Patent Publication Number: US-8994486-B2

Title: Electromagnetic coil assemblies including disparate wire splice connectors, disparate wire splice connectors, and associated methods

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation-in-part of co-pending U.S. application Ser. No. 13/251,902, filed Oct. 3, 2011. 
    
    
     TECHNICAL FIELD 
     The present invention relates generally to coiled-wire devices and, more particularly, to electromagnetic coil assemblies including disparate wire splice connectors, as well as to methods for joining disparate wires utilizing specialized splice connectors. 
     BACKGROUND 
     There is an ongoing demand in the aerospace industry for low cost electromagnetic coils suitable for usage in coiled-wire devices, such as actuators (e.g., solenoids and motors) and sensors (e.g., rotary and linear variable differential transformers), capable of providing prolonged and reliable operation in high temperature environments and, specifically, while subjected to temperatures in excess of 260° C. It is known that low cost electromagnetic coils can be produced utilizing aluminum wire, which is commercially available at minimal cost, which provides suitable conductive properties, and which can be anodized to form an insulative alumina shell over the wire&#39;s outer surface. Aluminum wire is, however, highly susceptible to working hardening and mechanical fatigue during physical manipulation, especially if the aluminum wire is of a relatively fine gauge; e.g., 30-38 American Wire Gauge. Work hardening of the aluminum wire may result in breakage of the wire during assembly and/or termination, including termination to wires of differing diameters and material types. Work hardening may accelerate open circuit failure during subsequent device operation. Thus, to reduce the application of stress to a relatively fine gauge aluminum wire during manufacture of an electromagnetic coil assembly, it may be desirable to splice each end of the aluminum wire to a different wire less susceptible to work hardening and breakage. 
     Crimping has long been utilized to electrically and mechanically join wires together. Crimping of the fine gauge aluminum wire can, however, result in work hardening of the aluminum wire of the type described above. In addition, for instances wherein the aluminum wire is crimped to a second wire fabricated from a metal having a hardness exceeding that of aluminum, the deformation induced by crimping may be largely concentrated in the aluminum wire and an optimal physical mechanical and/or electrical bond may not be achieved. In contrast to crimping, soldering does not require the application of deformation forces to the wire-to-wire interface, which can cause the above-noted issues with fine gauge aluminum wire. However, soldering of fine gauge aluminum wire also presents certain difficulties. Due to its relatively low melt point and thermal mass, fine gauge aluminum wire can easily be overheated and destroyed during the solder processing. The likelihood of inadvertently overheating the aluminum wire is especially pronounced when soldering is carried-out in a relatively confined space utilizing, for example, a microtorch. Heating during soldering can also result in formation of oxides along the wires&#39; outer surfaces increasing electrical resistance across the solder joint. As a still further drawback, moisture present at the solder interface can accelerate corrosion and eventual connection failure when aluminum wire is joined to a secondary wire formed from a metal, such as copper, having an electronegative potential that differs significantly as compared to aluminum wire. 
     It would thus be desirable to provide methods and means for reliably soldering aluminum wire, especially fine gauge aluminum wire, to a secondary wire that avoids the above-noted limitations associated with conventional soldering processes. Ideally, such a soldering method and means would facilitate the formation of a wire-to-wire solder connection having a relatively low ohmic resistance and a relatively high corrosion resistance. It would also be desirable for such an aluminum wire soldering method and means to be usefully applied in the production of electromagnetic coil assemblies, such as high temperature electromagnetic coil assemblies included within coiled-wire devices (e.g., actuators and sensors) deployed onboard aircraft. It would still further be desirable if such methods and means could also be utilized to join non-aluminum magnet wires, such as silver magnet wires, to disparate or dissimilar wires utilizing a solder-type connection. Other desirable features and characteristics of the present invention will become apparent from the subsequent Detailed Description and the appended Claims, taken in conjunction with the accompanying Drawings and the foregoing Background. 
     BRIEF SUMMARY 
     Embodiments of method are provided including the steps of providing a splice connector having a first blind bore and a second blind bore, inserting a segment of a coiled magnet wire into the first blind bore, and inserting a segment of the secondary wire into the second blind bore. The splice connector is soldered to these wire segments to electrically couple the coiled magnet wire and the secondary wire through the splice connector. 
     Embodiments of a disparate wire splice connector are further provided. In one embodiment, the disparate wire splice connector includes a generally cylindrical body, a first blind bore formed within a first end portion of the generally cylindrical body, a second blind bore formed within a second end portion of the generally cylindrical body, and a partitioning wall separating the first blind bore and the second blind bore. Solder material is disposed within the first blind bore and formulated for usage in conjunction with aluminum wire. 
