Abstract:
The invention is directed to designs for heater-sensor sub-assemblies for soldering cartridges and de-soldering cartridges for soldering systems. The designs provide a high thermal capacity and accurate tip temperature sensing and control features. The coil portion of the heater assembly is spaced proximally from the distal end of the subassembly to segregate the coil from the thermocouple temperature sensor. The solder cartridges include connector wires of dissimilar sizes and materials to couple the heater coil wire to the connections of a handle and the soldering station to reduce heat conduction to the handle.

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a heater and tip assembly for use in soldering and desoldering systems. More specifically, the present invention relates to a heater-sensor subassembly for a soldering iron or desoldering tool for use environments requiring a soldering tip or desoldering tip with a high thermal capacity adapted for use in working electrical components designed to allow high current utilization.) 
     Descriptions of Related Art 
     Certain specialty automobile electrical parts for use in Electric Vehicles (EVs) and Hybrid Electric Vehicles (HEVs) as well as power supply components such as power conditioners used in solar power generation require very high thermal capacity when soldering because the required current flow to heat the soldering device is very high, and the parts to be soldered, sometimes referred to as the land of the substrate, are generally large and as a result the parts have a high thermal capacity. 
     Therefore, in the field of soldering large parts that are designed for high currents, there is a problem in that the solder does not melt properly, or workability is very bad with conventional soldering equipment. The heater sensor complex with high thermal capacity is required because heater sensor complex can be fabricated with 2 leads with sensing function. 
     An exemplary prior art soldering iron heater assembly described in U.S. Pat. No. 6,054,678 (Japanese Patent 3124506), hereby incorporated by reference, is depicted in  FIGS. 1 and 2 . The principal part of the soldering iron heater according to the prior art included a cylindrical insulating pipe having an axial bore and a heater-sensor complex mounted thereon. The insulating pipe may, for example, be an alumina pipe.  FIG. 1  to illustrates the main components of the prior art heater-sensor complex, including a distal tip of a coil-shaped heating wire  3  welded to a distal tip of a linear non-heating wire  4  by argon welding. The base or proximal end of the heating wire  3  is welded to a linear non-heating wire  5 . The heating wire  3  was made of iron-chromium alloy. Among such iron-chromium alloys, kanthal D (a kanthal wire manufactured by Kanthal Co.) was preferred. The proportions of its principal constituent elements are Cr=22.0 and Al=4.8. Such alternative compositions as Cr=22.0, Al=5.8, Cr=22.0, Al=5.3, and Cr=20.0, Al=4.0 can also be employed. 
       FIG. 2  depicts the heater-sensor complex of  FIG. 1  as configured in a soldering iron tip assembly. The non-heating wire  4  is passed into and through the bore of an insulating pipe and the heating wire  3  is wound around the periphery of the insulating pipe forming a coil, with the respective distal ends secured together to form a thermocouple. The coil is secured to the insulating pipe and then the heater assembly including the thermal couple is inserted into and secured within a tip  9 , having an axial bore that extends over the coil portion of the heater assembly to conduct heat to the distal end of the tip  9 . In this configuration, the thermocouple is used to determine the tip temperature  1  and the coil is positioned as close as possible to the distal end of the tip. 
       FIG. 3  depicts a mechanical drawing of an exemplary heater-sensor complex made according to the teachings of the a prior art of  FIGS. 1 and 2 , depicting the coil having a length of about 10.5 mm extending proximally from a position about 1.5 mm from the distal end of the insulating pipe and within 3.5 mm of the end of the thermocouple. This assembly was configured for use in the handle assembly as depicted in FIG. 7 of the U.S. Pat. No. 6,054,678. The products made according to the design have been well received in the marketplace and as a result there are a substantial number of power stations and handles for use with the cartridges having the design in use in the industry. The configuration is very well adapted to use with small works, such as electrical circuit boards and fine wire electrical components. These types of works require precise temperature control of the soldering tip, and rapid heating of the tip by the application of power to the coil. 
