JP2005172483A - Pressure sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a diaphragm type pressure sensor coping with miniaturization and price-reduction. <P>SOLUTION: The diaphragm type pressure sensor is constituted of an insulation substrate, a diaphragm, and a printed circuit board laminated successively, on the upper surface of the diaphragm, a movable electrode and lead electrode patterns are provided, and on the lower surface of the insulation substrate a fixed electrode, a first wiring pattern, and a second wiring pattern are provided, wherein the movable electrode is facing the fixed electrode with a prescribed interval, the insulation substrate and the thick part of the diaphragm are anode jointed so that the lead electrode pattern and the second wiring pattern abut on each other, The first and the second circuit patterns formed on the under surface of the insulation substrate are characteristically fixed with the electrode pad provided on the printed wiring board with a conductive bond. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a pressure sensor, and more particularly to a diaphragm type pressure sensor that solves various problems that occur when anodic bonding is used as a means for connecting a diaphragm and an insulating substrate.

  A pressure sensor using semiconductor technology is suitable for miniaturization because of its structure, but when mounting a pressure sensitive element on a printed circuit board according to the purpose of use, it is important to devise a technique to prevent the stress strain of the diaphragm from remaining. is there. Furthermore, semiconductor diaphragm type pressure sensors that are widely used mainly in automobiles are required to be maintenance-free and cost-effective as they move from industrial use to consumer use.

As a conventional diaphragm type pressure sensor (hereinafter referred to as “pressure sensor”), for example, there is one disclosed in Japanese Patent Application Laid-Open No. 2002-243564, and FIG. 3 is a longitudinal sectional view showing the configuration of the package. is there.
A conventional pressure sensor 100 includes an upper insulating substrate 101 having a pressure discharge port penetrating substantially the center of a substantially rectangular glass substrate, and a lower portion having a pressure introducing port penetrating substantially the center of the substantially rectangular glass substrate. A diaphragm 103 integrally forming an insulating substrate 102, a thin film portion formed by recessing both main surfaces of a conductive silicon substrate, and a thick support portion 103a surrounding the film portion, and an upper surface And an annular piezoelectric member 104 having an electrode 105 formed thereon, and a structure in which the lower insulating substrate 102, the diaphragm 103, the piezoelectric member 104, and the upper insulating substrate 101 are layered on each other from below and anodically bonded. It has become.

Between the lower surface of the upper insulating substrate 101 and the upper surface of the diaphragm 103 (the support portion 103a) through the piezoelectric member 104, that is, through the metal film (the electrode 105), the glass substrate (upper insulating substrate 101) and the piezoelectric substrate. As an anodic bonding method for three types of members made of different materials from the piezoelectric substrate 104 and the piezoelectric substrate and the silicon substrate (diaphragm 103), for example, as disclosed in Japanese Patent Application Laid-Open No. 2000-281463 As shown in FIG. 4, between the first glass member 201 and the silicon substrate 202, between the silicon substrate 202 and the second glass member 203, that is, between members having greatly different thermal expansion coefficients. Thermal strain (generated by heating a metal layer 204 at a predetermined temperature and applying a predetermined voltage) It can be joined by a buffer against.
JP 2002-243564 A JP 2000-281463 A

  However, in the anodic bonding method, the metal layer 204 (as a buffer material) is required evenly in the gaps between the members, and therefore the metal layer 204 (corresponding metal film) of the pressure sensor 100 is not interposed. It is impossible to perform anodic bonding between the lower surface of the piezoelectric member 104 and the upper surface of the diaphragm 103. Therefore, a method of attaching a bonding metal film to the lower surface of the piezoelectric member 104 can be considered, but the electrode 105 and the bonding metal film formed across the piezoelectric member 104 are electrically short-circuited and do not function as a pressure sensor. There was a risk of the problem occurring.

  The problem to be solved is that it is impossible to provide a diaphragm type pressure sensor that can be reduced in size and reduced in price by using anodic bonding.

  In order to solve the above problems, the invention according to claim 1 of the present invention is characterized in that an insulating substrate, a diaphragm in which a thin portion and a thick portion at the periphery of the thin portion are integrally formed, and predetermined wiring are applied. A pressure sensor having a structure in which the printed wiring boards are sequentially laminated, and a movable electrode disposed on the thin portion on the upper surface of the diaphragm, and a lead electrode pattern extending from the movable electrode to the vicinity of the periphery of the diaphragm And a first wiring pattern extending from the fixed electrode to the vicinity of the periphery of the insulating substrate and a position extending from the position corresponding to the lead electrode pattern to the vicinity of the periphery of the insulating substrate. The movable electrode is opposed to the fixed electrode at a predetermined interval, and the lead electrode pattern and the second wiring pattern are in contact with each other. In this way, the insulating substrate and the thick part of the diaphragm are anodically bonded, and the first wiring pattern and the second wiring pattern formed on the lower surface of the insulating substrate are arranged on the upper surface of the printed wiring substrate. Each of the two electrode pads is fixed by conduction with a conductive adhesive.

