KR20120119556A - A thick film type pressure measuring sensor and manufacturing method of pressure measuring sensor - Google Patents

Abstract

PURPOSE: A thick-film pressure measuring sensor with a metal diaphragm and a method for manufacturing the same are provided to form an insulating film or a protective film or a sensing film on a diaphragm so that a high yield rate and low costs can be possible through mass production. CONSTITUTION: A method for a thick-film pressure measuring sensor with a metal diaphragm(1) is as follows. A metal diaphragm taking a role of a pressure receiving unit is formed in the upper part of a sensor by treating stainless steel. An electronic insulation film in which a ceramic paste is spread is formed in the upper part of the diaphragm. A pressure sensing film and a laser trimming unit are formed on the electronic insulation film. Electrode patterns are formed on the pressure sensing film. An upper protective film and an electrode unit are formed on the electrode patterns.

Description

Thick film type pressure measuring sensor having a metal diaphragm and a manufacturing method of the pressure measuring sensor {A thick film type pressure measuring sensor and manufacturing method of pressure measuring sensor}

The present invention relates to a thick-film type pressure measuring sensor having a metal diaphragm and a manufacturing method of the pressure measuring sensor, and more specifically, a stainless steel is processed to form a diaphragm acting as a hydraulic part on an upper portion thereof. An electrical insulating layer coated with a ceramic paste is formed on the diaphragm, a pressure sensing film made of a metal oxide having a dielectric property and a laser trimming part are formed on the electrical insulating layer, and an electrode pattern is formed on the pressure sensing film. It is manufactured in such a way that the upper protective film coated with the glass paste on the electrode pattern and the electrode part are formed, and the overall heat resistance is higher than the existing thin film type pressure measuring sensor during the design process, and mass production and low price are possible by using the technology of the thick film process. Metal dies with low temperature resistance coefficient and high pressure sensitivity The present invention relates to a diaphragm type pressure measuring sensor having excellent durability, safety and reproducibility, and a method of manufacturing the pressure measuring sensor.

The conventional method of manufacturing a strain gauge pressure sensor is made by sanding a flat metal sheet to roughen the surface, and attaching a film strain gauge using an adhesive thereon, and a film type strain gauge is formed on a polyimide film. The foil gauge is patterned into a thick film using a screen printer, or it is manufactured by a pattern process by pasting it through a laminating process.

Such a strain gauge pressure sensor used in the related art is used by attaching a foil gauge on a metal diaphragm or by processing a thin film of silicon made of polysilicon. Since the adhesive is used when the foil gauge is attached, there is a problem that the creep phenomenon occurs, there is a measurement deviation and the stability is not excellent.

In the conventional strain gauge type pressure measuring sensor, the sensitivity of the gauge is expressed by a gauge factor G. This means that when the resistance change rate of the gauge is ΔR / R and the strain is Δl / l, G = (ΔR / R ) / (Δl / l), and in such a conventional strain gauge pressure sensor, Δl / l changes predominantly, and assuming that the volume change rate of the resistor and the change rate of the resistivity are equal, G is about 2 In the case of a thin film resistor used as a sensing film, a metal or a metal alloy is used, and generally, a gauge ratio (2.0) is low and a specific resistance is low.

1 is a cross-sectional view of a metal diaphragm-type pressure measuring sensor using a ready-made thin film, and a diaphragm 1 vibrating according to pressure is formed on an upper portion of a stainless body, and an upper portion of the diaphragm 1 is formed. The insulating layer 2 is formed by the vapor deposition method. The insulating layer 2 is formed by vapor deposition for electrical insulation between the metal diaphragm 1 and the pressure sensing film 3 described later. Pressure sensing film (3) for sensing the pressure to change the resistance is designed in a thin film type 0.4 ~ 1.0㎛ position the stress increase, the stress reducing portion. In this case, metal oxides and metal alloys manufactured in the form of thin films are used. Since the specific resistance is small, the target resistance is formed by fine patterning in a large area. The resistance of the pattern and the electrode are integrally single patterned, and the upper protective film 5 is formed by vacuum deposition in order to prevent external physical and chemical shock and damage, and then the pressure sensor output is transmitted to the outside. According to this, the electrode part 4 is designed separately from a material such as nickel, gold, silver, platinum, and the like, and is formed by a plating or vapor deposition method. There is a problem in that miniaturization is difficult due to space constraints in such a patterned fabrication.

