Abstract:
A technology is provided that can seal the opening in a wiring board using a transfer mold insulating resin from the opening. A mold die is used which includes a first die having a recess in a predetermined form and a second flat die. The first die is disposed on a surface of a wiring board which has a plurality of openings and on which a semiconductor chip is mounted via an elastic material. The second die is disposed on a back surface of the wiring board opposite the surface on which the semiconductor chip is mounted. The mold is used for sealing with an insulating resin the periphery of the semiconductor chip and at least one of the openings of the wiring board, wherein the above-described second die has a protrusion around an area overlapping the opening to be sealed with the insulating resin.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to a mold die and to a method of manufacture of a semiconductor device using the mold die; and, more particularly, the invention relates to a technology in which a die is used effectively for sealing a semiconductor chip, which is mounted on a wiring board via an elastic material and an opening of the wiring board, by transfer mold processing. 
   One example of conventional semiconductor devices having a form referred to as a BGA (Ball Grid Array) includes a semiconductor chip, an interposer (wiring board) having an insulating substrate on which a conductive pattern is provided, and an elastic material (elastomer) disposed therebetween for providing stress relaxation. The semiconductor device hereafter referred to includes the above-described elastic material, unless otherwise specified. 
   The above-described semiconductor device includes, for example as shown in  FIG. 9 , an opening  4  in the interposer, which includes an insulating substrate  101  on which the conductive pattern  102  is provided, and in the elastic material  2 . The conductive pattern  102  and an external electrode  301  of the semiconductor chip  3  are electrically connected by way of the opening  4 . 
   In addition to the opening  4 , the described insulating substrate  101  also includes an opening (not shown) for forming an external connecting terminal  6 . The opening  4  over which the conductive pattern  102  and the external electrode  301  of the semiconductor chip  3  are connected is hereafter referred to as a bonding opening. The opening for forming the external connecting terminal  6  is hereafter referred to as an external terminal opening. 
   In the above-described semiconductor device, an insulating resin  5  seals the periphery of the semiconductor chip  3 , for example as shown in  FIG. 9 . The insulating resin  5  also seals the bonding opening  4 . The periphery of the semiconductor chip  3  and the bonding opening  4  may be sealed, for example, by transfer mold processing. 
   The above-described transfer mold processing is carried out, for example, as shown in  FIG. 10 , by sandwiching the interposer (insulating substrate  101 ) bearing the semiconductor chip  3  between a first die (hereafter referred to as a top die)  7  having a recess  7 A of predetermined form and a second flat die (hereafter referred to as a bottom die)  8 , by causing the insulating resin  5  to flow into the resulting space formed therebetween, and by curing the resin  5  (see for example Japanese application patent laid-open publication No. 2002-353361). 
   Semiconductor devices in a similar form to the above-described semiconductor device include a semiconductor device in which the conductive pattern  102  and the external electrode  301  of the semiconductor chip  3  are electrically connected via a bonding wire. The semiconductor device using a bonding wire may be transfer molded using a groove (recess) provided on a portion overlapping the bonding opening  4  of the interposer to ensure the sealing of the loop of the bonding wire (see for example Japanese application patent laid-open publication No. 2000-058711 (FIG. 6)). 
   SUMMARY OF THE INVENTION 
   In the above-described conventional technologies, however, the bottom die  8  has a flat surface  8 A which is brought into contact with the insulating substrate  101 . Thus, any bending or distortion of the insulating substrate  101  may cause a space to appear between the bottom die  8  and the insulating substrate  101 , which is sandwiched between the top die  7  and bottom die  8 , as shown in  FIG. 11 . 
   In particular, each opening of the insulating substrate  101 , which is generally formed by stamping with a die, may thus often have bending or distortion around the opening. The bonding opening  4  also may be subjected to a load caused by the electrical connection of the conductive pattern  102  and the external electrode  301  of the semiconductor chip  3 . Thus, bending or distortion often occurs around the bonding opening  4 . 
   With any bending or distortion generated around the bonding opening  4 , the transfer mold may allow the insulating resin  5  which flows into the bonding opening  4  to leak into the space formed between the bottom die  8  and the insulating substrate  101 , as shown in  FIG. 11 . The thin insulating substrate  101  cannot bear the injection pressure from the flow of the insulating resin  5  and may float. As a result, the insulating resin  5  may spread over the surface of the insulating substrate  101 , as shown in  FIG. 12 . 
   The insulating substrate  101  includes, for example, as shown in  FIG. 12 , external terminal openings  101 A outside the bonding opening  4 . Thus, if the insulating resin  5  which flows into the bonding opening  4  during the above-described transfer mold operation leaks out, the front end  5 A of the leaked insulating resin  5  may spread over the area of the above-described external terminal openings  101 A and flow into the above-described external terminal openings  101 A. The insulating resin  5  which flows into the external terminal openings  101 A may cause poor electrical conduction between the external connecting terminal  6  formed and the conductive pattern  102 . 
