WO2022093182A1

WO2022093182A1 - Covers for electronic devices

Info

Publication number: WO2022093182A1
Application number: PCT/US2020/057487
Authority: WO
Inventors: Qingyong GUO; Ya Cheng Chuang; Kuan-Ting Wu
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2020-10-27
Filing date: 2020-10-27
Publication date: 2022-05-05

Abstract

The present disclosure is drawn to covers for electronic devices. In one example, a hybrid substrate can include a first portion including an aluminum alloy and a second portion including a magnesium alloy. A protective treatment layer can be on the hybrid substrate. A paint coating layer can be on the protective treatment layer. A milled edge can be along a corner of the aluminum alloy of the first portion of the hybrid substrate. The milled edge can cut through the protective treatment layer and the paint coating layer to create exposed portions of the aluminum alloy. An alkaline anodizing layer can be over the exposed portions of the aluminum alloy.

Description

COVERS FOR ELECTRONIC DEVICES BACKGROUND [0001] The use of personal electronic devices of all types continues to increase. Cellular phones, including smart phones, have become nearly ubiquitous. Tablet computers have also become widely used in recent years. Portable laptop computers continue to be used by many for personal, entertainment, and business purposes. For portable electronic devices in particular, much effort has been expended to make these devices more useful and more powerful while at the same time making the devices smaller, lighter, and more durable. The aesthetic design of personal electronic devices is also of concern in this competitive market. Devices such as mobile phones, tablets and portable computers are generally provided with a casing. The casing typically provides a number of functional features, e.g. protecting the device from damage. BRIEF DESCRIPTION OF THE DRAWING [0002] FIGS.1A-1B are cross-sectional views illustrating example covers for electronic devices in accordance with examples of the present disclosure; [0003] FIGS.2A-2B are cross-sectional views illustrating example covers for an electronic device with a milled edge in accordance with examples of the present disclosure; [0004] FIG.3 is a top down view and a partial cross-sectional view taken at 90 degrees of an example cover for an electronic device in accordance with the present disclosure; [0005] FIG.4 is a cross-sectional view of another example electronic device in accordance with the present disclosure; [0006] FIG.5 is a flowchart illustrating an example method of making a cover for an electronic device in accordance with the present disclosure; and [0007] FIGS.6A-6F are cross-sectional views depicting an example method of making a cover for an electronic device in accordance with the present disclosure. DETAILED DESCRIPTION [0008] The present disclosure describes covers for electronic devices. In one example, the cover includes a hybrid substrate including a first portion including an aluminum alloy and a second portion including a magnesium alloy. The cover includes a protective treatment layer on the hybrid substrate. The cover includes a paint coating layer on the protective treatment layer. The cover includes a milled edge along a corner of the aluminum alloy of the first portion of the hybrid substrate, wherein the milled edge cuts through the protectixx treatment layer and the paint coating layer to create exposed portions of the aluminum alloy. The cover includes an alkaline anodizing layer over the exposed portions of the aluminum alloy. The protective treatment layer can be a micro-arc oxidation layer or a passivation layer. The milled edge can be a chamfered edge formed by computer numeric control, diamond cutting, or laser engraving. The alkaline anodizing layer can be formed using about 3 wt% to about 10 wt% of borax and about 2 wt% to about 8 wt% of sodium silicate, potassium silicate, sodium hydroxide, potassium hydroxide, sodium carbonate, and a complexing agent. The cover can further include a sealing layer over the alkaline anodizing layer, wherein the sealing layer includes aluminum fluoride, nickel fluoride, cerium fluoride, cerium acetate, chromium(III) hydroxide, aluminum acetate, and/or nickel acetate. The alkaline anodizing layer can include a dye material, and the dye material can be methylene blue, basic fuchsin, crystal violet, eosin, acid fuchsin, congo red, gentian violet, methyl violet, brilliant crystal glue, romanowsky dye, anthraquinone dyes, acridine orange, quinone-imine dyes, xanthene dyes, 2-amino-4-(azoyl)-azo-thiazole, or a combination thereof. The magnesium alloy can be more than about 50 wt% elemental magnesium and is alloyed with aluminum, lithium, zinc, titanium, niobium, stainless, copper, or an alloy thereof; and the aluminum alloy can be more than about 50 wt% elemental aluminum and is alloyed with magnesium, lithium, zinc, titanium, niobium, stainless, copper, an alloy thereof. The aluminum alloy can be about 10 wt% to about 45 wt% of the hybrid substrate and the magnesium alloy can be about 55 wt% to about 90 wt% of the hybrid substrate. The magnesium alloy can be forged or thixo-molded and the aluminum alloy can be welded to the magnesium alloy; or the magnesium alloy can be insert molded on the aluminum alloy using thixo-molding. The paint coating layer can include a primer coat, a base coat, a top coat, or an anti-fingerprint coat, or a combination thereof. [0009] In another example, an electronic device includes an electronic component. The electronic device further includes a cover enclosing a portion or all of the electronic component. The cover includes a hybrid substrate including a first portion including an aluminum alloy and a second portion including a magnesium alloy. The cover includes a protective treatment layer on the hybrid substrate. The cover includes a paint coating layer on the protective treatment layer. The cover includes a milled edge along a corner of the aluminum alloy of the first portion of the hybrid substrate, wherein the milled edge cuts through the protective treatment layer and the paint coating layer to create exposed portions of the aluminum alloy. The cover includes an alkaline anodizing layer over the exposed portions of the aluminum alloy. The protective treatment layer can be a micro-arc oxidation layer or a passivation layer. The electronic device can be a laptop, a desktop computer, a keyboard, a mouse, a smart phone, a tablet, a monitor, a television, a speaker, a game console, a video player, an audio player, or a combination thereof, and the milled edge can be located at an edge of a touchpad, an edge of a fingerprint scanner, an edge of surrounding housing, or an edge of a logo. [0010] In another example, a method of making a cover for an electronic device includes, for example, forming an enclosure with a hybrid substrate including a first portion including an aluminum alloy and a second portion including a magnesium alloy. The method further includes applying a protective treatment layer on a surface of the hybrid substrate that covers a portion or all of the aluminum alloy and a portion or all of the magnesium alloy. The method further includes applying a paint coating layer over the protective treatment layer. The method further includes milling an edge along a corner of the aluminum alloy of the hybrid substrate, wherein the milling cuts through the protective treatment layer and the paint coating layer to create exposed portions of the aluminum alloy. The method further includes applying an alkaline anodizing layer over the exposed portions of the aluminum alloy. The method can further include forming the enclosure by forging or thixo-molding the magnesium alloy and welding