JPS62226031A - Pressure sensor unit - Google Patents

Abstract

PURPOSE:To expand a utilization range of a pressure sensor unit for micropressure being below the atmospheric pressure, by sealing airtightly a package opening part by a sheet-shape diaphragm. CONSTITUTION:An opening part 31 of a package 3 is sealed airtightly by a sheet-shaped waveform diaphragm 4. Accordingly, electrical and mechanical protections of the surface of a pressure sensor chip 1 are executed by the sheet- shaped diaphragm 4. In such a state, a measurement can be executed in the atmosphere such as air containing moisture or corrosive gas, and in a liquid such as water, etc., and a utilization range of a pressure sensor unit for micropressure being below the atmospheric pressure can be expanded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to the structure of a pressure sensor unit that converts pressure into an electrical signal by using the piezoresistance effect of a semiconductor diffused resistor, and is particularly suitable for use in micro-pressure applications below atmospheric pressure. The present invention relates to a pressure sensor unit.

[Conventional technology]

In recent years, with the development of IC manufacturing technology, pressure sensor units have been manufactured that have a diaphragm type semiconductor pressure sensor chip that forms a semiconductor diffused resistor on the surface of a single crystal silicon chip and uses the semiconductor diffused resistor as a strain gauge. Became.

The pressure sensor unit utilizes the piezoresistance effect, in which electrical resistance changes due to the stress of an external force applied to a conductor or semiconductor, and by configuring the strain gauge in a bridge type circuit, pressure changes are converted into electrical resistance. This device attempts to convert this into a voltage change and then capture this as a voltage change in a bridge type circuit, and its performance is much superior to that of conventional pressure gauges or pressure-electric transducers, so it is widely used for industrial measurement and consumer use. Use and demand are increasing.

FIG. 4 is a sectional view showing the structure of the pressure sensor unit as described above, and shows the structure of a conventional pressure sensor unit.

41 is a diaphragm-type semiconductor pressure sensor chip that converts pressure into an electrical signal by using the piezoresistance effect of semiconductor diffused resistance, and 42 is a pedestal, such as +7740 borosilicate glass (registered trademark Pyrex glass), which is a pressure sensor chip. Since the pressure sensor chip 41 is designed to easily feel stress, a material with a small difference in coefficient of thermal expansion from the pressure sensor chip 41 is selected for the pedestal 42. The pressure sensor chip 41 and the pedestal 42 are airtightly fixed by a fixing method that does not cause any generation. 46 is the pressure sensor chip 4.
1 is a pressure introduction pipe provided with an atmosphere introduction path 43a for directly exposing one side 41a of the pressure medium to the atmosphere (for example, air, N2 gas, etc.) serving as a measurement pressure medium; 44 is an airtight terminal body;
The pressure introduction pipe 46 is brazed and fixed to the airtight terminal body 44. A stem 45 serves as a power supply terminal and an output terminal of the pressure sensor chip 41, and the stem 45 is hermetically fixed to the airtight terminal body 44 using a sealing glass 46.

The airtight terminal body 44 with the pressure introduction pipe 46 and stem 45 fixed together as described above, and the pedestal 42 with the pressure sensor chip 41 fixed thereto are made to have a low profile so as not to cause distortion during bonding. The pressure sensor chip 4 is hermetically fixed with melting point glass, silicone rubber, etc.
1 and the stem 45 are electrically connected by wire bonding.

47 is a sealed tube, and after the airtight terminal body 44 and the pedestal 42 are fixed, the other surface 4Ib of the pressure sensor chip 41 is sealed.
The pressure sensor unit 40 is hermetically fixed to the airtight terminal body 44 with solder or the like in a vacuum so that the side thereof is in a vacuum, thereby forming an absolute pressure type pressure sensor unit 40. In addition, relative pressure (differential pressure)
When constructing a type pressure sensor unit, the sealing tube 4
7 is used with holes.

[Problem that the invention seeks to solve]

The advantages of the conventional pressure sensor unit 40 as described above are that it can be lowered in price, higher in reliability, and higher in performance.As can be seen from its structure, the pressure sensor chip 41 is Since it is always directly exposed to the atmosphere that is the measurement pressure medium through the atmosphere introduction path 43a of the pipe 46, it has the disadvantage that the atmosphere that is the measurement pressure medium must be limited to water-free air such as water vapor or non-corrosive gas. There is.

In particular, in pressure sensor units that detect minute pressures below atmospheric pressure, the detected pressure value itself is very small.
The detection capability must be improved by direct exposure to the atmosphere, and the atmosphere has the drawback of being limited to moisture-free air such as water vapor or non-corrosive gas.

Regarding the influence of moisture, for example, the pressure introduction pipe 46
If we consider the case where moisture intrudes from the atmosphere introduction path 43a, it is strange.

If water droplets are placed on the pressure sensor chip 41, not only will the sensitivity change depending on the load on the pressure sensor tip 41, but the water droplets will also cause leakage current from the pressure sensor chip 41, making it impossible to perform accurate measurements.

Furthermore, if water droplets form on the diffusion resistance side of the pressure sensor chip 41, a short circuit may occur between the pads, a local battery may be formed in the wire bonded area, and the aluminum layer may eventually be destroyed. Therefore, correct measurement is impossible.

