JPH0573509U - Strain sensor - Google Patents

Abstract

(57) [Abstract] [Purpose] When cutting out a plurality of strain sensors that are edited and arranged on a metal substrate by the laser cutting method, it has a reference point for accurately determining the coordinates, and it also serves as a reference after cutting. Provided is a strain sensor which can be used as a point and has a structure for ensuring the reliability of a strain detection circuit. [Structure] A strain detecting circuit 10 formed by a thin film technique on a metal substrate 1 is provided on an organic insulating film in a first region 8, and a coordinate position recognition pattern 11 is formed on a second region 9 which is completely separated from the organic insulating film. To provide. As a result, the strain detection circuit in the first region can be independently covered with the organic protective film immediately after the circuit is formed, so that the reliability of the strain detection circuit can be improved and the reference point can be used in the subsequent processes. it can.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a strain sensor, and more particularly to a strain sensor in which a strain sensor circuit is formed on a metal substrate by thin film technology.

[0002]

[Prior Art]

 Generally, strain sensors are manufactured by forming strain sensor circuits by thin film technology on a metal substrate.

FIG. 4 is a sectional view of a substrate forming such a conventional strain sensor, FIG. 5 is a plan view, and FIG. 6 is an enlarged plan view.

As shown in FIG. 4, in the conventional strain sensor, a heat-resistant insulating resin film 2 made of polyimide is formed on the main surface of a stainless substrate 1, and a resistor 3 and a conductor thin film 4 are attached thereon. After that, a predetermined circuit is formed by a photo-etching method, the resistance value is adjusted, and then it is divided into individual parts, and then parts and terminals are attached and a protective resin is attached. At the time of division, the reference point 5 for determining the cutout position is the peripheral portion of the metal substrate on which the strain sensor is not formed as shown in FIG. 5 or the cutout portion 7 removed at the time of cutout as shown in FIG. It was generally formed.

[0005]

[Problems to be solved by the device]

 The conventional strain sensor described above has the following problems.

Generally, it is difficult to completely smooth the substrate, and there are deformations such as warpage and undulation. When a circuit is formed using thin film technology, the substrate is adsorbed by vacuum adsorption, the substrate is smoothed as much as possible, and the photomask pattern is transferred to the substrate by photoetching. Therefore, when a strain sensor is cut out from a metal substrate by the laser cutting method, the position irradiated with the laser beam is affected by the deformation of the substrate and must be the initial position unless the substrate is smoothed similarly. It becomes impossible to cut out the strain sensor having the desired shape. If the metal substrate can be smoothed, the strain sensor can be cut out accurately, but if the reference point for determining the cutting position is the conventional method, it cannot be cut out accurately for the following reasons.

1. When the reference point is formed around the metal substrate When the substrate is placed in a groove like a ceramic substrate and the substrate is divided by applying mechanical force later, the laser beam for substrate division does not reach the metal back surface. Since the smooth surface of the substrate can be smoothed by contacting the entire back surface of the substrate and adsorbing and fixing the substrate, there is little deviation of the cutting position from the reference point formed around the substrate. However, if this method is applied to a metal substrate and a groove is formed in the metal substrate and then the substrate is divided by mechanical force, mechanical stress will be applied, resulting in new deformation such as waviness or warpage on the substrate. Residual stress also occurs. Then, this residual stress is gradually released, which causes an error in the strain sensor. Therefore, when splitting a metal substrate, the laser beam may be penetrated to the back surface of the substrate and the strain sensor may be cut into individual pieces. In order to prevent the strain sensors from scattering due to wind pressure, it is necessary to adsorb and fix the strain sensors on an individual unit basis using a stand having an area smaller than each strain sensor. In this way, when adsorbing in the unit of individual pieces, it is difficult to smooth the entire surface of the metal substrate, and the substrate remains deformed, and the cutting position is likely to be displaced.

2. When the reference point is formed on the metal substrate cutoff part When the reference point is formed on the cutout part, it is considered that the reference point can be formed adjacent to each strain sensor, so it is unlikely to be affected by the warp of the substrate. Since there is no reference point after irradiation with laser light because it is in the cutting margin, for example, when a strain sensor is cut out randomly from the substrate, the reference point may not remain around the strain sensor you want to cut out. In this case, for example, it may be impossible to accurately cut out the strain sensor because it is necessary to refer to reference points that remain at distant positions.

Further, there is a problem that the reference point of the thin film directly formed on the stainless steel substrate becomes difficult to recognize when the color tone between the stainless steel and the thin film is close. Moreover, since the average surface roughness of ordinary stainless steel is about 0.3 μm, thin films with a thickness of about 1 μm or less cannot absorb surface irregularities and are formed on a mirror-like substrate. There is a problem that the amount of light scattering increases and the recognizability is further reduced compared to the case. Further, when the reference point is formed on the same organic insulating film as the strain detection circuit, there is a problem that the heat of the laser beam causes the organic insulating film to burn and the adhesiveness of the organic insulating film to deteriorate.

[0010]

[Means for Solving the Problems]

 According to the present invention, an insulating film is provided on a metal substrate, a first resistor region and a second resistor region are provided on the insulating film, and a strain detection circuit is provided on the first resistor region. And a strain sensor having a position confirmation pattern on the second resistor region is obtained.

Further, according to the present invention, the above-mentioned strain sensor using polyimide as the insulating film can be obtained.

[0012]

【Example】

 Next, the present invention will be described with reference to the drawings.

FIG. 1 is a plan view of a strain sensor before cutting showing a first embodiment according to the present invention, and FIGS. 2 and 3 show a manufacturing process of the strain sensor according to the first embodiment of the present invention. It is a plan view.

