JP7652384B2 - Method and device for inspecting adhesive application condition - Google Patents

Description

The present invention relates to a method and device for inspecting the state of adhesive application, and in particular to a method and device for non-destructively inspecting the state of adhesive application on specimens in which metal plates are bonded together with an adhesive.

In recent years, in order to reduce the weight of automobiles and other vehicles, a method of bonding the metal plates that make up the body with adhesive has been adopted. As the number of places where adhesive is used increases during the mass production process of car bodies, there has been a demand for in-line non-destructive inspection of the state of adhesive application between metal plates to ensure quality.

As a method for non-destructively inspecting the state of adhesive application, Patent Document 1 describes a method in which one of two bonded steel plates is heated and the state of adhesive application is inspected from the temperature change of the steel plate. In this method, first, the outer surface of the first steel plate located on the lower side of a specimen consisting of a first steel plate and a second steel plate bonded with adhesive is heated with hot air. Next, the outer surface of the second steel plate located on the upper side is imaged with an infrared camera, and the heat conducted from the first steel plate to the second steel plate is detected to measure the distribution of the surface temperature of the second steel plate. After that, the adhesive area is found by computer-aided analysis based on the measured surface temperature distribution and the adhesive gap between the first steel plate and the second steel plate that was measured in advance.

The method described in Patent Document 1 allows for non-destructive inspection of the specimen, but it takes time to heat the specimen with hot air. In addition, this method requires measuring the gaps in the adhesive of the specimen in advance, which lengthens the inspection time, making it unsuitable for in-line inspection in mass production processes.

In the field of semiconductor substrates, a method of heating a specimen by irradiating it with light has been adopted as a method of inspecting the adhesive state of two plate materials from temperature changes by heating the specimen in a short period of time. For example, Patent Document 2 describes a method of heating the first wafer, which is made up of a first wafer and a second wafer that are bonded together, by irradiating the outer surface of the first wafer with light that includes infrared rays. In this inspection method, after irradiating the light, the reflected infrared rays are detected by an infrared camera that images the outer surface of the first wafer, and the adhesive state is inspected from the temperature change of the first wafer caused by the detected infrared rays.

In this method, the first wafer can be heated in a short time by the infrared radiation energy contained in the irradiated light. Also, since heat transfer from the first wafer to the second wafer occurs more quickly in the bonded area than in the non-bonded area, the bonding condition can be inspected by detecting this temperature change with an infrared camera.

JP 2018-146425 A Japanese Unexamined Patent Publication No. 7-161596

When the method described in Patent Document 2 is applied to steel plates, the first steel plate can be heated in a short time and the effort required to measure the adhesive gap between the two steel plates can be eliminated. However, the following problems arise due to the difference in characteristics between the metal plate and the wafer.

First, the metal plate has a higher thermal conductivity than the wafer, so when the temperature difference between the bonded and non-bonded areas becomes large due to heat conduction through the adhesive, heat is transferred from the non-bonded areas to the bonded areas due to the effects of thermal diffusion that occurs within the metal plate. Therefore, with a metal plate, it is necessary to detect temperature changes more accurately and in a shorter time than with a wafer.

In order to detect temperature changes accurately in a short time, it is necessary to detect the temperature change immediately after heating. However, because metal plates have a high light reflectivity, when light reflected from the first steel plate enters the infrared camera, the infrared camera will be blown out. While the infrared camera is blown out, it cannot detect the temperature of the first steel plate, so the temperature detection time is shortened and the inspection sensitivity is reduced.

Therefore, with metal plates, it is not possible to inspect the adhesive areas in the same way as with semiconductor substrates, and in-line inspection during mass production is not possible.

The present invention was made in consideration of the above problems, and aims to provide an inspection method and an inspection device that can perform highly accurate inspection in a short time in an adhesive application state inspection method that nondestructively inspects the adhesive area between metal plates of a test object in which metal plates are bonded together with an adhesive.

