JP2019132803A - Gas sensor - Google Patents

Abstract

To provide a gas sensor that can increase the strength of the weld between a conduction member and a pad part on the sensor element side.SOLUTION: A gas sensor 15 has first to fourth heater pad parts 91, 93, 95, and 97, and the heater pad parts contain alumina as a common basis material, which is ceramic of the same component as that of a ceramic part. The first to fourth heater pad parts contain the common basis material less than a A-heater and a B-heater does. That is, the content of the Pt in the first to fourth heater pad parts is larger than that of the Pt in the A-heater and the B-heater. Accordingly, metal first to fourth conduction members 17, 19, 21, and 23, which are welded (specifically, resistance-welded) to the first to fourth heater pad parts, respectively, are strongly welded to the first to fourth heater pad parts.SELECTED DRAWING: Figure 2

Description

  The present disclosure relates to a gas sensor that detects the concentration of a specific gas component, for example. For example, the present invention relates to a gas sensor that can be applied to general gas measurement such as environmental management and process management.

Conventionally, as a kind of metal oxide sensor of a gas sensor, a structure in which a sensor element is suspended and fixed in an opening of a wiring board by wire bonding or the like is known (see Patent Document 1).
In this metal oxide sensor, the sensor element is suspended in the air to reduce the heat capacity and thermal influence of the sensor element, thereby improving gas detection accuracy and responsiveness.

  By the way, in the sensor element, a heater for heating the element part to the operating temperature is arranged on the surface of the detection part, for example, in addition to the detection part having an element part made of metal oxide for detecting the concentration of the specific gas component. ing.

  For this reason, in the above-described prior art, a sensor in which the wire bonding is shrunk or broken due to thermal stress when the wire bonding is heated by the heating of the heater and then cooled down is repeated. There is a problem that the pad of the element is pulled and dropped.

As a countermeasure against this, in recent years, a technique in which a sensor element, for example, a heater and a wiring board surrounding the sensor element are suspended by a plate-shaped energizing member having a curved portion has been studied.
Specifically, one end of a current-carrying member (that is, a Pt ribbon) made of platinum is welded to an end portion (that is, a heater-side pad portion) of platinum (Pt) as a main component formed on the surface of the sensor element, and The sensor element is opened on the wiring board by welding the other end of the current-carrying member to the end of the wiring pattern mainly composed of gold (Au) formed on the surface of the wiring board (that is, the wiring-side pad). Techniques for hanging and fixing in the department are being studied.

JP 2007-298508 A

  However, in the above-described prior art, a common element, which is the same type of material as the material constituting the ceramic part, is added to the heater and the heater side pad part in order to improve the adhesion with the ceramic part including the detection part. Therefore, the following problems may occur.

  That is, the heater side pad portion to which the Pt ribbon is welded contains the same proportion of the common substrate as the heater, so the welding strength between the Pt ribbon and the heater side pad portion tends to be small, and the gas sensor is being used. Due to the mechanical or thermal shock, the Pt ribbon peeled off from the heater side pad part, and there was a risk of disconnection.

  The present disclosure has been made in view of such a background, and an object of the present disclosure is to provide a gas sensor that can improve the welding strength between the energization member and the pad portion on the sensor element side.

  (1) The first aspect of the present disclosure is mainly composed of a wiring board having an opening, a detection unit having an element part whose electrical characteristics change according to the state of the measurement target gas, and a metal that heats the detection unit. A sensor element comprising: a heater comprising: a heater pad portion mainly composed of metal that is electrically connected to the heater so that at least a portion thereof overlaps the end portion of the heater; and wiring the sensor element The present invention relates to a gas sensor including a metal energization member that is fixed in a suspended state in an opening of a substrate.

  In this gas sensor, the detection unit includes a ceramic unit whose main component is ceramic, and a heater and a heater pad unit are disposed on the surface of the ceramic unit. One end of the energizing member is welded to the heater pad portion. Furthermore, the content rate of the common substrate made of ceramic for improving the adhesion to the ceramic portion contained in the heater pad portion is smaller than the content rate of the common substrate contained in the heater.

  Thus, in this 1st aspect, since the heater pad part contains the common substrate which is ceramic (for example, the same kind of ceramic as the ceramic part), the adhesiveness between the heater pad part and the ceramic part is high. There are advantages.

  In addition, the content of the common element contained in the heater pad is smaller than the content of the common element contained in the heater, that is, the content of the metal contained in the heater pad is the content of the metal contained in the heater. Since the ratio is greater than the rate, for example, the metal energization member welded to the heater pad portion by resistance welding is firmly welded to the heater pad portion.

Therefore, even when a mechanical shock or a thermal shock is received during use of the gas sensor, the energizing member is hardly peeled off from the heater pad portion, and therefore, there is a remarkable effect that disconnection hardly occurs.
(2) In the second aspect of the present disclosure, when the heater pad unit includes the first layer and the second layer from the detection unit side, the content ratio of the common substrate in the second layer is It may be less than the content of the common base in the layer.

