Patent Grant
9643021
In human hearing, hair cells in the cochlea respond to sound waves and produce corresponding auditory nerve impulses. These nerve impulses are then conducted to the brain and perceived as sound.
Damage to the hair cells results in loss of hearing because sound energy which is received by the cochlea is not transduced into auditory nerve impulses. This type of hearing loss is called sensorineural deafness. To overcome sensorineural deafness, cochlear implant systems, or cochlear prostheses, have been developed. These cochlear implant systems bypass the defective or missing hair cells located in the cochlea by presenting electrical stimulation directly to the ganglion cells in the cochlea. This electrical stimulation is supplied by an electrode array which is implanted in the cochlea. The ganglion cells then generate nerve impulses which are transmitted through the auditory nerve to the brain. This leads to the perception of sound in the brain and provides at least partial restoration of hearing function.
A cochlear prosthesis may typically comprise both an external unit that receives and processes ambient sound waves and an implant that receives data from the external unit and uses that data to directly stimulate the auditory nerve. Because the internal unit is surgically implanted, failure of the internal unit requires a surgical procedure to replace the damaged component. Failure of the internal unit may result from a variety of causes, such as damage from an impact.
The accompanying drawings illustrate various embodiments of the principles described herein and are a part of the specification. The illustrated embodiments are merely examples and do not limit the scope of the claims.
Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements.
As mentioned above, a cochlear implant may be used to partially restore hearing in a patient by directly stimulating nerve cells. One component of the cochlear implant is an internal unit which is typically implanted underneath the skin above the ear. The internal unit receives signals from an exterior unit and transfers those signals into electrical impulses. These electrical impulses travel along wires which run from the internal unit to electrodes which directly stimulate the cochlea.
To prevent bodily fluids from damaging electronic components which may be present within the device, the circuitry included with the internal unit is often enclosed within a hermetically sealed case. An electrical feedthrough may be used to transfer signals from the circuitry inside the hermetic case to the exterior of the case and vice versa. This electrical feedthrough maintains the integrity of the hermetic seal, while allowing electrical signals to pass through.
To increase comfort and ease of implantation, as well as minimize surgical trauma, it is desirable that the cochlear implant be as small as possible. Depending on the design, reducing the size of the implant may also reduce the risk of damage to the implant from blows or impacts. However, reducing the size of the implant has the associated challenge of shrinking the size of the hermetic feedthroughs. Each hermetic feedthrough design has manufacturing and material limitations on how much they can be scaled down, i.e., there are limitations imposed by the fabrication method, structure, leak path, etc. of the feedthrough.
The present specification relates to an electrical feedthrough disposed within a metallic plate which forms a perimeter wall of a hermetically sealed case. According to one illustrative embodiment, the case may be generally cylindrical in shape having a large diameter to height ratio. The case may be hollow in the center so as to allow electrical circuitry to be placed within. The outer radial wall of the feedthrough material may be connected to the interior of a hole in the metallic material through a brazing or other joining process.
According to one illustrative embodiment, a small diameter electrical feedthrough is formed using a co-fired ceramic, either high temperature or low temperature. However, the ceramic feedthrough is not used as a hybrid circuit, but is used in combination with a separate hybrid circuit which is electrically connected to the feedthrough. This unique architecture allows the feedthrough to be as small as allowed by fabrication limits because it is not directly integrated with electrical components. This feedthrough architecture has several advantages that are difficult, if not impossible, to obtain with other feedthroughs. For example, the height and pitch can be reduced relative to pin-based feedthroughs; the mechanical reliability is increased relative to large co-fired feedthroughs; the smaller feedthrough can be located in different portions of a hermetic case; changes to the hybrid circuit do not mechanically affect the feedthrough; and the routing of the feedthrough can be optimized to maximize hermeticity and reliability.
In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present systems and methods. It will be apparent, however, to one skilled in the art that the present apparatus, systems, and methods may be practiced without these specific details. Reference in the specification to “an embodiment,” “an example,” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment or example is included in at least that one embodiment, but not necessarily in other embodiments. The various instances of the phrase “in one embodiment” or similar phrases in various places in the specification are not necessarily all referring to the same embodiment.