   In particular, recent semiconductor devices, which tend to be smaller and to be provided with a higher density, are characterized by a smaller distance between the bonding opening  4  and the external terminal openings  101 A. The external terminal openings  101 A also tend to have a smaller area. Thus, the leaked insulating resin may more readily cause poor electrical conduction. 
   As described above, there has been a problem with the conventional method using transfer mold processing for manufacturing the semiconductor device in that the above-described semiconductor devices may have a reduced manufacturing yield. 
   Accordingly, an object of the present invention is to provide a technique with which it is possible seal the opening of the interposer during transfer mold processing to prevent leakage of the insulating resin from the opening, thereby improving the manufacturing yield of the semiconductor devices. 
   These and other objects and novel features of the present invention will become apparent upon review of the following description in this specification and the accompanying drawings. 
   The present invention as disclosed in this application will be summarized as follows. 
   (1) A mold die includes a first die having a recess in a predetermined form and a second flat die, the first die being disposed on a surface of a wiring board which has a plurality of openings, which surface bears a semiconductor chip via an elastic material, and the second die is disposed on a back surface of the wiring board opposite to the surface which bears the semiconductor chip. The molding die is used for sealing, with an insulating resin, a periphery of the semiconductor chip and at least one of the openings in the wiring board, wherein the second die comprises a protrusion disposed around an area overlapping the opening which is sealed with the insulating resin. 
   According to the above-described Example (1), when the first die and the second die sandwich the wiring board, the protrusion on the second die can press up against and apply pressure to the wiring board (insulating substrate). With the protrusion pressing up against the wiring board, the elastic material can deform and exert a force which attempts to return it to its original shape. The wiring board (insulating substrate) may then receive from the elastic material a force opposite to the force applied from the protrusion of the second die. 
   A higher degree of contact can thus be provided between the second die and the wiring board (insulating substrate), thereby preventing the insulating resin which flows into the opening from leaking in between the wiring board (insulating substrate) and the second die. 
   (2) A method of manufacture of a semiconductor device by sealing, by transfer mold processing using a die, a semiconductor chip mounted on a wiring board via an elastic material, which board includes an insulating substrate having a plurality of openings thereon and on which a conductive pattern is formed, and by sealing at least one of the above-described openings, wherein a die having a protrusion disposed around an area overlapping the sealed opening to be sealed is used for the back die member which bears against the surface of the wiring board opposite to the surface on which the semiconductor chip is mounted. 
   The above-described Example (2) is a method of manufacture of a semiconductor device using the above-described Example (1). Use of the mold die of the above-described Example (1) can prevent the insulating resin which flows into the opening from leaking out and from flowing into an opening that should not be sealed by the insulating resin. It is thus possible to improve the manufacturing yield of the semiconductor device. 
   In the following, the present invention, as well as its embodiments (examples), will be described in more detail with reference to the accompanying drawings. 
   Like reference characters indicate functionally identical elements throughout all the illustrative drawings, and a repeated description thereof is omitted. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a diagrammatic plan view of the configuration of a semiconductor device according to the present invention. 
       FIG. 2  is a cross-sectional view taken along line A-A′ in  FIG. 1 . 
       FIG. 3  is a diagram of the configuration of a mold die in an example according to the present invention. 
       FIG. 4  is an enlarged cross-sectional view of a characteristic part of the mold die shown in  FIG. 3 . 
       FIG. 5  is a cross-sectional diagram illustrating the operational advantage of the mold die during the molding process. 
       FIG. 6  is a cross-sectional diagram illustrating the operational advantage of the mold die after the molding process. 
       FIG. 7  shows a back view of the semiconductor device illustrating the operational advantage of the mold die after the molding process. 
       FIG. 8  is a cross-sectional diagram illustrating an application of an example of the mold die. 
       FIG. 9  is a cross-sectional diagram of a conventional BGA type semiconductor device. 
       FIG. 10  is a cross-sectional diagram of a conventional mold die. 
       FIG. 11  is a diagram illustrating the problems of the conventional mold die. 
       FIG. 12  is a diagram further illustrating the problems of the conventional mold die. 
   

   DESCRIPTION OF THE INVENTION 
   Before describing the examples of the present invention, the schematic configuration of a semiconductor device according to the present invention will be described. 
     FIGS. 1 and 2  are diagrams which show the configuration of the semiconductor device according to the present invention.  FIG. 1  is a plan view of the semiconductor device.  FIG. 2  is a cross-sectional view taken along line A-A′ in  FIG. 1 . 
