JP2023023688A - Force sensor device - Google Patents

Abstract

To provide a force sensor device which regulates a height relation between an electrode of a sensor chip and an electrode of a substrate in consideration of connection by a bonding wire.SOLUTION: A force sensor device has a sensor chip for detecting displacement in a predetermined axial direction, a strain body for transmitting force applied to an input part to the sensor chip, and a substrate for inputting and outputting a signal from/to the sensor chip, wherein the sensor chip and the substrate are fixed to different parts of the strain body so that each upper surface faces the same side; the substrate has a first electrode; the sensor chip has a second electrode electrically connected to the first electrode through a metal wire, and is mounted on the strain body so that one side faces the side face of the input part; and the upper surface of the second electrode is below the upper surface of the input part, and is positioned at the same height as the upper surface of the first electrode.SELECTED DRAWING: Figure 22

Description

The present invention relates to a force sensor device.

2. Description of the Related Art Conventionally, there has been known a force sensor device having a sensor chip for detecting displacement in a predetermined axial direction and a strain body for transmitting applied force to the sensor chip. In this force sensor device, a substrate on which electrodes are formed is fixed to a strain generating body, and the electrodes of the substrate and the electrodes of the sensor chip are electrically connected by bonding wires (see, for example, Patent Document 1).

JP 2019-56684 A

In wire bonding, the height relationship among the strain-generating body, the sensor chip electrode, and the substrate electrode is important, but has not been sufficiently studied in the past.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a force sensor device in which the height relationship between the electrodes of the sensor chip and the electrodes of the substrate is specified in consideration of the bonding wire connection.

This force sensor device (1) comprises a sensor chip (110) for detecting displacement in a predetermined axial direction, and a strain body for transmitting force applied to an input part (24a, etc.) to the sensor chip (110). (20) and a substrate (30) for inputting and outputting signals to and from the sensor chip (110), and the sensor chip (110) and the substrate (30) have the same top surface. Fixed to different parts of said strain body (20) facing sideways, said substrate (30) comprises a first electrode (31), said sensor chip (110) comprises said first electrode (31) and a second electrode (15) electrically connected via a metal wire (80) to the strain body (20) so that one side faces the side of the input section (24a etc.) The top surface of the second electrode (15) is positioned below the top surface of the input section (24a, etc.) and at the same height as the top surface of the first electrode (31).

It should be noted that the reference numerals in the above parentheses are attached to facilitate understanding, are merely examples, and are not limited to the embodiments shown in the drawings.

According to the disclosed technique, it is possible to provide a force sensor device in which the height relationship between the electrodes of the sensor chip and the electrodes of the substrate is defined in consideration of connection with bonding wires.

1 is a perspective view illustrating a force sensor device according to an embodiment; FIG. It is a figure which illustrates the force sensor apparatus which concerns on this embodiment. 3 is a circuit block diagram illustrating active components 32-35; FIG. It is the figure which looked the sensor chip|tip 110 from the Z-axis direction upper side. It is the figure which looked the sensor chip|tip 110 from the Z-axis direction lower side. 4 is a diagram illustrating the arrangement of piezoresistive elements of the sensor chip 110; FIG. 4 is a diagram illustrating electrode arrangement and wiring in the sensor chip 110. FIG. 4 is an enlarged plan view illustrating temperature sensors of the sensor chip 110; FIG. FIG. 3 is a diagram (part 1) illustrating the strain-generating body 20; FIG. 2 is a diagram (part 2) illustrating the strain-generating body 20; FIG. 3 is a diagram (part 3) illustrating the strain-generating body 20; FIG. 4 is a diagram (part 1) illustrating a manufacturing process of the force sensor device 1; FIG. 10 is a diagram (part 2) illustrating a manufacturing process of the force sensor device 1; FIG. 3 is a diagram (part 3) illustrating a manufacturing process of the force sensor device 1; FIG. 4 is a diagram (part 4) illustrating a manufacturing process of the force sensor device 1; FIG. 3 is a partially enlarged view of FIG. 2; FIG. 17 is a cross-sectional view taken along line DD of FIG. 16; FIG. 17 is a partially enlarged view of FIG. 16; FIG. 19 is a partially enlarged view of FIG. 18; It is a figure explaining the positional relationship of the electrode of a sensor chip, and an electrode arrangement|positioning part. FIG. 17 is a cross-sectional view taken along line EE of FIG. 16; FIG. 4 is a diagram schematically showing the positional relationship between the electrodes of the sensor chip and the input section;

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.

(Schematic configuration of the force sensor device 1)
FIG. 1 is a perspective view illustrating a force sensor device according to this embodiment. 2A and 2B are diagrams illustrating the force sensor device according to the present embodiment, FIG. 2A being a plan view and FIG. 2B being a side view. 1 and 2, the force sensor device 1 has a sensor chip 110, a strain body 20, and a substrate 30. As shown in 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.

The sensor chip 110 has a function of detecting displacement in predetermined axial directions up to six axes. As shown in FIG. 1 and FIG. 4 to be described later, force in the X-axis direction is Fx, force in the Y-axis direction is Fy, and force in the Z-axis direction is Fz. 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.

