Abstract:
The present invention relates to a structure of a composite lead frame generally having a die bonding layer and a solder layer and may further have an cohesive layer between the die bonding layer and the solder layer. The die bonding layer is made of flex substrate and the solder layer is made of traditional lead frame. Thus, the composite lead frame structure is suitable for the flip chip or wire bonding packaging process of LED and also suitable for semiconductor IC packaging process. It is good in electric and heat conductivity, and also with higher mechanical strength, resulting high pin counts and minimization of resulted IC.

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a lead frame structure, particularly a composite structure of flex substrate and lead frame suitable for the flip chip or wire bonding packaging process of LED and also semiconductor IC packaging process. 
     Brief Description of the Prior Art 
     A general flex substrate is made of copper foil and Polyimide, PI stacked together. Electric circuitry shall be formed by etching process and plating process to complete a flex substrate. Referring to  FIG. 1  which shows an illustrative sectional view of a general flex substrate, the flex substrate  8  mainly comprises a flex base material  80 , an upper metal layer  81  and an adhesive layer  82 . A plating layer  83  is formed on top of the upper metal layer  81 . During the manufacturing process of having an IC  84  eutectic using the flex substrate  8 , a carrier (not show in the figure) must be used to enhance the mechanical strength of the flex substrate  8  and also improve the yield rate of IC packaging process. It is noted that the heat conductive coefficient of the flex base material  81  being approximately 0.1-0.35 W/mK which is very much lower than the heat conductive coefficient 398 W/mK of a copper metal lead frame. 
     A conventional lead frame is shown in  FIG. 2  which is an illustrative sectional view of the same. The lead frame  9  comprises conductive leads  90  which having plating layers  91  formed on the upper and lower surfaces thereof. Because of the thickness of the lead frame  9  usually greater than the flex substrate, conductive leads space of lead frame greater than conductive lead space of the flex substrate, it results the number of the conductive leads of the lead frame  9  much less than the number of conductive leads of the flex substrate. Therefore, the dimension of resulted IC after packaging process becomes relatively large. 
     SUMMARY OF THE INVENTION 
     The principal objective of present invention is to provide a composite lead frame structure suitable for the flip chip or wire bonding packaging process of LED and also suitable for semiconductor IC packaging process. 
     The advantages of the composite lead frame according to the present invention are good in electric and heat conductivity, higher mechanical strength, resulting high pin counts and minimization of resulted IC. 
     There are several principle features according to the present invention. The first principal feature of one embodiment of the composite lead frame according to the present invention is to provide a composition of traditional lead frame and flex substrate used for flip chip or wire bonding packaging of LED or IC. The composite lead frame structure comprises a die bonding layer and a solder layer. A plurality of lead frame cells have lead frame cell gap in between one another. Each lead frame cell gap is provided with a first lead frame cell gap, a second lead frame cell gap and a third lead frame cell gap. The third lead frame cell gap is filled with insulating material. Lead frame cell has a die bonding unit and a solder unit. The die bonding unit comprises insulating clearance and a plurality of conductive leads and a plurality of conductive body holes. Each of the conductive leads of the die bonding unit sequentially contains upper metal layer, upper adhesive layer, tape layer and lower adhesive layer. The insulating clearance of die bonding unit comprises conductive lead clearance and tape clearance. The insulating clearance is formed between various conductive leads. The solder unit comprises a plurality of conductive leads and an insulating clearance which being formed between lead tips of conductive leads. The conductive leads of die bonding unit are vertically aligned with conductive leads of the solder unit and lower adhesive layer is also tightly attached with the conductive leads of the solder unit. 
     Another feature of one embodiment of the composite lead frame according to the present invention is to provide a composite lead frame in which the upper adhesive layer and lower adhesive layer are insulating paste. The conductive lead of the die bonding layer are made of copper foil. The plurality conductive leads of solder layer are made of copper, iron or aluminum. Upon the plurality of conductive lead of the die bonding unit, there is formed a plating layer which is a material of one selected from silver, gold, nickel, palladium and tin or combination thereof. The width of the insulating clearance of the die bonding unit can be greater, smaller or equal to the width of the insulating clearance of the solder unit. The plurality of conductive body holes are filled with either of gold, silver, copper and aluminum. 
