Sealed crimp connection methods

Methods of making a sealed crimp connection attaching a terminal to a wire conductor are provided. A layer of fluid conformal coating is applied to overlie a terminal and underlie at least a lead of the wire conductor upon at least the lead being received into the terminal. The terminal, the fluid layer, and at least the lead of the wire conductor are crimped to form the crimp connection. Fluid conformal coating is displaced where an abutting surface of the terminal makes contact with at least the lead of the wire conductor. The fluid conformal coating is cured to a non-fluid state. The fluid conformal coating may be formed of an acrylated urethane material that may provide an increased pull force and a low crimp resistance in the crimp connection. The crimp connection may be constructed using a manufacturing process on an automated assembly line.

TECHNICAL FIELD

The invention relates to a connection between a terminal and a wire conductor.

BACKGROUND OF INVENTION

Referring toFIG. 1, it is known to apply a sealant to a lead of the wire conductor (1) having wire strands (2) and crimp the sealed lead (3) to the core wings (4) of a terminal (5) and attach the terminal (5) to the wire conductor (1) that affords protection against contaminants that may negatively affect the electrical and mechanical operating performance therein. The insulator wings (6) of the terminal (5) are crimped to the insulative cover (7) of the wire conductor (1) and are spaced apart from the core wings (4) crimped to the sealed lead (3) by a notch (8).

Terminal/wire conductor connections are common in wiring harnesses used in many industries, such as the automotive and trucking industries. Wiring harnesses provide the conduit for electrical signal transmission that support the operation of vehicular electrical systems. In the automotive industry, it is increasingly desirable to use light weight wire conductors that may assist to provide increased fuel economy for the vehicle. These lighter weight wire conductors are often connected to commercially available terminals where the wire conductors and the terminals are constructed using dissimilar materials. Thus, it remains a goal to provide protection of the connection which is the interface where these dissimilar materials meet. The protection of the connection is especially desired to retard the formation of galvanic corrosion. Galvanic corrosion may degrade the connection such that transmission of an electrical signal through the connection is prohibited. It also remains a desirable goal to provide protection to the connection while maintaining or improving the electrical and mechanical properties of the terminal/wire conductor connection.

Accordingly, there is a need for an improved sealed connection attaching a terminal to a wire conductor having robust electrical and mechanical operating performance.

SUMMARY OF THE INVENTION

One aspect of the invention is improving the protection at the terminal/wire conductor connection, or crimp connection that may further prevent the onset of galvanic corrosion in the crimp connection.

Conventional thinking in the wiring arts is that a dielectric, insulating seal material added to a crimp connection may yield an increased crimp resistance to the crimp connection, and hence, decrease the electrical performance of the crimp connection. To this end, another aspect of the invention is the discovery of a fluid conformal coating formed from an acrylic urethane material used in the construction of the crimp connection that improves the electrical and mechanical properties of the connection while also providing an effective sealing at the crimp connection. More specifically, the crimp connection using the acrylic urethane material may have a low crimp resistance over a prolonged period of time and an increased pull force in contrast to a similarly constructed crimp connection that does not contain any seal material.

Based on the desire to improve the crimp connection to retard galvanic corrosion, the discovery of the increased pull force and low crimp resistance, and in accordance to the principles of the invention, a crimp connection is made to attach a terminal to a wire conductor by forming a layer of fluid conformal coating to overlie the terminal and underlie the lead when at least the lead is received into the terminal. The lead is received into the terminal, and the terminal, the fluid layer, and at least the lead are crimped together to produce a crimp connection that attaches the terminal to the wire conductor. The fluid conformal coating in, and about the crimp connection is cured to a non-fluid state.

DETAILED DESCRIPTION

Referring toFIG. 2-6, a cable, or wire conductor10is disposed along a longitudinal axis A. Wire conductor10has an insulative outer cover12and an aluminum-based inner core14. The term “aluminum based” as used in this document herein is defined to mean pure aluminum or an aluminum alloy where aluminum is the main metal in the alloy. Cover12surrounds inner core14. Inner core14is constructed of a plurality of individual wire strands16that are bundled and twisted together. Wire strands16are useful to provide flexation of conductor10when conductor10is installed in a wiring application (not shown), such as during the manufacture of a vehicle. Alternately, the inner core of the wire conductor may be a single wire strand. An end portion (not shown) of cover12of conductor10is removed to expose a portion of inner core14. Exposed portion of inner core14is a lead18of wire conductor10. Lead18extends from an axial edge20of cover12.