     Embodiments of an electromagnetic coil assembly are still further provided. In one embodiment, the electromagnetic coil assembly includes a coiled magnet wire, a secondary wire, and an disparate wire splice connector. The disparate wire splice connector has a first blind bore into which a segment of the coiled magnet wire is inserted, as well as a second blind bore into which a segment of the secondary wire is inserted. A first solder material fills at least a portion of the first blind bore to electrically couple the coiled magnet wire to the splice connector, and a second solder material fills at least a portion of the second blind bore to electrically coupling the secondary wire to the splice connector and, therefore, to the coiled magnet wire. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       At least one example of the present invention will hereinafter be described in conjunction with the following figures, wherein like numerals denote like elements, and: 
         FIG. 1  is a simplified cross-sectional view of an electromagnetic coil assembly illustrated in accordance with an exemplary embodiment of the present invention; 
         FIGS. 2 and 3  are isometric and cross-sectional views, respectively, of an exemplary disparate wire splice connector included within the electromagnetic coil assembly shown in  FIG. 1  and illustrated in a post-solder state; 
         FIG. 4  is a cross-sectional view of the exemplary disparate wire splice connector shown in  FIGS. 2 and 3  and illustrated in a pre-solder state; and 
         FIGS. 5 and 6  are simplified isometric views illustrating one manner in which the electromagnetic coil assembly shown in  FIG. 1  may be sealed within a hermetic canister. 
     
    
    
     DETAILED DESCRIPTION 
     The following Detailed Description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding Background or the following Detailed Description. 
     The following describes exemplary embodiments of a method for joining a magnet wire to a secondary wire, such as a lead wire or the conductor of a feedthrough structure, utilizing a specialized splice connector. The method described herein is especially useful for joining fine gauge aluminum wire, which is prone to mechanical fatigue and work hardening, to a secondary wire less susceptible to such issues. This notwithstanding, the method described herein can be utilized to join secondary wires (the term “wire” encompassing any electrical conductor) to various different types of magnet wires including fine gauge silver magnet wire. The secondary wire can be fabricated from one or more metals (e.g., copper, nickel, or silver) relatively resistant to mechanical fatigue and work hardening. Additionally or alternatively, the secondary wire may have a lower gauge (larger diameter) as compared to the magnet wire. As a still further possibility, the secondary wire may be a wire braid; that is, a plurality of conductive filaments interwoven into a braided cylinder, tube, or flattened ribbon. Embodiments of the below-described disparate wire solder method may be carried-out in the context of a larger fabrication process utilized to produce an electromagnetic coil assembly. Embodiments of the wire solder method and splice connector are especially useful in the production of high temperature electromagnetic coil assemblies, which can be employed within various different types of high temperature actuators (e.g., motors solenoids) and high temperature sensors (e.g., rotary and linear variable differential transformers). For this reason, an exemplary wire solder method and an exemplary wire-to-wire splice connector are described below in the context of high temperature electromagnetic coil assemblies; however, is it emphasized that embodiments of the solder method and splice connector described herein are by no means limited to application within electromagnetic coil assemblies and can be advantageously utilized in any application or platform wherein it is desired to form a soldered connection between disparate or dissimilar wires, such an aluminum or silver magnet wire and a secondary wire. 
       FIG. 1  is a cross-sectional view of an electromagnetic coil assembly  10  illustrated in accordance with an exemplary embodiment of the present invention. Electromagnetic coil assembly  10  is suitable for usage within high temperature operating environments characterized by temperatures exceeding the threshold at which organic materials breakdown and decompose (approximately 260° C.) and, in preferred embodiments, characterized by temperatures approaching or exceeding 400° C. In view of its high temperature capabilities, electromagnetic coil assembly  10  is well-suited for usage in high temperature coiled-wire devices, such as those utilized in avionic applications. More specifically, and by way of non-limiting example, embodiments of high temperature electromagnetic coil assembly  10  are well-suited for usage within actuators (e.g., solenoids and motors) and position sensors (e.g., variable differential transformers and two position sensors) deployed onboard aircraft. This notwithstanding, it will be appreciated that embodiments of electromagnetic coil assembly  10  can be employed in any coiled-wire device, regardless of the particular form assumed by the coiled-wire device or the particular application in which the coiled-wire device is utilized. 