2 is a plan view of a metal diaphragm using the thin film. The pressure sensing film 3 has a structure in which an electrode pattern and one electrode part 4 are formed at the same time, and the pressure sensing film 3 is made of four resistors. The pressure sensing film 3 is manufactured in a fine patterned form because it is necessary to form the maximum high resistance within the stress change portion required as the low resistivity sensing film. The resistance of the pattern is complicated, and there is a problem in that expensive equipment having high technical performance and high performance is required to reproduce the thin film in an etching process at a minute portion.

As such, in the case of a pressure measuring sensor integrated in a metal diaphragm using a thin film, the process equipment for forming a thin film is expensive and must be manufactured with high vacuum, and it is difficult to pattern with a mass production equipment generalized to semiconductor processing equipment as a three-dimensional structure. There was a problem.

An object of the present invention is to solve this problem, and has the advantage of a metal diaphragm, without using the existing pressure-sensitive dual pressure sensor in the use of pressure sensor creep phenomenon and cracking of the mounting surface without the error of measurement It is designed to manufacture the pressure sensor that is integrated so that it is excellent, and to improve the sensitivity to pressure, which is a problem in the existing metal thin film, and to manufacture the high resistance material to obtain the impedance value required for the low resistance sensing film. Manufacture of thick film type pressure measuring sensor and pressure measuring sensor equipped with metal diaphragm that can solve these problems by solving the limitations and eliminating the need for investment of equipment and developing mass production of three-dimensional structure. To provide a way.

This object of the present invention is to form a surface within the surface roughness of 0.1㎛, flatness within 1㎛ by lapping the surface, the high temperature atmosphere heat treatment to control the partial pressure of nitrogen and oxygen to form a diaphragm and an oxide layer and a nitride layer of the surface and An insulating film formed of a thickness of 3 to 8 탆 integrally by screen printing and tape-casting an electrical insulating film such as a silicon oxide film, an aluminum oxide film, and a magnesium oxide film as a thick film on the diaphragm; and a ceramic oxide on the insulating film. After forming a thick film of 3 ~ 8㎛ thick, the pressure sensing film printed with a paste, which is a metal oxide of ruthenium oxide (RhO2), zinc oxide (ZnO2), zirconium oxide (ZrO2), and can reduce the resistance deviation on the pressure sensing film Laser trimming so that each pattern resistance variation is minimized. Print the resistance connection between turns with a thickness of 3 ~ 4㎛ to connect the line, the electrode pattern formed by overlapping the electrode portion on the end of the pressure sensing film, the pressure sensing film and the electrode pattern on the upper portion of the pressure sensing film and the electrode pattern It is achieved by a thick film type pressure measuring sensor with a metal diaphragm according to the invention comprising an upper protective film formed of 1-4 μm thick with an epoxy for electrical insulation and a low melting point glass paste.

The object of the present invention is to process a diaphragm to form a flattened surface by lapping and polishing a surface of a metal diaphragm, which is a hydraulic part, by processing stainless steel, and a silicon oxide film, an aluminum oxide film, and a thick film on the diaphragm. Forming a dielectric film with a thickness of 3 to 8 μm by using screen printing and tape casting on a ceramic electrical insulating film such as a magnesium oxide film; ruthenium oxide (RuO 2), zirconium oxide (ZrO 2), Forming a trimming pattern part by using a pressure sensing film and laser trimming to a thickness of 3 to 4 μm by a thick film printing process on a paste on a metal oxide material having a displacement according to pressure such as zinc oxide (ZnO 2), and the like; It is connected by 4 electrode patterns, and is on top of the trimming part pattern part. The pole pattern is formed, and after the electrode pattern is cut by laser trimming, the resistance of the surface is patterned to increase the resistance to produce a precise resistor up to the final target resistance, and to protect the pressure sensing film. It is achieved by a method of manufacturing a pressure measuring sensor according to the present invention comprising the step of forming a top protective film by heat-treating the fused silicon oxide film or polymer-based epoxy, Teflon liquid to a thick film.

