JP7302780B2 - Force sensor device - Google Patents

Description

The present invention relates to a force sensor device.

Conventionally, there is a force sensor device that detects a multiaxial force by attaching a sensor element to a strain-generating body made of metal and detecting the elastic deformation of the strain-generating body caused by the application of an external force with the sensor element. Are known. In such a force sensor device, for example, an electrical signal corresponding to strain is output from the sensor element to an active component such as an IC that is separately prepared, and the active component performs predetermined signal processing (see, for example, Patent Documents 1-3).

Patent No. 4011345 Patent No. 3970640 JP 2018-185296 A

In the force sensor device described above, the electrical signal may fluctuate due to expansion or contraction of the strain generating body due to changes in the outside air temperature or the like, or due to temperature characteristics of the sensor element. If the temperature distribution in the force sensor device is uniform, it is possible to correct the temperature with an active component or the like by providing a temperature sensor for temperature correction.

However, in the force sensor device, heat is conducted mainly through air, which has a low thermal conductivity, and temperature distribution tends to occur. It is not easy to catch and correct the problem.

In particular, due to the low thermal conductivity of air, it is difficult to correct the temperature in response to rapid temperature changes. Such rapid temperature changes are caused, for example, by the fact that the active parts generate heat by themselves when the force sensor device is activated, or that the strain-generating body made of metal and having high thermal conductivity is easily affected by heat from the outside. can occur.

The disclosed technique has been made in view of the above points, and aims to suppress the influence of temperature change.

The disclosed technique includes a sensor element for detecting a force applied in a predetermined axial direction or around an axis, an active component electrically connected to the sensor element, the sensor element and the active component attached, and applying force. a strain body for transmitting the applied force to the sensor element; a cover mounted to cover the sensor element and the active component; and a medium injected into the cover and having a higher thermal conductivity than air. and wherein the medium is mixed with a heat transfer filler .

According to the disclosed technique, it is possible to suppress the influence of temperature change.

1 is a perspective view showing the appearance of a force sensor device according to a first embodiment; FIG. 1 is a perspective view of a force sensor device in a state where a substrate is attached to a strain body; FIG. 2A and 2B are a plan view and a side view of the force sensor device in a state where the board is attached to the strain body; FIG. It is the figure which looked the sensor chip from the Z-axis direction upper side. It is the figure which looked the sensor chip from the Z-axis direction lower side. It is a figure explaining the code|symbol which shows the force and moment which act on each axis|shaft. FIG. 4 is a diagram illustrating the arrangement of piezoresistive elements of a sensor chip; It is a figure which illustrates electrode arrangement|positioning and wiring in a sensor chip. 4 is an enlarged plan view illustrating a temperature sensor of a sensor chip; FIG. FIG. 1 is a diagram (part 1) exemplifying a strain-generating body; FIG. 2 is a diagram (part 2) exemplifying a strain-generating body; FIG. 3 is a diagram (part 3) exemplifying a strain-generating body; FIG. 11 is a diagram (part 1) illustrating a manufacturing process of the force sensor device; FIG. 12 is a diagram (part 2) illustrating the manufacturing process of the force sensor device; FIG. 13 is a diagram (part 3) illustrating the manufacturing process of the force sensor device; FIG. 10 is a diagram (part 4) illustrating the manufacturing process of the force sensor device; FIG. 11 is a diagram (No. 5) exemplifying the manufacturing process of the force sensor device; FIG. 11 is a diagram (No. 6) illustrating a manufacturing process of the force sensor device; It is a longitudinal cross-sectional view of the force sensor device after completion. It is a figure which shows the 1st modification of a force sensor apparatus. It is a figure which shows the 2nd modification of a force sensor apparatus.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings. In each drawing, the same components are denoted by the same reference numerals, and redundant description may be omitted.

<First Embodiment>
(Outline configuration)
FIG. 1 is a perspective view showing the appearance of the force sensor device according to the first embodiment. FIG. 2 is a perspective view of the force sensor device in a state where the substrate is attached to the strain body. FIG. 3(a) is a plan view, and FIG. 3(b) is a side view. FIG. 4 is a perspective view illustrating a sensor chip and a strain body.

1 to 3, the force sensor device 1 has a sensor chip 110, a strain body 20, a substrate 30, a force receiving plate 40, and a cover 50. FIG. The force sensor device 1 is, for example, a multi-axis force sensor device mounted on an arm or finger of a robot used in a machine tool or the like.

A substrate 30 is attached to the strain body 20 (see FIG. 2), and a cover 50 is attached so as to cover the upper side of the base 21 of the strain body 20 to which the substrate 30 is attached and the sensor chip 110 . (See Figure 1). The cover 50 is made of, for example, a metal material whose surface is plated with nickel. The cover 50 is provided with openings for exposing the input portions 24a to 24d of the strain body 20, and the force receiving plate 40 is provided on the input portions 24a to 24d.

Although the details will be described later, the cover 50 is filled with a medium made of gel, rubber, liquid, or the like, which has a higher thermal conductivity than air. Note that the inside of the cover 50 refers to an internal space formed between the cover 50 and the base 21 of the strain generating body 20 . More specifically, the inside of the cover 50 is defined as the space (outer peripheral portion) between the strain body 20 and the cover 50 where the sensor chip 110 and the active components 32 to 35 are present, and the space inside the strain body 20. and refers to the space (hollow portion) in which the pillar 28 as the sensor chip mounting portion exists.

The sensor chip 110 has a function of detecting displacement in predetermined axial directions up to six axes. The strain body 20 has the function of transmitting the applied force to the sensor chip 110 . In the following embodiments, as an example, a case where the sensor chip 110 detects 6 axes will be described, but the sensor chip 110 is not limited to this, and for example, the sensor chip 110 may detect 3 axes.

The sensor chip 110 is adhered to the upper surface of the strain-generating body 20 so as not to protrude from the strain-generating body 20 . Further, one end side of a substrate 30 for inputting and outputting signals with respect to the sensor chip 110 is bonded to the upper surface and each side surface of the strain generating body 20 in a state of being appropriately bent. The sensor chip 110 and each electrode 31 of the substrate 30 are electrically connected by a bonding wire or the like (not shown).

(active parts)
Active parts 32 to 35 are arranged on the sides of the strain generating body 20 . Specifically, the active components 32 to 35 are mounted on one surface of a substrate 30 (eg, flexible printed circuit board), and the other surface of the substrate 30 is fixed to the side surface of the strain generating body 20 . Active components 32 to 35 are electrically connected to corresponding electrodes 31 via wiring patterns (not shown) formed on substrate 30 .

More specifically, an active component 32 is mounted on the substrate 30 in a region located on the first side surface of the strain body 20 . An active component 33 and a passive component 39 are mounted on the substrate 30 in a region located on the second side surface of the strain-generating body 20 . An active component 34 and a passive component 39 are mounted on the substrate 30 in a region located on the third side surface of the strain-generating body 20 . An active component 35 and a passive component 39 are mounted on the substrate 30 in a region located on the fourth side surface of the strain-generating body 20 .

The active component 33 is, for example, an analog electric signal from a bridge circuit that detects the X-axis direction force Fx output from the sensor chip 110, and a bridge that detects the Y-axis direction force Fy output from the sensor chip 110. It is an IC (AD converter) that converts an analog electrical signal from a circuit into a digital electrical signal.

