JP2018096806A - Dielectric spectroscopic sensor and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dielectric spectroscopic sensor which is easy to attach and fix, and with which it is possible to measure reflection coefficient with a high S/N ratio.SOLUTION: A quasi-coaxial structure is constructed on substrates 11, 21 in such a way that vias 13A, 23A constitute internal conductors and vias 13B, 23B constitute external conductors, a sample placement face is provided on the substrate 11 surface for use of the quasi-coaxial structure a coaxial probe, a coplanar line or microstrip line is provided on the substrate 21 surface, and a metal pattern 22A constituting a signal wire for the line and the via 23A constituting the internal conductor are connected. Thus, a quasi-coaxial sensor of planar type can be formed, and it is made possible to provide a dielectric spectroscopic sensor which is easy to attach and fix and with which it is possible to measure reflection coefficient with a high S/N ratio.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a sensor interface technique for obtaining a complex dielectric constant of a sample.

  As aging progresses, the response to adult diseases has become a major issue. Tests such as blood glucose levels are a heavy burden on patients because they need to collect blood. Therefore, a non-invasive component concentration measuring apparatus that does not collect blood has attracted attention.

  As a non-invasive component concentration measurement device, microwave-submillimeter wave electromagnetic waves are used because of less scattering in the living body compared to optical methods such as near-infrared light and low energy of one photon. A method using the method has been proposed.

  For example, there is a method using a resonance structure shown in Non-Patent Document 1. In this method, a device having a high Q value such as an antenna or a resonator is brought into contact with a measurement sample, and frequency characteristics around the resonance frequency are measured. Since the resonance frequency is determined by the complex dielectric constant around the device, the component concentration is estimated from the shift amount of the resonance frequency by predicting in advance the correlation between the shift amount of the resonance frequency and the component concentration.

  As another technique using electromagnetic waves in the microwave-millimeter wave band, dielectric spectroscopy shown in Patent Document 1 has been proposed. In dielectric spectroscopy, an electromagnetic wave is irradiated into the skin, the electromagnetic wave is absorbed according to the interaction of blood components to be measured, for example, glucose molecules and water, and the amplitude and phase of the electromagnetic wave are observed. The dielectric relaxation spectrum is calculated from the amplitude and phase with respect to the frequency of the observed electromagnetic wave. The dielectric relaxation spectrum is generally expressed as a linear combination of relaxation curves based on the Cole-Cole equation, and the complex dielectric constant is calculated. In the measurement of biological components, for example, the complex dielectric constant has a correlation with the amount of blood components such as glucose and cholesterol contained in blood, and is measured as an electrical signal (amplitude, phase) corresponding to the change. A calibration model is constructed by measuring the correlation between the complex dielectric constant change and the component concentration in advance, and the component concentration is calibrated from the measured change in the dielectric relaxation spectrum. In addition, it is considered that the technique using dielectric spectroscopy is advantageous for concentration analysis in an aqueous solution composed of a multicomponent system by performing multivariate analysis such as PLS regression analysis on the obtained dielectric relaxation spectrum.

  Dielectric spectroscopy uses a transmission line capable of transmitting a wide-band electrical signal, such as a microstrip line, a coplanar line, or a coaxial probe. 10 and 11 show examples of conventional transmission lines used for dielectric spectroscopy. FIG. 10A shows a conventional example using a microstrip line, and FIG. 10B shows a conventional example using a coplanar line. In a microstrip line or a coplanar line dielectric spectroscopic sensor, a line is formed of a wiring metal 62 on a substrate 61, and a micro flow path 63 is disposed on the line. FIG. 11 is a diagram of a coaxial line for connecting a coaxial probe. A coaxial probe is connected to a high-frequency connector 71 disposed at the end of a coaxial cable composed of an inner conductor 72A, an outer conductor 72B, and a dielectric 73.

JP 2013-32933 A

M. Hofmann, G. Fischer, R. Weigel, and D. Kissinger, “Microwave-Based Noninvasive Concentration Measurements for Biomedical Applications”, IEEE Trans. Microwave Theory and Techniques, Vol.61, No.5, pp. 2195-2203 .

