Abstract:
A method of making a flexible elongate member includes the steps of providing a core wire having a proximal region and a distal region, attaching an electrical device to the distal region of the core wire, the electrical device being electrically connected to at least one electrical conductor. A substantially cylindrical electrical connector is formed from a substrate having a first edge and a second edge, the first edge and the second edge of the substrate being bonded substantially flush to each other, the electrical connector including a plurality of conductive bands and a plurality of electrically conductive runners interconnected to the plurality of bands. An electrically conductive bond is formed between the electrical conductors and the plurality of electrically conductive runners. The substantially cylindrical electrical connector is attached to the proximal region of the core wire.

Description:
“This is a continuation of Application Ser. No. 09/261,935, filed on Mar. 3, 1999, now U.S. Pat. No. 6,210,339, which is incorporated by references.” 
    
    
     FIELD OF THE INVENTION 
     This invention relates in general to the field of medical devices, more particularly, this invention relates to a flexible elongate member such as a medical guide wire or catheter having one or more electrical contacts. 
     BACKGROUND OF THE INVENTION 
     Flexible elongate members used in medical applications such as guide wires, catheters, etc., which have electrical devices (e.g., pressure sensors, ultrasound transducers, pressure flow measurement devices, etc.) need to have one or more electrical contacts typically close to the proximal end of the member. The electrical contacts allow for the electrical interconnection of the electrical device found on the flexible elongate member, for example, a pressure sensor, to an external monitoring apparatus. 
     Currently there is some difficulty in manufacturing small electrical contacts on flexible elongate members such as guide wires having a diameter in the order of 0.018 inch or less. In FIG. 1 there is shown a prior art guide wire  100  having an electrical device in the form of a pressure sensor  110  located in proximity to the distal end of the guide wire  100 . Pressure guide wire  100  includes a plurality of electrical contacts  104  separated by insulator bands (spacers)  116  which help form a cylindrical connector located close to the proximal extremity  102  off the pressure guide wire  100 . These electrical contacts  104  are electrically interconnected to pressure sensor  110  and allow for the connection of the pressure sensor to an external monitoring apparatus. 
     The pressure guide wire  100  further includes a shaft also referred to as a hypotube  106  typically formed of stainless steel, a flexible coil member  108  located on one side of the pressure sensor  110 , a radiopaque coil  112  located on the other side of pressure sensor  110 , and a tip  114 . The pressure sensor  110  is electrically interconnected to contacts  104  via a plurality of electrical conductors (not shown), which run through the inside of the flexible coil  108  and shaft  106 . 
     The cylindrical guide wire connector formed by contacts  104  is interconnected to a female connector  200  shown in FIG.  2 . The proximal end  102  of pressure wire  100  is inserted in to the nose section  206  of connector  200  such that contacts  104  become electrical coupled to corresponding contacts located inside of the swivel head  204 . The other end of connector  200  includes a pin plug  202 , which interconnects to an appropriate monitoring apparatus, in this case a pressure monitor (not shown). In use, the distal end of pressure wire  100  is inserted into a vessel (e.g., artery) of a patient in order to measure the pressure at certain locations along the vessel, which is under investigation. 
     One problem with pressure guide wire  100  is that the individual electrical contacts  104  are very difficult and expensive to integrate into the guide wire. Contacts  104  are individual metal bands, which are separated by non-electrically conductive spacers  116 . During manufacture, each of the individual contacts  104  have to be soldered to the appropriate electrical conductor (not shown, e.g., electrical wire), which is attached to pressure sensor  110 . 
     After the appropriate electrical conductor is soldered or welded to its corresponding contact  104 , each individual contact has to be adhesively bonded to the rest of the guide wire  100 . The spacers  116  also have to be individually inserted and bonded to the adjacent contact(s)  104 . The bonding of the spacers  116  and contacts  104  causes further problems in that the adhesive which bonds them together tends to seep between the joints and has to be removed from the exterior portions of the proximal end of the guide wire  100 . Given the small size of the guide wire  100 , all of these time consuming steps have to be performed by assembly workers using microscopes which further increase the opportunity for manufacturing mistakes to occur. 
     Problems can also occur with the contacts  104  or spacers  116  becoming separated from the rest of the assembly due to bad bonding of a particular contact  104  or spacer  116 . Another manufacturing problem occurs with the solder joints, which interconnect the electrical conductors coming from pressure sensor  110  to the individual contacts  104 . Given that the electrical conductors have to be soldered to the inside surface of the contacts  104 , there is very little room in which to solder the contact with a soldering tool, thus some bad solder joints can occur during production. 
