Improved heat transfer across ablation electrodes

Abstract

The present invention is entitled "Improved Heat Transfer Across Ablation Electrodes." The present invention provides a device comprising a flexible, electrically insulating substrate including an outer surface and an inner surface. The substrate is shaped to define a plurality of channels passing between the inner and outer surfaces, at least some of which are concave channels. The device also includes 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; and corresponding posts of conductive metal filling the channels to connect the outer layer to the inner layer.

Description

Technical Field

[0001] The present invention relates to an intracorporeal probe and its use in an ablation procedure. Background Art

[0002] In some ablation procedures, an electrode disposed at the distal end of an intracorporeal probe is brought into contact with tissue, and radiofrequency (RF) energy is then delivered from the electrode into the tissue.

[0003] U.S. Patent Application Publication 2018 / 0110562 (the disclosure of which is incorporated herein by reference) describes a catheter comprising an insertion tube, a flexible substrate, and one or more electrical devices. The insertion tube is configured for insertion into a patient. The flexible substrate is configured to wrap around the distal end of the insertion tube and includes an electrical interconnect. The electrical device is coupled to the flexible substrate and connected to the electrical interconnect. Summary of the Invention

[0004] According to some embodiments of the present invention, a device is provided that includes a flexible electrically insulating substrate. The substrate includes an inner surface and an outer surface, and is shaped to define a plurality of channels passing between the inner and outer surfaces, at least some of the channels being concave. The device also includes 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; and corresponding posts of conductive metal filling the channels to connect the outer layer to the inner layer.

[0005] In some embodiments, each of the concave channels comprises:

[0006] a circular center channel portion; and

[0007] One or more peripheral channel portions have an arcuate perimeter and open into the central channel portion.

[0008] In some embodiments, the peripheral channel segments consist of between two and eight peripheral channel segments.

[0009] In some embodiments, the peripheral channel portion consists of six peripheral channel portions.

[0010] In some embodiments, some of the channels are circular channels, and the channels are arranged such that each circular channel of at least some of the circular channels is surrounded by respective three of the concave channels.

[0011] In some embodiments, each of the concave channels comprises:

[0012] a polygonal center channel portion; and

[0013] One or more peripheral channel portions, the one or more peripheral channel portions opening into the central channel portion.

[0014] In some embodiments, the central channel portion and the peripheral channel portion are rectangular.

[0015] In some embodiments, each of the concave channels has a star shape.

[0016] In some embodiments, the total area of ​​the respective outer openings of the channels is at least 30% of the area of ​​the outer surface.

[0017] In some embodiments, the conductive metal includes gold.

[0018] In some embodiments, the apparatus further comprises:

[0019] a probe configured for insertion into a body of a subject; and

[0020] A support structure is bonded to the inner layer and coupled to the distal end of the probe.

[0021] In some embodiments, the support structure includes a plurality of ribs surrounding the cavity, with consecutive ones of the ribs separated from one another by openings that are wider than each of the ribs.

[0022] In some embodiments, the surface of the inner layer is shaped to define a plurality of recesses.

[0023] In some embodiments, the recesses are circular and are arranged in a closely packed pattern.

[0024] In some embodiments, the average cross-sectional area of ​​each of the concave channels is 345 μm 2 Up to 15700 μm 2 between.

[0025] According to some embodiments of the present invention, a method is also provided, the method comprising inserting a distal end of a probe into a subject's body, the probe comprising a substrate having an inner surface and an outer surface, the inner surface being at least partially covered by an inner metal layer, the outer surface being at least partially covered by an outer metal layer, the substrate being shaped to define a plurality of channels that pass between the inner surface and the outer surface and are filled with metal pillars, at least some of the channels being concave channels. The method further comprises: after inserting the distal end of the probe into the subject's body, contacting the subject's tissue with the outer metal layer. The method further comprises: while contacting the tissue, transferring an electric current into the tissue via the outer metal layer, so that heat is generated in the tissue and transferred to the inner metal layer via the metal pillars. The method further comprises: discharging heat from the inner metal layer into the subject's blood by passing an irrigation fluid through the substrate.

[0026] In some embodiments, the tissue comprises cardiac tissue of a subject.

[0027] According to some embodiments of the present invention, a method is also provided, comprising: forming a plurality of channels in a flexible electrically insulating substrate, at least some of the channels being concave channels, such that the channels pass between an inner surface and an outer surface of the substrate. The method further comprises: at least partially covering the inner and outer surfaces with a conductive metal and filling the channels.

[0028] In some embodiments, forming the channel comprises:

[0029] A tightly packed pattern forming circular channels; and

[0030] After the close-packed pattern is formed, concave channels are formed by expanding some of the circular channels so that each of the expanded circular channels opens to surrounding six of the circular channels.

[0031] In some embodiments, the method further comprises:

[0032] bonding the conductive metal covering the inner surface to the support structure; and

[0033] A support structure is coupled to a distal end of a probe configured for insertion into a body of a subject.

[0034] In some embodiments, the method further includes forming a plurality of recesses in the surface of the inner layer.

[0035] In some embodiments, forming the recesses includes forming rounded recesses in a closely packed pattern.

[0036] The present disclosure will be more fully understood through the following detailed description of embodiments of the present invention in conjunction with the accompanying drawings, in which: BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is a schematic diagram of a system for ablating tissue of a subject according to some embodiments of the present invention;

[0038] Figure 2A is a schematic diagram of an ablation electrode according to some embodiments of the present invention;

[0039] Figure 2B Schematically illustrating a method of passing through a Figure 2A A longitudinal section of the ablation electrode shown in ;

[0040] Figure 3A According to some embodiments of the present invention, Figure 2ASchematic diagram of a cross section of the surface of the ablation electrode shown in ;

[0041] Figure 3B According to some embodiments of the present invention, Figure 2A Schematic diagram of the heat dissipation holes on the surface of the ablation electrode shown in;

[0042] Figure 3C According to some embodiments of the present invention, Figure 2A Schematic diagram of the irrigation holes on the surface of the ablation electrode shown in;

[0043] Figure 4 is a flow chart of a method of manufacturing an ablation electrode according to some embodiments of the present invention;

[0044] Figure 5 is a schematic diagram of an ablation electrode before deformation according to some embodiments of the present invention;

[0045] Figure 6A is a schematic diagram of a method for forming a recess in a surface of a support structure according to some embodiments of the present invention;

[0046] Figure 6B is a schematic diagram of a method for forming protrusions on a surface of a support structure according to some embodiments of the present invention;

[0047] Figure 7 schematically illustrates heat transfer to the interior of an ablation electrode according to some embodiments of the present invention;

[0048] Figure 8 is a schematic diagram of a support structure according to some embodiments of the present invention;

[0049] Figure 9 is a schematic diagram of various types of concave channels according to some embodiments of the present invention; and

[0050] Figure 10 is a schematic diagram of an arrangement of channels according to some embodiments of the present invention. DETAILED DESCRIPTION

[0051] Glossary

[0052] A concave perimeter protrudes inwardly so that a line connecting two points within the perimeter at opposite sides of the protrusion extends beyond the perimeter. In contrast, any line joining two points within a convex (or "non-concave") perimeter does not extend beyond the perimeter.

