Mechanical measurement device

Abstract

To improve the performance of a mechanical quantity measuring device.SOLUTION: A mechanical quantity measuring device 1 includes a semiconductor chip 2 on which a strain sensing circuit is formed, and an insulating base plate 3 on which the semiconductor chip 2 is mounted. The semiconductor chip 2 is bonded to the base plate 3 via a bonding material 5, and the bonding material 5 is preferably made of solder or metal nanoparticles. The mechanical quantity measuring device 1 is attached to an object 7 to be measured using a conductive bonding material 8. The strain generated in the object to be measured 7 is transmitted to the semiconductor chip 2 via the bonding material 8, the base plate 3, and the bonding material 5.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a mechanical quantity measuring device. [Background technology]

[0002] Japanese Patent Laid-Open Publication No. 2009-264976 (Patent Document 1) describes a technique relating to a semiconductor strain sensor, and discloses a semiconductor strain sensor in which a strain sensor chip is mounted on a base plate.

[0003] Japanese Patent Application Laid-Open No. 2012-47608 (Patent Document 2) describes a technique relating to a mechanical quantity measuring device using a bridge circuit. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-264976 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-47608 [Non-patent literature]

[0005] [Non-Patent Document 1] AHChokshi, A.Rosen, J.Karch and H.Gleiter;Scripta METALLURGICA:Vol23,1989,pp.1679-1684 Summary of the Invention [Problem to be solved by the invention]

[0006] Mounting the strain sensor chip on a base plate makes the semiconductor strain sensor easier to handle. However, in the case of a semiconductor strain sensor with a strain sensor chip mounted on a metal base plate, limitations are placed on how the semiconductor strain sensor can be used, making the semiconductor strain sensor less user-friendly and potentially reducing its performance.

[0007] For example, if a semiconductor strain sensor with a strain sensor chip mounted on a metal base plate is attached to a metal measurement object, the measurement object and the base plate may become electrically conductive, causing a current to flow between the semiconductor strain sensor and the measurement object, and there is a concern that the semiconductor strain sensor may be affected by electrical noise from the measurement object.However, if a semiconductor strain sensor with a strain sensor chip mounted on a metal base plate is attached to the measurement object using an insulating adhesive to prevent electrical conduction between the semiconductor strain sensor and the measurement object, there is a risk that the performance of the semiconductor strain sensor will be reduced compared to when a conductive bonding material such as solder is used.

[0008] Other objects and novel features will become apparent from the description of this specification and the accompanying drawings. [Means for solving the problem]

[0009] According to one embodiment, a mechanical quantity measuring device includes a strain detection unit and an insulating structure on which the strain detection unit is mounted. [Effects of the Invention]

[0010] According to one embodiment, the mechanical quantity measuring device can be made easier to use, and the performance of the mechanical quantity measuring device can be improved. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a plan view showing a mechanical quantity measuring device according to a first embodiment. [Figure 2] 1 is a cross-sectional view showing a mechanical quantity measuring device according to a first embodiment. [Figure 3] FIG. 3 is a cross-sectional view schematically showing a state in which the mechanical quantity measuring device of FIGS. 1 and 2 is attached to a measurement object. [Figure 4] FIG. 3 is an explanatory diagram showing a planar configuration of a semiconductor chip used in the mechanical quantity measuring device of FIGS. 1 and 2. [Figure 5]1 is a cross-sectional view schematically showing a state in which the academic quantity measuring device of the study example is attached to an object to be measured. [Figure 6] FIG. 10 is an explanatory diagram showing the results of analyzing stress distribution. [Figure 7] FIG. 10 is a plan view showing a mechanical quantity measuring device according to a second embodiment. [Figure 8] FIG. 10 is a cross-sectional view showing a mechanical quantity measuring device according to a second embodiment. [Figure 9] 10 is a graph showing an example of the results of analyzing strain transmission rates. [Figure 10] FIG. 10 is a plan view showing a mechanical quantity measuring device according to a third embodiment. [Figure 11] FIG. 10 is a cross-sectional view showing a mechanical quantity measuring device according to a third embodiment. [Figure 12] FIG. 10 is a plan view showing a mechanical quantity measuring device according to a fourth embodiment. [Figure 13] FIG. 10 is a plan view perspective view showing a mechanical quantity measuring device according to a fourth embodiment. [Figure 14] FIG. 10 is a cross-sectional view showing a mechanical quantity measuring device according to a third embodiment. [Figure 15] FIG. 10 is a cross-sectional view showing a mechanical quantity measuring device according to a third embodiment. [Figure 16] FIG. 10 is a cross-sectional view showing a mechanical quantity measuring device according to a third embodiment. [Figure 17] FIG. 10 is a plan view perspective view showing a mechanical quantity measuring device according to a fifth embodiment. [Figure 18] FIG. 10 is a cross-sectional view showing a mechanical quantity measuring device according to a fifth embodiment. [Figure 19] FIG. 10 is a cross-sectional view showing a mechanical quantity measuring device according to a fifth embodiment. [Figure 20] FIG. 13 is a plan view showing a mechanical quantity measuring device according to a sixth embodiment. [Figure 21] FIG. 13 is a cross-sectional view showing a mechanical quantity measuring device according to a sixth embodiment. [Figure 22] FIG. 13 is a plan view showing the mechanical quantity measuring device of the sixth embodiment before a flexible substrate is attached. [Figure 23] FIG. 13 is a cross-sectional view showing the mechanical quantity measuring device of the sixth embodiment before a flexible substrate is attached. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments will be described in detail with reference to the drawings. In all drawings for explaining the embodiments, components having the same functions are designated by the same reference numerals, and repeated explanations thereof will be omitted. In the following embodiments, explanations of the same or similar parts will not be repeated unless particularly necessary.

[0013] In the drawings used in the embodiments, hatching may be omitted even in cross-sectional views to make the drawings easier to see, and hatching may be added even in plan views to make the drawings easier to see.

[0014] (Embodiment 1) <Configuration of mechanical quantity measuring device> A mechanical quantity measuring device 1 of this embodiment will be described with reference to the drawings.

[0015] FIG. 1 is a plan view (top view) showing the mechanical quantity measuring device 1 of this embodiment, and FIG. 2 is a cross-sectional view showing the mechanical quantity measuring device 1 of this embodiment. FIG. 1 shows a plan view of the upper surface side of the mechanical quantity measuring device 1, and the cross-sectional view taken along line A1-A1 in FIG. 1 roughly corresponds to FIG. 2. The X and Y directions shown in FIG. 1 and the subsequent figures are directions perpendicular to each other. The X and Y directions are also directions approximately parallel to the upper surface of the base plate 3, and therefore are also directions approximately parallel to the main surface of the semiconductor chip 2.

[0016] 1 and 2, a mechanical quantity measuring device 1 of this embodiment has a semiconductor chip (strain sensor chip) 2 as a strain detection unit, and a base plate (structure) 3 as a structure for mounting (supporting and fixing) the semiconductor chip 2. The semiconductor chip 2 is mounted on the base plate 3 via a bonding material 5.

[0017] The semiconductor chip 2 is a semiconductor chip on which a strain detection circuit (strain detection circuit, strain sensor circuit) is formed, i.e., a strain sensor chip. The semiconductor chip 2 has the function of detecting strain, and therefore can be considered a strain detection unit. The base plate 3 is an insulating structure on which the semiconductor chip 2 is mounted.

[0018] Specifically, the base plate 3 is a base plate (substrate) made of an insulating material, and a conductor pattern (conductor layer, wiring layer) 4 is formed on the base plate 3 as needed. The conductor pattern 4 can also be considered as part of the components of the base plate 3. In other words, the base plate 3 is mainly made of an insulating material, but can also include the conductor pattern 4.

[0019] 1 and 2, conductor patterns 4a and 4b are formed on the upper surface of the base plate 3 as the conductor pattern 4. Of these, conductor pattern 4a is formed in an area on the upper surface of the base plate 3 where the semiconductor chip 2 is mounted. Furthermore, conductor pattern 4b is formed around the area on the upper surface of the base plate 3 where the semiconductor chip 2 is mounted. The base plate 3 is preferably made of ceramic (ceramic material). Therefore, the base plate 3 is preferably made of a ceramic substrate. The conductor pattern 4 is preferably made of a metal material, such as an alloy film of molybdenum (Mo) and tungsten (W). The upper surface of the base plate 3 corresponds to the main surface on which the semiconductor chip 2 is mounted, and the lower surface of the base plate 3 corresponds to the main surface opposite the upper surface.

[0020] In a plan view, the semiconductor chip 2 has a planar shape that is point-symmetric with respect to the center of the semiconductor chip 2, and the planar shape of the semiconductor chip 2 is preferably a square (approximately square). In addition, in a plan view, the base plate 3 has a planar shape that is point-symmetric with respect to the center of the base plate 3, and the planar shape of the base plate 3 is preferably a square. In the case of Fig. 1, each of the semiconductor chip 2 and the base plate 3 has a square shape with sides parallel to the X direction and sides parallel to the Y direction.