Referring now to the figures,
As indicated above, the cochlear implant (100) is a surgically implanted electronic device that provides a sense of sound to a person who is profoundly deaf or severely hard of hearing. As also noted above, in many oases, deafness is caused by the absence or destruction of the hair cells in the cochlea, i.e., sensorineural hearing loss. In the absence of properly functioning hair cells, there is no way auditory nerve impulses can be directly generated from ambient sound. Thus, conventional hearing aids, which amplify external sound waves, provide no benefit to persons suffering from complete sensorineural hearing loss.
Unlike hearing aids, the cochlear implant (100) does not amplify sound, but works by directly stimulating the auditory nerve (160) with electrical impulses. Consequently, providing a cochlear prosthesis typically involves the implantation of electrodes into the cochlea. The cochlear prosthesis operates by direct electrical stimulation of the auditory nerve cells, bypassing the defective cochlear hair cells that normally traduce acoustic energy into electrical energy.
External components of the cochlear implant include a microphone (170), speech processor (175), and transmitter (180). The microphone (170) picks up sound from the environment and converts it into electrical impulses. The speech processor (175) selectively filters and manipulates the electrical impulses and sends the processed electrical signals through a cable to the transmitter (180). The transmitter (180) receives the processed electrical signals from the processor (175) and transmits them to the cochlear implant (100) by electromagnetic induction and/or by using radio frequencies.
The cochlear implant (100) may include an antenna (187) and an internal processor (185). The antenna (187) and internal processor (185) are secured beneath the user's skin, typically above and behind the external ear (110). The internal processor (185) includes electronic circuitry housed in a hermetically sealed enclosure. This electronic circuitry is connected to via a hermetically sealed feedthrough to the antenna (187). The antenna (187) receives power and signals from the transmitter (180) via electromagnetic induction and/or radio frequency signals. The internal processor (185) processes the received signals and sends modified signals through a hermetic feedthrough to cochlear lead (190) and electrodes (195). The electrodes (195) are inserted info the cochlea (150) and provide electrical stimulation to the auditory nerve (160).
The implant works by using the tonotopic organization of the cochlea. The cochlea is arranged tonotopicaily, also referred to as “frequency-to-place” mapping. The tonotopic structure of the cochlea enables human beings to hear a broad range of acoustic frequencies. The nerve cells sense progressively lower frequencies from the basal end of the cochlea to the apex. For normal hearing, the brain is presented with the electrical signals from the different regions of the cochlea and, because of the tonotopic configuration of the cochlea, is able to discern the acoustic frequencies being heard. A cochlear implant simulates with its electrode contacts along the length of the cochlea to mimic this process.
The outer case (408) of the hermetically sealed portion (400) may be made of metallic material or other suitable material. According to one illustrative embodiment, the outer casing is made up of a multiple pieces. These pieces may be connected through a variety of methods including, but not limited to, brazing, welding or gluing. One of such pieces may be an electrical feedthrough (404). The feedthrough (404) contains a number electrical vies (406).
According to one illustrative embodiment, the feedthrough (404) may be made of a ceramic material. The feedthrough (404) is connected to the outer case (408) through a braze joint (410) which is sandwiched between the ceramic feedthrough (404) and the case (408). To maintain the integrity of the feedthrough (404) and improve its impact resistance, the feedthrough is relatively thick. Additionally, some amount of flexure in the components surrounding the feedthrough may be desirable. This flexure accommodates any thermally induced differences in dimension between the ceramic feedthrough (404) and the other components. The sandwich style braze joint (410), feedthrough thickness, and flexure design may increase the overall height (414) of the hermetically sealed case.
The dimension of the feedthrough (405) may be much smaller than the diameter of the metallic plate (418) in which the feedthrough is placed. In some embodiments, the electrical paths which pass through the feedthrough (405) may be as small as allowed by fabrication limits of the manufacturing process or electrical constraints of the overall electronic design (such as resistance, current, capacitance, etc). This results in much smaller feedthroughs (405) which can be located in different portions of a hermetic case.
A wiring harness (412) includes a number of wires which are attached to the vias (409). According to one illustrative embodiment, the wires are connected to the vias (409) using a welding process, such as laser welding or electrical resistance welding. A variety of other connection techniques may be used, including wire bonding, tape automated bonding, and soldering.
