JPH09178596A - Pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a highly reliable pressure sensor by making an atmosphere introduction hole through the body with the outer open end thereof being located on the opposite side to a mounting board with respect to the body thereby preventing a foreign matter from intruding into the pressure sensor when it is mounted on the mounting board. SOLUTION: A pressure introduction tube 11 has a flow-in hole 11b communicating between the inside 1a and outside and an object for pressure measurement, i.e., a fluid, flows into the flow-in hole 11b. Since the outer open end 12a of atmosphere introduction hole 12b made through the body 1 is located on the opposite side to a mounting board 8, a pressure sensor chip 2 is not susceptible to corrosion due to gas intruding into the body 1 through introduction hole 12b on the contrary to a conventional structure where the introduction hole 12b is made through a cover 6. Consequently, the service life of chip 2 is prolonged and the introduction hole 12b is not choked with a foreign matter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called differential pressure type pressure sensor in which terminals are mounted on a mounting board and the fluid pressure is measured based on the differential pressure between the fluid pressure and the atmospheric pressure.

[0002]

2. Description of the Related Art Conventionally, as a pressure sensor of this type, FIG.
There exists a thing of a structure shown in FIG. This includes a resin-made body B on which a cover A is covered, a pressure introducing pipe C which communicates the inside B1 of the body with the outside and into which a fluid whose pressure is to be measured flows, and a pressure inside the body B1. A pressure sensor chip D that is tightly fixed to the end surface C1 of the introduction tube and converts pressure into an electric signal, and a printed circuit board E that is mounted on the body B and is connected to the pressure sensor chip D by wire bonding.
A terminal F connected to the printed circuit board E and led to the outside of the body B, and the inside B of the body B from the external opening end A1.
1 has an air introduction hole A2 for introducing the atmosphere.

[0003]

In the conventional pressure sensor described above, since the cover A is provided with the atmosphere introduction hole A2, the atmospheric pressure in the inside B1 of the body B is equal to the outside atmospheric pressure which serves as a reference for measurement. By making them equal, the differential pressure between the fluid pressure and the external atmospheric pressure can be measured correctly.

However, when the terminal F is mounted on the mounting board G by being inserted into the insertion hole G1, foreign matter such as flux of solder enters the inside B1 of the body B through the air introduction hole A2 during soldering. There are cases where the pressure sensor chip D is adversely affected by corrosion and the reliability of the pressure sensor chip D is impaired. Further, when the element (not shown) mounted on the mounting board G is sealed with resin in order to have a waterproof structure, the resin enters the air introduction hole A2 and the resin blocks the air introduction hole A2. There were cases.

The present invention has been made in view of the above circumstances, and an object thereof is to prevent foreign matter such as solder flux from entering the inside of a body even when it is mounted on a mounting board, and to provide a highly reliable pressure. To provide a sensor.

[0006]

In order to solve the above-mentioned problems, according to a first aspect of the present invention, a body made of resin having a cover and a pressure measuring object communicating the inside and the outside of the body. The pressure introducing pipe into which the fluid flows, the pressure sensor chip that is fixed in close contact with the end surface of the pressure introducing pipe inside the body and converts pressure into an electric signal, and mounted on the body and connected to the pressure sensor chip by wire bonding. A printed circuit board, a terminal connected to the printed circuit board and led to the outside of the body, and an air introduction hole for introducing the atmosphere into the body from the external opening end, and the terminal is mounted on the mounting board, In a pressure sensor that measures the pressure of a fluid based on the pressure difference between the pressure of the fluid and the atmosphere, the atmosphere introduction hole has the outer opening end located on the side opposite to the mounting substrate with respect to the body. It is the configuration provided in sea urchin the body.

According to a second aspect of the present invention, in the first aspect, the printed circuit board is covered with silicon gel, and the air introduction hole is formed in a cylindrical shape and protrudes from the printed circuit board surface. It has been configured.

