JP2001296197A - Pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a stress being applied to a sensing element from a protective member on the high elasticity side in a pressure sensor where the protective member covering the sensing element and the electric joint is arranged to exhibit different elasticity in order to suppress generation of bubbles in the protective member. SOLUTION: A sensing element 20 is mounted on a resin case 10 where an insert pin 30 is insert-molded, and the electrically connected sensing element 20 and pin 30 are covered with an electrically insulating protective member 50. The protective member 50 comprises a high elasticity first protective member 51 of rubber material, and a low elasticity second protective member 52 of gel substance laminated thereon. A wall part 60 for sectioning the sensing element 20 and the pin 30 is formed in the resin case 10 so that the first protective member 51 is located only at a position closer to the pin 30 side than the wall part 60.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for mounting a sensing element for detecting a pressure and generating an electric signal of a level corresponding to the detected value on a resin case, and using the sensing element and an electrical connection portion as protective members. The present invention relates to a pressure sensor that is covered and protected, and is suitably used, for example, as a sensor for measuring an engine intake pressure in an automobile.

[0002]

2. Description of the Related Art Conventionally, as a pressure sensor of this type, a pressure sensor described in Japanese Patent Application Laid-Open No. H11-304609 has been proposed. This is a resin case in which a conductor portion made of a conductive material is insert-molded, and a sensing element (sensor) for pressure detection that is mounted on the resin case and detects pressure and generates an electric signal at a level corresponding to the detected value. Chip), a conducting wire (bonding wire) for electrically connecting the sensing element and the conductor, and a protective member having electrical insulation to cover and protect the conductor, the sensing element and the conductor. It is.

[0003] A protective member is provided on a first protective member (rubber material or the like) having a relatively high Young's modulus and a low elasticity having a lower Young's modulus than the first protective member. It has a two-layer structure in which two protective members (such as a gel-like substance) are laminated. According to it, the high elasticity of the first
Since the conductor portion and its peripheral portion are covered by the protective member, air trapped in the gap between the insert-molded conductor portion and the resin case becomes bubbles and grows or moves in the protective member. Can be suppressed, and a decrease in insulation performance of the protection member can be prevented.

[0004]

By the way, the present inventors have examined the above publication and found that the following problems occur. According to the above publication, the first protection member is provided so as to expose the sensing portion, but is provided in contact with the sensing element on the outer peripheral surface other than the sensing portion.

[0005] Each protective member is formed through curing by heat treatment or the like. When the temperature is returned to normal temperature after curing, stress remains at the interface between the sensing element and the protective member due to the difference in the coefficient of thermal expansion between the two. In particular, since the first protective member has high elasticity, the stress applied from the first protective member to the sensing element is large, and therefore, the accuracy of the sensing element deteriorates.

In view of the above problems, the present invention provides a protective member for covering and protecting a sensing element and an electrical connection.
In a pressure sensor having a different elasticity so as to suppress the generation of bubbles in the protective member, an object of the present invention is to reduce the stress of the protective member on the high elasticity side applied to the sensing element.

[0007]

To achieve the above object, according to the first aspect of the present invention, a sensing element (20) for detecting pressure is provided in a resin case (10) in which a conductor (30) is insert-molded. In the mounted state, the sensing element and the conductor are electrically connected, and the conductor and the sensing element are covered and protected by a protective member (50) having electrical insulation. In a pressure sensor in which a second protection member (52) having lower elasticity than the first protection member is laminated outside the protection member (51), the first protection member is connected to a sensing element. A wall portion (60) is provided in the resin case so as to partition between the sensing element and the conductor portion, with the portion being exposed so as to cover at least the conductor portion and its peripheral portion. Located in the first It is characterized in that so as to prevent from entering the sensing element side of the protective member.

According to the present invention, first, since the conductor portion and its peripheral portion are covered by the first protective member having high elasticity, the air trapped in the gap between the conductor portion and the resin case formed by insert molding. Can be suppressed from being generated as bubbles in the protection member, and a decrease in insulation performance of the protection member can be prevented.

