JP2009053005A - Semiconductor strain sensor, and mounting method of semiconductor strain sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress a change of a sensor characteristic caused by temperature rise or thermal deformation by improving heat radiation from a sensor chip, in a semiconductor strain sensor using a semiconductor strain gage. <P>SOLUTION: In this semiconductor strain sensor having a strain sensor chip wherein a piezo resistance element is formed on a semiconductor, a metallic base plate, and a wiring part for leading out wiring from an electrode of the sensor chip to the outside, the sensor chip is bonded to the base plate with a metal material, and connection areas to be connected to a measuring object are provided on at least two spots sandwiching a bonding part of the sensor chip on the base plate. Since the sensor chip is bonded to the metallic base plate with the metal material, heat generated in the sensor chip easily escapes from the sensor chip rear surface to the base plate, to thereby prevent thermal deformation caused by temperature rise of the sensor chip and temperature unevenness between the sensor chip and the base plate. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a strain sensor used for measuring strain and stress of a structure, and more particularly to a semiconductor strain sensor using a semiconductor strain gauge.

A strain gauge called a strain gauge is often used for measuring strain and stress of a structure. The strain gauge is a wiring pattern of a metal thin film of Cu-Ni alloy or Ni-Cr alloy,
The structure is covered with a flexible polyimide or epoxy resin film, and a strain gauge is used by adhering it to an object to be measured with an adhesive. The amount of strain can be calculated from the resistance change when the metal thin film is deformed due to strain.

There is a semiconductor strain gauge using a semiconductor piezoresistor formed by doping impurities in a semiconductor such as silicon instead of a metal thin film. A semiconductor strain gauge has a resistance change rate with respect to strain as large as several tens of times that of a strain gauge using a metal thin film, and can measure a minute strain. In addition, since the strain gauge of the metal thin film has a small resistance change, it is necessary to amplify the electric signal obtained, and thus an external amplifier is required. Since the strain change of the semiconductor strain gauge is large, the obtained electrical signal can be used without using an external amplifier, and an amplifier circuit can be built in the chip of the semiconductor strain gauge. The use and convenience of use are expected to greatly expand. In this specification, a strain sensor and a strain gauge are used synonymously.

A semiconductor strain gauge is obtained by forming impurities after doping or wiring on a silicon wafer using a conventional semiconductor manufacturing technique and then forming a chip. It is important that the strain of the measurement object is correctly transmitted to this chip (hereinafter referred to as a strain sensor chip), and the point is modularization of the strain sensor chip and attachment to the measurement object.

Patent Document 1 discloses a structure in which a semiconductor strain gauge is a practical module.
FIG. 10a) shows a perspective view of a semiconductor strain gauge. After a semiconductor strain gauge is formed on the surface of the silicon wafer, the silicon wafer is etched to a thickness of several μm, and then chipped to obtain a strain sensor chip 52. A wiring 53 is formed and sandwiched between polyimide films 54 to obtain a semiconductor strain gauge 51. Since the strain sensor chip 52 and the wiring 53 are modularized, a semiconductor strain gauge can be handled like a conventional strain gauge.

Patent Document 2 discloses a strain detection sensor 56 in which a strain sensor chip 52 is bonded to a glass pedestal 57 using a low melting point glass 58. FIG. 10b) shows a side view of the strain detection sensor. Fix the glass pedestal to the object to be measured with bolts. Since there is no resin adhesive between the strain sensor chip and the glass pedestal, between the glass pedestal and between the objects to be measured, the temperature drift caused by the difference in thermal expansion coefficient between the adhesive resin and the strain detection sensor is suppressed. Can do.

JP 2001-264188 A JP 2001-272287 A

The semiconductor strain gauge of Patent Document 1 can be used by being attached to a measurement object using a resin adhesive, similarly to a strain gauge using a conventional metal thin film. Since the resin adhesive is used, there is a problem that the sensitivity and the zero point are easily changed when the resin adhesive is altered or deteriorated. This is a problem in terms of stability of characteristics when used for a long time. Since a highly sensitive semiconductor strain gauge is used, the influence of the characteristic change appears more conspicuously.

