Fusion joining copper to nitinol

Abstract

A medical device includes a medical catheter having a nitinol body and a copper wire coupled to the nitinol body with a fusion weld.

Description

Attorney Docket No.215364-0109-WO01 Medtronic Docket No. A0013173US01 FUSION JOINING COPPER TO NITINOL CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application No.63 / 701,327, filed September 30, 2024, the entire contents of which are incorporated herein by reference. FIELD

[0002] The present technology is generally related to welding techniques, and more specifically to welding techniques that may be implemented to weld together components of a medical device such as a medical catheter. BACKGROUND

[0003] Medical catheters, including ablation catheters, often include one or more components (e.g., wires, electrodes, etc.) that are coupled together during a manufacturing process to form the overall medical catheter. Current methods of joining together components in a medical catheter include the use of soldering. Soldering is often implemented, for example, to join together two different components formed from different types of metal. SUMMARY

[0004] The techniques of this disclosure generally relate to the use of fusion welding techniques to weld together components of a medical device (e.g., a medical catheter), including components formed from different types of metal. These techniques may replace the use of soldering. The fusion welding techniques described herein include the use of laser welding to weld a copper wire to a nitinol body in a medical catheter, and also the use of resistance welding to similarly weld a copper wire to a nitinol body in a medical catheter. Use of the fusion welding techniques described herein has been found to provide unexpected results, and to offer advantages not found with other techniques such as soldering.Attorney Docket No.215364-0109-WO01 Medtronic Docket No. A0013173US01

[0005] In one aspect, the disclosure provides a medical device having a medical catheter that includes a nitinol body and a copper wire that is coupled to the nitinol body with a fusion weld.

[0006] In another aspect, the disclosure provides a method of forming a medical device, the method including fusion welding a copper wire to a nitinol body.

[0007] The details of one or more aspects of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the techniques described in this disclosure will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG.1 is a schematic view of a medical catheter according to one example, the medical catheter having a nitinol body and a copper body fusion welded to the nitinol body.

[0009] FIG.2 is a partial, perspective view of one example of the nitinol body and the copper body.

[0010] FIG.3 is a schematic, cross-sectional view of a proximal neck of the nitinol body of FIG.2, illustrating how a laser welding technique may be used to weld the copper body to the proximal neck of the nitinol body.

[0011] FIG.4 is a perspective view of the proximal neck of the nitinol body after the laser welding of the copper body to the proximal neck of the nitinol body.

[0012] FIG.5 is a partial, perspective view of the nitinol body and another copper body.

[0013] FIG.6 is a schematic, cross-sectional view of the proximal neck of the nitinol body, illustrating how a resistance welding technique may be used to weld the copper body of FIG.5 to the proximal neck of the nitinol body.Attorney Docket No.215364-0109-WO01 Medtronic Docket No. A0013173US01

[0014] FIG.7 is a perspective view of the proximal neck of the nitinol body of FIG.5, after the resistance welding of the copper body of FIG.5 to the proximal neck of the nitinol body. DETAILED DESCRIPTION

[0015] FIG.1 schematically illustrates a medical device in the form of a medical catheter 110. The illustrated medical catheter 110 is an ablation catheter for ablating tissue in the body, including the ablation of pulmonary veins for the treatment of atrial fibrillation. In other examples, the medical catheter 110 is a different type of catheter, is used to treat other conditions, and / or is a catheter used for purposes other than ablation (e.g., as a guide catheter).

[0016] With reference to FIG.1, the medical catheter 110 includes a main catheter body 114, a nitinol body 118, and a copper body 122. As described further herein, the copper body 122 may be coupled to the nitinol body 118 via a fusion weld. In some examples, and as illustrated in FIG.1, the nitinol body 118 is coupled to the main catheter body 114, and / or the copper body 122 is coupled to the main catheter body 114. Additionally, in some examples, the medical catheter 110 further includes a source of energy 126 coupled to the copper body 122 to deliver energy through the copper body 122 to the nitinol body 118, and / or a controller 130 (e.g., coupled to the source of energy 126) to control the energy delivered to the nitinol body 118, and / or to control other features of the medical catheter 110.

