Abstract:
A lead frame comprises a die pad and leads arranged around the die pad. Through holes are provided in the die pad, and the through holes are located in the peripheries, i.e., margin area of the die pad. The through holes serve to be passed through by the metal wires connected with the leads. By means of the above-described lead frame, the subsequent packaging process of the semiconductor chip; including dual chips and/or multi-chips assembly, is simplified and the effect of the manufacturing process is improved, at the same time, the manufacturing cost is reduced.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to the field of semiconductor chip packaging, in particular to a lead frame used in the packaging process of the semiconductor chip. 
       BACKGROUND ART 
       [0002]    With the ever-increasing requirements of miniaturization, lightweight and multifunction of electronic components, the density of semiconductor packaging keeps increasing, thus the packaging dimension and the packaging area have to be reduced. In the technologies developed for fulfilling the above requirements, the semiconductor packaging technology for multi-chip plays a significant role in relation to overall cost, efficiency and reliability of chip packaging. 
         [0003]    In the process of packaging semiconductor chip, a lead frame is required for electrically connecting a semiconductor chip with an exterior circuit so as to provide the functions performed by the semiconductor chip to the exterior circuit. Additionally, the lead frame can also physically support the semiconductor chip. 
         [0004]    The structure of the conventional lead frame is disclosed, see for example, U.S. Pat. No. 4,289,922 granted on Sep. 15, 1981. For illustration,  FIG. 1  shows a lead frame  100  of the type of Quad Flat Package (QFP) comprises a die pad  104  for mounting a semiconductor chip, and a plurality of leads  102  arranged around the die pad  104 . 
         [0005]    The conventional lead frame has a single-layer structure, which is adapted to be used in single-chip semiconductor packaging with the chip being placed on the die pad. If it is desired to form a multi-chip semiconductor packaging, the chips need to be stacked on the die pad. If the chips are placed on the different zones of the die pad, the placed orientations of the chips on two opposite zones are different. In this situation, the chip on one of the two zones need to be further rewired so as to enable the interior connecting lines of the chips on two zones to be symmetric, U.S. Pat. No. 6,674,173 granted on Jan. 6, 2004 disclosed a method of assembly stacked dual chips and/or multi-chips package with rewired substrate wafer and single layer lead frame, which increases the complication of the manufacturing process, reduces the reliability of the semiconductor packaging and increases the cost. 
       DISCLOSURE OF INVENTION 
       [0006]    The problem to be resolved by the present invention is to provide a lead frame, which can prevent the increase of the complication of the manufacture process, the reduction of the reliability of the semiconductor packaging and the increase of the cost. 
         [0007]    In order to resolve the above problem, the present invention provides a lead frame comprising a die pad and leads arranged around the die pad. The die pad is provided with through holes at the peripheries of the die pad. Said through holes serve to be passed through by the metal wires connected with the leads. 
         [0008]    The through holes have the shape of regular or irregular polygon. 
         [0009]    The side lines of said polygon may be linear lines, arcuate lines or a combination of the linear and the arcuate lines. 
         [0010]    Said through holes are closed, being not in communication with the leads; or opened, being in communication with the leads. 
         [0011]    Said lead frame has a single-layer structure. 
         [0012]    The material of said lead frame is metal or alloy. 
         [0013]    Said lead frame is of the type of Quad Flat Package or Dual In-line Package. 
         [0014]    Compared with the prior art, the present invention has the following advantages: according to the present invention, the die pad is provided with through holes located in the margin area (i.e., peripheries area) of the die pad, so that the chips mounted subsequently on the two side portions of the die pad can be placed in the same orientation; therefore, interior connecting lines of the chips on two side portions of the die pad are symmetric, which simplifies the packaging process of the semiconductor chips, improves the flexibility and the effect of the manufacturing process, and reduces the cost at the same time. 