the aluminum alloy to the magnesium alloy; or insert molding the magnesium alloy on the aluminum alloy using thixo-molding. [0011] It is noted that when discussing the cover, the electronic device, or the method of manufacturing the cover, such discussions of one example are to be considered applicable to the other examples, whether or not they are explicitly discussed in the context of that example. Thus, in discussing a metal alloy in the context of the cover, such disclosure is also relevant to and directly supported in the context of the electronic device, the method of making a cover for an electronic device, and vice versa. Covers for Electronic Devices [0012] The present disclosure describes covers or enclosures for electronic devices that can be formed from a hybrid substrate with an alkaline anodizing process. The hybrid substrate can have a first portion including an aluminum alloy and a second portion joined to the first portion and including a magnesium alloy. The aluminum alloy and magnesium alloy can be joined using welding or can be insert molded using thixo-molding. A protective treatment layer can be formed over the hybrid substrate. A corner of the aluminum alloy can be milled along an edge to form a chamfer that cuts through the protective treatment layer to expose the aluminum alloy. An alkaline anodizing layer can be deposited over the exposed portions of the aluminum alloy. The resulting cover or enclosure can be light weight, durable, and have an anodized high glossy finish over the aluminum alloy portions that were exposed at the chamfer. Such a high glossy finish can be difficult to achieve over a hybrid substrate in an acidic anodizing chemical bath since magnesium alloy may be unable to tolerate the acidic anodizing bath and may become corroded and develop oxidation. The present technology can protect the magnesium alloy using the protective treatment layer and the paint coating layer prior to the alkaline anodizing process. [0013] Therefore, the present technology can result in a cover for an electronic device with a surface finish that is lower in cost compared to processes using electrophoretic deposition that may use paint masking at the inner side of the enclosure. Furthermore, using a hybrid substrate with both a magnesium alloy portion and an aluminum alloy portion provides a solution that is lighter in weight compared to a solution that employs an aluminum alloy substrate without a magnesium alloy portion. The aluminum alloy portion of the hybrid substrate also can provide more mechanical strength compared to a substrate that employs a magnesium alloy without an aluminum alloy. [0014] FIG.1A shows an example cover 100 for an electronic device. The cover 100 includes a hybrid substrate including a first portion 110 and a second portion 120. The first portion can include a magnesium alloy. The magnesium alloy can include any number or combinations of aluminum, lithium, zinc, titanium, niobium, stainless, copper, or alloys thereof. In one example, the magnesium alloy of the first portion in this example includes more than about 50 wt% magnesium. In one example, the first portion includes a minimum of about 55 wt% of magnesium. [0015] The second portion 120 of the hybrid substrate can include an aluminum alloy. The aluminum alloy can include any number or combinations of magnesium, lithium, zinc, titanium, niobium, stainless, copper, or alloys thereof. In one example, the aluminum alloy of the second portion includes more than about 50 wt% aluminum. In one example, the second portion includes about 50 wt% to about 70 wt% of aluminum. In one example, the second portion includes about 30 wt% to about 50 wt% of magnesium. [0016] In one example, the hybrid substrate can include about 55 wt% to about 90 wt% of the first portion 110 (the magnesium alloy) and about 10 wt% to about 45 wt% of the second portion 120 (the aluminum alloy). It is appreciated that the hybrid substrate can include more than two portions or regions including magnesium alloy and aluminum alloy. For example, corners or edges of the hybrid substrate can include aluminum alloy including openings such as openings in the cover for a track pad or a fingerprint scanner. Thus, the individual corners or edges of the hybrid substrate can include a portion or region of the aluminum alloy while portions between the corners and edges can include the magnesium alloy. The portions of the hybrid substrate that include the aluminum alloy can provide additional strength to the resulting cover as compared to a cover including a substrate of only a magnesium alloy. The hybrid substrate can be described as a light metal substrate. For example, light metals can include magnesium, aluminum, lithium, zinc, titanium, niobium, stainless, copper, or an alloy thereof. The hybrid substrate can have a thickness of about 0.3 mm to about 2.0 mm. [0017] The hybrid substrate can be formed by joining the first portion 110 to the second portion 120. For example, the aluminum alloy of the second portion can be shaped using a process such as computer numeric control (CNC). The aluminum alloy can then be welded to the magnesium alloy of the first portion. The magnesium alloy can be shaped using techniques such as forging or thixo-molding. In another example, the magnesium alloy of the first portion is insert molded onto a shaped aluminum alloy of the second portion. The insert molding can be accomplished using thixo-molding. Once the second portion and the first portion are joined together, the joined first and second portion can be shaped using CNC and then polished to form the hybrid substrate. [0018] The aluminum alloy portion may be sandblasted before being joined to the magnesium alloy portion using insert molding. After the aluminum alloy portion is joined to the magnesium alloy to form the hybrid substrate, the hybrid substrate may be further shaped using a technique such as CNC. In one example, the surfaces of the hybrid substrate can be polished prior to depositing the protective treatment layer. [0019] A protective treatment layer 130 can be deposited on a surface of the hybrid substrate. For example, the protective treatment can be formed using micro-arc oxidation (MAO) or passivation. The protective treatment layer can have a thickness of about 3 μm to about 15 μm. The protective treatment layer can protect the surfaces of the hybrid substrate from corrosion or oxidation. The protective treatment layer can also protect surfaces of the magnesium alloy portion during an alkaline anodizing process. [0020] A paint coating layer 140 can be deposited over the protective treatment layer 130. The paint coating layer can further protect the hybrid substrate and can provide a color. The paint coating layer can include multiple layers. For example, the paint coating layer can include a primer layer or coat, a base layer or coat, a top layer or coat, and/or an anti-fingerprint layer or coat, or any combination thereof. The primer coat can include epoxy, epoxy-polyester, polyester, polyurethane, polyurethane copolymer, or a combination thereof. The primer coat can be about 5 to about 20 micrometers thick. The primer coat can be cured at about 60 to about 80 degrees Celsius for about 15 to about 40 minutes. The base coat can include polyester, polyacrylic, polyurethane, polyurethane copolymer or a combination thereof. The base coat can have pigments including carbon black, titanium dioxide, clay, mica, talc, barium sulfate, calcium carbonate, synthetic pigment, metallic powder, aluminum oxide, an organic powder, an inorganic powder, plastic bead, color pigments, dyes, or a combination thereof. The base coat can be about 10 to about 20 micrometers thick. The base coat can be cured at about 60 to about 80 