WO2021154275A1

WO2021154275A1 - Enclosures for electronic devices

Info

Publication number: WO2021154275A1
Application number: PCT/US2020/016054
Authority: WO
Inventors: Chi Hao Chang; Kuan-Ting Wu; Chien-Ting Lin
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2020-01-31
Filing date: 2020-01-31
Publication date: 2021-08-05

Abstract

Examples of an enclosure and method for forming an enclosure have been described. In an example, method for forming the enclosure is described wherein protrusions are fabricated on an aluminum alloy-based substrate; a thermally formed magnesium alloy-based substrate is stamped on to the aluminum alloybased substrate to obtain a pre-enclosure; a portion of the pre-enclosure is chamfered to obtain a chamfered pre-enclosure; and the chamfered pre-enclosure is treated to obtain the enclosure. In another example, the enclosure is described which comprises a first metal substrate; a second metal substrate; at least one passivation layer; at least one protective layer; at least one transparent passivation layer; and at least one sealing layer.

Description

ENCLOSURES FOR ELECTRONIC DEVICES

BACKGROUND

[0001] Electronic devices, such as smartphones, tablets, keyboards, tablets, laptops, intelligent wearable devices and the like are becoming lighter and thinner. These light and thin devices are easily susceptible to being deformed. Therefore, enclosure for such devices needs to impart mechanical strength. Accordingly, lightweight metal alloys may be employed for fabrication of such enclosures. Further, the factor of aesthetics cannot be overlooked. The outer surface of the enclosure may be suitably treated to provide different visual appearances or cosmetic effects.

BRIEF DESCRIPTION OF DRAWINGS

[0002] The following detailed description references the drawings, wherein: [0003] Fig. 1 is a flow chart illustrating a method for forming an enclosure for an electronic device, according to an example of the present disclosure;

[0004] Fig. 2 is a flow chart illustrating a method for forming an enclosure for an electronic device, according to another example of the present disclosure [0005] Fig. 3 is a flow chart illustrating a method for forming an enclosure for an electronic device comprising depositing a sealing layer, according to an example of the present disclosure

[0006] Fig. 4 illustrates a device with a sectional view of an enclosure, according to another example of the present disclosure;

DETAILED DESCRIPTION

Definitions

[0007] For convenience, before further description of the present disclosure, certain terms employed in the specification, and examples are described here. These definitions should be read in the light of the remainder of the present disclosure. The terms used herein have the meanings recognized and known to those of skill in the art, however, for convenience and completeness, particular terms and their meanings are set forth below. [0008] The articles "a”, “an”, and “the” are used to refer to one or to more than one (i.e., to at least one) of the grammatical object of the article.

[0009] The term “about" when referring to a numerical value is intended to encompass the values resulting from variations that can occur during the normal course of performing a method. Such variations are usually within plus or minus 5 to 10 percent of the stated numerical value.

[0010] Enclosures, or body of electronic devices, are made of metal substrates that have strength, and resistance towards corrosion. Examples of this disclosure pertain to suitable materials for such enclosures, that have aesthetic appeal, are light in weight and at the same time impart acceptable mechanical strength. The examples herein pertain to enclosures and methods of forming the enclosure. As used herein the terms ''enclosure" may be used interchangeably with “housing" and "cover or protective cover". Such enclosures may form a back surface of an electronic device and/or any of the edges of the electronic device. [0011] The term "alloy” refers to the class of materials that may be referred to as a solid solution of metals. The aluminum alloy-based substrate in the present disclosure formed from aluminum alloy selected from AL575, AL1050, AL1060, AL1100, AL1199, AL2014, AL2024, AL2219, AL3004, AL4041, AL5005, AL5010, AL5019, AL5024, AL5026, AL5050, AL5052, AL5056, AL5059, AL5083, AL5086, AL5154, AL5182, AL5252, AL5254, AL5356, AL5454, AL5456, AL5457, AL5557, AL5652, AL5657, AL5754, AL6005, AL6005A, AL6060, AL6061 , AL6063, AL6066, AL6070, AL6082, AL6105, AL6151 , AL6162, AL6205, AL6262, AL6351 , AL6463, AL7005, AL7022, AL7068, AL7072, AL7075, AL7079, AL7116, AL7129, AL7175, AL7475, AL7178, or combinations thereof. The magnesium alloy-based substrate in the present disclosure is formed from magnesium alloy selected from AZ61, AZ81, AZ91 , AM50, AM60, AZ31 , AZ63, AZ80, AE44, AJ62A, ALZ391, AMCa602, LZ9, or combinations thereof. In case if titanium based alloys are used in the present disclosure, the titanium alloy may be selected from Ti-3%AI-8%V- 6%Cr-4%Zr-4%Mo, Ti-15%Mo-3%Nb-3%AI-0.2%Si, Ti-6%AI-4%V, Ti-4%AI- 4%Mo-2%Sn-0.5%Si, Ti-6%AI-6%V-2%Sn, Ti-10%V-2%Fe-3%AI, Ti-15%V- 3%Cr-3%Sn-3%AI, Ti-8%AI-1 %Mo-1 %V, Ti-6%AI-5%Zr-0.5%Mo-0.2%Si, Ti- 6 %A I- 2 %Sn-4%Zr-2% Mo , Ti-5.5%AI-3.5%Sn-3%Zr-1 %Nb-0.3%Mo-0.3%Si, Ti- 6%AI-2%Sn-4%Zr-6%Mo, Ti-5.8%AI-4%Sn-3.5%Zr-0.7%Nb-0.5%Mo-0.3%Si . If a zinc-based alloy is used in the present disclosure, the zinc alloy may be selected from Zn-AI (Al 3.9-4.3 wt%), Zn-Ni (Ni 1.9-13.9 wt%), Zn-Co (Co 0.4-1.2 wt%), or Zn-Fe (Fe 0.4-1.5 wt%).

[0012] The term “metal substrate” used herein refers to substrates made of magnesium, aluminum, zinc, titanium, or a combination thereof, that are strong, and are light in weight. Such metal substrates are used for manufacturing body parts, housings, and enclosures of portable or handheld devices, such as mobile phones, tablets, laptops, styluses, keyboards, and the like.

[0013] The term “CNC” used herein refers to computerized numerical control. The numerical control is an automated control for chamfering the surfaces.

[0014] The term “mechanically stable”, used herein refers to substrates having high tensile strength and/or high resistance to breakage and/or high corrosion resistance.

[0015] The term “coating", and variations, such as "coat” and "coated", used herein refer to deposition on a surface.

[0016] The term “high gloss edges”, used herein refers to chamfered surfaces (in particular, the edges) of the substrate that reveal shiny edges.

[0017] The term "thermally formed” used herein refers to magnesium-based alloys, which are super-plastically formed having superior formability, yet uniform tensile ductility. The super-plastically formed magnesium-based alloys have greater design flexibility and dimensional control. For instance, the pure magnesium alloys, such as AZ61 alloy, and AZ81 alloy deform at higher temperatures, but the thermally formed AZ61 alloy elongates up to 12 % at a temperature of 350 °C and has a tensile strength of 419 MPa. Similarly, AZ81 has elongation of more than 10 % at a temperature of 350 °C. The superplastic forming process has an operating temperature of from about 300 °C to about 650 °C and a pressure of from about 60 kg/cm² to about 180 kg/cm².

[0018] In the case of manufacturing enclosures of electronic devices, conditions are employed, not just on the surface finish (aesthetic reasons) but also to obtain a surface that is optimal in a forming point of view. Besides this, enclosures which are light in weight and corrosion resistant are needed. Reducing weight without compromising aesthetics, and mechanical strength is achieved by moving from a heavier material to a lighter material to the extent wherein it is both financially and technically viable. Weight reduction may be achieved by switching to lightweight metals, such as aluminum alloy, magnesium alloy, titanium alloy, zinc alloy, and the like. However, a purely aluminum alloy-based enclosure could result in an increase in weight. Moreover, aluminum alloys offer relatively poor compatibility with known processing techniques. Purely magnesium alloy-based enclosures are prone to corrosion and, also suffer from poor tensile strength. Therefore, a hybrid or bimetallic structure which allows for a light-weight enclosure with the high mechanical strength, while maintaining the aesthetics is needed.

[0019] In an example, the bimetallic structure (or the pre-enclosure) is obtained by fabricating protrusions on an aluminum alloy-based substrate, followed by stamping a thermally formed magnesium alloy-based substrate on top of the aluminum alloy-based substrate to form a pre-enclosure. The protrusions may be formed on the aluminum alloy-based substrate by a process selected from CNC process, thermal molding process, thixo-molding, or anodization process. The protrusions allow increased bond strength between the aluminum alloy-based substrate and thermally formed magnesium alloy-based substrate. This pre-enclosure may be then chamfered for aesthetic and/or tactile purposes. Chamfering is carried out on portions of the magnesium alloy-based substrate, for example, to create rounded edges of keyboards, electronic notebook, laptops, tablets, smartphones, and the like. Chamfering may be carried out on a portion of the pre-enclosure, i.e., at portions of the pre-enclosure where a different aesthetic appeal is to be provided, such as cover edge, touch pad, click-pad, fingerprint scanner, edge, or sidewall, logo area, and the like as compared to the rest of the enclosure. These chamfered portions may be then treated by a process selected from transparent passivation, sealing, electrophoretic deposition, or combinations thereof, so as to obtain an enclosure for an electronic device. [0020] Overall, the methodology of fabricating protrusions on an aluminum alloy-based substrate, followed by stamping a thermally formed magnesium alloy- based substrate onto the aluminum alloy-based substrate and further chamfering, and treating the chamfered portion according to the present subject matter, is simple, less time and resource consuming, and cost-efficient. Further, the enclosures thus obtained are aesthetically appealing, light in weight, while also being mechanically stable.