[0053] In the context of this application, including the claims, the "perimeter" of a channel or through-hole generally refers to the perimeter of the cross-section of the channel or through-hole. Similarly, unless otherwise specified, the "shape" of a channel or through-hole generally refers to the shape of the perimeter of the channel or through-hole.

[0054] In the context of this application, including the claims, a concave channel or through-hole is a channel or through-hole having a concave perimeter. Conversely, a convex channel or through-hole is any channel or through-hole having a convex perimeter. (Generally speaking, a channel or through-hole that is slightly concave due to imperfections in the manufacturing techniques used to form the channel or through-hole is considered convex, not concave, herein.)

[0055] Overview

[0056] Embodiments of the present invention include an ablation electrode comprising at least one flexible printed circuit board (PCB) bonded to a support structure by an adhesive. The flexible PCB comprises a flexible electrically insulating substrate comprising 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. As further described below, the metal can be deposited onto the substrate by placing the substrate in a plating tank for a period of time.

[0057] The inner surface can further support one or more electronic components electrically isolated from the inner metal layer, such as sensors (e.g., thermocouples) and traces. After depositing these electronic components and coating the substrate, the PCB is bonded to the support structure. After or simultaneously with bonding, the flexible PCB can be deformed into any suitable shape. For example, in some embodiments, the flexible PCB is deformed into a sleeve-shaped electrode, hereinafter referred to as a "tip electrode." The electrode is then coupled to the distal end of the intracorporeal probe.

[0058] During the ablation process, the outer metal layer is brought into contact with the tissue to be ablated, and the ablation current is then delivered into the tissue via the outer metal layer. When the ablation current is applied to the tissue, the sensor can obtain any relevant physiological readings from the tissue. Typically, plated vias through the electrode provide electrical connections between the inner and outer metal layers, such that the ablation current can pass outward through the plated vias, and electrographic signals from the tissue can pass inward through the plated vias. Electrical connections can also be provided by blind vias, each such via being formed by removing a portion of the substrate so that the outer metal layer directly contacts the underlying trace.

[0059] The plated through-holes also provide fluid communication between the inner and outer surfaces of the electrode, allowing irrigation fluid (e.g., saline) to pass through the plated through-holes into the surrounding blood. The irrigation fluid removes heat from the interior of the electrode into the blood and additionally dilutes the blood at the tissue-electrode interface, thereby reducing the likelihood of coagulation or charring. Given the fact that the plated through-holes provide a passage for the irrigation fluid to pass through, the plated through-holes may also be referred to as "irrigation channels" or "irrigation holes."

[0060] When using electrodes of the type described above, a challenge 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. This in turn limits the amount of heat that can be removed by the irrigation fluid.

[0061] U.S. Patent Applications 15 / 990,532 and 16 / 103,806 (the disclosures of each of which are incorporated herein by reference) address this challenge by providing closed through-holes, hereinafter referred to as "thermal vias," that increase thermal conductivity between the two surfaces of the electrode. Such thermal vias may comprise, for example, gold posts that fill channels drilled through the substrate and thereby connect the outer metal layer to the inner metal layer. The thermal vias increase the amount of heat transferred to the interior of the electrode, thereby facilitating heat removal via the irrigation fluid.

[0062] Generally speaking, the degree of thermal conductivity provided by a via is a function of the total cross-sectional area of ​​the metal filling the via. However, as the inventors have discovered, it can be difficult to achieve a sufficient total cross-sectional area using vias having a convex cross-sectional profile (such as a circular cross-sectional profile). Specifically, if the cross-sectional area of ​​any of the vias is too large, it can take a relatively long time to fill the via during the plating process, such that the metal layer covering the surface of the substrate can become too thick while the via is being filled. Hypothetically, a large number of smaller vias could be provided; however, this might require placing the vias too close together, thereby compromising the structural integrity of the substrate.

[0063] Thus, embodiments of the present invention provide concave thermal vias in which the perimeter of the through-hole protrudes into the through-hole. The protrusion provides additional area onto which metal can nucleate during the plating process and also reduces the distance from the perimeter to the interior of the through-hole, thereby accelerating the filling of the through-hole. As a result, each concave thermal via can have a relatively large cross-sectional area without unduly increasing the duration of the plating process. In some embodiments, the concave thermal vias are interspersed with smaller convex thermal vias.

[0064] Alternatively or in addition, various other techniques can be used to facilitate heat transfer to the irrigation fluid, as described in detail below. For example, the support structure can be shaped to define large openings that expose the inner metal layer to the irrigation fluid. Furthermore, the inner metal layer can be shaped to define a plurality of recesses that increase turbulence in the fluid flowing over the inner metal layer.

[0065] System Description

[0066] First reference Figure 1 , which is a schematic diagram of a system 20 for ablating tissue of a subject 26, according to some embodiments of the present invention.

[0067] Figure 1 A physician 28 is depicted performing an ablation procedure on a subject 26 using an intracorporeal probe 22. In the procedure, the physician 28 first inserts an ablation electrode 40 disposed at the distal end of the probe 22 into the subject and then navigates the electrode 40 to the tissue to be ablated. For example, the physician may advance the electrode through the subject's vasculature until the electrode contacts cardiac tissue belonging to the subject's heart 24. Next, when the electrode 40 contacts the tissue, the physician passes a radiofrequency (RF) current between the ablation electrode and another electrode such that the current generates heat in the tissue. For example, in a monopolar ablation procedure, current may be passed between the ablation electrode and a neutral electrode patch 30 coupled to the exterior of the subject (e.g., the subject's back).

[0068] To facilitate navigation of the probe 22, the probe may include one or more electromagnetic position sensors that generate a signal that varies with the position of the sensor in the presence of an external magnetic field. Alternatively or in addition, any other suitable tracking system may be used, such as an impedance-based tracking system. For example, both electromagnetic tracking and impedance-based tracking may be used, as described, for example, in U.S. Patent No. 8,456,182, the disclosure of which is incorporated herein by reference.

[0069] The probe 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 patch 30 is also typically connected to the console 34 via a cable 42.) During an ablation procedure, the signal generator 27 generates the ablation currents described above. These currents are transmitted to the electrodes 40 via one or more wires passing through the probe 22. In addition, the pump 25 supplies an irrigation fluid, such as saline, to the distal end of the probe, as described below with reference to FIG. Figures 2A to 2B as well as Figure 3C Further described.