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 six axes will be described, but the sensor chip 110 is not limited to this, and the sensor chip 110 detects forces in the X-axis direction, the Y-axis direction, and the Z-axis direction. It is also possible to select the axis to be detected from the moment of X-axis rotation, Y-axis rotation, and Z-axis rotation, and to detect, for example, three 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 of a substrate 30 for inputting and outputting signals to and from the sensor chip 110 is bonded to the upper surface and each side surface of the strain generating body 20 in an appropriately bent state. 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 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 . In addition to the active component 32 , a passive component 39 may be mounted in the area arranged on the first side surface of the strain generating body 20 as necessary.

FIG. 3 is a circuit block diagram illustrating active components 32-35. As shown in FIG. 3, the active component 33 is electrically connected to the sensor chip 110, for example, an analog electrical signal from a bridge circuit that detects the X-axis direction force Fx output from the sensor chip 110, and An analog electrical signal is input from a bridge circuit that detects the force Fy in the Y-axis direction output from the sensor chip 110 . The active component 33 is, for example, a control IC having a function of converting an analog electric signal output from the sensor chip 110 into a digital electric signal, internally performing temperature correction, amplitude correction, etc., and outputting it as a digital electric signal. is.

The active component 34 is electrically connected to the sensor chip 110. For example, an analog electrical signal from a bridge circuit that detects the force Fz in the Z-axis direction output from the sensor chip 110 and an analog electrical signal output from the sensor chip 110 An analog electrical signal is input from a bridge circuit that detects a moment Mx rotating about the X axis. The active component 34 is, for example, a control IC having a function of converting an analog electric signal output by the sensor chip 110 into a digital electric signal, internally performing temperature correction, amplitude correction, etc., and outputting it as a digital electric signal. is.

The active component 35 is electrically connected to the sensor chip 110. For example, 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, and the analog electric signal from the sensor chip 110 An analog electrical signal is input from a bridge circuit that detects the moment Mz that rotates about the output Z-axis. The active component 35 is, for example, a control IC having a function of converting an analog electric signal output from the sensor chip 110 into a digital electric signal, internally performing temperature correction, amplitude correction, etc., and outputting it as a digital electric signal. is.

The active component 32 is electrically connected to the active components 33 to 35. For example, the active components 33, 34, and 35 perform a predetermined operation on digital electrical signals output by the active components 33, 34, and 35 to generate the forces Fx, Fy, and It is an arithmetic IC having a function of converting Fz and moments Mx, My, and Mz into units of force or moment and outputting them to the outside. The active component 32 can, for example, output forces Fx, Fy, and Fz in units of [N], and moments Mx, My, and Mz in units of [N·cm]. The active component 32 may be FPGA (Field Programmable Gate Array), ASIC (Application Specific Integrated Circuit), or the like. The passive components 39 are resistors, capacitors, etc. connected to the active components 33-35.

In the case of digitizing all the 6-axis outputs from the sensor chip 110, or performing digitization and correction calculation, normally one control IC is required for each axis. In this case, if a mounting space for the control IC is to be provided in the force sensor device 1, it is necessary to secure an arrangement space for at least six ICs, and the size of the force sensor device 1 must be increased. It is conceivable to realize digitization of output without increasing the size of the force sensor device 1 by connecting a control board module on which a control IC is mounted externally. Unfavorable because it increases. It is also conceivable to integrate control ICs having performance and functions for six axes into a single chip. If it is provided inside the device 1, the size of the force sensor device 1 must be increased.

Therefore, in this embodiment, three 2-in-1 package control ICs, in which two chips are stacked and housed in one package, are used. Since the 1-chip package and the 2-in-1 package do not differ greatly in size, the control IC can be arranged on the side surface of the strain generating body 20 . This makes it possible to mount control ICs for six axes in the force sensor device 1 without enlarging the size of the force sensor device 1 . That is, it is possible to reduce the size of the force sensor device 1 including active components. Moreover, the output signal of the sensor chip 110 can be digitized without enlarging the size of the force sensor device 1 .

The number of ICs to implement the functions of the active components 32 to 35 can be arbitrarily determined. Also, the number of ICs to be mounted in the force sensor device 1 can be arbitrarily determined. For example, a form in which only one control IC is mounted in the force sensor device 1 may be employed.

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, input/output terminals (not shown) are arranged which are capable of electrical input/output with an external circuit (control device, etc.) connected to the force sensor device 1. FIG.

In this way, by arranging the active parts (control IC, etc.) on the side surface of the strain-generating body 20, the total size of the force sensor device 1 can be minimized, and the digital signal adjusted or corrected by the active parts can be obtained. can be realized.

Further, by using a 2-in-1 package control IC, digital output can be achieved without increasing the size of the force sensor device 1 .

In addition, since a digital electric signal is output from the substrate 30, noise resistance can be improved compared to the case where an analog electric signal is output.

In the present embodiment, for the sake of convenience, in the force sensor device 1, the side on which the sensor chip 110 is provided is the upper side or one side, and the opposite side is 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 can be 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

(Sensor chip 110)
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. In FIG. 5(b), for the sake of convenience, surfaces of the same height are shown with the same pear-skin pattern. 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 Between the support portions 111b and 111c, reinforcing beams 112b for reinforcing the structure are provided, both ends of which are fixed to the support portions 111b and 111c (connecting adjacent support 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 opposite 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.