In order to achieve the above-mentioned object, one embodiment of the present invention is an inspection method for inspecting the state of adhesive application on a specimen in which a first metal plate and a second metal plate are bonded with an adhesive, the method including the steps of heating the outer surface of the first metal plate by light irradiation, detecting the temperature of the outer surface with an infrared camera, and determining the area where the adhesive is applied based on the detected data, wherein the light irradiation and temperature detection are performed so as to include the bonded area on the first metal plate where adhesive is applied and the surrounding non-bonded areas where adhesive is not applied, and the wavelength range of the irradiation wavelength used in the light irradiation is different from the wavelength range of the detection wavelength by the infrared camera.

With this configuration, the first metal plate can be heated in a short time by irradiating it with light, and since the wavelength range of the irradiation wavelength used to heat the first metal plate is different from the wavelength range of the detection wavelength of the infrared camera, the infrared camera can measure the surface temperature of the first metal plate without being blown out by the light reflected from the first metal plate. This ensures a long period of time during which the temperature can be detected by the infrared camera, and allows for highly accurate inspection results.

In addition, one embodiment of the present invention is characterized in that in the inspection method, the wavelength range of the irradiation wavelength is set to the shorter wavelength side than the wavelength range of the detection wavelength.

According to this configuration, the metal plate has a higher light absorption rate in the short wavelength range and receives a larger amount of heat input than in the long wavelength range. Therefore, by making the wavelength range of the irradiation wavelength shorter than the inspection wavelength, the heating time of the metal plate can be shortened. This makes it possible to prevent a decrease in inspection accuracy due to thermal diffusion occurring within the first metal plate caused by a longer heating time.

In addition, one embodiment of the present invention is characterized in that in the inspection method, a principal component analysis is performed on the data detected by the infrared camera, and the coating area is determined based on the data after the principal component analysis.

According to this configuration, the measurement results from the infrared camera contain unnecessary data, such as noise data caused by the electronic circuitry of the infrared camera. However, by performing principal component analysis to eliminate the unnecessary data, the data caused by the presence of adhesive can be emphasized, making it possible to clarify the difference between the area where the adhesive is applied and other areas.

In addition, one embodiment of the present invention is characterized in that in the inspection method, the wavelength range of the detection wavelength is in the range of 1.5 μm to 5.0 μm.

With this configuration, the infrared camera has high temperature detection sensitivity in the range of 1.5 μm to 5.0 μm, so by using this wavelength range as the inspection wavelength, inspection accuracy can be improved.

Moreover, one embodiment of the present invention relates to an inspection device for inspecting the state of adhesive application on a specimen in which a first metal plate and a second metal plate are bonded with an adhesive, the inspection device comprising: a heating device for heating the outer surface of the first metal plate by irradiating it with light; an infrared camera for detecting the temperature of the outer surface; and a control device for determining the area in which the adhesive is applied from the detection results of the infrared camera , wherein the light irradiation range by the heating device and the detection range by the infrared camera are set to include the adhesive area on the first metal plate where adhesive is applied and the surrounding non-adhesive areas where adhesive is not applied, and the wavelength range of the irradiation wavelength by the heating device is different from the wavelength range of the detection wavelength by the infrared camera.

The adhesive application condition inspection method and inspection device of the present invention can quickly and accurately inspect the adhesive application area of a test object in which metal plates are bonded together with an adhesive.

1 is a schematic explanatory diagram of an inspection device for inspecting the applied state of an adhesive according to an embodiment of the present invention; 10A and 10B are explanatory diagrams of a method for inspecting the state of application of an adhesive; 1 is a graph showing the relationship between the relative output of the irradiation wavelength and the detection wavelength, and the relationship between the light absorptance of a steel sheet and the irradiation wavelength. FIG. 2 is a schematic diagram illustrating heat transfer within a subject. FIG. 2 is a schematic diagram illustrating heat transfer within a subject. FIG. 2 is a schematic diagram illustrating heat transfer within a subject. 4 is a graph showing the change over time in the surface temperature of a first metal plate. 1 is a graph showing the relationship between surface temperature and time based on data before principal component analysis. 13 is a graph showing the relationship between surface temperature and time based on data after principal component analysis. 11 is a diagram showing an example of a measurement result of the temperature distribution on the outer surface of a first metal plate based on temperature data before principal component analysis. FIG. 11 is a diagram showing an example of a measurement result of the temperature distribution on the outer surface of a first metal plate based on temperature data after principal component analysis. FIG.