         [0015]    The present invention has further advantages: according to the present invention, the shapes of the through holes on the die pad are regular or irregular polygon, the shapes of the through holes can be selected depending on the actual situations, which further improves the flexibility of the manufacturing process. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is a schematic view of the structure of a lead frame of type of Quad Flat Package according to the prior art; 
           [0017]      FIG. 2  is a schematic view of the first structure of a lead frame of the type of Dual In-line Package according to the first embodiment of the present invention; 
           [0018]      FIG. 3  is a schematic view of the second structure of a lead frame of the type of Dual In-line Package according to the first embodiment of the present invention; 
           [0019]      FIG. 4  is a schematic view of the first structure of a lead frame of the type of Dual In-line Package according to the second embodiment of the present invention; 
           [0020]      FIG. 5  is a schematic view of the second structure of a lead frame of the type of Dual In-line Package according to the second embodiment of the present invention; 
           [0021]      FIG. 6  is a schematic view of the first structure of a lead frame of the type of Quad Flat Package according to the first embodiment of the present invention; 
           [0022]      FIG. 7  is a schematic view of the second structure of a lead frame of the type of Quad Flat Package according to the first embodiment of the present invention; 
           [0023]      FIG. 8  is a schematic view of the first structure of a lead frame of the type of Quad Flat Package according to the second embodiment of the present invention; 
           [0024]      FIG. 9  is a schematic view of the second structure of a lead frame of the type of Quad Flat Package according to the second embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0025]    The die pad of the conventional lead frame is a unitary connecting body, which is adapted to be used in the single-chip semiconductor packaging with the chips being placed on the die pad. If it is desired to form a multi-chips semiconductor packaging, the chips need to be stacked on the die pad. If the chips are placed on the different area of the die pad, the placed orientations of the chips on two side areas are different. In this situation, the chip on one of the two areas need to be further rewired so as to enable the interior connecting lines of the chips on two areas to be symmetric, which increases the complication of the manufacturing process, reduces the reliability of the semiconductor packaging and increases the cost. In the present invention, the die pad is provided with the through holes at the peripheries of the die pad, so that the chips mounted subsequently on the two opposite areas of the die pad can be placed in the same orientation; therefore, the interior connecting lines of the chips on two area of the die pad are symmetric, which simplifies the packaging process of the semiconductor chip, improves the flexibility and the effect of the manufacturing process, and reduces the cost. Hereafter, the embodiments of the present invention will be described in detail with reference to the accompanying drawings. 
         [0026]    The lead frame of the present invention comprises a die pad and leads arranged around the die pad; the die pad is provided with through holes at the margin of the die pad; said through holes serve as passages for the metal wires connected with the leads passing through. 
         [0027]      FIG. 2  is a schematic view of the first structure of a lead frame of the type of Dual In-line Package according to the first embodiment of the present invention. As shown in  FIG. 2 , the lead frame  200  comprises a die pad  202  and leads  1 ,  2 ,  3 ,  4 ,  5 ,  6 ,  7 ,  8 ,  9 ,  10 ,  11 ,  12 ,  13  and  14  arranged around the die pad  202 , the leads  1 ,  2 ,  3 ,  4 ,  5 ,  6 ,  7 ,  8 ,  9 ,  10 ,  11 ,  12 ,  13  and  14  being extended outward and spaced from the die pad  202  in a shape of comb; the die pad  202  has closed through holes a, b, c, d, e, f, g, h, i, j, k, l, m, and n, with the same shape, and the number and the location of the closed through holes correspond to those of the leads  1 ,  2 ,  3 ,  4 ,  5 ,  6 ,  7 ,  8 ,  9 ,  10 ,  11 ,  12 ,  13  and  14 , the closed through holes a, b, c, d, e, f, g, h, i, j, k, l, m, and n are located in the peripheries (i.e., margin area) of the die pad  202 ; wherein the closed through hole a corresponds to the lead  1 , the closed through hole b corresponds to the lead  2 , the closed through hole c corresponds to the lead  3 , the closed through hole d corresponds to the lead  4 , the closed through hole e corresponds to the lead  5 , the closed through hole f corresponds to the lead  6 , the closed through hole g corresponds to the lead  7 , the closed through hole h corresponds to the lead  8 , the closed through hole i corresponds to the lead  9 , the closed through hole j corresponds to the lead  10 , the closed through hole k corresponds to the lead  11 , the closed through hole l corresponds to the lead  12 , the closed through hole m corresponds to the lead  13 , and the closed through hole n corresponds to the lead  14 . 
         [0028]    In the present embodiment, the dimensions of the closed through holes a, b, c, d, e, f, g, h, i, j, k, l, m, and n are greater than 0.2 mm×0.2 mm. In addition to the size adopted in this embodiment, the dimensions of the closed through holes a, b, c, d, e, f, g, h, i, j, k, l, m, and n can be freely selected, as long as the die pad  202  is not disconnected with the whole lead frame  200  and the die pad  202  has an area for carrying the chip. 
         [0029]    The shapes of the closed through holes a, b, c, d, e, f, g, h, i, j, k, l, m, and n may be regular or irregular polygon, wherein the side lines of the polygon may be linear line, arcuate lines or a combination of the linear and arcuate lines. In the present embodiment, the shapes of the closed through holes a, b, c, d, e, f, g, h, i, j, k, l, m, and n are quad, specifically, square or rectangle. In addition to the embodiment, the closed through holes a, b, c, d, e, f, g, h, i, j, k, l, m, and n may be circle, semicircle, ellipse, semi-ellipse, triangle, pentagon, hexagon, heptagon, octagon, enneagon, decagon, hendecagon, dodecagon, triangle with rounded corners, quad with rounded corners, pentagon with rounded corners, hexagon with rounded corners, heptagon with rounded corners, octagon with rounded corners, enneagon with rounded corners, decagon with rounded corners, hendecagon with rounded corners, or dodecagon with rounded corners and so on. Furthermore, the shapes of the closed through holes a, b, c, d, e, f, g, h, i, j, k, l, m, and n may be different from each other. However, since the metal wires which pass through the closed through holes a, b, c, d, e, f, g, h, i, j, k, l, m, and n, and connect with the leads has circular sections, the shapes of the closed through holes a, b, c, d, e, f, g, h, i, j, k, l, m, and n are preferably circle or ellipse in order to match the shapes of the metal wires. 