[0021] The semiconductor chip 2 is preferably mounted in the center of the upper surface of the base plate 3, and more preferably, the semiconductor chip 2 is arranged so that the center of the semiconductor chip 2 substantially coincides with the center of the base plate 3 in a plan view. Furthermore, when the semiconductor chip 2 and the base plate 3 are square, it is more preferable that the semiconductor chip 2 is arranged so that the four sides of the semiconductor chip 2 are parallel to the four sides of the base plate 3, respectively, and this is shown in FIG. 1. In another embodiment, the semiconductor chip 2 may be arranged so that each side of the semiconductor chip 2 is inclined at 45° with respect to each side of the base plate 3. Here, the plan view corresponds to the case where the semiconductor chip 2 is viewed from a plane substantially parallel to the main surface of the semiconductor chip 2 or the upper surface of the base plate 3.

[0022] The semiconductor chip 2 is bonded and fixed onto the conductor pattern 4a on the upper surface of the base plate 3 via a bonding material (bonding layer) 5. That is, the bonding material 5 is interposed between the semiconductor chip 2 and the conductor pattern 4a. Although an insulating adhesive can be used as the bonding material 5, a conductive bonding material is more preferable, and solder or metal nanoparticles can be suitably used. Here, metal materials made of metal particles with an average particle size of 1 to several hundred nm are typically called metal nanoparticles. When metal nanoparticles are used as the bonding material 5, copper nanoparticles, for example, can be suitably used.

[0023] The conductor pattern 4a is provided to facilitate bonding of the semiconductor chip 2 to the base plate 3 with the bonding material 5. If the semiconductor chip 2 can be directly bonded to the upper surface of the base plate 3 with the bonding material 5 without the conductor pattern 4a, it is not necessary to form the conductor pattern 4a on the upper surface of the base plate 3. However, if a conductive bonding material is used as the bonding material 5 instead of an insulating bonding material, it is difficult to bond the semiconductor chip 2 to the base plate 3 via the conductive bonding material 5 without the conductor pattern 4a. For this reason, in this embodiment, the conductor pattern 4a is formed on the upper surface of the base plate 3, and the semiconductor chip 2 is mounted on the conductor pattern 4a via the conductive bonding material 5. This allows the semiconductor chip 2 to be firmly bonded to the conductor pattern 4a via the conductive bonding material 5, and the semiconductor chip 2 to be mounted and fixed on the base plate 3.

[0024] The conductor patterns 4b are electrodes (terminals) for electrically connecting to the electrodes 2a of the semiconductor chip 2, and a plurality of the conductor patterns 4b are formed on the upper surface of the base plate 3. Hereinafter, the conductor patterns 4b may be referred to as electrodes 4b. The semiconductor chip 2 has a plurality of electrodes (pad electrodes) 2a, which are formed on the main surface (upper surface) of the semiconductor chip 2. The plurality of electrodes 2a of the semiconductor chip 2 and the plurality of electrodes 4b formed on the upper surface of the base plate 3 are electrically connected via a plurality of conductive wires (bonding wires) 6. The wires 6 are made of thin metal wires. One end of the wires 6 is connected to the electrodes 2a of the semiconductor chip 2, and the other end of the wires 6 is connected to the electrodes 4b formed on the upper surface of the base plate 3.

[0025] Furthermore, in this embodiment, the multiple electrodes 2a of the semiconductor chip 2 and the multiple electrodes 4b formed on the upper surface of the base plate 3 are electrically connected via multiple wires 6, but as another embodiment, there may be a case where the electrodes 4b are not formed on the upper surface of the base plate 3. In that case, a flexible substrate may be connected to the base plate 3, and the multiple electrodes of the flexible substrate and the multiple electrodes 2a of the semiconductor chip 2 may be electrically connected via multiple wires.

[0026] FIG. 3 is a cross-sectional view that schematically shows a state in which the mechanical quantity measuring device 1 is attached (attached) to a measurement object 7. As shown in FIG.

[0027] As shown in Fig. 3, when the mechanical quantity measuring device 1 is attached (attached) to the measurement object 7, the lower surface of the base plate 3 of the mechanical quantity measuring device 1 is joined and fixed to the measurement object 7 via a bonding material 8. The bonding material 8 can be an insulating adhesive, but is more preferably a conductive bonding material, such as solder. The measurement object 7 may also be conductive and may be made of, for example, a metal material.

[0028] Since the base plate 3 is an insulating base plate, when the object to be measured 7 is made of a conductive material (preferably a metal material), even if a conductive bonding material (preferably solder) is used as the bonding material 8, electrical continuity between the object to be measured 7 and the base plate 3 can be avoided, and therefore electrical continuity between the object to be measured 7 and the semiconductor chip 2 can be avoided.

[0029] Furthermore, in order to facilitate bonding of the base plate 3 and the measurement object 7 with the bonding material 8, a conductor pattern (not shown) may also be formed on the lower surface of the base plate 3, and the conductor pattern on the lower surface of the base plate 3 and the measurement object 7 may be bonded via the bonding material 8. In this case, it is preferable that the conductor pattern on the lower surface of the base plate 3 is not electrically connected to the conductor patterns 4a and 4b on the upper surface of the base plate 3 or the semiconductor chip 2.

[0030] By attaching (sticking) the mechanical quantity measuring device 1 to the measurement object 7, the strain generated in the measurement object 7 can be detected by the mechanical quantity measuring device 1. That is, the strain generated in the measurement object 7 is transmitted to the base plate 3 via the bonding material 8, and further transmitted from the base plate 3 via the bonding material 5 to the semiconductor chip 2. The strain transmitted from the measurement object 7 to the semiconductor chip 2 via the bonding material 8, base plate 3, and bonding material 5 is detected by a strain detection circuit formed in the semiconductor chip 2. Therefore, the bonding material 5 not only serves to fix the semiconductor chip 2 to the base plate 3, but also to transmit the strain from the base plate 3 to the semiconductor chip 2.

[0031] Here, the mechanical quantity measuring device 1 of this embodiment is illustrated and described as being attached to the object to be measured 7, but the same applies when the mechanical quantity measuring devices 1a to 1e of embodiments 2 to 6 described below are attached to the object to be measured 7.

[0032] Next, an example of a manufacturing process for the mechanical quantity measuring device 1 will be described.

[0033] To manufacture the mechanical quantity measuring device 1, first, a semiconductor chip 2 and a base plate 3 are prepared. Then, the semiconductor chip 2 is mounted and bonded to the base plate 3 via a bonding material 5. Then, a wire bonding process is performed to electrically connect the plurality of electrodes 2a of the semiconductor chip 2 to the plurality of electrodes 4b on the upper surface of the base plate 3 via the plurality of wires 6. Thereafter, a sealing resin (not shown) for sealing the semiconductor chip 2 may be formed.

[0034] <About semiconductor chips> Next, an example of the configuration of the semiconductor chip 2 will be described with reference to Fig. 4. Fig. 4 is an explanatory diagram showing the planar configuration of the semiconductor chip 2.

[0035] The semiconductor chip 2 is a semiconductor chip on which a strain detection circuit is formed, i.e., a strain sensor chip. The semiconductor substrate 11 constituting the semiconductor chip 2 is made of, for example, silicon (specifically, a single crystal silicon substrate). The semiconductor substrate 11 has a planar shape that is point-symmetric with respect to the center of the semiconductor chip 2, and preferably has a square planar shape.

[0036] As shown in FIG. 4, four diffused resistance regions 12a, 12b, 12c, and 12d are formed on a semiconductor substrate 11 constituting the semiconductor chip 2, and are arranged point-symmetrically with respect to the center of the semiconductor chip 2. These four diffused resistance regions 12a, 12b, 12c, and 12d function as piezo-resistance elements that detect strain as a change in electrical resistance. For example, the diffused resistance regions 12a and 12c function as piezo-resistance elements that detect strain in the Y direction as a change in electrical resistance, and the diffused resistance regions 12b and 12d function as piezo-resistance elements that detect strain in the X direction as a change in electrical resistance. Therefore, these four diffused resistance regions 12a, 12b, 12c, and 12d form a strain detection circuit.

[0037] In the strain detection circuit formed on the semiconductor chip 2, the four diffused resistance regions 12a, 12b, 12c, and 12d form a bridge circuit, and a signal corresponding to the difference between the strain occurring in the X direction and the strain occurring in the Y direction is output based on the change in electrical resistance in the four diffused resistance regions 12a, 12b, 12c, and 12d. For example, the strain detection circuit formed on the semiconductor chip 2 is configured to output, as a voltage value, the change in electrical resistance corresponding to the difference between the strain occurring in the X direction and the strain occurring in the Y direction. In this way, a strain detection circuit that outputs a signal corresponding to the difference between the strain occurring in the X direction and the strain occurring in the Y direction has the advantage of improving the strain detection sensitivity because the output signal (output voltage) from the strain detection circuit is large.

