JPH03186247A - Pulse wave detecting device - Google Patents

Abstract

PURPOSE:To prevent a sudden change of a pressure signal waveform in the course of detecting a pulse wave by providing a shield layer consisting of a conductive material on one face of a semiconductor substrate in which a pressure sensitive element is formed on one face. CONSTITUTION:By providing a semiconductor substrate 98 in which a pressure sensitive element is formed on one face, and pressing one face of the substrate 98 against the skin of a living body, a pressure pulse wave generated from an artery positioned under the skin is detected. Also, a shield layer 118 consisting of conductive silicone rubber, etc., is provided on one face of the semiconductor substrate 98. As a result, the device comes to be scarcely influenced by static electricity generated in the living body, and it does not occur that an offset of a pressure signal is changed suddenly, or the pressure signal is fluctuated by responding to an external flux light.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a pulse wave detection device that detects pressure pulse waves in an artery of a living body by pressing a pressure detection element from the skin of the living body toward the artery. It is related to.

Prior Art A semiconductor substrate on which a pressure detection element is formed is a type of pulse wave detection device that detects pressure pulse waves in an artery of a living body by pressing a pressure detection element from the skin of the living body toward the artery. There is one that is formed so that one side of the body is pressed against the skin of the living body.

For example, there is a pulse wave detection device described in Utility Model Application Publication No. 1-43905.

Problems to be Solved by the Invention However, according to the above-mentioned conventional pulse wave detection device, a thin part is formed in a part of the semiconductor substrate so that distortion occurs when pressure from a detection target is propagated, and this thin part Pressure is converted into an electrical signal by a semiconductor strain gauge formed in the sensor, and the pressure is output as a pressure signal. However, when pressure detection is continued with a pressure detection element formed on one side of a semiconductor substrate pressed against the skin of a living body, there is sometimes an offset in the pressure signal waveform even though there is no change in pressure. There is a problem in that the pressure signal fluctuates due to sudden changes or in response to external light.

The present invention has been made against the background of the above circumstances,
The purpose is to provide a pulse wave detection device in which the pressure signal waveform does not suddenly change during pulse wave detection.

Means for Solving the Problems In order to remotely achieve this objective, the present inventors conducted various studies and conducted confirmation tests, and as a result, they discovered that static electricity generated in living organisms affects pressure signals. The present invention has been made based on this knowledge.

In other words, the gist of the present invention is to provide a semiconductor substrate on which a pressure-sensitive element is formed on one side, and to press one side of the semiconductor substrate against the skin of a living body to detect pressure-sensitive elements generated from arteries located under the skin. In a pulse wave detection device for detecting pressure pulse waves, a shield layer made of a conductive material is provided on one surface of the semiconductor substrate.

Operation and Effects of the Invention In this manner, a shield layer made of a conductive material is provided on one surface of the semiconductor substrate on which the pressure-sensitive element is formed, so that the pressing surface of the semiconductor substrate is electrostatically shielded. Therefore, it is less susceptible to the effects of static electricity generated in the living body, and it is possible to eliminate sudden changes in the offset of the pressure signal or fluctuations in the pressure signal in response to external light.

EXAMPLE Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 2 is a sectional view showing a pulse wave detection device which is an embodiment of the present invention. The housing 10 is made of resin and has a container-like shape as a whole, and the basic shape of the longitudinal side surface is formed in a crescent shape, and the widthwise middle part of the bottom wall has a predetermined shape along the longitudinal direction. It is said to have a protruding shape. Such a housing 10 is configured to be removably attached using a mounting band 14 with its open end facing a surface 12 of a part of a living body such as a wrist.

In order to fix the reduction gear unit 22 to the housing 10, a support plate 24 made of resin and having an angular cross section is fixed to the reduction gear unit 22 by screw members 23, and a pair of brackets 26 (only one of which (shown) are fixed to opposing side walls 18 of the housing 10 by screw members 25. The reduction gear unit 22 is
a second gear 32 that meshes with the first gear 30;
a third gear 34 coaxially fixed to the third gear 34; a fourth gear 36 meshing with the third gear 34; a fifth gear 38 coaxially fixing the fourth gear 36; and a drive motor in mesh with the fifth gear 38. A sixth gear 44 fixed to the output shaft 42 of 40 is rotatably provided within the metal frame member 28. The first gear 30 is fixed to one end of a feed screw 48 that passes through a resin bearing 46 fitted to the frame member 28. As a result, the feed screw 48 and the drive motor 4
0 are operatively connected to each other, and the feed screw 48 is rotationally driven by the drive motor 40. Note that the drive motor 40 is fixed to the frame member 28.