A copper-based terminal22includes a mating end24, a middle portion26, and an open wing end28. The term “copper-based” as used in this document herein is defined to mean pure copper, or a copper alloy where copper is the main metal in the alloy. Middle portion26is intermediate ends24,28. Terminal22may be received into a connector (not shown) that may include a plurality of terminals (not shown) that is part of wiring harness (not shown) used in a vehicle (not shown) and the connector (not shown) may mate with a corresponding mating connector (not shown) used in the vehicle. Mating end24is a male mating end30. Male mating end30may be received into a corresponding female receiving terminal (not shown), such as may be found in the corresponding mating connector (not shown) disposed in the vehicle (not shown), that electrically joins an electrical signal disposed on conductor10with another electrical circuit attached with the corresponding female receiving terminal (not shown). Alternately, male mating end30may be a female mating end. Middle portion26includes an inwardly facing tab32adapted to communicate with a shoulder in the connector (not shown) so that terminal22does not easily disengage from the connector (not shown) once tab32is inserted past the shoulder (not shown). Wing end28includes a pair of combination insulator and core wing, or elongate terminal wings34that extend outwardly away from terminal22in a direction generally perpendicular to axis A. Elongate wing34does not include the notch (8) in the terminal (5) as shown in the prior art ofFIG. 1. The construction of elongate terminal wings34is different than the separate and distinct insulator wings (6) and core wings (4) as shown in the prior art ofFIG. 1. Wings34are formed of a single unitary structure along an axial length of wing end28of terminal22and cover additional area to further encapsulate lead18upon being crimped to conductor10to form an effective mechanical connection of terminal22attached to conductor10. Thus, elongate wings34are effective to decrease the amount of surface area of lead18that is exposed to open air and possible electrolyte contaminant that may facilitate undesired galvanic corrosion of lead18in terminal22when conductor10is crimped to terminal22. Alternately, a single elongate wing may be employed.

Terminal22is chosen such that wing end28is sized sufficiently large to receive lead18and portion of outer cover12adjacent lead18to allow for an effective crimp between terminal22and conductor10. Typically, a size of the terminal is related to an AWG size of the wire conductor. AWG is a term known in the wire arts as American Wire Gauge. Elongate wing34is effective to receive lead18and a portion of cover12adjacent lead18into terminal22. A height of elongate wing34is sized to sufficiently wrap around and cover a substantial portion of lead18and a substantial portion of cover12adjacent lead18when conductor10is crimped to terminal22. Wing end28includes an inner surface, or abutting surface36that engages inner core14of lead18when conductor10is crimped to terminal22to provide electrical connection between conductor10and terminal22.

A fluid conformal coating40is disposed on an outer surface of lead18including an end38of lead18, and over edge20and extending on to a portion of outer cover12adjacent lead18. A seal covering42of fluid conformal coating40entombs lead18so as to provide a corrosion-resistant protective layer for lead18of conductor10when wire conductor10is received into wing end28of terminal22. “Fluid” is defined as being as “being able to flow.” The viscosity of coating40may be altered to allow coating40to properly flow onto wire conductor10so as to achieve a sufficient thickness of coating40. Seal covering42of fluid coating40may be applied to conductor10by dripping, spraying, electrolytic transfer, and brush and sponge applications, and the like.

Preferably, coating40is applied by dipping lead18and a portion of cover12adjacent lead18in bath of fluid conformal coating (not shown) and subjecting the dipped lead to applied pressure which drives the coating into voids, or interstices44between strands16of lead18across a cross section area of lead18, as shown inFIGS. 5 and 6. Referring toFIG. 6, seal covering42is sufficiently applied to ensure a cross section of lead18along an axial length of lead18is saturated by coating40upon application of pressure.

As the diameter of the inner core of the wire conductor increases, a larger amount of conformal coating is needed to saturate and cover the lead of a wire conductor. When interstices44of wire strands16of lead18are saturated with conformal coating40, a more complete coating of the lead18may increase corrosion protection for lead18of wire conductor10. Alternately, the inner core may be dipped to only apply conformal coating to an outer surface of the lead of the wire conductor. Fluid conformal coating40may include silicon, epoxy, wax, paint, grease, and the like. Preferably, fluid coating40is formed from an acrylated urethane material. A suitable conformal coating made of an acrylated urethane material is commercially available from Dymax Corporation under conformal coating number 29985.