Further, the first protective member located closer to the conductor than the wall is prevented from entering the sensing element by the wall partitioning between the sensing element and the conductor in the resin case. Therefore, the first protection member can be arranged such that the amount of the first protection member on the sensing element side with respect to the wall portion is completely absent or is reduced as much as possible on the conductor portion side. Therefore,
According to the present invention, it is possible to reduce the stress of the first protective member on the high elasticity side applied to the sensing element.

Here, if the wall portion (60) is formed so as to protrude from the resin case (10), the first protection member (51) can be used as the sensing element. This is preferable because it is not necessary to increase the volume for depositing the protective member because it is prevented from entering the (20) side.

According to the third aspect of the present invention, the sensing element (20) and the conductor (30) are connected to the resin case (10).
The conductor portion is provided in one of the recesses, and the wall portion (60) is provided with the sensing element arrangement portion and the conductor portion arrangement portion in the recess. It is characterized by being separated into chambers. According to this, since the conductors are concentrated at one location and are partitioned by the wall, the first protection member can be easily injected.

Although the first protection member may be slightly present on the sensing element side within an allowable range, the first protection member (51) may be replaced with the first protection member (51). If the resin case (10) is provided only on the conductor part (30) side with the wall part (60) as a boundary, the effect of the first aspect can be realized at a higher level.

The wall portion may be formed separately from the resin case.
Is molded integrally with the resin case (10),
Manufacturing costs can be reduced. Further, when the wall portion is formed separately, a gap may be formed between the wall portion and the resin case, and bubbles may be generated from the gap. Such a problem can also be avoided.

Here, the first protective member (51) can be made of a rubber-based material, and the second protective member (52) is made of a gel-like substance. Can be adopted. It should be noted that reference numerals in parentheses of the above-described units are examples showing the correspondence with specific units described in the embodiments described later.

[0015]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a first embodiment of the present invention. FIG. 1 is a schematic cross-sectional view of the pressure sensor 100 according to the present embodiment, and FIG. 2 is a schematic plan view of the pressure sensor 100 as viewed from the direction of arrow A in FIG. The resin case 10 is made of, for example, an epoxy resin filled with a filler, a resin of PPS (polyphenylene sulfide), a resin of PBT (polybutylene terephthalate), or the like. On the upper surface of the resin case 10, a concave portion 11 having a rectangular shape for mounting a sensing element 20 described later is formed.

In the resin case 10, a plurality of insert pins (corresponding to the conductor portion in the present invention) 30 made of a conductive material such as copper are integrally provided by insert molding. Three of these predetermined insert pins 30 are:
It is arranged so as to be exposed on one side of the bottom surface of the concave portion 11 (see FIG. 2).

In this case, the recess 11 of the insert pin 30
Each exposed portion is configured to function as a bonding pad 31 by being subjected to gold plating. Further, the insert pin 30 can be connected to an external device (not shown) (not shown) at a portion (not shown) other than the bonding pad 31.

A sensing element 20 mounted in the recess 11 of the resin case 10 detects a pressure and generates a sensor chip 21 made of a semiconductor for generating an electric signal of a level corresponding to the detected value, and holds the sensor chip 21. And a glass pedestal 22.

The sensor chip 21 has a well-known configuration utilizing a piezoresistive effect, and has a configuration in which a diaphragm 21a as a sensing portion and a diffusion resistor (not shown) are provided on the upper surface thereof. The sensor chip 21 is die-bonded to the bottom surface of the concave portion 11 via a glass pedestal 22 with an adhesive 23 such as silicone rubber.

Each input / output terminal 2 of the sensor chip 21
1b (see FIG. 2, three in this example) is the insert pin 3
0 is electrically connected to the bonding pad 31 via a bonding wire 40 such as gold or aluminum. Thus, the sensing element 20 is
It is electrically connected to the insert pin 30 in a state where it is mounted in the concave portion 11 of No. 0.

