JPH08125093A - Semiconductor device - Google Patents

Abstract

PURPOSE: To provide a semiconductor device in which the thermal resistance of a package is sufficiently small, and the heat resistance is excellent without reducing wire bondability. CONSTITUTION: A die pad 11 is formed at the part sealed in the package body 16 of a radiating fin 12, a semiconductor element 10 is fixed to the pad 11, and the ends of a plurality of lead terminals 13 disposed at the periphery of the pad 11 are connected to the elements 10 via metal fine wires 14. Thus, the elements 10 and the wires 14 are sealed in the body 16, and the other ends of the fin 12 and the terminal 13 are extended from the body 16 in a semiconductor device. A metal heat sink 15 of the size to be superposed with the end of the terminal 13 from the top view is connected directly to the lower surface of the pad 11 via a small gap between the ends of the terminals 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device suitable for encapsulating a semiconductor element having a relatively large amount of heat generation such as a motor driver, a voice amplification power IC, and a high speed operation logic element. Regarding

[0002]

2. Description of the Related Art As a conventional package structure of a semiconductor device of this type, there is known a semiconductor device in which a metal plate for heat dissipation is incorporated in a package body. This will be described below with reference to FIG. The semiconductor element 1 is die-bonded to a heat-dissipating metal plate 2, and is electrically connected to a plurality of lead terminals 3 by thin metal wires 4. Each lead terminal 3 is led out of the package body 5 and is bent in a substantially L-shape. Since the heat-dissipating metal plate 2 has such a large area that it overlaps with the tip portions of the lead terminals 3 in a plan view, it is not possible to form the heat-dissipating metal plate 2, the lead terminals 3, etc. by punching a single metal plate. Can not. Therefore, the heat dissipation metal plate 2 is formed separately from the lead frame including the lead terminals 3 and the like, and is connected to the lead terminals 3 via the insulating adhesive 6 before the semiconductor element 1 is assembled.

On the other hand, another type of package structure in which heat radiation fins are derived from the package body is also known. This will be described below with reference to FIG. The semiconductor element 1 is die-bonded to a projecting portion (die pad) 8 formed on one side of the heat radiation fin 7 formed of a metal plate and having a substantially rectangular shape and sealed in the package body 5. Semiconductor element 1
Is wire-bonded to each lead terminal 3 with a thin metal wire 4, and the semiconductor element 1 and the thin metal wire 4 are sealed in a package body 5. The other side of the heat radiation fin 7 is led out of the package body 5 and is used by being connected to another heat radiation fin having a large heat radiation effect at the time of mounting.

[0004]

However, the prior art having such a structure has the following problems. That is, according to the conventional semiconductor device shown in FIG. 10, the heat resistance of the insulating adhesive 6 is not so high.
There is a restriction that the lead frame cannot be exposed to a high temperature in the process of assembling the semiconductor device. When a lead frame is placed on the heater block in the wire bonding step, heat from the heater block is transmitted to the distal end of the lead terminal 3 via the metal plate 2 for heat radiation and the insulating adhesive 6. You. Since the insulating adhesive 6 has low thermal conductivity, the lead terminal 3 is hard to be heated. for that reason,
There is also a problem that the temperature of the lead terminal 3 at the time of wire bonding becomes low in combination with the above-mentioned thermal restrictions, which adversely affects the connection of the thin metal wires 4.

According to the conventional device shown in FIG. 11, in order to prevent a short circuit with the die pad 8 due to the hanging of the fine metal wire 4, the tip of the lead terminal 3 is provided around the die pad 8 (close to the semiconductor element 1). Since it is necessary to dispose the portions close to each other, the portion of the die pad 8 cannot be made too large, which causes a problem that it is difficult to sufficiently reduce the thermal resistance of the package.

The present invention has been made in view of such circumstances, and has a sufficiently small thermal resistance of a package.
Moreover, it is an object of the present invention to provide a semiconductor device which is excellent in heat resistance and does not deteriorate wire bondability.

[0007]

The present invention has the following constitution in order to achieve such an object. That is, according to the present invention, a die pad is formed in a portion sealed inside the package body of the heat dissipation fin, a semiconductor element is fixed to the die pad, and a tip portion of a plurality of lead terminals arranged around the die pad and a semiconductor In a semiconductor device in which the element and the thin metal wire are connected to each other by a metal wire, the semiconductor element and the metal wire are sealed in the package body, and the heat radiation fin and the other end of the lead terminal are led out from the package body, in plan view A heat dissipation plate having a size overlapping the tip portion of the lead terminal is directly joined to the lower surface of the die pad with a small gap interposed between the heat dissipation plate and the tip portion of the lead terminal.

