JP2002043472A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the environmental resistance of a semiconductor sensor or the like to a semiconductor device. SOLUTION: In a semiconductor device wherein a semiconductor chip is incorporated in a resin case insert-molding a lead terminal for outside leading- out and a coating resin is filled into a resin case to be sealed, the resin case comprises a thermoplastic resin injection molding. The linear expansion coefficient of the molding material is near the linear expansion coefficient of a lead terminal material, and the resin wherein the ratio (fluidity direction/orthogonal direction) of the linear expansion coefficient of the fluidity direction of the resin oriented from injection molding and the linear expansion coefficient of the fluidity direction and orthogonal direction is within 1.0-3.0 is used to mold the resin case. Thereby a gap between the resin case and the lead terminal occurs, the bubble occurrence of the case caused thereby is effectively suppressed, and stress transmitted from the resin case to the semiconductor chip is lowered to improve the reliability of environmental resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device such as a semiconductor pressure sensor and a semiconductor acceleration sensor widely used for automobiles and consumer use, and a semiconductor chip mounted in a resin case. The present invention relates to a hermetically sealed semiconductor device.

[0002]

2. Description of the Related Art FIG. 2 shows a structure of a surface pressure type semiconductor pressure sensor as a semiconductor sensor to which the present invention is applied. In the figure, 1 is a pressure-sensitive sensor chip having a measurement circuit including a semiconductor strain gauge formed on the surface of a silicon chip, 2 is a glass pedestal (spacer) on which the pressure-sensitive sensor chip 1 is mounted and anodically bonded, 3 is a resin case, Reference numeral 4 denotes a lead terminal for external derivation made of phosphor bronze or the like integrally molded with the resin case 3, 5 denotes a bonding wire connecting the circuit of the pressure-sensitive sensor chip 1 and the lead terminal 4, and 6 denotes a sensing wire. A soft coating resin such as silicone gel sealed to protect the pressure sensor chip 1 and the bonding wire 5 from contaminants and moisture, and 7 is a cap with a pressure guiding port connected to the resin case 3.

The operating principle of such a semiconductor pressure sensor is well known. When a measured pressure is applied to the surface of the pressure-sensitive sensor chip 1 through the pressure-guiding port of the cap 7, the thin diaphragm portion 1a formed on the pressure-sensitive sensor chip 1 is formed. Is deformed, the gauge resistance of the semiconductor strain gauge changes, and an electric signal corresponding to the measured pressure is taken out from the lead terminal 4 to an external circuit.

FIG. 3 shows a configuration of a semiconductor acceleration sensor as another example of a semiconductor sensor. In the figure, 8
Is a sensor chip, a cantilever portion 8a and a beam portion 8b are formed on the silicon chip, and a semiconductor strain gauge 8c is formed on the beam portion 8b. This sensor chip 8
A glass cover 9 and a glass pedestal 10 are anodically bonded to the upper and lower surfaces to form a sensor unit. The sensor unit is housed in a resin case 11, and is further connected to an external lead-out lead terminal 12 insert-molded in the resin case 11. The connection with the sensor chip 8 is made by a bonding wire 13. The sensor chip 8 and the bonding wire 13 are filled with a JCR (Junction Coati
(ng Regin) and the like. A resin cap 15 is attached to the upper surface of the resin case 11.

It is well known that when acceleration is applied to the sensor chip 8 in such a configuration, the gauge resistance of the strain gauge 8c changes to detect an electric signal corresponding to the acceleration. Here, the resin cases 3 and 11 are made of PPS.
(Polyphenylene sulfide), PBT (polybutylene terephthalate) and other thermoplastic resins are used as injection molding products.

[0006]

By the way, with respect to the above-mentioned semiconductor type sensor, the conventional product has a high resistance to use environment,
There are the following problems in terms of reliability. (1) When the high and low temperature cycles are repeatedly applied, the resin cases 3 and 11 themselves shrink during molding and the difference in linear expansion coefficient between the resin cases and the lead terminals 4 and 12 causes a difference between the two. The bonding interface peels off and a minute gap is generated. For this reason, in the semiconductor pressure sensor shown in FIG. 2, when a negative pressure is applied in a cycle test in which pressurization and depressurization are repeated, the above described pressure generated between the resin case 3 and the lead terminal 4 as shown in FIG. Air and moisture are sucked from the outside through the minute gap and enter the resin case, and bubbles are generated in the layer of the gel-like coating resin 6. In addition, the bubbles generated in the coating resin layer gradually grow with the repetition of the change in the measured pressure, causing the bonding wire 5 to break, and the measured pressure introduced into the pressure sensor is correctly transmitted to the pressure-sensitive sensor chip 1. And the measurement characteristics of the pressure sensor are adversely affected. Further, there is also a problem that the bonding wire (aluminum wire) 5 is corroded or disconnected due to the moisture that has entered together with the air.