[0070] The console 34 also includes a controller 35 that the physician can use to control the parameters of the ablation current. Specifically, in response to the physician 28 manipulating the controller 35, the processor 23 can adjust the parameters of the ablation current by outputting appropriate instructions to the signal generator 27 over any suitable wired or wireless communication interface. The processor 23 can similarly control the pump 25 through any suitable wired or wireless interface. In addition, the processor can receive and process any relevant signals from the distal end of the catheter, such as signals received from any sensor described herein.

[0071] In some embodiments, system 20 also includes a display 38 that can display relevant output to physician 28 during surgery.

[0072] although Figure 1 A particular type of procedure is depicted in the figures, but it is noted that the embodiments described herein may be applied to any other suitable type of ablation procedure, such as otolaryngology or neurology ablation procedures, or any other procedure that requires heat transfer through a flexible PCB, such as to dissipate heat from the circuit board into a surrounding fluid.

[0073] Ablation electrodes

[0074] Now refer to Figure 2A , which is a schematic diagram of an ablation electrode 40 according to some embodiments of the present invention. Figure 2B , which schematically illustrates a longitudinal section through an electrode 40 according to some embodiments of the present invention.

[0075] As mentioned above Figure 1 As depicted, the probe 22 includes at least one ablation electrode 40, such as Figures 2A to 2B . The electrode 40 comprises a plated, flexible, electrically insulating substrate 41 that is adhesively bonded to the support structure 36 at the distal end of the probe 22. The substrate 41 can be made of any suitable flexible, electrically insulating material, such as a flexible polymer (e.g., polyimide) or a liquid crystal polymer (LCP). The support structure 36 can be made of any suitable strong material, such as cobalt chromium, stainless steel, magnesium, or a polymer. For example, the support structure can include an alloy of cobalt chromium, such as L-605 cobalt chromium tungsten nickel alloy, or polyetheretherketone (PEEK), such as glass-filled PEEK.

[0076] Generally speaking, the electrode 40 can have any suitable shape. In some embodiments, such as Figures 2A to 2BAs shown, the electrode 40 is cannulated and includes a cylindrical portion 40b terminated by a dome-shaped portion 40a. Typically, a tab 47 located at the proximal end of the electrode includes a pad to which a wire extending along the length of the probe can be soldered to establish an electrical connection between the electrode and the proximal end of the probe. Figures 4 and 5 These pads are described in further detail.

[0077] Now refer to Figure 3A , which is a schematic diagram of a cross-section through the surface of electrode 40 according to some embodiments of the present invention. Figure 3A and Figure 2A Corresponding to the cross section indicated as "AA".

[0078] Substrate 41 includes an inner surface 76 facing toward support structure 36 and an outer surface 45 facing away from support structure 36. Typically, the thickness T0 of the substrate (i.e., the distance between the inner and outer surfaces of the substrate) is between 5 microns and 75 microns (e.g., between 12 microns and 50 microns). At least a portion of the inner surface is covered by an inner layer 70 of conductive metal (e.g., gold). Typically, inner layer 70 has a thickness T1 between 10 microns and 50 microns. Similarly, at least a portion of outer surface 45 is covered by an outer metal layer 50. Typically, outer layer 50 has a thickness T2 between 1 micron and 50 microns (e.g., 5 microns to 35 microns).

[0079] Typically, the outer layer 50 is discontinuous in that it includes a main portion 54 and one or more isolated portions that are electrically isolated from the main portion 54 by exposed portions of the substrate. These isolated portions may include one or more "islands" that serve as sensing microelectrodes 56. For example, the outer layer 50 may include 3 to 7 microelectrodes 56 distributed around the circumference of the electrode. Alternatively or in addition, the isolated portion may include a sensing ring electrode 43 that may be disposed, for example, near the proximal end of the electrode 40.

[0080] A corresponding conductive trace 78 is provided beneath each sensing electrode, electrically isolated from the inner layer 70 by an exposed portion of the inner surface 76. Figure 4 As further described, prior to forming the sensing electrodes, holes, referred to herein as blind holes 80, are formed (e.g., drilled) in the substrate above the traces 78. Subsequently, when the sensing electrodes are deposited onto the outer surface of the substrate, the sensing electrodes at least partially fill the blind holes 80, thereby contacting the traces. Thus, during a procedure, electrographic signals from the subject's cardiac tissue sensed by the sensing electrodes can be transmitted via the traces 78 to the wires that pass through the probe 22 to the proximal end of the probe. The signals can thus be delivered to the processor 23 ( Figure 1 ) for analysis.

[0081] Now refer to Figure 3B , which is a schematic diagram of heat dissipation holes passing through the surface of the electrode 40 according to some embodiments of the present invention. Figure 3B and Figure 2A The cross section "BB" is indicated in FIG.

[0082] The substrate 41 is formed to define a plurality of channels 46 passing between the substrate's inner surface 76 and outer surface 45. Typically, each channel 46 tapers along its length in that the channel has a slightly larger cross-sectional area at the substrate's inner surface than at the outer surface.

[0083] If you can Figure 2A As observed in FIG, at least some of the channels 46 are concave channels 49, which will be referred to below. Figures 9 and 10 Further detailed description. Optionally, the channel may further include one or more convex channels 51. In some embodiments, each convex channel 51 is circular with a diameter d0 between 5 microns and 50 microns (eg, between 5 microns and 30 microns).

[0084] As described above in the overview, the cross-sectional area A0 of each channel 49 can be relatively large due to the concavity of the channels 49. For example, the average cross-sectional area of ​​each of these concave channels can be 345 μm 2 Up to 15700 μm 2 Alternatively or in addition, the total area of ​​the respective outer openings of the channels 46 (including the concave channels and any convex channels) may be at least 30% of the area of ​​the outer surface.

[0085] The channels 46 are filled with corresponding posts 48 of conductive metal, which connect the outer layer 50 to the inner layer 70. The posts 48 can have any suitable three-dimensional shape, which depends on the three-dimensional shape of the channels 46. Because heat is conducted through the posts 48, the filled channels 46 are referred to herein as heat dissipation vias 74. (For simplicity, Figure 3A The heat dissipation holes described above are not shown.)

[0086] Now refer to Figure 3C , which is a schematic diagram of irrigation holes 72 through the surface of electrode 40, according to some embodiments of the present invention. Figure 3C and Figure 2A Corresponding to the cross section indicated as "CC".

[0087] Typically, substrate 41 is also shaped to define a plurality of wider channels 44, each of which is plated with a plated layer 52 of conductive metal, which connects outer layer 50 to inner layer 70. Typically, each wider channel 44 is circular, having a diameter d1 between 50 microns and 300 microns. Due to the fact that the cross-sectional area of ​​each channel 44 is generally greater than the cross-sectional area of ​​each channel 46, channels 44 are referred to herein as "wider" channels. For the same reason, channels 46 are hereinafter referred to as "narrower channels."