[0038] Note that the number of diffused resistor regions is not necessarily four if the circuit configuration is such that the difference between the distortion occurring in the X direction and the distortion occurring in the Y direction is measured. For example, if they are arranged in parallel, the number is not limited to four and may be more than four. In other words, if the circuit is equivalent to that shown in Figure 4, the number of diffused resistor regions is not limited to four.

[0039] <Main features and effects> One of the main features of this embodiment is that the semiconductor chip 2 (strain sensor chip) on which the strain detection circuit is formed is mounted (implemented) on an insulating base plate 3. Mounting the semiconductor chip 2 on the base plate 3 makes it easier to handle the mechanical quantity measuring device 1. For example, as shown in FIG. 3 above, by joining the base plate 3 of the mechanical quantity measuring device 1 to a measurement object 7, the mechanical quantity measuring device 1 can detect strain occurring in the measurement object 7.

[0040] FIG. 5 is a cross-sectional view schematically illustrating a state in which a mechanical quantity measuring device 101 of an example studied by the present inventor is attached to a measurement object 107, and corresponds to FIG. 3 above. The mechanical quantity measuring device 101 of the example shown in FIG. 5 has a conductive base plate 103 made of a metal material and a semiconductor chip 102 mounted on the base plate 103 via a bonding material 105. The semiconductor chip 102 corresponds to the semiconductor chip 102 of the present embodiment and is a semiconductor chip (strain sensor chip) on which a strain detection circuit is formed. As shown in FIG. 5, when the mechanical quantity measuring device 101 of the example is attached to the measurement object 107, the lower surface of the base plate 103 of the mechanical quantity measuring device 101 is bonded and fixed to the measurement object 107 via a bonding material 108.

[0041] In the mechanical quantity measuring device 101 of the studied example, the base plate 103 is a conductive base plate. When the base plate 103 is a conductive base plate, there is a risk of malfunction depending on how the mechanical quantity measuring device 101 is used, which may limit how the mechanical quantity measuring device 101 is used, making the mechanical quantity measuring device 101 less user-friendly and possibly degrading the performance of the mechanical quantity measuring device 101.

[0042] For example, if the measurement object 107 is made of a metal material (conductive material), there is a risk that electrical conduction will occur between the base plate 103 and the measurement object 107, causing a current to flow between the mechanical quantity measuring device 101 and the measurement object 107, and there is a concern that the mechanical quantity measuring device 101 will be affected by electrical noise from the measurement object 107. Furthermore, the above-mentioned Patent Document 1 (JP 2009-264976 A) describes that it is preferable that the base plate on which the strain sensor chip is mounted be made of the same material as the measurement object or a material with a thermal expansion coefficient that is approximately the same as that of the measurement object, and therefore, if the measurement object is made of a metal material, the base plate on which the strain sensor chip is mounted will also be made of a metal material. If both the base plate 103 on which the strain sensor chip (semiconductor chip 102) is mounted and the measurement object 107 are made of metal materials, as described above, there is a risk that the base plate 103 and the measurement object 107 will be electrically connected, causing a current to flow between the mechanical quantity measuring device 101 and the measurement object 107, and there is a concern that the mechanical quantity measuring device 101 will be affected by electrical noise from the measurement object 107. This will degrade the performance of the mechanical quantity measuring device 101.

[0043] For this reason, it is necessary to use an insulating adhesive as the bonding material 108 that bonds the base plate 103 made of a metal material to the measurement object 107 made of a metal material. This makes it possible to prevent conduction between the base plate 103 made of a metal material and the measurement object 107 made of a metal material, thereby preventing current from flowing between the mechanical quantity measuring device 101 and the measurement object 107, and suppressing or preventing the mechanical quantity measuring device 101 from being affected by electrical noise from the measurement object 107.

[0044] However, insulating adhesives are disadvantageous compared to conductive bonding materials such as solder as the bonding material 108 used to bond the mechanical quantity measuring device 101 to the measurement object 107. Specifically, when an insulating adhesive is used as the bonding material 108, there is a concern that the range of strain that the mechanical quantity measuring device 101 can measure may be limited due to the bonding strength, yield stress, fatigue strength, and stress relaxation characteristics of the insulating adhesive. There is also a concern that the sensitivity of the mechanical quantity measuring device 101 may be reduced due to the elastic modulus of the insulating adhesive and softening due to temperature increases. There is also a concern that the long-term reliability of the mechanical quantity measuring device 101 may be reduced due to the fatigue strength, stress relaxation characteristics, and environmental resistance of the insulating adhesive. These concerns lead to a decrease in the performance of the mechanical quantity measuring device 101, and therefore, it is desirable to resolve or improve these concerns. In order to eliminate or improve these concerns, it would be effective to use a conductive bonding material such as solder as bonding material 108 instead of an insulating adhesive. However, if a conductive bonding material such as solder is used, there is a concern that malfunctions may occur due to electrical conduction between base plate 103 and object to be measured 107, as described above.

[0045] Therefore, in this embodiment, the semiconductor chip 2 (strain sensor chip) on which the strain detection circuit is formed is mounted on the base plate 3, which is an insulating structure. Therefore, even if the measurement object 7 to which the mechanical quantity measuring device 1 is attached is made of a conductive material such as a metal material, the base plate 3 of the mechanical quantity measuring device 1 is not made of a metal body but of an insulating base plate. In this embodiment, since the semiconductor chip 2 is mounted on the insulating base plate 3 rather than a metal base plate, when the mechanical quantity measuring device 1 is attached to the measurement object 7, it is possible to prevent current from flowing between the semiconductor chip 2 of the mechanical quantity measuring device 1 and the measurement object 7, and it is possible to suppress or prevent the semiconductor chip 2 of the mechanical quantity measuring device 1 from being affected by electrical noise from the measurement object 7. This makes it possible to improve the performance of the mechanical quantity measuring device 1.

[0046] Furthermore, in this embodiment, the insulating base plate 3 can prevent electrical continuity between the semiconductor chip 2 and the measurement object 7. Therefore, when attaching (sticking) the mechanical quantity measuring device 1 to the measurement object 7, an insulating adhesive or a conductive bonding material such as solder can be used as the bonding material 8 bonding the base plate 3 and the measurement object 7. That is, even if a conductive bonding material such as solder is used as the bonding material 8 bonding the base plate 3 and the measurement object 7 when the measurement object 7 is made of a metal material, current can be prevented from flowing between the semiconductor chip 2 of the mechanical quantity measuring device 1 and the measurement object 7, thereby suppressing or preventing the semiconductor chip 2 of the mechanical quantity measuring device 1 from being affected by electrical noise from the measurement object 7. Furthermore, the use of a conductive bonding material such as solder as the bonding material 8 bonding the base plate 3 and the measurement object 7 can eliminate or improve the above-mentioned concerns when using only insulating adhesives. For example, the strain range measurable by the mechanical quantity measuring device 1 can be expanded, and the sensitivity of the mechanical quantity measuring device 1 can be improved. Furthermore, the long-term reliability of the mechanical quantity measuring device 1 can be improved.

[0047] In this way, in this embodiment, by mounting the semiconductor chip 2 (strain sensor chip) on which the strain detection circuit is formed on the base plate 3, which is an insulating structure, there are fewer restrictions on the usage of the mechanical quantity measuring device, making the mechanical quantity measuring device easier to use and also improving the performance of the mechanical quantity measuring device.

[0048] In this embodiment, an insulating base plate 3 is used, and an insulating ceramic material is preferably used as the material for the insulating base plate 3. That is, it is preferable to use a base plate 3 made of an insulating ceramic material.

[0049] The base plate 3 also plays a role in transmitting strain from the measurement object 7 to the semiconductor chip 2, and if it is too soft (and therefore has too low an elastic modulus), strain will not be easily transmitted from the measurement object 7 to the semiconductor chip 2. For this reason, the elastic modulus of the base plate 3 is required to have a value that allows strain to be transmitted between the measurement object 7 and the semiconductor chip 2. From this perspective, it is preferable that the elastic modulus of the base plate 3 is higher than that of the semiconductor chip 2. Ceramic materials are insulating materials with high elastic moduli, and are therefore preferred as materials for the base plate 3. As an example, a ceramic material with an elastic modulus of about 310 GPa can be used for the base plate 3.

[0050] As described above, in this embodiment, solder or metal nanoparticles can be suitably used as the bonding material 5 for bonding the semiconductor chip 2 to the base plate 3.

[0051] When solder is used as the bonding material 5, a high-melting-point solder having a eutectic point of 275°C or higher, such as gold-tin solder, can be suitably used. Using high-melting-point solder as the bonding material 5 makes it easier to prevent the solder used as the bonding material 5 from melting and causing problems when the mechanical quantity measuring device 1 is attached to the measurement object 7 using solder or the like. Furthermore, if the bonding material 5 is conductive, it makes it easier to conduct heat generated in the semiconductor chip 2 to the base plate 3, making it easier to suppress a temperature rise in the semiconductor chip 2 during operation.

