JPH03274799A - Metallic insulating substrate of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent a leak current from flowing on a metallic plate side by constructing a metallic insulting substrate by embedding a shielding metallic foil in an organic insulting layer. CONSTITUTION:Divided insulating layers (epoxy resin) 2a, a shielding metallic foil 5 with the same external form as that of a metallic plate 1, divided insulating layers (epoxy resin) 2b and a wiring metallic foil 4 are sequentially laminated to integrally form a metallic insulating substrate, A through-hole 2c is formed in the divided insulating layers 2b in advance and connection is simply performed between the shielding metallic foil 5 and a circuit side conductor.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the structure of a substrate for a semiconductor device, particularly a metal insulating substrate.

[Conventional technology]

Nowadays, metal insulating substrates, which are inexpensive to manufacture, are often used as substrates for semiconductor devices instead of conventional ceramic substrates.

The structure of this metal insulating substrate is, as shown in FIG. 2, on a metal base plate l made of aluminum, for example, and an organic insulating layer 2 made of epoxy resin or the like. A copper foil 4 patterned into a required shape as a wiring conductor for circuit components such as a semiconductor chip 3 is laminated and integrated.

[Object to be Solved by the Invention II] By the way, when the metal insulating substrate described above is employed as a substrate for a high voltage, high frequency power semiconductor device, there are the following problems.

That is, when a voltage is applied to the semiconductor device, a leakage current flows to the metal base plate through the insulating layer.

Moreover, if this leakage current is large, there is a risk of heat generation and electric shock, and in general electric appliances, it is specified that the leakage current should be suppressed to several mA or less to prevent fires.

Here, the leakage current I flowing through the substrate when voltage is applied is
is expressed by the following formula.

■−2π fcV−・−・・・・・−・・・−・・−・
・−・−(1) C deprivation ε, εPA/l ・・・・−・・−・
・－・－･･････････････････････････････････････････････････････････････････However, [: operating frequency, ■: applied voltage, C: capacitance of insulating layer, ε,: dielectric constant in vacuum, ε,: relative dielectric constant, A: area of substrate , t: Thickness of the insulating layer As is clear from the above equations (1) and (2), the leakage current ■ is proportional to the capacitance of the substrate insulating layer, and the capacitance has a relative dielectric constant ε1. If the substrate area A is constant, it is inversely proportional to the thickness t of the insulating layer.

On the other hand, especially in power semiconductor devices, circuit elements generate a large amount of heat, and in order to maintain the temperature rise within a specified temperature range, it is important from a mounting standpoint to perform appropriate thermal design. Such points,
If the thickness of the insulating layer (dielectric material) of the substrate is reduced, the thermal resistance to the circuit elements can be lowered, but on the other hand, the capacitance increases and leakage current increases as described above.

In this regard, when comparing a metal insulated substrate and a ceramic insulated substrate, the dielectric constant t1 of both is almost similar, but the thermal conductivity (W/c+e''c) is 1 higher than that of the ceramic substrate. Therefore, in order to suppress the thermal resistance of the board to the same level as that of a ceramic board, the thickness of the insulating layer on the metal insulating board must be significantly reduced. The capacitance C of the insulating layer (epoxy resin) of the substrate is about 6.6 times that of the ceramic substrate (made of alumina).

For this reason, when a metal insulating substrate with the conventional structure shown in Figure 2 is used as a substrate for a high-voltage, high-frequency power semiconductor device, increasing the thickness of the insulating layer in order to suppress leakage current reduces thermal resistance. On the other hand, reducing the thickness of the insulating layer to suppress thermal resistance increases leakage current. This is a major reason why it is difficult to

The present invention has been made in view of the above points, and aims to provide a metal insulating substrate for a semiconductor device that can prevent leakage current from flowing to the metal base plate side by improving the structure of the substrate. purpose.

[Means to solve the problem]

In order to solve the above problems, the metal insulating substrate of the present invention
A shielding metal foil is embedded in an organic insulating layer.

(Function) In the above configuration, the shielding metal foil is connected to, for example, a zero-potential circuit conductor inside the semiconductor device. Therefore, the leakage current flowing in the substrate when the semiconductor device is energized is collected by the shielding metal foil. This means that no leakage current flows through the metal base plate.

〔Example〕

FIG. 1 shows the structure of a metal insulating substrate according to an embodiment of the present invention, and the same members corresponding to FIG. 2 are given the same reference numerals.

That is, according to the present invention, the organic insulating layer (
The epoxy resin (epoxy resin) 2 is divided into two layers 2a and 2b, and a shielding metal foil indicated by reference numeral 5 is interposed between the divided layers 2a and 2b. This shielding metal M5 is, for example, a copper foil made by rolling. In addition, in order to manufacture such a metal insulating substrate, for example, on a metal base plate 1 such as an apple, a divided insulating layer 2a + a metal foil 51 for shielding having the same external shape as the metal base plate 1, a divided insulating layer 2b, a metal foil for wiring, etc. 4 are stacked one on top of the other in order to form one piece. In addition, by forming roughened through holes 2C in the divided insulating layer 2b as shown in the figure, shielding gold can be removed. Connection between the KFfi5 and the conductor on the circuit side can be easily made.

〔Effect of the invention〕

Since the metal insulating substrate of the semiconductor device according to the present invention is configured as described above, it achieves the following effects.

(1) Leakage current that flows into the substrate when the semiconductor device is energized can be disposed of inside the semiconductor device through the conductive foil for shielding, and there is no risk of heat generation or electric shock on the metal base plate side.

(2) As a result, when applying a metal insulating substrate directly to high-voltage, high-frequency power semiconductor devices, a metal that satisfies both the requirements of low thermal resistance in consideration of heat dissipation and prevention of leakage current to the metal base plate. An insulating substrate can be obtained.

[Brief explanation of drawings]

Fig. 1 is a partial sectional view showing the structure of a metal insulating substrate according to an embodiment of the present invention, and Fig. 2 is a partial sectional view of a conventional metal insulating substrate. Layer, 2a, 2b: Divided insulating layer, 3: Semiconductor chip, 4: Wiring metal technique 1 Z area

Claims (1)

[Claims] 1) A metal insulating substrate for a semiconductor device having a structure in which an organic insulating layer and a conductive foil for wiring are stacked on a metal base plate, characterized in that a shielding metal foil is embedded within the insulating layer. Metal insulating substrate for semiconductor devices.