Patent Application
20240125000
The present disclosure relates to electroplating polymeric parts, and more particularly to electroplating polymeric parts for motor vehicle applications with specific finish requirements.
The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Plating plastic parts with chromium or other similar materials is generally carried out in order to provide improved aesthetics of exterior components of a motor vehicle, such as by way of example a front grille or other trim components. Conventional processes for coating polymeric, or plastic parts with chromium involves a multi-step process to render the surface of the plastic part electrically conductive.
Referring to
The thickness of a chromium or metal coating on plastic parts according to conventional processes can vary across the plastic part as a function of part geometry. For example, an automobile grille plated according to conventional processes may yield thickness variations ranging from about 4 micrometers to 50 micrometers. Such variations can result from deep surfaces of the part to be coated (e.g., a fog lamp surround). To offset such dimensional variations, the geometry of the substrate itself can be tailored (e.g., to narrow the depth of crevices, pockets, depressions, and the like of the substrate) or by increasing the dwell time the substrate is immersed in the electroless bath. Auxiliary anodes may also be employed to facilitate metal plating over the surfaces of a substrate having deeper crevices, pockets depressions, or the like. Unfortunately, further finishing is required to provide an even layer of a metallic coating on the substrate when thickness tolerances are exceeded, thus contributing to increased costs and cycle time.
The present disclosure addresses these and other issues related to coating plastic parts with an aesthetically pleasing material such as chromium or nickel.
This section provides a general summary of the disclosure and is not a comprehensive disclosure of its full scope or all of its features.
According to one form of the present disclosure, a method of plating a substrate includes etching at least a portion of a surface of the substrate to form voids within the surface. The substrate includes a composite material having a network of electrically conductive nanostructures disposed within a thermoplastic matrix. Electrodes are attached to the substrate, and the substrate is placed into a bath of a first electrically conductive metal. A voltage is applied to the substrate through the electrodes, and the voltage is conducted through the network of electrically conductive nanostructures to deposit a first electrically conductive metal layer onto the surface of the substrate. A second electrically conductive metal is electroplated onto the first electrically conductive metal layer to form a second electrically conductive metal layer.
In variations of this form, which may be implemented individually or in any combination: the electrically conductive nanostructures are in an amount of about 0.5 wt. % of the composite material; the first electrically conductive metal is copper, and the second electrically conductive metal is nickel; the first electrically conductive metal includes at least one of copper, copper alloys, nickel, and nickel alloys; the thermoplastic matrix comprises at least one of acrylonitrile-butadiene-styrene (ABS) and polycarbonate/acrylonitrile-butadiene-styrene (PC/ABS); the network of electrically conductive nanostructures comprises carbon nanotubes; the first electrically conductive metal layer has a thickness between about 20 μm to about 40 μm; the voltage conducted through the auxiliary anodes is disposed along a periphery of the substrate; an electroless plating process is not used to plate the substrate; a third electrically conductive metal is electroplated onto the second electrically conductive metal layer to form a third electrically conductive metal layer; the second electrically conductive metal is nickel, and the third electrically conductive metal is chrome; and a part is plated according to the present method.
According to another form of the present disclosure, a method of plating a substrate includes etching at least a portion of a surface of the substrate to form voids within the surface. The substrate includes a composite material having a network of electrically conductive nanostructures disposed within a thermoplastic matrix. The network of electrically conductive nanostructures is in an amount of about 0.5 wt. % of the composite material. Electrodes are attached to the substrate, and the substrate is placed into bath of a first electrically conductive metal. A voltage is applied to the substrate through the electrodes, and the voltage is conducted through the network of electrically conductive nanostructures to deposit a first electrically conductive metal layer onto the surface of the substrate, and a second electrically conductive metal is electroplated onto the first electrically conductive metal layer to form a second electrically conductive metal layer.
In variations of this form, which may be implemented individually or in any combination: the first electrically conductive metal layer has a thickness between about 20 μm to about 40 μm; the voltage conducted through the auxiliary anodes is disposed along a periphery of the substrate; and the first electrically conductive metal is copper, and the second electrically conductive metal is nickel.
In yet another form of the present disclosure, a method of plating a substrate includes etching at least a portion of a surface of the substrate to form voids within the surface. The substrate includes a composite material having a network of electrically conductive nanostructures disposed within a thermoplastic matrix, and the network of electrically conductive nanostructures are in an amount of about 0.5 wt. % of the composite material. Electrodes are attached to the substrate, and the substrate is placed into a bath comprising a first electrically conductive metal including one copper and a copper alloy. A voltage is applied to the substrate through the electrodes, and the voltage is conducted through the network of electrically conductive nanostructures to deposit a first electrically conductive metal layer onto the surface of the substrate in a thickness between about 20 μm to about 40 μm. A second electrically conductive metal is electroplated onto the first electrically conductive metal layer to form a second electrically conductive metal layer.
