Patent Publication Number: US-6335223-B1

Title: Method for producing a resin-sealed semiconductor device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional application of U.S. Ser. No. 09/009,232, filed Jan. 20, 1998, now U.S. Pat. No. 6,215,174. 
    
    
     BACKGROUND OF THE INVENTION 
     1. FIELD OF THE INVENTION 
     The present invention relates to a lead frame having at least two leads and usable for resin-sealing a semiconductor chip, a mold for producing a resin-sealed semiconductor device using such a lead frame, a resin-sealed semiconductor device using such a lead frame, and a method for producing a resin-sealed semiconductor device using such a lead frame. 
     2. DESCRIPTION OF THE RELATED ART 
     Recently, semiconductor devices have an increased number of pins used for electrodes in accordance with an increase in complexity of the circuit structure mounted therein, the incorporation of various devices into a system, and the diversification of uses. The withstanding voltage characteristic (hereinafter, referred to as the “withstanding voltage”) of semiconductor devices has been increased. Therefore, a significantly high voltage may be applied between adjacent leads of a semiconductor device. Accordingly, the distance between such adjacent leads needs to be increased. For example, the minimum possible distance between two adjacent leads is generally considered to be 5 mm in the case of a semiconductor device having a withstanding voltage of 600 V. Such a trend in development requires development of special packages for semiconductor devices and new production facilities, which results in a higher cost for the semiconductor devices. 
     As one proposal for coping with the above-mentioned development trend, common use of components such as packages and lead frames for semiconductors having different specifications have been researched. 
     FIG. 29 is a plan view of a conventional lead frame  1  for resin-sealing a semiconductor chip  2 . The lead frame  1  includes five leads, namely, two leads  1   a , two leads  1   b and one lead  1   c.    
     The semiconductor chip  2  is resin-sealed using the lead frame  1  in the following manner. 
     The semiconductor chip  2  is bonded on a dismount portion  1   d  of the lead frame  1 , and the semiconductor chip  2  is connected to the leads  1   a  via thin metal wires  3 . The semiconductor chip  2  and the lead frame  1  are resin-sealed in a resin-seal body  6  except for the outer ends of the five leads  1   a ,  1   b  and  1   c . Then, the lead  1   c  which is not connected to the semiconductor chip  2  is cut along an outer peripheral surface of the resin-seal body  6  by appropriate machining. 
     Conventionally, a common lead frame is used for resin-sealing semiconductor chips having different manners of wire connection in order to allow for use of a common mold. After the semiconductor chip is resin-sealed, the unnecessary lead (such as  1   c ) which is not connected to the semiconductor chip is cut off in an appropriate manner. Consequently, circuits having complicated structures are produced with relative ease. 
     However, in the manner of resin-sealing described with reference to FIG. 29, after the unnecessary lead  1   c  is cut off, a part  1   c ′ thereof is left on the outer peripheral surface of the resin-seal body  6 . During the flow-soldering or dip-soldering performed subsequent to the resin-seal, solder H adheres to the part  1   c ′. This causes the part  1   c ′ to be a separate conductive part existing between the two respective leads  1   a , resulting in potential electric connection of the two leads  1   a  to each other. When such a phenomenon (the solder adherence) gets too large, the withstanding voltage of the semiconductor device is lowered and sometimes the device does not function. 
     As the number of pins connected to a semiconductor chip increases, the distance between two adjacent leads is decreased. As the withstanding voltage of a semiconductor device rises, the voltage applied between the leads also rises. In order to cope with such a trend, a sufficient withstanding voltage should be obtained between the shortened lead distance. 
     In order to prevent the withstanding voltage between leads from decreasing, a lead frame and a mold specially used for each of various types of semiconductor devices are used. This raises the cost of the molds and also increases the number of mold replacements, thus raising the production cost of the semiconductor devices. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the invention, a lead frame used for a resin-sealed semiconductor device includes a die-mount portion on which a semiconductor chip rests; and a plurality of leads arranged along a common portion of the lead frame. The plurality of leads include at least one adjusting lead, and the adjusting lead has a length that is less than the others of the plurality of leads such that a tip of the adjusting lead is sufficiently proximate to an outer peripheral surface of a resin-seal body to prevent resin flash during a formation of the semiconductor device and to allow the adjusting lead to be removed after the resin-seal body is formed over a portion of the lead frame. 
     In one embodiment of the invention, the adjusting lead projects into the resin-seal body. 
     In one embodiment of the invention, the tip of the adjusting lead is tapered. 
     In one embodiment of the invention, the tip of the adjusting lead is squared. 
     In one embodiment of the invention, the adjusting lead has a length that is less than the others of the plurality of leads such that a tip of the adjusting lead is located at one of a position outside an outer peripheral surface of the resin-seal body and a position in contact with the outer peripheral surface of the resin-seal body during a formation of the semiconductor device. 
     In one embodiment of the invention, the tip of the adjusting lead is squared. 
     In one embodiment of the invention, an end surface of the tip of the adjusting lead and the outer peripheral surface of the resin-seal body is substantially parallel to each other. 
     In one embodiment of the invention, one or more of the leads other than the adjusting lead has a shape for preventing the one or more leads from removing from the resin-seal body after the resin-seal body is formed over the portion of the lead frame. 
     In one embodiment of the invention, the lead frame further includes a tie-bar for transversely connecting the plurality of leads, thereby substantially preventing a bending of the plurality of leads. 
