Abstract:
A push-back circuit board frame on which a semiconductor device is mounted, including a circuit board, the board being detached from the frame and being returned to an original position in the frame, a cavity formed at an edge of the circuit board in the frame, a semiconductor chip mounted on the circuit board, a resin sealing the semiconductor chip on the circuit board, and a support base made of the same material as the resin, formed in the cavity, where all of the resin is formed simultaneously, and connected each other.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority benefit of Japanese Patent Application No. 11-029482, filed Feb. 8, 1999, the entire subject matter of which is incorporated herein of reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a circuit board frame and a method for manufacturing a semiconductor device using it and more particularly, to a circuit board frame which is formed by a push-back technology. 
     2. Description of the Related Art 
     Currently, based on requirements of high integration, a circuit board frame which is formed by push-back technology (called as push-back circuit board frame, hereinafter) is used to manufacture a semiconductor device. A push-back circuit board frame is formed by the following process. First, a circuit board is punched out completely from the circuit board frame. Then, the circuit board is returned to the original location. Therefore, the circuit board is supported by the frame with a frictional force only. 
     To manufacture a semiconductor device, a semiconductor chip is mounted on the circuit board which is pushed back by the method described above, and then, the semiconductor chip are connected to the circuit board by bonding wires. Then, the semiconductor chip is sealed by a resin. After that, the circuit board is removed from the push-back circuit board frame. The push-back circuit board frame is effective for highly integrated semiconductor device because it is easy to remove the circuit board from the frame without stressing the semiconductor device. 
     On the other hand, as the circuit board is supported by the frame with a frictional force only, it is easy for the circuit board to come off from the frame during an assembly process that includes a chip mounting process, a wiring process, and a molding process. 
     SUMMARY OF THE INVENTION 
     An objective of the invention is to resolve the above-described problem and to provide a push-back circuit board frame having a circuit board which is firmly supported by the frame during the assembling process. 
     The objective is achieved by a push-back circuit board frame on which a semiconductor device is mounted, including a circuit board, the board being detached from the frame and being returned to an original position in the frame, a cavity formed at an edge of the circuit board in the frame, a semiconductor chip mounted on the circuit board, a resin sealing the semiconductor chip on the circuit board, and a support base made of the same material as the resin, formed in the cavity, where all of the resin is formed simultaneously, and connected each other. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be more particularly described with reference to the accompanying drawings in which: 
     FIG. 1 is a prospective view of a push-back circuit board frame of a first embodiment of the invention; 
     FIGS. 2A-2C show a process to form a push-back circuit board frame 
     FIG. 3A is a sectional view showing a process to manufacture a semiconductor device with a frame of a first embodiment using a first mold; 
     FIG. 3B is a prospective view of a push-back circuit board frame on which a molded semiconductor chip is mounted, of a first embodiment of the invention; 
     FIG. 3C is a sectional view showing a process to manufacture a semiconductor device with a frame of a first embodiment using a second mold; 
     FIG. 4 is an enlarged view of an area A shown in FIG. 3, of the first embodiment of the invention; 
     FIG. 5 is a prospective view of a semiconductor device which is manufactured by using the push-back circuit board frame. 
     FIG. 6 is a sectional view of the semiconductor device shown in FIG. 5; 
     FIG. 7 is a plan view of a push-back circuit board frame of a second embodiment of the invention; 
     FIG. 8 is a plan view of a push-back circuit board frame of the second embodiment of the invention after removing a circuit board frame material from a push-back area; 
     FIG. 9 is plan view of a push-back circuit board frame of the second embodiment of the invention after a semiconductor device is removed from the frame; 
     FIG. 10 is an enlarged view of an area A shown in FIG. 9 before the semiconductor device is removed from the push-back circuit board frame; and 
     FIG. 11 is an enlarged view of an area A shown in FIG. 9 after the semiconductor device is removed from the push-back circuit board frame. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 1, a push-back circuit board frame  1  has a rectangularly-shaped circuit board  2  and a cavity  11  at each of the four corners of the circuit board  2 . The circuit board  2  is defined in the circuit board frame  1  by a push-back line  3 . Circuit patterns are formed on the circuit board  2 . 
     The push-back circuit board frame  1  is formed by the following process shown in FIG.  2 A through FIG.  2 C. First, the four cavities  11  are formed in the frame  1  at the corners of the circuit board  2 . Then the frame  1  is fixed between a die  4  and a punch guide  7 . Then, the circuit board  2  is cut along the push-back line  3  by sliding a push-back punches  5 ,  6  down. After that, the circuit board  2  is returned to the original position in the circuit board frame  1  by sliding the punches  5 ,  6  upward. 