[0088] Typically, the electrode includes 30 to 100 wide channels. The plated wide channels provide electrical and thermal conductivity between the metal outer layer and the metal inner layer. In addition, the plated wide channels provide fluid passages between the interior and exterior of the electrode, allowing the pump 25 ( Figure 1 ) The supplied flushing fluid 39 can flow through it. Therefore, the wider plated channels are referred to herein as "flushing holes" 72. (The diameter of each flushing hole is smaller than the diameter d1 by about twice the thickness of the plated layer 52.)

[0089] from Figure 2B As can be seen in FIG, the support structure 36 is formed to define an opening 62 that is aligned with the flushing hole 72 so that the support structure does not block the flushing hole. Figure 8 As further described, the openings 62 also expose a relatively large area of ​​the inner layer 70, thereby increasing the transfer of heat to the irrigation fluid by exposing the inner layer to the fluid.

[0090] Typically, the probe 22 includes a fluid delivery tube (not shown) that extends through the entire length of the tubular body 22m of the probe 22. The fluid delivery tube is coupled distally to a diversion element 60 that is shaped to define one or more fluid flow openings 64. The diversion element 60 diverts fluid 39 received from the proximal end of the probe via the fluid delivery tube through the fluid flow openings 64. In such embodiments, the electrode 40 can be coupled to the base 58 of the diversion element 60 such that the diversion element is disposed within the lumen of the electrode. For example, the support structure 36 can be bonded to the base 58. Alternatively or in addition, the base 58 can be shaped to define a plurality of protrusions, and the support structure 36 can be shaped to define a plurality of complementary holes such that the protrusions snap into the holes.

[0091] As mentioned above Figure 1 As described, during the ablation procedure, physician 28 brings the tissue of subject 26 into contact with electrode 40, specifically, outer layer 50. While bringing the tissue into contact with outer layer 50, the physician delivers an electrical current into the tissue via the outer layer. The electrical current generates heat in the tissue, causing an ablation lesion to form in the tissue. This heat is transferred to inner layer 70 via heat dissipation holes 74 (i.e., via posts 48). Simultaneously, pump 25 ( Figure 1 ) Pumping irrigation fluid 39 through the fluid delivery tube causes the fluid to flow into the interior of the electrode through the fluid flow openings 64 of the flow diverting element 60. The fluid then flows out of the electrode through the openings 62 and the irrigation holes 72, thereby dissipating heat from the inner layer 70 into the subject's blood.

[0092] It is noted that the outer layer 50, inner layer 70, plating layer 52, and posts 48 can be collectively described as a single metal body covering the substrate. It is also noted that in some embodiments, the narrower channels 46 are not plated, similar to the wider channels 44. However, even in such embodiments, a significant amount of heat can be transferred to the interior of the electrode.

[0093] Fabrication of ablation electrodes

[0094] Now refer to Figure 4 , which is a flow chart of a method 82 for manufacturing an electrode 40 according to some embodiments of the present invention. Figure 5 , which is a schematic diagram of an electrode 40 before its deformation according to some embodiments of the present invention. ( Figure 5 The interior of electrode 40 is shown, i.e., the various elements coupled to the inner surface of substrate 41.)

[0095] Figure 4 It is assumed that at least the inner surface of the substrate is initially coated with a layer of copper. Therefore, method 82 begins with an etching step 84 in which all other copper on the inner surface is etched away except for copper trace 114, which will be connected to the sensing electrode on the outer portion of the electrode. (Any copper on the outer surface is also etched away.) This etching can be performed, for example, by placing a mask over the copper portion designated for trace 114 and then chemically removing the exposed copper. Alternatively, if the inner surface of the substrate is initially exposed, copper trace 114 can be deposited on the inner surface.

[0096] Subsequently, at a trace deposition step 86, constantan traces 118 for the thermocouples are deposited onto the inner surface of the substrate. Trace deposition step 86 can be performed, for example, by physical vapor deposition (PVD), such as sputtering. For example, a mask can be placed over all portions of the inner surface except those designated for constantan traces 118. Subsequently, a seed layer of a base metal, such as titanium-tungsten, can be sputtered onto the substrate. Finally, constantan can be sputtered onto the base metal.

[0097] Typically, to minimize the required wiring, the constantan traces terminate at a common constantan trace pad 120. In some embodiments, a hole (or "stub via") is drilled through the substrate at the location of the pad 120 before the constantan is deposited. The deposited constantan then fills the hole, and the pad 120 is formed over the hole. Alternatively, a recess can be drilled into the substrate so that the deposited constantan fills the recess, rather than drilling completely through the substrate. In either case, the pad 120 is "staked" to the substrate by the constantan below the pad. (To facilitate filling the hole or recess, a draft angle can be used to taper the hole or recess, as described immediately below for narrower and wider channels.)

[0098] Next, at a drilling step 88, narrower channels and wider channels are drilled through the substrate, typically using laser drilling. Figure 5 ) Typically, the channels are drilled from the inner surface of the substrate, with a draft angle being used to gradually narrow the channels as they approach the outer surface; this facilitates the collection of metal on the walls of the channels during the subsequent sputtering process. Alternatively, blind vias 80 can be drilled (e.g., laser drilled) from the outer surface of the substrate through the substrate at those portions of the outer surface designated for sensing electrodes, with the copper traces 114 acting as apertures. (In other words, portions of the substrate disposed over the copper traces can be removed, exposing the copper traces.) Typically, a draft angle is used for the blind vias so that the blind vias gradually narrow as they approach the inner surface of the substrate; this facilitates the collection of metal on the walls of the blind vias.

[0099] (Typically, after the drilling step 88, the substrate is treated with plasma to remove heat-damaged portions of the substrate. Typically, the channels are widened as a result of this treatment; therefore, the dimensions of each channel drilled may be narrower than the desired final dimensions of the channel.)

[0100] Next, at a first masking step 90, the copper and constantan traces, as well as the isolation regions 91 designated for isolating these traces (i.e., the exposed portions of the inner surface of the substrate), are masked. (The portions of the constantan traces designated for thermocouple junctions are not masked.) Also masked are additional isolation regions designated for isolating gold traces that will intersect the constantan traces (thus forming constantan-gold thermocouples). Additionally, masked are isolation regions on the outer surface designated for isolating the sense electrodes.

[0101] Subsequently, at a deposition step 92, a thin layer of gold is deposited onto the inner and outer surfaces of the substrate and into the channels. Deposition step 92 can be performed, for example, by physical vapor deposition (PVD), such as sputtering. (Typically, a seed layer of a base metal, such as titanium-tungsten, is sputtered onto the substrate before the gold is sputtered.) By means of the mask, gold is not deposited onto the traces or isolation areas.