         [0030]    In the present embodiment, the material of the lead frame  200  is metal or alloy. 
         [0031]      FIG. 3  is a schematic view of the second structure of a lead frame of the type of Dual In-line Package according to the first embodiment of the present invention. As shown in  FIG. 3 , the lead frame  200  comprises a die pad  202  and leads  1 ,  2 ,  3 ,  4 ,  5 ,  6 ,  7 ,  8 ,  9 ,  10 ,  11 ,  12 ,  13  and  14  arranged around the die pad  202 , the leads  1 ,  2 ,  3 ,  4 ,  5 ,  6 ,  7 ,  8 ,  9 ,  10 ,  11 ,  12 ,  13  and  14  being extended outward and spaced from the die pad  202  in a comb shape; the die pad  202  in its peripheries, i.e., margin area has opened through holes a, b, c, d, e, f, g, h, i, j, k, l, m, and n with the same shape, the number and location of the opened through holes correspond to those of the leads  1 ,  2 ,  3 ,  4 ,  5 ,  6 ,  7 ,  8 ,  9 ,  10 ,  11 ,  12 ,  13  and  14 , the opened through holes a, b, c, d, e, f, g, h, i, j, k, l, m, and n are located in the peripheries of the die pad  202 ; wherein the opened through hole a corresponds to the lead  1 , the opened through hole b corresponds to the lead  2 , the opened through hole c corresponds to the lead  3 , the opened through hole d corresponds to the lead  4 , the opened through hole e corresponds to the lead  5 , the opened through hole f corresponds to the lead  6 , the opened through hole g corresponds to the lead  7 , the opened through hole h corresponds to the lead  8 , the opened through hole i corresponds to the lead  9 , the opened through hole j corresponds to the lead  10 , the opened through hole k corresponds to the lead  11 , the opened through hole l corresponds to the lead  12 , the opened through hole m corresponds to the lead  13 , and the opened through hole n corresponds to the lead  14 . 
         [0032]    In the present embodiment, the opened through holes a, b, c, d, e, f, g, h, i, j, k, l, m, and n are open in the edges of the die pad  202 ,being in communication with the leads  1 ,  2 ,  3 ,  4 ,  5 ,  6 ,  7 ,  8 ,  9 ,  10 ,  11 ,  12 ,  13  and  14 . 
         [0033]    The dimensions of the opened through holes a, b, c, d, e, f, g, h, i, j, k, l, m, and n are 0.2 mm×0.3 mm. In addition to the size adopted in this embodiment, the dimensions of the opened through holes a, b, c, d, e, f, g, h, i, j, k, l, m, and n can be freely selected, as long as the die pad  202  is not disconnected with the whole lead frame  200  and the die pad  202  has an area for carrying the chip. 
         [0034]    The shapes of the opened through holes a, b, c, d, e, f, g, h, i, j, k, l, m, and n may be regular or irregular polygon, wherein the side lines of the polygon may be linear lines, arcuate lines or a combination of the linear and arcuate lines . In the present embodiment, the shapes of the opened through holes a, b, c, d, e, f, g, h, i, j, k, l, m, and n are quad, specifically, square or rectangle. In addition to the embodiment, the opened through holes a, b, c, d, e, f, g, h, i, j, k, l, m, and n may be circle, semicircle, ellipse, semi-ellipse, triangle, pentagon, hexagon, heptagon, octagon, enneagon, decagon, hendecagon, dodecagon, triangle with rounded corners, quad with rounded corners, pentagon with rounded corners, hexagon with rounded corners, heptagon with rounded corners, octagon with rounded corners, enneagon with rounded corners, decagon with rounded corners, hendecagon with rounded corners, or dodecagon with rounded corners and so on. Furthermore, the shapes of the opened through holes a, b, c, d, e, f, g, h, i, j, k, l, m, and n may be different from each other. However, since the metal wires connected with the leads through the opened through holes a, b, c, d, e, f, g, h, i, j, k, l, m, and n has circular sections, the shapes of the opened through holes a, b, c, d, e, f, g, h, i, j, k, l, m, and n are preferably semi-circle or semi-ellipse in order to match the shapes of the metal wires. 
         [0035]    In the present embodiment, the material of the lead frame  200  is metal or alloy. 
         [0036]      FIG. 4  is a schematic view of the first structure of a lead frame of the type of Dual In-line Package according to the second embodiment of the present invention. As shown in  FIG. 4 , the lead frame  300  comprises a die pad  302  and a plurality of leads  304  arranged around the die pad  302 , the plurality of the leads  304  being extended outward and spaced from the die pad  302  in a comb-shape; the die pad  302  is provided with a single closed through hole  306  corresponding to each group of the leads  304 , the closed through holes  306  are located in the peripheries, i.e., margin area of the die pad  302 . 