degrees Celsius for about 15 to about 40 minutes. In one example, the top coat can include polyester, acrylic, polyurethane, polyurethane copolymer, or a combination thereof. In such an example, the top coat can be cured at a temperature of about 60 to about 80 degrees Celsius for about 15 to about 40 minutes. In another example, the top coat can be an ultraviolet coat that can include polyacrylic, polyurethane, urethane acrylates, acrylic acrylates, epoxy acrylates, or a combination thereof. The ultraviolet coat can have a thickness of about 10 to about 25 micrometers. The ultraviolet coat can be cured at a temperature of about 50 to about 60 degrees Celsius for about 10 to about 15 minutes followed by ultraviolet exposure at about 700 to about 1,200 mJ/cm² for about 10 to about 30 seconds. [0021] FIG.1B shows an example cover 170 for an electronic device. The cover depicts the hybrid substrate including the first portion 110 and the second portion 120 that have two opposing surfaces covered by the protective treatment layers 130 and 150 and the paint coating layers 140 and 160. The protective treatment layers can be deposited at the same time as one another. The paint coating layers can be deposited at the same time as one another. [0022] FIG.2A shows an example cover 200 for an electronic device with a hybrid substrate including a first portion 210 and a second portion 220. The first portion can include a magnesium alloy and the second portion can include an aluminum alloy. The second portion is depicted as being a corner section of the hybrid substrate and the cover. For example, the depicted cross section of the second portion is depicted as an L shape. The first or second portion can also be formed into other shapes. The cover is depicted with a protective treatment layer 230 over surfaces of the hybrid substrate. For example, the protective treatment layer covers a first surface 215 of the first portion and a second surface 235 facing in an opposite direction of the first surface. The protective treatment layer also is depicted as covering a third surface 225, a fourth surface 245, and a fifth surface 255 of the second portion. The protective treatment layer is depicted as covering the surfaces of the L shape of the second portion. The protective treatment layer can be formed using MAO or passivation. A paint coating layer 240 is depicted as covering the protective treatment layer. The paint coating layer can be formed of multiple layers. [0023] The cover 200 is depicted with a chamfer 260. The chamfer can be described as a milled edge along a corner of the L shaped second portion 220. After the protective treatment layer 230, the paint coating layer 240, and the alkaline anodizing layer 250 are deposited, the chamfer or milled edge cuts through the passivation layer 230 and the paint coating layer 240 to expose a surface 260 of the second portion or aluminum alloy. The chamfer may not cut through the first portion 210 or magnesium alloy. The chamfer may cut off a corner of the L shaped second portion. The exposed aluminum alloy of the second portion formed by the chamfer may not be treated or coated. The chamfer may be formed using diamond cutting. The diamond cutting may be controlled via CNC. In one example, second portion or aluminum alloy is milled or otherwise altered to remove material along about a 90 degree angled edge of the second portion. The exposed surface of the second portion may be formed at an angle to the third surface 225. The angle may be about 45 degrees. The angle may be in a range of about 45 to about 125 degrees. It should be appreciated that any surface, edge, or corner can be cut away from the second portion of the hybrid substrate at any angle. Depending on the shape and design of a cover for an electronic device, the cover may have many different edges. Any of these edges can be shaped or chamfered depending on the desired final appearance of the cover. The resulting chamfered or milled edges of the present technology may expose shiny surfaces of the aluminum alloy of the second portion. [0024] The surface 260 of the aluminum alloy of the second portion 220 exposed by the chamfer can be covered by an alkaline anodizing layer 250. The alkaline anodizing layer can also cover portions of the protective treatment layer 230. Portions of the the paint coating layer 240 exposed by the chamfer may or may not be covered by the alkaline anodizing layer. In one example, the alkaline anodizing layer can have a thickness of about 5 to about 15 microns. In one example, the alkaline anodizing layer can have a thickness of about 3 to about 6 microns. The alkaline anodizing layer can be formed using an alkaline anodizing process. The alkaline anodizing process can include multiple steps and techniques. It should be appreciated that the protective treatment may form an alkaline anodizing layer using all or some of the steps described herein for alkaline anodizing processes. An alkaline anodizing process can include steps of degreasing, washing, neutralizing, washing, alkaline anodizing, washing with an ultrasonic cleaner, dyeing, washing, sealing, washing, warm washing, and/or drying. [0025] The alkaline anodizing step of an alkaline anodizing process can include alkaline anodizing materials that can be composed of about 3 wt% to about 10 wt% of borax (sodium tetraborate), and about 2 wt% to about 8 wt % of sodium silicate, potassium silicate, sodium hydroxide, potassium hydroxide, and sodium carbonate, of a complexing agent. The alkaline anodizing material can have a pH of about 9 to about 13. The alkaline anodizing process can be at a temperature of about 15 to about 50 degrees Celsius (C). The alkaline anodizing process can be applied for a time of about 20 to about 50 minutes. The alkaline anodizing process can be applied at a voltage of about 100 to about 300 volts and a current of about 20 to about 40 amps with a frequency of about 30 to about 80 hertz. [0026] Degreasing can be accomplished using a degreasing process with a degreasing chemical. The degreasing chemical can have a pH control of about 9 to about 13 and can be controlled by sodium carbonate and NaOH. The degreasing chemical can have a surfactant that is about 0.3 wt% to about 1.5 wt% of the degreasing chemical. The surfactant can include sodium caseinate, sodium polyacrylate, sodium polyoxyethylene alkyl ether carboxylate, sodium lauryl sulphate, and/or sodium dodecyl sulfate. The degreasing process can be applied for a duration of time of about 30 to about 180 seconds. A bath temperature of the degreasing process can be about 25 to about 60 degrees C. [0027] Neutralization can be accomplished using a neutralization process with a neutralization chemical. The neutralization chemical can be composed of sulfuric acid, nitric acid, hydrophilic acid, and/or phosphate acid. The neutralization chemical can have a control pH of about 3 to about 5. The neutralization process can have a duration time of about 30 to about 120 seconds. The neutralization process can have a bath temperature of about 25 to about 60 degrees C. [0028] The alkaline anodizing step of the alkaline anodizing process can have a duration of time of about 20 to about 50 minutes. Washing steps of the alkaline anodizing process can have a duration of time of about 20 to about 90 seconds. An ultrasonic cleaning step of the alkaline anodizing process can have a duration of time of about 60 to about 180 seconds. A warm washing step of the alkaline anodizing process can have a duration of time of about 30 to about 60 seconds and can have a temperature of about 60 to about 80 degrees C. A drying step of the alkaline anodizing process can have a duration of time of about 10 to about 15 minutes and can have a temperature