A hybrid circuit (422) may be used in conjunction with the smaller diameter feedthrough (405) rather than directly attaching electronic components to a larger diameter feedthrough (404) as illustrated in
On the interior side of the electrical feedthrough (405), connections (407) may be made between the hybrid circuit (422) and the feedthrough (405). According to one illustrative embodiment, the hybrid circuit (422) is attached to the underlying electrical feedthrough (405) using a blind attachment technique. Blind attachment refers to situations where only one side of a workplace is accessible for component assembly and making electrical connections. In this case, the hybrid circuit (422) may entirely cover the electrical feedthrough (405), rendering it not visible during the attachment process. The blind attachment may be done using a variety of methods including, but not limited to anisotropic-conductive film, anisotropic-conductive paste, conductive epoxy, conductive silicone, solder, ball-grid array, and other compatible approaches.
The reduced diameter feedthrough (405) may have a number of advantages over the configuration shown in
In this embodiment, a flange (435) is included in the aperture formed in the metallic plate (418). As discussed above, the flange (435) may have a number of benefits, including increasing the diffusion path through the joint, increasing the bonding area, and holding the ceramic feedthrough (405) in place during the joining operation.
Additionally or alternatively, a groove, slot or other thickness-reducing feature (432) may reduce the stresses transferred from the metallic plate (418) to the ceramic feedthrough (405). These features (432) may allow for small amounts of flexure of the metal surrounding the feedthrough (405). This deformation may accommodate an increased level of impact or thermal related stress without causing damage to the ceramic feedthrough (405). The thickness-reducing features (432) may be formed in the one or both sides of the metallic plate (418).
As shown in
However, use of two separate components provides a number of benefits which are not provided by the conventional co-fired feedthrough and would not be apparent to one of skill in the art. First, by separating the co-fired feedthrough from electronics, the co-fired feedthrough no longer has to provide surface area on which to mount the electronics. This allows the size of the co-fired feedthrough to be drastically reduced. In some embodiments, the co-fired ceramic feedthrough may use minimum sized features. For example, if the minimum feature size of a particular manufacturing process is 5 mils, the individual vias and spacing between the vias could be on the order of 5 mils. This surprising reduction in size can significantly improve the reliability of the implant.
Second, the miniaturization of the feedthrough can allow the feedthrough to be located to in portions of the implant case where feedthroughs have not been previously viable. In cochlear implants, conventional large diameter feedthroughs are so large that they can only be located in the top and bottom of the cylindrical cases. These feedthroughs are located on the bottom of the case to provide additional protection to the wiring harnesses and electrical connections between the wiring harness and the electrical feedthrough. However, as discussed below, the miniaturization of the feedthrough allows the feedthrough to be located in the sidewall of the cylindrical case. This can reduce the overall height of the implant because the wiring is no longer underneath the implant. It can also increase the ruggedness of the implant because the implant can have a continuous metal bottom. Further, a side wall mounted feedthrough may reduce the overall wiring length and provide a convenient location for a connectorized harness.
The reduced diameter feedthrough (405) may be the reduction of the overall height of the implanted device compared to pin-based approaches. For most pin-based approaches the height of the implant will be driven by the need to include a braze length that provides a suitable leak path and enough space for the pins to extend sufficiently beyond the braze joint for bonding on both sides of the feedthrough.
Modularization of the electrical feedthrough can provide additional flexibility and reduced expense in changing the design of the hybrid circuit. In the illustrative embodiment of
A number of brazing techniques can be used to form a hermetically sealed braze joint (506) between the metallic plate (502) and the ceramic feedthrough (504). For example, the ceramic feedthrough (504) could be metalized on its perimeter to provide a surface to which the braze material adheres. The metallization of the ceramic surface may be accomplished in a number of ways. By way of example and not limitation, conductive portions of ceramics can be coated by screen printing using platinum, titanium, nickel, gold, or other suitable metals or metal combinations. The materials used in implanted devices must be carefully selected for long term reliability and chemical stability. Particularly, the materials must not have significant adverse effects on the patient's health. For example, metal combinations with a large percentage of copper are typically avoided because copper has a tendency to corrode when implanted, thereby releasing copper oxides and other copper derivatives into the surrounding tissues.