     According to another aspect of the invention, a lead frame used for a resin-sealed semiconductor device includes a die-mount portion on which a semiconductor chip rests; a plurality of leads which are arranged along a common portion of the lead frame, wherein at least two of the plurality of leads are spaced apart from each other a predetermined distance, wherein the predetermined distance is at least twice a distance between the others of the plurality of leads; a tie-bar for transversely connecting the plurality of leads, thereby substantially preventing a bending of the plurality of leads. 
     According to still another aspect of the invention, a mold for producing a resin-sealed semiconductor device using a lead frame is provided. The lead frame includes a plurality of leads arranged along at least one outer peripheral surface of the mold. The plurality of leads include at least one adjusting lead. The adjusting lead projects into the mold a predetermined distance which is sufficiently small to allow the adjusting lead to be easily removed from the resin-sealed semiconductor without resin flash after the resin-sealed semiconductor is formed. The mold has a part for holding the adjusting lead and extending to a vicinity of the tip of the adjusting lead during a formation of the semiconductor device. 
     According to still another aspect of the invention, a resin-sealed semiconductor device produced using a lead frame is provided, in which the resin-sealed semiconductor device includes a resin-seal body surrounding a portion of the lead frame for protecting a semiconductor chip thereon. The lead frame includes a plurality of leads arranged along at least one outer peripheral surface of the resin-seal body. The plurality of leads include at least one adjusting lead, which projects into the resin-seal body a sufficiently small distance to allow the adjusting lead to be removed. The outer peripheral surface has a recess from which the adjusting lead is removed during a formation of the semiconductor device. 
     In one embodiment of the invention, a part of the outer peripheral surface defining the recess is formed of an insulative material for insulating two of the plurality of leads which have the recess therebetween. 
     In one embodiment of the invention, a creeping distance of the part formed of the insulative material is larger than a minimum distance between the two leads which have the recess therebetween. 
     According to still another aspect of the invention, a resin-sealed semiconductor device produced using a lead frame is provided, in which the resin-sealed semiconductor device includes a resin-seal body surrounding a portion of the lead frame for protecting a semiconductor chip thereon. The lead frame includes a plurality of leads arranged along at least one outer peripheral surface of the resin-seal body. The plurality of leads include at least one adjusting lead. The adjusting lead has a tip facing the outer peripheral surface, wherein the tip is outside the outer peripheral surface of the resin-seal body. The outer peripheral surface has a projection in contact with the tip of the adjusting lead during a formation of the semiconductor device. 
     According to still another aspect of the invention, a resin-sealed semiconductor device produced using a lead frame is provided, in which the resin-sealed semiconductor device includes a resin-seal body surrounding a portion of the lead frame for protecting a semiconductor chip thereon. The lead frame includes a plurality of lead which are arranged along a common portion of the lead frame. At least two of the plurality of leads are spaced apart from each other a predetermined distance. The predetermined distance is at least twice a distance between the others of the plurality of leads. The lead frame further includes a tie-bar for transversely connecting the plurality of leads, thereby substantially preventing a bending of the plurality of leads. The outer peripheral surface has a projection in contact with the tie-bar during a formation of the semiconductor device. 
     According to still another aspect of the invention, a method for producing a resin-sealed semiconductor device is provided. The method includes the step of incorporating a portion of the lead frame in a mold for producing a resin-seal body which surrounds the portion of the lead frame in the resin-seal body, the lead frame including a plurality of leads arranged along at least one outer peripheral surface of the mold. The plurality of leads include at least one adjusting lead, and the adjusting lead has a length that is less than the others of the plurality of leads such that a tip of the adjusting lead is sufficiently proximate to an outer peripheral surface of the resin-seal body to prevent resin flash during a formation of the semiconductor device and to allow the adjusting lead to be removed after the resin-seal body is formed over the portion of the lead frame. The method further includes the steps of resin-sealing the semiconductor device together with the portion of the lead frame by the mold to form a resin-seal body; taking out the resin-seal body from the mold; and removing the at least one adjusting lead from the resin-seal body. 
     In one embodiment of the invention, the method further includes the step of cutting the plurality of leads. The adjusting lead of the lead frame projects into the resin-seal body. 
     A resin-sealed semiconductor device produced by such a method is provided. 
     In one embodiment of the invention, the method further includes the step of cutting the plurality of leads. A tip of the adjusting lead is located at one of a position outside the outer peripheral surface of the resin-seal body and a position in contact with the outer peripheral surface of the resin-seal body. 
     A resin-sealed semiconductor device produced by such a method is provided. 
     According to still another aspect of the invention, a method for producing a resin-sealed semiconductor device is provided. The method includes the steps of incorporating a portion of the lead frame in a mold for producing a resin-seal body which surrounds the portion of the lead frame in the mold. The lead frame including a plurality of leads arranged along at least one outer peripheral surface of the resin-seal body and a tie-bar for transversely connecting the plurality of leads, thereby substantially preventing a bending of the plurality of leads. The method further includes the steps of resin-sealing the semiconductor device together with the portion of the lead frame by the mold to form a resin-seal body having a projection of the other peripheral surface that contacts the tie-bar; taking out the resin-seal body from the mold; and removing the tie-bar to leave the projection on the outer peripheral surface of the resin-seal body. 
     A resin-sealed semiconductor device produced by such a method is provided. 
