JPH06132424A - Switching semiconductor device - Google Patents

Abstract

PURPOSE:To sharply reduce a noise generated by a switching operation without spoiling the intrinsic switching characteristic of a semiconductor device. CONSTITUTION:This semiconductor device is constituted in such a way that the assembly of a switching semiconductor element 1 and a lead frame 2 is sealed with a molding resin 3, that its circumference is covered with a shielding metal case 4 and that a grounding terminal 4a is installed in the metal case. A noise generated by a switching operation is made to escape to the ground side through an electrostatic capacity by the metal case and through the metal case so as to prevent that the noise is propagated to the circumference.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching semiconductor device intended for a switching power device used in a switching power supply, an inverter and the like.

[0002]

2. Description of the Related Art In switching power supplies, PWM control inverters and the like, switching power devices using power transistors as switching elements are widely adopted in order to promote miniaturization and high efficiency. In addition, such switching power devices tend to have higher switching frequencies with higher functionality, but on the other hand, high-frequency noise is generated with the switching operation of the switching power devices and propagates as inductive noise to the surroundings. It is known that the noise disturbance affects peripheral circuits and peripheral devices, and the influence of the noise disturbance increases with the increase of switching frequency. Therefore, the noise reduction measure is one of the important issues imposed on switching semiconductor devices. It is one.

On the other hand, as a noise reduction measure for a switching semiconductor device, noise reduction measures such as inserting ferrite beads (a kind of choke coil) into the lead terminal of a switching power device or connecting a gate resistor for adjustment have been adopted. Are known.

[0004]

By the way, in the above-mentioned conventional noise reduction measures, not only the number of parts, assembly and adjustment man-hours increase, but also the switching frequency can be suppressed low in terms of the switching characteristics of the switching power device, There is a problem that it causes an increase in switching loss.

The present invention has been made in view of the above points, and an object of the present invention is to provide a switching semiconductor which is capable of significantly reducing noise generated by a switching operation without impairing the original switching characteristics. To provide a device.

[0006]

To achieve the above object, in a switching semiconductor device of the present invention, an assembly of a switching semiconductor element and a frame is sealed with resin, and a shield metal case is coated around the assembly. Shall be configured. Further, as an embodiment of the above configuration, there is a configuration in which a ground terminal is provided in the metal case.

[0007]

According to the above structure, an electrostatic capacitance having a sealing resin as a dielectric is formed between the switching semiconductor element and the metal case, and the metal case is grounded here so that the metal case is It is held at zero potential (ground potential). Therefore, the noise generated by the switching operation of the switching element escapes to the ground side through the capacitance and the metal case. That is, since the metal case functions as an electromagnetic shield, the noise propagating from the switching semiconductor device to the surroundings can be significantly reduced without using noise suppressing parts such as ferrite beads. The metal case also functions as an electromagnetic shield against external noise, and acts to protect the switching element from external noise.

The ground terminal provided on the metal case is used as a ground terminal when the switching semiconductor device is incorporated in a switching power supply or the like.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2, 1 is a switching semiconductor element such as a power transistor, 2 is a lead frame, 2
a is an external lead drawn from the lead frame 2, 3 is a molding resin that seals the periphery of the assembly of the switching semiconductor element 1 and the lead frame 2, and 4 is a metal case for shielding that surrounds the periphery of the molding resin 3, The metal case 4 has a ground terminal 4a in the same direction as the external lead 2a.
Has been pulled out. Then, when the switching semiconductor device is mounted on a printed wiring board such as a switching power supply and an inverter, the ground terminal 4a is simultaneously connected to the ground side.

[0010]

As described above, according to the present invention, the assembly of the switching semiconductor element and the frame is sealed with the resin, and the metal case for shielding is covered around the assembly, whereby While maintaining high switching characteristics, it is possible to prevent noise generated by switching operation from escaping to the ground side and propagating to the surrounding area, and the metal case also functions as a shield against external noise. Protect the element. As a result, parts such as ferrite beads and gate resistance in the conventional device can be omitted, and a switching semiconductor device that is inexpensive and highly reliable against noise can be provided.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a switching semiconductor device according to an embodiment of the present invention.

FIG. 2 is a sectional view of FIG.

[Explanation of symbols]

 1 Switching semiconductor element 2 Lead frame 2a External lead 3 Mold resin 4 Metal case 4a Ground terminal

Claims (2)

[Claims] 1. A switching semiconductor device characterized in that an assembly of a switching semiconductor element and a frame is sealed with a resin, and a metal case for shielding is covered around the assembly. 2. The switching semiconductor device according to claim 1, wherein the metal case is provided with a ground terminal.