JPH01138434A - Semiconductor pressure sensor - Google Patents

Abstract

PURPOSE:To detect fluid pressure with high sensitivity and to improve the reliability of a diaphragm by providing a thin plate type diaphragm which has a much wider pressure detection surface than a silicone diaphragm. CONSTITUTION:Fluid to be measured which flows in from a fluid intake port 11 fills a pressure chamber 10 to apply equally distributed pressure to the surface of the diaphragm 6. This additional pressure causes the diaphragm 6 to flex matching with the pressure to place a one-point concentrated load on the silicone diaphragm 1 through a columnar projection 7. Consequently, the silicone diaphragm 1 is strained to cause the mismatching of the resistance value of Wheatstone bridge constitution by the piezoelectric resistance effect of silicon, so that the resistance mismatching is detected as an output. In this case, when pressure exceeding the breakdown pressure of the silicone diaphragm 1 is applied, the columnar projection 7 slides right before the breakage pressure to deform rubbery silicone resin 8 elastically, and thus the silicone diaphragm 1 is prevented from breaking, thereby improving the reliability of the diaphragm.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor pressure sensor, and particularly to a semiconductor pressure sensor that detects low pressure fluid pressure with high sensitivity.

[Conventional technology]

Conventionally, this type of semiconductor pressure sensor has a diffusion gauge resistor with a Wheatstone bridge structure embedded in the surface of a silicon diaphragm for measuring fluid pressure, and in particular, the distortion of the diaphragm caused by external pressure is measured by voltage using the piezoresistance effect of silicon. It is a structure that is converted into and detected.

[Problem that the invention attempts to solve]

The conventional semiconductor pressure sensor described above uses a silicon thick film as a pressure sensing medium. Therefore, in order to increase detection sensitivity to minute pressures, if the diaphragm area is uniform, the film thickness must be made thin, and if the film thickness is uniform, the diaphragm area must be made large. However, since the fluid pressure detection output sensitivity is inversely proportional to the square of the diaphragm film thickness, it is generally more efficient to reduce the film thickness than to enlarge the area. However, it is difficult to obtain a thick silicon film of approximately 20 μm or less by the enchiging method.

For example, when the silicon film thickness is 20 μm, 1 kg/
An output of about 150mV can be obtained with an air pressure of cm2, but
In order to detect a pressure of 4 to 5 g/cm2, the thickness of the diaphragm must be 5 μm and the area must be increased four times. Even in such a case, the output that can be obtained is at most 50 to 60
It is about mV.

As described above, simply changing the design constants of the diaphragm has the disadvantage that it is difficult to realize this in terms of manufacturability and reliability due to thinning.

The object of the present invention is to be able to detect such fluid pressure with high sensitivity,
It is an object of the present invention to provide a semiconductor pressure sensor that improves the manufacturability of the diaphragm and its reliability by making the film thinner.

[Means for solving problems]

The semiconductor pressure sensor of the present invention includes a silicon diaphragm in which a gauge resistor for pressure measurement is embedded and supported by a resin case, a columnar protrusion that abuts the center of the surface of the silicon diaphragm in a vertical direction, and a columnar protrusion that slides on the silicon diaphragm. a thin plate-like diaphragm which is freely held in the center by a rubber-like silicone resin and whose outer peripheral edge is fixed to the resin case; one end is fixed to the outer edge of the thin plate-like diaphragm and a fluid introduction part is disposed at the other end; The thin plate-like diaphragm and the cover form a pressure chamber for the fluid to be measured, and the pressure of the fluid causes the columnar protrusion to slide.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a longitudinal sectional view of a semiconductor pressure sensor for explaining one embodiment of the present invention.

As shown in FIG. 1, a silicon diaphragm 1 of such a semiconductor pressure sensor is fixed to a plastic case 3 via a glass member 2, and lead terminals 4 are embedded in this case 3. One end of this lead terminal 4 is electrically connected via a bonding wire 5 to a gauge resistor (not shown) buried in the surface of the silicon diaphragm 1 . Further, the tip of a columnar projection 7 held vertically at the center of a thin plastic diaphragm 6 is in contact with the center of the surface of the silicon diaphragm 1 . This columnar projection 7 is slidably inserted into a hole (not shown) provided in the center of the diaphragm 6 and is held on the diaphragm 6 by a rubber-like silicone resin 8. One side (lower side) of the outer edge of the diaphragm 6 is fixed to the outer edge of the plastic case 3, and the opposite side (upper side) is fixed to the outer edge of a cover 9 having a fluid introduction port 11 at one end. A space between the diaphragm 6 and the cover 9 forms a pressure chamber 10 for applying the pressure of the fluid introduced from the fluid introduction port 11 to the diaphragm 6 in an even distribution.

Next, the operation of the semiconductor pressure sensor having such a configuration will be explained. First, the fluid to be measured that flows in through the fluid introduction port 11 fills the pressure chamber 10 and applies uniformly distributed pressure to the surface of the diaphragm 6 . This additional pressure causes the diaphragm 6 to deflect in proportion to the pressure, applying a concentrated load to the silicon diaphragm 1 via the columnar projections 7.

As a result, the silicon diaphragm 1 is distorted, causing a mismatch in the resistance values configured in the Wheatstone bridge due to the piezoresistive effect of silicon.

This resistance misalignment is detected as an output. in this case,
If a pressure exceeding the breaking pressure of the silicon diaphragm 1 is applied, the columnar projections 7 slide before the breaking pressure and elastically deform the rubber-like silicone resin 8, thereby preventing the silicon diaphragm 1 from breaking. .

〔Effect of the invention〕

As explained above, the semiconductor pressure sensor of the present invention is provided with a thin plate-shaped diaphragm having a much wider pressure receiving surface than that of the silicon diaphragm on which the columnar projections are attached, and the pressure is applied to the silicon diaphragm as a single point concentrated load. By applying it to the diaphragm surface, there is an effect that fluid pressure can be detected with high sensitivity. In addition, by supporting the sliding movement of the columnar protrusions with rubber-like silicone resin, the silicone diaphragm can be prevented from being destroyed even if unexpected high pressure or pressure higher than specified is applied. be.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a high-sensitivity semiconductor pressure sensor for explaining one embodiment of the present invention. 1... Silicon diaphragm, 3... Plastic case, 6... Plastic diaphragm, 7...
Columnar projection, 8... Rubber-like silicone resin, 9... Cover, 10... Pressure chamber, 11... Fluid introduction boat.

Claims (1)

[Claims] A silicon diaphragm with a gauge resistor embedded therein for pressure measurement supported by a resin case, a columnar protrusion vertically abutting the center of the surface of the silicone diaphragm, and a rubber-like silicon diaphragm at the center that can freely slide over the columnar protrusion. A thin plate-shaped diaphragm held by resin and having an outer peripheral edge fixed to the resin case, and a cover having one end fixed to the outer edge of the thin plate-shaped diaphragm and a fluid introduction part arranged at the other end. A semiconductor pressure sensor, characterized in that a pressure chamber for a fluid to be measured is formed by the thin plate-like diaphragm and the cover, and the columnar protrusion is caused to slide by the pressure of the fluid.