The active component 34 detects, for example, an analog electric signal from a bridge circuit that detects a force Fz in the Z-axis direction output from the sensor chip 110, and a moment Mx output from the sensor chip 110 that rotates about the X-axis. It is an IC (AD converter) that converts an analog electric signal from a bridge circuit to be detected into a digital electric signal.

For example, the active component 35 rotates about the Z-axis output from the sensor chip 110 and the analog electric signal from the bridge circuit that detects the moment My that rotates about the Y-axis output from the sensor chip 110. It is an IC (AD converter) that converts an analog electrical signal from a bridge circuit that detects moment Mz into a digital electrical signal.

Active component 32, for example, performs predetermined operations on the digital electrical signals output from active components 33, 34, and 35 to indicate forces Fx, Fy, and Fz and moments Mx, My, and Mz. An IC that generates a signal and outputs it to the outside. The passive components 39 are resistors, capacitors, etc. connected to the active components 32-35.

The number of ICs to implement the functions of the active components 32 to 35 can be arbitrarily determined. Also, it is possible to adopt a configuration in which the active components 32 to 35 are not mounted on the substrate 30, but are mounted on the side of an external circuit connected to the substrate 30. FIG. In this case, an analog electrical signal is output from the substrate 30 .

The substrate 30 is bent outward below the first side surface of the strain generating body 20, and the other end side of the substrate 30 is pulled out to the outside. On the other end side of the substrate 30, terminals (not shown) capable of electrical input/output with an external circuit (control device, etc.) connected to the force sensor device 1 are arranged.

In this embodiment, for convenience, the side on which the sensor chip 110 is provided in the force sensor device 1 is referred to as the upper side or one side, and the opposite side thereof is referred to as the lower side or the other side. The surface on which the sensor chip 110 of each part is provided is defined as one surface or upper surface, and the opposite surface is defined as the other surface or lower surface. However, the force sensor device 1 can be used upside down or arranged at an arbitrary angle. Planar view means viewing an object from the normal direction (Z-axis direction) of the upper surface of the sensor chip 110, and planar shape means viewing the object from the normal direction (Z-axis direction) of the upper surface of the sensor chip 110. ) shall refer to the shape viewed from

(force receiving plate)
The planar shape of the force receiving plate 40 is, for example, circular. On the upper surface side of the force receiving plate 40, four concave portions 40x having a rectangular planar shape and four through holes 40y having a circular planar shape are provided. In addition, one concave portion 40z having a circular planar shape is provided in the central portion of the upper surface side of the force receiving plate 40 .

The four recesses 40x are arranged to cover the input portions 24a to 24d of the strain body 20, respectively, and the bottom surface of each recess 40x protrudes toward the strain body 20 so as to cover the input portions 24a to 24d of the strain body 20. in contact with the top surface. However, the planar shapes of the recess 40x, the through hole 40y, and the recess 40z can be arbitrarily determined.

Although not shown, projections (or projection receiving portions) are formed on the upper surfaces of the input portions 24a to 24d, and projection receiving portions (or projections) are formed on the bottom surfaces of the recesses 40x projecting toward the strain body 20. The force receiving plate 40 and the strain generating body 20 may be positioned by fitting the projections (or projection receiving portions) on the upper surfaces of the portions 24a to 24d and the projection receiving portions (or projections) on the bottom surface of the recess 40x. .

The concave portion 40x and the concave portion 40z can be used for positioning when the force sensor device 1 is attached to the fixed portion as necessary. Further, the through hole 40y is a screw hole for fastening the force sensor device 1 to the fixed portion using a screw or the like.

As a material of the force receiving plate 40, for example, SUS (stainless steel) 630 or the like can be used. The force receiving plate 40 can be fixed to the strain body 20 by welding, for example.

By providing the force receiving plate 40 in this manner, force can be input from the outside to the input portions 24 a to 24 d of the strain generating body 20 via the force receiving plate 40 .

(sensor chip)
4A and 4B are views of the sensor chip 110 viewed from above in the Z-axis direction, with FIG. 4A being a perspective view and FIG. 4B being a plan view. 5A and 5B are views of the sensor chip 110 viewed from below in the Z-axis direction, FIG. 5A being a perspective view, and FIG. 5B being a bottom view. The direction parallel to one side of the upper surface of the sensor chip 110 is the X-axis direction, the vertical direction is the Y-axis direction, and the thickness direction of the sensor chip 110 (the normal direction of the upper surface of the sensor chip 110) is the Z-axis direction. . The X-axis direction, Y-axis direction, and Z-axis direction are orthogonal to each other.

The sensor chip 110 shown in FIGS. 4 and 5 is a MEMS (Micro Electro Mechanical Systems) sensor chip capable of detecting up to six axes with one chip, and is formed from a semiconductor substrate such as an SOI (Silicon On Insulator) substrate. The planar shape of the sensor chip 110 can be, for example, a square of about 3000 μm square.

The sensor chip 110 has five columnar support portions 111a to 111e. The planar shape of the support portions 111a to 111e can be, for example, a square of about 500 μm square. The support portions 111 a to 111 d, which are the first support portions, are arranged at the four corners of the sensor chip 110 . The support portion 111e, which is the second support portion, is arranged in the center of the support portions 111a to 111d.

The support portions 111a to 111e can be formed, for example, from an active layer, a BOX layer, and a support layer of an SOI substrate, and each can have a thickness of, for example, about 500 μm.

Reinforcing beams 112a for reinforcing the structure are provided between the supporting portions 111a and 111b, both ends of which are fixed to the supporting portions 111a and 111b (connecting adjacent supporting portions). It is Reinforcing beams 112b for reinforcing the structure are provided between the supporting portions 111b and 111c, both ends of which are fixed to the supporting portions 111b and 111c (connecting adjacent supporting portions). It is

Between the supporting portion 111c and the supporting portion 111d, a reinforcing beam 112c for reinforcing the structure is provided, which is fixed at both ends to the supporting portion 111c and the supporting portion 111d (connects adjacent supporting portions). It is Between the supporting portions 111d and 111a, reinforcing beams 112d for reinforcing the structure are provided, both ends of which are fixed to the supporting portions 111d and 111a (connecting adjacent supporting portions). It is

In other words, four reinforcing beams 112a, 112b, 112c, and 112d, which are the first reinforcing beams, are formed in a frame shape, and corners forming intersections of the respective reinforcing beams are support portions 111b, 111c, and 111d. , 111a.

The inner corner of the support portion 111a and the opposite corner of the support portion 111e are connected by reinforcing beams 112e for reinforcing the structure. The inner corner of the support portion 111b and the opposing corner of the support portion 111e are connected by a reinforcing beam 112f for reinforcing the structure.

The inner corner of the support portion 111c and the opposing corner of the support portion 111e are connected by a reinforcing beam 112g for reinforcing the structure. The inner corner of the support portion 111d and the opposing corner of the support portion 111e are connected by a reinforcing beam 112h for reinforcing the structure. The reinforcing beams 112e to 112h, which are the second reinforcing beams, are arranged obliquely with respect to the X-axis direction (Y-axis direction). That is, the reinforcing beams 112e to 112h are arranged non-parallel to the reinforcing beams 112a, 112b, 112c, and 112d.