[0052] Gold-tin solder has an elastic modulus of 69 GPa and a yield stress of 275 MPa after solidification, which are higher than those of common semiconductor chip bonding materials, such as silver paste, etc. Therefore, from the viewpoint that the bonding material 5 has the role of transmitting strain from the base plate 3 to the semiconductor chip 2, gold-tin solder is suitable as the bonding material 5.

[0053] However, when solder is used as the bonding material 5, a process occurs in which the metal solder used as the bonding material 5 goes from a molten state to solidify in the process of bonding the semiconductor chip 2 to the base plate 3. Residual stress resulting from the difference in the amount of thermal deformation between the bonding material 5 and the semiconductor chip 2 generated in this process may cause distortion in the semiconductor chip 2. Since distortion in the semiconductor chip 2 in the process of bonding the semiconductor chip 2 to the base plate 3 may affect the initial measurement value of the mechanical quantity measuring device 1, it is desirable to suppress this as much as possible.

[0054] In the mechanical quantity measuring device 101 of the above-mentioned study example, the base plate 103 is made of a metal material, and therefore there is a relatively large difference in the thermal expansion coefficient between the base plate 103 and the semiconductor chip 102. For this reason, in the case of the mechanical quantity measuring device 101 of the above-mentioned study example, the difference in the amount of thermal deformation between the bonding material 105 and the semiconductor chip 102 that occurs in the process of the metal solder used as the bonding material 105 solidifying from a molten state becomes quite large, and the residual stress becomes quite large, so that the distortion that occurs in the semiconductor chip 2 becomes quite large.

[0055] Compared to the mechanical quantity measuring device 101 of the studied example that uses a base plate 103 made of metal, in the case of the mechanical quantity measuring device 1 that uses a base plate 3 made of an insulating material such as a ceramic material, the difference in the thermal expansion coefficient between the base plate 3 and the semiconductor chip 2 is relatively small. Therefore, compared to the mechanical quantity measuring device 101 of the studied example, even when the semiconductor chip 2 is joined to the base plate 3 by soldering, the mechanical quantity measuring device 1 of this embodiment has a smaller difference in the amount of thermal deformation between the joining material 5 and the semiconductor chip 2 that occurs in the process of metal solder solidifying from a molten state, and it is possible to suppress distortion that occurs in the semiconductor chip 2.

[0056] However, even if the difference in thermal expansion coefficient between the base plate 3 and the semiconductor chip 2 can be reduced by using a base plate 3 made of an insulating material such as ceramic, when solder is used as the bonding material 5, distortion of the semiconductor chip 2 is unavoidable due to residual stress caused by the difference in the amount of thermal deformation between the bonding material 5 and the semiconductor chip 2 that occurs as the solder solidifies from a molten state.

[0057] Therefore, in this embodiment, it is more preferable to use metal nanoparticles as the bonding material 5 that bonds the semiconductor chip 2 to the base plate 3. Copper nanoparticles are particularly suitable as the metal nanoparticles.

[0058] Because metal nanoparticles (preferably copper nanoparticles) can undergo metallic bonding without heating, a stabilizer is mixed with the metal nanoparticles at the raw material stage to disperse the metal nanoparticles and inhibit metallic bonding. The metallic bonding of the metal nanoparticles, which is inhibited by the stabilizer, progresses when the stabilizer is removed from the metal nanoparticles by heating or other methods, and the metal nanoparticles bond with each other and also with other metals. Therefore, when metal nanoparticles (preferably copper nanoparticles) are used as the bonding material 5, the process of melting and then solidifying the bonding material 5 is not required during the process of bonding the semiconductor chip 2 to the base plate 3.

[0059] That is, when solder is used as the bonding material 5, the process of bonding the semiconductor chip 2 to the base plate 3 requires a process of melting the solder and then solidifying it, which causes distortion in the semiconductor chip 2. However, when metal nanoparticles (preferably copper nanoparticles) are used as the bonding material 5, by performing heating to remove the stabilizer in the process of bonding the semiconductor chip 2 to the base plate 3, metallic bonding of the metal nanoparticles progresses without melting the bonding material 5, and the semiconductor chip 2 can be accurately bonded to the conductor pattern 4a on the upper surface of the base plate 3 via the bonding material 5. Therefore, when metal nanoparticles (preferably copper nanoparticles) are used as the bonding material 5, the residual stress generated due to the difference in the amount of thermal deformation between the bonding material 5 and the semiconductor chip 2 is smaller than when solder is used as the bonding material 5, and distortion generated in the semiconductor chip 2 is reduced. Therefore, when metal nanoparticles (preferably copper nanoparticles) are used as the bonding material 5, the distortion that occurs in the semiconductor chip 2 during the process of bonding the semiconductor chip 2 to the base plate 3 can be suppressed, and the distortion can be prevented from affecting the initial measurement value of the mechanical quantity measuring device 1.

[0060] Copper nanoparticles are suitable as the metal nanoparticles used as the bonding material 5, and by making the average particle size of the copper nanoparticles Φ100 nm or less, it is possible to achieve metal bonding with a yield stress suitable for the bonding portion of the semiconductor chip 2.

[0061] Here, the yield strength required for the bonding material 5 of the mechanical quantity measuring device 1 can be found by estimating the stress that can be applied to the bonding material 5 from the range of strain to be measured by the mechanical quantity measuring device 1. For example, the range of strain to be measured by the mechanical quantity measuring device 1 is set to +1000 με, and the results of analyzing the stress distribution (stress distribution at the position of line BB in FIG. 6) on the upper surface of the base plate 3 and the bonding surface between the base plate 3 and the bonding material 5 using predetermined physical property values are shown in FIG. 6. The graph in FIG. 6 shows that stress is concentrated on the end surface (side end surface) of the bonding material 5, with a maximum stress of 400 MPa acting on it, and that if the bonding material 5 has a yield strength of 400 MPa or more, yielding will not occur.

[0062] On the other hand, the yield stress of the copper nanoparticles used in the bonding material 5 is estimated using the Hall-Petch equation of the following Equation 1. σ y =σ0+k / √d (Equation 1)

[0063] where σ y is the yield stress of the copper nanoparticles, σ0 is the yield stress of the single crystal, k is the material constant, and d is the average particle size.

[0064] In addition, the yield stress σ0 is estimated from the following formula 2 when the yield ratio is set to 0.65. σ0=σ S ×0.65 (Formula 2)

[0065] where σ S is the tensile strength and is estimated from Equation 3 below. σ S =(2.5~3.0)×Hv (Equation 3)

[0066] Here, the Vickers hardness Hv of copper single crystal can be estimated from the following mathematical formula 4 in the above-mentioned Non-Patent Document 1. Hv=52+60 / √d (Equation 4)

[0067] The yield stress σ0 of a single crystal is 84.5 to 101.4 MPa (2.5 to 3.0 × 52 × 0.65) from the above formula 2. In addition, the material constant k = 60 (Hv √μm) that indicates the resistance to the sliding propagation of the grain boundary in the above formula 1 can be calculated as the tensile strength σ S = 2.7 × k × 0.65 (MPa √μm), k = 60 (Hv √μm) = 105 (MPa √μm) = 3330 (MPa √nm).

[0068] σ y If the average particle diameter of copper nanoparticles is Φ100 nm, then from the above formula 1, σ y= (84.5 to 101.4) + (3330 / √100) = 417.5 to 434.4 MPa. In this case, it is possible to ensure a yield stress of 400 MPa or more, which is necessary for the bonding material 5. If it is desired to measure a wider range of strain amounts with the mechanical quantity measuring device 1, copper nanoparticles with an even smaller average particle size can be used.

[0069] In this way, when metal nanoparticles are used as the bonding material 5, the yield strength of the bonding material 5 can be increased by reducing the average particle size of the metal nanoparticles used, thereby widening the range of strain that can be measured by the mechanical quantity measuring device 1. Therefore, when copper nanoparticles are used as the bonding material 5, copper nanoparticles with an average particle diameter of Φ100 nm or less can be suitably used.

[0070] Furthermore, the semiconductor chip 2 has the function of detecting (calculating) and outputting the difference (difference) in the amount of strain in two mutually orthogonal directions (X direction and Y direction). Therefore, when thermal deformation of the base plate 3 occurs due to a temperature change, if the amount of thermal deformation of the base plate 3 is approximately equal in the X direction and the Y direction, the distortion of the base plate 3 caused by the thermal deformation will not affect the measurement value of the distortion detection circuit formed on the semiconductor chip 2. From this perspective, it is preferable that the base plate 3 has a planar shape that is point-symmetric with respect to the center of the base plate 3. By doing so, the amount of thermal deformation of the base plate 3 becomes approximately equal in the X direction and the Y direction, so that the distortion of the base plate 3 caused by the thermal deformation can be suppressed or prevented from affecting the measurement value of the mechanical quantity measuring device 1. Therefore, the mechanical quantity measuring device 1 can accurately detect the strain caused in the measurement object 7 while suppressing or preventing the influence of the thermal deformation of the base plate 3.