[0017] The main catheter body 114 may include, for example, one or more elongate tubular bodies, a handle, and / or other structures commonly found in medical catheters. As illustrated in FIG.1, the main catheter body 114 includes a proximal end 134 and a distal end 138 located opposite the proximal end 134. The main catheter body 114 may be flexible in one or more portions between the proximal end 134 and the distal end 138, to facilitate insertion of the medical catheter 110 into the human body, and to facilitate maneuvering and / or positioning of the distal end 138 of the main catheter body 114 and the nitinol body 118.

[0018] With continued reference to FIG.1, in some examples, one or both of the nitinol body 118 and the copper body 122 are positioned at least partially within the main catheter bodyAttorney Docket No.215364-0109-WO01 Medtronic Docket No. A0013173US01 114, and extend through the main catheter body 114. In some examples, at least a portion of the nitinol body 118 and / or the copper body 122 extends outwardly from the main catheter body 114 (e.g., extends distally from the distal end 138 of the main catheter body 114), and / or extends along an exterior of the main catheter body 114 (e.g., along an outer surface of the main catheter body 114).

[0019] The nitinol body 118 may have any of a number of shapes and / or sizes suitable for use with a medical catheter. In some examples, the nitinol body is an electrode, or forms part of an electrode. In some examples, the nitinol body 118 additionally or alternatively is a wire, or forms part of a wire. In some examples, the nitinol body 118 additionally or alternatively is a cage, or forms part of a cage.

[0020] With reference to FIGS.2-4, in the illustrated example the nitinol body 118 itself is an electrode, and extends at least partially from the main catheter body 114 (e.g., from the distal end 138) along an axis A1. The nitinol body 118 is configured to deliver ablation energy (e.g., pulsed field ablation and / or radiofrequency ablation) to one or more locations within the human body (e.g., at the pulmonary veins).

[0021] With reference to FIG.2, in the illustrated example the nitinol body 118 includes a proximal neck 142 and a distal cage 146 extending from the proximal neck 142. The proximal neck 142 includes a neck collar 150 formed partially or entirely from nitinol. The neck collar 150 is cylindrical, and defines a central opening 154 (FIG.3). The proximal neck 142 further includes a plurality of legs 158 each formed partially or entirely from nitinol. Each of the legs 158 is coupled to a radially outer surface of the neck collar 150, and is also coupled to the distal cage 146 (e.g., to connect the proximal neck 142 to the distal cage 146). As illustrated in FIGS. 2 and 3, the legs 158 are spaced apart from one another (e.g., evenly) circumferentially around the neck collar 150.

[0022] With continued reference to FIG.2, in the illustrated example the distal cage 146 is formed partially or entirely from nitinol (e.g., from a lattice of nitinol), and is generally spherical overall in shape, although in other examples the distal cage 146 has other shapes and sizes than that illustrated (e.g., shapes more oblong in shape than spherical in shape). AsAttorney Docket No.215364-0109-WO01 Medtronic Docket No. A0013173US01 illustrated in FIG.2, the distal cage 146 is larger in diameter than the of the neck collar 150, and is also larger in diameter than the main catheter body 114, although other examples include different diameters and proportions that that illustrated.

[0023] In some examples, the distal cage 146 is flexible and / or expandable (e.g., radially expandable), due to the flexible nature of the nitinol lattice forming the distal cage 146. Accordingly, the shape of the distal cage 146 may be configured to change. In some examples the medical catheter 110 includes a slidable outer sheath, pull wire, and / or other structure that facilitates expansion and / or contraction of the distal cage 146 during use of the medical catheter 110.

[0024] With continued reference to FIG.2, in some examples the medical catheter 110 additionally includes one or more separate mapping electrodes 162 or other detectable structures (e.g., radiopaque structures) selectively positioned along the distal cage 146. The mapping electrodes 162 may be used, for example, to map a location of the distal cage 146 within the human body.

[0025] Other examples of the medical catheter 10 include a nitinol body 118 having other shapes and sizes than that illustrated, and other numbers of components and uses. For example, the neck collar 150 may not be cylindrical, and / or the neck collar 150 may be coupled directly to the distal cage 146 without the legs 158. In some examples, the legs 158 are not spaced evenly apart from one another, and / or the number of legs 158 differs from that shown. In some examples, the nitinol body 118 may not itself be an electrode, and / or may not be configured to deliver ablation energy, and / or may not include mapping electrodes 162, and / or may not be a cage or be flexible and expandable. Overall, the nitinol body 118 may be any type of nitinol structure forming part of the medical catheter 110 or other medical device, and is not limited to the example of the nitinol body 118 illustrated specifically in FIGS.2-4.

