JPH1056113A - Resin-encapsulated semiconductor device with heatsink and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device provided with a heatsink of a thin metallic plate which can ensure a sufficiently long interface with molding resin from the exposed part to the semiconductor die. SOLUTION: A heatsink 4 is formed by pressing a thin metallic plate. The heatsink 4 is provided with a lead supporting surface 19 around it, a hollow semiconductor die mounting surface 20 and an exposed protuberance on the opposite side. The heatsink 4 has a long interface with encapsulating resin 10 to reduce penetration of contaminants into the package. A rolled thin metallic plate is easy to work continuously and is relatively less expensive. A support bar 6 is connected to the heatsink 4 by caulking. An insulating sheet 7 to which no adhesive is applied is sandwiched between the heatsink 4 and leads 5. The reliability of connection is improved by eliminating the adhesive. The operations such as curing adhesive and dry-cleaning the leads can be eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin-sealed semiconductor device, and more particularly to a structure of a semiconductor device including a heat sink partially exposed to the outside of a sealing resin and a method of manufacturing the same.

[0002]

2. Description of the Related Art In a semiconductor device of a type in which a semiconductor die having an integrated circuit is enclosed in a plastic package, in order to efficiently release heat from the semiconductor die,
Incorporation of a metal heat sink into a package has been performed. Japanese Patent Laid-Open Publication No. 6-5746 describes a semiconductor device in which a part of the surface of a heat sink is exposed to the outside of a plastic package. The heat sink supports the semiconductor die on the first surface at a sufficient distance from the outer surface of the plastic package, and exposes the second surface opposite to the first surface to the outside of the plastic package. Therefore, a relatively large distance between the first surface and the second surface, that is, a relatively large thickness is required. The heat sink is formed by punching a relatively thick flat metal plate. Thick plates are heavy and relatively expensive. Since a thick material plate cannot be processed into a roll, it is in the form of a short plate, is not suitable for continuous processing, and is inconvenient to handle. Another problem is that precise punching of a thick plate is not easy. Forming the heat sink with a thin flat plate reduces the distance from the heat sink exposed from the plastic package to the semiconductor die, allowing contaminants outside the plastic package to reach the semiconductor die along the interface between the molded plastic and the heat sink. There is a problem that it becomes easier. When the heat sink is formed of a thin metal plate, it is difficult to form a seal ring around the heat sink.

[0003]

SUMMARY OF THE INVENTION The present invention enables a heat sink to be formed from a thin metal plate that is relatively easy to process, thereby reducing the cost and the weight of the product. It is an object of the present invention to secure a sufficiently long interface between the heat sink and the mold resin to reduce the intrusion of contaminants into the package.

[0004]

In the present invention, a heat sink is formed by pressing a relatively thin metal plate. The heat sink includes a mounting surface of the semiconductor die recessed with respect to a peripheral lead support surface, and a raised exposed surface opposite the mounting surface of the semiconductor die. Thus, the shape of this heat sink forms a long interface between the heat sink and the surrounding encapsulation resin, and contaminants must travel a long distance from the outside of the package to reach the internal semiconductor die. . This contributes to reducing the intrusion of contaminants into the package. Since the thin metal plate exists in the form of being wound in a coil shape, continuous processing is easy. Compared to the case of using a thick metal plate, it is inexpensive and contributes to a reduction in product cost. Also, compared to using a thick metal plate,
Contribute to product weight reduction.