The substantially central portion in the longitudinal direction of the detection beam 113g and the 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, about 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 force 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 force point 114c is provided on the lower surface side of the detection beam 113g in the center in the longitudinal direction (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 illustrating the arrangement of the piezoresistive elements of the sensor chip 110. As shown in FIG. Piezoresistive elements, which are a plurality of strain sensing elements, are arranged at predetermined positions of each sensing block corresponding to the four power points 114a to 114d.

Specifically, referring to FIGS. 4 and 6, 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). The piezoresistive elements FyR3 and FyR4 are located on the reinforcing beam 112a side of the line that bisects the sensing beam 113a in the longitudinal direction, and in a region far from the sensing beam 113c of the sensing beam 113a. 113c are positioned symmetrically about a line that bisects 113c longitudinally.

In addition, the piezoresistive elements MzR3′ and MzR4′ are located on a line that bisects the detection beam 113a in the longitudinal direction and are connected to the support portions 111a and 111b of the detection beam 113a and the force point 114a. They are arranged at symmetrical positions with respect to a line that bisects the detection beam 113c in the longitudinal direction in the vicinity of the midpoint of the connecting position.

Here, the width of the detection beam 113a at the position where the piezoresistive elements MzR3′ and MzR4′ are formed is larger than the width of the detection beam 113a at the position where the support portions 111a and 111b or the force point 114a is connected. width is smaller. The detection beam 113a has a portion where the beam width is narrowed between the position where the beam width is connected to the support portions 111a and 111b and the position where the force point 114a is connected. Piezoresistive elements MzR3' and MzR4' are formed on the beam 113a.

In the sensing block corresponding to the force point 114b, the piezoresistive elements MyR3 and MyR4 sense on a line that bisects the sensing beam 113d in the longitudinal direction and in a region of the sensing beam 113d close to the sensing beam 113f. They are arranged at symmetrical positions with respect to a line that bisects the beam 113f in the longitudinal direction (X direction). The piezoresistive elements FxR3 and FxR4 are located on the side of the reinforcing beam 112b from the line that bisects the sensing beam 113d in the longitudinal direction and in a region far from the sensing beam 113f of the sensing beam 113d. 113f are arranged symmetrically about a line that bisects 113f in the longitudinal direction.

In addition, the piezoresistive elements MzR3 and MzR4 are on a line that bisects the detection beam 113d in the longitudinal direction and are connected to the support portions 111b and 111c of the detection beam 113d and to the force point 114b. symmetrical with respect to a line that bisects the detection beam 113f in the longitudinal direction near the midpoint of the position where the detection beam 113f is located.

Here, the width of the detection beam 113d at the position where the piezoresistive elements MzR3 and MzR4 are formed is larger than the width of the detection beam 113d at the position where it is connected to the support portions 111b and 111c or the force point 114b. smaller. The detection beam 113d has a portion where the width of the beam is narrowed between the position where the support portions 111b and 111c are connected and the position where the power point 114b is connected. Piezoresistive elements MzR3 and MzR4 are formed on the beam 113d.

The piezoresistive elements FzR2 and FzR3 are located on a line that bisects the sensing beam 113e in the longitudinal direction and bisects the sensing beam 113f in the longitudinal direction in a region near the sensing beam 113f of the sensing beam 113e. They are arranged symmetrically with respect to the dividing line. The piezoresistive elements FzR1' and FzR4' are on a line that bisects the sensing beam 113e in the longitudinal direction and extend along the sensing beam 113f in the region far from the sensing beam 113f. They are arranged symmetrically about the line that bisects them.

Here, the detection beam 113e has a straight portion and an inclined portion connected to the straight portion by a connecting portion. The linear portion is a portion where the beam width of the detection beam 113e is substantially constant. The inclined portion is provided at the end of the detection beam 113e or at the portion connected to the detection beam 113f, and the beam width of the inclined portion gradually increases with increasing distance from the connecting portion. The piezoresistive elements FzR2, FzR3, FzR1', and FzR4' are arranged on the inclined portion side of the connecting portion in the detection beam 113e having the above configuration.

That is, it can be said that the piezoresistive elements FzR2, FzR3, FzR1', and FzR4' are arranged not on the straight portion of the sensing beam 113e but inside the inclined portion. Further, the piezoresistive elements FzR1' and FzR4' are formed so that a part of the piezoresistive elements FzR1' and FzR4' overlaps the reinforcing beam 112g or the reinforcing beam 112f, respectively.

In the sensing block corresponding to the force point 114c, the piezoresistive elements MxR1 and MxR2 sense on a line that bisects the sensing beam 113g in the longitudinal direction and in a region of the sensing beam 113g close to the sensing beam 113i. They are arranged at symmetrical positions with respect to a line that bisects the beam 113i in the longitudinal direction (Y direction). 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 in a region far from the sensing beam 113i of the sensing beam 113g. 113i are arranged symmetrically about a line that bisects 113i in the longitudinal direction.

The piezoresistive elements MzR1′ and MzR2′ are on a line that bisects the detection beam 113g in the longitudinal direction, and are connected to the support portions 111c and 111d of the detection beam 113g and to the force point 114c. symmetrical with respect to a line that bisects the detection beam 113i in the longitudinal direction in the vicinity of the midpoint of the position.

Here, the width of the detection beam 113g at the position where the piezoresistive elements MzR1′ and MzR2′ are formed is larger than the width of the detection beam 113g at the position where it is connected to the support portions 111c, 111d or the force point 114c. width is smaller.