When lead18of conductor10is not received in wing end28of terminal22, a connection, or crimp connection46between terminal22and conductor10does not occur and a mechanical and an electrical connection between terminal22and conductor10does not exist.

Referring toFIG. 2, conductor10includes seal cover42as previously described herein. Lead18is axially received into wing end28of terminal22. Seal cover42is arranged as layer48on terminal22and extends past edge20onto the portion of outer covering12of conductor10which is useful to create a more hermetic seal for lead18and provide increased protection against the formation of galvanic corrosion in conductor10when crimp connection46is formed. For example, on wire conductor having a14AWG size, conformal coating40may extend onto covering12about 2 millimeters past edge20. If conformal coating is only applied to the edge of the outer covering, the surface area of the outer covering perpendicular to axis A may not be sufficient for sealing the lead especially with flexation of the wire conductor. A further step54in method48is receiving at least lead18of conductor10in terminal22to allow arrangement of a layer52of fluid conformal coating40to underlie lead18and a portion of lead18adjacent lead18, and overlie terminal22. End38of lead18moves past a rearward edge56and a forward edge58of elongate terminal wing34so that conductor10is disposed in wing end28. Edge20of outer cover12moves past rearward edge58of elongate terminal wings34. Alternately, the end of the lead is received between the forward and the rearward edges of the elongate terminal wings.

Referring toFIGS. 3 and 4, another step60in method48is crimping wings34, fluid layer48, lead18, and portion of outer cover12adjacent lead18together to form crimp connection46. A crimp of a wire conductor and a terminal, as readily understood in the art, is defined as compressing or deforming a portion of the terminal around the wire conductor so as to at least make an electrical connection between the terminal and the wire conductor. A crimp of a terminal to a wire conductor may be performed by a die, or applicator press, as is known in the art. The positioning of wings34relative to the disposition of lead18is useful to ensure that wings34at least substantially wrap around inner core14of lead18when crimp connection46is formed to maximize the electrical connection between terminal22and lead18of conductor10. Connection46includes wings34enclosing around lead18and a portion of cover12adjacent lead18and span over edge20of outer cover12. A rearward portion of wings34enclose a portion of cover12adjacent lead18and a forward portion of wings34encloses lead18. The crimping process moves, displaces, and pushes layer48of fluid coating40about connection46that further fills interstices44in lead18disposed in connection46. Conformal coating40displaced during crimping may also be pushed out towards edges56,58of terminal22. Metal-to-metal contact with lead18may occur anywhere abutting surface36makes contact with lead18along an axial length of lead18in crimp connection46. Thus, wire strands16may not have continuous line-to-line contact with inner surface36of wings34, rather, more particularly, at a microscopic level there are a plurality of points of metal-to-metal contact of abutting surface36that are intermingled with a plurality of points of conformal coating40that are intermediate surface36and lead18. Abutting surface36of wings34of terminal22contacts at least an outer surface of inner core14of lead18to ensure effective electrical connection between lead18of conductor10and terminal22.

Referring toFIG. 5, with the crimp of cable10to terminal22to form crimp connection46, a seam62is formed where terminal wings34come together. Seam62defines a gap64intermediate axial forward and rearward edges56,58of wings34. Gap64also allows displaced conformal coating40during the crimping of connection46to extrude out from connection46and form and puddle in gap64of seam62. Layer52of fluid conformal coating40is sufficiently applied to cover inner core14at gap64with coating40along seam62after crimp connection46is formed and may fill further voids. It is important to ensure that any exposed wire strands16in crimp connection46are covered with coating40after crimp connection46is formed to prevent an entry point for galvanic corrosion that may develop in crimp connection46. During the crimping process an enlarged rearward portion of wings34adjacent rearward edge56is formed tapering to a smaller forward portion adjacent forward edge58of wings34that is also formed that may further direct, or funnel excess fluid conformal coating toward forward edge58to extrude out past edge58.

Alternately, the longitudinal edges of the terminal wings may contact each other at the seam. The compression of the wings34against lead18and cover12of conductor10is effective to mechanically secure terminal22to conductor10.

After the crimping of terminal22onto conductor10, layer52of coating40is cured in step66of method48to a non-fluid state. Non-fluid state of coating40is when coating40is in a solid form. Preferably, conformal coating40is cured by ultraviolet (UV) light (not shown) along the assembly line (not shown) that produces connection46. The UV light may be provided, for example, by a UV lamp. Also, preferably, the UV cure is conducted after formation of crimp connection46. If the layer of conformal coating was in solid form and then crimped to form the crimp connection, an effective seal and electrical operating performance connection46may not be realized.

