JPS59175733A - Insulated type semiconductor device - Google Patents

Abstract

PURPOSE:To eliminate the possibility of denaturation or damage based on thermal strain by bonding a metallic plate for loading a semiconductor base body onto a metallic layer consisting of a plurality of inorganic insulating members with a metallic solder. CONSTITUTION:An alumina plate 2 is bonded with one main surface of a metallic support plate 1, and a metallized layer 201 and a copper layer 203 are formed on the bonding surface. A metallized layer 202 and a copper layer 204 are shaped on one surface of the plate 2. A metallic plate 3 is bonded on the layer 204 with a solder layer 102. The layers 203, 204 are unified, and a thermal expansion coefficient as the whole of the composite alumina plate 2 is brought close to that of the metallic plate 3. According to such constitution, heat cycle resistance can be improved without substantially lowering radiant property.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a semiconductor device, and particularly to an insulated semiconductor device having a structure electrically insulated from a semiconductor substrate support member.

[Prior Art J] In conventional semiconductor devices of this type, the supporting member that supports the device often doubles as one electrode of the semiconductor device. In recent years, structures have emerged that can electrically insulate all electrodes of a semiconductor device from a metal support member, thereby increasing the degree of freedom in circuit application of the semiconductor device. For example, an insulated triac is made by placing a bidirectional three-terminal TRIAC substrate on a ceramic plate and enclosing this ceramic plate in a metal package. The structure is such that it is drawn out to the outside. Because of this configuration, even in applications where the pair of main electrodes are electrically floating from the ground potential on the circuit, the package can be fixed to the ground potential regardless of the electrode potential. Therefore, mounting of the semiconductor device becomes easy.

In addition, since a hybrid integrated circuit device or a semiconductor module device (hereinafter collectively referred to as hybrid IC) generally incorporates a certain set of electric circuits including semiconductor elements, at least a part of the circuit and the hybrid IC It is necessary to electrically insulate metal parts such as supporting members or heat dissipating members. In a typical hybrid IC, the above-mentioned insulation is achieved by disposing an inorganic or organic insulating layer on a metal support member and assembling a predetermined electric circuit on this insulating layer. Such a hybrid IC is also an insulated semiconductor device.

On the other hand, in order to operate the semiconductor device safely and stably, it is necessary to effectively dissipate heat generated during the operation of the semiconductor device to the outside of the package. This heat dissipation is normally transferred from the semiconductor substrate, which is the heat source, to the air through the members bonded to the semiconductor substrate. The insulated semiconductor device includes an adhesive layer used in the middle of the heat conduction path, the insulating layer, and the part where the insulating layer and the semiconductor substrate are bonded.

Furthermore, the higher the voltage handled by a circuit including a semiconductor device, or the higher the required reliability (stability over time, moisture resistance, heat resistance, etc.), the more perfect insulation is required. Furthermore, the heat resistance required for semiconductor devices is the heat resistance when the temperature around the semiconductor device increases due to external causes, and the heat resistance when the semiconductor device handles a large amount of power and the heat generated from the semiconductor substrate increases. This includes heat resistance.

By the way, if the heat generation within the insulated semiconductor device is relatively small and the withstand voltage and required reliability are not particularly high, then any insulating layer or adhesive layer may be used. No particular problems occur.

However, in cases where heat generation is large or reliability is required to be high, inorganic materials such as ceramics are selected as the insulating layer.

Further, as the adhesive layer, for example, a metal solder such as lead-tin solder is selected.

In such a case, the following problems will arise that need to be solved.

That is, an insulated semiconductor device generally has a semiconductor substrate mounted on an insulating layer via a metal plate.

The metal plate of the insulated semiconductor device acts as a conductive path connecting the semiconductor substrate and an external power source, and also as a heat conduction path that effectively transfers heat generated from the semiconductor substrate to the insulating layer.

This metal plate is made of a metal having low resistance and high thermal conductivity, such as copper. However, this metal and the insulating layer have different coefficients of thermal expansion. For example, when the insulating layer is made of alumina, the thermal expansion coefficient is 6.3 x 10-6/l, whereas the thermal expansion coefficient of copper is 18 x 10-6/U.
However, the coefficient of thermal expansion of copper is extremely large.

Therefore, due to this difference in coefficient of thermal expansion, there is a risk that the metal solder portion of the insulated semiconductor device will be destroyed due to thermal fatigue during use.