A hole 52 into which an eccentric bearing 50 is fitted is formed at the end of the housing 10, and the other end of the feed screw 48 is supported by the eccentric bearing 50. As a result, the feed screw 48 is rotatably attached to the housing 10.
It is located at the center in the width direction. This eccentric bearing 50
By changing the rotational position of the feed screw 48, the other end of the feed screw 48 fitted into the eccentric hole 58 can be displaced in the vertical and horizontal directions in FIG.

Pressing device No. 66, a threaded member 68 threaded onto the feed screw 48 and a diaphragm 70 underneath the threaded member 68.
It is composed of a rectangular tubular member 72 fixed via a cylindrical member 72. A pulse wave sensor 74 is fixed to the center of the diaphragm 70. A pressure chamber 76 is formed by the screw member 68 and the diaphragm 70, so when a predetermined pressure is supplied to this pressure chamber 76 from a pressure regulating device (not shown), the pulse wave sensor 74 detects the pressure in the pressure chamber 76. It is pressed toward the surface 12 of the living body with a pressing force corresponding to the pressure. On the pressing surface 78 of the pulse wave sensor 74,
As will be described later, a semiconductor substrate is provided on which a plurality of pressure detection elements such as semiconductor strain resistors and pressure-sensitive diodes are arranged, and when driven by the drive motor 40, the pulse wave sensor 74 is positioned directly above the artery 80. In addition to being located in
A pressure pulse wave generated from the artery 80 in synchronization with the heartbeat is detected while a portion of the wall of the artery 80 is pressed flat.

As shown in detail in FIG. 1, the pulse wave sensor 74 has a case member 86 in which conductors are laminated and wired, and an amplification IC 82, a multiplexer IC 84, etc. are fixed to the back surface.
A ceramic substrate 88 is fitted into the opening of the case member 86, and the ceramic substrate 88 is made of an electrically insulating material such as ceramic or resin, and is wired on the front and back sides through through holes. It includes a support plate 90 that is fitted, and a sensor main body 92 that is supported by being fixed to the center of the support plate 90. As shown in the perspective view of FIG. 3, this sensor body 92 includes a back-up plate 96 made of a relatively rigid material, and a semiconductor substrate 98 bonded to the surface of this back-up plate 96. It consists of

The backup plate 96 and the semiconductor substrate 9 are preferably bonded together using epoxy resin, silicone rubber, or the like. As the backup plate 96, a thick inner plate made of quartz glass or the same semiconductor as the semiconductor substrate 98 is used.

In order to eliminate the influence of the difference in thermal expansion, the most preferable combination is to bond the semiconductor substrate 98 onto a backup plate 96 made of the same semiconductor as the semiconductor substrate 98 using silicone rubber.

In this embodiment, the semiconductor substrate 98 is a silicon single crystal plate, and as shown in FIG. 3, a plurality of pressure sensitive elements 100 for detecting contact pressure are arranged in one direction in the center thereof. has been done. In the pulse wave detection device of this embodiment, the pulse wave sensor 74 is pressed when the pressure sensing element 100 is positioned directly above the artery 80 and the arrangement direction thereof is perpendicular to the artery 80. There is. 500μm to 1500um
The back-up plate 96, which has increased rigidity by having a thickness of A through hole 102 is provided for this purpose. The semiconductor substrate 98 has a thickness of about 3005 ξcm, and by forming a longitudinal concave portion on the back surface, a thin portion 10 having a thickness of several to tens of ξcm is formed.
6 is formed. As shown in FIG. 4, a plurality of protrusions 108 are formed at regular intervals in the thin portion 106 and have a height lower than the thickness of the semiconductor substrate 98 and cross the longitudinal recessed portion. Projection 10 of the thin wall portion 106
A plurality of the pressure sensitive elements 100 are provided in the portion located between the pressure sensitive elements 8 and 8.