     While the configuration according to the prior art U.S. Pat. No. 6,054,678 has been very well received and exceptionally adapted for use with small works, the soldering cartridges are not as well suited for use with large works, as for example the electrical parts for use in EVs and HEVs as well as power supply components such as power conditioners used in solar power generation. Accordingly, the present invention contemplates a soldering cartridge design and heater-sensor assembly having a very high thermal capacity for use with works having large surface areas, and which are useable with the installed base of soldering stations configured for use with the cartridges of the prior design. 
     SUMMARY OF THE INVENTION 
     The present invention discloses several designs for heater-sensor complexes or sub-assemblies for soldering cartridges and de-soldering systems having a high thermal capacity and accurate tip temperature sensing and control features. In the configurations of the present invention, the coil portion of the heater assembly is spaced proximally from the distal end of the subassembly to segregate the coil from the thermocouple temperature sensor. A solder tip for the cartridge may extend proximally to include a thick annular section surrounding the coil portion of the heater assembly to provide a high thermal capacity. The solder cartridges may include connector wires of dissimilar sizes and materials to couple the heater coil wire to the connections of a handle and the soldering station to reduce heat conduction to the handle. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a schematic drawing of a prior art heater-sensor complex for a soldering cartridge; 
         FIG. 2  is a schematic drawing of the distal end portion of a prior art soldering cartridge using the heater-sensor complex of  FIG. 1 ; 
         FIG. 3  is a mechanical drawing of components of a heater-sensor sub-assembly that embodied the design of the prior art of  FIGS. 1 and 2  used with conventional 70 W soldering systems; 
         FIG. 4  is a mechanical drawing of components of a heater-sensor sub-assembly according to the present invention; 
         FIG. 5  is side view drawing of the heat conducting tip of the soldering cartridge according to the present invention; 
         FIG. 6  is a mechanical drawing of the heater-sensor assembly and a cross section of the heat conducting tip having an axial bore into which the heater-sensor assembly is inserted for the soldering cartridge according to the present invention; 
         FIG. 7  A, B are perspective views of a plug base for positioning the proximal ends of the return wire and conductor within the insulating pipe according to the present invention; 
         FIG. 8  is a cross sectional end view of a plug base for positioning the return wire and conductor within the insulating pipe according to the present invention; 
         FIG. 9  is a schematic side view drawing of a soldering cartridge according to the present invention; 
         FIG. 10  is a side view drawing of a soldering cartridge of the present invention and a handle for the soldering cartridge; 
         FIG. 11  is a side view drawing of a soldering cartridge according to an embodiment of the present invention inserted into a handle to identify various temperature measurement locations; 
         FIG. 12  is a mechanical drawing of components of a heater-sensor sub-assembly according to a conventional 150 W soldering system application; 
         FIG. 13  is a mechanical drawing of components of a heater-sensor sub-assembly for a 70 W soldering system cartridge of the present invention; 
         FIGS. 14A and 14B  provide a side view and cross sectional view of an alternative embodiment of the soldering cartridge according to a conventional 150 W soldering system; 
         FIG. 15  is side view and cross sectional view of an embodiment of the soldering cartridge according to an embodiment of the present invention; 
         FIG. 16  is another alternative embodiment of the heater-sensor subassembly for the soldering cartridge according to the present invention 
         FIG. 17  is a side cross sectional view of a de-soldering assembly using the concepts of the heater-sensor sub-assembly of the present invention; 
         FIG. 18  is side cross sectional view of the heater-sensor sub-assembly of the de-soldering assembly of  FIG. 18  according to an embodiment of the present invention; 
         FIG. 19  is a table showing temperature measurements for three different cartridge designs at locations depicted in  FIG. 11 , where the tip was heated to a temperature of 500° C., and the handle was placed in a holder at a 45° angle. 
         FIG. 20  is a CHART that graphs temperature measurements as a function of time at locations A-D as shown in  FIG. 11 , graphed for the 300 W solder cartridge with a 0.8 mm iron-chromium alloy connector wire. 