         [0037]    In the present embodiment, the dimensions of the closed through holes  306  are greater than 0.2 mm×0.2 mm. In addition to the embodiment, the dimensions of the closed through holes  306  can be freely selected, as long as the die pad  302  is not disconnected with the whole lead frame  300  and the die pad  302  has an area for carrying the chip. 
         [0038]    The shapes of the closed through holes  306  may be regular or irregular polygon, wherein the side lines of the polygon may be linear lines, arcuate lines or a combination of the linear and arcuate lines . In the present embodiment, the shapes of the closed through holes  306  are quad, specifically, square or rectangle. In addition to the embodiment, the closed through holes  306  may be circle, semi-circle, ellipse, semi-ellipse, triangle, pentagon, hexagon, heptagon, octagon, enneagon, decagon, hendecagon, dodecagon, triangle with rounded corners, quad with rounded corners, pentagon with rounded corners, hexagon with rounded corners, heptagon with rounded corners, octagon with rounded corners, enneagon with rounded corners, decagon with rounded corners, hendecagon with rounded corners, or dodecagon with rounded corners and so on. Furthermore, the shapes of the closed through holes  306  may be different from each other. However, since the metal wires which pass through the closed through holes  306  and connect with the leads have circular sections, the shapes of the closed through holes  306  are preferably circle or ellipse in order to match the shapes of the metal wires. 
         [0039]    In the present embodiment, the material of the lead frame  300  is metal or alloy. 
         [0040]      FIG. 5  is a schematic view of the second structure of a lead frame of the type of Dual In-line Package according to the second embodiment of the present invention. As shown in  FIG. 5 , the lead frame  300  comprises a die pad  302  and a plurality of leads  304  arranged around the die pad  302 , the plurality of the leads  304  being extended outward and spaced from the die pad  302  in a comb-shape; the die pad  302  has a single opened through hole  306  corresponding to each group of the leads  304 , the opened through holes  306  are open in the edges of the die pad  302 , being in communication with the leads  304 . 
         [0041]    In the present embodiment, the dimensions of the opened through holes  306  are greater than 0.3 mm×2 mm. In addition to the embodiment, the dimensions of the opened through holes  306  are optional, as long as the die pad  302  is not disconnected with the whole lead frame  300  and the die pad  302  has an area for carrying the chip. 
         [0042]    The shapes of the opened through holes  306  may be regular or irregular polygon, wherein the side lines of the polygon may be linear lines, arcuate lines or a combination of the linear and arcuate lines. In the present embodiment, the shapes of the opened through holes  306  are quad, specifically, square or rectangle. In addition to the embodiment, the opened through holes  306  may be circle, semi-circle, ellipse, semi-ellipse, triangle, pentagon, hexagon, heptagon, octagon, enneagon, decagon, hendecagon, dodecagon, triangle with rounded corners, quad with rounded corners, pentagon with rounded corners, hexagon with rounded corners, heptagon with rounded corners, octagon with rounded corners, enneagon with rounded corners, decagon with rounded corners, hendecagon with rounded corners, or dodecagon with rounded corners and so on. Furthermore, the shapes of the opened through holes  306  may be different from each other. However, since the metal wires which pass through the opened through holes  306  and connected with the leads have circular sections, the shapes of the opened through holes  306  are preferably semi-circle or semi-ellipse in order to match the shapes of the metal wires. 
         [0043]    In the present embodiment, the material of the lead frame  300  is metal or alloy. 
         [0044]      FIG. 6  is a schematic view of the first structure of a lead frame of the type of Quad Flat Package according to the first embodiment of the present invention. As shown in  FIG. 6 , the lead frame  400  comprises a die pad  402  and leads A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z, A′ and B′ arranged around the die pad  402 , the leads A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z, A′ and B′ being extended outward in a comb shape and spaced from the die pad  402 ; the die pad  402  is provided with closed through holes  21 ,  22 ,  23 ,  24 ,  25 ,  26 ,  27 ,  28 ,  29 ,  30 ,  31 ,  32 ,  33 ,  34 ,  35 ,  36 ,  37 ,  38 ,  39 ,  40 ,  41 ,  42 ,  43  and  44  therein, which are located in the peripheries of the die pad  402 ; wherein the dimensions of the closed through holes  22 ,  23 ,  24 ,  25 ,  26 ,  28 ,  29 ,  30 ,  31 ,  32 ,  34 ,  35 ,  36 ,  37 ,  38 ,  40 ,  41 ,  42 ,  43  and  44  are same, and the closed through hole  22  corresponds to the lead B, the closed through hole  23  corresponds to the lead C, the closed through hole  24  corresponds to the lead D, the closed through hole  25  corresponds to the lead E, the closed through hole  26  corresponds to the lead F, the closed through hole  28  corresponds to the lead I, the closed through hole  29  corresponds to the lead J, the closed through hole  30  corresponds to the lead K, the closed through hole  31  corresponds to the lead L, the closed through hole  32  corresponds to the lead M, the closed through hole  34  corresponds to the lead P, the closed through hole  35  corresponds to the lead Q, the closed through hole  36  corresponds to the lead R, the closed through hole  37  corresponds to the lead S, the closed through hole  38  corresponds to the lead T, the closed through hole  40  corresponds to the lead W, the closed through hole  41  corresponds to the lead X, the closed through hole  42  corresponds to the lead Y, the closed through hole  43  corresponds to the lead Z, the closed through hole  44  corresponds to the lead A′, while the lead A and the lead B′ correspond to the same closed through hole  21 , the lead G and the lead H correspond to the same closed through hole  27 , the lead O and the lead N correspond to the same closed through hole  33 , the lead U and the lead V correspond to the same closed through hole  39 . 