of about 70 to about 105 degrees C. [0029] A dyeing step of the alkaline anodizing process can be performed before a sealing layer is deposited. The dyeing step can be used to provide color to the alkaline anodizing layer 250. The dyeing step can include dye materials. The dye materials can be methylene blue, basic fuchsin, crystal violet, eosin, acid fuchsin, congo red, gentian violet, methyl violet, brilliant crystal glue, romanowsky dye, anthraquinone dyes, acridine orange, quinone-imine dyes, xanthene dyes, and/or 2-amino-4-(azoyl)-azo-thiazole. After the dyeing step is performed, an additional washing step can be performed before a sealing step is performed. [0030] FIG.2B shows an example cover 270 for an electronic device with a hybrid substrate including a first portion 210 and a second portion 220. The cover is depicted with a sealing layer 275 over the alkaline anodizing layer 250. The sealing layer can be deposited during the alkaline anodizing process described above. The sealing layer may be a treatment that includes a sealing chemical composition. The sealing chemical composition can include about 0.5 wt% to about 5.0 wt% of aluminum fluoride, nickel fluoride, cerium fluoride, cerium acetate, chromium(III) hydroxide, aluminum acetate, and/or nickel acetate. The sealing layer can be deposited at a temperature of about 25 to about 100 degrees C for a duration of time of about 15 to about 180 seconds. The sealing chemical composition can further include about 0.3 wt% to about 2 wt% of a surfactant in deionized water. In one example, the sealing process is performed at about 80 to about 90 degrees C for a duration of time of about 25 to about 30 minutes. [0031] FIG.3 shows another example cover 300 for an electronic device. This example is a top cover for the keyboard portion of a laptop (sometimes referred to as a “laptop cover C”). The cover includes key openings 360 for the keyboard buttons (not shown) to be positioned therethrough, hinge recesses 362 to receive a hinge (not shown), a track pad opening 364 to receive a track pad (not shown), and a fingerprint scanner opening 366 to receive a fingerprint scanner (not shown). These are merely examples of structures that may be present, and are illustrative of many of a number of other structural components used with this type of top cover. The cover can be mostly made up of a hybrid substrate with a first portion 310 including a magnesium alloy and a second portion 320 including an aluminum alloy. Surfaces of the first and second portion of the hybrid substrate can be covered with a protective treatment layer 330. The protective treatment layer can be covered with a paint coating layer 340. The paint coating layer may include a plurality of paint coatings. A corner of the second portion can be milled along an edge to create a chamfer or milled edge that cuts away part of the second portion at an angle and exposes a surface of the second portion. In this example, milled edges or chamfers have been formed at three different locations: a track pad milled edge 333 surrounding the track pad opening 364, a fingerprint scanner milled edge 352 surrounding the fingerprint scanner opening 366 of a fingerprint scanner, and a rear milled edge 334 along the rear edge of the cover near the hinge. The individual milled edges expose a surface of the aluminum alloy of the hybrid substrate. The exposed surfaces of the aluminum alloy can be covered with an alkaline anodizing layer 350. [0032] To show the various materials in this example more clearly, a partial cross-sectional view is shown along plane “A” designated further by the dashed and dotted lines/arrows. This cross-sectional view shows the chamfer 324 which is bordering the track pad opening 364 and forms the track pad milled edge 333. The chamfer cuts through the protective treatment layer 330 and the paint coating layer 340 as depicted. As shown in the figure, in this example the milled edge includes a sloping face that slopes downward toward the track pad opening. When the cover is assembled with other components to make a complete laptop, this chamfered edge can provide a more comfortable edge around the track pad compared to a sharp 90° edge. Similarly, the milled edge around the fingerprint scanner can slope downward toward the fingerprint scanner in some examples. [0033] As used herein, “cover” refers to the exterior shell of an electronic device that includes or is in the form of an enclosure, and a portion thereof (or the structure thereof) includes a light metal substrate. In other words, the cover can be adapted to contain the internal electronic components of the electronic device. The cover can be an integral part of the electronic device. The term “cover” is not meant to refer to the type of removable protective cases that are often purchased separately for an electronic device (especially smart phones and tablets) and placed around the exterior of the electronic device. Covers as described herein can be used on a variety of electronic devices. For example, a laptop, a desktop, a keyboard, a mouse, a printer, a smart phone, a tablet, a monitor, a television, a speaker, a game console, a video player, an audio player, or a combination thereof. In various examples, the hybrid substrate for these covers can be formed by molding, casting, machining, bending, working, stamping, CNC, forging, or another process. In one example, the cover can be made from multiple panels as depicted in FIG.4. For example, laptop covers sometimes include four separate cover pieces forming the complete cover of the laptop. The four separate pieces of the laptop cover are often designated as cover A (back cover of the monitor portion of the laptop), cover B (front cover of the monitor portion), cover C (top cover of the keyboard portion) and cover D (bottom cover of the keyboard portion). Covers can also be made for smart phones and tablet computers with a single metal piece or multiple metal panels. [0034] As used herein, a layer that is referred to as being “on” a lower layer can be directly applied to the lower layer, or an intervening layer or multiple intervening layers can be located between the layer and the lower layer. Generally, the covers described herein can include a hybrid substrate including a magnesium alloy portion and an aluminum alloy portion and are coated with a protective treatment layer and a sealing layer. Accordingly, a layer that is “on” a lower layer can be located further from the hybrid substrate. Furthermore, the paint coating itself may include multiple layers, such as a base layer, a topcoat layer, and any other intervening layers. A “higher” layer applied “on” a “lower” layer may be located farther from the hybrid substrate and closer to a viewer viewing the cover from the outside. [0035] It is noted that when discussing covers for electronic devices, the electronic devices themselves, or methods of making covers for electronic devices, such discussions can be considered applicable to one another whether or not they are explicitly discussed in the context of that example. Thus, for example, when discussing the metals used in the hybrid substrate in the context of one of the example covers, such disclosure is also relevant to and directly supported in the context of the electronic devices and/or methods, and vice versa. It is also understood that terms used herein will take on their ordinary meaning in the relevant technical field unless specified otherwise. In some instances, there are terms defined more specifically throughout or included at the end of the present disclosure, and thus, these terms are supplemented as having a meaning described herein. Electronic Devices [0036] A variety of electronic devices can be made with the covers