Abstract:
A corrosion resistant electrical connection structure has an electrically conductive cable with a core made from a first electrically conductive material and an insulative outer cover. A terminal is electrically connected to the core at a lead extending beyond the insulative outer cover. A conformal coating covers and seals the lead of the core not in direct contact with the terminal.

Description:
CROSS-REFERENCE TO CLAIM OF PRIORITY 
     This application claims the priority of co-pending U.S. Provisional Application Ser. No. 61/243,672 filed Sep. 18, 2009. 
    
    
     TECHNICAL FIELD 
     The field of this invention relates to a connection between an aluminum based cable and a copper based electrical terminal. 
     BACKGROUND OF THE DISCLOSURE 
     Insulated copper based cable is commonly used for automotive wiring. Copper has high conductivity, good corrosion resistance and adequate mechanical strength. However, copper and copper based metals are relatively expensive metals and are also heavy. 
     Interest is weight savings and cost savings in automotive electrical wiring applications have made aluminum based cables an attractive alternative to copper based wires. However, some wiring and electrical connectors may remain copper based. Thus, there may be a transition somewhere in the electrical circuit between an aluminum based portion of the circuit and a copper based portion of the circuit. Often this transition may occur at the terminal because the terminal may remain copper based for reasons of size and complexity of shape that can be more easily achieved with copper based materials over aluminum based materials. The connection of aluminum based cable to a copper based terminal can produce a galvanic corrosion of the aluminum, if an electrolyte, for example salt water, is present. The galvanic reaction corrodes the aluminum because the aluminum or aluminum alloy has a different galvanic potential than the copper or copper alloys of the terminals. “Copper based” as used in this document means pure copper, or a copper alloy where copper is the main metal in the alloy. Similarly, “aluminum based” as used in this document means pure aluminum or an aluminum alloy where aluminum is a main metal in the alloy. 
     Referring now to  FIG. 1 , significant corrosion is known to occur between dissimilar materials when an electrolyte such as salt water is present. A conventional copper based terminal  35  as shown in  FIG. 1  has a pair of insulator wings  36  and a pair of core wings  38  with a notch  40  therebetween. A stranded aluminum based cable  12  may have its connected exposed strand ends  15  of lead  16  substantially corrode when it is attached to a terminal  35  made from a more noble metal such as pure copper, brass, or another copper alloy. A four day long salt fog test has been demonstrated to substantially corrode away almost the entire aluminum lead  16 . The notch  40  allows greater access of the salt and other electrolytes to contact the exposed strands  15 . The lead  16  when corroded completely away causes a break in the electrical connection between the cable  12  and the terminal  35 . 
     What is needed is an improved corrosion resistant connection between a cable and its connected terminal. What is also needed is a connection between aluminum based cable and copper based terminals with improved corrosion resistance through an improved seal to seal the aluminum cable from an electrolyte while maintaining electrical contact with the terminal. 
     SUMMARY OF THE DISCLOSURE 
     In accordance with one aspect of the invention, an electrical connection structure has a conductive cable with a core being aluminum based and an insulative outer cover. A terminal is copper based and electrically attached to the core. The terminal has a mating end and an opposite end with a first combination insulation and core wing. The combination insulation and core wing is crimped onto the insulative outer cover, spans over an edge of the insulative outer cover of the conductive cable, and is crimped onto and makes electrical contact with a lead of the core that axially extends beyond the insulative outer cover. A cured conformal coating is over remaining portions of the lead of the core that is not in direct contact with the terminal. 
     Preferably, the terminal has a second combination insulation and core wing at the opposite end for also being crimped onto the insulative outer cover, spanning over the edge of the insulative outer cover and crimped onto and making electrical contact with the lead of the core. The first and second combination insulator and core wings are crimped toward each other about the lead of the cable. In one embodiment, a narrow gap is formed between the first and second insulator and core wings. The gap is filled with the cured conformal coating. The core is a plurality of strands that when crimped has voids which are filled with the cured conformal coating. 
     In accordance with another aspect of the invention, an electrical terminal has a body with a mating end. The body has an opposite end with a combination insulation and core wing for crimping onto the insulative outer cover of each cable, spanning over an edge of an insulative outer cover of the cable and crimped onto and making electrical contact with the lead of the core extending beyond the insulative outer cover. 
     Preferably, the terminal has a second combination insulation and core wing at the opposite end for also being crimped onto the insulative outer cover, spanning over the edge of the insulative outer cover and crimped onto and making electrical contact with the lead of the core. 
     In accordance with another aspect of the invention, a corrosion resistant electrical connection structure has an electrically conductive cable having a core made from a first electrically conductive material and an outer insulative cover. A terminal is electrically connected to the core at a lead extending beyond the outer insulative cover. The terminal is made of a second electrically conductive material that is more electro-positive than the first electrically conductive material when exposed to an electrolytic environment. A conformal coating covers and seals the lead of the core not in direct contact with the terminal. 
     Preferably, the terminal has a mating end. The terminal has an opposite end with a combination insulation and core wing for crimping onto a lead of a conductive core of the cable. The combination insulation and core wing is crimped onto the insulative outer cover, spans over an edge of an insulative outer cover of the cable, and is crimped onto and makes electrical contact with the lead of the core extending beyond the insulative outer cover. 