     A second principal feature of one embodiment of a composite lead frame according to the present invention is to provide a composite lead frame which comprises a die bonding layer, a solder layer and a cohesive layer. Each of the conductive leads of the die bonding unit sequentially contains upper metal layer, upper adhesive layer and tape layer. The cohesive layer between the die bonding layer and the solder layer and the lead frame cell further have a cohesive unit between the die bonding unit and the solder unit. 
     Another feature of one embodiment of the composite lead frame according to the present invention is to provide a composite lead frame in which the cohesive unit can be a conductive paste that attached or joined together with die bonding unit and solder unit. 
     Another feature of one embodiment of the composite lead frame according to the present invention is to provide a composite lead frame in which the cohesive unit can comprises an upper cohesive unit under the conductive lead of the die bonding unit and a lower cohesive unit above the conductive leads of the solder unit. The cohesive unit consists of an upper cohesive unit and a lower cohesive unit made of eutectic material. Therefore, the attachment of die bonding unit and solder unit is made through the upper cohesive unit and lower cohesive unit of the cohesive unit formed with eutectic materials of gold, silver or tin and being joined together by eutectic process. 
     A third principle feature of one embodiment of the composite lead frame according to the present invention is to provide a composite lead frame in which the die bonding unit further comprises a die pad which comprises a plurality of heat conductive holes and also sequentially have an upper metal layer, an upper adhesive layer, a tape layer and a lower adhesive layer. The solder unit comprises a die pad and an insulating clearance which being formed between lead tips of conductive leads and the die pad. The conductive leads and die pad of the die bonding unit are vertically aligned with conductive leads and die pad of the solder unit and the lower adhesive layer being tightly attached with conductive leads and die pad of the solder unit. 
     Another feature of one embodiment of the composite lead frame according to the present invention is to provide a composite lead frame in which the die pad of the die bonding layer are made of copper foil. The die pad of the solder layer is made of copper, iron or aluminum. On top of the die pad of the die bonding unit, and also at the bottom of the die pad of the solder unit, there is formed a plating layer which is a material of one selected from silver, gold, nickel, palladium, and tin or combination thereof. The heat conductive holes are filled with gold, silver, copper or aluminum. 
     A fourth principal feature of one embodiment of the composite lead frame according to the present invention is to provide a lead frame which comprises a die bonding layer, a solder layer and a cohesive layer. Each conductive leads of the die bonding unit sequentially contain an upper metal layer, an upper adhesive layer and a tape layer. The cohesive layer between the die bonding layer and the solder layer and the lead frame cell further have a cohesive unit between the die bonding unit and the solder unit. The die pad further comprises a plurality of heat conductive holes and also sequentially has an upper metal layer, an upper adhesive layer, a tape layer and a lower adhesive layer. There are insulating clearance formed between lead tip of conductive lead and die pad. And the solder unit further comprises a die pad, an insulating clearance which being formed between the lead tips of the conductive leads and die pad. The conductive leads and the die pad of the die bonding unit are vertically aligned with conductive leads and die pad of the solder unit and the lower adhesive layer is tightly attached with conductive leads and die pad of the solder unit. 
     Another feature of one embodiment of the composite lead frame according to the present invention is to provide a composite lead frame in which the cohesive unit can be a conductive paste that attached to joined together with die bonding unit and solder unit. 
     Another feature of one embodiment of the composite lead frame according to the present invention is to provide a composite lead frame in which the cohesive unit can comprises an upper cohesive unit under the conductive lead of the die bonding unit and a lower cohesive unit above the conductive leads of the solder unit. The cohesive unit consists of an upper cohesive unit and a lower cohesive unit made of eutectic material. Therefore, the attachment of die bonding unit and solder unit is made through the upper cohesive unit and lower cohesive unit of the cohesive unit formed with eutectic materials of gold, silver or tin and being joined together by eutectic process. 
