JPS5813313Y2 - Pressure-electric conversion device - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a compact pressure-to-electricity converter in which a pressure sensitive element and its peripheral circuit elements are embedded and sealed in a single sealed body with a large spring constant.

Generally, the pressure sensitive element and the peripheral circuitry for driving the pressure sensitive element and amplifying its output are usually installed and used in separate locations.

However, in this case, the pressure-sensitive element and its peripheral circuit elements must be interconnected with long leads, which is not only inconvenient to use, but also has poor signal-to-noise (S/N) characteristics. The purpose of this invention is to provide a new pressure-to-electricity converter that eliminates this kind of disadvantage.

One of the features of this invention is that the pressure sensing element and its peripheral circuits are designed to minimize the influence of the sensed pressure exerted on the surrounding circuits and to maximize the sensed pressure transmitted to the pressure sensing element. The main point is that the elements are embedded in the same sealed body.

The sealing body has a spring constant as large as that of the pressure-sensitive element, and is preferably made of synthetic resin, thereby effectively transmitting the sensed pressure to the pressure-sensitive element chip. Highly sensitive and highly accurate pressure detection can be achieved.

The hermetic body is provided with a first region that substantially deforms when a sensed pressure is applied and a second region that does not substantially deform, with a pressure sensitive element chip within the first region and a second region that deforms substantially when a sensed pressure is applied. Each peripheral circuit element chip is buried and sealed within the area.
Therefore, while pressure is smoothly transmitted to the pressure sensitive element chip, undesired pressure transmission to the peripheral circuit element chip is avoided.

By following these features, a compact and convenient to use pressure-to-electrical converter device is realized that can achieve highly sensitive pressure sensing in a stable manner.

The invention will now be described in detail with reference to preferred embodiments shown in the accompanying drawings.

FIG. 1 shows the circuit configuration of a pressure-to-electricity converter according to an embodiment of this invention, in which 10 is a pressure detection section, 12.
Reference numeral 22 indicates a gate bias terminal, reference numerals 14 and 16 indicate a pair of power supply terminals, reference numerals 18 and 20 indicate a pair of output terminals, and reference numeral 30 indicates a peripheral circuit section.

In the pressure detection unit 10, MO8 type field effect transistors (hereinafter simply referred to as MOS transistors) TI, T
2°T4. T5 is provided, and a pressure sensitive MO3) transistor T4. T5 is a pair of pressure sensitive and amplifying MOS transistors T1.T5 whose sources 81 and 82 are commonly connected. T2
are connected to respective transistors TI and T2 to act as load resistors, respectively.

The gate G4 and the drain D4 of the transistor T4 are interconnected to the gate G5 and the drain D5 of the transistor T5 at an interconnection point D45, and the interconnection point D45 is connected to one power supply to which a power supply voltage -vD is applied. Terminal 14 is connected.

. Drain D1 of transistor T1 and transistor T4
Output terminals 18 and 20 are connected to an interconnection point J14 between the source S4 of the transistor T2 and an interconnection point J25 between the drain D2 of the transistor T2 and the transistor T5, respectively.

The gate G1 of the transistor T1 and the transistor button gate G2 are interconnected at an interconnection point G12 connected to the gate bias terminal 12, and the sources S1 and S
The interconnection point 812 to which 2 is connected is the constant current source MO8)
It is connected to the drain D3 of the transistor T3.

The gate G3 and source S3 of the transistor T3 are connected to the gate bias terminal 22 and the other power supply terminal 16 at voltage +vD, respectively.

Turn on the circuit like the one above and set the power supply voltage to V.

By appropriately determining the value of , and the value of the gate bias voltage to be applied to the gate bias terminal 12.22, the transistor T3 becomes the transistor TI.

T2 can be driven with a constant current to perform differential amplification operation,
As a result, output terminals 18 and 20 output a differential amplification output corresponding to the sensed pressure.

can be taken out.

