JP2958948B2 - Semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device, and more particularly to a semiconductor device capable of preventing a harmful substance having an adverse effect on electrical characteristics from entering the inside.

[0002]

2. Description of the Related Art For example, as disclosed in Japanese Utility Model Publication No. 4-52999, a semiconductor chip made of a soft resin, that is, a rubber-like resin, is used as an element for rectifying the output of an AC generator (alternator) used in an automobile. Sealed resin-sealed diodes are known. This resin-sealed diode will be described with reference to FIG.

The diode 1 has a flat base portion 2a, a bowl-shaped support electrode 2 having a side portion 2b bent and extending from the base portion 2a and formed with a concave portion 2c, a flange-shaped header 3a and a header 3a. 3a, a lead electrode 3 comprising a lead portion 3b having a smaller cross section, and a base portion 2a.
A semiconductor chip 4 connected between the semiconductor chip 4 and the header 3a;
A silicon resin 5 that fills the recess 2 c and seals the semiconductor chip 4. Upper surface 4 of semiconductor chip 4
a and the lower surface 4b are respectively connected to the header 3a by the solder 6.
It is bonded to the upper surface 2a ₁ of the lower surface 3a ₁ and the base portion 2a.

The base 2a of the bowl-shaped support electrode 2, which radiates heat generated when the semiconductor chip 4 operates, has a thickness of about 1 mm. The side portion 2b that bends and extends from the base portion 2a is a ring having a diameter of about 9.5 mm, a height of about 2.3 mm, and a thickness of about 0.5 mm. The header 3a of the lead electrode 3 has a diameter of about 5 mm and a thickness of about 0.5 mm. The lead 3b extending upward from the header 3a has a diameter of about 1.5 mm and a length of about 18 mm. The lead portion 3b bends 3b ₁ of the U-shaped is formed. However, without providing the bent portions 3b ₁ of the U-shaped lead portion 3b
May be formed linearly.

A nickel electrode (not shown) is formed on both main surfaces 4a and 4b of the semiconductor chip 4. Solder 6
Pb-S with 95% by weight of lead (Pb) and 5% by weight of tin (Sn)
It is an n-based alloy. Bowl-shaped support electrode 2 and lead electrode 3
Is a copper material coated with nickel. Silicon resin 5
Are formed so as to slightly rise from the concave portion 2c of the bowl-shaped support electrode 2, and the side surface 4c of the semiconductor chip 4 and the header 3
The lower portion of the lead portion 3b following the portion a and the concave portion 2c side of the bowl-shaped support electrode 2 are covered. The silicon resin 5 is formed by fixing the semiconductor chip 4 and the lead electrode 3 to the bowl-shaped support electrode 2 and then pouring a resin-forming mucus into the recess 2 c of the bowl-shaped support electrode 2 and performing a heat treatment.

[0006]

However, since the silicon resin 5 has a large thermal expansion coefficient and a large curing shrinkage with respect to the metal forming the support electrode 2, the silicon resin 5 easily peels off at the bonding interface with the support electrode 2, and the electrical connection between the silicon resin 5 and the metal is difficult. There is a possibility that the characteristics are deteriorated. That is, the adhesion of the silicon resin 5 to the support electrode 2 and the lead electrode 3 is easily broken by the presence of an acid or an alkali. In addition, in the heat treatment step of solidifying the silicon resin 5, the silicon resin 5 shrinks, and stress concentrates on the bonded portions indicated by arrows A and B. Therefore, the bonding portion A
And silicone resin 5 becomes easy peel state from the lead part 3b or bowl-shaped upper portion 2b ₂ of the surface of the support electrode 2 of the lead electrode 3 in B. Therefore, when the diode 1 is used for a long period of time in a severe environment, the lead portion 3b of the lead electrode 3 or the bowl-shaped support electrode 2 starts from the bonding portions A and B.
Peeling the silicon resin 5 proceeds along the surface of the side 2b of the upper surface 3a of the ultimately header 3a ₂ and the side surface 3a ₃
Alternatively, the side surface 4 of the semiconductor chip 4 passes through the inner surface 2b ₁ of the side portion 2b of the bowl-shaped support electrode 2 and the upper surface 2a ₁ of the base portion 2a.
The peeling of the silicon resin 5 may reach c. In the state in which the peeling has progressed, the diode 1 has characteristics such as an increase in the reverse current due to harmful substances such as moisture and ionic impurities penetrating into the side surface 4c of the semiconductor chip 4 from the peeled portion of the silicon resin 5. Failure occurs.

