JP2617174B2 - Pressure measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a structure of a pressure sensor unit having a diaphragm type semiconductor pressure sensor chip for converting pressure into an electric signal by utilizing a piezoresistive effect of a semiconductor diffusion resistor. In particular, the present invention relates to a pressure sensor unit mounting structure suitable for mounting on a small-sized pressure measuring device.

[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 that forms a semiconductor diffusion resistor on the surface of a single crystal silicon chip and uses the semiconductor diffusion resistor as a strain gauge has been created. Became.

The pressure sensor unit utilizes a piezoresistive effect in which the electric resistance changes due to the stress of an external force applied to a conductor or a semiconductor, and the pressure change is changed by forming the strain gauge into a bridge type circuit. It is intended to convert this into a voltage change of a bridge type circuit, and its performance is much better than that of a conventional pressure gauge or pressure-electrical converter. And demand is increasing.

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

31 is a diaphragm type semiconductor pressure sensor chip that converts pressure into an electric signal by using a piezoresistive effect of a semiconductor diffusion resistor, 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 hermetically 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 hermetic terminal body 34 to which the stem 35 is fixed as described above and the pedestal 32 to which the diaphragm type semiconductor pressure sensor chip 31 is fixed are hermetically fixed, and furthermore, a wire bond is provided between the diaphragm type semiconductor pressure sensor chip 31 and the stem 35. Are electrically connected to each other.

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 bonding, and then airtightly fixed to the airtight terminal body 34, and thus a relative pressure (differential pressure) type pressure sensor. A unit 30 is configured.

38 is a circuit board of the pressure measuring device, 39 is solder, and the pressure sensor unit 30 is generally a circuit board using solder 39.
It is fixed to 38 and is electrically connected to a circuit of a pressure measuring device (not shown). 37 is a tube, a general pressure sensor unit 30 having a diaphragm-type semiconductor pressure sensor chip 31 is such that pressure is usually applied using a tube 37, and the shape itself of the pressure sensor unit 30 is also large. This makes it impossible to incorporate it into a compact pressure measuring device. At the same time, when the diffusion resistance forming surface 31a of the diaphragm type semiconductor pressure sensor chip 31 is directly exposed to the pressure medium as shown in FIG. 3, the pressure medium is limited to a non-corrosive gas.

FIG. 4 is a main part showing a structure of a pressure sensor unit having a semiconductor pressure sensor chip used in a conventional pressure measuring device developed to eliminate these disadvantages and a mounting structure of an exterior of the pressure measuring device. It is sectional drawing.

41 is a diaphragm type semiconductor pressure sensor chip that converts pressure into an electric signal by utilizing the piezoresistive effect of a semiconductor diffusion resistor, and 42 is a pedestal, for example, formed by polishing # 7740 borosilicate glass. The diaphragm-type semiconductor pressure sensor chip 41 and the pedestal 42 are hermetically fixed. Reference numeral 43 denotes a substrate made of, for example, an epoxy resin containing glass. The substrate 43 is bonded to a base 42, and the diaphragm-type semiconductor pressure sensor chip 41 and the substrate 43 are electrically connected by wire bonding. 44 is a pressure sensor chip 41
The cap 43 is made of, for example, ceramics and the like, and is electrically connected to the substrate 43 and the cap 44 by soldering the stem 45 to the substrate 43 and the cap 44. 40 are configured.

47 is an O-ring, 48 is an exterior of the pressure measuring device, 49 is a fixing ring, and a screw portion 49a provided on the outer periphery of the fixing ring 49 is screwed into a screw portion 48a provided on the exterior 48 of the pressure measuring device, The pressure sensor unit 40 is fixed to the exterior 48 while compressing the O-ring 47. That is,
Since the O-ring 47 is compressed, the pressure sensor unit 40 is airtightly fixed to the exterior 48 while ensuring a waterproof function. The pressure receiving surface of the diaphragm type semiconductor pressure sensor chip 41 of the pressure sensor unit 40 is a surface 41b opposite to the diffusion resistance forming surface 41a, and has a structure in which a pressure medium can be a gas or a fluid.

FIG. 5 is a sectional view of a main part of a water pressure detecting device showing a conventional embodiment devised as a method of mounting a pressure sensor unit on the exterior of a small pressure measuring device.
The conventional mounting method described in Japanese Patent Application Laid-Open Publication No. H10-260,000 is shown, and a strain gauge, a semiconductor pressure sensor chip, or another element may be used as the pressure detecting element.

