JPS6138864B2 - - Google Patents

Abstract

PURPOSE:To obtain a device having superior electrical insulation, heat radiation and small noise by uniting a semiconductor element substrate and a supporting substance through polyimide covered with the resin of ethylene fluoride group. CONSTITUTION:A polyimide insulating film 3 and adhesive layers of ethylene fluoride, 4,4' are placed in piles on a copper supporting substance 2. And a semiconductor element 1 is placed on a copper plate 5 by adhering the copper plate 5 for unification. The connector lead wire 8 of the element 1 is installed through the copper plate 5 and emitter and base lead wires 6, 7 are installed. In this composition, the ethylene fluoride 4,4' will flow when the supporting substance 2 and the copper plate 5 are united. And deterioration or transformation will not occur for the good insulating polyimide even if a thin film is locally generated. And high insulating dielectric strength will be noted by leaving the polyimide. Furthermore, the space between the supporting substance 2 and the copper plate 5 will be filled by the flow of the films 4,4' and thermal resistance will become low. Furthermore, heat fatigue is hard to generate because the supporting plate 2 will be insulted from the pellet 1, noise will be reduced owing to the possibility of ground and the coefficient reduced owing to the possibility of ground and the coefficient of thermal expansion for the united section is almost same.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor device, and particularly to a semi-moving device having a structure in which at least a semiconductor element is mounted on a support with an insulator interposed therebetween.

In a high-output transistor, which is an example of a semiconductor device, a collector current of several amperes or more flows.
At this time, heat is generated inside the transistor pellet as a semiconductor element. In order to avoid instability of characteristics and accelerated deterioration of lifetime due to this heat generation, methods are used to prevent the temperature of the transistor pellet from rising beyond the permissible limit temperature.

One method to prevent temperature rise has traditionally been to attach the stem, which serves as a support for the transistor pellet, to a radiator, and to release the heat generated by the transistor pellet to the outside via the stem and the radiator. It's here.

In the case of high-output transistors, a large collector current flows as described above, so it is necessary to secure a current path and efficiently dissipate heat, so the transistor pellet is mounted so that the collector region is directly fixed to the stem. However, since this type of transistor is usually used with the emitter or base grounded, the collector terminal or stem cannot be directly attached to a heat sink (or chassis) etc. which is often grounded.

For this reason, an insulating plate such as mica or polyester terephthalate (Mylar) is usually sandwiched between the stem and the heatsink to electrically insulate the stem and the heatsink, and in order to aid heat dissipation, the stem and the insulating plate and between the insulating plate and The stem and the radiator were fixed by screwing through an insulating washer and using grease to fill the gap between the radiators.

However, even in this case, since the collector region is electrically connected to the stem (the stem cannot be grounded), it is difficult to avoid the effects of noise due to electromagnetic interference.

On the other hand, in an attempt to achieve electrical insulation, efficient heat dissipation, and prevention of electromagnetic interference, there are examples in which a semiconductor device is mounted on a metal support via beryllia porcelain or alumina porcelain. However, when using beryllia porcelain, (1) beryllium itself is highly toxic, so strict care must be taken when handling it, and it is difficult to obtain and expensive.

(2) The coefficient of thermal expansion of Beryliya porcelain is 7.6×10 ^-6 /℃
Copper (18×
10 ^-6 /℃) and aluminum (25 x 10 ^-6 /℃), so if left as is, thermal fatigue is likely to occur at the bond between the Berylliya porcelain and the support or between the Beryllya porcelain and the mounting plate. Strong integration between the two is difficult.

(3) To alleviate thermal fatigue at the bonded area, it is necessary to provide a buffer area for strain relief.For this purpose, for example, the solder layer at the bonded area may be made thicker, or molybdenum (thermal expansion coefficient: 5.2×10 ^- It is necessary to use a spacer made of tungsten (4.3 x 10 ^-6 /℃) or tungsten ( ^4.3 will also be disadvantageous.

(4) Molybdenum and tungsten, which are essential spacers when using Beryllium porcelain as an insulating plate, are heavy metals (the specific gravity of molybdenum is
10.27, and the specific gravity of tungsten is 19.3).
This becomes an obstacle when trying to reduce the weight of semiconductor devices.

There are problems such as. On the other hand, even when alumina porcelain is used, problems similar to those of beryllia porcelain mentioned above are involved, except for the problem of toxicity.

In the above, we have explained the shortcomings of conventional semiconductor devices using transistors as an example, but similar problems remain not only in transistors but also in other semiconductor devices such as diodes and thyristors, or in semiconductor devices that constitute hybrid integrated circuits. was.