         [0045]    In the present embodiment, the lead A and the lead B′ share the closed though hole  21 , the lead G and the lead H share the closed though hole  27 , the lead O and the lead N share the closed though hole  33 , the lead U and the lead V share the closed though hole  39 , in order to avoid lowering the whole structural strength of the die pad  402 . 
         [0046]    In the present embodiment, the dimensions of the closed through holes  22 ,  23 ,  24 ,  25 ,  26 ,  28 ,  29 ,  30 ,  31 ,  32 ,  34 ,  35 ,  36 ,  37 ,  38 ,  40 ,  41 ,  42 ,  43  and  44  are same and greater than 0.2 mm×0.2 mm; the dimensions of the closed though holes  21 ,  27 ,  33  and  39  are same and greater than 0.4 mm×0.4 mm. In addition to the embodiment, the dimensions of the closed through holes  21 ,  22 ,  23 ,  24 ,  25 ,  26 ,  27 ,  28 ,  29 ,  30 ,  31 ,  32 ,  33 ,  34 ,  35 ,  36 ,  37 ,  38 ,  39 ,  40 ,  41 ,  42 ,  43  and  44  can be freely selected, as long as the die pad  402  is not disconnected with the whole lead frame  400  and the die pad  402  has an area for carrying the chip. 
         [0047]    The shapes of the closed through holes  21 ,  22 ,  23 ,  24 ,  25 ,  26 ,  27 ,  28 ,  29 ,  30 ,  31 ,  32 ,  33 ,  34 ,  35 ,  36 ,  37 ,  38 ,  39 ,  40 ,  41 ,  42 ,  43  and  44  may be regular or irregular polygon, wherein the side lines of the polygon may be linear lines, arcuate lines or a combination of the linear and arcuate lines. In the present embodiment, the shapes of the closed through holes  21 ,  22 ,  23 ,  24 ,  25 ,  26 ,  27 ,  28 ,  29 ,  30 ,  31 ,  32 ,  33 ,  34 ,  35 ,  36 ,  37 ,  38 ,  39 ,  40 ,  41 ,  42 ,  43  and  44  may be quad, specifically, square or rectangle. In addition to the embodiment, the closed through holes  21 ,  22 ,  23 ,  24 ,  25 ,  26 ,  27 ,  28 ,  29 ,  30 ,  31 ,  32 ,  33 ,  34 ,  35 ,  36 ,  37 ,  38 ,  39 ,  40 ,  41 ,  42 ,  43  and  44  may also be circle, semi-circle, ellipse, semi-ellipse, triangle, pentagon, hexagon, heptagon, octagon, enneagon, decagon, hendecagon, dodecagon, triangle with rounded corners, quad with rounded corners, pentagon with rounded corners, hexagon with rounded corners, heptagon with rounded corners, octagon with rounded corners, enneagon with rounded corners, decagon with rounded corners, hendecagon with rounded corners, or dodecagon with rounded corners and so on. Furthermore, the shapes of the closed through holes  21 ,  22 ,  23 ,  24 ,  25 ,  26 ,  27 ,  28 ,  29 ,  30 ,  31 ,  32 ,  33 ,  34 ,  35 ,  36 ,  37 ,  38 ,  39 ,  40 ,  41 ,  42 ,  43  and  44  may be different from each other. However, since the metal wires passing through the closed through holes  21 ,  22 ,  23 ,  24 ,  25 ,  26 ,  27 ,  28 ,  29 ,  30 ,  31 ,  32 ,  33 ,  34 ,  35 ,  36 ,  37 ,  38 ,  39 ,  40 ,  41 ,  42 ,  43  and  44  and connected with the leads have circular sections, the shapes of the closed through holes  21 ,  22 ,  23 ,  24 ,  25 ,  26 ,  27 ,  28 ,  29 ,  30 ,  31 ,  32 ,  33 ,  34 ,  35 ,  36 ,  37 ,  38 ,  39 ,  40 ,  41 ,  42 ,  43  and  44  are preferably circle or ellipse in order to match the shapes of the metal wires. 
