Abstract:
An LED unit includes an LED and an optical element. The LED includes a substrate, an LED chip fixed on the substrate and an encapsulation encapsulating the LED chip. The LED further includes a first magnet fixed on the substrate. The optical element includes an optical adjustment layer and a second magnet. The second magnet attracts the first magnet to fix the optical element on the LED. The LED unit can be adjusted to have different optical characteristics by replacing the optical element thereof with another optical element.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The disclosure relates to light emitting diodes, and particularly to an LED unit. 
         [0003]    2. Description of the Related Art 
         [0004]    Light emitting diodes (LEDs) have many advantages, such as high luminosity, low operational voltage, low power consumption, compatibility with integrated circuits, easy driving, long term reliability, and environmental friendliness. These advantages have promoted a wide use of the LEDs as a light source. Now, the light emitting diodes are commonly applied in environmental lighting. 
         [0005]    Light from a common LED transfers to the specific wavelength by a fluorescent layer. However, an encapsulation of the LED is fixed on the substrate. The optical characteristics of the common LED cannot be adjusted, according to the specific needs. 
         [0006]    Therefore, it is desirable to provide an LED unit which can overcome the described limitations. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Many aspects of the disclosure can be better understood with reference to the drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present LED units. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the views. 
           [0008]      FIG. 1  is a cross-sectional view of an LED unit in accordance with a first embodiment. 
           [0009]      FIG. 2  is an exploded view of the LED unit of  FIG. 1 . 
           [0010]      FIG. 3  is a top view of the LED unit of  FIG. 1 . 
           [0011]      FIG. 4  is a cross-sectional view of an optical element of the LED unit in accordance with a second embodiment. 
           [0012]      FIG. 5  is a cross-sectional view of an optical element of the LED unit in accordance with a third embodiment. 
           [0013]      FIG. 6  is a cross-sectional view of an LED unit in accordance with a four embodiment. 
           [0014]      FIG. 7  is an exploded view of the LED unit of  FIG. 6 . 
           [0015]      FIG. 8  is a top view of the LED unit of  FIG. 6 . 
           [0016]      FIG. 9  is a cross-sectional view of an optical element of the LED unit of  FIG. 6  in accordance with a fifth embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    Embodiments of an LED unit as disclosed are described in detail here with reference to the drawings. 
         [0018]    Referring to  FIGS. 1 to 3 , an LED unit  1  includes an LED  10  and an optical element  20  on the LED  10 . The LED  10  includes a substrate  12 , two lead frames  14  on the substrate  12 , an LED chip  16  electrically connecting to the two lead frames  14 , an encapsulation  18  covering the LED chip  16 , and a first magnet  100  fixed on a top surface of the substrate  12 . The substrate  12  can be epoxy resin, silicone, or other insulating materials. The substrate  12  is ceramic in a first embodiment. A cavity defined on the top surface of the substrate  12  receives the LED chip  16 . The two lead frames  14  are respectively arranged at two sides of the substrate  12  and mutually electrically insulated. Each of the lead frames  14  includes a wire portion  142 , a contact portion  146  parallel to the wire portion  142 , and a connection  144  perpendicularly connected to the wire portion  142  and the contact portion  146 . The wire portion  142  passing through the substrate  12  and exposed in the cavity is used for electrically connecting to the LED chip  16 . The contact portion  146  arranged on a bottom of the substrate  12  is used for connecting to an external circuit (not shown). The connection  144  attached on the outside surface of the substrate  12  is used for conducting the current from the contact potion  146  to the wire portion  142 . 
         [0019]    The LED chip  16  is arranged on a top surface of the wire portion  142  of one of the lead frames  14 . According to a color of light from the LED chip  16 , the LED chip  16  can be made of different materials, such as InGaAlP, GaN, or GaP. The LED chip  16  is made of the semiconductor material emitting blue light in this embodiment. 
         [0020]    Two electrodes (not shown) of the LED chips  16  electrically connect to the top surfaces of the wire portions  142  of the two lead frames  14  by two gold wires. The first magnet  100  which is ring-shaped and arranged on a top surface of the substrate  12  by glue includes an upwards first magnetic pole (for example north magnetic pole), and a downwards second magnetic pole (for example south magnetic pole). The encapsulation  18  is filled into the cavity and has the same height as a top surface of the first magnet  100 . The encapsulation  18  protects the LED chip  16 . The encapsulation  18  can be epoxy resin, silicone, glass or, other transparent materials. Light from the LED chip  16  travels through the encapsulation  18  and emits outwards. 
         [0021]    The optical element  20  includes an optical adjustment layer  22  and a second magnet  200 . The second magnet  200  which is a ring includes an upwards first magnetic pole and a second downwards magnetic pole. The second magnetic pole of the second magnet  200  is in contact with the first magnetic pole of the first magnet  100 . 