In other words, the detection beam 113g has a portion where the width of the beam is narrowed between the position where the support portions 111c and 111d are connected and the position where the power point 114c is connected. Piezoresistive elements MzR1' and MzR2' are formed on the sensing beam 113g.

In the sensing block corresponding to the force point 114d, the piezoresistive elements MyR1 and MyR2 sense on a line that bisects the sensing beam 113j in the longitudinal direction and in a region of the sensing beam 113j close to the sensing beam 113l. They are arranged at symmetrical positions with respect to a line that bisects the beam 113l in the longitudinal direction (X direction). The piezoresistive elements FxR1 and FxR2 are located on the reinforcing beam 112d side of the line that bisects the sensing beam 113j in the longitudinal direction, and in a region far from the sensing beam 113l of the sensing beam 113j. 113l are positioned symmetrically about a line that bisects 113l in the longitudinal direction.

The piezoresistive elements MzR1 and MzR2 are located on a line that bisects the detection beam 113j in the longitudinal direction, and are connected to the support portions 111d and 111a of the detection beam 113j and to the force point 114d. are arranged at symmetrical positions with respect to a line that bisects the detection beam 113l in the longitudinal direction in the vicinity of the midpoint of .

Here, the width of the detection beam 113j at the position where the piezoresistive elements MzR1 and MzR2 are formed is larger than the width of the detection beam 113j at the position where it is connected to the support portions 111d and 111a or the force point 114d. smaller.

That is, the detection beam 113j has a portion where the beam width is narrowed between the position where it is connected to the support portions 111d and 111a and the position where it is connected with the power point 114d. Piezoresistive elements MzR1 and MzR2 are formed on the sensing beam 113j.

The piezoresistive elements FzR1 and FzR4 are located on a line that bisects the sensing beam 113k in the longitudinal direction, and in a region far from the sensing beam 113l of the sensing beam 113k, the sensing beam 113l is bisected in the longitudinal direction. They are arranged symmetrically with respect to the dividing line. The piezoresistive elements FzR2′ and FzR3′ are on a line that bisects the sensing beam 113k in the longitudinal direction, and extend the sensing beam 113l in the longitudinal direction in a region of the sensing beam 113k near the sensing beam 113l. They are arranged symmetrically about the line that bisects them.

Here, the detection beam 113k has a straight portion and an inclined portion connected to the straight portion by a connecting portion. The linear portion is a portion where the beam width of the detection beam 113k is substantially constant. The sloped portion is provided at the end of the detection beam 113k or at the portion connected to the detection beam 113l, and the beam width of the sloped portion gradually increases with increasing distance from the connecting portion. The piezoresistive elements FzR1, FzR4, FzR2', and FzR3' are arranged on the inclined portion side of the connecting portion in the beam 113k for detection having the above configuration.

That is, it can be said that the piezoresistive elements FzR1, FzR4, FzR2', and FzR3' are arranged not on the straight portion of the sensing beam 113k but inside the inclined portion. Further, the piezoresistive elements FzR1 and FzR4 are formed so that a part of the piezoresistive elements FzR1 and FzR4 respectively overlaps the reinforcing beam 112h or the reinforcing beam 112e.

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.

Further, 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, The structure is such that the lengths of the detection beams 113b, 113e, 113h, and 113k are secured as much as possible. 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 load resistance can be improved.

Further, in the sensor chip 110, no piezoresistive elements are arranged on the detection beams 113c, 113f, 113i, and 113l. 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) can be 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 and FzR1' to FzR4' detect force Fz. The piezoresistive elements MxR1-MxR4 detect the moment Mx, the piezoresistive elements MyR1-MyR4 detect the moment My, and the piezoresistive elements MzR1-MzR4, MzR1'-MzR4' detect the moment Mz. In this embodiment, the force Fz may be detected from the piezoresistive elements FzR1 to FzR4 by using the piezoresistive elements FzR1′ to FzR4′ as dummies. Alternatively, the moment Mz may be detected from the piezoresistive elements MzR1 to MzR4 by using the piezoresistive elements MzR1′ to MzR4′ as dummies.

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 the plurality of piezoresistive elements arranged on the predetermined beam is changed, and the output of the predetermined axis is changed. 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 first detection beams 113a, 113d, 113g, and 113j.

In the sensor chip of the present embodiment described above, the detection beam 113e has a linear portion and an inclined portion connected to the linear portion by the connecting portion, and the piezoresistive elements FzR2, FzR3, FzR1', and FzR4' , in the detection beam 113e configured as described above, are arranged closer to the inclined portion than the connecting portion. The sensing beam 113k has a straight portion and an inclined portion connected to the straight portion by a connecting portion. , it is arranged closer to the inclined portion than the connecting portion.

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. 7 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. 7, 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. 8 is an enlarged plan view illustrating temperature sensors of the sensor chip 110. FIG. As shown in FIGS. 7 and 8, 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.

A piezoresistive element is a representative example of the strain sensing element according to the present invention.

(Strain generating body 20)
9A and 9B are diagrams (part 1) illustrating the strain generating body 20, FIG. 9A being a perspective view, and FIG. 9B being a side view. 10A and 10B are diagrams (part 2) illustrating the strain generating body 20, in which FIG. 10A is a plan view, and FIG. is. In FIG. 10(a), for the sake of convenience, surfaces of the same height are shown with the same pear-skin pattern. 11A and 11B are diagrams (part 3) illustrating the strain-generating body 20, FIG. 11(a) being a longitudinal sectional view taken along line BB of FIG. 11(a) is a cross-sectional view taken along line CC of FIG.