The recess 11 is filled with a protective member 50 made of an electrically insulating material so as to fill the sensing element 20 and the bonding wire 40. The protective member 50 covers the sensing element 20, the insert pin 30, the bonding wire 40, the connection between the sensor chip 21 and the bonding wire 40, and the connection between the insert pin 30 and the bonding wire 40. Protection, securing of electrical insulation, anticorrosion, and the like are achieved.

The protection member 50 has a two-layer structure in which a second protection member 52 having lower elasticity than the first protection member 51 is laminated on the first protection member 51. . The first protection member 51 is a rubber-based material having a high modulus of elasticity in order to suppress the generation of air bubbles from a gap between the insert pin 30 and the resin case 10.
2 is the sensing element 20 and the bonding wire 40
It is a gel-like film with a low modulus of elasticity that does not give stress.

More specifically, the first protective member 51 has an electrically insulating property and a relatively high Young's modulus (for example, 0.1 MPa or more, preferably 0.3 MPa or more,
In this case, it is difficult to measure the penetration because it is relatively hard.) A fluorine-based or fluorosilicone-based rubber material can be used. The second protective member 52 is made of fluorine having electrical insulation and a relatively low Young's modulus (for example, a penetration of 10 or more, in which case it is soft and difficult to accurately measure the Young's modulus). Or fluorosilicone-based gel-like substances can be employed.

The first protection member 51 includes the sensing element 2
It is provided so as to cover the insert pin 30 and its peripheral portion in a state where the zero sensing portion (diaphragm 21a and the diffusion resistance) is exposed. Further, a wall portion 60 protrudes from the bottom surface of the concave portion 11 of the resin case 10 and is formed integrally with the resin case 10, and the wall between the sensing element 20 and the insert pin 30 is partitioned with the wall portion 60 as a boundary. I have.

Then, the first protection member 51 is connected to the wall portion 60.
With only the recess 11 on the insert pin 30 side
Filled within the height of the wall 60, the second protection member 52
Is filled in the entire area of the recess 11. The wall 6
The height of 0 is such that the thickness of the first protection member 51 is sufficient to cover and protect the insert pin 30 and the connection portion between the insert pin 30 and the bonding wire 40, and that the connection of the bonding wire 40 is prevented. It is determined in consideration of things that must not be done.

Therefore, in the recess 11, on the insert pin 30 side of the wall 60, a two-layer structure is formed in which the first protection member 51 is a lower layer and the second protection member 52 is an upper layer. On the side, the second protection member 52
Has a one-layer structure. Then, the first protection member 51
The sensing element 20 and the bonding wire 40 that are exposed from are covered with the second protection member 52.

Such a protective member 50 is provided by mounting the sensing element 20 on the resin case 10 and
After connecting the wire and the bonding pad 31 of the insert pin 30 by wire bonding, the first protection member 5
The first and second protection members 52 are formed in this order by filling the inside of the concave portion 11 in a vacuum or in the air and performing a thermosetting treatment.

As described above, in the present embodiment, the first protection member 5 located closer to the insert pin 30 than the wall portion 60 is.
1 is blocked by the wall portion 60 to prevent the first protection member from entering the sensing element 20 side, and a highly elastic first protection member 51 is provided around the sensing element 20.
And the sensing element 20 is covered only with the low elasticity second protection member 52.

When the pressure sensor 100 configured as described above is used, for example, as a sensor for measuring the engine intake pressure in an automobile, the recess 11 is housed in a housing (not shown) and the recess 11 is inserted into the engine intake passage in the automobile. Are placed in communication with the
Thus, the sensing element 20 is configured to detect a negative pressure.

By the way, according to the present embodiment, the highly elastic first protective member 5 located in the lower layer of the protective member 50 is provided.
1, the insert pin (conductor portion) 30 and its peripheral portion are covered, so that the air trapped in the gap between the insert pin 30 and the resin case 10 becomes bubbles and is generated in the protective member 50. Can be suppressed.

