JP2504737B2 - Pressure sensor unit - Google Patents

Description

TECHNICAL FIELD The present invention relates to a structure of a pressure sensor unit that converts pressure into an electric signal by utilizing a piezoresistive effect of a semiconductor diffusion resistance.

[Conventional technology]

In recent years, along with the development of IC manufacturing technology, a pressure sensor unit having a diaphragm type semiconductor pressure sensor chip in which a semiconductor diffusion resistance is formed on the surface of a single crystal silicon chip and the semiconductor diffusion resistance is used as a strain gauge is made. Became. The pressure sensor unit uses the piezoresistive effect that the electric resistance changes due to the stress of an external force applied to the conductor or the semiconductor, and the strain gauge is configured in a bridge type circuit to change the electric resistance due to the pressure change. It is intended to be taken as a voltage change in a bridge-type circuit, and its performance is far superior to that of conventional pressure gauges or pressure-electric converters. Business and demand are increasing.

FIG. 3 is a sectional view of a pressure sensor unit having a conventional semiconductor pressure sensor chip.

Reference numeral 31 is a diaphragm-type semiconductor pressure sensor chip that converts pressure into an electric signal by utilizing the piezoresistive effect of semiconductor diffusion resistance, and 32 is a pedestal, which is formed of, for example, # 7740 borosilicate glass, and is a diaphragm-type semiconductor. The pressure sensor chip 31 and the pedestal 32 are airtightly fixed. 34 is an airtight terminal body, 35 is the diaphragm type semiconductor pressure sensor chip
Stem that is the power supply terminal and output terminal of 31
Is hermetically fixed to the hermetic terminal body 34 using a sealing glass 36.

The airtight terminal body 34 to which the stem 35 is fixed and the pedestal 32 to which the diaphragm-type semiconductor pressure sensor chip 31 is fixed are airtightly fixed, and the diaphragm-type semiconductor pressure sensor chip 31 and the stem 35 are wire-bonded. Are electrically connected by.

37 is a potting resin that turns into a gel state after curing. It is cured on the diaphragm type semiconductor pressure sensor chip 31 to become a gel, and the diaphragm type semiconductor pressure sensor chip
Provides 31 electrical and mechanical protection.

33 is a pressure introducing pipe 33 for mechanically protecting the diaphragm type semiconductor pressure sensor chip 31 and the internal mounting part.
With the cap with a, the diaphragm type semiconductor pressure sensor chip 31 and the stem 35 are electrically connected by wire bond, and after covering the diaphragm type semiconductor pressure sensor chip 31 with the potting resin 37, the airtight terminal body 34 is sealed. The pressure sensor unit 30 of the relative pressure (differential pressure) type is thus configured.

38 is a circuit board of a pressure measuring device (not shown), 39 is solder, and the pressure sensor unit 30 is generally solder 39.
Is fixed to the circuit board 38 and is electrically connected to a circuit of a pressure measuring device (not shown). Reference numeral 40 is a tube, and the general pressure sensor unit 30 having the diaphragm type semiconductor pressure sensor chip 31 is adapted to normally apply pressure using the tube 40.

[Problems to be Solved by the Invention] However, in the case of the structure of the pressure sensor unit 30 as described above, the diffusion resistance forming surface 31a of the diaphragm type semiconductor pressure sensor chip 31 is exposed to the pressure medium, and the pressure sensor chip 31 Since the gel-like potting resin covering the surface 31a is sticky and impurities such as dust tend to adhere, the pressure medium is limited to clean air or clean non-corrosive gas. Could not be applied as a liquid.

However, a proposal for making the pressure sensor unit 30 a structure suitable for a liquid such as water has been made in a patent application or the like, and the main ones are shown below.

A method of exposing a surface 31b opposite to the diffusion resistance forming surface 31a to a pressure medium.

A metal diaphragm is installed on the front surface side of the diffusion resistance forming surface 31a, the liquid pressure is temporarily received by the metal diaphragm, and the pressure is transmitted to the diaphragm type semiconductor pressure sensor chip 31 via an intermediate pressure medium such as silicone oil. Method.