The thick film type pressure measuring sensor having a metal diaphragm and the manufacturing method of the pressure measuring sensor according to the present invention are formed by processing the diaphragm of the upper part of the stainless steel measuring body integrally with the measuring body and thus do not adhere or weld to creep. It is less stable and has excellent stability, and it is possible to form an insulating film, a protective film or a sensing film on the diaphragm by a thick film technology, so that high yield and low price can be achieved by mass production, and the ceramic thick film resistor has a higher sensitivity to pressure than a general metal resistor. It is 2 ~ 5 times higher, high resistance material, high resolution, high resolution, easy to measure precisely, and easy to apply laser trimming technology to pressure sensing film due to excellent adhesion to ceramic insulator layer. By heat treatment, higher temperature characteristics than conventional pressure sensor It can be used at high temperature above 200 ℃, and there is no need for expensive high vacuum deposition equipment and semiconductor equipment line for existing thin film pressure sensor or semiconductor type pressure sensor. The product also has an excellent effect of being able to respond.

1 is a cross-sectional view of a conventional diaphragm type pressure measuring sensor
2 is a plan view of the diaphragm-type pressure measuring sensor of FIG.
3 is a cross-sectional view of a thick-film pressure measuring sensor having a metal diaphragm according to a first embodiment of the present invention.
4 is a plan view of a thick-film pressure sensor having a metal diaphragm according to a first embodiment of the present invention;
5A and 5B are laser trimming process patterns and processing diagrams of a thick-film pressure measuring sensor having a metal diaphragm according to a first embodiment of the present invention.
Figure 6 is a thick film pressure sensor pattern resistance and trimming resistance table of the thick film pressure sensor with a metal diaphragm according to a first embodiment of the present invention
7 is a bridge circuit diagram to which laser trimming of a thick film type pressure measuring sensor having a metal diaphragm according to the first embodiment of the present invention is applied.
8 is a sensitivity output graph according to the pressure of the pressure sensing film and the diaphragm of the thick film type pressure measuring sensor having the metal diaphragm according to the first embodiment of the present invention.

3 is a sectional view of a diaphragm-type pressure measuring sensor A according to a first embodiment of the present invention.

The diaphragm type pressure measuring sensor (A) forms a surface within a surface roughness of 0.1 μm and a flatness of 1 μm by lapping the surface, and performs a high temperature atmosphere heat treatment to control the partial pressure of nitrogen and oxygen to nitride the surface with an oxide layer. A layered diaphragm 1 and an electrical insulating film such as a silicon oxide film, an aluminum oxide film, and a magnesium oxide film as a thick film on the diaphragm 1 are formed into a paste by screen printing and tape casting adhesion. After forming the insulating film 10 and the 3 to 8㎛ thick film of ceramic oxide on the insulating film 10, and then printed with a paste of metal oxide of ruthenium oxide (RhO2), zinc oxide (ZnO2), zirconium oxide (ZrO2) The pressure sensing film 11 and the upper portion of the pressure sensing film 11 to minimize the resistance variation of each pattern through laser trimming to reduce the resistance deviation. The electrode pattern 12 having the edger trimming part 25 formed adjacent to each other, and the pressure sensing film 11 and the electrode pattern 12 on the pressure sensing film 11 and the electrode pattern 12 may be electrically An upper protective film 14 formed of an insulating epoxy and a low melting point glass paste having a thickness of 1 to 4 μm is included.

The metal diaphragm 1 is manufactured on the upper part of the stainless steel body S by using CNC machining using stainless steel having high corrosion resistance and high heat resistance such as SUS630 and SUS316.

