Abstract:
A method of manufacturing a packaged semiconductor device includes mounting a semiconductor device having multiple leads. The leads are formed by mounting the semiconductor device in a lead frame and punching and sealing the leads in the semiconductor device using a resin. The leads are bent to a predetermined configuration while substantially simultaneously bending a connecting member that is used for connecting the leads to a frame. The resulting packaged semiconductor device has leads that are not cut off from the lead frame, and the connection between the two can be maintained even after a bending process is finished.

Description:
CROSS REFERENCE TO RELATED APPICATION 
     This is a Divisional Application of application Ser. No. 09/481,685 filed Jan. 12, 2000 now U.S. Pat. No. 6,344,681. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a packaged semiconductor and a process for manufacturing the packaged semiconductor. 
     2. Description of the Related Art 
     A conventional packaged semiconductor  10  is, as shown in FIG. 10, provided with a package  14  in which a semiconductor device (not shown) mounted on an island (not shown) and a part of a lead frame  12  (see FIG. 7) are sealed with a resin and a plurality of leads  12   a  extending from the side of the package  14 . 
     As shown in FIG. 7, each lead  12   a  is formed by punching the lead frame  12 . The leads  12   a  are connected to each other by tie bars A 2  and each outside lead  12   a  is connected to the lead frame  12  by a tie bar B 2 . 
     Dam bars (also called “tie bars”) Al having the function of blocking the flow of the resin during the molding of the package  14  are used to connect the leads  12   a  to each other and each lead  12   a  with the lead frame  12 . Also, the island is connected to the lead frame  12  through an island support pins  18 . 
     A plurality of guide holes  20  which are openings used for positioning during the process of bending the leads  12   a  are formed in the lead frame  12 . It is to be noted that the material generally used for the lead frame  12  is a  42  alloy (Fe, Ni) or a copper alloy with a plate thickness of approximately 0.15 mm. 
     The surface of the molded lead frame  12  (including the lead  12   a ) is provided with solder plating through electrical connection of the lead frame  12  to an external section. In the solder plating method, as shown in FIG. 11, the lead frame  12  and a solder electrode  11  (anode) are dipped in an acidic electrolyte  13  (solder plating bath) in which Sn and Pb have been dissolved as solder components in advance and are electrically connected to each other and energized, thereby electrodepositing solder (Sn and Pb) on the surface of the lead frame  12  (cathode). 
     After the solder plating is finished, the lead  12   a  is processed into a predetermined shape. Specifically, in the step of processing the lead  12   a , as shown in FIG.  7  and FIG. 8, all dam bars A 1  are punched and next the tie bars B 2  at both ends are punched using a metal mold. Thereafter bending of the lead  12   a  is performed. 
     This bending of the leads  12   a  is carried out using a forming die  22  as shown in FIG.  9 . Namely, the lead frame  12  is automatically conveyed to and placed on a bending die  24  of the forming die  22  and an upper die  25  is allowed to descend. At this time, the pilot pin  26  mates with the guide hole  20  to position the lead frame  12 . Next, the leads  12   a  disposed in the vicinity of the package  14  are sandwiched between a knockout  28  pushed by a spring  30  and the bending die  24 . Thereafter, as shown in FIG.  8  and FIG. 9, the bending punch  32  is lowered so as to push down the end of each lead  12   a , thereby performing the bending. 
     Next, the end portion of each lead  12   a  which includes the tie bar A 2  is cut and the island support pins  18  are cut off from the lead frame  12  to complete the manufacture of the packaged semiconductor  10  shown in FIG.  10 . 
     SUMMARY OF THE INVENTION 
     In the above bending process using a forming die, however, the solder plating on the surface of the lead is rubbed by the bending punch during the processing and the rubbed off solder plating is pressed against and laminated on the punching surface of the bending punch to create solder residue. 
     Moreover, this solder residue then comes off the punching surface of the bending punch during the bending of the lead and adheres again to the surface of the lead. 
     As a consequence, the above bending causes short circuiting between the leads as well as a deteriorated appearance, giving rise to serious problems in the quality of the product. 
     It is therefore necessary that the operation of the apparatus be frequently suspended to clean the forming die, remarkably impairing the production efficiency of the packaged semiconductor. 