     Thus, the invention described herein makes possible the advantages of (1) providing a lead frame having leads commonly usable for different types of semiconductors without leaving a protruding portion associated with a cutting operation and thus avoiding deterioration of the withstanding voltage of the semiconductor devices, a mold used for resin-sealing a semiconductor chip using such a lead frame, a resin-sealed semiconductor device using such a lead frame, and a method for producing a resin-sealed semiconductor device using such a lead frame; and (2) providing a lead frame allowing lead arrangement to be changed in accordance with the type of semiconductor device, a mold used for resin-sealing a semiconductor chip using such a lead frame, a resin-sealed semiconductor device using such a lead frame, and a method for producing a resin-sealed semiconductor device using such a lead frame. 
     These and others advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plan view of a resin-sealed semiconductor device with a lead frame in a first example according to the present invention; 
     FIG. 2A is a plan view of a semiconductor chip bonded on the lead frame before being resin-sealed in the first example; 
     FIG. 2B is a side view of the semiconductor chip and the lead frame shown in FIG. 2A; 
     FIG. 3A is a plan view of a mold holding the semiconductor chip bonded on the lead frame during resin-sealing in the first example; 
     FIG. 3B is a cross-sectional view of FIG. 3A taken along line IIIB—IIIB; 
     FIG. 3C is a cross-sectional view of FIG. 3A taken along line IIIC—IIIC; 
     FIG. 4A is a plan view of the resin-seal body and the lead frame subsequent to being formed in the mold in the first example; 
     FIG. 4B is a plan view of a resultant resin-sealed semiconductor device after the common portion of the lead frame is cut off and the adjusting lead is removed in the first example; 
     FIG. 5 is a flowchart illustrating a method for resin-sealing the semiconductor using the lead frame in the first example; 
     FIG. 6 is a plan view of a resin-sealed semiconductor device with a lead frame in an alternative example of the first example according to the present invention; 
     FIGS. 7A and 7B are plan views illustrating the shape of the tip of the adjusting leads shown in FIG. 6; 
     FIG. 8 is a plan view of a resin-sealed semiconductor device with a lead frame in another alternative example of the first example according to the present invention; 
     FIG. 9 is a plan view of a mold used for producing the resin-seal body shown in FIG. 8; 
     FIG. 10 is a plan view of the resin-sealed semiconductor device shown in FIG. 6 after the common portion of the lead frame is cut off; 
     FIG. 11 is a plan view of the resin-sealed semiconductor device shown in FIG. 9 after the common portion of the lead frame is cut off; 
     FIG. 12 is a plan view of a resin-sealed semiconductor device with a lead frame in a second example according to the present invention; 
     FIG. 13 is a plan view of the semiconductor chip bonded on the lead frame before being resin-sealed in the second example; 
     FIG. 14 is a plan view of a mold holding the semiconductor chip bonded on the lead frame during resin-sealing in the second example; 
     FIG. 15A is a plan view of the resin-seal body and the lead frame subsequent to being formed in the mold in the second example; 
     FIG. 15B is a plan view of the resultant resin-sealed semiconductor device after the common portion of the lead frame is cut off and the adjusting lead is removed in the second example; 
     FIG. 16 is a flowchart illustrating a method for resin-sealing the semiconductor using the lead frame in the second example; 
     FIG. 17 is a plan view of a resin-sealed semiconductor device with a lead frame in a third example according to the present invention; 
     FIG. 18A is a plan view of the semiconductor chip bonded on the lead frame before being resin-sealed in the third example; 
     FIG. 18B is a side view of the semiconductor chip and the lead frame shown in FIG. 18A; 
     FIG. 19A is a plan view of a mold holding the semiconductor chip bonded on the lead frame during resin-sealing in the third example; 
     FIG. 19B is a cross-sectional view of FIG. 19A taken along line XIXB—XIXB; 
     FIG. 19C is a cross-sectional view of FIG. 19A taken along line XIXC—XIXC; 
     FIG. 19D is a cross-sectional view of FIG. 19A taken along line XIXD—XIXD; 
     FIG. 20 is a plan view of the resin-seal body with the lead frame subsequent to being formed in a mold in the third example; 
     FIG. 21 is a plan view of the resin-seal body illustrating the step of cutting off the common portion of the lead frame in the third example; 
     FIG. 22 is a plan view of a resultant resin-sealed semiconductor device after the common portion of the lead frame is cut off in the third example; 
     FIG. 23 is a plan view of a resin-sealed semiconductor device in a fourth example according to the present invention; 
     FIG. 24 is a plan view of a semiconductor chip bonded on the lead frame before being resin-sealed in the fourth example; 
     FIG. 25 is a plan view of a mold holding the semiconductor chip bonded on the lead frame during resin-sealing in the fourth example; 
     FIG. 26A is a plan view of the resin-seal body and the lead frame subsequent to being formed in a mold in the fourth example; 
     FIG. 26B is a side view of FIG. 26A; 
     FIG. 27 is a plan view of a semiconductor device having a large number of pins which is resin-sealed using a lead frame having adjusting leads in the fourth example; 
     FIG. 28 is a plan view of a resin-sealed semiconductor device with a lead frame in a fifth example according to the present invention; and 
     FIG. 29 is a plan view of a conventional lead frame for resin-sealing a semiconductor chip. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, the present invention will be described by way of illustrative examples with reference to the accompanying drawings. 
