Abstract:
A composite of metal and resin and a manufacturing method require a metal piece and a resin piece, and the surface of the metal piece is etched to include a number of micropores. Each micropore includes a first inclined hole and a second inclined hole, the first inclined hole and the second inclined hole diverging from each other below the surface of the metal piece. The first inclined hole and the second inclined hole extend downwards from a common starting hole which is symmetric around an axis perpendicular to the surface of the metal piece. The resin is embedded in the micropores to combine with the metal piece, where the bonding strength of the composite of metal and resin is increased.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application is a divisional application of U.S. patent application Ser. No. 14/515,935, filed on Oct. 16, 2014, which claims priority to Chinese Application No. 201310503354.3 filed on Oct. 24, 2013, the contents of which are entirely incorporated by reference herein. 
     
    
     FIELD 
       [0002]    This disclosure generally relates to a composite of metal and resin suitable for casings of electronic devices, housings of home electric appliances, structural components, machinery parts, for example, and also to a method for manufacturing the composite. 
       BACKGROUND 
       [0003]    Composites of metal and resin are used in a variety of industrial fields. For example, a metal layer and a resin layer can be joined together by an adhesive material. Recently, a new method of injection joining for manufacturing composites of metal and resin has be introduced. In this method, a molten resin material is injected onto a metal piece that has been previously inserted into an injection molding mold. The surface of the metal combines with the resin. Before inserting the metal piece into the mold, a surface of the metal piece is treated by an etchant to form a number of micropores so that a stronger bond may be formed with the resin material. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]    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. 
           [0005]      FIG. 1  is a cross-sectional view of a composite of metal and resin, in accordance with an exemplary embodiment. 
           [0006]      FIG. 2  illustrates a cross-sectional view of a portion of an exemplary composite of metal and resin processed in accordance with an initial step of an exemplary method of the present application. 
           [0007]      FIG. 3  illustrates a cross-sectional view of a portion of an exemplary composite of metal and resin processed in accordance with an intermediate step of an exemplary method of the present application. 
           [0008]      FIG. 4  illustrates a cross-sectional view of a portion of an exemplary composite of metal and resin processed in accordance with an intermediate step of an exemplary method of the present application. 
           [0009]      FIG. 5  illustrates a cross-sectional view of a portion of an exemplary composite of metal and resin processed in accordance with an intermediate step of an exemplary method of the present application. 
           [0010]      FIG. 6  illustrates a cross-sectional view of a portion of an exemplary composite of metal and resin processed in accordance with an intermediate step of an exemplary method of the present application. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    This disclosure is illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which like reference numerals indicate similar elements. It should be noted that references to “an” or “one” embodiment in this disclosure are not necessarily to the same embodiment, and such references mean “at least one”. 
         [0012]      FIG. 1  illustrates a composite  10  of metal and resin. The composite  10  can include a metal piece  20  and a resin piece  30 . 
         [0013]    The metal piece  20  can include a surface  21  defining a plurality of micropores  22 . At least one of the micropores  22  can be in the shape of an inverted “V”. Each micropore  22  can include a first inclined hole  221  and a second inclined hole  222  which are both inclined with respect to the surface  21  of the metal piece  20 . The first inclined hole  221  and the second inclined hole  222  can be symmetrical around line N shown in  FIG. 1 . The line N represents an axis (N-axis) substantially perpendicular to the surface  21  of the metal piece  20 . The first inclined hole  221  and the second inclined hole  222  extend downwards in a diverging manner into the metal piece  20  from a common starting hole (not explicitly labeled) on the surface  21  of the metal piece  20 . The first inclined hole  221  and the second inclined hole  222  can be communicated with each other and share a common opening on the surface  21 . The material of the metal piece  20  can be selected from a group consisting of aluminum alloy, magnesium alloy, stainless steel alloy, copper, and copper alloy. 
         [0014]    In the illustrated embodiment, the first inclined hole  221  and the second inclined hole  222  can be each sloped at an angle θ in relation to the N-axis, and the angle θ can be in a range from about 15 degrees to about 45 degrees. The micropores  22  can be positioned in an array. In other exemplary embodiments, the micropores  22  can be positioned randomly. 
         [0015]    The first inclined hole  221  and the second inclined hole  222  each have a diameter defined as t1, and a depth defined as t2. In one exemplary embodiment, t1 can be in a range from about 100 nanometers (nm) to about 300 nm, and a width-to-depth ratio (t1/t2) can be in a range from about 1:3 to about 1:5. 
         [0016]    The resin piece  30  becomes bonded to the metal piece  20  when molten resin material is inserted into a mold holding the metal piece  20 , wherein the molten resin material is embedded into the micropores  22 . The resin material is a thermoplastic resin which crystallizes as it cools. The crystallized-type thermoplastic resin material can be selected from the group consisting of a composite of polyphenylene sulfide and glass fiber, polyamide, polyethylene terephthalate, and polybutylene terephthalate. When using the polyphenylene sulfide and glass fiber composite, the percentage composition of the glass fiber is in a range from 20 percent to 50 percent. 
         [0017]    Each micropore  22  can include the first inclined hole  221  and the second inclined hole  222 . When an external force is applied to separate the metal piece  20  and the resin piece  30 , the external force is divided into a first force parallel to the bottom of the second inclined hole  222  and a second force vertical to the bottom of the first inclined hole  221 . Therefore, the composite  10  of this disclosure has a larger sliding friction than the conventional composite of vertical micropores, allowing an increased bonding strength. 