Reference numeral 51 denotes a water pressure detecting element, 53 denotes a ceramic substrate, and the water pressure detecting element 51 is provided above the center of the ceramic substrate 53. 54 is a detection device case, 56 is a protection cover, a ceramic substrate 53 is fixed to the lower surface of the detection device case 54 by soldering or the like, and a protection cover 56 is attached to the upper surface of the detection device case 54, and the water pressure detection device, The pressure sensor unit 50 is configured.

57 is an airtight packing, 58 is a watch case, and a water pressure detecting device, that is, the pressure sensor unit 50 compresses the airtight packing 57 by screwing a screw portion 54a of the detecting device case 54 into a screw portion 58a of the watch case 58. While being fixed to the watch case 58. That is, airtight packing 57
Since the pressure sensor is compressed, the pressure sensor unit 50 has a structure in which the pressure sensor unit is airtightly fixed while ensuring a waterproof function.

As still another conventional example of the pressure sensor unit, there are JP-A-59-159083 and JP-A-59-159084, which have already been filed by the present applicant. A method for protecting a sensor chip has been proposed.

That is, JP-A-59-159083 discloses that a pressure sensor chip is fixed to a concave portion of a mounting base formed by an insulating material having a plurality of conductive pins therein, and the mounting base is provided with a packing through the exterior. The pressure sensor unit stored in the case is stored, and JP-A-59-159084 discloses that
In addition to the above structure, there is described a structure for protecting the pressure sensor chip by filling a rubber-like or agar-like elastic material into a portion of the sensor mount that comes into contact with the outside of the pressure sensor chip.

[Problems to be solved by the invention]

Generally, semiconductor pressure sensor chips are very sensitive to stress, and as shown in FIGS. 3 and 4, the heights of the pedestals 32 and 42 are minimized in order to minimize thermal or mechanical stress other than the stress caused by the applied pressure. In the structure of the pressure sensor unit 40 as shown in FIG. 4 in which the O-ring 47 is directly compressed by the pedestal 42 to secure a waterproof function, the pedestal 42
It is necessary to remove the mechanical stress from the O-ring that has been processed into a substantially E-shaped cross section, and the pressure sensor unit 30 using the diaphragm type semiconductor pressure sensor chips 31, 41,
It was difficult to reduce the thickness of the 40, and there was a disadvantage that the processing cost was high.

As for the size of the pressure sensor unit, the pressure sensor unit 40 shown in FIG.
Compared with 30, the pressure sensor unit 40 cannot be incorporated unless the inner diameter D4 of the threaded portion 48a of the outer case 48 of the pressure measuring device is larger than the shape D3 of the pedestal 42, although the cap 33 is smaller. Therefore, after all, the pressure sensor unit
When the diameter of 40 is held down to D3, the inner diameter is larger by D4-D3
A thread 48a having a valley diameter D5 having D4 is required for the exterior 48.
Furthermore, by using the fixing ring 49, it is necessary to mount the fixing ring 49 for the thickness (t1), and the size including the mounting structure of the pressure sensor unit 40 is generally large both in thickness and diameter. It also had the disadvantage that it would be.

Similarly, in the case as shown in FIG. 5 shown as a conventional example of a method of attaching the pressure sensor unit 50 to the exterior of the small pressure measuring device, the diameter D6 required for the pressure sensor unit 50 is
Since the waterproofness cannot be secured unless the inner diameter D7 of the airtight packing 57 is large, a large hole having an inner diameter D8 is required for the exterior 58, and the thickness (t2) is required to compress the packing 57. Therefore, also in this case, the size including the mounting structure of the pressure sensor unit 50 is disadvantageously increased as a whole.

Also, when viewed from the structure of the pressure sensor unit, the fourth
In the structure as shown in the figure, the pressure medium has a structure that can also be made of a fluid, but the size of the pressure introducing hole 42a is determined by the size of the diaphragm type semiconductor pressure sensor chip 41, so it is too large. If the pressure introduction hole 42a cannot be used and is repeatedly used in a liquid (for example, seawater) mixed with impurities, the pressure introduction hole 42a is blocked by the adhesion of the impurities. Further, since no specific element name is described as the pressure detecting element 51 in FIG. 5, it cannot be said anything. However, seawater directly penetrates the pressure detecting element 51 as it is. One of the major issues was how to protect them.

In JP-A-59-159083 or JP-A-59-159084, a pressure sensor is directly attached to a windshield or a sensor mounting base so as to seal a through hole formed in the windshield and a through hole of a sensor mounting base. Although the chip is fixed, if the windshield or sensor mounting base is fixed to the watch case or windshield through waterproof packing, the distortion stress is transmitted to the semiconductor pressure sensor chip, which is extremely sensitive to stress. Would be. In addition, thermal strain due to the difference in the coefficient of thermal expansion between the windshield and the sensor mounting base and the watch case, the windshield and the waterproof packing is also transmitted to the semiconductor pressure sensor chip. Since the apparent pressure information is as if the tip was under pressure, this resulted in a measurement error, which prevented correct measurement.

