JP4796825B2 - Sensor for measuring minute mass - Google Patents

Description

        The present invention relates to a highly reliable sensor for measuring a small mass suitable for measurement in a liquid phase sample.

        Conventionally, a sensor element for measuring a minute mass (QCM Quartz Crystal Microbalance sensor element) using an AT-cut quartz crystal resonator uses a thickness-shear vibration mode of quartz. For the metal film material formed on the surface of the quartz substrate, considering adhesion to the quartz substrate, the base material is, for example, chromium (Cr), nickel chromium (NiCr), titanium (Ti), etc. As the ground material, gold (Au), silver (Ag), aluminum (Al), or the like is used. When such a sensor element for measuring a minute mass is immersed in a solution, the previous vibration mode is suppressed by the resistance force of the solution and cannot be used as a sensor element for measuring a minute mass. Therefore, by setting the metal film of the quartz substrate on the side where the reaction of the solution is not detected to be in a gas phase state, it is possible to detect the vibration mode of the sensor element for measuring the minute mass even when immersed in the solution.

        In order to keep the metal film on one side of the quartz substrate in a gas phase, the entire periphery of the sensor element for measuring a minute mass (hereinafter referred to as a QCM sensor element) is fixed with an adhesive or the like to prevent the solution from entering. There must be. In general, in order to make the influence on the vibration mode of the QCM sensor element as small as possible, a silicon-based insulating adhesive material having a low adhesive stress is often used. When used, depending on the skill level of an operator who assembles a sensor for measuring a minute mass (hereinafter referred to as a QCM sensor), the amount of adhesive applied varies greatly between the individual QCM sensor elements. It is difficult to fix the sensor to the QCM sensor container accurately and horizontally, and in each case, the sensitivity of the detection of the QCM sensor element is made different due to variations in the amount of adhesive applied. As for the QCM sensor element, there is a risk that the sensitivity of detection of the QCM sensor element may be lowered as a result of a slight stress strain of the adhesive.

        Furthermore, when the adhesive is cured, by-products such as organic substances are generated from the adhesive, and there is a risk that the by-products may adhere to the surface of the QCM sensor element for detecting an extremely fine reaction. is there. As a specific example, particularly when a silicon-based adhesive is used, low molecular siloxane may be generated as a by-product and may adhere to the surface of the metal film. Once this low molecular weight siloxane adheres to the surface of the metal film, there is a risk that the detection sensitivity of the QCM sensor element will be significantly reduced.

        Further, when the QCM sensor is immersed in a sample solution of an organic solvent as a QCM sensor for use in a liquid phase measurement, if the QCM sensor element is fixed to the sensor container with a silicon adhesive, the silicon adhesive The material swells about 3 to 4 times in both mass and volume from the point of contact with the organic solvent, and stress is applied to the QCM sensor element. As a result, the detection sensitivity of the QCM sensor element may be significantly reduced here as well. was there.

        In addition, in a conventional QCM sensor using a type of quartz crystal that is immersed in a solution, a lead wire is drawn from the QCM sensor element inside the QCM sensor housing and connected to instruments that measure the detection value. In this case, the detection sensitivity may be reduced due to the occurrence of a contact accident of the lead wire in the casing or the influence of external noise.

Japanese Patent Laid-Open No. 1994-18394 Japanese Patent Laid-Open No. 11-14525 JP 2001-153777 A

        In addition, the applicant did not find any prior art documents related to the present invention by the time of filing of the present application other than the prior art documents specified by the above prior art document information.

        By using an adhesive to fix the QCM sensor element to a sensor container for measuring a small mass (hereinafter referred to as a QCM sensor container), the adhesive by-product adheres to the surface of the QCM sensor element. However, there is a problem that the detection sensitivity may be non-uniform and the detection sensitivity may be significantly reduced.

        Further, when immersed in a sample solution of an organic solvent as a QCM sensor for use in liquid phase measurement, particularly when the QCM sensor element is fixed to the sensor container with a silicon-based adhesive, the adhesive Swells in both mass and volume from the point of contact with the organic solvent, the QCM sensor element oscillates in an inclined state with non-uniform stress applied, and the adhesive swells and corresponds to the increased mass As a result, there is a possibility that the detection sensitivity of the QCM sensor element is significantly reduced.

