Active solid-state devices (e.g. – transistors – solid-state diode – Lead frame
Reexamination Certificate
1998-04-13
2001-06-05
Williams, Alexander O. (Department: 2826)
Active solid-state devices (e.g., transistors, solid-state diode
Lead frame
C257S684000, C257S796000, C257S675000, C257S696000, C257S692000, C257S693000, C257S698000, C257S712000, C257S676000, C257S706000, C361S310000, C361S704000, C361S712000, C174S050510, C438S123000
Reexamination Certificate
active
06242797
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a semiconductor device, and more particularly to a semiconductor device having a pellet mounted on a radiating plate thereof and a method of manufacturing the semiconductor device.
2. Description of the Related Art
Conventionally, semiconductor devices such as an LSI (Large Scale Integrated Circuit) and a transistor chip are utilized in various electronic apparatus. In such apparatus as just mentioned, generally a pellet including a semiconductor circuit is encapsulated in a resin member, and a large number of lead terminals each formed from an elongated conductive plate are provided on the opposite sides of the resin member.
Since those lead terminals are connected to connection pads of the pellet in the inside of the resin member, if the semiconductor device is mounted on a circuit board and the lead terminals are connected to signal lines, then various signals can be inputted to and outputted from the pellet.
However, such a semiconductor device as described above inevitably generates heat when the pellet inputs/outputs a signal. For example, in a semiconductor device used for transmission of radiowaves of a portable telephone set, since it consumes a large amount of power, the pellet generates a large amount of heat. Therefore, it is required to radiate the heat efficiently.
In a semiconductor device disclosed, for example, in Japanese Patent Laid-open No. 209054/94, the radiating plate is exposed at a central portion thereof to the bottom of the resin member so that heat generated by the pellet may be radiated from the central portion of the radiating plate.
However, since the central portion of the radiating plate cannot be connected to a conductor pattern of the circuit board by solder, the effect of heat radiation at this position cannot be anticipated.
On the other hand, in another semiconductor device which is disclosed in Japanese Patent Laid-open No. 224326/94, the radiating plate is exposed at a central portion thereof to the bottom of the resin member and is exposed at four corner portions thereof to the top of the resin member so that heat generated by the pellet may be radiated from the central portion and the four corner portions of the radiating plate.
However, the four corner portions of the radiating plate exposed to the top of the resin member cannot be connected to conductor patterns of the circuit board by solder and cannot contribute very much to heat radiation.
Meanwhile, in a further semiconductor device which is disclosed in Japanese Patent Laid-open No. 63142/90, the radiating plate is exposed not only at a central portion thereof but also at an end portion thereof to the bottom of the resin member so that heat generated by the pellet may be radiated from the central portion and the end portion of the radiating plate.
However, while the end portion of the radiating plate exposed to the bottom of the resin member contributes to heat radiation since it can be connected to a conductor pattern of the circuit board by solder, this is not sufficient to achieve sufficient radiation of heat generated by the pellet.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a semiconductor device which can efficiently radiate heat generated by a pellet.
In a conventional semiconductor device to which the present invention is applied, a pellet including a semiconductor circuit having a plurality of connection pads provided thereon is mounted on a radiating plate, and a plurality of lead terminals each formed from an elongated conductive plate are disposed on the outer sides of the pellet. The lead terminals and connection pads of the pellet are individually connected to each other by bonding wires, and at least part of the radiating plate, the pellet, the bonding wires and inner portions of the lead terminals are encapsulated in the inside of a resin member.
In the present invention of the semiconductor device having such a construction as described above, the radiating plate is formed in such a shape that a central portion thereof is positioned higher than both end portions thereof, and an upper face of the central portion of the radiating plate is exposed to the top of the resin member while the pellet is mounted on a lower face of the central portion of the radiating plate.
Accordingly, since the central portion of the radiating plate which is positioned higher than both end portions is exposed to the top of the resin member and the pellet is mounted on the lower face of the central portion of the radiating plate whose upper face is exposed from the resin member in this manner, heat generated by the pellet can be radiated efficiently from the central portion of the radiating plate.
It is to be noted that, in the present invention, the direction in which the semiconductor device is mounted on a circuit board is referred to as upper direction and a direction perpendicular to the direction is referred to as sideward direction. However, such directions are used conveniently in order to simplify description and do not restrict any direction when the device is manufactured or actually used.
Further, the radiating plate in the present invention signifies a member on which a pellet is mounted and which contributes to radiation of heat from the pellet, and allows, for example, an island made of a metal.
In the semiconductor device of the present invention, both end portions of the radiating plate may be exposed to lower faces of both end portions of the resin member.
Accordingly, both end portions of the radiating plate can be connected directly to conductor patterns of a circuit board by solder. In this instance, since heat generated by the pellet can be radiated not only from the central portion of the radiating plate but also from both end portions of the radiating plate, the heat radiation property can be further improved efficiently. Further, soldering to the circuit board can be performed with certainty, and a dispersion in thermal resistance which arises from non-uniform soldering can be decreased.
In the semiconductor device of the present invention, the bonding wires may connect the connection pads on a lower face of the pellet and lower faces of the inner portions of the lead terminals to each other.
Accordingly, although the pellet is disposed in a vertically inverted condition to that in a conventional arrangement, the connection pads are connected from the same direction as the lead terminals. In particular, the connection pads positioned on the lower face of the pellet can be connected readily from the same direction to the lead terminals by the bonding wires.
In the semiconductor device of the present invention, the lead terminals may be formed in such a shape that outer portions thereof are positioned flush with the lower face of the resin member and the inner portions thereof are positioned higher than the outer portions.
Accordingly, since the lower faces of the inner portions of the lead terminals to which the bonding wires are connected are positioned higher than the bottom of the resin member, the bonding wires connecting to the lower faces of the inner portions of the lead terminals are not exposed from the bottom of the resin member at all.
In the semiconductor device of the present invention, a heat sink may be provided on the upper face of the central portion of the radiating plate which is exposed from the resin member.
Accordingly, although the central portion of the radiating plate exposed to the top of the resin member cannot be connected to a conductor pattern of a circuit board, it contributes to radiation of heat efficiently through the heat sink. Consequently, the heat radiating property of the central portion of the radiating plate can be improved by the heat sink.
In a conventional method of manufacturing a semiconductor device to which the present invention is applied, a single lead frame wherein a plurality of lead terminals and a single radiating plate are connected integrally to each other by tie bars and/or a runner is formed. A
Ichikawa Seiji
Kitakoga Toru
Miya Tatsuya
Nishibe Toshiaki
Nishimura Yoshikazu
Hayes, Soloway, Hennessey, Gossman & Hage, P.C.
NEC Corporation
Williams Alexander O.
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