Connection terminals equipped with a silver-graphite layer

Abstract

To provide a process for manufacturing a connector and a connector. [Solution] A process for manufacturing an electrical connection terminal having a contact portion with a first contact area configured to establish an electrical connection with a second contact area of ​​another connection terminal includes one or more metal deposition steps over the first contact area. One or more metal deposition steps include a silver-graphite layer deposition step which is advantageously selectively performed by electroplating over at least the first contact area.

Description

[Technical Field]

[0001] The present disclosure generally relates to electrical connection terminals, and in particular to connection terminals for automotive applications. For example, such electrical connection terminals are adapted in connectors for safety restraint systems (SRS). [Background Art]

[0002] Typically, in an electrical connection terminal, the area intended to become the contact region in the finished connection terminal is provided with a gold layer (possibly containing other elements). Gold has exceptional properties in terms of conductivity, tribology, corrosion resistance and the like. Gold is deposited, for example, by an electrochemical process that forms a highly uniform layer. However, the gold deposition process is costly due to the price of gold, and its performance in terms of greenhouse gas generation (specifically CO₂) is also insufficient.

[0003] Research is being conducted to replace gold with silver in some applications. However, when the silver layer deposited on the contact area of ​​the male connector comes into contact with the silver layer deposited on the contact area of ​​the female connector, a phenomenon called cold soldering tends to occur (silver atoms on one side of the interface between the contact areas diffuse to the other side of this interface, and vice versa). Therefore, when the male and female connectors are subjected to vibration or moved relative to each other (for example, when they are disconnected), there is a risk that one or more layers of silver on either side of the interface may be removed. Silver also has a tendency to oxidize. To overcome this drawback, a passivation film is sometimes applied to the surface of the silver layer. This may not be a problem for high current or relatively high current applications, as the voltage across the interface may be sufficient to restore conductivity through any insulating layer that may be present. On the other hand, in other applications, such as pyrotechnic systems used in SRS applications like airbags and pretensioners, the currents involved are small, and a voltage of 0.1 volts may be insufficient to push the current through this insulating layer. Furthermore, the tribological properties of silver are not as good as those of gold. [Overview of the project] [Problems that the invention aims to solve]

[0004] Therefore, particularly when certain electrical terminals are intended for use in connectors for SRS devices, there is a demand to replace the layer of gold deposited on those terminals with a layer of other material whose properties are similar, equivalent, or better than gold.

[0005] For this purpose, a method for manufacturing a connector and the connector itself are described below. [Means for solving the problem]

[0006] More specifically, a method for manufacturing electrical connection terminals (also called electrical contacts) is disclosed. Such terminals may be male or female. Typically, such terminals have a mounting portion and a contact portion. For example, the mounting portion is mechanically mounted (by crimping, soldering, or press-fitting) and configured to be electrically connected to other conductors (cables, wires, printed circuits, etc.). For example, the contact portion is configured to mechanically mate into a mating terminal and be electrically connected. The contact portion has a contact area configured to establish an electrical connection with the contact area of ​​another connection terminal (i.e., the mating terminal). For clarity, in this document, the contact area of ​​a connection terminal being processed according to the method described herein is referred to as the first area, while the contact area of ​​the mating connection terminal is referred to as the second area.

[0007] The method includes a step of depositing a silver-graphite layer over the first contact region, and one or more metal deposit steps over the first contact region.

[0008] Thanks to the silver-graphite layer, the first contact area exhibits excellent properties in terms of conductivity, tribology, and corrosion inertia. This specifically allows for the replacement of connectors with gold-plated contact areas with connectors manufactured using this method, particularly in low-current applications (e.g., SRS applications). The silver-graphite layer eliminates the need for any other protective layers.

[0009] Other advantages include, for example, the presence of a silver-graphite layer provides improved wear resistance against friction, increasing the coefficient of friction compared to pure silver, which can extend the service life of the connecting terminals under mechanical switching operations and / or reduce the mating force of the terminals.

[0010] This method provides a solution for depositing the silver-graphite layer onto the first contact area, including the implementation of reel-to-reel deposition. Reel-to-reel deposition allows for high deposition rates, is cost-effective, and is advantageous from a packaging and logistics standpoint.

