JP3531970B2 - Sensor to detect gas or humidity - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sensor for detecting a gas such as a combustible gas or a toxic gas, or water vapor generated during a cooking process in a microwave oven. . 2. Description of the Prior Art Applicant, fixing a plurality of frames to the base, together with the die-bonding the substrate to the one, and the wiring by bonding wires to electrode pads of the substrate to the frame moth
Proposed a sensor for detecting heat or humidity
-159,744). FIG. 6 shows such a gas filter.
Or a sensor for detecting humidity . In the figure, 2 is a substrate, 4, 6, 8, and 10 are frames, which penetrate a base (not shown). The frames 4 and 6 are integrated in the base, and three frames are drawn out of the base. The substrate 2 has three electrode pads, and is wire-bonded to the frames 6, 8, and 10. However, the inventor has found that when a drop test is performed on such a sensor, disconnection of the wire frequently occurs. In the wire bonding, as shown in FIG. 5, the frames 6, 8, and 10 were first-bonded and the substrate 2 was second-bonded. The disconnection position was the bonding portion, and the lead wires 12 were not disconnected at other positions. Also, disconnection was the same when the substrate 2 was used as the first bond. The frequency of disconnection depends on the loop height of the lead wire 12, and when the loop height was increased, the frequency of disconnection decreased. In addition, after drop test, a gas or humidity detection
When the cap of the sensor was removed and the inside was inspected, the substrate 2 was tilted as shown by the broken line in FIG. 6, and the frame 4 was twisted accordingly. Here, although the problem was shown about the drop test, the break of the lead wire 12 similarly occurred in the vibration test. [0004] An object of the present invention is to detect gas or humidity.
An object of the present invention is to increase the durability of the output sensor against impacts such as dropping and vibration, and to prevent breakage of the lead wire. According to the present invention, a gas or humidity detecting system according to the present invention is provided.
The sensor is fixed to the base with multiple frames,
An electrode pad of a substrate of a sensor for detecting gas or humidity and a frame are wired by wire bonding, and a gas or moisture in which the back surface of the substrate is die-bonded to one of the frames.
In the sensor for detecting the degree, a branch frame for connecting the substrate die-bonded to one of the other frames is provided , and the branch frame is separated from the base closer to the substrate than the base.
When the frame with the substrate die-bonded falls or vibrates
It is characterized by preventing deformation at the time . Moth
The type of sensor that detects gas or humidity is arbitrary, such as a metal oxide semiconductor gas sensor, a metal oxide semiconductor humidity sensor,
A contact combustion type gas sensor, a proton conductor gas sensor, a solid electrolyte gas sensor, etc. Die bonding is performed using glass, a metal conductive layer, or the like. According to the present invention, a branch frame is provided in which a frame on which a substrate is die-bonded is connected to one of the other frames. As is clear from FIG. 6, the main cause of the disconnection of the lead frame is that a large force is applied to the substrate by G (gravitational acceleration) at the time of drop or vibration, and the die-bonded frame 4 is deformed by this force. That is, the substrate has a certain weight, and a force proportional to the substrate weight is applied when the substrate is dropped or vibrated. When the frame is twisted by this force and the substrate is tilted, excessive force is applied to the lead wire, and the lead wire is disconnected at the bonding portion. Further, the reason why the disconnection frequency decreases as the loop height of the lead wire becomes higher is because the substrate is tilted due to the deformation of the loop. If a branch frame is provided here, the branch frame becomes a kind of glazing or a beam between frames,
Deformation of the frame to which the substrate is die-bonded can be prevented, and disconnection of the lead wire can be prevented. FIG. 1 shows an embodiment, and FIGS. 2 to 4 show modified examples. In FIG. 1, reference numeral 2 denotes a substrate made of, for example, alumina or glass, which is made of a heat-resistant insulating material. Reference numeral 12 denotes a lead wire having a diameter of 3
Reference numeral 14 denotes a branch frame for connecting the frame 4 to which the substrate 2 is die-bonded and a frame 6 using a gold wire of 0 μm.
Reference numeral 16 denotes a base, which is formed integrally with the frames 4, 6, 8, and 10, and the frames 4, 6, 8, and 10 penetrate the base 16. The frames 4 and 6 are integrated by a connecting portion 18 in the base 16. The connecting portion 18 is the base 1
6, and does not have the function of preventing the deformation of the frame 4, so it is not considered as a branch frame. Branch frame 14
May be located closer to the substrate 2 than the base 16.
The required number of frames is the number of terminals of the substrate 2 + 1. In the embodiment, a sensor for detecting gas or humidity of three terminals is used, so that the number of frames is four. The substrate 2 will be described. 20 is an electrode pad, 22 is a heater in the form of a film, and 24 is a gas sensitive body, here a thick film of SnO2. Since the resistance value of the gas sensing element 24 changes due to water vapor, flammable gas, or toxic gas, it becomes a humidity sensor when detecting water vapor accompanying cooking in a microwave oven or the like. Is detected, a gas sensor is used. As shown in FIG. 5, the lead wires 12 are first bonded on the frames 6, 8 and 10 and
I made a second bond on the side. However, conversely, first bonding may be performed on the substrate 2 side, and second bonding may be performed on the frames 6, 8, and 10 side. The frames 4, 6, 8, and 10 and the branch frame 14 are originally lead frames joined to tie bars (not shown), and the branch frame 14 can be formed only by changing the etching pattern when etching the lead frame from a thin metal plate. . Furthermore, the base 16
In the state of the lead frame with the tie bar, frame 4,
It is molded integrally with 6, 8, 10. Next, the back surface of the substrate 2 (the surface opposite to the gas sensitive body 24) is die-bonded to the frame 4, and glass, a metal conductive layer, or the like is used for the die bond. Moth
Other sensors for detecting heat or humidity include a cap with a wire mesh or the like. The operation of the embodiment will be described. Detect gas or humidity
If the sensor to be dropped is dropped or strong vibration is applied, an impact proportional to the weight of the substrate 2 is applied. In the conventional example of FIG. 6, the frame 4 is deformed by the impact, and the substrate 2 is tilted to the position indicated by the broken line. Then, the lead wire 12 is disconnected. In the conventional example, the frames 4 and 6 are integrated at the joint portion 18 in the base 16. However, in order to reduce heat loss from the substrate 2, the frame 4 is elongated, and a large space is provided between the die bond portion and the base 16. Because of the distance, it is not effective in preventing deformation of the frame 4. Even if the connecting portion 18 is not provided, the frames 4 and 6 are fixed to the base 16, and the connecting portion 18 is not effective in preventing the deformation of the frame 4. On the other hand, in the embodiment, the branch frame 14 is a kind of a hint, and the deformation of the frame 4 can be prevented. Accordingly, disconnection of the lead wire 12 is prevented. Test Example As an example, the gas or humidity shown in FIG. 1 is detected.
The same sensor was used except that the branch frame 14 was not provided as a comparative example. A gold paste layer was applied and baked on the back surface of the substrate 2, and was bonded to the frame 4 by passing a welding current using a parallel gap welding machine. The parallel gap of the welding machine is brought into contact with the back surface of the frame 4, and when a welding current is applied, the gold paste layer on the back surface of the substrate 2 is welded to the frame 4. The welding energy was 65 J per one welding point, and welding was performed at two places. The conditions of the wire bonding are as follows: the frames 6, 8, and 10 are first-bonded, the electrode pad 20 is second-bonded, and the bonding is performed by ultrasonic thermocompression bonding. At this time, the temperatures of the frames 6, 8, 10 and the substrate 2 were 200 ° C., and the ultrasonic energy was 1 W on the first bond side and 3 W on the second bond side.
Example of a sensor for detecting such gas or humidity ,
In the conventional example, 100 pieces were manufactured and dropped from the height of 1 m onto the concrete floor once each so that the lead wire 12
Was examined for damage. In the comparative example, the number of pieces broken by the drop test is 23/100, and in the example, 0/100.
Was individual. Modified Examples FIGS. 2 to 4 show modified examples. Except for the points particularly pointed out, the embodiment is the same as the embodiment of FIG. 1, and in FIG. 2, an oblique branch frame 30 is used. In FIG. 3, a pair of branch frames 32 and 34 are used to further strengthen the connection between the frames 4 and 6. FIG. 4 shows a case in which two lead wires 12 are wire-bonded to one pad 20 two times. If one of the pair of lead wires 12 is damaged, the other remains, so that the reliability is improved. Things. According to the present invention, it is possible to prevent the lead wire from being broken by an impact such as dropping or vibration, and to prevent gas or moisture from breaking.
The durability of the sensor for detecting the degree can be increased.

