JP2015075422A - Pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the selectivity of an adhesive while suppressing the reduction in detection accuracy.SOLUTION: In the pressure sensor, a joint member 50 formed by mixing a plurality of spherical beads 52 into an adhesive 51 is disposed between a sensor unit 10 and a member 40 to be mounted. The thickness of the adhesive 51 is made thicker than the Young's modulus [MPa] of a 20.7 [μm/MPa] × adhesive.

Description

  The present invention relates to a pressure sensor in which a sensor unit that outputs a sensor signal corresponding to pressure is mounted on a mounted member via a joining member.

  Conventionally, the following is proposed as this kind of pressure sensor (for example, refer to patent documents 1).

  That is, in this pressure sensor, the sensor unit is configured by joining a sensor chip that outputs a sensor signal corresponding to pressure and a pedestal. And the surface on the opposite side to the sensor chip side among the pedestals is mounted on the mounted member via the joining member. In the joining member, spherical beads for ensuring the thickness of the adhesive are mixed in the adhesive. Note that the diameter of the beads of the joining member is appropriately defined so that the thickness of the adhesive is 40 μm or more.

  According to this, since the adhesive is thickened, the stress applied from the mounted member can be relaxed by the adhesive, and the detection accuracy can be prevented from being lowered.

JP-A-10-170367

  However, in Patent Document 1, the thickness of the adhesive is specified, but the Young's modulus (elastic modulus) of the adhesive is only described as 1 MPa or less. For this reason, the selectivity of the adhesive is low, which leads to an increase in cost.

  An object of this invention is to provide the pressure sensor which can raise the selectivity of an adhesive agent, suppressing the fall of a detection precision in view of the said point.

  In order to achieve the above object, according to the first aspect of the present invention, a sensor portion (10) in which a thin diaphragm (22) is formed on one surface (20a) side and a gauge resistance (23) is formed on the diaphragm. And a mounted member (40) for mounting the sensor portion on one surface (40a), and a joining member (50) disposed between the sensor portion and the mounted member for joining the sensor portion and the mounted member. The joining member is configured by mixing a plurality of spherical beads (52) in the adhesive (51), and the adhesive has a thickness of 20.7 [μm / MPa] × Young's modulus of the adhesive [MPa]. It is characterized by being thicker.

  As described above, since the adhesive can be selected even if the thickness is 20.7 [μm / MPa] × Young's modulus [MPa] of the adhesive, even if the Young's modulus is higher than 1 MPa, the detection accuracy is high. The selectivity of the adhesive can be increased while suppressing the decrease (see FIG. 3).

  Further, as in the invention described in claim 2, the sensor portion has a pad (24) electrically connected to the gauge resistor on one side and a bonding wire (70) connected to the pad. The adhesive can be made thinner than 55.6 [μm / MPa] × Young's modulus [MPa] of the adhesive.

  According to this, it can suppress that a sensor part carries out an excessive displacement when performing wire bonding (refer FIG. 3).

  In addition, the code | symbol in the bracket | parenthesis of each means described in this column and the claim shows the correspondence with the specific means as described in embodiment mentioned later.

It is sectional drawing of the pressure sensor in 1st Embodiment of this invention. It is a surface view of the sensor chip shown in FIG. It is a figure which shows the relationship between the Young's modulus and thickness of an adhesive agent. It is sectional drawing of the pressure sensor in 2nd Embodiment of this invention. It is a reverse view of the base shown in FIG. It is sectional drawing of the pressure sensor in 3rd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other will be described with the same reference numerals.

(First embodiment)
A first embodiment of the present invention will be described with reference to the drawings. Note that the pressure sensor of this embodiment is preferably used for an air conditioner refrigerant pressure sensor, an intake pressure sensor, or the like for an automobile.

  As shown in FIG. 1, the pressure sensor is configured such that the sensor unit 10 is mounted on a case 40 via a joining member 50.

  The sensor unit 10 is configured such that a pedestal 30 is joined to a sensor chip 20 that outputs a sensor signal corresponding to pressure.

  As shown in FIGS. 1 and 2, the sensor chip 20 has a rectangular plate shape, and is configured using a silicon substrate whose surface 20 a is a (100) plane. And it has the thin-walled diaphragm 22 comprised by forming the hollow part 21 of the cross-section rectangular shape in the back surface 20b on the opposite side to the surface 20a, and the gauge resistance 23 is comprised so that this diaphragm 22 may comprise a bridge circuit. Is formed.