A corrosion inhibitor68may be further applied after curing conformal coating40. Inhibiter68is useful to fill microscopic voids (not shown) in cured conformal coating40disposed on lead18of wire conductor10. Inhibitor68may also fill surface irregularities in outer insulative cover12of wire conductor10, terminal22, in an area around crimp connection46. Corrosion inhibitor68may be applied using similar techniques as applying seal cover42to a lead of a wire conductor as previously described herein. Corrosion inhibiter68may be formed of a dielectric material that includes oils, waxes, and greases, and the like. Corrosion inhibitor68may also be applied in the manufacturing process flow on the automated assembly line along with method48.

The steps of method50are successively performed in a manufacturing process flow on an automated assembly line (not shown). In this manner, the conformal coating40is fluidly applied and remains fluid along the assembly line (not shown) until coating40is cured to a non-fluid state. Preferably, fluid coating40is cured on the assembly line (not shown) during operation of the assembly line (not shown) to make the crimp connections. It is also preferable to not let fluid crimp connections lie at rest on the assembly line when the assembly line is idled. More preferably, fluid coating40, including coating40of layer52, is cured on the assembly line (not shown) with ultraviolet (UV) light to a solid state before coating40air dries to a solid state. Air drying a fluid conformal coating in a manufacturing environment is undesired as this may take a week of time or longer for the fluid conformal coating to attain the non-fluid, or solid state. Additionally, material handling of fluid crimp connections may create undesired quality issues that negatively affect the mechanical and electrical operating performance of the crimp connection. Coating40made from the acrylated urethane material may have tensile strength upwards of 6000 pound per square inch (PSI) when in a solid state. Dipping wire conductor10to apply seal covering42and applying pressure to seal covering as described herein, is preferably conducted on the assembly line using method50. Preferably, fluid coating40having the acrylated urethane material is used on the automated assembly line also using method50.

Using conformal coating40formed of an acrylated urethane material, shows an increased pull force of crimp connection46and a low crimp resistance of crimp connection46. This discovery, as previously described herein, was understood by doing USCAR21 testing of crimp connection46. USCAR21 includes testing methodologies used in the automobile industry to test the operating performance of cables, wire conductors, and the like.

Referring toFIGS. 8-11, the graphs show pull force and crimp resistance data for crimp connection46having a layer52of conformal coating40formed of an acrylated urethane material in contrast with similarly made crimp connection that do not contain a layer of conformal coating of any kind. For the data with coating40formed of an acrylated urethane material, this corresponds to inner core14of wire conductor10. The set of graphs included withFIGS. 8,9,10, and11represent data for varying increasing diameter sizes of the inner core of the wire conductor.FIGS. 8A-8Dillustrate data for an inner core having a diameter of about 0.75 millimeters2.FIGS. 9A-9Dillustrate data for an inner core having a diameter of about 1.25 millimeters2.FIGS. 10A-10Dillustrate data for an inner core of about 1.75 millimeters2.FIGS. 11A-11Dillustrate data an inner core having a diameter of about 2.0 millimeters2. The crimp resistance of the crimp connection was measured before and after accelerated environmental life testing of the connection. Accelerated environmental life testing corresponds to at least 10 years of usage life for the crimp connection disposed in an environment commensurate with that found in a vehicle.

Similar elements to those inFIG. 8A-8Din the graphs ofFIGS. 9-11have reference numbers differing by 100. Graphs8A-8B,9A-9B,10A-10B, and11A-11B illustrate pull force and crimp resistance data for a crimp connection void of a conformal coating material. The respective corresponding graphs8C-8D,9C-9D,10C-10D, and11C-11D illustrate pull force and crimp resistance data for crimp connection46having coating40made of the acrylated urethane material.

Pull Force

Graph data74,174,274,374show a pull force for a crimp connection that does not contain conformal coating for different heights of the crimp core. In contrast, graph data77,177,277,377show a pull force for crimp connection46having conformal coating having the acrylated urethane material. The pull force data for corresponding crimp connection46amongst the various inner core wiring sizes is generally increased over the similarly made crimp connection that contains no sealing material.

While not limited to any particular theory, it is believed that the fluid layer of conformal coating having the acrylated urethane material allows the pull force to be increased because the acrylated urethane material bonds the wire strands of the lead together into a single wire strand having a larger tensile strength than the combination of the tensile strength of the individual wire and the tensile strength of the acrylate urethane material.