BRIEF DESCRIPTION OF THE DRAWINGS [Figure 1] Example of a main sensor <br/> for detecting a fragmentary cross-sectional view FIG. 2 gas or humidity variation of the sensor <br/> for detecting a gas or humidity FIG. 3 is a sectional view of another modified example for detecting gas or humidity.
Fragmentary plan view of capacitors Figure 4 further detects gas or moisture other variations
Fragmentary plan view of the sensor of FIG. 5 substrate and partial side view showing the wire bonding to the lead 6 conventional example of a sensor for detecting <br/> gas or humidity fragmentary plan view [sign Description 2 Board 4, 6, 8, 10 Frame 12 Lead wire 14, 30, 32, 34 Branch frame 16 Base 18 Joint 20 Electrode pad 22 Heater 24 Gas sensitive body

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-127945 (JP, A) JP-A-63-159744 (JP, A) JP-A-63-159745 (JP, A) (58) Investigation Field (Int.Cl. ⁷ , DB name) G01N 27/12

Claims (1)

(57) [Claim 1] A plurality of frames are fixed to a base, an electrode pad of a substrate of a sensor for detecting gas or humidity is wired to the frame by wire bonding, and one of the frames is provided. The gas with the backside of the substrate die- bonded
Or a sensor for detecting humidity , wherein a frame in which the substrate is die-bonded is connected to one of the other frames by a branch frame closer to the substrate than the base.
And the substrate is die-bonded.
A sensor for detecting gas or humidity, wherein the sensor is configured to prevent deformation at the time of dropping or vibration of the arm.