The diaphragm 1 is manufactured to the required thickness in accordance with the pressure in the internal hydraulic pressure portion 15 of the stainless steel body S, and a subsequent process is performed on the upper portion of the diaphragm 1 opposite to the hydraulic pressure portion 15. The surface was formed with roughness Rm ≦ 0.1 μm and flatness Fm ≦ 1 μm by lapping and polishing. In this embodiment, the surface was formed with roughness Rm = 0.1 μm and flatness Fm = 1 μm.

In order to perform electrical insulation with the diaphragm 1, an insulating film 10 of a thick film having a thickness of at least 3 to a maximum of 10 μm is formed, and at this time, a thickness of 3 to 8 μm using a screen printing process or a slurry for tape casting To form. When the thickness is small, the insulation resistance is low due to the passage of current through a high voltage, and the output of the vibration and low reproducibility is generated at the pressure sensor output. On the other hand, if the thickness is too large, it is somewhat difficult in the printing process from the thick film, and the output sensitivity of the sensor due to pressure is lowered. For this reason, heat treatment at high temperatures requires a rather thick design for electrical insulation at rather high temperatures.

The material of the insulating film 10 is generally used as a silicon oxide film paste and slurry, and alumina and impurities are added to improve heat resistance and to suit a required temperature. In this embodiment, it was printed with a high temperature glass paste applied to a low temperature co-fired ceramic (LTCC). The insulating layer 10 prepared in this manner is sintered in a paste form through high temperature heat treatment at 600 ° C. to 850 ° C. to obtain a solid insulating layer 10 having a thickness of 3 to 8 μm.

After the insulating film 10 of the thick film is formed, the pressure-sensitive film 11 of the thick film of 3 to 4 µm is printed and produced. The applied material for this embodiment was used ruthenium oxide (RhO2), was prepared by purchasing a ready-made product made in the form of a paste. The sheet resistance of the pressure sensing film 11 is a high resistor of 3.6 to 4.4 kPa / sq, and the pressure sensitivity is 2 to 5 times higher than that of ordinary metal. When the thickness is small, since the specific resistance is high, the resistance of the pressure sensing film 11 is high. After that, when the histone bridge is formed in the circuit, the setting is difficult because the impedance value does not match, and the resistance of most pressure sensors is set within 3 to 7 kΩ. The pressure sensor pattern is designed by selecting the area and thickness.

In the structure in which the pressure sensing film 11 of the thick film is formed, the resistance connection between the patterns is printed by the electrode pattern 12 to connect the lines, and the electrode part of the electrode pattern 12 overlaps the end of the thick film pressure sensing film 11. (12a) was formed to improve stability to contact. The electrode pattern 12 was formed to a thickness of 3 ~ 4㎛. In the thick film process, the thickness is minimized so that the portion overlapping the pressure sensing film 11 and the electrode pattern 12 is not large. If the thickness is too high, a large thickness of the protective film or treatment is required for the design in a future process.

The upper protective film 14 was formed by a printing method for external moisture, temperature shock and physical protection of the pressure sensing film 11 of the thick film and the electrode pattern 12 of the thick film having a thickness of 3 to 4 μm. The upper protective film 14 has a thickness of 1 to 4 µm, and was manufactured to have a thickness of 3 µm in this embodiment. The material that can be used in the formation of the upper protective film 14 can be applied to a portion used at a somewhat high temperature by using a low fusion glassy paste, and can be used by printing with silicone rubber and epoxy when used at a low temperature. Do.

After the upper passivation layer 14 is formed, the electrode part 12a may be manufactured by soldering and other bonding methods when fabricating the electrode part 12a in general silver, but gold must be separately formed for wire ball bonding. Nickel or gold is formed into a thick film having a thickness of 3 to 4 μm in accordance with the above bonding process, and formed by plating to prepare the electrode part 12a. Too small a thickness will result in poor adhesion in the bond and, conversely, a thick process will require cost and time for the process.