     A need thus exists in the art for a contact assembly, which can overcome the problems associated with the prior art mentioned above. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a prior art pressure guide wire. 
     FIG. 2 shows a prior art connector that interconnects the guide wire of FIG. 1 to a monitoring apparatus. 
     FIG. 3 shows an electrical connector in accordance with the preferred embodiment of the invention before it is rolled-up into a substantially cylindrical shape. 
     FIG. 4 shows the electrical connector of FIG. 3 interconnected to a plurality of electrical conductors in accordance with the invention. 
     FIG. 5 shows the assembly of FIG. 4 in a rolled-up form. 
     FIG. 6 shows the rolled-up assembly of FIG. 5 mounted to a portion of a core wire. 
     FIG. 7 shows the assembly of FIG. 6 with a shaft attached to the electrical connector in accordance with the invention. 
     FIG. 8 shows a cross-sectional view of FIG.  7 . 
     FIG. 9 shows an alternate embodiment of the electrical connector. 
     FIG. 10 shows a pressure guide wire in accordance with the invention. 
     FIG. 11 shows an alternative embodiment in which a tubular substrate is used to form the electrical connector. 
     FIG. 12 shows the tubular member of FIG. 11 after metallization of its outer surface. 
     FIG. 13 shows the tubular member of FIG. 12 after it has been cut and overlapped. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings and in particular to FIG. 3, there is shown a circuit carrier (substrate) such as a substantially cylindrical electrical connector  300  comprising substrate  302  and three electrically conductive bands  304 ,  306  and  308 . The electrical connector  300  is the preferred embodiment is formed from a “flex” circuit or flex circuit board  302  which is preferably manufactured from a polyimide such as KAPTON™ manufactured by Dupont, Inc., or other flexible materials used in the art. The thickness of substrate  302  should be such that it can be re-shaped in a relatively tight radius of curvature. The flex circuit could, for example, be of the order of 25 μm thick, or less. 
     The flexible substrate  302  preferably includes an extension portion  310 , which provides termination points for parallel runners  312 ,  314  and  316  which are interconnected to bands  304 ,  306  and  308 . Runners  312 ,  314  and  316  have a pitch in the order of 0.002 to 0.004 inch. This pitch is required in order to interface the circuit to the group so electrical wires that travel along the length of the flexible elongate member to the electrical device (e.g., pressure sensor, etc.). Since the guide wire has a small cross-sectional diameter, the wires have to be small, and are therefore close together. Ideally, the pitch of the runners  312 ,  314  and  316  matches the pitch of the wires so that when the wires are bonded to the flex circuits there is no need to spread the wires, and the assembly fits within the profile of the flexible elongate member. The wires may be stripped of insulation and attached with conventional means such as soldering or welding. 
     In FIG. 4 the flexible circuit board  300  is shown attached to three electrical conductors  402  in the form of a cable also known as a trifilar. Each of the bands has a corresponding electrical conductor that is attached by soldering, welding or by another well-known attachment technique. 
     In FIG. 5 the assembly of FIG. 4 is shown folded in a substantially cylindrical fashion with ends  502 ,  504  of the flexible circuit board  300  being slightly overlapped in order to pass over the runners  312 ,  314  and  316 . The overlapping maintains the bands  304 ,  306  and  308  in alignment. The ends of the flexible circuit board are then bonded using any one of a number of conventional adhesives in order for the electrical connector  300  to remain in its substantially cylindrical state. Once bonded, the metallization bands  304 ,  306  and  308  form three parallel cylindrical bands that run around the periphery of the connector  300 . Alternatively, in other designs, the bands  304 ,  306  and  308  do not have to run around the entire periphery of connector  300 . 
     In FIG. 6, the electrical connector  300  and cable  402  are shown mounted to a core wire  602  (only a portion shown) which forms the backbone for the pressure guide wire  100 . The electrical connector  300  is attached a certain distance  604  from the proximal end  606  of core wire  602 . The flexible circuit  300  is filled with adhesive between core wire  602  and the inner surface of the flexible circuit board  300  in order to fix and stiffen the electrical connector  300 . 