As shown in FIGS. 9 to 11, the strain 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 apart 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 a polygon or the like (for example, a 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 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. The structure in which the column 28 is fixed to the columns 22a to 22d via the connection beams 28a to 28d without directly fixing the column 28 to the upper surface of the base 21 increases the size of the entire force sensor device. Therefore, it is possible to reduce the Fz output (offset) of the sensor chip 110 during screw fastening.

In addition, 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, thereby reducing the moment (Mx, My) input. Separability between moment components (Mx, My) and translational force components (Fx, Fy) can be improved.

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.

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 by the dark satin pattern in FIG. 10A, the beam 23a on which excessive stress concentration occurs when Mx, My, and Mz are applied to the force sensor device 1 23d in the longitudinal direction is thicker than both ends. 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 portion in the longitudinal direction are projected 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. 1, 2, 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. 2 ( a), see FIG. 2(b), etc.).

Input portions 24a to 24d project upward from the longitudinal central portions of the upper surfaces of the beams 23a to 23d, respectively. The input sections 24a-24d are, for example, rectangular, but may be circular, elliptical, or other more complicated shapes. 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 projections 27a to 27d are connected to the beams 23a to 23d, which are movable parts, so that when a 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 the force sensor device 1)
12 to 15 are diagrams illustrating the manufacturing process of the force sensor device 1. FIG. First, in the process shown in FIG. 12, an adhesive 41 is applied to the upper surfaces of the pillars 25a to 25e and the projections 27a to 27d of the strain body 20. As shown in FIG. Then, the sensor chip 110 is placed under pressure in the strain generating body 20 so that the lower surface of the sensor chip 110 is in contact with the adhesive 41 applied to the upper surfaces of the columns 25a to 25e and the upper surfaces of the protrusions 27a to 27d. . 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 power points 114a to 114d are fixed on the protrusions 27a to 27d, respectively. be done.

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.

As the adhesive 41, for example, an adhesive such as modified silicone can be used. The Young's modulus of the adhesive 41 is preferably 130 MPa or more and 1.5 GPa or less, and the thickness of the adhesive 41 is preferably 10 μm or more and 40 μm or less.

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 process shown in FIG. 13, the board 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 fixed to the top surfaces (end surfaces) of the columns 22a to 22d. In FIG. 13, the area crossed by the cross is the end face fixing portion 30a. Electrodes 31 (bonding pads) are provided at the 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. An input/output terminal (not shown) capable of electrical input/output with an external circuit (such as a control device) connected to the force sensor device 1 is arranged at the end of the extended portion 30f.

The end face 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 faces) of the columns 22a to 22d in the process of FIG. 14(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.

After preparing the substrate 30 as described above, 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. 14(a), the substrate 30 is attached to the strain body 20 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. place on top. 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. 14B, the adhesive 43 is applied (for example, two places in the vertical direction) on 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 lower 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.

Next, in the process shown in FIG. 15(a), the side surface fixing portions 30b to 30e protruding in the horizontal direction from the end surface fixing portion 30a arranged 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 pillars 22a to 22d in plan view of the end surface fixing portion 30a. This is the region with the least strain when force is applied to the portions 24a-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 since the number of positions to be aligned can be kept to a minimum, it is easy to mount. It is possible to suppress the deterioration of accuracy due to the cause.

Further, in the strain body 20, the connection points with the sensor chip 110 (upper surfaces of the pillars 25a to 25e and upper surfaces of the protrusions 27a to 27d) are all on the same plane. 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. 15(b), a step of adhering the cover may be further provided. In the step shown in FIG. 15B, 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. The input portions 24a to 24d protrude to the upper surface side of the cover 50 through the openings. 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.

The substrate 30 is adhered to the strain-generating body 20, and the portion of the substrate 30 on which 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 the mounting 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 .

Here, the shape of the substrate 30 will be described in more detail.

16 is a partially enlarged view of FIG. 2. FIG. 17 is a cross-sectional view taken along line DD of FIG. 16. FIG. 18 is a partially enlarged view of FIG. 16. FIG. 16 to 18, the four corners of the end surface fixing portion 30a shown in FIG. 13 are used as electrode placement portions 61 to 64, respectively.

For example, the sensor chip 110 is rectangular in plan view, and the pillars 22a to 22d are arranged on extension lines of two diagonal lines of the rectangle in plan view. Electrode placement portions 61 to 64 are fixed to the upper surface of each column. The electrode arrangement portions 61 to 64 may have a line-symmetrical shape with respect to the diagonal line of the rectangle of the sensor chip 110 in plan view. The electrode arrangement portions 61 to 64 may have the same shape in plan view. The same shape here includes rotationally symmetrical shapes.

The lower surfaces of the electrode arrangement portions 61 to 64 are fixed to the upper surfaces of the columns 22a to 22d, respectively, with resin (adhesive 42 in FIG. 13). The side fixing portions 30b to 30e extend from the electrode arrangement portions 61 to 64, and the lower surfaces of the side fixing portions 30b to 30e are fixed to the side surfaces of the columns 22a to 22d with resin (adhesive 43 in FIG. 14). . However, in FIG. 17, illustration of the adhesives 42 and 43 is omitted.