[0021] The following detailed description refers to the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the following description to refer to the same or similar parts. While several examples are described in the description, modifications, adaptations, and other implementations are possible. Accordingly, the following detailed description does not limit the disclosed examples. Instead, the proper scope of the disclosed examples may be defined by the appended claims.

[0022] The present subject matter describes examples for method for forming enclosures for an electronic device, wherein the method comprises fabricating protrusions on an aluminum alioy-based substrate; stamping a thermally formed magnesium alloy-based substrate on to the aluminum alloy- based substrate to obtain a pre-enclosure; chamfering a portion of the pre- enclosure to obtain a chamfered pre-enclosure; and, treating the chamfered pre- enclosure to obtain an enclosure.

[0023] Fig. 1 illustrates a method for forming an enclosure for an electronic device 100, according to an example of the present disclosure. Protrusions may be fabricated on an aluminum alloy-based substrate. In an example, fabricating protrusions on an aluminum alloy-based substrate, 102, may be carried out by a CNC process. The CNC process may be carried out at a rotation speed of from about 3000 rpm to about 90,000 rpm for a period of from about 5 minutes to about 25 minutes. In another example, fabricating protrusions on an aluminum alloy- based substrate, 102, may be carried out by a thermal molding process. The thermal molding process may be carried out a temperature of from about 500 °C to about 900 °C at a pressure of from about 700 psi to about 1000 psi. In yet another example, fabricating protrusions on an aluminum alloy-based substrate, 102, may be carried out by die-casting or thixo-molding process. The thixo- molding process may be carried out a temperature of from about 350 °C to about 750 °C at a pressure of from about 2000 psi to about 20,000 psi. In some examples, fabricating protrusions on an aluminum alloy-based substrate, 102, may be carried out by an anodization process. The protrusions fabricated by the above mentioned processes lead to the formation of the protruded aluminum alloy-based substrate, wherein the protrusions may have various shapes and sizes. In an example, the protrusions may have size of from about 0.2 to about 1.5 mm.

[0024] The aluminum alloy-based substrate on to which protrusions are fabricated may have a varied thickness in an example of the present disclosure. In one example, the aluminum alloy-based substrate may have a thickness of from about 0.3 mm to about 2.0 mm. In another example, the aluminum alloy- based substrate may have a thickness of from about 0.4 mm to about 1.9 mm. In yet another example, the aluminum alloy-based substrate may have a thickness of from about 0.5 mm to about 1.8 mm. In some examples, the aluminum alloy- based substrate may have a thickness of about 0.7 mm.

[0025] The protruded aluminum alloy-based substrate may be cleaned, dried, washed, polished, degreased, and activated. The cleaning and washing may be performed using a buffer solution, which may help in removing foreign particles, if any, present on the surface of the protruded aluminum alloy-based substrate. Further, the protruded aluminum alloy-based substrate may be chemically polished using abrasives to remove irregularities that may be present on the surface of the protruded aluminum alloy-based substrate. The protruded aluminum alloy-based substrate may also be degreased through ultrasonic degreasing methods to remove impurities, such as fat, grease, or oil from the surface of the protruded aluminum alloy-based substrate. Further, the protruded aluminum alloy-based substrate may also be activated through acid treatment for removing the natural oxide layer, if any, present on the surface of the protruded aluminum alloy-based substrate.

[0026] As shown by block 104, of Fig. 1, a thermally formed magnesium alloy-based substrate may be stamped on to the aluminum alloy- based substrate to obtain a pre-enclosure. In an example, the stamping may be carried out at a temperature of from about 20 °C to about 250 °C at a pressure of from about 2 kg/cm² to about 150 kg/cm². In another example, stamping may be carried out at a temperature of from about 25 °C to about 200 °C at a pressure of from about 5 kg/cm² to about 150 kg/cm². In an example, the stamping process may be carried out to trim the extra substrate.

[0027] The thermally formed magnesium alloy may be made by a superplastic forming process at an operating temperature of from about 300 °C to about 650 °C and a pressure of from about 60 kg/cm² to about 180 kg/cm². In another example, thermally formed magnesium alloy may be made a superplastic forming process at an operating temperature of from about 400 °C to about 600 °C and a pressure of from about 65 kg/cm² to about 170 kg/cm². In yet another example, thermally formed magnesium alloy may be made a superplastic forming process at an operating temperature of from about 450 °C to about 550 °C and a pressure of from about 65 kg/cm² to about 150 kg/cm²,

[0028] The pre-enclosure may have defects, and in order to eliminate the defects and give the edges of the portions a more even surface with improved strength, they may be chamfered. The stamping of thermally formed magnesium alloy-based substrate on to the aluminum alloy- based substrate may result in the formation of pre-enclosure, wherein defects on the surface of pre-enclosure may be minimal. As a result, the chamfering time may be reduced to 15 minutes. Block 106, of Fig. 1, shows that a portion of the pre-enclosure may be chamfered. In an example, the method for forming an enclosure for an electronic device 100, comprises chamfering a portion of the pre-enclosure to obtain a chamfered pre- enclosure. The chamfering 106, may be carried out at portions, such as cover edge, touch pad, fingerprint scanner, click pad, side wall, logo area, among others. The chamfering involves abrasive removal of edge material that may give it the desired finishing and also shape its form. In an example, chamfering may be carried out by a CNC diamond cutting machine. In another example, the chamfering may be carried out with a CNC diamond cutting machine at speed of from about 5000 to about 90000 rpm for a period in a range of from about 3 to about 8 minutes. In yet another example, the chamfering may be carried out with a CNC diamond cutting machine at speed of from about 6000 to about 80000 rpm.

[0029] The chamfered pre-enclosure may be cleaned, degreased, washed and dried, prior to treating the chamfered pre-enclosure 108. In an example, the cleaning may be carried out in the presence of at least one aqueous alkaline compound, such as sodium hydroxide. The degreasing may be carried out by ultrasonic degreasing methods to remove impurities, such as fat, grease, or oil from the surface of the chamfered pre-enclosure.

[0030] Further, the chamfered pre-enclosure may be treated to obtain an enclosure, i.e., treating the chamfered pre-enclosure by a process selected from transparent passivation, sealing, electrophoretic deposition, or combinations thereof to obtain an enclosure. In an example, the transparent passivation treatment may be carried out in the presence of transparent chemicals selected from ethylenediaminetetraacetic acid (EDTA), ethylenediamine, nitrilotriacetic acid (NTA), diethylenetriaminepenta(methylenephosphonic acid) (DTPPH) and nitrilotris(methylenephosphonic acid) (NTMP), 1-hydroxyethane-1,1- diphosphonic acid (HEDP), phosphoric acid, and salts thereof to obtain a transparent passivation layer. In an example, the transparent passivation treatment may be done throughout the surface of the enclosure. In another example, the transparent passivation treatment may be done at the exposed surface of the enclosure, post immersing in transparent chemicals. In an example, the transparent chemicals concentration may be of from about 1 wt % to about 10 wt % based on the total concentration. In another example, the transparent chemicals concentration may be of from about 2 wt % to about 8 wt % based on the total concentration. In yet another example, the transparent chemicals concentration may be 6 wt % based on the total concentration. In an example, the transparent passivation treatment may be carried out by immersing in a chemical bath at a temperature of from about 20 °C to about 40 °C for a period of from about 30 seconds to about 180 seconds.

[0031] In another example, the transparent passivation treatment may be carried out in the presence of a transparent chemical, such as ethylenediaminetetraacetic acid (EDTA), and salts thereof. In another example, the transparent chemical may be selected from zinc (II) EDTA complex or nickel (II) EDTA complex.

[0032] In an example, the transparent passivation layer may have a thickness of from about 0.03 μm to about 1 μm. In another example, the transparent passivation layer may have a thickness of from about 0.05 μm to about 0.8 μm. In yet another example, the transparent passivation layer may have a thickness of from about 0.1 μm to about 0.6 μm. In some examples, the transparent passivation layer may have a thickness of about 0.5 μm.

[0033] In another example, the chamfered pre-enclosure may be treated by sealing the chamfered pre-enclosure. Sealing the chamfered pre-enclosure results in the formation of a sealing layer. In an example, the sealing may be carried out in the presence of a compound selected from aluminum fluoride, nickel fluoride, cerium fluoride, cerium acetate, aluminum acetate, nickel acetate, or combinations thereof. In another example, the sealing may be carried out in the presence of aluminum fluoride. In yet another example, the sealing may be carried out in the presence of nickel fluoride. In an example, the compound may be utilized in the form of an aqueous dispersion further comprising a surfactant having a strength of from about 0.1 % to about 2,0 % with respect to the dispersion. Post sealing, a process of baking may be carried out, wherein baking may be carried out at a temperature of from about 60 °C to about 90 °C for a period of from about 15 seconds to about 180 seconds. In an example, the baking may be carried out at a temperature of from about 62 °C to about 88 °C for a period of from about 30 seconds to about 60 seconds. In another example, the baking may be carried out at a temperature of 70 °C for a period of 45 seconds. The sealing layer thus obtained may have a thickness of from about 1.0 μm to about 3.0 μm. In another example, the sealing layer may have a thickness of from about 1.2 μm to about 2.8 μm.

