Abstract:
An exemplary printed circuit board ( 200 ) has a substrate ( 210 ); a circuit ( 230 ) on the substrate; and a plurality of pins ( 220 ) peripherally located on the substrate, electrically connected to the circuit. The printed circuit board further has a plurality of accommodating spaces ( 223 ) formed at the plurality of pins.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to liquid crystal displays (LCDs), and particularly to an LCD with in-plane switching (IPS) mode and providing a highly precise alignment of liquid crystal molecules therein. 
         [0003]    2. General Background 
         [0004]    Conventional chip packages such as leadframe-based Chip Scale Packages (CSPs) are soldered onto PCBs using solder paste. Leadframe-based CSPs are CSPs having no peripheral leads that typically extend out from chip packages. A conventional leadframe-based CSP includes a leadframe divided into a die attach. pad centrally located therein and a plurality of wire bonding pads peripherally located therein. The conventional leadframe-based CSP further includes one or more dies or chips mounted on the die attach pad, bonding wires for electrically connecting the dies to the wire bonding pads, and a mold compound for encapsulating all these components in a package structure. A variety of different types of leadframe-based CSPs are available in the market, such as Micro-Lead Packages (MLPs), Micro-Lead-Frames (MLFs), Leadless Package Chip Carriers (LPCC), etc. Joint Electron Device Engineering Counsel (JEDEC), which is a committee for establishing industry standards and packaging outlines, has defined a package outline named “MO-220” for leadframe-based CSPS. 
         [0005]    A typical PCB is made of conductive layers and dielectric layers stacked up in an alternating manner. The top conductive layer on the PCB is divided into a center pad centrally located therein and a plurality of I/O (input/output) pins peripherally located therein. Typically, solder paste is deposited on certain portions of the center pad and the I/O pins. An electronic package such as a leadframe-based CSP is then placed onto the PCB and fixedly mounted thereon by solder paste. During the mounting of the leadframe-based CSP, the die attach pad of the leadframe-based CSP is aligned with the center pad of the PCB and the wire bonding pads of the leadframe-based CSP are aligned with the I/O pins of the PCB. 
         [0006]    As shown in  FIG. 5  and  FIG. 6 , a typical PCB is disclosed. The PCB  100  includes a substrate  110 , a circuit  130  centrally located thereon and a plurality of I/O pins  120  peripherally located thereon. The plurality I/O pins  120  are rectangular copper foil, which are parallel to each other, extending along a first extending direction. The plurality I/O pins  120  is connected to the circuit  130  for electrically connecting the circuit  130  with an outer PCB or other outer elements. 
         [0007]      FIG. 6  is a partially enlarged, cross-sectional view of the PCB of  FIG. 1 , taken along a line VI-VI. The plurality of pins  120  formed on the substrate  110  has a plurality of guiding textures  121 , and a soldering flux  122  covering an external surface of the pins  120 . The soldering flux  122  is generally made from tin or anisotropic conductive film. The guiding texture  121  extends along the first extending direction of the pins  120 , which is used to guide the flowing direction of the melting soldering flux  122  when an outer element is soldered on the pins  120 . The guiding texture  121  can prevent short circuit between two adjacent pins  120 , which is influenced by overflow of the melting soldering flux  122  from two sides of the pins  120 . 
         [0008]    However, some superfluous melting soldering flux  122  flows to tail ends of the pins  120  or concentrates at the tail end to form a solder ball, under a pressure thereon produced in the process of bonding the outer elements on the PCB  100 . Thus, a short circuit is easy to produce when the soldering flux  122  is thicker or a pitch between two adjacent pins  120  is small (as shown in  FIG. 7 ). 
         [0009]    Thus, what is needed is an improved PCB which can overcome the above-mentioned disadvantages. 
       SUMMARY OF THE INVENTION 
       [0010]    An exemplary printed circuit board has a substrate; a circuit on the substrate; and a plurality of pins peripherally located on the substrate, electrically connected to the circuit. The printed circuit board further has a plurality of accommodating spaces formed at the plurality of pins. 
         [0011]    Another exemplary printed circuit board has a substrate; a circuit on the substrate; and a plurality of pins peripherally located on the substrate, electrically connected to the circuit. The printed circuit board further has at least one opening are formed at the plurality of pins. 