According to a third aspect of the present invention, in the second aspect, the atmosphere introducing hole is formed integrally with the body.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the printed circuit board is provided with an auxiliary terminal that abuts and is fixed to the terminal.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS.

Reference numeral 1 denotes a body, which is provided with a cylindrical pressure introducing pipe 11 integrally formed at a central position by an insulating resin, and has an inside 1a formed by a cover 6 described later. The pressure introducing pipe 11 has a base end projecting and opening to the outside, a tip part similarly projecting and opening to the inside 1a at the pressure introducing pipe end face 11a, and an inflow hole communicating the inside 1a and the outside. A fluid having a pressure measurement target flows into the inflow hole 11b. Further, an air introduction pipe 12 is provided.

The atmosphere introducing pipe 12 is cylindrical and has a pressure introducing pipe 1.
1 is formed substantially in parallel with the axis of the body 1 and has an air introduction hole 12b for introducing the atmosphere into the body interior 1a from the outer opening end 12a, and one end 12c is opened to the outside and the other end 1 is formed.
2d opens to the inside 1a of the body 1.

Reference numeral 2 denotes a pressure sensor chip, which is a silicon semiconductor element, is provided with an electrode 2a, and is closely adhered and fixed to the pressure introducing pipe end surface 11a by soldering or a silicon-based adhesive, and the inflow hole 11b of the pressure introducing pipe 11 is provided. The strain gauge is formed by shielding the piezoresistor and placing a piezoresistor on the silicon diaphragm to convert the fluid pressure into an electric signal.

Reference numeral 3 is a printed circuit board on which a circuit is formed by a ceramic substrate, and four circular holes 3a, one circular hole 3b and one square through hole 3c are provided at four corners. An element 3e having an amplifier circuit is mounted, and a thick film resistor (not shown) for temperature compensation is formed.
It is attached to the body 1. At this time, the air introduction pipe 12
The other end portion 12d of the pressure sensor chip 2 is projected and led out from the hole 3b, and the pressure sensor chip 2 is positioned in the through hole 3c.

Reference numeral 4 denotes a terminal, which is made of a metal such as Cu or a Cu alloy and is formed into a long and substantially L-shape, and fixed to the side wall 1b. Two terminals are provided on each side of the body 1. Has an internal terminal 41 arranged inside and an external terminal 42 arranged outside, and a protruding piece 41a is provided on the internal terminal 41, and the protruding piece 41a is led out to the hole 3a of the printed circuit board 3 42 is drawn out to the opposite side to the outer open end 12 a of the atmosphere introducing pipe 12 and the body 1.

Reference numeral 5 denotes a wire, which is a thin metal wire of Au or Al, and a terminal connects the electrode 2a of the pressure sensor chip 2 and the electrode 3d of the printed board 3 by wire bonding. Reference numeral 6 denotes a cover, which is covered with resin on the body 1. Reference numeral 7 denotes a silicon gel, which is made of a resin containing an organic substance and becomes a gel when dried in a liquid state at the time of application, and covers the mounting surfaces of the pressure sensor chip 2 and the printed board 3.

Here, the printed circuit board 3 is mounted on the body 1, and the protruding pieces 41a of the internal terminals 41 are soldered in the holes 3a of the printed circuit board 3 to electrically connect the printed circuit board 3 and the terminals 4. At the same time, the body 1 and the printed circuit board 3 are fixed. The pressure sensor chip 2 is closely fixed to the end surface 11a of the pressure introducing pipe, and the electrode 2a of the pressure sensor chip 2 and the electrode 3d of the printed board 3 are wire-bonded with the wire 5 to electrically connect them. Here, wire bonding is a method of bonding by applying ultrasonic vibration while applying pressure.