Also, in a semiconductor acceleration sensor, moisture enters from the outside through a gap remaining at the interface between the resin case 11 and the lead terminal 12 due to a heat cycle accompanying a change in ambient temperature or the like. This causes problems such as corrosion of the lead terminals 12 and the bonding wires 13 and disconnection of the bonding wires.

(2) When high and low temperature cycles are repeatedly applied, when the resin of the resin cases 3 and 11 has anisotropy, the stress generated in the resin case causes the sensor chip mounted on the resin case. In addition, the sensor characteristics become unstable. SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and is intended for a semiconductor type pressure sensor, acceleration sensor, or the like described above, by suppressing generation of a gap at an interface between a resin case and a lead terminal. Effectively suppresses the intrusion of air and moisture into the case and the generation of bubbles in the coating resin layer, and reduces the stress transmitted from the resin case to the sensor chip, and withstands use in harsh operating environments. It is an object to provide a highly reliable semiconductor device.

[0009]

According to the present invention, a semiconductor chip is incorporated into a resin case in which an external lead terminal is insert-molded, and a space between the semiconductor chip and the lead terminal is provided. In a semiconductor device which is electrically connected and filled with a coating resin in a resin case and sealed, (1) the molding resin of the resin case is a thermoplastic resin, and the linear expansion coefficient of the lead terminal and the molding The ratio to the linear expansion coefficient of the resin (molded resin / lead terminal) is 0.7 to 2.5
(Claim 1).

(2) The molding resin of the resin case is a thermoplastic resin, and the linear expansion coefficient in the flow direction (flow direction) of the molding resin oriented by injection molding and the direction perpendicular to the flow direction (perpendicular direction). The ratio (perpendicular direction / flow direction) to the linear expansion coefficient is set to 1.0 to 3.0 (Claim 2). (3) A semiconductor device is configured by using the configurations described in the above (1) and (2) together (Claim 3).

(4) Further, a semiconductor sensor is constituted by the constitution described in any one of the above items (1) to (3). That is, in order to confirm the performance evaluation of the resin-encapsulated semiconductor device, the inventors examined the relationship between the ratio of the linear expansion coefficient of the molded resin / lead terminal and the bubble generation rate in the resin case through a temperature cycle test. The following became clear.

That is, when phosphor bronze is used for the lead terminal and PPS (polyphenylene sulfide) is used for the molding resin of the resin case, as shown in FIG. When the ratio to the expansion coefficient (molded resin / lead terminal) exceeds 2.5, the bonding interface between the lead terminal and the resin case is separated due to the temperature cycle, and a minute gap is generated. air,
It was found that the rate of bubble generation increased rapidly due to the penetration of moisture. On the other hand, the coefficient of linear expansion of the molding resin is close to the coefficient of linear expansion of the lead terminal, and the ratio of the coefficients of linear expansion is 0.7 to 0.7.
When it was within 2.5, it was confirmed that even when a temperature cycle was applied, almost no bubbles were generated in the coating resin layer filled in the resin case.

The injection molding of the resin case is a molding method in which the molding resin is injected into the cavity at a high pressure through the gate of the mold. By this molding method, the molecules of the molding resin are oriented in the flow direction, and the molecules of the resin are formed. The chains become oriented in a fixed direction. For this reason, anisotropy occurs in the physical properties of the molded product (resin case), and the linear expansion coefficient in the resin flow direction (flow direction) differs from the linear expansion coefficient in the direction perpendicular to the resin flow direction (perpendicular direction). Become.

Therefore, the inventor of the present invention injection-molded a resin having various ratios of the linear expansion coefficient in the flow direction of the molding resin and the linear expansion coefficient in the direction perpendicular to the flow direction (perpendicular direction / flow direction). The same test as above was performed using a resin case as a test sample. From this test result, as shown in FIG. 1 (b), it was confirmed that when the linear expansion coefficient ratio (perpendicular direction / flow direction) of the molding resin exceeds 3.0, the bubble generation rate sharply increased. In addition, the distortion of the resin case caused by the temperature cycle due to the anisotropy of the molding resin is applied as stress to the semiconductor chip mounted on the resin case, which adversely affects the characteristics. In particular, it has been found that a semiconductor sensor chip adversely affects sensor characteristics. On the other hand, the linear expansion coefficient ratio (perpendicular / perpendicular) of the flow direction of the molding resin and the direction perpendicular to the direction of flow is 1.0 to 3.0.
The resin case whose composition has been adjusted to fit within
As shown in FIG. 1 (b), it was confirmed that almost no bubbles were generated in the coating resin layer filled in the case even when the temperature cycle was applied.

[0015]

Embodiments of the present invention will be described below. That is, in the semiconductor pressure sensor of FIG. 2 and the semiconductor acceleration sensor of FIG.
The resin cases 3 and 11 integrally molded with 2 are made of, for example, PPS
(Polyphenylene sulfide) is formed by injection molding as a molding resin, wherein the molding resin has a coefficient of linear expansion close to that of the lead terminals 4 and 12 and a direction perpendicular to the flow direction of the molding resin. A resin having a small difference in linear expansion coefficient and a small anisotropy is used.