  When the content of the common substrate in the second layer is smaller than the content of the common substrate in the first layer as in the second aspect, the energizing member is more firmly welded to the heater pad portion. . In addition, the heater pad portion is more firmly adhered to the ceramic portion.

  (3) In the third aspect of the present disclosure, the sensor element is electrically connected to the surface of the ceramic portion, the metal as a main component, and at least partly overlapping the end portion of the conductive pattern. And a conductive pad portion whose main component is a metal connected to.

  The conductive pad portion may be welded to a current-carrying member different from the current-carrying member joined to the heater. One end of another energizing member may be welded to the conductive pad portion. Furthermore, the content rate of the common substrate made of ceramic for improving the adhesion to the ceramic portion contained in the conductive pad portion may be smaller than the content rate of the common substrate contained in the conductive pattern.

  Thus, in the third aspect, when the conductive pad portion contains a ceramic substrate (for example, the same kind of ceramic as the ceramic portion), the adhesion between the conductive pad portion and the ceramic portion is high. There is an advantage.

  In addition, when the content of the common substrate contained in the conductive pad portion is smaller than the content of the common substrate contained in the conductive pattern, that is, the content of the metal contained in the conductive pad portion is included in the conductive pattern. When the content of the metal is larger than the metal content, the metal energization member welded to the conductive pad portion by, for example, resistance welding is firmly welded to the conductive pad portion.

Therefore, even when a mechanical shock or a thermal shock is applied during use of the gas sensor, there is a remarkable effect that the current-carrying member is not easily peeled off from the conductive pad portion, and thus disconnection is hardly generated.
(4) In the fourth aspect of the present disclosure, in the case where the conductive pad portion includes the first layer and the second layer from the detection portion side, the content of the communal base in the second layer is It may be less than the content of the common base in one layer.

  When the content of the common substrate in the second layer is lower than the content of the common substrate in the first layer as in the fourth aspect, the energizing member is more firmly welded to the conductive pad portion. . In addition, the conductive pad part is more firmly adhered to the ceramic part.

<The configuration of the present disclosure will be described below>
The “measurement target gas state” includes the concentration of a specific gas component contained in the measurement target gas. Examples of the specific gas component include NO _x such as NO and NO ₂ , CO, CO ₂ , HC, H ₂ , various alcohols, aldehydes, and ketones.

-"Content rate" shows content per unit mass (namely, mass%).
-Examples of “metal” include simple metals and metal alloys.
The “community base” is a ceramic component added to improve the adhesion between the heater, the heater pad portion, the conductive pad portion and the ceramic portion. A ceramic component of the same type as the ceramic component constituting the ceramic part is preferable. For example, when the ceramic part is a sintered body mainly composed of alumina, alumina is preferable as the common substrate.

It is a perspective view which decomposes | disassembles and shows the gas sensor of 1st Embodiment. It is a top view which shows the wiring board of the gas sensor of 1st Embodiment, and the 1st surface side of a sensor element. It is the bottom face which shows the 2nd surface side of the wiring board of the gas sensor of 1st Embodiment, and a sensor element. It is a top view which shows the 1st surface side of the sensor element of the gas sensor of 1st Embodiment. (A) is a top view which expands and shows the 1st heater pad part etc. of a sensor element, (b) is sectional drawing which shows the AA cross section of (a). It is a perspective view which shows the 1st electricity supply member of the gas sensor of 1st Embodiment, and its vicinity. It is sectional drawing which fractures | ruptures and shows the 1st heater pad part etc. of the sensor element of 2nd Embodiment in the thickness direction. It is a top view which shows the 1st surface side of the sensor element of the gas sensor of 3rd Embodiment. It is explanatory drawing which shows the test apparatus of an experiment example. It is a graph which shows the experimental result of an experimental example. (A) is a top view which shows the 1st heater pad part etc. of the modification 1 of embodiment, (b) is a top view which shows the 1st heater pad part etc. of the modification 2, (c) is the 3rd of modification 3. It is a top view which shows 1 heater pad part.

Hereinafter, an embodiment of a gas sensor to which the present disclosure is applied will be described with reference to the drawings.
[1. First Embodiment]
[1-1. Overall configuration of gas sensor]
As shown in FIGS. 1 and 2, the gas sensor 1 of the first embodiment is a gas sensor 1 that detects the concentration of a specific gas component in the measurement target gas (for example, the concentration of NO _x such as NO or NO ₂ ).

  This gas sensor 1 has a plate-like wiring board 3 in plan view (that is, when viewed from a direction perpendicular to the paper surface of FIG. 2) and one surface on the tip side (upper side in FIG. 2) of the wiring board 3. A box-shaped first cover member 7 that covers (the first surface 5 in the upper part of FIG. 1) and a box-shaped cover that covers the other surface (the second surface 9 in the lower part of FIG. 1) on the tip side of the wiring board 3. A second cover member 11.

  An opening 13 that is a through-hole penetrating the wiring board 3 in the plate thickness direction is formed on the front end side of the wiring board 3. The opening 13 has a rectangular shape in plan view. As will be described in detail later, the sensor element 15 having a plate shape and a square shape in plan view includes four energizing members (that is, the first energizing member). 17, the second energizing member 19, the third energizing member 21, and the fourth energizing member 23) are fixed in a suspended state.