[0026] With continued reference to FIGS.2-4, in the illustrated example the copper body 122 includes a first copper wire 166a and a second copper wire 166b. The first copper wire 166a includes a first distal end 170a, and the second copper wire 166b includes a second distal end 170b. Each of the first and second distal ends 170a, 170b is coupled (e.g., fusion welded) to theAttorney Docket No.215364-0109-WO01 Medtronic Docket No. A0013173US01 proximal neck 142. In other examples the copper body 122 includes just a single copper wire, or more than two copper wires, or includes a copper body other than a copper wire. Additionally, in other examples one or more of the first and second copper wires 166a, 166b may be coupled to other locations of the nitinol body 118 than that illustrated (e.g., to a different location on the proximal neck 142 than that illustrated, or to the distal cage 146 instead of the proximal neck 142). In yet other examples, the copper body 122 may be a structure other than a wire (e.g., may be a copper cage or lattice, or any other copper structure forming part of the medical catheter 110 or other medical device). Overall, the copper body 122 may be any type of copper structure forming part of the medical catheter 110, and is not limited to the example of the copper body 122 illustrated specifically in FIGS.2-4.

[0027] With continued reference to FIGS.2-4, and as described above, the copper body 122 may be coupled to the nitinol body 118 with a fusion weld. For example, and as illustrated in FIGS.3 and 4, each of the first and second distal ends 170a, 170b may be separately fusion welded to the proximal neck 142 with a laser weld.

[0028] In the illustrated example, and with reference to FIG.3, the process of fusion welding one or both of the first and second distal ends 170a, 170b includes first positioning one or both of the first and second distal ends 170a, 170b along an exterior of the neck collar 150, such that the first and / or second distal ends 170a, 170b are positioned radially outwardly of the neck collar 150 and rest on the neck collar 150. The first and second distal ends 170a, 170b are also positioned (e.g., circumferentially) together between two of the legs 158. In other examples, the first and second distal ends 170a, 170b may be separated from one another for example by one or more of the legs 158, or may otherwise be positioned in a different manner on the proximal neck 142.

[0029] With continued reference to FIG.3, a laser welding source 174 is then positioned to direct laser energy toward the first distal end 170a of the first copper wire 166a and the neck collar 150, to melt both the copper of the first copper wire 166a and the nitinol of the neck collar 150, and to form a first weld bead 178a. As illustrated in FIG.3, the laser welding source 174 directs the laser energy toward a location that is offset from the first copper wire 166a itself toAttorney Docket No.215364-0109-WO01 Medtronic Docket No. A0013173US01 form the first weld bead 178a. Accordingly, the laser welding source 174 is positioned not to direct the energy directly at the first distal end 170a of the first copper wire 166a. Rather, the laser welding source 174 is intentionally positioned to direct the energy to a location slightly away and offset from the first copper wire 166a (or at least offset from a center of the first copper wire 166a). In some examples, and as illustrated in FIG.3, a portion of one or more of the nitinol legs 158 is also melted and / or forms part of the resulting first weld bead 178a.

[0030] With continued reference to FIG.3, once the first distal end 170a has been laser welded, the laser welding source 174 is then moved relative to the medical catheter 110 (or the medical catheter 110 itself is moved relative to the laser welding source 174), such that the laser welding source 174 is positioned to direct laser energy toward a location that is offset from the second copper wire 166b (or at least offset from a center of the second copper wire 166b), to form a second weld bead 178b. As illustrated in FIG.3, the first weld bead 178a is generally positioned to one side of the first copper wire 166a (e.g., along a first circumferential direction), and the second weld bead 178b is generally positioned to an opposite side of the second copper wire 166b (e.g., along a second circumferential direction), such that the first and second copper wires 166a, 166b (or portions thereof) are generally positioned (e.g., circumferentially) between the first and second weld beads 178a, 178b.