         [0048]    In the present embodiment, the material of the lead frame  400  is metal or alloy. 
         [0049]      FIG. 7  is a schematic view of the second structure of a lead frame of the type of Quad Flat Package according to the first embodiment of the present invention. As shown in  FIG. 7 , the lead frame  400  comprises a die pad  402  and leads A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z, A′ and B′ arranged around the die pad  402 , the leads A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z, A′ and B′ being extended outward in a comb shape and spaced from the die pad  402 ; the die pad  402  is provided with opened through holes  22 ,  23 ,  24 ,  25 ,  26 ,  28 ,  29 ,  30 ,  31 ,  32 ,  34 ,  35 ,  36 ,  37 ,  38 ,  40 ,  41 ,  42 ,  43  and  44  as well as closed through holes  21 ,  27 ,  33  and  39 , the opened through holes  22 ,  23 ,  24 ,  25 ,  26 ,  28 ,  29 ,  30 ,  31 ,  32 ,  34 ,  35 ,  36 ,  37 ,  38 ,  40 ,  41 ,  42 ,  43  and  44  are open in the edges of the die pad  402 , being in communication with the corresponding leads; wherein the dimensions of the opened through holes  22 ,  23 ,  24 ,  25 ,  26 ,  28 ,  29 ,  30 ,  31 ,  32 ,  34 ,  35 ,  36 ,  37 ,  38 ,  40 ,  41 ,  42 ,  43  and  44  are same, and the opened through hole  22  corresponds to the lead B, the opened through hole  23  corresponds to the lead C, the opened through hole  24  corresponds to the lead D, the opened through hole  25  corresponds to the lead E, the opened through hole  26  corresponds to the lead F, the opened through hole  28  corresponds to the lead I, the opened through hole  29  corresponds to the lead J, the opened through hole  30  corresponds to the lead K, the opened through hole  31  corresponds to the lead L, the opened through hole  32  corresponds to the lead M, the opened through hole  34  corresponds to the lead P, the opened through hole  35  corresponds to the lead Q, the opened through hole  36  corresponds to the lead R, the opened through hole  37  corresponds to the lead S, the opened through hole  38  corresponds to the lead T, the opened through hole  40  corresponds to the lead W, the opened through hole  41  corresponds to the lead X, the opened through hole  42  corresponds to the lead Y, the opened through hole  43  corresponds to the lead Z, the opened through hole  44  corresponds to the lead A′, while the lead A and the lead B′ correspond to the same closed through hole  21 , the lead G and the lead H correspond to the same closed through hole  27 , the lead O and the lead N correspond to the same closed through hole  33 , the lead U and the lead V correspond to the same closed through hole  39 . 
         [0050]    In the present embodiment, the lead A and the lead B′ share the closed though hole  21 , the lead G and the lead H share the closed though hole  27 , the lead O and the lead N share the closed though hole  33 , the lead U and the lead V share the closed though hole  39 , in order to avoid lowering the whole structural strength of the die pad  402 . 
         [0051]    In the present embodiment, the dimensions of the opened through holes  22 ,  23 ,  24 ,  25 ,  26 ,  28 ,  29 ,  30 ,  31 ,  32 ,  34 ,  35 ,  36 ,  37 ,  38 ,  40 ,  41 ,  42 ,  43  and  44  are same in 0.2 mm×0.3 mm; the dimensions of the closed though holes  21 ,  27 ,  33  and  39  are same in 0.4 mm×0.4 mm. In addition to the embodiment, the dimensions of the opened through holes  22 ,  23 ,  24 ,  25 ,  26 ,  28 ,  29 ,  30 ,  31 ,  32 ,  34 ,  35 ,  36 ,  37 ,  38 ,  40 ,  41 ,  42 ,  43 ,  44  and the closed through holes  21 ,  27 ,  33  and  39  can be optionally selected, as long as that the die pad  402  is not disconnected with the whole lead frame  400  and the die pad  402  has an area for carrying the chip. 