  In the first cover member 7, a first air hole 27, which is a through hole penetrating in the thickness direction, is provided in the bottom plate 25 that is the bottom of the box. On the other hand, as for the 2nd cover member 11, the 2nd ventilation hole 31 which is a through-hole penetrated in the plate | board thickness direction is provided in the baseplate 29 which is a bottom part of a box.

[1-2. Wiring board]
Next, the wiring board 3 will be described.
As shown in FIG. 2, the wiring board 3 is a ceramic substrate whose main component is alumina.

  On the first surface 5 of the wiring substrate 3, four wiring patterns (that is, the first wiring pattern 33, the second wiring pattern 35, the third wiring pattern 37, and the fourth wiring pattern 39) are arranged in the longitudinal direction (FIG. 2). Are arranged in parallel along the vertical direction). In addition, the front end side (upper side in FIG. 2) of the first to fourth wiring patterns 35 to 39 is partially cranked along the periphery of the opening 13.

  The first to fourth wiring patterns 33 to 39 are linear lead portions extending in the same width (that is, the first lead portion 41, the second lead portion 43, the third lead portion 45, and the fourth lead portion 47). And a front end side pad portion (that is, a first front end side pad portion 49, a second front end side pad portion 51, a third front end side pad portion 53, a first end portion, which are disposed on the front end side of the first to fourth lead portions 41 to 47. 4 front end side pad portion 55), and rear end side pad portions (ie, first rear end side pad portion 57, first rear end side) disposed on the rear end side (downward in FIG. 2) of the first to fourth lead portions 41 to 47. 2 rear end side pad part 59, third rear end side pad part 61, fourth rear end side pad part 63).

  Among these, the 1st front end side pad part 49 and the 2nd front end side pad part 51 are arrange | positioned in order from the front end side along the inner peripheral part (namely, left side) of the left side of FIG. . Similarly, the 3rd front end side pad part 53 and the 4th front end side pad part 55 are arrange | positioned in order from the front end side along the inner peripheral part (namely, right side) of the right side of FIG. .

  Note that the widths (dimensions in the horizontal direction in FIG. 2) of the first to fourth front end side pad portions 49 to 53 and the first to fourth rear end side pad portions 57 to 63 are respectively the first to fourth lead portions. It is wider than the width (line width) of 41-47.

The first to fourth wiring patterns 33 to 39 are made of, for example, a material mainly composed of gold (Au). Other than the main component, for example, glass is included.
On the other hand, as shown in FIG. 3, two wiring patterns (that is, a fifth wiring pattern 65 and a sixth wiring pattern 67) are arranged in parallel along the longitudinal direction on the second surface 9 of the wiring substrate 3. Has been. Note that the fifth and sixth wiring patterns 65 and 67 are partially crank-shaped on the front end side along the periphery of the opening 13.

  The fifth and sixth wiring patterns 65 and 67 have linear lead portions (that is, a fifth lead portion 69 and a sixth lead portion 71) extending with the same width, and fifth and sixth lead portions 69 and 71, respectively. After being disposed on the rear end side of the front end side pad portion (that is, the fifth front end side pad portion 73, the sixth front end side pad portion 75) disposed on the front end side, and the fifth and seventh lead portions 69 and 71, respectively. End side pad portions (that is, a fifth rear end side pad portion 77 and a sixth rear end side pad portion 79).

Among these, the 5th front end side pad part 73 is arrange | positioned along the left side of FIG. Similarly, the sixth tip side pad portion 75 is arranged on the right side of FIG.
The widths of the fifth and sixth front end side pad portions 73 and 75 and the fifth and sixth rear end side pad portions 77 and 79 are wider than the width (line width) of the fifth and sixth lead portions 65 and 67. It has become.

The fifth and sixth wiring patterns 65 and 67 are made of, for example, a material mainly composed of gold (Au). Other than the main component, for example, glass is included.
[1-3. Sensor element]
Next, the sensor element 15 will be described.

<Configuration of heater section>
As shown in FIG. 4, the sensor element 15 has platinum (Pt) as a main component on the element-side first surface 16, specifically on one surface of a detection unit 81 having a square plan view described later. A pair of heater parts (namely, A heater part 83 and B heater part 85) are formed symmetrically.

  Among them, the A heater portion 83 is electrically connected to an A heater 87 that is a linear resistance heating element formed to meander with the same line width, and one end of the A heater 87 (the upper end in FIG. 4). A first heater pad portion 91 formed as described above, and a second heater pad portion 93 formed so as to be electrically connected to the other end of the A heater 87 (the lower end in FIG. 4).

  Similarly, the B heater unit 85 is electrically connected to a B heater 89 that is a linear resistance heating element formed to meander with the same line width, and one end of the B heater 89 (the upper end in FIG. 4). A third heater pad portion 95 formed as described above, and a fourth heater pad portion 97 formed so as to be electrically connected to the other end (lower end in FIG. 4) of the B heater 89.