To explain in more detail, as the semiconductor device is repeatedly energized and stopped, the above-mentioned junction is repeatedly brought into a high temperature state (approximately 100 to 150 tons) and a low temperature state (ambient temperature). It turns out. Each period of such high-temperature and low-temperature cycles is called a heat cycle, each member of the semiconductor device repeats expansion and contraction based on its own coefficient of thermal expansion. Since the members are fixed to each other, the difference in the amount of expansion and contraction based on the difference in the coefficient of thermal expansion of each member is applied as thermal strain to the solder layer, which is the softest member. As the number of heat cycles increases, the solder layer gradually becomes brittle due to the periodic and summer-like application of tensile strain and compressive strain, eventually leading to thermal fatigue phenomena. For example, cracks occur in the solder layer, causing a decrease in adhesive strength, a decrease in thermal conductivity, and the like. Such a phenomenon is remarkable at the exposed end face of the solder layer.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an improved insulated semiconductor device that solves the above-mentioned problems, reduces thermal strain occurring in the bonded portion during operation, and is free from deterioration or damage.

[Summary of the invention]

In order to achieve the above object, the present invention provides an insulated semiconductor device in which a metal solder is provided on the metal layer of a plurality of inorganic insulating members in which a metal layer is formed on a metallized layer formed on the surface of an inorganic insulating member. , is characterized in that a metal plate for conductively bonding the semiconductor substrate is bonded.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings, but before that, a detailed explanation of the present invention will be given.

In the present invention, as will be described later, in order to particularly improve heat cycle resistance, thermal fatigue of the metal solder interposed between the inorganic insulating member and the metal plate bonded on the insulating member is prevented. It is a means. That is, the above-mentioned means includes a metal plate having a metallized layer sintered by a wet method on the surface of an inorganic insulating member, and a metal layer such as a copper layer plated on the metallized layer. is formed by bonding the metal layer onto the metal layer using a metal solder. At this time, the thermal expansion coefficient α of the entire inorganic insulating member with the metal layer integrated therein is adjusted to the thermal expansion of the metal plate as much as possible. The aim is to reduce thermal fatigue of metal solder joints by bringing the coefficient close to that of the metal solder. The overall thermal expansion coefficient α of the composite inorganic insulating member is the apparent value of the composite inorganic insulating member.

Therefore, when the composite inorganic member is made of n layers of material, the coefficient of thermal expansion of the material of each layer is αI (C), the longitudinal elastic modulus is E i (Kg/ltm), and the thickness is t t (capacity). ), the thermal expansion coefficient α is approximated by the following equation (1).

Σ 1=IBiti In particular, in large hybrid ICs, there is a lot of heat generation in the semiconductor substrate, so a large heat diffusion plate is required, and multiple semiconductor substrates are used, so the area of the metal plate, and therefore the The bonding area with the insulating member is much larger than the bonding area between the semiconductor substrate and the support electrode in a normal individual semiconductor device. In such cases, it has been found that providing a plated copper layer on the metallized layer is extremely effective in preventing thermal fatigue of the solder metal.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings, taking a hybrid IC as an example.

FIG. 1 shows an embodiment of the present invention at 1200 V.

FIG. 2 is a perspective view showing the main parts of a 60A class hybrid IC. In the figure, two alumina plates 2 are placed on a metal support plate 1 made of a copper plate.
are lined up and adhered, and on each alumina plate 2, a metal plate 3 made of a copper plate having approximately the same shape as this alumina plate 2 is adhered, respectively. Note that, in FIG. 1, metal solder between each member is not shown for the purpose of simplifying the drawing.

As shown in the figure, a semiconductor substrate is adhered onto the metal plate 3 mentioned above, and the circuit shown in FIG. 2 is assembled therewith. That is, the cyrisk 401 and the flywheel diode 402 are each directly soldered onto the metal plate 3. There are each circuit element. Also, code 4101.41
02 and 4103 are external terminals, and external terminal 410
1 is directly glued on the metal plate 3, and the other external terminal 4102
and 4103 are installed on a wiring metal piece 430 bonded to an insulating alumina plate 420 bonded to the metal plate 3.

What is important in this embodiment is that the size of the metal plate 3 is approximately the same as that of the alumina plate 2, and all the circuit elements are placed on it. The metal plate 3 is continuous around the periphery of the metal plate 402 with a sufficient area to function as a heat diffusion plate.

FIG. 3 is a cross-sectional view schematically showing only the portion from the metal support plate 1 to the metal plate 3 of the structure of the embodiment according to the present invention. In the figure, the metal support plate l has a thickness of 3.2 [■
It is a copper plate with dimensions of 30 mm in width and 92 mm in length. On one main surface of the metal support plate 1, two alumina plates 2 are attached with a solder layer 1 made of 40% lead-60% tin.
It is glued by 01. The thickness of the solder layer 101 is approximately 0.1 tm. A metallized layer 201 is formed on the adhesive surface of the alumina plate 2, and a copper layer 203 as a metal layer formed by plating is further formed thereon to provide wettability to solder.

