Abstract:
The electromagnetic interference shielding structure disclosed comprises a first metal layer, a second metal layer, a dielectric layer inter-disposed between the first metal layer and the second metal layer, an adhesive layer located on the second metal layer, and a release film located on the adhesive layer. The electromagnetic interference shielding film prevent the neighbouring circuits and components from the electromagnetic wave interference, the theories applied are reflections of the electromagnetic waves, and absorption of the electromagnetic waves.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a structure against electromagnetic interference used for electronic devices, wirings and components, such as an electromagnetic interference shielding structure of a printed circuit board, in particular relates to a structure against electromagnetic interference of flexible electronic substrate. 
       DESCRIPTION OF RELATED ART 
       [0002]    Currently, the technologies of electronic industries are dedicated to develop electronic devices which are lighter, thinner and smaller. Printed circuit boards are required materials in electronic devices, and are becoming thinner, more compact and are high voltages resistance. Accordingly, the electromagnetic interference has become a major issue as electronic devices become lighter, thinner and smaller. 
         [0003]    Generally speaking, an electromagnetic interference shielding structure comprises a dielectric layer and a metal layer. As shown in  FIG. 2 , an electromagnetic interference shielding structure  200  comprises a metal layer  202  using materials such as silver, copper and nickel, a second dielectric layer  204  above the metal layer  202  using materials such as soft epoxy resin, a first dielectric layer  206  above the second dielectric layer  204  using materials such as high wear resistant acrylic resin, a coverlay  208  above the first dielectric layer  206 , and a conductive adhesive layer  210  used as a junction point of ground loop for the flexible printed circuit board (FPC), and a release film  212  for protecting the conductive adhesive layer form contaminating by external environment. Though the above electromagnetic interference shielding structure having outstanding flexibility, it is required to add grounding copper foils attached to the conductive adhesive layer at a source of the electromagnetic wave in the stack structure of the above-described materials. Accordingly, extra costs are generated from adding coverlays, and adding conductive glues for electromagnetic interference shielding structures. 
       SUMMARY OF THE INVENTION 
       [0004]    The objective of the present invention is to provide an electromagnetic interference shielding structure for reducing the cost of electromagnetic interference shielding structures, reducing the thickness of electromagnetic interference shielding structures and simplify the manufacturing procedures in FPC production. 
         [0005]    In order to achieve the above objectives of the present invention, an electromagnetic interference shielding structure is provided comprising: a first metal layer, a second metal layer, a dielectric layer inter-disposed between the first metal layer and the second metal layer, an adhesive layer located on second metal layer, and a release film located on adhesive layer. 
         [0006]    The advantages provided by an electromagnetic interference shielding structure of the presen            
         [0007]    1. Reducing the cost of electromagnetic interference shielding structures: providing lateral chemical deposition stacking on the dielectric layer, growing a metal film on lateral sides of dielectric layers by vapor deposition or other methods, with thickness ranging from 6 (nm), which greatly reduces the overall cost. 
         [0008]    2. Reducing the thickness of electromagnetic interference shielding structures: the thickness of a metal layer is reduced and the thickness of a dielectric layer is reduced by 1 micron, and the thickness used by a coverlay on a FPC is reduced. 
         [0009]    3. Reducing FPC manufacturing procedures: an electromagnetic interference shielding structure can be used without a coverlay on a FPC, which reduces the cost. 
         [0010]    The detailed characteristics and advantages are disclosed in the following description in order to facilitate understanding of the technical contents of the present invention for implementing the present invention for person skilled in the art. Accompany with disclosed contents, claims and diagrams in the application, it is apparent to any person skilled in the art to comprehend the objectives and advantages of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF DRAWING 
         [0011]    The features of the invention believed to be novel are set forth with particularity in the appended claims. The invention itself, however, may be best understood by reference to the following detailed description of the invention, which describes an exemplary embodiment of the invention, taken in conjunction with the accompanying drawings, in which: 
           [0012]      FIG. 1  illustrates the electromagnetic interference shielding structure of an embodiment according to the present invention; and 
           [0013]      FIG. 2  illustrates a related art electromagnetic interference shielding structure 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0014]      FIG. 1  illustrates the electromagnetic interference shielding structure of an embodiment according to the present invention. As shown in  FIG. 1 , the electromagnetic interference shielding structure  100  according to a top-down order comprises a first metal layer  102 , a dielectric layer  104 , a second metal layer  106 , an adhesive layer  108  and a release film  110 . 
         [0015]    The components of the first metal layer  102  can be gold, silver, copper, iron, tin, lead, cobalt, aluminum, nickel or alloys using above metals as the principal components or any conductive metals, with thickness ranging from 0.002 micron (μm) to 12 micron. Because the first metal layer  102  is thin, electromagnetic waves penetrate into the electromagnetic interference shielding structure  100  through the gaps. In addition, a coverlay can be added to a first metal layer  102  (not shown in the diagram), the function of the coverlay is to protect a first metal layer  102  from interfering from external environment (such as oxidation, dusts, scratches, bumping . . . etc.). 
