. In addition, the processor can receive and process any relevant signals from the distal tip of the catheter, such as signals received from any of the sensors described herein.

[0043] In some embodiments, the system 20 further comprises a display 38 that may display relevant output to the physician 28 during the procedure.

[0044] It should be noted that although a particular type of procedure is illustrated in FIG. 1, the embodiments described herein may be applied to any suitable type of ablation procedure or any other procedure that requires the transfer of heat through a flexible PCB.

[0045] Distal tip of the catheter Reference is now made to Figure 2A, which is a schematic illustration of distal tip 32, according to some embodiments of the present invention. Reference is now also made to Figure 3, which is a schematic illustration of a longitudinal cross section through distal tip 32, according to some embodiments of the present invention.

[0046] The distal tip 32 comprises at least one ablation electrode 40, such as the tip electrode illustrated in Figures 2A and 3. The electrode 40 comprises a plated, flexible, electrically insulating substrate 41 bonded to a support structure 36 at the distal end of the catheter 22 by an adhesive. The substrate 41 may be made of any suitable, flexible, electrically insulating material, such as a flexible polymer (e.g., polyimide) or liquid crystal polymer (LCP). The support structure 36 may be made of any suitable, strong material, such as cobalt chromium, stainless steel, magnesium, and / or alloys of any of the foregoing. For example, the support structure 36 may comprise L-605 cobalt-chromium-tungsten-nickel alloy.

[0047] In general, the electrode 40 can have any suitable shape. In some embodiments, as shown in Figures 2A and 3, the electrode 40 is thimble-shaped, including a cylindrical portion 40b capped by a dome-shaped portion 40a. Typically, a tab 47 at the proximal end of the electrode provides a soldering pad to which a wire extending the length of the catheter can be soldered to establish an electrical connection between the electrode and the proximal end of the catheter. These soldering pads are described in more detail below with reference to Figures 4 and 5.

[0048] As shown in the "AA" cross-section of FIG. 2A, the substrate 41 has an inner surface 76 facing the support structure 36 and an outer surface 45 facing away from the support structure 36. Typically, the thickness T0 of the substrate (i.e., the distance between the inner and outer surfaces of the substrate) is 5 to 75 (e.g., 12 to 50) micrometers. At least a portion of the inner surface is coated with an inner layer 70 of a conductive metal such as gold. Typically, the inner layer 70 has a thickness T1 of 10 to 50 micrometers. Similarly, at least a portion of the outer surface 45 is coated with an outer layer 50 of metal. Typically, the outer layer 50 has a thickness T2 of 1 to 5 micrometers.

[0049] Typically, the outer layer 50 is discontinuous in that it includes a main portion 54 and one or more insulating portions that are electrically insulated from the main portion 54 by exposed portions of the substrate. These insulating portions may include one or more "islands" that function as sensing microelectrodes 56. For example, the outer layer 50 may include three to seven microelectrodes 56 distributed around the periphery of the distal tip. Alternatively or additionally, the insulating portions may include a sensing ring electrode 43, which may be disposed, for example, near the proximal end of the distal tip 32.

[0050] Disposed beneath each of the sensing electrodes is a respective conductive trace 78, electrically insulated from the inner layer 70 by the exposed portion of the inner surface 76. As further described below with reference to FIG. 4, prior to forming the sensing electrodes, holes, referred to herein as blind vias 80, are formed (e.g., drilled) in the substrate above the traces 78. When the sensing electrodes are subsequently deposited on the outer surface of the substrate, the sensing electrodes at least partially fill the blind vias 80, thereby contacting the traces. Thus, during treatment, electrical potential signals from the subject's cardiac tissue sensed by the sensing electrodes can be conveyed via the traces 78 to wires extending through the catheter 22 to the proximal end of the catheter. In this manner, the signals can be delivered to the processor 23 for analysis.

[0051] Reference is now additionally made to Figure 2B, which is a schematic illustration of a cross section of a portion of electrode 40 according to some embodiments of the present invention. Figure 2B corresponds to the "BB" cross section shown in Figure 2A.

[0052] The substrate 41 is shaped to define a plurality of channels passing between the inner and outer surfaces of the substrate, including a plurality of narrow channels 46 and one or more wider channels 44. Typically, each channel is tapered along its length, with the cross-sectional area of ​​the channel at the inner surface of the substrate being slightly larger than the cross-sectional area at the outer surface. The cross-sectional area (or average cross-sectional area) of each narrow channel 46 is smaller than the cross-sectional area of ​​each wide channel 44.