The present invention improves the above-mentioned drawbacks, provides excellent electrical insulation between the semiconductor element and the support, efficient heat dissipation, noise prevention due to electromagnetic interference, and strong connection between the support or mounting plate and the insulating carrier. Bonding and weight reduction
The purpose of the present invention is to provide a semiconductor device that is capable of reducing costs.

A semiconductor device of the present invention that achieves the above object includes at least a semiconductor element, a metal mounting plate on which the semiconductor element is mounted, a metal support on which the metal mounting plate is mounted, and at least one surface of the semiconductor device. A polyimide film coated with a fluorinated ethylene resin is characterized in that the film is interposed and integrated between the metal mounting plate of the semiconductor element and the metal support.

In the present invention, polyimide has a volume resistivity of 10 ¹⁸ Ωcm.
(25℃), dielectric breakdown strength of about 280kv/mm (25℃), thermal expansion coefficient of 20×16 ^-6 /℃ (room temperature), and density of 1.42g/cm ³ . It has a large coefficient of thermal expansion, is relatively lightweight, can be made as thin as 10 μm, and is low cost. On the other hand, fluorinated resin has insulation properties and a coefficient of thermal expansion equivalent to that of polyimide. In addition to this, it begins to soften at a temperature (approximately 250°C) that does not cause deterioration of polyimide properties, so it acts as an effective adhesive.

In particular, in the present invention, the semiconductor element mounting plate and the support are integrated via polyimide coated with a fluorinated ethylene resin, and the fluorinated ethylene resin is used as an adhesive for integration. It has the most significant feature.

Therefore, even if uneven parts occur in the fluorinated ethylene resin layer as an adhesive due to heat treatment during integration, the polyimide layer remains uniform, so the electrical Electrical insulation between semiconductor elements or hybrid integrated circuit elements and the support on which they are mounted can be easily realized without impairing insulation properties.

In addition, the coefficient of thermal expansion of polyimide and fluorinated ethylene for insulation is extremely close to that of copper and aluminum, which are widely used as supports and mounting plates, making it possible to form a strong, integrated structure that is less likely to cause thermal fatigue at the bonded part. becomes possible. Furthermore, the weight of the insulating layer is so light that it can be virtually ignored compared to other parts, and there is no need to insert an extra spacer between the insulating layer and the support or mounting plate, which reduces the weight and size of semiconductor devices. It is effective for Although the thermal conductivity of the insulating material itself is small at ~5×10 ^-4 cal/cm・s・℃,
It was confirmed that by making the layer thinner, it was possible to ensure heat dissipation to a level that would not cause any practical problems.

The fluorinated ethylene used as the adhesive in the present invention is preferably a tetrafluoroethylene-hexafluoropropylene polymer or polytetrafluoroethylene. In contrast, epoxy or acrylic adhesives, which are commonly known as insulating adhesives, are thermosetting and are processed at temperatures of around 150°C, but are usually processed at higher temperatures. semiconductor process (for example, approximately 200
Not only is it difficult to apply it to the soldering process (which is carried out at ~350°C), but also hardening progresses constantly due to use under severe temperature conditions. In this point,
The above-mentioned fluorinated ethylene type can be processed at temperatures up to about 400°C, and since it is thermoplastic, curing does not proceed excessively.

The present invention will be explained in detail below with reference to Examples.

Example 1 As shown in FIG. 1, a semiconductor device in this example consists of a silicon transistor pellet 1 as a semiconductor element on a copper support 2, a polyimide layer 3 as an insulating layer, and a fluorinated ethylene layer as an adhesive. It is mounted on a copper mounting plate 5 which is fixed and integrated via 4 and 4'.

The emitter and base regions of the transistor pellet 1 are electrically connected by aluminum leads 6 and 7, respectively, and the collector region is electrically connected to an aluminum lead 8 via a copper mounting plate 5. The aluminum leads 6, 7 and 8 are then connected to the copper leads (not shown) in a conventional manner, and at least the aforementioned parts, except for the copper support 2 and a portion of the copper leads, are completely exposed to the outside air. It is molded with resin (not shown) so that it is cut off.

In the semiconductor device obtained with such a configuration, the dielectric strength between the copper lead and the copper support 2 is 2000 V or more,
The thermal resistance between the transistor pellet 1 and the copper support 2 was less than 1°C/W. In addition, noise due to electromagnetic interference is caused by transistor pellet 1 - copper support 2.
It is about 30 dB lower than when there is no electrical insulation between the transistor pellets 1 and 125
Copper support 2- when subjected to 1000 thermal changes between ℃
No abnormality was found in the fixed and integrated portion between the copper mounting plates 5.