The first to fourth heater pad portions 91 to 97 have a rectangular shape in plan view, and the line width (dimension in the short direction) is larger than the line widths of the A heater 87 and the B heater 89.
Among these, as shown in an enlarged view in FIG. 5A, for example, in the A heater portion 83, the first heater pad portion 91 is formed as shown in FIG. 5A so as to cover a part of one end of the A heater 87. It is provided so as to extend in the left-right direction.

As will be described later, the first energization member 17 is welded to the surface of the first heater pad portion 91 so as to extend in the left-right direction in FIG. 5A (resistance welding in the first embodiment). ing.
In the first embodiment, the A heater 87 and the first heater pad 91 have platinum as a main component, and in addition to the main component, adhesion (adhesion strength) at the time of simultaneous firing with the ceramic unit 103 described later. A common substrate (in this case alumina) is included. In particular, the content of alumina contained in the first heater pad portion 91 is set to be smaller than the content of alumina contained in the A heater 87.

  For example, the content ratio of alumina contained in the first heater pad portion 91 is 3.5% by mass with external blending (in addition, the external blending is the mass proportion of alumina when the Pt mass is 100%). The content of alumina contained in the A heater 97 is 6.0% by mass in the case of external blending.

  In the A heater portion 83, the first heater pad portion 91 and the second heater pad portion 93 have the same configuration (particularly the composition), and the A heater portion 83 and the B heater portion 85 have the same configuration (particularly the composition). Therefore, the description of the second heater pad portion 93 and the B heater portion 85 is omitted below.

<Configuration of detector>
As shown in FIG. 5B, the sensor element 15 has an A heater portion 83, a B heater portion 85, and the like formed on the surface of the plate-like detection portion 81 (element-side first surface 16). The detection unit 81 includes a plate-like element portion 101 having a square shape in plan view and a plate-like ceramic portion 103 having a square shape in plan view so as to cover the surface of the element portion 101.

  That is, the sensor element 15 has the A heater portion 83 and the B heater portion 85 arranged on the surface (the upper surface in FIG. 5B) side of the ceramic portion 103, and the element portion 101 arranged on the lower surface side of the ceramic portion 103. The A heater unit 83, the B heater unit 85, and the element unit 101 have an integrated structure in which the ceramic unit 103 is stacked above and below.

The ceramic portion 103 is an electrical insulating layer mainly composed of alumina.
The element unit 101 is made of a material whose electrical characteristics (for example, resistance value) change according to the concentration of the specific gas component. Therefore, the concentration of the specific gas component can be detected by detecting an electrical signal indicating the changed electrical characteristics using a pair of electrodes (not shown).

As this element part 101, the well-known metal oxide semiconductors, such as a tin oxide etc. which change a resistance value according to the density | concentration of a specific gas component, etc. can be employ | adopted, for example.
[1-4. Configuration for connecting wiring board and sensor element]
Next, a configuration in which the wiring board 3 and the sensor element 15 are connected, that is, a configuration in which the sensor element 15 is suspended and fixed in the opening 13 of the wiring board 3 will be described.

As shown in FIGS. 1 and 2, the first to fourth current-carrying members 17 to 23 described above are used to suspend and fix the sensor element 15 to the opening 13 of the wiring board 3.
As shown in FIG. 6, the first to fourth energization members 17 to 23 are long plate-like members made of, for example, platinum, and the central portion thereof is on one side (upper side in FIG. 6). The curved portion 105 is curved in an arc shape. In addition, in FIG. 6, although the 1st electricity supply member 17 is illustrated, the other 2nd-4th electricity supply members 19-23 are also the same shape.

  Specifically, as shown in FIGS. 2 and 4, one end (the sensor element 15 side) of the first energizing member 17 is welded to the first heater pad portion 91 by resistance welding, The other end (wiring board 3 side) is welded to the first tip side pad portion 49 by resistance welding.

  Similarly, one end of the second energizing member 19 is welded to the second heater pad portion 93 by resistance welding, and the other end of the second energizing member 19 is welded to the second tip side pad portion 51 by resistance welding. ing.

  Similarly, one end of the third energizing member 21 is welded to the third heater pad portion 95 by resistance welding, and the other end of the third energizing member 21 is welded to the third tip side pad portion 53 by resistance welding. ing.

  Similarly, one end of the fourth energizing member 23 is welded to the fourth heater pad portion 97 by resistance welding, and the other end of the fourth energizing member 23 is welded to the fourth tip side pad portion 55 by resistance welding. ing.

  With this configuration, that is, the sensor element 15 is placed in the opening 13 of the wiring board 3 by the first to fourth current-carrying members 17 to 23 whose one end and the other end are welded to the sensor element 15 and the wiring board 3, respectively. It is fixed suspended in the air.

  On the other hand, as shown in FIG. 3, on the second surface 9 of the wiring substrate 3 and the element-side second surface 18 of the sensor element 15, the corner portion (upper left of FIG. 3) of the sensor element 15 (specifically, the element portion 101). ) And the fifth tip side pad portion 73 of the wiring board 3 are joined by a gold (Au) wire 107 so as to electrically and mechanically connect the corner portion and the fifth tip side pad portion 73. Has been.