     Electromagnetic coil assembly  10  includes a support structure around which at least one magnet wire is wound to produce one or more electromagnetic coils. In the illustrated example, the support structure assumes the form of a hollow spool or bobbin  12  having an elongated tubular body  14 , a central channel  16  extending through tubular body  14 , and first and second flanges  18  and  20  extending radially outward from opposing ends of body  14 . In embodiments wherein electromagnetic coil assembly  10  is incorporated into a sensor, such as an LVDT, bobbin  12  is preferably fabricated from a substantially non-ferromagnetic material, such as aluminum, a non-ferromagnetic 300 series stainless steel, or a ceramic. However, in embodiments wherein assembly  10  is incorporated into a solenoid, a motor, or the like, either a ferromagnetic or non-ferromagnetic material may be utilized to produce bobbin  12 . Although not shown in  FIG. 1  for clarity, an insulative shell may be formed over or an outer insulative coating may be deposited over the outer surface of bobbin  12  to provide electrical insulation between wire coil  22  (described below) and bobbin  12 . For example, in embodiments wherein bobbin  12  is fabricated from a stainless steel, bobbin  12  may be coated with an outer dielectric material utilizing, for example, a brushing or spraying process; e.g., a glass may be brushed onto bobbin  12  as a paste or paint, dried, and then fired to form an electrically-insulative coating over selected areas of bobbin  12 . As a second example, in embodiments wherein electromagnetic coil assembly  10  is disposed within an airtight or at least a liquid-tight package, such as a hermetic canister of the type described below in conjunction with  FIGS. 5 and 6 , an electrically-insulative inorganic cement of the type described below may be applied over the outer surfaces of bobbin  12  and cured to produce the electrically-insulative coating and thereby provide a breakdown voltage standoff. As a still further possibility, in embodiments wherein bobbin  12  is fabricated from aluminum, bobbin  12  may be anodized to form an insulative alumina shell over the bobbin&#39;s outer surface. 
     At least one magnet wire is wound around bobbin  12  to form one or more electromagnetic coils. In the illustrated example, a single magnet wire is wound around tubular body  14  of bobbin  12  to produce a multi-turn, multi-layer coiled magnet wire  22 . In one group of embodiments, the magnet wire is preferably fabricated at least partially from aluminum and will consequently be primarily referred to as an “aluminum magnet wire” herein below; it is emphasized, however, that other types of magnet wires can also be employed, including silver magnet wires. Advantageously, aluminum wire provides excellent conductivity enabling the dimensions and overall weight of high temperature electromagnetic coil assembly  10  to be reduced, which is especially desirable in the context of avionic applications. As a further advantage, aluminum wire is readily commercially available at minimal cost. Regardless of the particular material or materials from which magnet wire  22  is fabricated, magnet wire  22  is preferably a high temperature wire; that is, a wire capable of usage at temperatures exceeding 260° C. without melting or other structural compromise. Winding of the magnet wire around bobbin  12  to produce the electromagnetic coil or coils can be carried-out utilizing a conventional wire winding machine. Coiled magnet wire  22  is preferably formed from a magnet wire having a relatively fine gauge; e.g., in many embodiments, the magnet wire (e.g., the aluminum or silver magnet wire) from which the electromagnetic coil or coils are formed will have a wire gauge of approximately 30-38 American Wire Gauge (“AWG”). If desired, the magnet wire utilized to form the electromagnetic coils may be anodized to provide additional electrical insulation between neighboring turns of coiled magnet wire  22  and between wire  22  and bobbin  12  to further reduce the likelihood of shorting and breakdown voltage during operation of electromagnetic coil assembly  10 . 
     An electrically-insulative inorganic body  24  is deposited around tubular body  14  and between flanges  18  and  20  of bobbin  12 . That is, the annular volume of space defined by the outer circumferential surface of tubular body  14  and the inner radial faces of flanges  18  and  20  is at least partially potted with an inorganic dielectric material or medium to form electrically-insulative body  24 . Coiled magnet wire  22  is at least partially encapsulated within electrically-insulative body  24  and, preferably, wholly embedded therein. Electrically-insulative body  24  provides mechanical isolation, position holding, and electrical insulation between neighboring turns of coiled magnet wire  22  through the operative temperature range of the electromagnetic coil assembly  10 . Electrically-insulative inorganic body  24  is preferably formed from a ceramic medium or material; i.e., an inorganic and non-metallic material, whether crystalline or amorphous. In embodiments wherein coiled magnet wire  22  is fabricated from aluminum, electrically-insulative inorganic body  24  is preferably formed from a material having a coefficient of thermal expansion (“CTE”) approaching that of aluminum (approximately 23 parts per million per degree Celsius), but preferably not exceeding the CTE of aluminum, to minimize the mechanical stress applied to coiled magnet wire  22  during thermal cycling. More specifically, electrically-insulative body  24  is preferably formed to have a CTE exceeding approximately 10 parts per million per degree Celsius (“ppm per ° C.”) and, more preferably, a CTE between approximately 16 and approximately 23 ppm per ° C. Suitable materials include inorganic cements, and certain low melt glasses (i.e., glasses or glass mixtures having a melting point less than the melting point of anodized aluminum wire), such as leaded borosilicate glasses. As a still more specific example, electrically-insulative inorganic body  24  may be produced from a water-activated, silicate-based cement, such as the sealing cement bearing Product No. 33S and commercially available from the SAUEREISEN® Cements Company, Inc., headquartered in Pittsburgh, Pa. 