In an alternative embodiment, a metal hydride or active braze could be used to join the ceramic feedthrough (405) and the feedthrough case (408). The metal hydride and active brazes possess the ability to wet ceramic surfaces that have not been previously metalized. For example, a hydride, usually of titanium or zirconium, is reduced and brazed simultaneously in a controlled atmosphere. In one embodiment, following the metal hydride application, a platinum, gold, other suitable metals, or other eutectic braze alloys can then used in the brazing process. For hermetic feedthroughs which are not used in implantable devices, the range of available materials is even greater and may include metals or metal alloys such include copper and nickel.
An active metal typically uses a layered structure of two metals that have a eutectic point in their phase diagram. The braze perform melts at the eutectic composition and the melt joins the ceramic to the metal case. This process can eliminate the need to metalize the ceramic prior to brazing. By way of example and not limitation, these active elements may include titanium, zirconium, hafnium, vanadium, and aluminum or combinations thereof. According to one illustrative embodiment, the active braze material may be approximately 50% titanium and 50% nickel.
According to one embodiment, the braze joint may incorporate ceramic particulates. These ceramic particulates can increase the strength of the braze material, decrease its permeability, and reduce its coefficient of thermal expansion to more closely match the ceramic material. In one embodiment, the inclusion of as little of 5% (by volume) of ceramic particulates increases the strength of the reinforced active metal alloy over un-reinforced active metal alloy by approximately 30%. By including ceramic particulates in the braze joint, the joint is less likely to fail when subjected to temperature extremes or other forces.
For example, subsequent manufacturing processes, such as welding and soldering, may heat the ceramic and or titanium components of the case. The inclusion of ceramic particulates provides a braze material with an intermediate coefficient of thermal expansion that is greater than the ceramic but lower than the adjoining metal. The braze joint then acts as a buffer which reduces the thermal stress at any one surface and makes the joint less likely to fail at either the metal or ceramic interface.
According to one illustrative embodiment, a compression braze joint may be used to secure the ceramic feedthrough (504) in a titanium plate (502). The compression braze joint (506) may be formed by first heating the ceramic feedthrough (504) and the titanium plate (502) to a temperature which above the melting point of the braze material. Typically the braze material is drawn by capillary action into the joint. The assembly is then cooled. At some point in the cooling process, the braze material solidifies. As the assembly continues to cool, the titanium plate contracts slightly more than the ceramic feedthrough. This compresses both the braze joint (506) and the ceramic feedthrough. It is intended that the residual compression stress inhibit crack propagation by imposing a closure stress on any cracks or flaws, which typically grow under a mode I driving force, i.e., tensile opening. However, it is understood that at small size scales and with multiple interfaces there may be mixed-mode loading conditions for cracks or defects in the feedthrough that can affect the driving force for crack propagation and the performance of the feedthrough.
The electrical vias (508, 510) may have a variety of shapes and geometries. According to one illustrative embodiment, the vias (510) may have a cross section which is on the order of 5 to 10 mils in diameter. Other larger electrical paths (508) may be formed where a lower resistance is particularly desirable or where higher current flow occurs. The spacing between the vias may be approximately 5-10 mils. For 5 mil vias with 5 mil spacing, the center-to-center pitch between vias is 10 mils. This results in linear via density of 100 vias per inch and a via density of approximately 10,000 vies per square inch. The ratio of the device diameter to the feedthrough diameter in this example is 15 to 1. According to one illustrative embodiment, the device diameter to the feedthrough diameter is greater than 5 to 1. These small diameter feedthroughs can significantly increase the robustness of the implant device
According to certain illustrative embodiments, a number of vias (612) may be grouped together and share the same connection pads (604, 606) on either or both ends. Grouping them on both ends will reduce the electrical resistance measured between top metallic connection pad (604) and the bottom metallic connection pad (608) because electrical current can flow through all of the connected vias. This lower resistance may be beneficial for some signals. For example, the signals coming in from the antenna may be more prone to unacceptable signal degradation. Thus, it may be desirable to have the signals from the antenna travel through a via within the feedthrough where electrical resistance is minimized. Other electrical connections may have smaller connection pads and use only one via for conduction of electricity through the feedthrough. These individual electrical paths may be used for conducting electrical signals which have less current or are less sensitive to high connection resistances. For example, the individual vias may be used to pass electrical signals out of the processor and into the cochlear lead.
