JPH08160071A - Silicon accelerometer - Google Patents

Abstract

PURPOSE: To improve the yield of the upper stopper (IC) of an accelerometer and prevent the performance deterioration of the accelerometer caused by the abnormal vibration of the upper stopper (IC) and, at the same time, to improve the reliability of the connection between the IC and a sensor chip (pendulum). CONSTITUTION: A pendulum 1 is composed of a single-crystal silicon substrate and is provided with a frame section 3, weight section 2 and beam section 4. An upper stopper (IC) 6 and lower stopper 7 are respectively superposed upon the upper and lower surfaces of a pendulum 1 with gaps Ga and Gb in between. A plurality of piezo-resistance elements 5a are formed on the beam section 4 and a bridge circuit 5 connecting the elements 5a to each other is constituted on the pendulum 1. The output of the bridge circuit 5 is detected by means of a signal detecting circuit 8. The detecting circuit 8 is formed on the internal surface of the upper stopper 6 and the stopper 6 is connected to the frame section 3 with an anisotropic conductive adhesive layer 21. In addition, the bridge circuit 5 is electrically connected to the detecting circuit 8 and the lower stopper 7 is joined to the frame section 3 through a spacer 22. Moreover, the upper stopper 6 is composed of an insulating substrate or semiconductor substrate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon accelerometer, and more particularly to improving the yield of an upper stopper (IC), improving the performance of a signal detection circuit and connecting an upper stopper (IC) and a pendulum (sensor chip). Involved in improving reliability.

[0002]

2. Description of the Related Art As an example of a conventional silicon accelerometer, an accelerometer disclosed in Japanese Patent Laid-Open No. 6-242141 will be described with reference to FIG. The pendulum (sensor chip) 1 is made of a silicon single crystal substrate, and has a frame portion 3, a weight portion 2 arranged in an island shape in the frame portion 3 with a gap, and a weight portion 2.
A thin beam portion 4 that bridges and supports the frame portion 3 is formed by chemical etching. An upper stopper (IC) 6 and a lower stopper 7 for holding the beam portion 4 by limiting the displacement of the weight portion 2 are joined to the upper side and the lower side of the pendulum 1, respectively. Recesses 6 a and 7 a are formed on the bottom surface of the upper stopper 6 and the upper surface of the lower stopper 7 at the portions facing the beam portion 4 and the weight portion 2, and voids Ga and Gb are formed between the pendulum 1 and the dentrum 1. A plurality of piezoresistive elements 5a are formed on the beam portion 4 and are connected to each other to form a bridge circuit 5 on the pendulum 1.

A signal detection circuit 8 is formed on the upper surface of the upper stopper (IC) 6. The circuit 8 is a circuit for detecting the output of the bridge circuit according to the input acceleration. The bridge circuit 5 on the pendulum 1 and the signal detection circuit 8 are connected by a plurality of bonding wires 9. A terminal (11) for external connection is provided on a base (pedestal) 10 to which the lower stopper 7 is attached, and a signal detection circuit 8 is connected to the terminal 11 through a bonding wire 12.

The signal detection circuit 8 is connected to the bridge circuit 5
There is also a case where a circuit for supplying a drive voltage to the circuit and a signal processing circuit for compensating for the temperature variation due to the piezoresistive element with respect to the detection output of the bridge circuit.

[0005]

As described above, in the conventional accelerometer, the concave portion 6a is formed on the back surface of the upper stopper (IC) 6 on which the signal detection circuit 8 is formed, and the concave portion 6a is formed. Process is I
Since it is necessary in the initial step of the manufacturing process of C, there is a problem that the yield of IC manufacturing is reduced by the amount of defective products in the recess forming step.

Further, the formation of the concave portion 6a causes a stress different from that of a normal IC having no concave portion to be applied to the signal detecting circuit 8, which may adversely affect the performance of the signal detecting circuit 8. Since the IC 6 and the pendulum (sensor chip) 1 are connected by many bonding wires 9, the connection reliability is low.