     EXAMPLE 1 
     A lead frame in a first example according to the present invention will be described with reference to figures. 
     FIG. 1 is a plan view of a resin-sealed semiconductor chip  14  with a lead frame  10  in the first example according to the present invention. The semiconductor chip  14  is resin-sealed in a resin-seal body  16  to electrically insulate the semiconductor chip  14 . 
     The lead frame  10  includes a strip-shaped common portion  11  and a generally C-shaped electrode pin section  12  having a die-mount portion  12   b  and two leads  12   a  extending from the die-mount portion  12   b . In a space U defined by the generally C-shaped electrode pin section  12  and the common portion  11 , the lead frame  10  further includes two leads  13   a  and  13   c  projecting from the common portion  11  and located between the leads  12   a , and an adjusting lead  113   b  also projecting from the common portion  11  and located between the leads  13   a  and  13   c . 
     The leads  13   a  and  13   c  are connected to the semiconductor chip  14  (which is bonded to the die-mount portion  12   b ) via thin metal wires  15 . A distance D 2 , which represents the distance the adjusting lead  113   b  projects from the common portion  11 , is shorter than a distance D 1 , which represents the distance the leads  13   a  and  13   c  project from the common portion  11 . Namely, D 2 &lt;D 1 . 
     The resin-seal body  16  is formed by resin-molding the semiconductor chip  14 , the lead frame  10 , and the thin metal wires  15  while leaving leg portions of the leads  12   a ,  13   a ,  113   b  and  13   c  and the common portion  11  outside. 
     A distance d 2 , which represents the distance the adjusting lead  113   b  projects into the resin-seal body  16 , is shorter than a distance d 1 , which represents the distance the leads  13   a  and  13   c  project into the resin-seal body  16 . Namely, d 2 &lt;d 1 . 
     The adjusting lead  113   b  projects into the resin-seal body  16  from an outer peripheral surface  16   a  of the resin-seal body  16  by such a distance (d 2 ) as to allow the adjusting lead  113   b  to be removed (e.g., pulled out) from the resin-seal body  16  after the resin-sealing is completed. Such a distance (sufficiently proximate) is preferably about 1 mm to about 1.2 mm. Although this range is preferred, any distance can be used as long as the adjusting lead  113   b  is removed from the resin-seal body  16  with sufficient ease. 
     Herein, the expression “with sufficient ease” has two meanings. 
     First, the expression “with sufficient ease” refers to a degree to which the resin-seal body  16  and the semiconductor chip  14  are not mechanically damaged when the adjusting lead  113   b  is removed. For example, in the case where the adjusting lead  113   b  is bent (like, for example, the leads  13   a  and  13   c ) for preventing the lead  113   b  from being pulled out, the resin-seal body  16  is mechanically damaged when the adjusting lead  113   b  is pulled out. 
     Furthermore, the resin-seal body  16  needs to protect the semiconductor chip  14  after the adjusting lead  113   b  is removed. For example, when the adjusting lead  113   b  is excessively long, the distance between the tip of the adjusting lead  113   b  and the die-mount portion  12   b  is too small to avoid cracking of the resin-seal body  16  in this portion. The resin-seal body  16  in such a state is less protective for the semiconductor chip  14 . 
     Secondary, the expression “with sufficient ease” refers to a degree to which the adjusting lead  113   b  is removed when the outer end of the adjusting lead  113   b  is pulled but does not come out by slight vibration or unintentional contact during the transportation of the semiconductor device. The adjusting lead  113   b  should be removed only in a prescribed step in order to avoid the situation in which a great number of adjusting leads come out during another production step and become garbage. By avoiding such a situation, the garbage is collected and processed only at a prescribed site. In addition, adjusting leads will not undesirably interfere with other production steps. 
     With reference to FIGS. 2A,  2 B,  3 A,  3 B,  3 C,  4 A,  4 B, and  5 , a method for resin-sealing the semiconductor chip  14  using the lead frame  10  will be described. Identical elements previously discussed with respect to FIG. 1 will bear identical reference numerals therewith and the descriptions thereof will be omitted. 
     FIG. 2A is a plan view of the semiconductor chip  14  bonded on the lead frame  10  before being resin-sealed, and FIG. 2B is a side view of the semiconductor chip  14  and the lead frame  10  shown in FIG.  2 A. FIG. 3A is a plan view of a mold  116  where an inside portion of the mold  116  is shown to illustrate a lead frame portion inside the mold  116  (hereinafter, referred to as a “plan view”.) As shown in FIG. 3A, the semiconductor chip  14  is bonded on the lead frame  10  held by the mold  116  during resin-sealing, FIG. 3B is a cross-sectional view thereof taken along line IIIB—IIIB of FIG. 3A, and FIG. 3C is a cross-sectional view thereof taken along line IIIC—IIIC of FIG.  3 A. FIG. 4A is a plan view of the resin-seal body  16  with the lead frame  10  subsequent to being formed in the mold  116 , and FIG. 4B is a plan view of a resultant resin-sealed semiconductor device after the common portion  11  of the lead frame  10  is cut off and the adjusting lead  113   b  is pulled out. FIG. 5 is a flowchart illustrating a method for resin-sealing the semiconcutor  14  using the lead frame  10 . 
     Hereinafter, the method for resin-sealing the semiconductor chip  14  using the lead frame  10  will be described in accordance with FIG. 5 with reference to FIGS. 2A,  2 B,  3 A,  3 B,  3 C,  4 A and  4 B. 