[0053] In some embodiments, the channels have a circular cross-section. In such embodiments, the average diameter d0 of each of the narrow channels can be less than 50% (e.g., less than 25%) of the average diameter d1 of each of the wide channels. Alternatively or additionally, diameter d0 can be 5 to 50 micrometers (e.g., 5 to 30 micrometers), and / or diameter d1 can be 50 to 300 micrometers. In other embodiments, at least some of the channels can have a cross-section having a square shape, or any other suitable shape. (In such embodiments, the average cross-sectional area of ​​each of the channels can correspond to those suggested above by the ranges for d0 and d1.)

[0054] Typically, the electrode includes 30 to 100 wide channels. Each wide channel 44 is plated with a conductive metal plating layer 52, which connects the outer layer 50 to the inner layer 70. The plated wide channels thus provide electrical and thermal conductivity between the outer and inner metal layers. Furthermore, the plated wide channels provide a fluid passageway between the interior and exterior of the distal tip 32, through which irrigation fluid 39 supplied by the pump 25 (see FIG. 1) can flow. Therefore, the plated wide channels may be referred to as "irrigation holes" 72. (The diameter of each irrigation hole is smaller than the diameter d1 by an amount corresponding to approximately twice the length of the plating layer 52.) The support structure 36 is shaped to define openings 62 that are aligned with the irrigation holes 72, ensuring that the support structure does not obstruct the irrigation holes.

[0055] Typically, the number of narrow channels 46 is relatively large. For example, the substrate 41 may be molded to define at least 1,000, 5,000, 10,000, or 20,000 narrow channels. Alternatively or additionally, the ratio of the number of narrow channels to the number of wide channels may be at least 300:1. Alternatively or additionally, the total area of ​​the outer opening of each of the narrow channels (i.e., the opening of the narrow channel at the outer surface of the substrate) may be at least 10%, 20%, or 30% of the area of ​​the outer surface of the substrate. Thus, for example, if the area of ​​the outer surface of the substrate (including the narrow channels) is 27 mm 2 and each narrow channel has a diameter of 25 micrometers (hence 0.0005 mm 2 When the circular outer opening with an area of ​​1.5 mm is included, the number of narrow channels is approximately 16,500 (total area 8.1 mm). 2 ), and the outer opening of the narrow channel may occupy about 30% of the outer surface.

[0056] In contrast to the wider channels, the narrow channels 46 are not simply plated, but rather are filled with respective columns 48 of conductive metal connecting the outer layer 50 to the inner layer 70. (The columns 48 are not necessarily cylindrical because, as noted above, the narrow channels 46 do not necessarily have a circular cross-section. Furthermore, as noted above, the cross-sectional area of ​​each column may vary along its length. Note that the outer layer 50, inner layer 70, plated layer 52, and columns 48 may collectively be described as a single body of metal coating the substrate.) Due to the large number of channels 46 and the filling of each of these channels, a large amount of heat can be transferred through the channels 46. Thus, the filled narrow channels may be referred to as "thermal vias" 74. (For ease of illustration, the thermal vias are not shown in the "AA" cross-section of FIG. 2A.)

[0057] Notwithstanding the above, it should be noted that in some embodiments, the narrow channels are not filled, but rather are simply plated in the same manner as the wide channels. Even in such embodiments, a large amount of heat can be transferred to the interior of the electrode.

[0058] Typically, the catheter 22 includes a fluid supply tube (not shown) that extends through the entire length of the tubular body 22m of the catheter 22. The fluid supply tube is distally coupled to a flow diverter 60 shaped to define one or more fluid flow openings 64. The flow diverter 60 redirects fluid 39 received from the proximal end of the catheter via the fluid supply tube through the fluid flow openings 64. In such embodiments, the electrode 40 may be coupled to a base 58 of the flow diverter 60 such that the flow diverter is disposed inside the electrode's internal lumen. For example, the support structure 36 may be coupled to the base 58. Alternatively or additionally, the base 58 may be shaped to define a plurality of protrusions, and the support structure 36 may be shaped to define a plurality of complementary holes such that the protrusions snap into the holes.