As shown in FIG. 18 , in plan view, the contour of the electrode placement portion 61 includes a first portion 611 that is a boundary with the side fixing portion 30e and a second portion that is continuous with the end portion of the first portion 611 on the input portion 24a side. 2 parts 612 . In a plan view, the second portion 612 is located near the input portion 24a with respect to a first imaginary straight line L1 drawn in a direction perpendicular to the longitudinal direction of the beam 23a through the end of the first portion 611 on the input portion 24a side. It has a part that sticks out. A portion of the second portion 612 that protrudes toward the input portion 24a with respect to the first imaginary straight line L1 may protrude to the extent that it touches the base of the input portion 24a in a cross-sectional view.

Further, in a plan view, the contour of the electrode arrangement portion 61 is composed of a third portion 613 that forms a boundary with the side fixing portion 30b, and a fourth portion 614 that is continuous with the end portion of the third portion 613 on the input portion 24d side. include. In a plan view, the fourth portion 614 is located on the input portion 24d side with respect to a second imaginary straight line L2 drawn in a direction perpendicular to the longitudinal direction of the beam 23d through the end of the third portion 613 on the input portion 24d side. It has a part that sticks out. A portion of the fourth portion 614 that protrudes toward the input portion 24d with respect to the second imaginary straight line L2 may protrude to the extent that it touches the base of the input portion 24d in a cross-sectional view.

Note that the longitudinal direction of the beam refers to the direction of a straight line that connects the centers of gravity of the upper surfaces of adjacent columns in a plan view.

In plan view, the side of the second portion 612 opposite to the side connected to the first portion 611 is continuous with the side opposite to the side connected to the third portion 613 of the fourth portion 614 . In addition, in the pillar 22a, the side surface to which the side fixing portion 30e is fixed and the side surface to which the side fixing portion 30b is fixed are not parallel in plan view. For example, in a plan view, the side surface to which the side fixing portion 30e is fixed and the side surface to which the side fixing portion 30b is fixed are oriented in a substantially orthogonal direction.

As described above, in the force sensor device 1, the electrode placement portion 61 of the substrate 30 is provided with the second portion 612 and the fourth portion 614 having portions protruding toward the input portion side. As a result, even if the amount of the resin (adhesive 42) applied to the upper surface of the column 22a is large to some extent, the area inscribed with the second portion 612 and the fourth portion 614 of the electrode placement portion 61 is located on the upper surface side of the electrode placement portion 61. It becomes possible to suppress the resin from creeping up.

If the amount of resin applied to the upper surface of the pillar 22a is small, the flatness of the electrode placement portion 61 cannot be sufficiently obtained, and wire bonding is hindered. In the force sensor device 1, since the amount of resin applied can be increased to some extent, it is possible to obtain sufficient flatness of the electrode arrangement portion 61, and wire bonding can be performed stably.

In plan view, the second portion 612 may have a constricted portion 615 constricted in the opposite direction of the input portion 24a. For example, by controlling the application amount of the resin (adhesive 42), as shown in FIG. A portion of the adhesive 42) can be wrapped around.

Further, in plan view, the fourth portion 614 may have a constricted portion 616 constricted in the opposite direction of the input portion 24d. For example, by controlling the application amount of the resin (adhesive 42), as shown in FIG. A portion of the adhesive 42) can be wrapped around.

In this way, by controlling the amount of resin (adhesive 42) to be applied and causing part of the resin (adhesive 42) to wrap around the upper surface of the electrode placement portion 61, the electrode placement portion 61 is fixed to the column 22a. It can improve the fixing strength at the time. Further, it is possible to visually confirm from the upper surface side of the electrode arrangement portion 61 that the resin is sufficiently applied to the lower surface side of the electrode arrangement portion 61 .

It is preferable to provide an insulating layer 70 that covers at least a portion of the outer edge of the upper surface of the electrode placement portion 61 and exposes a portion of the center side. The insulating layer 70 is a so-called solder resist layer, and is made of, for example, an epoxy resin or the like. The thickness of the insulating layer 70 is, for example, about 30 μm. Electrodes 31 and conductor layers such as plated wires extending from the electrodes 31 are formed on the upper surface of the electrode placement portion 61 exposed from the insulating layer 70 . 16, 18, and 19, the insulating layer 70 is indicated by a satin pattern. In FIG. 17, illustration of the insulating layer 70 is omitted.

By providing the insulating layer 70 covering at least a part of the outer edge of the upper surface of the electrode placement portion 61 , it is possible to prevent the resin (adhesive 42 ) from creeping up on the upper surface of the electrode placement portion 61 . In addition, by covering the ends of the conductor layers with the insulating layer 70, short circuits between the conductor layers can be prevented. More preferably, the insulating layer 70 annularly covers the outer edge of the upper surface of the electrode arrangement portion 61 . Thereby, it is possible to further prevent the resin (adhesive 42 ) from creeping up on the upper surface of the electrode arrangement portion 61 . In addition, short-circuiting between conductor layers can be further prevented.