[0102] The deposited gold includes an initialization layer for the inner layer 70, the outer layer 50, the plated layer 52, and the pillars 48. The deposited gold also includes a gold trace 122 covering the constantan trace at the thermocouple junction 124. Each gold trace 122 terminates at a corresponding gold trace pad 126. The deposited gold also includes a corresponding copper trace pad 116 for each copper trace. In some embodiments, the copper trace pad 116 and / or the gold trace pad 126 are staked to the substrate as described above for the constantan-trace pad. The deposited gold also includes at least one gold pad 128 connected to the inner layer 70. The gold pad 128 can also be staked to the substrate.

[0103] After deposition, the mask (and any gold deposited on it) is removed at a mask removal step 93. Subsequently, at a second masking step 94, a mask is applied to the traces, the inner surface isolation regions surrounding the traces, and the entire outer surface of the substrate.

[0104] After the second masking step 94, while keeping the traces and outer surfaces masked, the substrate is plated in a gold plating bath for a first time interval at a first plating step 98. Plating the substrate fills any gaps in the gold and further increases the thickness of the gold so that, for example, the thickness of the inner layer 70 reaches 5 to 40 microns, while the diameter of the wider channels is reduced to between 30 and 200 microns. In addition, the narrower channels may be completely filled.

[0105] Typically, the plating of the substrate is electrochemical, whereby a current is passed through gold already coated on the substrate causing the gold to attract gold ions in the plating bath. The amplitude and duration of the current can be controlled to achieve the desired thickness of the gold.

[0106] After the first plating step 98, at a demasking step 100, portions of the inner and outer surfaces of the substrate are demasked, except for the isolation regions designated for isolating the sensing electrodes. Next, at a coverlay application step 101, at least one coverlay 130 is applied over the traces and the inner surface isolation regions. (In some embodiments, such as Figure 5 As shown in the insert portion of FIG, the cover 130 is transparent or nearly transparent. )

[0107] Typically, the proximal portion of cover 130 covering tab 47 is shaped to define windows 132 that expose the pads, allowing the pads to be thickened during a subsequent plating process. (An additional cover 142 having windows aligned with windows 132 can cover the proximal portion of the cover.) Typically, the pads are not fully exposed, but rather remain "captive" by cover 130, as one or more edges of each pad are covered by the sides of window 132. Thus, cover 130 helps retain the pads on substrate 41 during a subsequent soldering process.

[0108] Subsequently, at the second plating step 102 place, in plating tank, substrate is plated to reach the second time interval, so that any gap in outer layer 50 is filled, and inner layer, outer layer and plated layer all thicken.For example, the second plating can make the thickness of inner layer be increased to between 10 microns to 50 microns, while making the diameter of wider passage be reduced to between 15 microns to 150 microns.Usually, the final thickness of inner layer is identical with the thickness of overcoat, so as to obtain smooth inner surface.(in order to avoid any confusion, term " inner surface " is used to refer to the surface formed by overcoat and inner gold layer in this article, and term " inner surface " is used to refer to the lower surface of substrate.) In addition, if during the first plating step 98, do not fill narrower passage completely, then during the second plating step 102, fill these passages completely.As in the case of the first plating step 98, can control the amplitude and the duration of electric current in the plating tank, make to obtain desired thickness.

[0109] (In some embodiments, a mask is applied to the outer surface prior to depositing step 92 so that no gold is deposited on the outer surface during depositing step 92. In such embodiments, a thin layer of gold is deposited on the outer surface after the demasking step 100 and before the second plating step 102.)

[0110] In some embodiments, as Figures 4 and 5 As shown, the support structure 36 includes a support sheet that is deformed into a suitable three-dimensional shape after the PCB (i.e., the substrate together with the various components disposed thereon) is bonded to the support sheet. In such an embodiment, at a drilling step 104 following the second plating step 102, openings 62 are drilled through the support sheet. (As an alternative to drilling, any other suitable technique (such as chemical etching) may be used to form the openings.) Subsequently, recesses and / or protrusions may be formed in the surface of the sheet. The recesses and protrusions and the steps by which they may be formed (including a third masking step 105, a chemical etching step 107, and a sheet removal step 109) are described below with reference to FIG. Figures 6A to 6B Provide a description.

[0111] After the second plating step 102 and optionally drilling the openings and / or forming the recesses and / or protrusions in the support sheet, a bonding step 106 is performed. At the bonding step 106, an adhesive is applied between the outer surface of the support structure and the inner surface of the PCB formed by the cover 130 and the inner layer 70 so that the adhesive bonds the two surfaces to each other. Typically, the support structure is bonded to the inner surface so that the openings 62 are aligned with the flushing holes 72. Typically, the area of ​​the openings is larger than the area of ​​the flushing holes so as to compensate for any small misalignments during bonding. In some embodiments, as described below with reference to Figure 8As depicted, the opening is much larger than the flushing hole so as to additionally expose a larger portion of the interior surface to the flushing fluid.

[0112] After or simultaneously with bonding, the electrode 40 is deformed into the desired shape at a deformation step 108. For example, assuming the support structure initially comprises Figure 5 If the flat support sheet shown is used, the electrode can be inserted into a forming jig after the bonding step 106. The forming jig forms the electrode around a suitable mandrel. After the electrode is inserted into the jig, the jig is placed in an oven. The oven then heats the electrode to the appropriate temperature while applying pressure to the electrode. The combination of heat and pressure causes the electrode to bond itself into the desired shape.

[0113] Generally speaking, the base and support sheet can be deformed into any desired shape. However, typically during the deforming step 108, the base and support sheet are formed to define an interior cavity at least partially enclosed by the interior surface of the sheet. For example, as described above with reference to Figures 2A to 2B As described, the substrate and support sheet may be formed to define a sleeve.

[0114] In some embodiments, to facilitate the manufacture of a cannula-shaped electrode, the substrate 41 includes two portions that are continuous with one another: a distal circular portion 41a and a proximal rectangular portion 41b. Similarly, the support sheet includes two portions that are continuous with one another: a distal support portion 36a, which may include 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 interior surface of the circular portion 41a, and adhesive is applied to the outer surface of the distal support portion 36a, such as the outer surface of each spoke 134. Additionally, the proximal support portion 36b is bonded to the interior surface of the rectangular portion 41b, leaving some distal portion of the interior surface exposed. Adhesive is applied to the outer surface of the overhanging tab 138 of the proximal support portion 36b, which depends on the side of the rectangular portion 41b. (The proximal support portion 36b may also depend on the proximal end of the rectangular portion 41b.)

[0115] Subsequently, during the deformation step 108, the distal support portion 36a and the circular portion 41a are folded over the top of the mandrel, while the proximal support portion 36b and the rectangular portion 41b are rolled around the mandrel. To maintain this configuration, the outer surface of the distal support portion 36a (e.g., the outer surface of each spoke 134) is bonded to the exposed distal portion of the inner surface of the rectangular portion 41b, and the outer surface of the tab 138 is bonded to the opposite end of the proximal support portion 36b. (Alternatively, the inner surface of at least one spoke may be bonded to the tab 138.) Thus, the distal support portion 36a and the circular portion 41a are formed into the dome-shaped portion 40a ( Figure 2A), while the proximal support portion 36b and the rectangular portion 41b are formed into a cylindrical portion 40b.

