JP3304227B2 - Lead wire and odor sensor using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead wire and an odor sensor using the lead wire, and more particularly to a gold / platinum lead wire having good workability and an odor sensor for detecting odor in a specific gas or environment using the lead wire. Things.

[0002]

2. Description of the Related Art Conventionally, an odor sensor as a kind of a fire sensor for detecting a fire has been provided with a sensitive film having a resistance value which changes according to an increase or decrease of a specific gas generated at the time of a fire, for example, CO gas or burnt odor. Are known. FIG. 6 is a side sectional view showing an example of a conventional odor sensor. This odor sensor comprises an insulating substrate, for example, an alumina substrate 1, and a plurality of, for example, two pairs formed above and below the alumina substrate 1 at intervals. A gold electrode 2, a pair of gold electrodes 2 on the upper surface of the alumina substrate 1, and an alumina substrate 1 between them are formed, for example, vapor-deposited, and a metal oxide semiconductor such as SnO ₂ , ZnO, TiO ₂
The sensitive film 3 detects gas, odor, and the like by changing a resistance value according to increase and decrease of adsorption of odor and the like.
And a pair of gold electrodes 2 on the lower surface of the alumina substrate 1 and the alumina substrate 1 between them are formed, for example, by paste molding, and made of a heater material such as platinum or ruthenium oxide.
To a predetermined temperature.

[0003] The odor sensor further includes a plurality of terminals 5 provided outside the alumina substrate 1 and protruding from a substrate or a socket (not shown) provided with an electric circuit.
A gold wire 6 of the same material as the gold electrode 2 for connecting each terminal 5 to each gold electrode 2 is provided. In addition, alumina-based
Plate 1 had been the gold wire 6 connected to the terminal 5 to the suspended, because due to the functional and manufacturing problems as odor sensor. In other words, the purpose is to efficiently heat the sensitive film 3 to a predetermined temperature by the heater film 4 and to prevent excessive heat and shock from being applied to the sensitive film 3. As a result, the gold wire 6 is connected to the terminal 5 and the gold electrode 2. They were connected by so-called wedge bonding.

The conventional odor sensor is configured as described above. When the odor or the like is adsorbed on the sensitive film 3, the sensitive film 3
There are two types: N-type, which obtains electrons and changes its resistance value, and P-type, which deprives electrons and changes its resistance value. In both cases, the resistance value changes when odor or the like is adsorbed.
Therefore, if the change in the resistance value is extracted as, for example, a change in voltage, a change in odor or the like can be detected.

By the way, the gold wire 6 connected to the gold electrode 2
The mechanical strength of a platinum wire having a diameter of 50μ, particularly the tensile strength is 120g, whereas the mechanical strength of a gold wire 6 having a diameter of 50μ is only 40g, which is weak. May break easily.
Moreover, since the gold wire 6 has too low resistance and does not generate heat, spot welding cannot be used, so that the joining of the gold wire 6 and the terminal 5 has to rely on soldering. However, during use, the odor sensor is always exposed to a high temperature of 300 ° C. or more, and the heat reaches the soldered portion along the gold wire 6 and when the soldered portion is heated for a long period of time, the so-called “gold” The embrittlement of gold, which is said to be "eating,"
Will be disconnected.

[0006]

In short, the conventional odor sensor has a low mechanical strength because it uses a gold wire.
There was a problem that spot welding could not be used, and the wires would be broken by soldering. Further, when a platinum wire and a platinum electrode are used instead of the gold wire, there is a problem that the connection by bonding becomes difficult.

Therefore, the present invention has been made to solve such a problem, and an object of the present invention is to provide a lead wire having good workability and an odor sensor using the same.

[0008]

To achieve this object, a lead wire according to claim 1 of the present invention comprises a platinum core material and a gold coating material concentrically covering the outside of the core material. Made up of

According to a second aspect of the present invention, there is provided an odor sensor, wherein the lead wire according to the first aspect is used, and an insulating substrate and an electrode formed on at least one surface of the insulating substrate at intervals. A surface of the insulating substrate and an electrode formed on the surface of the insulating substrate, which is made of a metal oxide semiconductor, has a sensitive film for detecting gas or odor, and a terminal of a substrate or a socket provided with an electric circuit. Are connected to the lead wires by spot welding, and the lead wires are connected to the electrodes by bonding.
The odor sensor according to a third aspect of the present invention is the odor sensor according to the second aspect, wherein the odor sensor is formed on the other surface of the insulating substrate opposite to the one surface and the electrode on the other surface thereof, And a heater film for heating the sensitive film is added.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to an embodiment shown in the accompanying drawings. FIG. 1 is a perspective view showing one embodiment of a lead wire according to the present invention. In the figure, the lead wire 7 is composed of a platinum core material 71 having a diameter of, for example, 25 μm, and a gold coating material 72 that concentrically covers the outside of the core material 71 with a thickness of, for example, 25 μm.

