Patent ID: 12188872

DETAILED DESCRIPTION

JP-A No. 2005-265533 discloses an inclined cutting method of a sample, and discloses analyzing, measuring, observing, and evaluating an inclined cutting surface by various analysis methods including, for example, an FT-IR method, a laser Raman method, an EPMA method, and a TOF-SIMS method. JP-A No. 2020-55144 discloses joining a metal member and another member by an adhesive, and so cutting the adhesion joining part as to have an inclination at an angle of 5 degrees by an oblique cutting apparatus from an adhesive layer toward the metal part. JP-A No. 2020-55144 further discloses analyzing the joining surface by an IR analysis, a TEM observation, and a TOF-SIMS analysis.

The methods disclosed in JP-A Nos. 2005-265533, 2008-34786, and 2020-55144, however, involve difficulties in accurately analyzing an adhesion interface. For example, observing the inclined cutting surface by the FT-IR method or the laser Raman method allows for an observation of an enlarged cross-section following the inclined cutting, only allowing for an analysis where hydrogen bonding is cut at an interface, i.e., only allowing for a so-called destructive analysis at the interface. Accordingly, it is difficult to perform an accurate analysis of the adhesion interface.

The TOF-SIMS analysis uses in combination the inclined cutting and sputtering to fabricate a sample, only allowing for the destructive analysis at the adhesion interface as with the methods described above. Accordingly, it is difficult to perform the accurate analysis of the interface.

The IR analysis is disadvantageous in resolution in a depth direction, which is in the order of about several micrometers, making it difficult to acquire information of interest on an interface of a sample configured by a metal and an adhesive and having a thickness of tens of nanometers, for example.

It is desirable to provide an adhesion interface observation method that makes it possible to observe, by a surface-enhanced Raman scattering spectroscopy, a region in the vicinity of an adhesion interface following adhesion and curing of an adhesive that is coated on adhered members and adheres the adhered members to each other.

In the following, some example embodiments of the disclosure are described in detail with reference to the accompanying drawings. Note that the following description is directed to illustrative examples of the disclosure and not to be construed as limiting to the disclosure. Factors including, without limitation, numerical values, shapes, materials, components, positions of the components, and how the components are coupled to each other are illustrative only and not to be construed as limiting to the disclosure. Further, elements in the following example embodiments which are not recited in a most-generic independent claim of the disclosure are optional and may be provided on an as-needed basis. The drawings are schematic and are not intended to be drawn to scale. Throughout the present specification and the drawings, elements having substantially the same function and configuration are denoted with the same reference numerals to avoid any redundant description. In addition, elements that are not directly related to any embodiment of the disclosure are unillustrated in the drawings.

In an example embodiment, an adhered member may be a steel plate, and an adhesive may be an epoxy-based adhesive.

FIG.1is a diagram schematically illustrating a configuration of a surface-enhanced Raman scattering spectrometer10to which an adhesion interface observation method according to the example embodiment of the disclosure is applied. The surface-enhanced Raman scattering spectrometer10may include a piezo stage12, an unillustrated excitation laser, an objective lens26, and a plasmon sensor24. The piezo stage12may be a stage on which a sample18is to be placed. The excitation laser may be a light source of excitation light28to be applied to the sample18. The objective lens26may focus the excitation light28and cause the focused excitation light28to be applied onto the sample18. The plasmon sensor24may amplify Raman scattering light generated from the sample18.

As described later in greater detail, the sample18may be a resultant in which: the adhered members14are attached to each other by the adhesive16; one of the adhered members14is removed after curing of the adhesive16to expose the cured adhesive16; and the adhesive16is cut by an oblique cutting apparatus, or a surface and interfacial cutting analysis system (SAICAS), to be described later. The sample18may be placed on the piezo stage12. The piezo stage12may be moved in an optical axis direction of the objective lens26to adjust a focal position of the objective lens26. For example, this allows for an adjustment of the focal position of the objective lens26to a surface of the adhesive16of the sample18and to a joining surface between the adhered members14and the adhesive16. In the example embodiment, the piezo stage12may be moved with the objective lens26being fixed to adjust the focal position of the objective lens26. In some embodiments, the objective lens26may be moved with the piezo stage12being fixed to adjust the focal position of the objective lens26.

The excitation light28from the unillustrated excitation laser may be applied to the sample18through the objective lens26. The application of the excitation light28may cause the Raman scattering light to be emitted from the sample18. The Raman scattering light emitted from the sample18may generate a plasmon electric field30. The Raman scattering light emitted from the sample18may be amplified by the plasmon sensor24. The Raman scattering light amplified by the plasmon sensor24may enter the objective lens26. With this configuration, the objective lens26may condense the excitation light28from the excitation laser onto the sample18, and may condense surface-enhanced Raman scattering light32amplified by the plasmon sensor24. In the example embodiment, the excitation light28may be measurement light, and the surface-enhanced Raman scattering light32may be detection light. It should be noted inFIG.1that the plasmon electric filed30and the surface-enhanced Raman scattering light32are both schematically illustrated.