In some alternative embodiments, the vias (612) within the feedthrough (610) may have more complex routing. For example, a via may connect to two or more pads, branch, and/or interconnect with other vias. In some embodiments, vias may attach to ground planes or form shielding around or between other vias.
In certain embodiments, the metallic connection pad (604) on the interior side (602) may comprise a different material than the metallic connection pad (606) on the exterior side (608) of the feedthrough (610). For example, it may be beneficial to use platinum on the exterior side (608), as that side will be in contact with human tissue. It may be advantageous to use a material such as gold for the metallic plating (604) on the interior side (602), as that side will be in contact with the internal circuitry.
A variety of structures could be used to create a feedthrough (610) with vias (612). For example, a feedthrough may be formed from a monolithic slab of conductive material by fabricating electrically isolated pins out of the monolithic slab. This technique is described in U.S. App. No. 61/288,700, entitled “Hermetic Electrical Feedthrough” to Kurt J. Koester et al. which is incorporated herein by reference in its entirety. Other techniques may also be used, including the techniques described below.
The serpentine shape of the electrical vias (704) can provide several benefits. First, the serpentine path of the electrical vias (704) can be used to route the electrical connection to a different location on the inner surface of the feedthrough (700). Second, discontinuities in the feedthrough (700), such as interfaces between the vias and the surrounding matrix can provide paths along which vapor or liquid tends to travel. The serpentine path may create a longer diffusion path for any vapor or liquid through the feedthrough (700) and decrease the overall permeability of the ceramic feedthrough (700). The serpentine shape of the electrical vias (704) may extend outside the footprint of the associated metallic pad (710). The electrical vias (704) may have two or more geometries. In some cases, each electrical via (704) may have a different geometry. Alternately, a first electrical via (704) may have a first geometry and a second electrical via (704) may have a second geometry. In some examples, the metallic pads (710) may be arranged in a line. In other examples, the metallic pads (710) may be arranged in two or more parallel lines. One or more of the lines may not be coincident with a diameter of the feedthrough (700).
However, it is believed that the serpentine conduction paths may increase or decrease the overall toughness of the ceramic feedthrough (700) depending on material properties, loading conditions, and other factors. The benefits and advantages of creating serpentine conduction paths through the ceramic feedthrough (700) can be evaluated for a given design and appropriately implemented. Consequently, for a given design, a feedthrough may or may not have serpentine conduction paths.
As discussed above, ceramics fail mechanically due to crack propagation. Therefore, a goal of the feedthrough assembly design is to minimize the driving force for crack propagation. Typically, this corresponds to minimizing the tensile stress. Depending on feedthrough assembly geometry, position within the body, and location and direction of applied force, during impact events, the exterior outer layers (712) or interior outer layers (714) of the feedthrough (700) may be subject to more tensile stress than the more central layers (716) that are closer to the neutral axis (720). The exact position of the neutral axis will depend on the layout of the materials and the loading conditions, but a reasonable estimate is that the neutral axis coincides with the midplane of the cross section. For example, when a force is applied to an edge of an implanted case (408) (see, for example,
The geometry of the electrical vias can be selected to provide the desired balance between toughness and impermeability of the feedthrough. For example, if toughness is the primary design factor, the vias can be straight. If impermeability is the primary design factor, the vias may follow long convoluted paths through the ceramic feedthrough. Typically, a balance between toughness and impermeability, as well as other factors such as size, cost, and manufacturability is desired. Consequently, the geometry of the vias may be selected to provide a balance between toughness, impermeability, and other factors. As discussed above, this balance may include forming straight portions of the vias through the more highly stressed outer layers of the ceramic feedthrough and jogging the vias in the lower stressed interior layers to increase the impermeability of the feedthrough. As shown in
According to one illustrative embodiment, the electrical vias (704) may be formed from two or more conductive metals. The composition of the electrical via (704) may change through the thickness of the feedthrough. For example, in the exterior layers a via may be formed from a more biocompatible material such as platinum or titanium, in interior layers, the via may be formed from a different material which has one or more characteristics which are mechanically or electrically superior to the more biocompatible material. The interior layers are protected from biological contact by the exterior layers. Consequently, there may be a wider range of materials which may be suitable for use. For example, portions of a via which pass through the interior layers may be formed from gold or a gold alloy. Gold may have superior electrical and bonding properties, but is not as inert as platinum.