         FIG. 21  is a CHART that graphs temperature measurements as a function of time at locations A-D as shown in  FIG. 11 , graphed for the 300 W solder cartridge with a 0.7 mm nickel connector wire. 
         FIG. 22  is a CHART that graphs temperature measurements over time for locations on or inside of the solder cartridges having a configuration as shown in  FIGS. 4, 9  for the 300 W solder cartridge with a 0.8 mm iron-chromium alloy connector wire. 
         FIG. 23  is a CHART that graphs temperature measurements over time for locations on or inside of the solder cartridges having a configuration as shown in  FIGS. 4, 9  for the 300 W solder cartridge with a 0.6 mm nickel connector wire. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The design of the prior art heater-sensor sub-assembly and cartridge tip according to the prior art is described above with respect to  FIGS. 1-3 , and in detail in the U.S. Pat. No. 6,054,678 incorporated by reference herein. The design of the prior art heater-sensor sub-assembly for a soldering cartridge configured for use with a 70 Watt (W) power source is depicted in  FIG. 3 . 
     A solder cartridge according to the present invention includes a heater-sensor sub-assembly  20  according to a first embodiment of the present invention depicted in  FIG. 4 , and its associated heat conducting tip  22  is depicted in  FIG. 5 . The heater-sensor sub-assembly  20  includes an insulating pipe  24 , return wire  26 , thermocouple  28  and a heater wire  30 . The heater wire  30  has a proximal portion  32  extending from a proximal location on the insulating pipe  24  to a coil  34 , and a distal portion  36 . The coil  34  is wound around the insulating pipe  24 . The insulating pipe  24  preferably has an axial length about twice the axial length of the coil  34 , and the coil  34  is positioned along the center of the insulating pipe  24 . By this configuration, the distal end of the coil  34  is spaced from the distal end of the insulating pipe a length of about one-half the length of the coil  34 . Accordingly, the length of the distal portion  36  of the heater wire  30  is about one-half the axial length of the coil  34 . 
     The heater wire  30  is preferably formed from an iron-chromium alloy wire material, such as “Kanthal” brand wire available from Sandvik Materials Technology based in Sweden. The heater wire  30  preferably has a 0.3 mm to 0.45 mm diameter and the coil  34  has thirty to thirty-two windings and a length of about 18 mm to 20 mm. The heater wire  30  is connected at its proximal portion  32  to a conductor  38 , which extends proximally and roughly parallel to the return wire  26 . The conductor  38  is preferably formed from the same material as the heater wire  30 , however, the conductor preferably has a diameter of 0.8 mm to 1.2 mm, or about 3 times the diameter of the heater wire  30 . This configuration results in the heat generation upon application of an alternating current from a power supply to be localized within the coil  34 . 
       FIG. 4  also depicts that it is contemplated that the proximal end of the conductor  38  may be welded to another axially extending connector wire  70  having a smaller diameter. The example the 1.2 mm diameter conductor  38  could be coupled to a 0.7 mm connector wire  70  formed from a metallic material having a lower volume resistivity than the conductor  38  to reduce excess heat generation, or the same material as return wire  26  or from a nickel or nickel alloy material. 
     The heater-sensor sub-assembly  20  has the non-heating return wire  26  extending axially through the insulating pipe  24  to the distal end of the insulating pipe  24 , where the distal tip of the return wire  26  is welded to the distal tip of the heater wire  30 . The return wire  26  is preferably formed from a nickel material having a diameter of 0.6 mm being preferred, however, a larger diameter wire can be used. Welding the nickel material of the return wire  26  to the iron-chromium alloy material of the heater wire  30  forms the thermocouple  28 , which acts as a temperature sensor. 