Since the strain detection sensor of Patent Document 2 does not use a resin adhesive, it is considered that long-term stability is better than that of Patent Document 1. However, since low melting point glass is used for joining the glass pedestal and the pedestal to the strain sensor chip, the thermal conductivity is poor, and it is difficult to escape the heat from the strain sensor chip. A semiconductor piezoresistor has a large electric resistance and therefore generates a large amount of heat. When an amplifier is formed on a strain sensor chip using CMOS technology, heat from the amplifier is also added. Since the strain sensor chip is fixed to the glass pedestal with a low melting point glass, it is difficult for the heat of the strain sensor chip to escape, so that the temperature of the strain sensor chip increases more and more. Since the semiconductor piezoresistor has a large temperature coefficient of resistance change, the characteristic change becomes large. In addition, since the temperature from the strain sensor chip to the measurement object is difficult to be uniform, the temperature is easily affected by the stress generated by the thermal expansion difference, resulting in variation in characteristics.

An object of the present invention is to provide a semiconductor strain sensor that uses a highly sensitive semiconductor strain gauge, has stable characteristics for a long period of time, and hardly changes in characteristics even with heat generated by the strain sensor chip.

A semiconductor strain sensor according to the present invention includes a strain sensor chip in which a piezoresistive element is formed on a semiconductor substrate, a metal base plate, and a wiring portion that draws wiring to the outside from an electrode of the strain sensor chip. It is preferable that the back surface and the base plate surface are bonded with a metal bonding material, and the base plate portion that protrudes to the side of the strain sensor chip has at least two connection areas that are fixed to the measurement object.

Since the strain sensor chip is bonded to the metal base plate using a metal material, the heat generated in the strain sensor chip is transmitted through the back surface of the sensor chip and easily conducted to the base plate. Also,
Since the metallic base plate has a larger planar area than the strain sensor chip, heat is efficiently dissipated. Since heat dissipation is good, the temperature rise of the strain sensor chip can be prevented, and the temperature of the base plate and the strain sensor chip can be easily kept uniform. Because the temperature of the semiconductor strain sensor can be made uniform, changes in the piezoresistance coefficient due to temperature changes, and changes in characteristics caused by changes in the stress applied to the piezoresistive elements due to thermal deformation due to temperature nonuniformity between the sensor chip and the base plate Can be suppressed. In addition, since metal bonding is used between the strain sensor chip and the base plate, creep, alteration, deterioration, and alteration are unlikely to occur and excellent long-term stability of characteristics.

Since the strain sensor chip is made of a conductive material up to the base plate in contact with the measurement object, it is resistant to electrical noise. If an insulating material is interposed between the strain sensor chip and the measurement object, when the potential fluctuates due to current flowing through the measurement object, the area between the strain sensor chip and the measurement object Have parasitic capacitance. When parasitic capacitance occurs, the potential also fluctuates and noise is likely to occur. In the semiconductor strain sensor of the present invention, since the ground of the strain sensor chip can be electrically connected to the measurement object through the back surface of the strain sensor chip, noise is generated because the ground of the sensor chip fluctuates in accordance with the potential of the measurement object. Can be difficult.

For the base plate, a metal such as nickel, iron, copper, or an alloy such as SUS can be used. By using a material having a thermal expansion coefficient close to that of silicon, such as an iron-nickel alloy or an iron-nickel-cobalt alloy, a change in characteristics with respect to a temperature change can be reduced. Since the back surface of the strain sensor chip and the surface of the base plate are fixed using a metal bonding material, it is necessary to have a melting point sufficiently higher than the melting point of the metal bonding material so that the base plate does not melt or deform when fixed. A metal that easily rusts, such as iron, can be used by plating with tin or zinc. Since it is important that the base plate does not deform when the semiconductor strain sensor is attached to the measurement object, it is preferable to use a hard metal material.