As shown in FIG. 2, in this embodiment, a 0.3 mm-thick stainless steel substrate (10 cm with a thickness of 1 is used to form a polyimide film 2 as an organic insulating film by spin coating, and then a first photoetching method is used to form a polyimide film 2. The unnecessary portion of the polyimide is removed leaving only the region 8 and the second region 9. The polyimide is cured at 350 ° C. for 60 minutes, and the film thickness after curing is about 4 μm.

Next, a tantalum nitride (Ta ₂ N) film 4 having a thickness of about 1000 angstroms is formed as a resistor film, and NiCr (about 1000 angstroms) and Pd (about 1000 angstroms) are formed thereon as conductor films. ) And Au (about 7,000 angstroms) are formed by a magnetron sputtering method. The strain detecting circuit 10 is formed on the first area of the polyimide film, and the coordinate position recognizing reference pattern (diamond pattern of about 0.4 mm square) 11 is formed on the second area. After patterning by the photo-etching method, the heat treatment for stabilizing the resistor 12 is performed at 250 ° C. for 7 hours.

Then, as shown in FIG. 3, after adjusting the resistance value by the laser trimming method, the first region is exposed so that only the external terminal connecting conductor portion (about 1 mm square) 13 of the strain detection circuit is exposed. An epoxy-based organic protective film 14 having a thickness of about 30 μm is attached to the entire surface of 8 and the peripheral portion of the first region by a printing method. At this time, the organic protective film is not attached to the second region 9 in order to expose the reference point.

When cutting out the strain sensor with the YAG laser, the coordinates are determined using the reference points on the second region, and the strain sensor is cut into a predetermined shape (size of about 5 cm × 3 cm). Since the polyimide film has good smoothness, the reference point pattern can be as smooth as the film attached on the mirror surface. Further, since the color tone of the polyimide film (brown) and the conductor film (gold in the embodiment) are completely different, the reference point can be easily recognized. Similar effects can be obtained when aluminum or copper is used for the conductor film.

The parts and terminals are soldered to the cut pieces 15 (FIG. 4), and the moisture absorbed in the manufacturing process is dried at 130 ° C. for about 1 hour to be removed, and then the final moisture-proof film is formed. A strain sensor element is obtained by attaching butyl rubber.

Since the reference point used for cutting out is attached to each strain sensor, by referring to this, the terminals and components can be mounted with high accuracy. Moreover, since the reference point is located at a distance of about 500 μm from the cut-out position, the heat of the laser beam does not adversely affect the adhesion of the organic insulating film. Further, since the first region is covered with the protective film after the strain detection circuit is formed, it is possible to largely prevent moisture absorption in the subsequent steps. This can improve the reliability of the distortion detection circuit. Since the reference point of the second area is used as a reference for alignment until the formation of the moisture-proof film, the amount of moisture absorption increases because the time during which the thin film is exposed is long. Therefore, by completely separating the organic insulating film in the first region and the second region, it is possible to improve the reliability of the circuit in the first region to which the protective film can be attached independently.

[0020]

[Effect of the device]

 As described above, since the strain sensor of the present invention has the reference point pattern on the organic insulating film in the second region in the strain sensor element, the strain sensor can be accurately cut out from the metal substrate. It can also be used as a reference point for alignment when mounting parts after cutting.

Further, since the organic insulating film in the first region is formed completely separated from the insulating film in the second region, moisture absorption is largely suppressed by the organic protective film attached after the circuit is formed, and the reliability is improved. A highly accurate strain sensor can be made. If the organic insulating films in the first and second regions are not separated and are connected to each other, the moisture that permeates the exposed organic insulating film in the second region is transferred through the connection point part of the region to the first region. Deterioration of the performance of the strain sensor due to a decrease in the adhesion between the thin film that reaches the region 1 and forms the strain detection circuit and the organic insulating film, and further a decrease in the adhesion between the organic insulating film and the metal substrate. Bring Since the organic insulating film and the thin film in the second area have nothing to do with the strain detection function, the influence of moisture absorbed in the manufacturing process can be ignored, but it is necessary to store them in a moisture-absorbed state for an unnecessarily long time. I won't. The organic protective film also functions as a protective film when connecting the terminals with solder.

[Brief description of drawings]

FIG. 1 is a plan view of a strain sensor before cutting according to a first embodiment of the present invention.

FIG. 2 is a plan view showing a manufacturing process of the strain sensor of the first embodiment according to the present invention.

FIG. 3 is a plan view showing a manufacturing process of the strain sensor of the first embodiment according to the present invention.

FIG. 4 is a sectional view of a substrate forming a conventional strain sensor.

FIG. 5 is a plan view of a conventional strain sensor before cutting.

FIG. 6 is an enlarged plan view of a conventional strain sensor before cutting.

[Explanation of symbols]

 1 Stainless Steel Substrate 2 Heat Resistant Insulating Resin Film 3 Resistor Thin Film 4 Conductor Thin Film 5 Reference Point 6 Strain Sensor Forming Area 7 Cutting Area 8 First Area 9 Second Area 10 Strain Detection Circuit 11 Coordinate Position Recognition Pattern 12 Resistance Body 13 Conductor part for external terminal connection 14 Organic protective film 15 Pieces cut out

Claims (2)

[Scope of utility model registration request] 1. A strain detecting device having an insulating film on a metal substrate, having a first resistor region and a second resistor region on the insulating film, and detecting strain on the first resistor region. A circuit, the second
A strain sensor having a pattern for recognizing position coordinates on the resistor area of. 2. The strain sensor according to claim 1, wherein polyimide is used as the insulating film.