  That is, in the sensor chip 20 of the present embodiment, when pressure is applied to the diaphragm 22, the resistance value of the gauge resistor 23 changes and the voltage of the bridge circuit changes, and a sensor signal is output in accordance with the change of the voltage. Semiconductor diaphragm type.

  In addition, the hollow part 21 does not need to be rectangular in cross section, and may be in a trapezoidal cross section, for example. Moreover, the sensor chip 20 in FIG. 1 is equivalent to the II cross section in FIG.

  Further, on the surface 20a of the sensor chip 20, four pads 24 that are electrically connected to the gauge resistor 23 through a diffusion resistor or the like (not shown) are formed in a region outside the diaphragm 22. In the present embodiment, each pad 24 is formed so as to be point-symmetric with respect to the center of the surface 20 a of the sensor unit 10.

  The pedestal 30 is formed of a rectangular plate-like silicon substrate or the like having the same size as the sensor chip 20, and as shown in FIG. 1, the surface of the pedestal 30 is configured so that a reference pressure chamber 60 is formed between the pedestal 30 and the sensor chip 20. 30a is joined and integrated with the back surface 20b of the sensor chip 20. In the present embodiment, the sensor chip 20 and the pedestal 30 are joined so that the reference pressure chamber 60 has a vacuum pressure.

  Although not particularly illustrated, an insulating film is disposed between the sensor chip 20 and the pedestal 30, and the sensor chip 20 and the pedestal 30 are electrically separated. In the present embodiment, the front surface 20a of the sensor chip 20 corresponds to one surface of the sensor unit of the present invention, and the back surface 30b of the pedestal 30 corresponds to the other surface of the sensor unit of the present invention.

  The sensor unit 10 is mounted on the one surface 40a of the case 40 via the bonding member 50 so that the back surface 30b of the base 30 faces the one surface 40a of the case 40. In the sensor unit 10, the pad 24 is electrically connected to a wiring pattern or the like formed on the one surface 40 a of the case 40 via a bonding wire 70.

  Note that the case 40 is formed by molding a resin, for example, and corresponds to the mounted member of the present invention in this embodiment. Further, the bonding member of the present embodiment is configured by mixing spherical beads 52 made of an elastic material such as a resin into an adhesive 51 such as a silicone-based adhesive.

  The above is the basic configuration of the pressure sensor in the present embodiment. Next, a specific configuration of the joining member 50, which is a characteristic point of the present embodiment, will be described with reference to FIG.

  In such a pressure sensor, the output error of the sensor signal due to the influence of the case 40 increases as the Young's modulus of the adhesive 51 increases, and increases as the thickness of the adhesive 51 decreases. Then, the present inventors have found that in order to make the output error of the sensor signal less than or equal to 2.5% FS required at present, it is necessary to experimentally satisfy the following formula 1.

(Equation 1) Adhesive thickness [μm]> 20.7 [μm / MPa] × Adhesive Young's modulus [MPa]
The unit of output error% FS is a value obtained by dividing the output voltage error of the sensor unit 10 by the full scale of the output voltage. FIG. 3 shows a sensor chip 20 that uses a silicon substrate having a square shape with a side of 3.0 mm, a thickness of 0.3 mm, and a surface 20 a having a (100) plane. This is a result of using a silicon substrate having a square shape with a side of 3.0 mm and a thickness of 0.7 mm.

  Further, such a pressure sensor is manufactured by mounting the sensor unit 10 on the one surface 40a of the case 40 via the bonding member 50 and then performing wire bonding on the sensor unit 10 to form the bonding wire 70. .

  Here, when wire bonding is performed on the sensor unit 10, it is preferable that the sensor unit 10 does not cause excessive displacement during bonding. And wire bondability becomes so high that the Young's modulus of the adhesive agent 51 becomes high, and it becomes so high that the thickness of the adhesive agent 51 becomes thin. For this reason, the present inventors have found that in order to perform wire bonding without causing excessive displacement of the sensor unit 10, it is sufficient to experimentally satisfy the following formula 2.