         [0022]    Thus, when the second magnet  200  is arranged on the first magnet  100 , the second magnet  200  and the first magnet  100  are mutually attracted by magnetic force. The optical element  20  is fixed on the LED  10 . 
         [0023]    Because the optical element  20  connects to the LED  10  by magnetic force, the optical element  20  and the LED  10  are easily separated without any tools. An external diameter of the second magnet  200  is the same as that of the first magnet  100 . An internal diameter of the second magnet  200  is also the same as that of the first magnet  100 . The second magnet  200  surrounds the optical adjustment layer  22 . The optical adjustment layer  22  can be epoxy resin, silicone, or glass transparent materials. The optical adjustment layer  22  is a round-plate structure. A top surface of the optical adjustment layer  22  is parallel to a bottom surface of the optical adjustment layer  22 . The bottom surface of the adjustment layer  22  directly contacts a top surface of the encapsulation  18 . A plurality of fluorescent powders  24  are filled into the adjustment layer  22 . The fluorescent powders  24  can be garnet nitride, sulfide, nitrogen oxides, or silicate. The fluorescent powders  24  are used for transferring an original light from the LED  10  to the different wavelength. 
         [0024]    The optical adjustment layer  22  can be other optic structures, according to a specific optic field. Referring to  FIG. 4 , the top surface of the optical adjustment layer  22  can change other optical structure type and adjusts the optical field, according to specific needs. Referring to  FIG. 4 , the top surface of the optical adjustment layer  22  is formed as a convex. Thus, the optical adjustment layer  22  has a function of a light condenser. Referring to  FIG. 5 , the top surface of the optical adjustment layer  22  can be a rough surface. Thus, the optical adjustment layer  22  has a function of scattering light from the LED chip  16 . Light from the LED chip  16  is uniform due to the rough surface. 
         [0025]    Alternatively, just like the encapsulation  18 , the optical adjustment layer  22  can also do not include the fluorescent powders  24  and is just for adjusting optical paths of light from the LED chip  16 . Still alternatively, light scattering particles can be filled into the optical adjustment layer  22 , causing light from the LEC chip  16  to be more uniform. 
         [0026]    The bottom surface of the optical adjustment layer  22  can also form a protrusion (not shown). A hole (not shown) defined at the top surface of the encapsulation  18  of the LED  10  corresponds to the protrusion. Thus, the optical adjustment layer  22  is precisely arranged on the surface of the LED  10  by the protrusion inserted in the hole. 
         [0027]      FIGS. 6-8  show that an LED  10   a  of multi chip package and an optical element  20   a  in fourth embodiment. A substrate  12   a  of the LED  10   a  is rectangle. A plurality of LED chips  16   a  is arranged on a top surface of the substrate  12   a . According to the specific needs, the LED chips  16   a  can emit the same color or emit different colors. The LED chips  16   a  are arranged inside an encapsulation  18   a.  A ring-shaped first magnet  100   a  is fixed on the top surface of the substrate  12   a  surrounding the encapsulation  18   a.  The first magnet  100   a  has an upwards first magnetic pole and a downwards second magnetic pole. A thickness of the first magnet  100   a  is smaller than that of the encapsulation  18   a.  Thus, a portion of the encapsulation  18   a  is exposed outside. 
         [0028]    The optical element  20   a  also includes a second magnet  200   a  and an optical adjustment layer  22   a  surrounded by the second magnet  200   a.  A plurality of fluorescent powders  24   a  are arranged inside the optical adjustment layer  22   a , adjusting the color of light from the LED chips  16   a.  A thickness of the second magnet  200   a  exceeds that of the optical adjustment layer  22   a.  The second magnet  200   a  has an upwards first magnetic pole and a downwards second magnetic pole. The second magnetic pole of the second magnet  200   a  is in contact with the first magnetic pole of the first magnet  100   a.  Thus, the second magnet  200   a  arranged on the first magnet  100   a  and the first magnet  100   a  are mutually attracted by magnetic force. Because the optical element  20   a  connects to the LED  10   a  by magnetic force, the optical element  20   a  and the LED  10   a  are easily separated manually. 
         [0029]    Referring to  FIG. 9 , a plurality of protruding lenses  26   a  is formed on the optical adjustment layer  22   a,  adjusting light respectively from each of the LED chips  16   a.    
         [0030]    Because the optical elements  20 ,  20   a  connect to the LEDs  10 ,  10   a  by magnetic force, the optical elements  20 ,  20   a  and the LEDs  10 ,  10   a  are easily separated manually. Thus, according to specific needs, the optical elements  20 ,  20   a  on the LEDs  10 ,  10   a  can easily be replaced. 
         [0031]    While the disclosure has been described by way of example and in terms of exemplary embodiment, it is to be understood that the disclosure is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.