FIGS. 2 and 3 are a side sectional view and a top view, respectively, showing one embodiment of the odor sensor according to the present invention using the lead wire 7 shown in FIG. The odor sensor is formed between the alumina substrate 1 described above, two pairs of gold electrodes 2 formed above and below the alumina substrate 1 at intervals, and a pair of gold electrodes 2 on the upper surface side of the alumina substrate 1. Sensitive film 3
And a heater film 4 formed between a pair of gold electrodes 2 on the lower surface side of the alumina substrate 1.

The odor sensor further includes a plurality of, for example, four terminals 5 and four lead wires 7 for connecting the terminals 5 to the gold electrodes 2 respectively.

The connection between the terminal 5 and the lead wire 7 is performed by spot welding, which allows a strong current to flow and can be joined with metals of different materials. In this spot welding, as shown in FIG. 4, the lead wire 7 is sandwiched between a terminal 5 attached to a jig (not shown) and a welding head 8, and then the lead wire 7 is energized. Heat is generated by electrical resistance and welds. These terminals 5 use pins projecting from a circuit board (not shown) formed as a socket, but may be directly connected to a conductive pattern on the circuit board. Further, the terminal 5 and the lead wire 7 may be connected by soldering. Further, the connection between the lead wire 7 and the gold electrode 2 is performed by wedge bonding because spot-welding in which a strong current flows may break the sensitive film 3. This wedge bonding is performed in advance as shown in FIG.
The lead wire 7 is pressure-bonded with the bonding head 9 to the gold electrode 2 which has been heated to ℃, and instantaneously welded by ultrasonic waves. This bonding is performed by the gold covering material 72 of the lead wire 7 and the gold electrode 2.
Therefore, the connection is easy. Note that a platinum electrode or the like may be used instead of the gold electrode 2. Further, not only wedge bonding but also ball bonding may be used. As shown in FIG. 3, the odor sensor configured as described above is suspended by the four terminals 5 so that tension is equally applied to each lead wire 7.

[0014]

The lead wire according to the first aspect of the present invention has a high mechanical strength because the core material is platinum, and can be connected to the electrode by bonding because the coating material covering the core material is gold. The effect that workability is good is produced.

According to a second aspect of the present invention, there is provided an odor sensor, wherein the lead wire according to the first aspect is used, and an insulating substrate and an electrode formed at least on one surface of the insulating substrate at intervals. And a sensitive film formed on one surface of the insulating substrate and an electrode on the one surface, made of a metal oxide semiconductor, and detecting gas or odor. The odor sensor according to claim 3, wherein In addition to further comprising a heater film that is formed on the other surface and the electrode on the other surface opposite to the one surface and is formed of a heater material and heats the sensitive film,
Both odor sensors are provided with a board or socket terminal provided with an electric circuit, and the terminal and the lead wire are connected by spot welding and the lead wire and the electrode are connected by bonding, so the terminal is connected to the lead wire. In addition to the fact that spot welding is possible and the workability is good, even if soldered for some reason, the platinum of the core of the lead wire reinforces the embrittlement of the gold of the coating material and is used for a long time. This has the effect that it becomes possible.

[Brief description of the drawings]

FIG. 1 is a perspective view showing one embodiment of a lead wire according to the present invention.

FIG. 2 is a side sectional view showing one embodiment of the odor sensor according to the present invention.

FIG. 3 is a top view showing an embodiment of an odor sensor.

FIG. 4 is a diagram illustrating spot welding.

FIG. 5 is a diagram illustrating wedge bonding.

FIG. 6 is a schematic configuration diagram illustrating an example of a conventional odor sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Alumina substrate 2 Gold electrode 3 Sensitive film 4 Heater film 5 Terminal 6 Gold wire 7 Lead wire 71 Core material 72 Coating material 8 Welding head 9 Bonding head

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-310557 (JP, A) JP-A-6-333180 (JP, A) JP-A-53-114094 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) G08B 17/00 G01N 27/12 G08B 17/06

Claims (5)

(57) [Claims] 1. A lead wire comprising a platinum core material and a gold coating material which concentrically covers the outside of the core material. 2. An insulating substrate, an electrode formed on at least one surface of the insulating substrate at intervals, and a metal oxide semiconductor formed on one surface of the insulating substrate and the electrode on one surface thereof, An odor sensor comprising a sensitive film for detecting gas or odor, a terminal of a substrate or a socket provided with an electric circuit, and the lead wire according to claim 1 for connecting the terminal to the electrode. 3. The heater according to claim 2, further comprising a heater film formed on the other surface of the insulating substrate opposite to the one surface and the electrode on the other surface, made of a heater material, and heating the sensitive film. Odor sensor. 4. The odor sensor according to claim 2, wherein the terminal and the lead wire are connected by spot welding, and the lead wire and the electrode are connected by bonding. 5. The method according to claim 2, wherein the electrode is a gold electrode.
Odor sensor.