JPH0727786A - Semiconductor-type acceleration sensor - Google Patents

Abstract

PURPOSE:To reduce the aged deterioration of sensor characteristics and to enhance the stability and the temperature characteristic of an acceleration sensor by a method wherein a ceramic substrate is bonded to a metal stem by silicone-based adhesive which is provided with elasticity after hardening. CONSTITUTION:A semiconductor-type acceleration sensor element in which a beam part 4 is formed, provided with a plate spring part in its base part and a mass part 7 in its tip part, and a peripheral circuit 10 are mounted on a ceramic substrate 9, and the substrate 9 is bonded to a metal stem 1 via an adhesive layer 13. Then, the adhesive layer is formed so as to be divided into a plurality of stripes, spaces 20 are formed in divided adhesive layers 13, the air flows through the spaces 20 and the hardening of the adhesive layers 13 is promoted. As an adhesive which forms the adhesive layers 13, a thermoset resin and a room-temperature hardening resin are enumerated. However, in order to reduce thermal damage to an electronic component mounted on the ceramic substrate 9, a room-temperature hardening-type silicone-based adhesive is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor type acceleration sensor.

[0002]

2. Description of the Related Art The structure of a conventional semiconductor type acceleration sensor will be described with reference to FIGS. In the figure, reference numeral 1 is a flat metal stem, and a plurality of through holes for electrical connection with the outside are formed in the peripheral portion thereof, and a hard glass 2 is welded to each of the plurality of through holes. By doing so, the lead terminal 3 is fixed. Lead terminal 3 and stem 1
Are electrically insulated from each other by the hard glass 2, and the hard glass 2 is well airtightly interposed. A semiconductor type acceleration sensor element including a cantilever (beam portion) 4 and a pedestal 5 is mounted on the stem 1.

The cantilever 4 is fixed to the pedestal 5 by forming a thin plate spring portion 6 on the base by etching the substrate. In addition, the thick-walled portion formed at the tip portion thereof has a free end formed as a mass portion 7 that is capable of displacing a part thereof according to the acceleration to be measured. Further, a strain gauge is formed in the leaf spring portion 6, and the strain gauge is electrically connected to a peripheral circuit 10 formed on the ceramic substrate 9 by wire bonding, and the peripheral circuit 10 wire-bonds a wire wire 11. Is electrically connected to the lead terminal 3.

Reference numeral 12 denotes a stopper, the cross-sectional shape of which is an inverted L-shape and is erected so as to limit the maximum amount of upward displacement of the cantilever 7. Reference numeral 13 denotes an adhesive layer that adheres and fixes the ceramic substrate 9 to the metallic stem 1, and a thermosetting epoxy adhesive is used, and is applied to the entire opposing surfaces to which both can be adhered.

Reference numeral 14 is a metallic shell having a flange portion 15 formed on the peripheral portion thereof, and a concave portion is formed by pressing to form a box shape, and the peripheral portion is welded to the peripheral portion of the metallic stem 1 and hermetically sealed. Has been done. In addition, this airtight seal is the stem 1
The metal shell 14 is covered with the stem 1 from above so that the peripheral portion of the metal shell 14 is aligned with the collar portion 15 of the metal shell 14, and after contacting them, a pressure is applied by a press between the metal shell 14 and the stem 1. The two are welded by energizing them.

When an acceleration is applied to the semiconductor type acceleration sensor constructed as above in the vertical direction,
The mass portion 7 formed at the free end of the cantilever 4 vibrates in the vertical direction, and as a result, the leaf spring portion 6 is distorted. The resistance value of the semiconductor strain gauge changes according to the magnitude of the strain, and is detected as an electric signal.

[0007]

However, since the ceramic substrate 9 is adhesively fixed to the metallic stem 1 through the epoxy adhesive layer 13 as described above, the following problems occur. That is, firstly, since the epoxy adhesive has a property of being usually heated and cured, residual stress remains as a stress inside the adhesive layer 13 after thermal curing.

Secondly, an epoxy adhesive layer 13 and
Due to the difference in thermal expansion coefficient between the ceramic substrate 9 and the metal stem 1, thermal stress is applied to the ceramic substrate 9 and the temperature characteristics of the semiconductor type acceleration sensor element change.