[0034] In case the chamfered pre-enclosure is treated by the electrophoretic deposition process, the electrophoretic deposition (ED)D layer may be deposited on the chamfered pre-enclosure. Electrophoretic deposition on the chamfered pre-enclosure may be carried out in the presence of at least one dye. Electrophoretic deposition at the chamfered pre-enclosure may provide a multi- colored finish to the chamfered pre-enclosure. In an example, chamfered pre- enclosure is a keyboard having a first color at the base and a second color at the fingerprint scanner area and a third color at the touch pad area. In an example, an electrophoretic deposition may be carried out subsequent to the formation of the transparent passivation layer to introduce colors and to provide aesthetically improved finish. The thickness of the ED layer achieved may be directly related to the potential applied and time for the electrophoretic deposition. In an example, the electrophoretic deposition may be carried out by applying a potential of from about 30 to about 150 V for a period of from about 20 to about 120 seconds. In another example, the electrophoretic deposition may be carried out by applying a potential of from about 50 to about 130 V for a period of from about 20 to about 100 seconds. In yet another example, the electrophoretic deposition may be carried out by applying a potential of about 120 V for a period of about 80 seconds.

[0035] In an example, the ED layer deposited by electrophoretic deposition may comprise various dyes selected from red dye, blue dye, orange dye, yellow dye: Quinoline Yellow WS to obtain different colors at portions, such as cover edge, touch pad, fingerprint scanner, click pad, side wall, logo area, among others. In an example, to obtain red colored in the ED layer, a red dye may be used and may be selected from Alexa Fluor 594 dye, or Texas Red. In another example to obtain red color, a pigment may be used, such as pigment Red 168 MF. In an example to obtain blue colored finish in the ED layer, a blue dye may be used, such as Pacific Blue dye. In an example, to obtain orange colored finish in the ED layer, an orange dye may be used, such as Pacific Orange. In an example, to obtain yellow colored finish in the ED layer a yellow dye may be used, such as quinoline yellow WS. In another example, to obtain yellow color, a pigment may be used, such as Pigment Yellow 191. The method as described hereinabove for the method for forming an enclosure of Fig. 1 , may be applied for forming enclosures for a range of electronic devices, such as keyboards, laptops, tablets, mobile phones, among others.

[0036] In an example, the method for forming an enclosure as illustrated in

Fig. 1 may provide an enclosure having a tensile strength of from about 200 MPa to about 700 MPa as measured by American Society for Testing and Materials (ASTM) D790. In another example, the enclosure may have a tensile strength of from about 250 MPa to about 600 MPa as measured by American Society for Testing and Materials (ASTM) D790. In yet another example, the enclosure may have a tensile strength of from about 350 MPa to about 600 MPa as measured by American Society for Testing and Materials (ASTM) D790.

[0037] Another method for forming an enclosure for an electronic device is illustrated in Fig. 2. Similar to the description given for Fig. 1 , block 202 of Fig. 2, shows that protrusions may be fabricated on a first metal substrate. Fabricating protrusions on the first metal substrate results in the formation of a protruded metal substrate. These protrusions may have a variety of shapes and sizes on the first metal substrate. The first metal substrate on which the protrusions are fabricated, may be an aluminum alloy-based substrate, and the aluminum alloy- based substrate may be selected from AL575, AL1050, AL1060, AL1100, AL1199, AL2014, AL2024, AL2219, AL3004, AL4041 , AL5005, AL5010, AL5019, AL5024, AL5026, AL5050, AL5052, AL5056, AL5059, AL5083, AL5086, AL5154, AL5182, AL5252, AL5254, AL5356, AL5454, AL5456, AL5457, AL5557, AL5652, AL5657, AL5754, AL6005, AL6005A, AL6060, AL6061 , AL6063, AL6066, AL6070, AL6082, AL6105, AL6151, AL6162, AL6205, AL6262, AL6351, AL6463, AL7005, AL7022, AL7068, AL7072, AL7075, AL7079, AL7116, AL7129, AL7175, AL7475, AL7178, or combinations thereof.

[0038] In an example, fabricating protrusions on a first metal substrate, 202, may be carried out by a CNC process. The CNC process may be carried out at a rotation speed of from about 3000 rpm to about 90,000 rpm for a period of from about 5 minutes to about 25 minutes. In another example, fabricating protrusions on a first metal substrate, 202, may be carried out by a thermal molding process. The thermal molding process may be carried out a temperature of from about 500 °C to about 900 °C at a pressure of from about 700 psi to about 1000 psi. In yet another example, fabricating protrusions on a first metal substrate, 202, may be carried out by die-casting or thixo-molding process. The thixo-molding process may be carried out a temperature of from about 350 °C to about 750 °C at a pressure of from about 2000 psi to about 20,000 psi. In some examples, fabricating protrusions on a first metal substrate, 202, may be carried out by an anodization process. The protrusions fabricated by the above mentioned processes lead to the formation of a protruded metal substrate, wherein the protrusions may have various shapes and sizes. In an example, the protrusions may have size of from about 0,2 to about 1.5 mm.

[0039] The first metal substrate on to which protrusions are fabricated may have a varied thickness in an example of the present disclosure. In one example, the first metal substrate may have a thickness of from about 0.3 mm to about 2.0 mm. In another example, the first metal substrate may have a thickness of from about 0.4 mm to about 1.9 mm. In yet another example, the first metal substrate may have a thickness of from about 0.5 mm to about 1.8 mm. In some examples, the first metal substrate may have a thickness of about 0.7 mm.

[0040] The protruded metal substrate may be cleaned, dried, washed, polished, degreased, and activated. The cleaning and washing may be performed using a buffer solution, which may help in removing foreign particles, if any, present on the surface of the protruded metal substrate. Further, the protruded metal substrate may be chemically polished using abrasives to remove irregularities that may be present on the surface of the protruded metal substrate. The protruded metal substrate may also be degreased through ultrasonic degreasing methods to remove impurities, such as fat, grease, or oil from the surface of the protruded metal substrate. Further, the protruded metal substrate may also be activated through acid treatment for removing the natural oxide layer, if any, present on the surface of the protruded metal substrate.

[0041] As shown by block 204, of Fig. 2, a thermally formed second metal substrate may be disposed of on to the protruded metal substrate to obtain a base frame. Disposing a thermally formed second metal substrate on to the protruded metal substrate may be carried out by superplastic forming process. The superplastic forming process may be carried out at an operating temperature of from about 300 °C to about 650 °C and a pressure of from about 60 kg/cm² to about 180 kg/cm². In another example, superplastic forming process may be carried out at an operating temperature of from about 400 °C to about 600 °C and a pressure of from about 65 kg/cm² to about 170 kg/cm². In yet another example, superplastic forming process may be carried out at an operating temperature of from about 450 °C to about 550 °C and a pressure of from about 65 kg/cm² to about 150 kg/cm².

[0042] In an example, disposing a thermally formed second metal substrate on to the protruded metal substrate results in the formation of a base frame. In an example, the base frame may have a thickness of from about 0.3 mm to about 2.0 mm. In another example, the base frame may have a thickness of from about 0.4 mm to about 1.9 mm. In yet another example, the base frame may have a thickness of from about 0.5 mm to about 1.8 mm. In some examples, the base frame may have a thickness of about 0.7 mm,

[0043] In an example, the second metal substrate is a magnesium alloy- based substrate, and may be selected from AZ61, AZ81 , AZ91 , AM50, AM60, AZ31, AZ63, AZ80, AE44, AJ62A, ALZ391 , AMCa602, LZ9, or combinations thereof.

[0044] As per the block, 206 of Fig. 2, the base frame may be machined to provide shape to the base frame. Providing shape to the base frame may result in the formation of a pre-enclosure. In an example, providing shape to the base frame may be carried out by CNC process. In another example, the CNC process may be carried out with a CNC diamond cutting machine at speed of from about 5000 to about 90000 rpm for a period in a range of from about 3 to about 8 minutes. In yet another example, the CNC process may be carried out with a CNC diamond cutting machine at speed of from about 6000 to about 80000 rpm. [0045] The method 200, for forming an enclosure for an electronic device comprises depositing a passivation layer on to the pre-enclosure to obtain a passivated pre-enclosure. Block 208 of Fig. 2 includes depositing a passivation layer on to the pre-enclosure by a process selected from chemical passivation treatment, electro-chemical passivation treatment, or combinations thereof. Prior to depositing a passivation layer on to pre-enclosure, the pre-enclosure may be cleaned, degreased, neutralized, washed and dried, so as to remove the oil and dirt. In an example, the cleaning may be carried out in the presence of at least one aqueous alkaline compound, such as sodium hydroxide. The degreasing may be carried out by ultrasonic degreasing methods to remove impurities, such as fat, grease, or oil from the surface of the pre-enclosure.

