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-1C are cross-sectional views illustrating example covers for electronic devices in accordance with examples of the present disclosure;

[0003] FIG. 2 is a cross-sectional view illustrating an alternative example cover 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, a cover for an electronic device includes a hybrid substrate comprising a first portion including an aluminum alloy and a second portion including a magnesium alloy. The cover also includes a chromium passivation layer on a surface of the hybrid substrate that covers at least a portion of the aluminum alloy and a portion of the magnesium alloy. The cover also includes a sealing layer on the passivation layer. The cover can further include a milled edge along a corner of the aluminum alloy, where the milled edge cuts through the chromium passivation layer and the sealing layer to expose the aluminum alloy. The chromium passivation layer can be formed using chromium(lll) potassium sulfate, fluorozirconium chromium(lll) potassium, sodium fluoride, chromium(lll) hydroxide, and nickel fluoride. The sealing layer can be formed using a chelating agent including ethylene diamine tetra acetic acid (EDTA), nitrilotriacetic acid, glutaric acid, and methyl-glycinediacetic acid in combination with sodium silicate. The magnesium alloy can include more than about 50 wt% magnesium and can be in combination with aluminum, lithium, zinc, titanium, niobium, stainless, copper or alloys thereof. The aluminum alloy can include more than about 50 wt% aluminum and can be in combination with magnesium, lithium, zinc, titanium, niobium, stainless, copper or alloys thereof. The aluminum alloy can 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. The aluminum alloy can be welded onto the magnesium alloy, and wherein the magnesium alloy can be forged or thixo-molded. The magnesium alloy can be insert molded on the aluminum alloy using thixo-molding. The cover can further include a coating layer over the sealing layer, the coating layer including a primer coat, a base paint 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 the electronic component. The cover includes a hybrid substrate comprising a first portion including an aluminum alloy and a second portion including a magnesium alloy. The cover further includes a chromium passivation layer on a surface of the hybrid substrate that covers at least a portion of the aluminum alloy and a portion of the magnesium alloy. The cover further includes a sealing layer on the passivation layer. The cover can further include a milled edge along a corner of the aluminum alloy, wherein the milled edge cuts through the chromium passivation layer and the sealing layer to expose the aluminum alloy. 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 wherein the milled edge can be located at an edge of a touchpad, an edge of a fingerprint scanner, 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 comprising a first portion including an aluminum alloy and a second portion including a magnesium alloy. The method further includes applying a chromium passivation layer on a surface of the hybrid substrate that covers at least a portion of the aluminum alloy and a portion of the magnesium alloy. The method further includes applying a sealing layer on the passivation layer. The method can further include milling an edge along a comer of the aluminum alloy, wherein the milled edge cuts through the chromium passivation layer and the sealing layer to expose the aluminum alloy. Forming the enclosure can include 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 anti-corrosion pretreatment 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 chromium passivation layer can be formed over the hybrid substrate and a sealing layer can be formed over the chromium passivation layer. A comer of the aluminum alloy can be milled to form a chamfer that cuts through the chromium passivation layer and the sealing layer to expose the aluminum alloy. The resulting cover or enclosure can be light weight, durable, and corrosion resistant. For example, in some examples, the resulting cover can pass a 48 hour salt fog test compared to traditional passivation treatment on a magnesium enclosure that cannot pass longer than a 12 hour test. An example of the present technology with a hybrid substrate can resolve high reactive metal surface issues that may be present with a substrate formed of a material such as magnesium alloy. For example, by offering dual surface finishing features (e.g. the hybrid substrate with a magnesium alloy and an aluminum alloy) the resulting cover or enclosure can have a metallic luster feeling on portable electronic devices. The hybrid substrate with the second portion including an aluminum alloy can also resolve issues of poor color stability and chemical resistance than may be found in a substrate of only a magnesium alloy.

[0013] 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.

[0014] 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.

[0015] 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, each corner or edge 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.

[0016] The hybrid substrate can be formed by joining the first portion 110 to the second portion 120. For example, the aluminum alloy forthe 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.