     In step S 101 , the semiconductor chip  14  is attached to the die-mount portion  12   b  (FIGS.  2 A and  2 B). The semiconductor chip  14  is connected to the leads  13   a  and  13   c  via the thin metal wires  15 . 
     In step S 102 , resin-sealing of the semiconductor chip  14  is performed using the mold  116  including an upper mold  116   a  and a lower mold  116   b  which can be engaged together. As shown in FIGS. 3A,  3 B and  3 C, the semiconductor chip  14  and the die-mount portion  12   b  are held between the upper mold  116   a  and the lower mold  116   b . The leads  12   a ,  13   a  and  13   c  and the adjusting lead  113   b  are also partially held between the upper mold  116   a  and the lower mold  116   b . In step S 103 , the semiconductor chip  14  and the above-mentioned parts of the lead frame  10  are molded and sealed together in the resin-seal body  16  by the mold  116 . 
     In step S 104 , the resin-seal body  16  is taken out of the mold  116  as shown in FIG.  4 A. Then, the leads  12   a ,  13   a ,  113   b  and  13   c  which are projecting from the common portion  11  are cut along chain line C 1  so as to have a pierced tip as shown in FIG.  4 B. 
     In step S 105 , the adjusting lead  113   b  which is not connected to the semiconductor chip  14  is pulled out from the resin-seal body  16  (FIG.  4 B). As described above, the adjusting lead  113   b  can be pulled out sufficiently easily due to the relatively short distance by which the adjusting lead  113   b  projects into the resin-seal body  16 . 
     As shown in FIG. 3A, respective ends  113   a  and  113   c  of the leads  13   a  and  13   c  in the resin-seal body  16  are bent at a right angle for preventing the leads  13   a  and  13   c  from being pulled out. The leads  13   a  and  13   c  also project into the resin-seal body  16  deeper than the adjusting lead  113   b.    
     As can be appreciated from the above description, the lead frame  10  and the method for producing a resin-sealed semiconductor device in the first example according to the present invention, semiconductor chips having various specifications can be resin-sealed by the common mold  116  and also the adjusting lead  113   b  which is made unnecessary due to the specifications of the semiconductor can be removed from the resin-seal body  16 . 
     In the lead frame  10  having such a structure, the adjusting lead does not remain in the resin-seal body  16  as does in the case of the conventional lead frame, shortcircuiting is therefore reduced when the semiconductor chip  14  is soldered to the printed circuit board and thus the deterioration in the withstanding voltage of the semiconductor chip  14  is avoided. 
     The structure of the lead frame is not limited to the one described above. The structure is sufficient as long as the lead frame includes a plurality of leads arranged along at least one outer peripheral surface of the resin-sealed body and at least one of the plurality of leads is an adjusting lead. 
     FIG. 6 is a plan view of a resin-sealed semiconductor chip  14  with a lead frame  10  in an alternative example of the first example according to the present invention. FIGS. 7A and 7B are amplified fragmentary plan views illustrating the shape of the tip of the adjusting lead  113   b.    
     The adjusting lead  113   b  shown in FIG. 1 has a square-shaped tip. The adjusting lead  113   b  may have an inwardly tapered shape extending into the resin-seal body  16  a distance L as shown in FIG. 6 in order to allow the adjusting lead  113   b  to be pulled out more easily. The shape of the tip of the lead  113   b  may be trapezoidal as shown in FIG. 7A or rounded as shown in FIG.  7 B. 
     A length L 1  of the tapered part of FIG. 7A and a length L 2  of the tapered part in FIG. 7B are each preferably about 0.3 mm to about 0.8 mm. When the lengths L 1  and L 2  are each more than about 0.8 mm, the adjusting lead  113   b  is difficult to pull out for the following reasons. 
     When the lengths L 1  and L 2  are each more than about 0.8 mm, the contact area between the resin in the resin-seal body  16  and the adjusting lead  113   b  increases and the adjusting lead  113   b  reaches deep in the resin-seal body  16 , thus becoming stable in the resin-seal body  16  against the transverse vibration. As a result, the friction between the adjusting lead  113   b  and the resin increases thereby increasing the force required to pull out the adjusting lead  113   b.    
     The cross-sectional shape of the adjusting lead  113   b  along the outer peripheral surface  16   a  of the resin-seal body  16  needs to be substantially identical with the cross-sectional shape of each of the other leads  12   a ,  13   a  and  13   c  along the outer peripheral surface  16   a . Otherwise, in the case where the tapered part extends outside the outer peripheral surface  16   a  of the resin-seal body  16 ; if the cross section of the adjusting lead  113   b  along the outer peripheral surface  16   a  is smaller than the cross section of each of the other leads  12   a ,  13   a  and  13   c  along the outer peripheral surface  16   a , a space will be formed undesirably between the mold (not shown) and the adjusting lead  113   b , resulting in resin flash. 
     When the lengths L 1  and L 2  are each less than about 0.3 mm, the effect that the adjusting tip  113   b  is more easily pulled out is not obtained. 
     FIG. 8 is a plan view of a resin-sealed semiconductor chip  14  with a lead frame  10  in another alternative example of the first example according to the present invention. FIG. 9 is a plan view of a mold  116  used for producing the resin-seal body  16  shown in FIG.  8 . 