  In the method using a microstrip line or a coplanar line, it is necessary to accurately grasp the length of the portion where the sample and the line are in contact. For this reason, a microchannel for measurement is often provided on the track. Although it is possible to contact the line directly to the skin without providing a flow path, it is difficult to accurately grasp the length of the contact portion. In addition, the living body contains a large amount of moisture, and there is a problem that the transmission loss increases and the S / N ratio at the time of measurement decreases.

  In the method using the coaxial probe, it is not necessary to calculate the length of the contact portion, and since only the reflected wave is used, a high S / N ratio can be expected. However, a coaxial probe cannot be manufactured on a printed circuit board like a microstrip line or a coplanar line. The shape of the coaxial probe is a rod, and since the coaxial probe is brought into contact with an arm or a finger while standing, there is a problem that it is difficult to fix the coaxial probe.

  The present invention has been made in view of the above, and an object thereof is to provide a dielectric spectroscopic sensor that can be easily attached and fixed to a living body and can measure a reflection coefficient with a high S / N ratio.

  A dielectric spectroscopic sensor according to a first aspect of the present invention is a dielectric spectroscopic sensor that measures a reflection coefficient using a quasi-coaxial structure formed of vias as a coaxial probe, and includes a first dielectric substrate and the first dielectric substrate. A first via disposed through the first dielectric substrate, a plurality of second vias disposed in a circle around the first via, and the first dielectric A second dielectric substrate disposed over the body substrate, a third via disposed through the second dielectric substrate at a position corresponding to the first via, and the second dielectric A signal line arranged in conduction with the third via on a surface of the substrate on which the first dielectric substrate is not overlapped, and the second via at a position corresponding to the second via at a position not conducting with the signal line. A plurality of fourth vias disposed through the dielectric substrate. It is characterized in.

  A method for manufacturing a dielectric spectroscopic sensor according to a second aspect of the present invention is a method for manufacturing a dielectric spectroscopic sensor that measures a reflection coefficient using a quasi-coaxial structure formed of vias as a coaxial probe, and penetrates the first dielectric substrate. Forming a first through hole; forming a plurality of second through holes penetrating the first dielectric substrate at a circular position centered on the first through hole; and the first through hole. Forming a third through hole penetrating the second dielectric substrate at a position corresponding to the hole, and the second dielectric at a position corresponding to the second through hole and excluding a position where the signal line is formed. Forming a fourth through hole penetrating the body substrate, filling the first to fourth through holes with a metal to form a via, and forming the via on the surface of the second dielectric substrate. Forming a signal line that is electrically connected to the via formed in the through hole, and bonding the first dielectric substrate and the surface of the second dielectric substrate on which the signal line is not formed. It is characterized by that.

  According to the present invention, it is possible to provide a dielectric spectroscopic sensor that can be easily attached and fixed to a living body and can measure a reflection coefficient with a high S / N ratio.

It is a perspective view which shows the structure of the dielectric spectroscopy sensor of this Embodiment. It is a top view of the board | substrate which has a sample arrangement | positioning surface of the dielectric spectroscopy sensor of this Embodiment. It is a top view of the board | substrate which has a track | line of the dielectric spectroscopy sensor of this Embodiment. It is a top view of another example of composition of a substrate which has a track of a dielectric spectroscopic sensor of this embodiment. It is process drawing which shows an example of the manufacturing process of the dielectric spectroscopy sensor of this Embodiment. It is an equivalent circuit of the part which adhere | attaches the sample of the dielectric spectroscopy sensor of this Embodiment. It is a figure which shows the example of the measurement system using the dielectric spectroscopy sensor of this Embodiment. It is a figure which shows the example of another measuring system using the dielectric spectroscopy sensor of this Embodiment. It is a figure which shows the example of another measuring system using the dielectric spectroscopy sensor of this Embodiment. It is a figure which shows the example of the transmission line used for the conventional dielectric spectroscopy which used the microstrip line and the coplanar line. It is a figure which shows the example of the transmission line used for the conventional dielectric spectroscopy using a coaxial line.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a perspective view showing a configuration of a dielectric spectroscopic sensor in the present embodiment. The dielectric spectroscopic sensor of FIG. 1 has a structure in which a substrate 11 and a substrate 21 which are dielectric substrates are laminated. FIG. 1A is a perspective view when a substrate 11 having a sample arrangement surface on which a sample is arranged is turned up. FIG.1 (b) is a perspective view when the board | substrate 12 which has the track surface which formed the track | line is turned up. When the dielectric spectroscopic sensor shown in FIG. 1A is turned over, the state shown in FIG.