Each alumina plate 2 has a width of 25 [■] and a length of 30 [■]
, the thickness is 0.3[:m].

A metal plate 3 is bonded onto the copper layer 204 of each alumina plate 2 with a solder layer 102 having the same composition and thickness as the solder layer 101. A metallized layer 202 similar to that described above is formed on one side of the alumina plate 2, and a copper layer 204 as a metallized layer is further formed by plating thereon.

This metal plate 3 has a thickness of 2 [tall], a width of 22 [tall], and a length of 2
7 (am).The above-mentioned metallization layer 201
and 202 are made of tungsten as a main component and formed by a well-known wet method. Further, the copper layers 203 and 204 as metal layers are directly electroplated on the metallized layers 201 and 202, respectively, and have a thickness of about 10100 C].

The important point here is that the copper layer 203°204 as metal scrap
The thermal expansion coefficient of the alumina plate 2 as a whole, which is made into a composite by integrating the two, is made close to that of the metal plate 3. For example, the composite alumina plate in this embodiment has a thickness of about 9.7 x 10-', /l:', and the alumina plate that does not form the copper layers 203 and 204 as metal layers has a thickness of about 6.
．． 3.times.10.sup.-6/l: The coefficient of thermal expansion of the copper plate as the metal plate 3 is adjusted to be close to 18.times.10.about.6/C.

The apparent coefficient of thermal expansion of the composite inorganic insulating material is
It can be adjusted by changing the type and thickness of the material of the inorganic insulating member and the thickness of the metal layer such as the copper layer formed by plating.

According to this embodiment, from the thyristor 401 to the metal support plate 1
The thermal resistance of the path leading to is 0.35'[tr/WE,
Compared to (i, 3 [C/W)], an insulated semiconductor device with a conventional structure in which an alumina plate 2, a metal plate 3, and a semiconductor substrate are sequentially soldered and laminated on a metal support plate 1, the heat dissipation property is substantially improved. It was possible to improve the heat cycle resistance without lowering it to the extent that it became a problem. This effect was most noticeable when the area of the composite alumina plate and therefore the metal plate (the area of the heat diffusion plate of the kabura) became large. An example of this will be explained in detail with reference to FIG.

FIG. 4 is a graph showing the relationship between the failure rate of the hybrid IC after applying a predetermined heat cycle to the area of one alumina plate in the hybrid IC having the structure of this embodiment and the conventional structure (G). be. In FIG. 4, the horizontal axis shows the area [-], and the vertical axis shows the number of failures. The heat cycle was repeated 150 times between temperatures of -55 and +150C. According to Figure 4, structure A is used until the area of alumina plate is about 500 [mi].
Both No. 1 and B have a failure rate of 0, but when the value exceeds about 500, the failure rate increases at an accelerating rate in Structure B, while in Structure A it is still 0. Note that failure here mainly refers to the occurrence of cracks or partial peeling of the solder layer.

FIG. 5 is a sectional view showing another embodiment of the present invention. In the same figure, two metal plates 3 are glued side by side on an alumina plate 2, and a semiconductor substrate similar to that of the previous embodiment is soldered onto the metal plate 3. The circuit is configured.

At this time, on the surface of the alumina plate 2 facing the metal plate 3, a metallized layer 202 and a copper layer 2 formed by plating, similar to those in the previous embodiment, are provided.
04 is formed. Alumina plate 2 has a width of 25 [■],
It has a length of 70 mm and a thickness of 0.4 mm, and the thickness of the copper layer 204 as a metal layer is about 0.1 mm. The metal plate 3 bonded via the solder layer 102 (thickness: 0.1 mm) has a width of 22 [■], a length of 27 [Simplified], and a thickness of 2 [Extreme]. The structure integrated as described above is fitted into the hollow part of the sampling member 4, and is integrated with the protection member 4 by an adhesive 5 made of silicone resin. This protective member 4 has a thickness of 10 [m] and a width of 40 [m].
[mi:), a hollow hole is provided in the center of a copper plate with a length of 92 [w++]. The space formed by the protection member 4 and the alumina plate 2 is finally filled with resin and hermetically sealed.

What is important in this embodiment is that the surface of the alumina plate 2 on which no electric circuit is formed is exposed to the outside, and that the exposed surface of the alumina plate 2 comes into direct contact with the heat dissipation means when a hybrid IC is used. No. 2, the surface on which no electric circuit is formed has no metal layer such as the above-mentioned metallized layer or copper layer formed by bonding.