       FIG. 5  depicts a side view of the heat conducting tip  22 . The heat conducting tip  22  is preferably formed from a material having high thermal conductivity, such as copper, iron or an iron alloy.  FIG. 6  shows a cross sectional view of the heat conducting tip  22  as well as the heater-sensor sub-assembly  20 . As illustrated in the depictions in  FIG. 5  and  FIG. 6 , the heat conducting tip  22  has a first sleeve portion  42 , a central portion  44  and a tip end  46 . The heat conducting tip  22  has an axial bore  48  extending through the first sleeve portion  42 , central portion  44  and into a portion of the tip end  46 , although the majority of the tip end  46  is solid. The axial bore  48  is generally cylindrical with the distal end of the axial bore  48  forming a cone shaped indent into the center of the tip end  46  to accept the thermocouple  28  when the heater-sensor sub-assembly  20  is inserted into the axial bore  48  of the heat conducting tip  22 . 
     The heat conducting tip  22  is sized so that when the heater-sensor sub-assembly  20  is inserted into the axial bore  48 , first sleeve portion  42  surrounds the proximal half of coil  34  and the central portion  44  surrounds the distal half of the coil  34  as well as the exposed distal end of the insulating pipe  24 . The central portion has a larger outer diameter than the first sleeve portion  42 , to provide a high thermal mass. The heat conducting tip  22  may include beveled or rounded transitions between the respective outer sections. However, the configuration is intended to promote the flow of heat from the portions of the heat conducting tip  22  surrounding the coil  34  distally to the tip end  46 . 
     The design according to  FIGS. 4, 5 and 6  is adapted for use as a high thermal capacity soldering cartridge powered by a 300 W power supply. The design according to  FIGS. 4, 5 and 6  provides suitable thermal properties for large work soldering and accurate temperature control while avoiding heat influence from the coil  34  on the thermocouple  28 , thereby allowing accurate feedback control by the use of the thermocouple  28  as a tip temperature sensor. 
     In a preferred embodiment, the insulating pipe  24  preferably has an axial length of about 35 mm to 40 mm and the axial length of the coil  34  is about 19 mm. In this embodiment, the distal end of the coil  34  is positioned about 10 mm from the thermocouple  28 . Also, the proximal end of the heating wire  30  is welded to a conductor  38  having a diameter 2 to 4 times that of the diameter of the heater wire  30 . The proximal end of the conductor  38  may be secured to a smaller diameter connector wire  70  formed from a different material such as nickel or a nickel alloy. 
       FIGS. 7A, 7B and 8  depict a perspective view and cross sectional view, respectively, of a plug base  50 . The plug base  50  as shown in  FIGS. 7A and 7B  is configured to have a distal end  52  and a proximal end  54  that may be inserted into or abut a stainless steel pipe (not shown). The plug base  50  is preferably formed from a polyamide material. The plug base  50  has an axial, part cylinder shaped cutout section  56  and a generally cylindrical shaped cutout  58  offset from the axis of the plug base  50 . The conductor  38  is sized to fit into the cutout  58  while the return wire  26  is positioned coaxially in the center of the plug base  50  as shown in  FIG. 7A . 
       FIG. 9  is a side view of the assembled solder cartridge  60  of the present invention. As depicted in  FIG. 9 , the solder cartridge has the central portion  44  and a tip end  46  of the heat conducting tip  22  at the distal end of the solder cartridge  60 . The first sleeve portion  42  (not shown) of the heat conducting tip  22  is encased in a housing  62 . The housing  62  may have a first diameter portion  64  at its distal end sized so as to securely receive the first sleeve portion  42  of the heat conducting tip  22 , a tapering portion  66  near its center where the plug base  50  is located, and a proximal cylindrical section  68  having an outer diameter properly dimensioned to a diameter of about 5.5 mm for use in existing handles. The proximal cylindrical section  68  may also include electrical contacts for interconnecting the proximal ends of the return wire  26  and conductor  38  to electrical contacts in the handle (not shown). The housing  62  is preferably formed from stainless steel to provide rigidity and yet not conduct heat proximally toward the handle. 
       FIG. 10  depicts the solder cartridge  60  with the proximal cylindrical section  68  of the housing  62  inserted into a standard handle  72 . As depicted, the reduced diameter of the proximal cylindrical section  68  of the housing  62  is necessary to allow the cartridge  60  to be used with existing handles. It is contemplated that the handle may be redesigned to receive a larger diameter cartridge, whereby the housing  62  of the solder cartridge  60  may be formed of a uniform diameter tube. 