  FIG. 2 is a plan view of the substrate 11. FIG. 2A is a plan view of the sample arrangement surface of the substrate 11. FIG. 2B is a plan view of the bonding surface of the substrate 11 that is bonded to the substrate 21.

  FIG. 3 is a plan view of the substrate 21. FIG. 3A is a plan view of the bonding surface of the substrate 21 that is bonded to the substrate 11. FIG. 3B is a plan view of the line surface of the substrate 21.

  As materials for the substrates 11 and 21, glass epoxy, Teflon, alumina, quartz, Si, or the like used at high frequencies is used. The size of the substrates 11 and 21 is several centimeters × several centimeters, and the substrate thickness is several hundred μm to several mm. The substrates 11 and 21 have a low dielectric constant having a relative dielectric constant of 2 to 3.

  Metal patterns 12A and 12B provided with circular openings are provided on both surfaces of the substrate 11. The diameter of the opening is several hundred μm to several mm. As a material for the metal patterns 12A and 12B, a metal used for a high-frequency substrate, such as Cu or Au, is used. Since the metal patterns 12A and 12B have the same shape, patterns required for design can be reduced.

  A via 13 </ b> A penetrating the substrate 11 is provided at the center of the opening of the substrate 11. In addition, a via 13B is provided along the circumference of the opening so as to be electrically connected to the metal patterns 12A and 12B. That is, the via 13B is provided in a circular shape centering on the via 13A. The vias 13A and 13B are filled with a conductor. As materials for the vias 13A and 13B, conductive ink, copper paste, silver paste, copper plating, or the like is used. Alternatively, a metal pin having the same diameter as the vias 13A and 13B may be embedded. Due to the quasi-coaxial structure in which the via 13A is an inner conductor and the via 13B is an outer conductor, a TEM mode electromagnetic wave propagates in the plane direction of the substrate 11. The surface of the quasi-coaxial substrate 11 composed of the vias 13A and 13B and the substrate 11 serves as a sample arrangement surface on which the sample is arranged. The via diameters of the vias 13A and 13B are several tens of μm to several mm, and are appropriately determined according to the cutoff frequency required for the coaxial structure and the penetration depth of the electric field in the sample direction. The inner conductor diameter and the opening diameter are determined in accordance with the characteristic impedance of the measuring instrument connected to the present dielectric spectroscopic sensor.

  On the line surface of the substrate 21, metal patterns 22A and 22B constituting a coplanar line are provided. The metal pattern 22A becomes a signal line of a coplanar line, and the metal pattern 22B becomes a ground line. The width of the metal pattern 22A and the width of the gap between the metal patterns 22A and 22B are several tens of μm to several mm. In accordance with the characteristic impedance of the measuring instrument connected to the present dielectric spectroscopic sensor, each dimension of the coplanar line is designed to be, for example, 50Ω or 75Ω. The material of the metal patterns 22A and 22B is the same as that of the metal patterns 12A and 12B of the substrate 11.

  The substrate 21 is provided with vias 23A and 23B constituting a quasi-coaxial structure corresponding to the positions of the vias 13A and 13B of the substrate 11. The via 23A is electrically connected to the via 13A and the metal pattern 22A. The via 23B is electrically connected to the via 13B and the metal pattern 22B. With this configuration, the substrate 21 plays a role of coplanar line-quasi-coaxial conversion. The via 23B is arranged so as not to contact the metal pattern 22A that becomes a signal line. In the present embodiment, the via 23B at the position in contact with the metal pattern 22A is not formed even at the position corresponding to the via 13B of the substrate 11.