Further, according to the present embodiment, the first protection member 51 located on the insert pin 30 side is moved toward the sensing element 20 side by the wall portion 60 formed between the sensing element 20 and the insert pin 30. Since the sensing element 20 side and the pin 30 side are partitioned so as not to enter, the first protection member 51 does not exist on the sensing element 20 side with respect to the wall portion 60 in the concave portion 11.
The first protection member 51 can be provided.

That is, a wall portion 60 is formed in the resin case 10 for partitioning between the sensing element 20 and the insert pin 30, and the first protection member 51 is provided on the pin 30 side with the wall portion 60 as a boundary. By arranging it within the height of the portion 60, the protection member 50 has a two-layer structure on the pin 30 side and a single-layer structure of only the second protection member 52 on the sensing element 20 side with the wall 60 as a boundary. .

Therefore, according to the present embodiment, the stress of the highly elastic first protection member 51 can be prevented from being directly applied to the sensing element 20, and the stress can be reduced. In FIG. 2, among the hatchings applied to the protection member 50, the one-sided hatched area indicates the surface of the one-layer structure, and the cross-hatched area indicates the surface of the two-layer structure.

FIG. 3 is a diagram showing a specific mechanism for the deterioration of the accuracy of the sensing element 20 due to the stress of the first protection member 51 in the configuration based on the conventional pressure sensor. As described above, this kind of protection member is
It is formed through curing by heat treatment or the like. In FIG.
(A) is a schematic cross-sectional view of the sensor during heat curing, (b),
(C) is a schematic plan view and schematic cross-sectional view of the sensor when the temperature is returned to normal temperature after curing.

In the conventional sensor, the first protection member 51
Are provided so as to expose the sensing unit, but are provided in contact with the sensing element 20 on the outer peripheral surface other than the sensing unit. When the temperature is returned to normal temperature after curing, the protection member 50 contracts from the state of FIG. 3A to the state of FIG. 3C.

At this time, stress remains at the interface between the sensing element 20 and the protection member 50 due to the difference in the coefficient of thermal expansion between them. In particular, since the first protective member 51 has high elasticity, the stress applied to the sensing element 20 from the first protective member 51 is large, and the stress is as shown in FIG.
It acts on the sensing element 20 as shown by the white arrow in (c). Then, since this stress is also transmitted to the diaphragm 21a of the sensing unit that should be deformed by pressure, a shift in pressure characteristics occurs, and the accuracy of the sensing element 20 deteriorates.

In this regard, according to the present embodiment, only the low-elastic second protection member 52 that does not apply stress to the sensing element 20 comes into contact with the sensing element 20.
The stress of the first protection member 51 is
Do not join. Therefore, as shown by the dashed arrow in FIG.
Is reduced to such an extent that the accuracy of the sensing element 20 can be maintained satisfactorily.

In this embodiment, as shown in FIG.
The insert pins 30 are all collected on one side of the rectangle among the rectangular recesses 11, and the recesses 11 are divided by the wall 60 into two chambers on the sensing element 20 side and the insert pin 30 side. As described above, since the insert pins 30 are collected at one location partitioned by the wall portion 60, it is preferable that the first protection member 51 is easily injected when the first protection member 51 is injected.

That is, in the case of the position of the conventional insert pin 30 as shown in FIG. 3, if all of the insert pin 30 is separated from the sensing element 20 side by the wall 60, the recess 11 is formed by the wall 60. Is divided into an outside and an inside. In this case, the region where the first protection member 51 is injected has a frame shape surrounding the sensing element 20, and the protection member is injected along the frame, which is not preferable. If this is the case, it is only necessary to inject the protection member into one place, so that the efficiency is high.

In this embodiment, the wall portion 60 may be separate from the resin case 10 and joined to the resin case 10. However, the wall portion 60 may be formed integrally with the resin case 10. Is preferred. If the wall portion 60 is integrally formed when the resin case 10 is formed, the manufacturing cost can be reduced. When the wall portion 60 is formed separately,
There is a possibility that a gap is generated between the wall portion 60 and the resin case 10 and a bubble is generated from the gap. However, such a problem can be avoided by integrally molding.