     In embodiments wherein electrically-insulative inorganic body  24  is formed from a material susceptible to water intake, such as a porous inorganic cement, it is desirable to prevent the ingress of water into body  24 . As will be described more fully below, electromagnetic coil assembly  10  may further include a container, such as a generally cylindrical canister, in which bobbin  12 , electrically-insulative body  24 , and coiled magnet wire  22  are hermetically sealed. In such cases, the ingress of moisture into the hermetically-sealed container and the subsequent wicking of moisture into electrically-insulative body  24  is unlikely. However, if additional moisture protection is desired, a liquid sealant may be applied over an outer surface of electrically-insulative inorganic body  24  to encapsulate body  24 , as indicated in  FIG. 1  at  26 . Sealants suitable for this purpose include, but are not limited to, waterglass, silicone-based sealants (e.g., ceramic silicone), low melting (e.g., lead borosilicate) glass materials of the type described above. A sol-gel process can be utilized to deposit ceramic materials in particulate form over the outer surface of electrically-insulative inorganic body  24 , which may be subsequently heated, allowed to cool, and solidify to form a dense water-impenetrable coating over electrically-insulative inorganic body  24 . 
     To provide electrical connection to the electromagnetic coil embedded within of electrically-insulative inorganic body  24 , lead wires are joined to opposing ends of coiled magnet wire  22 . As appearing herein, the term “lead wire” denotes a wire coupled between an electromagnetic coil and a lead, such as feedthrough pin provided through the wall of a hermetically-sealed canister. In accordance with embodiments of the present invention, each of the opposing ends of coiled magnet wire  22  is joined to a lead wire by way of a specialized splice connector adapted for joining disparate or dissimilar types of wires. Further illustrating this point,  FIG. 1  depicts an terminal segment  28  of coiled magnet wire  22  joined to a neighboring terminal segment  30  of a lead wire  32  (partially shown) by way of a disparate wire splice connector  34 . Splice connector  34  is described in more detail below in conjunction with  FIGS. 2-4 . However, it is useful to note at this juncture that splice connector  34  joins coiled magnet wire  22  to lead wire  34  in a manner that provides solder joints having relatively low electrical resistance and relatively high corrosion resistance. It can be seen in  FIG. 1  that disparate wire splice connector  34 , and thus terminal segment  28  of coiled magnet wire  22 , are embedded or buried within electrically-insulative inorganic body  24 . Coiled magnet wire  22  is thus mechanically isolated from bending and pulling forces exerted on the external segments of lead wire  32 . As a result, in embodiments wherein coiled magnet wire  22  is produced utilizing a fine gauge magnet wire prone to mechanical fatigue and work hardening, such as a fine gauge aluminum magnet wire, the application of strain and stress to coiled magnet wire  22  is minimized and work hardening of wire  22  is avoided. Although not shown in  FIG. 1  for clarity, one or more additional layers of wire coils may also be wound over splice connector  34  in further embodiments to provide additional mechanical support or protection to the splice connector interface. The opposing end portion of coiled magnet wire  22  may likewise be joined to a second lead wire utilizing a similar splice connector (not shown). 
     Lead wire  32  projects through the outer surface of electrically-insulative inorganic body  24  at an entry/exit point  36 . The protruding segment of lead wire  32  will consequently be subject to unavoidable mechanical forces (e.g., bending, twisting, pulling, etc.) at this interface due to manipulation of lead wire  32  during manufacture of electromagnetic coil assembly  10 . However, in contrast to coiled magnet wire  22 , lead wire  32  is able tolerate these forces without significant mechanical fatigue or work hardening for at least one of three reasons. First, lead wire  32  may be formed from a non-aluminum metal having a mechanical strength exceeding that of aluminum wire, such as stainless steel, silver, or copper. Depending upon the particular metal or alloy from which lead wire  32  is formed, lead wire  32  may also be plated or clad with various metals or alloys to increase electrical conductivity, to enhance crimping properties, and/or to improve oxidation resistance. Suitable plating materials include, but are not limited to, nickel, aluminum, gold, palladium, platinum, and silver. Second, in further embodiments, lead wire  32  may be a single conductor or non-braided wire having a diameter significantly larger than the wire diameter of coiled magnet wire  22 ; e.g., in certain embodiments, the diameter of lead wire  32  may be approximately 18-24 AWG, while, as previously noted, the wire diameter of coiled magnet wire  22  may be approximately 30-38 AWG or, more generally, less than about 30 AWG. In this case, lead wire  32  may or may not be fabricated from aluminum. Third, in still further embodiments, lead wire  32  assumes the form of a braided wire; i.e., a plurality of filaments or conductors woven into an elongated flexible cylinder or tube. Such a braided wire has an extremely high flexibility and is consequently capable of bending with relative ease to accommodate the physical manipulation of lead wire  32  during production and assembly of electromagnetic coil assembly  10 . 