[0005]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a partially cutaway perspective view showing a semiconductor device 1 according to the present invention. A semiconductor die 2 is mounted on a heat sink 4 with a suitable thermally conductive adhesive 3. A plurality of leads 5 and a support bar 6 are arranged around the heat sink 4 in a substantially radial direction.
Although the figure shows a semiconductor device having leads 5 on all four sides, the present invention is also applicable to semiconductor devices having leads 5 on fewer than four sides. The lead 5 and the support bar 6 are supported on the heat sink 4 with an electrically insulating sheet 7 interposed. In the illustrated example, the support bars 6 are arranged at four corners, and are caulked on the heat sink 4 with an electrically insulating sheet 7 interposed between the support bar 6 and the heat sink 4 at the inner portion. Bond wires 8 connect the inner ends of each of the leads 5 to selected contact pads 9 on the semiconductor die 2. A sealing material 10 surrounds the heat sink 4, the semiconductor die 2, the bond wires 8, the inner parts of the leads 5, and the support bars 6. Although not visible in the figure, a part of the side surface of the heat sink 4 on the side where the semiconductor die 2 is not attached is exposed to the outside of the sealing material 10.

The semiconductor device 1 shown in FIG. 1 is manufactured by a method generally described below. FIG. 2 is a perspective view showing a lead frame 11 having a plurality of leads 5 and support bars 6, an electrically insulating sheet 7, and a heat sink 4. The lead 5 and the support bar 6 are held at predetermined positions by an outer ring 12. A hole 13 is formed in an inner portion of the support bar 6. The lead frame 11 is manufactured from various kinds of metals that are well known in the art for forming leads. The lead frame 11 is flat,
It is manufactured by stamping or etching from a desired metal plate. Although the shapes of the outer ring 12 and the opening 14 shown are substantially square, any shape is arbitrary, and the shape is determined by the shape of the semiconductor die placed inside.

The electrically insulating sheet 7 is manufactured by punching out an electrically insulating synthetic resin sheet such as polyimide. The electrically insulating sheet 7 has a substantially square annular shape, has a substantially square central opening 15 slightly smaller than the opening 14 of the lead frame 11, and has holes 16 at four corners. Since the electrically insulating sheet 7 is not covered with the adhesive, it can be obtained at relatively low cost.

The heat sink 4 is manufactured by press-forming a relatively thin metal plate such as aluminum having good heat conductivity. The heat sink 4 is substantially square and has a first surface 1.
7 and a second surface 18 on the opposite side. A lead support surface 19 is provided around the first surface 17, and a die mounting surface 20 which is recessed in parallel with the lead support surface 19 is surrounded by the lead support surface 19. The die mounting surface 20 is substantially square, which is slightly smaller than the opening 15 of the electrically insulating sheet 7. A peripheral surface 21 opposite to the lead supporting surface 19 and a peripheral surface 2
1 has an exposed surface 22 opposite the die mounting surface 20 raised parallel to a peripheral surface 21. The exposed surface 22 is exposed to the outside of the sealing material 10 and contributes to dissipating heat generated in the semiconductor die 2 to the outside. This shape of the heat sink 4 makes it possible to manufacture a heat sink having an exposed surface from a thin plate material. Since the thin plate material is stored in a roll of a long material, it is suitable for continuous processing and is convenient to handle. Processing is also easy. This shape of the heat sink 4 also provides a long interface with the sealing substance 10. The long interface helps prevent contaminants from entering the interior along the interface. Projections 23 are formed on the lead support surface 19 at four corners of the heat sink 4.
The protrusions 23 are arranged so as to match the holes 13 of the support bar 6 of the lead frame 11 and the holes 16 at the four corners of the electrically insulating sheet 7.

FIG. 3 to FIG.
3 shows a state in which the lead frame assembly 24 is formed by integrating the three members of the electrically insulating sheet 7 and the heat sink 4. The electrically insulating sheet 7 is provided on the lead supporting surface 1 of the heat sink 4.
9 and the projection 23 is inserted into the hole 16. The inner part of the lead 5 and the inner part of the support bar 6 of the lead frame 11 are placed on the electrically insulating sheet 7, and the projection 23 of the heat sink 4 is inserted into the hole 13 of the support bar 6. Then, the top of the projection 23 is crushed by a punch, and the lead frame 11, the electrically insulating sheet 7, and the heat sink 4 are integrated into a lead frame assembly 24.
Is formed. The heat sink 4 is supported on the lead frame 11 by four support bars 6. Since the heat sink 4 is made of a thin metal plate, it is relatively lightweight, so there is no risk of deforming the support bar 6.

