Abstract:
A vacuum nozzle device for picking up and moving a light emitting diode comprises a tube having a lower end for contacting the light emitting diode and an image sensor located in the vacuum nozzle device. A negative pressure can be generated at the lower end of the tube when the vacuum nozzle device is in operation. The image sensor detects alignment keys on a light generating chip of the LED to precisely move the vacuum nozzle device to a desired position on the light emitting diode.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The disclosure generally relates to a vacuum nozzle device for sucking and positioning an optoelectrical element, and particularly to a vacuum nozzle for precisely sucking and positioning a light emitting diode (LED), whereby the light emitting diode can be precisely mounted on a target object, which is, for example, a printed circuit board. 
         [0003]    2. Description of Related Art 
         [0004]    In recent years, due to excellent light quality and high luminous efficiency, light emitting diodes (LEDs) have increasingly been used as substitutes for incandescent bulbs, compact fluorescent lamps and fluorescent tubes as light sources of illumination devices. 
         [0005]    In assembly, an LED is picked up by a nozzle and placed at a predetermined position of a substrate, which is, for example, a printed circuit board (PCB) or a metal cored printed circuit board (MCPCB). Generally, an image sensor, for example, a charge-coupled device (CCD) is provided below the LED to identify the position of the LED, thereby avoiding the LED being deviated from the predetermined position to be picked up by the nozzle. The image sensor detects the geometric shape of the LED to decide the center of the LED. The nozzle picks up the LED by sucking the geometric center of the LED. A deviation of 50 μm can happen between the sucked position of the nozzle and the geometric center of the LED by such technology. For an optoelectrical element like an LED, the positional deviation of 50 μm is not good enough for the more and more demanding requirement of precise positioning of the LED. Furthermore, the chip of the LED from which light of the LED comes may not be at the geographic center of the LED due to the packaging tolerance. When this happens, even the nozzle picks up the LED by sucking the geographic center of the LED, the light from the LED chip is still deviated from its intended position. Finally, the relative position between the nozzle and the image sensor needs to be frequently calibrated thereby making sure that the nozzle can be moved to the correct position. The calibration is time consuming, thereby being costly. 
         [0006]    What is needed, therefore, is a vacuum nozzle device to overcome the above described disadvantages. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Many aspects of the present embodiments can be better understood with reference to the following 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 embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
           [0008]      FIG. 1  is a cross-sectional view showing a light emitting diode. 
           [0009]      FIG. 2  is a cross-sectional view showing a vacuum nozzle device in accordance with the present disclosure which is positioned on the light emitting diode of  FIG. 1 . 
           [0010]      FIG. 3  is a top view of the vacuum nozzle device of  FIG.2 . 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    An embodiment of a vacuum nozzle device for precisely positioning a light emitting diode will now be described in detail below and with reference to the drawings. 
         [0012]    Referring to  FIG. 1 , an optoelectrical element, such as a light emitting diode  10  is provided. The light emitting diode  10  includes a U-shaped substrate  11  and an LED chip  12  received in the substrate  11  and on a top of a bottom wall of the substrate  11 . The LED chip  12  is for generating light for the light emitting diode  10 . In this embodiment, a cylindrical recess  13  is defined at a central portion of the substrate  11 , and the LED chip  12  is arranged at a bottom of the recess  13 . Two alignment keys (not shown) are formed on an upper surface of the LED chip  12 . The alignment keys usually are cross marks on the upper surface of the LED chip  12 , which are well known to person skilled in the art and use for positioning the LED chip  12  at the required position when packaging the LED chip  12  in the light emitting diode  10 . Preferably, the recess  13  further includes a transparent encapsulation  15  to cover the LED chip  12 . The transparent encapsulation  15  can also be doped with phosphors to convert light from the LED chip  12  into light with a different wavelength. 
         [0013]    Referring also to  FIG. 2 , a vacuum nozzle device  20  in accordance with the present disclosure is provided. The vacuum nozzle device  20  includes a tube  21 . The tube  21  defines an opening  22  in a bottom thereof to pick up the light emitting diode  10 . 
         [0014]    When the opening  22  of the tube  21  is closed by a top face of the light emitting diode  10 , the tube  21  is vacuumed to generate a negative pressure at the opening  22 , thereby making the light emitting diode  10  being sucked by the tube  21 . Referring also to  FIG. 3 , the vacuum nozzle device  20  further includes a fixing ring  23  located inside the tube  21 . The fixing ring  23  is secured to the tube  21  by supporting poles  24 . A passage  25  is defined between every two adjacent supporting poles  24  for exhaustion of air from the tube  21  when the vacuum nozzle device  20  is operated to pick up the light emitting diode  10 . 
         [0015]    The vacuum nozzle device  20  further includes an image sensor  30  positioned inside the tube  21 . The image sensor  30  determines a position of the LED chip  12  by detecting the alignment keys on the upper surface of the LED chip  12 . In this embodiment, the image sensor  30  is a charge-coupled device (CCD), which is secured on the fixing ring  23 . A transparent glass layer  31  is formed between the image sensor  30  and the fixing ring  23  to prevent the image sensor  30  from being contaminated by dust or other particles when the vacuum nozzle device  20  is in operation. 
         [0016]    In operation to pick up the light emitting diode  10 , the image sensor  30  positioned inside the vacuum nozzle device  20  detects the position of the LED chip  12  by sensing the positions of the alignment keys, rather than a geometry shape of the light emitting diode  10 . By such technology, a possible deviation between the actually sucked position of the vacuum nozzle device  20  and its intended position is within 10 μm, whereby the light emitting diode  10  can be more precisely positioned by the vacuum nozzle device  20 . Furthermore, even though the LED chip  12  is deviated from a predetermined position inside the light emitting diode  10 , since the vacuum nozzle device  20  picks up the LED  10  by detecting the alignment keys on the LED chip  12  rather the geometry shape of the LED  10 , the tube  21  is aligned with the LED chip  12  during the pick-up operation. Accordingly, the LED chip  12  can be located at its intended position after it is moved by the vacuum nozzle device  20  to be positioned on a target object, for example, a printed circuit board or a metal cored printed circuit board. Thus, light generated by the LED chip  12  will not be unduly deviated from its intended position. 
         [0017]    The tube  21  of the vacuum nozzle device  20  can be made of a transparent material selected from a group consisting of glass, polycarbonate (PC), and polymethyl methacrylate (PMMA). Light from outer environment can pass through the transparent tube  21  and illuminate the LED chip  21  inside the light emitting diode  10 . Therefore, the image sensor  30  can determine the position of the LED chip  21  more efficiently and correctly. In addition, a light source can be positioned inside the tube  21  to illuminate the light emitting diode  10  to facilitate the image sensor  30  to sense the position of the LED chip  12 . 
         [0018]    The use of the vacuum nozzle device  20  is illustrated hereafter. First, the vacuum nozzle device  20  is moved to a place generally above the light emitting diode  10 . The image sensor  30  is then operated to detect the position of the alignment keys of the LED chip  12  whereby the vacuum nozzle device  20  is further moved to its intended position over the light emitting diode  20  at which the tube  21  of the vacuum nozzle device  20  is aligned with the LED chip  12 . The vacuum nozzle device  20  is lowered to have the tube  21  in contact with a top surface of the LED  10 . The vacuum nozzle device  20  is then operated to generate a vacuum pressure on the light emitting diode  10  whereby the light emitting diode  10  can be picked up by the vacuum nozzle device  20  and moved thereby to a desired position. 
         [0019]    It is to be further understood that even though numerous characteristics and advantages of the present embodiments have been set forth in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.