  The substrate 11 and the substrate 21 are bonded with an adhesive or the like. The metal pattern 12B between the substrate 11 and the substrate 21 serves as the ground, and the substrate 21 and the metal patterns 12B, 22A, and 22B constitute a coplanar line with a back surface ground. The presence of the back ground reduces the influence of the electric field in the substrate direction of the coplanar line on the quasi-coaxial structure.

  A microstrip line may be used for the line of the substrate 21 instead of the coplanar line.

  Further, in order to make the potential of the ground line portion of the coplanar line of the substrate 21 and the potential of the metal pattern 12B of the substrate 11 equal, an additional via 23C penetrating the substrate 21 is provided in the ground line portion as shown in FIG. Also good.

  Next, manufacturing of the dielectric spectroscopic sensor in the present embodiment will be described.

  FIG. 5 is a process diagram showing an example of a manufacturing process of the dielectric spectroscopic sensor in the present embodiment.

  The substrate is cut into a predetermined size to produce substrates 11 and 21 (step S1). Through holes are formed at positions corresponding to the vias 13A, 13B, 23A and 23B of the substrates 11 and 21 (step S2), and via metals are filled in the through holes to form vias 13A, 13B, 23A and 23B (step S2). S3). After forming the vias 13A, 13B, 23A, and 23B, the surfaces of the substrates 11 and 21 are polished (step S4). A predetermined metal pattern is formed on the surfaces of the substrates 11 and 21 (step S5). The substrates 11 and 21 are bonded together to obtain a dielectric spectroscopic sensor (step S6).

  When the through metal is filled in the through hole, the diameter of the metal portion on the surface of the substrates 11 and 21 may be larger than the via diameter. In order to prevent unnecessary inductance and capacitance at the connection between the substrates 11 and 21 and the contact portion with the sample, it is ideal to polish both surfaces of the substrates 11 and 21 after metal filling. A quasi-coaxial structure can be formed.

  Next, measurement of the complex dielectric constant of the sample will be described.

FIG. 6 is an equivalent circuit of a portion where the sample of the dielectric spectroscopic sensor is adhered. Here, C _f is the flange capacitance of the dielectric spectroscopic sensor, and C ₀ (ε _m ^* ) and G ₀ (ε _m ^* ) are the capacitance of the opening and the radiation conductance, which are functions of the complex dielectric constant of the sample. .

  By sweeping a desired frequency, for example, 10 MHz to 50 GHz and measuring the reflection coefficient, the complex dielectric constant of the sample can be measured based on the following formulas (1) and (2).

Here, ε ^* is a dielectric constant of an unknown sample, and ε _i ^* (i = A, B, C) is a dielectric constant of a standard sample. ρ ^* is a complex reflection coefficient, and can be described as follows, where Γ _{i is} the reflection coefficient obtained by measurement and φ _i is the phase.

  Air, metal, and liquid samples are used as standard samples. As the metal, copper, indium, mercury, gold, or the like is used. As the liquid sample, pure water, methanol, ethanol, formamide or the like is used.

  FIG. 7 is a diagram illustrating an example of a measurement system using the dielectric spectroscopic sensor of the present embodiment.

  As shown in FIG. 7A, the high frequency connector 3 is connected to the coplanar line portion of the dielectric spectroscopic sensor. For the high frequency connector 3, for example, a K connector, a V connector, a 1 mm connector, a GPPO connector, or a G3PO connector is used.

  As shown in FIG. 7B, the dielectric spectroscopic sensor is connected to the measuring instrument 4 by a high frequency cable. As the measuring instrument 4, a vector network analyzer, an impedance analyzer, a reflectometer, or the like is used. For example, a semi-rigid cable or a soft rigid cable is used as the high-frequency cable, and a transmission band of DC to several tens GHz is used, for example.