A pressure sensor chip is obtained by measuring the output voltage value from the external terminal 42 by raising and lowering the temperature in a state where a fluid such as air is flown into the inflow hole 11b of the pressure introducing pipe 11 and pressure is applied. The temperature characteristic of 2 is measured. Based on the temperature characteristic measurement result, the printed circuit board 3
The resistance value of the thick film resistor for temperature compensation is adjusted. In this state, the silicon gel 7 is applied to the surfaces of the pressure sensor chip 2 and the printed circuit board 3. At this time, the air introduction pipe 1
Since the other end portion 12d of 2 is projected and led out from the hole 3b of the printed circuit board 3, the silicon gel 7 is attached to the atmosphere introduction hole 1
2b does not enter, and the atmosphere introduction hole 12b is not clogged. Then, a resin cover 6 is provided on the body 1 to shield the outside from the inside 1a of the body 1.

Here, when the external terminal 42 is inserted into the insertion hole 8a of the mounting board 8 and mounted on the mounting board 8 by the soldering portion 8b, the mounting board 8 is opened to the outside of the atmosphere introducing tube 12 and the outside. The opening end 12a and the body 1 are located on the opposite side.

The operation of the above will be described. A fluid such as air is introduced into the inflow hole 11b of the pressure introducing pipe 11, and at this time, the inflow hole 11b is shielded by the pressure sensor chip 2 and the pressure sensor chip 2 is closely fixed to the pressure introducing pipe end surface 11a. , Never leak. When the pressure of the fluid is applied to the pressure sensor chip 2, the silicon diaphragm formed on the silicon semiconductor element bends in proportion to the difference between the fluid pressure and the atmospheric pressure. Then, the resistance value of the piezoresistor formed on the silicon diaphragm changes in proportion to the size of the deflection, and the resistance value is temperature-compensated by the resistance value of the thick film resistor provided on the printed circuit board 3. Then, the electric signal is amplified by the element 3e and output to the terminal 4.
In this way, the pressure difference between the fluid pressure and the atmospheric pressure is measured.

In the pressure sensor of the first embodiment, if the external terminals 42 are mounted on the mounting substrate 8 as described above, the atmosphere introducing hole 12b for introducing the atmosphere from the outside into the inside 1a of the body 1 is formed. Since the external opening end 12a is located on the side opposite to the mounting substrate 8, foreign matter such as solder flux during soldering is different from the conventional case where the atmosphere introducing hole is provided in the cover.
The pressure sensor chip 2 is not corroded by entering the inside 1a of the body 1 through the air introduction hole 12b, the life of the pressure sensor chip 2 can be extended, and foreign matter does not clog the air introduction hole 12b.

If the pressure sensor chip 2 and the printed circuit board 3 are wire-bonded and then the surface of the printed circuit board 3 is covered with the silicon gel 7, the air introduction hole 12b is formed by the cylindrical air introduction tube 12 and printed. Board 3
Since it protrudes from the surface, the silicon gel 7 is applied to the printed circuit board 3 without difficulty by entering the air introduction hole 12b, and the wire bonding portion and the circuit formed on the printed circuit board 3 enter the inside 1a of the body 1. You can protect it from moisture.

Further, the air introducing hole 12b formed in a cylindrical shape.
Is integrally formed with the body 1, the air introduction hole 12
No new tubular part is required to obtain b, and the cost can be reduced.

In the first embodiment, the air introduction hole 12
Although b is formed by the cylindrical air introduction tube 12, the outer opening end 12a may be a hole provided in the body 1 located on the opposite side of the body 1 from the mounting substrate 8, and is not limited.

A second embodiment of the present invention will be described below with reference to FIG. In the second embodiment, the functions different from those in the first embodiment will be described, and the members having substantially the same functions as those in the first embodiment are designated by the same reference numerals.

The printed circuit board 3 is mounted on the body 1 with auxiliary terminals 3f made of metal and having a substantially L shape and having protruding pieces provided at four corners. At this time, the protruding piece of the auxiliary terminal 3f comes into contact with the protruding piece 41a of the internal terminal 41, and is joined by laser welding at the abutting portion to electrically connect the printed board 3 and the terminal 4, and The body 1 and the printed circuit board 3 are fixed.