More specifically, when the lead terminals 4 and 12 are made of phosphor bronze (linear expansion coefficient is 1.78 × 10 ^-5 / ° C.), as a molding material for the resin case, as shown in FIG. As described in (b), the linear expansion coefficient is 0.7 to 0.7 of the linear expansion coefficient of phosphor bronze.
2.5 or less, and the ratio of the coefficient of linear expansion in the flow direction of the resin to the coefficient of linear expansion in the direction perpendicular to the flow direction (perpendicular /
The resin cases 3 and 11 are molded using a molding resin prepared such that the flow direction) is within 1.0 to 3.0.

As a result, even if a high-temperature and low-temperature cycle is repeatedly applied in an actual use state, the bonding interface between the lead terminal and the resin case is peeled off due to the difference in linear expansion coefficient, and the coating resin layers 6 and 14 are not used. The generation of bubbles is effectively suppressed, and corrosion and disconnection of the bonding wires 5 and 13 caused by the bubbles and adverse effects on sensor characteristics can be effectively prevented.

The stress σ generated in the resin due to thermal expansion and contraction due to the temperature cycle is given by the following equation.

[0019]

Σ = ∫E · α · dt where E: Young's modulus, α: Linear expansion coefficient Therefore, as the molding resin for the resin cases 3 and 11, the ratio of the linear expansion coefficient to the lead terminal is as described above. By using a resin that is small and has a small linear expansion coefficient ratio (perpendicular direction / flow direction) in the direction perpendicular to the flow direction of the molding resin and low anisotropy, the sensor chip 1 mounted on the resin case can be used.
8 can reduce the stress applied thereto and secure stable sensor characteristics.

Although the semiconductor pressure sensor and the semiconductor acceleration sensor have been described above, it goes without saying that similar effects can be obtained by implementing the present invention for various semiconductor devices other than these semiconductor sensors.

[0021]

As described above, according to the present invention, in a semiconductor device in which a resin case integrally formed with an external lead-out terminal is formed by injection molding of a thermoplastic resin, a linear expansion coefficient is used as a molding material. Is close to the linear expansion coefficient of the lead terminal material, and the ratio of the linear expansion coefficient in the flow direction of the resin oriented by injection molding to the linear expansion coefficient in the direction perpendicular to the flow direction (perpendicular direction / flow direction) is 1. By using a resin within a range of 0 to 3.0, peeling of the bonding interface between the resin case and the lead terminal is prevented, and the inside of the coating resin layer filled in the case by invasion of air and moisture from the surroundings is prevented. This effectively suppresses the generation of air bubbles and reduces the stress applied to the semiconductor chip mounted on the resin case. Location can be obtained.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram obtained by a performance test of a semiconductor device according to the present invention, and (a) a diagram showing a relationship between a linear expansion coefficient ratio between a molded resin / lead terminal and a bubble generation rate in a resin case; b) is a diagram showing the relationship between the ratio of the linear expansion coefficient of the molding resin in the perpendicular direction / flow direction and the bubble generation rate in the resin case.

FIG. 2 is a configuration sectional view of a semiconductor pressure sensor to which the present invention is applied;

FIG. 3 is a configuration sectional view of a semiconductor acceleration sensor to which the present invention is applied;

[Explanation of symbols]

 1,8 Sensor chip 3,11 Resin case 4,12 Lead terminal 5,13 Bonding wire 6,14 Coating resin

Claims (4)

[Claims] 1. A semiconductor chip is incorporated in a resin case in which lead terminals for external lead-out are insert-molded, an electrical connection is made between the semiconductor chip and the lead terminals, and a coating resin is filled in the resin case and sealed. In the stopped semiconductor device, the molding resin of the resin case is made of a thermoplastic resin, and the ratio of the linear expansion coefficient of the lead terminal to the linear expansion coefficient of the molding resin (molding resin / lead terminal) is 0.7 to 2; 5. The semiconductor device according to claim 5, wherein 2. A semiconductor chip is incorporated in a resin case in which lead terminals for external lead-out are insert-molded to electrically connect the semiconductor chip and the lead terminals, and the resin case is filled with a coating resin and sealed. In the stopped semiconductor device, the molding resin of the resin case is made of a thermoplastic resin, and has a linear expansion coefficient in a flow direction (flow direction) of the molding resin oriented by injection molding and a direction perpendicular to the flow direction (perpendicular direction). Wherein the ratio (perpendicular direction / flow direction) to the linear expansion coefficient is 1.0 to 3.0. 3. A semiconductor device comprising a combination of the constitutions of claim 1 and 2. 4. The semiconductor device according to claim 1, wherein the semiconductor device is a semiconductor sensor.