Figure 4 shows a plan view of a diaphragm-type pressure measuring sensor according to a first embodiment of the present invention. The pressure sensing film 11 is a thick film having a high specific resistance, and may be designed to be small in size of 1 to 1.2 mm in width and 0.4 to 0.6 mm in length. There are four pressure sensing films 11 in the pressure measuring sensor A, and there is a laser trimming part 25 in a separate rectangular pattern for laser trimming. The pattern resistance of the pressure sensing film 11 formed of the thick film has a resistance value of 4.75 to 5.25 kPa. The resistances of the four pressure sensing membranes 11 of the pressure measuring sensor A are somewhat ± 0.5 ㏀ because the thickness in the thick film process is larger than the thin film formation. At this time, the resistance is increased while patterning the surface of the laser trimming part 25 by laser processing as a correction for the resistance deviation, and the pressure sensing film 11 within ± 0.1% of the error is produced at 5.5 에 to the final resistance. .

 5A illustrates an example of a thick film pressure detector 11, a laser trimmer 25, an electrode part 12a, and an electrode pattern 12 applied for thick film laser trimming. When the resistance of the electrode portion 12a of the pressure measuring sensor A is measured, the resistance value across the line of the electrode pattern 12 can be known. The resistance of the pressure sensing unit 11 is a reference of 5 kW in the design, and the resistance of the laser trimming unit 25 is connected by a line of the electrode pattern 12 having a small specific resistance, so that there is almost no resistance. A representative figure for laser trimming is illustrated in FIG. 5B. In the method of trimming the thick film by laser, the resistance is increased as the pattern is cut while cutting the line of the electrode pattern 12 over the laser trimming part 25 and then cut from the middle of the laser trimming part 25. At this time, the laser resistance is stopped when the target resistance is 5.5㏀ while measuring the pattern resistance on the electrode portion 12a as a whole ±. The trimming is performed on the four patterns, which are resistors used as the pressure measuring sensor (A). .

6 shows the result of the representative pattern resistance processed while printing the electrode pattern 12. The electrode pattern resistance of the pressure measuring sensor (A) is formed from a minimum of 4.75 kPa to 5.25 kPa. The electrode pattern resistance of the pressure measuring sensor (A) is somewhat different in resistance due to thickness variation in printing and heat treatment. Thus, the laser trimming shown in FIG. 5B is performed to change the electrode pattern resistance to trim to 5.5k resistance. According to the trimming speed, laser focus and power, it is possible to set precise resistance value. In this product production, the resistance is set within ± 0.1%. The laser trimming technique is applied as a general technique in a technique for manufacturing electronic components and a special circuit board of a general industrial industry, but in the embodiment of the present invention, laser trimming is not performed on the pressure sensing unit 11, and separate laser trimming is performed. The upper electrode pattern 12 is connected by fabricating the part 25, and when the laser trimming is performed, the resistance is increased after trimming the electrode pattern 12 to increase the resistance of the electrode pattern 12.

In FIG. 6, the pattern resistance of the pressure measuring sensor before laser trimming was 4.75 ~ 5.25 kΩ at the minimum, but increased to 0.75 ~ 0.25 kΩ at the maximum by laser trimming, so that the resistance of the final electrode pattern was uniformly measured at 5.5 kΩ. Can be.

FIG. 7 is a diagram illustrating a connection of the resistance of the pressure detecting unit 11 and the laser trimming unit 25 of the diaphragm type pressure measuring sensor according to the first embodiment of the present invention with a histone bridge. When the histone bridge circuit is configured using four resistors of the pressure sensor resistor without laser trimming, the voltage output of the pressure measuring sensor (A) is highly varied. In this case, to reduce the deviation of the bridge voltage due to pressure, a passive processor or an expensive processor capable of adjusting the offset in the processor should be applied. And in this part, the final output through the module processor appears to be non-linear, depending on the pressure, the offset output in the temperature environment is unstable, and it is difficult to set high precision. However, in the present exemplary embodiment, the resistance of the electrode pattern 12 can be controlled by a laser trimming process, and thus, in the case of the pressure measuring sensor A manufactured at 5.5k, the processor is easily offset by the processor without applying a passive element. The resistance change of the electrode pattern 12 of each pressure measuring sensor (A) has a nearly negligible change because the resistance is the same as that of the same material.