     Another principle feature of one embodiment of the composite lead frame according to the present invention is to provide a composite lead frame in which the die pad of the die bonding layer are made of copper foil. The die pad of the solder layer is made of copper, iron or aluminum. On top of the die bonding unit, and also at the bottom of the solder unit, there is formed a plating layer which is a material of one selected from silver, gold, nickel, palladium, and tin or combination thereof. The heat conductive holes are filled with gold, silver, copper or aluminum. 
     A fifth principle feature of one embodiment of the composite lead frame according to the present invention is to provide a composite lead frame in which the number of the plurality of conductive lead and of die bonding unit and solder unit being greater than two. There will be a insulating space consists of conductive lead space and a tape space formed between the conductive lead of the die bonding unit. There is another insulating space formed between the conductive lead of the solder unit. These insulating space of the solder unit are filled with insulating material. 
     With aforementioned features of the composite lead frame according to the present invention, the advantages become apparent and can be summarized as below. 1. The die bonding unit comprises insulating clearance and a plurality of conductive leads and a plurality of conductive body holes. Therefore, the composite lead frame of the invention has very good electric conductivity. 2. A die pad of the solder layer is provided with heat conductive holes to communicate with die bonding layer resulting good heat conductivity. 3. Insulating materials are filled with filled within the insulating clearance and insulating gaps of the solder layer. Therefore, the composite lead frame has a high mechanical strength. 4. All the insulating gaps and insulating clearance are very thin in their dimension. Therefore the composite lead frame according to the present invention can be used as one of high pin counts achieving the minimization of resulted IC. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The objectives, effectiveness, characteristics and structures of the present invention will become more fully understood from the detailed description given below by way of embodiments with reference to the accompanying drawings, wherein: 
         FIG. 1  shows an illustrative sectional view of a conventional flex substrate, 
         FIG. 2  shows an illustrative sectional view of a conventional copper metal lead frame; 
         FIG. 3  shows a plan and sectional view of a first embodiment of a composite lead frame according to the present invention used for flip chip packaging of a LED; 
         FIG. 4  shows another plan and sectional view of a first embodiment of a composite lead frame according to the present invention used for flip chip packaging of a LED; 
         FIG. 5  shows a plan and sectional view of a second embodiment of a composite lead frame according to the present invention used for flip chip packaging of a LED; 
         FIG. 6  shows a plan and sectional view of a third embodiment of a composite lead frame according to the present invention used for IC packaging; 
         FIG. 7  shows another plan and sectional view of the third embodiment of a composite lead frame according to the present invention used for IC packaging; 
         FIG. 8  shows a plan and sectional view of a fourth embodiment of a composite lead frame according to the present invention used for IC packaging; 
         FIG. 9  shows an illustrative and sectional view of a fifth embodiment of a composite lead frame according to the present invention suitable to be used for IC packaging; 
         FIG. 10  shows another illustrative and sectional view of the fifth embodiment of a composite lead frame according to the present invention suitable for used in IC packaging. 
         FIG. 11  is a perspective sectional view of the fifth embodiment of a composite lead frame according to the present invention showing tape layer; 
         FIG. 12  is an illustrative and sectional view of a sixth embodiment of the composite lead frame according to the present invention suitable for IC packaging; 
         FIG. 13  is a perspective sectional view of the sixth embodiment of the composite lead frame according to the present invention as shown in  FIG. 12 ; and 
         FIG. 14  is an illustrative and sectional view of a seventh embodiment of a composite lead frame according to the present invention used for IC wire bonding. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring to  FIG. 3  and  FIG. 4  conjunctively which show a plan and sectional view of a first embodiment of composite lead frame according to the present invention used for flip chip packaging of a LED, the composite lead frame structure  1  comprises a die bonding layer  10  and a solder layer  11 . 