         [0018]      FIG. 2  through  FIG. 6  illustrate an exemplary method for manufacturing a composite  10  of metal and resin. 
         [0019]      FIG. 2  illustrates that a provided metal piece  20 , after being shaped, can be cleaned with a degreasing agent solution. Any process, such as machining or casting, can form the metal piece  20 . 
         [0020]    The metal piece  20  can be immersed in the degreasing agent solution having a temperature in an approximate range from 20° C. to 30° C. for 1 to 6 minutes. The concentration of degreasing agent contained in the solution can be in an approximate range of 90 grams/liter (g/l) to 150 grams/liter (g/l). The metal piece  20  is washed with distilled water after being removed from the solution. 
         [0021]      FIG. 3  illustrates that a patterned photoresist layer  40  with a plurality of openings  41  can be formed on the surface  21  of the metal piece  20 . In one exemplary embodiment, each of the openings  41  can be substantially circular and arranged in an array. In other exemplary embodiments, the openings  41  can be substantially square or other shapes. The openings  41  can be through holes or blind holes in the patterned photoresist layer  40 . Each of the openings  41  may have a diameter in a range from about 100 nm to about 300 nm. 
         [0022]      FIG. 4  illustrates that a plurality of first inclined holes  221  can be formed on the surface  21  of the metal piece  20  by plasma etching, and the first inclined holes  221  can be arranged so as to be inclined toward the surface  21 . 
         [0023]    In detail, the first inclined holes  221  can be formed by a first plasma etching process with the patterned photoresist layer  40  as a mask. The first plasma etching process can be an isometric plasma etching process applied to the surface  21 . The first inclined holes  221  extend through the corresponding openings  41  into the metal piece  20 . The plasma can be argon gas or other gases. An etching direction of the plasma can be sloped at an angle tilted from the N-axis, and an etching angle can be in a range from about 5 degrees to 75 degrees. 
         [0024]    In one exemplary embodiment, the first inclined hole  221  can be sloped at the angle θ with the N-axis, and the angle θ can be in a range from about 15 degrees to about 45 degrees. The diameter of first inclined hole  221  is t1, and the depth of the first inclined hole  221  is t2. In one exemplary embodiment, t1 can be in a range of about 100 nm to about 300 nm, and a width-to-depth ratio of the first inclined hole  221  can be in a range of about 1:3 to about 1:5. 
         [0025]      FIG. 5  illustrates that a plurality of second inclined holes  222  can be formed on the surface  21  of the metal piece  20  by plasma etching, the first inclined hole  221  and the second inclined hole  222  to be disposed symmetrically around the N-axis, to form the micropore  22 . 
         [0026]    In detail, the second inclined holes  222  can be formed by a second plasma etching process with the patterned photoresist layer  40  as a mask. The second plasma etching process can be an isometric plasma etching process applied to the surface  21 . The second inclined holes  222  extend through the corresponding openings  41  into the metal piece  20 . The plasma can be argon gas or other gases. An etching direction of the plasma can be sloped at an angle tilted from the N axis, and an etching angle can be in a range from about 5 degrees to 75 degrees. 
         [0027]    In one exemplary embodiment, the second inclined hole  222  can be sloped at the angle θ with the N axis, and the angle θ can be in a range of about 15 degrees to about 45 degrees. The diameter of second inclined hole  222  is t1, and the depth of the second inclined hole  222  is t2. In one exemplary embodiment, t1 can be in a range from about 100 nm to about 300 nm, and the width-to-depth ratio of the second inclined hole  222  can be in a range from about 1:3 to about 1:5. The second inclined hole  222  has a shape substantially similar to the shape of the first inclined hole  221 . 
         [0028]      FIG. 6  illustrates the patterned photoresist layer  40  being removed. The metal piece  20  can be inserted into a mold (not shown), and can be heated to a temperature in a range from 100° C. to 350° C. The heating can be accomplished using electromagnetic induction. 
         [0029]      FIG. 1  illustrates the composite  10  of metal and resin. Molten resin material is injected into the mold and onto the metal piece  20 . The resin material can be crystallizing-type thermoplastic resin. The molten resin material becomes embedded in the micropores  22  and bonds with the metal piece  20  when the resin material  30  is cooled. The crystallizing-type thermoplastic resin material can be selected from the group consisting of a composite of polyphenylene sulfide and glass fiber, polyamide, polyethylene terephthalate, or polybutylene terephthalate. When using the polyphenylene sulfide and glass fiber composite, the percentage composition of the glass fiber is in a range from 20 percent to 50 percent. 
         [0030]    When the resin material  30  is embedded in the micropores  22  on the surface  21  of the metal piece  20 , the combination strength between the resin and the metal is increased. The method of manufacturing such composite of metal and resin does not need strong acids or alkalis, so the method is more environmentally friendly than the conventional method. Furthermore, normal pressures can be used in the process, and the difficulty of processing is reduced, therefore, the method is more suitable for mass production. 
         [0031]    It is believed that the present exemplary embodiments and their advantages will be understood from the foregoing description, and it will be apparent that various changes can be made thereto without departing from the spirit and scope of the exemplary embodiments or sacrificing all of its material advantages.