JP3063299B2 - Substrate for mounting semiconductor devices - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a substrate for mounting a semiconductor device, and more particularly, to a substrate for mounting a semiconductor device provided with a radiation fin.

[0002]

2. Description of the Related Art Heretofore, as a ceramic substrate for mounting a semiconductor device such as a power module, in particular, a ceramic substrate provided with heat radiation fins has a structure as shown in FIG. In this embodiment, a semiconductor chip 22 is mounted on a ceramic substrate 21 made of alumina or the like via a thin plate 20 for forming a circuit. A heat sink 23 made of, for example, a metal such as copper is attached to a lower surface side of the ceramic substrate 21 via a thin plate 27 made of a metal such as copper, for example, a solder 26 (Pb-Sn alloy or the like). Further, a heat radiating fin 24 made of aluminum or copper is fixed to the lower surface of the heat sink 23 with a screw 25. Therefore, the heat generated by the high power IC chip 22 is absorbed by the heat sink 23 via the alumina substrate 21 and further radiated from the heat radiation fins 24.

[0003]

However, in such a conventional ceramic substrate, heat cycle,
Deterioration due to thermal fatigue of the solder and the brazing material (metal-ceramics interface) is caused by intermittent conduction and the like. That is, the adhesiveness between the ceramic substrate and the metal thin plate (and thus the heat sink) has been reduced. In addition, since the heat sink is formed of copper and the heat sink and the radiation fin are screwed, there is a problem that the weight of the entire substrate increases. Further, since these two members are screwed, there is a problem that the number of manufacturing steps increases.

[0004]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a ceramic substrate for mounting a semiconductor device, in which the number of manufacturing steps is reduced, the weight of the entire substrate is reduced, and the adhesion between the substrate and the radiation fins is improved. That is the purpose.

[0005]

According to a first aspect of the present invention, there is provided an aluminum nitride-based sintered body substrate on which a semiconductor device is mounted on a front surface, and an aluminum nitride-based sintered body on a back surface of the aluminum nitride-based sintered body. Semiconductor device having an aluminum plate joined via a silicon-based alloy brazing material, and aluminum or aluminum alloy radiating fins joined to the back surface of the aluminum plate via an aluminum-silicon-based alloy brazing material This is a mounting substrate.

[0006]

In the semiconductor device mounting board according to the first aspect, a heat dissipation fin made of aluminum or an aluminum alloy is joined to the aluminum nitride-based sintered body via an aluminum plate and a brazing material. Therefore, screws for joining are unnecessary. Therefore, the overall weight can be reduced. Further, by appropriately selecting the brazing material, the adhesion can be improved. Moreover, the heat dissipation is enhanced by the heat dissipation fins. Also,
Aluminum radiating fins made of aluminum alloy
When a silicon alloy is used, warpage of the substrate due to thermal stress can be reduced.

[0007]

An embodiment of the present invention will be described below with reference to FIG. As shown in this figure, a circuit-forming thin plate 10 made of, for example, aluminum is formed on an upper surface of an aluminum nitride substrate 16 which is an aluminum nitride-based sintered body.
4 bonded together. Specifically, the surface of the aluminum nitride substrate 16 is oxidized to form an alumina layer, and the surface of the alumina layer is further coated with silicon dioxide (SiO 2).
₂ ) The layer is formed. And, on the surface of this silicon dioxide layer, a brazing material 14 is adhered. Brazing material 14
Are, for example, Al-13% (wt%, the same applies hereinafter) Si alloy, Al-7.5% Si alloy, Al-7.5% Si-1
An Al-Si based alloy such as a 0% Ge alloy is used. Further, a semiconductor chip 12 is mounted on the upper surface of the thin plate 10 by, for example, soldering. In FIG. 1, 1
Reference numeral 5 denotes a solder.

The aluminum-silicon alloy brazing material 14 is provided on the back surface of the aluminum nitride substrate 16.
The aluminum plate 17 is joined via the. Aluminum radiating fins 19 are joined to the back surface of the aluminum plate 17 via an aluminum-silicon alloy brazing material 14. The radiation fins 19 may be made of, for example, Al-2.5% besides pure aluminum.
Mg-0.2% Cr alloy, Al-1% Mn alloy, Al-
A 20 to 40% Si alloy or the like can be used. Al-
As the Si alloy, one obtained by adding a Si powder to a super-quenched Al powder and performing hot extrusion or hot forging into a predetermined shape so that the Si content weight is, for example, 40% is used. When an Al-40% Si alloy is used as the radiation fin 19, its thermal expansion coefficient is smaller than that of pure aluminum, so that warpage due to thermal stress generated in the entire semiconductor device mounting substrate can be reduced. For example, while the thermal expansion coefficient of pure aluminum is 23.13 × 10 ⁻⁶ / K, the thermal expansion coefficient of Al-40% Si is 14.11 ×
10 ⁻⁶ K.

The alumina layer is, for example, 0.2 to 2
0 μm thickness, the silicon dioxide layer is 0.01-10 μm
m. As the silicon dioxide layer, zirconium oxide (Zr
O ₂ ) and titanium oxide (TiO ₂ ).
In addition, as the aluminum nitride-based sintered body, the aluminum nitride substrate was used as it is (5 to 5% by using Y ₂ O ₃ as a sintering aid).
10%) can also be used. Further, a material obtained by simply oxidizing the surface of aluminum nitride, a material obtained by coating the surface of aluminum nitride with SiC, or the like can be used.

In the substrate for mounting a semiconductor device according to this embodiment, it is possible to reduce the warpage due to thermal stress generated in the entire substrate for mounting a semiconductor device. In addition, by bonding a heat dissipation fin made of an aluminum alloy to an existing aluminum nitride substrate for forming a circuit with an aluminum-based brazing material 14 with an aluminum plate interposed therebetween, the semiconductor device mounting substrate according to the present invention can be easily manufactured. be able to.

[0011]

According to the present invention, the number of steps for manufacturing a semiconductor device mounting substrate can be reduced. The weight of the entire semiconductor device mounting substrate can be reduced. Further, the adhesiveness between the semiconductor device mounting substrate and the radiation fins can be improved. In addition, by using an aluminum nitride-based sintered body as a substrate, heat dissipation can be improved. Also, warpage due to thermal stress can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a ceramic substrate for mounting a semiconductor device according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a conventional ceramic substrate.

[Description of Signs] 12 semiconductor chips, 14 aluminum-silicon alloy brazing material, 16 aluminum nitride substrate, 17 aluminum plate, 19 aluminum radiating fins.

Continuation of the front page (56) References Hikaru Hei 2-68448 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 23/373 H01L 23/12

Claims (1)

(57) [Claims] 1. An aluminum nitride-based sintered body substrate on which a semiconductor device is mounted on the front surface, and aluminum bonded to the back surface of the aluminum nitride-based sintered body substrate via an aluminum-silicon alloy brazing material. A semiconductor device mounting substrate comprising: a plate; and a radiating fin made of aluminum or an aluminum alloy joined to a back surface of the aluminum plate via a brazing material made of an aluminum-silicon alloy.