       FIGS. 2 and 3  are isometric and cross-sectional views, respectively, illustrating disparate wire splice connector  34 , terminal segment  28  of coiled magnet wire  22 , and terminal segment  30  of a lead wire  32  in greater detail. In the exemplary embodiment illustrated in  FIGS. 2 and 3 , splice connector  34  includes a generally cylindrical body having a first end portion  40 , a second end portion  42  opposite first end portion  40 , and a central or intermediate portion  44  between end opposing portions  40  and  42 . As shown most clearly in  FIG. 3 , a first blind bore  48  is formed in first end portion  42 , and a second blind bore  50  is formed in second end portion  44 . As appearing herein, the phrase “blind bore” denotes a tunnel, hole, cavity, or the like having a closed or substantially closed terminal end regardless of the manner in which the blind bore is formed. First blind bore  48  and second blind bore  50  converge inwardly toward intermediate portion  44  of splice connector  34 . In the illustrated example, blind bore  48  and  50  are substantially co-axial and have ssubstantially cylindrical inner geometries and substantially equivalent inner diameters. In further embodiments, blind bores  48  and  50  may have varying geometries and/or dimensions, which may be tailored based upon unique the physical characteristics of coiled magnet wire  22  and lead wire  32 . Splice connector  34  is preferably fabricated from a metal or alloy, such as brass, aluminum, stainless steel, or the like. Splice connector  34  may be plated with gold or another material in certain embodiments to increase electrical conductivity, to enhance crimping properties, and/or to improve oxidation resistance, as desired. In one specific example, splice connector  34  is a machined brass component having a gold plating, coiled magnet wire  22  is an aluminum wire, and lead wire  32  is a copper wire. 
     First and second solder materials  54  and  56  are disposed within blind bores  48  and  50 , respectively. In  FIGS. 2 and 3 , splice connector  34  is illustrated after soldering and, thus, solder materials  54  and  56  are illustrated in a post-flow state. A partitioning wall  52  ( FIG. 3 ) separates blind bores  48  and  50  and serves as a solder dam to prevent intermixing of solder materials  54  and  56 , as described below. Solder material  54  electrically and, to a certain extent, mechanically couples terminal segment  28  of coiled magnet wire  22  to splice connector  34 . Similarly, solder material  56  electrically and mechanically bonds terminal segment  30  of lead wire  32  to splice connector  34  and, therefore, to magnet wire  22 . As indicated in  FIGS. 2 and 3 , a sufficient volume of solder material  54  is preferably disposed within blind bore  48  to fill the majority, and preferably the substantial entirety, of bore  48  and create a meniscus  58  ( FIG. 3 ) near the open end thereof. A sufficient volume of solder material  56  is likewise disposed within blind bore  50  to fill the majority, and preferably the entirety, of bore  50  and form a meniscus  60  ( FIG. 3 ) near the mouth thereof. By substantially filling bores  48  and  50  with solder material, the interior surface area of splice connector  34  mechanically and electrically bonded to the exterior surface area of wires  22  and  32  can be maximized to optimize the mechanical and electrical coupling between coiled magnet wire  22 , lead wire  32 , and disparate wire splice connector  34 . 
     To decrease electrical resistance across the solder interface, it is desired to minimize voiding or the presence of pocketed gases within post-flow solder materials  54  and  56 . To a certain extent, gasses initially trapped within solder materials  54  and  56  prior to soldering will be released during the soldering process as solder materials  54  and  56  are drawn into their respective blind bores  48  and  50  by capillary action. To further promote the inward wicking of solder materials  54  and  56 , and to allow the release of trapped gases from within blind bores  48  and  50 , one or more weep holes may be formed in disparate wire splice connector  34 . For example, as shown in  FIGS. 2 and 3 , a first weep hole  62  may be formed through the annular sidewall of splice connector  34  to fluidly couple the closed terminal end of blind bore  48  to ambient and thereby allow the outflow of trapped gas during soldering; and a second weep hole  64  may likewise be formed through the annular sidewall of splice connector  34  to fluidly couple the closed terminal end of blind bore  50  to the ambient environment. 
     Solder materials  54  and  56  may have any formulation suitable for bonding coiled magnet wire  22  and lead wire  32  to splice connector  34 , respectively. In general, solder materials  54  and  56  will be formulated based, at least in part, on metallurgical compatibility with the metals and/or alloys from which magnet wire  22 , lead wire  32 , and splice connector  34  are fabricated. In embodiments wherein coiled magnet wire  22  and lead wire  32  are each fabricated from aluminum, the composition of solder materials  54  and  56  may be identical or similar. By contrast, in embodiments wherein one or both of coiled magnet wire  22  and lead wire  32  are fabricated from a non-aluminum metal or metals, solder materials  54  and  56  may be specifically formulated for compatibility with the non-aluminum metal or metals and with the material from which splice connector  34  is fabricated. In preferred embodiments wherein at least coiled magnet wire  22  is fabricated from either aluminum or silver, solder material  54  may be formulated for usage in conjunction with aluminum or silver wire, respectively, and the material from which splice connector  34  is fabricated. As solder intermixing is prevented by partitioning wall  52 , the composition of solder materials  54  and  56  can be specifically tailored to provide optimal metallurgical compatibility with wires  22  and  32 . Solder materials  54  and  56  are also chosen to have a melt point less than that of coiled magnet wire  22 . 