[0031] With reference to FIGS.3 and 4, in some examples the first weld bead 178a includes a first center of mass 182a (FIG.3). After the welding has taken place, the first copper wire 166a is positioned over the neck collar 150 along a first direction (e.g., radial direction), and the first weld bead 178a is formed between the neck collar 150 and the first copper wire 166a. The first center of mass 182a of the first weld bead 178a is offset and / or spaced away from the first copper wire 166a (e.g., offset from a center of the first copper wire 166a and / or offset entirely from the first copper wire 166a) along a second direction (e.g., circumferential direction) that is perpendicular to the first direction. The offset may be 15 microns, or between 13 and 17 microns, or between 10 and 20 microns, or between 10 and 30 microns, or between 10 and 40 microns, or between 10 and 50 microns, or other values and ranges of values.Attorney Docket No.215364-0109-WO01 Medtronic Docket No. A0013173US01

[0032] Similarly, the second weld bead 178b includes a second center of mass 182b (FIG.3). After the welding has taken place, the second copper wire 166b is positioned over the neck collar 150 along a first direction (e.g., radial direction), and the second weld bead 178b is formed between the neck collar 150 and the second copper wire 166b. The second center of mass 182b of the second weld bead 178b is offset and / or spaced away from the second copper wire 166b (e.g., offset from a center of the second copper wire 166b and / or offset entirely from the second copper wire 166b) along a second direction (e.g., circumferential direction) that is perpendicular to the first direction. The offset may be 15 microns, or between 13 and 17 microns, or between 10 and 20 microns, or between 10 and 30 microns, or between 10 and 40 microns, or between 10 and 50 microns, or other values and ranges of values.

[0033] With continued reference to FIGS.3 and 4, in some examples the first weld bead 178a is formed between the neck collar 150 and the first copper wire 166a, such that after the welding is complete, greater than 50% of a volume of the first weld bead 178a is positioned to one side of the first copper wire 166a (e.g., offset from a center of the first copper wire 166a and / or offset entirely from the first copper wire 166a) along a first (e.g., circumferential) direction. Similarly, in some examples the second weld bead 178b is formed between the neck collar 150 and the second copper wire 166b, such that after the welding is complete, greater than 50% of a volume of the second weld bead 178b is positioned to one side of the second copper wire 166b (e.g., offset from a center of the second copper wire 166b and / or offset entirely from the second copper wire 166b) along a second (e.g., circumferential) direction that is opposite to the first direction.

[0034] In other examples, greater than 60%, greater than 70%, greater than 80%, or greater than 90% of the volume of the first weld bead 178a is positioned to one side of the first copper wire 166a. Similarly, in some examples, greater than 60%, greater than 70%, greater than 80%, or greater than 90% of the volume of the first weld bead 178a is positioned to one side of the second copper wire 166b.

[0035] The laser welding source 174 itself may be any laser welding source, including a semi-automated laser welding source 174. In some examples, the laser welding source 174 has aAttorney Docket No.215364-0109-WO01 Medtronic Docket No. A0013173US01 peak power of between 50W-90W, a laser wavelength of 1070nm, a pulse width of between 4.3- 4.7ms, and / or a frequency of 5-6Hz. In some examples, the laser welding source 174 has a travel speed of 1.5”-2.0” / min, and / or a beam spot size of between 0.004” – 0.006”, and / or a beam target offset of 10% - 20% of a theoretical spot size. Additionally, in some examples the laser welding source 174 uses Argon as a cover gas, although examples may use other gas.

[0036] The welding parameters chosen for any of the laser welds may depend, however, upon the geometries and / or sizes of the components being welded (e.g., the geometries and / or sizes of the first and second distal ends 170a, 170b, and the proximal neck 142 including the neck collar 150 and the legs 158). In the illustrated example, each of the first and second distal ends 170a, 170b has a diameter of 0.16mm, the neck collar 150 has a thickness of 0.152mm, and each of the legs 158 has a thickness of 0.13mm. Other examples include other diameters and thicknesses.