     The mold  116  used for resin-molding to produce the resin-seal body  16  includes an upper mold and a lower mold which can be engaged together as described above. In the example shown in FIG. 9, the mold  116  further has holding parts  117  for holding the adjusting lead  113   b . The holding parts  117  project to the vicinity of the tip of the adjusting lead  113   b.    
     As shown in FIG. 8, the resin-seal body  16  produced by the mold  116  having the holding parts  117  is recessed as defined by a part S along an outer peripheral surface  16   a . The adjusting lead  113   b  projects into the resin-seal body  16  at the recess S. A distance d 3  from the tip end of the adjusting lead  113   b  to the recessed outer peripheral surface S of the resin-seal body  16  is shorter than that in the example shown in FIG.  1 . Accordingly, the adjusting lead  113   b  is pulled out more easily. 
     Conversely, the leads  12   a ,  13   a  and  13   c  project deep into the resin-seal body  16  so as not to be pulled out easily. The leads  13   a  and  13   c  respectively have bent parts  113   a  and  113   c  to avoid being pulled out as described above. 
     The distance d 3  is preferably about 1 mm to about 1.2 mm. When the distance d 3  is less than about 1 mm, resin flash could possibly occur if the taper length is 0.8 mm or greater. When the distance d 3  is more than about 1.2 mm, the adjusting lead  113   b  is difficult to pull out. 
     FIG. 10 is a plan view of the resin-sealed semiconductor chip  14  with the lead frame  10  shown in FIG. 6 after the lead frame  10  is cut off. 
     As can be appreciated from FIG. 10, the common portion  11  is cut off from the leads  12   a ,  13   a ,  113   b  and  13   c  after the semiconductor chip  14  is resin-sealed. The adjusting lead  113   b  has been pulled off from the resin-seal body  16  and therefore is deleted. 
     FIG. 11 is a plan view of the resin-sealed semiconductor chip  14  with the lead frame  10  shown in FIG. 9 after the lead frame  10  is cut off. The outer peripheral surface  16   a  is recessed as indicated by the letter S. A length L 3  of the recessed part S of the resin-seal body  16  is less than a length L 4  of the other part of the resin-seal body  16 . 
     As shown in FIG. 11, an electrically insulative material  20  (shown by a thick line in FIG. 11) may be applied to a part of the outer peripheral surface  16   a  between the leads  13   a  and  13   c . In this case, the recessed part S is electrically insulated from the area therearound. Since the leads  13   a  are electrically insulated from each other with certainty, the withstanding voltage is improved. 
     When the resin-seal body  16  is recessed as defined by the part S, a creeping distance C formed of the insulative material  20  is longer than a distance B between the adjacent leads  13   a  and  13   c . Accordingly, the electrical insulation between the leads  13   a  and  13   c  is further improved. 
     EXAMPLE 2 
     A lead frame in a second example according to the present invention will be described. Elements corresponding to those discussed with respect to FIG. 1 will bear identical reference numerals therewith and the detailed descriptions thereof will be omitted. 
     FIG. 12 is a plan view of a resin-sealed semiconductor chip  14  with a lead frame  20  in the second example according to the present invention. The lead frame  20  in this example is different from the lead frame shown in FIG. 1 in that a tip of an adjusting lead  213   b  is outside the resin-seal body  16 . 
     A distance D 7  between the common portion  11  and the tip of the adjusting lead  213   b  is shorter than a distance D 4  between the common portion  11  and the outer peripheral surface  16   a  of the resin-seal body  16 . The tip of the adjusting lead  213   b  is square-shaped. An end surface  13   d  of the tip of the adjusting lead  213   b  and the outer peripheral surface  16   a  are substantially parallel to each other. A distance D 3  between the end surface  13   d  of the adjusting lead  213   b  and the outer peripheral surface  16   a  of the resin-seal body  16  is preferably about 0.1 mm to about 0.2 mm in order to allow the adjusting lead  213   b  to be removed sufficiently easily. 
     With reference to FIGS. 13,  14 ,  15 A,  15 B and  16 , a method for resin-sealing the semiconductor chip  14  using the lead frame  20  will be described. Elements corresponding to those discussed with respect to FIG. 1 will bear identical reference numerals therewith and the detailed descriptions thereof will be omitted. 
     FIG. 13 is a plan view of the semiconductor chip  14  bonded on the lead frame  20  before being resin-sealed. FIG. 14 is a plan view of a mold  116  holding the semiconductor chip  14  bonded on the lead frame  20  during resin-sealing. FIG. 15A is a plan view of the resin-seal body  16  and the lead frame  20  subsequent to being formed in the mold  116  in the second example, and FIG. 15B is a plan view of a resultant resin-sealed semiconductor device after the common portion  11  of the lead frame  20  is cut off. FIG. 16 is a flowchart illustrating a method for resin-sealing the semiconductor  14  using the lead frame  20  in the second example. 
     Hereinafter, the method for resin-sealing the semiconductor chip  14  using the lead frame  20  will be described in accordance with FIG. 16 with reference to FIGS. 13,  14 ,  15 A and  15 B. 
     In step S 201 , the semiconductor chip  14  is attached to the die-mount portion  12   b  (FIG.  13 ). The semiconductor chip  14  is connected to the leads  13   a  and  13   c  via the thin metal wires  15 . 