         [0052]    The shapes of the opened through holes  22 ,  23 ,  24 ,  25 ,  26 ,  28 ,  29 ,  30 ,  31 ,  32 ,  34 ,  35 ,  36 ,  37 ,  38 ,  40 ,  41 ,  42 ,  43 ,  44  and the closed through holes  21 ,  27 ,  33  and  39  may be regular or irregular polygon, wherein the side lines of the polygon may be linear lines, arcuate lines or a combination of the linear and arcuate line. In the present embodiment, the shapes of the opened through holes  22 ,  23 ,  24 ,  25 ,  26 ,  28 ,  29 ,  30 ,  31 ,  32 ,  34 ,  35 ,  36 ,  37 ,  38 ,  40 ,  41 ,  42 ,  43 ,  44  and the closed through holes  21 ,  27 ,  33  and  39  are quad, specifically, square or rectangle. In addition to the embodiment, the shapes of the opened through holes  22 ,  23 ,  24 ,  25 ,  26 ,  28 ,  29 ,  30 ,  31 ,  32 ,  34 ,  35 ,  36 ,  37 ,  38 ,  40 ,  41 ,  42 ,  43 ,  44  and the closed through holes  21 ,  27 ,  33  and  39  may also be circle, semi-circle, ellipse, semi-ellipse, triangle, pentagon, hexagon, heptagon, octagon, enneagon, decagon, hendecagon, dodecagon, triangle with rounded corners, quad with rounded corners, pentagon with rounded corners, hexagon with rounded corners, heptagon with rounded corners, octagon with rounded corners, enneagon with rounded corners, decagon with rounded corners, hendecagon with rounded corners, or dodecagon with rounded corners and so on. Furthermore, the shapes of the opened through holes  22 ,  23 ,  24 ,  25 ,  26 ,  28 ,  29 ,  30 ,  31 ,  32 ,  34 ,  35 ,  36 ,  37 ,  38 ,  40 ,  41 ,  42 ,  43 ,  44  and the closed through holes  21 ,  27 ,  33  and  39  may be different from each other. However, since the metal wires connected with the leads and passing through the opened through holes  22 ,  23 ,  24 ,  25 ,  26 ,  28 ,  29 ,  30 ,  31 ,  32 ,  34 ,  35 ,  36 ,  37 ,  38 ,  40 ,  41 ,  42 ,  43 ,  44  and the closed through holes  21 ,  27 ,  33  and  39  have circular sections, the shapes of the opened through holes  22 ,  23 ,  24 ,  25 ,  26 ,  28 ,  29 ,  30 ,  31 ,  32 ,  34 ,  35 ,  36 ,  37 ,  38 ,  40 ,  41 ,  42 ,  43 ,  44  are preferably semi-circle or semi-ellipse as well as the shapes of the closed through holes  21 ,  27 ,  33  and  39  are preferably circle or ellipse in order to match the shapes of the metal wires. 
         [0053]    In the present embodiment, the material of the lead frame  400  is metal or alloy. 
         [0054]      FIG. 8  is a schematic view of the first structure of a lead frame of the type of Quad Flat Package according to the second embodiment of the present invention. As shown in  FIG. 8 , the lead frame  500  comprises a die pad  502  and leads A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z, A′ and B′ arranged around the die pad  502 , the leads A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z, A′ and B′ being extended outward and in a comb shape and spaced from the die pad  502 ; the die pad  502  is provided with closed through holes  51 ,  52 ,  53 ,  54 ,  55 ,  56 ,  57  and  58  which are located in the peripheries, i.e., margin area of the die pad  502 ; wherein the dimensions of the closed through holes  51 ,  52 ,  53 ,  54 ,  55 ,  56 ,  57  and  58  are same, and the leads W, X, Y, Z, A′ correspond to the same closed through holes  52 , the leads B, C, D, E, F correspond to the same closed through holes  53 , the leads I, J, K, L, M correspond to the same closed through holes  55 , the leads P, Q, R, S, T correspond to the same closed through holes  57 ; the dimensions of the closed through holes  51 ,  54 ,  56 ,  58  are same and smaller than those of the closed through holes  52 ,  53 ,  55  and  57 , wherein the lead A and the lead B′ correspond to the same closed through hole  51 , the lead G and the lead H correspond to the same closed through hole  54 , the lead O and the lead N correspond to the same closed through hole  56 , the lead U and the lead V correspond to the same closed through hole  58 . 
         [0055]    In the present embodiment, the dimensions of the closed through holes  52 ,  53 ,  55  and  57  are same and greater than 0.2 mm×2 mm; the dimensions of the closed though holes  51 ,  54 ,  56  and  58  are same in 0.4 mm×0.4 mm. In addition to the embodiment, the dimensions of the closed through holes  51 ,  52 ,  53 ,  54 ,  55 ,  56 ,  57  and  58  can be optionally selected, as long as die pad  502  is not disconnected with the whole lead frame  500  and the die pad  502  has an area for carrying the chip. 