Since the strain sensor chip is metal-bonded to the base plate that is larger in plane area than the strain sensor chip, the base plate projects to the side of the strain sensor chip. The overhang is at least on both sides of the strain sensor chip. This overhanging portion is called a connection area, and the semiconductor strain sensor is fixed to the measurement object in this connection area. Two to four connection areas can be formed. The four connection areas are states formed on the four sides (entire circumference) of the strain sensor chip. The shape of the base plate at this time can be a substantially cross shape or a square shape.

When the semiconductor strain sensor having the first and second connection areas is used, the strain in the direction (referred to as the X direction) connecting the first connection area, the strain sensor chip, and the second connection area generated in the measurement object is It can be transmitted to the base plate and the strain sensor chip via the first and second connection areas, and the amount of strain can be detected from the change in electrical resistance of the semiconductor piezo element. When the semiconductor strain sensor having the first to fourth connection areas is used, the strain in the direction connecting the third connection area, the strain sensor chip, and the fourth connection area (referred to as the Y direction) is the third and fourth connections. It can be transmitted to the base plate and the strain sensor chip via the area, and the amount of strain can be detected from the change in electric resistance of the semiconductor piezo element. A semiconductor strain sensor having two connection areas is only in the X direction, but a semiconductor strain sensor having four connection areas can measure strain in the X direction and the Y direction. Using a semiconductor strain sensor having four connection areas, 45 in the X and Y directions.
By detecting the amount of strain in the direction of the degree, it can also be used for a torque detection sensor.

The wiring portion of the semiconductor strain sensor of the present invention includes a flexible wiring board that is resin-bonded on a base plate, a metal wire that electrically connects the wiring of the flexible wiring board and the electrodes of the strain sensor chip, and at least a strain sensor. It is preferable to be comprised with resin which covers the electrode and metal wire of a chip | tip.

Conductivity can be obtained between the flexible wiring board and the strain sensor chip by ultrasonic welding or soldering an uncoated metal wire. As the metal wire, a bare gold wire having a diameter of 10 μm to 200 μm can be used. By covering the metal wire and its connection part and electrode with resin, electrical insulation and insulation from the outside air can be secured. Not only the wiring part but also the strain sensor chip may be covered with resin. If the rigidity of the flexible wiring board and the adhesive for bonding the flexible wiring board is large, there is a risk that creep, deterioration, or alteration of the flexible wiring board or the adhesive affects the rigidity of the entire semiconductor strain sensor. It is preferable to reduce the elastic modulus and volume of the flexible wiring board and adhesive as much as possible.

In the wiring portion of the semiconductor strain sensor of the present invention, it is preferable that a part of the wiring of the flexible wiring board is directly connected to the metal bump provided on the electrode of the strain sensor chip.

By providing metal bumps on the electrodes of the strain sensor chip, the flexible wiring board can be directly connected to the surface of the strain sensor chip, and there is no need to bond the flexible wiring board to the base plate.
For this reason, the degree of freedom in designing the connection area arranged on the side of the strain sensor chip can be increased. The flexible wiring board is preferably made as thin as possible so as not to affect the rigidity of the semiconductor strain sensor.

The wiring portion of the semiconductor strain sensor of the present invention includes a base plate electrode formed on the base plate via an insulating film, a metal wire that electrically connects the base plate electrode and the electrode of the strain sensor chip, and at least It is preferable that it is comprised with resin which covers the electrode of a metal wire and a strain sensor chip.

By using a base plate having electrodes, a flexible wiring board can be eliminated. By connecting the base plate electrode and the electrode of the strain sensor chip with a metal wire and providing a covering wire on the base electrode, an electric signal of the strain sensor chip can be taken out of the chip. Since the flexible wiring board is not bonded to the base plate, the degree of freedom in designing the connection area arranged on the side of the strain sensor chip can be increased. By covering the metal wire and its connection part and electrode with resin, electrical insulation and insulation from the outside air can be secured.