[0071] Therefore, it is preferable that the base plate 3 has a planar shape that is point-symmetric with respect to the center of the base plate 3, and from this viewpoint, the planar shape of the base plate 3 can be a square, a circle, a regular hexagon, a regular octagon, or the like. Of these, a square (approximately square) is the most suitable planar shape of the base plate 3. This makes it easier to manufacture the mechanical quantity measuring device 1 and to handle the mechanical quantity measuring device 1.

[0072] In the case of FIG. 1, the planar shape of the semiconductor chip 2 is square. An example of the dimensions of the semiconductor chip 2 is 2.5 mm × 2.5 mm × 0.13 mm (width × length × thickness), and an example of the dimensions of the base plate 3 is 7.5 mm × 7.5 mm × 0.2 mm (width × length × thickness), which is three times the width and length of the semiconductor chip 2. If the base plate 3 is too thick, it becomes difficult to transmit strain from the measurement object 7 to the semiconductor chip 2, so it is preferable that the thickness of the base plate 3 is somewhat thin. However, if the base plate 3 is too thin, it becomes difficult to manufacture the mechanical quantity measuring device 1. For this reason, here, the thickness of the base plate 3 is set to, for example, about 0.2 mm.

[0073] (Embodiment 2) Fig. 7 is a plan view (top view) showing the mechanical quantity measuring device 1 of the present embodiment 2, and Fig. 8 is a cross-sectional view showing the mechanical quantity measuring device 1 of the present embodiment 2, which correspond to Fig. 1 and Fig. 2 of the above-mentioned embodiment 1, respectively. The cross-sectional view at the position of line A2-A2 in Fig. 7 approximately corresponds to Fig. 8. The mechanical quantity measuring device 1 of the present embodiment 2 will be given the reference symbol 1a and will be referred to as the mechanical quantity measuring device 1a below.

[0074] The mechanical quantity measuring device 1a of the present embodiment 2 is mainly different from the mechanical quantity measuring device 1 of the above-described embodiment 1 in the base plate 3. Hereinafter, the base plate 3 of the present embodiment 2 will be given the reference symbol 3a and referred to as the base plate 3a.

[0075] The base plate 3a of the present embodiment 2 has a planar shape that is basically the same as that of the base plate 3 of the above-mentioned embodiment 1. However, while the base plate 3 of the above-mentioned embodiment 1 has a substantially uniform thickness, the base plate 3a of the present embodiment 2 has a relatively thick outer periphery (frame portion 21).

[0076] That is, the base plate 3a of the second embodiment has a frame portion (thick portion, frame portion) 21 on the outer periphery of the base plate 3a. The frame portion 21 is a thickened portion of the base plate 3a, or from another perspective, a protruding portion of the upper surface of the base plate 3a. Because the frame portion 21 is provided on the outer periphery of the base plate 3a, it can also be considered as the outer periphery of the base plate 3a.

[0077] In a plan view, the frame portion 21 is provided on the outer periphery of the base plate 3a, and the thickness of the frame portion 21 is thicker than the thickness of the base plate 3a inside the frame portion 21. Hereinafter, the region of the base plate 3a inside the frame portion 21 will be referred to as the inner region 22. In a plan view, the inner region 22 is surrounded by the frame portion 21, and the thickness of the inner region 22 is thinner than the thickness of the frame portion 21. The height position of the upper surface of the frame portion 21 is higher than the height position of the upper surface of the inner region 22, and the frame portion 21 protrudes from the upper surface of the inner region 22. The lower surface of the base plate 3a is formed in the same plane. That is, the lower surfaces of the frame portion 21 and the inner region 22 are at the same height and form the same plane. The thicker the portion of the base plate 3a, the higher the rigidity. Because the thickness of the frame portion 21 is thicker than the thickness of the inner region 22, the rigidity of the frame portion 21 is higher than the rigidity of the inner region 22.

[0078] The semiconductor chip 2 is mounted on the inner region 22 of the base plate 3a via a bonding material 5. Specifically, a conductor pattern 4a is formed on the upper surface of the inner region 22 of the base plate 3a, and the semiconductor chip 2 is bonded and fixed onto the conductor pattern 4a via the bonding material 5. It is preferable that the conductor pattern 4a be formed, but it can be omitted if not necessary.

[0079] In the case of Fig. 7, the width of the frame portion 21 is almost uniform. In this case, the planar shape of the inner region 22 is almost the same as the planar shape of the base plate 3a (however, the planar dimensions are smaller), and if the planar shape of the base plate 3a is square, the planar shape of the inner region 22 will also be square. Also, in the case of Fig. 8, the inner wall (inner side surface, inner peripheral side surface) 33 of the frame portion 21 is almost perpendicular to the upper surface of the inner region 22. As another embodiment, the inner wall 33 of the frame portion 21 may be inclined with respect to the upper surface of the inner region 22.

[0080] Other configurations of the mechanical quantity measuring device 1a of the second embodiment are almost the same as those of the mechanical quantity measuring device 1 of the first embodiment, so repeated explanations thereof will be omitted here.

[0081] From the viewpoint of making the mechanical quantity measuring device easier to handle, it is desirable that the base plate on which the semiconductor chip 2 is mounted has high rigidity. However, in the case of the above-mentioned embodiment 1, since the thickness of the base plate 3 is uniform, if the overall thickness of the base plate 3 on which the semiconductor chip 2 is mounted is increased, the rigidity of the entire base plate 3 will increase, but the thickness of the base plate 3 directly below the semiconductor chip 2 will also increase, and the rigidity will also increase, so that strain generated in the measurement object 7 will be less likely to be transmitted to the semiconductor chip 2 via the base plate 3.

[0082] In contrast, in the second embodiment, the base plate 3a has a frame portion 21 that is thicker on the periphery, and the semiconductor chip 2 is mounted in a thinner inner region 22 surrounded by the frame portion 21. The thick frame portion 21 on the periphery of the base plate 3a increases the rigidity of the base plate 3a, making the mechanical quantity measuring device 1a easier to handle. Mounting the semiconductor chip 2 in the inner region 22 that is thinner than the frame portion 21 reduces the thickness of the base plate 3a directly below the semiconductor chip 2 (corresponding to the thickness of the inner region 22) and reduces its rigidity. Therefore, when the mechanical quantity measuring device 1a is attached to the measurement object 7, the thickness of the base plate 3a (corresponding to the thickness of the inner region 22) located between the semiconductor chip 2 and the measurement object 7 is reduced and its rigidity is reduced, so that strain generated in the measurement object 7 is more likely to be transmitted to the semiconductor chip 2 via the base plate 3a. This makes it possible to improve the sensitivity of the mechanical quantity measuring device 1a, and to accurately detect the strain occurring in the measurement object 7 by the mechanical quantity measuring device 1a.

[0083] FIG. 9 is a graph showing an example of the results of an analysis of the thickness of a base plate directly below a strain sensor chip (corresponding to semiconductor chip 2) mounted on a mechanical quantity measuring device, and the strain transmissibility when strain is transmitted from the measurement object to the strain sensor chip via the base plate. FIG. 9 shows that when the thickness of the base plate on which the strain sensor chip is mounted is greater than 300 μm, the strain transmissibility decreases as the base plate thickness increases. However, when the base plate thickness is 300 μm or less, the strain transmissibility is 80% or more. Even when the base plate thickness is thinner than 300 μm, the strain transmissibility does not increase any further. For this reason, it is preferable to set the thickness of the base plate 3a directly below the semiconductor chip 2, i.e., the thickness of the inner region 22, to approximately 300 μm or less. This allows strain generated in the measurement object 7 to be efficiently transmitted to the semiconductor chip 2 via the base plate 3a, thereby enabling the mechanical quantity measuring device 1a to accurately detect the strain generated in the measurement object 7. Furthermore, taking into consideration the productivity and ease of handling of the mechanical quantity measuring device, it is more preferable that the thickness of the base plate 3a directly below the semiconductor chip 2, that is, the thickness of the inner region 22, is about 100 to 300 μm.

[0084] Furthermore, it is more preferable to set the thickness of the frame portion 21 so that the height position of the upper surface of the frame portion 21 is higher than the height position of the top of the wire 6. This ensures that the top of the wire 6 is also covered by the sealing portion 31 when the sealing portion 31 described below is formed, making it easier to prevent the wire 6 from being exposed through the sealing portion 31. For example, if the thickness of the inner region 22 is 100 μm, the thickness of the semiconductor chip 2 is 100 μm, and the height position of the top of the wire 6 is 40 μm higher than the top surface of the semiconductor chip 2, it is preferable to set the thickness of the frame portion 21 to 240 μm or more, so that the height position of the upper surface of the frame portion 21 is higher than the height position of the top of the wire 6. Here, the top of the wire 6 corresponds to the highest part of the wire 6 in the Z direction and refers to the top of the loop-shaped wire 6.