Thirdly, in order to match the coefficient of thermal expansion of the ceramic substrate 9 with the coefficient of thermal expansion of the metal stem 1, the coefficient of thermal expansion of the ceramic substrate 9 must be close to the coefficient of thermal expansion of the metal stem 1. is there. That is, it is necessary to use an expensive material such as a nickel alloy or Kovar having a small thermal expansion coefficient, which causes an increase in cost.

[0010]

A semiconductor type acceleration sensor according to the present invention comprises a beam portion, a plate spring portion at the base of the beam portion, and a mass portion at the tip. A sensor element, a substrate on which the semiconductor type acceleration sensor element and its peripheral circuits are mounted, a metal stem to which the substrate is bonded via an adhesive layer, and a metal stem covering the stem from above the metal stem. In a semiconductor acceleration sensor having a metallic shell whose peripheral portions are welded to each other, the adhesive layer is divided into a plurality of portions, and the adhesive layer is made of a silicone adhesive.

[0011]

According to the above structure, the ceramic substrate is adhered to the metallic stem with a silicone adhesive having elasticity after curing, and the elasticity of the adhesive layer is used to absorb and accumulate thermal stress. To prevent

[0012]

Embodiments of the present invention will be described in detail with reference to FIGS. 1 and 2, the same or equivalent elements as those in the configurations described in FIGS. 5 and 6 are designated by the same reference numerals, and detailed description thereof will be omitted. That is, the adhesive layer 13 shown in FIG. 1 and FIG.
Spaces are formed between the adhesive layers 13 by dividing the adhesive layers 13 into strips (or three rows), and air flows through the spaces 20 to promote curing of the adhesive layers 13. In addition,
The adhesive forming the adhesive layer 13 includes a thermosetting type and a room temperature curing type. In order to reduce thermal damage to electronic components mounted on the ceramic substrate 9, the room temperature curing type adhesive is used. You can use one. The room temperature curing type includes a type that reacts with moisture in the air and a dealcohol type. In addition, the provision of the space 20 promotes release of gas and the like contained in the adhesive layer 13 into the air during curing.

Further, although the adhesive layer 13 is divided into a plurality of strips in the above embodiment, in order to further shorten the time required for the adhesion, as shown in FIGS. 3 and 4, the adhesive layer 13 is made finer. Needless to say, it may be divided into squares. In FIGS. 3 and 4, the same or equivalent components as those shown in FIGS. 5 and 6 are designated by the same reference numerals and the description thereof is omitted.

[0014]

As described above, according to the present invention, the following effects are exhibited. That is, after curing,
Since the adhesive layer has rubber elasticity, the residual stress is smaller than that of the epoxy adhesive, the secular change of the sensor characteristics is small, and the stability and temperature characteristics of the sensor characteristics can be improved.

Further, the thermal strain due to the difference in thermal expansion coefficient between the ceramic substrate and the metal stem is absorbed by the rubber elasticity. Therefore, a general and inexpensive steel plate can be used as the material of the metal stem, and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional explanatory view for explaining an embodiment according to the present invention.

FIG. 2 is an explanatory plan view of the embodiment shown in FIG.

FIG. 3 is a sectional explanatory view for explaining another embodiment according to the present invention.

FIG. 4 is an explanatory plan view of another embodiment shown in FIG.

FIG. 5 is a perspective view of a semiconductor type acceleration sensor for explaining a conventional example.

6 is a cross-sectional view taken along the line XX of the explanatory view shown in FIG.

[Explanation of symbols]

 1 Metal Stem 4 Cantilever 5 Pedestal 6 Leaf Spring Part 7 Mass Part 9 Ceramic Substrate 10 Peripheral Circuit 13 Adhesive Layer 20 Space

Claims (1)

[Claims] 1. A semiconductor type acceleration sensor element comprising a beam (4), a leaf spring (6) at the base of the beam, and a mass (7) at the tip. A substrate (9) on which the semiconductor type acceleration sensor element and its peripheral circuit (10) are mounted, and the substrate is an adhesive layer (13).
A semiconductor acceleration (1) having a metal stem (1) adhered thereto via a metal shell, and a metal shell (14) covering the stem from above the metal stem and having peripheral portions (15) welded to each other. In the sensor, the semiconductor type acceleration sensor characterized in that the adhesive layer (13) is provided in a plurality of divided portions, and the adhesive layer (13) is formed of a silicone adhesive.