The semiconductor strain sensor of the present invention is mounted so that the back surface of the base plate of the semiconductor strain sensor faces the object to be measured, and the semiconductor strain sensor is fixed so that at least a part of the connection area of the base plate is fixed to the member to be measured. It is preferred that

It is necessary that at least a part of the connection area of the base plate is fixed to the measurement object. Since the strain of the measurement object is transmitted to the base plate through the fixing portion, if the area of the fixing portion is small, there is a risk that the strain is concentrated and the fixing portion is plastically deformed. If the area of the fixed part is secured so that the fixed part is not plastically deformed in the strain range to be measured, it is not necessary to fix the entire connection area. Of course, the entire connection area may be fixed to the object to be measured. The base plate and the measurement object other than the connection area do not have to be fixed, and may have a gap. In order to efficiently dissipate the heat generated from the strain sensor chip, it is preferable that the strain sensor chip is in close contact with no gap.

In the semiconductor strain sensor of the present invention, it is preferable that the semiconductor strain sensor and the measurement object are attached so that at least two or more connection areas, and each connection area is fixed by at least one welded portion.

For the welding, laser welding or resistance spot welding can be used. Although the object to be measured is limited to those that can be welded, creep, deterioration, and alteration are unlikely to occur in the welded portion, and thus excellent long-term stability. Welding can be performed only with the material of the connection area and the material of the measurement object, but a metal such as a brazing material can be interposed between the connection area and the measurement object. If a hand-held spot welder is used, the semiconductor strain sensor of the present invention can be easily installed on site even for existing devices and structures. Further, since no force is directly applied to the strain sensor chip at the time of attachment, the risk of breaking the strain sensor chip or changing the strain sensor chip characteristics by applying unnecessary strain can be reduced.

In the semiconductor strain sensor of the present invention, it is preferable that the semiconductor strain sensor and the measurement object are attached so that at least two or more connection areas are provided, and each connection area is fixed by at least one screw portion.

Although it is necessary to form a screw hole in the measurement object, the semiconductor strain sensor of the present invention can be easily attached to a measurement object made of a material that cannot be welded. In addition, since the semiconductor strain sensor is not required to be installed with a laser welding machine or a spot welding machine, it can be easily installed in a narrow place or a high place.

With a strain sensor using a highly sensitive semiconductor strain gauge, it was possible to provide a semiconductor strain sensor whose characteristics are stable for a long period of time and whose characteristics do not easily change even when the strain sensor chip generates heat.

Hereinafter, the present invention will be described in detail based on examples with reference to the drawings. In order to make the explanation easy to understand, the same reference numerals are used for the same parts and parts.

The structure and manufacturing method of the semiconductor strain sensor according to the first embodiment of the present invention will be described with reference to FIGS.
Will be described below. FIG. 1 is a plan view of a state in which the strain sensor of the first embodiment is attached to a measurement object, and FIG. 2 is a cross-sectional view taken along the line kk ′ of FIG. A silicon strain sensor chip 2 that functions as a semiconductor strain gauge on which a piezoresistive element (not shown) is formed is connected to a metal base plate 3.
Was fixed with a metal solder 4 as a metal bonding material. The base plate 3 has a rectangular shape that is long in the X direction in FIG. 1, and connection areas 11 and 12 are provided on both sides of the strain sensor chip connection portion 15. The first connection area 11, the strain sensor chip connection part 15, and the second connection area 12 are arranged in the X direction. The strain sensor chip 2 having a smaller planar area than the strain sensor chip connection portion 15 is fixed to the substantially central portion of the strain sensor chip connection portion 15. The approximate dimensions are 6 mm wide in the Y direction of the base plate, 5 mm in the first connection area in the X direction, 4.5 mm in the strain sensor chip connection portion, and 4.5 mm in the second connection area. Strain sensor chip is 2.5m in Y direction
m, X direction is 2.5 mm. The base plate 3 is made of iron 58-nickel 42 close to silicon.
An alloy with a thickness of 0.3 mm. The thickness of the strain sensor chip 2 is 0.16 mm.