     Although by no means required, solder materials  54  and  56  will each typically include a braze component and a flux component. In preferred embodiments, solder materials  54  and  56  are pre-loaded or pre-inserted into blind bores  48  and  50 , respectively, to facilitate subsequent soldering. For example, in on implementation, the constituents of solder materials  54  and  56  (e.g., the braze component and the flux component) may be combined to form a mixture, which is then molded into a cylindrical or annular body and press-fit into blind bores  48  and  50 . Alternatively, the braze component and flux component may be disposed within blind bores  48  and  50  as discrete bodies or volumes of material, which intermix during the solder process. This may be more fully appreciated by referring to  FIG. 4 , which solder materials  54  and  56  prior to soldering in accordance with one possible and non-limiting implementation. In this case, solder materials  54  and  56  each include an annular braze insert  66 , which has been molded and matingly inserted (e.g., press-fit) into blind bores  48  and  50 . The annular braze insert may be produced from a braze rod, which is machined to fit the inner diameter of the blind bore or hole. Notably, such an annular braze insert helps to ensure proper wetting of the wire and connector surfaces before significant oxidation can occur during soldering. As further shown in  FIGS. 2 and 3 , the interior of each braze insert  66  has further been packed with a flux powder  68 . Immediately prior to soldering, end portions  28  and  30  of wires  22  and  32  are inserted into flux powders  68  packed into blind bores  48  and  50 , respectively. The entire assembly is then heated, in either a uniform or non-uniform manner (described below), to flow the solder material and yield the finished solder connection shown in  FIGS. 2 and 3 . Due to shrinkage of the solder material during soldering, each annular braze insert  66  may have a length exceeding the bore depth such that the insert  66  projects outward from the bore opening (shown in  FIG. 4 ) to ensure that a sufficient volume of solder material is provided to fill the bore during the soldering process. 
     It is desired that clamping or frictional forces are applied to terminal segments  28  and  30  to physically retain wires  22  and  32  in place prior to and during soldering. In embodiments wherein the solder materials are relatively soft in their pre-flowed state, this may be accomplished by utilizing cylindrical solder material inserts and manually pressing the wire ends into the solder inserts immediately prior to soldering. Alternatively, holes may be drilled or otherwise formed in each solder insert prior to wire insertion. In this case, each hole may be formed to have an inner diameter generally conformal with (e.g., slightly greater than) the outer diameter of the wire to be inserted therein. To further help retain the wires in place during soldering and to provide additional mechanical strength to the finished solder joint, opposing ends  40  and  42  of splice connector  34  may also be crimped to exert a circumferential clamping force on wires  22  and  32 , respectively, through solder materials  54  and  56 . For example, as shown in  FIG. 3 , end portion  40  of splice connector  34  may be crimped over terminal segment  28  of magnet wire  22  (indicated in  FIG. 3  at  70 ), while end portion  42  of splice connector may be crimped over terminal segment  30  of lead wire  32  (indicated in  FIG. 3  at  72 ). Crimping may be performed such that first end portion  40  of splice connector  34  is less severely deformed than is second end portion  42  of splice connector  34  to minimize the clamping force applied to magnet wire  22 . When crimped in this manner, splice connector  34  is imparted with a double-concave crimped profile, as viewed from the side, wherein end portion  40  and end portion  42  are inwardly deformed, while intermediate portion  44  remains uncrimped. Such a crimp may be achieved in a single step process utilizing a specialized crimping tool having two double convex platens or jaws (not shown), which converge to contact and simultaneously exert an inward deformation force on end portions  40  and  42  of splice connector  34 . 
