Patent Application
20170298493
The present invention relates to processes of cladding materials that can be used for electrical terminal connectors.
Conventional electrical terminal connectors are commonly made of lead and are can be attached to a conductor during the casting operation by casting techniques. The conductor is inserted into the mold cavity of a die casting machine and the lead is injected around the end of the conductor in the shape of the connector. The primary desirable properties of these electrical terminal connectors for automotive electronics are high electrical conductivity, specific strength, good ductility, compatibility with joining materials, and low cost. This is especially the case for battery terminal connectors.
New developments in electrical engineering, i.e. Automotive Electro-Mechanical Drive Systems and Consumer Electronics, are utilizing Lithium-Ion, (Li-Ion), batteries. The construction of Li-Ion batteries typically have positive (+) aluminum and negative (−) copper terminals. Connection of these dissimilar metals in either series (multiple battery configurations of positive (aluminum) to negative (copper) configurations and/or parallel (multiple series connections to a main Busbar) configuration of either a positive (aluminum) terminal to mono-metal copper Busbar or negative (copper) terminal to an mono-metal aluminum Busbar all present a challenge for robust terminations.
Conventional joining techniques of mechanical fasteners of welding have resulted in either marginal or complete failures. There is need for better “transition-metal” interconnector. Some of the metals of interest for battery terminal connectors have one or more of the desirable properties, but typically not all of them. For example, mono-metal aluminum battery terminal connectors have good electrical conductivity, fair specific strength, good ductility, and low cost. Copper has excellent electrical conductivity, good specific strength, very good ductility, but poor joint compatibility and has a moderately high cost.
Therefore, there is a need for a transition material that has all of the desirable properties of electrical terminal connectors.
The present invention is related to a method for producing a material that has the primary desirable properties that can be used for electrical terminal connectors. In an aspect, the present invention is directed at a clad material having are high electrical conductivity, specific strength, good ductility, compatibility with joining materials, and low cost properties, and the method for making the material. In an aspect, the cladded material is made from one or more metals that collectively, have the properties discussed above. In an aspect, the cladded material is a transition-metal interconnector for electrical terminal connectors. In an exemplary aspect, the material is cladded aluminum and copper.
The present invention relates to cladding materials built for use in connecting materials with different properties (e.g., aluminum and copper) in cathodes and anodes. The conducting cells can be interconnected by various welding and mechanical fastening techniques, and can streamline the cell module assembly process and increase reliability.
The present invention relates to a battery terminal connector construction. More specifically, the invention relates to means for the terminals of a storage battery of the type used in industrial applications and in automobiles so as to eliminate corrosion and improve performance of the terminals. The primary advantage of the clad metal product is the same metal-to-metal relationship between terminals and busbars/interconnector (e.g., copper to copper and aluminum to aluminum). In an aspect, the clad metal joint between the different metals of the interconnector is a hermetic metallurgical joint providing superior electrical and mechanical joining while sealing out the possibility of galvanic corrosion. The invention, in embodiments, also lengthens the life of the battery by holding the battery or groups of cells securely in position during use.
Numerous other embodiments are described throughout herein. All of these embodiments are intended to be within the scope of the invention herein disclosed. Although various embodiments are described herein, it is to be understood that not necessarily all objects, advantages, features or concepts need to be achieved in accordance with any particular embodiment. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught or suggested herein without necessarily achieving other objects or advantages as may be taught or suggested herein. These and other features, aspects, and advantages of the present invention will become readily apparent to those skilled in the art and understood with reference to the following description, appended claims, and accompanying figures, the invention not being limited to any particular disclosed embodiment(s).
So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and the invention may admit to other equally effective embodiments.
Other features of the present embodiments will be apparent from the Detailed Description that follows.
In the following detailed description of the embodiments, reference is made to the accompanying drawings, which form a part hereof, and within which are shown by way of illustration specific embodiments by which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the invention. Electrical, mechanical, logical and structural changes may be made to the embodiments without departing from the spirit and scope of the present teachings. The following detailed description is therefore not to be taken in a limiting sense, and the scope of the present disclosure is defined by the appended claims and their equivalents.
A new process for creating a material for use in electrical terminal connectors is described herein. The present invention, in embodiments, is directed at a method for producing a material with primary desirable properties for electrical terminal connectors. In an aspect, the primary desirable properties include high electrical conductivity, specific strength, good ductility, compatibility with joining materials, and low cost. In an aspect, the material comprises cladding two or more metals that have some of these properties together.