     Referring to FIGS. 3A and 3B, to form a semiconductor device  20 , first, a semiconductor chip  8  is mounted on the frame  1 , which is formed by the process described above. Then, the frame  1  is placed in a first mold  51 . The mold  51  has an unillustrated cavity in which a resin tablet is placed, an unillustrated first runner which acts as a pass between the cavity of the mold  51  and a room  52  where the semiconductor chip  8  is located, and an second runner  53  which acts as a pass between the cavity  11  of the frame  1  and the room  52 . The resin tablet is melted, then, the melted resin flows through the first runner to the room  52 . The melted resin also flows through the second runner  53  into the cavity  11 . After the melted resin becomes a solid  10 , the semiconductor device  20  is detached from the frame  1  along the push-back line  3 . The detached semiconductor device is shown in FIG. 5, and a sectional view of the detached semiconductor device  20  is shown in FIG.  6 . 
     Referring to FIG. 4, the semiconductor device  20 , which is not detached from the frame  1  yet, is illustrated as an enlarged drawing of an area A in FIG.  3 . As the mold has the second runners and the frame  1  has four cavities  11 , a support member  12  of the solid resin  10  is formed where the second runners are located, and a support base  13  is formed in each of the cavities  11  of the frame  1 . Therefore, the semiconductor device  20  is supported by the frame  1  with the four support members  12  and the support bases  13 . 
     According to the first embodiment of the invention, as the circuit board  2  is supported by the frame  1  with the support members  12  and the support base  13  in addition to a frictional force, the semiconductor device  20  is not easily detached from the frame during the assembling process, after the molding process. 
     Referring to FIG. 3C, a second mold  61  as the alternative is used. A difference between the first mold  51  shown in FIG.  3 A and the second mold  61  is that the second mold has no second runner which flows the melted resin to the cavity  11 . Therefore, when the frame  1  is placed in the second mold  61 , a room  52  of the second mold  61  is directly connected to the cavities  11  of the frame  1 . So, the melted resin, which is introduced in the room  52 , flows to the cavities  11  of the frame  1 . The melted resin in the cavities  11  of the frame  1  becomes a sold to be a support base  13 . In the case that the second mold  61  is used, although the circuit board  2  is supported by the frame  1  with the support base  13  only in addition to a frictional force, it is enough to support the circuit board  2  with it. The shape of the second mold  61  is simpler than that of the first mold  51 . 
     A second embodiment of the invention is explained with reference to FIG.  7  through FIG. 11. A push-back circuit board frame  21  includes a plurality of push-back members  22  and a circuit board  23 . The push-back members  22  are formed in a push back area  30  where is at circumferentical location of the circuit board  23 , specifically, at each corner of the circuit board  23 . The push-back members  22  are isolated from each other by supporting members  25  which is a part of the circuit board frame  21 . The width W of the supporting member  25  equals to 1 to 3 times the thickness of the circuit board frame  21 . The push-back process for forming the push-back member  22  is performed by the method which is described above with respect to the first embodiment. That is, the frame  21  is fixed by a die and the punch guide, and then the push-back punches are placed on areas where the push-back members  22  are formed. After that, by sliding the punches down, the push-back members  22  are detached from the frame  21 , and then, by sliding the punches upward, the push-back members  22  are returned to the original positions. After the push-back process is performed, a semiconductor chip is mounted on the circuit board  23 , and then a wire bonding process and a molding process are performed. FIG. 7 illustrates a semiconductor device  100  which is molded by a resin  24 . In this condition, the semiconductor device is still on the circuit board frame  21 . After that, referring to FIG. 8, the push-back members  22  are removed. The semiconductor device  100  is still supported only by the support members  25 . 
     Referring to FIG. 9, the support members  25  are cut, and then the semiconductor device  100  is completely detached from the circuit board frame  21 . This detaching process is explained with reference to FIG.  10  and FIG.  11 . The circuit board frame  21  is fixed between a die and a punch guide. Then, a push-back punch and a punch are aligned in an area which is shown by a broken line  26  and then, the push-back punch and the punch are moved down to cut the support member  25  along the broken line. As a result, the semiconductor device is completely detached from the circuit board frame  21 , as shown in FIG.  11 . 
     According to the second embodiment of the invention, as the circuit board  23  is supported by the frame  21  with the support members  25  during the mounting process of the semiconductor chip, the wire bonding process and the molding process, the semiconductor device  20  is not detached from the frame  21  through the assembly process. 
     While the invention has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. For example, although the cavities  11  are formed at a corner of the circuit board in the first embodiment, the cavities can be formed at any sides of the circuit board. Further, although the rectangularly shaped circuit board is illustrated in the first and the second embodiments respectively, circular shaped circuit board can be used in the both of the embodiments. Various modifications of the illustrated embodiments, as well as other embodiments of the invention, will be apparent to those skilled in the art on reference to this description. Therefore, the appended claims are intended cover any such modifications or embodiments as fall within the true scope of the invention.