In certain embodiments, a connector (810) may be configured to connect the wires (812) which run to the electrodes and the antenna directly to the electrical vias in the feedthrough (808). The head of the connector (810) may be shaped to match the electrical vias in the feedthrough (808). The connector may be standardized so that new designs to the implant device may still be compatible with older electrode and antenna components or vice versa. In some embodiments, the connector and feedthrough may be configured such that the connector is detachable from and re-attachable to the feedthrough. This may advantageously allow hermetically sealed electronics to be replaced without removing the cochlear electrode array from the cochlea. The cochlear electrode array could simply be disconnected from the hermetically sealed electronics and reattached to a new or upgraded hermetically sealed electronic package.
The feedthroughs (910, 915) in this embodiment include linear arrays of vias (912, 920). This allows the feedthroughs (910, 915) to include a large number of vias while reducing the overall height of the feedthroughs (910, 915) and housing component (900). For example, the overall height of the feedthroughs (910, 915) may be on the order of 0.030-0.040 inches. The feedthroughs (910, 915) are then thin enough that the height of the electronics and circuit board will dominate the height of the implant.
As shown in
A ceramic feedthrough is then formed with a number of electrical vias (step 1004). As discussed above, the ceramic feedthrough may be formed in a variety of ways including using patterned green ceramic tape lay up and low temperature ceramic co-firing. The geometry of the vias can be selected to provide the desired balance between the toughness of the feedthrough and impermeability. For example, for a tougher and more impact resistant feedthrough, the vias may pass straight through two or more adjacent outer layers of the feedthrough. To increase the impermeability of the feedthrough, the vias may jog through the central layers of the feedthrough. Before firing, the ceramic feedthrough may be machined to ensure that the feedthrough has the proper shape and size to be brazed in the hole in the metallic plate. Connection pads are formed on either side of the electrical vias (step 1006). The connection pads may be formed in a variety of ways, including silk screening, lithographic, and other deposition techniques.
A hermetic joint is formed to seal the ceramic feedthrough into the metallic plate (step 1008). For example, a compression braze joint may be used to hermetically seal the ceramic feedthrough into the metallic plate. According to one illustrative embodiment, the ceramic feedthrough and metallic plate materials may be specifically selected such that they have a slight mismatch in CTE, with the CTE of the ceramic feedthrough being less than that of the braze materials and the metallic plate. The ceramic feedthrough and metallic plate are heated above a melting or softening point of a braze material. According to one illustrative embodiment, the braze material may be deposited in the joint prior to heating. For example, the braze material may be previously deposited on the ceramic feedthrough and/or metallic plate prior to heating. After the braze material has adhered to both the ceramic feedthrough and the metallic plate and substantially filled the joint volume, the temperature is reduced. As the temperature is reduced the braze material solidifies and the metallic plate compresses the ceramic feedthrough and braze material. According to one illustrative embodiment, the ceramic feedthrough has a circular shape which distributes the stress more uniformly through the volume of the shape. However, the ceramic feedthrough may have any of a number of shapes, including oval, elliptical, rectangular, square, or other suitable shape. In most embodiments, sharp corners can be avoided to reduce the likelihood of stress concentrations and fractures.
The internal and external components can then be attached to the feedthrough. For example, an electrical connection could be made between a separate co-fired ceramic hybrid circuit and the feedthrough (step 1010). An external connection could be made between a wiring harness and the feedthrough. The wires could be connected in a variety of ways, including wire bonding and resistance welding techniques. In some embodiments, the external connection may be made to a connector.
In sum, a small diameter modularized feedthrough may provide a number of advantages including closer via spacing, increased mechanical reliability relative to large co-fired feedthroughs; the much smaller feedthrough can be located in different portions of a hermetic case; changes to the hybrid circuit do not mechanically affect the feedthrough; and the routing of the feedthrough can be optimized to maximize hermeticity and reliability.
The preceding description has been presented only to illustrate and describe embodiments and examples of the principles described. This description is not intended to be exhaustive or to limit these principles to any precise form disclosed. Many modifications and variations are possible in light of the above teaching.
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| Number | Date | Country | |
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| 20160106988 A1 | Apr 2016 | US |
| Number | Date | Country | |
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| Parent | 13643992 | Jan 2013 | US |
| Child | 14873987 | US |