Figure 1 is a schematic diagram of an inspection device 10 for inspecting the state of application of adhesive (hereinafter also referred to as "inspection device 10") according to one embodiment of the present invention. The inspection device 10 is a device that inspects the state of application of adhesive on an object 50 in which multiple metal plates are bonded with an adhesive. The inspection device 10 of this embodiment includes a mounting table 12 on which the object 50 is placed, a heating device 20, an infrared camera 30, and a control device 40.

As shown in Figs. 1 and 2, the specimen 50 is a laminate of at least two metal plates bonded together with an adhesive 54, and in this embodiment, the specimen 50 is formed by bonding a first metal plate 51 and a second metal plate 52 together. The metal plates 51 and 52 can be, for example, steel plates or aluminum plates. The metal plates 51 and 52 may be made of the same material or different materials. The thicknesses of the metal plates 51 and 52 can be set appropriately. As an example, the first metal plate 51 and the second metal plate 52 in this embodiment are steel plates having the same thickness.

The heating device 20 is a device having a heat source for heating an object, and in particular, a device having a light source for irradiating the object with light as a heat source. In this embodiment, a xenon lamp is used as the heating device 20.

The infrared camera 30 detects infrared rays emitted by an object and measures the temperature of the object. In this embodiment, the outer surface 51a of the first metal plate 51 of the subject 50 is imaged to measure the surface temperature of the first metal plate 51.

The wavelength range of the irradiation wavelength of the heating device 20 and the wavelength range of the detection wavelength of the infrared camera 30 are set to different wavelength ranges. Fig. 2 is an explanatory diagram of the method for inspecting the application state of an adhesive of this embodiment. In Fig. 2, the magnitude relationship of the wavelengths is wavelength λ _A < wavelength λ _B < wavelength λ _C , and the wavelength range λ _A to λ _B of the irradiation wavelength of the heating device 20 of this embodiment is set to the shorter wavelength side than the wavelength range λ _B to λ _C of the detection wavelength of the infrared camera 30. Note that the wavelength range of the irradiation wavelength may be set to the longer wavelength side than the wavelength range of the detection wavelength.

In addition, in this embodiment, the wavelength range of the detection wavelength of the infrared camera 30 is set to the range of 1.5 μm to 5.0 μm. Note that the wavelength range of the detection wavelength is not limited to this, but since the infrared camera 30 of this embodiment has high sensitivity for temperature detection in the range of 1.5 μm to 5.0 μm, using this wavelength range as the detection wavelength can improve inspection accuracy. Note that since the wavelength range of the infrared camera 30 with high sensitivity varies depending on the specifications, the wavelength range of the detection wavelength may be set to 1.5 μm or less or 5.0 μm or more to match the specifications of the infrared camera 30.