A metal solder joint was used for fixing the strain sensor chip 2 and the base plate 3. A Cr—Ni—Au three-layer metallization was formed on the side surface of the strain sensor chip 2 facing the base plate by sputtering, and an Sn-based metal solder material was formed thereon by vapor deposition. A Cr—Ni—Au three-layer metallization was also formed on the side surface of the base plate 3 facing the strain sensor chip by sputtering. After aligning the strain sensor chip 2 to the substantially central portion of the base plate, the metal solder was heated and melted to fix the strain sensor chip to the base plate. The three-layer metallization on the base plate side may be formed only on the portion to which the strain sensor chip is fixed, but may be formed on the entire surface of the base plate in order to save time and labor such as mask sputtering.

The flexible wiring board 5 was used for drawing the wiring from the electrode 16 of the strain sensor chip. The surface opposite to the surface where the wiring at the tip of the flexible wiring board 5 is exposed was adhered to a position adjacent to the Y direction of the sensor chip joint on the base plate using an epoxy resin adhesive. Between the wiring of the flexible wiring board 5 and the electrode 16 of the strain sensor chip, a bare Au wire 17 having a diameter of 20 μm was connected by ultrasonic welding. A cover resin 18 was applied so as to cover the electrode 16 of the strain sensor chip, the Au wire 17 and the wiring of the flexible wiring board 5. The cover resin 18 was a thermosetting resin. When the elastic modulus of the resin adhesive to be applied is high or when the coating thickness must be increased, the adhesive is applied not only to the wiring part but also at least to the symmetrical position of the wiring part in order to eliminate uneven stress due to the resin. It is good to apply. Resin can also be applied to cover the entire strain sensor chip. Also, the piezoresistive element of the strain sensor is affected by light,
When it is desired to suppress the influence of light, it is desirable to cover the entire strain sensor chip with a colored resin.

The strain sensor chip 2 was joined with the metal solder 4 on the base plate 3, and the semiconductor strain sensor 1 that was wired was attached to the measurement object 6. After the semiconductor strain sensor 1 is installed at a desired position of the measurement object 6, 10 points of spot welding are performed on the first connection area 11 and the second connection area 12, and the semiconductor strain sensor 1 is attached to the measurement object 6. Stuck. The spot welding of 10 points is in 2 columns and 5 rows, and the welding points 19 are arranged at equal intervals of 5 points in the Y direction so that the third welding point is on the center line in the Y direction of the base plate.

The strain sensor chip 2 is formed with a piezoresistive element so that strain in the X direction and the Y direction can be detected. Although details are omitted, a bridge circuit is formed using a plurality of piezoresistive elements so that an output proportional to the amount of strain in the X and Y directions can be obtained. In this embodiment, the first
Only the piezoresistive element that measures the amount of strain in the direction is used. When the measurement object 6 is pulled in the X direction to generate distortion, the distortion is transmitted to the base plate of the semiconductor strain sensor through the spot weld, and distortion occurs in the base plate 3 and the strain sensor chip 2. Due to the resistance change of the piezoresistive element, an electrical signal output corresponding to the amount of strain of the measurement object is obtained. Due to the rigidity of the base plate 3 and the strain sensor chip 2, the strain amount generated in the strain sensor chip 2 does not match the strain amount of the measurement object, but it is used as a practical strain sensor by obtaining a conversion coefficient in advance. be able to.