[0007] In order to solve this problem, a method has been known in which a silicon resin contains silica powder to reduce the coefficient of thermal expansion so that the coefficient of thermal expansion of the protective resin approaches the coefficient of thermal expansion of the support electrode. With this protective resin, peeling does not occur under a normal environment. However, it has been found that when the protective resin is placed in an electric field in a state where moisture is attached to the protective resin and an electric field is applied, the separation preventing effect is impaired.

Accordingly, the present invention provides a semiconductor device having a high ability to prevent harmful substances having an adverse effect on electrical characteristics from entering into the inside without causing the protective resin to peel off from the support electrode even when used in a severe environment. The purpose is to provide.

[0009]

A semiconductor device according to the present invention comprises a support electrode (2) formed of a metal containing copper as a main component and having a recess, a lead electrode (3), and a support electrode (2). The semiconductor chip (4) connected between the bottom of the recess (2c) and the lead electrode (3), and the protective resin (7) filling the recess (2c) and covering the semiconductor chip (4). For use as an output rectifier for automotive alternators. Protection resin (7)
Contains 100 parts by weight of a silicone resin and 80 to 140 parts by weight of a filler material, and the filler material has silica powder and alumina powder. ５０50 parts by weight. In the present invention, the protection resin (7) does not peel off from the support electrode (2) even when an electric field is applied in a state where moisture is attached to the protection resin (7).

[0010]

[Function] The silica powder and the alumina powder contained in the protective resin (7) have a smaller coefficient of thermal expansion than the silicon resin, and the coefficient of thermal expansion of the protective resin (7) is reduced to thereby increase the coefficient of thermal expansion with the support electrode (2). It has the effect of reducing the difference. Since the protective resin (7) contains the filler material composed of silica powder and alumina powder in the range of 80 to 140 parts by weight with respect to 100 parts by weight of the silicon resin, the protective resin (7) has a good coefficient of thermal expansion and a good cure shrinkage. In addition, the silica powder mixed into the filler at a content of 20 parts by weight or more with respect to 100 parts by weight of the silicone resin is uniformly distributed in the protective resin (7), and the entire protective resin (7) becomes homogeneous. . Further, since silica powder is mixed into the filler at a content of 50 parts by weight or less with respect to 100 parts by weight of the silicone resin, even if an electric field is applied while moisture is attached to the protective resin (7), the protective resin (7 ) Does not peel off from the support electrode (2), and can effectively prevent intrusion of harmful substances as an output rectifying element of an automotive alternator exposed to a particularly severe environment.

[0011]

FIG. 1 shows an embodiment of a semiconductor device according to the present invention applied to a rectifier diode for an automobile. In FIG. 1, the same portions as those shown in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted.

A rectifier diode 10 according to the present embodiment shown in FIG.
3 differs from the conventional rectifier diode 1 shown in FIG. 3 in that the protective resin 7 is made of a silicon resin containing a filler material composed of silica powder and alumina powder.

In this embodiment, the protective resin 7 is made of silicon resin 1
The filler material is contained in an amount of 110 parts by weight based on 00 parts by weight. The ratio of the silica powder in the filler material was 40 parts by weight with respect to 100 parts by weight of the silicone resin, and the balance was alumina powder.

