JP2010190701A - Mounting structure of pressure sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mounting structure of a pressure sensor for avoiding reduction in detection accuracy of pressure to be measured. <P>SOLUTION: In this mounting structure of the pressure sensor, the capacitance type pressure sensor 11 where the pressure to be measured is introduced to a pressure introducing chamber 15 is mounted to a lead frame 14 via a pressure introducing hole 17 disposed so as to penetrate the lead frame 14 constituting a mounting substrate. A through-hole 16 that penetrates the lead frame 14 and communicates the inside to the outside of the pressure introducing chamber 15 is disposed around the pressure introducing hole 17 disposed in the lead frame 14. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a pressure sensor mounting structure for mounting a pressure sensor on a mounting board.

  Conventionally, as a technique of a pressure sensor that detects a pressure to be measured as a change in capacitance, for example, those described in the following documents are known (see Patent Document 1). In this document, a capacitor is formed by a fixed electrode formed on the surface of a substrate, and a movable electrode (diaphragm) that is opposed to the fixed electrode through a cavity (gap) and is displaced according to a change in pressure. Describes the technology of a pressure sensor that detects the pressure applied from the outside by detecting the change of the capacitance by changing the capacitance of the capacitor due to the deformation of the movable electrode due to the external pressure. Yes.

JP 2007-86002 A

  In such a capacitance-type pressure sensor, when the pressure introduction chamber into which the pressure to be measured received by the diaphragm is introduced to the outside, when a conductive liquid enters the pressure introduction chamber from the outside, Further, there is a possibility that a parasitic capacitance is formed in which the diaphragm is used as one electrode, the mounting substrate that supports and mounts the pressure sensor is used as the other electrode, and the invading liquid is a dielectric sandwiched between both electrodes.

  Such a parasitic capacitance is formed so as to be electrically connected in parallel to a pressure detecting capacitance whose capacitance changes according to the pressure to be measured. For this reason, the capacitance value of the capacitance for pressure detection, which is built with the capacitance value fixed in advance, changes, and the accuracy of detecting the pressure to be measured is reduced, so that the pressure to be measured is accurately detected. There is a risk of inconvenience such as being unable to do so.

  Therefore, the present invention has been made in view of the above, and an object of the present invention is to provide a pressure sensor mounting structure that prevents a decrease in detection accuracy of a pressure to be measured.

  In order to achieve the above object, the pressure sensor mounting structure according to the present invention includes a mounting substrate having a pressure sensor into which a pressure to be measured is introduced into a pressure introducing chamber through a pressure introducing hole provided through the mounting substrate. In the mounting structure of the pressure sensor mounted on the first surface, the first feature is that the peripheral surface of the pressure introducing hole is formed in a tapered shape.

  The pressure sensor mounting structure according to the present invention includes a pressure sensor mounting in which a pressure sensor into which a pressure to be measured is introduced into a pressure introducing chamber is mounted through a pressure introducing hole provided through the mounting substrate. In the structure, a second feature is that a communication path that connects the pressure introduction chamber and the outside is formed through the mounting substrate.

  The pressure sensor mounting structure according to the present invention is characterized in that, in the second feature, the communication path is configured by a plurality of through holes provided so as to surround the pressure introduction chamber. Three features.

  In the pressure sensor mounting structure according to the first aspect of the present invention, the liquid that has entered the pressure introduction chamber is easily discharged to the outside, the formation of parasitic capacitance due to the liquid is suppressed, and the pressure detection accuracy decreases. Can be prevented.

  In the pressure sensor mounting structure according to the second aspect of the present invention, the liquid that has entered the pressure introduction chamber is easily discharged to the outside, the formation of parasitic capacitance due to the liquid is suppressed, and the pressure detection accuracy is reduced. Can be prevented.

  In the pressure sensor mounting structure according to the third aspect of the present invention, the liquid that has entered the pressure introduction chamber is easily discharged to the outside, the formation of parasitic capacitance due to the liquid is suppressed, and the pressure detection accuracy decreases. Can be prevented.

It is a figure which shows the mounting structure of the pressure sensor which concerns on Example 1 of this invention. 1 is a cross-sectional view illustrating a configuration of a pressure sensor mounted in Example 1. FIG. It is sectional drawing which shows the mode of the retention of the liquid at the time of mounting a pressure sensor. It is a figure which shows the connection relation of the capacity | capacitance in the circuit which measures a to-be-measured pressure. It is a figure which shows the mounting structure of the pressure sensor which concerns on Example 2 of this invention. It is a figure which shows the mounting structure of the pressure sensor which concerns on Example 3 of this invention.

  Embodiments for carrying out the present invention will be described below with reference to the drawings.

  1A and 1B are views showing a mounting structure of a pressure sensor according to a first embodiment of the present invention. FIG. 1A is a top view, FIG. 1B is a bottom view, and FIG. It is sectional drawing along the AA line of (b).