  Similarly, the corner of the sensor element 15 (specifically, the element portion 101) (lower right in FIG. 3) and the sixth tip side pad portion 75 are connected to the corner and the sixth tip side pad portion 75 of the wiring board 3. Are connected to each other electrically and mechanically. A gold (Au) wire 109 is bonded thereto.

[1-5. Manufacturing method of gas sensor]
Next, a method for manufacturing the gas sensor 1 having the above-described configuration will be described.
Since the manufacturing method of the wiring board 3 is the same as the conventional method, here, the manufacturing method of the sensor element 15 will be mainly described.

  Although not shown, a heater pattern to be the A heater 87 and the B heater 89 was formed on the surface of the alumina green sheet to be the ceramic portion 103 of the sensor element 15 by screen printing using the first Pt paste.

  The alumina green sheet contains alumina as a main component as a solid component, and also contains a known sintering aid. In addition, it is a well-known binder, a solvent, etc. other than a solid component (hereinafter the same). Further, the first Pt paste contains Pt as a solid component, and contains 6.0% by mass of alumina as an external compound when Pt is 100% by mass.

  Next, the pad patterns to be the first to fourth heater pad portions 91 to 97 are respectively attached to both ends of the heater pattern to be the A heater 87 and to both ends of the heater pattern to be the B heater 89. It was formed by screen printing using

  At this time, printing was performed such that a part of each pad pattern overlapped on both ends of both heater patterns. The second Pt paste contains Pt as a solid component, and contains 3.5% by mass of alumina as an external base when Pt is 100% by mass.

Next, the alumina green sheet was cut into a shape to be the ceramic portion 103.
Next, the cut alumina green sheet was degreased and fired as is well known, and the A heater part 83 and the B heater part 85 were formed on the surface of the ceramic part 103 by simultaneous firing with the ceramic part 103. In addition, as conditions for baking, the conditions baked for 2 hours at 1520 degreeC in air | atmosphere atmosphere are employable, for example.

  Next, a paste of, for example, a metal oxide semiconductor to be the element portion 101 was applied to the back surface of the ceramic portion 103 (that is, the surface opposite to the A heater portion 83 and the B heater portion 85). Thereafter, firing was performed as is well known to obtain a detection unit 81 including the element unit 101 on the back surface of the ceramic unit 103. Note that a method for forming a pair of electrodes provided in the element portion 101 is omitted.

That is, by the manufacturing method described above, the sensor element 15 including the A heater unit 83 and the B heater unit 85 on one surface of the ceramic unit 103 and the element unit 101 on the other surface was obtained.
After that, by placing one ends of the first to fourth current-carrying members 17 to 23 on the first to fourth tip side pad portions 49 to 55 on the wiring board 3 and performing resistance welding, respectively, 4 tip side pad parts 49-55 and one end of the 1st-the 4th energization members 17-23 were welded, respectively.

  Next, the first to fourth heater pad portions 91 to 97 on the sensor element 15 are arranged with the other ends of the first to fourth energization members 17 to 23, respectively, and are subjected to resistance welding, thereby providing the first to first heater pads 91 to 97. The fourth heater pad portions 91 to 97 were welded to the other ends of the first to fourth energization members 17 to 23, respectively.

Thereby, the gas sensor 1 in which the sensor element 15 was suspended and fixed in the opening 13 of the wiring board 3 by the first to fourth energization members 17 to 23 was obtained.
[1-6. Operation of gas sensor]
Next, the basic operation of the gas sensor 1 will be described.

  When the sensor element 15 detects the concentration of the specific gas component in the measurement target gas, the first vent hole 27 to the second vent hole of the gas sensor 1 are heated with the element portion 101 of the sensor element 15 heated to the operating temperature. A measurement target gas is supplied to 31.

  When the element portion 101 of the sensor element 15 is heated to the operating temperature, the A heater 87 generates heat by energizing between the first wiring pattern 33 and the second wiring pattern 35 and passing a current through the A heater 87. Let At the same time, the B heater 89 generates heat by energizing the third wiring pattern 37 and the fourth wiring pattern 39 and causing a current to flow through the B heater 89.

The element unit 101 heated to the operating temperature by the A heater 87 and the B heater 89 changes its resistance value, for example, according to the concentration of the specific gas component, and detects its electrical signal.
The electrical signal output from the element unit 101 is output to an external detection circuit via the fifth wiring pattern 63 and the sixth wiring pattern 65. Note that the concentration of the specific gas component can be obtained by processing the electric signal output from the element unit 101 by an external detection circuit.

[1-7. effect]
Next, the effect of the first embodiment will be described.
In the first embodiment, since the first to fourth heater pad portions 91 to 97 contain alumina as a common substrate which is a ceramic having the same component as the ceramic portion 103, the first to fourth heater pad portions There exists an advantage that the adhesiveness of 91-97 and the ceramic part 103 is high.