[0085] (Embodiment 3) Fig. 10 is a plan view (top view) showing the mechanical quantity measuring device 1 of the present embodiment 3, and Fig. 11 is a cross-sectional view showing the mechanical quantity measuring device 1 of the present embodiment 3. The cross-sectional view taken along line A3-A3 in Fig. 10 roughly corresponds to Fig. 11. In Fig. 10, when the sealing portion 31 is seen through, it is the same as Fig. 7 above. The mechanical quantity measuring device 1 of the present embodiment 3 will be given the symbol 1b and referred to as mechanical quantity measuring device 1b below.

[0086] The mechanical quantity measuring device 1b of the present embodiment 3 differs from the mechanical quantity measuring device 1a of the above-described embodiment 2 in that a sealing portion (sealing resin portion) 31 is provided on the base plate 3a so as to cover the semiconductor chip 2. The semiconductor chip 2 and the plurality of wires 6 are sealed by the sealing portion 31.

[0087] The sealing portion 31 is made of a resin material. The elastic modulus of the sealing portion 31 is preferably lower than that of the semiconductor chip 2. The elastic modulus of the sealing portion 31 can be, for example, about 4 to 14 GPa. The sealing portion 31 is preferably formed on the entire inner region 22 surrounded by the frame portion 21 so as to cover the semiconductor chip 2. Furthermore, the sealing portion 31 preferably fills a space (region, cavity) 32 on the base plate 3a surrounded by an inner wall (inner side surface, inner peripheral side surface) 33 of the frame portion 21. The planar shape and planar dimensions of the space 32 surrounded by the inner wall 33 of the frame portion 21 match the planar shape and planar dimensions of the inner region 22.

[0088] Because the outer periphery of the sealing portion 31 contacts the inner wall 33 of the frame portion 21, the planar shape of the sealing portion 31 conforms to the inner wall 33 of the frame portion 21 and is therefore the same as the planar shape of the space 32 surrounded by the inner wall 33 of the frame portion 21. In the case of FIG. 10 , the width of the frame portion 21 is substantially constant regardless of location. In this case, the planar shape of the space 32 surrounded by the inner wall 33 of the frame portion 21 is basically the same as the planar shape of the base plate 3a, and the planar dimensions of the space 32 surrounded by the inner wall 33 of the frame portion 21 are smaller than the planar dimensions of the base plate 3a by the width of the frame portion 21. Therefore, if the planar shape of the base plate 3a is point-symmetric with respect to the center of the base plate 3a, the planar shapes of the space 32 surrounded by the inner wall 33 of the frame portion 21 and the planar shapes of the sealing portion 31 can also be point-symmetric with respect to the center of the base plate 3a (and therefore with respect to the center of the sealing portion 31). Furthermore, if the planar shape of the base plate 3a is square, the planar shape of the space 32 surrounded by the inner wall 33 of the frame portion 21 and the planar shape of the sealing portion 31 can also be square.

[0089] Except for the provision of the sealing portion 31, the mechanical quantity measuring device 1b of the third embodiment is substantially the same as the mechanical quantity measuring device 1a of the second embodiment, and therefore a repeated description thereof will be omitted here.

[0090] In the third embodiment, the provision of the sealing portion 31 makes it possible to protect the semiconductor chip 2 and the plurality of wires 6. This makes it easier to handle the mechanical quantity measuring device 1b, and also improves the reliability of the mechanical quantity measuring device 1b.

[0091] Furthermore, there is a concern that thermal deformation of the sealing portion 31 due to temperature changes may cause stress in the semiconductor chip. However, since the semiconductor chip 2 has a function of detecting (calculating) and outputting the difference (difference) in the amount of strain in two mutually perpendicular directions (X direction and Y direction), if thermal deformation of the sealing portion 31 occurs due to temperature changes, as long as the amount of thermal deformation of the sealing portion 31 is approximately equal in the X direction and the Y direction, the thermal deformation of the sealing portion 31 will not affect the measurement value of the strain detection circuit formed on the semiconductor chip 2. From this perspective, it is preferable that the sealing portion 31 has a planar shape that is point-symmetric with respect to the center of the sealing portion 31. In the case of FIG. 10, the planar shape of the sealing portion 31 is square. This makes the amount of thermal deformation of the sealing portion 31 approximately equal in the X direction and the Y direction, thereby suppressing or preventing the thermal deformation of the sealing portion 31 from affecting the measurement value of the mechanical quantity measuring device 1b. Therefore, the influence of thermal deformation of the sealing portion 31 can be suppressed or prevented, and the strain occurring in the measurement object 7 can be accurately detected by the mechanical quantity measuring device 1b.

[0092] In the mechanical quantity measuring device 1 of the first embodiment, a sealing resin portion (corresponding to the sealing portion 31) for sealing the semiconductor chip 2 and the wires 6 can also be formed on the base plate 3.

[0093] (Fourth embodiment) Fig. 12 is a plan view (top view) showing the mechanical quantity measuring device 1 of the fourth embodiment, Fig. 13 is a plan perspective view showing the mechanical quantity measuring device 1 of the fourth embodiment, and Figs. 14 to 16 are cross-sectional views showing the mechanical quantity measuring device 1 of the fourth embodiment. In Fig. 13, the sealing portion 31 is seen through. The cross-sectional view taken along line A4-A4 in Fig. 13 approximately corresponds to Fig. 14, the cross-sectional view taken along line C4-C4 in Fig. 13 approximately corresponds to Fig. 15, and the cross-sectional view taken along line D4-D4 in Fig. 13 approximately corresponds to Fig. 16. The mechanical quantity measuring device 1 of the fourth embodiment will be denoted by reference symbol 1c and referred to as mechanical quantity measuring device 1c below.

[0094] The mechanical quantity measuring device 1c of the present embodiment 4 differs from the mechanical quantity measuring device 1b of the above-described embodiment 3 mainly in the base plate 3. Hereinafter, the base plate 3 of the present embodiment 3 will be given the reference symbol 3c and referred to as the base plate 3c.

[0095] The base plate 3c of the fourth embodiment differs from the base plate 3a of the third embodiment in the following points.

[0096] In the fourth embodiment, in the vicinity of the corner 41 of the base plate 3c, the inner wall 33 of the frame part 21 is recessed so as to approach the corner 41 (i.e., so as to move away from the center of the base plate 3c). In other words, in the vicinity of the corner 41 of the base plate 3c, the inner wall 33 of the frame part 21 is recessed outward (away from the center of the base plate 3c).

[0097] Specifically, except for the vicinity of corners 41 of the base plate 3c, the width of the frame portion 21 is approximately uniform, and the inner walls 33 of the frame portion 21 extend along the sides of the base plate 3c, but near the corners 41 of the base plate 3c, the inner walls 33 of the frame portion 21 are recessed (curved) toward the corners 41, i.e., away from the center of the base plate 3c. In the case of FIGS. 12 and 13, since the planar shape of the base plate 3c is square, the inner walls 33 of the frame portion 21 are recessed (curved) near each of the four corners 41, toward the corners 41, i.e., away from the center of the base plate 3c. By the amount that the inner walls 33 of the frame portion 21 are recessed toward the corners 41, the thinner inner region 22 expands toward the corners 41 (i.e., away from the center of the base plate 3c). 12 and 13, a region 42 (hereinafter sometimes referred to as the recessed region 42) formed by recessing the inner wall 33 of the frame portion 21 toward the corner 41 has a circular (almost circular) planar shape. Therefore, near the corner 41 of the base plate 3c, the inner wall 33 of the frame portion 21 is configured as a curved surface without right-angled corners. Note that the recessed region 42 is part of the inner region 22, and can also be considered as an extension of the inner region 22. In the case of FIG. 13, the four corners of the square-shaped inner region 22 are extended outward (away from the center of the base plate 3c) to form the recessed region 32. Furthermore, although a circular shape is preferable for the recessed region 42, it can also be formed in a shape other than a circle, such as a quadrilateral (preferably a rectangular or square).

[0098] 12 and 13, the base plate 3c has a side that is approximately parallel to the X direction and a side that is approximately parallel to the Y direction. In this case, by setting back the inner wall 33 of the frame portion 21 near the corner 41 of the base plate 3c so that it approaches the corner 41, it is possible to prevent the inner wall 33 of the frame portion 21 that is approximately parallel to the X direction and the inner wall 33 of the frame portion 21 that is approximately parallel to the Y direction from intersecting at a right angle near the corner of the base plate 3c.

[0099] The outer periphery of the sealing portion 31 is in contact with the inner wall 33 of the frame portion 21, and the sealing portion 31 has a planar shape that fits along the inner wall 33 of the frame portion 21. Therefore, the sealing portion 31 is also arranged (filled) in a region 42 where the inner wall 33 of the frame portion 21 is recessed so as to approach a corner 41.

[0100] Other configurations of the mechanical quantity measuring device 1c of the fourth embodiment are almost the same as those of the mechanical quantity measuring device 1b of the third embodiment, so repeated explanations thereof will be omitted here.

