JPH0654273B2 - Pressure sensor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure sensor, and more particularly to a PCB on-board mountable on a printed circuit board (PCB) using a CAN-sealed semiconductor pressure converter. Type pressure sensor.

[Conventional technology]

Conventionally, as a semiconductor pressure converter having a reference pressure chamber, a method is known in which a reference pressure chamber is formed between a recess on the back surface side of a silicon gauge chip and a pedestal, and is suitable for PCB on-board use. However, this method has a drawback that sufficient reliability cannot be obtained for liquids. Therefore, in order to improve the liquid resistance, various methods have been proposed in which a reference pressure chamber is formed on the surface side of the silicon gauge chip by CAN sealing.

FIG. 3 shows P using a semiconductor pressure transducer of CAN sealing type.
It is sectional drawing for demonstrating the prior art example of a CB on-board type pressure sensor.

In the figure, a piezoresistive element is formed on the front surface of a silicon gauge chip 1 and a recess is formed on the back surface, and the silicon gauge chip 1 is joined to a pedestal 2 made of glass having a through hole. The pedestal 2 is bonded in the recess of the pressure introducing pipe 3 with solder 5, and the pressure introducing pipe 3 is integrated with the metal stem 4 by means such as welding. A lead pin 6 is hermetically sealed by a glass 7 on the metal stem 4, and the lead pin 6 is connected to an input / output terminal of a piezoresistive element of the silicon gauge chip 1 via a thin metal wire 8. A vacuum reference pressure chamber 10 is formed by fixing the cap 9 to the metal stem 4 by covering the silicon gauge chip 1 and introducing pressure into the suction hole 12 of the pressure introduction port 11 made of polybutylene terephthalate resin. By inserting the pipe 3 and adhering the port 11 to the metal stem 4 via the silicone adhesive 13, a CAN-sealed semiconductor pressure converter is formed.

On the other hand, the cap 9 is attached to the thick film circuit board 1 via the adhesive 14.
5, the CAN-sealed semiconductor pressure transducer is mechanically connected to the thick film circuit board 15. Further, the semiconductor pressure transducer and the thick film circuit board 15 are electrically connected by welding the lead pin 6 to the welding pad 16 on the thick film circuit board 15. The thick film circuit board 15 is provided with a drive circuit and an amplifier circuit for the piezoresistive element of the silicon gauge chip 1, and a plurality of lead pins 17 for connecting to a PCB which is an external circuit. There is.

In the above-mentioned pressure sensor, since the silicon-based adhesive 13 relaxes the thermal stress caused by the difference in thermal expansion coefficient between the metal stem 4 and the pressure introduction port 11 made of resin, cracking or peeling when the temperature condition changes. Is prevented. Also, CAN
Since the cap 9 side of the sealed semiconductor pressure transducer is joined to the thick film circuit board 15, the metal stem 4
It is considered to be suitable as a PCB on-board type pressure sensor that has a large degree of freedom in the shape of the pressure introduction port 11 attached to the board and is highly liquid resistant.

In addition, as for the device related to this kind of device,
No. 0-15643 is mentioned.

[Problems to be solved by the invention]

By the way, such a PCB on-board type pressure sensor is often used for measuring the intake pressure of an automobile engine, but in that case, the medium to be measured contains a corrosive substance such as gasoline. However, in the above-mentioned conventional technique, since the silicon-based adhesive 13 having the function of relieving thermal stress has gasoline permeability, the silicone-based adhesive 13 permeates the silicon-based adhesive 13 to allow gasoline to deposit on the thick film circuit board 15 and the PCB. Leakage may occur, and as a result, octenoic acid contained in gasoline may act on various electronic components and solder connection parts to generate corrosive substances, which may cause problems such as poor conduction.

Therefore, it is an object of the present invention to provide a PCB that has good liquid resistance and corrosion resistance and does not lose reliability even when the medium to be measured contains a corrosive substance such as gasoline.
An object is to provide an onboard pressure sensor.

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention joins the cap side of a CAN-sealed semiconductor pressure transducer to a thick film circuit board, and the pressure introduction pipe of the semiconductor pressure transducer is inserted into a pressure introduction port, In a PCB on-board type pressure sensor in which the port is joined to a metal stem integral with a pressure introducing pipe, an annular groove is formed in an outer wall of the pressure introducing pipe, and an O ring is attached to the annular groove. Was brought into close contact with the inner wall of the pressure introducing port.

[Action]

That is, according to the present invention, the inner wall of the pressure introducing port for guiding the medium to be measured to the silicon gauge chip and the outer wall of the pressure introducing pipe inserted into the port are hermetically sealed by the O-ring. Therefore, there is no risk that corrosive substances such as gasoline contained in the medium to be measured will leak onto the thick film circuit board or PCB.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a pressure sensor according to an embodiment of the present invention,
FIG. 2 is a plan view thereof, and portions corresponding to those in FIG. 3 are designated by the same reference numerals.