  In addition, the content of the common base contained in the first to fourth heater pad portions 91 to 97 is smaller than the content of the common base contained in the A heater 87 and the B heater 89, that is, the first to fourth. Since the content rate of Pt contained in the heater pad portions 91 to 97 is larger than the content rate of Pt contained in the A heater 87 and the B heater 89, the first to fourth heater pad portions 91 to 97 are respectively formed by resistance welding. The welded metal first to fourth energizing members 17 to 23 are firmly welded to the first to fourth heater pad portions 91 to 97.

  Therefore, even when a mechanical shock or a thermal shock is received during use of the gas sensor 1, the first to fourth energization members 17 to 23 are difficult to peel off from the first to fourth heater pad portions 91 to 97, respectively. Therefore, there is a remarkable effect that disconnection hardly occurs.

[1-8. Correspondence of wording]
Here, the correspondence of the wordings in the present disclosure and the first embodiment will be described.
In the first embodiment, the opening 13, the wiring board 3, the element part 101, the detection part 81, the A and B heaters 87 and 89, the first to fourth heater pad parts 91 to 97, the sensor element 15, the first to first elements 4 energization members 17 to 23, gas sensor 1, ceramic part 103, first to fourth wiring patterns 33 to 39, respectively, are an opening part, a wiring board, an element part, a detection part, a heater, a heater pad part, It corresponds to an example of a sensor element, a current-carrying member, a gas sensor, a ceramic part, and a wiring pattern.

[2. Second Embodiment]
Next, the second embodiment will be described, but the description of the same configuration as that of the first embodiment will be omitted. In addition, about the structure similar to 1st Embodiment, the same symbol is used.

  As shown in FIG. 7, in the gas sensor 111 of the second embodiment, for example, the A heater 87 of the A heater unit 83 is disposed on the surface of the detection unit 81 of the sensor element 15 as in the first embodiment. . Further, a first heater pad portion 91 is provided so as to partially overlap one end of the A heater 87, and the first energization member 17 is welded to the first heater pad portion 91.

  In particular, in the second embodiment, the first heater pad portion 91 containing Pt as a main component is composed of a lower first layer 91a and an upper second layer 91b, and alumina in the second layer 91b. The content is less than the content of alumina in the first layer 91a.

That is, the content rate of alumina is second layer 91b <first layer 91a <A heater 87. In other words, the content ratio of Pt is second layer 91b> first layer 91a> A heater 87.
The other configurations, for example, the configurations of the B heater unit 85 and the second to fourth heater pad units 93 to 97 are the same as described above, and thus the description thereof is omitted.

  The second embodiment has the same effects as the first embodiment. In the second embodiment, since the alumina content is second layer 91b <first layer 91a <A heater 87, the first heater pad portion 91 is connected to the detection portion 81 (specifically, the ceramic portion 103). The first energization member 17 is further strongly welded to the first heater pad portion 91 while being further strongly welded.

[3. Third Embodiment]
Next, the third embodiment will be described, but the description of the same configuration as that of the first embodiment will be omitted. In addition, about the structure similar to 1st Embodiment, the same symbol is used.

  As shown in FIG. 8, the gas sensor 121 of the third embodiment includes a sensor element 123, and the sensor element 123 includes a detection unit 81 having a ceramic part 103 on the surface, as in the first embodiment. ing.

  A heater 125, which is a resistance heating element, is formed on the surface of the detection unit 81 (and hence the ceramic unit 103) so as to meander with the same line width. A first heater pad portion 127 is formed at one end of the heater 125, and a second heater pad portion 129 is formed at the other end of the heater 125.

  The heater 125 and the first and second heater pad portions 127 and 129 are made of a material containing Pt as a main component and a common substrate. The content rate of alumina that is a common substrate in the first and second heater pad portions 127 and 129 is less than the content rate of alumina that is a common substrate in the heater 125.

  In addition to the heater 125, a temperature element pattern 131 that extends in a straight line with the same line width having Pt as a main component is disposed in the detection unit 81. The temperature element pattern 131 is a temperature sensor whose resistance value varies with temperature. A first conductive pad portion 133 mainly composed of Pt is formed so as to partially overlap one end of the temperature element pattern 131, and Pt is formed so as to partially overlap the other end of the temperature element pattern 131. A second conductive pad portion 135 containing as a main component is formed.

The content of alumina that is a common substrate in the first and second conductive pad portions 133 and 135 is less than the content of alumina that is a common substrate in the temperature element pattern 131.
The first and second heater pad portions 127 and 129 are welded (specifically, resistance welding) to the first and second current-carrying members 137 and 139 made of Pt plates, respectively. The pad parts 133 and 135 are welded (specifically, resistance welding) with third and fourth current-carrying members 141 and 143 made of Pt plates, respectively.

  In the third embodiment, energization is performed between the first and second energization members 137 and 139 connected to a pair of wiring patterns (for example, the first wiring pattern 33 and the third wiring pattern 37) formed on the wiring board 3, respectively. As a result, the heater 125 generates heat.

