JP2000009569A - Manufacture of pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the output characteristic of a sensor from being degraded due to bubbles in a glass layer by an Si chip is bonded through the glass layer and inspecting the bubbles in the glass layer to assemble a good sensing body to a housing. SOLUTION: To a diaphragm 2a of a sensing body 2 an Si chip 4 with a diffusion gage 3 formed thereat is bonded through a glass layer 5, a step of inspecting bubbles in the glass layer 5 is provided after this bonding, the sensing body 2 is assembled to a housing, if its inspection result is good whereby a pressure sensor the output of which is never influenced by bubbles in the glass layer 5, and the effect of the bubbles in the glass layer 5 below the center gage is esp. great esp., when a diffusion gage 3 is composed of a center gage and side gage, and this part is pref. inspected. The bubble inspection can be made by an infrared microscope, ultrasonic flaw searching method, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a pressure sensor for detecting pressure.

[0002]

2. Description of the Related Art Japanese Patent Publication No. 7-11461 discloses a pressure sensor having a structure in which a sensing body in which a silicon chip is bonded to a surface of a metal diaphragm for pressure reception via a glass layer is assembled in a housing. Have been. More specifically, as shown in FIG. 4A, a silicon chip 4 having a diffusion gauge 3 is bonded to the surface of a diaphragm 2a of a metal sensing body 2 via a glass layer 5, and is subjected to pressure. The deflection of the diaphragm 2a is transmitted to the silicon chip 4 via the glass layer 5, and the resistance of the diffusion gauge 3 changes. The diffusion gauge 3 is connected so as to form a bridge circuit, and an electric signal corresponding to the pressure is output from the bridge circuit. The pressure sensor configured as described above uses metal for the diaphragm and has high reliability even under high pressure conditions and can be used for a high pressure sensor such as a fuel pressure sensor.

[0003]

DISCLOSURE OF THE INVENTION The present inventors have studied the above-mentioned pressure sensor, and found that if bubbles are generated in the glass layer, the bubbles affect the sensor characteristics. I found it. That is, when manufacturing the above-described pressure sensor, a glass paste is printed on the surface of the diaphragm 2a, the silicon chip 4 is mounted thereon, and then baked. For example, the flatness of the diaphragm 2a is poor. Then, FIG. 4 (b)
As shown in (1), bubbles 6 are trapped in the glass layer 5. If bubbles 6 are generated in the glass layer 5, the glass layer 5 cannot accurately transmit the deflection of the diaphragm 2a to the silicon chip 4, or the bubbles 6 expand and contract due to a temperature change. This is a factor that deteriorates the temperature characteristics of the sensor.

An object of the present invention is to solve the above problems.

[0005]

Means for Solving the Problems The present inventors have conducted the following studies on the effects of the above-mentioned bubbles. In FIG.
The figure which looked at the silicon chip 4 from the upper surface is shown. The silicon chip 4 has a plane orientation of (110), and the diffusion gauge 3 has center gauges 3a and 3b arranged at the center of a displacement area (area where the diaphragm 2a exists below) which is displaced by pressure. And side gauges 3c and 3d arranged on the periphery. And the glass layer 5
Of the bubbles 6 generated in the above, the position below the center gauge is A, the position next to it is B, the position below the side gauge is C,
FIG. 6 shows the sensitivity of the sensors at the bubble generation positions A to D when the horizontal position is D and the bubble diameter is 500 μm, and the temperature characteristics thereof, as compared with those without bubbles 6. Show.

[0006] From the results shown in FIG. 6, it is understood that the sensitivity and the temperature characteristics thereof are affected by the presence of the bubbles 6. In particular, when the bubble 6 exists at the bubble position A below the center gauge, the influence of the bubble is very large.
In addition, even when there is a bubble at the bubble position C below the side gauge, the air bubble is affected by the bubble, but is not greatly affected as in the case of the bubble position A. This is because the generated stress is smaller at the side gauge forming position than at the center gauge forming position.

The sensitivity of the above-described sensor is obtained from the sensor output voltage Vs when a pressure of 20 MPa is applied to the diaphragm 2a by Vs / 20.
Sensitivity S _{25 at} 25 ° C. and S _{120 at} 120 ° C.
From seeking at _{(S 120 -S 25) / S} 25 / (120-25). Further, in the case where the bubble 6 exists at the bubble position A, the sensitivity to the bubble size (bubble diameter) and the temperature characteristics thereof were examined. 7 and 8 show the results. From these figures, it can be seen that if the bubble size is 200 μm or less, the sensitivity and the temperature characteristics with respect to the sensitivity are not substantially affected by the bubble.