Cladding dissimilar metals together is a method to attain multiple desirable metal properties in a single resulting product since each individual layer(s) will contribute to the bulk properties. In an aspect, the primary metal configuration cladded together is aluminum and copper. Aluminum brings to the clad metal the properties of good electrical and thermal conductivity, low weight, low cost, and moderate ductility along with the compatibility to be joined to aluminum battery terminals without concern for formation of detrimental metallurgical compounds which weaken the joint and increase electrical resistance. Copper brings to the clad metal the properties of excellent electrical and thermal conductivity, moderate cost, and good ductility along with the compatibility to be joined to copper battery terminals without concern for formation of detrimental metallurgical compounds which weaken the joint and increase electrical resistance. Therefore, cladding aluminum and copper together in a side-by-side configuration combines metals which optimize the electrical, thermal, metallurgical, and mechanical properties—while providing the most cost effective option. In an aspect, the copper is placed in an inlay clad option, with the aluminum surrounding the copper almost in its entirety.
The clad material method and resulting product discussed above offers the most basic bonding configuration(s) eliminating multiple processing requirements and offering a robust clad product. Other clad options require multiple bonding, annealing, and cleaning steps. Also, depending on the product requirements, the inlay clad option can minimize the amount of copper (the more expensive and higher density material), and maximize the amount of aluminum (i.e., the lower cost and less dense) to fill the volumetric space of the final product.
In an aspect, the ratio of aluminum to copper is dependent on the specific needs of the application. Generally, the terminal connectors require between 10% to 50% copper ratio by thickness. In an aspect, the copper needs to be located within the interconnector in the area connecting to the copper terminal/busbar. Conversely, the aluminum is located in the area connecting to the aluminum terminal or busbar. In an aspect, the inlay product can minimize the copper content by only locating the copper in a limited area specific to the connection interface.
In other aspects of the present invention, other combinations of dissimilar metals, including more than two metals, can be made into the terminal connectors discussed herein. In such aspects, the composition of the terminal connector is dependent on the specific application requirements. In one aspect, the copper and aluminum interconnector discussed above can include nickel on exposed copper surface to protect against corrosion, which facilitates laser welding. In another aspect, the terminal connectors can be a cladded material made of copper and nickel. In another aspect, the terminal connector can be a cladded material made with a copper core layer surrounded by a stainless steel outer layer. In exemplary aspects of the SS/CU/SS terminals, a nickel inter-layer can be utilized to enhance the bond strength between the stainless steel layers. As discussed above, the configuration of the metals and ratios is dependent on the specific application.
In some aspects, the cladded interconnector can also include over-molding, wherein thermal plastics are used to encapsulate the clad transition joints to prevent the potential of galvanic corrosion and provide custom mounting options. For example, in some thin-gauge Li-Ion battery tab products, a polyimide tape type film with adhesive can be used to encapsulate the clad joint of the copper to the aluminum.
In an aspect, the cladded product can be made by submitting the dissimilar materials to a bonding process. A number of different methods for cladding dissimilar metals can be utilized, including, but not limited to, cold roll bonding, pressure plate bonding, hot roll bonding, explosion bonding, and impact bonding. Regardless of the bonding process used, it is desirable that the metals be bonded in a matter that prevents intermetallic phases at the interface between the dissimilar metals. Roll bonding, both cold and hot, can be further broken down into sheet and continuous-coil bonding. Impact bonding, explosion bonding, and sheet roll bonding are all discrete processes that tend to be more expensive and less well suited to high production rates than continuous roll bonding. Any bonding process that utilizes applied heat in bonding is susceptible to creating detrimental intermetallic phases. Therefore, cold roll bonding and pressure plate bonding are considered to be low cost bonding processes with high productivity, which creates bonds without the formation of intermetallic phases at the interface.