The reason why such a high dielectric strength voltage was obtained is that when the copper support 2 and the copper mounting plate 5 are integrated, the fluorinated ethylene 4, 4', which also serves as an adhesive, flows and is This is because even if a thin portion is formed, the polyimide 3, which has excellent insulating properties, will remain without deterioration or deformation. In addition, fluorinated ethylene 4,4', which also serves as an adhesive, has low thermal resistance.
However, during the integration heat treatment, it flows to some extent and fills the gap between the copper support 2 and the copper mounting plate 5, resulting in the formation of a thin insulating layer with fewer gaps.

The reason why the noise can be reduced is that since the copper support plate 2 is electrically insulated from the transistor pellet 1, it becomes possible to ground the copper support plate 2. In addition, the copper support 2 or the copper mounting plate 5 was able to be integrated in a robust manner that does not cause thermal fatigue.
This is because the polyimide 3 and the fluorinated ethylene 4 and 4' have substantially the same coefficient of thermal expansion, so that changes in residual stress due to temperature changes in the integrated portion can be reduced.

Note that the semiconductor device in this example does not have a heavy metal plate or solder metal interposed between the support plate or mounting plate and the insulating carrier, so it is approximately 20% lighter than the equivalent conventional semiconductor device, and It was confirmed that this method is economically advantageous because the number of parts and processing steps required for integration are reduced.

Example 2 As shown in FIG. 2, a semiconductor device according to this example includes silicon diode pellets 21a, 21a', 21b, and 21b' as semiconductor elements on a copper support 22 and a polyimide layer as an insulating layer. 23
This is a hybrid integrated circuit device mounted on copper mounting plates 25a, 25b which are integrated via a, 23b and fluorinated ethylene 241a, 242a, 241b, 242b as an adhesive.

Each diode pellet has a lead wire 26.
a, 26a', 26b, 26b', and lead wires 27a, 27b are also provided on the copper mounting plates 25a, 25b.
The four diodes are electrically connected so as to each serve as a part of a rectifier circuit, and are resin-molded so that at least the silicon diode pellets are isolated from the outside air.

The insulation properties, heat dissipation properties, noise prevention effects, and thermal fatigue resistance of the semiconductor device obtained with such a configuration were equivalent to those of Example 1. This is due to the same reason as in the first embodiment.

In addition, in the case of this embodiment, the mounting plates 25a, 25b
Since a plurality of semiconductor elements are attached to the insulating layer, the insulation properties are not impaired even though the area of the insulating layer becomes large. When the support plate 22 and the mounting plates 25a, 25b are integrated, the fluorinated ethylene 241a, b, 241b, which also serves as an adhesive,
The polyimide film 23 has excellent insulation properties even if 42a and 42b flow and create locally thin parts.
This is because a and b remained without alteration or deformation.

As described above, it has been demonstrated that the use of polyimide coated with fluorinated ethylene as an insulating carrier is also useful in the case of a circuit device in which a plurality of semiconductor elements are integrated.

Example 3 As shown in FIG. 3a, a semiconductor device in this example includes a silicon diode pellet 31 as a semiconductor element, a polyimide layer 34 as an insulating layer, and fluorine as an adhesive on a copper support 32. The chip is placed on the integrated copper mounting plate 33 via the fluorinated ethylene 35, 35', and a chip resistor 36 and a chip are placed on the exposed portion of the fluorinated ethylene 35 without the copper mounting plate 33. This is a hybrid integrated circuit device in which a capacitor 37 and a copper electrode plate 38 are respectively mounted.

Further, as shown in FIG. 3B, aluminum wires 39a and 3 are connected between each element so that an electric circuit is formed in which the resistor 36 and the capacitor 37 are connected in series, and the diode 31 is connected in parallel.
9b, 39c and lead frames 40a, 40b,
40c, and the various circuit elements described above are resin molded.

The insulation, heat dissipation, noise prevention effect, thermal fatigue resistance, etc. of the semiconductor device obtained with such a configuration were the same as those of Example 1. This is due to the same reason as in the first embodiment.

Furthermore, since the polyimide 34 serving as the insulating layer is coated with fluorinated ethylene 35, 35' which also has properties as an insulating layer and also acts as an adhesive, the chip resistor 34 is coated thereon.
6, the chip capacitor 37, and the electrode plate 38 can be directly mounted, and as a result, metallization treatment for mounting these passive elements is no longer necessary, and it has been confirmed that the economical efficiency is further improved.