In order to confirm the curing of the present invention, a number of rectifier diode samples having the same structure as in FIG. 1 but having different silica powder contents were manufactured and subjected to an electric field quality test. After each sample is immersed in salt water, the sample is placed in a thermostat to evaporate water in the sample, and a predetermined voltage is applied between the support electrode 2 and the lead electrode 3 to apply the predetermined voltage to the protective resin 7 and the support electrode 2. The state of adhesion with the sample was inspected.

The graph shown in FIG. 2 shows the results of an electric field quality test of a number of rectifier diode samples in which the content of the silica powder in the filler material was changed. Samples having a silica powder content of more than 50 parts by weight and less than 20 parts by weight with respect to 100 parts by weight of the silicone resin showed peeling at the interface between the protective resin 7 and the support electrode 2 in less than 8 tests. . The reason is that the content of silica powder is 50% by weight.
Is exceeded, Si contained as impurities in the silica powder
Unreacted substances such as O (silicon monoxide) and Si (silicon) have an adverse effect, and when the content of the silica powder is less than 20 parts by weight, alumina powder having a larger specific gravity than the silica powder is used. It is considered that the content rate is relatively increased and the filler material is not uniformly distributed in the protective resin 7. In addition, when all the filler materials were made of alumina powder, the sedimentation of the filler material was remarkable, and it was confirmed that the effect of preventing peeling was not sufficiently exhibited.

The protective resin 7 according to the present invention contains 100 parts by weight of a silicone resin and 80 to 140 parts by weight of a filler material. The protective resin containing 80 to 140 parts by weight of a filler material composed of silica powder and alumina powder with respect to 100 parts by weight of the silicon resin has a good thermal expansion coefficient and a curing shrinkage rate, and furthermore, after curing, is used as a support electrode. Good adhesion. If the content of the filler material is less than 80 parts by weight or more than 140 parts by weight, desired thermal expansion coefficient and curing shrinkage cannot be obtained. Further, the filler material according to the present invention has a silica powder and an alumina powder, and the content of the silica powder is 20 parts by weight with respect to 100 parts by weight of the silicone resin.
Since it is 50 parts by weight, even if an electric field is applied in a state where moisture is attached, no separation occurs, and the filler material can be uniformly distributed in the protective resin.

The embodiments of the present invention are not limited to the above-described embodiments, but can be modified. The present invention can be applied to semiconductor devices other than rectifier diodes for automobiles. In addition, other additives such as a curing accelerator, a softening agent, and an adhesive may be mixed into the protective resin 7 in addition to the filler material as long as the effects of the present invention are not impaired.

[0018]

According to the semiconductor device of the present invention, even if the semiconductor device is used in a severe environment in which an electric field is applied in a state where moisture is attached, peeling between the sealing resin body and the electrode hardly progresses, which is harmful. A highly reliable semiconductor device with an enhanced ability to prevent entry of a substance can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a semiconductor device according to the present invention applied to an automotive rectifier diode.

FIG. 2 is a graph showing the relationship between the change in the content of silica powder and the number of tests.

FIG. 3 is a cross-sectional view of a conventional rectifier diode for an automobile.

[Explanation of symbols]

2. . Support electrode, 2a. . Base part, 2b. . side,
2c. . Recess, 3. . Lead electrode, 3a. . Header, 3b. . Lead part, 4. . Semiconductor chips,
6. . 6. solder, . Protective resin,

Claims (1)

(57) [Claims] A support electrode formed of a metal containing copper as a main component and having a recess; a lead electrode; a semiconductor chip connected between a bottom of the recess of the support electrode and the lead electrode; A semiconductor resin used as an output rectifying element of an automotive alternator, comprising a protective resin filled in the recess and covering the semiconductor chip, wherein the protective resin comprises 100 parts by weight of silicone resin;
To 140 parts by weight of a filler material, wherein the filler material has silica powder and alumina powder, and the content of the silica powder is 20 to 100 parts by weight of the silicon resin.
50 parts by weight, wherein the protective resin does not peel off from the support electrode even when an electric field is applied in a state where moisture is attached to the protective resin.