  And if the temperature of the detection part 81 rises by heat_generation | fever of the heater 125, the temperature of the temperature element pattern 131 will rise and the resistance value will change (for example, increase). Therefore, the resistance value is obtained by a known electric circuit connected to a pair of wiring patterns (for example, the second wiring pattern 35 and the fourth wiring pattern 39) connected to the third and fourth energizing members 141 and 143, respectively. The temperature of the detection unit 81 can be detected from the resistance value.

  The third embodiment has the same effects as the first embodiment. In the third embodiment, the sensor element 113 can be suspended and fixed by the first to fourth energization members 137 to 143.

  In the third embodiment, alumina is contained in the first and second heater pad portions 127 and 129 and the first and second conductive pad portions 133 and 135 as a common substrate which is a ceramic having the same component as the ceramic portion 103. Therefore, there is an advantage that the adhesion between the first and second heater pad portions 127 and 129 and the first and second conductive pad portions 133 and 135 and the ceramic portion 103 is high.

  In addition, the content of the common substrate contained in the first and second heater pad portions 127 and 129 is smaller than the content of the common substrate contained in the heater, that is, the first and second heater pad portions 127 and 129. Since the content rate of Pt contained in the heater is larger than the content rate of Pt contained in the heater 125, the first and second current-carrying members 137 made of metal welded to the first and second heater pad portions 127 and 129, 139 is firmly welded to the first and second heater pad portions 127 and 129.

  Similarly, the content of the common substrate contained in the first and second conductive pad portions 133 and 135 is smaller than the content of the common substrate contained in the temperature element pattern 131, that is, the first and second conductive pads. Since the content ratio of Pt included in the portions 133 and 135 is larger than the content ratio of Pt included in the temperature element pattern 131, the metal third and third bonded to the first and second conductive pad portions 133 and 135 are provided. The fourth energization members 141 and 143 are firmly welded to the first and second conductive pad portions 133 and 135.

  Therefore, even when a mechanical shock or a thermal shock is received during use of the gas sensor 121, the first and second current-carrying members 137 and 139 are difficult to peel off from the first and second heater pad portions 127 and 129, respectively. In addition, the third and fourth current-carrying members 141 and 143 are difficult to peel off from the first and second conductive pad parts 133 and 135, respectively. Therefore, the gas sensor 121 has a remarkable effect that disconnection is less likely to occur.

  The first and second heater pad portions 127 and 129 and the first and second conductive pad portions 133 and 135 are formed in two layers as in the second embodiment, and the upper second layer common substrate is formed. The content ratio may be less than the content ratio of the lower layer (the detection unit 81 side) of the second layer.

[4. Experimental example]
Next, experimental examples performed for confirming the effects of the present disclosure will be described.
In this experimental example, the welding strength of the Pt wire resistance-welded to the heater pad portion as in the first embodiment (that is, the strength by welding: here, the tensile strength) is examined.

As a test apparatus, the test apparatus shown in FIG. 9 was prepared.
Specifically, in order to prepare a plurality of samples, a plurality (more specifically, 28) of alumina substrates having the same composition as the alumina part were prepared.

  Next, two types of test pad portions with different compositions were formed on the surface of each alumina substrate in the same shape as the heater pad portion. Specifically, as samples within the scope of the present disclosure, 18 samples were formed on an alumina substrate on which a test pad portion containing 3.5% by mass of alumina when Pt was 100% by mass was formed. Created. In addition, as samples outside the scope of the present disclosure, 10 samples were formed on the alumina substrate and formed with a test pad portion containing alumina in an external composition of 6.0% by mass when Pt was 100% by mass. Created.

  Then, a plate-like Pt ribbon having a width of 250 mm and a thickness of 40 μm as an energizing member was resistance-welded to the surface of the test pad portion of each sample after bending it into an L shape. Then, in the L-shaped Pt ribbon, the end portion of the linear portion located on the side opposite to the resistance-welded side is sandwiched with tweezers as shown in FIG. ) Can be pulled.

And with the following test method, the tensile test (namely, pull strength test) was done with respect to each sample using the bond tester, and the tensile strength until Pt line peeled was measured.
<Test method>
・ Testing machine: All-purpose bond tester
Daisy (model: series 400)
・ Use load cell: TP5KG
・ Range: 5N
Test temperature: normal temperature (23 ° C)
Note that TP5KG of the load cell used indicates the model number of the load cell. The range is the maximum value that can be measured.

  The test results are shown in FIG. 10, and the sample in the range of the present disclosure was suitable because it had a tensile strength of 550 mN or more. On the other hand, a sample outside the scope of the present disclosure is not preferable because the tensile strength is as small as 320 mN or less.

[5. Other Embodiments]
Needless to say, the present disclosure is not limited to the above-described embodiment, and can be implemented in various forms without departing from the present disclosure.

  (1) For example, as shown in FIG. 11A, a pad portion 153 having a size (for example, vertical and horizontal dimensions) larger than the width (w) of the heater 151 at the end of the heater 151 and similar to the composition of the heater 151. And a heater pad portion 155 having the same shape and composition as in the first embodiment may be provided on the pad portion 153.