[0046] Post treating the pre-enclosure, a passivation layer may be deposited on the pre-enclosure to obtain a passivated enclosure. In an example, depositing the passivation layer may be carried out by electro-chemical passivation treatment. The electro-chemical passivation treatment is a micro-arc oxidation process which may be carried out at a voltage of from about 150 V to about 550 V at a temperature of from about 10 °C to about 45°C for a period of from about 2 minutes to about 25 minutes. In another example, the deposition of the passivation layer may be carried out by micro-arc oxidation carried out at a voltage of from about 250 V to about 450 V at a temperature of from about 12 °C to about 42°C for a period of from about 5 minutes to about 22 minutes. In an example, the passivation layer formed by micro-arc oxidation may have a thickness of from about 1 μm to about 15 μm. In another example, the passivation layer formed by micro-arc oxidation may have a thickness of from about 3 μm to about 12 μm. In yet another example, the passivation layer formed by micro-arc oxidation may have a thickness of from about 3 μm to about 7 μm.

[0047] In an example, depositing the passivation layer on to the pre- enclosure carried out by electro-chemical passivation treatment may be carried out in the presence of at least one chemical selected from sodium silicate, metal phosphates, potassium fluoride, potassium hydroxide, sodium hydroxide, fluoro- zirconates, sodium hexametaphosphate, sodium fluoride, ferric ammonium oxalate, phosphoric acid salt, graphite powder, silicon dioxide powder, aluminum oxide powder, and combinations thereof. In an example, the chemical may be employed at a dosage of from about 0.05% to about 15% in the presence of water at a pH of from about 9.0 to about 13. In another example, the chemical may be employed at a dosage of from about 0.1% to about 12% in the presence of water at a pH of from about 9.0 to about 12.0,

[0048] In another example, depositing a passivation layer on to the pre- enclosure, 208 may be carried out by a process of dip coating for a period of from about 20 seconds to about 120 seconds. In yet another example, depositing a passivation layer on to the pre-enclosure, 208 may be carried out by a process of dip coating for a period of from about 30 seconds to about 120 seconds. In an example, the passivation layer obtained by the process of dip coating may have a thickness of from about 1 μm to about 5 μm. In another example, the passivation layer obtained by the process of dip coating may have a thickness of from about 1.5 μm to about 3.0 μm.

[0049] In an example, the dip coating may be carried out in the presence of at least one salt of manganese, molybdates, vanadate, phosphate, chromate, stannate, and combinations thereof. In an example, the at least one salt may be manganese. In an example, the salt may be dispersed in the form of an aqueous solution having a concentration of from about 3% to about 15% based on the total weight of the aqueous solution. In another example, the salt may be dispersed in the form of an aqueous solution having a concentration of from about 5% to about 12% based on the total weight of the aqueous solution.

[0050] The method for forming an enclosure for an electronic device, as illustrated in Fig. 2, further comprises coating at least one protective layer on to the passivated pre-enclosure, 210. In an example, coating at least one protective layer on the passivated pre-enclosure may result in the formation of coated pre- enclosure. In an example, the coating of the protective layer may be carried out by spray coating.

[0051] In an example, the at least one protective layer may have a thickness of from about 5.0 μm to about 70.0 μm. In another example, the at least one protective layer may have a thickness of from about 10.0 μm to about 68.0 μm. In yet another example, the at least one protective layer may have a thickness of from about 10.0 μm to about 65.0 μm.

[0052] The coating of at least one protective layer on to the passivated pre- enclosure carried out by spray coating may be carried out in a manner, whereby the protective layer thus formed may comprise multiple layers, such as primer, base coat, and top coat. In an example, the spray-coated protective layer comprises sequentially deposited coats of primer coat having a thickness of from about 5.0 μm to about 20.0 μm, followed by base coat having a thickness of from about 10.0 μm to about 20.0 μm, followed by top coat having a thickness of from about 10.0 μm to about 25.0 μm. [0053] The passivated pre-enclosure may be cleaned, degreased, washed, and dried prior to the coating of at least one protective layer. The at least one protective layer may comprise primer, either alone or in combination with additional layers. The primer may also be applied as single or multiple coats to achieve the desired thickness and finish. In an example, the primer may have a thickness of from about 5.0 μm to about 20.0 μm. In another example, the primer may have a thickness of from about 8.0 μm to about 18.0 μm. In yet another example, the primer may have a thickness of about 12.0 μm.

[0054] In an example, the primer may be coated on the pre-enclosure or the passivated pre-enclosure by spray coating polyurethanes followed by heat treatment at a temperature of from about 60 °C to about 80 °C for a period of from about 15 to about 40 minutes. In another example, the primer may be coated by spray coating polyurethane followed by heat treatment at a temperature of from about 62 °C to about 78 °C for a period of from about 18 to about 38 minutes. In yet another example, the primer may be coated by spray coating thermoplastics, such as polyurethanes followed by heat treatment at a temperature of about 70 °C for a period of about 25 minutes.

[0055] The at least one protective layer may comprise a base coat, in combination with additional layers. The base coat may also be applied as single or multiple coats to achieve the desired thickness and finish. In an example, the base coat may have a thickness of from about 10.0 μm to about 20.0 μm. In another example, the base coat may have a thickness of from about 12.0 μm to about 18.0 μm. In yet another example, the base coat may have a thickness of about 15.0 μm. In an example, the base coat may be a polyurethane containing pigments selected from carbon black, titanium dioxide, clay, mica, talc, barium sulfate, calcium carbonate, aluminum powder, plastic bead, dyes, and combinations thereof. In an example, the spray-coated base coat comprises polyurethane containing carbon black. In another example, the spray-coated base coat comprises polyurethane containing titanium dioxide. In yet another example, the spray-coated base coat comprises polyurethane containing clay.

[0056] In another example, the base coat coated by spray coating may be followed by heat treatment at a temperature of from about 60 °C to about 80 °C for a period of from about 15 to about 40 minutes. In another example, the base coat coated by spray coating may be followed by heat treatment at a temperature of from about 62 °C to about 78 °C for a period of from about 18 to about 38 minutes. In yet another example, the base coat coated by spray coating may be followed by heat treatment at a temperature of about 70 °C for a period of about 25 minutes. [0057] The at least one protective layer may comprise top coat, in combination with additional layers. The top coat may also be applied as single or multiple coats to achieve the desired thickness and finish.

[0058] In an example, the top coat may have a thickness of from about 10.0 μm to about 25.0 μm. In another example, the top coat may have a thickness of from about 12.0 μm to about 22.0 μm. In yet another example, the top coat may have a thickness of about 17.0 μm.

[0059] In an example, the top coat may be made of polyacrylic acid, polyurethane, urethane acrylates, acrylic acrylates, epoxy acrylates, or combinations thereof. In another example, the top coat may be made of polyacrylic acid. In yet another example, the top coat may be made of polyurethane. In some examples, the top coat may be made of urethane acrylates.

[0060] In an example, the top coat coated by spray coating may be followed by UV treatment in a range of from about 700 mJ/cm²to about 1200 mJ/cm² for a period of from about 10 seconds to about 30 seconds. In another example, the top coat coated by spray coating may be followed by UV treatment of from about 800 mJ/cm² to about 1100 mJ/cm² for a period of from about 15 seconds to about 25 seconds. In yet another example, the top coat coated by spray coating may be followed by UV treatment of about 950 mJ/cm² for a period of about 20 seconds.

[0061] In some examples, the top coat coated by spray coating a polyurethane may be followed by heat treatment at a temperature of from about 60 °Cto about 80 °C for a period of from about 15 to about 40 minutes. In another example, the top coat coated by spray coating may be followed by heat treatment at a temperature of from about 62 °C to about 78 °C for a period of from about 18 to about 38 minutes. In yet another example, the top coat coated by spray coating may be followed by heat treatment at a temperature of about 70 °C for a period of about 25 minutes.

[0062] The coated pre-enclosure may have defects, and in order to eliminate the defects and give the edges of the portions of the coated pre- enclosure, a more even surface with improved strength, they may be chamfered. Block 212, of Fig. 2, shows that at least a portion of the coated pre-enclosure may be chamfered. In an example, the method for forming an enclosure for an electronic device 200, comprises chamfering at least a portion of the coated pre- enclosure to obtain a chamfered pre-enclosure. The chamfering may be carried out at portions, such as cover edge, touch pad, fingerprint scanner, click pad, side wall, logo area, among others. The chamfering involves abrasive removal of edge material that may give it the desired finishing and also shape its form. In an example, chamfering may be carried out by a CNC diamond cutting machine. In another example, the chamfering may be carried out with a CNC diamond cutting machine at speed of from about 5000 to about 90000 rpm for a period in a range of from about 3 to about 8 minutes. In yet another example, the chamfering may be carried out with a CNC diamond cutting machine at speed of from about 6000 to about 80000 rpm.

[0063] The chamfered pre-enclosure may be cleaned, degreased, washed and dried, prior to passivating the chamfered pre-enclosure, 214. In an example, the cleaning may be carried out in the presence of at least one aqueous alkaline compound, such as sodium hydroxide. The degreasing may be carried out by ultrasonic degreasing methods to remove impurities, such as fat, grease, or oil from the surface of the chamfered pre-enclosure.