The reinforcing beams 112a-112h can be formed, for example, from the active layer, the BOX layer and the supporting layer of the SOI substrate. The thickness (width in the lateral direction) of the reinforcing beams 112a to 112h can be, for example, approximately 140 μm. The top surfaces of the reinforcing beams 112a to 112h are substantially flush with the top surfaces of the support portions 111a to 111e.

On the other hand, the lower surfaces of the reinforcing beams 112a to 112h are recessed upward by several tens of micrometers from the lower surfaces of the support portions 111a to 111e and the power points 114a to 114d. This is to prevent the lower surfaces of the reinforcing beams 112a to 112h from contacting the opposite surfaces of the strain body 20 when the sensor chip 110 is adhered to the strain body 20. FIG.

In this manner, by arranging the stiffening reinforcing beams which are thicker than the sensing beams and have high rigidity, separately from the sensing beams for sensing strain, the rigidity of the sensor chip 110 as a whole can be increased. This makes it difficult for the beams other than the detection beams to deform with respect to the input, so that good sensor characteristics can be obtained.

Inside the reinforcing beam 112a between the supporting portion 111a and the supporting portion 111b, both ends were fixed to the supporting portion 111a and the supporting portion 111b in parallel with the reinforcing beam 112a with a predetermined interval (adjacent to each other). The support portions are connected to each other), and a detection beam 113a for detecting strain is provided.

Between the detection beam 113a and the support portion 111e, a detection beam 113b is provided parallel to the detection beam 113a with a predetermined gap from the detection beam 113a and the support portion 111e. The detection beam 113b connects the end of the reinforcing beam 112e on the side of the supporting portion 111e and the end of the reinforcing beam 112f on the side of the supporting portion 111e.

The substantially central portion in the longitudinal direction of the detection beam 113a and the substantially central portion in the longitudinal direction of the opposing detection beam 113b are the detection beams arranged so as to be orthogonal to the detection beams 113a and 113b. 113c.

Inside the reinforcing beam 112b between the supporting portion 111b and the supporting portion 111c, both ends are fixed (adjacent The support portions are connected to each other), and a detection beam 113d for detecting strain is provided.

Between the detection beam 113d and the support portion 111e, a detection beam 113e is provided parallel to the detection beam 113d with a predetermined gap from the detection beam 113d and the support portion 111e. The detection beam 113e connects the end of the reinforcing beam 112f on the support portion 111e side and the end of the reinforcing beam 112g on the support portion 111e side.

The substantially central portion in the longitudinal direction of the detection beam 113d and the substantially central portion in the longitudinal direction of the opposing detection beam 113e are the detection beams arranged so as to be orthogonal to the detection beams 113d and 113e. 113f.

Inside the reinforcing beam 112c between the supporting portion 111c and the supporting portion 111d, both ends are fixed to the supporting portion 111c and the supporting portion 111d in parallel with the reinforcing beam 112c at a predetermined interval (adjacent to each other). The supporting portions are connected to each other), and a detection beam 113g for detecting strain is provided.

Between the detection beam 113g and the support portion 111e, a detection beam 113h is provided parallel to the detection beam 113g with a predetermined gap from the detection beam 113g and the support portion 111e. The detection beam 113h connects the end portion of the reinforcing beam 112g on the support portion 111e side and the end portion of the reinforcing beam 112h on the support portion 111e side.

A substantially central portion in the longitudinal direction of the detection beam 113g and a substantially central portion in the longitudinal direction of the opposing detection beam 113h are the detection beams arranged so as to be perpendicular to the detection beams 113g and 113h. 113i.

Inside the reinforcing beam 112d between the supporting portion 111d and the supporting portion 111a, both ends were fixed to the supporting portion 111d and the supporting portion 111a in parallel with the reinforcing beam 112d with a predetermined interval (adjacent to the supporting portion 111d). The support portions are connected to each other), and a detection beam 113j for detecting strain is provided.

Between the detection beam 113j and the support portion 111e, a detection beam 113k is provided parallel to the detection beam 113j with a predetermined gap from the detection beam 113j and the support portion 111e. The detection beam 113k connects the end of the reinforcing beam 112h on the support portion 111e side and the end of the reinforcing beam 112e on the support portion 111e side.

The substantially central portion in the longitudinal direction of the detection beam 113j and the substantially central portion in the longitudinal direction of the opposing detection beam 113k are the detection beams arranged orthogonal to the detection beams 113j and 113k. 113l.

The detection beams 113a to 113l are provided on the upper end side in the thickness direction of the supporting portions 111a to 111e, and can be formed from, for example, an active layer of an SOI substrate. The thickness (width in the lateral direction) of the detection beams 113a to 113l can be, for example, approximately 75 μm. The top surfaces of the detection beams 113a to 113l are substantially flush with the top surfaces of the support portions 111a to 111e. The thickness of each of the detection beams 113a to 113l can be, for example, approximately 50 μm.

A force point 114a is provided on the lower surface side of the central portion of the detection beam 113a in the longitudinal direction (the intersection of the detection beam 113a and the detection beam 113c). The detection beams 113a, 113b, and 113c and the power point 114a form a set of detection blocks.

A power point 114b is provided on the lower surface side of the detection beam 113d in the center in the longitudinal direction (the intersection of the detection beam 113d and the detection beam 113f). The detection beams 113d, 113e, and 113f and the power point 114b form a set of detection blocks.

A power point 114c is provided on the lower surface side of the longitudinal central portion of the detection beam 113g (the intersection of the detection beam 113g and the detection beam 113i). The detection beams 113g, 113h, and 113i and the power point 114c form a set of detection blocks.

A power point 114d is provided on the lower surface side of the central portion of the detection beam 113j in the longitudinal direction (the intersection of the detection beam 113j and the detection beam 113l). The detection beams 113j, 113k, and 113l and the power point 114d form a set of detection blocks.

Force points 114a-114d are locations where external forces are applied, and can be formed, for example, from the BOX layer and support layer of an SOI substrate. The lower surfaces of the power points 114a-114d are substantially flush with the lower surfaces of the support portions 111a-111e.

In this way, by taking in force or displacement from the four force points 114a to 114d, different deformations of the beam can be obtained for each type of force, so a sensor with good six-axis separability can be realized.

In addition, in the sensor chip 110, from the viewpoint of suppressing stress concentration, it is preferable that the portion forming the internal angle be rounded.

FIG. 6 is a diagram for explaining symbols indicating forces and moments applied to each axis. As shown in FIG. 6, let Fx be the force in the X-axis direction, Fy be the force in the Y-axis direction, and Fz be the force in the Z-axis direction. Let Mx be the moment of rotation about the X axis, My be the moment of rotation about the Y axis, and Mz be the moment of rotation about the Z axis.

FIG. 7 is a diagram illustrating the arrangement of the piezoresistive elements of the sensor chip 110. As shown in FIG. A piezoresistive element is arranged at a predetermined position of each detection block corresponding to the four power points 114a to 114d.

Specifically, referring to FIGS. 4 and 7, in the sensing block corresponding to the force point 114a, the piezoresistive elements MxR3 and MxR4 are on a line that bisects the sensing beam 113a in the longitudinal direction, and In a region of the detection beam 113a close to the detection beam 113c, they are arranged at symmetrical positions with respect to a line that bisects the detection beam 113c in the longitudinal direction (Y direction). Further, the piezoresistive elements FyR3 and FyR4 detect in a region on the reinforcing beam 112a side of the line that bisects the detection beam 113a in the longitudinal direction and farther from the detection beam 113c of the detection beam 113a. They are arranged at symmetrical positions with respect to a line that bisects the beam 113c in the longitudinal direction.