described herein. In various examples, such electronic devices can include various electronic components enclosed by the cover. As used herein, “encloses” or “enclosed” when used with respect to the covers enclosing electronic components can include covers completely enclosing the electronic components or partially enclosing the electronic components. Many electronic devices include openings for charging ports, input/output ports, headphone ports, and so on. Accordingly, in some examples the cover can include openings for these purposes. Certain electronic components may be designed to be exposed through an opening in the cover, such as display screens, keyboard keys, buttons, track pads, fingerprint scanners, cameras, and so on. Accordingly, the covers described herein can include openings for these components. Other electronic components may be designed to be completely enclosed, such as motherboards, batteries, sim cards, wireless transceivers, memory storage drives, and so on. Additionally, in some examples a cover can be made up of two or more cover sections, and the cover sections can be assembled together with the electronic components to enclose the electronic components. As used herein, the term “cover” can refer to an individual cover section or panel, or collectively to the cover sections or panels that can be assembled together with electronic components to make the complete electronic device. [0037] FIG.4 shows a cross-sectional schematic view of an example electronic device 400 in accordance with examples of the present disclosure. This example includes a top cover 402 and a bottom cover 404 enclosing an electronic component 490. The top cover includes a hybrid substrate that includes a first portion 410 including a magnesium alloy that is joined to a second portion 420 and a third portion 430 including an aluminum alloy. The second and third portions are depicted as forming corner or L shaped pieces of the hybrid substrate. Similarly, the bottom cover 404 includes a hybrid substrate that has a first portion 415 including magnesium alloy as well as a second portion 425 and a third portion 435 including an aluminum alloy. The hybrid substrates of the top and bottom covers are covered with a protective treatment layer 440. The protective treatment layer is covered with a paint coating layer 450. The second portion 420 and the third portion 430 are milled along an edge to form chamfer 470 and chamfer 480 to expose a surface of the aluminum alloy of the first and third portions. The chamfers also cut through portions of the protective treatment layer and the paint coating layer. The exposed surfaces of the aluminum alloy can be covered with alkaline anodizing layers 472 and 482. [0038] In further examples, the electronic device can be a laptop, a desktop, a keyboard, a mouse, a printer, a smart phone, a tablet, a monitor, a television, a speaker, a game console, a video player, an audio player, or a variety of other types of electronic devices. In certain examples, the chamfered edge or edges can be located in decorative locations on the cover. Some examples include chamfered edges around track pads, around fingerprint scanners, around an edge of a logo, and so on. In further detail, there may be outer periphery locations of the hybrid substrate that can be similarly chamfered. Methods of Making Covers for Electronic Devices [0039] In some examples, the covers described herein can be made from an aluminum alloy portion. This can be accomplished using a variety of processes, including CNC milled, molding, insert molding, forging, casting, machining, stamping, bending, working, and so on. The aluminum alloy portion is then joined to a magnesium alloy portion to form a hybrid substrate for the cover. It should be appreciated that a cover or a panel for a cover may include a plurality of aluminum alloy portions and a plurality of magnesium alloy portions meaning that the hybrid substrate could have more than one portion including aluminum alloy and more than one portion including magnesium alloy. In one example, the aluminum alloy portion is joined to the magnesium alloy portion by welding the aluminum alloy portion onto an extrusion of magnesium alloy. In such an example, the hybrid substrate can then be further shaped using CNC milling. The hybrid substrate can then be polished. [0040] In another example, the aluminum alloy portion is first formed using CNC milling and then sandblasted. The magnesium alloy portion is insert molded onto the aluminum alloy portion using thixo-molding to form the hybrid substrate. Prior to the insert molding, the aluminum alloy portion can be shaped using the CNC milling to form an interlock structure used for the insert molding process. After the aluminum alloy portions and the magnesium alloy portions have been joined to form the hybrid substrate, the hybrid substrate can be CNC milled to further shape the hybrid substrate. [0041] After using either technique for forming the hybrid substrate, a protective treatment layer can be deposited using MOA or passivation treatments. A paint coating layer can then be deposited over the protective treatment layer. The paint coating layer can be composed of multiple paint layers. A chamfer can then be formed by milling along an edge of a corner of the aluminum alloy portion of the hybrid substrate to expose a surface of the aluminum alloy. The chamfer can be formed using diamond cutting. The exposed surface of the aluminum alloy may then be covered by an alkaline anodizing layer. The alkaline anodizing layer can be dyed and can be covered by a sealing layer. [0042] FIG.5 is a flowchart illustrating an example method 500 of making a cover for an electronic device. The method includes forming 510 an enclosure with a hybrid substrate including a first portion including an aluminum alloy and a second portion including a magnesium alloy. The method further includes applying 520 a protective treatment layer on a surface of the hybrid substrate that covers a portion or all of the aluminum alloy and a portion or all of the magnesium alloy. The method further includes applying 530 a paint coating layer over the protective treatment layer. The method further includes milling 540 an edge along a corner of the aluminum alloy of the hybrid substrate, wherein the milling cuts through the protective treatment layer and the paint coating layer to create exposed portions of the aluminum alloy. The method further includes applying 550 an alkaline anodizing layer over the exposed portions of the aluminum alloy. The method can further include forming the enclosure by forging or thixo-molding the magnesium alloy and welding the aluminum alloy to the magnesium alloy; or insert molding the magnesium alloy on the aluminum alloy using thixo-molding. [0043] FIGS.6A-6F show cross-sectional views illustrating another example method of making a cover for an electronic device. In FIG.6A, a first portion 610 can include magnesium alloy. The first portion can be formed using forging or insert molding such as thixo-molding. In FIG.6B, the first portion 610 is joined to a second portion 620 and a third portion 630. The second and third portions can include aluminum alloy and can be formed using CNC milling. The first portion can be joined to the second porting using welding or the first portion can be insert molded onto the second and third portion. The first, second and third portions form a hybrid substrate for the electronic device. In FIG.6C, the hybrid substrate is coated or covered with a protective treatment layer 640. The protective treatment layer can coat all exposed surfaces of the hybrid substrate. The protective treatment layer can be formed using micro-arc oxidation or passivation. In FIG.6D, the chromium