An object of the present invention is to solve these conventional problems, improve the yield of the IC (upper stopper), prevent the performance deterioration due to the recess of the signal detection circuit, and prevent the IC.
It aims to improve the reliability of the connection between the pendulum and the pendulum.

[0008]

[Means for Solving the Problems]

(1) In the invention of claim 1, the signal detection circuit is formed on the inner surface of the upper stopper facing the pendulum, and the frame portion of the pendulum and the upper stopper are joined by an anisotropic conductive adhesive layer. The bridge circuit and the signal detection circuit are electrically connected to each other through the conductive adhesive layer.

(2) In the invention of claim 2, in the above-mentioned (1), the anisotropic conductive adhesive layer interposed between the pendulum and the upper stopper also functions as a spacer, and has a thickness substantially equal to that of the spacer. Spaced voids are formed. (3) In the invention of claim 3, in the above (1), the upper stopper is made of an insulating substrate or a semiconductor substrate.

(4) In the invention of claim 4, in (1), a spacer is interposed between the frame portion of the pendulum and the lower stopper. (5) In the invention of claim 5, in any one of (1) to (4), a terminal portion for connecting the signal detection circuit to the outside is formed at an end portion of the upper surface of the frame portion of the pendulum.
A part of the upper stopper facing the terminal portion is cut out.

(6) In the invention of claim 6, in the above item (5), the terminal portion is connected through a bonding wire to an external terminal provided on the base (pedestal) to which the lower stopper is attached. (7) In the invention of claim 7, in any one of the above (1) to (4), a part of the periphery of the upper stopper is extended and projected from the end edges of the opposing pendulum and lower stopper, A terminal portion for external connection is formed on the inner surface.

(8) In the invention of claim 8, in the above item (7), the terminal portion is connected to an external terminal provided on a base (pedestal) to which a lower stopper is attached by a conductive adhesive.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention is shown in FIG. 1 by giving the same reference numerals to the portions corresponding to those in FIG. In the present invention, the concave portion 6a conventionally formed on the inner surface of the upper stopper 6 is eliminated, and the signal detection circuit 8 is formed on the inner surface. The frame portion 3 of the pendulum 1 and the upper stopper 6 are joined by the anisotropic conductive adhesive layer 21. As is well known for the anisotropic conductive adhesive layer 21, conductive beads (metal particles, or polymer compound particles or glass particles plated with metal) are dispersed in an insulating adhesive. In the case of FIG. 1, there is conductivity in the vertical direction but not in the horizontal direction. Therefore, even if a plurality of conductive paths exist in the vertical direction, they do not short-circuit with each other. Through this anisotropic conductive adhesive layer 21, the terminals 2 on the frame 3 are
3 (including the terminal derived from the bridge circuit 5) and the terminal 8a derived from the signal detection circuit 8 are electrically connected (claim 1). As a result, the conventional connection by the bonding wire 9 is abolished, and the reliability of the connection is improved.

In the example of FIG. 1, the anisotropic conductive adhesive layer 21 also functions as a spacer, and voids Ga are formed at intervals substantially equal to its thickness (claim 2). As the material of the upper stopper (IC) 6, an insulating substrate such as glass or ceramic or a semiconductor substrate such as a silicon single crystal substrate can be used (claim 3). On the other hand, the lower stopper may use the same material as the upper stopper 6, but since it does not particularly form an electronic circuit, a conductor such as metal may be used. In this example, the recess 7a conventionally formed on the upper surface of the lower stopper 7 is eliminated because the number of steps required for its manufacture is large and the cost is high. Instead, a spacer 22 is sandwiched between the frame 3 and the lower stopper 7. They are joined (claim 4). Then, the gap Gb is formed at intervals substantially equal to the thickness of the spacer 22.