[0037] As described above, soldering is typically used to join components such as nitinol and copper, due in large part to the different melting temperatures of nitinol (1240 - 1310 °C) and copper (1085 °C). The use of fusion welding, including laser welding, has generally not been considered or expected to work sufficiently for these types of materials, particularly in the context of a medical catheter. Specifically, an attempt to directly weld nitinol to copper (e.g., where directly means without an offset as described herein) might result in the elevated melting temperature of nitinol as compared to the melting temperature of copper would result in “too much” of the copper melting, such that an integrity of the precise structure of the copper might be negatively impacted. This is of particular concern in the context of a medical catheter that might have a significant number of copper conductors that need to be insulated from each other while also being securely coupled to an electrode / sensor / etc. at the distal tip of the catheter. However, it has been found that laser fusion welding is in fact possible in a medical catheter (e.g., so long as the laser energy is directed to one side of the copper body 122, thereby forming a weld bead that is offset as described above). The methods and arrangements described herein thus permit the use and welding of both of these specific metal materials in a medical catheter, despite their different melting temperatures.Attorney Docket No.215364-0109-WO01 Medtronic Docket No. A0013173US01

[0038] With reference to FIGS.5-7, the fusion weld may alternatively be a resistance weld. For example, and as illustrated in FIGS.6 and 7, each of the first and second distal ends 170a, 170b may be separately fusion welded to the proximal neck 142 with a resistance weld.

[0039] In the illustrated example, and with reference to FIG.6, the process of resistance welding one or both of the first and second distal ends 170a, 170b includes first positioning the first and / or second distal ends 170a, 170b along an exterior of the neck collar 150, such that the first and / or second distal ends 170a, 170 are positioned radially outwardly of the neck collar 150 and rest on the neck collar 150. The first distal end 170a is positioned (e.g., circumferentially) between two of the legs 158, and the second distal end 170b is positioned (e.g., circumferentially) between two of the legs 158, such that at least one of the legs 158 is positioned (e.g., circumferentially) between the first and second distal ends 170a, 170b. In other examples, each of the first and second distal ends 170a, 170b are positioned together between two legs 158.

[0040] With continued reference to FIG.6, a first resistance electrode 186a is then positioned inside of the central opening 154 of the neck collar 150, and a second resistance electrode 186b is positioned outside of the neck collar 150 and radially outwardly of the first distal end 170a of the first copper wire 166a. The first and second resistance electrodes 186a, 186b direct an electric current (e.g., radially) through the nitinol of the neck collar 150 and the copper of the first distal end 170a, thereby melting the copper and nitinol materials and forming a first welded region 190a (FIG.7) along the first copper wire 166a.

[0041] The first and second electrodes 186a, 186b are then moved relative to the medical catheter 110 (or the medical catheter 110 itself is moved relative to the first and second electrodes 186a, 186b), such that the second electrode 186b is positioned over the second distal end 170b of the second copper wire 166b. The first and second electrodes 186a, 186b again direct an electric current (e.g., radially) through the nitinol of the neck collar 150 and the copper of the second distal end 170b, thereby melting the copper and nitinol materials and forming a second welded region 190b (FIG.7) along the second copper wire 166b.Attorney Docket No.215364-0109-WO01 Medtronic Docket No. A0013173US01

[0042] The first and second electrodes 186a, 186b may be any electrodes or other resistance welding sources. In some examples, the first and second electrodes 186a, 186b and / or the overall resistance welding itself may be semi-automated. In some examples, the resistance welding used to form the fusion weld includes a current of between 170A – 180A, and / or a weld duration of 4-6ms. The first (e.g., lower) resistance electrode 186a may be formed for example from copper or other suitable material, and the second (e.g., upper) resistance electrode 186b may be formed from tungsten / copper, molybdenum, or other suitable material. In some examples, the resistance welding uses an electrode force of between 1-2lbs, and / or uses Argon as a cover gas, although other examples may use other types of gas.

[0043] The welding parameters chosen for any of the resistance welds may depend, however, upon the geometries and / or sizes of the components being welded (e.g., the geometries and / or sizes of the first and second distal ends 170a, 170, and the proximal neck 142 including the neck collar 150 and the legs 158). In the illustrated example, each of the first and second distal ends 170a, 170b has a diameter of 0.16mm, the neck collar 150 has a thickness of 0.152mm, and each of the legs 158 has a thickness of 0.13mm. Other examples include other diameters and thicknesses.