Next, reference is made to FIG. The semiconductor die 2 is mounted on the die mounting surface 20 of the heat sink 4 in the lead frame assembly 24. Semiconductor die 2 has a first surface 25 and a second surface 26 opposite the first surface 25. A plurality of contact pads 9 are provided on the first surface 25. A second surface 26 is adhered to the die mounting surface 20 of the heat sink 4 by the thermally conductive adhesive 3. One end of the conductive bond wire 8 is connected to any one of the contact pads 9 on the semiconductor die 2, and the other end is connected to any one of the leads 5 on the lead frame 11. Lead 5
Is directly supported on the electrically insulating sheet 7 having relatively poor elasticity without interposing an adhesive or the like, so that it is difficult to move when the bond wire 8 is connected, so that a reliable connection can be obtained. .

Next, reference is made to FIG. The lead frame assembly 24 on which the semiconductor die 2 is mounted is connected to the two halves 27 and 2.
Mold cavity 3 of mold assembly 29 having
0, the two halves 27 and 28 are closed and the mold cavity 30 is filled with the sealing substance 10. When the two halves 27 and 28 are closed, the exposed surface 2 of the heat sink 4 is closed.
2 is pressed against the inner surface of the mold cavity 30. By filling the sealing material 10, the heat sink 4, the semiconductor die 2, the inner portion of the conductive lead 5, the electrically insulating sheet 7 and the bond wires 8 are sealed, and the exposed surface 22 of the heat sink 4 is Then, the outer portion of the conductive lead 5 and the outer portion of the support bar 6 are exposed to the outside. Sealing material 10
After cooling and solidifying, release the mold assembly 29,
The semiconductor device 1 is taken out. Then, lead frame 11
The outer ring 12 is cut off, and each lead 5 and the support bar 6 are cut.
Independently form the individual leads 5 of the semiconductor device 1.
The support bar 6 does not extend outside the sealing substance 10. If necessary, the outer portion of the lead 5 extending outside the sealing material 10 can be bent.

FIG. 8 shows another method of forming the lead frame assembly 24 by integrating the three components of the lead frame 11, the electrically insulating sheet 7, and the heat sink 4. In this embodiment, holes 31 are formed instead of forming protrusions on the heat sink 4. And three holes 13,1
The lead frame 11, the electrically insulating sheet 7, and the heat sink 4 are integrated by inserting the stud 32 into the 6, 31 and crushing the tip of the stud 32 with a punch.

FIGS. 9 and 10 show an example in which an electrically insulating tape 34 coated with a polyimide organic adhesive 33 is used instead of the electrically insulating sheet 7 not coated with an adhesive. The tape 34, the lead frame 11, and the heat sink 4 are integrated, and the lead frame assembly 2
4 will be described. In this embodiment, since the heat sink 4 and the lead frame 11 are bonded to each side surface of the electrically insulating tape 34, the support bar 6 for connecting the heat sink 4 and the lead frame 11 is formed on the lead frame 11. It has not been. The leads 5 of the lead frame 11 are adhered to the lead support surface 19 of the heat sink 4 via an electrically insulating tape 34. Using this lead frame assembly 24, a semiconductor device is manufactured through the same steps as in the above embodiment.

[0014]

As described above, in the present invention, the heat sink formed by press-molding a relatively thin metal plate is provided with a mounting surface of the semiconductor die recessed with respect to the peripheral lead supporting surface, A raised exposed surface opposite the mounting surface of the semiconductor die. This shape of the heat sink provides a long interface between the heat sink and the surrounding encapsulation resin and contributes to reducing the intrusion of contaminants into the package interior. Since the thin metal plate as the material of the heat sink in the present invention is in the form of a long object wound in a coil shape, continuous processing is easy. Compared to the case of using a thick metal plate, it is inexpensive and contributes to a reduction in product cost. Also, it contributes to weight reduction of the product as compared with the case where a thick metal plate is used.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view showing a semiconductor device 1 according to the present invention.