[0101] The sealing portion 31 and the base plate have different linear expansion coefficients. Therefore, when a temperature change occurs, stress may occur between the sealing portion 31 and the base plate due to the difference in the contraction rate between the sealing portion 31 and the base plate. In the case of the above-described third embodiment (FIGS. 7, 10, and 11), the inner wall 33 of the frame portion 21, which is approximately parallel to the X direction, and the inner wall 33 of the frame portion 21, which is approximately parallel to the Y direction, intersect at a right angle near the corner of the base plate 3a, where stress generated between the sealing portion 31 and the base plate 3a is concentrated. Therefore, in the case of the above-described third embodiment (FIGS. 7, 10, and 11), when the mechanical quantity measuring device is subjected to repeated temperature changes, peeling due to fatigue may occur in the sealing portion 31 at the corner of the space 32 surrounded by the inner wall 33 of the frame portion 21 (or, from another perspective, at the corner of the inner region 22).

[0102] In contrast, in the fourth embodiment (FIGS. 12 to 16), the inner wall 33 of the frame part 21 is recessed near the corner 41 of the base plate 3c so as to approach the corner 41, thereby making it possible to suppress or alleviate the local concentration of stress generated between the sealing part 31 and the base plate 3a. This makes it difficult for the sealing part 31 to peel off when the mechanical quantity measuring device is subjected to repeated temperature changes.

[0103] Specifically, the inner wall 33 of the frame portion 21, which is substantially parallel to the X direction, and the inner wall 33 of the frame portion 21, which is substantially parallel to the Y direction, can be prevented from intersecting at right angles near the corners of the base plate 3c. This prevents or alleviates localized concentration of stress between the sealing portion 31 and the base plate 3a near the corners of the base plate 3c. Furthermore, the inner wall 33 of the frame portion 21 is configured as a curved surface near the corners 41 of the base plate 3c. This prevents or alleviates localized concentration of stress between the sealing portion 31 and the base plate 3c near the corners of the base plate 3c. This reduces the likelihood of peeling of the sealing portion 31 when the mechanical quantity measuring device is subjected to repeated temperature changes. This improves the long-term reliability of the mechanical quantity measuring device.

[0104] Furthermore, compared to when the recessed region 42 is not provided, when the recessed region 42 is provided, the sealing portion 31 is less likely to peel off due to the anchor effect caused by the sealing portion 31 being filled in the recessed region 42.

[0105] Furthermore, since the mechanical quantity measuring device is used for the purpose of measuring strain, stress may occur between the sealing portion 31 and the base plate due to not only temperature changes but also external forces. In the fourth embodiment, even when stress occurs between the sealing portion 31 and the base plate 3c due to not only temperature changes but also external forces, it is possible to suppress or mitigate the local concentration of stress.

[0106] (Embodiment 5) Fig. 17 is a planar perspective view showing the mechanical quantity measuring device 1 of the fifth embodiment, and Figs. 18 and 19 are cross-sectional views showing the mechanical quantity measuring device 1 of the fifth embodiment. In Fig. 17, the sealing portion 31 is seen through. The cross-sectional view taken along line A5-A5 in Fig. 17 is similar to Fig. 14, the cross-sectional view taken along line C5-C5 in Fig. 17 roughly corresponds to Fig. 18, and the cross-sectional view taken along line D5-D5 in Fig. 17 roughly corresponds to Fig. 19. The mechanical quantity measuring device 1 of the fifth embodiment will be denoted by reference symbol 1d and referred to as mechanical quantity measuring device 1d below.

[0107] In the fourth embodiment, in order to reduce the rigidity of the base plate 3c in the mounting area of the semiconductor chip 2 and its periphery, the thickness of the inner region 22 of the base plate 3c is made thin (preferably 300 μm or less) and the thickness of the frame portion 21 on the periphery of the base plate 3c is made thick. The semiconductor chip 2 mounted on the inner region 22 of the base plate 3c is covered with a sealing portion 31. If a stress is applied to the sealing portion 31 that pushes it in the thickness direction of the base plate 3c, there is a possibility that the sealing portion 31 will peel off from the base plate 3c.

[0108] Therefore, in the fifth embodiment, a recessed portion (concave portion) 51 is provided in the recessed region 42. The recessed portion 51 is a portion locally recessed with respect to the upper surface of the inner region 22. The recessed portion 51 is recessed in the thickness direction of the base plate 3c. A portion of the sealing portion 31 penetrates into this recessed portion 51. From another perspective, a portion of the sealing portion 31 is filled into the recessed portion 51. As a result, even if a stress that pushes the sealing portion 31 in the thickness direction of the base plate 3c is applied to the sealing portion 31, the anchor effect (the anchor effect of the sealing portion 31 filled in the recessed portion 51) can suppress or prevent the sealing portion 31 from peeling off from the base plate 3c. This can further improve the long-term reliability of the mechanical quantity measuring device.

[0109] Other configurations of the mechanical quantity measuring device 1d of the fifth embodiment are almost the same as those of the mechanical quantity measuring device 1c of the fourth embodiment, so repeated explanations thereof will be omitted here.

[0110] (Sixth embodiment) FIG. 20 is a plan view (top view) showing the mechanical quantity measuring device 1 of the sixth embodiment, and FIG. 21 is a cross-sectional view showing the mechanical quantity measuring device 1 of the sixth embodiment. The cross-sectional view taken along line A6-A6 in FIG. 20 roughly corresponds to FIG. 21. FIG. 22 is a plan perspective view showing the mechanical quantity measuring device 1 before the flexible substrate 61 is attached to the base plate 3e, and FIG. 23 is a cross-sectional view showing the mechanical quantity measuring device 1 before the flexible substrate 61 is attached to the base plate 3e. In FIG. 22, the sealing portion 31 is seen through. Also, the cross-sectional view taken along line A7-A7 in FIG. 22 roughly corresponds to FIG. 23. The mechanical quantity measuring device 1 of the sixth embodiment will be referred to as the mechanical quantity measuring device 1e below, with the reference symbol 1e attached. Also, the base plate 3 of the sixth embodiment will be referred to as the base plate 3e below, with the reference symbol 3e attached.

[0111] In the mechanical quantity measuring device 1e of the sixth embodiment, a flexible substrate 61 is attached (connected) to the base plate 3e in order to extract the electrical signal output from the semiconductor chip 2 to the outside of the mechanical quantity measuring device 1e.

[0112] In the sixth embodiment, the base plate 3e has a plurality of electrodes 4c as part of the conductor pattern 4 of the base plate 3e. The electrodes 4c are electrically connected to a plurality of electrodes 2a of the semiconductor chip 2, and signals output from the electrodes 2a of the semiconductor chip 2 can be output from the electrodes 4c of the base plate 3e. The plurality of electrodes 4c are preferably formed on the upper surface of the frame portion 21. In the base plate 3e, the electrodes 4c formed on the upper surface of the frame portion 21 and the electrodes 4b formed on the upper surface of the inner region 22 are electrically connected via wiring 4d inside the base plate 3e. For example, the base plate 3e can be formed of a laminate of a plurality of insulating layers, and the wiring 4d can be formed by wiring between the insulating layers or wiring in vias (via wiring) provided in the insulating layers. The electrodes 2a of the semiconductor chip 2 are electrically connected to the electrodes 4c of the base plate 3e via the wires 6, the electrodes 4b of the base plate 3e, and the wiring 4d.

[0113] The plurality of electrodes 4c of the base plate 3e are electrically connected to the plurality of electrodes 62 of the flexible substrate 61. For example, the plurality of electrodes 4c of the base plate 3e and the plurality of electrodes 62 of the flexible substrate 61 are joined via a conductive bonding material 63 such as solder, thereby providing an electrical connection. Because the electrodes 4c are formed on the upper surface of the frame portion 21, the flexible substrate 61 is joined and fixed to the frame portion 21.

[0114] Therefore, the electrodes 62 of the flexible substrate 61 are electrically connected to the semiconductor chip 2 (electrodes 2a) via the conductive bonding material 63, the electrodes 4c, wiring 4d and electrodes 4b of the base plate 3e, and the wires 6. Therefore, the base plate 3e has wiring 4d for electrically connecting the electrodes 62 of the flexible substrate 61 to the semiconductor chip 2 (electrodes 2a).

[0115] Other configurations of the mechanical quantity measuring device 1e of the sixth embodiment are substantially the same as those of the mechanical quantity measuring device 1b of the third embodiment, and therefore a repeated description thereof will be omitted here. Note that while the illustration and description here shows a case where the mechanical quantity measuring device 1b of the third embodiment is applied as the basic structure of the mechanical quantity measuring device 1e, any of the mechanical quantity measuring devices 1, 1a, 1b, 1c, and 1d of the first to fifth embodiments can also be applied as the basic structure of the mechanical quantity measuring device 1e. Therefore, the sixth embodiment can be combined with any of the first to fifth embodiments. Furthermore, when the sixth embodiment is combined with the first embodiment, since the base plate 3 does not have the frame portion 21, for example, a plurality of electrodes 4c can be provided near the end of the upper surface of the base plate 3, and the plurality of electrodes 4c can be joined to the electrodes 62 of the flexible substrate 61 via a conductive bonding material 63.