     The overall composite lead frame structure  1  consists of a plurality of lead frame cells  12  with lead frame cell gap  13  in between one another. Each lead frame cell gap  13  is provided with a first lead frame cell gap  130 , a second lead frame cell gap  131  and a third lead frame cell gap  132 . The third lead frame cell gap  132  is filled with insulating material. Lead frame cell  12  has die bonding unit  120  and a solder unit  121 . The die bonding unit  120  comprises insulating clearance  1201  and a plurality of first conductive leads  1200  and a plurality of conductive body holes  1202 . Each of the first conductive leads  1200  sequentially contains upper metal layer  1203 , upper adhesive layer  1204 , tape layer  1205  and lower adhesive layer  1206 . The insulating clearance  1201  of die bonding unit  120  comprises conductive lead clearance  12010  and tape clearance  12011 . The insulating clearance  1201  is formed between various conductive lead tips. 
     The solder unit  121  comprises insulating clearance  1211  and a plurality of second conductive leads  1210 . The insulating clearance  1211  of the solder unit  121  filled with insulating material. The insulating clearance  1211  is formed between various conductive lead tips. The first conductive lead  1200  and the second conductive lead  1210  are vertically aligned so that the lower adhesive layer  1206  of the die bonding unit  120  is tightly attached with solder unit  121 . 
     The upper adhesive layer  1204  and lower adhesive layer  1206  are insulating paste. The upper metal layer  1203  of the die bonding layer  10  are made of copper foil. The plurality second conductive leads  1210  of solder layer  11  are made of copper, iron or aluminum. Upon the plurality of first conductive lead  1200 , there is formed a plating layer  14  which is a material of one selected from silver, gold, nickel, palladium and tin or combination thereof. The width of the insulating clearance  1201  of the die bonding unit  120  can be greater, smaller or equal to the width of the insulating clearance  1211  of the solder unit  121 . The plurality of conductive body holes  1202  are filled with either of gold, silver, copper and aluminum. 
     As particularly shown in  FIG. 4 , the tape layer  1205  is made of Polyimide, PI. The second lead frame cell gap  131  and conductive lead clearance  12010  are also made of Polyimide, PI. 
     Referring to  FIG. 5  which shows a plan and sectional view of a second embodiment of a composite lead frame according to the present invention used for flip chip packaging of a LED, with reference to  FIG. 4  of the first embodiment, the die bonding layer is a double layered metal layer. It can be seen the composite lead frame structure  2  consists of die bonding layer  20 , cohesive layer  21  and solder layer  22 . 
     The overall composite lead frame structure  2  consists of a plurality of lead frame cells  23  with lead frame cell gap  24  in between one another. Each lead frame cell gap  24  is provided with a first lead frame cell gap  240 , a second lead frame cell gap  241  and a third lead frame cell gap  242 . The third lead frame cell gap  242  is filled with insulating material. 
     Lead frame cell  23  has die bonding unit  230 , a cohesive unit  231  and a solder unit  232 . The die bonding unit  230  comprises a plurality of first conductive leads  2300  and insulating clearance  2301  and the first conductive leads  2300  comprises a plurality of conductive body holes  2302 . Each of the first conductive leads  2300  sequentially contains upper metal layer  2303 , upper adhesive layer  2304 , tape layer  2305 , lower adhesive layer  2306  and lower metal layer  2307 . The insulating clearance  2301  of the die bonding unit  230  comprises conductive lead clearance  23010  and tape clearance  23011 . The insulating clearance  2301  is formed between various conductive lead tips. 
     The solder unit  232  comprises insulating clearance  2321  and a plurality of second conductive leads  2320 . The insulating clearance  2321  of the solder unit  232  filled with insulating material. The insulating clearance  2321  is formed between various conductive lead tips. 
     The first conductive leads  2300  and the second conductive leads  2320  are vertically aligned so that the die bonding unit  230  is tightly attached with the solder unit  232 . The cohesive unit  231  can be a conductive paste which further comprises an upper cohesive unit  2310  under the first conductive leads  2300  and a lower cohesive unit  2311  above the second conductive leads  2320 . The cohesive unit  231  consists of the upper cohesive unit  2310  and lower cohesive unit  2311  made of eutectic material. Therefore, the attachment of die bonding unit  230  and solder unit  232  is through the upper cohesive unit  2310  and lower cohesive unit  2311  of the cohesive unit  231  formed with eutectic materials of gold, silver or tin and being joined together by eutectic process. 