The plasmon sensor24may include a vitreous silica20and a plurality of Ag particles having flat end faces that cover a surface of the vitreous silica20. The surface of the vitreous silica20may be covered with the flat end faces of the Ag particles by a method such as a vacuum evaporation method or sputtering. As illustrated inFIG.1, the Ag particles22may be of a buried type or an implanted type, and may have a semispherical shape in which a lower half part of a sphere is cut and removed. The Ag particles22may be regularly disposed at a predetermined interval on the surface of the vitreous silica20. The plasmon electric field30may be generated at faces, of the Ag particles22, that are brought close to the sample18, allowing the surface-enhanced Raman scattering light32to be obtained in which an intensity of the Raman scattering light emitted from the sample18is increased 15,000 times.

FIG.2is a diagram illustrating a method of producing the sample18to be used for the adhesion interface observation method according to the example embodiment of the disclosure.

The two adhered members14may be attached together by the adhesive16, and one of the adhered members14may be removed after the curing of the adhesive16to expose the adhesive16. This process may be referred to as an adhesive exposing process. Part (a) and part (b) ofFIG.2each illustrate the adhered member14and the adhesive16following the adhesive exposing process.FIG.2illustrates an example of the sample18in which the adhesive16is so coated on the adhered member14as to have an adhesion thickness of 0.1 mm and to have an adhesion length of 10 mm. A direction of the adhesion thickness may correspond to a direction in which the excitation light28is to be applied.

The adhered member14may be the steel plate and may include a metal in the example embodiment. In some embodiments, the adhered member14may be a nonmetal for an observation of an adhesion interface. The adhesive16may be the two-pack room temperature curable epoxy-based resin in the example embodiment. In some embodiments, the adhesive16may be a one-pack room temperature curable epoxy-based resin, a urethane-based resin, or an acrylic-based resin.

Thereafter, a predetermined part of the adhesive16may be cut by a predetermined thickness to reduce a thickness of the predetermined part of the adhesive16as illustrated in part (c) and part (d) ofFIG.2. This process may be referred to as an observation region formation process. A cut width or a process width is denoted by a reference sign W, and may be 0.5 mm in the example embodiment. The process may be performed multiple times until a thickness of the adhesive16becomes 10 μm from 0.1 mm, thereby defining an observation region.

Setting the process width to 0.5 mm allows for an analysis while avoiding a concern of an interference. In a case where the cut width is small, the spherical plasmon sensor24can interfere with the adhesive16(a region having a thickness of 0.1 mm inFIG.2) around an observation possible region K, which can prevent the plasmon sensor24from sufficiently coming into contact with the observation possible region K and makes it difficult to perform the analysis. The plasmon sensor24may have a diameter of 2.5 mm and the process width W may be set to 0.5 mm in the example embodiment, which helps to perform the analysis without causing the interference of the plasmon sensor24with the adhesive16around the observation possible region K. This means that, in the example embodiment, it helps to receive the Raman scattering light properly while avoiding the concern of the interference.

Thereafter, the adhesive16may be cut obliquely as illustrated in part (e) and part (f) ofFIG.2. This process may be referred to as an oblique cutting process. For example, the adhesive16may be subjected to parallel cutting, following which the adhesive16in the cut width W may be subjected to oblique cutting at 1,000 times the ratio of a cutting speed in a thickness direction to a cutting speed in a horizontal direction. The oblique cutting may be so performed that a process length by which the thickness of the adhesive16becomes 0.1 μm or less is at least 100 μm.

As described above, the cutting process that reduces the thickness of the adhesive16within a predetermined region may be performed to fabricate the observation possible region K. The observation possible region K may be irradiated with the excitation light28, making it possible to receive the Raman scattering light properly in the observation possible region K and thereby to evaluate a state of adhesion of the adhesive16in the vicinity of an interface between the unremoved adhered member14and the adhesive16.

In the example embodiment, the observation method based on the surface-enhanced Raman scattering light may be applied to the observation possible region K to analyze a bonding state of the adhesion interface. Thus, it helps to directly evaluate a thickness of an interface boundary layer, a bonding state of the interface boundary layer, and a distribution of concentration in the depth direction of a functional group of the interface boundary layer. It also helps to perform a degradation structural analysis associated with an adhesion joining part. Further, it helps to directly confirm the bonding state of the adhesion interface, which helps to confirm whether desired bonding and a desired structure are formed at the adhesion interface by a surface treatment.

FIG.3is a diagram illustrating an example of a profile obtained by the adhesion interface observation method according to the example embodiment of the disclosure.FIG.3illustrates a Raman spectrum of the surface-enhanced Raman scattering light obtained on the basis of a change in an intensity of the Raman scattering light generated in the vicinity of a focal point with a focal position being moved in a depth direction Z, i.e., in a thickness direction of the adhesive16. The thus-obtained profile is a depth profile in the vicinity of a joining surface, by which it is possible to appreciate the distribution of concentration in the depth direction of a functional group from a surface of a substance toward the inside of the substance. InFIG.3, a horizontal axis indicates an observation position in the depth direction in nanometer unit, a left vertical axis indicates the intensity of the Raman scattering light, and a right vertical axis indicates the number of functional groups.