       FIG. 11  depicts a standard solder cartridge inserted into a handle with positions A-F on the handle identified where sensors were positioned to allow measurements of temperatures at various locations for the solder cartridges of the present invention. The measurements of the respective temperatures for the various cartridges are tabulated in table  1 , discussed below. 
       FIG. 12  depicts a conventional 150 W soldering system heater-sensor sub-assembly  120 . The heater-sensor sub-assembly  120  has the non-heating return wire  126  extending axially through the insulating pipe  124  to the distal end of the insulating pipe  124 , where the distal tip of the return wire  126  is welded to the distal tip of the heater wire  130 . The return wire  126  is preferably formed from a nickel material having a diameter of 0.6 mm being preferred, however, a larger diameter wire can be used. Welding the nickel material of the return wire  126  to the iron-chromium alloy material of the heater wire  130  forms the thermocouple  128 , which acts as a temperature sensor. The heater wire  130  has a proximal portion  132  extending from a proximal location on the insulating pipe  124  to a coil  134 , and a distal portion  136 . The coil  134  is wound around the insulating pipe  124 . The insulating pipe  124  preferably has an axial length about twice the axial length of the coil  134 . In this embodiment, the coil  134  is positioned from the center of the insulating pipe  124  distally 8 to 10 mm, ending about 5 mm from the thermocouple  128 . The proximal end of the heating wire  130  is welded to a conductor  138  having a diameter two to four times that of the diameter of the heater wire  130 . 
       FIG. 13  depicts an improved version of a 70 W solder system heater-sensor sub-assembly  320 . The heater-sensor sub-assembly  320  has the non-heating return wire  326  extending axially through the insulating pipe  324  to the distal end of the insulating pipe  324 , where the distal tip of the return wire  326  is welded to the distal tip of the heater wire  330 . The return wire  326  is preferably formed from a nickel material having a diameter of 0.6 mm being preferred, however, a larger diameter wire can be used. Welding the nickel material of the return wire  326  to the iron-chromium alloy material of the heater wire  330  forms the thermocouple  328 , which acts as a temperature sensor. The heater wire  330  has a proximal portion  332  extending from a proximal location on the insulating pipe  324  to a coil  334 , and a distal portion  336 . The coil  334  is wound around the insulating pipe  324 . The insulating pipe  324  preferably has an axial length of about 25 mm to 30 mm and the axial length of the coil  334  is about 8 mm. In this embodiment, the distal end of the coil  334  is positioned about 6.5 mm from the thermocouple  328 . The proximal end of the heating wire  330  is welded to a conductor  338  having a diameter two to four times that of the diameter of the heater wire  330 . Between the thermocouple  328  at the distal end of the insulating pipe  324  and the distal end of the coil  334 , the heater wire may have a wider pitch of 1.2 mm for the last four windings. 
       FIGS. 14A and 14B  depicts a heater-sensor sub-assembly  420  as components of a conventional 150 W solder cartridge  410  depicted in a side view ( FIG. 14A ) and in a side-cross sectional view ( FIG. 14B ). In the side view of  FIG. 14A , the distal tip portion of the heat conducting tip  422  at the distal end of the solder cartridge  410  is depicted extending from the housing  462 . The housing  462  includes a distal cylindrical section  464  and a proximal cylindrical section  468  and a central transition  466  there-between. The proximal cylindrical section  468  terminates at a connector assembly  480 . The housing  462  is preferably made from a rigid metallic material with low heating conducting capacity such as stainless steel. 