     The upper adhesive layer  2304  and lower adhesive layer  2306  are insulating paste. The upper metal layer  2303  and upper adhesive layer  2304  of the die bonding layer  20  are made of copper foil. A plurality of second conductive leads  2320  of solder layer  22  are made of copper, iron or aluminum. Upon a plurality of first conductive leads  2300 , and also below the plurality of second conductive leads  2300 , there is formed a plating layer  25  which is a material of one selected from silver, gold, nickel, palladium and tin or combination thereof. The width of the insulating clearance  2301  of the die bonding unit  230  can be greater, smaller or equal to the width of the insulating clearance  2321  of the solder unit  232 . There are plurality of conductive body holes  2302  filled with either of gold, silver, copper and aluminum. 
     As the same particularly shown in  FIG. 5 , the tape layer  2305  is made of Polyimide, PI. The second lead frame cell gap  241  and insulating clearance  23011  are also made of Polyimide, PI. 
     Referring to  FIGS. 6 and 7  conjunctively which shows a composite lead frame structure used for IC packaging, the composite lead frame structure  1  comprises a die bonding layer  30  and a solder layer  31 . 
     The overall composite lead frame structure  1  consists of a plurality of lead frame cells  32  with lead frame cell gap  33  in between one another. Each lead frame cell gap  33  is provided with a first lead frame cell gap  330 , a second lead frame cell gap  331  and a third lead frame cell gap  332 . The third lead frame cell gap  332  is filled with insulating material. 
     Lead frame cell  32  has die bonding unit  320  and a solder unit  321 . The die bonding unit  320  comprises insulating clearance  3201  and a plurality of first conductive leads  3200  and the first conductive leads  3200  comprises a plurality of conductive body holes  3202 . Each of the first conductive leads  3200  sequentially contains upper metal layer  3203 , upper adhesive layer  3204 , tape layer  3205  and lower adhesive layer  3206 . The insulating clearance  3201  of the die bonding unit  320  comprises conductive lead clearance  32010  and tape clearance  32011 . The insulating clearance  3201  is formed between various conductive lead tips 
     The solder unit  321  comprises insulating clearance  3211  and a plurality of second conductive leads  3210 . The insulating clearance  3211  of the solder unit  321  filled with insulating material. 
     The insulating clearance  3211  of the solder unit  321  is formed between various conductive leads. The first conductive lead  3200  and the second conductive lead  3210  are vertically aligned so that the lower adhesive layer  3206  of the die bonding unit  320  is tightly attached with solder unit  321 . 
     The upper adhesive layer  3204  and lower adhesive layer  3206  are insulating paste. The upper metal layer  3203  is made of copper foil. The plurality conductive leads  3210  of the solder layer  31  are made of copper, iron or aluminum. Upon the plurality of first conductive leads  3200 , and also below the plurality of second conductive leads  3210 , there is formed a plating layer  34  which is a material of one selected from silver, gold, nickel, palladium, and tin or combination thereof. The width of the insulating clearance  3201  of the die bonding unit  320  can be greater, smaller or equal to the width of the insulating clearance  3211  of the solder unit  321 . The plurality of conductive body holes  3202  are filled with either of gold, silver, copper and aluminum. 
     It is to be noted and according to the structure of this embodiment the number of plurality first conductive leads  3200  and second conductive leads  3210  is greater than two. There will be a conductive lead space  3207  and a tape space  3208  formed between the first conductive leads  3200 . There is another insulating space  3212  between the second conductive leads  3210 . This insulating space  3212  is filled with insulating material. 
