JP2551281Y2 - Acceleration sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an acceleration sensor integrated with a circuit board in which an acceleration sensor unit is not mounted on a circuit board.

[Conventional technology and its problems]

A semiconductor type acceleration sensor using a semiconductor substrate uses a small cantilever manufactured by anisotropic etching or the like. However, in order to extract signals from this chip, wire bonding must be performed after bonding to a hybrid integrated circuit (HIC) substrate or the like, which requires a bonding surface and space for wire bonding. There was not much merit of the small size of the chip, and the cost was increased by mounting.

An object of the present invention is to provide a high-sensitivity acceleration sensor integrated with a circuit board in which the acceleration sensor section and the circuit board section are configured on the same board, and the mounting of the acceleration sensor section on the circuit board is eliminated. .

[Means for solving the problem]

In order to achieve the above object, in the acceleration sensor of the present invention, a part of the ceramic substrate is formed in a thin portion of a cantilever structure, and a weight portion formed by a thick portion is integrally provided at a tip of the thin portion. The present invention is configured to include a cantilever for sensing vibration, a strain gauge provided on the ceramic substrate and arranged on the cantilever, and a circuit for processing a detection signal of the strain gauge.

[Action]

By providing the cantilever with a thin portion, distortion is more likely to occur. When the vibration is transmitted to the stem, the cantilever having a free weight portion swings with high sensitivity, and is detected by a strain gauge due to the stress applied to the root portion of the cantilever at this time.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an acceleration sensor unit made of a ceramic substrate before a cover is closed.

A substrate 2 is adhered to the center of the metal stem 1, and an output pin 3 is arranged close to the substrate 2. The output pin 3 is fixed to the stem 1 by a glass seal 4 as shown in FIG.

The substrate 2 is, for example, a ceramic substrate such as alumina, on which a processing circuit section 6 such as an amplifier circuit and a temperature compensation circuit and an acceleration sensor section 7 for detecting vibration are integrally formed.

The processing circuit unit 6 is connected to the output pin 3 by a wire 5, and a signal is extracted from the output pin 3. Wire 5
Is made by wire bonding with an Al wire or an Au wire.

The acceleration sensor unit 7 is constituted by a cantilever 8 having a cantilever structure integrally formed and located in the concave portion 1a of the stem 1 and a strain gauge 9 for sensing vibration. As shown in FIG. 3, the cantilever 8 is formed integrally with a thin portion 10 and a thick portion 11, which forms a weight portion, of a part of the ceramic substrate. The strain gauge 9 is formed by printing a thick-film strain resistor on a root portion 12 to which stress is applied when the cantilever 8 bends, and the resistor is connected to the processing circuit section 6 by a thick-film-printed conductor. ing. Reference numeral 13 denotes a metallic protective cover which is hermetically welded to the stem 1.

Next, a specific example of manufacturing the cantilever of the acceleration sensor unit will be described.

(1) Method by ceramic powder molding The ceramic substrate produces powder dried by a spray dryer from a liquid obtained by mixing ceramic powder in a solvent,
Using this powder, a shape including the cantilever of the acceleration sensor portion is injection molded, and then fired. As shown in FIG. 1, the cantilever has a cantilever structure penetrated in a U-shape, and has a thin portion thinner than the thickness of the substrate and a tip of the substrate, as shown in FIG. The same thick portion as the thickness is provided. This thick portion acts as a weight for improving the sensitivity.

(2) Method using a laminate substrate A liquid in which a ceramic powder is mixed with a solvent is dried on a conveyor to a predetermined thickness to produce a green sheet, which is processed, cut, drilled, laminated, and the like. Bake.

When a ceramic substrate is formed using two green sheets, one flat plate and a flat plate with a hole are laminated on one part thereof, and the preliminarily fired ceramic substrate 20 is laser-processed and then fired to finish. That is, the ceramic substrate 20
As shown in FIG. 4, a portion shown by a broken line 21 is cut by a laser to form a cantilever 22 of the same acceleration sensor section as in FIG. In the ceramic substrate 20 using the laminated substrate as described above, the thin portion 23 of the cantilever and the thick portion 24 forming the weight can be formed at the same time, as shown in FIG.

Next, the operation of the above embodiment will be described. When the vibration is transmitted to the stem 1, the free cantilever 8 swings due to the vibration because the ceramic substrate 2 on which the processing circuit section 6 is formed is adhered and fixed to the stem 1. At this time, the vibration (acceleration) is measured by detecting the strain caused by the vibration with the strain gauge 9 because the weight 11 at the tip of the cantilever 8 swings with high sensitivity.

[Effect of the invention]

As described above, according to the present invention, since the processing circuit board and the cantilever are manufactured on the same substrate, the connection between the sensor section of the cantilever and the processing circuit section can be performed in the same step as the conductor for forming the processing circuit section. In addition, the processing circuit board and the cantilever of the acceleration sensor part are made thinner with a part of the ceramic substrate and the tip is made thicker to unify the weight, eliminating the need to glue the weight later. And the sensitivity of the sensor can be increased. Furthermore, the cantilever is slightly larger than when a semiconductor acceleration sensor is mounted, but the mounting (the bonding surface and the place where wire bonding is performed) is not required, so the same downsizing is possible.

[Brief description of the drawings]

1 is a plan view of the acceleration sensor unit, FIG. 2 is a cross-sectional view taken along the line AA in FIG. 1 before the cover is sealed, and FIG. 3 is FIG.
FIG. 4 is a cross-sectional view taken along line B-C, FIG. 4 is a plan view of the laminate substrate before cutting, and FIG. 5 is a cross-sectional view taken along line CC in FIG. DESCRIPTION OF SYMBOLS 1 ... stem, 2 ... ceramic board, 6 ... processing circuit part, 7 ... acceleration sensor part, 8 ... cantilever, 9 ...
… Strain gauge, 11… weight part.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Koichi Itoigawa No. 1 Noda, Toyota, Oguchi-cho, Niwa-gun, Aichi Prefecture Inside Tokai Rika Electric Works, Ltd. (56) References JP-A-1-315173 (JP, A JP-A-61-97572 (JP, A) JP-A-2-41165 (JP, U) JP-A-3-91972 (JP, U)

Claims (1)

(57) [Scope of request for utility model registration] 1. A cantilever for sensing vibration, wherein a part of a ceramic substrate is formed in a thin portion of a cantilever structure, and a weight portion formed by a thick portion is integrally provided at a tip of the thin portion; An acceleration sensor provided on a substrate, comprising: a strain gauge disposed on the cantilever; and a circuit for processing a detection signal of the strain gauge.