In variations of this form, which may be implemented individually or in any combination: the voltage conducted through the auxiliary anodes is disposed along a periphery of the substrate; an electroless plating process is not used to plate the substrate; a third electrically conductive metal is electroplated onto the second electrically conductive metal layer to form a third electrically conductive metal layer.
Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
In order that the disclosure may be well understood, there will now be described various forms thereof, given by way of example, reference being made to the accompanying drawings, in which:
The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.
The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.
The present disclosure provides a method of plating substrates (e.g., plastic parts) with a metal layer without the need for an intermediary electroless plating step (set forth above). Generally, substrates having a surface resistivity less than 1×108 ohm meter (Ω·m) are suitable to achieve an electrostatic surface for plating a metal layer (e.g., chromium) over the surface of the substrate. In one form, the substrate has a surface resistivity less than 1×104 ohm meter (Ω·m).
Referring to
As used herein, the phrase “network of electrically conductive nanostructures” should be construed to mean a crosslinked network of nanostructures connected at a plurality of nodes 28, which together form an electrically conductive pathway throughout the composite material 20. In one form, the nanostructures are carbon nanostructures. The network of electrically conductive nanostructures 24 further reduces the electrical resistivity of the composite material 20, improving the efficiency of the plating process. Therefore, the conductive network of linked nanostructures 24 provides enough conductivity to result in a composite material 20 that is statically dissipative, thus enabling efficient plating, as described in greater detail below. It should be understood that while the network of electrically conductive nanostructures 24 are connected at nodes 28 as shown, not all of the network of electrically conductive nanostructures 24 need be connected while remaining within the scope of the present disclosure. The network of electrically conductive nanostructures 24 are provided in an amount to provide the desired resistivity of the composite material 20 for plating processes.
To form the network of electrically conductive nanostructures 24 that are adequate for the desired conductivity, a high amount of shear is required in processing the nanostructures to untangle the nanostructures, which enables further improvement in conductivity. More specifically, the amount of shear processing during the compounding of the composite material 20 has a significant impact on the final material properties. Accordingly, the conductivity and surface resistivity of the composite material 20 can be tuned as desired, depending on the amount of nanostructures introduced and the amount of shear used in processing the nanostructures.
Referring to
The thermoplastic matrix 22 may be any of a variety of thermoplastic materials, including by way of example, an acrylonitrile-butadiene-styrene (ABS) or a polycarbonate/acrylonitrile-butadiene-styrene (In one form, the thermoplastic matrix 22 includes plateable grades of ABS (i.e., ABS having a higher concentration of butadiene than standard grades), which enables effective etching of the surface of the substrate, thereby creating more voids and surface area for copper to fill, as described in greater detail below.
In one form of the present disclosure, the network of electrically conductive nanostructures 24 are added in an amount of about 0.5% by weight to achieve a surface resistivity of about 1×103 ohm meter (Ω·m). It is contemplated that lower or higher amounts of electrically conductive nanostructures 24 may be implemented depending on the desired resistivity. Substrates prepared according to the present disclosure exhibit improved electrical conductivity, which allows for elimination of electroless plating of the substrate required under conventional processes for metal plating substrates. Moreover, substrates plated according to the present disclosure exhibit more uniform metal plating thicknesses than substrates plated under conventional processes.
In one form of the present disclosure, before electroplating, at least a portion of the surface of the substrate is etched. Etching forms voids within the surface to of the substrate, which facilitates bonding with the deposited metal.
Referring now to
In one form, the first electrically conductive metal is copper, and the second electrically conductive metal is nickel, though the present disclosure should be interpreted to include other metals that allow for further processing/plating according to the teaching of the present disclosure. By way of nonlimiting example, other metals include copper, copper alloys, nickel, and nickel alloys, among others. Optionally, a third electrically conductive metal is electroplated onto the second electrically conductive metal layer to form a third electrically conductive metal layer. In this form, the third electrically conductive metal layer is chrome.
In one form of the present disclosure, voltage is conducted through auxiliary anodes disposed along a periphery of the substrate, which are not shown for purposes of clarity.
The plated parts disclosed herein may be used in various applications where it is desirable to have a more uniform, streamlined process to plate the parts with a metal layer without the need for an intermediary electroless plating step. Such parts may include, by way of example, grilles and trim parts in the automobile and motor vehicle industry but are not limited thereto.
Unless otherwise expressly indicated herein, all numerical values indicating mechanical/thermal properties, compositional percentages, dimensions and/or tolerances, or other characteristics are to be understood as modified by the word “about” or “approximately” in describing the scope of the present disclosure. This modification is desired for various reasons including industrial practice, material, manufacturing, and assembly tolerances, and testing capability.
As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A OR B OR C), using a non-exclusive logical OR, and should not be construed to mean “at least one of A, at least one of B, and at least one of C.”
The description of the disclosure is merely exemplary in nature and, thus, variations that do not depart from the substance of the disclosure are intended to be within the scope of the disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the disclosure.