[0044] As described above, soldering is typically used to join components such as nitinol and copper, due in large part to the different melting temperatures of nitinol (1240 - 1310 °C) and copper (1085 °C). The use of fusion welding, including resistance welding, has generally not been considered or expected to work sufficiently for these types of materials, particularly in the context of a medical catheter. However, it has been found that resistance welding is in fact possible in a medical catheter. The methods and arrangements described herein thus permit the use and welding of both of these specific metal materials in a medical catheter, despite their different melting temperatures.

[0045] Overall, the use of fusion welding as described above has demonstrated benefits over soldering. For example, soldering of a copper body (e.g., a copper wire) to a nitinol body (e.g., having a proximal neck and distal cage) typically requires about eleven minutes of manufacturing time. Additionally, soldering requires the use of an aggressive acidic fluxAttorney Docket No.215364-0109-WO01 Medtronic Docket No. A0013173US01 (cleaning solution). Over the course of time (e.g., while a medical catheter product is sitting on a shelf or is otherwise not used), this acidic flux may begin to eat into the soldered junction.

[0046] In contrast, a fusion weld (e.g., a laser weld or resistance weld as described above) has been shown to have a much shorter manufacturing time. In some examples, the fusion weld may be completed within one minute, which is a significant time savings, particularly in a large-scale manufacturing process. Additionally, the fusion weld does not require the use of an aggressive acidic flux (cleaning solution), or the use of soldering material. The fusion weld requires less material, is more robust, can last longer, and is stronger (e.g., can withstand larger forces trying to break the weld). Additionally, use of fusion welding allows for semi-automated processes and controls to be used (e.g., via controlled operation of a laser welding source 174 and / or first and second resistance welding electrodes 186a, 186b), rather than manual soldering operations that require human and operator control.

[0047] It should be understood that various aspects disclosed herein may be combined in different combinations than the combinations specifically presented in the description and accompanying drawings. It should also be understood that, depending on the example, certain acts or events of any of the processes or methods described herein may be performed in a different sequence, may be added, merged, or left out altogether (e.g., all described acts or events may not be necessary to carry out the techniques). In addition, while certain aspects of this disclosure are described as being performed by a single module or unit for purposes of clarity, it should be understood that the techniques of this disclosure may be performed by a combination of units or modules associated with, for example, a medical device.