  The pressure sensor 11 mounted in the mounting structure according to the first embodiment is, for example, a capacitance type pressure sensor that detects the tire air pressure of a vehicle, and converts the capacitance detected by the pressure sensor 11 into a pressure. Dedicated circuit 12 that functions as a dedicated integrated circuit (ASIC) that performs predetermined processing for wirelessly transmitting tire pressure information obtained by conversion to a receiving system mounted on the vehicle, and detecting rotation of the tire Along with the traveling sensor 13, a MEMS structure is mounted and formed on the same mounting substrate (lead frame) 14 using a semiconductor microfabrication technique.

  The lead frame 14 in which the pressure sensor 11 is mounted has a through hole 16 that functions as a communication path that connects the pressure introduction chamber 15 into which the pressure to be measured measured by the pressure sensor 11 is introduced and the outside. Is provided. As shown in FIG. 1B, the through hole 16 introduces a pressure to be measured into the pressure introduction chamber 15, and the pressure introduction hole along the periphery of the pressure introduction hole 17 provided through the lead frame 14. Two are formed so as to surround 17.

  FIG. 2 is a cross-sectional view showing a configuration of the pressure sensor 11 shown in FIG.

  In FIG. 2, the pressure sensor 11 is mounted on a lead frame 14 serving as a mounting substrate via an insulating film 21 and formed on a support substrate 22 made of a semiconductor such as silicon. The support substrate 22 is formed with an inverted truncated pyramid-shaped recess that is open at the bottom, and this recess is formed narrowly at the top and wide at the bottom to constitute the pressure introducing chamber 15. The support substrate 22 in the upper part of the pressure introducing chamber 15 is thinned to form a diaphragm 23 serving as a pressure receiving surface (pressure-sensitive portion) that receives the pressure to be measured, and the support substrate 22 around the diaphragm 23 is thickened. A support portion 24 that supports the diaphragm 23 is formed.

  The support substrate 22 is bonded to the glass substrate 25 by anodic bonding or the like on the surface opposite to the surface bonded to the lead frame 14, and a vacuum chamber 26 is formed between the diaphragm 23 of the support substrate 22 and the glass substrate 25. Has been. A fixed electrode 27 is formed on the glass substrate 25 side of the vacuum chamber 26 so as to face the diaphragm 23, and the capacitance value changes according to the pressure to be measured between the fixed electrode 27 and the diaphragm 23 functioning as a movable electrode. A capacitance C1 for pressure detection is configured.

  The glass substrate 25 is provided with a through hole 28 extending to the support substrate 22, and a metal metallized surface 29 is formed on the peripheral surface of the through hole 28, and the fixed electrode 27 and the movable electrode are connected to the metal substrate 29 via the metal metallized surface 29. The support substrate 22 of the diaphragm 23 is electrically connected to the dedicated circuit 12, and the capacitance for pressure detection is electrically connected to the dedicated circuit 12.

  In such a mounting structure, when the through hole 16 employed in the first embodiment is not provided in the lead frame 14, the pressure introducing chamber is externally provided via the pressure introducing hole 17 as shown in the sectional view of FIG. If the conductive liquid 31 penetrates 15, the liquid 31 that has entered may stay near the peripheral surface of the support 24 in the pressure introducing chamber 15 or the surface of the lead frame 14 as shown in FIG. 3. When the conductive liquid 31 stays in the pressure introducing chamber 15, a parasitic capacitance C <b> 2 is parasitically formed between the support substrate 22 and the lead frame 14 by the liquid 31.

  The parasitic capacitance C2 formed in this manner is connected in parallel to the pressure detection capacitance C1 as shown in FIG. 4 as an electric circuit. That is, in FIG. 4, the capacitance C1 for pressure detection is connected in series with the input capacitance C3 on the side of the dedicated circuit 12 between the lead frame 14 set to the ground (ground) potential and the high-level power supply (VDD). In the configuration of the measurement circuit in which the detection signal is input to the dedicated circuit 12 from the series connection point, the parasitic capacitance C2 is connected in series with the liquid resistance component (parasitic resistance R2) between the lead frame 14 and the high-level power supply (VDD). Connected to.

  When the parasitic capacitance C2 is formed in this way, the capacitance seen from the dedicated circuit 12 side is that the parasitic capacitance C2 is added to the pressure detection capacitance C1, and the overall capacitance increases. become. For this reason, the initially set capacitance for pressure detection is different from that before the liquid enters the pressure introduction chamber 15, and an error occurs in the measured pressure, making it impossible to accurately measure the pressure to be measured. There was a risk that the detection accuracy would decrease.

