Patent Application
20120270067
The disclosure relates generally to attaching gold to other metals such as titanium and niobium.
A wide variety of implantable medical devices (IMDs) that sense one or more parameters of a patient, deliver a therapy to the patient, or both have been clinically implanted or proposed for clinical implantation in patients. An IMD may deliver therapy to or monitor a physiological or biological condition with respect to a variety of organs, nerves, muscles, tissues or vasculatures of the patient, such as the heart, brain, stomach, spinal cord, pelvic floor, or the like. The therapy provided by the IMD may include electrical stimulation therapy, drug delivery therapy or the like.
Recent developments have provided such IMD's that are much smaller than traditional IMDs. For example, IMD's have been developed having a size such that the device can be deployed within the vasculature of a patient. However, the miniaturization of such devices may present challenges for their manufacture due to the small size of components used to manufacture such devices.
In one embodiment, the disclosure provides a method of attaching a first metal comprising gold to a second metal comprising titanium or niobium or both by using a laser beam having a wavelength that is reflected by the first metal comprising gold, but is absorbed by the second metal comprising titanium or niobium. In one embodiment, the wavelength of laser light or energy used is approximately 1064 nm or 1080 nm. In contrast, gold absorbs laser energy having a wavelength of about 532 nm and titanium and niobium reflects such a wavelength.
In another aspect, a tool is used to hold the metals in contact with one another during exposure to light energy having a wavelength of about 1064 nm or about 1080 nm.
In another embodiment, the disclosure provides an article comprising a first metal wire having a diameter of from 0.025 mm 0.152 mm comprising gold attached to a second metal comprising titanium or niobium and forming a connection joint, wherein the connection joint has an impedance of 0.1 Ohm or less. In one aspect, the first metal wire is attached to a circuit. In another aspect, the circuit is part of an implantable medical device. In another embodiment, the second metal wire is a feedthrough pin.
In another embodiment, the disclosure provides an article comprising a first metal wire having a diameter of from 0.025 mm 0.152 mm comprising gold attached to a second metal comprising titanium or niobium and forming a connection joint, wherein the connection joint has a length along the gold wire of from 0.051 mm to 0.203 mm.
As IMD's become smaller, attachment of various electrical components within such devices becomes challenging. Traditional methods of attaching metals such as direct welding, brazing and soldering are made difficult by the very small sizes of the connectors. Conductive adhesives can be used but their use can result in variable impedance which is unacceptable for circuits in such IMDs. The methods described in this application typically provide connection joints having an impedance of about 0.1 ohm or less.
In one embodiment, the disclosure provides a method of attaching a first metal comprising gold to a second metal comprising titanium or niobium or both by using a laser beam having a wavelength that is reflected by the first metal comprising gold, but is absorbed by the second metal comprising titanium or niobium. In one embodiment, the wavelength of laser light or energy used is approximately 1064 nm or 1080 nm. In contrast, gold absorbs laser energy having a wavelength of about 532 nm and titanium and niobium reflects such a wavelength. The methods of the invention do not include exposure of the first and second metals to wavelengths of laser beams of about 532 nm or wavelengths that are substantially absorbed by alloys of gold.
In one embodiment, to join or attach the first metal to the second metal, the first and second metals are placed into contact with one another, and the laser beam is focused on an area of the contacted first and second metals where attachment of the metals is desired. The laser beam wavelength is absorbed by the second metal which causes the second metal to heat to a temperature at or near the second metal's melting temperature about 1668° C. for TI and about 2477° C. for Nb. The heat from the second metal is transferred to the first metal through contact and causes the first metal to partially melt and become welded or attached to the second metal. The attachment of the metals using the methods described herein is meant to be robust and permanent for the intended use.
The first metals used in this method can be pure metals or may be metal alloys provided that the first metal at least substantially reflects the wavelengths of light used to heat the second metal. For example, alloys of gold and silver can be used in the methods described in this application. The second metal can be pure metal or can be metal alloys provided that the second metal at least substantially absorbs light having wavelengths of 1064 nm or 1080 nm or approximately 1064 nm or approximately 1080 nm. For example, alloys of titanium including those of grades 1 through grade 23 containing amounts of aluminum and vanadium and alloys of titanium and niobium can be used in the methods described in this application.
In another embodiment, the disclosure provides a method of attaching a first metal wire comprising gold to a second metal wire comprising titanium or niobium using a laser beam having a wavelength of approximately 1064 nm or 1080 nm. To join the wire comprising gold to the wire comprising titanium or niobium, the wires are placed in contact with one another, and the laser beam is focused on an area of the contacted wires where attachment of the wires is desired.