When fixing the electrode arrangement portion 61 to the upper surface of the column 22a, the resin (adhesive 42) is applied to the upper surface of the column 22a, the electrode arrangement portion 61 is arranged on the resin, and the upper surface of the electrode arrangement portion 61 is The side is pressed by a jig with a flat surface. When the insulating layer 70 covers the outer edge of the upper surface of the electrode placement portion 61 in a ring shape, the entire electrode placement portion 61 can be evenly pressed by the flat surface of the jig through the ring-shaped insulating layer 70 . Therefore, the electrode placement portion 61 can be prevented from tilting with respect to the upper surface of the column 22a, and the fixing strength of the electrode placement portion 61 can be improved.

Since the second portion 612 and the fourth portion 614 of the electrode placement portion 61 are provided with portions protruding toward the input portion side, the area of the upper surface of the electrode placement portion 61 becomes larger than that of the conventional one. It became possible to provide the insulating layer 70 on the outer edge of the upper surface of the substrate, and the above effect can be obtained. The insulating layer 70 can ensure a width of about 200 to 300 μm even at the narrowest portion.

Although the electrode placement portion 61 has been described above, the electrode placement portions 62 to 64 also have the same effect as the electrode placement portion 61 does.

Here, wire bonding between the electrodes 15 of the sensor chip 110 and the electrodes 31 of the substrate 30 will be described in more detail.

As described above, the sensor chip 110 and the substrate 30 are fixed to different parts of the strain generating body 20 so that their upper surfaces face the same side. The sensor chip 110 is mounted on the strain-generating body 20 so that its side surface faces the side surface of the input section. The electrodes 15 of the sensor chip 110 are electrically connected to the electrodes 31 of the substrate 30 via bonding wires.

As described above, in order to perform wire bonding stably, the electrode placement portion having the electrode 31 on the upper surface of the pillars 22a to 22d, which is the region where the distortion is the least when force is applied to the input portions 24a to 24d. 61 to 64 are arranged. The electrode placement portions 61 to 64 are portions located at the four corners of the end surface fixing portion 30a shown in FIG.

On the other hand, if the electrodes 15 of the sensor chip 110 are arranged near the midpoint of each side, the capillaries used for wire bonding may interfere with the input sections 24a to 24d, and the bonding wires are long. turn into. Therefore, in order to avoid interference between the capillaries and the input portions 24a to 24d and to shorten the bonding wires, the electrodes 15 of the sensor chip 110 are preferably arranged at the four corners of the upper surface of the sensor chip 110 (FIG. 18). reference).

FIG. 20 is a diagram for explaining the positional relationship between the electrodes of the sensor chip and the electrode arrangement portion, and is a partial cross-sectional view taken along line FF of FIG. 16 is a line parallel to the upper surface of the cover 50. As shown in FIG. For example, when the force sensor device 1 has the cover 50, as shown in FIG. Suppose that it is positioned higher. In this case, the cover 50 is also moved upward so as not to come into contact with the bonding wires 80, so that the distance between the upper surfaces of the input sections 24a to 24d and the upper surface of the cover 50 is shortened.

A force receiving plate may be welded to the input portions 24a to 24d protruding from the cover 50. In this case, the upper surfaces of the input portions 24a to 24d and the cover 50 are separated from each other in order to suppress the scattering of spatter during welding. I want to increase the distance to the top surface to some extent. Therefore, the structure on the right side of the arrow in FIG. 20 is not preferable in that it is difficult to suppress scattering of spatter. In addition, in the structure on the right side of the arrow in FIG. 20, if the positions of the top surfaces of the input portions 24a to 24d are moved upward in order to suppress the scattering of spatter, the overall height of the force sensor device 1 increases. I don't like it.

Thus, the top surface of the electrode 15 of the sensor chip 110 is preferably positioned at the same height as the top surfaces of the electrode placement portions 61-64 or below the top surfaces of the electrode placement portions 61-64. As a result, contact between the bonding wires 80 and the lower surface of the cover 50 can be prevented without increasing the overall height of the force sensor device 1, and the distance between the upper surface of the input portions 24a to 24d and the upper surface of the cover 50 can be reduced. can be secured.

It is preferable that the wire bonding is first performed on the electrode 15 of the sensor chip 110 (1st bond) and then performed on the electrode arrangement portions 61 to 64 (2nd bond). This is because the 1st bond requires less stress on the object than the 2nd bond, so that a large stress is not applied to the delicate sensor chip 110 .

By the way, the top surface of the electrode 15 of the sensor chip 110 may not be positioned any lower than the top surfaces of the electrode placement portions 61 to 64 . 21 is a cross-sectional view along line EE in FIG. 16. FIG. 200 shown in FIG. 21 indicates a capillary used when connecting the bonding wire 80 shown in FIG. Since the capillary 200 has a tapered shape (conical shape) and is inserted at the position shown in FIG. 21, it is necessary to pay attention to interference with each input section including the input section 24b and the input section 24c.

FIG. 22 is a diagram schematically showing the positional relationship between the electrodes of the sensor chip and the input section. As described above, the input portion 24c protrudes upward from the longitudinal central portion of the beam 23c. In FIG. 22, BL indicates the boundary between the input portion 24c and the beam 23c. The boundary BL is located on the same plane as the surface of the strain generating body 20 to which the substrate 30 is fixed (upper surfaces of the pillars 22a to 22d). That is, the distance (height) h between BL and the upper surface of the electrode 15 of the sensor chip 110 shown in FIG. is equal to the distance (height) from the upper surface of the electrode 15.