In this case, the heater pad portion 155 having a plan view larger than that of the pad portion 153 can be used to cover the entire surface of the pad portion 153 and its periphery.
Further, as shown in FIG. 11B, a pad portion 163 that is larger than the width (w) of the heater 161 (for example, vertical and horizontal dimensions) and is similar to the composition of the heater 161 is integrated with the end portion of the heater 161. The heater pad portion 165 having the same shape and composition as in the first embodiment may be provided on the pad portion 163.

In this case, the heater pad portion 165 having the same shape as the pad portion 163 in plan view can be used to cover the entire surface of the pad portion 163.
Further, as shown in FIG. 11C, a pad portion 173 having a larger dimension (for example, vertical and horizontal dimensions) than the width (w) of the heater 171 and the same composition as the heater 171 is integrally formed at the end of the heater 171. The heater pad portion 175 having the same shape and composition as in the first embodiment may be provided on the pad portion 173.

In this case, it is possible to cover the central portion of the pad portion 173 using the heater pad portion 175 that is smaller in plan view than the pad portion 173.
(2) Further, the shape of the energization member and the number of energization members are not particularly limited as long as the function of the present disclosure is exhibited in addition to the configuration of each embodiment.

  For example, as the shape of the energizing member, a flat plate-like member having no curved portion can be employed. Further, the number of energization members is not limited to four as long as the sensor element can be suspended and fixed, and for example, three or five or more can be employed.

  (3) Moreover, the element part 101 is not limited to what consists of metal oxide semiconductors, You may employ | adopt the structure from which an electrical property (for example, electromotive force) changes according to the density | concentration of a specific gas component. For example, a sensor element is formed by forming, on a ceramic part 103, a mixed potential type element part 101 in which a solid electrolyte body made of zirconia is provided with a pair of electrodes made of different materials, and according to the concentration of a specific gas component. You may make it output the electromotive force which changes to an exterior via an electricity supply member and a wiring board.

  (4) The functions of one component in each of the above embodiments may be distributed as a plurality of components, or the functions of a plurality of components may be integrated into one component. Moreover, you may abbreviate | omit a part of structure of each said embodiment. In addition, at least a part of the configuration of each of the above embodiments may be added to or replaced with the configuration of each of the above other embodiments. In addition, all the aspects included in the technical idea specified from the wording described in the claims are embodiments of the present disclosure.

DESCRIPTION OF SYMBOLS 1, 111, 121 ... Gas sensor 3 ... Wiring board 13 ... Opening part 15, 123 ... Sensor element 17 ... 1st electricity supply member 19 ... 2nd electricity supply member 21 ... 3rd electricity supply member 23 ... 4th electricity supply member 33 ... 1st wiring Pattern 35 ... Second wiring pattern 37 ... Third wiring pattern 39 ... Fourth wiring pattern 81 ... Detection section 87 ... A heater 89 ... B heater 91, 127 ... First heater pad section 91a ... First layer 91b ... Second layer 93, 129 ... second heater pad portion 95 ... third heater pad portion 97 ... fourth heater pad portion 101 ... element portion 103 ... ceramic portion 125 ... heater 131 ... temperature element pattern 133 ... first conductive pad portion 135 ... second Conductive pad

Claims (4)

A wiring board having an opening;
A detection unit having an element part whose electrical characteristics change according to the state of the gas to be measured, a heater mainly composed of a metal that heats the detection unit, and at least a part of the end of the heater overlap. A heater pad portion mainly composed of a metal electrically connected to the heater, and a sensor element,
A metal energization member for fixing the sensor element in a suspended state in the opening of the wiring board;
A gas sensor comprising:
The detection unit includes a ceramic unit mainly composed of ceramic, and the heater and the heater pad unit are disposed on the surface of the ceramic unit.
One end of the energizing member is welded to the heater pad part,
The content rate of the common substrate made of ceramic for improving the adhesion with the ceramic portion included in the heater pad portion is less than the content rate of the common substrate included in the heater,
Gas sensor. The heater pad section includes a first layer and a second layer from the detection section side, and the content ratio of the common substrate in the second layer is more than the content ratio of the common substrate in the first layer. Few,
The gas sensor according to claim 1. The sensor element further includes a conductive pattern mainly composed of a metal on a surface of the ceramic portion, and a metal electrically connected to the conductive pattern so that at least a part of the conductive pattern overlaps an end portion of the conductive pattern. A conductive pad portion mainly composed of
The conductive pad portion is welded to a current-carrying member different from the current-carrying member welded to the heater,
One end of the another energizing member is welded to the conductive pad portion,
The content rate of the common substrate made of ceramic that improves the adhesion with the ceramic portion included in the conductive pad portion is less than the content rate of the common substrate included in the conductive pattern.
The gas sensor according to claim 1 or 2. The conductive pad portion includes a first layer and a second layer from the detection portion side, and the content of the common substrate in the second layer is greater than the content of the common substrate in the first layer. Few,
The gas sensor according to claim 3.

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