        The present invention has been made based on the technical background as described above. Therefore, the object of the present invention is to provide a highly reliable sensor for measuring a small mass suitable for measurement in a liquid phase sample. Is to provide.

In order to solve the above problems, the present invention provides a micromass measuring QCM sensor having a micro mass measuring sensor element formed by forming a metal film used as an electrode on the front and back surfaces of a quartz substrate. A sensor container for measuring a minute mass having a recess and a wiring inside the container in which the sensor element is fitted and mounted, and on the inner edge side of the horizontal surface inside the recess, has a frame-shaped joint surface, A metal film made of a bonding material is provided in an annular shape along an edge on the outer edge side of the bonding surface and an edge of the surface of the crystal substrate facing the bonding surface, and the metal film used as the electrode is The container internal wiring is provided at a position where one end is inside the metal film made of the bonding material on the bonding surface. The gold which becomes the electrode while being located In contact with the membrane,
The other end is located on the outer surface side of the sensor container for measuring the minute mass and serves as a signal output terminal, and the sensor element for measuring the minute mass is provided on one side of the sensor element for measuring the minute mass. The sensor element for measuring the minute mass and the minute mass measurement in the recess are formed by fitting the metal film made of the bonding material by anodic bonding. The space surrounded by the sensor container is airtight.

        According to the QCM sensor of the present invention, since no adhesive is used for fixing the QCM sensor element, there is no possibility that the by-product of the adhesive adheres to the QCM sensor element and decreases the detection sensitivity, and the handling is easy. In addition, a QCM sensor with extremely high reliability can be obtained.

        In addition, according to the QCM sensor of the present invention, the signal output end of the sensor element is extended to the outer surface of the QCM sensor container without using a lead wire, which is easy to handle and extremely reliable. A QCM sensor can be obtained.

        Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In addition, the same code | symbol in each figure shall show the same object.

FIG. 1 is a schematic top view of a QCM sensor 3 according to the present invention as viewed from above. That is, the QCM sensor 3 of the present invention is a sensor 3 for measuring a minute mass (QCM sensor) using a quartz resonator formed by forming a metal film 2 on the surface 1 of a quartz substrate, and a sensor element for measuring a minute mass. 4 (QCM sensor element) is fitted in and mounted in the QCM sensor container 6 and has a frame-like joint surface at the inner edge of the horizontal surface inside the recess. Airtightly joined and mounted. The QCM sensor element 4 placed inside the QCM sensor has, for example, a rectangular shape as shown in FIG. 4, which is formed by depositing a metal film material on a quartz substrate using a vapor deposition method or a sputtering apparatus. 2 is deposited on a quartz substrate. By using anodic bonding between the QCM sensor container 6 and the QCM sensor element 4 at the frame-shaped joint portion,
The QCM sensor element 4 can be fixed in the recess 5 of the QCM sensor container without using an adhesive. The frame-shaped bonding surface 7 as shown in FIG. 4 is obtained by depositing a metal bonding material such as aluminum used for anodic bonding by vapor deposition or the like around one side of the QCM sensor element 4. 4 is placed inside the QCM sensor container 6 and pressed while direct current is applied. The structure of the QCM sensor 3 of the present invention shown in FIG. 1 is an arrangement structure in which a metal film used for bonding and a metal film 2 used as an electrode formed on a quartz substrate are not in electrical contact with each other. It is made up. QCM
The end 8 of the exposed electrode of the QCM sensor element 4 mounted on the sensor 3 has a through-passage 10 connected to the back surface 9 of the QCM sensor element, and the surface of the QCM sensor element 4 on which the exposed electrode is present. The metal film used for bonding and the metal film 2 used as an electrode formed on the quartz substrate do not come into electrical contact with each other by the structure that is electrically connected to the connection terminal on the back side of the substrate. is doing. In addition, the through-passage 10 that conducts to the back surface 9 of the QCM sensor element at the exposed electrode end 8 of the QCM sensor element 4 mounted on the QCM sensor 3 is formed in a through hole (pinhole) having an extremely small diameter. In the use of the QCM sensor 3 of the present invention in the liquid phase formed by pouring and closing a conductive metal such as (Au), a liquid phase sample is not allowed to enter the airtight back side of the QCM sensor element 4 No.

