Abstract:
A housing having a coating is disclosed. The housing comprises a base substrate made of metallic material; a micro-arc oxide layer formed on the base substrate; and a protection outer film formed on the micro-arc oxide layer and comprising a coating layer and a metallic layer, wherein the metallic layer is formed on the micro-arc oxide layer and covers a portion of the micro-arc oxide layer; and the coating layer is formed on a remaining portion of the micro-arc oxide layer so that the micro-arc oxide layer is covered by the metallic layer and the coating layer.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present disclosure generally relates to housings, and particularly to a housing having a coating and a method for manufacturing the housing. 
         [0003]    2. Description of Related Art 
         [0004]    To make the electronic devices more fashionably and aesthetically appealing to users, housings of portable electronic devices may be decorated or coated to form a decorative layer on the corresponding outer surfaces. In addition, a logo may be often formed on the housing of the electronic device to distinguish it from other electronic devices. The logo may be often made of metallic materials and be adhered to the decorative layer of the housing directly. However, the logo may be easily peeled off from the housing, after the electronic device has been used for a long time. 
         [0005]    Therefore, there is room for improvement within the art. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout several views, and all the views are schematic. 
           [0007]      FIG. 1  shows a cross-sectional view of a housing according to a first embodiment of the present disclosure. 
           [0008]      FIG. 2  shows a cross-sectional view of a housing according to a second embodiment of the present disclosure. 
           [0009]      FIG. 3  is a flowchart of manufacturing processes of the housing in  FIG. 2 . 
           [0010]      FIG. 4  shows a cross-sectional view of a preformed housing obtained during the manufacturing processes. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    Referring to  FIG. 1 , a first embodiment of a housing  10  comprises a base substrate  12  made of metallic materials, a micro-arc oxide layer  14  formed on the base substrate  12 , and a protection outer film  16  formed on the micro-arc oxide layer  14 . The protection outer film  16  comprises a coating layer  162  and a metallic layer  164 . The metallic layer  164  is formed on the micro-arc oxide layer  14  and covers a portion of the micro-arc oxide layer  14 . The coating layer  162  is formed on a remaining portion of the micro-arc oxide layer  14 . The coating layer  162  and the metallic layer  164  cover the micro-arc oxide layer  14 . 
         [0012]    In the illustrated embodiment, the metallic layer  164  is formed on a substantially central portion of the micro-arc oxide layer  14 . The coating layer  162  is formed on a remaining portion of the micro-arc oxide layer  14  and surrounds the metallic layer  164 . The base substrate  12  is made of magnesium alloy. A thickness of the coating layer  162  is in a range from about 5 μm to about 10 μm. A thickness of the metallic layer  164  is in a range from about 1 μm to about 40 μm. The metallic layer  164  may be designed as a decorative pattern or a logo icon. 
         [0013]    The base substrate  12  may be made of metallic materials such as magnesium, aluminum, titanium, for example, or alloys such as aluminum alloy, magnesium alloy, titanium alloy, or any other suitable alloys. The coating layer  162  may be a paint layer, a printed ink layer, or a vacuum coating formed on the micro-arc oxide layer  14 . The coating layer  162  may comprise one, two, or more than two layers. 
         [0014]    Referring to  FIG. 2 , a second embodiment of a housing  20  is shown. The housing  20  has a shape and a structure similar to that of the housing  10  of the first embodiment. The housing  20  comprises a metallic base substrate  22 , a micro-arc oxide layer  24  formed on the base substrate  22 , and a protection outer film  26  formed on the micro-arc oxide layer  24 . The protection outer film  26  comprises a coating layer  262  and a metallic layer  264 . The difference between the housing  20  and the housing  10  is that, in housing  20 , the metallic layer  264  is a two-layered structure. The metallic layer comprises a first metallic layer  2642 , and a second metallic layer  2644  formed on the first metallic layer  2642 . The first metallic layer  2642  is made of copper and has a thickness in a range from about 1 μm to about 40 μm. The second metallic layer  2644  is made of chromium and has a thickness in a range from about 0.1 μm to about 30 μm. 
         [0015]    The second metallic layer  2644  may also be made of gold, nickel, tin, cobalt, silver, platinum, rhodium, palladium or other metallic material. The metallic layer  264  may also be a multi-layered structure. 
         [0016]    Also referring to  FIG. 3 , an exemplary method for making the housing  20  comprises the following steps S 101  to S 115 : 
         [0017]    In step S 101 , a metallic base substrate  22  is provided. In the illustrated embodiment, the base substrate  22  is made of magnesium alloy. The base substrate  22  has a length about 50 mm, a width about 30 mm and a thickness about 1 mm. The base substrate  22  may go through a cleaning process prior to Step S 101  to keep the base substrate  22  clean. During the cleaning process, the base substrate  22  may be first cleaned by means of an ultrasonic cleaning process, a pickling process, an alkaline cleaning process, or a washing process, and then dried in a drying process. 
         [0018]    In step S 103 , the base substrate  22  is oxidized to form a micro-arc oxide layer  24  by electrolysis. In the illustrated embodiment, the micro-arc oxide layer  24  is a porous metal oxide ceramic film. The oxidation process is taken under a positive voltage in a range from about 300 to about 550 volts, a current density in a range from about 1 to about 9 amperes per square decimeter, and an oxidation time for about 3 to about 30 minutes, thereby forming the micro-arc oxide layer  24  on a surface of the base substrate  22 . A thickness of the micro-arc oxide layer  24  is in a range from about 1 μm to about 200 μm. 