In one embodiment, the wire comprising gold and the wire comprising titanium or niobium are substantially perpendicular to one another when they are in contact with one another and the laser beam is focused on the contacted area. In general, the spot size of the laser beam is slightly larger than the diameter of the wire comprising gold. Typically, the spot size of the laser bean ranges from 0.002 (0.051 mm) to 0.008 inches (0.203 mm), and can be any size or range in between. The diameter of the spot size used relates to the length of the gold wire that is attached to the titanium or niobium that is the connection joint. In other words, the diameter of the spot size roughly equals the length of gold wire attached to the titanium or niobium below. The diameter of the first wire comprising gold can range from 0.001 inches (0.025 mm) to 0.006 inches (0.152 mm) and can be any diameter or range of diameters in between such range. The diameter of the second wire comprising titanium or niobium can range from 0.008 inches (0.203 mm) to 0.010 inches (0.254 mm) and can be any diameter or range of diameters in between such range.
In another embodiment, the disclosure provides a method of attaching a first metal wire comprising gold to a substrate comprising titanium or niobium using a laser beam having a wavelength of approximately 1064 nm or 1080 nm. The substrate could be for example, a housing or other metal component.
In one embodiment, a tool may be used to hold the first and second metal wires in contact during exposure to the laser beam. Desirably, the tool holds the first and second metals in intimate contact and substantially perpendicular and allows passage of the laser beam to the wires or metals in contact with one another. In other embodiments, a gold wire or a wire comprising gold connects electrical components to a titanium or niobium feedthrough wire and a gold wire connects to a ground wire which is connected to a titanium case of an IMD.
IMD 14 may be any of a variety of medical devices that sense one or more parameters of patient 12, provide therapy to patient 12 or a combination thereof. In one example, IMD 14 may be a leadless IMD. In other words, IMD 14 is implanted at a targeted site with no leads extending from IMD 14, thus avoiding limitations associated with lead-based devices. Instead, sensing and/or therapy delivery components are integrated with IMD 14. In the case of a leadless sensor, IMD 14 includes one or more sensors that measure the physiological parameter(s) of patient 12. In one example, IMD 14 may comprise an implantable device incorporating a pressure sensor that is placed within a vasculature or chamber of a heart of patient 12.
IMD 14 may, in some instances, provide therapy to patient 12. IMD 14 may provide the therapy to patient 12 as a function of sensed parameters measured by the sensor of IMD 14 or sensed parameters received from another device, such as another IMD or a body worn device. As one example, IMD 14 may be a leadless cardiac IMD that provides electrical stimulation therapy (e.g., pacing, cardioversion, defibrillation, and/or cardiac resynchronization therapy) to the heart of patient 12 via one or more electrodes as a function of sensed parameters associated with the heart. In yet a further example, IMD 14 may provide therapy to patient 12 that is not provided as a function of the sensed parameters, such as in the context of neurostimulation. Although described above in the context of electrical stimulation therapy, IMD 14 may provide other therapies to patient 12, such as delivery of a drug or other therapeutic agent to patient 12 to reduce or eliminate the condition of the patient and/or one or more symptoms of the condition of the patient, or provide no therapy at all.
IMD 20 includes a housing 22 and a fixation mechanism 24. Housing 22 and fixation mechanism 24 of IMD 20 may be sized and shaped to fit within a target location. In the example illustrated in
Commercially available ytterbium lasers can be used in the methods described in this application. Useful lasers include those that are rated to provide 10 mJ to 20 mJ of power at either 1064 nm or 1080 nm, for example lasers available from Lasag, Buffalo Grove, Ill. USA. Typical pulse times for attaching metals, for example, 0.025 mm gold wire to titanium or niobium, ranges from 0.25 ms to 0.45 ms. The pulse time of the laser depends upon the diameter of wires being bonded, the metal or composition of the wires, wave length used, and power or delivered energy of the laser. In general, for attaching gold to titanium or niobium, the pulse time may range from 0.05 ms to 0.7 ms and may be any time or range of times between 0.05 ms and 0.7 ms.
Referring back to
The tool can generally be made from tungsten carbide. Typically such a tool can be made using machine tools and electrical discharge machining (EDM). The dimensions of the tool depend upon the size of the metals, for example, gold, tantalum and niobium, to be attached. For example, for a spot size that ranges from 0.051 mm to 0.203 mm, an opening in the distal end of the tool can have a diameter of about 0.15 mm and an overall length of about 19 mm. In use, the laser beam is aligned to the center of the tool and the tool and the beam are aligned such that the proper spot size overlaps the metals to be attached, as described above. Wires are typically attached together while they are suspended in air.
Various examples have been described. These examples, however, should not be considered limiting of the techniques described in this disclosure. These and other examples are within the scope of the following claims.