[0116] Then, at welding step 110, the wire is welded to the pad. Specifically, the wire is delivered from the generator 27 ( Figure 1 ) are soldered to gold pads 128, while other wires that deliver signals to processor 23 are soldered to other pads.

[0117] Finally, at a coupling step 112, the electrode is coupled to the probe. For example, the proximal support portion 36b may be bonded to the base 58 ( Figure 2B ). Alternatively or in addition, as above with reference to Figure 2B As depicted, the protrusions belonging to the base 58 can snap into complementary holes 140 in the proximal support portion 36b. Subsequently, the bias element can be coupled to the fluid delivery tube belonging to the probe. (Alternatively, the bias element can be coupled to the fluid delivery tube before coupling the electrodes to the bias element.)

[0118] As an alternative to or in addition to the traces described above, any other suitable electrical or electronic components may be deposited on the inner surface of the substrate. Such components may include a thermistor for measuring the temperature of the tissue, a pressure sensor for measuring the pressure applied to the distal end of the probe, and / or an electromagnetic sensor for navigating the probe. Whenever such a masking or covering operation is required, these components (and appropriate surrounding isolation areas) may be masked or covered, as described above for the traces.

[0119] It should be noted that the scope of the present disclosure includes any suitable modifications to method 82 with respect to the order in which the steps are performed and / or with respect to the various materials used, which will be apparent to those skilled in the art. For example, any suitable conductive metal may be used instead of copper, gold, or constantan.

[0120] Heat transfer

[0121] To facilitate heat transfer to the irrigation fluid as the fluid flows through the electrodes, various techniques can be used to increase the surface area of ​​the interior surface of the support structure, increase the turbulence of the fluid flow, increase heat transfer from the PCB to the support structure, increase the area of ​​the interior surface of the PCB that the fluid can directly contact, and / or increase the cross-sectional area of ​​the heat dissipation holes.

[0122] In this regard, first refer to Figure 6A , which is a schematic diagram of a method for forming a recess in the surface of a support structure 36 according to some embodiments of the present invention. Figure 6B, which is a schematic diagram of a method for forming protrusions on another surface of a support structure 36 according to some embodiments of the present invention.

[0123] In some embodiments, as Figures 6A to 6B As shown, a plurality of recesses 144 are formed in an outer surface 146 of the support structure 36 (i.e., the surface of the structure designated for bonding to the PCB), and / or a plurality of protrusions 148 are formed on an inner surface 150 of the structure. Typically, the formation of the recesses 144 and / or protrusions 148 is performed for embodiments in which the support structure is initially a flat sheet, such as Figure 5 Therefore, when referring to the support structure, the following Figures 6A to 6B The description generally uses the term "sheet".

[0124] In some embodiments, to form the recessed portions 144, an outer mask 152 shaped to define a plurality of mask openings 154 is coupled to the outer surface 146. Subsequently, the sheet is placed in a chemical etching tank and retained in the tank for a predetermined duration such that portions of the outer surface 146 exposed by the mask openings 154 are etched away. Similarly, to form the protrusions 148, a plurality of inner masks 156 are coupled to the inner surface 150, and the sheet is placed in a chemical etching tank and retained in the tank for a predetermined duration such that portions of the inner surface disposed between the masks 156 are etched away.

[0125] Typically, both the recess 144 and the protrusion 148 are formed. In some embodiments, the recess and the protrusion are formed simultaneously. (In such embodiments, the height of the protrusion is approximately equal to the depth of the recess.) For example, Figure 4 At a third masking step 105, an outer mask 152 may be coupled to the outer surface of the sheet, and an inner mask 156 may be coupled to the inner surface of the sheet. Subsequently, at a chemical etching step 107, the sheet may be placed in the groove so that both recessed portions and protruding portions are formed. After the recessed portions and protruding portions are formed, the sheet is removed from the groove at a sheet removal step 109.

[0126] In other embodiments, the recesses and protrusions are formed at separate times. For example, during a first chemical etching step, the outer surface of the sheet can be masked with an outer mask 152, while the inner surface of the sheet is completely masked, resulting in recesses rather than protrusions. Subsequently, during a second chemical etching step, the inner surface of the sheet can be masked with an inner mask, while the outer surface of the sheet is completely masked, resulting in protrusions. Advantageously, this technique facilitates the protrusion height being different from the recess depth, as the respective durations of the two chemical etching steps can be different from each other.

[0127] In some embodiments, each mask opening 154 is circular, such that each recess 144 has a circular perimeter. In such embodiments, the diameter L2 of each mask opening can be between 0.01 mm and 0.2 mm. Alternatively, some or all of the mask openings can have any other suitable shape.

[0128] The mask openings 154 (and therefore the recesses 144) may be arranged in a grid pattern or in any other suitable arrangement. Figure 6A As shown, a plurality of circular mask openings can be arranged in a closely packed pattern, with a distance L3 between respective centers of adjacent mask openings being between 0.05 mm and 0.5 mm. In some embodiments, L3 is approximately twice L2.

[0129] In some embodiments, each inner mask 156 is rectangular, such that (the inner surface of) each protrusion 148 has a rectangular perimeter. For example, each inner mask can be square, having a length L0 between 0.01 mm and 0.2 mm. Alternatively, some or all of the inner masks can have any other suitable shape. For example, each inner mask can be star-shaped, such that the perimeter of (the inner surface of) each of the protrusions is star-shaped. Examples of such shapes (which provide a relatively large amount of surface area for contact with the flushing fluid and a large number of edges for generating turbulence) include the shape of an N-pointed star, where N is three or more.

[0130] The inner masks 156 (and therefore the protrusions 148) can be arranged in any suitable arrangement, such as a grid pattern. For example, a plurality of square inner masks can be arranged in a grid pattern, wherein adjacent squares are separated by a distance L1 between 0.05 mm and 0.5 mm. In some embodiments, the distance between adjacent squares is approximately equal to the length of each square, that is, L1 is approximately equal to L0.

[0131] Typically, the area of ​​each opening 154 is smaller than the area of ​​each inner mask 156, and the inner and outer masks are aligned so that the entire perimeter of each opening is opposite the corresponding inner mask. (This reduces the risk of accidentally forming a through hole during the chemical etching process.) Due to this size and alignment, each recess is completely opposite to the protrusion (e.g., Figure 7 which will be described below).

[0132] As an alternative to chemical etching, other techniques such as laser etching may be used to form the protrusions 148 and / or the recesses 144 .