     As particularly shown in  FIG. 7 , the tape layer  3205  is made of Polyimide, PI. The second lead frame cell gap  331  and insulating clearance  32011  are also made of Polyimide, PI 
     Referring to  FIG. 8  which shows a plan and sectional view of a fourth embodiment of a composite lead frame according to the present invention used for IC packaging process, and also referring to  FIG. 7  conjunctively, it can be seen the composite lead frame structure  4  consists of die bonding layer  40 , cohesive layer  41  and solder layer  42 . 
     The overall composite lead frame structure  4  consists of a plurality of lead frame cells  43  with lead frame cell gap  44  in between one another. Each lead frame cell gap  44  is provided with a first lead frame cell gap  440 , a second lead frame cell gap  441  and a third lead frame cell gap  442 . The third lead frame cell gap  442  is filled with insulating material. 
     Lead frame cell  43  has die bonding unit  430 , a cohesive unit  431  and a solder unit  432 . The die bonding unit  430  comprises first insulating clearance  4301  and a plurality of first conductive leads  4300  and the first conductive leads  4300  comprises a plurality of conductive body hole  4302 . Each of the first conductive leads  4300  of the die bonding unit  430  sequentially contains upper metal layer  4303 , upper adhesive layer  4304 , tape layer  4305 , lower adhesive layer  4306  and lower metal layer  4307 . The first insulating clearance  4301  of the die bonding unit  430  comprises conductive lead clearance  43010  and tape clearance  43011 . The first insulating clearance  4301  is formed between various conductive lead tips. 
     The solder unit  432  comprises second insulating clearance  4321  and a plurality of second conductive leads  4320 . The second insulating clearance  4321  of the solder unit  432  filled with insulating material. The second insulating clearance  4321  is formed between various conductive lead tips. 
     The first conductive lead  4300  of die bonding unit  430  and the second conductive lead  4320  of solder unit  432  are vertically aligned so that the die bonding unit  430  is tightly attached with solder unit  432 . The cohesive unit  431  is formed between the die bonding unit  430  and solder unit  432 . The cohesive unit  431  can be a conductive paste which further comprises an upper cohesive unit  4310  under the first conductive lead  4300  of the die bonding unit  430  and a lower cohesive unit  4311  above the second conductive lead  4320  of the solder unit  232 . The cohesive unit  431  consists of the upper cohesive unit  4310  and lower cohesive unit  4311  made of eutectic material. Therefore, the attachment of die bonding unit  430  and solder unit  432  is through the upper cohesive unit  4310  and lower cohesive unit  4311  of the cohesive unit  431  formed with eutectic materials of gold, silver or tin and being joined together by eutectic process. 
     The upper adhesive layer  4304  and lower adhesive layer  4306  are insulating adhesive. The upper metal layer  4303  and lower metal layer  4307  of the die bonding layer  40  are made of copper foil. A plurality second conductive leads  4320  of the solder layer  42  are made of copper, iron or aluminum. Upon the plurality of first conductive leads  4300  of the die bonding unit  430 , and also below the plurality of second conductive leads  4320  of the solder unit  432 , there is formed a plating layer  45  which is a material of one selected from either of silver, gold, nickel, palladium and tin or combination thereof. The width of the first insulating clearance  4301  of the die bonding unit  430  can be greater, smaller or equal to the width of the second insulating clearance  4321  of the solder unit  432 . There are plurality of conductive body holes  2302  filled with either of gold, silver, copper and aluminum. 
     It is to be noted and according to the structure of this embodiment that while the number of plurality first conductive leads  4300  and  4320  of die bonding unit  430  and solder unit  432  is greater than two, there will be an conductive lead space  4308  and a tape space  4309  between the first conductive leads  4300 . There is another insulating space  4322  between the second conductive leads  4320  of the solder unit  432 . This insulating space  4322  is filled with insulating material. 
     The tape layer  4305  is made of Polyimide, PI. The tape space  4309 , the second lead frame cell gap  441  and tape clearance  43011  are applied with Polyimide PI. This is equivalent to the tape space  3208 , second lead frame cell gap  331  and tape clearance  32011  are applied with Polyimide PI as shown particularly shown in  FIG. 6 . 