In addition, in the detection block corresponding to the force point 114b, the piezoresistive elements MyR3 and MyR4 are located on a line that bisects the detection beam 113d in the longitudinal direction and in an area of the detection beam 113d close to the detection beam 113f. are arranged at symmetrical positions with respect to a line that bisects the detection beam 113f in the longitudinal direction (X direction). In addition, the piezoresistive elements FxR3 and FxR4 detect in a region on the reinforcement beam 112b side of the line that bisects the detection beam 113d in the longitudinal direction and farther from the detection beam 113f of the detection beam 113d. They are arranged at symmetrical positions with respect to a line that bisects the beam 113f in the longitudinal direction.

In addition, the piezoresistive elements MzR3 and MzR4 detect in a region closer to the detection beam 113f than the line that bisects the detection beam 113d in the longitudinal direction and closer to the detection beam 113f. They are arranged at symmetrical positions with respect to a line that bisects the beam 113f in the longitudinal direction. The piezoresistive elements FzR2 and FzR3 are located on the support portion 111e side of the line that bisects the detection beam 113e in the longitudinal direction, and in a region of the detection beam 113e near the detection beam 113f. symmetrically about a line that bisects the

In addition, in the sensing block corresponding to the force point 114c, the piezoresistive elements MxR1 and MxR2 are located on a line that bisects the sensing beam 113g in the longitudinal direction and in an area of the sensing beam 113g close to the sensing beam 113i. , are arranged symmetrically with respect to a line that bisects the detection beam 113i in the longitudinal direction (Y direction). In addition, the piezoresistive elements FyR1 and FyR2 are located on the side of the reinforcing beam 112c from the line that bisects the sensing beam 113g in the longitudinal direction, and are located farther from the sensing beam 113i than the sensing beam 113g. They are arranged at symmetrical positions with respect to a line that bisects the beam 113i in the longitudinal direction.

In addition, in the detection block corresponding to the force point 114d, the piezoresistive elements MyR1 and MyR2 are located on a line that bisects the detection beam 113j in the longitudinal direction and in an area of the detection beam 113j close to the detection beam 113l. , are arranged at symmetrical positions with respect to a line that bisects the detection beam 113l in the longitudinal direction (X direction). In addition, the piezoresistive elements FxR1 and FxR2 are located on the reinforcement beam 112d side of the line that bisects the detection beam 113j in the longitudinal direction, and are located farther from the detection beam 113l than the detection beam 113j. They are arranged at symmetrical positions with respect to a line that bisects the beam 113l in the longitudinal direction.

In addition, the piezoresistive elements MzR1 and MzR2 are located on the sensing beam 113k side of the line that bisects the sensing beam 113j in the longitudinal direction, and are located near the sensing beam 113l of the sensing beam 113j. They are arranged at symmetrical positions with respect to a line that bisects the beam 113l in the longitudinal direction. The piezoresistive elements FzR1 and FzR4 are located on the support portion 111e side of the line that bisects the detection beam 113k in the longitudinal direction, and in a region far from the detection beam 113l of the detection beam 113k. symmetrically about a line that bisects the

In this way, in the sensor chip 110, a plurality of piezoresistive elements are separately arranged in each detection block. As a result, based on changes in the outputs of the plurality of piezoresistive elements arranged on the predetermined beams in accordance with the directions (axial directions) of the forces applied (transmitted) to the force points 114a to 114d, Up to 6 axes of displacement can be detected.

In the sensor chip 110, the detection beams 113c, 113f, 113i, and 113l are shortened as much as possible, and the detection beams 113b, 113e, 113h, and 113k are brought closer to the detection beams 113a, 113d, 113g, and 113j. , detection beams 113b, 113e, 113h, and 113k. With this structure, the detection beams 113b, 113e, 113h, and 113k can be easily bent in a bow shape, stress concentration can be alleviated, and the load capacity can be improved.

Further, in the sensor chip 110, no piezoresistive elements are arranged on the detection beams 113c, 113f, 113i, and 113l, which are shortened so that deformation against stress is small. Instead, the stresses in sense beams 113a, 113d, 113g, and 113j, which are thinner and longer than sense beams 113c, 113f, 113i, and 113l, and which are more likely to bow, and sense beams 113b, 113e, 113h, and 113k, are stressed. A piezoresistive element is placed in the vicinity of the position where . As a result, the sensor chip 110 can take in the stress efficiently, and the sensitivity (resistance change of the piezoresistive element with respect to the same stress) is improved.

In the sensor chip 110, dummy piezoresistive elements are arranged in addition to the piezoresistive elements used for strain detection. The dummy piezoresistive elements are arranged so that all the piezoresistive elements including the piezoresistive elements used for strain detection are point-symmetrical with respect to the center of the supporting portion 111e.

Here, piezoresistive elements FxR1 to FxR4 detect force Fx, piezoresistive elements FyR1 to FyR4 detect force Fy, and piezoresistive elements FzR1 to FzR4 detect force Fz. The piezoresistive elements MxR1 to MxR4 detect the moment Mx, the piezoresistive elements MyR1 to MyR4 detect the moment My, and the piezoresistive elements MzR1 to MzR4 detect the moment Mz.

In this way, in the sensor chip 110, a plurality of piezoresistive elements are separately arranged in each detection block. As a result, according to the direction (axial direction) of the force or displacement applied (transmitted) to the points of force 114a to 114d, the output of a plurality of piezoresistive elements arranged on a predetermined beam is changed, and a predetermined axis is generated. Directional displacement can be detected in up to six axes.

Specifically, in the sensor chip 110, the displacement (Mx, My, Fz) in the Z-axis direction can be detected based on the deformation of a predetermined detection beam. That is, the moments (Mx, My) in the X-axis direction and the Y-axis direction can be detected based on the deformation of the first detection beams 113a, 113d, 113g, and 113j. Also, the force (Fz) in the Z-axis direction can be detected based on the deformation of the detection beams 113e and 113k, which are the second detection beams.

In addition, in the sensor chip 110, displacements (Fx, Fy, Mz) in the X-axis direction and the Y-axis direction can be detected based on the deformation of predetermined detection beams. That is, the forces (Fx, Fy) in the X-axis direction and the Y-axis direction can be detected based on the deformation of the first detection beams 113a, 113d, 113g, and 113j. Also, the moment (Mz) in the Z-axis direction can be detected based on the deformation of the detection beams 113d and 113j, which are the first detection beams.

By varying the thickness and width of each detection beam, it is possible to make adjustments such as making the detection sensitivity uniform and improving the detection sensitivity.

However, it is also possible to reduce the number of piezoresistive elements and make a sensor chip that detects displacement in a predetermined axial direction of five axes or less.

FIG. 8 is a diagram illustrating the electrode arrangement and wiring in the sensor chip 110, and is a plan view of the sensor chip 110 viewed from above in the Z-axis direction. As shown in FIG. 8, the sensor chip 110 has a plurality of electrodes 15 for taking out electrical signals. Each electrode 15 is arranged on the upper surface of the support portions 111a to 111d of the sensor chip 110, which are least distorted when force is applied to the force points 114a to 114d. The wiring 16 from each piezoresistive element to the electrode 15 can be routed appropriately on each reinforcing beam and each detecting beam.