[0133] In some embodiments, the base and support sheet are shaped to define a ring or arc. In some such embodiments, multiple such ring-shaped and / or arc-shaped electrodes are coupled to each other at the distal end of the probe to define a sphere. By virtue of the spaces between the rings and / or arcs, blood can flow through the sphere during the ablation process. Thus, heat generated by the ablation can be transferred directly from the protrusion 148 to the subject's blood.

[0134] In general, any suitable masking technology can be used at each step where a mask is required. Examples of suitable masks include liquid and film photoresists.

[0135] Now refer to Figure 7 , which schematically illustrates the transfer of heat to the interior of the electrode 40 according to some embodiments of the present invention.

[0136] As mentioned above Figure 4 As described, adhesive 158 bonds support structure 36 to the interior surface of the PCB. Advantageously, in some embodiments, adhesive 158 fills recessed portions 144, thereby improving the support structure's adhesion to the PCB while also reducing the amount of adhesive interposed between the non-recessed portions of outer surface 146 and the PCB. In other words, because the adhesive accumulates in the recessed portions, outer surface 146 can contact or nearly contact the interior surface of the PCB. Consequently, more heat can be transferred to the support structure.

[0137] As further described above, during and / or after application of the ablation current, irrigation fluid 39 is caused to flow through the electrode such that, in some embodiments, the irrigation fluid flows over the surface of the protrusions 148. Due to the large surface area provided by the protrusions and / or due to the turbulence caused by the protrusions, a large amount of heat is transferred from the protrusions to the fluid 39. (As described above with reference to Figures 6A to 6B As described, in some embodiments, the subject's blood, rather than fluid 39, flows over the surface of the projections, allowing heat to be transferred directly from the projections to the blood.

[0138] In some embodiments, the height H1 of each protrusion and / or the depth H2 of each recess is between 5% and 60% of the thickness H0 of the support structure. Figures 6A to 6B As described, by forming the recesses and protrusions in two separate chemical etching steps, the depth of the recesses can be made different from the height of the protrusions.) For example, if H0 is between 0.025 mm and 0.2 mm, each of H1 and H2 can be between 0.00125 mm and 0.12 mm.

[0139] In some embodiments, instead of or in addition to forming recesses in the support structure, recesses are formed in the inner layer 70. Each recess (or "pit") can be formed, for example, by using a laser to melt a small portion of metal and displacing the molten metal radially outward. Upon solidification, the molten metal forms a rim around the recess.

[0140] Typically, the recesses are circular and are arranged in a closely packed pattern, e.g. Figure 6A Those recesses that are opposite the support structure can facilitate bonding of the PCB to the support structure (as described above with respect to recesses 144), while those recesses that are exposed to the flushing fluid can facilitate greater heat transfer to the flushing fluid by increasing the turbulence of the flow.

[0141] Now refer to Figure 8 , which is a schematic diagram of a support structure 36 according to some embodiments of the present invention.

[0142] In some embodiments, the support structure 36 includes a plurality of ribs 166 surrounding an inner cavity 168, as described above with reference to FIG. Figure 2B As described, the flushing fluid flows through the lumen. In such embodiments, the openings 62 (each of which separates a pair of continuous ribs 166 from each other) are typically relatively wide. For example, the width w0 of each opening may be wider than the width w1 of each rib, for example, 50% to 300% wider, such as 80% to 150% wider. In addition to exposing the flushing holes in the PCB, the openings also expose a relatively large portion of the interior surface of the PCB. Thus, heat can be transferred directly from the PCB to the flushing fluid. Heat transfer can be even further increased by providing a recessed portion in the interior surface of the PCB, as described above with reference to FIG. Figure 7 described.

[0143] (Another advantage of such an embodiment, relative to an embodiment in which the support structure is made of a flat sheet of metal, is that the ribs may enhance the structural integrity of the support structure.)

[0144] Typically, the ribs 166 are oriented circumferentially, with the ends of each rib being joined or continuous with support posts 170 that extend along the length of the structure. Typically, the ribs are arranged in multiple rows. For example, Figure 8 As shown, the support structure may include three rows of ribs: a first row disposed between the first support column 170a and the second support column 170b, a second row disposed between the second support column 170b and the third support column 170c, and a third row disposed between the third support column 170c and the first support column.

[0145] In some embodiments, the support structure 36 comprises a molded polymer such as PEEK, for example, glass-filled PEEK. In such embodiments, the outer surface 146 is typically rough due to the molding process. Alternatively or in addition, the outer surface can be roughened after the molding process; for example, the outer surface can be plasma etched to expose some of the glass-filled PEEK. The roughness of the outer surface can facilitate bonding and heat transfer, as described above with respect to the recessed portion 144 ( Figure 6A ).

[0146] In other embodiments, the support structure comprises machined metal.

[0147] To shape the electrode, the bonding step 106 and the deformation step 108 may be performed simultaneously ( Figure 4 ). In other words, after the adhesive is applied to the support structure, the PCB can be wrapped around the support structure. To facilitate bonding, heat and / or pressure can be applied to the electrodes during and / or after the wrapping of the PCB.

[0148] Now refer to Figure 9 , which is a schematic diagram of various types of concave channels 49 according to some embodiments of the present invention.

[0149] As mentioned above Figure 2A and Figure 3B As depicted, substrate 41 is shaped to define a plurality of concave channels 49 filled with metal pillars. Generally speaking, the scope of the present invention includes any suitable concave shape for channels 49 (and, therefore, for the metal pillars that fill the channels). By way of example, Figure 9 Shown are a concave channel 49a having a first shape, another concave channel 49b having a second shape, and yet another concave channel 49c having a third shape.

[0150] The concave channel 49a includes a circular central channel portion 160a and one or more (eg, 2-8) peripheral channel portions 162a leading to the central channel portion 160a. The peripheral channel portion 162a has an arcuate perimeter such that the peripheral channel portion is shaped as a partial circle.

[0151] Concave channel 49b and concave channel 49c each include a polygonal central channel portion and one or more peripheral channel portions leading to the central channel portion. In concave channel 49b, central channel portion 160b and peripheral channel portions 162b are rectangular. For example, central channel portion 160b and / or peripheral channel portions 162b may be square. Concave channel 49c has a star-like shape because it includes: central channel portion 160c shaped as an N-sided polygon, where N is three or more; along with N triangular peripheral channel portions 162c, each of which leads to central channel portion 160c at a different corresponding edge of the polygon.

[0152] Advantageously, as described above in the overview, the concave channel provides a relatively long perimeter on which metal can nucleate during the plating process, and also reduces the distance from the perimeter to the interior of the channel. Thus, the channel can provide a large cross-sectional surface area, yet still fill relatively quickly during the plating process.