     Referring to  FIGS. 9 to 11  which show illustrative and sectional views of a fifth embodiment of a composite lead frame according to the present invention, the composite lead frame structure  5  comprises a die bonding layer  50  and a solder layer  51 . This embodiment specifically includes a die pad in the die bonding unit and solder unit. There exists only one metal layer. 
     The overall composite lead frame structure  5  consists of a plurality of lead frame cells  52  with lead frame cell gap  53  in between one another. Each lead frame cell gap  53  is provided with a first lead frame cell gap  530 , a second lead frame cell gap  531  and a third lead frame cell gap  532 . The third lead frame cell gap  532  is filled with insulating material. 
     Lead frame cell  52  has die bonding unit  520  and a solder unit  521 . The die bonding unit  520  comprises a plurality of first conductive leads  5200 , first insulating clearance  5201 , a first die pad  5202  and also a plurality of conductive body holes  5203 . The first die pad  5202  of the die bonding unit  520  has a plurality of heat conductive holes  52020 . Each of the first conductive leads  5200  and first die pad  5202  of the die bonding unit  520  sequentially contains upper metal layer  5204 , upper adhesive layer  5205 , tape layer  5206  and lower adhesive layer  5207 . The first insulating clearance  5201  of the die bonding unit  520  comprises conductive lead clearance  52010  and tape clearance  52011 . The first insulating clearance  5201  of the die bonding unit  520  is formed between first die pad  5202  and various first conductive lead  5200 . 
     The solder unit  521  has second insulating clearance  5211  filled with insulating material. The second insulating clearance  5211  is formed between second die pad  5212  and various conductive lead tips. The first conductive lead  5200  of die bonding unit  520 , the second conductive lead  5210  of solder unit  521 , the first die pad  5202  of die bonding unit  520  and first die pad  5202  of solder unit  521  are vertically aligned so that the lower adhesive layer  5207  of the die bonding unit  520  is tightly attached with solder unit  521 . 
     The upper adhesive layer  5204  and lower adhesive layer  5206  are insulation paste. The upper metal layer  5204  and also the first die pad  5202  are made of copper foil. The plurality second conductive leads  5210  of the solder layer  51  and second die pad  5212  are made of copper, iron or aluminum. Above the plurality of first conductive lead  5200  of the die bonding unit  520  and the first die pad  5202 , there is formed a electro plating layer  54 . Also below the plurality of first conductive leads  5200  and first die pad  5202 , there is formed an electro plating layer  54  which is a material of one selected from either of silver, gold, nickel, palladium and tin or combination thereof. The width of the first insulating clearance  5201  of the die bonding unit  520  can be less than, greater or equal to the width of the second insulating clearance  5211  of the solder unit  521 . A plurality of heat conductive holes  52020  are filled with either of gold, silver, copper and aluminum. 
     It is to be noted and according to the structure of this embodiment, the number of plurality first conductive lead  5200  and  5210  of die bonding unit  520  and solder unit  521  may be greater than two. There will be an conductive lead space  5208  and a tape space  5209  between the first conductive leads  5200 . There is another insulating space  5213  between the second conductive lead  5201  of the solder unit  521 . This insulating space  5213  is filled with insulating material which is best shown in  FIG. 11 . 
     As shown in  FIG. 10 , the tape layer  5205  is made of Polyimide, PI. The second lead frame cell gap  531 , the tape space  5209  and tape clearance  52011  are also made of Polyimide PI. 
     Referring to  FIGS. 12 and 13  which show illustrative and sectional views of a sixth embodiment of a composite lead frame according to the present invention, the lead frame structure specifically includes a die pad in the die bonding unit and cohesive unit and there exists two metal layers contrast to the fifth embodiment which only has one metal layer. The overall composite lead frame structure  6  comprises a die bonding layer  60 , an adhesive layer  61  and a solder layer  51 . 