[0048] The invention may be further described by reference to the following numbered paragraphs: 1. A device comprising: a medical catheter comprising: a nitinol body; and a copper wire coupled to the nitinol body with a fusion weld.Attorney Docket No.215364-0109-WO01 Medtronic Docket No. A0013173US01 2. The device of paragraph 1, wherein the medical catheter is an ablation catheter, wherein the nitinol body is an electrode of the ablation catheter, and wherein the copper wire is an ablation wire configured to deliver ablation energy to the nitinol body. 3. The device of any of paragraphs 1 or 2, wherein the nitinol body includes a proximal neck and a distal cage extending from the proximal neck, wherein the copper wire is coupled to the proximal neck with the fusion weld. 4. The device of paragraph 3, wherein the copper wire is a first copper wire and the fusion weld is a first fusion weld, wherein the catheter includes a second copper wire coupled to the proximal neck with a second fusion weld. 5. The device of any of paragraphs 1-4, wherein the fusion weld is a resistance weld. 6. The device of any of paragraphs 1-4, wherein the fusion weld is a laser weld. 7. The device of paragraph 6, wherein the copper wire is positioned over the nitinol body along a first direction, wherein the laser weld includes a weld bead formed between the nitinol body and the copper wire, wherein a center of mass of the weld bead is offset and spaced away from the copper wire along a second direction that is perpendicular to the first direction. 8. The device of paragraph 7, wherein the first direction is a radial direction, and wherein the second direction is a circumferential direction. 9. The device of any of paragraphs 6-8, wherein the laser weld includes a weld bead formed between the nitinol body and the copper wire, wherein greater than 50% of a volume of the weld bead is positioned to one side of the copper wire.Attorney Docket No.215364-0109-WO01 Medtronic Docket No. A0013173US01 10. The device of any of paragraph 9, wherein greater than 60% of the volume of the weld bead is positioned to the one side of the copper wire. 11. The device of paragraph 10, wherein greater than 70% of the volume of the weld bead is positioned to the one side of the copper wire. 12. A method of forming a medical device comprising: fusion welding a copper wire to a nitinol body. 13. The method of paragraph 12, wherein the medical device is an ablation catheter, wherein the nitinol body is an electrode of the ablation catheter, and wherein the copper wire is an ablation wire configured to deliver ablation energy to the nitinol body, wherein the step of fusing welding includes fusion welding a distal end of the copper wire to the nitinol body. 14. The method of paragraph 13, wherein the nitinol body includes a proximal neck and a distal cage extending from the proximal neck, wherein the step of fusion welding includes welding the distal end of the copper wire to the proximal neck. 15. The method of any of paragraph 12-14, wherein the step of fusion welding includes forming a resistance weld between the copper wire and the nitinol body. 16. The method of paragraph 15, wherein the step of forming the resistance weld includes positioning the copper wire over the nitinol body, placing a first resistance electrode in contact with the nitinol body and a second resistance electrode in contact with the copper wire, and delivering between 170A-180A of electrical current through the copper wire and the nitinol body for between 4-6ms to weld the copper wire to the nitinol body. 17. The method of any of paragraphs 12-14, wherein the step of fusion welding includes forming a laser weld between the copper wire and the nitinol body.Attorney Docket No.215364-0109-WO01 Medtronic Docket No. A0013173US01 18. The method of paragraph 17, wherein the step of forming the laser weld includes positioning the copper wire over the nitinol body, and directing a laser beam with between 50W- 90W of power and a laser wavelength of 1070nm to the copper wire and the nitinol body. 19. The method of any of paragraphs 17 or 18, wherein the step of forming the laser weld includes positioning the copper wire over the nitinol body along a first direction and forming a weld bead between the nitinol body and the copper wire, such that a center of mass of the weld bead is offset and spaced away from the copper wire along a second direction that is perpendicular to the first direction. 20. The method of any of paragraphs 17-19, wherein the step of forming the laser weld includes forming a weld bead between the nitinol body and the copper wire, such that greater than 50% of a volume of the weld bead is positioned to one side of the copper wire. 21. A device comprising: a medical catheter comprising: a nitinol body; and a copper wire coupled to the nitinol body with a fusion weld. 22. The device of paragraph 21, wherein the medical catheter is an ablation catheter, wherein the nitinol body is an electrode of the ablation catheter, and wherein the copper wire is an ablation wire configured to deliver ablation energy to the nitinol body. 23. The device of paragraph 21, wherein the nitinol body includes a proximal neck and a distal cage extending from the proximal neck, wherein the copper wire is coupled to the proximal neck with the fusion weld. 24. The device of paragraph 23, wherein the copper wire is a first copper wire and the fusion weld is a first fusion weld, wherein the device includes a second copper wire coupled to the proximal neck with a second fusion weld.Attorney Docket No.215364-0109-WO01 Medtronic Docket No. A0013173US01 25. The device of paragraph 21, wherein the fusion weld is a resistance weld. 26. The device of paragraph 21, wherein the fusion weld is a laser weld. 27. The device of paragraph 26, wherein the copper wire is positioned over the nitinol body along a first direction, wherein the laser weld includes a weld bead formed between the nitinol body and the copper wire, wherein a center of mass of the weld bead is offset and spaced away from the copper wire along a second direction that is perpendicular to the first direction. 28. The device of paragraph 27, wherein the first direction is a radial direction, and wherein the second direction is a circumferential direction. 29. The device of paragraph 26, wherein the laser weld includes a weld bead formed between the nitinol body and the copper wire, wherein greater than 50% of a volume of the weld bead is positioned to one side of the copper wire. 30. The device of paragraph 29, wherein greater than 60% of the volume of the weld bead is positioned to the one side of the copper wire. 31. The device of paragraph 30, wherein greater than 70% of the volume of the weld bead is positioned to the one side of the copper wire. 32. A method of forming a medical device comprising: fusion welding a copper wire to a nitinol body. 33. The method of paragraph 32, wherein the medical device is an ablation catheter, wherein the nitinol body is an electrode of the ablation catheter, and wherein the copper wire is an ablation wire configured to deliver ablation energy to the nitinol body, wherein the step of fusing welding includes fusion welding a distal end of the copper wire to the nitinol body.Attorney Docket No.215364-0109-WO01 Medtronic Docket No. A0013173US01 34. The method of paragraph 33, wherein the nitinol body includes a proximal neck and a distal cage extending from the proximal neck, wherein the step of fusion welding includes welding the distal end of the copper wire to the proximal neck. 35. The method of paragraph 32, wherein the step of fusion welding includes forming a resistance weld between the copper wire and the nitinol body. 36. The method of paragraph 35, wherein the step of forming the resistance weld includes positioning the copper wire over the nitinol body, placing a first resistance electrode in contact with the nitinol body and a second resistance electrode in contact with the copper wire, and delivering between 170A-180A of electrical current through the copper wire and the nitinol body for between 4-6ms to weld the copper wire to the nitinol body. 37. The method of paragraph 32, wherein the step of fusion welding includes forming a laser weld between the copper wire and the nitinol body. 38. The method of paragraph 37, wherein the step of forming the laser weld includes positioning the copper wire over the nitinol body, and directing a laser beam with between 50W- 90W of power and a laser wavelength of 1070nm to the copper wire and the nitinol body. 39. The method of paragraph 37, wherein the step of forming the laser weld includes positioning the copper wire over the nitinol body along a first direction and forming a weld bead between the nitinol body and the copper wire, such that a center of mass of the weld bead is offset and spaced away from the copper wire along a second direction that is perpendicular to the first direction. 40. The method of paragraph 37, wherein the step of forming the laser weld includes forming a weld bead between the nitinol body and the copper wire, such that greater than 50% of a volume of the weld bead is positioned to one side of the copper wire.Attorney Docket No.215364-0109-WO01 Medtronic Docket No. A0013173US01