  According to a second aspect of the present invention, there is provided an insulating substrate, a diaphragm in which a thin portion and a thick portion at the periphery of the thin portion are integrally formed, and a printed wiring board provided with a predetermined wiring. A pressure sensor having a structure in which layers are sequentially laminated, the upper surface of the insulating substrate having a fixed electrode and a wiring pattern extending from the fixed electrode to the vicinity of the periphery of the insulating substrate, and the lower surface of the diaphragm A movable electrode disposed in the thin wall portion; a first lead electrode pattern extending from the movable electrode to the vicinity of the periphery of the diaphragm; and a second lead electrode pattern extending from a position corresponding to the wiring pattern to the vicinity of the periphery of the diaphragm. The insulating substrate so that the movable electrode is opposed to the fixed electrode at a predetermined interval, and the wiring pattern and the second lead electrode pattern are in contact with each other. And the thick part of the diaphragm are anodically bonded, and the first lead electrode pattern and the second lead electrode pattern formed on the lower surface of the diaphragm are provided on the upper surface of the printed wiring board. Each electrode pad is conductively fixed with a conductive adhesive.

  A third aspect of the present invention according to the present invention is characterized in that, in the first or second aspect, the diaphragm is a quartz crystal.

  According to a fourth aspect of the present invention related to the present invention, in any one of the first to third aspects, the insulating substrate is an alkali-containing glass.

  A fifth aspect of the present invention according to the present invention is characterized in that, in any one of the first to fourth aspects, the conductive adhesive is an epoxy-based or polyimide-based conductive adhesive.

  The pressure sensor according to the present invention includes three members, an insulating substrate, a diaphragm, and a printed wiring board, and mechanical connection between the three members, and the internal connection corresponding to the fixed electrode, the movable electrode, and the electrodes. There is an advantage that it is possible to reduce the size and cost by using anodic bonding and a conductive adhesive together for electrical connection with the terminal.

Hereinafter, the present invention will be described in detail based on the illustrated embodiment of the present invention.
The pressure sensor of the present invention has a gap between a diaphragm made of a piezoelectric material (having good mechanical and elastic properties) as a pressure detecting element and an insulating substrate made of glass having a thermal expansion coefficient approximate to the thermal expansion coefficient of the diaphragm. Capacitance type pressure sensor for detecting pressure by changing the capacitance of, for example, the pressure sensor, an electronic circuit unit for converting the capacitance change output to pressure, and the output of the electronic circuit unit to the outside The transmitter is integrated and used as a tire pressure sensor fixed to the disc wheel together with a tire valve (for injecting air into the tire) in a tire disc wheel of an automobile.

FIG. 1A is a longitudinal sectional view showing a configuration of a diaphragm type pressure sensor according to an embodiment of the present invention, and FIG. 1B is a development view of a pressure detection unit (described later) based on a straight line L.
As shown in FIG. 1, the pressure sensor according to the embodiment of the present invention includes a substantially rectangular diaphragm 1 having a substantially centered bottom surface and a planar outer shape having a substantially centered bottom surface recessed and at least larger than the planar contour of the diaphragm 1. A substantially rectangular insulating substrate 2 having a flat outer shape with an internal connection terminal (electrode pad) 3a on the upper surface and a planar outer shape that is the same as or slightly larger than the planar outer shape of the insulating substrate 2, It has.

The diaphragm 1 is formed by chemically etching a substantially central portion of one main surface (corresponding to the lower surface) of a piezoelectric substrate, for example, a quartz substrate, as shown in a top view (after development) in FIG. Thus, a thin annular portion 1b that supports the periphery of the displacement portion 1a is formed integrally with the thin portion of the recess portion as a displacement portion 1a. In addition, the movable electrode 11 and a portion extending from the movable electrode 11 to a predetermined end portion are disposed on the other flat main surface (corresponding to the upper surface) of the diaphragm 1 across the displacement portion 1a. The lead electrode (lead electrode pattern) 12 to be formed is formed.
As shown in the bottom view (after development) in FIG. 1B, the insulating substrate 2 has a concave portion at the center of one main surface (corresponding to the bottom surface) of a glass substrate, for example, an alkali-containing glass substrate. The bottom portion 2a of the recessed portion and the annular support portion 2b surrounding the bottom portion 2a are integrally formed. Further, a fixed electrode 21 and a lead electrode (first wiring pattern) extending from the fixed electrode 21 to a predetermined end portion of the upper surface of the annular support portion 2b (that is, the lowermost surface of the insulating substrate 2) substantially at the center of the bottom portion 2a. ) 22 and the fixed electrode 21, and a dummy electrode (second wiring pattern) 23 is formed on the upper surface of the annular support portion 2b facing the position where the terminal portion of the extraction electrode 22 is disposed. An insulating film 24 (not shown in FIG. 1B) such as SiO ₂ is deposited on the surface of the fixed electrode 21.