As shown in Figure 1, four pressure sensitive MOS transistors TI
, T2. T4. The pressure sensing section 10 including T5 and the peripheral circuit section 30 including the constant current source MOS transistor T3 are arranged in respective surface regions of separate semiconductor substrates 50 and 70 made of silicon, as shown in FIG. 2, for example. For example, each substrate 50.70 is formed integrally with the other.
and are integrally implemented as described below with respect to FIG. 3b.

Referring to FIG. 2, on the surface of the semiconductor substrate 500, the channel region 44 of the transistor T1 and the channel region 46 of the transistor T2 are at right angles to each other, and the channel region 54 of the transistor T4 and the channel region 56 of the transistor T5 are perpendicular to each other. Four MOS transistors TI are arranged such that their edges are at right angles to each other, their channel regions 44 and 56 are parallel to each other, and their channel regions 46 and 54 are staggered parallel to each other.

T2. T4. T5 is formed.

Source region 42 is connected to transistor T1. The common source electrode 812 is in ohmic contact with the common source region 42 .

Output electrodes Jl to be respectively connected to output terminals 18.20 4. The regions 48 and 52 of a predetermined conductivity type with which J25 is in ohmic contact each function as a source or a drain, and the transistors T1 and T4 are connected to each other through the region 48, and the transistor T2 is connected to the transistor T2 through the casing region 52. and T5 are interconnected, respectively.

Transistor T4. A common drain electrode D45 is in ohmic contact with a drain region 58 common to transistors T5, and the transistors T4. Gate electrode G4 of T5. G5
are electrically conductively connected to the common drain electrode D45, respectively.

The gate electrodes Gl, G2 of the transistors TI, T2 are also conductively connected to the common gate electrode G12.

In this way, four MOS transistors TI.

T2. T4. Source regions 72 . A constant current source MOS transistor T3 including a channel region 74 and a drain region 76 is formed.

S3. G3 and D3 are a source electrode, a gate electrode, and a drain electrode provided corresponding to each region.

Toshiin electrode D of transistor T3 & the above-mentioned substrate 50
It is electrically connected to the common source electrode S12 on the upper side via a connecting line 78.

As described above, it will be clear that the electrical equivalent circuit of the device of FIG. 2 corresponds to the circuit of FIG. 1.

In addition, as shown in FIG. 2, an insulating film made of silicon oxide (not shown) is formed on the surface of the substrate 50. The gate electrodes of each transistor and the wiring layer between the transistors are electrically insulated from the substrate surface by the insulating film.

Next, the mounting structure of the above device will be explained with reference to Figures 38 and 3b. In these figures, 80 is made of high hardness epoxy resin molded into a lever shape so as to have a spring constant larger than that of the board. A constant current source board 70 on the fixed end side and a pressure sensing board 50 on the free end side are buried inside the sealed body and are hermetically protected from the outside air.

The sealing body 80 is fixed to the mounting plate 88 via the spacer 86 by a set screw 90 inserted into the fixing hole 84 at one end thereof, and is attached to the opposite free end directly or by an auxiliary elastic member (for example, a plate). It deforms in the thickness direction by receiving pressure W through the spring 82, so it acts as a good pressure transmission means, and such deformation is effective for pressure detection because the spring constant of the sealing body 80 is large. The signal is transmitted to the substrate 50.

In this case, as is clear from the figure, the pressure sensing substrate 50
is sealed in the deformable area of the sealed body 80, while the constant current source substrate 70 is sealed in the non-deformable area, so the constant current output of the transistor T3 in the substrate TO changes due to the applied stress. I almost never receive it.

Although not shown, the substrates 50 and 70 are connected to a sealed body 80.
The board is electrically connected to a lead-out lead extending from the inside to the outside, and wiring between the boards is done inside or outside of the sealed body 80 as appropriate.

Here, a typical example of the operation of the pressure-to-electricity converter described above with reference to FIGS. 1 to 38 and 3b will be described as follows.