     As depicted in the cross sectional view of  FIG. 14B , the heat conducting tip  422  includes a sleeve portion  442  having a hollow cylindrical cross section that is press fit into the inner diameter of the distal cylindrical section  464  of the housing  462 . The sleeve portion  442  of the heat conducting tip  422  encases the distal end of the heater-sensor sub-assembly  420 , with the proximal end of the sleeve portion  442  extending at least to the proximal end of a coil  434  portion of the heater wire  430  of the heater-sensor sub-assembly  420 . As described with respect to the heater-sensor sub-assembly embodiments above, the distal end of the coil  434  is spaced from the thermocouple  428  at the distal tip of the heater-sensor sub-assembly by a length of about one-half the axial length of the coil  434 . The coil  434  is wrapped about an insulating pipe  424 . The return wire  426  passing axially through the insulating pipe  424  is preferably formed from a nickel material having a diameter of 0.6 mm being preferred, however, a larger diameter wire can be used. The heating wire  430  is preferably formed from a 0.3 mm iron-chromium alloy material. The proximal end of the heating wire  430  is welded to a conductor  438 , also preferably formed from an iron-chromium alloy material, but preferably having a diameter 0.8 mm so that heat generated at the coil  434  is localized to the vicinity of the coil  434  because of the smaller diameter the heater wire  430  as compared to the diameter of the conductor  438 . The conductor  438  and the return wire  426  may be enclosed inside of an insulating tube  482  made of a polytetrafluoroethylene or polyimide material within the proximal cylindrical section  468  of the housing  462 . 
       FIG. 15  depicts an embodiment of a heater-sensor sub-assembly  520  of the present invention as components of a 300 W solder cartridge  510  depicted in side-cross sectional view  FIG. 15 . The distal tip portion of the heat conducting tip  522  at the distal end of the solder cartridge  510  is depicted extending from the housing  562 . The housing  562  includes a first distal cylindrical section  564 , a transitional section  566  and a proximal cylindrical section  570 . The proximal cylindrical section  570  terminates at a connector assembly  580 . The housing  562  is preferably made from a rigid metallic material with low heating conducting capacity such as stainless steel. 
     As depicted in the cross sectional view of  FIG. 15 , the heat conducting tip  522  has a first sleeve portion  542 , a central portion  544  and a tip end  546 . The heat conducting tip  522  has an axial bore  548  extending through the first sleeve portion  542 , central portion  544  and into a portion of the tip end  546 , although the majority of the tip end  546  is solid. The axial bore  548  is generally cylindrical with the distal end of the axial bore  548  forming a cone shaped indent into the center of the tip end  546  to accept a thermocouple  528  when the heater-sensor sub-assembly  520  is inserted into the axial bore  548  of the heat conducting tip  522 . 
     The heat conducting tip  522  is sized so that when the heater-sensor sub-assembly  520  is inserted into the axial bore  548 , first sleeve portion  542  surrounds the proximal half of coil  534  and the central portion  544  surrounds the distal half of the coil  534  as well as the exposed distal end of the insulating pipe  524 . The central portion  544  has a larger outer diameter than the first sleeve portion  542 , to provide a high thermal mass. The heat conducting tip  522  may include beveled or rounded transitions between the respective outer sections. However, the configuration is intended to promote the flow of heat from the portions of the heat conducting tip  522  surrounding the coil  534  distally to the tip end  546 . 
     As described with respect to the heater-sensor sub-assembly embodiments above, the distal end of the coil  534  is spaced from the thermocouple  528  at the distal tip of the heater-sensor sub-assembly. The coil  534  is wrapped about an insulating pipe  524 . The return wire  526  passing axially through the insulating pipe  524  is preferably formed from a nickel material having a diameter of 0.6 mm being preferred, however, a larger diameter wire can be used. The heating wire  530  is preferably formed from a 0.4 mm to 0.45 mm iron-chromium alloy material. The proximal end of the heating wire  530  is welded to a conductor  538 , also preferably formed from an iron-chromium alloy material, but preferably having a diameter 1.2 mm so that heat generated at the coil  534  is localized to the vicinity of the coil  534  because of the smaller diameter the heater wire  530  as compared to the diameter of the conductor  538 . The conductor  538  is connected at a proximal end to a connector wire  70  preferably made of a metallic material having lower volume resistivity than the conductor  538 , or nickel or nickel alloy. The connector wire  70  and the return wire  526  may be enclosed inside of an insulating tube  582  made of a polyimide or polytetrafluoroethylene material. The insulating tube  582  is positioned within the proximal cylindrical section  570  of the housing  562 . The connector wire  70  and the return wire  526  terminate in a coupling assembly  580 . 