   The semiconductor device according to the present invention includes an interposer (wiring board) having an insulating substrate  101  on which a conductive pattern  102  is provided, and a semiconductor chip  3 , which is bonded on the above-described interposer via an elastic material (elastomer)  2 , as shown in  FIGS. 1 and 2 . 
   The conductive pattern  102  of the above-described interposer and the external electrode  301  of the semiconductor chip  3  are electrically connected over an opening  4  provided in the interposer (insulating substrate  101 ) and the elastic material  2 , as shown in  FIG. 2 . The opening  4  hereafter will be referred to as a bonding opening. 
   In the above-described semiconductor device, an insulating resin  5  seals the periphery of the described semiconductor chip  3 , as shown in  FIG. 2 . The insulating resin  5  also seals the bonding opening  4 . The conductive pattern  102  of the interposer is provided, for example, as shown in  FIG. 2 , on the surface where the semiconductor chip  3  is bonded. The conductive pattern  102  includes, for example, terminals for connection to a print wiring board, such as those referred to as a motherboard and a daughter board. 
   The insulating substrate  101  of the interposer includes openings in the regions of the terminals thereof. The openings include external connecting terminals  6  formed of a ball-like shaped bonding agent. The opening for providing the external connecting terminal  6  hereafter will be referred to as an external terminal opening. 
   The elastic material  2  is, for example, PTFE (poly-tetrafluoroethylene). The elastic material  2  has a thickness of, for example, about 150 μm. 
   The described semiconductor device can be manufactured by bonding the semiconductor chip  3  on the interposer via the elastic material  2 , followed by electrically connecting the conductive pattern  102  of the interposer and the external electrode  301  of the semiconductor chip  3 . The insulating resin  5  then seals, by transfer mold processing, the periphery of the semiconductor chip  3  and the bonding opening  4 . The external connecting terminal  6  is then formed in the external terminal opening. 
   Examples will be described below of the configuration of the die (hereafter referred to as a mold die) for use in the above-described transfer mold. 
   EXAMPLE 1 
     FIGS. 3 and 4  are diagrams of the configuration of the mold die representing an example according to the present invention.  FIG. 3  is a cross-sectional view of the entire configuration of the mold die.  FIG. 4  is an enlarged cross-sectional view of a characteristic part of the mold die. 
   The mold die in this example includes a pair of die members consisting of a top die  7  and a bottom die  8 , which sandwich the interposer bearing the semiconductor chip  3 , as shown in  FIG. 3 . The top die  7  includes a recess space  7 A into which the insulating resin flows for sealing the periphery of the semiconductor chip  3 . 
   The bottom die  8  includes a protrusion  8 B in a predetermined form on the upper surface thereof so as to come into close contact with the insulating substrate  101  (hereafter referred to as a reference contact surface), as shown in  FIGS. 3 and 4 . The protrusion  8 B is provided in the form of a loop around a rectangular opening, such as the bonding opening, to be sealed with insulating resin  5 . 
   The protrusion  8 B has such a width that, for example, the above-described protrusion  8 B come into contact with the insulating substrate  101  between the opening  4  and the opening  101 A for forming the external connecting terminal, as shown in  FIG. 4 . The protrusion  8 B has a height of, for example, about 10 μm. 
     FIGS. 5 to 7  are diagrams which illustrate the operational advantage of the mold die in the example 1.  FIG. 5  is a cross-sectional view of the condition during the molding process.  FIG. 6  is a cross-sectional view of the semiconductor device after the molding process is complete.  FIG. 7  shows a back view of the semiconductor device after completion of the molding process.  FIG. 5  shows the same cross section as in  FIG. 4 , although it omits the hatching (parallel oblique lines) representing the cross section.  FIG. 7  is a view from the back of  FIG. 1 . 
   The mold die in the example 1 can be used for the transfer mold by, as shown in  FIG. 4 , disposing the interposer bearing the semiconductor chip  3  between the top die  7  and the bottom die  8 ; followed by, for example, sandwiching the insulating substrate  101  between the top die  7  and the bottom die  8 , and fastening the substrate  101  with a predetermined pressure. 
   In the contact portion between the insulating substrate  101  and the protrusion  8 B of the bottom die  8 , the insulating substrate  101  will be distorted with the force F 1  from the protrusion  8 B of the bottom die  8 . The insulating substrate  101  will have a distorted portion that is pressed by the protrusion  8 B of the bottom die  8 , thereby the elastic material  2  also will be distorted. The elastic material  2  is in a contracted condition and tends to return to its original condition. Thus, the insulating substrate  101  also will receive from the elastic material  2  a force F 2 , which is opposite to the force F 1  from the protrusion  8 B of the bottom die  8 , as shown in  FIG. 5 . 