[0017] A chromium passivation layer 130 can be deposited on a surface of the hybrid substrate. For example, the chromium passivation layer can cover the surface 115 of the first portion 110 and a surface 125 of the second portion 120. The chromium passivation layer can include or be formed from passivation chemicals including chromium(lll) potassium sulfate, fluorozirconium chromium(lll) potassium, sodium fluoride, chromium(lll) hydroxide, and/or nickel fluoride. A passivation formula for the chromium passivation layer can include about 3 wt% to about 15 wt% of the passivation chemicals. The passivation chemicals can have a pH level of about 4 to about 6. The passivation formula can also include water. A thickness of the chromium passivation layer can be about 1 micrometer to about 5 micrometers. The chromium passivation layer can be deposited at a temperature of about 30 to about 40 degrees Celsius for about 3 to about 5 minutes.

[0018] A sealing layer 140 can be deposited on or over the chromium passivation layer 130. The sealing layer can include or be formed from sealing chemicals using a chelating agent including ethylene diamine tetra acetic acid (EDTA), nitrilotriacetic acid, glutaric acid, and/or methyl-glycinediacetic acid in combination with sodium silicate. A passivation formula for the sealing layer can include about 3 wt% to about 10 wt% of the sealing chemicals. The sealing chemicals can have a pH level of about 9 to about 11 . The sealing formula can also include water. A thickness of the sealing layer can be about 0.5 micrometers to about 3 micrometers. The sealing layer can be deposited at a temperature of about 80 to about 90 degrees Celsius for about 5 to about 10 minutes. After the chromium passivation layer and the sealing layer have been cured, the hybrid substrate with the chromium passivation layer and the sealing layer can be baked or cured at a temperature of about 60 to about 120 degrees Celsius for about 10 to about 30 minutes. [0019] FIG. 1 B 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 chromium passivation layers 130 and 150 and the sealing layers 140 and 160. The chromium passivation layers can be deposited at the same time as one another. The sealing layers can be deposited at the same time as one another.

[0020] FIG. 1C shows an example cover 180 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 chromium passivation layers 130 and 150 and the sealing layers 140 and 160. The chromium passivation layers can be deposited at the same time as one another. The sealing layers can be deposited at the same time as one another. The cover depicts a coating layer 190 over sealing layer 140. It should be appreciated that an example with both the sealing layers 140 and 160 may have a coating layer over sealing layer 140 and not over sealing layer 160, coating layer may be over both sealing layers. The coating layer may be referred to as a paint layer. The coating layer can include multiple layers. For example, the 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/cm ² for about 10 to about 30 seconds.

[0021] FIG. 2 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 chromium passivation layer 230 over surfaces of the hybrid substrate. For example, the chromium passivation 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 chromium passivation layer also is depicted as covering a third surface 225, a fourth surface 245, and a fifth surface 255 of the second portion. The chromium passivation layer is depicted as covering the surfaces of the L shape of the second portion. A sealing layer 240 is depicted as covering the chromium passivation layer. A coating layer 250 is depicted as covering the sealing layer in regions where the sealing layer covers the first surface 215, the third surface 225, and the fifth surface 255.

[0022] The cover 200 is depicted with a chamfer 260. The chamfer can be described as a milled edge along a comer of the L shaped second portion 220. After the chromium passivation layer 230, the sealing layer 240, and the coating layer 250 are deposited, the chamfer or milled edge cuts through each of the passivation layer 230, the sealing layer 240, and the coating layer 250 to expose a surface 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 comer 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.

[0023] 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 chromium passivation layer 330. The chromium passivation layer can be covered with a sealing layer 340. Portions of the sealing layer can be covered with a coating layer 350. The coating layer may include a plurality of paint coatings. A comer 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. Each of these milled edges exposes an aluminum alloy of a portion of the hybrid substrate.

[0024] 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 chromium passivation layer 330, the sealing layer 340, and the coating layer 350 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.

[0025] 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.

[0026] 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 chromium passivation 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.

[0027] 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

[0028] 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.

[0029] 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 chromium passivation layer 440. The chromium passivation layer is covered with a sealing layer 450. The portions of the sealing layer that are to form the outer portions of the electronic device are additionally covered with a coating layer 460. 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 chromium passivation layer, the sealing layer, and the coating layer.