There are two methods, but in the case of, the pedestal 32 that serves as a pressure introduction hole to the diaphragm type semiconductor pressure sensor chip 31.
Since the size of the hole portion 32a is determined by the size of the diaphragm-type semiconductor pressure sensor chip 31, it cannot be made very large, and if it is repeatedly used in a liquid containing impurities (for example, seawater), the hole There is a drawback that the portion 32a is blocked by the adhesion of impurities, and in the case of, the structure is complicated by using a metal diaphragm, and when the linearity of the metal diaphragm is considered, Since the diameter of the flexible diaphragm cannot be reduced, the size of the pressure sensor unit also becomes large. Further, since the diaphragm type semiconductor pressure sensor chip 31 uses a semiconductor diffusion resistor as its name suggests, if the surface of the pressure sensor chip is exposed to light, a pn junction and a leak occur, and the environment is such that light enters, such as the sun. It has the drawback that the pressure sensor unit cannot be used under light.

An object of the present invention is to solve the above-mentioned problems, and to provide a small and thin pressure medium and a pressure sensor unit in which the use environment is not limited.

[Means for Solving Problems] In order to achieve the above object, the present invention has the following configuration. That is, a package including a bottomed first concave portion and an opening-shaped second concave portion connected to the first concave portion, a pedestal fixed to the bottom of the first concave portion, and a pedestal fixed to the pedestal. A pressure sensor chip, wherein the potting resin is filled with potting resin in the first and second recesses, the potting resin is a gel-like resin for the first layer enclosing the pressure sensor chip, The second layer is a rubber-like resin, and at least one of the first layer and the second layer potting resin is a black resin.

〔Example〕

FIG. 1 is a cross-sectional view of a main part of a pressure sensor unit showing an embodiment of the present invention, showing a state in which a pressure measuring device is mounted on an exterior, and FIG. 2 shows the pressure sensor unit of FIG. It is a top view of a diver's watch with a depth gauge showing an application example used as a depth gauge.

1 is a diaphragm type semiconductor pressure sensor chip that converts pressure into an electric signal by utilizing the piezoresistive effect of semiconductor diffusion resistance, 2 is a pedestal, for example, # 7740 borosilicate glass, and diaphragm type semiconductor pressure sensor chip 1 Is hermetically fixed on the base 2. Reference numeral 3 denotes a package, which has a bottomed first recessed portion 3a and a second recessed portion 3b formed continuously with the first recessed portion 3a, and the first recessed portion 3a and the second recessed portion 3b have openings on the pressure introducing side. And the opening of the second recess 3b has a larger diameter than the opening of the first recess 3a, and is made of, for example, ceramics, and the pedestal 2 is provided on the bottom of the first recess 3a of the package 3. It is fixed. When the pedestal 2 and the package 3 are fixed to each other, when a rubber-based adhesive, particularly silicone rubber is used, the material is excellent in heat resistance and cold resistance, has appropriate elongation, and has strain recovery property. Since it has excellent properties and absorbs vibrations and shocks, it is a diaphragm type semiconductor pressure sensor such as thermal strain from the package 3 or mechanical strain of the package itself due to mounting of the package 3 or external force. The stress other than the pressure displacement with respect to the chip 1 can be absorbed by the silicone rubber, and the thickness of the pedestal 2 can be made much thinner than the thickness of the pedestal 32 in FIG.

Although not shown in the package 3, the first concave portion
A pattern is formed on the interface 3c between the third recess 3b and the lower surface 3e of the package and the lower surface 3e of the package, and the interface 3c and the lower surface 3e are electrically connected by a buried through hole.
By wire-bonding the above pattern and the pattern of the diaphragm type semiconductor pressure sensor chip 1 to each other, an electric signal is exchanged with the diaphragm type semiconductor pressure sensor chip 1 in the package 3 from the lower surface 3e of the package 3. There is.

4 and 5 are black potting resins, which are electrically connected by wire-bonding the diaphragm type semiconductor pressure sensor chip 1 and the package 3 and then filled and cured on the surface of the diaphragm type semiconductor pressure sensor chip 1. The surface of the pressure sensor chip is protected electrically and mechanically.
Is configured. The potting resin 4 is a resin that becomes a gel state after curing, for example, a gel-like silicone rubber, and the potting resin 5 is a resin that becomes a rubber state after curing,
For example, it is a rubber-like silicone rubber. That is, since the gel-like resin having a pressure loss of zero due to its physical properties has adhesiveness and impurities such as dust are likely to adhere to the gel-like resin, in the present invention, the gel-like resin 4 is used as the first layer and the second layer is used as the second layer. The rubber-like resin is used for. Although the potting resins 4 and 5 are black in this embodiment, at least one of them is black, and the thinner the rubber-like resin 5, the better.