     In FIG. 7 the partial guide wire assembly of FIG. 6 is shown with a shaft or hypotube  704  (similar to shaft  106 ) attached to the electrical connector  300 . The electrical connector  300  can be attached to hypotube  704  using one of a number of adhesives such as a polyurethane and oligomer mixture. An optional window  702  is provided in hypotube  704 , which could allow for the soldering of insulated electrical conductors  402  after the hypotube and electrical connector  300  have been mated. If optional window  702  is utilized, it is aligned with (also referred to as being in substantial registration with) extension portion  310  found in the substrate  302 . Once the electrical conductors  402  are soldered on to the electrical connector  300  the window  702  is covered with insulative “fill” adhesive such as epoxy. A cross-sectional view taken along line  8 — 8  is shown in FIG.  8 . The electrical connector  300  is attached to core wire  602  using a nonconductive adhesive such as epoxy  802 . The epoxy not only serves to attach the flexible circuit board to core wire  602  it also provides a backing material which helps stiffen the flexible circuit board used in this embodiment. The area between the core wire  602  and inner surface of electrical connector  300  is preferably filled with adhesive or other filler in order to stiffen the electrical connector  300 . 
     An alternate embodiment of the electrical connector of the present invention is shown in FIG.  9 . Instead of overlapping the ends of the flexible substrate  302  as shown in FIG. 5 the end portions  901  and  902  of the flexible substrate  302  are bonded substantially flush to each other using adhesive. There is no need to overlap the ends of the flexible substrate in this embodiment as compared to the one-sided embodiment shown in FIG. 5 because in this embodiment the flexible substrate  302  is a two-sided circuit board design. Conductive bands  914  are located on a first surface  910  and corresponding runners  906  are located on a second surface  912 . The bands  914  and runners  906  are interconnected using pass-through vias  904 . 
     In FIG. 10 there is shown a pressure guide wire  1000  in accordance with the present invention. Instead of using several individual conductive bands  104  and insulative spacers  116 , the pressure guide wire  1000  uses the electrical connector  300  of the present invention. By using the electrical connector  300  of the present invention the time to manufacture the pressure guide wire  1000  is reduced. Also, the problem with the individual bands  104  and spacers  116  becoming detached from the rest of the pressure guide wire assembly as found with the prior art guide wire  100  are eliminated. 
     In an alternate embodiment of the present invention, a tubular member or substrate  1100  is used as the starting point in place of a flexible flat substrate  302  as shown in FIG.  3 . Preferably, tubular member  1100  includes an extension portion  1102  similar to extension portion  310 . In FIG. 12 cylindrical bands  1202 ,  1204 ,  1206  and runners  1208 ,  1210  and  1212  are added using a conventional metallization technique such as sputtering. Other well-known metallization techniques can be used to attach the metallization to the outside surface of electrical connector  1200 . 
     A non-metallized area  1214  is left along the length of the tubular member. The non-metallized area is the area in which the tubular member is cut along its entire length. Once cut, the ends of the tubular member are overlapped in order to cross over the three runners  1208 ,  1210  and  1212 . Once overlapped as shown in FIG. 13, the outside surface of flexible connector includes three substantially cylindrical metal bands  1202 ,  1204  and  1206 . The overlapped ends are bonded together so the overlapped state is fixed. 
     An electrical connector cable  1302  is attached to the runners  1208 ,  1210  and  1212  at extension  1102 . Tubular member  1100  can be formed from a number of materials, which are amenable to metallization such as a polyimide tube. Although the embodiment shown in FIG. 3 requires a flexible circuit substrate since the starting point is a flat substrate, tubular member  1100  can be formed from semi-stiff or stiffer materials if so desired since the member is already in a substantial cylindrical state prior to metallization of its outer surface. 
     The present invention accomplishes a completely new way of forming an electrical connector on a flexible elongate member such as a cardiovascular guide wire  1000  The invention accomplishes this with a single member that forms the multiple connection requirements. The simplicity of the design also enables rapid and effective assembly techniques, and is compatible with automatic processes that can be performed by machines. The component cost is also reduced compared to the prior art. 
     The single substrate design can be mass produced using standard photo-lithographic techniques in the case where the flat substrate  302  is used, and standard metallization techniques such as sputtering in the case where the tubular substrate  1100  is utilized as the starting point. The present invention also eliminates a number of previously complicated assembly steps. In addition, the invention allows the electrical device (e.g. pressure sensor, flow sensor, etc.) and electrical conductor  300  to be attached and tested prior to completion of the guide wire  1000 . 
     While the invention has been described in conjunction with specific embodiments, it is evident that many alternatives, modifications, permutations and variations will become apparent to those skilled in the art in light of the foregoing description. For example, although in the present invention the preferred embodiment has been described as a pressure guide wire, other flexible elongate members such as those used to diagnose or treat coronary vascular areas can take advantage of the present invention.