FIG. 2 is a perspective view showing a lead frame, an electrically insulating sheet, and a heat sink.

FIG. 3 is a partially cutaway plan view showing the lead frame assembly.

FIG. 4 is a sectional view taken along line IV-IV in FIG.

FIG. 5 is a sectional view taken along line VV in FIG. 3;

FIG. 6 shows a semiconductor die mounted on a lead frame assembly;
It is sectional drawing of the state which connected the bond wire.

FIG. 7 is a cross-sectional view showing a molding step of a sealing material.

FIG. 8 is a partially enlarged cross-sectional view showing another method of forming the lead frame assembly.

FIG. 9 is a perspective view showing still another method of forming the lead frame assembly.

FIG. 10 is an enlarged sectional view of a part of the lead frame assembly.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor device 2 Semiconductor die 3 Heat conductive adhesive 4 Heat sink 5 Lead 6 Support bar 7 Electrical insulating sheet 8 Bond wire 9 Contact pad 10 Sealing substance 11 Lead frame 12 External ring 13 Hole 14 Opening 15 Opening 16 Hole 17 First surface 18 Second surface 19 Lead support surface 20 Die mounting surface 21 Peripheral surface 22 Exposed surface 23 Projection 24 Lead frame assembly 25 First surface 26 Second surface 27 Half 28 Half 29 Mold assembly 30 Mold cavity

Claims (8)