As is clear from the above, the conventional pressure sensor UniSoto for measuring micro-pressure has the drawback that it cannot measure corrosive gas pressure or liquid pressure, and its range of use is limited.

SUMMARY OF THE INVENTION An object of the present invention is to expand the range of use of a pressure sensor unit that operates at very low pressures below atmospheric pressure.

[Means for Solving the Problems] In order to achieve the above object, the present invention has the following configuration. That is, a package having an opening;
In a pressure sensor unit having a pressure sensor chip fixed to the bottom of the package, the opening of the package is hermetically sealed with a sheet-like diaphragm.

〔Example〕

Embodiments of the present invention will be described in detail below based on the drawings.

FIG. 1 is a sectional view of a pressure sensor unit showing one embodiment of the invention, and FIGS. 2 and 3 are sectional views showing other embodiments of the invention. Note that the same numbers in the drawings indicate the same members, and their explanations will be omitted.

1 is a diaphragm-type semiconductor pressure sensor chip that converts pressure into an electrical signal using the piezoresistance effect of semiconductor diffused resistance; 2 is a pedestal; for example, it is made of #7740 borosilicate glass; the pressure sensor chip 1 is connected to the pedestal 2 It is attached tightly to the top. A package 6 has an opening 31 and is made of an insulating material such as ceramics, and the base 2 is fixed to the bottom 62 of the package B. 6a,
3b is a pattern provided on package B, and patterns 6a and 6b are connected by an embedded through hole, although not shown. That is, by wire-bonding a pad (not shown) formed on the pressure sensor chip 1 to the pattern 3a, the lower surface 36 of the package B is provided to transmit and receive electrical signals to and from the pressure sensor chip 1 inside the package 3. pattern 3b
It is structured so that it can be performed from Reference numeral 4 denotes a sheet-like corrugated diaphragm, which in this embodiment is made of rubber-like resin and is easily deformed by slight pressure below atmospheric pressure. is fixed to. In other words, the opening 6 of package B
1 is hermetically sealed with a sheet-like corrugated diaphragm 4,
The structure is such that the surface of the pressure sensor chip 1 is electrically and mechanically protected by a sheet-like corrugated diaphragm 4.

In this way, the pressure sensor unit 10 is configured.

In the pressure sensor unit 10 shown in FIG. 1, even if a small pressure below atmospheric pressure is applied to the sheet-like corrugated diaphragm 4, the sheet-like corrugated diaphragm 4 deforms, and the air hermetically sealed in the package 6 or The structure is such that pressure is applied to the pressure sensor chip 1 using a gas such as nitrogen gas as a medium.

However, due to its structure, it is susceptible to the expansion and contraction of gas due to temperature changes (it is used in environments with relatively little temperature fluctuation).

On the other hand, the pressure sensor unit) 20 and the third
The pressure sensor unit 60 shown in the figure has a structure that improves the influence of the above-mentioned temperature change. That is, 5 is a gel-like resin, for example, gel-like silicone rubber, and 6 is silicone oil. After the pressure sensor chip 1 and the package 3 are electrically connected by wire bonding,
A space surrounded by a sheet-like corrugated diaphragm 4 and a package 6 is filled. The gel-like resin 5 or silicone oil 6 has very low pressure loss, excellent heat and cold resistance, and has a smaller coefficient of thermal expansion than gas, so the space surrounded by the sheet-like corrugated diaphragm 4 and the package 3 gel-like resin 5 or silicone oil 6
Excellent pressure sensor unit by filling with 20.
It is configured to 30.

In this embodiment, a rubber-like resin was used as the sheet-shaped corrugated diaphragm 4, but of course, the sheet-shaped corrugated diaphragm could also be made of a thin metal material that easily deforms in a micro-pressure trap below atmospheric pressure. It may be formed. The metallic corrugated diaphragm can be fixed to the package 6 by brazing, etc., and has excellent corrosion resistance, so it is selected depending on the pressure range and environment in which it will be used.

〔Effect of the invention〕

As is clear from the above embodiments, according to the present invention, the opening 61 of the package B is hermetically sealed with the sheet-like corrugated diaphragm 4, so that the surface of the pressure sensor chip 1 is electrically and mechanically protected. It is now possible to perform measurements using a sheet-like corrugated diaphragm 4, making it possible to measure in atmospheres such as air containing moisture or corrosive gases, and in liquids such as water. This has the effect of expanding the scope of use.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a pressure sensor unit showing one embodiment of the present invention, Figs. 2 and 3 are sectional views showing other embodiments of the invention, and Fig. 4 is a sectional view of a conventional pressure sensor unit. It is a diagram. 1.41...Pressure sensor chip, 3...
・Package, 4... Sheet-like corrugated diaphragm, 61...
····Aperture. Figure 1 Figure 2

Claims (3)

[Claims] (1) A pressure sensor unit having a package having an opening and a pressure sensor chip fixed to the bottom of the package, characterized in that the opening of the package is hermetically sealed with a sheet-like corrugated diaphragm. Pressure sensor unit. (2) The pressure sensor unit according to claim 1, wherein the space surrounded by the sheet-like corrugated diaphragm and the package is filled with gel-like resin. (3) The pressure sensor unit according to claim 1, wherein the space surrounded by the sheet-like corrugated diaphragm and the package is filled with silicone oil.