In the pressure sensor of the second embodiment, as described above, the printed circuit board 3 is provided with the auxiliary terminal 3f, abuts on the internal terminal 41, and is joined and fixed by the abutting portion. Since the circuit of the printed circuit board 3 and the terminal 4 are electrically connected and the heating part at the time of bonding is localized, the body 1 and the printed circuit board 3 can be shortened without increasing the temperature of the printed circuit board 3. By fixing the time, the circuit formed on the printed circuit board 3 and the mounted element 3e can be protected from thermal damage.

[0028]

According to the first aspect of the present invention, when the terminals are mounted on the mounting board, the outer opening end 12a of the air introduction hole provided in the body is located on the side opposite to the mounting board 8. Unlike the conventional method in which foreign matter such as solder flux penetrates the inside of the body through the air introduction hole and does not corrode the pressure sensor chip unlike the conventional case where the air introduction hole is provided in the cover, the life of the pressure sensor chip can be extended. Also, foreign matter does not block the air introduction hole.

According to a second aspect of the present invention, in addition to the effect of the first aspect, when the pressure sensor chip and the printed circuit board are wire-bonded to each other and the printed circuit board surface is covered with silicon gel, the air introduction hole is formed. Since it is formed in a cylindrical shape and protrudes from the surface of the printed circuit board, silicon gel is applied to the printed circuit board without difficulty by entering the air introduction hole, so that the wire bonding portion and the circuit formed on the printed circuit board can be formed inside the body. Protects against moisture that has penetrated into.

According to the third aspect, in addition to the effect of the second aspect, since the cylindrical air introduction hole is integrally formed with the body, a tubular shape for obtaining the air introduction hole is provided. Costs can be reduced without the need for new parts.

According to a fourth aspect of the present invention, in addition to the effect of the first aspect, an auxiliary terminal is provided on the printed circuit board, and the auxiliary terminal is brought into contact with the terminal to be joined and fixed at the contact portion. By electrically connecting the circuit and the terminal,
Moreover, since the heating part at the time of bonding is localized, the body and the printed circuit board are fixed in a short time without raising the temperature of the printed circuit board, and the circuit formed on the printed circuit board and the mounted elements are heated. Can protect from obstacles.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a first embodiment of the present invention.

FIG. 2 is a front view of the same.

FIG. 3 is a perspective view of the same.

FIG. 4 is a perspective view showing a second embodiment of the present invention.

FIG. 5 is a side sectional view showing a conventional example.

[Explanation of symbols]

 1 body 1a internal 11 pressure introduction pipe 11a pressure introduction pipe end face 11b inflow hole 12a external opening end 12b atmosphere introduction hole 2 pressure sensor chip 3 printed circuit board 3f auxiliary terminal 4 terminal 5 wire 6 cover 7 silicon gel 8 mounting substrate

Claims (4)

[Claims] 1. A resin body having a cover provided thereon,
A pressure introducing pipe that communicates the inside and outside of the body with the fluid to be measured flowing in, a pressure sensor chip that is tightly fixed inside the body to the end surface of the pressure introducing pipe and converts pressure into an electric signal, and A printed circuit board mounted and connected to the pressure sensor chip by wire bonding;
A terminal connected to the printed circuit board and led out to the outside of the body, and an atmosphere introduction hole for introducing the atmosphere into the body from the outer opening end are mounted on the mounting board, and the pressure of the fluid and the atmosphere. In the pressure sensor for measuring the pressure of the fluid based on the differential pressure, the atmosphere introducing hole is provided in the body so that the outer opening end is located on the side opposite to the mounting substrate with respect to the body. Characteristic pressure sensor. 2. The pressure sensor according to claim 1, wherein the printed circuit board is covered with silicon gel, and the air introduction hole is formed in a cylindrical shape and protrudes from the surface of the printed circuit board. 3. The pressure sensor according to claim 2, wherein the atmosphere introducing hole is formed integrally with the body. 4. The pressure sensor according to claim 1, wherein an auxiliary terminal that is brought into contact with and fixed to the terminal is provided on the printed circuit board.