Abstract:
A lead frame of a through-hole light emitting diode (LED) is used to carry an LED chip, and a lens is used to package the chip and a portion of the lead frame. The lead frame includes at least two leads. One lead is used to carry the chip and each of the leads is extended outward from the lens and has a positioning bump. The positioning bumps partially protrude from the lens, such that when the lead frame is disposed on a circuit board, the lead frame is positioned through the positioning bumps and aligns the lens to guide an optical axis of the through-hole LED, thereby achieving the purposes of convenient assembly, thinness, and a reduced thermal-conducting distance.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No(s). 095146148 filed in Taiwan, R.O.C. on Dec. 8, 2006, the entire contents of which are hereby incorporated by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of Invention 
         [0003]    The present invention relates to a lead frame of a light emitting diode (LED), and more particularly, to a lead frame of a thin through-hole LED. 
         [0004]    2. Related Art 
         [0005]    A lead frame of an LED is used to place an LED chip thereon and through the lead frame, two electrodes of the LED chip are connected to a circuit board, such that the LED is powered on to emit light. 
         [0006]    The lead frame of an LED is designed differently depending on various package styles, for example, a conventional, 2-pin, LED (shell-shaped) and a square shaped, 4-pin, through-hole LED (also called anthropophagi, fish LED) have different package methods and different lead frame structures. Here, the package of the anthropophagi fish LED is illustrated as an example. Referring to  FIGS. 1 ,  2 A, and  2 B at the same time,  FIG. 1  is a top view of a conventional lead support  10 , and  FIGS. 2A and 2B  are respectively a top view and a side view of the lead support  10  after being bent. As shown in the figures, the lead support  10  is constituted by a plurality of lead frames  11 . As for the package of the anthropophagi fish LED, the lead support  10  is usually formed of fifteen lead frames  11  in the art. 
         [0007]    The fabrication flow of the through-hole LED includes the following steps: 
         [0008]    (1) firstly punching a carrying portion  13  to form a spoon portion  14 ; (2) bending the lead support  10  along bending lines  12   a  and  12   b  in  FIG. 1 , so as to form the shapes shown in  FIGS. 2A and 2B ; 
         [0009]    (3) placing an LED chip  15  into the spoon portion  14  shown in the figures and performing wire bonding on electrodes of the LED chip  15  and the lead frames  11 , such that the electrodes are electrically connected to leads  16   a  and  16   b,  as shown in  FIG. 3 ; 
         [0010]    (4) placing the lead support  10  into a die and then encapsulating compound, so as to form a lens  17 ; 
         [0011]    (5) cutting structures  18   a,    18   b,  and  18   c,  and remaining positioning bumps  19   a  and  19   b,  thereby completing the LED of the anthropophagi fish package. 
         [0012]    With regard to the usage of the anthropophagi fish LED, referring to  FIG. 4 , the leads  16   a  and  16   b  of the LED are mainly inserted into a circuit board  90 , so as to make the positioning bumps  19   a  and  19   b  caught onto the circuit board  90  and then soldered to the circuit board. Therefore, through an appropriate design of the positioning bumps  19   a  and  19   b,  it can be ensured that a focus optical axis of a focus portion of the lens  17  is perpendicular to the circuit board  90 , thereby achieving the purpose of convenient assembly. 
         [0013]    Regarding the conventional lead support  10 , although the purposes of (a) enhancing the overall structural rigidity of the lead support  10  (through an appropriate design of the structures  18   a,    18   b,  and  18   c ) and (b) aligning the optical axis are achieved, the thinness requirement of the LED cannot be satisfied. The reason is that a specific distance exists between the positioning bumps  19   a,    19   b  and the lens  17  (formed by cutting the structure  18   b ), and thus during the soldering process, the distance cannot be eliminated, so the height of the LED after soldering cannot be reduced, resulting in departure from the thinness requirement. 
         [0014]    In order to solve the aforementioned problem, one method available in the art is to cut the positioning bumps  19   a  and  19   b  and then adjust the perpendicularity of the optical axis before soldering both by hand. Such a method is not only time-consuming, but also rather poor in accuracy and consistency, and thus, it cannot be employed in mass production. 