  The movable electrode 11 and the fixed electrode 21 are opposed to each other (via the insulating film 24), the lead electrode 12 and the lead electrode 22 are directed to face each other, and the opening of the recessed portion and the recessed portion is downward. The insulating substrate 2 is placed on the upper surface of the diaphragm 1 and the opening periphery of the recessed portion and the periphery of the upper surface of the diaphragm 1 in contact with the opening periphery are anodically bonded. The integrated diaphragm 1 and the insulating substrate 2 (hereinafter referred to as “pressure detection portion”) are placed on the upper surface of the printed wiring board 3 with the opening of the recessed portion facing downward, and the lower surface of the pressure detection portion. That is, between the lead-out electrode 22 exposed on the surface where the diaphragm 1 is disposed and the dummy electrode 23 electrically connected to the lead electrode 12 and the internal connection terminal 3a corresponding to each electrode. An electrically conductive adhesive 25 is embedded in the gap formed by embedding an epoxy or polyimide conductive adhesive 25, and the conductive adhesive 25 is also disposed on the side surface of the diaphragm 1 located in the gap. Thus, mechanical connection of the diaphragm 1, the insulating substrate 2, and the printed wiring board 3 is realized.

  The conductive adhesive 25 includes the lead electrode 12 and the dummy electrode 23 (metal film forming portion) and the diaphragm 1 (quartz substrate) or the insulating substrate 2 (alkali-containing glass substrate), and the diaphragm 1 ( Bonding of the pressure detection part by the fact that the anodic bonding part of the quartz substrate) and the insulating substrate 2 (alkali-containing glass substrate) coexist, that is, is not (cannot) be bonded under the optimum anodic bonding condition for the pressure detection part It also has a complementary function to reinforce strength variations. In the embodiment shown in FIG. 1, the conductive adhesive 25 is disposed only on one side (a total of two places) that are opposed and paired. However, if the mechanical connection strength is insufficient, As a countermeasure, the conductive adhesive 25 may be disposed on the other side. An insulating adhesive may be used because the other side is not questioned regarding electrical connection.

  When the electrical connection between the lead electrode 12 and the dummy electrode 23 becomes unstable due to the inability to perform anodic bonding under optimum conditions, the lead electrode 12 extends from the lead electrode 12. The lead electrode 12 and the internal connection terminal 3b corresponding to the lead electrode 12 are electrically connected via the conductive adhesive 25 by being disposed also on the side end surface of the diaphragm 1 adjacent to the end side of the diaphragm 1. And it becomes possible to connect mechanically. Alternatively, if the lead electrode 12 and the dummy electrode 23 are not electrically connected, that is, if they are not electrically connected, the lead electrode disposed on the side end surface of the diaphragm 1 by removing the dummy electrode 23 and the The internal connection terminals may be electrically and mechanically connected.

  The pressure sensor of the present invention utilizes the fact that the movable electrode 11 and the fixed electrode 21 are opposed to each other to form a capacitor, and the distance between the electrodes changes due to the stress applied to the movable electrode 11 and the capacitance value of the capacitor varies. Therefore, the thickness of the displacement portion 1a of the diaphragm 1 and the depth of the recessed portion of the insulating substrate 2, that is, the size of the gap between the movable electrode 11 and the fixed electrode 21 are as follows: It is determined by the specifications of the pressure sensor (of the present invention), for example, sensor sensitivity, pressure detection range (low pressure to low pressure range), and the like. That is, if it is possible to obtain a predetermined size of the gap (satisfying the specification as a pressure sensor), as a modified embodiment of the present invention, as shown in FIG. A structure in which a substrate 41, a diaphragm 42 having a recessed portion on the upper surface and a movable electrode 44 disposed on the inner bottom surface of the recessed portion, and a printed wiring board 45 having a recessed portion on the upper surface are sequentially stacked and integrated, or FIG. 1. Following the structure shown in FIG. 1, 2 in FIG. 1 (from the insulating substrate) is a diaphragm (ie, 21 in FIG. 1 is a movable electrode), and 1 in FIG. 1 and 11 may be a fixed sensor. However, the insulating film is preferably deposited on the surface of the fixed electrode. Furthermore, a structure may be adopted in which concave portions are formed on both main surfaces of the diaphragm, and the diaphragm is sandwiched between the flat insulating substrate and the printed wiring board.