The cold roll-bonding process bonds layers of metals together. In its conventional form, cold roll-bonding requires a significant amount of cold work be imparted in all of the layers being clad together, which significantly reduces the ductility of the clad metal. The reduction in ductility of the clad metal increases the hardness and mechanical strength. In order to regain the ductility, the clad metal is annealed in such a way that the each of the layers is annealed without creating detrimental intermetallic phases at the interface between the dissimilar metals. For metal combinations where each component anneals at similar temperatures, and intermetallic phases are not a concern, this is not much of a problem. In order to avoid this problem, the selection of the inter-liner layers along with controlling the processing parameters are done to minimize or totally eliminate the formation of detrimental intermetallic compounds. However, for metal clad configuration with heavy relative inlay layer thickness, (i.e. greater than 30% overall thickness), vertical edge bond strength is minimal at best due to the minimal transverse pressure generated in the vertical bonding interface during the cladding.
The minimal vertical edge-bond strength represents a possible product design limitation. Clad bonding produces high bond strength between horizontal material surfaces due to the extreme pressure generated during bonding. The vertical edge-bond is weak because the vertical material surfaces are not subjected to the extreme bond pressure—the material can displace “side-ways” between the mill rolls—because the material is not restricted; the tendency to spread minimizes the pressure on the vertical edge-bond. The minimal vertical edge-bond strength is inversely proportional to the inlay ratio thickness—heavy inlay ratio results in weaker vertical edge-bond strength and becomes very apparent if the finish connector has a bend/form in the area of the vertical edge. During forming the weak edge-bond can tend to separate and open along the seam.
Using an inlay or “stepped-material” clad technique (i.e., placing smaller layers in width on top of layers with greater width, or vice versa), shown in several of the figures, provides a significant improvement to the apparent strength of the vertical bond area, as well as an increase edge-bond strength, and electrical and thermal conductivity.
In step 2, shown in
In step 3, shown in
As shown in
As shown, the first metal components include a base layer 1100, two middle layer components 1110, 1120, and a top layer component 1130. The one second metal component 1200 is made to be placed in the middle layer 1030 between the middle layer components 1110, 1120 so that the second metal 1200 (metal 2) is completely surrounded by the first metal 1100, 1110, 1120, 1130 (metal 1) within the cladded material 1010. By eliminating the exposed edges of the core material (metal 2) 1200, the potential for corrosion is avoided. In an exemplary aspect, the first metal (metal 1) includes aluminum and the second metal (metal 2) includes copper. However, other combinations, as discussed above, are possible in other aspects.
In step 2, shown in
In step 3, shown in
As shown in
After the bores 1400 are made, the clad metal composite 1010 is processed to the finish strip 1500 size using standard metalworking techniques, such as rolling, annealing, slitting, and cleaning, as shown in
An example of use of such a connector follows: a main electrical connection coming from a battery module that has a copper terminal that needs to join along an aluminum bus bar. The attachment of the copper terminal can be a mechanical joint (bolt). The bolt connecting the copper terminal needs to be joined to copper—or risk a potential galvanic couple and corrosion (bolting the copper terminal directly to the aluminum bus bar). By removing material on the top and bottom layers, the opposite metals are exposed, enabling joining of the copper terminal to the copper and the aluminum terminal to the aluminum.
In an aspect, the process also includes selective metal removal as shown in the
In
Selective metal removal can expose lower-layer and/or center-layer metal for isolation of dissimilar metals in the terminal contact region. The actual technique to selectively remove the metal layer to expose the “other” metal is not specific. A standard milling cutter can be used to machine away the aluminum layer to create the circular pockets. It is also possible to remove the metal layer selectively by skiving. The removal of the metal layer using skiving is shown in
Having thus described exemplary embodiments of a method to produce metallic composite material, it should be noted by those skilled in the art that the within disclosures are exemplary only and that various other alternatives, adaptations, and modifications may be made within the scope of this disclosure. Accordingly, the invention is not limited to the specific embodiments as illustrated herein, but is only limited by the following claims.
In addition, while a particular feature of the teachings may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular function. Furthermore, to the extent that the terms “including”, “includes”, “having”, “has”, “with”, or variants thereof are used in either the detailed description and the claims, such terms are intended to be inclusive in a manner similar to the term “comprising.”
Other embodiments of the teachings will be apparent to those skilled in the art from consideration of the specification and practice of the teachings disclosed herein. The invention should therefore not be limited by the described embodiment, method, and examples, but by all embodiments and methods within the scope and spirit of the invention. Accordingly, the present invention is not limited to the specific embodiments as illustrated herein, but is only limited by the following claims.
This application claims priority from U.S. Provisional Patent Application No. 62/323,263, filed Apr. 15, 2016, which is incorporated herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62323263 | Apr 2016 | US |