[0008] The present invention has been made based on the above study,
According to the first aspect of the present invention, a silicon chip is bonded to the surface of the metal diaphragm in the sensing body via a glass layer, and after this bonding, an inspection step for inspecting bubbles in the glass layer is provided, and the inspection result is good The sensor body is assembled to the housing.

Accordingly, it is possible to manufacture a pressure sensor which is not affected by the sensor output due to bubbles in the glass layer. The invention according to claim 2 is characterized in that, in the inspection step, bubbles in the glass layer below the diffusion gauge are inspected. When bubbles are present in the glass layer below the diffusion gauge, the effects of the bubbles are directly exerted on the diffusion gauge, so that inspection of the portion enables efficient inspection of the bubbles.

[0010] In particular, when the diffusion gauge is constituted by the center gauge and the side gauge as in the third aspect of the present invention, the influence of bubbles in the glass layer below the center gauge is particularly affected as described above. Since it is large, it is preferable to inspect that part. Further, in this case, as in the invention described in claim 4, the bubbles are 200 μm.
If the inspection result is good in the following cases, it is possible to hardly be affected by the bubbles as described above.

The above-described inspection of air bubbles can be performed using an infrared microscope or an ultrasonic flaw detection method as described later.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a first embodiment of the present invention. FIG. 1 shows a cross-sectional structure of a pressure sensor according to an embodiment of the present invention. The pressure sensor measures the pressure of a high-pressure (for example, 20 MPa) fluid such as a fuel pressure of a fuel injection device in a vehicle or a brake oil pressure of a brake device.

In FIG. 1, a housing 1 is made of a weldable metal (for example, SUS430) having good corrosion resistance, has a screw 1a, and is fixed to an object to be detected (for example, a fuel pipe) by screwing. It is supposed to be. The sensing body 2 is made of a metal having a low coefficient of thermal expansion and a low coefficient of thermal expansion (for example, a material having a linear thermal expansion coefficient close to that of silicon such as Kovar), has a pressure introducing hole 2b inside, and has a thin end at its end. A diaphragm 2a is formed. The sensing body 2 is press-fitted into an inner cavity of the housing 1 and assembled to the housing 1.

A silicon chip (sensor chip) 4 is bonded to the upper surface of the diaphragm 2a of the sensing body 2, that is, the surface opposite to the pressure introducing side, via a glass layer 5 made of low-melting glass. Further, a signal processing circuit board 7 for processing an electric signal from the silicon chip 4 is arranged around the tip of the sensing body 2 as shown in FIG. The silicon chip 4 and the signal processing circuit board 7 are electrically connected by wires 8. The signal processing circuit board 7 includes a multilayer ceramic substrate 7a, a circuit chip 7b, and a post 7c.

Post 7c on signal processing circuit board 7
Is connected to the connector terminal 10a of the terminal assembly 10 by electric welding or the like. The terminal assembly 10 and the connector case 11 are connected to each other by the caulking portion 1b of the housing 1 via the O-ring 12.
It is fixed by swaging. Further, the upper surfaces of the sensing body 2 and the multilayer ceramic substrate 7 are coated with a coating material (for example, silicone gel) 9.

FIG. 2 is an enlarged sectional perspective view of the tip portion of the sensing body 2. As shown in FIG. As shown in the figure, a diffusion gauge 3 is provided on a diaphragm 2 a in the sensing body 2.
The silicon chip 4 on which is formed is bonded via the glass layer 5. The silicon chip 4 has a plane orientation of (11
It is configured using an N-type single crystal silicon substrate of 0). Although the diffusion gauge 3 is not clearly shown in FIG. 2, the center gauge 3 is similar to that shown in FIG.
a, 3b and side gauges 3c, 3d. The diffusion gauges 3a to 3d are connected by an aluminum wiring (not shown) so as to form a bridge circuit, are further electrically connected to a signal processing circuit board 7 by wires 8, and process an electric signal according to the displacement of the diaphragm 2a. Output to the circuit board 7.