A terminal portion 24 for connecting the signal detection circuit 8 to the outside is formed at the end of the upper surface of the frame portion 3, and the terminal portion 2 is formed.
A part of the upper stopper 6 which faces 4 is cut out (Claim 5). In the example of FIG. 1, the terminal portion 24 is connected through a bonding wire 12 to an external terminal 11 provided on the base (pedestal) 10 to which the lower stopper 7 is attached (claim 6).

FIG. 2 shows a modified embodiment, in which a part of the periphery of the upper stopper 6 is extended and protruded from the end edges of the pendulum 1 and the lower stopper 7 which are opposed to each other, and the inner surface thereof is used for external connection. The terminal portion 24 is formed (claim 7). The terminal portion 24 is connected to the external terminal 11 provided on the base 10 with the conductive adhesive 25, thereby further improving the connection reliability (claim 8).

[0017]

According to the present invention, since the concave portion 6a of the upper stopper (IC) 6 which has been a problem in the related art is eliminated, defects in the concave portion manufacturing process are eliminated and the IC yield can be improved accordingly. Further, since there is a concave portion in the related art, it is possible to eliminate the fact that abnormal stress acts on the IC (signal processing circuit) and the performance thereof is deteriorated.

In the present invention, the upper stopper (IC)
Since the connection between 6 and the pendulum 1 is performed by the anisotropic conductive adhesive layer 21 instead of the conventional bonding wire, the reliability of the connection can be greatly improved as compared with the conventional case.

[Brief description of drawings]

FIG. 1 is a principle cross-sectional view showing an embodiment of the present invention.

FIG. 2 is a sectional view showing the principle of another embodiment of the present invention.

FIG. 3 is a sectional view showing the principle of a conventional silicon accelerometer.

Claims (8)

[Claims] 1. A frame portion comprising a silicon single crystal substrate,
A pendulum having a weight portion arranged through a gap in the frame portion and a thin beam portion that bridges the weight portion to the frame portion to support the pendulum, and is stacked on the upper and lower sides of the pendulum, An upper stopper and a lower stopper each having a space formed between the beam portion and the weight portion; a bridge circuit formed on the upper surface of the pendulum by connecting the piezoresistive element formed on the beam portion; A silicon accelerometer having a signal detection circuit for detecting an output of a bridge circuit according to acceleration, wherein the signal detection circuit is formed on an inner surface of the upper stopper facing the pendulum, and a frame portion of the pendulum and an upper stopper. Is bonded with an anisotropic conductive adhesive layer, and the bridge circuit and the signal detection circuit are electrically connected through the anisotropic conductive adhesive layer. The butterfly, silicon accelerometers. 2. The anisotropic conductive adhesive layer interposed between the pendulum and the upper stopper also functions as a spacer, and the voids are formed at intervals substantially equal to the thickness thereof. A silicon accelerometer characterized by being used. 3. The silicon accelerometer according to claim 1, wherein the upper stopper is made of an insulating substrate or a semiconductor substrate. 4. The silicon accelerometer according to claim 1, wherein a spacer is interposed between the frame portion of the pendulum and the lower stopper. 5. The terminal portion for connecting the signal detection circuit to the outside is formed at an end portion of an upper surface of a frame portion of the pendulum according to claim 1, and the terminal portion is opposed to the terminal portion. Silicon accelerometer characterized in that a part of the upper stopper is cut out. 6. The silicon accelerometer according to claim 5, wherein the terminal portion is connected to an external terminal provided on a base (pedestal) to which the lower stopper is attached through a bonding wire. 7. The method according to claim 1, wherein a part of the periphery of the upper stopper is extended and protrudes from the end edges of the pendulum and the lower stopper which are opposed to each other, and is connected to an inner surface thereof for external connection. A silicon accelerometer in which a terminal portion is formed. 8. The silicon accelerometer according to claim 7, wherein the terminal portion is connected to an external terminal provided on a base (pedestal) to which the lower stopper is attached by a conductive adhesive. .