8 shows a graph comparing the characteristics of a conventional pressure measuring sensor made of a metal thin film with NiCr and a pressure measuring sensor to which a pressure sensing film of RuO 2 applied in this embodiment is applied. In the case of NiCr pressure sensing film, a bridge voltage of 8.9mV appeared when an input voltage of 5V was applied for 20Bar displacement at 0Bar. The pressure sensitivity was 1.78 mV / V and compared with this, in the pressure measuring sensor (A) of the present embodiment, the bridge voltage is 22.4 mV and the high sensitivity of 4.48 mV / V in the pressure sensing film of RuO2.

In the present invention, it was verified by applying a pressure-sensitive film having a high specific resistance and high sensitivity. In the case of using a metal thin film having a small specific resistivity, spatial constraints are required in manufacturing the target resistance of the required resistance. However, in the present invention, since the specific resistance is large, the micro diaphragm can be manufactured in a small size, and the high pressure can be measured. It can be applied as a pressure measuring sensor.

The thick film type pressure measuring sensor having a metal diaphragm and the manufacturing method of the pressure measuring sensor according to the present invention can repeatedly execute the same manufacturing method in the industry of manufacturing the pressure measuring sensor and repeatedly produce the same product. It will be said that the invention is an industrially applicable invention.

10. Insulation film 11. Pressure sensing film 12. Electrode pattern
12a. Electrode part 14. Upper protective film 15. Hydraulic part
25. Laser trimming part

Claims (2)

In the manufacturing method of the pressure measuring sensor,
Machining the surface of the diaphragm with roughness Rm ≦ 0.1 μm and flatness Fm ≦ 1 μm so that the metal diaphragm, which is a hydraulic pressure part, is processed into stainless steel by lapping and polishing the surface surface to form a flattened surface;
Forming a thick film on the diaphragm into a 3 ~ 8 μm integral thickness by using a screen printing and tape casting on a ceramic electrical insulating film such as a silicon oxide film, an aluminum oxide film and a magnesium oxide film on a paste;
Resistor of the pressure sensing film with a thickness of 3 to 8 μm in a thick film printing process on a metal oxide material having the same displacement according to pressure such as ruthenium oxide (RuO 2), zirconium oxide (ZrO 2), and zinc oxide (ZnO 2) on a paste. And forming a laser trimming part,
It is connected to a plurality of electrode patterns formed on the pressure sensing film, an electrode pattern is formed on the upper portion of the laser trimming part, and after cutting the electrode pattern by laser trimming, the resistance is patterned while cutting the laser trimming part to increase the resistance. To form and form a precise resistor to the final target resistance;
Method of manufacturing a pressure measuring sensor comprising the step of forming a top protective film by screen-treating a low-melting silicon oxide film or a polymer-based epoxy, Teflon liquid to a thick film for the protection of the pressure-sensitive film.
In the diaphragm type pressure measuring sensor A,
The diaphragm type pressure measuring sensor (A) forms a surface within a surface roughness of 0.1 μm and a flatness of 1 μm by lapping the surface, and performs a high temperature atmosphere heat treatment to control the partial pressure of nitrogen and oxygen to nitride the surface with an oxide layer. A layered diaphragm,
An insulating film formed on the diaphragm as a thick film by using an electric insulating film such as a silicon oxide film, an aluminum oxide film, or a magnesium oxide film as a paste by using screen printing and tape casting;
After forming a thick film of 3 ~ 8㎛ with a ceramic oxide on top of the insulating film and printed on the pressure-sensitive film and the pressure-sensitive film printed with a metal oxide paste of ruthenium oxide (RhO2), zinc oxide (ZnO2), zirconium oxide (ZrO2). An adjacent laser trimming unit,
An electrode pattern formed to minimize resistance variation of each pattern through laser trimming so as to reduce resistance variation on the pressure sensing layer;
Diaphragm-type pressure comprising an upper protective film formed on the pressure sensing film and the electrode pattern on the upper surface of the 1 to 4 ㎛ thickness of the epoxy and low melting point glass paste for electrical insulation to protect the pressure sensing film and the electrode pattern. Measuring sensor

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