[0011] According to an advantageous embodiment, the deposition step of the silver-graphite layer is carried out by electroplating. Electroplating enables the formation of connectors with excellent adhesion to the underlying substrate, which reduces the risk of layer delamination of the connectors and the risk of failure during operation. Electroplating enables improved corrosion resistance, wear resistance, conductivity, and aesthetics. Electroplating also allows for precise control of thickness and composition of the deposited layer. Electroplating is highly scalable and can be easily integrated into existing manufacturing lines, resulting in high deposition rates. Therefore, electroplating results in cost-effective production of high-quality connectors.

[0012] According to other advantageous embodiments, the silver-graphite layer deposition step is carried out selectively across surfaces, including the surface of the first contact area (i.e., selectively on a specific surface or surface portion of the connection terminal). This reduces the amount of material deposited, thereby reducing costs. It is also possible to adapt the deposited material to the function of the terminal portion (the contact area may require a different coating than the contact area of ​​the weld portion).

[0013] Other embodiments are associated with various other advantages and / or technical effects.

[0014] According to one embodiment, the method is - A step of providing a metal plate, for example, the metal being copper or a copper alloy, and - One or more first forming steps applied to a metal plate in at least one area intended to be a contact portion having a first contact area in a completed connector, comprising one or more first forming steps selected from cutting, stamping, punching, pressing, and bending operations, - One or more metal deposition steps over at least a first contact region, including the deposition step of at least one silver-graphite layer, following the one or more first forming steps, - One or more second forming steps applied to a metal plate in the completed connector terminal, in at least one area intended to be a different area from the first contact area, the first forming step being selected from cutting, stamping, punching, pressing, and bending operations. Includes.

[0015] In other words, forming steps that impose significant stress on the metal sheet, specifically in areas or regions intended to become the first contact area in the completed connector (e.g., cutting, stamping, and bending steps), can be performed first, before the deposition of potentially brittle layers, while other forming steps necessary to complete the manufacture of the connector can be performed later, completely or partially avoiding the first contact area. This has the advantage that areas and / or regions of the connector (specifically, the first contact area of ​​the connector) that may be brittle and / or fragile, and / or delaminate from the underlying metal (e.g., a layer of nickel over a copper sheet), are not subjected to stresses that could damage them.

[0016] According to one embodiment, the one or more metal deposition steps include a silver layer deposition step, and the at least one silver-graphite layer deposition step follows the silver layer deposition step. The advantage is that the silver layer forms a shield (without graphite flakes) that prevents gases (e.g., oxygen) passing through the graphite flakes from reaching an underlying layer (e.g., a nickel layer) that may be corroded (e.g., by oxidation). Other advantages include, for example, that the incorporation of a silver layer enhances the conductivity of the connection terminals, providing a low-resistance path for current; the silver layer is protected by a silver-graphite layer to protect the electrical performance of the underlying silver layer; the silver layer prevents potential chemical interactions between graphite and nickel; the silver layer beneath the silver-graphite layer provides enhanced adhesion between the layers, enabling a layered structure that results in improved mechanical integrity of the connection terminals; and the silver-graphite layer prevents the silver layer from blackening (thus resulting in a better visual appearance, smaller mating forces, and improved quality inspection by camera on the assembly line, especially when blackening is not constant and uniform).

[0017] According to one embodiment, the one or more metal deposition steps include a nickel layer deposition step, and the at least one silver layer deposition step follows the nickel layer deposition step. The advantage is that the nickel layer forms a shield that prevents the diffusion of elements from the underlying metal (e.g., copper of the metal plate) to the upper layer (e.g., silver and / or silver-graphite). Because the nickel layer is very hard, this improves the tribological properties of the terminal, and the hard underlayer is covered by a softer layer that acts as a lubricant.

[0018] Also disclosed is an electrical connection terminal comprising a contact portion having a first contact area configured to establish an electrical connection with a second contact area of ​​another connection terminal. The first contact area is at least partially covered by a nickel layer, a silver layer at least partially covering the nickel layer, and a silver-graphite layer at least partially covering the silver layer.

[0019] According to one embodiment, the silver layer is positioned between the nickel layer and the silver-graphite layer.

[0020] The advantages of silver-graphite layers, silver layers, and nickel layers have already been mentioned above. Depositing silver-graphite layers is less costly than depositing gold layers and does not produce as many greenhouse gases.

[0021] According to one embodiment, the silver-graphite layer is a surface layer extending at least over a first contact region. In other words, there is no passivation layer, protective layer, etc., extending over the surface layer of the silver-graphite layer.