         [0015]    Besides, the leads  16   a  and  16   b  further have a thermal-conducting function. However, due to the disposition of the positioning bumps  19   a  and  19   b,  the LED chip  15  is far away from the circuit board  90 , resulting in a long thermal-conducting distance and poor heat dissipation efficiency. Such a circumstance really cannot cope with the industrial trend that the power of an LED becomes even higher and the heat productivity thereof even greater. 
       SUMMARY OF THE INVENTION 
       [0016]    In order to solve the aforementioned problems, the present invention provides a lead frame and a lead support of a through-hole LED, so as to facilitate the soldering and assembly, satisfy the requirement of a thin through-hole LED, reduce a thermal-conducting distance, and enhance the heat dissipation efficiency. 
         [0017]    The lead frame of a through-hole LED provided by the present invention is used to carry an LED chip and electrically connected to a plurality of electrodes of the LED chip. The LED chip and a portion of the lead frame are encapsulated in a lens which guides a light emitted from the LED chip. The lead frame of the through-hole LED comprises at least two leads. A portion of the leads is encapsulated in the lens and a carrying portion is extended from one of the leads. The carrying portion is encapsulated by the lens and carries the LED chip. The electrodes of the LED chip are electrically connected to the leads, respectively. Each of the leads has a positioning bump. The positioning bumps partially protrude from the lens to constitute a reference plane, which forms a specific angle with the direction of guiding the light. 
         [0018]    Secondly, a lead support of a through-hole LED further provided by the present invention is used to carry a plurality of LED chips which are encapsulated by a plurality of lenses, respectively. Edge lines of the encapsulation of the lens form a plurality of lens package lines on the lead support. The lead support of the through-hole LED comprises a plurality of lead frames and a plurality of structures. The structures are connected to the lead frames to form a lead support of the through-hole LED. Each of the lead frames comprises at least two leads and a carrying portion is extended from one of the leads to carry the LED chip. Each of the leads has a positioning bump and at least one lens package line passes through the positioning bumps. 
         [0019]    Therefore, the positioning bumps protrude from the lenses appropriately to form a reference plane, such that when a through-hole unit (LED) is inserted in a circuit board, the positioning bumps press against the circuit board to position the through-hole LED. In this manner, the lenses guide the optical axis of the through-hole LED to form a predetermined angle with the circuit board, thereby achieving the purposes of thinness and easy assembly. Furthermore, since the positioning bumps slightly protrude from the lenses, the distance between the LED chips and the circuit board is much smaller than the conventional design, thus reducing the thermal-conducting distance and enhancing the heat dissipation efficiency. 
         [0020]    In view of the above, the problems in the prior art can be solved effectively by the technical means provided by the present invention, so as to achieve the purposes of thinness, simple through-hole configuration, and enhancement of the heat dissipation efficiency. Therefore, the technical means of the present invention truly has industrial application, novelty, and is an inventive step. 
         [0021]    The features and practice of the preferred embodiments of the present invention will be illustrated below in detail with reference to the drawings. 