         [0019]    In step S 105 , an electrophoresis layer  25  (see  FIG. 4 ) is formed on the micro-arc oxide layer  24  of the base substrate  22  by an electrophoresis coating process. In order to improve the conductivity of the micro-arc oxide layer  24  of the base substrate  22 , the oxidized base substrate  22  may be electroplated, sputtered, or sprayed with conductive paint prior to the step S 105 . In the illustrated embodiment, the base substrate  22  is immersed into an electrophoresis tank for receiving an electrophoresis coating, under a positive voltage in a range from about 25 to about 100 volts, and an electrophoresis time for about 30 to about 180 seconds, thereby forming the electrophoresis layer  25 . A thickness of the electrophoresis layer  25  is in a range from about 0.5 μm to about 15 μm. An electrophoresis paint used in S 105  may be selected from epoxy ester anode electrophoresis paint, a pure melt bond anode electrophoresis paint, a polybutadiene anode electrophoresis paint, a maleic anhydride oil anodic electrophoresis paint. 
         [0020]    In step S 107 , a portion of the electrophoresis layer  25  is removed, thereby forming a concavity  27  recessed from the electrophoresis layer  25  toward the micro-arc oxide layer  24 , to form a preformed housing  20   a  (see  FIG. 4 ). In the illustrated embodiment, the concavity  27  is formed by a ray carving process. The concavity  27  has a width about 3 mm and a length about 6 mm. A bottom of the concavity  27  is the micro-arc oxide layer  24 . 
         [0021]    In step S 109 , a first metallic layer  2642  is formed on the bottom micro-arc oxide layer  24  and positioned within the concavity  27  of the preformed housing  20   a . In the illustrated embodiment, the first metallic layer  2642  is made of copper material. A thickness of the first metallic layer  2642  is in a range from about 1 μm to about 40 μm. The first metallic layer  2642  may be formed on the micro-arc oxide layer  24  by the following sub-steps. First, alkalizing the preformed housing  20   a  by being immersed the preformed housing  20   a  into an alkaline liquid tank under room temperature for about 3-10 minutes. In one embodiment, the alkaline liquid is mixed with sodium tetrachloropalladate(II), 2-morpholinyl ethane sulfonic acid and sodium chloride, which, the density of the Sodium tetrachloropalladate(II) is about 0.05-0.3 g/L. Second, immersing the alkalized, preformed housing  20   a  into a sodium hydroxide solution with a density about 5-15 g/L for about 0.5-2 minutes. Third, immersing the preformed housing  20   a  a liquid mixture mixed by copper sulfate, sodium potassium tartrate, sodium hydroxide, sodium carbonate, formaldehyde and thiocarbamide, for about 3-10 minutes. In the illustrated embodiment, the density of the copper sulfate is 3.5-10 g/L, the density of the sodium potassium tartrate is about 30-50 g/L, the density of the sodium hydroxide is about 7-10 g/L, the density of the sodium carbonate is about 0-3 g/L, the density of the formaldehyde is about 10-15 ml/L, and the density of the thiocarbamide is about 7-10 g/L. Finally, electroplating a copper layer on the exposed micro-arc oxide layer  24  of the preformed housing  20   a . In the illustrated embodiment, the electroplating process of the copper layer is taken place under a temperature of about 50-60° C., and a current density in a range from about 0.5 to about 10 amperes per square decimeter. During the electroplating process, the preformed housing  20   a  is put into an electroplating tank filled with plating solution mixed by copper pyrophosphate and potassium pyrophosphate, and thereby forming the copper layer (namely the first metallic layer  2642 ) on the micro-arc oxide layer  24  of the preformed housing  20   a . A density of the copper pyrophosphate is about 70-100 g/L, and a density of the potassium pyrophosphate is about 300-400 g/L. A thickness of the copper layer is in a range from about 1 μm to about 40 μm. 
         [0022]    In step S 111 , a rest of the electrophoresis layer  25  of the preformed housing  20   a  is removed to expose the bottom micro-arc oxide layer  24 . In the illustrated embodiment, the rest of the electrophoresis layer  25  is removed by an electrophoresis paint remover. 
         [0023]    In step S 113 , a coating layer  262  is formed on the micro-arc oxide layer  24  and the first metallic layer  2642  of the preformed housing  20   a . In the illustrated embodiment, a thickness of the coating layer  262  is in a range from about 5 μm to about 10 μm. 
         [0024]    In step S 115 : the coating layer  262  formed on the first metallic layer  2642  of the preformed housing  20   a  is removed by a ray carving process and a second metallic layer  2644  is formed by electroplating process to cover the first metallic layer  2642 . In the illustrated embodiment, the second metallic layer  2644  is a decorative pattern or a logo icon. A thickness of the second metallic layer  2644  is in a range from about 0.1 μm to about 30 μm. The second metallic layer  2644  is made of gold, nickel, tin, cobalt, silver, platinum, rhodium, palladium or other metallic material. 
         [0025]    Since the protection outer film  16  of the housing  10  includes a coating layer  162  and a metallic layer  164 , the metallic layer  164  is firmly formed on a portion of the micro-arc oxide layer  14  by electroplating process, thereby preventing the metallic layer  164  from peeling or falling off the housing  10 . 
         [0026]    Finally, while various embodiments have been described and illustrated, the disclosure is not to be construed as being limited thereto. Various modifications can be made to the embodiments by those skilled in the art without departing from the true spirit and scope of the disclosure as defined by the appended claims.