SUMMARY OF THE INVENTION An object of the present invention is to provide a pressure sensor unit which is small, thin, and has a small measurement error by solving the above problems.

[Means for solving the problem]

In order to achieve the above object, the present invention has the following configuration. That is, the bottomed first concave portion and the first concave portion
A package having an opening-shaped second recess formed in continuity with the recess, a pedestal fixed to the bottom of the first recess, a pressure sensor chip fixed on the pedestal, and an exterior housing the package A pressure measuring device having a pressure sensor unit electrically connecting the upper surface of the pressure sensor chip and the lower surface of the second concave portion with a wire, and filling a potting resin in the first and second concave portions. While conducting electrical conduction from the bottom of the second recess to the outside through the inside of the package, the pressure sensor chip is formed in a diaphragm type, and the pressure sensor chip is fixed on the pedestal so that the recess is airtight,
The pedestal is fixed to the bottom of the first concave portion with a rubber-based adhesive, the pressure sensor chip is covered with silicone rubber as the potting resin, and a step inner peripheral portion is provided on the exterior, and an outer periphery of the package is provided. The waterproof function is ensured by compressing the resin ring between the surface and the inner peripheral portion of the step of the exterior.

〔Example〕

FIG. 1 is a sectional view of a main part showing a structure of a pressure sensor unit having a semiconductor pressure sensor chip according to one embodiment of the present invention and a mounting structure of an exterior of a pressure measuring device, and FIG. It is a top view of a diver's watch with a depth gauge showing an application example used as a gauge.

Reference numeral 1 denotes a diaphragm type semiconductor pressure sensor chip which converts pressure into an electric signal by utilizing a piezoresistance effect of a semiconductor diffusion resistor. Reference numeral 2 denotes a pedestal, for example, # 7740 borosilicate glass, which is a diaphragm type semiconductor pressure sensor chip. Is hermetically fixed on the pedestal 2. 3 is a bottomed first concave portion 3a
And a second concave portion 3b having an opening shape formed in continuation with the first concave portion 3a having a bottom. The package 2 is formed of, for example, ceramics. It is fixed to the bottom of 3a with a rubber-based adhesive. Especially when silicone rubber is used as the rubber-based adhesive, it is a material with excellent heat resistance and cold resistance, has a suitable elongation, and is excellent in strain recovery, absorbs vibration and shock. Therefore, stress other than pressure displacement on the diaphragm-type semiconductor pressure sensor chip 1 such as thermal strain from the package 3 or mechanical strain of the package itself due to attachment of the package 3 or external force, etc., is caused by silicone rubber. The thickness of the pedestal 2 can be reduced by adjusting the thickness of the pedestals 32 and 42 in FIGS.
It is possible to make it very thin compared to the thickness.

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.
The upper pattern and the pattern of the diaphragm-type semiconductor pressure sensor chip 1 are wire-bonded to each other to transmit and receive electric signals to and from the diaphragm-type semiconductor pressure sensor chip 1 in the package 3 from the lower surface 3e of the package 3. .

Reference numerals 4 and 5 denote potting resins. After the diaphragm type semiconductor pressure sensor chip 1 and the package 3 are electrically connected to each other by wire bonding, the surface of the diaphragm type semiconductor pressure sensor chip 1 is filled and cured. The surface of the diaphragm type semiconductor pressure sensor chip 1 is electrically and mechanically protected, and thus the pressure sensor unit 10 is configured. As the potting resins 4 and 5, it is desirable to use a gel-like silicone rubber having a pressure loss of zero. When clean air or an inert gas is a pressure medium, the potting resins 4 and 5 are made of the same gel-like material. Silicone rubber is good. When the pressure medium is a fluid containing impurities, the gel silicone rubber is sticky and impurities such as dust easily adhere thereto. It is preferable to use silicone rubber which becomes rubbery after curing as a potting resin to be seen. This embodiment shows an example in which the second layer is covered with rubber-like silicone rubber.

Reference numeral 7 denotes a resin ring, for example, made of Delrin, Teflon, nylon, polyethylene, or the like. Reference numeral 8 denotes an exterior of the pressure measuring device, and the exterior 8 is provided with a concave step 8a. The resin ring 7 is an inner peripheral portion of a step 8a of the exterior 8.
8b, and is pushed into the inner peripheral portion 7a of the resin ring 7 so that the outer peripheral portion 3d of the package 3 of the pressure sensor unit 10 compresses the resin ring 7. That is, since the resin ring 7 is compressed by the inner peripheral portion 8b of the step 8a of the exterior 8 and the outer peripheral portion 3d of the package 3, the pressure sensor unit 10 is fixed to the exterior and the waterproof function is secured. Has become.