         [0056]    The shapes of the closed through holes  51 ,  52 ,  53 ,  54 ,  55 ,  56 ,  57  and  58  may be regular or irregular polygon, wherein the side lines of the polygon may be linear lines, arcuate lines or a combination of the linear and arcuate lines. In the present embodiment, the shapes of the closed through holes  51 ,  52 ,  53 ,  54 ,  55 ,  56 ,  57  and  58  are quad, specifically, square or rectangle. In addition to the embodiment, the closed through holes  51 ,  52 ,  53 ,  54 ,  55 ,  56 ,  57  and  58  may also be circle, semi-circle, ellipse, semi-ellipse, triangle, pentagon, hexagon, heptagon, octagon, enneagon, decagon, hendecagon, dodecagon, triangle with rounded corners, quad with rounded corners, pentagon with rounded corners, hexagon with rounded corners, heptagon with rounded corners, octagon with rounded corners, enneagon with rounded corners, decagon with rounded corners, hendecagon with rounded corners, or dodecagon with rounded corners and so on. Furthermore, the shapes of the closed through holes  51 ,  52 ,  53 ,  54 ,  55 ,  56 ,  57  and  58  may be different from each other. However, since the metal wires connected with the leads and passing through the closed through holes  51 ,  52 ,  53 ,  54 ,  55 ,  56 ,  57  and  58  have circular sections, the shapes of the closed through holes  51 ,  52 ,  53 ,  54 ,  55 ,  56 ,  57  and  58  are preferably circle or ellipse in order to match the shapes of the metal wires. 
         [0057]    In the present embodiment, the material of the lead frame  500  is metal or alloy. 
         [0058]      FIG. 9  is a schematic view of the second structure of a lead frame of the type of Quad Flat Package according to the second embodiment of the present invention. As shown in  FIG. 9 , the lead frame  500  comprises a die pad  502  and leads A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z, A′ and B′ arranged around the die pad  502 , the leads A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z, A′ and B′ being extended outward and in a comb shape and spaced from the die pad  502 ; the die pad  502  is provided with opened through holes  52 ,  53 ,  55 ,  57  in the same dimension as well as closed through holes  51 ,  54 ,  56  and  58  in the same dimension which is smaller than those of the opened through holes  52 ,  53 ,  55 ,  57 , the opened through holes  52 ,  53 ,  55 ,  57  are open in the edges of the die pad  502 , being in communication with the corresponding leads; wherein the leads W, X, Y, Z, A′ correspond to the same opened through holes  52 , the leads B, C, D, E, F correspond to the same opened through holes  53 , the leads I, J, K, L, M correspond to the same opened through holes  55 , the leads P, Q, R, S, T correspond to the same opened through holes  57 ; the lead A and the lead B′ correspond to the same closed through hole  51 , the lead G and the lead H correspond to the same closed through hole  54 , the lead O and the N correspond to the same closed through hole  56 , the lead U and the V correspond to the same closed through hole  58 . 
         [0059]    In the present embodiment, the dimensions of the opened through holes  52 ,  53 ,  55  and  57  are same and greater than 0.3 mm×2 mm; the dimensions of the closed though holes  51 ,  54 ,  56  and  58  are same in 0.4 mm×0.4 mm. In addition to the embodiment, the dimensions of the opened through holes  52 ,  53 ,  55 ,  57  and the closed through holes  51 ,  54 ,  56  and  58  can be optionally selected such that the die pad  502  is not disconnected with the whole lead frame  500  and the die pad  502  has an area for carrying the chip. 
         [0060]    The shapes of the opened through holes  52 ,  53 ,  55 ,  57  and the closed through holes  51 ,  54 ,  56  and  58  may be regular or irregular polygon, wherein the side lines of the polygon may be linear lines, arcuate lines or a combination of the linear and arcuate lines. In the present embodiment, the shapes of the opened through holes  52 ,  53 ,  55 ,  57  and the closed through holes  51 ,  54 ,  56  and  58  are quad, specifically, square or rectangle. In addition to the embodiment, the opened through holes  52 ,  53 ,  55 ,  57  and the closed through holes  51 ,  54 ,  56  and  58  may also be circle, semi-circle, ellipse, semi-ellipse, triangle, pentagon, hexagon, heptagon, octagon, enneagon, decagon, hendecagon, dodecagon, triangle with rounded corners, quad with rounded corners, pentagon with rounded corners, hexagon with rounded corners, heptagon with rounded corners, octagon with rounded corners, enneagon with rounded corners, decagon with rounded corners, hendecagon with rounded corners, or dodecagon with rounded corners and so on. Furthermore, the shapes of the opened through holes  52 ,  53 ,  55 ,  57  and the closed through holes  51 ,  54 ,  56  and  58  may be different from each other. However, since the metal wires connected with the leads and passing through the opened through holes  52 ,  53 ,  55 ,  57  and the closed through holes  51 ,  54 ,  56  and  58  have circular sections, the shapes of the opened through holes  52 ,  53 ,  55 ,  57  are preferably semi-circle or semi-ellipse as well as the shapes of the closed through holes  51 ,  54 ,  56  and  58  are preferably circle or ellipse in order to match the shapes of the metal wires. 
         [0061]    In the present embodiment, the material of the lead frame  500  is metal or alloy. Furthermore, the lead frame can also be of the type of Leadless Chip Carrier Package, the type of Single Inline Package, or the type of SD Memory Card Package. 
         [0062]    Although the invention has been disclosed with reference to preferred embodiments thereof, many possible changes and modifications of the invention may become apparent to those skilled in the art without departing from the spirit and scopes of the invention. Therefore, the protection scopes of the present invention are only limited by what defined in the claims.