It goes without saying that the present invention is not limited to quartz (said diaphragm) but can be applied to other piezoelectric materials such as langasite, lithium tetraborate, lithium tantalate, lithium niobate and the like.
Further, since the printed wiring board is for connecting to the external device (the pressure detection unit), not only the ceramic wiring board but also a resin board such as glass epoxy or silicon may be used.

BRIEF DESCRIPTION OF THE DRAWINGS It is the schematic block diagram which showed the structure of the diaphragm type pressure sensor of the 1st Embodiment of this invention, (a) is a longitudinal cross-sectional view, (b) is the expanded view of the pressure detection part in 1st Embodiment. It is. FIG. 6 is a longitudinal sectional view showing the structure of a diaphragm type pressure sensor according to a modified embodiment of the present invention. It is a longitudinal cross-sectional view of the conventional diaphragm type pressure sensor. It is a schematic diagram for demonstrating the anodic bonding concerning this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 .. Diaphragm 2 .... Insulation board 3 .... Printed wiring board 1a ... Displacement part 1b ... Ring surrounding part 2a ... Bottom part 2b ... Ring support part 3a ... Internal connection terminal 11 ... Movable electrode 12 .... Lead electrode 21 .. Fixed electrode 22 .. Lead electrode 23 .. Dummy electrode 24 .. Insulating film 25 .. Conductive adhesive 41 .. Insulating substrate 42 .. Diaphragm 43 .. Fixed electrode 44. · Printed wiring board 100 · · Pressure sensor 101 · · Upper insulating substrate 102 · · Lower insulating substrate 103 · · Diaphragm 103a · · Supporting portion 104 · · Piezoelectric member 105 · · Electrode 201 · · First glass member 202 · · Silicon substrate 203 .. Second glass member 204 .. Metal layer

Claims (5)

A pressure sensor having a structure in which an insulating substrate, a diaphragm in which a thin portion and a thick portion at the periphery of the thin portion are integrally formed, and a printed wiring board on which predetermined wiring is provided are sequentially laminated. ,
The upper surface of the diaphragm has a movable electrode disposed in the thin portion and a lead electrode pattern extending from the movable electrode to the vicinity of the periphery of the diaphragm,
A fixed electrode, a first wiring pattern extending from the fixed electrode to the vicinity of the periphery of the insulating substrate, and a second wiring pattern extending from a position corresponding to the lead electrode pattern to the vicinity of the periphery of the insulating substrate are provided on the lower surface of the insulating substrate. Have
The insulating substrate and the thick part of the diaphragm are anodically bonded so that the movable electrode faces the fixed electrode at a predetermined interval and the lead electrode pattern and the second wiring pattern are in contact with each other. Is,
The first wiring pattern and the second wiring pattern formed on the lower surface of the insulating substrate are conductively fixed to the two electrode pads provided on the upper surface of the printed wiring substrate, respectively, with a conductive adhesive. Pressure sensor. A pressure sensor having a structure in which an insulating substrate, a diaphragm in which a thin portion and a thick portion at the periphery of the thin portion are integrally formed, and a printed wiring board on which predetermined wiring is provided are sequentially laminated. ,
The upper surface of the insulating substrate has a fixed electrode and a wiring pattern extending from the fixed electrode to the vicinity of the periphery of the insulating substrate,
The lower surface of the diaphragm has a movable electrode disposed in the thin portion, a first lead electrode pattern extending from the movable electrode to the vicinity of the periphery of the diaphragm, and a second extending from the position corresponding to the wiring pattern to the vicinity of the periphery of the diaphragm. A lead electrode pattern,
The insulating substrate and the thick part of the diaphragm are anodically bonded so that the movable electrode faces the fixed electrode at a predetermined interval and the wiring pattern and the second lead electrode pattern are in contact with each other. Is,
Conductive fixing of the first lead electrode pattern and the second lead electrode pattern formed on the lower surface of the diaphragm to each of two electrode pads provided on the upper surface of the printed wiring board with a conductive adhesive. A featured pressure sensor. The pressure sensor according to claim 1, wherein the diaphragm is a crystal. The pressure sensor according to claim 1, wherein the insulating substrate is an alkali-containing glass. The pressure sensor according to claim 1, wherein the conductive adhesive is an epoxy-based or polyimide-based conductive adhesive.

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