     In light of the above problem, an object of the present invention is to provide a packaged semiconductor produced by performing solder plating after the bending of the leads has been completed so that no solder residue is created. Another object of the present invention is to provide a process for manufacturing a packaged semiconductor. According to a first aspect of the present invention, there is provided a packaged semiconductor comprising: 
     a semiconductor having a plurality of leads extending therefrom, the leads having been formed by mounting the semiconductor device in a lead frame and punching and sealing the leads in the semiconductor device using a resin, wherein the leads have been bent to a predetermined configuration; and 
     connecting means for connecting said leads to said frame, said connecting means being bent substantially simultaneously as when said leads are bent to the predetermined configuration. 
     According to this structure, the lead frame is connected to the leads by the connecting means in the packaged semiconductor produced by processing the lead frame by punching in order to form the plurality of leads and by mounting the semiconductor device on the lead frame and then sealing it with resin. This connecting means is bent at the same time the leads are bent. Hence a connection can be maintained between the leads and the lead frame after the bending of the leads is finished. 
     According to another aspect of the present invention, there is provided a process for manufacturing a packaged semiconductor, comprising the steps of: 
     mounting a semiconductor device having leads in a lead frame by using connecting means to connect the semiconductor device to the lead frame; 
     sealing said semiconductor device using a resin; 
     bending the leads of the semiconductor device to a predetermined configuration and substantially simultaneously bending the connecting means; 
     dipping said lead frame and a solder electrode in an acidic electrolyte to connect said lead frame to said solder electrode electrically thereby coating the surface of said leads with solder plating; and thereafter 
     disconnecting the connection made by said connecting means. 
     According to this process, the packaged semiconductor provided with a package in which a semiconductor device is mounted on a lead frame in which a plurality of leads have been formed by punching and which is sealed using a resin, wherein the leads extending from the side of the package are formed by bending, is manufactured by the first to fourth steps given below. 
     Specifically, in the first step, the lead frame and the semiconductor device are sealed with a resin to form a package. 
     In the second step, the connecting means which connects the lead to the lead frame is bent at the same time the lead is bent. 
     In the third step, the lead frame and the solder electrode are dipped in the acidic electrolyte and the lead frame is electrically connected to the solder electrode to provide the surface of the lead with solder plating. 
     Finally, in the fourth step, the connection made by the connecting means is terminated. 
     The production of a packaged semiconductor according to the above manufacturing process ensures that since solder plating can be provided on the surface of the lead after the lead is bent, the solder plating formed on the surface of the lead does not peel off and no solder residue is produced. 
     According to another aspect of the present invention, there is provided a device for forming a packaged semiconductor, the device comprising: 
     a semiconductor having a plurality of leads extending therefrom; 
     a lead frame in which the semiconductor device is mounted; and 
     an elongated connection member having opposite longitudinal edges, with one longitudinal edge connected to the lead frame and the opposite longitudinal edge connected to a lead of the semiconductor device. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top plan view showing the condition of a lead frame before it is bent, the lead frame being used in a packaged semiconductor according to a first embodiment of the present invention. 
     FIG. 2A is a top plan view showing the condition of the lead frame shown in FIG. 1 after it is bent and FIG. 2B is a side view thereof. 
     FIG. 3 is a perspective view showing the condition of the lead frame after it is bent, the lead frame being used in the packaged semiconductor according to the first embodiment of the present invention. 
     FIG. 4 is a top plan view showing the condition of a lead frame before it is bent, the lead frame being used in a packaged semiconductor according to a second embodiment of the present invention. 
     FIG. 5A is a top plan view showing the condition of the lead frame shown in FIG. 4 after it is bent and FIG. 5B is a side view thereof. 
     FIG. 6 is a perspective view showing the condition of the lead frame after it is bent, the lead frame being used in the packaged semiconductor according to the second embodiment of the present invention. 
     FIG. 7 is a top plan view showing the condition of a conventional lead frame before it is bent. 
     FIG. 8A is a top plan view showing the condition of the conventional lead frame after it is bent and FIG. 8B is a side view thereof. 
     FIG. 9 is a schematic structural view of a forming die for bending. 
     FIG. 10 is a perspective view of a packaged semiconductor. 
     FIG. 11 is a schematic structural view of a solder plating apparatus. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A packaged semiconductor according to a first embodiment of the present invention will be hereinafter explained with reference to the drawings. FIG. 1 is a top plan view showing the condition of a lead frame before the leads are bent. FIG. 2A is a top plan view showing the condition of the lead frame after the leads and connecting means are bent and FIG. 2B is a side view thereof. 