     In accordance with another aspect of the invention, an electrical connection structure has a cable with an electrically conductive core and an insulative outer cover. An electrically conductive terminal is electrically connected to the core at a lead of the core extending beyond the insulative outer cover. The terminal has a mating end and an opposite end with a combination insulation and core wing for crimping onto a lead of a conductive core of the cable. The combination insulation and core wing is crimped onto the insulative outer cover spanning over an edge of an insulative outer cover of the cable, and crimped onto and making electrical contact with the lead of the core extending beyond the insulative cover. The terminal preferably has a second combination insulation and core wing at the opposite end for also being crimped onto the insulative outer cover, spanning over the edge of the insulative outer cover and crimped onto and making electrical contact with the lead of the core. A conformal coating covers and seals the lead of the core not in direct contact with the terminal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Reference now is made to the accompanying drawings in which: 
         FIG. 1  is a plan view of a conventional prior art aluminum based cable and copper based terminal illustrating the exposed strand ends of the aluminum based wire in phantom that have been substantially corroded away; 
         FIG. 2  is a perspective and exploded view of copper based terminal and the treated cable of  FIG. 2  an aluminum based cable with its end being removed of its insulative outer cover and undergoing a spray of conformal coating in the axial direction toward the exposed end of the conductive cable core in accordance with one embodiment of the invention before assembly; 
         FIG. 3  is a perspective view of the terminal and the aluminum based cable assembled onto the terminal; 
         FIG. 4  is a cross-sectional view taken along lines  4 - 4  shown in  FIG. 3 ; and 
         FIG. 5  is a cross-sectional view taken along lines  5 - 5  shown in  FIG. 4 . 
         FIG. 6  is a magnified view of the aluminum based cable as indicated in  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIG. 2 , a cable  10  has an insulative outer cover  12  and an aluminum based core  14 . The core  14  is made of a plurality of individual strands  15  bundled and twisted together. An end portion of the insulative outer cover  12  is removed to expose a lead  16  of the core  14 . A spray machine  18  sprays a conformal coating  20  onto the lead  16  of the core. The position of the spray head  23  is pointed to be directed away from cover  12  and toward the axial distal end  21  of the lead  16 . The direction of the spray is axially directed away from the insulative outer cover  12  and toward the axial distal end  21 . The spray head  23  may commence spraying the conformal coating  20  before the cable is moved into the spray of conformal coating  20 . The cable is then moved axially into the spray such that axial ends  21  hit the spray and is coated with conformal coating  20 . The cable may rotate or the spray head  18  may orbit about the cable  12  to assure the lead  16  is coated 360° around. As the cable is moved forward toward terminal  22 , the spray head  23  may be axially aligned with the insulative outer cover  12  and provide conformal coating  20  over edge  43  of insulative outer cover  12 . The entire lead  16  is coated. 
     While the conformal coating is still wet, the cable  10  is positioned relative to a terminal  22  as best shown in  FIG. 3 . The terminal  22  has a mating end  31 . The terminal  22  is then crimped at its opposite end onto the cable  10  such that it makes electrical contact with the lead  16  of core  14  at best shown in  FIGS. 4 ,  5  and  6 . 
     As the terminal is crimped onto the cable  10 , the conformal coating  20  on the lead  16  is displaced to allow direct contact between the terminal  22  and the lead  16 . The conformal coating is displaced to fill voids  24  between the strands  15  as highlighted in  FIG. 6 , and other exposed surfaces of the lead  16  that are not in direct contact with the terminal  22 , for example in an area  42  between the wings  26  and at the end  21  as best shown in  FIG. 4 . After the crimping of the terminal  22  onto the cable  10 , the conformal coating is allowed to cure to complete the assembly of the electrical connection  30 . 
     The terminal  22  has wings  26  that eliminate the conventional notch  40  shown in  FIG. 1 . The wings  26  are crimped over the insulative outer cover  12  and span over an edge  43  of the insulative outer cover  12  and are crimped onto the lead  16 . The wings  26  can be referred to as combination insulator and core wings. 
     Each wing  26  is crimped onto the lead  16  while the conformal coating  20  is still wet. The conformal coating  20  is displaced from the abutting surfaces of the terminal  22  and lead  16  to provide an electrical interface and connection between the terminal  22  and lead  16 . The conformal coating  20  is displaced to areas of the lead  16  that are not in direct contact with the terminal, for example within the gap  42  formed between the crimped wings  26  and within the voids  24  and at the axial outer end  21  of the lead  16 . 
     The conformal coating  20  is then cured in position to complete the electrical assembly  30 . 
     By sealing the electrical connection from electrolyte such as salt water, significant reduction of galvanic corrosion occurs between aluminum based cable and copper based electrical terminals. The displacement of the conformal coating  20  while it is still wet greatly enhances the structural sealing of the entire lead and aluminum based core while providing a sealed electrical interface and contact between the terminal and lead. The combination insulator and core wing also reduces exposure of the lead to the elements that can otherwise increase risk of electrolytic corrosion. 
     While the main application of this invention is for an interface between to two dissimilar metals, it is foreseen that application of this seal can also provide advantages for an interface between a terminal and lead interface made from similar or identical metals. 
     Other variations and modifications are possible without departing from the scope and spirit of the present invention as defined by the appended claims.