In the semiconductor strain sensor of the first embodiment of the present invention, since the strain sensor chip 2 is fixed to the metal base plate 3 using a metal material, the heat generated in the strain sensor chip 2 is conducted through the base plate. It is easy to dissipate heat. Since the piezoresistive element has a high electric resistance, it easily generates heat, and when a CMOS amplifier circuit is formed in the strain sensor chip, the amplifier circuit also generates heat. As described above, the semiconductor strain sensor of the present embodiment is easy to conduct heat by conducting heat to the base plate as described above, so that not only can the temperature rise of the strain sensor chip be minimized, but also the base plate and the strain sensor chip It is easy to keep the temperature uniform. As a result, it was possible to suppress changes in characteristics caused by changes in the piezoresistive coefficient due to changes in the piezoresistive element due to changes in the piezoresistance coefficient due to temperature changes and thermal deformation due to temperature nonuniformity between the strain sensor chip and the base plate. If an organic material such as a resin adhesive is interposed between the layers from the strain sensor chip 2 to the measurement object 6, the organic material will creep after a long time in a strained state, and the strain detection zero point There was a problem that changed. Furthermore, there is a problem that strain transmission is hindered due to deterioration or alteration of the organic material, and strain detection sensitivity changes. In the semiconductor strain sensor of this embodiment, the metal sensor is used for fixing the strain sensor chip and the base plate, and welding is used for mounting the base plate and the measurement object, so that the characteristic change as described above due to the organic material can be achieved. A strain sensor with excellent sensor characteristics and long-term stability was obtained. There is a possibility that minute creep may occur even in the metal material used for fixing, but there is a significant difference compared to the case of using resin adhesive, so it is sufficient for long-term stability. There is.

The semiconductor strain sensor of this embodiment is resistant to noise because the strain sensor chip is connected to the object to be measured with a conductive material. A schematic equivalent circuit when the strain sensor chip and the object to be measured are connected by a conductive material is shown in FIG. 3a), and a schematic equivalent circuit when an insulating material is interposed between the two is shown in FIG. 3b). As shown in FIG. 3a), since the semiconductor strain sensor of this embodiment can electrically connect the ground of the strain sensor chip to the measurement object 6, the ground of the strain sensor chip fluctuates in accordance with the potential of the measurement object. (Fluctuates), so noise is hard to occur. As in the conventional semiconductor strain sensor, when an insulating material is interposed between the strain sensor chip and the measurement object, when the electric potential fluctuates due to current flowing through the measurement object, the sensor as shown in FIG. Since each part in the chip circuit 21 has the parasitic capacitance 22 between the object to be measured, the electric potential in the sensor chip circuit 21 is also fluctuated in various ways, so that noise is easily generated.

In the semiconductor strain sensor of this embodiment, the ease of attachment to the measurement object is sufficiently taken into consideration. The purpose of strain measurement is various, and the shape and size of the measurement object are also various. There are things that the measurement object is in a narrow place or high place, or that cannot be moved from the installation place. If the back surface of the strain sensor chip can be directly metal-bonded to the object to be measured, there is no need to provide a metal base plate. In order to directly bond the metal to the measurement object, it is necessary to form a metallization on the surface of the measurement object or to heat and melt the solder material. It is very difficult to form a metallized object or heat and melt a solder material on a measurement object that cannot be moved from the installation location. The semiconductor strain sensor of the present invention is a module in which a strain sensor chip is previously metal-bonded to a base plate and a flexible circuit board wiring is also connected. The strain amount can be measured simply by welding the connection area of the semiconductor strain sensor of the present invention to the measurement object. Portable spot resistance welders are also available on the market, so it is possible to bring spot resistance welders into the field and mount them on objects that cannot be moved. Further, not only spot resistance welding but also laser welding or seam welding can be used. Since the strain sensor chip is attached to the measurement object via the base plate, it is possible to reduce the risk of damaging the strain sensor chip during mounting work or changing unnecessary characteristics by applying unnecessary strain.

A semiconductor strain sensor according to a second embodiment of the present invention will be described. The difference from the first embodiment is the method of attaching to the measurement object. FIG. 4 is a plan view showing a state in which the strain sensor of the second embodiment is attached to a measurement object, and FIG. Bolt holes 23 are formed in the first connection area 11 and the second connection area 12 of the base plate 3 to connect the semiconductor strain sensor 1 to the measurement object 6.
It was fixed with bolts 24. Although it is necessary to form the screw hole 25 for the bolt 24 in the measuring object 6, the measuring object of the first embodiment is limited to a material that can be welded. However, in this embodiment, if the screw hole can be formed, It can also be applied to ceramics that cannot be welded. Conversely, it is also possible to attach a bolt to the measurement object and pass it through the bolt hole 23 in the connection area and fix it with a nut.