[0153] By way of example, to illustrate this advantage, it will be assumed that in channel 49b, each peripheral channel portion is a square having a length of one arbitrary unit (AU), and the central channel portion is a square having a length of 3 AU. Assuming these dimensions, the cross-sectional area of ​​the channel is 13 AU 2 , and the circumference of the channel is 20AU. In contrast, although formed into a length of A (convex) square channel of the AU would provide the same cross-sectional area (and therefore, the same amount of heat transfer), but the perimeter of the channel would only be (approximately 14.4) AU. Furthermore, although the Hausdorff distance d from the interior of channel 49b (assuming the above dimensions) to the periphery of the channel is H It is only 1.58AU, but the Hausdorff distance from the interior to the periphery of the convex channel will be 1.8AU.

[0154] Now also refer to Figure 10 , which is a schematic diagram of the arrangement of channels 46 according to some embodiments of the present invention.

[0155] Typically, the concave channel 49a includes exactly six peripheral channel portions leading to a central channel portion. In such embodiments, to form the concave channel 49a, the drilling step 88 ( Figure 4 ) can be executed in two stages. Specifically, Figure 10As shown, during a first pass of the drill, a tightly packed pattern of circular channels 46 can be drilled through the substrate. (In such a tightly packed pattern, the distance between the respective centers of adjacent channels can be, for example, between 20 μm and 60 μm.) Next, during a second pass of the drill, some of the circular channels can be expanded so that each of the expanded circular channels opens into six surrounding channels, thereby forming concave channels 49 a. An advantage of forming channels in this manner is that only circular cuts are required.

[0156] For example, Figure 10 As indicated by the dotted line expansion indicator 164 in the vertical direction and the horizontal direction, every three channels can be expanded. After every three channels are expanded, the channels 46 are arranged so that each convex channel in at least some of the convex channels 51 is surrounded by corresponding three concave channels in the concave channels.

[0157] Alternatively, by tracing the respective perimeters of both the circular channel and the concave channel, the Figure 10 The arrangement of the channels is shown.

[0158] In some embodiments, at least one of the convex thermal vias has a length that is at least twice the width of the through-hole. (Such through-holes can be shaped, for example, as an ellipse or a rectangle.) Advantageously, such through-holes can provide a relatively large perimeter while also providing a relatively small distance from the perimeter to the interior of the through-hole.

[0159] In general, the embodiments described herein may be combined with any of the embodiments described in U.S. Patent Application Publication No. 2018 / 0110562 or U.S. Patent Application Publication No. 2019 / 0117296, the disclosures of each of which are incorporated herein by reference.

[0160] It will be understood by those skilled in the art that the present invention is not limited to the contents specifically shown and described above. On the contrary, the scope of the embodiments of the present invention includes both the combination and sub-combination of the various features described above, as well as variations and modifications that are not within the scope of the prior art that may occur to those skilled in the art when reading the above description. The documents incorporated by reference into this patent application are considered to be an integral part of this application, except that if any term defined in these incorporated documents conflicts with the definition explicitly or implicitly given in this specification, only the definition in this specification should be considered.

Claims

1. An apparatus for improving heat transfer, comprising: a flexible electrically insulating substrate comprising an inner surface and an outer surface and shaped to define a plurality of channels passing therethrough between the inner surface and the outer surface, at least some of the channels being concave channels; an outer layer of conductive metal, said outer layer covering at least a portion of said outer surface; an inner layer of the conductive metal, the inner layer covering at least a portion of the inner surface; and respective pillars of the conductive metal, the respective pillars filling respective ones of the vias to connect the outer layer to the inner layer, Each of the concave channels comprises: Center channel section; and One or more peripheral channel portions open into the central channel portion and the one or more peripheral channel portions include at least three peripheral channel portions.

2. The apparatus of claim 1 , wherein each of the concave channels comprises: a circular center channel section; and One or more peripheral channel portions having an arcuate perimeter and opening into the central channel portion.

3. The apparatus of claim 2, wherein the peripheral channel segments consist of between three and eight peripheral channel segments.

4. The apparatus of claim 3, wherein the peripheral channel portion consists of six peripheral channel portions.

5. The apparatus of claim 4, wherein some of the channels are circular channels, and wherein the channels are arranged such that each circular channel of at least some of the circular channels is surrounded by respective three of the concave channels.

6. The apparatus of claim 1 , wherein each of the concave channels comprises: polygonal central channel section; and One or more peripheral channel portions, the one or more peripheral channel portions opening into the central channel portion.

7. The apparatus of claim 6, wherein the central channel portion and the peripheral channel portion are rectangular.

8. The apparatus of claim 6, wherein each of the concave channels has a star shape.

9. The apparatus of claim 1, wherein the total area of ​​the respective outer openings of the channels is at least 30% of the area of ​​the outer surface.

10. The apparatus of claim 1, wherein the conductive metal comprises gold.

11. The apparatus according to claim 1 , further comprising: a probe configured for insertion into a body of a subject; and A support structure is bonded to the inner layer and coupled to the distal end of the probe.

12. The apparatus of claim 11, wherein the support structure comprises a plurality of ribs surrounding a cavity, consecutive ones of the ribs being separated from one another by openings that are wider than each of the ribs.

13. The apparatus of claim 1, wherein a surface of the inner layer is shaped to define a plurality of recesses.

14. The apparatus of claim 13, wherein the recesses are circular and arranged in a closely packed pattern.

15. The apparatus according to claim 1, wherein the average cross-sectional area of ​​each of the concave channels is within 345 μm 2 Up to 15700 μm 2 between.

16. A method of making a device for improving heat transfer, comprising: forming a plurality of channels in a flexible electrically insulating substrate, at least some of the plurality of channels being concave channels such that the channels pass between an inner surface of the substrate and an outer surface of the substrate; as well as using a conductive metal, at least partially covering the inner and outer surfaces and filling the channels and forming respective pillars of the conductive metal, the respective pillars filling the channels so as to connect the outer layer to the inner layer, Each of the concave channels comprises: Center channel section; and One or more peripheral channel portions open into the central channel portion and the one or more peripheral channel portions include at least three peripheral channel portions.

17. The method of claim 16, wherein each of the concave channels comprises: a circular center channel section; and One or more peripheral channel portions having an arcuate perimeter and opening into the central channel portion.

18. The method of claim 17, wherein forming the channel comprises: A tightly packed pattern forming circular channels; as well as After the close-packed pattern is formed, concave channels are formed by expanding some of the circular channels so that each of the expanded circular channels opens to surrounding six of the circular channels.

19. The method according to claim 16, further comprising: bonding the conductive metal covering the inner surface to a support structure; as well as The support structure is coupled to a distal end of a probe configured for insertion into a body of a subject.

20. The method of claim 19, wherein the support structure comprises a plurality of ribs surrounding a cavity, consecutive ones of the ribs being separated from one another by openings that are wider than each of the ribs.

21. The method of claim 16, further comprising forming a plurality of recesses in a surface of the inner layer.

22. The method of claim 21, wherein forming the recessed portions comprises forming circular recessed portions in a closely packed pattern.

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