[0022] According to one embodiment, the silver-graphite layer is between 2 μm and 5 μm thick. Thicker silver-graphite layers are more costly. Thinner silver-graphite layers may be insufficient to resist wear, for example, and could reduce the reliability of the connection terminals. Advantageously, the silver-graphite layer is thicker than the graphite flakes, and at least slightly thicker, so that at least a portion of the flakes is completely embedded in the silver. Advantageously, the silver-graphite layer has a good mixture of silver and graphite on its surface. The graphite improves the friction coefficient of the silver without degrading its electrical performance. As a result, the thickness of the silver-graphite layer is advantageously proportional to the flake size. Advantageously, the flakes should not be too small; otherwise, the silver-graphite layer will lose its lubricating effect.

[0023] According to one embodiment, the silver-graphite layer contains graphite flakes distributed in a range of 1 μm to 5 μm in maximum size. The size of the flakes also affects the homogeneity of the electrolytic cell. The size of the flakes also affects the cost. In fact, larger flakes result in a thicker silver-graphite layer (and thus greater silver consumption).

[0024] According to one embodiment, the silver layer has a thickness between 0.1 μm and 1 μm (preferably between 0.1 μm and 0.5 μm). Thicker silver layers are more costly. Thinner silver layers are insufficient, for example, to prevent gas diffusion into any underlying layers.

[0025] According to one embodiment, the nickel layer has a thickness between 1 μm and 3 μm. Thicker layers of nickel will incur higher costs. Thinner layers of nickel are insufficient, for example, to form an effective shield to prevent migration of elements (e.g., copper atoms) into the overlying layer.

[0026] According to one embodiment, the connection terminal is a female terminal, and the contact portion is made of copper or a copper alloy. Copper has suitable mechanical and electrical properties for producing connection terminals of excellent quality. However, other conductive materials can be used to form the connection terminal (e.g., aluminum, aluminum alloys, iron alloys, etc.). According to another embodiment, the connection terminal is a male terminal, and the contact portion is made of a nickel-iron alloy (e.g., NiFe45 or NiFe47), steel, or the like.

[0027] According to one embodiment, graphite in the silver-graphite layer has a weight percent between 0.5% and 2% relative to silver. Within this percentage range, there is sufficient graphite for the silver-graphite layer to have a self-lubricating effect (that is, graphite reduces the friction coefficient) without increasing, or without substantially increasing, contact resistance.

[0028] According to one embodiment, graphite is uniformly distributed in the silver-graphite layer. A relatively high volume percentage of graphite uniformly distributed in the silver matrix allows the connection terminal to benefit from the uniform self-lubricating properties of graphite throughout the layer, reduces the possibility of hot spots, and improves the performance of the connection terminal, particularly under high load conditions.

[0029] In summary, the present document provides a solution that eliminates (or reduces) the use of gold while maintaining or improving the durability and reliability of electrical connection terminals. More generally, when considering any type of connection terminal, the silver-graphite layer can result in a reduction in maintenance requirements and replacement costs, since the connection terminal will retain its functionality over a longer period of time.

[0030] This disclosure is illustrated by example in the accompanying drawings, where similar reference numerals indicate similar elements, and is not limited to the accompanying drawings. Embodiments of this application will be described here with reference to the accompanying drawings. [Brief explanation of the drawing]

[0031] [Figure 1] This diagram shows an example of a pair of male connector terminals that are still attached to each other during the manufacturing process. [Figure 2] This is an example diagram of three female connectors that are still attached to each other during the manufacturing process. [Figure 3] This diagram shows the three female connectors of Figure 2 in a manufacturing stage prior to the manufacturing stage corresponding to Figure 2, with an enlargement of the contact blades. [Figure 4] This is a diagram illustrating an example of a specific step in a method for manufacturing a connector terminal. [Figure 5] This figure shows specific steps in a method for manufacturing a connector terminal. [Figure 6] These are scanning electron microscope images of cross-sections of nickel, silver, and silver-graphite layers deposited on copper connectors. [Modes for carrying out the invention]

