Mold die for a semiconductor device

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.

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 inFIG. 9, an opening4in the interposer, which includes an insulating substrate101on which the conductive pattern102is provided, and in the elastic material2. The conductive pattern102and an external electrode301of the semiconductor chip3are electrically connected by way of the opening4.

In addition to the opening4, the described insulating substrate101also includes an opening (not shown) for forming an external connecting terminal6. The opening4over which the conductive pattern102and the external electrode301of the semiconductor chip3are connected is hereafter referred to as a bonding opening. The opening for forming the external connecting terminal6is hereafter referred to as an external terminal opening.

In the above-described semiconductor device, an insulating resin5seals the periphery of the semiconductor chip3, for example as shown inFIG. 9. The insulating resin5also seals the bonding opening4. The periphery of the semiconductor chip3and the bonding opening4may be sealed, for example, by transfer mold processing.

The above-described transfer mold processing is carried out, for example, as shown inFIG. 10, by sandwiching the interposer (insulating substrate101) bearing the semiconductor chip3between a first die (hereafter referred to as a top die)7having a recess7A of predetermined form and a second flat die (hereafter referred to as a bottom die)8, by causing the insulating resin5to flow into the resulting space formed therebetween, and by curing the resin5(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 pattern102and the external electrode301of the semiconductor chip3are 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 opening4of 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 die8has a flat surface8A which is brought into contact with the insulating substrate101. Thus, any bending or distortion of the insulating substrate101may cause a space to appear between the bottom die8and the insulating substrate101, which is sandwiched between the top die7and bottom die8, as shown inFIG. 11.

In particular, each opening of the insulating substrate101, which is generally formed by stamping with a die, may thus often have bending or distortion around the opening. The bonding opening4also may be subjected to a load caused by the electrical connection of the conductive pattern102and the external electrode301of the semiconductor chip3. Thus, bending or distortion often occurs around the bonding opening4.

With any bending or distortion generated around the bonding opening4, the transfer mold may allow the insulating resin5which flows into the bonding opening4to leak into the space formed between the bottom die8and the insulating substrate101, as shown inFIG. 11. The thin insulating substrate101cannot bear the injection pressure from the flow of the insulating resin5and may float. As a result, the insulating resin5may spread over the surface of the insulating substrate101, as shown inFIG. 12.

The insulating substrate101includes, for example, as shown inFIG. 12, external terminal openings101A outside the bonding opening4. Thus, if the insulating resin5which flows into the bonding opening4during the above-described transfer mold operation leaks out, the front end5A of the leaked insulating resin5may spread over the area of the above-described external terminal openings101A and flow into the above-described external terminal openings101A. The insulating resin5which flows into the external terminal openings101A may cause poor electrical conduction between the external connecting terminal6formed and the conductive pattern102.

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 opening4and the external terminal openings101A. The external terminal openings101A 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.

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 2are diagrams which show the configuration of the semiconductor device according to the present invention.FIG. 1is a plan view of the semiconductor device.FIG. 2is a cross-sectional view taken along line A-A′ inFIG. 1.

The semiconductor device according to the present invention includes an interposer (wiring board) having an insulating substrate101on which a conductive pattern102is provided, and a semiconductor chip3, which is bonded on the above-described interposer via an elastic material (elastomer)2, as shown inFIGS. 1 and 2.

The conductive pattern102of the above-described interposer and the external electrode301of the semiconductor chip3are electrically connected over an opening4provided in the interposer (insulating substrate101) and the elastic material2, as shown inFIG. 2. The opening4hereafter will be referred to as a bonding opening.

In the above-described semiconductor device, an insulating resin5seals the periphery of the described semiconductor chip3, as shown inFIG. 2. The insulating resin5also seals the bonding opening4. The conductive pattern102of the interposer is provided, for example, as shown inFIG. 2, on the surface where the semiconductor chip3is bonded. The conductive pattern102includes, for example, terminals for connection to a print wiring board, such as those referred to as a motherboard and a daughter board.

The insulating substrate101of the interposer includes openings in the regions of the terminals thereof. The openings include external connecting terminals6formed of a ball-like shaped bonding agent. The opening for providing the external connecting terminal6hereafter will be referred to as an external terminal opening.

The elastic material2is, for example, PTFE (poly-tetrafluoroethylene). The elastic material2has a thickness of, for example, about 150 μm.

The described semiconductor device can be manufactured by bonding the semiconductor chip3on the interposer via the elastic material2, followed by electrically connecting the conductive pattern102of the interposer and the external electrode301of the semiconductor chip3. The insulating resin5then seals, by transfer mold processing, the periphery of the semiconductor chip3and the bonding opening4. The external connecting terminal6is 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.

FIGS. 3 and 4are diagrams of the configuration of the mold die representing an example according to the present invention.FIG. 3is a cross-sectional view of the entire configuration of the mold die.FIG. 4is 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 die7and a bottom die8, which sandwich the interposer bearing the semiconductor chip3, as shown inFIG. 3. The top die7includes a recess space7A into which the insulating resin flows for sealing the periphery of the semiconductor chip3.

The bottom die8includes a protrusion8B in a predetermined form on the upper surface thereof so as to come into close contact with the insulating substrate101(hereafter referred to as a reference contact surface), as shown inFIGS. 3 and 4. The protrusion8B is provided in the form of a loop around a rectangular opening, such as the bonding opening, to be sealed with insulating resin5.