As can be appreciated fromFIG.3, it was confirmed that a methylol group and an epoxy group were aggregated in the vicinity of the adhesion interface. Thus, using the adhesion interface observation method according to any embodiment of the disclosure helps to analyze the bonding state of the adhesion interface, and to directly evaluate the thickness of the interface boundary layer, the bonding state of the interface boundary layer, and the distribution of concentration in the depth direction a functional group of the interface boundary layer. Accordingly, it helps to provide information on a chemical structure of the buried adhesion interface.

It also helps to provide information on a change in the chemical structure caused by a degradation of the adhesion interface. This means that it helps to clarify a factor that changes by the degradation for the degradation of the adhesion interface, which is considered to be a cause of a time degradation of the adhesion joining part. Further, it helps to assure a quality of a surface treatment that improves an adhesion property. This means that it helps to directly confirm the bonding state of the adhesion interface, which thereby helps to confirm whether the desired bonding and the desired structure are formed at the adhesion interface by the surface treatment.

The adhesion interface observation method according to the example embodiment uses the surface and interfacial cutting analysis system to obliquely cut the adhesive on the joining surface between the adhered member and the adhesive. The adhesion interface observation method helps to directly observe the Raman scattering light at the adhesion interface on the basis of the surface-enhanced Raman scattering (SERS) spectroscopy, by causing the oblique cutting to achieve a thickness of the adhesive that is equal to or less than a predetermined value at which the Raman scattering light is receivable. Accordingly, it helps to accurately evaluate the chemical structure of the buried adhesion interface in a non-destructive manner.

Although some example embodiments of the disclosure have been described in the foregoing by way of example with reference to the accompanying drawings, the disclosure is by no means limited to the embodiments described above. It should be appreciated that modifications and alterations may be made by persons skilled in the art without departing from the scope as defined by the appended claims. The disclosure is intended to include such modifications and alterations in so far as they fall within the scope of the appended claims or the equivalents thereof.

For example, the sample may include the steel plate and the epoxy-based adhesive in the example embodiment. However, a configuration of the sample is not limited to that described in the example embodiment. In addition, the sample may be placed on the piezo stage in the example embodiment. However, the sample may be provided on any moving device as long as the moving device is adjustable at a level of 0.1 nm or less.

The adhesion interface observation method according to at least one embodiment of the disclosure first forms the observation region by cutting a part of the cured adhesive exposed by removing one of the adhered members. Further, the observation region is further cut obliquely by, for example, a surface and interfacial cutting analysis system (SAICAS) to form the observation possible region in a region that is positioned on a side, of a part of the observation region having been subjected to the oblique cutting, on which a thickness of the part of the observation region having been subjected to the oblique cutting is small. The surface-enhanced Raman scattering (SERS) spectroscopy applies the excitation light with the plasmon sensor being placed still on the observation possible region and brought into contact with the observation possible region to perform a high precision analysis in the order of the depth resolution of 0.1 nm. Thus, the adhesion interface observation method helps to properly receive the Raman scattering light in the observation possible region and to accurately evaluate the state of adhesion of the adhesive in the vicinity of the interface between the unremoved adhered member and the adhesive.

In the observation method based on the SERS according to at least one embodiment of the disclosure, the oblique cutting by the SAICAS is for the formation of the observation possible region and is not intended to increase information in the depth direction as disclosed in at least one of JP-As described above, allowing for a non-destructive analysis of the interface. In addition, it helps to reduce a damage on the adhesion interface as much as possible. Accordingly, it helps to perform an accurate chemical analysis of a state of the buried adhesion interface, which helps to directly evaluate, in a non-destructive manner, a factor such as the bonding state of the adhesive and the adhered member (e.g., a hydrogen bonding that bonds the adhesive and an adhered member interface) or the distribution of concentration in the depth direction of a functional group. In any existing method, the hydrogen bonding is destructed during fabrication of a sample, preventing the hydrogen bonding from being analyzed.

In some embodiments, it helps to place, into a more suitable state for the observation, a region in which the excitation light is to be applied and the Raman scattering light is to be generated, i.e., the observation possible region. Thus, it helps to acquire accurate analysis information.

In some embodiments, the process width is 0.5 millimeters or greater. In the surface-enhanced Raman scattering (SERS) spectroscopy, the spherical plasmon sensor can interfere with the adhesive around the observation possible region in a case where the cut width is small, preventing the plasmon sensor from coming into contact with the observation possible region and making it difficult to perform the analysis. Accordingly, allowing the process width to be 0.5 millimeters or greater helps to allow for the analysis without causing the interference between the plasmon sensor and the adhesive around the observation possible region.

The adhesion interface observation method according to at least one embodiment of the disclosure helps to observe, by the surface-enhanced Raman scattering spectroscopy, a region in the vicinity of the joining interface in which the adhered member and the adhesive are adhered. Accordingly, the adhesion interface observation method according to at least one embodiment of the disclosure helps to evaluate directly, accurately, and in a non-destructive manner, a factor such as the bonding state of the adhesive and the adhered member or a distribution of concentration in the depth direction of a functional group.