Patent Publication Number: US-2013245988-A1

Title: Machine for mounting leds to a circuit board

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a mounting machine for mounting electronic components to a circuit board, and more particularly, to a mounting machine for mounting LEDs (light emitting diodes) to a circuit board with high precision. 
     2. Description of Related Art 
     Owing to many advantages, such as high luminosity, low operational voltage, low power consumption, compatibility with integrated circuits, easy driving, long term reliability, and environmental friendliness, LEDs have been widely promoted as a light source. 
     It needs to precisely place an LED on a predetermined position of a printed circuit board (PCB), whereby light from the LED can precisely illuminate a required object, such as a light guide of a backlight module. A conventional LED mounting machine is to provide an optical sensor, for example, a CCD (charge-coupled device) to check the profile of the LED thereby to find a center of the LED. To mount the LED to a circuit board, the LED is moved to the circuit board with the center of the LED aligned with a predetermined position of the circuit board. However, such a mounting technology cannot always precisely mount the LED to the circuit board at the predetermined position, due to measuring error of the profile of the LED and positioning error of moving the LED. For an optoelectronic component, such as LEDs, the precise positioning of the LEDs on their predetermined positions of the circuit board is essential. 
     Therefore, what is needed is a mounting machine for mounting LEDs on a circuit board which can overcome the above described shortcomings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagrammatic view of a machine for mounting LEDs to a circuit board, in accordance with an exemplary embodiment of the present disclosure. 
         FIG. 2  is a diagrammatic view showing a precise adjustment of positions of LEDs on the circuit board. 
         FIG. 3  is a diagrammatic view showing the precise adjustment of the positions of LEDs on the circuit board from another aspect. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1-3 , an exemplary embodiment of a mounting machine  200 , in accordance with the present embodiment, is shown. 
     The mounting machine  200  includes a main body  20 , a mounting area  21  arranged in the main body  20 , a conveyer  22  extending through the main body  20 , and a precise adjusting area  100  arranged in the main body  20  and located at a downstream side of the mounting area  21 . 
     The precise adjusting area  100  is used to precisely adjust the positions of LEDs  32  to predetermined positions of a PCB  31 . In the present embodiment, the PCB  31  has two positioning points  311  arranged on two opposite ends thereof, respectively. The LEDs  32  are arranged on the PCB  31  via the mounting machine  200 . The LEDs  32  are first mounted on the PCB  31  via the mounting area  21  of the mounting machine  200 , wherein the first mounting area  21  has a function like a conventional mounting machine, which mounts the LEDs  32  to the PCB  31  by detecting profiles of the LEDs  32  by an optical sensor such as a CCD. However, according to the present disclosure, each LED  32  further has an optical identification point  321  near an end thereof. Generally, the optical identification point  321  is formed on a top surface of the LED  32  when the LED  32  is manufactured. 
     The precise adjusting area  100  includes a sensor  11 , a processing unit  12  and an adjusting unit  13 . 
     The sensor  11  is used to detect the position of the positioning points  311  of the PCB  31  and the position of the optical identification point  321  of each LED  32 . The sensor  11  is an optical sensor such as a charge-coupled device (CCD). In the present embodiment, the sensor  11  includes an image sensor with a magnification ranges from 50 times magnification to 100 times magnification. The image sensor catches images of the positioning points  311  of the PCB  31  and image of the optical identification point  321  of each LED  32  and then determines the position of the positioning points  311  and the optical identification point  321  according to the image. 
     The processing unit  12  receives the detected result from the sensor  11  and then compares the position of the optical identification point  321  of each LED  32  with the position of the positioning points  311  of the PCB  31 ; the processing unit  12  obtains the compared result and judges whether the LED  32  is deviated from its intended mounting position and the degree of the deviation if any. In the present embodiment, the two positioning points  311  of the PCB  31  each act as a reference point. When the optical identification point  321  of an LED  32  and the two positioning points  311  of the PCB  31  are in a straight line, it represents that the LED  32  is precisely arranged on the predetermined position to be mounted; therefore, it does not need to adjust the position of the LED  32  by the adjusting unit  13 , and the adjusting unit  13  does not act on the LED  32 . When the optical identification point  321  of the LED  32  and the two positioning points  311  of the PCB  31  are not in a straight line, it represents that the LED  32  is misplaced and needs to be adjusted by the adjusting unit  13 . 
     The adjusting unit  13  receives the compared result from the processing unit  12 , and selectively adjusts the position of the LED  32  according to the compared result. When the LED  32  is misplaced, the adjusting unit  13  adjusts the position of the LED  32  to make sure that the optical identification point  321  of the LED  32  and the two positioning points  311  of the PCB  31  are in a straight line. When the LED  32  is moved by the adjusting unit  13  to the predetermined position of the PCB  31 , the adjusting unit  13  stops acting on the LED  32 . 
     In the present embodiment, the sensor  11  can monitor the adjusted result from the adjusting unit  13  to see whether the adjusting unit  13  has moved the deviated LED  32  to its intended position precisely. The adjusting unit  13  can be a step motor or piezoelectric driver, which can precisely move the LED  32  to its intended position. The sensor  11  obtains a series of images of the LED  32  when the adjusting unit  13  adjusts the position of the LED  32 , and transmits them to the processing unit  12 . The processing unit  12  receives the images and judges whether the LED  32  is moved to the predetermined position, and asks the adjusting unit  13  to continue its adjustment if the LED  32  has not yet reached its intended precise mounting position. When the images of the LED  32  represent that the optical identification point  321  of the LED  32  and the two positioning points  311  of the PCB  31  are in a straight line, the processing unit  12  controls the adjusting unit  13  to stop working. When the images of the LED  32  represent that the optical identification point  321  of the LED  32  and the two positioning points  311  of the PCB  31  are not in a straight line, the processing unit  12  controls the adjusting unit  13  to continue work to adjust the position of the LED  32  until the LED  32  reaches the predetermined position. 
     In process of mounting the LEDs  32 , the PCB  31  is arranged on the conveyer  22  of the mounting machine  200 . The conveyer  22  drives the PCB  31  to the mounting area  21  wherein the LEDs  32  are mounted on the PCB  31 ; then the conveyer  22  transfer the PCB  31  together with the LEDs  32  to the precise adjusting area  100 , wherein the precise adjusting area  100  adjusts the positions of LEDs  32 , if necessary, to make sure that the LEDs  32  are all positioned on the predetermined positions, and at last the PCB  31  together with the LEDs  32  is driven out of the precise adjusting area  100  by the conveyer  22  to be ready to be processed by a downstream working station, which usually is a reflow oven for soldering the LEDs  32  to the PCB  31  by surface mounting technology (SMT). The precise adjusting area  100  has a simple structure, an easy operation, and can place the LEDs  32  on a predetermined position with high precision. 
     It is to be further understood that even though numerous characteristics and advantages have been set forth in the foregoing description of embodiments, together with details of the structures and functions of the embodiments, the disclosure is illustrative only; and that 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.