Here, the first protection member 51 may be slightly present on the sensing element 20 side as long as the characteristic variation of the sensing element 20 is allowed. FIG. 4A is a schematic cross-sectional view showing a first modified example of the present embodiment having such a configuration, and the amount of the first protection member 51 is changed with the wall portion 60 as a boundary with the insert pin 30 side. , And reduced toward the sensing element 20 side.

According to the present modification, the first protection member 51 located closer to the insert pin 30 than the wall 60 is prevented from invading the sensing element 20 by the wall 60, so that the sensing element 20 The amount of the first protection member 51 can be reduced as much as possible in comparison with the pin 30 side in a range where the characteristic variation of the sensing element 20 is allowed. Of the protective member 51 can be reduced.

In each of the above examples, the wall portion 60 is
Although it is formed so as to protrude from the resin case 10, it may be a second modified example shown in FIG. 4B. As shown in FIG. 4B, by providing a further recessed groove (recess) on the insert pin 30 side on the bottom surface of the recess 11 of the resin case 10, the wall portion 60 is formed.
Is configured as a step between the bottom surface on the sensing element 20 side and the groove. Even with such a wall portion 60, the same effect as described above can be obtained.

(Other Embodiments) The sensor chip is not limited to a diaphragm type using a piezoresistive effect, but may be another type such as a semiconductor sensor chip of a capacitance type. good. Further, the present invention can be widely applied to pressure sensors for detecting the pressure of an intake system or an exhaust system of an internal combustion engine using gasoline, light oil, or the like, in addition to a pressure sensor for measuring an engine intake pressure in an automobile.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a pressure sensor according to an embodiment of the present invention.

FIG. 2 is a schematic plan view of the pressure sensor shown in FIG.

FIG. 3 is a diagram showing a mechanism of deterioration in accuracy of a sensing element in the conventional pressure sensor.

FIG. 4A is a schematic sectional view showing a pressure sensor as a first modification of the embodiment, and FIG. 4B is a schematic sectional view showing a pressure sensor as a second modification of the embodiment. is there.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Resin case, 20 ... Sensing element, 30 ... Insert pin, 50 ... Protective member, 51 ... 1st protective member,
52: second protection member, 60: wall.

Claims (6)

[Claims] 1. A resin case (10) in which a conductor part (30) made of a conductive material is insert-molded, and electrically connected to the conductor part in a state of being mounted on the resin case to detect pressure. A sensing element (20) for generating an electric signal of a level corresponding to the detected value; and a protective member (50) having an electrically insulating property for covering and protecting the conductor and the sensing element. In a pressure sensor having a two-layer structure in which a second protection member (52) having lower elasticity than the first protection member is laminated on the outside of the first protection member (51), The first protection member is provided so as to cover at least the conductor portion and a peripheral portion thereof in a state where a sensing portion of the sensing element is exposed, and the resin case includes the sensing element and A wall portion (60) is formed to partition between the conductor portion and the first protection member located closer to the conductor portion than the wall portion to the sensing element side. A pressure sensor characterized in that intrusion is prevented. 2. The pressure sensor according to claim 1, wherein the wall (60) is formed so as to protrude from the resin case (10). 3. The sensing element (20) and the conductor (30) are provided in a recess (11) formed in the resin case (10), and the conductor is one of the recesses. The wall part (60) is provided at one place, and separates the arrangement part of the sensing element and the arrangement part of the conductor part in the recess into two chambers. Pressure sensor. 4. The first protection member (51) is provided only on the conductor (30) side of the resin case (10) with the wall (60) as a boundary. The pressure sensor according to any one of claims 1 to 3, wherein: 5. The wall (60) is connected to the resin case (1).
2. The method according to claim 1, wherein the first and second parts are integrally formed.
The pressure sensor according to any one of claims 1 to 4. 6. The method according to claim 1, wherein the first protection member is made of a rubber-based material, and the second protection member is made of a gel-like material. A pressure sensor according to any one of the preceding claims.