3 is a graph showing the relationship between the relative output of the irradiation wavelength of this embodiment and the conventional irradiation wavelength and the detection wavelength by the heating device 20, and the relationship between the light absorptivity of the steel plate and the irradiation wavelength. As shown in the illustrated example, the wavelength range of the irradiation wavelength of the light heating used in the inspection of the bonding state of the conventional semiconductor substrate (wavelength range shown by the dashed line in FIG. 3) overlaps with the wavelength range of the detection wavelength of the infrared camera (see the detection wavelength range in FIG. 3). In contrast, in this embodiment, the wavelength range of the irradiation wavelength of the heating device 20 and the wavelength range of the detection wavelength of the infrared camera 30 are set to different wavelength ranges, that is, the wavelength range of the irradiation wavelength of the heating device 20 (wavelength range shown by the solid line in FIG. 3) and the wavelength range of the detection wavelength of the infrared camera 30 are set so that they do not substantially overlap. Here, being set to different wavelength ranges (substantially not overlapping) means that in addition to the wavelength range of the irradiation wavelength and the detection wavelength not overlapping at all as shown in FIG. 3, the wavelength range of the irradiation wavelength and the detection wavelength also slightly overlapping. For example, the wavelength range of the irradiation wavelength is 0.1 μm to 1.1 μm, the wavelength range of the detection wavelength is 1.0 μm to 6.0 μm, and the peaks of each wavelength range are offset, but the bases of each wavelength range may slightly overlap. Also, as shown by the dashed line in Figure 3, the light absorptivity of the steel plate is higher on the short wavelength side. Therefore, by setting the wavelength range of the heating device 20 to the short wavelength side, it is possible to shorten the heating time of the first metal plate 51.

The control device 40 is configured with information processing means such as a central processing unit (CPU) or an application specific integrated circuit (ASIC), storage means such as RAM or ROM, an input/output interface, etc. The control device 40 is equipped with a display device 42 having a screen 44 capable of visually displaying information. The control device 40 is connected to the heating device 20 and the infrared camera 30, and controls their operation, analyzes data acquired from the infrared camera 30, and displays the analysis results on the display device 42. The control device 40 of this embodiment also includes a PCA processing unit that performs principal component analysis on the temperature measurement data acquired by the infrared camera 30.

Next, a method for inspecting the adhesive application state of the specimen 50 using the above-mentioned inspection device 10 will be described. The inspection method of this embodiment includes a step of setting the specimen 50 (specimen setting step), a step of heating the specimen 50 (heating step), a step of detecting the temperature of the specimen 50 using the infrared camera 30 (temperature detection step), a step of performing principal component analysis on the detected data (PCA processing step), and a step of determining the application area of the adhesive 54 based on the data after the principal component analysis (determination step). Each step will be described in detail below.

As shown in Figures 1 and 2, in the specimen setting process, the specimen 50 is set on the mounting table 12 so that the first metal plate 51 is on the upper side of the specimen 50 and the second metal plate 52 is on the lower side. In the next heating process, the heating device 20 is used to irradiate the outer surface 51a of the first metal plate 51 of the specimen 50 with light to heat the specimen 50. The range of light irradiation is appropriately set to include the adhesive application area. The infrared camera 30 continuously images the specimen 50 before and after the light irradiation to obtain time-series data on the temperature of the outer surface 51. The obtained data is transmitted to the control device 40.

In the temperature detection process, the temperature of the outer surface 51a of the first metal plate 51 is detected by the infrared camera 30. In this embodiment, the control device 40 detects the temperature distribution of the outer surface 51a based on the data acquired from the infrared camera 30.

Figures 4A to 4C are diagrams illustrating the state of heat transfer in the specimen 50 after heating by the heating device 20. In each diagram, the heated area is marked with dots, and the darker the dot, the higher the temperature.

As shown in FIG. 4A, when the specimen 50 is irradiated with light, the outer surface 51a of the first metal plate 51 is heated first. Then, as shown in FIG. 4B, heat is transferred from the first metal plate 51 to the second metal plate 52 through the adhesive 54 and the air present in the gap S between the first metal plate 51 and the second metal plate 52. As shown by the arrows in FIG. 4B, in the region 56 where the adhesive 54 is applied (hereinafter also referred to as the "adhesive region 56"), heat is transferred to the second metal plate 52 faster than in the region 58 where the adhesive 54 is not applied (hereinafter also referred to as the "non-adhesive region 58"). Therefore, the temperature of the adhesive region 56 drops faster than that of the non-adhesive region 58. As a result, when a temperature difference occurs between the adhesive region 56 and the non-adhesive region 58, heat diffusion occurs from the non-adhesive region 58 to the adhesive region 56 in the first metal plate 51, as shown in FIG. 4C. The infrared camera 30 detects the temperature change of the first metal plate 51 over the course of approximately several seconds from FIG. 4A to FIG. 4C as temperature measurement data for inspecting the application state of the adhesive 54.