[0032] Examples of male connectors 10 and female connectors 20 are described below. Using the example, Figure 1 shows male connectors 10 in a manufacturing process. More specifically, Figure 1 shows two male connectors 10 still connected together (the two male connectors 10 are separated from each other in a later stage of the manufacturing process). Each male connector 10 has a pin portion 14 with a contact portion 11. The contact portion 11 has a contact area 12 configured to establish an electrical connection with a contact area 22 of a female connector 20. An example of such a female connector 20 is shown in Figure 2. More specifically, Figure 2 shows three female connectors 20 still connected together (the three female connectors 20 are separated from each other in a later stage of the manufacturing process). According to this example, each female connector 20 has a contact portion 21. Each contact portion 21 comprises three elastic blades 23, each having a contact area 22 toward its free end. For example, each elastic blade 23 is deformed at its free end to form a curved contact area 22, and more specifically, in the finished connector, to form a radially protruding area toward the inside of a cage 24 formed by the three blades 23, the cage 24 is configured to receive the contact portion 11 of the male connector 10. The number of blades 23, the shape of the blades 23, the shape of the contact areas 12, 22, the shape of the male connector 10 and the female connector 20 themselves, etc., are not limited to the examples shown in the figures. Essentially, any type of connector can be manufactured using the manufacturing method as described herein, and similar methods, and variations thereof.

[0033] An example of a method for manufacturing a female connector 20 is described below, which is essentially equivalent to the method for manufacturing a male connector 10 with respect to the main forming steps 100, 300 and the electroplating step 200.

[0034] For example, these main forming steps 100, 300 and electroplating step 200 are as follows (see Figures 4 and 5). - Step 90 provides a metal sheet 1. In the example of the embodiment of the manufacturing method, the metal sheet 1 is a copper sheet, and in this example, the metal sheet 1 is the raw material (i.e., the metal sheet 1 is not yet plated, but in deformation, for example, the metal sheet 1 may have undergone one or more treatments such as plating). - One or more first forming steps 100 applied to at least one area of ​​a metal sheet 1. In an example of the embodiment of the manufacturing method, such area corresponds to a contact portion 21, and more specifically, the first forming step 100 is applied to an area of ​​the contact portion 21 that is intended to become blades 23 and their respective contact portions 22 in the finished connector terminal, and the first forming step 100 includes at least one operation, such as cutting, pre-stamping, punching, embossing, and bending, to form the blades 23 and their respective contact portions 22. - One or more metal deposition steps or plating steps 200 following the one or more first forming steps 100. In an example of the embodiment of the manufacturing method, the metal deposition step 200 successively includes electrodeposition 201 of nickel layer A, electrodeposition 202 of silver layer B, and electrodeposition 203 of silver-graphite layer C, and of course other steps (e.g., washing, rinsing, drying, etc.) may be performed before or after the electrodeposition of each of layers A, B, and C, and the metal deposition step 200 is carried out over at least the contact area 22, and more specifically, for example, the metal deposition step 200 may be limited to the end of the blade 23 including the contact area 22, or it may cover the entire length of the blade 23. - One or more second forming steps 300 following the one or more metal deposition steps 200. The second forming step 300 specifically includes at least one operation such as cutting, stamping, punching, pressing, bending, or separating to form a cage 24, and the second forming step 300 is applied to the metal plate 1 in at least one area of ​​the completed connector 20 that is intended to be a different area from the contact area 22.

[0035] The first forming step 100 and the second forming step 300 are of a type well known to those skilled in the art of manufacturing connection terminals.

[0036] The metal deposition step 200 is advantageously carried out in an electrolytic cell by electroplating technology.

[0037] First, a nickel layer A is formed on a portion of the copper connector terminal 20(10). For example, the nickel bath used is a product commercially available from Umicore under the name Niruna 800. For example, a nickel layer A of 1 μm to 3 μm is formed by passing the end of the blade 23 (or the end of the pin portion 14) through this bath for 1.5 to 2 minutes with appropriate current and temperature parameters.

[0038] Secondly, strikes of silver B are deposited across the nickel layer A. For example, the silver bath is a commercially available product from Umicore. For example, a silver layer B of 0.5 μm to 1 μm is formed by passing the end of the blade 23 (or the end of the pin portion 14) through this bath with appropriate time, current, and temperature parameters.

[0039] Thirdly, a silver-graphite layer C is deposited over the silver layer B. For example, the silver-graphite tank is a silver-graphite dispersion electrolyte commercially available from Umicore under the name Arguna® C-100. For example, a silver-graphite layer C of 1 μm to 5 μm is formed by passing the end of the blade 23 (or the end of the pin portion 14) through this tank with appropriate time, current, and temperature parameters.