Reference numeral 7 is made of a resin ring such as Delrin or Teflon. Reference numeral 8 indicates the exterior of the pressure measuring device, for example, the exterior of the diver's watch with a depth gauge shown in FIG.
A recessed step portion 8a is provided in the. The resin ring 7 is disposed on the inner peripheral portion 8b of the stepped portion 8a of the exterior 8, and the pressure sensor unit 10 further includes an inner portion of the resin ring 7 so that the outer peripheral portion 3d of the package 3 compresses the resin ring 7. Circumference 7a
And is fixed to the exterior 8. That is, since the resin ring 7 is compressed by the inner peripheral portion 8b of the stepped portion 8a of the outer casing 8 and the outer peripheral portion 3d of the package 3, the pressure sensor unit 10 is thus fixed to the outer casing 8 and a waterproof function is secured. It has become like.

Reference numeral 6 denotes a protective plate having a hole having a shape as shown in 6a of FIG. 2, for example, so that the diaphragm type semiconductor pressure sensor chip 1 is not directly struck by a rod or the like, or some object does not hit the potting resin 5. It is for the purpose of doing so and may be omitted when there is no danger as described above.

Reference numeral 11 is a spring, and 12 is a circuit board. The pattern on the lower surface 3e of the package 3 of the pressure sensor unit 10 and the circuit board 12 are electrically connected via the spring 11, and an electric power of a pressure measuring device not shown. It is electrically connected to the circuit.

An application example of the pressure sensor unit as described above is the diver's watch with a water depth gauge shown in FIG. 2, which is an embodiment showing application to a small portable device.

14 is a liquid crystal cell, 15, 16, and 17 are push buttons,
By pressing the push button 17, the water depth measurement mode is called up. At this time, when the pressure sensor unit 10 detects the water pressure, the liquid crystal cell 14 can display a water depth such as "20 m".

〔The invention's effect〕

As is apparent from the above examples, according to the present invention, since the diaphragm type semiconductor pressure sensor chip is covered with the potting resin, it is possible to measure the pressure of not only the gas but also the liquid having impurities, and the pressure medium is not limited. .
Further, since the metal diaphragm is not used, the structure is simple, the size and thickness can be reduced, and not only the cost can be reduced but also the device can be used for a small portable device such as a wristwatch.

In addition, since at least one of the potting resins uses a black resin, at least one of them is exposed to the sun such as barometric pressure, or when it is exposed to the sun such as when using a water depth gauge. In a usage condition where sunlight is likely to enter, such as when exposed to light, it is possible to prevent leakage due to light, and in an environment where light enters,
For example, the pressure sensor unit can be used even under the sun.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part of a pressure sensor unit showing an embodiment of the present invention, and FIG. 2 is a plan view of a diver's watch with a depth gauge showing an application example in which the pressure sensor unit of FIG. 1 is used as a depth gauge. FIG. 3 is a sectional view of a pressure sensor unit having a conventional semiconductor pressure sensor chip. 1, 31 ... Diaphragm type semiconductor pressure sensor chip,
2, 32 ... Pedestal, 3 ... Package, 4 ... Gel-like potting resin, 5 ... Rubber-like potting resin.

Claims (1)

(57) [Claims] 1. A bottomed first concave portion and a second concave portion formed so as to be continuous with the first concave portion, wherein the first concave portion and the second concave portion have an opening on a pressure introducing side. And a pedestal fixed to the bottom of the first recess of a package in which the opening of the second recess has a larger diameter than the opening of the first recess, and a pressure sensor chip fixed to the pedestal. In the pressure sensor unit in which the potting resin is filled in the first and second recesses, the potting resin is a gel-like resin for the first layer wrapping the pressure sensor chip,
A pressure sensor unit, wherein the second layer is a rubber-like resin, and at least one of the first layer and the second layer potting resin is a black resin.