In FIGS. 1 and 2, a piezoresistive element is formed on the front surface of the silicon gauge chip 1 by diffusion or the like and a thinned recess is formed on the back surface by etching or the like. The silicon gauge chip 1 has through-holes. And has a coefficient of thermal expansion substantially equal to that of silicon and is bonded to the pedestal 2 made of Pyrex glass by the anodic bonding method. The pedestal 2 is inserted into the recess of the pressure introducing pipe 3 made of Fe-Ni alloy and adhered with the solder 5, and before the soldering, the glass bonding surface of the pedestal 2 is covered with Ti-Pt.
-Metalized with Au. However, when a silicon pedestal is used, a plating treatment such as Ni-Au is performed in advance. An annular groove 20 is formed on the upper outer wall of the pressure introducing pipe 3, and when the pressure introducing pipe 3 is inserted into the suction hole 12 of the pressure introducing port 11, which will be described later, the annular groove 20 is made of a fluorine-based material. The O-ring 21 is attached. Further, the pressure introducing pipe 3 is integrated with a metallic stem 4 made of Fe by means such as welding, and a lead pin 6 is hermetically sealed by glass 7 on the metallic stem 4, and the lead pin 6 is made of a fine gold wire. It is connected via 8 to the input / output terminals of the piezoresistive element of the silicon gauge chip 1. Further, by performing ring projection welding in a vacuum, the cap 9 made of Fe is fixed to the metal stem 4 by covering the silicon gauge chip 1, and the vacuum reference pressure chamber 10 is formed on the surface side of the silicon gauge chip 1. To do. The pressure introducing port 11 made of polybutylene terephthalate resin, into which the pressure introducing pipe 3 is inserted, has a silicone adhesive 13
It is adhered to the metal stem 4 via
An O-ring 21 hermetically seals a gap between the inner wall of the pressure guide pipe 3 and the outer wall of the pressure introducing pipe 3.

In the CAN-sealed semiconductor pressure converter described above, the cap 9 side is provided with the thick film circuit board 1 via the silicon adhesive 14.
The lead pin 6 is mechanically and electrically connected to the thick film circuit board 15 by being bonded to the thick film circuit board 5 and being welded to the welding pad 16. The thick film circuit board 15 has lead terminals 1 for PCB connection.
7 and I as a driving circuit and an amplifying circuit for the piezoresistive element
A C package 18 is provided.

Such a pressure sensor is a PC of the control unit.
In addition to the advantage that it can be mounted on B as it is and the degree of freedom of the shape of the pressure introducing port 11 attached to the metal stem 4 is large, the sealing effect of the O-ring 21 prevents leakage of corrosive substances such as gasoline. Therefore, it has a high practical value as a PCB on-board type pressure sensor having excellent liquid resistance and corrosion resistance. That is, when the intake pressure of an automobile engine is measured using this pressure sensor, the cylinder gauge chip 1 is passed through the intake hole 12 of the pressure introduction port 11.
The medium to be measured, which is guided to, contains a corrosive substance such as gasoline, and the corrosive substance is used as the silicone adhesive 13
When it reaches the temperature, it leaks onto the thick film circuit board 15 and the PCB to cause a defect such as conduction failure. However, as in the present embodiment, the O-ring 2 is used as the flow path leading to the silicon adhesive 13.
If you seal with 1, you do not have to worry. Therefore, a polybutylene terephthalate resin having a wide operating temperature range is used as the pressure introducing port 11, and a silicon-based adhesive is used to alleviate thermal stress caused by the difference in thermal expansion coefficient between the port 11 and the metal stem 4. Even with the use of No. 13, a highly reliable PCB on-board type pressure sensor is realized without the possibility of interfering with the intake pressure measurement of the automobile engine as in the conventional example.

When the cap 9 and the thick film circuit board 15 are joined by solder instead of the adhesive 14, they can be joined at the same time when components are mounted on the thick film circuit board 15 and reflowed. The process can be simplified.

〔The invention's effect〕

As described above, the cap side of the CAN-sealed semiconductor pressure transducer is bonded to the thick film circuit board, and the inner wall of the pressure introducing port for guiding the medium to be measured to the silicon gauge chip and the pressure inserted in the port. According to the present invention in which the gap between the outer wall of the introduction pipe and the outer wall is hermetically sealed with an O-ring, even if a corrosive substance such as gasoline is contained in the medium to be measured, it may leak onto the thick film circuit board or PCB. Since this is not the case, it is suitable for measuring the intake pressure of an automobile engine, and it is possible to provide a highly reliable PCB on-board type pressure sensor that is rich in liquid resistance and corrosion resistance.

[Brief description of drawings]

FIG. 1 is a sectional view of a pressure sensor according to an embodiment of the present invention,
FIG. 2 is a plan view thereof, and FIG. 3 is a sectional view showing a conventional example. 1 ... Silicon gauge chip, 2 ... Pedestal, 3 ... Pressure introducing pipe, 4 ... Metal stem, 6 ... Lead pin, 9
...... Cap, 10 ...... Standard pressure chamber, 11 ...... Pressure introducing port, 15 ...... Thick film circuit board, 17 ...... PCB connection lead pin, 20 ...... annular groove, 21 ...... O ring.

Claims (2)

[Claims] 1. A silicon gauge chip having a piezoresistive element formed on its surface is joined to a pedestal having a through hole, the pedestal is inserted and fixed to a pressure introducing pipe, and the pressure introducing pipe is integrated with a metal stem. A lead pin held by a metal stem is connected to an input / output terminal of the piezoresistive element, and a CAN seal type in which a reference pressure chamber is formed on the surface side of the silicon gauge chip by fixing a cap to the metal stem. A semiconductor pressure converter and a thick film circuit board having a lead pin for connecting the drive circuit and the printed circuit board of the piezoresistive element, the cap side of the semiconductor pressure converter is bonded to the thick film circuit board, The pressure introducing pipe is inserted into a pressure introducing port, and the port is joined to the metal stem. A pressure sensor, characterized in that the O-ring is attached to the annular groove to form an annular groove in the outer wall, and the O-ring is adhered to the inner wall of the pressure introduction ports. 2. The pressure sensor according to claim 1, wherein the pressure introducing port is made of polybutylene terephthalate resin.