JPS6029628A - Semiconductor type pressure sensor - Google Patents

Abstract

PURPOSE:To hold with a high accuracy a measuring function of an external pressure, to simplify a structure, and to execute easily an assembly by forming a bottom plate of a vessel by a metal whose coefficient of thermal expansion is approximate to that of a ceramic substrate, and sticking the ceramic substrate to the bottom plate by means of brazing. CONSTITUTION:A ceramic substrate 9 has a coefficient of thermal expansion which is approximate to that of a stem 16, so that it is stuck directly to the latter, and as for a metal of the stem 16, for instance, an iron and nickel alloy is formed to an optimum composition and used, by which a distortion caused by a thermal stress is extremely small, and it neither occurs that a coefficient of correction of a circuit on the ceramic substrate 9 is varied nor that the ceramic substrate 9 peels off from the stem 16.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention forms a reference pressure chamber by a metal container and a semiconductor pressure-sensitive diaphragm, and furthermore, an outer pressure chamber is connected to a strain gauge of the diaphragm on the reference pressure chamber side of the bottom plate of the metal container. This invention relates to a semiconductor pressure top 1 in which a ceramic substrate equipped with a circuit for measuring the pressure of liquid or gas is sealed and sealed in the same container.

[Prior art and its problems]

Such a pressure sensor has already been filed by the applicant (Japanese Patent Application No. 57-29296). The present invention is a further improvement thereof.

FIG. 1 shows an example of a conventional pressure sensor, in which a metal package consisting of a metal cap 1 and a metal stem (bottom plate) 2 such as those used for semiconductor devices, such as a product equivalent to MD18, is used as a container for the sensor.

However, the stem 2 has an opening 3 in the center and the pipe 7
, and the pressure conduction size type 7 is
4. The stem 2 is supported via a metal cap 8.

A ceramic substrate 9 is bonded by brazing or the like to the upper surface of the stem 2 made of inexpensive iron on the inner space 10 side, surrounding the pressure-sensitive diaphragm 6, via a support 11 made of an iron-nickel alloy or the like. The support plate 11 is the stem 2
For example, it is locally joined only with soft solder 12 at a portion close to the opening 3.

Although not shown, an operational amplifier chip, a diode chip, etc. are mounted on the ceramic substrate 9 via a thick film circuit to form an amplification and adjustment circuit, and the bridge of the strain gauge formed on the pressure-sensitive diaphragm 6 is connected to the ceramic substrate 9. They are connected by bonding a thin conducting wire 13 to measure external pressure.

Furthermore, the output side of the adjustment and amplification circuit is connected by wire bonding of a thin conductor 15 similarly to the post 14 which is insulated from the stem 2 by a hermetic seal, so that the output side of the output side of the adjustment and amplification circuit is connected to the post 14 by wire bonding of a thin conductor 15. Sensor output can be taken out to an external device.

This sensor output depends on the difference between the measured pressure guided from the pressure pipe 7 to one side of the pressure sensitive diaphragm 6 through the through hole 5 of the pedestal 4 and the pressure in the reference pressure chamber 10 inside the cap 1. , the sensor output level can be adjusted by adjusting the pressure in the reference pressure chamber 10.

This adjustment adjusts the sensor output level by adjusting the helium or helium-containing inert gas introduced through the insertion pipe 17 for the purpose of protecting the pressure-sensitive diaphragm in the container, the thick film circuit on the ceramic substrate, or the semiconductor chip and checking the airtightness. This is done by stopping the process when the value reaches a specified value and sealing off the enclosing pipe 17.

However, in such a pressure sensor, the ceramic substrate 9 is locally coupled to the stem 2 via the support plate 11, so the method for fixing the ceramic substrate 9 is complicated, the number of parts is large, and the assembly process is complicated. The process was complicated and the yield was sometimes poor.

[Purpose of the invention]

In view of these points, it is an object of the present invention to provide an inexpensive pressure sensor having a simple structure and easy assembly while maintaining a highly accurate external pressure measurement function in the semiconductor pressure sensor. shall be.

[Key points of the invention]

In the present invention, in the semiconductor sensor, the bottom plate of the container is formed of a metal whose coefficient of thermal expansion is similar to that of the ceramic substrate, and the ceramic substrate is fixed to the bottom plate by brazing.

[Embodiments of the invention]

An embodiment of the present invention will be described with reference to the drawings.

Parts that are the same as those in Figure 1 are given the same reference numerals.

In FIG. 2, the ceramic substrates 9 are directly fixed to the stem 16 and have similar thermal expansion coefficients. For example, the thermal expansion coefficient of the ceramic substrate 9 is 7×
As the metal for the stem 16, which has a coefficient of thermal expansion close to 1O, if an iron-nickel alloy is formed into an optimal composition using known technology, distortion due to thermal stress will be extremely small, and the ceramic substrate will be This is most desirable because it prevents the correction coefficient of the circuit on the stem 9 from fluctuating and further prevents the ceramic substrate 9 from peeling off from the stem 16.

The configuration of other parts is exactly the same as that in FIG. 1, so explanations will be omitted.

〔Effect of the invention〕

As described above, the present invention provides a circuit board that has a coefficient of thermal expansion similar to that of a semiconductor pressure-sensitive diaphragm so as to prevent thermal stress distortion caused by temperature fluctuations from occurring in the circuit board sealed in the same container as the semiconductor pressure-sensitive diaphragm. Since the pressure sensor is directly brazed to the stem made of a metal material (metallic force), it is possible to reduce the occurrence of stress and strain, that is, to reduce measurement errors, and to obtain an extremely high-precision semiconductor pressure sensor.

Moreover, at the same time, there are fewer components and it is easier to assemble.
Therefore, since it is inexpensive, the effect in terms of productivity is very large.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a conventional semiconductor pressure sensor, and FIG. 2 is a cross-sectional view of an embodiment of the semiconductor pressure sensor according to the present invention.

Claims (1)

[Scope of Claims] 1) A semiconductor pressure-sensitive diaphragm that introduces external pressure into the bottom plate of a metal container whose internal space forms a reference pressure chamber, on a surface opposite to a surface in contact with the reference pressure chamber; A circuit board connected to the strain gauge of the diaphragm to measure external pressure is fixed, and the circuit board is a metal bottom plate having a coefficient of thermal expansion approximate to that of the circuit board built around the reference pressure chamber. A semiconductor pressure sensor characterized by being fixed to a. 2. In the pressure sensor according to claim 1,
A semiconductor pressure sensor characterized by using an iron-nickel alloy as a metal bottom plate having a thermal expansion coefficient close to that of a circuit board.