The protrusion8B has such a width that, for example, the above-described protrusion8B come into contact with the insulating substrate101between the opening4and the opening101A for forming the external connecting terminal, as shown inFIG. 4. The protrusion8B has a height of, for example, about 10 μm.

FIGS. 5 to 7are diagrams which illustrate the operational advantage of the mold die in the example 1.FIG. 5is a cross-sectional view of the condition during the molding process.FIG. 6is a cross-sectional view of the semiconductor device after the molding process is complete.FIG. 7shows a back view of the semiconductor device after completion of the molding process.FIG. 5shows the same cross section as inFIG. 4, although it omits the hatching (parallel oblique lines) representing the cross section.FIG. 7is a view from the back ofFIG. 1.

The mold die in the example 1 can be used for the transfer mold by, as shown inFIG. 4, disposing the interposer bearing the semiconductor chip3between the top die7and the bottom die8; followed by, for example, sandwiching the insulating substrate101between the top die7and the bottom die8, and fastening the substrate101with a predetermined pressure.

In the contact portion between the insulating substrate101and the protrusion8B of the bottom die8, the insulating substrate101will be distorted with the force F1from the protrusion8B of the bottom die8. The insulating substrate101will have a distorted portion that is pressed by the protrusion8B of the bottom die8, thereby the elastic material2also will be distorted. The elastic material2is in a contracted condition and tends to return to its original condition. Thus, the insulating substrate101also will receive from the elastic material2a force F2, which is opposite to the force F1from the protrusion8B of the bottom die8, as shown inFIG. 5.

As a result, the degree of contact between the insulating substrate101and the protrusion8B of the bottom die8will be higher than, for example, the degree of contact between the insulating substrate101and the reference contact surface8A of the bottom die8. Even when the insulating substrate101is distorted in the area around the bonding opening4, for example, as shown inFIG. 11, the protrusion8B of the bottom die8can 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 resin5which flows into the bonding opening4from leaking through between the insulating substrate101and the bottom die8. It is thus possible, for example, as shown inFIGS. 6 and 7, to prevent any spreading of the front end5A of the insulating resin5which flows into the bonding opening4, and to prevent the flow of the insulating resin5into an opening101A for forming the external connecting terminal.

When the protrusion8B on the surface of the bottom die8is provided outside the edge of the bonding opening4, as shown inFIG. 4, the insulating resin5which flows into the described bonding opening4can reach the back of the surface of the insulating substrate101, specifically, the surface on which the semiconductor chip3is bonded, so that the front end5A of the insulating resin5can reach outside the edge of the bonding opening4, as shown inFIGS. 6 and 7. As a result, the interface delamination will occur less frequently between the insulating substrate101and the insulating resin4around the bonding opening4.

As described above, in the mold die of example 1, a higher degree of contact is produced between the bottom die8and the periphery of the bonding opening4provided on the interposer, thereby preventing the insulating resin5which flows into the bonding opening4from leaking in between the insulating substrate101and the bottom die8. It is thus possible to prevent the insulating resin5from spreading over the surface of the insulating substrate101, as shown inFIG. 12, and from flowing into the opening101A for forming the external connecting terminal, thereby improving the manufacturing yield of the semiconductor device.

FIG. 8is a cross-sectional diagram illustrating an application of the example.

The mold die in the example 1 uses a bottom die8on which the area inside the protrusion8B is approximately the same height as the reference surface8A, as shown inFIG. 3. Additionally, the area inside the protrusion8B may include a recess8C, as shown inFIG. 8. The recess8C may have a depth of about 70 μm from the reference surface8A.

The bottom die8with the recess8C can also include, around the recess8C, the protrusion8B with a height of about 10 μm from the reference surface8A to give higher degree of contact between the bottom die8and the insulating substrate101around the periphery of the bonding opening4.

It is thus possible to prevent the insulating resin5which flows into the bonding opening4from leaking in between the interposer (insulating substrate101) and the bottom die8.

When the recess8C is provided, the insulating resin5which flows into the bonding opening4may run into the recess8C. The insulating resin5in the recess8C may be cured to provide the complete semiconductor device in which the cured insulating resin5may have a front end5A, as shown inFIG. 6, of greater thickness than in the example.

With the bottom die8as shown in the example, the edge of the bonding opening4may contact with the reference surface8A of the bottom die8, so that the front end5A of the insulating resin5may have various shapes.

On the other hand, with the bottom die8shown inFIG. 8, the base of the recess8C is lower than the reference surface8A to prevent the edge of the bonding opening4from contacting the bottom die8. The front end5A of the insulating resin5can thus have less varied shapes (thicknesses), and the interface delamination will occur much less frequently between the insulating substrate101and the insulating resin5.

The above-described example 1 provides an illustration of a semiconductor device in which the conductive pattern102is deformed to be electrically connected with the external electrode301of the semiconductor chip3. Additionally, the semiconductor device may be one in which, for example, the conductive pattern102is connected with the external electrode301of the semiconductor chip3via a bonding wire. In this case, to ensure the sealing of the bonding wire, the bottom die with the recess8C, as shown inFIG. 8, may preferably be used rather than the bottom die8described 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.