In this way, each reinforcing beam can also be used as a detour when wiring is drawn out as needed, so by arranging the reinforcing beams separately from the detection beams, the degree of freedom in wiring design is improved. be able to. This makes it possible to arrange each piezoresistive element at a more ideal position.

FIG. 9 is an enlarged plan view illustrating temperature sensors of the sensor chip 110. FIG. As shown in FIGS. 8 and 9, the sensor chip 110 includes a temperature sensor 17 for temperature correction of the piezoresistive element used for strain detection. The temperature sensor 17 has a configuration in which four piezoresistive elements TR1, TR2, TR3, and TR4 are bridge-connected.

Of the piezoresistive elements TR1, TR2, TR3, and TR4, two opposing ones have the same characteristics as the piezoresistive element MxR1 used for strain detection. Among the piezoresistive elements TR1, TR2, TR3, and TR4, the other two facing each other have different characteristics from those of the piezoresistive elements MxR1 and the like by changing the impurity concentration with an impurity semiconductor. This makes it possible to detect the temperature because the balance of the bridge is lost due to the change in temperature.

The piezoresistive elements (MxR1, etc.) used for strain detection are all arranged horizontally or vertically with respect to the crystal orientation of the semiconductor substrate (silicon, etc.) forming the sensor chip 110 . This makes it possible to obtain a larger change in resistance for the same strain, and to improve the measurement accuracy of the applied force and moment.

On the other hand, the piezoresistive elements TR1, TR2, TR3, and TR4 forming the temperature sensor 17 are arranged at an angle of 45 degrees with respect to the crystal orientation of the semiconductor substrate (silicon or the like) forming the sensor chip 110. . As a result, resistance change due to stress can be reduced, so only temperature change can be detected with high accuracy.

Moreover, the temperature sensor 17 is arranged on the upper surface of the support portion 111a of the sensor chip 110, which is least distorted when force is applied to the force points 114a to 114d. This can further reduce the change in resistance to stress.

(Strain-generating body)
10A and 10B are diagrams (part 1) illustrating the strain body 20, FIG. 10(a) being a perspective view and FIG. 10(b) being a side view. 11A and 11B are diagrams (part 2) illustrating the strain generating body 20, FIG. 11A being a plan view, and FIG. is. 12A and 12B are diagrams (part 3) illustrating the strain-generating body 20, FIG. 12(a) being a longitudinal sectional view taken along the line BB in FIG. 11(a), and FIG. 12(a) is a cross-sectional view taken along line CC of FIG.

As shown in FIGS. 10 to 12, the strain generating body 20 includes a base 21 directly attached to the fixed portion, a pillar 28 serving as a sensor chip mounting portion for mounting the sensor chip 110, and spaced around the pillar 28. and pillars 22a-22d arranged in parallel with each other.

More specifically, in the strain generating body 20, four pillars 22a to 22d are arranged on the upper surface of a substantially circular base 21 so as to be even (point symmetrical) with respect to the center of the base 21. Frame-shaped beams 23a to 23d are provided to connect opposite sides of the base 21 to each other. A pillar 28 is arranged above the center of the upper surface of the base 21 . Note that the planar shape of the base 21 is not limited to a circle, and may be polygonal or the like (for example, square or the like).

The pillar 28 is thicker and shorter than the pillars 22a-22d. The sensor chip 110 is fixed on the column 28 so as not to protrude from the upper surfaces of the columns 22a to 22d.

The pillars 28 are not directly fixed to the upper surface of the base 21, but are fixed to the pillars 22a to 22d via connecting beams 28a to 28d. Therefore, there is a space between the top surface of the base 21 and the bottom surface of the pillar 28 . The lower surface of the column 28 and the lower surface of each of the connecting beams 28a-28d can be flush with each other.

The cross-sectional shape of the portion of the column 28 to which the connection beams 28a to 28d are connected is, for example, a rectangle, and the four corners of the rectangle and the columns 22a to 22d facing the four corners of the rectangle are connected via the connection beams 28a to 28d. It is The positions 221 to 224 where the connecting beams 28a to 28d are connected to the columns 22a to 22d are preferably lower than the middle of the columns 22a to 22d in the height direction. The reason for this will be described later. The cross-sectional shape of the portion of the column 28 to which the connection beams 28a to 28d are connected is not limited to a rectangle, and may be circular or polygonal (for example, hexagonal).

The connecting beams 28a to 28d are arranged substantially parallel to the upper surface of the base 21 with a predetermined gap therebetween so as to be even (point symmetrical) with respect to the center of the base 21. As shown in FIG. The thickness and thickness (rigidity) of the connection beams 28a-28d are preferably thinner and thinner than the columns 22a-22d and the beams 23a-23d so as not to hinder the deformation of the strain generating body 20.

Thus, the upper surface of the base 21 and the lower surface of the pillar 28 are separated by a predetermined distance. The predetermined distance can be, for example, approximately several millimeters. If the column 28 is not directly fixed to the top surface of the base 21 but is fixed to the columns 22a to 22d via the connection beams 28a to 28d, the distance between the top surface of the base 21 and the bottom surface of the column 28 is , the deformation of the column 28 during screw fastening is reduced, and as a result, the Fz output (offset) of the sensor chip 110 is reduced. On the other hand, the longer the distance between the upper surface of the base 21 and the lower surface of the column 28, the lower the output of the sensor chip 110 (the lower the sensitivity).

That is, it is preferable that the column 28 be connected to the lower side of the middle of the columns 22a to 22d. As a result, the Fz output (offset) of the sensor chip 110 during screw fastening can be reduced while ensuring the sensitivity of the sensor chip 110 .

If an attempt is made to reduce the Fz output (offset) of the sensor chip 110 during screw fastening by increasing the rigidity of the base 21, the thickness of the base 21 must be increased, which increases the overall size of the force sensor device. turn into. By fixing the column 28 to the columns 22a to 22d via the connection beams 28a to 28d instead of directly fixing the column 28 to the upper surface of the base 21, the size of the entire force sensor device does not increase. , the Fz output (offset) of the sensor chip 110 during screw fastening can be reduced.

In addition, by fixing the column 28 to the columns 22a to 22d via the connection beams 28a to 28d instead of directly fixing the column 28 to the upper surface of the base 21, the moment (Mx, My) when inputting the moment It is possible to improve the separation between the components (Mx, My) and the force components (Fx, Fy) in the translational direction.

The base 21 is provided with a through hole 21x for fastening the strain generating body 20 to a fixed portion using a screw or the like. In this embodiment, the base 21 is provided with four through-holes 21x, but the number of through-holes 21x can be arbitrarily determined.

In addition, one through hole 21a is provided in the central portion of the base 21. As shown in FIG. The through-hole 21a is used for injecting the above-described medium that communicates with the internal space formed by the cover 50 and the strain body 20 .

The general shape of the strain body 20 excluding the base 21 can be, for example, a rectangular parallelepiped shape with a length of about 5000 μm, a width of about 5000 μm, and a height of about 7000 μm. The cross-sectional shape of the pillars 22a to 22d can be, for example, a square of about 1000 μm square. The cross-sectional shape of the column 28 can be, for example, a square of about 2000 μm square.