     In steps S 202  and S 203 , resin-sealing of the semiconductor chip  14  is performed using the mold  116  including an upper mold  116   a  and a lower mold  116   b  which can be engaged together. As shown in FIG. 14, the semiconductor chip  14  and the die-mount portion  12   b  are held between the upper mold  116   a  and the lower mold  116   b  (S 202 ). The leads  12   a ,  13   a  and  13   c  and the adjusting lead  213   b  are also partially held between the upper mold  116   a  and the lower mold  116   b . In step S 203 , the semiconductor chip  14  and the above-mentioned parts of the lead frame  20  are molded and sealed together in the resin-seal body  16  by the mold  116 . 
     In step S 204 , the resin-seal body  16  is taken out of the mold  116  as shown in FIG.  15 A. Then, the leads  12   a ,  13   a  and  13   c  projecting from the common portion  11  are cut along chain line C 2  so as to have a pierced tip as shown in FIG.  15 B. The adjusting lead  213   b  is then blown off by air when the leads  12   a ,  13   a  and  13   c  are cut off. Since there is a space  21   c  between the resin-seal body  16  and the tip of the adjusting lead  213   b , a projection  16   b  formed of the resin entering the space  21   c  is formed on the outer surface  16   a  of the resin-seal body  16  (FIG. 15A) after the adjusting lead  213   b  is removed. 
     In the second example, the adjusting lead  213   b  is removed by air during the cutting step of the common portion  11 . Since air blows away the lead  213   b  during the cutting, the step of removing the lead  213   b  is eliminated. The effects described in the first example are also achieved. 
     Referring to FIG. 15B, in the case where an insulative material is applied to the projection  16   b , a creeping distance E formed by the insulative material is larger than the distance between the leads  13   a  and  13   c . Accordingly, the electrical insulation between the leads  13   a  and  13   c  is further improved. 
     The structure of the lead frame is not limited to the one described above. The structure is sufficient as long as the lead frame includes a plurality of leads arranged along at least one after surface of the resin-seal body and at least one of the plurality of leads is an adjusting lead. 
     EXAMPLE 3 
     A lead frame in a third example according to the present invention will be described. Elements corresponding to those discussed with respect to FIG. 1 will bear identical reference numerals therewith and the detailed descriptions thereof will be omitted. 
     FIG. 17 is a plan view of a resin-sealed semiconductor chip  14  with a lead frame  30  in the third example according to the present invention. The lead frame  30  in this example is different from the lead frame shown in FIG. 1 in that the lead frame  30  in this example includes a tie-bar  17 . 
     The tie-bar  17  is provided in the vicinity of the outer peripheral surface  16   a  of the resin-seal body  16  for connecting the leads  12   a ,  13   a ,  313   b  and  13   c . The adjusting lead  313   b  projects into the resin-seal body  16 . The tie-bar  17  connecting the leads  12   a ,  13   a ,  313   b  and  13   c  prevents the leads  12   a ,  13   a ,  313   b  and  13   c  from being bent. 
     With reference to FIGS. 18A,  18 B,  19 A,  19 B,  19 C,  19 D,  20 ,  21  and  22 , a method for resin-sealing the semiconductor chip  14  using the lead frame  30  will be described. Elements corresponding to those discussed with respect to FIG. 1 will bear identical reference numerals therewith and the detailed descriptions thereof will be omitted. 
     FIG. 18A is a plan view of the semiconductor chip  14  bonded on the lead frame  30  before being resin-sealed, and FIG. 18B is a side view of the semiconductor chip  14  and the lead frame  30  shown in FIG.  18 A. FIG. 19A is a plan view of a mold  116  holding the semiconductor chip  14  bonded on the lead frame  30  during resin-sealing, FIG. 19B is a cross-sectional view thereof taken along line XIXB—XIXB of FIG. 19A, FIG. 19C is a cross-sectional view thereof taken along line XIXC—XIXC of FIG. 19A, and FIG. 19D is a cross-sectional view thereof taken along line XIXD—XIXD of FIG.  19 A. FIG. 20 is a plan view of the resin-seal body  16  with the lead frame  30  subsequent to being formed in a mold, and FIG. 21 is a plan view of the resin-seal body illustrating the step of cutting off the common portion of the lead frame. FIG. 22 is a plan view of a resultant semiconductor device after the common portion  11  of the lead frame  30  is cut off. 
     As in the first example, resin-sealing of the semiconductor chip  14  is performed using the mold  116  including an upper mold  116   a  and a lower mold  116   b  which can be engaged together. As shown in FIG. 19A,  19 B,  19 C and  19 D, the mold  116  produces the resin-seal body  16  while holding the leads  12   a ,  13   a  and  13   c  and the adjusting lead  313   b  between the upper mold  116   a  and the lower mold  116   b.    
     In the third example, resin enters a space  21   c  shown in FIG. 19C by the thickness of the common portion  11  (about 0.1 mm to about 0.5 mm). Accordingly, as shown in FIG. 20, the resin-sealed body  16  includes projections  16   b  after completion of the resin-molding. 
     As shown in FIG. 21, the tie-bar  17  is cut off along chain line C 3 . In the same step, the projections  16   b  may be cut off. 
     As shown in FIG. 22, after the tie-bar  17  and the projections  16   b  cut off, the adjusting lead  313   b  is pulled out from the resin-seal body  16 . The adjusting lead  313   b , which projects into the resin-seal body  16  by a smaller distance than the leads  12   a ,  13   a  and  13   c , is pulled out with sufficient ease. 