[0030] 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

[0031] 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 a 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 the magnesium alloy portion where the magnesium alloy portion was formed or shaped using forging techniques or molding techniques such as thixo-molding. In another example, the aluminum alloy portion is first formed using CNC milling and the magnesium alloy portion is insert molded onto the aluminum alloy portion using thixo-molding to form the hybrid substrate. 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. The hybrid substrate may then be polished. The polished hybrid substrate may then be coated with a chromium passivation layer. The chromium passivation layer may be coated with a sealing layer. The hybrid substrate with the chromium passivation layer and the sealing layer may then be baked or cured. After the baking, a primer coat may be deposited on the sealing layer or a portion of the sealing layer. A base coat may be deposited on the primer coat. A top coat may be deposited on the basecoat. After the top coat is deposited, the entire cover may be baked and then subjected to ultraviolet exposure. Finally, a comer of the aluminum alloy portion may be milled along an edge to chamfer a surface of the aluminum alloy portion and expose a surface of the aluminum alloy portion at an angle.

[0032] 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 comprising a first portion including an aluminum alloy and a second portion including a magnesium alloy. The method further includes applying 520 a chromium passivation 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 sealing layer on the chromium passivation layer. The method can optionally include milling 540 an edge along a corner of the aluminum alloy of the hybrid substrate, wherein the milling cuts through the chromium passivation layer and the sealing layer to expose 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. Alternatively, the method can further include insert molding the magnesium alloy on the aluminum alloy using thixo-molding. The method can optionally include applying a coating layer between steps 530 and 540. The coating layer may include a plurality of applied layers such as a primer coat, a base coat, a top coat, and/or an anti-fingerprint coating.

[0033] 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 with a chromium passivation layer 640. The chromium passivation layer can coat all exposed surfaces of the hybrid substrate. In FIG. 6D, the chromium passivation layer is coated with a sealing layer 650. The sealing layer can coat all exposed surfaces of the chromium passivation layer. In FIG. 6E, the sealing layer is coated with a coating layer 660. The coating layer can cover the portion of the sealing layer that is to be the outer surface of the electronic device and may not coat the sealing 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. 6F, a comer of the second portion is milled along an edge to form a chamfer 670 that exposes a surface of the second portion. A comer 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 chromium passivation layer, the sealing layer, and the coating layer.

Passivation Coatings for Electronic Device Covers

[0034] In one example, a chromium passivation 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 at least one of molybdates, vanadates, phosphates, chromates, stannates and manganese salts. The passivation layer may have a thickness of 1-5 pm. Paint Coatings

[0035] The paint coating 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

[0036] 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.

[0037] 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.

[0038] As used herein, “colorant” can include dyes and/or pigments.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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 pm to about 0.5 pm should be interpreted to include the explicitly recited limits of 0.1 pm to 0.5 pm, and to include thicknesses such as about 0.1 pm and about 0.5 pm, as well as subranges such as about 0.2 pm to about 0.4 pm, about 0.2 pm to about 0.5 pm, about 0.1 pm to about 0.4 pm etc.

PROPHETIC EXAMPLES

[0043] 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 spirit and scope of the present disclosure. The appended claims are intended to cover such modifications and arrangements. Example 1

[0044] A laptop cover for an electronic device is made using Computer Numerical Control (CNC) milling of an aluminum alloy portion for the comer regions of a laptop cover, including all comers of openings in the laptop cover. In this example, the aluminum alloy includes from 50 wt% to 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 as 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 chromium passivation layer and cured at from about 30° C to about 40° C about 3 minutes to about 5 minutes. A sealing layer is then applied to the chromium passivation layers an cured at from about 80° C to about 90° C about 5 minutes to about 10 minutes. The coated hybrid substrate is then baked at from about 60° C to about 120° C about 10 minutes to about 30 minutes. A primer coat is deposited over surfaces of the sealing 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 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 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 about 10 minutes to about 30 minutes. The top coat is then subjected to ultraviolet exposure at 700 mJ/cm ² to 1 ,200 mJ/cm ² for 10 to 30 seconds. Corners of the aluminum alloy portions are then milled using diamond cutting controlled via CNC milling at an angled along an edge to expose a surface of the aluminum alloy.

Example 2

[0045] 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.