(Equation 2) Adhesive thickness [μm] <55.6 [μm / MPa] × Adhesive Young's modulus [MPa]
The excessive displacement is that the sensor unit 10 is displaced so that wire bonding cannot be performed. FIG. 3 shows the results when wire bonding is performed at a frequency of 120 kHz.

  That is, in the hatched portion in FIG. 3, it is possible to prevent the sensor unit 10 from being excessively displaced during wire bonding while satisfying 2.5% FS. For this reason, the thickness of the adhesive 51 of this embodiment is 20.7 [μm / MPa] × Young's modulus [MPa] of the adhesive 55.6 [μm / MPa] × Young's modulus of the adhesive [ MPa].

  As described above, in the present embodiment, the thickness of the adhesive 51 is greater than 20.7 [μm / MPa] × Young's modulus [MPa] of the adhesive. That is, the adhesive 51 having a Young's modulus higher than 1 MPa can be selected as long as the thickness is greater than 20.7 [μm / MPa] × Young's modulus [MPa] of the adhesive. For this reason, it is possible to increase the selectivity of the adhesive 51 while suppressing a decrease in detection accuracy.

  Moreover, the thickness of the adhesive 51 is made thinner than 55.6 [μm / MPa] × Young's modulus [MPa] of the adhesive. For this reason, it is possible to prevent the sensor unit 10 from being excessively displaced when performing wire bonding.

(Second Embodiment)
A second embodiment of the present invention will be described. In the present embodiment, a convex portion is formed on the back surface 30b of the pedestal 30 with respect to the first embodiment, and the other parts are the same as those in the first embodiment, and thus the description thereof is omitted here.

  As shown in FIG. 4, in the present embodiment, a convex portion 31 is formed on the back surface 30 b of the pedestal 30. Specifically, as shown in FIGS. 4 and 5, the convex portion 31 is point-symmetric with respect to the center of the back surface 30 b in the portion of the back surface 30 b of the pedestal 30 that faces each pad 24. Is formed. In other words, the convex part 31 is formed so as to be point-symmetric with respect to an axis extending in the stacking direction of the sensor chip 20 and the pedestal 30 through the center of the sensor part 10.

  In this embodiment, the convex portion 31 is tapered so as to taper toward the front end surface in the protruding direction, and is configured by forming a concave portion 32 by etching a portion different from the portion facing the pad 24. Is done. Moreover, in this embodiment, the convex part 31 is equivalent to the crushing means of this invention.

  A part of the beads 52 included in the joining member 50 is arranged in a state of being crushed and elastically deformed between the convex portion 31 and the one surface 40a of the case 40. The remaining part of the beads 52 included in the joining member 50 is arranged without being crushed between the back surface 30b of the base 30 and the one surface 40a of the case 40 so that the thickness of the adhesive 51 satisfies the above formula 1. Has been. That is, in this embodiment, the distance between the portion of the pedestal 30 that is different from the portion where the convex portion 31 is formed and the one surface 40 a of the case 40 is the thickness of the adhesive 51.

  According to this, the beads 52 positioned below the pad 24 are arranged in a state of being crushed and elastically deformed between the convex portion 31 and the one surface 40 a of the case 40. For this reason, the apparent Young's modulus of this part in the joining member 50 can be increased. Accordingly, it is possible to further suppress the sensor unit 10 from being excessively displaced when performing wire bonding.

  In the present embodiment, the convex portion 31 is formed point-symmetrically with respect to the center of the back surface 30 b of the pedestal 30. For this reason, it can suppress that the sensor part 10 inclines with respect to the one surface 40a of case 40, and is mounted.

(Third embodiment)
A third embodiment of the present invention will be described. In the present embodiment, the first and second depressions are formed on the pedestal 30 with respect to the first embodiment, and the other parts are the same as those in the first embodiment, and thus the description thereof is omitted here.

  As shown in FIG. 6, in the present embodiment, first and second recessed portions 33 and 34 are formed on the back surface 30 b of the pedestal 30. Specifically, the first depression 33 is formed so as to be point-symmetric with respect to the center of the back surface 30b in a portion of the back surface 30b of the pedestal 30 that faces each pad 24. The second dent portion 34 is formed in a portion of the back surface 30 b of the pedestal 30 that is different from the portion facing the pad 24, and is deeper than the first dent portion 33.