A semiconductor strain sensor according to a third embodiment of the present invention will be described. The arrangement of the connection areas and the wiring drawing method are different from the first embodiment. FIG. 6 is a plan view of a state in which the strain sensor of the third embodiment is attached to a measurement object, and FIG. 7 is a cross-sectional view taken along line nn ′ of FIG. As shown in FIG.
In addition to the first connection area 11 and the second connection area 12 that sandwich the sensor chip connection part 15 in the direction, the third connection area 13 and the fourth connection area 14 are arranged at a position that sandwiches the sensor chip connection part 15 in the Y direction. did. In the first to fourth connection areas, spot resistance welding was performed on the measurement object, and the semiconductor strain sensor 1 was fixed to the measurement object 6. The strain applied to the measurement object in the X direction is transmitted to the strain sensor chip 2 via the first connection area 11 and the second connection area 12, and the strain applied in the Y direction is the third connection area 13 and the fourth connection area. The strain is transmitted to the strain sensor chip 2 via 14, and the amount of strain applied to the measurement object can be detected.

Since the first to fourth connection areas are formed so as to surround the entire circumference of the strain sensor chip, the flexible wiring board 5 is disposed on the strain sensor chip 2. Metal bumps 26 were formed on the electrodes 16 of the strain sensor chip, and the flexible wiring board 5 was connected. In order to reduce the influence of the stress on the flexible wiring board, the flexible wiring board 5 is disposed so as to cover the strain sensor chip 2 instead of providing the flexible wiring board on one side of the strain sensor chip 2. A cover resin 18 was applied to the gap between the flexible wiring board 5 and the strain sensor chip 2. The cover resin 18 was an epoxy resin. The cover resin 18 serves not only to electrically insulate the wiring portion from the outside air but also to increase the bonding force between the flexible wiring board and the strain sensor chip. Since the flexible wiring board was disposed on the strain sensor chip, the flexible wiring board did not interfere with the welding operation when welding the first to fourth connection areas and the measurement object.

The semiconductor strain sensor of this embodiment is also suitable for torque detection. An example of torque detection is shown in FIG. A cylindrical member 27 to which torque is applied was used as an object to be measured, a notch groove 28 was formed on the cylindrical side surface of the cylindrical member, and the semiconductor strain sensor 1 of the present example was attached to a flat portion of the groove bottom. The semiconductor strain sensor of this example was fixed to a measurement object by welding at four connection areas around the strain sensor chip. Since strain is transmitted in both the X direction and the Y direction, the shear strain due to the torsion of the measurement object is also transmitted to the strain sensor chip 2, and the shear strain proportional to the torque can be calculated and obtained. In this embodiment, the piezoresistive elements in the strain sensor chip are arranged in parallel to the X direction and the Y direction. However, if a strain sensor chip in which a piezoresistive element is arranged in advance at 45 degrees with respect to the X direction and the Y direction is used, the strain in the shear direction can be directly measured.

A semiconductor strain sensor according to a fourth embodiment of the present invention will be described. The wiring drawing method is different from the first embodiment. FIG. 9 is a plan view of the semiconductor strain sensor of the fourth embodiment. A base plate electrode 32 was formed on the base plate 3 via an insulating film 31. The base plate electrode 32 and the electrode 16 of the strain sensor chip 2 were connected by an Au wire 17, and the tip of the clothing wiring 33 peeled off was soldered to the base plate electrode. Cover resin 18 was applied so as to cover the strain sensor chip including the wiring portion. When the stress due to the resin is large, the application of the cover resin can be performed only at the wiring portion or at a symmetrical position between the wiring portion and the wiring portion. According to the present embodiment, by using the base plate 3 on which the base plate electrode 32 is formed in advance, a flexible wiring board becomes unnecessary, and an assembly process such as adhesion of the flexible wiring board to the base plate can be omitted. The wiring drawing structure is suitable when the number of drawing wirings is small.