First, as shown in FIG. 3b, when a sensed pressure W is applied to the free end of the sealing body 80 via the auxiliary elastic member 82,
As shown in the figure, the pressure sensing substrate 50 disposed within the area to be deformed within the sealing body 80 is subjected to tensile strain and compressive strain due to the deformation of the sealing body 80.

Within substrate 50 channel regions 44, 46 . ko4,
Since the transistors 56 are arranged as shown in FIGS. 2 and 3a, when tensile strain is applied to transistors T2 and T4, compressive strain is applied to transistors TI and T5.

In this case, as mentioned above, almost no strain is applied to the constant current source substrate 70, and the transistor T3 in the substrate 70 has a constant drain current determined by its gate bias voltage, and the transistors TI, T2 is driven at a constant current.

In this way, external stress causes transistors TI, T5 to
and transistor T2. When T4 operates differentially, a differential amplification output V is generated between the output terminals 18 and 20 in accordance with the sensed pressure W, according to the principle of a differential amplifier.

can be obtained. In this case, the pressure detection sensitivity depends on the mutual conductance gm of the transistors TI and T2,
Sensitivity can be increased by increasing gm.

Furthermore, in this example, the transistors T4 and T5 also operate differentially as strain sensors, so there is an advantage that greater pressure detection sensitivity can be obtained.

Since the constant current source MOS transistor T3 is not subjected to stress, the transistor T1. T2 can be driven stably, and highly stable differential amplification becomes possible.

Note that fluctuations in temperature and power supply voltage that cause similar changes in drain current Idl*Id2 are canceled out as a result of the differential amplification circuit, resulting in a differential amplification output V.

It is clear that it has no effect on

As described above, the pressure-to-electricity converter according to the actual example operates as a differential amplifier circuit using a pair of pressure-sensitive MOS transistors as amplifier elements, so it is possible to increase the differential gain. It is possible to increase the sensitivity and increase the common-mode input rejection ratio to improve stability against temperature and power supply voltage fluctuations.Furthermore, it can be easily realized as an integrated circuit structure and can be housed in a single sealed body. Since it can be put to practical use in a compactly stored form, it is extremely convenient to use and has good S/N characteristics.

Next, another embodiment of this invention will be described with reference to FIGS. 4 and 5.

One of the features of the pressure-to-electricity converter according to this embodiment is:
As shown in the circuit configuration in FIG. 4, the output voltage (2) from the output terminals 18 and 20 of the pressure sensing section 10 described above.

The other features are that the differential amplifier circuit DA using MOS) transistors for amplifying the constant current source is integrated into the peripheral circuit section 30 together with the MO8) transistor T3 for the constant current source, and integrated on one semiconductor substrate. As shown in FIG. 5, one semiconductor substrate 104 on which the pressure sensing section 10 is integrated and the other semiconductor substrate 106 on which the peripheral circuit section 30 is integrated are embedded in an improved sealed body 100 having a large spring constant.・The reason is that it is sealed and integrated.

These features will be explained in turn. As shown in FIG. 4, the differential amplifier circuit DA includes a pair of MOS transistors T6 and T7 whose gates are respectively connected to the output terminals 18 and 20 of the pressure sensing section 10, and loads of these transistors T6 and T7, respectively. A pair of M connected to act as a resistor
OS) transistor T9. TIO and transistor T6.
The drains are connected to the commonly connected sources of transistors T6. and a constant current source transistor T8 for driving T7 with a constant current.

Transistor T9. The gate and drain of TIO are connected to one power supply terminal 14 of voltage -■, and the gate and source of transistor T8 are respectively connected to gate pipes terminal 22 and the other power supply terminal 16 of voltage +vD, and transistors T7 and T10 The amplified output vont is available via an output terminal 28 connected to the interconnection point with the .