[0064] Further, the chamfered pre-enclosure may be passivated to obtain an enclosure, i.e., passivating the chamfered pre-enclosure by a transparent passivation treatment process selected from transparent passivation, sealing, electrophoretic deposition, or combinations thereof to obtain an enclosure. In an example, the transparent passivation treatment may be carried out in the presence of transparent chemicals selected from ethylenediaminetetraacetic acid (EDTA), ethylenediamine, nitrilotriacetic acid (NTA), diethylenetriaminepenta(methylenephosphonic add) (DTPPH) nitrilotris(methylenephosphonic acid) (NTMP), 1-hydroxyethane-1,1- diphosphonic acid (HEDP), phosphoric acid, and salts thereof to obtain a transparent passivation layer. In an example, the transparent passivation treatment may be done throughout the surface of the chamfered pre-enclosure. In another example, the transparent passivation treatment may be done at the exposed surface post immersing in transparent chemicals. In an example, the transparent chemical concentration may be of from about 1 wt % to about 10 wt % based on the total concentration. In an example, the transparent chemical concentration may be of from about 2 wt % to about 8 wt % based on the total concentration. In yet another example, the transparent chemical concentration may be 6 wt % based on the total concentration. In an example, the transparent passivation treatment may be carried out by immersing in a chemical bath at a temperature of from about 20 °C to about 40 °C for a period of from about 30 seconds to about 180 seconds.

[0065] In another example, the transparent passivation treatment may be carried out in the presence of transparent chemicals, such as ethylenediaminetetraacetic acid (EDTA), and salts thereof. In another example, the transparent chemical may be selected from zinc (II) EDTA complex or nickel (II) EDTA complex.

[0066] In an example, the transparent passivation layer obtained by 214 block, may have a thickness of from about 0.03 μm to about 1 μm. In another example, the transparent passivation layer may have a thickness of from about 0.05 μm to about 0.8 μm. In another example, the transparent passivation layer may have a thickness of from about 0.1 μm to about 0.6 μm. In some examples, the transparent passivation layer may have a thickness of about 0.5 μm.

[0067] Further, details of a method 300 for forming an enclosure for an electronic device, are described with reference to Fig. 3. Similar to the description given for Fig. 2, block 302 of Fig. 3, shows that protrusions may be fabricated on a first metal substrate. Fabricating protrusions on the first metal substrate results in the formation of protruded metal substrate. These protrusions may have a variety of shapes and sizes on the first metal substrate. The first metal substrate on which the protrusions are fabricated, may be an aluminum alloy-based substrate, and the aluminum alloy-based substrate may be selected from AL575, AL1050, AL1060, AL1100, AL1199, AL2014, AL2024, AL2219, AL3004, AL4041, AL5005, AL5010, AL5019, AL5024, AL5026, AL5050, AL5052, AL5056, AL5059, AL5083, AL5086, AL5154, AL5182, AL5252, AL5254, AL5356, AL5454, AL5456, AL5457, AL5557, AL5652, AL5657, AL5754, AL6005, AL6005A, AL6060, AL6061, AL6063, AL6066, AL6070, AL6082, AL6105, AL6151, AL6162, AL6205, AL6262, AL6351 , AL6463, AL7005, AL7022, AL7068, AL7072, AL7075, AL7079, AL7116, AL7129, AL7175, AL7475, AL7178, or combinations thereof.

[0068] In an example, fabricating protrusions on a first metal substrate, 302, may be carried out by a CNC process. The CNC process may be carried out at a rotation speed of from about 3000 rpm to about 90,000 rpm for a period of from about 5 minutes to about 25 minutes. In another example, fabricating protrusions on a first metal substrate, 302, may be carried out by a thermal molding process. The thermal molding process may be carried out a temperature of from about 500 °C to about 900 °C at a pressure of from about 700 psi to about 1000 psi. In yet another example, fabricating protrusions on a first metal substrate, 302, may be carried out by die-casting or thixo-molding process. The thixo-molding process may be carried out a temperature of from about 350 °C to about 750 °C at a pressure of from about 2000 psi to about 20,000 psi. In some examples, fabricating protrusions on a first metal substrate, 302, may be carried out by an anodization process. The protrusions fabricated by the above mentioned processes lead to the formation of a protruded metal substrate, wherein the protrusions may have various shapes and sizes. In an example, the protrusions may have size of from about 0.2 to about 1.5 mm.

[0069] The first metal substrate on to which protrusions are fabricated may have a varied thickness in an example of the present disclosure. In one example, the first metal substrate may have a thickness of from about 0.3 mm to about 2.0 mm. In another example, the first metal substrate may have a thickness of from about 0.4 mm to about 1.9 mm. In yet another example, the first metal substrate may have a thickness of from about 0.5 mm to about 1.8 mm. In some examples, the first metal substrate may have a thickness of about 0.7 mm. [0070] The protruded metal substrate may be cleaned, dried, washed, polished, degreased, and activated. The cleaning and washing may be performed using a buffer solution, which may help in removing foreign particles, if any, present on the surface of the protruded metal substrate. Further, the protruded metal substrate may be chemically polished using abrasives to remove irregularities that may be present on the surface of the protruded metal substrate. The protruded metal substrate may also be degreased through ultrasonic degreasing methods to remove impurities, such as fat, grease, or oil from the surface of the protruded metal substrate. Further, the protruded metal substrate may also be activated through acid treatment for removing the natural oxide layer, if any, present on the surface of the protruded metal substrate.

[0071] As shown by block 304, of Fig. 3, a thermally formed second metal substrate may be disposed on to the protruded metal substrate to obtain a base frame. Disposing a thermally formed second metal substrate on to the protruded metal substrate may be carried out by superplastic forming process. The superplastic forming process may be carried out at an operating temperature of from about 300 °C to about 650 °C and a pressure of from about 60 kg/cm² to about 180 kg/cm². In another example, superplastic forming process may be carried out at an operating temperature of from about 400 °C to about 600 °C and a pressure of from about 65 kg/cm² to about 170 kg/cm². In yet another example, superplastic forming process may be carried out at an operating temperature of from about 450 °C to about 550 °C and a pressure of from about 65 kg/cm² to about 150 kg/cm².

[0072] In an example, disposing a thermally formed second metal substrate on to the protruded metal substrate results in the formation of a base frame. In an example, the base frame may have a thickness of from about 0.3 mm to about 2.0 mm. In another example, the base frame may have a thickness of from about 0.4 mm to about 1.9 mm. In yet another example, the base frame may have a thickness of from about 0.5 mm to about 1.8 mm. In some examples, the base frame may have a thickness of about 0.7 mm.

[0073] In an example, the second metal substrate is a magnesium alloy- based substrate, and may be selected from AZ61, AZ81 , AZ91 , AM50, AM60, AZ31, AZ63, AZ80, AE44, AJ62A, ALZ391 , AMCa602, LZ9, or combinations thereof.

[0074] As per the block, 306 of Fig. 3, the base frame may be machined to provide shape to the base frame. Providing shape to the base frame may result in the formation of a pre-enclosure. In an example, providing shape to the base frame may be carried out CNC process. In another example, the CNC process may be carried out with a CNC diamond cutting machine at speed of from about 5000 to about 90000 rpm for a period in a range of from about 3 to about 8 minutes. In yet another example, the CNC process may be carried out with a CNC diamond cutting machine at speed of from about 6000 to about 80000 rpm. [0075] The method 300, for forming an enclosure for an electronic device comprises depositing a passivation layer on to the pre-enclosure to obtain a passivated pre-enclosure. Block 308 of Fig. 3 includes depositing a passivation layer on to the pre-enclosure by a process selected from chemical passivation treatment, electro-chemical passivation treatment, or combinations thereof. Prior to depositing a passivation layer on to pre-enclosure, the pre-enclosure may be cleaned, degreased, neutralized, washed, and dried so as to remove the oil and dirt. In an example, the cleaning may be carried out in the presence of at least one aqueous alkaline compound, such as sodium hydroxide. The degreasing may be carried out by ultrasonic degreasing methods to remove impurities, such as fat, grease, or oil from the surface of the pre-enclosure.

[0076] Post treating the pre-enclosure, a passivation layer may be deposited on the pre-enclosure to obtain a passivated enclosure. In an example, depositing the passivation layer may be carried out by electro-chemical passivation treatment. The electro-chemical passivation treatment is a micro-arc oxidation process which may be carried out at a voltage of from about 150 V to about 550 V at a temperature of from about 10 °C to about 45°C for a period of from about 2 minutes to about 25 minutes. In another example, the deposition of the passivation layer may be carried out by micro-arc oxidation carried out at a voltage of from about 250 V to about 450 V at a temperature of from about 12 °C to about 42°C for a period of from about 5 minutes to about 22 minutes. In an example, the passivation layer formed by micro-arc oxidation may have a thickness of from about 1 μm to about 15 μm. In another example, the passivation layer formed by micro-arc oxidation may have a thickness of from about 3 μηη to about 12 μm. In yet another example, the passivation layer formed by micro-arc oxidation may have a thickness of from about 3 μm to about 7 μm.

[0077] In an example, depositing the passivation layer on to the pre- enclosure carried out by electro-chemical passivation treatment may be carried out in the presence of at least one chemical selected from sodium silicate, metal phosphates, potassium fluoride, potassium hydroxide, sodium hydroxide, fluoro- zirconates, sodium hexametaphosphate, sodium fluoride, ferric ammonium oxalate, phosphoric acid salt, graphite powder, silicon dioxide powder, aluminum oxide powder, and combinations thereof. In an example, the chemical may be employed at a dosage of from about 0.05% to about 15% in the presence of water at a pH of from about 9.0 to about 13. In another example, the chemical may be employed at a dosage of from about 0.1% to about 12% in the presence of water at a pH of from about 9.0 to about 12.0.