     The parts having the same structures as in the conventional art are represented by the same symbols in the following explanations for the sake of convenience. 
     As shown in FIG. 1, the plurality of leads  12   a  are formed by processing a lead frame  40  by punching. These leads  12   a  are joined (connected) with each other through two tie bars C 1  and D 1 . One of these tie bars C 1  and D 1  is a dam bar D 1  having the function of blocking the flow of resin in the molding of the package  14  explained below. 
     Four leads  12   a  (these particular leads are hereinafter called “end leads S”) positioned on the outermost sides of the plurality of leads  12   a  formed in the lead frame  40  are connected to a extraneous leads T 1  (the shaded portion in FIG.  1 ), which are integrated with the lead frame  40 , through tie bars C 3  and D 3 . The extraneous leads T 1  are connected to the lead frame  40  through two tie bars C 2  and D 2 . 
     It is to be noted that the extraneous leads T 1  are formed by punching the lead frame  40  in the same shape as the other leads  12   a  and have a shape of substantially the same dimensions as each of the other leads  12   a  with respect to length and width. 
     In the center position of the lead frame  40 , an island portion on which with an unillustrated semiconductor device is to be mounted, is integrated with the lead frame  40 . The island portion is connected to the lead frame  40  at a section corresponding to the outer frame of the lead frame  40  through an island pin  18 . 
     It is to be noted that circular guide holes  20  for positioning the lead frame  40  on a forming die  22  are formed in the lead frame  40  during the bending of the leads  12   a.    
     Next, a process for manufacturing a packaged semiconductor according to this embodiment will be explained. 
     First, a semiconductor device (chip) is mounted on the above island portion of the lead frame  40  and sealed using a resin together with the lead frame  40  to produce the package  14  (the first step). Then, the tie bars C 2  and D 2  which connect the lead frame  40  to the extraneous leads T 1  are cut by punching using a metal mold. At the same time, the tie bars D 1  and D 3  are cut by punching. At this time, the leads  12   a  are connected to each other through the tie bar C 1  and also to the extraneous leads T 1  through the tie bar C 3 . The extraneous leads T 1  are integrated with the lead frame  40 . 
     Next, when the lead frame  40  is automatically conveyed onto a bending die  24  of the forming die  22  for bending as shown in FIG. 9, the upper die  25  descends whereby pilot pins  26  penetrate through the guide holes  20  of the lead frame  40 . At this time, the leads  12   a  located in the vicinity of the package  14  are sandwiched together with the package  14  between a knockout  28  forced by a spring  30  and the bending die  24 . The lead frame  40  is thereby positioned in the forming die  22 . 
     Subsequently, the bending punch  32  descends to push down the lead  12   a  and the extraneous leads T 1  at the same time thereby performing bending. When the bending is performed, as shown in FIG. 2B, the leads  12   a  and the extraneous leads T 1  are bent respectively into the form of an L-character in section (the second step). 
     Here, as shown in FIG. 3, even after the leads  12   a  are bent, the leads  12   a  are not separated from the lead frame  40  since the extraneous leads T 1  are connected to the lead frame  40 . 
     Next, the surface of the lead frame  40  is provided with solder plating (the third step). Specifically, as shown in FIG. 11, the bent lead frame  40  is immersed together with a solder electrode  11  in an acidic electrolyte  13  to connect the solder electrode  11  electrically to the lead frame  40 . Then, as described in the section “Prior art”, the lead frame  40  is energized to deposit solder on the surface of the lead frame  40  (leads  12   a ). 
     Thereafter, the lead frame  40  on which the solder is deposited is taken out of the electrolyte  13  and the distal end of the leads  12   a  and extraneous leads T 1  are cut together with the tie bars C 1  and C 3 . By further cutting the island support pins  18 , the package  14  and the leads  12   a  are cut off from the lead frame  40  to obtain a packaged semiconductor  10  (see FIG. 10) (the fourth step). 
     According to the packaged semiconductor  10  of this embodiment, as stated above, the leads  12   a  are connected to the extraneous leads T 1  which is integrated with the lead frame  40 . Also, each lead  12   a  and the extraneous lead T 1  is bent at the same time so that the connection between the leads  12   a  and the lead frame  40  can be maintained. 