        FIG. 2 is a schematic cross-sectional view of the QCM sensor 3 of the present invention shown in FIG. 1 as viewed from the short side surface direction B-B ′ of the sensor element 4. The quartz substrate has various shapes and sizes, and FIG. 1 is an example. Therefore, when the quartz substrate is not a rectangular plate but a square plate or a circular shape, or the outer shape of the QCM sensor container 6 may be a polygonal shape, these cases are also within the technical scope of the present invention. Needless to say, it is included. In addition, the QCM sensor 3 of the present invention has a structure that is very suitable for using the exposed one side of the sensor element 4 in a liquid phase state and the other side in a gas phase state, but is immersed in a liquid phase sample. Thus, it can be used as a QCM sensor 3 that is used in a gas phase state on both sides without being used.

        FIG. 3 is a schematic side cross-sectional view of the QCM sensor 3 of the present invention shown in FIG. 1 as viewed from the position of the long side surface direction A-A ′ of the sensor element 4. As shown in FIG. 3, the shape is such that it can be handled without touching the exposed electrode surface, which makes it very easy to perform a minute mass measurement operation using the QCM sensor 3 of the present invention.

        FIG. 4 is a schematic top view of the QCM sensor container 6 of the present invention as seen from the top surface direction. The QCM sensor element 4 written in FIG. 4 is fitted and mounted in the recess 5 provided in the QCM sensor container 6, and the signal output end 11 of the QCM sensor element 4 is formed by an internal metallization layer of the QCM sensor container. It extends to the outer surface 12 of the QCM sensor container through the completed wiring.

        FIG. 5 is a schematic top perspective view of a conventional QCM sensor element 4 alone as viewed obliquely from above. The quartz substrate has various shapes and sizes, and FIG. 5 is an example.

It is the schematic upper surface figure which looked at the QCM sensor of the present invention from the upper surface direction. FIG. 2 is a schematic cross-sectional view of the QCM sensor of the present invention of FIG. 1 as viewed from the short side surface direction B-B ′ of the sensor element. FIG. 2 is a schematic side cross-sectional view of the QCM sensor of the present invention of FIG. 1 as viewed from the position of the long side surface direction A-A ′ of the sensor element. FIG. 4 is a schematic top view of the QCM sensor container according to the present invention as seen from above. It is the outline top perspective view which looked at the conventional QCM sensor element simple substance from the slanting upper direction.

Explanation of symbols

1 Surface of crystal substrate 2 Metal film 3 Sensor for measuring minute mass (QCM sensor)
4 Sensor element for measuring minute mass (QCM sensor element)
5 Recess 6 Sensor container for measuring minute mass (QCM sensor container)
7 Metal film made of bonding material 8 Exposed electrode end 9 Back surface of sensor element for measuring micromass 10 Through passage 11 Signal output end 12 External surface of sensor container for measuring micromass

Claims (1)

In a sensor for measuring a minute mass comprising a sensor element for measuring a minute mass formed by forming a metal film used as an electrode on the front and back surfaces of a quartz substrate,
A sensor container for measuring a minute mass having a recess and a wiring inside the container in which the sensor element for measuring the minute mass is fitted and mounted;
On the inner edge side of the horizontal surface inside the recess, it has a frame-shaped joint surface,
A metal film made of a bonding material is provided in an annular shape along an edge on the outer edge side of the bonding surface and an edge of the surface of the quartz substrate facing the bonding surface side,
The metal film used as the electrode is provided at a position not in contact with the metal film made of the bonding material provided on the quartz substrate,
The container internal wiring is in contact with the metal film serving as the electrode while one end is positioned on the inner side of the metal film made of the bonding material on the bonding surface, and the other end is the sensor container for measuring micro mass. Located on the outer surface side of
The sensor element for measuring a minute mass is mounted by being fitted to the concave portion so that the periphery of one surface of the sensor element for measuring the minute mass is aligned with the joint surface,
Since the metal film made of the bonding material is bonded by anodic bonding, the space surrounded by the sensor element for measuring the minute mass and the sensor container for measuring the minute mass in the recess is airtight. A sensor for measuring minute mass.

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