         [0016]    The components of the dielectric layer  104  comprise dielectric layers formed by one or more than one of the polymer materials including polyimide (PI), polyethylene (PE), epoxy resin (EPOXY), polyethylene terephthalate (PET), polycarbonate (PC), polypropene (PP), bismaleimide (BMI) and acrylic polymers etc. In addition, filler materials can be added to the dielectric layer  104  facilitating diffraction of the electromagnetic waves with different phases in the dielectric layer  104  and accordingly the electromagnetic waves diminishes faster. The functions of the dielectric layer  104  are (1) providing insulation separating the first metal layer  102  from the second metal layer  106 , (2) changing the incident angle of the electromagnetic waves such that the electromagnetic waves diffract among the dielectric layer  104 , the first metal layer  102 , and second metal layer  106  for diminishing the electromagnetic waves. The thickness of the dielectric layer  104  can be for example 5 micron to 200 micron. 
         [0017]    The components of second metal layer  106  can be gold, silver, copper, iron, tin, lead, cobalt, aluminum, nickel or alloys using above metals as the principal components or any conductive metals. The thickness of the second metal layer  106  can be for example 0.002 micron (μm) to 12 micron. Because the second metal layer  106  is thin, electromagnetic waves penetrate into the electromagnetic interference shielding structure  100  through the gaps. 
         [0018]    The components of the adhesive layer  108  comprise one or more than one polymers materials including PI, EPOXY, PE, PET, PC, PP, BMI and acrylic polymers etc. Filler materials can be added to the adhesive layer  108 . The function of the adhesive layer  108  is providing insulation function for protecting circuits and binding the electromagnetic interference shielding materials with substrates. The thickness of the adhesive layer  108  can be 1 micron to 500 micron. 
         [0019]    The components of the release film  110  comprise one or more than one polymers materials including PI, EPOXY, PE, PET, PC, PP, BMI and acrylic polymers etc. Filler materials can be added to the release film  110 . The function of the release film  110  is to protect the adhesive layer from contaminating by external environment (such as hydrolysis, dusts . . . etc.). The release film  110  should be removed before using electromagnetic interference shielding structure  100 . The thickness of the release film  110  can be 1 micron to 50 micron. 
         [0020]    The achieved advantages by implementing the present invention are: 
         [0021]    1. The thickness of an electromagnetic interference shielding structure (comprising a first metal layer  102 , a dielectric layer  104 , a second metal layer  106 , an adhesive layer  108  and a release film  110 ) is controlled within 6 micron which meet the demand to miniaturize electronic products. 
         [0022]    2. An electromagnetic interference shielding structure can be used as a electromagnetic shielding coverlay and reduce the product costs. 
         [0023]    3. It is not required to add large size copper sheet for grounding in a substrate of an electromagnetic interference shielding structure, which reduces the cost for FPC manufacturers and meet the demand of offering lightweight products. 
       EMBODIMENTS 
     The First Embodiment 
     The Ultra Slim Electromagnetic Interference Shielding Structure 
       [0024]    The ultra slim electromagnetic interference shielding structure can be produced by the following manufacturing procedures, the steps are: 
         [0025]    Provide a polyimide thin film which is 6 micron thick and coarsen the surface of the polyimide by the plasma or the corona method. Coat a silver layer (about 0.5 micron each) on any two dies of the polyimide thin film by sputtering (or vapor deposition), and coat epoxy resin of 3 micron thickness on one of the side. Then baking with high temperature (160° C.) to remove the solvent, laminate a release film onto the epoxy resin side to form a electromagnetic interference shielding structure unit of 10 micron thickness. 
       The Second Embodiment 
     The High Shielding Electromagnetic Interference Shielding Structure 
       [0026]    The high shielding electromagnetic interference shielding structure can be produced by the following manufacturing procedures, the steps are: 
         [0027]    Provide a glue-free polyimide substrate of 36 micron thickness having two sides covered by copper foil, and coat epoxy resin of 5 micron thickness on any of the sides. Then bake with high temperature (160° C.) to remove the solvent, and laminate a release film onto the epoxy resin side to form a electromagnetic interference shielding structure unit of 41 micron thickness. 
       The Third Embodiment 
     The Asymmetric Metal Electromagnetic Interference Shielding Structure 
       [0028]    The asymmetric metal electromagnetic interference shielding structure can be produced by the following manufacturing procedures, the steps are: 
         [0029]    Provide a glue-free polyimide substrate of 25 micron having one side covered by copper foil, and coarsen the surface of the polyimide by the plasma or the corona method. Coat a silver layer (about 0.5 micron each) on any two dies of the polyimide thin film by sputtering (or vapor deposition), and coat epoxy resin of 3 micron thickness on one the copper foil side or the silver foil side. Then bake with high temperature (160° C.) to remove the solvent, and laminate a release film onto the epoxy resin side to form a electromagnetic interference shielding structure unit of 30 micron thickness. 
         [0030]    As the skilled person will appreciate, various changes and modifications can be made to the described embodiments. It is intended to include all such variations, modifications and equivalents which fall within the scope of the invention, as defined in the accompanying claims.