[0078] In another example, depositing a passivation layer on to the pre- enclosure, 308 may be carried out by a process of dip coating for a period of from about 20 seconds to about 120 seconds. In yet another example, depositing a passivation layer on to the pre-enclosure, 308 may be carried out by a process of dip coating for a period of from about 30 seconds to about 120 seconds. In an example, the passivation layer obtained by the process of dip coating may have a thickness of from about 1 μm to about 5 μm. In another example, the passivation layer obtained by the process of dip coating may have a thickness of from about 1.5 μm to about 3.0 μm.

[0079] In an example, the dip coating may be carried out in the presence of at least one salt of manganese, molybdates, vanadate, phosphate, chromate, stannate, and combinations thereof. In an example, the at least one salt may be manganese. In an example, the salt may be dispersed in the form of an aqueous solution having a concentration of from about 3% to about 15% based on total weight of the aqueous solution. In another example, the salt may be dispersed in the form of an aqueous solution having a concentration of from about 5% to about 12% based on total weight of the aqueous solution. [0080] The method for forming an enclosure for an electronic device, as illustrated in Fig. 3, further comprises coating at least one protective layer on to the passivated pre-enclosure, 310. In an example, coating at least one protective layer on to the passivated pre-enclosure may result in the formation of coated pre-enclosure. In an example, the coating of the protective layer may be carried out by spray coating.

[0081] In an example, the at least one protective layer may have a thickness of from about 5.0 μm to about 70.0 μm. In another example, the protective layer may have a thickness of from about 10.0 μm to about 68.0 μm. In yet another example, the protective layer may have a thickness of from about 10.0 μm to about 65.0 μm.

[0082] The coating of at least one protective layer on to the passivated pre- enclosure carried out by spray coating, may be carried out in a manner, whereby the protective layer thus formed may comprise multiple layers, such as primer, base coat, and top coat. In an example, the spray-coated protective layer comprises sequentially deposited coats of primer coat having a thickness of from about 5.0 μm to about 20.0 μm, followed by base coat having a thickness of from about 10.0 μm to about 20.0 μm, followed by top coat having a thickness of from about 10.0 μm to about 25.0 μm.

[0083] The passivated pre-enclosure may be cleaned, degreased, washed, and dried prior to the coating of at least one protective layer. The protective layer may comprise primer, either alone or in combination with additional layers. The primer may also be applied as single or multiple coats to achieve the desired thickness and finish. In an example, the primer may have a thickness of from about 5.0 μm to about 20.0 μm. In another example, the primer may have a thickness of from about 8.0 μm to about 18.0 μm. In yet another example, the primer may have a thickness of about 12.0 μm.

[0084] In an example, the primer may be coated on the pre-enclosure or the passivated pre-enclosure by spray coating polyurethanes followed by heat treatment at a temperature of from about 60 °C to about 80 °C for a period of from about 15 to about 40 minutes. In another example, the primer may be coated by spray coating polyurethane followed by heat treatment at a temperature of from about 62 °C to about 78 °C for a period of from about 18 to about 38 minutes. In yet another example, the primer may be coated by spray coating thermoplastics, such as polyurethanes followed by heat treatment at a temperature of about 70 °C for a period of about 25 minutes.

[0085] The at least one protective layer may comprise a base coat, in combination with additional layers. The base coat may also be applied as single or multiple coats to achieve the desired thickness and finish. In an example, the base coat may have a thickness of from about 10.0 μm to about 20.0 μm. In another example, the base coat may have a thickness of from about 12.0 μm to about 18.0 μm. In yet another example, the base coat may have a thickness of about 15.0 μm. In an example, the base coat may be a polyurethane containing pigments selected from carbon black, titanium dioxide, clay, mica, talc, barium sulfate, calcium carbonate, aluminum powder, plastic bead, dyes, and combinations thereof. In an example, the spray-coated base coat comprises polyurethane containing carbon black. In another example, the spray-coated base coat comprises polyurethane containing titanium dioxide. In yet another example, the spray-coated base coat comprises polyurethane containing clay.

[0086] In another example, the base coat coated by spray coating may be followed by heat treatment at a temperature of from about 60 °C to about 80 °C for a period of from about 15 to about 40 minutes. In another example, the base coat coated by spray coating may be followed by heat treatment at a temperature of from about 62 °C to about 78 °C for a period of from about 18 to about 38 minutes. In yet another example, the base coat coated by spray coating may be followed by heat treatment at a temperature of about 70 °C for a period of about 25 minutes. [0087] The at least one protective layer may comprise top coat, in combination with additional layers. The top coat may also be applied as single or multiple coats to achieve the desired thickness and finish.

[0088] In an example, the top coat may have a thickness of from about 10.0 μm to about 25.0 μm. In another example, the top coat may have a thickness of from about 12.0 μm to about 22.0 μm. In yet another example, the top coat may have a thickness of about 17.0 μm. [0089] In an example, the top coat may be made of polyacrylic acid, polyurethane, urethane acrylates, acrylic acrylates, epoxy acrylates, or combinations thereof. In another example, the top coat may be made of polyacrylic acid. In yet another example, the top coat may be made of polyurethane. In some examples, the top coat may be made of urethane acrylates.

[0090] In an example, the top coat coated by spray coating may be followed by UV treatment of from about 700 mJ/cm² to about 1200 mJ/cm² for a period of from about 10 seconds to about 30 seconds. In another example, the top coat coated by spray coating may be followed by UV treatment of from about 800 mJ/cm² to about 1100 mJ/cm² for a period in a range of from about 15 seconds to about 25 seconds. In yet another example, the top coat coated by spray coating may be followed by UV treatment of about 950 mJ/cm² for a period of about 20 seconds.

[0091] In some examples, the top coat coated by spray coating a polyurethane may be followed by heat treatment at a temperature of from about 60 °C to about 80 °C for a period of from about 15 to about 40 minutes. In another example, the top coat coated by spray coating may be followed by heat treatment at a temperature of from about 62 °C to about 78 °C for a period of from about 18 to about 38 minutes. In yet another example, the top coat coated by spray coating may be followed by heat treatment at a temperature of about 70 °C for a period of about 25 minutes.

[0092] The coated pre-enclosure may have defects, and in order to eliminate the defects and give the edges of the portions of the coated pre- enclosure, a more even surface with improved strength, they may be chamfered. Block 312, of Fig. 3, shows that at least a portion of the coated pre-enclosure may be chamfered. In an example, the method for forming an enclosure for an electronic device 300, comprises chamfering at least a portion of the coated pre- enclosure to obtain a chamfered pre-enclosure. The chamfering may be carried out at portions, such as cover edge, touch pad, fingerprint scanner, click pad, side wall, logo area, among others. The chamfering involves abrasive removal of edge material that may give it the desired finishing and also shape its form. In an example, chamfering may be carried out by a CNC diamond cutting machine. In another example, the chamfering may be carried out with a CNC diamond cutting machine at speed of from about 5000 to about 90000 rpm for a period in a range of from about 3 to about 8 minutes. In yet another example, the chamfering may be carried out with a CNC diamond cutting machine at speed of from about 6000 to about 80000 rpm.

[0093] The chamfered pre-enclosure may be cleaned, degreased, washed and dried, prior to passivating the chamfered pre-enclosure, 314. In an example, the cleaning may be carried out in the presence of at least one aqueous alkaline compound, such as sodium hydroxide. The degreasing may be carried out by ultrasonic degreasing methods to remove impurities, such as fat, grease, or oil from the surface of the chamfered pre-enclosure.

[0094] Further, the chamfered pre-enclosure may be passivated to obtain an enclosure, i.e., passivating the chamfered pre-enclosure by a transparent passivation treatment. process selected from transparent passivation, sealing, electrophoretic deposition, or combinations thereof to obtain an enclosure. In an example, the transparent passivation treatment may be carried out in the presence of transparent chemicals selected from ethylenediaminetetraacetic acid (EDTA), ethylenediamine, nitrilotriacetic acid (NTA), diethylenetriaminepenta(methylenephosphonic acid) (DTPPH) nitrilotris(methylenephosphonic acid) (NTMP), 1 -hydroxyethane-1 , 1 - diphosphonic acid (HEDP), phosphoric acid, and salts thereof to obtain a transparent passivation layer. In an example, the transparent passivation treatment may be done throughout the surface of the chamfered pre-enclosure. In another example, the transparent passivation treatment may be done at the exposed surface post immersing in transparent chemicals. In an example, the transparent chemical concentration may be of from about 1 wt % to about 10 wt % based on the total concentration. In an example, the transparent chemical concentration may be of from about 2 wt % to about 8 wt % based on the total concentration. In yet another example, the transparent chemical concentration may be 6 wt % based on the total concentration. In an example, the transparent passivation treatment may be carried out by immersing in a chemical bath at a temperature of from about 20 °C to about 40 °C for a period of from about 30 seconds to about 180 seconds.

[0095] In another example, the transparent passivation treatment may be carried out in the presence of transparent chemical, such as ethylenediaminetetraacetic acid (EDTA), and salts thereof. In another example, the transparent chemical may be selected from zinc (II) EDTA complex or nickel (II) EDTA complex. In an example, the transparent passivation layer obtained by bloc 314, may have a thickness of from about 0.03 μm to about 1 μm. In another example, the transparent passivation layer may have a thickness of from about 0.05 μm to about 0.8 μm. In another example, the transparent passivation layer may have a thickness of from about 0.1 μm to about 0.6 μm. In some examples, the transparent passivation layer may have a thickness of about 0.5 μm. The transparent passivation layer helps to preserve the glossy finish.