According to this embodiment, since the alumina plate 2 is not bonded to the metal support plate 1 and has a structure in which it directly contacts the heat radiating means, there is also the effect that heat dissipation is improved compared to the case of the previous embodiment. Furthermore, the metal plate 3 is the only metal member that is soldered to the alumina plate 2, resulting in a simplified structure with fewer adhesive layers, and therefore has high heat cycle resistance.

Next, various modified examples of the present invention will be illustrated.

The present invention can be implemented in various embodiments other than the embodiments described above.

First, as an inorganic insulating material, alumina aluminum (A2N), boron nitride (BN), silicon carbide (SiC), silicon nitride (Si3N4), beryllium oxide (Bed), etc., or a mixture containing these as components. etc. can be used. In this case, multilayer metal films such as chromium-nickel-silver, chromium-copper-gold, and titanium-nickel-silver formed by a method such as vapor deposition are effective as the metallization layer, as well as inorganic insulating materials. In the case of silicon carbide, a metal layer formed by a molybdenum-tungsten paste firing method (dry method) or a metal layer bonded with copper foil using a copper-manganese eutectic alloy may also be used. Even in the case where the metal layer is formed by a multi-layer laminated metal film or a metal layer formed by a molybdenum-tungsten paste baking method (dry method), it is also possible to use the metal layer described above.

The metal layer formed on the metallized layer may be formed directly on the metallized layer, but for example, it may be formed on the nickel layer after forming a nickel layer by a plating method or the like without any problem. In addition, when the metallized layer is a copper layer, in order to prevent deterioration of the surface of the copper layer during storage, a metal such as nickel may be placed on the copper layer. It is preferable to keep it coated. As the solder used for bonding, in addition to the composition of 40% lead-60% tin, for example, a composition of 95% lead-5% tin, or a solder containing silver or the like as a third component can be used. Its thickness is also 0.
The thickness is not limited to 1 (mm) and may be thicker or thinner.Generally, a thicker solder layer absorbs thermal distortion better, but since the thermal conductivity of the solder itself is not very high, the heat of the hybrid IC The dissipation performance is reduced.By using a composite inorganic insulating material with copper plating as in the above embodiment, the occurrence of thermal strain can be suppressed, so the thickness of the solder layer can be effectively reduced. Another advantage of the present invention is that the heat dissipation properties of the hybrid IC can be improved.

Next, it goes without saying that the present invention can be applied to any semiconductor element (including those using semiconductors other than silicon) and circuits as to the type of semiconductor substrate placed on the metal plate and the circuit configuration.

Furthermore, it is also effective to use a composite material such as a composite metal plate made by directly integrating copper and India (iron-36% nickel mixture) or a copper plate containing carbon fibers as the metal plate or metal support plate. In this case, the thermal expansion coefficient of the composite metal plate or composite material is adjusted to be close to that of the inorganic insulating material, so the thermal distortion that occurs in the solder layer becomes slight, and the heat cycle resistance is further improved. .

〔Effect of the invention〕

As explained above, according to the present invention, a metal layer is formed on the metallized layer formed on at least one surface of the flat inorganic inorganic material, and a metal plate for mounting a semiconductor substrate is attached to the metal layer using a metal solder. Since they are bonded together, it is possible to provide an improved insulated semiconductor device with no fear of deterioration or damage due to thermal strain.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an embodiment of an insulated semiconductor device according to the present invention, FIG. 2 is a circuit diagram showing an electric circuit obtained by the structure of FIG. 1, and FIG. 4 is a cross-sectional view showing the main parts, FIG. 4 is a graph showing the relationship between the failure rate of a hybrid IC and the bonding area of the inorganic insulating member of conventional example ①, and FIG. FIG. 2 is a sectional view showing the main parts of the embodiment. 1... Metal support plate, 2... Alumina plate, 3... Metal plate. Scale 1 bacteria certain 20 41θ3 qllJ Ko ￥3 figure / 14 figure rod flash

Claims (1)

[Claims] 1. A semiconductor substrate is conductively bonded onto a metal plate, and a wiring member having a wiring metal piece insulated from the metal plate is bonded to the metal plate, and the semiconductor substrate is bonded to the semiconductor substrate. In a semiconductor device in which an electrical region formed on a surface opposite to the metal plate is electrically connected to the wiring metal piece, the metal plate is formed on at least one surface of the flat inorganic insulator. An insulated semiconductor device, characterized in that the insulated semiconductor device is bonded to the metal layer of a plurality of inorganic insulating members formed by forming a metal layer on a metallized layer using a metal solder. 2. The insulated semiconductor device according to claim 1, wherein the flat inorganic insulator is an alumina plate. 3. The insulated semiconductor device according to claim 1, wherein the metallized layer is formed by sintering molybdenum or tungsten on at least one surface of the flat insulator. type semiconductor device.