[0116] In the sixth embodiment, the electrical signal output from the semiconductor chip 2 can be taken out to the outside of the mechanical quantity measuring device 1e via the flexible substrate 61.

[0117] Furthermore, in the sixth embodiment, the flexible substrate 61 is joined and fixed to the frame portion 21, which has a large thickness and therefore high rigidity, thereby making it possible to stably fix the flexible substrate 61 to the base plate 3e. In addition, in the cases of FIGS. 20 to 23, the electrodes 4c are provided on the four sides of the frame portion 21, and therefore the flexible substrate 61 is joined and fixed to the four sides of the frame portion 21, which also makes it possible to stably fix the flexible substrate 61 to the base plate 3e. This makes it possible to improve the long-term reliability of the mechanical quantity measuring device 1e.

[0118] Furthermore, since the frame portion 21 is spaced apart from the semiconductor chip 2 and has high rigidity, the frame portion 21 makes little contribution to the transmission of strain from the measurement object 7 to the semiconductor chip 2, and in the base plate 3e, the transmission of strain from the measurement object 7 to the semiconductor chip 2 is mostly carried out by the inner region 22. In the sixth embodiment, the flexible substrate 61 is fixed to the frame portion 21, which makes almost no contribution to the transmission of strain from the measurement object 7 to the semiconductor chip 2, so that it is possible to suppress or prevent the bonding of the flexible substrate 61 to the frame portion 21 from affecting the measurement values of the mechanical quantity measuring device 1e.

[0119] Unlike the sixth embodiment, the electrodes 2a of the semiconductor chip 2 and the electrodes of the flexible substrate may be directly connected via wires. However, in this case, if a change in the connection relationship or an expansion of the function of the semiconductor chip 2 occurs, it is not possible to address the change simply by changing the wire connection, and a change in the design of the flexible substrate is required, resulting in a complex structure of the flexible substrate. In contrast, in the sixth embodiment, the electrodes 62 of the flexible substrate 61 are connected to the electrodes 4c of the base plate 3e, and are electrically connected to the electrodes 2a of the semiconductor chip 2 via the wiring (conductor pattern) of the base plate 3e and the wires 6. Therefore, even if a change in the connection relationship or an expansion of the function of the semiconductor chip 2 occurs, it can be addressed by changing the wiring and wire connections of the base plate 3e without changing the flexible substrate 61. This eliminates the need to change the design of the flexible substrate 61, and allows the flexible substrate 61 to have a simple structure.

[0120] Furthermore, unlike the sixth embodiment, if the base plate is conductive, the wires must be connected directly to the flexible substrate rather than to the base plate, and therefore the flexible substrate must be connected to the base plate with an insulating adhesive. Because the insulating adhesive used to attach the flexible substrate may change in properties due to long-term moisture absorption, it is desirable to protect the connection between the base plate and the flexible substrate by covering it with resin (sealing resin). However, if the sealing resin covering the connection between the base plate and the flexible substrate is thermally deformed, this may affect the measured values of the mechanical quantity measuring device. In contrast, in the sixth embodiment, the electrodes 4c for connecting the flexible substrate 61 are provided on the thick frame portion 21, and the flexible substrate 61 can be joined to the frame portion 21 using a bonding material with high long-term reliability, such as solder. This eliminates the need to cover the connection between the flexible substrate 61 and the base plate 3e with resin (sealing resin). This prevents thermal deformation of the resin covering the connection between the flexible substrate 61 and the base plate 3e from affecting the measured values of the mechanical quantity measuring device.

[0121] The invention made by the inventor has been specifically described above based on the embodiments thereof, but it goes without saying that the present invention is not limited to the above-described embodiments and can be modified in various ways without departing from the spirit of the invention.

[0122] For example, a strain gauge can be used as the strain detector instead of the semiconductor chip 2 (strain sensor chip) on which a strain detection circuit is formed. In this case, the strain gauge can be mounted on an insulating structure (base plate 3). [Explanation of symbols]

[0123] 1,1a,1b,1c,1d,1e Mechanical quantity measuring device 2. Semiconductor chips 2a electrode 3, 3a, 3c, 3d base plate 4,4a Conductor pattern 4b Conductor pattern (electrode) 4c electrode 4d wiring 5 Bonding material 6 wire 7 Measurement object 8 Bonding material 11 Semiconductor substrate 12a, 12b, 12c, 12d Diffusion resistance region 21 Frame section 22 Inner area 31 Sealing part 32 Space 33 Inner wall 41 Corner 42 Retreat area 51 recess 61 Flexible PCB 62 electrodes 63 Bonding material 101 Mechanical quantity measuring device 102 Semiconductor Chip 103 Base Plate 105 Bonding material 107 Measurement object 108 Bonding material

Claims

1. a distortion detection unit; an insulating structure on which the strain detection unit is mounted; A mechanical quantity measuring device comprising: a thickness of the outer periphery of the structure is thicker than a thickness of a first region of the structure that is located more inward than the outer periphery; the strain detection unit is mounted on the first region, a sealing resin portion that seals the strain detection portion on the first region, The structure has wiring for extracting a signal from the strain detection unit inside the structure, The wiring is drawn out to an upper surface of the outer periphery.

2. 2. The mechanical quantity measuring device according to claim 1, The mechanical quantity measuring device, wherein the strain detection unit is a strain sensor chip or a strain gauge.

3. 2. The mechanical quantity measuring device according to claim 1, A mechanical quantity measuring device, wherein the strain detection unit is mounted on the first region of the structure via a conductive first bonding material.

4. 4. The mechanical quantity measuring device according to claim 3, The mechanical quantity measuring device, wherein the first bonding material is made of solder.

5. 4. The mechanical quantity measuring device according to claim 3, The mechanical quantity measuring device, wherein the first bonding material is made of metal nanoparticles.

6. 6. The mechanical quantity measuring device according to claim 5, The mechanical quantity measuring device, wherein the metal nanoparticles are copper nanoparticles.

7. 7. The mechanical quantity measuring device according to claim 6, The mechanical quantity measuring device, wherein the copper nanoparticles have an average particle size of Φ100 nm or less, which allows the first bonding material to withstand a stress of 1000 με of strain measured by the strain detection unit.

8. 2. The mechanical quantity measuring device according to claim 1, The strain detection unit outputs a signal corresponding to a difference between a first strain in a first direction and a second strain in a second direction perpendicular to the first direction.

9. 2. The mechanical quantity measuring device according to claim 1, The structure has a planar shape that is point-symmetric with respect to the center of the structure.

10. 2. The mechanical quantity measuring device according to claim 1, A mechanical quantity measuring device, wherein the planar shape of the structure is square.

11. 2. The mechanical quantity measuring device according to claim 1, A mechanical quantity measuring device, wherein the outer periphery of the structure has higher rigidity than the first region.

12. The mechanical quantity measuring device according to claim 11, A mechanical quantity measuring device, wherein the thickness of the structure directly below the strain detection unit is 300 μm or less, at which point the strain transmission rate from the measurement object to the strain detection unit is 80% or more.

13. 2. The mechanical quantity measuring device according to claim 1, A mechanical quantity measuring device, wherein an inner wall of the outer periphery of the structure is recessed near a corner of the structure so as to approach the corner.

14. The mechanical quantity measuring device according to claim 13, A mechanical quantity measuring device, wherein the region of the structure where the inner wall is recessed so as to approach the corner has a circular planar shape.

15. The mechanical quantity measuring device according to claim 13, a recessed portion is provided in a region where the inner wall of the structure is recessed so as to approach the corner portion, A mechanical quantity measuring device, wherein a part of the sealing resin portion intrudes into the recess portion.

16. 2. The mechanical quantity measuring device according to claim 1, The mechanical quantity measuring device further comprises a flexible substrate bonded to the upper surface of the outer periphery of the structure.

17. 17. The mechanical quantity measuring device according to claim 16, The wiring of the structure is electrically connected to the electrodes of the flexible substrate.

18. 2. The mechanical quantity measuring device according to claim 1, A mechanical quantity measuring device, wherein the structure is attached to a conductive measurement object using a conductive second bonding material.

19. a distortion detection unit; an insulating structure on which the strain detection unit is mounted; A mechanical quantity measuring device comprising: a thickness of the outer periphery of the structure is thicker than a thickness of a first region of the structure that is located more inward than the outer periphery; the strain detection unit is mounted on the first region, a sealing resin portion that seals the strain detection portion on the first region, an inner wall of the outer periphery of the structure is recessed in the vicinity of a corner of the structure so as to approach the corner, a recessed portion is provided in a region where the inner wall of the structure is recessed so as to approach the corner portion, A mechanical quantity measuring device, wherein a part of the sealing resin portion intrudes into the recess portion.

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