However, in the strain body 20, from the viewpoint of suppressing stress concentration, it is preferable that the portion forming the internal angle be R-shaped. For example, it is preferable that the center side surface of the upper surface of the base 21 of the columns 22a to 22d is formed in a rounded shape at the top and bottom. Similarly, the surfaces of the beams 23a to 23d facing the upper surface of the base 21 are preferably rounded on the left and right sides.

It should be noted that the greater the radius of curvature of the R-shaped portion, the greater the effect of suppressing stress concentration. However, if the radius of curvature of the R-shaped portion is made too large, the strain-generating body 20 becomes large, and as a result, the force sensor device 1 also becomes large. There is

Therefore, in the present embodiment, as shown in FIG. 11(a), when Mx, My, and Mz are applied to the force sensor device 1, the longitudinal length of the beams 23a to 23d where excessive stress concentration occurs The central portion in the direction is made thicker than the both end portions. The central portions of the beams 23a to 23d in the longitudinal direction are provided with projecting portions projecting inwardly and outwardly from the side surfaces of the pillars 22a to 22d.

As a result, the cross-sectional areas of the central portions in the longitudinal direction of the beams 23a to 23d are increased, so that when Mx, My, and Mz are applied to the force sensor device 1, the beams 23a to 23d on which the stress was originally concentrated It is possible to reduce the stress generated in the central portion in the longitudinal direction of the . That is, it is possible to relax the stress concentration on the longitudinal central portions of the beams 23a to 23d.

In addition, since the side surfaces of the beams 23a to 23d in the central part in the longitudinal direction protrude outward from the side surfaces of the columns 22a to 22d to provide the projecting portions, surplus spaces are generated on the four side surfaces of the strain generating body 20. Therefore, at least a portion of each of the active components 32 to 35 can be inserted into the surplus space, and can be efficiently arranged on the side surface of the strain generating body 20 (see FIGS. 2, 3, etc.).

For example, the active parts 32 to 35 can be arranged so that at least a part of the overhanging portion overlaps the side surface of the strain generating body 20 closer to the base 21 than the beams 23a to 23d (FIG. 3 ( a), see FIG. 3(b), etc.).

Projections that protrude upward from the longitudinal centers of the beams 23a to 23d are provided at the longitudinal center portions of the top surfaces of the beams 23a to 23d, respectively. ~24d are provided. The input portions 24a to 24d are portions to which force is applied from the outside, and when force is applied to the input portions 24a to 24d, the beams 23a to 23d and the columns 22a to 22d are deformed accordingly.

By providing the four input portions 24a to 24d in this manner, the load resistance of the beams 23a to 23d can be improved compared to the structure of one input portion, for example.

Four pillars 25a to 25d are arranged at the four corners of the upper surface of the pillar 28, and a fourth pillar 25e is arranged at the central portion of the upper surface of the pillar 28. As shown in FIG. The pillars 25a-25e are formed at the same height.

That is, the upper surfaces of the columns 25a to 25e are located on the same plane. The upper surface of each of the pillars 25a to 25e serves as a joint that is adhered to the lower surface of the sensor chip 110. As shown in FIG.

Beams 26a to 26d projecting inward in the horizontal direction from the inner surfaces of the beams 23a to 23d are provided at the longitudinal central portions of the inner surfaces of the beams 23a to 23d, respectively. The beams 26a-26d are beams that transmit the deformation of the beams 23a-23d and the columns 22a-22d to the sensor chip 110. FIG. Protrusions 27a to 27d projecting upward from the tip sides of the upper surfaces of the beams 26a to 26d are provided on the tip sides of the upper surfaces of the beams 26a to 26d, respectively.

The protrusions 27a to 27d are formed at the same height. That is, the upper surfaces of the protrusions 27a to 27d are positioned on the same plane. The upper surface of each of the protrusions 27a to 27d serves as a joint portion that is adhered to the lower surface of the sensor chip 110. As shown in FIG. The beams 26a to 26d and the protrusions 27a to 27d are connected to the beams 23a to 23d, which are movable parts, so that when force is applied to the input parts 24a to 24d, they deform accordingly.

Note that when no force is applied to the input portions 24a-24d, the upper surfaces of the columns 25a-25e and the upper surfaces of the protrusions 27a-27d are positioned on the same plane.

In the strain generating body 20, the base 21, the columns 22a to 22d, the columns 28, the beams 23a to 23d, the input portions 24a to 24d, the columns 25a to 25e, the beams 26a to 26d, and the protrusions 27a to 27d are rigid. is preferably formed integrally from the viewpoint of securing and manufacturing with high accuracy. As a material of the strain generating body 20, for example, a hard metal material such as SUS (stainless steel) can be used. Among them, SUS630, which is particularly hard and has high mechanical strength, is preferably used.

In this way, like the sensor chip 110, the strain-generating body 20 also has a structure including columns and beams, so that different deformations are exhibited in each of the six axes depending on the applied force. A good deformation can be transmitted to the sensor chip 110 .

That is, the forces applied to the input portions 24a to 24d of the strain generating body 20 are transmitted to the sensor chip 110 via the columns 22a to 22d, the beams 23a to 23d, and the beams 26a to 26d, and the sensor chip 110 causes displacement. detect. In the sensor chip 110, an output of each axis can be obtained from a bridge circuit formed for each axis.

(Manufacturing process of force sensor device)
13 to 18 are diagrams illustrating the manufacturing process of the force sensor device 1. FIG. First, as shown in FIG. 13(a), a strain body 20 is produced. The strain-generating body 20 can be integrally formed by, for example, molding, cutting, wire discharge, or the like. As a material of the strain generating body 20, for example, a hard metal material such as SUS (stainless steel) can be used. Among them, SUS630, which is particularly hard and has high mechanical strength, is preferably used. When the strain-generating body 20 is produced by molding, for example, metal particles and a binder resin are placed in a mold and molded, and then sintered to evaporate the resin, thereby forming a strain-generating body 20 made of metal. A body 20 can be made.

Next, in the step shown in FIG. 13B, an adhesive 41 is applied to the upper surfaces of the pillars 25a to 25e and the upper surfaces of the protrusions 27a to 27d. As the adhesive 41, for example, an epoxy-based adhesive or the like can be used. From the standpoint of resistance to externally applied force, the adhesive 41 preferably has a Young's modulus of 1 GPa or more and a thickness of 20 μm or less.

Next, in the process shown in FIG. 14A, the sensor chip 110 is manufactured. The sensor chip 110 can be manufactured, for example, by a well-known method of preparing an SOI substrate and subjecting the prepared substrate to an etching process (for example, reactive ion etching, etc.). Also, the electrodes and wiring can be produced by, for example, forming a metal film of aluminum or the like on the surface of the substrate by sputtering or the like, and then patterning the metal film by photolithography.

Next, in the step shown in FIG. 14B, the sensor chip 110 is placed so that the lower surface of the sensor chip 110 is in contact with the adhesive 41 applied to the upper surfaces of the pillars 25a to 25e and the upper surfaces of the protrusions 27a to 27d. It is placed in the strain generating body 20 while being pressurized. Then, the adhesive 41 is heated to a predetermined temperature and cured. As a result, the sensor chip 110 is fixed inside the strain generating body 20 . Specifically, the support portions 111a to 111d of the sensor chip 110 are fixed on the columns 25a to 25e, respectively, the support portion 111e is fixed on the column 25e, and the force points 114a to 114d are fixed on the protrusions 27a to 27d, respectively. be done.