Fig. 5 is a graph showing the change over time in temperature of the outer surface 51a of the first metal plate 51 in the bonded region 56 and the non-bonded region 58, and shows the temperature change in the case where no thermal diffusion occurs between the bonded region 56 and the non-bonded region 58. In Fig. 5, time _t1 shows the timing at which light is irradiated by the heating device 20, and time _t3 shows the timing at which thermal diffusion occurs between the bonded region 56 and the non-bonded region 58. Furthermore, time _t2 shows the timing at which the infrared camera returns to proper exposure after becoming overexposed due to reflected light from the specimen 50 when a conventional heating device and infrared camera are used.

As shown in Fig. 5, before light irradiation, the temperatures of the bonded area 56 and the non-bonded area 58 are equal. When light is irradiated by the heating device 20 at time _t1 , the surface temperature rises from temperature _X1 to temperature _X2 . Thereafter, heat is transferred to the second metal plate 52 with the passage of time, and the temperature of the outer surface 51a decreases. The infrared camera 30 detects the temperature difference between the bonded area 56 and the non-bonded area 58 that occurs as the temperature decreases. The control device 40 can detect the area of the specimen 50 to which the adhesive 54 is applied, based on the detected temperature difference.

In the graph of FIG. 5, a temperature difference exists between the adhesive region 56 and the non-adhesive region 58 even after time _t3 , for example, at time _t4 . However, in reality, the difference between the adhesive region ₅₆ and the non-adhesive region 58 becomes smaller due to thermal diffusion after time t3, so that the temperature detection time for adhesive inspection is substantially from time _t1 to time _t3 . This temperature detection time is in units of several seconds. Here, when a conventional adhesive inspection device for semiconductor substrates is applied to the specimen 50, whiteout occurs in the infrared camera between time _t1 and time _t2 , and the surface temperature of the first metal plate 51 cannot be detected. Therefore, the temperature detection time is shortened, and the inspection sensitivity is reduced. In contrast, in the inspection device 10 of this embodiment, the wavelength range of the irradiation wavelength of the heating device 20 and the wavelength range of the inspection wavelength of the infrared camera 30 are different, so that the infrared camera 30 does not receive reflected light and is not overexposed. Therefore, it is possible to secure a long temperature detection time and improve the inspection sensitivity.

The temperature data acquired by the infrared camera 30 is subjected to principal component analysis processing by the PCA processing unit of the control device 40. In this PCA processing step, unnecessary data is removed from the acquired temperature data, and data due to the presence of the adhesive 54 is emphasized.

6A and 6B are diagrams for explaining an outline of the principal component analysis process performed by the PCA processing unit, in which FIG. 6A is a graph showing the relationship between surface temperature and time based on data before the principal component analysis, and FIG. 6B is a graph showing the relationship between surface temperature and time based on data after the principal component analysis. Note that time _t1 in FIG. 6 indicates the timing at which light is irradiated onto the specimen 50 by the heating device 20. As shown in FIG. 6A, the temperature data acquired by the infrared camera 30 includes, in addition to the temperature data caused by the adhesive 54 shown by the thick solid line, noise data caused by the electronic circuit of the infrared camera 30 shown by the thin solid line, and temperature data unrelated to the adhesive 54 shown by the two-dot chain line, one-dot chain line, and dashed line. By performing the principal component analysis process on such data, data caused by the adhesive 54 is extracted as shown in FIG. 6B, and the temperature change of this data is emphasized.