Example 4 In the semiconductor device of this example, as shown in FIG. 4, the thyristors 51 and 51', which generate the most heat among the circuit elements, are made of an insulating layer made of a polyimide film coated on both sides with fluorinated ethylene. 53, the metal mounting plates 54, 54' with a large area fixedly integrated with the support plate 52 are directly alloyed and mounted, while the passive elements 55, 55', which generate less heat, are mounted. formed on the placing plates 54, 54';
Diodes 57, 5 which are placed directly on the insulating layer 56 having the same structure as described above and which generate less heat are provided.
7' was alloyed and placed on small-area metal mounting plates 59, 59' which were fixed and integrated on the mounting plates 54, 54' via insulating layers 58, 58' similar to those described above. This is a hybrid integrated circuit device for current control.

The insulation properties, heat dissipation properties, noise prevention effects, and thermal fatigue resistance of the semiconductor device obtained with such a configuration were equivalent to those of Example 1. This is due to the same reason as in the first embodiment.

In addition, in the case of this semiconductor device, circuit elements that generate a large amount of heat are placed on a mounting plate with a large surface area, and circuit elements that do not require much heat dissipation are placed on a mounting plate that is stacked on top of that. , so to speak, is characterized by a structure that allows for efficient use of vertical space. As a result, heat dissipation is effective,
Since circuit components could be mounted vertically, the area occupied by the hybrid integrated circuit device could be reduced.

Although the present invention has been described above using examples, the present invention is not limited thereto, and the effects and advantages of the present invention can be enjoyed even in the following cases, for example.

(1) The polyimide film 61 constituting a part of the insulating layer has a structure in which only one surface is coated with fluorinated ethylene 62, as shown in FIG. 5a.
Alternatively, as shown in FIG. 5B, it may have a structure in which fluorinated ethylene 62 is metallized on one surface and metal 63 is metallized on the other surface.

(2) The support or mounting plate may be made of metal other than copper, such as aluminum.

(3) At least the method of insulating the semiconductor element from the outside air does not have to be the resin molding method, and other methods such as the can seal method may be used.

(4) Semiconductor elements are made of germanium, gallium arsenide,
It may be made of a semiconductor material other than silicon, such as gallium phosphide or silicon carbide.

As explained above, according to the present invention, the following advantages and effects can be achieved.

(1) The insulating layer has a structure in which at least one side of the polyimide film is coated with a fluorinated ethylene resin that also serves as an adhesive.
Even if the fluorinated ethylene resin flows and some thin parts occur locally, the polyimide, which has excellent insulating properties, will remain without deterioration or deformation. As a result, the semiconductor element or other circuit element can be electrically insulated favorably from the support.

(2) The fluorinated ethylene resin, which also serves as an adhesive, flows to some extent during the integration heat treatment and plays the role of filling the voids, resulting in the formation of a thin insulating layer with few voids, improving the heat dissipation of the semiconductor element. .

(3) Since the semiconductor element is electrically insulated from the support, the support can be grounded. As a result, the electrical characteristics of the semiconductor device are not affected by electromagnetic interference.

(4) Since the thermal expansion coefficients of the support or mounting plate and the insulating layer are close to each other, thermal fatigue at the integrated portion can be avoided.

(5) The insulating layer can be thin, and there is no need to interpose other metal spacers between the insulating layer and the support or mounting plate, so it is possible to reduce the weight of the semiconductor device and further reduce the number of parts. The semiconductor device can be manufactured economically because the number of manufacturing steps and the number of manufacturing steps are reduced.

(6) Passive elements can be placed directly on the insulating layer, so
No metallization process is required for mounting, increasing economic efficiency.

(7) Since multiple circuit elements and circuit components can be stacked and mounted, efficient heat dissipation and efficient use of space are possible, allowing the hybrid integrated circuit device to be miniaturized.

[Brief explanation of the drawing]

1, 2, 3 and 4 are sectional views of embodiments of the present invention, and FIG. 5 is a sectional view of another example of the structure of the insulating layer. 1...Silicon transistor pellet, 2...
Copper support, 3... polyimide, 4,4'... fluorinated ethylene, 5... copper mounting plate.

Claims (1)

[Claims] 1 At least a semiconductor element, a metal mounting plate on which the semiconductor element is placed, a metal support on which the metal placement plate is placed, and interposed between the metal placement plate and the metal support, 1. A semiconductor device comprising a polyimide film whose at least one surface is coated with a fluorinated ethylene resin, and which are fixedly integrated with each other.