         [0012]    Other objects, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a plane view of a PCB in accordance with a first preferred embodiment of the present invention; 
           [0014]      FIG. 2  is a partially enlarged cross-sectional view of the PCB of  FIG. 1  taken along a line II-II; 
           [0015]      FIG. 3  is a plane view of a PCB in accordance with a second preferred embodiment of the present invention; 
           [0016]      FIG. 4  is a plane view of a PCB in accordance with a third preferred embodiment of the present invention; 
           [0017]      FIG. 5  is a plane view of a conventional PCB; 
           [0018]      FIG. 6  is a partially enlarged cross-sectional view of the PCB of  FIG. 5 . taken along a line VI-VI; and 
           [0019]      FIG. 7  is plane view of the PCB of  FIG. 5 , showing a short circuit phenomenon. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0020]    Hereinafter, a preferred embodiment of the present invention will be explained in more detail with reference to the accompanying drawings. 
         [0021]    Referring to  FIG. 1 , a plane view of a PCB according to a preferred first embodiment of the present invention is shown.  FIG. 2  is a partially enlarged, cross-sectional view of the PCB of  FIG. 1 , taken along a line of II-II. The PCB  200  has a substrate  210 , a circuit  230  centrally located thereon and a plurality of I/O pins  220  peripherally located thereon. The plurality I/O pins  220  are rectangular copper foil, which are parallel to each other, extending along a first extending direction. Two adjacent pins  220  are insulated. The plurality I/O pins  220  are connected to the circuit  130  for electrically connecting the circuit  230  with an outer element. 
         [0022]    The plurality of pins  220  formed on the substrate  210  has a plurality of guiding textures  221  formed at an external surface of the pins  220 , a soldering flux  222  covering the external surface, and an accommodating space  223  at a tail end of each pin  220 . The soldering flux  222  is generally made from tin or anisotropic conductive film. The guiding texture  221  extends along the first extending direction of the pins  220 , which is used to guide the flowing direction of the melting soldering flux  222  when an outer element is soldered on the pins  220 . The accommodating space  223  is a depressed portion at the tail end of the pins  220 , which has a deepness same to a thickness of the pins  220 . 
         [0023]    In use, when an outer element is bonded on the pins  220  of the PCB  200 , the guiding textures  221  guide the melting soldering flux  222  flowing along the first extending direction of the guiding textures  221 . The guiding texture  221  can prevent overflow of the melting soldering flux  222  from two sides of the pins  220 , and avoid short circuit between two adjacent pins  220  or forming soldering ball or forming soldering joints. And, superfluous melting soldering flux  222  can flow in the accommodating space  223 . Thus, amount of the superfluous melting soldering flux  222  can be lessened, and the probability of producing the short circuit can be lowered. 
         [0024]      FIG. 3  shows a PCB according to a second preferred embodiment of the present invention. The PCB  300  has a similar structure to that of the PCB  200  except that an accommodating space  323  is formed at a center region of pins  320 , which is a concave hole or a through hole. In use, when an outer element is bonded on the pins  320  of the PCB  300 , a plurality of guiding textures  321  of the pins  320  guide the melting soldering flux (not shown) flowing along the first extending direction of the guiding textures  321 . The guiding texture  321  can prevent overflow of the melting soldering flux from two sides of the pins  320 , and avoid short circuit between two adjacent pins  320  or forming solder ball. And, superfluous melting soldering flux can flow in the accommodating space  323 . Thus, amount of the superfluous melting soldering flux can be lessened, and the probability of producing the short circuit can be lowered. 
         [0025]      FIG. 4  shows a PCB according to a third preferred embodiment of the present invention. The PCB  400  has a similar structure to that of the PCB  200  except that a first accommodating space  423  and a second accommodating space  424  are formed. The first accommodating space  423  is formed at a tail end of each pin  420 , which is a depressed portion, and the second accommodating space  424  is formed at a center region of each pin  420 , which is a concave hole. In use, when an outer element is bonded on the pins  420  of the PCB  400 , a plurality of guiding textures (not labeled) of the pins  420  guide the melting soldering flux (not shown) flowing along the extending direction of the guiding textures. The guiding texture can prevent overflow of the melting soldering flux from two sides of the pins  420 , and avoid short circuit between two adjacent pins  420  or forming solder ball. And, superfluous melting soldering flux can flow in the accommodating spaces  423 ,  424 . Thus, amount of the superfluous melting soldering flux can be lessened, and the probability of producing the short circuit can be lowered. 
         [0026]    In various alternate modifications, the accommodating space can be formed at other positions of the pins. Each pin can have one or two or more than three accommodating space. The deepness of each pin can be equal to or higher than or lower than the thickness of corresponding pin. 
         [0027]    It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, 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 invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.