         [0022]    Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    The present invention will become more fully understood from the detailed description given herein below for illustration only, and thus is not limitative of the present invention, and wherein: 
           [0024]      FIG. 1  is a schematic diagram of a conventional lead support of a square shaped, 4-pin, through-hole LED; 
           [0025]      FIG. 2A  is a top view of the conventional lead support of the LED after being bent; 
           [0026]      FIG. 2B  is a side view of the conventional lead support of the LED after being bent; 
           [0027]      FIG. 3  is a schematic diagram of packaging the conventional lead frame of the LED to a lens; 
           [0028]      FIG. 4  is a schematic diagram of soldering the conventional LED to a circuit board; 
           [0029]      FIG. 5  is a schematic diagram of a lead support of a through-hole LED according to the present invention; 
           [0030]      FIG. 6A  is a top view of the lead support of the through-hole LED after being bent according to the present invention; 
           [0031]      FIG. 6B  is a side view of the lead support of the through-hole LED after being bent according to the present invention; 
           [0032]      FIG. 7  is a schematic diagram of packaging the lead frame of the through-hole LED to the lens according to the present invention; 
           [0033]      FIG. 8  is a schematic diagram of soldering the lead frame of the through-hole LED to a circuit board according to the present invention; 
           [0034]      FIG. 9  is a top view of a lead support of a through-hole LED according to another embodiment of the present invention; 
           [0035]      FIG. 10  is a front view of the lead support of the through-hole LED according to another embodiment of the present invention; 
           [0036]      FIG. 11  is a right side view of the lead support of the through-hole LED according to another embodiment of the present invention; 
           [0037]      FIG. 12  is a schematic diagram of packaging the lead frame of the through-hole LED to a lens according to another embodiment of the present invention; and 
           [0038]      FIG. 13  is a schematic diagram of soldering the lead frame of the through-hole LED to a circuit board according to another embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0039]    Referring to  FIG. 5 , a schematic diagram of the lead support of a through-hole LED according to the present invention is shown. As shown in  FIG. 5 , the lead support  20  of the through-hole LED consists of a plurality of lead frames  30  and a plurality of structures  22   a,    22   b,  and  22   c.  In the art, a lead support is usually constituted by fifteen lead frames  30  together with a plurality of structures  22   a,    22   b,  and  22   c.  Of course, herein, the lead support  20  may also be formed of twenty or ten lead frames  30 , and the quantity of the lead frames  30  is determined depending on the die of a lens, structural strength, and process conditions. Additionally, the positions of the structures  22   a,    22   b,  and  22   c  should be determined upon considering the rigidity of the whole lead support  20 , such that the lead support  20  may have the functions of providing structural rigidity and bearing the load generated during the processes of chip attachment, wire bonding, mold release and shear of package. 
         [0040]    It can be seen from  FIG. 5  that each of the lead frames  30  in this embodiment has four leads  32   a,    32   b,    32   c,  and  32   d.  However, the present invention may also be implemented even if there are only three or two leads  32   a  and  32   b,  or  32   c  and  32   d  in this embodiment, and the leads are soldered to a circuit board (described later). The leads  32   a,    32   b,    32   c,  and  32   d  are disposed symmetrically and any two of the leads are electrically connected with each other, while  FIG. 5  merely shows that the leads  32   a  and  32   c  are electrically connected with each other and the leads  32   b  and  32   d  are electrically connected with each other. A carrying portion  34  is extended from one of the leads  32   a,    32   b,    32   c,  and  32   d  to carry an LED chip  92  (as shown in  FIG. 7 ). In order to make the carrying portion  34  carry the LED chip  92  more stably, a spoon portion  36  is further punched in the carrying portion  34  to accommodate the LED chip. When the LED chip  92  is disposed in the spoon portion  36 , a wire bonding operation is performed, such that a plurality of electrodes of the LED chip  92  is electrically connected to the leads  32   a,    32   b,    32   c,  and  32   d,  so as to power on the LED chip  92  through the leads  32   a,    32   b,    32   c,  and  32   d  to emit light. 
         [0041]    Referring to  FIG. 5  again, two bending lines  24   a  and  24   b  which are symmetric relative to the carrying portion  34  are shown. Each of the lead frames  30  is bent along the bending lines  24   a  and  24   b  to be shaped as shown in  FIGS. 6A and 6B .  FIG. 6A  is a top view after the lead support is bent, and  FIG. 6B  is a side view after the lead support is bent. The shape of the spoon portion  36  is obviously seen in the figures. 
         [0042]    After the lead support  20  is bent, the package and mold release operation of the lens  40  is performed, as shown in  FIG. 7 . The lens  40  is used to guide the light emitted from the LED chip  92  to be focused or defocused. The package operation of the lens  40  is often performed by means of compound encapsulation. 