     According to the process for the production of the packaged semiconductor  10  provided with the lead frame  40 , the connection between the leads  12   a  and the lead frame  40  can be maintained by bending the leads  12   a  and the extraneous leads T 1  at the same time. The lead frame  40  can be provided with solder plating accordingly after the bending process. 
     As a result, the solder plating of the lead  12   a  is not peeled off by the bending punch  32  and no solder residue is produced. This prevents a reduction in the quality of the packaged semiconductor  10  and avoids the necessity of cleaning the forming die  22  to remove solder residue. Thus, a highly productive and high quality packaged semiconductor  10  can be manufactured. 
     Next, a packaged semiconductor according to a second embodiment will be explained. 
     The lead frame  41  used in the packaged semiconductor  10  according to the second embodiment is the same as the packaged semiconductor of the first embodiment except that the shape of the extraneous lead T 1  of the lead frame  40  used in the first embodiment is changed. Therefore, the parts having the same structure as in the first embodiment are represented by the same symbols and are omitted where appropriate from the explanation below. 
     As shown in FIG. 4, extraneous leads T 2  (the shaded portion in FIG. 4) connected to leads  12   a  are integrated with a lead frame  41  and the distal end thereof is connected to a side of an end lead S. The extraneous leads T 2  are formed in an L-character form when seen in plan view. 
     On the other hand, the distal ends of the leads  12   a  are connected to each other through a tie bar E 1  and also the end leads S are connected to the lead frame  41  through the tie bar E 1 . Further, the leads  12   a  located in the vicinity of the package  14  are connected to each other through a tie bar F 1 . The end leads S are connected to the extraneous leads T 2  through a tie bar F 3  and the extraneous lead T 2  are connected to the lead frame  41  through a tie bar F 2 . 
     Moreover, an island portion is connected to the lead frame  41  through island pins  18 . 
     Next, in a process for manufacturing the packaged semiconductor  10  provided with the lead frame  41 , firstly the tie bars E 1  connecting the end leads S to the lead frame  41 , the tie bars F 2  connecting the extraneous leads T 2  to the lead frame  41 , the tie bars F 3  connecting the extraneous leads T 2  to the end leads S and the tie bars F 1  connecting the leads  12   a  to each other are cut in the same manner as in the first embodiment. 
     Next, as shown in FIG.  5 A and FIG. 5B, each lead  12   a  and useless lead T 2  is bent at the same time by the forming die  22 . Then, as shown in FIG. 11, the lead frame  41  and the solder electrode  11  are immersed the acidic electrolyte  13  to connect the lead frame  41  electrically to the solder electrode  11 . Thereafter, the lead frame  41  is energized to provide the surface of the lead frame  41  (leads  12   a ) with solder plating by utilizing electric energy. 
     The leads  12   a  provided with solder plating are cut to a prescribed length (cut at a position closer to the side of the package  14  than the joint portion between the extraneous leads T 2  and the end leads S). Further, the island support pins  18  are cut. The packaged semiconductor  10  as shown in FIG. 10 is thus obtained. 
     In this embodiment also, as stated above, the leads  12   a  and the useless leads T 2  are bent at the same time. Therefore, the connection between the leads  12   a  and the useless leads T 2 , that is, between the leads  12   a  and the lead frame  41  can be maintained. 
     Also, according to the packaged semiconductor  10  provided with the lead frame  41 , the lead frame  41  can be plated using solder after the leads  12   a  are bent and hence the solder plating of the lead  12   a  is not peeled off by the punch  32  in the bending process thereby preventing the production of solder residue. As a result, the necessity of cleaning the forming die  22  to remove the solder residue is avoided. Thus, a highly productive and high quality packaged semiconductor  10  can be manufactured. 
     Incidentally, the lead frames  40  and  41  respectively used in each of the above embodiments are represented in a form applicable to the semiconductor  10 . However, if extraneous leads are formed on the outside of the end leads S and the lead frame  40  or  41  is still connected to the leads  12   a  after the bending process is finished, this lead frame  40  or  41  can be applied to other electronic parts which are to be provided with solder plating. 
     According to the packaged semiconductor of the present invention a lead is not cut off from a lead frame, and the connection between the two can be maintained even after a bending process is finished. 
     According to the process for the production of a packaged semiconductor, since the surface of a lead frame can be provided with solder plating after a lead is bent, the solder plating formed on the surface of the lead is not peeled off by bending and hence the production of solder residue can be avoided.