Crimp Resistance

Graph data75,175,275,375show crimp resistance for a crimp connection that does not contain conformal coating for different heights of the crimp core, or connection. Graph data76,176,276,376show crimp resistance for a crimp connection that does not contain conformal coating for different heights of the crimp connection after accelerated environmental testing. This crimp connection with no conformal coating shows a general undesired increase in the crimp resistance after the accelerated environmental life testing. An increase in crimp resistance relates to lower electrical conductivity through the crimp connection. Graph data78,178,278,378show a crimp resistance for crimp connection46that contains conformal coating made of the acrylated urethane material for different heights of crimp connection46. Graph data79,179,279,379show a crimp resistance for a crimp connection that does not contain conformal coating for different heights of crimp connection after accelerated environmental testing. This data shows a desired, generally smaller increase in the crimp resistance measured after the accelerated environmental life testing than corresponding crimp resistance data of a crimp connection that has no conformal coating. A smaller resistance differences relates to enhanced electrical conductivity at the crimp connection.

While not limited to any particular theory, it is believed that the layer of conformal coating having the acrylated urethane material has low crimp resistance over a prolonged period of time because the metal-to-metal contact between the abutting surface of the terminal and the wire strands of the lead may not leave residual solids in the voids of the wire stands like other conformal coatings that do not have the acrylated urethane material that may interfere with the metal-to-metal contact and may result in increased resistance in the crimp connection, but not so much so as to have zero resistance in the crimp connection.

Alternately, any technique that effectively applies a layer of fluid conformal coating disposed intermediate the terminal and the lead of the wire conductor when the lead is received in the terminal may be used. For example, conformal coating may be applied to the terminal which arranges the layer to overlie the terminal and underlie at least the lead of the wire conductor. Conformal coating may be applied to the terminal by similar techniques used to apply conformal coating to the wire. Another example may include painting the fluid conformal coating on either the lead or the terminal in contact with the lead using a paint brush.

Still yet alternately, the conformal coating may be applied to both the terminal and the lead before the crimp connection is formed.

While the preferred embodiment of this invention is for an interface between to two dissimilar metals as described herein, a further alternate embodiment may include a terminal and lead made from similar or identical metals, such as pure copper or copper alloy materials. For example, the wire conductor may be made of an aluminum material and the terminal may also be made of an aluminum material.

Still yet alternately, the layer of conformal coating may be applied between a lead of a wire conductor of any diameter size connected to an associated terminal.

Applying a layer of fluid conformal coating and crimping this fluid layer to form a crimp connection provides a robust crimp connection connecting a terminal to a wire conductor. This robust crimp connection may keep an electrolyte such as salt water, from penetrating and degrading the crimp connection. Applying a seal covering of fluid conformal coating on the lead and a portion of the insulative outer cover adjacent the lead to entomb the lead provides a more effective hermetic seal of the lead and greater confidence that the lead is sealed against contaminants that may penetrate the crimp connection. Exposing the fluid seal covering on the lead to applied pressure drives the seal covering into the interstices of the wire strands of the lead that provides even greater structural sealing for the entire crimp connection. The displacement of the fluid conformal coating during crimping to form the crimp connection also further enhances the structural sealing of the lead and provides for a sealed electrical interface and contact between the terminal and lead. The elongate terminal wings further reduce exposure of the lead to the containments that may otherwise increase risk of undesired galvanic corrosion. A gap in the seam of the crimped elongate wings and the open areas at the forward and rearward edges of the elongate terminal wings provide an outlet for displaced fluid conformal coating when the terminal is crimped to the wire conductor. Extra thickness of conformal coating at these locations provides even further protection to keep contaminants from penetrating the crimp connection. Using a conformal coating having an acrylated urethane coating may provide the mechanical and electrical benefits of an increased pull force and a low crimp resistance of the connection over a prolonged period of time where the prolonged period of time is at least the projected service life of the crimp connection. In the automotive industry this may be at least 10 years of projected service life. Applying a corrosion inhibiter after curing the conformal coating to the crimp connection and the elements associated with the crimp connection may fill voids and irregularties that have developed in the cured, exposed conformal coating or other elements of the crimp connection to make a further contribution to prevent galvanic corrosion from exploiting the crimp connection.

Other variations and modifications are possible without departing from the scope and spirit of the present invention as defined by the appended claims.

While this invention has been described in terms of the preferred embodiment thereof, it is not intended to be so limited, but rather only to the extent set forth in the claims that follow.