[0059] As previously described with reference to FIG. 1 , during an ablation procedure, the physician 28 contacts the distal tip 32, particularly the outer layer 50, with tissue of the subject 26. While contacting the tissue with the outer layer 50, the physician passes an electric current through the outer layer and into the tissue. The electric current generates heat within the tissue, causing a lesion to form therein. This heat is transferred to the inner layer 70 via the thermal vias 74 (i.e., via the columns 48). Simultaneously, the pump 25 ( FIG. 1 ) pumps irrigation fluid 39 through the fluid supply tube, causing the fluid to flow into the interior of the electrode through the fluid flow openings 64 of the flow diverter 60. The fluid then flows out of the distal tip through the openings 62 and the irrigation holes 72, thereby discharging heat from the inner layer 70 into the subject's blood.

[0060] Distal tip fabrication Reference is now made to Figure 4, which is a flow chart of a method 82 for fabricating electrode 40, according to some embodiments of the present invention. Reference is now also made to Figure 5, which is a schematic illustration of electrode 40 prior to deformation, according to some embodiments of the present invention. (Figure 5 shows various elements coupled to the interior of electrode 40, i.e., the inner surface of substrate 41.)

[0061] 4 assumes that at least the interior surface of the substrate is initially coated with a layer of copper. Thus, method 82 begins with an etching step 84 in which all copper is etched away from the interior surface except for copper traces 114 connected to the outer sensing electrodes of the electrodes. (Copper on the exterior surfaces is also etched away.) This etching may be performed, for example, by placing a mask over the copper portions designated for traces 114 and then chemically removing the exposed copper. Alternatively, if the interior surface of the substrate is initially exposed, copper traces 114 may be deposited on the interior surface.

[0062] Subsequently, in a trace deposition step 86, a constantan trace 118 used for the thermocouple is deposited on the interior surface of the substrate. The trace deposition step 86 may be performed by physical vapor deposition (PVD), such as sputtering deposition. For example, a mask may be placed over the entire interior surface except for the portion of the interior surface designated for the constantan trace 118. Subsequently, a seed layer of a base metal, such as titanium tungsten, may be sputtered onto the substrate. Finally, constantan may be sputtered onto the base metal.

[0063] Typically, to minimize the wiring required, the constantan traces terminate at a common constantan trace soldering pad 120. In some embodiments, holes (or "pile vias") are drilled into the substrate at the locations of the soldering pads 120 before the constantan is deposited. The holes are then filled with the deposited constantan, and the soldering pads 120 are then formed over the holes. Alternatively, instead of drilling holes completely through the substrate, depressions can be drilled into the substrate and filled with the deposited constantan. In either case, the soldering pads 120 are "pile-mounted" to the substrate by the constantan beneath the soldering pads. (A draft angle may be used to tape the holes or depressions to facilitate filling of the holes or depressions, as described immediately below for narrow and wide channels.)

[0064] Next, in a drilling step 88, a plurality of narrow channels and one or more wide channels 44 are drilled into the substrate, typically using laser drilling techniques. (The narrow channels are visible in FIG. 5, but the narrow channels are not.) Typically, the channels are drilled from the inner surface of the substrate using a draft angle so that the channels narrow as they approach the outer surface. This facilitates metal collection on the walls of the channels during the subsequent sputtering process. Additionally, blind vias 80 can be drilled (e.g., laser drilled) through the substrate from the outer surface of the substrate at portions of the outer surface designated for sensing electrodes, using copper traces 114 as defining portions. (In other words, portions of the substrate disposed over the copper traces can be removed to expose the copper traces.) Typically, a draft angle is used for the blind vias so that they narrow as they approach the inner surface of the substrate. This facilitates metal collection on the walls of the blind vias.

[0065] Next, in a first masking step 90, the copper and constantan traces are masked, along with designated exclusion zones 91 (i.e., exposed portions of the substrate's inner surface) for insulating these traces. (However, portions of the constantan traces designated for thermocouple junctions are not masked.) Additional exclusion zones designated for insulating gold traces that intersect with the constantan traces (thus forming constantan-gold thermocouples) are also masked. In addition, exclusion zones on the outer surface designated for insulating the sensing electrodes are masked.

[0066] Thereafter, in a deposition step 92, a thin layer of gold is deposited on the interior and exterior surfaces of the substrate, and also within the channels. Deposition step 92 may be performed, for example, by physical vapor deposition (PVD), such as sputter deposition. (Typically, a seed layer of a base metal, such as titanium-tungsten, is sputtered onto the substrate prior to sputtering the gold.) Thanks to the mask, the gold is not deposited on the traces or on the exclusion zones.