[0008]

The operation of the present invention is as follows. According to the present invention, the heat generated from the semiconductor element when the semiconductor device is driven is transmitted from the die pad to the radiating fins and released to the outside, and the heat is efficiently transferred from the die pad to the radiating plate having a large heat capacity. It is well transmitted and further released from the heat sink through the package body and lead terminals. Since the heat radiating plate is directly joined to the lower surface of the die pad, there is no thermal restriction as in the case where the heat radiating plate is connected to the lead terminal via an adhesive. During wire bonding, the tip of the lead terminal is pressed against the radiator plate and brought into contact with it, so that the heat of the heater block normally provided on the lower surface of the radiator plate is efficiently transmitted to the lead terminal via the radiator plate. You.

[0009]

An embodiment of the present invention will be described below with reference to the drawings. 1 is a perspective view showing the configuration of an embodiment of a semiconductor device according to the present invention, and FIG. 2 is a sectional view taken along the line 02-02 of FIG. Note that, in FIG. 1, for convenience, only the outer shape of the package body is shown by a chain line.

The semiconductor element 10 is die-bonded onto the die pad 11 with a low melting point metal such as solder or silver paste. The die pad 11 is formed so as to project from one side portion of the radiating fin 12 having a substantially rectangular shape, and both are integrated. The tips of a plurality of lead terminals 13 are arranged around the die pad 11, and these lead terminals 13 and the semiconductor element 10 are electrically connected to each other by the thin metal wires 14. The die pad 11, the radiation fins 12, and the lead terminals 13 are formed separately from the same lead frame made of a copper alloy, an iron / nickel alloy, or the like.
The base end of the die pad 11 is bent downward, so that the die pad 11 is slightly sunk below the lead terminals 13.

A metal plate 15 for heat radiation is provided on the lower surface of the die pad 11.
Are directly joined without using an adhesive or the like. The heat-dissipating metal plate 15 has a rectangular shape that is large enough to overlap the tip end portion of the lead terminal 13 in a plan view. Heat dissipation metal plate 15
Is formed of a copper alloy or aluminum having good thermal conductivity. Since the heat-dissipating metal plate 15 is bonded to the lower surface of the die pad 11 that has been unset, there is a small gap between the heat-dissipating metal plate 15 and the lead terminal 13.
This gap is, for example, about 0.2 to 0.4 mm. As a method of directly bonding the heat-dissipating metal plate 15 to the die pad 11, for example, ultrasonic bonding, spot welding, crimping bonding, or the like can be used. However, ultrasonic bonding is preferable from the viewpoint of easy bonding and wide range of good bonding properties. The joining method using ultrasonic waves will be described later in detail.

The above-mentioned semiconductor element 10, thin metal wire 13,
The package body 16 is formed by integrally molding the heat-dissipating metal plate 15 with epoxy resin or the like. The radiation fins 12 and the lead terminals 13 are led out of the package body 16.

When the semiconductor device constructed as described above is mounted and driven on a printed wiring board or the like, the heat generated from the semiconductor element 10 is transmitted from the die pad 11 to the radiating fins 12 and released to the outside. At the same time, the heat is efficiently transmitted from the die pad 11 to the heat dissipating metal plate 15 having a large heat capacity, and further discharged from the heat dissipating metal plate 15 to the outside via the package body 16 and the lead terminals 13.

Next, a method of manufacturing the above-described semiconductor device will be described. As shown in FIG. 3, in order to assemble the above-described semiconductor device, a lead frame 20 in which a die pad 11, a radiation fin 12, a lead terminal 13, and the like are integrally formed is used. Before the semiconductor element 10 is incorporated into the lead frame 20, the heat dissipating metal plate 15 is bonded to the lower surface of the die pad 11 by ultrasonic waves. Hereinafter, description will be made with reference to FIGS.

As shown in FIG. 4, a heat dissipating metal plate 15 is placed on a receiving metal fitting 31, and a lead frame 20 is positioned and placed so that the heat dissipating metal plate 15 and the die pad 11 abut and overlap. I do. An ultrasonic horn 32 for supplying ultrasonic waves is provided above the receiving metal member 31, and a holding metal member 33 is attached to a distal end portion thereof. Bracket 3
1 and a large number of small projections 3
1a and 33a are formed respectively.

When the positioning of the metal plate 15 for heat dissipation and the lead frame 20 is completed, the ultrasonic horn 32 descends and presses the die pad 11 with the metal fitting 33 as shown in FIG. And apply ultrasonic waves. The lower surface of the heat-dissipating metal plate 15 digs into the small protrusion 31a of the receiving metal fitting 31, and the upper surface of the die pad 11 digs into the small projection 33a of the pressing metal fitting 33, so that no slip between the metal fittings 31 and 33 occurs. . As a result, the applied ultrasonic wave acts on the interface between the metal plate for heat radiation 15 and the die pad 11, so that the metal plate for heat radiation 15 and the die pad 11 are joined. FIG. 6 shows the joined state. On the lower surface of the heat-dissipating metal plate 15, a small recess 15a, which is a mark of the small protrusion 31a of the receiving metal fitting 31, is formed.