Next, a method for manufacturing the above-described pressure sensor will be described. FIG. 3 shows the manufacturing process. First, a sensing body in which the pressure introducing hole 2b and the diaphragm 2a are formed is prepared, and the surface thereof is subjected to acid cleaning and decarburization treatment, and thereafter, oxidation treatment is performed. These processes are the same as those described in Japanese Patent Publication No. Hei 7-11461.

Next, a glass paste is printed on the surface of the diaphragm 2a and calcined at about 400 ° C. to form a glass layer 5. Then, the silicon chip 4 is placed on the calcined glass layer 5 and is baked at about 500 ° C. to join the silicon chip 4. Thereafter, a bubble inspection of the glass layer 5 is performed. Since infrared rays pass through the silicon to some extent, bubbles can be seen by observing from above the silicon chip 4 with an infrared microscope. In this embodiment, the glass layer 5 below the center gauges 3a, 3b has 20
Inspect for air bubbles larger than 0 μm. 200
When there is an air bubble larger than μm, the sensing body 2 is prevented from flowing to the subsequent process, and when the air bubble is 200 μm or less, the sensing body 2 is caused to flow to the subsequent process.

Then, an assembly assembling step is performed using the sensing body 2 having a good inspection result in the inspection step. That is, the sensing body 2 is mounted on the housing 1 and wire bonding is performed to complete the pressure sensor shown in FIG. In the above-described embodiment, the case where the bubble inspection is performed using the infrared microscope has been described. However, the bubble inspection may be performed using the ultrasonic flaw detection method. This ultrasonic flaw detection method is a method of placing a sample in water, applying ultrasonic waves, and observing the internal structure from reflected waves.

In the above-described embodiment, the bubble inspection is performed on the glass layer 5 under the center gauges 3a and 3b. However, the same bubble inspection is performed on the glass layer 5 under the side gauges 3c and 3d. It may be performed.
Further, when the silicon chip 4 having a plane orientation of (100) is used, the arrangement relationship of the center gauge and the side gauge does not exist. In this case, the bubble inspection of the glass layer below each gauge is performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a cross-sectional structure of a pressure sensor according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional perspective view of a tip portion of a sensing body 2 in FIG.

FIG. 3 is a process chart showing a method for manufacturing the pressure sensor shown in FIG.

FIG. 4 is a diagram for explaining the operation of a pressure sensor using a metal diaphragm.

FIG. 5 shows bubble generation positions A to D studied by the present inventors.
FIG.

FIG. 6 is a diagram showing the results of comparing sensor sensitivity and temperature characteristics when bubbles are present at bubble generation positions A to D with those without bubbles.

FIG. 7 is a diagram illustrating a relationship between sensor size and bubble sensitivity when bubbles are present at a bubble position A;

FIG. 8 is a diagram showing a relationship between a bubble size and a temperature characteristic of a sensor sensitivity when a bubble is present at a bubble position A;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Housing, 2 ... Sensing body, 2a ... Diaphragm, 3 ... Diffusion gauge, 4 ... Silicon chip, 5 ... Glass layer, 6 ... Bubble.

Continuing from the front page (72) Inventor Yasutoshi Suzuki 1-1-1, Showa-cho, Kariya-shi, Aichi F-term in DENSO Corporation (reference) 2F055 AA23 BB16 CC02 DD05 EE14 FF01 FF15 GG01 GG13 HH01 4M112 AA01 BA01 CA02 CA05 CA09 DA17 DA18 EA03 EA11 EA13 FA05 GA01

Claims (4)

[Claims] 1. A silicon chip having a diffusion gauge formed thereon is bonded to a metal diaphragm of a sensing body having a metal diaphragm via a glass layer. After the bonding, the sensing body is assembled to a housing. In the method of manufacturing a pressure sensor, an inspection step of inspecting bubbles in the glass layer after the bonding is provided, and the sensing body whose inspection result is determined to be good is attached to the housing. Production method. 2. The method for manufacturing a pressure sensor according to claim 1, wherein the inspecting step inspects air bubbles in the glass layer below the diffusion gauge. 3. The silicon chip has a plane orientation of (11).
0), wherein the diffusion gauge is constituted by a center gauge and a side gauge, and the inspection step is to inspect bubbles in the glass layer below the center gauge. A method for manufacturing the pressure sensor according to claim 2. 4. The method according to claim 1, wherein the air bubbles are 200 μm.
4. The method according to claim 3, wherein the inspection result is improved when the following conditions are satisfied.