[0067] The deposited gold includes the inner layer 70, the outer layer 50, the plating layer 52, and an initialization layer for the columns 48. The deposited gold further includes gold traces 122 that cover the constantan traces at the thermocouple junctions 124. Each gold trace 122 terminates in a respective gold trace soldering pad 126. The deposited gold further includes a respective copper trace soldering pad 116 for each of the copper traces. In some embodiments, the copper trace soldering pads 116 and / or the gold trace soldering pads 126 are staked to the substrate, as previously described with respect to the constantan trace soldering pads. The deposited gold further includes at least one gold soldering pad 128 connected to the inner layer 70. The gold soldering pad 128 may also be staked to the substrate.

[0068] After deposition, the mask (along with any gold deposited on it) is removed in a mask removal step 93. Subsequently, in a second masking step 94, the traces, the interior surface exclusion zones surrounding the traces, and the entire exterior surface of the substrate are masked.

[0069] Following the second masking step 94, the substrate is plated in a gold plating bath for a first time interval in a first plating step 98, with the traces and exterior surfaces remaining masked. Plating the substrate fills any voids in the gold, further increasing the gold thickness so that, for example, the inner layer 70 reaches a thickness of 5-40 micrometers, while the diameter of the wide channels decreases to 30-200 micrometers. Narrow channels may also be completely filled.

[0070] Typically, plating of the substrate is electrochemical, whereby the gold already coating the substrate is caused to attract gold ions in the plating bath by the flow of current through the gold. The amplitude and duration of the current may be controlled to achieve the desired thickness of gold.

[0071] Following the first plating step 98, the interior and exterior surfaces of the substrate are unmasked in a mask removal step 100, except for the aforementioned exclusion zones designated to insulate the sensing electrodes. Next, at least one coverlay 130 is applied over the traces and the interior surface exclusion zones in a coverlay application step 101. (In some embodiments, the coverlay 130 is transparent or nearly transparent, as illustrated in the inset of FIG. 5.)

[0072] Typically, the proximal portion of the coverlay 130 covering the tabs 47 is shaped to define windows 132 that expose the solder pads, allowing the solder pads to be thickened during a subsequent plating process. (An additional cover 142 having a window aligned with the window 132 may cover the proximal portion of the coverlay.) Typically, the solder pads are not completely exposed, but rather are kept "captured" by the coverlay 130, in that one or more edges of each solder pad are covered by the rim of the window 132. Thus, the coverlay 130 helps to hold the solder pads down against the substrate 41 during the subsequent soldering process.

[0073] Subsequently, in a second plating step 102, the substrate is plated in the plating bath for a second time interval to fill any voids in the outer layer 50 and thicken the inner, outer, and plated layers. For example, the second plating can increase the thickness of the inner layer to 10-50 micrometers while reducing the diameter of the wide channels to 15-150 micrometers. Typically, the final thickness of the inner layer is the same as the thickness of the coverlay to achieve a smooth inner surface. (To avoid any confusion, the term "inner surface" is used herein to refer to the surface formed by the coverlay and inner gold layer, while the term "inner surface" is used to refer to the underlying surface of the substrate.) Additionally, if any narrow channels were not completely filled during the first plating step 98, these channels will be completely filled during the second plating step 102. As with the first plating step 98, the amplitude and duration of the current in the plating bath can be controlled to achieve the desired thickness.

[0074] (In some embodiments, the exterior surface is masked prior to deposition step 92 so that gold is not deposited on the exterior surface during deposition step 92. In such embodiments, a thin layer of gold is deposited on the exterior surface after mask removal step 100 and before second plating step 102.)

[0075] Following the second plating step 102, openings 62 are drilled through the support structure 36 in an opening drilling step 104. (Instead of drilling, the openings may be formed using any other suitable technique, such as chemical etching.) Next, in a bonding step 106, the support structure is bonded to the inner surface by applying a suitable adhesive between the support structure 36 and the smooth inner surface formed by the coverlay 130 and inner layer 70, aligning the openings 62 with the irrigation holes 72. Typically, the area of ​​the openings is larger than the area of ​​the irrigation holes to compensate for any minor misalignments when bonding the support structure.