7A and 7B are diagrams showing the measurement results of the temperature distribution of the outer surface 51a based on the temperature data acquired by the infrared camera 30, where FIG. 7A shows the measurement results based on the temperature data before the principal component analysis, and FIG. 7B shows the measurement results based on the temperature data after the principal component analysis. These measurement results can be displayed on the screen 44 of the display device 42. In the black and white images of each measurement result, the adhesive region 56 of the outer surface 51a of the first metal plate 51 is displayed with a high black density, and the non-adhesive region 58 is displayed with a low black density. In addition, in the measurement result after the principal component analysis shown in FIG. 7B, the difference in black density between the adhesive region 56 and the non-adhesive region 58 becomes clearer by performing the principal component analysis, and the accuracy of determining the application area of the adhesive 54 on the test object 50 can be improved. In this way, the application area of the adhesive 54 on the test object 50 can be determined by identifying the difference in the displayed colors, and the accuracy of the determination can be improved by performing the principal component analysis. This determination may be performed by the control device 40 or by the inspector.

As described above, in the inspection method of this embodiment, the first metal plate 51 of the specimen 50 can be heated in a short time by light irradiation. In addition, since the wavelength range of the light heating irradiation wavelength and the wavelength range of the detection wavelength of the infrared camera 30 are different, the infrared camera 30 does not receive light reflected by the first metal plate 51 and does not become overexposed. This makes it possible to secure a long temperature detection time by the infrared camera 30 and obtain highly accurate inspection results. In this way, the inspection device 10 and the inspection method of this embodiment can perform highly accurate inspection in a short time, so that it is possible to perform non-destructive in-line inspection of the application state of the adhesive 54 between the metal plates 51 and 52 that constitute the vehicle body in the mass production process of the vehicle body. In addition, by performing a principal component analysis process on the temperature data acquired by the infrared camera 30, the temperature data caused by the adhesive 54 can be emphasized, and the difference between the adhesive region 56 and other regions can be clarified, and a highly accurate judgment can be made.

The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit of the invention.

REFERENCE SIGNS LIST 10 Inspection device 12 Mounting table 20 Heating device 30 Infrared camera 40 Control device 42 Display device 50 Test object 51 First metal plate 52 Second metal plate 54 Adhesive

Claims (5)

1. An inspection method for inspecting an adhesive application state of a test object in which a first metal plate and a second metal plate are bonded with an adhesive, comprising:
heating an outer surface of a first metal plate by light irradiation;
detecting a temperature of the outer surface by an infrared camera and determining an area to which the adhesive is applied based on the detected temperature data;
the light irradiation and the temperature detection are performed so as to include a bonding region in the first metal plate where an adhesive is applied and a surrounding non-bonded region in which no adhesive is applied;
An inspection method, characterized in that the wavelength range of the irradiation wavelength used in the light irradiation is different from the wavelength range of the detection wavelength used by the infrared camera. The inspection method according to claim 1, characterized in that the wavelength range of the irradiation wavelength is set to the shorter wavelength side than the wavelength range of the detection wavelength. The inspection method according to claim 1 or 2, characterized in that a principal component analysis is performed on the data detected by the infrared camera, and the coating area is determined based on the data after the principal component analysis. The inspection method according to any one of claims 1 to 3, characterized in that the wavelength range of the detection wavelength is in the range of 1.5 μm to 5.0 μm. An inspection apparatus for inspecting an adhesive application state of a test object having a first metal plate and a second metal plate bonded with an adhesive, comprising:
a heating device that heats an outer surface of the first metal plate by light irradiation;
an infrared camera for detecting the temperature of the outer surface;
a control device that determines the application area of the adhesive based on the detection result of the infrared camera,
a light irradiation range by the heating device and a detection range by the infrared camera are set so as to include a bonding area in the first metal plate where an adhesive is applied and a surrounding non-bonded area in which no adhesive is applied;
An inspection device, characterized in that the wavelength range of the irradiation wavelength by the heating device is different from the wavelength range of the detection wavelength by the infrared camera.