[0096] Block 316 of Fig. 3 shows depositing a sealinl layer on the chamfered pre-enclosure. The chamfered pre-enclosure may be treated with transparent chemicals to deposit a transparent passivation layer on to the chamfered pre- enclosure. In an example, the transparent passivation layer may be deposited throughout the surface of the pre-enclosure. In another example, the transparent passivation layer may be deposited on to the chamfered portions, such as cover edge, touch pad, click-pad, fingerprint scanner, edge, or sidewall, logo area, and the like.

[0097] In an example, the sealing may be carried out in the presence of a compound selected from aluminum fluoride, nickel fluoride, cerium fluoride, cerium acetate, aluminum acetate, nickel acetate, or combinations thereof. In another example, the sealing may be carried out in the presence of aluminum fluoride. In yet another example, the sealing may be carried out in the presence of nickel fluoride. In an example, the compound may be utilized in the form of an aqueous dispersion further comprising a surfactant having a strength of about 0.1 % to about 2.0 % with respect to the dispersion. Post sealing, a process of baking may be carried out., wherein baking may be carried out at a temperature in the range of from about 60 °C to about 90 °C for a period in the range of about 15 seconds to about 180 seconds. In an example, the baking may be carried out at a temperature in the range of from about 62 *C to about 88 °C for a period in the range of about 30 seconds to about 60 seconds. In another example, the baking may be carried out at a temperature of 70 °C for a period of 45 seconds. In an example, the sealing layer thus obtained may have a thickness of about 1.0 μm to about 3.0 μm. In another example, the sealing layer may have a thickness of about 1.2 μm to about 2.8 μm. Post the deposition of the sealing layer, an electrophoretic deposition layer may be deposited on the sealing layer. The electrophoretic deposition may be carried out in the presence of at least one dyeto provide a multi-colored finish to the pre-enclosure. In an example, pre-enclosure is a keyboard having a first color at the base and a second color at the fingerprint scanner area and a third color at the touch pad area. In an example, an electrophoretic deposition may be carried out subsequent to the formation of the sealing layer to introduce colors and to provide aesthetically improved finish. The thickness of the ED layer achieved maybe directly related to the potential applied and time for the electrophoretic deposition. In an example, the electrophoretic deposition may be carried out by applying a potential of from about 30 to about 150 V for a period of from about 20 to about 120 seconds. In another example, the electrophoretic deposition may be carried out by applying a potential of from about 50 to about 130 V for a period of from about 20 to about 100 seconds. In another example, the electrophoretic deposition may be carried out by applying a potential of about 120 V for a period of about 80 seconds.

[0098] In an example, the ED layer deposited by electrophoretic deposition may comprise various dyes selected from red dye, blue dye, orange dye, yellow dye: Quinoline Yellow WS to obtain different colors at portions, such as cover edge, touch pad, fingerprint scanner, click pad, side wall, logo area, among others. In an example, to obtain red colored in the ED layer, a red dye may be used and may be selected from Alexa Fluor 594 dye, or Texas Red. In another example to obtain red color, a pigment may be used, such as pigment Red 168 MF. In an example to obtain blue colored finish in the ED layer, a blue dye may be used, such as Pacific Blue dye. In an example, to obtain orange colored finish in the ED layer, an orange dye may be used, such as Pacific Orange. In an example, to obtain yellow colored finish in the ED layer a yellow dye may be used, such as quinoline yellow WS. In another example, to obtain yellow color, a pigment may be used, such as Pigment Yellow 191.

[0099] The method as described hereinabove for the method for forming an enclosure of Fig. 3, may be applied conveniently for forming enclosures for a range of electronic devices, such as keyboards, laptops, tablets, mobile phones, among others.

[00100] In an example, the method for forming an enclosure as illustrated in Fig. 3 may provide an enclosure having a tensile strength of from about 200 MPa to about 700 MPa as measured by American Society for Testing and Materials (ASTM) D790. In another example, the enclosure may have a tensile strength of from about 250 MPa to about 600 MPa as measured by American Society for Testing and Materials (ASTM) D790. In yet another example, the enclosure may have a tensile strength of from about 350 MPa to about 600 MPa as measured by American Society for Testing and Materials (ASTM) D790.

[00101] A method for forming an enclosure for an electronic device as illustrated in Fig. 1 or Fig. 2 or Fig. 3, results in the formation of an enclosure, 400. A 3D-sectional view of the enclosure comprising a first metal substrate 402, a second metal substrate 404, at least one passivation layer 406, at least one protective layer 408, at least one transparent passivation layer 410, and at least one sealing layer 412 is illustrated in Fig. 4. In an example, the layering the enclosure may be such that the second metal substrate 404, may be deposited on the first metal substrate 402, to obtain a pre-enclosure/base frame. A passivation layer 406, may be deposited on the pre-enclosure to form a passivated pre-enclosure. In an example, the passivation layer may be deposited on the second metal substrate 404. A protective layer 408, may be deposited on the passivated pre-enclosure to form a protected pre-enclosure. In an example, the protective layer 408, may be deposited on the passivation layer 406. Further, a transparent passivation layer 410, may be deposited on the protected pre- enclosure. In an example, the transparent passivation layer may be deposited on the protective layer. Additionally, a sealing layer 412, may be deposited on the protective layer, followed by depositing a finishing layer to obtain the enclosure. [00102] The enclosure may comprise: a first metal substrate having a thickness of from about 0.3 mm to about 2.0 mm; a second metal substrate having a thickness of from about 0.3 mm to about 2.0 mm; at least one passivation layer having a thickness of from about 1 μm to about 15 μm; at least one protective layer having a thickness of from about 5 μm to about 65 μm; at least one transparent passivation layer having a thickness of from about 30 nm to about 3 μm; and at least one sealing layer having a thickness of from about 1 μm to about 3 μm.

[00103] In an example, the first metal substrate 402, and the second metal substrate 404, may together form a pre-enclosure. The first metal substrate 402, may be an aluminum alloy-based substrate, and the aluminum alloy-based substrate may be selected from AL575, AL1050, AL1060, AL1100, AL1199, AL2014, AL2024, AL2219, AL3004, AL4041 , AL5005, AL5010, AL5019, AL5024, AL5026, AL5050, AL5052, AL5056, AL5059, AL5083, AL5086, AL5154, AL5182, AL5252, AL5254, AL5356, AL5454, AL5456, AL5457, AL5557, AL5652, AL5657, AL5754, AL6005, AL6005A, AL6060, AL6061 , AL6063, AL6066, AL6070, AL6082, AL6105, AL6151, AL6162, AL6205, AL6262, AL6351, AL6463, AL7005, AL7022, AL7068, AL7072, AL7075, AL7079, AL7116, AL7129, AL7175, AL7475, AL7178, or combinations thereof. In one example, the first metal substrate may have a thickness of from about 0.3 mm to about 2.0 mm. In another example, the first metal substrate may have a thickness of from about 0.4 mm to about 1.9 mm. In yet another example, the first metal substrate may have a thickness of from about 0.5 mm to about 1.8 mm. In some examples, the first metal substrate may have a thickness of about 0.7 mm.

[00104] In an example, the second metal substrate, 404 may be present on the first metal substrate 402. In an example, the second metal substrate is a magnesium alloy-based substrate, and may be selected from AZ61 , AZ81 , AZ91 , AM50, AM60, AZ31 , AZ63, AZ80, AE44, AJ62A, ALZ391, AMCa602, LZ9, or combinations thereof. In an example, the second metal substrate may have a thickness of from about 0.3 mm to about 2.0 mm. In another example, the second metal substrate may have a thickness of from about 0.4 mm to about 1.9 mm. In yet another example, the second metal substrate may have a thickness of from about 0.5 mm to about 1.8 mm. In some examples, the second metal substrate may have a thickness of about 0.7 mm.

[00105] In an example, the presence of the second metal substrate 404, on to the first metal substrate 402, renders the base frame/pre-enclosure mechanically stable. The base frame/pre-enclosure, may as a consequence has enhanced tensile strength owing to the disposition of the thermally formed second metal substrate on to the first metal substrate.

[00106] In an example, base frame/pre-enclosure may have a thickness of from about 0.3 to 2.0 mm. In another example, the base frame/pre-enclosure may have a thickness of from about 0.5 to 1.8 mm. In yet another example, the base frame/pre-enclosure may have a thickness of 0.7 mm.

[00107] Enclosure 400, provided in Fig. 4 includes at least one passivation layer, 406, which may be deposited on the base frame/pre-enclosure. In an example, the passivation layer may be deposited by a micro-arc oxidation process or may be deposited by a dip coating process.

[00108] In the case of micro-arc oxidation process, the passivation layer, 406, may have a thickness of from about 2 μm to about 15 μm. In another example, the passivation layer deposited by micro-arc oxidation may have a thickness of from about 3 μm to about 12 μm. In yet another example, the passivation layer deposited by micro-arc oxidation may have a thickness of from about 3 μm to about 7 μm.

[00109] In an example, when the passivation layer, 406, is deposited by a dip- coating process, the passivation layer, 406, may have a thickness of from about 1 μm to about 5 μm. In another example, the passivation layer obtained by the process of dip coating may have a thickness of from about 1 .5 μm to about 3.0 μm.