[0076] Next, in a deformation step 108, the electrode 40 is deformed into the desired shape. For example, the electrode may be inserted into a forming jig that forms the electrode around a suitable mandrel. After the electrode is inserted into the jig, the jig is placed in a furnace. The furnace then heats the electrode to a suitable temperature while pressure is applied to the electrode. The combination of heat and pressure causes the electrode to bond to itself in the desired shape.

[0077] Generally, the substrate and support structure can be deformed into any desired shape. Typically, however, during the deforming step 108, the substrate and support structure are shaped to define an internal lumen; for example, the substrate and support structure can be shaped to define a thimble including an internal lumen, as previously described with reference to Figures 2A and 3. Alternatively, for example, the substrate and support structure can be shaped to define an annulus.

[0078] Typically, to facilitate the fabrication of thimble-shaped electrodes, the substrate 41 includes two continuous portions: a distal circular portion 41a and a proximal rectangular portion 41b. Similarly, the support structure 36 includes two continuous portions: a distal support portion 36a including a plurality of spokes 134 radiating from a central hub 136, and a proximal support portion 36b. During the bonding step 106, the distal support portion 36a is bonded to the inner surface of the circular portion 41a, and adhesive is applied to the outer surfaces of the spokes 134 (these surfaces are opposite those shown in FIG. 5). Additionally, the proximal support portion 36b is bonded to the inner surface of the rectangular portion 41b, leaving a distal portion of the inner surface exposed. Adhesive is applied to the outer surface of an overhanging tab 138 of the proximal support portion 36b, which overhangs the side of the rectangular portion 41b. (Proximal support portion 36b may also overhang the proximal end of rectangular portion 41b.)

[0079] Subsequently, during deformation step 108, distal support portion 36a and circular portion 41a are folded over the top of the mandrel, while proximal support portion 36b and rectangular portion 41b are wrapped around the mandrel. To maintain this configuration, the outer surfaces of spokes 134 are bonded to the exposed distal portions of the inner surfaces of rectangular portion 41b, and the outer surfaces of tabs 138 are bonded to the opposite ends of proximal support portion 36b. (Also, the inner surface of at least one of the spokes may be bonded to tab 138.) Thus, distal support portion 36a and circular portion 41a are formed into dome-shaped portion 40a (see FIG. 2A), while proximal support portion 36b and rectangular portion 41b are formed into cylindrical portion 40b.

[0080] Thereafter, wires are soldered onto the soldering pads in a soldering step 110. Specifically, wires that deliver RF current from generator 27 (see FIG. 1) are soldered onto gold soldering pads 128, while other wires that deliver signals to processor 23 are soldered to other soldering pads.

[0081] Finally, in a coupling step 112, the electrodes are coupled to the catheter. For example, the proximal support portion 36b may be bonded to the base 58 of the flow diverter (see FIG. 3). Alternatively or additionally, protrusions on the base 58 may snap into complementary holes 140 in the proximal support portion 36b, as previously described with reference to FIG. 3. The flow diverter may then be coupled to a fluid supply tube on the catheter. (Alternatively, the flow diverter may be coupled to the fluid supply tube before the electrodes are coupled to the flow diverter.)

[0082] In general, any suitable masking technique may be used in each of the steps where a mask is required. Examples of suitable masks include liquid and film photoresists.

[0083] In place of, or in addition to, the traces described above, any other suitable electrical or electronic components may be deposited on the interior surface of the substrate. Such components may include a thermistor for measuring tissue temperature, a pressure sensor for measuring pressure applied to the distal end of the catheter, and / or an electromagnetic sensor for navigating the catheter. These components (along with any suitable surrounding exclusion zones) may be masked or covered whenever masking or covering is necessary, as previously described for the traces.

[0084] It should be noted that the scope of the present disclosure includes any suitable modifications made to method 82 with respect to the order of steps performed and / or with respect to the various materials used, as would be apparent to one of ordinary skill in the art. For example, any suitable conductive metal could be used in place of copper, gold, or constantan.

[0085] In general, the embodiments described herein can be combined with any of the embodiments described in U.S. Patent Application Publication No. 2018 / 0110562 or U.S. Patent Application No. 15 / 793126, the disclosures of each of which are incorporated herein by reference.