       FIG. 16  depicts an alternative embodiment of the heater-sensor sub-assembly that may be used in the soldering cartridge  510 . The heater-sensor sub-assembly of  FIG. 16  includes the heating wire  530  and its coil  534  wound about an insulating pipe  524 . The proximal end of the heating wire  530  is welded to a larger diameter conductor  538  made from the same material as the heating wire  530 . Preferably, the heating wire  530  is a 0.4 mm to 0.45 mm diameter iron-chromium alloy and the conductor  538  is a 1.2 mm diameter iron-chromium alloy. The distal end of the coil  534  is spaced 10 mm to 12 mm from a thermocouple  528  at the distal tip of the heater-sensor sub-assembly. The heating wire  530  is connected to a distal wire  590  made of the same material as the material of the heating wire  530 , thus preferably an iron-chromium alloy, but having a larger diameter than that of the heating wire  530 . Thus, for a heating wire having a preferred diameter of 0.4 mm, the distal wire  590  has a preferred diameter of at least 0.5 mm, and preferably in the range 0.5 mm to 0.7 mm. The larger diameter of the distal wire  590  reduces heat generation within distal wire  590  and also reduces heat transfer from the coil  534  to the thermocouple  528  along the distal wire  590 . Also as depicted in  FIG. 16 , the conductor  538  is connected at a proximal end to a connector wire  70  preferably made of a nickel or nickel alloy. 
       FIG. 17  and  FIG. 18  depict an alternative configuration of the heater-sensor sub-assembly  610  adapted for use in a de-soldering assembly  600 . The heater-sensor sub-assembly  610  as depicted in  FIG. 17  and  FIG. 18  must be adapted to allow solder that is liquefied by the heating tip to pass through a central tube  602  that is connected at its distal end to a negative pressure source or vacuum. Accordingly, the return wire cannot be co-axially mounted within an insulating tube or pipe. Accordingly, as depicted, the heating wire  630  has a coil  634  wrapped around a metallic or ceramic hollow central tube  602 . A return wire  626  is preferably a nickel material that may be a flat wire including an insulator laid along the outer circumference of the hollow central tube  602  under the coil  634 , extending forward of the distal end of the coil  634  preferably an axial length of between 0.5 to 1 times the axial length of the coil  634 . 
     The heater wire  630  has a distal portion extending from the distal end of the coil  634  which terminates in a connection to the distal end of the return wire  626  to form a thermocouple  628  spaced from the distal end of the coil  634 . The heater-sensor sub-assembly  610  is inserted into an axial recess of a heat conducting member  622  which either extends to a nozzle tip  624 . Alternatively, the heat conducting member  622  may terminate at its distal end with a flat or cone shaped surface which mates with a similar flat or cone shaped surface at the proximal end of a replaceable nozzle  624 . The heat conducting member  622  and nozzle are preferably formed from a high heat conductivity material such as copper or iron. The heat conducting member  622  and a portion of the nozzle  624  are constrained within a housing  662  formed from a low thermal conducting material such as stainless steel. 
     The coil  634  of the heating wire  630  is preferably formed from an iron-chromium alloy wire having a diameter of 0.3 mm to 0.45 mm. The proximal end of the heating wire may be connected to a conductor  638  of the same material but having a diameter significantly larger than the diameter of the heating wire, for example, the conductor  638  may have a diameter of 0.6 mm to 1.2 mm. The proximal end of the conductor  638  may itself be connected to a connector wire  670  formed of a different material, for example a nickel or nickel alloy material which may have a diameter less than the diameter of the conductor  638 . For example, when the conductor  638  has a diameter of 1.2 mm, the connector wire may have a diameter of 0.7 mm. Also, the distal end of the heating wire  630  may be connected to a distal wire (not shown) formed of a similar material but having a diameter larger than that of the heating wire  630 . 