passivation layer is coated with a paint coating layer 650. The coating layer can cover the portion of the protective treatment layer that is to be the outer surface of the electronic device and may not coat the protective treatment layer that is to be the inner surface of the electronic device. The coating layer can include multiple layers such as a primer coat, a base coat, a top coat, and/or an anti-fingerprinting coat. In FIG.6E, a corner of the second portion is milled along an edge to form a chamfer 670 that exposes a surface of the second portion. A corner of the third portion is milled along an edge to form a chamfer 680 that exposes a surface of the third portion. The chamfers also cut through the protective treatment layer and the paint coating layer. In FIG. 6F, the chamfers are covered with alkaline anodizing layers 675 and 685. The alkaline anodizing layers can be dyed and can be covered with a sealing layer. Light Metal Substrates for Electronic Device Covers [0044] In one example, the hybrid substrate can be composed of a light metal substrate. The light metal substrate can be made from a single metal, a metallic alloy, a combination of sections made from multiple metals, or a combination of metal and other materials. In certain examples, the light metal substrate can include aluminum, magnesium, lithium, niobium, titanium, zinc, or an alloy thereof. In further particular examples, the light metal substrate can include aluminum, an aluminum alloy, magnesium, or a magnesium alloy. Non-limiting examples of elements that can be included in aluminum or magnesium alloys can include aluminum, magnesium, titanium, lithium, niobium, zinc, bismuth, copper, cadmium, iron, thorium, strontium, zirconium, manganese, nickel, lead, silver, chromium, silicon, tin, gadolinium, yttrium, calcium, antimony, cerium, lanthanum, or others. [0045] In some examples, the light metal substrate can include an aluminum magnesium alloy made up of about 0.5% to about 13% magnesium by weight and 87% to 99.5% aluminum by weight. Examples of specific aluminum magnesium alloys can include 1050, 1060, 1199, 2014, 2024, 2219, 3004, 4041, 5005, 5010, 5019, 5024, 5026, 5050, 5052, 5056, 5059, 5083, 5086, 5154, 5182, 5252, 5254, 5356, 5454, 5456, 5457, 5557, 5652, 5657, 5754, 6005, 6005A, 6060, 6061, 6063, 6066, 6070, 6082, 6105, 6162, 6262 ,6351, 6463, 7005, 7022, 7068, 7072, 7075 ,7079, 7116, 7129, and 7178. [0046] In further examples, the light metal substrate can include magnesium metal, a magnesium alloy that is 99% or more magnesium by weight, or a magnesium alloy that is from about 50% to about 99% magnesium by weight. In a particular example, the light metal substrate can include an alloy including magnesium and aluminum. Examples of magnesium-aluminum alloys can include alloys made up of from about 91% to about 99% magnesium by weight and from about 1% to about 9% aluminum by weight, and alloys made up of from about 0.5% to about 13% magnesium by weight and from about 87% to about 99.5% aluminum by weight. Specific examples of magnesium-aluminum alloys can include AZ63, AZ81, AZ91, AM50, AM60, AZ31, AZ61, AZ80, AE44, AJ62A, ALZ391, AMCa602, LZ91, and Magnox. [0047] The light metal substrate can be shaped to fit any type of electronic device, including the specific types of electronic devices described herein. In some examples, the light metal substrate can have any thickness suitable for a particular type of electronic device. The thickness of the metal in the light metal substrate can be selected to provide a desired level of strength and weight for the cover of the electronic device. In some examples, the light metal substrate can have a thickness from about 0.5 mm to about 2 cm, from about 1 mm to about 1.5 cm, from about 1.5 mm to about 1.5 cm, from about 2 mm to about 1 cm, from about 3 mm to about 1 cm, from about 4 mm to about 1 cm, or from about 1 mm to about 5 mm, though thicknesses outside of these ranges can be used. Micro-Arc Oxidation Coatings for Electronic Device Covers [0048] In one example, the protective treatment layer can be applied to the hybrid substrate and can be a micro-arc oxidation layer on a surface thereof. Micro-arc oxidation, also known as plasma electrolytic oxidation, is an electrochemical process where the surface of a metal is oxidized using micro-discharges of compounds on the surface of the substrate when immersed in a chemical or electrolytic bath, for example. The electrolytic bath may include predominantly water with about 1 wt% to about 5 wt% electrolytic compound(s), e.g., alkali metal silicates, alkali metal hydroxide, alkali metal fluorides, alkali metal phosphates, alkali metal aluminates, the like, or a combination thereof. The electrolytic compounds may likewise be included at from about 1.5 wt% to about 3.5 wt%, or from about 2 wt% to about 3 wt%, though these ranges are not considered limiting. In one example, a high-voltage alternating current can be applied to the substrate to create plasma on the surface of the substrate. In this process, the substrate can act as one electrode immersed in the electrolyte solution, and the counter electrode can be any other electrode that is also in contact with the electrolyte. In some examples, the counter electrode can be an inert metal such as stainless steel. In certain examples, the bath holding the electrolyte solution can be conductive and the bath itself can be used as the counter electrode. A high direct current or alternating voltage can be applied to the substrate and the counter electrode. In some examples, the voltage can be about 200 V or higher, such as about 200 V to about 600 V, about 250 V to about 600 V, about 250 V to about 500 V, or about 200 V to about 300 V. Temperatures can be from about 20 ºC to about 40 ºC, or from about 25 ºC to about 35 ºC, for example, though temperatures outside of these ranges can be used. This process can oxidize the surface to form an oxide layer from the substrate material. Various metal or metal alloy substrates can be used, including aluminum, titanium, lithium, magnesium, and/or alloys thereof, for example. The oxidation can extend below the surface to form thick layers, as thick as 30 μm or more. In some examples the oxide layer can have a thickness from about 1 μm to about 25 μm, from about 1 μm to about 22 μm, or from about 2 μm to about 20 μm. Thickness can likewise be from about 2 μm to about 15 μm, from about 3 μm to about 10 μm, or from about 4 μm to about 7 μm. The oxide layer can, in some instances, enhance the mechanical, wear, thermal, dielectric, and corrosion properties of the substrate. The electrolyte solution can include a variety of electrolytes, such as a solution of potassium hydroxide. In some examples, the substrate can include a micro-arc oxidation layer on one side, or on both sides. Passivation Coatings for Electronic Device Covers [0049] In one example, a protective treatment layer is a passivation layer that is an opaque passivation layer. The passivation layer may refer to a layer or coating over the hybrid substrate. Passivation may refer to the use of a light coat of a protective material, such as metal oxide, to create a shell against corrosion. Chemicals may be applied to the surface of the light metal substrate to induce the passivation layer. For example, the chemicals may include a salt of molybdate, vanadate, phosphate, chromate, stannate, manganese, or a combination thereof. The passivation layer may have a thickness of about 1 μm to about 5 μm. Paint Coatings [0050] The paint coating layer may include a transparent primer coating as well as other paint coatings. The paint coatings may include one, two, three or four layers or any other number of layers. The paint coating may include a primer coat, a