[0086] It will be understood by those skilled in the art that the present invention is not limited to what has been specifically shown and described herein. Rather, the scope of the embodiments of the present invention includes both combinations and subcombinations of the various features described herein, as well as variations and modifications of features that are not present in the prior art, which would occur to one skilled in the art upon reading the above description. Documents incorporated by reference into this patent application are deemed to be part of this application, except that if any term is defined in these incorporated documents in a way that contradicts the definition given herein, either expressly or impliedly, then only the definition given herein shall be considered.

[0087] [Embodiment] (1) a flexible, electrically insulating substrate having an inner surface and an outer surface, the substrate being shaped to define (i) a plurality of narrow channels passing between the inner surface and the outer surface, and (ii) one or more wider channels passing between the inner surface and the outer surface; an outer layer of conductive metal covering at least a portion of the outer surface; an inner layer of the conductive metal covering at least a portion of the inner surface; a plating layer of the conductive metal plating the wide channel so as to connect the outer layer to the inner layer; and respective columns of the conductive metal filling the narrow channels so as to connect the outer layer to the inner layer. (2) The device of claim 1, wherein the substrate is shaped to define at least 1,000 narrow channels. (3) The device of embodiment 1, wherein the total area of ​​the outer openings of each of the narrow channels is at least 10% of the area of ​​the outer surface. (4) The device of embodiment 1, wherein the conductive metal comprises gold. (5) at least one constant trace disposed on the inner surface and electrically insulated from the inner layer; 5. The device of claim 4, further comprising at least one gold trace disposed on the inner surface, electrically insulated from the inner layer, and covering the constantan trace at a thermocouple junction.

[0088] (6) further comprising a support structure coupled to the inner layer; 2. The device of claim 1, wherein the substrate and the support structure are shaped to define an internal lumen. (7) The device of embodiment 6, wherein the substrate and the support structure are shaped to define a thimble containing the internal lumen. (8) further comprising a catheter configured for insertion into the body of the subject; 7. The device of embodiment 6, wherein the support structure is connected to the distal end of the catheter. (9) The distal end of the catheter comprises a flow diverter configured to redirect fluid received from the proximal end of the catheter; 9. The device of claim 8, wherein the support structure is connected to the flow diverter such that the flow diverter is disposed within the inner lumen. (10) The device of embodiment 1, wherein each of the narrow channels has an average diameter of 5 to 50 micrometers.

[0089] (11) The device of embodiment 1, wherein the narrow channel average diameter of each of the narrow channels is less than 50% of the wide channel average diameter of each of the wide channels. (12) The device according to embodiment 1, wherein the thickness of the substrate is 5 to 75 micrometers. (13) further comprising one or more conductive traces disposed on the inner surface and electrically insulated from the inner layer; the substrate is shaped to define respective holes opposite the traces; The outer layer is The main part and 2. The device of claim 1, further comprising: one or more islands electrically insulated from the main portion and each contacting the trace by at least partially filling the hole. (14) Inserting into a body of a subject a distal end of a catheter including a substrate, the substrate having an inner surface at least partially coated with an inner metal layer and an outer surface at least partially coated with an outer metal layer, and shaped to define: (i) a plurality of narrow channels passing between the inner and outer surfaces and filled with metal columns; and (ii) one or more wider plated channels passing between the inner and outer surfaces; contacting tissue of the subject with the outer metallic layer following insertion of the distal end of the catheter into the body of the subject; passing an electric current through the tissue through the outer metallic layer while in contact with the tissue, so as to generate heat within the tissue and transfer it to the inner metallic layer through the metallic column; and dissipating the heat from the inner metal layer into the subject's blood by passing an irrigation fluid through the plated wide channels. (15) The method of embodiment 14, wherein the tissue comprises cardiac tissue of the subject.

[0090] (16) The outer metal layer is The main part and one or more islands electrically isolated from the main portion; 16. The method of embodiment 15, wherein the method further comprises sensing an electrogram signal from the cardiac tissue using the islet. (17) drilling a plurality of narrow channels and one or more wide channels through a flexible, electrically insulating substrate to pass between an inner surface of the substrate and an outer surface of the substrate; and at least partially coating the interior and exterior surfaces with a conductive metal, completely filling the narrow channels, and plating the wide channels. 18. The method of claim 17, wherein drilling the narrow channels comprises drilling at least 1,000 narrow channels. (19) The method of embodiment 17, wherein the total area of ​​the outer openings of each of the narrow channels is at least 10% of the area of ​​the outer surface. 20. The method of claim 17, wherein the conductive metal comprises gold.