     Soldering may be performed in any manner wherein solder materials  54  and  56  are heated to temperatures beyond their respective melting points, while magnet wire  22  is maintained below its melting point. In a first exemplary technique, the entire assembly may be placed within an oven or furnace and uniformly heated to a temperature that is greater than the melting points of the solder materials and less than the melting point of magnet wire  22 . In this case, the oven may be purged with an inert gas, such as argon, to reduce the formation of oxides on the wire and splice connector surfaces during heating. In a second technique, splice connector  34  may be exposed to an open flame utilizing, for example, a microtorch to bring solder materials  54  and  56  to their respective melting points. In this case, opposing end portions  40  and  42  of splice connector  34  may be heated unevenly to minimize heat transfer to end portion  40  of splice connector  34  to prevent overheating of magnet wire  22 . Disparate heating may be achieved by varying the proximity and/or duration of flame exposure. In addition, heat transfer to end portion  40  of splice connector  34  may be reduced by fabricating splice connector  34  to include a reduced cross-sectional area, and therefore a reduced thermal conductivity, when moving from end portion  42  to end portion  40 . For example, as indicated in  FIGS. 1-4 , an annular groove  74  may be cut around intermediate portion  44  of splice connector  34 . To still further reduce the heating of end portion  40  and wire  22 , end portion  40  may be placed in contact with a heat sink and/or actively cooled by, for example, exposure to forced airflow during the soldering process. 
     Splice connector  34  may be produced from utilizing a wide variety of manufacturing process. In one exemplary and non-limiting manufacturing process, an elongated metal cylinder (e.g., a brass rod) may first be cut or sectioned into a series of cylindrical blanks Drilling may then be performed to remove material from the opposing ends of each blank and thereby create opposing blind bores  48  and  50 . Additional machining may then be performed to create the other structural features of splice connector  32  and/or to fine-tune critical dimensions; e.g., weep holes  62  and  64  may be formed utilizing a drill press, and annular groove  67  may be formed within intermediate portion  44  utilizing a cutting tool. If desired, splice connector  34  may then be plated with gold or another plating material. Finally, braze inserts (e.g., inserts  66  shown in  FIG. 4 ) may be press-fit or otherwise installed within blind bores  48  and  50  to finish production of splice connector  34 . 
     After the above-described soldering process is complete, and after formation of inorganic dielectric body  24  ( FIG. 1 ) encapsulating coiled magnet wire  22  and splice connector  34 , bobbin  12  and the potted coil (i.e., magnet wire  22  and dielectric body  24 ) and may be installed within a sealed canister. For example, and with reference to  FIG. 5 , electromagnetic coil assembly  10  further includes a canister  80  having a cavity  82  into which bobbin  12  and the potted coil  84  are inserted. Canister  80  assumes the form of a generally tubular casing having an open end  86  and an opposing closed end  88 . The cavity of canister  80  may be generally conformal with the geometry and dimensions of bobbin  12  such that, when fully inserted into canister  80 , the trailing flange of bobbin  12  effectively plugs or covers open end  86  of canister  80 , as described below in conjunction with  FIG. 6 . At least one feedthrough connector  90  is mounted through a wall of canister  80  to enable electrical connection to potted coil  84  while bridging the hermetically-sealed environment within canister  80 . For example, as shown in  FIG. 5 , feedthrough connector  90  may be mounted within a tubular chimney structure  92 , which extends through the annular sidewall of canister  80 . Feedthrough connector  90  includes a plurality of conductive terminal pins, which extend through a glass body, a ceramic body, or other insulating structure. In the illustrated example, feedthrough connector  90  includes three pins; however, the number of pins included within the feedthrough assembly, as well as the particular feedthrough assembly design, will vary in conjunction with the number of required electrical connections and other design parameters of electromagnetic coil assembly  10 . In further embodiments, feedthrough connector  90  may assume the form of a mineral-insulated cable, including a metal tube containing two or more non-insulated or bare metal wires fabricated from one or more metals or alloys (e.g., stainless steel-clad copper wires) and prevented from contacting within the metal tube by a dielectric packing (e.g., a tightly-packed, inorganic powder). Various other types of feedthrough structures can also be employed. Regardless of the particular feedthrough structure employed, embodiments of the splice connectors described herein can be utilized to join the magnet wire or wires directly to the conductors of the feedthrough structure (e.g., the wires of a mineral-insulated cable) or to one or more intermediate conductors or lead wires, which are, in turn, joined to the conductors of the feedthrough structure. 
       FIG. 6  is an isometric view of electromagnetic coil assembly  10  in a fully assembled state. As can be seen, bobbin  12  and potted coil  84  (identified in  FIG. 5 ) have been fully inserted into canister  80  such that the trailing flange of bobbin  12  has effectively plugged or covered open end  86  of canister  80 . In certain embodiments, the empty space within canister  80  may be filled or potted after insertion of bobbin  12  and potted coil  84  ( FIG. 5 ) with a suitable potting material. Suitable potting materials include, but are by no means limited to, high temperature silicone sealants (e.g., ceramic silicones), inorganic cements of the type described above, and ceramic powders (e.g., alumina or zirconia powders). In the case wherein potted coil  84  is further potted within canister  80  utilizing a powder or other such filler material, vibration may be utilized to complete filling of any voids present in the canister with the powder filler. In certain embodiments, potted coil  84  may be inserted into canister  80 , the free space within canister  80  may then be filled with a potting powder or powders, and then a small amount of dilute cement may be added to loosely blind the powder within canister  80 . A circumferential weld or seal  94  has been formed along the annular interface defined by the trailing flange of bobbin  12  and open end  86  of canister  80  to hermetically seal canister  80  and thus complete assembly of electromagnetic coil assembly  10 . Electromagnetic coil assembly  10  may then be integrated into a coiled-wire device. In the illustrated example wherein electromagnetic coil assembly  10  includes a single wire coil, assembly  10  may be included within a solenoid. In alternative embodiments wherein electromagnetic coil assembly  10  is fabricated to include primary and secondary wire coils, assembly  10  may be integrated into a linear variable differential transducer or other sensor. Due at least in part to the inorganic composition of potted dielectric body  24 , electromagnetic coil assembly  10  is well-suited for usage within avionic applications and other high temperature applications. 