base coat, and/or a top coat. The paint coating may be applied using any number of techniques including spray painting or inkjet painting. The paint may include a variety of materials. In one example, a primer coat can include a polyester, epoxy, epoxy-polyester, epoxy-polyamide, a polyurethane, or a copolymer thereof. In one example, a base coat can include a polyester, a polyurethane, polyacrylic, polyester-imide, and epoxy-polyamide, or a copolymer thereof. In one example, a top coat can include a polyurethane, a polyacrylic or polyacrylate, a urethane, an epoxy, or a copolymer thereof. The paint coatings can be any number of colors and can be transparent, semi-transparent, or opaque. Definitions [0051] It is noted that, as used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the content clearly dictates otherwise. [0052] The term "about" as used herein, when referring to a numerical value or range, allows for a degree of variability in the value or range, for example, within 5% or other reasonable added range breadth of a stated value or of a stated limit of a range. The term “about” when modifying a numerical range is also understood to include the exact numerical value indicated, e.g., the range of about 1 wt% to about 5 wt% includes 1 wt% to 5 wt% as an explicitly supported sub-range. [0053] As used herein, “colorant” can include dyes and/or pigments. [0054] As used herein, “dye” refers to compounds or molecules that absorb electromagnetic radiation or certain wavelengths thereof. Dyes can impart a visible color to an ink if the dyes absorb wavelengths in the visible spectrum. [0055] As used herein, “pigment” generally includes pigment colorants, magnetic particles, aluminas, silicas, and/or other ceramics, organo-metallics or other opaque particles, whether or not such particulates impart color. Thus, though the present description primarily exemplifies the use of pigment colorants, the term “pigment” can be used more generally to describe pigment colorants and other pigments such as organometallics, ferrites, ceramics, etc. In one specific example, however, the pigment is a pigment colorant. [0056] As used herein, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a common list for convenience. However, these lists should be construed as though the individual members of the list are individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. [0057] Concentrations, dimensions, amounts, and other numerical data may be presented herein in a range format. It is to be understood that such range format is used merely for convenience and brevity and should be interpreted flexibly to include the numerical values explicitly recited as the limits of the range, and also to include all the individual numerical values or sub-ranges encompassed within that range as if individual numerical values and sub-ranges are explicitly recited. For example, a layer thickness from about 0.1 μm to about 0.5 μm should be interpreted to include the explicitly recited limits of 0.1 μm to 0.5 μm, and to include thicknesses such as about 0.1 μm and about 0.5 μm, as well as subranges such as about 0.2 μm to about 0.4 μm, about 0.2 μm to about 0.5 μm, about 0.1 μm to about 0.4 μm etc. PROPHETIC EXAMPLES [0058] The following illustrates examples of the present disclosure. However, it is to be understood that the following are illustrative of the application of the principles of the present disclosure. Numerous modifications and alternative compositions, methods, and systems may be devised without departing from the present disclosure. The appended claims are intended to cover such modifications and arrangements. Example 1 [0059] A laptop cover for an electronic device is made using Computer Numerical Control (CNC) milling of an aluminum alloy portion for the corner regions of a laptop cover, including all corners of openings in the laptop cover. In this example, the aluminum alloy includes from about 50 wt% to about 70 wt% aluminum. The magnesium alloy portion is prepared by forging, and the magnesium alloy includes more than about 55 wt%. The aluminum alloy portions are welded to the magnesium alloy portions to form a hybrid substrate. The hybrid substrate includes from about 10 wt% to about 45 wt% of the aluminum alloy and from about 55 wt% to about 90 wt% of the magnesium alloy. CNC milling is then used to shape the hybrid substrate for the laptop cover including forming a “C” shape and/or a keyboard surface with openings therein for keys, a track pad, a fingerprint pad, etc. The hybrid substrate can then be polished. The exposed surfaces of the hybrid substrate are then coated with a protective treatment layer formed using micro-arc oxidation. A primer coat is deposited over surfaces of the protective treatment layer that are to make up the outer surfaces of the laptop cover. The primer coat is cured at from about 60° C to about 80° C for about 30 minutes to about 60 minutes, followed by a base coat over the primer coat, which is also cured at from about 60° C to about 80° C for about 30 minutes to about 60 minutes. A top coat is deposited over the base coat and cured at from about 50° C to about 60° C for about 10 minutes to about 30 minutes. The top coat is then subjected to ultraviolet exposure at 700 mJ/cm² to 1,200 mJ/cm² for 10 to 30 seconds. Corners of the aluminum alloy portions are then milled using diamond cutting controlled via CNC milling at an angle along an edge to expose a surface of the aluminum alloy. The exposed surface of the aluminum alloy is then coated with an alkaline anodizing layer. The alkaline anodizing layer is formed using a concentration of about 3 wt% to about 10 wt% of borax (sodium tetraborate), and about 2 wt% to about 8 wt % of sodium silicate, potassium silicate, sodium hydroxide, potassium hydroxide, and sodium carbonate, of a complexing agent with a pH of about 9 to about 13. The alkaline anodizing layer is formed at a temperature of about 15 to about 50 degrees C. The alkaline anodizing layer is formed by applying electricity at a voltage of about 100 to about 300 volts with a current of about 20 to about 40 amps and with a frequency of about 30 to about 80 hertz for about 20 to about 50 minutes. Example 2 [0060] A laptop cover for an electronic device using a thixo-molding process is prepared the same as in Example 1, except that rather than forming the protective treatment layer using micro-arc oxidation, the protective treatment is formed using passivation. Example 3 [0061] A laptop cover for an electronic device using a thixo-molding process is prepared the same as in Example 1, except that rather than forging the magnesium alloy, the magnesium alloy portions for the laptop cover are joined with the aluminum alloy portions using thixo-molding to form the hybrid substrate. Example 4 [0062] A laptop cover as in Example 1 further including the alkaline anodizing layer being dyed using methylene blue, basic fuchsin, crystal violet, eosin, acid fuchsin, congo red, gentian violet, methyl violet, brilliant crystal glue, romanowsky dye, anthraquinone dyes, acridine orange, quinone-imine dyes, xanthene dyes, and/or 2-amino-4-(azoyl)-azo-thiazole. Example 5 [0063] A laptop cover as in Example 1 further including the alkaline anodizing layer being coated by a sealing layer formed with a sealing chemical composition that includes about 0.5 wt% to about 5.0 wt% of aluminum fluoride, nickel fluoride, cerium fluoride, cerium acetate, chromium(III) hydroxide, aluminum acetate, and/or nickel acetate. The sealing layer is deposited at a temperature of about 25 to about 100 degrees C for a duration of time of about 15 to about 180 seconds. The sealing chemical composition further includes about 0.3 wt% to about 2 wt% of a surfactant in deionized water.