That is, the thickness of the resin ring 7 after compression is represented by (t).
Then, the exterior 8 has the inner diameter D2, that is, the outer diameter of the package.
By merely providing the step portion 8a having an inner diameter of D1 + 2 × t, the sensor unit can be fixed while the waterproof function is secured to the exterior 8.

Reference numeral 6 denotes a protective plate having a hole having a shape as shown in FIG.
However, if the object is directly poked with a stick or the like,
It is intended to prevent a collision, and may be omitted when there is no danger as described above.

Reference numeral 11 denotes a spring, and 12 denotes a circuit board. The lower surface 3e of the package 3 of the pressure sensor unit 10 and the circuit board 12 are electrically connected to each other via a spring 11, and are connected to an electric circuit of a pressure measuring device (not shown). Electrically connected.

An application example of the pressure sensor unit 10 having a small size including the mounting structure as described above is a diver's watch with a 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〕

According to the present invention, the diaphragm-type semiconductor pressure sensor chip, which is very sensitive to stress, is fixed to the pedestal, and the pedestal to which the diaphragm-type semiconductor pressure sensor chip is further fixed is provided at the bottom of the first concave portion of the package. Since it is fixed with a rubber-based adhesive, stresses other than pressure displacement on the diaphragm-type semiconductor pressure sensor chip, such as thermal distortion from the package or mechanical distortion of the package itself due to mounting of the package or external force, etc. It is possible to absorb with a rubber-based adhesive, the thickness of the pedestal can be reduced, and correct pressure measurement not affected by stress other than pressure displacement can be performed.

Further, since the thickness of the pedestal can be reduced, despite the use of a diaphragm-type semiconductor pressure sensor chip, it is thin, the pressure medium is not limited, and the size including its mounting structure is small, It has become possible to supply a pressure measuring device having a pressure sensor unit excellent in high-pressure waterproofing, and it has become possible to apply it to a small portable device that could not be used until now.

Furthermore, since there is no need for a thread cutting step in processing the exterior of the pressure measuring device for fixing the pressure sensor unit,
Processing is simplified, and the number of parts is reduced, which has the effect of reducing costs.

[Brief description of the drawings]

1 is a sectional view of a main part showing a structure of a pressure sensor unit having a semiconductor pressure sensor chip according to one embodiment of the present invention and a mounting structure of an exterior of a pressure measuring device, and FIG. 2 is a pressure sensor of FIG. FIG. 3 is a plan view of a diver's watch with a depth gauge showing an application example in which the unit is used as a depth gauge, FIG. 3 is a cross-sectional view of a very common pressure sensor unit having a semiconductor pressure sensor chip, and FIG. 4 is a conventional semiconductor pressure sensor. FIG. 5 is a cross-sectional view of a main part showing a structure of a pressure sensor unit having a chip and an outer structure of a pressure measuring device, and FIG. 5 is a cross-sectional view of a main part of a water pressure detecting device showing a conventional mounting structure of the pressure sensor unit on the outer case. It is. 1, 31, 41 ... diaphragm type semiconductor pressure sensor chip, 3 ... package, 10, 30, 40, 50 ... pressure sensor unit, 8, 48, 58 ... exterior of pressure measuring device, 8a ...
Recessed step, 7 ... resin ring.

Claims (1)

(57) [Claims] 1. A package having a bottomed first recess and an opening-shaped second recess connected to the first recess, a pedestal fixed to the bottom of the first recess, and on the pedestal. A pressure sensor chip fixed to the package, and an exterior housing the package. The top surface of the pressure sensor chip and the bottom surface of the second recess are electrically connected by a wire, and a potting resin is provided in the first and second recesses. Pressure measuring device having a pressure sensor unit filled with
The package is electrically connected to the outside of the package from the bottom surface of the concave portion to the outside, and the pressure sensor chip is formed in a diaphragm type, and the pressure sensor chip is fixed on the pedestal so that the concave portion is airtight. Is fixed to the bottom of the first concave portion with a rubber-based adhesive, the pressure sensor chip is covered with silicone rubber as the potting resin, and a step inner peripheral portion is provided on the exterior, and an outer peripheral surface of the package is provided. A pressure measuring device, wherein a waterproof function is secured by compressing a resin ring between the step and the inner peripheral portion of the exterior.