         [0043]    Referring to  FIG. 7 , after the package operation of the lens  40  is completed, the structures  22   a,    22   b,  and  22   c  are sheared off, and only the lead frame  30  is remained. It can be seen from  FIG. 7  that the method of shearing off the structures  22   a,    22   b,  and  22   c  is different from the conventional method. In the present invention, all of the structures are sheared off without remaining any positioning elements in the structures  22   a,    22   b,  and  22   c.  Instead, the positioning bumps  38   a,    38   b,    38   c,  and  38   d  are disposed at the leads  32   a,    32   b,    32   c,  and  32   d,  respectively. The positioning bumps  38   a,    38   b,    38   c,  and  38   d  are partially merged in the lens  40  while partially exposed outside the lens  40 , and the top of the exposed portion of each of the positioning bumps  38   a,    38   b,    38 c, and  38   d  forms a reference plane  60 , as shown in  FIG. 7 . It can be seen from  FIG. 7  that the reference plane is disposed outside of the surface of the lens  40  and forms a specific angle with the direction of the lens guiding a light  62 , such as 90° (perpendicular) or 70 to 110°. The degree of the angle is determined depending on the practical application of the LED, i.e., in the range of 70 to 110°. Therefore, when the lead frame  30  is disposed on the circuit board  90 , as shown in  FIG. 8 , the reference plane  60  may serve as a reference of the lead frame  30  being attached to the circuit board  90 , such that the optical axis of the light  62  emitted from the LED chip  92  forms a specific angle with the circuit board  90 . 
         [0044]    Further referring to  FIG. 8 , it can be seen that the sections of another ends of the leads  32   a,    32   b,    32   c,  and  32   d  opposite to the LED chip  92  are convergent, such that the lead frame  30  can be inserted into the circuit board  90  more easily. 
         [0045]    Since the positioning bumps  38   a,    38   b,    38   c,  and  38   d  are disposed on the edge of the lens  40 , the distance between the LED chip  92  and the circuit board  90  is smaller than the conventional design, so as to conduct the heat generated by the LED chip  92  more efficiently. 
         [0046]    Furthermore, back to  FIG. 5 , it can be seen that each of the lead frames  30  of the lead support  20  has a lens package line  42  (only one lens package line  42  is shown for simplifying the figure). The lens package line represents a virtual edge line of the lens  40  being packaged after the spoon portion  36  has been punched and the lead frame  30  has been bent, thus forming a closed area. It can be obviously seen from the figure that the lens package line passes through each of the positioning bumps  38   a,    38   b,    38   c,  and  38   d,  and the distances between the positioning bumps  38   a,    38   b,    38   c,  and  38   d  and the lens package line are substantially the same, such that the exceeded (protruding) portions form the aforementioned reference plane to serve as a reference when the lead frame  30  is disposed on the circuit board  90 . 
         [0047]    Referring to  FIGS. 9 ,  10 , and  11 , a top view, a front view, and a right side view of another embodiment of the present invention are shown, respectively. This embodiment is applied to the conventional, 2-pin, LED element (shell-shaped) package. It can be seen from the figures that a lead support  80  consists of a plurality of structures  82   a  and  82   b  and a plurality of lead frames  50 . Each of the lead frames  50  has two leads  52   a,    52   b  and two positioning bumps  54   a,    54   b,  and a spoon portion  56  is disposed on the top of the lead  52   b  to accommodate an LED chip (not shown). Referring to  FIG. 12 , it can be seen from the figure that the positions of the positioning bumps  54   a  and  54   b  are just on the surface of a lens  58 . The positioning bumps  54   a  and  54   b  are partially merged in the lens  58  while partially exposed outside of the lens  58 , and the tops of the exposed portions of the positioning bumps  54   a  and  54   b  form a reference plane  60 . Therefore, when the LED element is disposed on the circuit board  90  (referring to  FIG. 13 ), the exposed tops of the positioning bumps  54   a  and  54   b  press against the circuit board  90  to be positioned, so as to achieve the purposes of easy assembly, thinness, and a reduced thermal-conducting distance. Of course, the electrodes of the LED chip in this embodiment should also be electrically connected to the leads  52   a  and  52   b,  which is the same as the previous embodiment and will not be repeated herein again. 
         [0048]    The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.