After the semiconductor element 10 is die-bonded on the die pad 11 to which the heat-dissipating metal plate 15 has been joined as described above, the semiconductor element 10 and the lead terminals 13 are connected by the thin metal wires 14. This wire bonding process is shown in FIG. The lead frame 20 to which the semiconductor element 10 is die-bonded is placed on the heater block 34. Then, the vicinity of the distal end of the lead terminal 13 is pressed by the ring-shaped pressing plate 35, so that the lead terminal 13 is elastically deformed and is brought into pressure contact with the lower metal plate 15 for heat radiation. As a result, the heat of the heater block 34 is efficiently transmitted to the lead terminals 13 via the heat-dissipating metal plate 15, so that the wire bonding property is improved. In addition,
Reference numeral 36 in the figure denotes a capillary for wire bonding. When the pressing plate 35 is lifted after the wire bonding, the lead terminals 13 are elastically restored, and a gap between the lead terminals 13 and the metal plate 15 for heat radiation is secured.

The wire-bonded lead frame 20 is sent to a molding step, and is molded by a well-known transfer molding method to form a package body 16. At this time, as shown in FIG.
Since the molding resin 16a enters into a large number of small recesses 15a formed on the lower surface of, the contact area between the heat dissipation metal plate 15 and the molding resin 16a is expanded. As a result, the bonding strength between the heat-dissipating metal plate 15 and the molding resin 16a is improved, and peeling of the heat-dissipating metal plate 15 from the molding resin 16a, cracking of the package body 16, and the like can be prevented.

The present invention is not limited to the above-described embodiment.
For example, modifications can be made as follows. In the embodiment shown in FIG. 1, the radiating fin 12 has the package body 16
Although a semiconductor device derived from only one of the side portions has been described as an example, the present invention is not limited to this, and can be applied to, for example, a semiconductor device as shown in FIG.
In this semiconductor device, both ends of the heat radiation fin 12 are led out from both sides of the package body 16. A narrow intermediate portion of the heat radiation fin 12 is set down to form the die pad 11. The metal plate 15 for heat radiation is directly joined to the lower surface of the die pad 11. With the semiconductor device having such a structure, the thermal resistance of the package can be sufficiently reduced as in the first embodiment.

In the above embodiment, the metal plate is used as the heat dissipation plate to be bonded to the lower surface of the die pad, but the heat dissipation plate is not necessarily limited to the metal plate and may be any plate material having good thermal conductivity.

[0021]

As is apparent from the above description, according to the present invention, in a semiconductor device in which the radiating fin is led out of the package body, the heat generated from the semiconductor element is radiated outside from the die pad through the radiating fin. At the same time, the heat is transmitted to the package body and the lead terminals via the heat radiating plate directly joined to the lower surface of the die pad and is emitted to the outside, so that a package having sufficiently small thermal resistance can be realized.

Further, as compared with the case where the heat dissipation plate is connected to the lead terminal via the adhesive, there are less thermal restrictions in the assembly process of the semiconductor device. Further, in the wire bonding step, the tip of the lead terminal is pressed against and brought into contact with the heat dissipation plate, so that heat from the heater block normally arranged on the lower surface of the heat dissipation plate can be efficiently transferred to the lead terminal through the heat dissipation plate. Therefore, the reliability of wire bonding can be improved.

Further, according to the present invention, an adhesive for attaching the heat radiating plate is unnecessary, and a lead frame with a general heat radiating fin can be used as a lead frame formed separately from the heat radiating plate. Therefore, the manufacturing cost can be reduced.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration of a first embodiment.

FIG. 2 is a sectional view taken along the line 02-02 of FIG.

FIG. 3 is a perspective view of a lead frame and a heat dissipation metal plate.

FIG. 4 is a view showing a joining process of a metal plate for heat radiation.

FIG. 5 is a view showing a joining process of a metal plate for heat radiation.

FIG. 6 is a cross-sectional view showing a state in which a heat-dissipating metal plate is joined.

FIG. 7 is a diagram showing a wire bonding process.

FIG. 8 is an enlarged sectional view of a main part after molding.

FIG. 9 is a perspective view of another embodiment.

FIG. 10 is a sectional view of a conventional example.

FIG. 11 is a partially cutaway perspective view of another conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Semiconductor element 11 ... Die pad 12 ... Heat radiation fin 13 ... Lead terminal 15 ... Metal plate for heat radiation 16 ... Package body

Claims (1)

[Claims] 1. A die pad is formed in a portion of the heat radiation fin sealed inside the package body, a semiconductor element is fixed to the die pad, and the tip end of a plurality of lead terminals arranged around the die pad and the semiconductor element. And a thin metal wire are respectively connected to each other, the semiconductor element and the thin metal wire are sealed in the package body, and the radiation fin and the other end of the lead terminal are led out from the package body. A semiconductor device, wherein a heat dissipation plate having a size overlapping the tip portion of the lead terminal is directly bonded to the lower surface of the die pad with a small gap interposed between the heat dissipation plate and the tip portion of the lead terminal.