     The foregoing has thus provided embodiments of an electromagnetic coil assembly suitable for usage within high temperature coiled-wire devices (e.g., solenoids, linear variable differential transformers, and three wire position sensors, to list but a few) wherein mechanical stress and work hardening of magnet wire is reliably avoided during manufacture. In particular, a magnet wire, such as a fine gauge aluminum wire or silver wire, is soldered to a larger diameter wire or a weave or braid of several conductors utilizing a specialized splice connector to alleviate issues associated with work hardening leading that may otherwise result in breakage or resistance hot spot failure. A specialized disparate wire splice connector is utilized to create this solder connection, while ensuring that the magnet wire is not overheated and destroyed during the soldering process, especially when fabricated from aluminum. In preferred embodiments, the splice connector is buried or embedded within an inorganic electrically-insulative body to mechanical isolate the fine gauge magnet wire from bending forces occurring during production and assembly of the electromagnetic coil assembly. Embodiments of the electromagnetic coil assembly described above are capable of providing prolonged and reliable operation in high temperature environments characterized by temperatures exceeding approximately 400° C. 
     While described above in conjunction with an electromagnetic coil assembly, it is emphasized that embodiments of the disparate wire splice connector can be utilized in various other applications wherein a magnet wire, such as a fine gauge aluminum or silver magnet wire, is joined to a secondary wire, which is fabricated from one or more metals having a greater resistance to work hardening and mechanical fatigue as compared to the magnet wire, which has a larger diameter (smaller gauge) than does the magnet wire, and/or is a braided wire comprised of a plurality of interwoven conductive filaments. In this regard, the foregoing has provided embodiments of a disparate wire splice connector including a generally cylindrical body, a first blind bore formed within a first end portion of the generally cylindrical body, and a second blind bore formed within a second end portion of the generally cylindrical body. A partitioning wall separates the first blind bore and the second blind bore, and a solder material is disposed within the first blind bore and formulated for usage in conjunction with the magnet wire. 
     The foregoing has also further provided embodiments of a method for joining an magnet wire, such as a coiled aluminum or silver magnet wire, to a secondary wire, such as a lead wire. In one embodiment, the method includes the steps of providing a splice connector having a first blind bore and a second blind bore, inserting a segment (e.g., an end portion) of the magnet wire into the first blind bore, and inserting a segment (e.g., an end portion) of the secondary wire into the second blind bore. The magnet wire is preferably fabricated from aluminum or silver. The splice connector is then soldered to the segments of the magnet wire and the secondary wire inserted into the first and second blind bores, respectively, to electrically couple the magnet wire and the secondary wire through the splice connector. In certain embodiments, solder material is disposed along with flux within the first blind bore and formulated for usage in conjunction with the magnet wire. The solder material may be inserted into the blind bore as, for example, an annular body having a hollow center with an inner diameter slightly larger than the wire diameter. The solder material can protrude from the body enough to allow for shrinkage upon melting. The gap between the solder material and wire is preferably large enough to allow for the application of flux to the wire prior to insertion. Prior to application of the flux, the surface of the magnet wire should ideally be free of any oxide. The second blind bore is treated in a similar manner allowing for a different wire size and material type, as appropriate. 
     In certain embodiments described above, solder material was disposed along with flux within the first blind bore and formulated for usage in conjunction with the metal or metals from which the magnet wire is fabricated. The solder material may be inserted into the blind bore, as for example, an annular body having a hollow center with an inner diameter slightly larger than the wire diameter. Additionally, the solder material can protrude from the body enough to allow for shrinkage upon melting. The gap between the solder material and wire is preferably large enough to allow for the application of flux to the wire prior to insertion. Prior to application of the flux, the surface of the magnet wire should ideally be free of any oxide. The second blind bore is treated in a similar manner allowing for a different wire size and material type, as appropriate. 
     While multiple exemplary embodiments have been presented in the foregoing Detailed Description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing Detailed Description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention. It being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set-forth in the appended Claims.