[00110] The enclosure, 400, may comprise at least one protective layer 408, onto the at least one passivated layer 406. In an example, the protective layer may have a thickness of from about 5.0 μm to about 70.0 μm. In another example, the protective layer may have a thickness of from about 10.0 μm to about 68.0 μm. In yet another example, the protective layer may have a thickness of from about 10.0 μm to about 65.0 μm. [00111] In another example, the at least one protective layer may be a single layer or may comprise multiple layers, such as primer coat, base coat, and top coat.

[00112] In an example, the at least one protective layer comprises sequentially a primer coat having a thickness of from about 5.0 μm to about 20.0 μm, a base coat having a thickness of from about 10.0 μm to about 20.0 μm, and a top coat having a thickness of from about 10.0 μm to about 25.0 μm.

[00113] The protective layer may comprise primer, either alone or in combination with additional layers. The primer may also be applied as single or multiple coats to achieve the desired thickness and finish. In an example, the primer may have a thickness of from about 5.0 μm to about 20.0 μm. In another example, the primer may have a thickness of from about 8.0 μm to about 18.0 μm. In yet another example, the primer may have a thickness of about 12.0 μm.

[00114] The protective layer may comprise a base coat, in combination with additional layers. The base coat may also be applied as single or multiple coats to achieve the desired thickness and finish. In an example, the base coat may have a thickness of from about 10.0 μm to about 20.0 μm. In another example, the base coat may have a thickness of from about 12.0 μm to about 18.0 μm. In yet another example, the base coat may have a thickness of about 15.0 μm.

[00115] The protective layer may comprise top coat, in combination with additional layers. The top coat may also be applied as single or multiple coats to achieve the desired thickness and finish. In an example, the top coat may have a thickness of from about 10.0 μm to about 25.0 μm. In another example, the top coat may have a thickness of from about 12.0 μm to about 22.0 μm. In yet another example, the top coat may have a thickness of about 17.0 μm.

[00116] The enclosure 400 of Fig. 4, further comprises transparent passivation layer 410. In an example, the transparent passivation layer may have a thickness of from about 0.03 μm to about 1 μm. In another example, the transparent passivation layer may have a thickness of from about 0.05 μm to about 0.8 μm. In another example, the transparent passivation layer may have a thickness of from about 0.1 μm to about 0.6 μm. In another example, the transparent passivation layer may have a thickness of about 0.5 μm. The transparent passivation layer helps to preserve the glossy finish.

[00117] Enclosure 400 of Fig. 4, may comprise a sealing layer 412, on the transparent passivation layer 410. In an example, the sealing layer may have a thickness of about 1.0 μm to about 3.0 μm. In another example, the sealing layer may have a thickness of about 1.2 μm to about 2.8 μm.

[00118] In an example, the transparent passivation layer 410, and sealing layer 412, may be present individually on the chamfered portions selected from the group consisting of cover edge, touch pad, fingerprint scanner, click pad, side wall, logo area, and combinations thereof. In another example, the transparent passivation layer 410, and sealing layer 412, may be present throughout the surface of the base-frame/pre-enclosure.

[00119] In an example, the enclosure 400, may comprise at least one finishing layer having a thickness of from about 5 μm to about 40 μm. In an example, the finishing layer may have a thickness of from about 6 μm to about 30 μm. In yet another example, the finishing layer may have a thickness of from about 8 μm to about 20 μm. The finishing layer may be a layer deposited by an electrophoretic deposition process. The finishing layer may provide a multi-colored finish to the enclosure. In an example, to obtain red colored in the finishing layer, a red dye may be used and may be selected from Alexa Fluor 594 dye, or Texas Red. In another example to obtain red color, a pigment may be used, such as pigment Red 168 MF. In an example to obtain blue colored finish in the finishing layer, a blue dye may be used, such as Pacific Blue dye. In an example, to obtain orange colored finish in the finishing layer, an orange dye may be used, such as Pacific Orange. In an example, to obtain yellow colored finish in the finishing layer a yellow dye may be used, such as quinoline yellow WS. In another example, to obtain yellow color, a pigment may be used, such as Pigment Yellow 191. [00120] The enclosure 400, may reveal an enhanced gloss value of from about 80 to about 95 units as measured by American Society for Testing and Materials (ASTM) D523 at a viewing angle of about 60°. In another example, the enclosure 400, may reveal a gloss value of from about 82 to about 93 units. In yet another example, the enclosure 400, may reveal a gloss value of about 92 units. [00121] In an example, the enclosure 400, may have a tensile strength of from about 200 MPa to about 700 MPa as measured by American Society for Testing and Materials (ASTM) D790. In another example, the enclosure, 400, a tensile strength of from about 250 MPa to about 600 MPa as measured by American Society for Testing and Materials (ASTM) D790. In yet another example, the enclosure, 400, a tensile strength of from about 350 MPa to about 600 MPa as measured by American Society for Testing and Materials (ASTM) D790.

[0001] In an example, the enclosure of the present disclosure may be employed for electronic devices, such as keyboards, tablets, mobile phones, smartwatches, laptops, and the like. In another example, the enclosure 400 may be used as body or frame for keyboards of computer or laptops.

[0002] Although examples for the present disclosure have been described in a language specific to structural features and/or methods, it is to be understood that the appended claims are not limited to the specific features or methods described herein. Rather, the specific features and methods are disclosed and explained as examples of the present disclosure.

Claims

We Claim:

1) A method for forming an enclosure of an electronic device, the method comprising: fabricating protrusions on an aluminum alloy-based substrate; stamping a thermally formed magnesium alloy-based substrate on to the aluminum alloy-based substrate to obtain a pre-enclosure; chamfering a portion of the pre-enclosure to obtain a chamfered pre- enclosure and, treating the chamfered pre-enclosure to obtain the enclosure.

2) The method as claimed in claim 1 , wherein fabricating protrusions on the aluminum alloy-based substrate is carried out by a process selected from CNC process, thermal molding process, thixo-molding, or anodization process.

3) The method as claimed in claim 1 , wherein stamping the thermally formed magnesium alloy-based substrate on to the aluminum alloy-based substrate is carried out at a temperature of from about 20 °C to about 250 °C at a pressure of from about 2 kg/cm² to about 150 kg/cm².

4) The method as claimed in claim 1 , wherein chamfering the portion of the pre-enclosure is carried out by a CNC diamond cutting machine.

5) The method as claimed in claim 1 , wherein treating the chamfered pre- enclosure is carried out by a process selected from transparent passivation, sealing, electrophoretic deposition, or combinations thereof

6) A method for forming an enclosure of an electronic device, the method comprising:

(a) fabricating protrusions on a first metal substrate to obtain a protruded metal substrate;

(b) disposing a thermally formed second metal substrate on to the protruded metal substrate to obtain a base frame;

(c) providing shape to the base frame to obtain a pre-enclosure;

(d) depositing a passivation layer on to the pre-enclosure to obtain a passivated pre-enclosure; (e) coating at least one protective layer on to the passivated pre-enclosure to obtain a coated pre-enclosure;

(f) chamfering at least a portion of the coated pre-enclosure to obtain a chamfered pre-enclosure; and

(g) passivating the chamfered pre-enclosure to obtain the enclosure.

7) The method as claimed in claim 6, wherein the first metal substrate is an aluminum alloy-based substrate, and the second metal substrate is a magnesium alloy-based substrate.

8) The method as claimed in claim 6, wherein disposing the thermally formed second metal substrate on to the protruded metal substrate is carried out by superplastic forming process.

9) The method as claimed in claim 6, wherein depositing the passivation layer on to the pre-enclosure is carried out by a process selected from chemical passivation treatment, electro-chemical passivation treatment, or combinations thereof.

10) The method as claimed in claim 6, wherein coating the at least one protective layer on to the passivated pre-enclosure by spray coating to obtain a coated pre-enclosure.

11) The method as claimed in claim 6, wherein passivating the chamfered pre- enclosure is carried out in presence of transparent chemicals selected from ethylenediaminetetraacetic acid (EDTA), ethylenediamine, nitrilotriacetic acid (NTA), diethylenetriaminepenta(methylenephosphonic acid) (DTPPH) and nitrilotris(methylenephosphonic acid) (NTMP), 1- hydroxyethane-1,1-diphosphonic add (HEDP), phosphoric acid, or salts thereof to obtain the enclosure.

12) The method as claimed in claim 6, comprises depositing the sealing layer on the chamfered pre-enclosure followed by electrophoretic deposition prior to obtaining the enclosure.

13) An enclosure for an electronic device, the enclosure comprising:

(a) a first metal substrate having a thickness of from about 0.3 mm to about 2.0 mm; (b) a second metal substrate having a thickness of from about 0.3 mm to about 2.0 mm;

(c) at least one passivation layer having a thickness of from about 1 pm to about 15 pm;

(d) at least one protective layer having a thickness of from about 5 pm to about 65 pm;

(e) at least one transparent passivation layer having a thickness of from about 0.03 pm to about 3 pm; and

(f) at least one sealing layer having a thickness of from about 1 pm to about 3 pm.

14) The enclosure as claimed in claim 13, comprises at least one finishing layer having a thickness of from about 5 pm to about 40 pm.

15) The enclosure as claimed in claim 13, wherein the enclosure exhibits a tensile strength of from about 200 MPa to about 700 MPa.