Next, in the step shown in FIG. 15(a), the substrate 30 on which the active components 32 to 35 and the passive component 39 are mounted is prepared.

The substrate 30 has an end surface fixing portion 30a that is fixed to the upper surfaces (end surfaces) of the pillars 22a to 22d in the step of FIG. 16(a). In FIG. 15(a), the area crossed by the cross is the end face fixing portion 30a. Electrodes 31 (bonding pads) are provided at four corners of the end surface fixing portion 30a.

The substrate 30 extends in four directions from the end fixing portion 30a, and has side fixing portions 30b to 30e that are bent with respect to the end fixing portion 30a and fixed to the side surfaces of the columns 22a to 22d in the process of FIG. I have.

In this embodiment, the active component 32 is mounted on the side fixed portion 30b, the active component 33 and the passive component 39 are mounted on the side fixed portion 30c, and the active component 34 and the passive component 39 are mounted on the side fixed portion 30d. An active component 35 and a passive component 39 are mounted on the side fixing portion 30e. However, it is not necessary to mount the active component on all of the side fixed portions 30b to 30e, and it is sufficient that at least one of the side fixed portions 30b to 30e is mounted with the active component.

The substrate 30 has an extension portion 30f extending from the side fixing portion 30b. Input/output terminals (not shown) capable of electrical input/output with an external circuit (control device, etc.) connected to the force sensor device 1 are arranged at the end of the extended portion 30f.

The end surface fixing portion 30a has an opening 30x that exposes the sensor chip 110 and the input portions 24a to 24d when it is fixed to the upper surfaces (end surfaces) of the columns 22a to 22d in the process of FIG. 16(a). The opening 30x extends from the end fixing portion 30a to part of each of the side fixing portions 30b to 30e.

In this way, the substrate 30 can have, for example, a cross-shaped outer shape due to the opening 30x, the ease of wiring, and the mounting of the active components 32-35.

Next, in the step shown in FIG. 15B, an adhesive 42 is applied to the upper surfaces of the columns 22a to 22d. As the adhesive 42, for example, an epoxy-based adhesive or the like can be used. The adhesive 42 is for fixing the substrate 30 onto the strain generating body 20, and since no force is applied from the outside, a general-purpose adhesive can be used.

Next, in the step shown in FIG. 16(a), the substrate 30 is attached to the strain-generating body so that the lower surfaces of the four corners of the end surface fixing portion 30a of the substrate 30 are in contact with the adhesive 42 applied to the upper surfaces of the columns 22a to 22d. 20. At this point, the side fixing portions 30b to 30e are not bent with respect to the end face fixing portion 30a.

Next, in the step shown in FIG. 16B, the adhesive 43 is applied (for example, two places each in the vertical direction) to the two side surfaces facing the outside of each of the columns 22a to 22d. However, in the area where the active component 32 is mounted and adhered to the back surface of the substrate 30, the adhesive 43 is applied so as to extend from the lower sides of the pillars 22a and 22d to the outer periphery of the upper surface of the base 21. FIG.

As the adhesive 43, for example, an epoxy-based adhesive or the like can be used. The adhesive 43 is for fixing the substrate 30 onto the strain generating body 20, and since force is not applied from the outside, a general-purpose adhesive can be used. As the adhesive 43, the same adhesive as the adhesive 42 may be used. Alternatively, as the adhesive 42, a filler-containing relatively hard (high Young's modulus) adhesive is used in order to secure wire bonding properties, and as the adhesive 43, flexibility to follow the deformation of the strain generating body 20 is secured. A relatively soft (low Young's modulus) adhesive may be used to Alternatively, the adhesive 43 may be applied together with the adhesive 42 in the process of FIG. 15(b).

Next, in the step shown in FIG. 17(a), the side surface fixing portions 30b to 30e protruding in the horizontal direction from the end surface fixing portion 30a disposed on the strain body 20 are bent toward the side surfaces of the strain body 20. . Then, the adhesives 42 and 43 are heated to a predetermined temperature and hardened while pressing the substrate 30 toward the strain generating body 20 side. Thereby, the substrate 30 is fixed to the strain generating body 20 . Note that the substrate 30 is a flexible substrate and is sufficiently soft with respect to the strain-generating body 20, and the substrate 30 and the strain-generating body 20 are partially bonded. do not impede

Next, the electrodes 31 of the substrate 30 and the corresponding electrodes 15 of the sensor chip 110 are electrically connected by bonding wires (metal wires such as gold wires and copper wires) or the like (not shown). In the substrate 30, the electrodes 31 are formed in the four corner regions overlapping the upper surfaces (end surfaces) of the columns 22a to 22d in plan view of the end surface fixing portion 30a. This is the region with the least distortion when force is applied to the input portions 24a to 24d. Therefore, this region can be easily pressurized with ultrasonic waves, and wire bonding can be performed stably. The force sensor device 1 is completed through the above steps.

In this way, since the force sensor device 1 can be manufactured with only three parts, the sensor chip 110, the strain-generating body 20, and the substrate 30, it is easy to assemble and requires only a minimum number of positions to be aligned. It is possible to suppress the deterioration of accuracy due to the cause.

In addition, in the strain body 20, the connection points with the sensor chip 110 (the top surfaces of the columns 25a to 25e and the top surfaces of the protrusions 27a to 27d) are all on the same plane, so the position of the sensor chip 110 with respect to the strain body 20 is It is easy to mount the sensor chip 110 on the strain-generating body 20 because only one alignment is required.

In addition, as shown in FIG. 17(b), a step of adhering the cover may be further provided. In the step shown in FIG. 17B, a cover 50 provided with openings for exposing the input portions 24a to 24d is placed on the outer periphery of the base 21 so as to cover the upper side of the base 21 of the strain body 20 and the sensor chip 110. to adhere to. As the cover 50, for example, a material obtained by plating the surface of a metal material with nickel or the like can be used. A through hole 50 a is provided in the center of the upper surface of the cover 50 . The through hole 21 a communicates with the space inside the cover 50 .

The substrate 30 is adhered to the strain-generating body 20, and the portion of the substrate 30 where the active components 32 to 35 are mounted is within the size of the strain-generating body 20 in the height direction when the substrate 30 is bent. It's settled. Therefore, the board 30 does not interfere with attachment of the cover 50 .

By providing the cover 50, dust prevention and electrical noise countermeasures can be achieved. In particular, noise resistance (signal stability) can be enhanced by electrically connecting the metal strain element 20 and the cover 50 to the GND of the substrate 30 using silver paste or the like. In this case, it is preferable that the substrate 30 is provided with a GND terminal of a different series from that of the sensor chip 110 and the active components 32 to 35 and that this GND terminal is electrically connected to the strain generating body 20 and the cover 50 .

Next, in the manufacturing process shown in FIG. 18( a ), with the base 21 of the strain body 20 facing downward, thermal conductivity from air is introduced into the cover 50 through the through hole 50 a provided in the cover 50 . Inject a medium with high fluidity and thermosetting properties. For injection of this medium, for example, a needle-type dispenser is used. As shown in FIG. 18(a), the medium is injected by inserting the needle 60 of the dispenser into the through hole 50a.

Next, in the manufacturing process shown in FIG. 18(b), with the base 21 of the strain generating body 20 facing upward, thermal conductivity from air flows into the cover 50 from the through hole 21a provided in the base 21. Inject a medium with high fluidity and thermosetting properties. As in the manufacturing process shown in FIG. 18A, the medium is injected by inserting the needle 60 of the dispenser into the through hole 21a. Note that the medium may be injected from a through hole 21x provided in the base 21 as a screw hole.