   As a result, the degree of contact between the insulating substrate  101  and the protrusion  8 B of the bottom die  8  will be higher than, for example, the degree of contact between the insulating substrate  101  and the reference contact surface  8 A of the bottom die  8 . Even when the insulating substrate  101  is distorted in the area around the bonding opening  4 , for example, as shown in  FIG. 11 , the protrusion  8 B of the bottom die  8  can prevent any space from appearing at the portion where the wiring or distortion occurs. 
   As described above, the mold die in the example 1 can prevent the insulating resin  5  which flows into the bonding opening  4  from leaking through between the insulating substrate  101  and the bottom die  8 . It is thus possible, for example, as shown in  FIGS. 6 and 7 , to prevent any spreading of the front end  5 A of the insulating resin  5  which flows into the bonding opening  4 , and to prevent the flow of the insulating resin  5  into an opening  101 A for forming the external connecting terminal. 
   When the protrusion  8 B on the surface of the bottom die  8  is provided outside the edge of the bonding opening  4 , as shown in  FIG. 4 , the insulating resin  5  which flows into the described bonding opening  4  can reach the back of the surface of the insulating substrate  101 , specifically, the surface on which the semiconductor chip  3  is bonded, so that the front end  5 A of the insulating resin  5  can reach outside the edge of the bonding opening  4 , as shown in  FIGS. 6 and 7 . As a result, the interface delamination will occur less frequently between the insulating substrate  101  and the insulating resin  4  around the bonding opening  4 . 
   As described above, in the mold die of example 1, a higher degree of contact is produced between the bottom die  8  and the periphery of the bonding opening  4  provided on the interposer, thereby preventing the insulating resin  5  which flows into the bonding opening  4  from leaking in between the insulating substrate  101  and the bottom die  8 . It is thus possible to prevent the insulating resin  5  from spreading over the surface of the insulating substrate  101 , as shown in  FIG. 12 , and from flowing into the opening  101 A for forming the external connecting terminal, thereby improving the manufacturing yield of the semiconductor device. 
     FIG. 8  is a cross-sectional diagram illustrating an application of the example. 
   The mold die in the example 1 uses a bottom die  8  on which the area inside the protrusion  8 B is approximately the same height as the reference surface  8 A, as shown in  FIG. 3 . Additionally, the area inside the protrusion  8 B may include a recess  8 C, as shown in  FIG. 8 . The recess  8 C may have a depth of about 70 μm from the reference surface  8 A. 
   The bottom die  8  with the recess  8 C can also include, around the recess  8 C, the protrusion  8 B with a height of about 10 μm from the reference surface  8 A to give higher degree of contact between the bottom die  8  and the insulating substrate  101  around the periphery of the bonding opening  4 . 
   It is thus possible to prevent the insulating resin  5  which flows into the bonding opening  4  from leaking in between the interposer (insulating substrate  101 ) and the bottom die  8 . 
   When the recess  8 C is provided, the insulating resin  5  which flows into the bonding opening  4  may run into the recess  8 C. The insulating resin  5  in the recess  8 C may be cured to provide the complete semiconductor device in which the cured insulating resin  5  may have a front end  5 A, as shown in  FIG. 6 , of greater thickness than in the example. 
   With the bottom die  8  as shown in the example, the edge of the bonding opening  4  may contact with the reference surface  8 A of the bottom die  8 , so that the front end  5 A of the insulating resin  5  may have various shapes. 
   On the other hand, with the bottom die  8  shown in  FIG. 8 , the base of the recess  8 C is lower than the reference surface  8 A to prevent the edge of the bonding opening  4  from contacting the bottom die  8 . The front end  5 A of the insulating resin  5  can thus have less varied shapes (thicknesses), and the interface delamination will occur much less frequently between the insulating substrate  101  and the insulating resin  5 . 
   The above-described example 1 provides an illustration of a semiconductor device in which the conductive pattern  102  is deformed to be electrically connected with the external electrode  301  of the semiconductor chip  3 . Additionally, the semiconductor device may be one in which, for example, the conductive pattern  102  is connected with the external electrode  301  of the semiconductor chip  3  via a bonding wire. In this case, to ensure the sealing of the bonding wire, the bottom die with the recess  8 C, as shown in  FIG. 8 , may preferably be used rather than the bottom die  8  described in connection with example 1. 
   While the present invention has been described with reference to an example, it should be understood that the invention is not limited to the above-described example and various modifications are possible without departing from the spirit thereof. 
   Representative examples of the invention disclosed in this specification can provide such effects as briefly described as follows. 
   The opening of the interposer can be sealed by transfer mold processing while preventing leakage of the insulating resin from the opening and reducing poor electrical conduction of the external connecting terminal due to leakage of insulating resin. It is thus possible to improve the manufacturing yield of the semiconductor device.