[0040] An example of a multilayer obtained by the above method is shown in Figure 6. For example, nickel layer A (not shown) is approximately 1.6 μm thick, silver layer B is approximately 1.5 μm thick, and silver-graphite layer C is approximately 5.6 μm thick. Silver-graphite layer C contains graphite D flakes with a maximum size of approximately 5 μm. The graphite D flakes are uniformly distributed in silver-graphite layer C. [Explanation of Symbols]

[0041] 1. Metal plate 10 Male connectors, electrical connectors 12 Contact area 14 Pin section 20 Female connectors, electrical connectors 22 Contact area 23 Elastic Blades 24 cages 100 First formation step 200 Metal deposition step, electroplating step 201 Electrodeposition of Nickel Layer A 202 Electrical deposition of silver layer B 203 Electrodeposition of Silver-Graphite Layer C 300 Second formation step A Nickel layer B Silver layer C Silver-graphite layer D Graphite

Claims

1. An electrical connection terminal (10, 20) having a contact portion (11, 21) with a first contact area (12, 22) configured to establish an electrical connection with a second contact area (22, 12) of another connection terminal (10, 20), Electrical connection terminals (10, 20) characterized in that the first contact area (12, 22) is at least partially covered by a nickel layer (A), a silver layer (B) that at least covers the nickel layer (A), and a silver-graphite layer (C) that at least partially covers the silver layer (B).

2. The connection terminal (10, 20) according to claim 1, wherein the silver layer (B) is positioned between the nickel layer (A) and the silver-graphite layer (C).

3. The connector terminal (10, 20) according to claim 1 or 2, wherein the silver-graphite layer (C) is a surface layer extending at least over the first contact region (12, 22).

4. The connection terminal (10, 20) according to any one of claims 1 to 3, wherein the silver-graphite layer (C) has a thickness between 2 μm and 5 μm.

5. The connection terminal (10, 20) according to any one of claims 1 to 4, wherein the silver layer (B) has a thickness between 0.1 μm and 1 μm.

6. The connection terminal (10, 20) according to any one of claims 1 to 5, wherein the nickel layer (A) has a thickness between 1 μm and 3 μm.

7. The connector (20) according to any one of claims 1 to 6, wherein the connector is a female connector and the contact portion (21) is made of copper or a copper alloy.

8. The connector (10) according to any one of claims 1 to 6, wherein the connector is a male connector and the contact portion (11) is made of a nickel-iron alloy.

9. The connector terminal (10, 20) according to any one of claims 1 to 8, wherein the graphite in the silver-graphite layer (C) has a weight percentage between 0.5% and 2% relative to the silver.

10. The connector terminal (10, 20) according to any one of claims 1 to 9, wherein the silver-graphite layer (C) includes graphite (D) flakes distributed in a range of 1 μm to 5 μm in maximum size.

11. A method for manufacturing an electrical connection terminal (10, 20) having a contact portion (11, 21) with a first contact area (12, 22) configured to establish an electrical connection with a second contact area (22, 12) of another connection terminal (20, 10), the method comprising one or more metal deposition steps (200) over the first contact area (12, 22), A method characterized in that the one or more metal deposition steps (200) include a step (203) of depositing a silver-graphite layer (C) selectively performed by electroplating over at least the first contact areas (12, 22).

12. - Step (90) of providing a metal plate (1), - One or more first forming steps (100) applied to the metal plate (1) in at least one area intended to become the contact portion (11, 21) with the first contact area (12, 22) in the completed connector, the first forming step (100) being selected from cutting, stamping, punching, pressing, and bending operations, - One or more metal deposition steps (200) over at least the first contact regions (12, 22), including the at least one deposition step of a silver-graphite layer (C) following the one or more first forming steps (100), - One or more second forming steps (300) applied to the metal plate (1) in the completed connector (10, 20) following the one or more metal deposition steps (200), in at least one area intended to be different from the first contact area (12, 22), the one or more second forming steps (300) selected from cutting, stamping, punching, embossing, and bending operations. The method according to claim 11, including the method described in claim 11.

13. The method according to claim 11 or 12, wherein the one or more metal deposition steps (200) include a deposition step (202) of a silver layer (B), and the at least one deposition step (203) of a silver-graphite layer (C) follows the deposition step (202) of the silver layer (B).

14. The method according to claims 11 to 13, wherein the one or more metal deposition steps (200) include a deposition step (201) of a nickel layer (A), and the at least one deposition step (202) of a silver layer (B) follows the deposition step (201) of the nickel layer (A).

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