     The overall composite lead frame structure  6  consists of a plurality of lead frame cells  63  with lead frame cell gap  64  in between one another. Each lead frame cell gap  64  is provided with a first lead frame cell gap  640 , a second lead frame cell gap  641  and a third lead frame cell gap  642 . The third lead frame cell gap  642  is filled with insulating material. 
     Lead frame cell  63  has die bonding unit  630 , a cohesive unit  631  and a solder unit  632 . The die bonding unit  630  comprises a plurality of first conductive leads  6300 , first insulating clearance  6301  and a first die pad  6302  and also a plurality of conductive body holes  6303 . The first die pad  6302  of the die bonding unit  630  has a plurality of heat conductive holes  63020 . Each of the first conductive leads  6300  and first die pad  6302  of the die bonding unit  630  sequentially contains upper metal layer  6304 , upper adhesive layer  6305 , tape layer  6306 , lower adhesive layer  6307  and lower metal layer  6308 . The first insulating clearance  6301  of the die bonding unit  630  comprises conductive lead clearance  63010  and tape clearance  63011 . The first insulating clearance  6301  of the die bonding unit  630  is formed between first die pad  6302  and various first conductive leads  6300 . 
     The solder unit  632  has a plurality of second insulating clearance  6321  filled with insulating material, a plurality of second conductive lead  6320  and a second die pad  6322 . The second die pad  6322  is arranged in between second conductive lead  6320 . An second insulating clearance  6321  is formed between second die pad  6322  and various second conductive lead  6320 . The cohesive unit  631  is between die bonding unit  630  and solder unit  632 . The first conductive leads  6300  of die bonding unit  630 , the second conductive lead  6320  of solder unit  632 , the first die pad  6302  of die bonding unit  630  and second die pad  6322  of solder unit  632  are vertically aligned so that the die bonding unit  630  is combined with the solder unit  632 . 
     The upper adhesive layer  6305  and lower adhesive layer  6307  are insulating paste. The upper metal layer  6304  and lower metal layer  6308  of the die bonding layer  60  and also the first die pad  6302  are made of copper foil. The plurality second conductive lead  6320  of the solder layer  62  and second die pad  6322  are made of copper, iron or aluminum. Above the plurality of first conductive leads  6300  of the die bonding unit  630  and the first die pad  6302 , there is formed a plating layer  67 . Also below the plurality of conductive leads  6320  and second die pad  6322 , there is formed a plating layer  67  which is a material of one selected from either of silver, gold, nickel, palladium and tin or combination thereof. The width of the first insulating clearance  6301  of the die bonding unit  630  can be greater, smaller or equal to the width of the second insulating clearance  6321  of the solder unit  632 . A plurality of conductive body holes  6303  are filled with either of gold, silver, copper and aluminum. A plurality of heat conductive holes  63020  are filled with either of gold, silver, copper and aluminum. 
     It is to be noted and according to the structure of this embodiment that while the number of plurality first conductive leads  6300  and  6320  of die bonding unit  630  and solder unit  632  is greater than two, there will be formed an conductive lead space  65  and a tape space  66  between the first conductive leads  6300 . There is another insulating space  6323  between the second conductive lead  6320  of the solder unit  632 . This insulating space  6323  is filled with insulating material which is best shown in  FIG. 13 . 
     As shown in  FIG. 10 , the tape layer  6306  is made of Polyimide, PI. The second lead frame cell gap  641 , the tape space  66  and tape clearance  63011  are also made of Polyimide, PI. 
     Referring to  FIG. 14  which shows an illustrative and sectional view of a seventh embodiment of a composite lead frame according to the present invention used for IC wire bonding, it can be seen that the die bonding layer  70  is a single face metal layer  74 . There is a die pad  77  provided in the die bonding unit  71  and solder unit  72 . For an IC chip  73  to be wire bonded, metal wires  75  shall be used to connect between electric circuitry. Of course, this application of the composite lead frame can also adopt the structure with double faces metal layer. 
     The present invention has been described herein above with preferred embodiments. It is noted still further changes and/or improvements can be made without departing from the spirit of the invention and the scope of defined in the Claims.