The wiring means of the strain sensor of the present invention is not limited to the configuration shown in the first to fourth embodiments. For example, flexible wiring is applied to the base plate electrode formed on the base plate via an insulating film. A method of electrically connecting a part of the wiring of the board using an anisotropic conductive adhesive can be used.

It is a top view of the mounting state of the semiconductor strain sensor of a 1st Example. It is sectional drawing of the mounting state of the semiconductor strain sensor of a 1st Example. It is an electrical model equivalent circuit in the mounting state of the semiconductor strain sensor of a 1st Example. It is a top view of the mounting state of the semiconductor strain sensor of a 2nd Example. It is sectional drawing of the mounting state of the semiconductor strain sensor of a 2nd Example. It is a top view of the mounting state of the semiconductor strain sensor of a 3rd Example. It is sectional drawing of the mounting state of the semiconductor strain sensor of a 3rd Example. It is a perspective view which shows the example of the torque measurement using the semiconductor strain sensor of 3rd Example. It is a top view of the mounting state of the semiconductor strain sensor of 4th Example. It is a figure which shows the external appearance of the conventional strain sensor.

Explanation of symbols

1 Semiconductor strain sensor,
2 Strain sensor chip,
3 Base plate,
4 Metal solder,
5 Flexible wiring board,
6 Measurement object,
11 First connection area,
12 Second connection area,
13 Third connection area,
14 Fourth connection area,
15 Strain sensor chip connection area,
16 electrodes,
17 wire,
18 Cover resin,
19 welding points,
21 sensor chip circuit,
22 parasitic capacitance,
23 bolt holes,
24 volts,
25 screw holes,
26 Metal bumps,
27 cylindrical member,
28 Notch groove,
31 insulating film,
32 Base plate electrode,
33 covered wire,
51 Semiconductor strain gauge,
52 Strain sensor chip,
53 Wiring,
54 Polyimide film,
56 strain detection sensor,
57 glass pedestal,
58 Low melting glass.

Claims (7)

It has a strain sensor chip in which a piezoresistive element is formed on a semiconductor substrate, a metal base plate, and a wiring portion for drawing wiring out from the electrodes of the strain sensor chip, and the back surface of the strain sensor chip and the base plate surface are made of metal. A semiconductor strain sensor characterized in that it has at least two or more connection areas to be fixed to a measurement object on a base plate portion joined by a joining material and projecting to the side of the strain sensor chip. The wiring section includes a flexible wiring board that is resin-bonded on the base plate, a metal wire that electrically connects the wiring of the flexible wiring board and the electrode of the strain sensor chip, and at least the electrode and the metal wire of the strain sensor chip. The semiconductor strain sensor according to claim 1, comprising a covering resin. The semiconductor strain sensor according to claim 1, wherein a part of the wiring of the flexible wiring board is directly connected to the metal bump provided on the electrode of the strain sensor chip. The wiring portion includes a base plate electrode formed on the base plate via an insulating film, a metal wire that electrically connects the base plate electrode and the electrode of the strain sensor chip, at least the base plate electrode and the metal wire, The semiconductor strain sensor according to claim 1, wherein the semiconductor strain sensor is made of a resin that covers an electrode of the strain sensor chip. Mounting of a semiconductor strain sensor characterized in that the back surface of the base plate of the semiconductor strain sensor faces the object to be measured, and the semiconductor strain sensor has at least a part of the connection area of the base plate fixed to the object to be measured. Method. 6. The semiconductor strain sensor according to claim 5, wherein the semiconductor strain sensor and the measurement object are fixed in at least two or more connection areas, and each connection area is fixed by at least one welded portion. Method. 6. The semiconductor strain sensor according to claim 5, wherein the semiconductor strain sensor and the measurement object are fixed at least in two or more connection areas, and each connection area is fixed by at least one screw portion. Method.

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