  And the bead 52 contained in the joining member 50 is arrange | positioned in the state engage | inserted by the 1st, 2nd hollow part 33,34. Specifically, the beads 52 are disposed in the first recess 33 in a state of being crushed and elastically deformed between the first surface 40a of the case 40. Further, the beads 52 are arranged in the second depression 34 so as not to be crushed between the one surface 40 a of the case 40. That is, in this embodiment, the distance between the portion of the pedestal 30 that is different from the portion where the first and second recessed portions 33 and 34 are formed and the one surface 40 a of the case 40 is the thickness of the adhesive 51. In the present embodiment, the first depression 33 corresponds to the crushing means of the present invention.

  According to this, since the beads 52 are placed in the first and second depressions 33 and 34, the distribution of the beads 52 can be suppressed from varying. For this reason, it can suppress that the sensor part 10 inclines with respect to the one surface 40a of case 40. FIG.

(Other embodiments)
The present invention is not limited to the embodiment described above, and can be appropriately changed within the scope described in the claims.

  For example, in each of the embodiments described above, the sensor chip 20 is configured using a silicon substrate whose surface 20a is the (100) plane, and therefore the circuit portion may be integrated.

  Moreover, in the said 2nd Embodiment, although the example which forms the convex part 31 in the back surface 30b of the base 30 was demonstrated, a convex part is formed in the one surface 40a of the case 40, and this convex part and the back surface 30b of the base 30 are the same. The beads 52 may be crushed between them to be elastically deformed. In this case, the convex portion formed on the one surface 40a of the case 40 corresponds to the crushing means of the present invention. Moreover, you may make it form a convex part in the back surface 30b of the base 30, and one surface 40a of the case 40. FIG.

  Further, the above embodiments may be combined. For example, the third embodiment may be combined with the second embodiment, and the convex portion 31 may be formed instead of forming the first hollow portion 33. Moreover, you may suppress that distribution of the bead 52 varies by forming a hollow part in the one surface 40a of the case 40.

10 Sensor part 20a One side 22 Diaphragm 23 Gauge resistance 40 Case (mounted member)
50 Bonding member 51 Adhesive 52 Bead

Claims (8)

A sensor part (10) in which a thin diaphragm (22) is formed on one surface (20a) side and a gauge resistance (23) is formed on the diaphragm;
A mounted member (40) for mounting the sensor unit on one surface (40a);
A bonding member (50) disposed between the sensor unit and the mounted member, for bonding the sensor unit and the mounted member;
The joining member is configured by mixing a plurality of spherical beads (52) in the adhesive (51),
The pressure sensor is characterized in that the adhesive is thicker than 20.7 [μm / MPa] × Young's modulus [MPa] of the adhesive. The sensor part has a pad (24) electrically connected to the gauge resistor on the one surface and a bonding wire (70) connected to the pad.
2. The pressure sensor according to claim 1, wherein the adhesive has a thickness smaller than 55.6 [μm / MPa] × Young's modulus [MPa] of the adhesive. Crushing means (31, 33) is provided on at least one of a portion facing the pad of the other surface (30b) opposite to the one surface of the sensor unit and a portion facing the pad of one surface of the mounted member. ) Is formed,
The pressure sensor according to claim 2, wherein the plurality of beads are made of an elastic material, and a part of the beads is arranged in an elastically deformed state by the crushing means.   4. The pressure sensor according to claim 3, wherein a convex portion protruding toward the mounted member as the crushing means (31) is formed on the other surface of the sensor portion. On the other surface of the sensor portion, a first dent portion is formed as the crushing means (33), and a depth different from the portion facing the pad is deeper than the first dent portion. A second recessed portion (34) is formed,
The pressure sensor according to claim 3, wherein the plurality of beads are fitted into the first and second recesses, respectively.   The pressure sensor according to any one of claims 3 to 5, wherein the crushing means is formed point-symmetrically with respect to an axis passing through the center of one surface of the sensor unit.   The pressure sensor according to any one of claims 1 to 6, wherein the sensor unit is configured by using a silicon substrate in which the one surface is a (100) surface. The pressure sensor according to claim 7, wherein the sensor unit is integrated with a circuit unit.

Images