     As can be appreciated from the above description, the provision of the tie-bar  17  prevents the lead from being bent. This is advantageous in QFP-type (quad flat package-type) ICs described below. The effects described in the first example are also achieved. 
     EXAMPLE 4 
     A lead frame in a fourth example according to the present invention will be described. Elements corresponding to those discussed with respect to FIG. 1 will bear identical reference numerals therewith and the detailed descriptions thereof will be omitted. 
     FIG. 23 is a plan view of a semiconductor chip  14  resin-sealed with a lead frame  40  in the fourth example according to the present invention. The lead frame  40  in this example is different from the lead frame shown in FIG. 1 in that a tip of an adjusting lead  413   b  is outside the resin-seal body  16  and that the lead frame  40  includes a tie-bar  17 . 
     The distance D 7  between the common portion  11  and the tip of the adjusting lead  413   b  is shorter than the distance D 4  between the common portion  11  and the outer peripheral surface  16   a  of the resin-seal body  16 . The distance D 3  between the tip of the adjusting lead  413   b  and the outer peripheral surface  16   a  of the resin-seal body  16  is preferably about 0.1 mm to about 0.2 mm in order to allow the adjusting lead  413   b  to be removed sufficiently easily. The tie-bar  17  connects the leads  12   a ,  13   a ,  413   b  and  13   c.    
     With reference to FIGS. 24,  25 ,  26 A and  26 B, a method for resin-sealing the semiconductor chip  14  using the lead frame  40  will be described. Elements corresponding to those discussed with respect to FIG. 1 will bear identical reference numerals therewith and the detailed descriptions thereof will be omitted. 
     FIG. 24 is a plan view of the semiconductor chip  14  bonded on the lead frame  40  before being resin-sealed. FIG. 25 is a plan view of a mold  116  holding the semiconductor chip  14  bonded on the lead frame  40  during resin-sealing process. FIG. 26A is a plan view of the resin-seal body  16  and the lead frame  40  subsequent to being formed in the mold  116  in the fourth example, and FIG. 26B is a side view of FIG.  26 A. 
     As in the first example, resin-sealing of the semiconductor chip  14  is performed using the mold  116 . The mold  116  produces the resin-seal body  16  while holding the leads  12   a ,  13   a  and  13   c  and the adjusting lead  413   b.    
     In the fourth example, resin enters spaces  21   a  and  21   b  shown in FIG. 25 by the thickness of the common portion  11  (about 0.1 mm to about 0.5 mm). Accordingly, the resin-sealed body  16  includes projections after completion of resin-molding. The projections are cut off together with the tie-bar  17  after the resin-sealing in the same manner as in the third example. 
     FIG. 27 is a plan view of a semiconductor device (QFP-type IC) having a large number of pins which is resin-sealed using a lead frame  40  having adjusting leads  413   b . The tip of each lead  413   b  is outside a resin-sealed body  16 . The lead frame  40  includes a tie-bar  17  for connecting the leads to prevents the leads from being bent. 
     As described above, in the fourth example, the provision of the tie-bar  17  prevents the lead from being bent. The effects described in the first and second examples are also achieved. 
     EXAMPLE 5 
     A lead frame in a fifth example according to the present invention will be described. Elements corresponding to those discussed with respect to FIG. 1 will bear identical reference numerals therewith and the detailed descriptions thereof will be omitted. 
     FIG. 28 is a plan view of a semiconductor chip  14  resin-sealed with a lead frame  50  in the fifth example according to the present invention. The lead frame  50  shown in FIG. 28 does not have an adjusting lead. 
     The lead frame  50  includes a common portion  11 , two leads  13   a  and  13   c  spaced apart from each other by a distance D 6 , which is greater than twice a distance D 5  between the lead  13   a  or  13   c  and the adjacent lead  12   a  thereto, and a tie-bar  17  provided in the vicinity of the outer peripheral surface  16   a  of the resin-seal body  16 . The tie-bar  17  connects the leads  12   a ,  13   a  and  13   c  and thus prevent the leads  12   a ,  13   a  and  13   c  from being bent. 
     The outer peripheral surface  16  has projections (not shown) formed by the resin entering spaces  21   d  between the resin-seal body  16  and the tie-bar  17 . 
     Since the lead frame  50  in the fifth example does not include any adjusting lead, the step of removing the adjusting lead  13   b  is eliminated. After completion of the resin-sealing, only the tie-bar  17  is cut off. 
     According to the present invention, the tip of the adjusting lead (e.g.,  113   b ) is located at a position which is sufficiently proximate to the outer peripheral surface  16   a  of the resin-seal body  16  to avoid a resin to flash from the adjusting lead  113   b  while the semiconductor chip  14  is resin-sealed and also sufficiently proximate to the outer peripheral surface  16   a  to allow the adjusting lead  113   b  to be removed from the resin-seal body  16  after the semiconductor chip  14  is resin-sealed with ease. 
     The lead frame according to the present invention can be used for resin-sealing various types of semiconductor chips without causing an unnecessary part thereof to remain in the resin-seal body. 
     Therefore, the withstanding voltage of the resin-sealed semiconductor devices using such a lead frame is not lowered. 
     Various other modifications will be apparent to and can be readily made by those skilled in the art without departing from the scope and spirit of this invention. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the description as set forth herein, but rather that the claims be broadly construed.