[0091] (21) further comprising depositing at least one constantan trace on the inner surface; 21. The method of claim 20, wherein at least partially coating the inner surface comprises depositing at least one gold trace on the inner surface, the gold trace coating the constantan trace, thereby forming a thermocouple junction. (22) The method of embodiment 17, wherein each of the narrow channels has an average diameter of 5 to 50 micrometers. 23. The method of claim 17, wherein the average narrow channel diameter of each of the narrow channels is less than 50% of the average wide channel diameter of each of the wide channels. (24) The method according to embodiment 17, wherein the thickness of the substrate is 5 to 75 micrometers. (25) At least partially coating the inner and outer surfaces, completely filling the narrow channels, and plating the wide channels; depositing the conductive metal on the inner and outer surfaces of the substrate and within the narrow and wide channels; Following depositing the conductive metal on the interior surface of the substrate, plating the substrate in a plating bath of the conductive metal for a first time interval while the exterior surface of the substrate is coated; subsequent to plating the substrate for the first time interval, at least partially stripping the coating from the exterior surface of the substrate; following at least partially stripping the coating from the exterior surface of the substrate, plating the substrate in the plating bath for a second time interval; 18. The method of claim 17, comprising at least partially coating the inner and outer surfaces, completely filling the narrow channels, and plating the wide channels by

[0092] (26) bonding the conductive metal coating on the inner surface to a support structure; 18. The method of claim 17, further comprising molding the substrate and the support structure to define an internal lumen. 27. The method of claim 26, wherein molding the substrate and the support structure comprises molding the substrate and the support structure to define a thimble including the internal lumen. (28) The method of embodiment 26, further comprising coupling the support structure to a distal end of a catheter configured for insertion into the body of a subject. (29) The distal end of the catheter comprises a flow diverter configured to redirect fluid received from the proximal end of the catheter; 29. The method of claim 28, wherein connecting the support structure to the distal end of the catheter includes connecting the support structure to the flow diverter so that the flow diverter is disposed within the inner lumen. (30) further comprising etching one or more conductive traces on the inner surface of the substrate; depositing the conductive metal onto the inner surface of the substrate includes depositing the conductive metal onto the inner surface of the substrate such that the conductive traces remain electrically insulated from the conductive metal; the method further comprising forming holes in the substrate on opposite sides of the traces; 18. The method of claim 17, wherein depositing the conductive metal on the outer surface of the substrate comprises depositing the conductive metal on the outer surface of the substrate to form (i) a main portion and (ii) one or more islands electrically insulated from the main portion and each contacting the trace by at least partially filling the hole.

Claims

1. 1. An apparatus comprising:

1. An ablation electrode comprising: a flexible, electrically insulating substrate having an inner surface and an outer surface, the substrate being shaped to define (i) a plurality of narrow channels passing between the inner surface and the outer surface, and (ii) one or more wider channels passing between the inner surface and the outer surface; an outer layer of conductive metal covering at least a portion of the outer surface; an inner layer of the conductive metal covering at least a portion of the inner surface; a plating layer of the conductive metal that plates the wide channel so as to connect the outer layer to the inner layer without blocking the wide channel; and respective columns of the conductive metal filling the narrow channels so as to connect the outer layer to the inner layer; and the device further comprising a support structure at the tip of the catheter having a dome-shaped distal portion; the inner layer is bonded to the dome-shaped distal portion of the support structure; The device, wherein the substrate comprises a distal circular portion and a proximal rectangular portion that are continuous with each other, and the support structure comprises a distal support portion and a proximal support portion that are continuous with each other and include a plurality of spokes.

2. The device of claim 1 , wherein the substrate is shaped to define at least 1,000 narrow channels.

3. The device of claim 1 , wherein the total area of ​​the outer openings of each of the narrow channels is at least 10% of the area of ​​the outer surface.

4. The device of claim 1 , wherein the conductive metal comprises gold.

5. at least one constant trace disposed on the inner surface and electrically insulated from the inner layer; 5. The apparatus of claim 4, further comprising at least one gold trace disposed on the inner surface, electrically insulated from the inner layer, and covering the constantan trace at a thermocouple junction.

6. The device of claim 1 , wherein the substrate and the support structure are shaped to define an internal lumen.

7. The device of claim 6 , wherein the substrate and the support structure are shaped to define a thimble containing the internal lumen.