Transistors T6 to T10 forming the differential amplifier circuit DA
When external pressure acts on the differential amplifier circuit DA, it is undesirable because the gain changes and instability and noise increase. However, according to the teachings of this invention, the peripheral circuit section 30 including the differential amplifier circuit DA It is integrated on a semiconductor substrate different from the semiconductor substrate on which the pressure sensing section 10 is integrated, and is embedded in a sealed body at a position where it is not substantially subjected to external stress.

FIG. 5 illustrates the mounting structure of the device shown in FIG. 4, and 104 and 106 are semiconductor substrates made of silicon, for example, on which the pressure sensing section 10 and the peripheral circuit section 30 are integrated, respectively.

After these semiconductor substrates 104 and 106 are adhesively fixed to a support plate 102 made of Kovar, for example, and connected to external lead leads (not shown), they are molded into a sealed body 100 made of a suitable high-hardness synthetic resin using a known molding technique. The sealed body 100 is sealed as shown in the figure, and at the same time, the bottom of the sealed body 100 is shaped into a desired shape.

In this case, the sealing body 100 as a whole is formed into an elongated lever shape as in the above-mentioned side, but recesses 108a and 108b are formed on the upper and lower surfaces, respectively, to facilitate the deformation in the area to be deformed.

An auxiliary elastic member 11 is provided on the upper surface of the sealing body 100 to efficiently transmit the sensed pressure W to help the sealing body 100 deform.
2 is fixed, and if desired, a fixing hole 110 is provided on the fixed end side.
is formed.

According to the pressure-to-electrical converter as detailed with respect to FIGS. 4 and 5, recesses 108a, 108
In addition to the addition of the amplifier circuit DA, the amplifier circuit DA is also integrated and integrated, so that the sensed pressure W is output from the output terminal 28.
This is advantageous in that it is possible to stably extract a large amplified output Vont that responds to with high sensitivity.

Therefore, even in a normal case, this amplified output Vont can be applied directly to a desired control system or other system without going through any other amplification system.

It will be obvious that the apparatus of this embodiment can also produce the same effects when used in conjunction with the apparatus of the embodiments previously described with reference to FIGS. 1 to 38 and 3b.

Although this invention is not limited to the above, it can naturally be applied to cases where, for example, peripheral circuit sections other than the constant current source section and the amplifier circuit section are integrated and integrated.

The pressure-to-electricity converter according to this invention is suitable for use in various touch controls of electronic musical instruments, for example.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a pressure-to-electricity converter according to an embodiment of the invention, FIG. 2 is a top view showing an example of an integrated structure of the device in FIG. 1, and FIGS. 38 and 3b are , FIG. 1 is a bottom view and a cross-sectional view of a main part thereof, respectively, showing an example of the mounting structure of the device, FIG. 4 is a circuit diagram showing a pressure-to-electricity converter according to another embodiment of the invention, and FIG. FIG. 5 is a cross-sectional view showing an example of the mounting structure of the device shown in FIG. 4. Explanation of symbols, 10... Pressure detection section, 30...
... Peripheral circuit section, 50, 104 ... Pressure detection section integrated board, 70, 106 ... Peripheral circuit integrated board, 80°100 ... Spring constant large sealed body.

Claims (1)

[Scope of utility model registration request] 1. A first substrate on which a pressure sensing section including a pressure sensing element is integrally formed, a second substrate on which an electric element forming a peripheral circuit of the pressure sensing section is integrally formed, and a sensing target. a sealing body having a first region that substantially deforms when pressure is applied and a second region that does not substantially deform and having a spring constant greater than that of the first substrate; A pressure-to-electricity conversion device characterized in that the first substrate is buried in the first region and the second substrate is buried in the second region. 2. Utility Model Registration Scope of Claims In the pressure-to-electricity converter according to claim 1, the first and second substrates are made of semiconductors, the sealing body is made of synthetic resin, and the pressure-sensitive element and the electric A pressure-to-electricity conversion device characterized in that all elements are composed of insulated gate field effect transistors.