[Claims] A first surface parallel to the first surface and a second surface opposite to the first surface, the periphery of the first surface having a lead support surface and being surrounded by the lead support surface; Inside has a die mounting surface recessed parallel to the lead support surface,
The peripheral portion of the second surface has a peripheral surface opposite to the lead supporting surface, and an inner surface surrounded by the peripheral surface and having an exposed surface opposite to the die mounting surface raised parallel to the peripheral surface. A heat sink; a semiconductor die having a first surface having a plurality of contact pads and a second surface opposite thereto, the second surface being mounted on a die mounting surface of the heat sink; An adhesive material for attaching a surface to a die attach surface on a first surface of the heat sink; an inner portion having an inner end and an outer end, respectively, and an inner portion including the inner end is a first portion of the heat sink. A plurality of conductive leads supported on a lead mounting surface on a surface; an electrical insulating material interposed between an inner portion of the conductive leads and a lead supporting surface of the heat sink; What on the pad A plurality of conductive bond wires connecting one to the inner portion of any one of the leads; the heat sink; a semiconductor die; an adhesive material; an inner portion of the conductive lead; A sealing material for sealing the bond wire and exposing an exposed surface on the second surface of the heat sink to the outside. 2. The resin-sealed semiconductor device according to claim 1, wherein said electrically insulating material is an adhesive-coated tape. 3. The resin-encapsulated semiconductor device according to claim 1, wherein the electric insulating material is an electric insulating sheet not covered with an adhesive. 4. A lead mounting surface having a first surface and a second, opposite surface parallel to the first surface, the periphery of the first surface having a lead mounting surface on which an inner portion of the lead is supported. A die mounting surface for mounting the second surface of the semiconductor die, which is recessed in parallel with the lead supporting surface, is provided on the inner side surrounded by the lead supporting surface. A semiconductor device having a peripheral surface opposite to the lead supporting surface, and having an exposed surface opposite to the die mounting surface protruding inside the peripheral surface in parallel with the peripheral surface and exposed from the sealing material. For heat sink. 5. A central opening for placing a semiconductor die,
Preparing a lead frame having a plurality of leads arranged around the central opening, a plurality of support bars, and an external ring connecting the leads and the support bars to each other; and mounting the lead frame on the opening. A first surface and a second surface opposite to the first surface, the second surface being parallel to the first surface.
A lead support surface on which an inner portion of the lead and the support bar are supported.
Further, a die mounting surface for mounting the semiconductor die, which is recessed in parallel with the lead support surface, is provided inside the lead support surface. An opposite peripheral surface, and an inner surface surrounded by the peripheral surface, having an exposed surface protruding parallel to the peripheral surface and located on the opposite side of the die mounting surface and exposed from a sealing material; Forming an electrically insulating sheet having a central opening for placing a semiconductor die and electrically insulating between the heat sink and the leads of the lead frame; Bonding the heat sink to the inner portion of the support bar with an electrically insulating sheet between the lead and support bar and the heat sink to form an assembly; Adhering onto a die mounting surface of a heat sink; connecting one end of each of the plurality of conductive bond wires to any one of contact pads on the semiconductor die; and the other end of the plurality of conductive bond wires. Respectively connecting to any one of the leads on the lead frame; sealing the heat sink, the semiconductor die, the inner portion of the conductive lead, the electrically insulating sheet, and the bond wire; Sealing the exposed surface on the second surface of the heat sink, the outer portion of the conductive lead, and the outer portion of the support bar with a sealing material so as to expose the outside, and cutting the outer ring. Separating the outer portions of the leads from each other, and cutting off the outer portion of the support bar extending from the sealing material. Production method. 6. The support bar of the lead frame,
A hole in an inner portion, the electrically insulating sheet has a corresponding hole at a position overlapping the hole in the support bar, and the heat sink has a hole in the support bar and the electrically insulating sheet on a lead support surface. And a protrusion inserted into the support frame of the heat sink, wherein an electrically insulating sheet and an inner portion of a support bar of the lead frame are overlapped on a lead support surface of the heat sink to form a lead frame assembly. 6. The method of claim 5, further comprising: inserting the support bar and the electrically insulating sheet into matching holes; and squeezing the protrusion to couple the heat sink to the support bar of the lead frame. Of manufacturing a resin-sealed semiconductor device. 7. The support bar of the lead frame,
A hole in an inner portion, the electrically insulating sheet has a corresponding hole at a position overlapping the hole in the support bar, and the heat sink has a hole in the support bar and the electrically insulating sheet on a lead support surface. The heat insulating sheet and the inner portion of the support bar of the lead frame are overlapped on the lead supporting surface of the heat sink to form a lead frame assembly. Stacking holes in the conductive sheet and the support bar; and inserting a stud through the stacked heat sink, the electrically insulating sheet and the hole in the support bar; and The method for manufacturing a resin-encapsulated semiconductor device according to claim 5, further comprising a step of coupling. 8. A central opening for placing a semiconductor die,
A step of preparing a lead frame having a plurality of leads arranged around the central opening and an external ring connecting the leads to each other; and a heat sink for mounting on the opening, A surface and a second opposite one thereof parallel to the first surface
A lead support surface on the periphery of the first surface on which the inner portion of the lead and the support bar are supported, and a lead support surface on the inside surrounded by the lead support surface. A die mounting surface for mounting the semiconductor die, which is recessed in parallel with respect to the second surface, a peripheral surface of the second surface opposite to the lead supporting surface, and an inner surface surrounded by the peripheral surface. Forming an elevated surface parallel to the peripheral surface and having an exposed surface exposed from the encapsulation material opposite the die mounting surface; anda central opening for placing the semiconductor die. Forming an electrically insulating sheet coated with an adhesive for electrically insulating between the heat sink and the lead of the lead frame; and forming the lead to form a lead frame assembly. Coated with adhesive between Bonding the heat sink to the inner part of the lead of the lead frame with the electrically insulating sheet interposed therebetween; bonding a semiconductor die onto a die mounting surface of the heat sink; Connecting one end to each one of the contact pads on the semiconductor die; connecting the other end of each of the plurality of conductive bond wires to any one of the leads on the lead frame; Sealing the heat sink, the semiconductor die, the inner portion of the conductive lead, the electrically insulating sheet, and the bond wire, and exposing the exposed surface on the second surface of the heat sink; And a step of cutting the outer ring to separate the outer portions of the leads from each other. Method of manufacturing Aburafutome type semiconductor device.