     The de-soldering assembly  600  further includes a base assembly  650  with electrical contacts for the respective return wire  626  and conductor  638  or connector wire  670 , to connect them to a power supply (not shown). The proximal end of the central tube  602  has a nipple  604  adapted to be connected to a negative pressure or vacuum (not shown). 
     The configurations of the present invention described above are particularly beneficial in focusing heat generation toward the distal end of the soldering tip (or de-soldering nozzle) and reducing the heating of the handle assembly for high power 300 W soldering systems and for isolating the temperature sensing thermocouple from the heating coil so that the measured temperature more accurately reflects the actual temperature of the soldering tip (or de-soldering nozzle). With respect to minimizing the heat transfer toward the proximal end of the soldering cartridges, referring again to  FIG. 11 , a standard handle  72  with an associated soldering cartridge  60  is depicted.  FIG. 11  also includes the identification of six locations, marked A, B, C, D, E and F where temperature measurements were taken for three different cartridge designs. In each case, the tip was heated to a temperature of 500° C., and the handle was placed in a holder at a 45° angle. The results of the testing are tabulated in the Table of  FIG. 19 . As reflected in the results of the temperature measurements in the Table of  FIG. 19 , the addition of the nickel connector wire  70  at the proximal end of the 1.2 mm conductor extending from the heater wire results in a substantial decrease in the temperatures measured at the locations A-D for a 300 W power supply solder cartridge even as compared to using a 0.8 mm iron-chromium alloy material for the connector wire  70 . The temperatures for the 300 W cartridge having the nickel connector wire  70  were even less than the temperature measurements of a 150 W cartridge which did not include the nickel connector wire  70 . 
     The test comparison as between the 300 W solder cartridge with the 0.8 mm iron-chromium alloy connector wire and the 300 W solder cartridge with the 0.7 mm nickel connector wire are further reflected in the appended Charts of  FIGS. 20 and 21 , which show various temperature measurements as a function of time. In the Chart of  FIG. 20 , the temperature measurements at locations A-D are graphed for the 300 W solder cartridge with the 0.8 mm iron-chromium alloy connector wire. In the Chart of  21 , the temperature measurements at locations A-D are graphed for the 300 W solder cartridge with the 0.7 mm nickel connector wire. As reflected in these graphs, the respective temperatures are all lower for the nickel connector wire designs, demonstrating the advantage of the use of the nickel over the iron-chromium alloy even though the nickel wire has a smaller diameter. These graphs also show that the temperatures stabilize after about 2000 seconds. 
     To further illustrate the differences as between the 300 W solder cartridge with the 0.8 mm iron-chromium alloy connector wire and the 300 W solder cartridge with the 0.6 mm nickel connector wire, the appended Charts of  FIGS. 22 and 23  graph various temperature measurements over time for locations on or inside of the solder cartridges having a configuration as shown in  FIGS. 4, 9 and 15 . The Charts of  FIGS. 22 and 23  are based on measurements taken when the tip of the solder cartridge is placed under water and the desired tip temperature is set to 500° C. for a 300 W solder cartridge. The Chart of  FIG. 22  shows the graphs for a solder cartridge having a 0.8 mm diameter iron-chromium alloy connector wire. The Chart of  FIG. 23  shows the graphs for a solder cartridge having a 0.6 mm diameter nickel connector wire. The submerged tip temperatures of both cartridges stabilized at about 125° C., as shown in point A. The temperature measurements at various locations along the length of the solder cartridges were similar with the nickel connector wire cartridge generally lower. However, at the location of the joinder of the 1.2 mm iron-chromium alloy conductor to either the 0.8 mm iron chromium alloy connector wire ( FIG. 22 ) or the 0.6 mm nickel connector wire ( FIG. 23 ), the solder cartridge having the nickel connector wire was consistently about 20° C. cooler that the iron-chromium alloy connector wire cartridge as shown in point G. 
     Those skilled in the art will readily appreciate that the disclosure herein is meant to be exemplary and actual parameters and materials depend upon the specific application for which the process and materials of the present invention are used. The foregoing embodiments are presented by way of example such that the scope of the invention is defined only by the appended claims.