The medium injected into the cover 50 is silicone gel, for example. The thermal conductivity of silicone gel is about 0.2 W/(m·K), which is about five times the thermal conductivity of air, which is about 0.041 W/(m·K). Therefore, by filling the inside of the cover 50 with a medium such as silicone gel, even if a temperature distribution occurs inside the cover 50, the high thermal conductivity will make the temperature distribution uniform in a short period of time, and a temperature equilibrium state will be reached. Become.

In order to further increase the thermal conductivity of the medium injected into the cover 50, it is also preferable to mix the medium with a heat transfer filler. As the heat transfer filler, for example, boron nitride is used, which has a heat transfer coefficient of about 100 W/(m·K), has insulating properties, and has no corrosive properties. By mixing a heat transfer filler into the medium, the thermal conductivity of the medium can be approximately 1 W/(m·K).

Note that it is not always necessary to perform both the manufacturing process shown in FIG. 18(a) and the manufacturing process shown in FIG. 18(b), and the medium may be injected into the cover 50 by either manufacturing process. .

After that, a baking process is performed to harden the medium injected into the cover 50 . Then, the lower surface of the force-receiving plate 40 is brought into contact with the upper surface of the input portions 24a to 24d of the strain-generating body 20, and the strain-generating body 20 and the force-receiving plate 40 are joined by welding or the like. The force sensor device 1 is completed.

FIG. 19 is a longitudinal sectional view of the force sensor device 1 after completion. FIG. 19 shows the same cross section as FIG. 12(a). As shown in FIG. 19, the medium 70 injected in the manufacturing process of FIGS. , and the space (hollow portion) in the strain generating body 20 in which the column 28 as the sensor chip mounting portion exists.

In this way, by filling the internal space of the force sensor device 1 with the medium 70 having high thermal conductivity, the thermal conductivity of the internal space is increased, and the responsiveness to heat is improved, resulting in uniform temperature distribution. do.

When the temperature of the force sensor device 1 changes due to some influence, detection errors may occur due to thermal expansion or contraction of the strain generating body 20 or changes in the characteristics of the sensor chip 110 and the active components 32-35. may occur. The temperature distribution in the internal space of the force sensor device 1 is such that, for example, the active parts 32 to 35 self-heat when the force sensor device 1 is activated, and the strain body 20 and the force receiving plate 40 with high thermal conductivity are It is caused by being affected by external heat. In addition, since the active components 32 to 35 are fixed to the side surface of the strain-generating body 20 via the substrate 30, the temperature change with respect to the external temperature change is delayed.

In the present embodiment, the internal space of the force sensor device 1 is filled with the medium 70 having high thermal conductivity, so that the temperature distribution is uniformed, and the temperature difference between the sensor chip 110 and the active components 32 to 35 is reduced. , the temperature difference between the strain-generating body 20 and the active components 32 to 35 is reduced, and detection errors due to temperature changes are reduced. Further, when an IC having a function of temperature-correcting the output from the sensor chip 110 is provided in the force sensor device 1, the temperature correction error is reduced.

Moreover, by covering the sensor chip 110 with the medium 70, adhesion of dust and foreign matter to the sensor chip 110 is suppressed, failures and abnormalities are prevented, and reliability is improved.

The medium 70 preferably has a higher thermal conductivity than air and is rigid enough not to hinder the deformation of the strain-generating body 20 and the sensor chip 110 . In addition, since the medium 70 contacts the bonding wires and pads of the sensor chip 110, it is preferable that the medium 70 be insulating and non-corrosive. Therefore, the medium 70 is preferably a gel (such as silicone gel), rubber, or liquid (such as silicone oil), which is a substance with high thermal conductivity, low stiffness and low Young's modulus. As described above, thermal conductivity can be improved by mixing the medium 70 with a heat transfer filler.

<Modification>
Next, a modified example of the first embodiment will be described. In the first embodiment, the medium 70 is injected into the outer peripheral portion between the strain-generating body 20 and the cover 50 and the hollow portion inside the strain-generating body 20, but the medium 70 is injected into only one of them. may

FIG. 20 is a longitudinal sectional view showing an example in which the outer peripheral portion between the strain generating body 20 and the cover 50 is filled with the medium 70. As shown in FIG. In order to fill only the outer peripheral portion with the medium 70 in this manner, the medium 70 may be injected from the through hole 50 a provided in the cover 50 .

By filling the medium 70 only in the outer peripheral portion, the temperature change of the outside air propagating through the cover 50 can be transmitted.

FIG. 21 is a vertical cross-sectional view showing an example in which a medium 70 is filled in the hollow portion of the strain generating body 20. As shown in FIG. In order to fill only the hollow portion with the medium 70 in this manner, the medium 70 may be injected from the through hole 21 a and/or the through hole 21 x provided in the strain generating body 20 .

Although the force receiving plate is connected to the strain body in the first embodiment, the force receiving plate is not essential to the force sensor device and may be omitted.

Further, the force sensor device according to the first embodiment has the MEMS sensor chip mounted on the strain body as the sensor element. It is also applicable to sensor devices.

The sensor element should detect at least one of the force applied in the axial direction and the force (moment) applied around the axis.

Although the preferred embodiment has been described in detail above, it is not limited to the above-described embodiment, and various modifications and substitutions can be made to the above-described embodiment without departing from the scope of the claims. can be added.

1 force sensor device, 17 temperature sensor, 20 strain element, 21 base, 21a through hole, 21x through hole, 22a to 22d pillar, 24a to 24d input section, 25a to 25e pillar, 28 pillar (mounting section), 30 Substrate 32 to 35 Active component 39 Passive component 40 Force receiving plate 50 Cover 50a Through hole 60 Needle 70 Medium 110 Sensor chip (sensor element)

Claims (5)

a sensor element that detects a force applied in or around a predetermined axis;
an active component electrically connected to the sensor element;
a strain body to which the sensor element and the active component are attached and which transmits the applied force to the sensor element;
a cover attached to cover the sensor element and the active component;
a medium injected into the cover and having a higher thermal conductivity than air;
has
The force sensor device , wherein the medium is mixed with a heat transfer filler . a sensor element that detects a force applied in or around a predetermined axis;
an active component electrically connected to the sensor element;
a strain body to which the sensor element and the active component are attached and which transmits the applied force to the sensor element;
a cover attached to cover the sensor element and the active component;
a medium injected into the cover and having a higher thermal conductivity than air;
has
The active component is mounted on one side of the substrate,
The other surface of the substrate is fixed to the side surface of the strain body,
The strain-generating body is
a mounting portion for mounting the sensor element;
a plurality of pillars spaced around the mounting portion;
The other surface of the substrate is fixed to the side surface of the adjacent pillar,
The medium is provided between the strain-generating body and the cover and in an outer peripheral portion where the sensor element and the active component exist, and a hollow portion in the strain-generating body where the mounting portion exists. A filled force sensor device. 3. The force sensor device according to claim 1 , wherein the medium is silicone gel. The force sensor device according to claim 1 , wherein the heat transfer filler is boron nitride. 4. The force sensor device according to claim 2 , wherein the sensor element is a MEMS sensor chip.

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