[0049] Although various aspects and examples have been described in detail with reference to certain examples illustrated in the drawings, variations and modifications exist within the scope and spirit of one or more independent aspects described and illustrated.

Claims

Attorney Docket No.215364-0109-WO01 Medtronic Docket No. A0013173US01 CLAIMS What is claimed is:

1. A device comprising: a medical catheter comprising: a nitinol body; and a copper wire coupled to the nitinol body with a fusion weld.

2. The device of claim 1, wherein the medical catheter is an ablation catheter, wherein the nitinol body is an electrode of the ablation catheter, and wherein the copper wire is an ablation wire configured to deliver ablation energy to the nitinol body.

3. The device of any of claims 1 or 2, wherein the nitinol body includes a proximal neck and a distal cage extending from the proximal neck, wherein the copper wire is coupled to the proximal neck with the fusion weld.

4. The device of claim 3, wherein the copper wire is a first copper wire and the fusion weld is a first fusion weld, wherein the device includes a second copper wire coupled to the proximal neck with a second fusion weld.

5. The device of any of claims 1-4, wherein the fusion weld is a resistance weld.

6. The device of any of claims 1-4, wherein the fusion weld is a laser weld.

7. The device of claim 6, wherein the copper wire is positioned over the nitinol body along a first direction, wherein the laser weld includes a weld bead formed between the nitinol body and the copper wire, wherein a center of mass of the weld bead is offset and spaced away from the copper wire along a second direction that is perpendicular to the first direction.Attorney Docket No.215364-0109-WO01 Medtronic Docket No. A0013173US01 8. The device of claim 7, wherein the first direction is a radial direction, and wherein the second direction is a circumferential direction.

9. The device of any of claims 6-8, wherein the laser weld includes a weld bead formed between the nitinol body and the copper wire, wherein greater than 50% of a volume of the weld bead is positioned to one side of the copper wire.

10. The device of any of claim 9, wherein greater than 60% of the volume of the weld bead is positioned to the one side of the copper wire.

11. The device of claim 10, wherein greater than 70% of the volume of the weld bead is positioned to the one side of the copper wire.

12. A method of forming a medical device comprising: fusion welding a copper wire to a nitinol body.

13. The method of claim 12, wherein the medical device is an ablation catheter, wherein the nitinol body is an electrode of the ablation catheter, and wherein the copper wire is an ablation wire configured to deliver ablation energy to the nitinol body, wherein the step of fusing welding includes fusion welding a distal end of the copper wire to the nitinol body.

14. The method of any of claims 12 or 13, wherein the step of fusion welding includes forming a resistance weld between the copper wire and the nitinol body.

15. The method of any of claims 12 or 13, wherein the step of fusion welding includes forming a laser weld between the copper wire and the nitinol body.

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