8. the catheter configured for insertion into a body of a subject; The device of claim 6 , wherein the support structure is coupled to a distal end of the catheter.

9. the distal end of the catheter comprising a flow diverter configured to redirect fluid received from the proximal end of the catheter; 9. The device of claim 8, wherein the support structure is coupled to the flow diverter such that the flow diverter is disposed within the inner lumen.

10. 10. The device of claim 1, wherein each of the narrow channels has an average diameter of 5 to 50 micrometers.

11. 10. The device of claim 1, wherein the average narrow channel diameter of each of the narrow channels is less than 50% of the average wide channel diameter of each of the wide channels.

12. The device of claim 1, wherein the substrate has a thickness of 5 to 75 micrometers.

13. further comprising one or more conductive traces disposed on the inner surface and electrically insulated from the inner layer; the substrate is shaped to define respective holes opposite the conductive traces; The outer layer is The main part and 10. The device of claim 1, further comprising: one or more islands electrically isolated from the main portion and each contacting the conductive trace by at least partially filling the hole.

14. 10. A method for manufacturing the device of claim 1, comprising: drilling the plurality of narrow channels and the one or more wide channels through the substrate to pass between the inner surface of the substrate and the outer surface of the substrate; and plating the wide channel with a conductive metal to at least partially coat the interior and exterior surfaces and completely fill the narrow channel and not block the wide channel.

15. The method of claim 14 , wherein drilling the narrow channels comprises drilling at least 1,000 narrow channels.

16. 15. The method of claim 14, wherein the total area of ​​the outer openings of each of the narrow channels is at least 10% of the area of ​​the outer surface.

17. The method of claim 14 , wherein the conductive metal comprises gold.

18. further comprising depositing at least one constantan trace on said inner surface; 18. The method of claim 17, wherein at least partially coating the inner surface comprises depositing at least one gold trace on the inner surface, the gold trace coating the constantan trace, thereby forming a thermocouple junction.

19. The method of claim 14, wherein each of the narrow channels has an average diameter of 5 to 50 micrometers.

20. 15. The method of claim 14, wherein the average narrow channel diameter of each of the narrow channels is less than 50% of the average wide channel diameter of each of the wide channels.

21. The method of claim 14, wherein the substrate has a thickness of 5 to 75 micrometers.

22. plating the wide channel so as to at least partially coat the inner and outer surfaces, completely fill the narrow channel, and not block the wide channel; depositing the conductive metal on the inner and outer surfaces of the substrate and within the narrow and wide channels; Following depositing the conductive metal on the interior surface of the substrate, plating the substrate in a plating bath of the conductive metal for a first time interval while the exterior surface of the substrate is coated; subsequent to plating the substrate for the first time interval, at least partially stripping the coating from the exterior surface of the substrate; following at least partially stripping the coating from the exterior surface of the substrate, plating the substrate in the plating bath for a second time interval; 15. The method of claim 14, comprising plating the wide channels to at least partially coat the inner and outer surfaces with a metal such that the narrow channels are completely filled and the wide channels are not blocked.

23. bonding the conductive metal coating the inner surface to the support structure; The method of claim 14, further comprising: molding the substrate and the support structure to define an internal lumen.

24. 24. The method of claim 23, wherein molding the substrate and the support structure comprises molding the substrate and the support structure to define a thimble including the internal lumen.

25. 24. The method of claim 23, further comprising coupling the support structure to a distal end of the catheter configured for insertion into a body of a subject.

26. the distal end of the catheter comprising a flow diverter configured to redirect fluid received from the proximal end of the catheter; 26. The method of claim 25, wherein coupling the support structure to the distal end of the catheter comprises coupling the support structure to the flow diverter such that the flow diverter is disposed within the inner lumen.

27. further comprising etching one or more conductive traces on the inner surface of the substrate; depositing the conductive metal onto the inner surface of the substrate includes depositing the conductive metal onto the inner surface of the substrate such that the conductive traces remain electrically insulated from the conductive metal; the method further comprising forming holes in the substrate on opposite sides of the conductive traces; 15. The method of claim 14, wherein depositing the conductive metal on the outer surface of the substrate comprises depositing the conductive metal on the outer surface of the substrate to form (i) a main portion and (ii) one or more islands electrically insulated from the main portion and each contacting the conductive trace by at least partially filling the hole.

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