In FIG. 22, D+P>TD/2+h·tan(θ/2) (1) must be satisfied so that the capillary 200 does not interfere with the input section 24c. In other words, even if the sensor chip 110 is moved downward within the range that satisfies the formula (1), the capillary 200 does not interfere with the input section 24c.

In equation (1), D is the distance [μm] between the opposing sides of the input section 24c and the sensor chip 110 in plan view, and P is the distance [μm] from the side of the sensor chip 110 to the center of the electrode 15 in plan view. , TD is the outer diameter [μm] of the tip of the capillary 200 used when connecting the bonding wire, and θ is the taper angle [deg] of the capillary 200 .

An example of numerical values is D=300 μm and P=100 μm. For such dimensions, a capillary with TD=150 μm and θ=20 deg is generally used. In this case, h=0 μm or more and 1800 μm or less. That is, in this case, even if the upper surface of the electrode 15 of the sensor chip 110 is located below the surface of the strain generating body 20 (upper surface of the columns 22a to 22d) to which the substrate 30 is fixed within a range of h=1800 μm, The capillary 200 does not interfere with the input section 24c. However, from the viewpoint of shortening the bonding wire, h=0 μm or more and 100 μm or less is preferable, and h=0 μm or more and 50 μm or less is more preferable.

Although the relationship between the sensor chip 110 and the input section 24c has been described in FIG. 22, the same applies to the relationship between the sensor chip 110 and the input sections 24a, 24b, and 24d.

To summarize the above, the top surface of the electrode 15 of the sensor chip 110 is below the top surface of each input section, and the surface of the strain generating body 20 to which the substrate 30 is fixed (the top surfaces of the columns 22a to 22d) is expressed by the formula (1). ) must be positioned below within the range of h [μm]. As a result, contact between the bonding wires 80 and the lower surface of the cover 50 can be prevented without increasing the overall height of the force sensor device 1, and the distance between the upper surface of each input section and the upper surface of the cover 50 can be secured. . And the capillary 200 does not interfere with each input section.

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, 15 electrode, 16 wiring, 17 temperature sensor, 20 elastic body, 21 base, 22a to 22d, 25a to 25d, 28 pillar, 23a to 23d, 26a to 26d beam, 24a to 24h input section, 27a-27d protrusions, 29a-29d junctions, 30 substrate, 30x openings, 31 electrodes, 32-35 active components, 39 passive components, 41, 42, 43 adhesives, 50 covers, 61-64 electrode arrangement portions, 70 insulating layer, 80 bonding wire, 110 sensor chip, 111a to 111e support portion, 112a to 112h reinforcing beam, 113a to 113l detection beam, 114a to 114d force point, 611 first portion, 612 second portion, 613 third Part 614 Fourth Part 615, 616 Constriction

Claims (6)

a sensor chip that detects displacement in a predetermined axial direction;
a strain-generating body that transmits the force applied to the input unit to the sensor chip;
a substrate for inputting and outputting signals to and from the sensor chip;
The sensor chip and the substrate are fixed to different parts of the strain body so that their top surfaces face the same side,
the substrate comprises a first electrode;
The sensor chip includes a second electrode electrically connected to the first electrode via a metal wire, and is mounted on the strain body so that one side surface faces a side surface of the input section,
The force sensor device, wherein the upper surface of the second electrode is located below the upper surface of the input section and at the same height as the upper surface of the first electrode. a sensor chip that detects displacement in a predetermined axial direction;
a strain-generating body that transmits the force applied to the input unit to the sensor chip;
a substrate for inputting and outputting signals to and from the sensor chip;
The sensor chip and the substrate are fixed to different parts of the strain body so that their top surfaces face the same side,
the substrate comprises a first electrode;
The sensor chip includes a second electrode electrically connected to the first electrode via a metal wire, and is mounted on the strain body so that one side surface faces a side surface of the input section,
The upper surface of the second electrode is below the upper surface of the input section and positioned below the surface of the strain body to which the substrate is fixed within a range of h [μm] that satisfies formula (1). , a force sensor device.
D+P>TD/2+h·tan(θ/2) (1)
However, in the formula (1), D is the distance [μm] between the facing sides of the input section and the sensor chip in plan view, and P is the distance from the side face of the sensor chip to the center of the second electrode in plan view. The distance [μm], TD is the outer diameter [μm] of the tip of the tapered capillary used for connecting the metal wire, and θ is the taper angle [deg]. The strain-generating body is
Four pillars arranged at the four corners,
a sensor chip mounting portion disposed inside the four pillars for mounting a sensor chip;
four beams connecting the adjacent pillars;
and four input portions including the input portion projecting upward from the longitudinal central portion of each of the beams;
the first electrode is fixed to each of the top surfaces of the four pillars of the substrate;
3. The force sensor device according to claim 1, wherein said sensor chip includes second electrodes electrically connected to said first electrodes via metal wires. In a plan view, the sensor chip is rectangular, and is mounted on the sensor chip mounting portion so that each side surface faces the side surface of each input portion,
4. The force sensor device according to claim 3, wherein said second electrodes are arranged at four corners of said rectangle. 5. The force sensor device according to claim 4, wherein the four pillars are arranged on extensions of two diagonal lines of the rectangle in plan view. Having a cover that covers the sensor chip,
The cover has an opening,
The force sensor device according to any one of claims 1 to 5, wherein the input section protrudes toward the upper surface of the cover through the opening.

Images