Claims

CLAIMS What is claimed is: 1. A cover for an electronic device comprising: a hybrid substrate comprising a first portion including an aluminum alloy and a second portion including a magnesium alloy; a protective treatment layer on the hybrid substrate; a paint coating layer on the protective treatment layer; a milled edge along a corner of the aluminum alloy of the first portion of the hybrid substrate, wherein the milled edge cuts through the protective treatment layer and the paint coating layer to create exposed portions of the aluminum alloy; and an alkaline anodizing layer over the exposed portions of the aluminum alloy.

2. The cover of claim 1, wherein the protective treatment layer is a micro-arc oxidation layer or a passivation layer.

3. The cover of claim 1, wherein the milled edge is a chamfered edge formed by computer numeric control, diamond cutting, or laser engraving.

4. The cover of claim 1, wherein the alkaline anodizing layer is formed using about 3 wt% to about 10 wt% of borax and about 2 wt% to about 8 wt% of sodium silicate, potassium silicate, sodium hydroxide, potassium hydroxide, sodium carbonate, and a complexing agent.

5. The cover of claim 1, further comprising a sealing layer over the alkaline anodizing layer, wherein the sealing layer includes aluminum fluoride, nickel fluoride, cerium fluoride, cerium acetate, chromium(III) hydroxide, aluminum acetate, and/or nickel acetate.

6. The cover of claim 1, wherein the alkaline anodizing layer includes a dye material, and wherein the dye material includes methylene blue, basic fuchsin, crystal violet, eosin, acid fuchsin, congo red, gentian violet, methyl violet, brilliant crystal glue, romanowsky dye, anthraquinone dyes, acridine orange, quinone-imine dyes, xanthene dyes, 2-amino-4-(azoyl)-azo-thiazole, or a combination thereof.

7. The cover of claim 1, wherein the magnesium alloy includes more than about 50 wt% elemental magnesium and is alloyed with aluminum, lithium, zinc, titanium, niobium, stainless, copper, or an alloy thereof; and the aluminum alloy includes more than about 50 wt% elemental aluminum and is alloyed with magnesium, lithium, zinc, titanium, niobium, stainless, copper, an alloy thereof.

8. The cover of claim 1, wherein the aluminum alloy forms about 10 wt% to about 45 wt% of the hybrid substrate and the magnesium alloy forms about 55 wt% to about 90 wt% of the hybrid substrate.

9. The cover of claim 1, wherein the magnesium alloy is forged or thixo-molded and wherein the aluminum alloy is welded to the magnesium alloy; or wherein the magnesium alloy is insert molded on the aluminum alloy using thixo-molding.

10. The cover of claim 1, wherein the paint coating layer can include a primer coat, a base paint coat, a top coat, or an anti-fingerprint coat, or a combination thereof.

11. An electronic device comprising: an electronic component; and a cover enclosing a portion or all of the electronic component, the cover comprising: a hybrid substrate comprising a first portion including an aluminum alloy and a second portion including a magnesium alloy; a protective treatment layer on the hybrid substrate; a paint coating layer on the protective treatment layer; a milled edge along a corner of the aluminum alloy of the first portion of the hybrid substrate, wherein the milled edge cuts through the protective treatment layer and the paint coating layer to create exposed portions of the aluminum alloy; and an alkaline anodizing layer over the exposed portions of the aluminum alloy.

12. The electronic device of claim 11, wherein the protective treatment layer is a micro-arc oxidation layer or a passivation layer.

13. The electronic device of claim 11, wherein the electronic device is a laptop, a desktop computer, a keyboard, a mouse, a smart phone, a tablet, a monitor, a television, a speaker, a game console, a video player, an audio player, or a combination thereof, and wherein the milled edge is located at an edge of a touchpad, an edge of a fingerprint scanner, an edge of surrounding housing, or an edge of a logo.

14. A method of making a cover for an electronic device comprising: forming an enclosure with a hybrid substrate comprising a first portion including an aluminum alloy and a second portion including a magnesium alloy; applying a protective treatment layer on a surface of the hybrid substrate that covers a portion or all of the aluminum alloy and a portion or all of the magnesium alloy; applying a paint coating layer over the protective treatment layer; milling an edge along a corner of the aluminum alloy of the hybrid substrate, wherein the milling cuts through the protective treatment layer and the paint coating layer to create exposed portions of the aluminum alloy; and applying an alkaline anodizing layer over the exposed portions of the aluminum alloy.

15. The method of claim 14, wherein forming the enclosure includes forging or thixo-molding the magnesium alloy and welding the aluminum alloy to the magnesium alloy; or insert molding the magnesium alloy on the aluminum alloy using thixo-molding.