  On the other hand, in the first embodiment, as described above, by adopting a mounting structure in which the lead frame 14 is provided with the through hole 16 that communicates the inside and outside of the pressure introduction chamber 15, the liquid that has entered the pressure introduction chamber 15 is It becomes easy to be discharged out of the pressure introduction chamber 15 through the through hole 16. That is, the through-hole 16 configured as a communication path that connects the pressure introduction chamber 15 and the outside has a discharge function that promotes the discharge of the liquid that has entered the pressure introduction chamber 15 to the outside of the pressure introduction chamber 15. As a result, the liquid that has entered the pressure introduction chamber 15 does not easily stay in the pressure introduction chamber 15, and the formation of the parasitic capacitance C2 due to the retention of the liquid as described above is suppressed and avoided.

  Therefore, it is possible to accurately measure the pressure to be measured with a simple mounting structure, and it is possible to prevent a decrease in detection accuracy.

  5A and 5B are views showing a mounting structure of a pressure sensor according to a second embodiment of the present invention. FIG. 5A is a top view, FIG. 5B is a bottom view, and FIG. It is sectional drawing along the AA line of (b).

  The feature of the second embodiment is that it functions in the same way as the through-hole 16 employed in the first embodiment, and a circular through-hole 51 having a smaller cross-sectional area than the through-hole 16 is formed in the pressure introducing hole 17. A large number are provided along the periphery, and the others are the same as in the first embodiment.

  Also in the second embodiment, it is possible to obtain the same effect as the first embodiment.

  6A and 6B are diagrams showing a mounting structure of a pressure sensor according to a second embodiment of the present invention. FIG. 6A is a top view, FIG. 6B is a bottom view, and FIG. It is sectional drawing along the AA line of (b).

  A feature of the third embodiment is that, instead of the through holes 16 and 51 employed in the first and second embodiments, a pressure whose peripheral surface is tapered as shown in FIG. The introduction hole 61 is formed in the lead frame 14, and the others are the same as in the first and second embodiments.

  The side surface of the pressure introducing hole 17 employed in the previous Examples 1 and 2 was perpendicular to the mounting surface of the lead frame 14 on which the pressure sensor 11 is mounted, whereas it was employed in this Example 3. As shown in FIG. 6C, the cross section of the pressure introduction hole 61 includes an end portion on the pressure introduction chamber 15 side of the circumferential surface of the pressure introduction hole 61 and an end portion on the lead frame 14 side of the circumferential surface of the pressure introduction chamber 15. It is formed in a conical shape that is inclined so as to be narrowed from the outside toward the inside of the pressure introduction chamber 15 so as to substantially coincide.

  By providing the pressure introducing hole 61 having such a structure, when the pressure sensor 11 is mounted on the lead frame 14, the lead frame 14 and the support portion 24 of the support substrate 22 can be connected to each other as in the first and second embodiments. The formation of corners between them is avoided. Thereby, the liquid that has entered the pressure introduction chamber 15 is easily discharged to the outside through the pressure introduction hole 61 whose peripheral surface is tapered.

  As a result, the liquid that has entered the pressure introduction chamber 15 does not easily stay in the pressure introduction chamber 15, and the formation of the parasitic capacitance C2 due to the retention of the liquid as described above is suppressed and avoided.

  Therefore, it is possible to accurately measure the pressure to be measured with a simple mounting structure, and it is possible to prevent a decrease in detection accuracy.

  The same effect can be obtained even if the tapered shape provided in the pressure introducing hole is formed in a conical shape that is inclined so as to spread outward from the pressure introducing chamber 15 contrary to the above. .

  Of course, the pressure measured by the pressure sensor 11 may be other various pressures than the tire pressure. In addition, the functions and the number of separate components mixed with the pressure sensor 11 are not limited to the dedicated circuit 12 and the travel sensor 13, and may be an electric circuit or a MEMS structure having various functions.

DESCRIPTION OF SYMBOLS 11 ... Pressure sensor 12 ... Dedicated circuit 13 ... Traveling sensor 14 ... Lead frame 15 ... Pressure introduction chamber 16, 28, 51 ... Through-hole 17, 61 ... Pressure introduction hole 21 ... Insulating film 22 ... Support substrate 23 ... Diaphragm 24 ... Support 25: Glass substrate 26 ... Vacuum chamber 27 ... Fixed electrode 29 ... Metal metallized surface 61 ... Pressure introduction hole

Claims (3)

In the pressure sensor mounting structure in which the pressure sensor in which the pressure to be measured is introduced into the pressure introducing chamber through the pressure introducing hole provided through the mounting substrate is mounted on the mounting substrate.
A pressure sensor mounting structure, wherein a peripheral surface of the pressure introducing hole is tapered. In the pressure sensor mounting structure in which the pressure sensor in which the pressure to be measured is introduced into the pressure introducing chamber through the pressure introducing hole provided through the mounting substrate is mounted on the mounting substrate.
A mounting structure of a pressure sensor, wherein a communication path that communicates between the pressure introducing chamber and the outside is formed through the mounting substrate. The pressure sensor mounting structure according to claim 2, wherein the communication path includes a plurality of through holes provided so as to surround the pressure introduction chamber.

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