  Alternatively, instead of connecting the high frequency connector 3 to the dielectric spectroscopic sensor, a GSG probe may be attached to the high frequency cable, and the probe may be applied to the line portion of the dielectric spectroscopic sensor for measurement.

  The measurement system is constructed by the method as described above, and the reflection coefficient of the sensor is measured in a state where the sample 100 is in contact with the quasi-coaxial structure of the sample arrangement surface of the dielectric spectroscopic sensor, and the equations (1) and (2) are obtained. By using this, the complex dielectric constant of the sample 100 can be obtained.

  As another measurement system, a dielectric spectroscopic sensor may be mounted on a substrate.

  For example, as shown in FIG. 8, the coplanar line portion of the dielectric spectroscopic sensor is electrically connected to the measurement IC 5 by the bonding wire 51. Alternatively, as shown in FIG. 9, the dielectric spectroscopic sensor and the measurement IC 5 may be electrically connected by flip chip mounting. The measurement IC 5 is composed of a plurality of IC chips and has the same function as the above-described measuring instrument.

  As described above, according to the present embodiment, the quasi-coaxial structure is formed on the substrates 11 and 21 so that the vias 13A and 23A serve as inner conductors and the vias 13B and 23B serve as outer conductors. By providing a sample arrangement surface using a quasi-coaxial structure as a coaxial probe, providing a coplanar line or a microstrip line on the surface of the substrate 21, and connecting a metal pattern 22A serving as a signal line of the line and a via 23A serving as an internal conductor, It is possible to provide a dielectric spectroscopic sensor that can form a planar quasi-coaxial sensor, can be easily attached and fixed to a living body, and can measure a reflection coefficient with a high S / N ratio.

DESCRIPTION OF SYMBOLS 11 ... Board | substrate 12A, 12B ... Metal pattern 13A, 13B ... Via 21 ... Board | substrate 22A, 22B ... Metal pattern 23A, 23B, 23C ... Via 3 ... High frequency connector 4 ... Measuring instrument 5 ... Measurement IC
51 ... Bonding wire 100 ... Sample

Claims (5)

A dielectric spectroscopic sensor for measuring a reflection coefficient using a quasi-coaxial structure constituted by vias as a coaxial probe,
A first dielectric substrate;
A first via disposed through the first dielectric substrate;
A plurality of second vias penetrating through the first dielectric substrate and arranged in a circle around the first via;
A second dielectric substrate disposed over the first dielectric substrate;
A third via disposed through the second dielectric substrate at a position corresponding to the first via;
A signal line disposed in conduction with the third via on a surface of the second dielectric substrate on which the first dielectric substrate is not overlapped;
A plurality of fourth vias disposed through the second dielectric substrate at positions corresponding to the second vias at positions not conducting to the signal line;
A dielectric spectroscopic sensor comprising:   The dielectric spectroscopic sensor according to claim 1, wherein the signal line is a microstrip line or a coplanar line.   3. The dielectric according to claim 1, further comprising a ground plate that is electrically connected to the second via and the fourth via between the first dielectric substrate and the second dielectric substrate. Spectroscopic sensor. A method for producing a dielectric spectroscopic sensor for measuring a reflection coefficient using a quasi-coaxial structure constituted by a via as a coaxial probe,
Forming a first through hole penetrating the first dielectric substrate;
Forming a plurality of second through holes penetrating the first dielectric substrate at a circular position centered on the first through hole;
Forming a third through hole penetrating the second dielectric substrate at a position corresponding to the first through hole;
Forming a fourth through hole corresponding to the second through hole and penetrating through the second dielectric substrate at a position excluding a position where the signal line is formed;
Filling the first through fourth through holes with metal to form vias;
Forming a signal line electrically connected to the via formed in the first through hole on the surface of the second dielectric substrate;
Bonding the surfaces of the first dielectric substrate and the second dielectric substrate that do not form the signal line;
A method for manufacturing a dielectric spectroscopic sensor, comprising:   5. The dielectric spectroscopic sensor according to claim 4, further comprising a step of polishing the surface of the first dielectric substrate and the surface of the second dielectric substrate after the step of forming the via. Method.

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