The height of the protrusion 10B is appropriately determined to prevent crosstalk.

FIG. 4 is a front view of the pressing surface of the semiconductor substrate 98, and shows the configuration of the pressure sensitive element 100 disposed in the thin portion 106 between the protrusions 108. In the figure, the arrangement and connection structure of one pressure sensitive element 100 is shown. four strain resistance elements 110a, 110b,
110c and 110d are formed using well-known semiconductor manufacturing techniques such as diffusion or implantation of predetermined impurities. In addition, the four strain resistance elements 11Oa,
The conductors 112a, 112b, 112c, and 112d for constituting the electric bridges 110b, 110C, and 1110d are also formed using well-known semiconductor manufacturing techniques such as diffusion or implantation of predetermined impurities. The strain resistance element 110
a, 110b, 110c, 110d and conductor 112a
, 112b, 112c, and 112d generates an electric signal corresponding to the strain applied to the thin wall portion 106 on which it is installed, so one pressure-sensitive element 1
00. Note that the strain resistance element 1
10a, 110b, 110c, 110d and conductor 11
2a, 112b, 112c.

112d is formed by locally increasing the impurity concentration of the semiconductor substrate 98, and therefore cannot normally be visually observed.

Returning to FIG. 1, bonding wires are connected between the amplification IC 82 and multiplexer IC 84 and the ceramic substrate 88, between the ceramic substrate 88 and the support plate 90, and between the semiconductor substrate 98 and the support plate 90. 114. The semiconductor substrate 98 is coated with an insulating protection layer 116 made of epoxy resin, silicone resin, or the like to protect the connection portion of the bonding wire 114. Moreover, the pressure-sensitive element 100 is electrostatically shielded by coating the entire surface of the insulating protection layer 116 with a shield layer 11B made of conductive silicone rubber. This shield layer 11
B is connected to the grounded case member 86 via the copper foil 120, so that it has a ground potential.

The shield layer 11B has a thickness of, for example, 20Ω/cm”
It has a sheet resistance value of about. Further, since the thickness of the insulating protective layer 116 and the shield layer 118 is 200 μm or less on the semiconductor substrate 9 days, pressure detection is not hindered.

The pulse wave detection device constructed as described above can be used to
0, and when a start operation button (not shown) is operated, a control circuit (not shown) controls the pressing device 66 to press the pulse wave sensor 74 to the extent that a flat portion is formed in the artery 80, and Maintain that state. In this state, the pressure pulse wave generated from the artery 80 is detected by the pressure sensing element 100, and in a measurement circuit (not shown), the pressure pulse wave generated from the artery 80 is detected based on the pressure signal output from the pressure sensing element 100 located at the optimal position. The blood pressure within the body is determined.

In this embodiment, as described above, since the semiconductor substrate 98 is electrostatically shielded by the shield layer 118, even if static electricity is generated in the living body while being pressed against the surface 12 of the living body, the pressure signal will not be detected. It is advantageous to prevent sudden offset changes in the waveform or fluctuations in the pressure signal in response to external light. The reason why an offset change in the pressure signal and a photosensitive phenomenon occur when static electricity is applied in a state where the shield layer 118 is not provided is presumed to be due to an effect similar to that of a MOSFET, but the exact reason is It is unknown. However, according to experiments conducted by the present inventors, a pulse wave sensor with a conventional structure in which the shield layer 118 is not provided has a static electricity of -20 kV.
By applying from electrodes spaced apart by 0 mm, it was possible to reproduce the offset change in the pressure signal waveform and the photosensitive phenomenon similar to when the pressure signal was pressed against the surface 12 of the living body. and,
When a similar experiment was conducted on the pulse wave sensor 74 provided with the shield layer 118 as in the above embodiment, no offset change in the pressure signal waveform or the photosensitive phenomenon was observed.

Although one embodiment of the present invention has been described above based on the drawings,
The invention also applies in other aspects.

For example, in the embodiment described above, the shield layer 118 made of conductive silicone rubber protects the semiconductor substrate 98.
The pressing surface side of the copper foil 12 was electrostatically shielded.
A thin metal film or a conductive plastic sheet may be electrically connected to the insulating layer 16 and fixed to the surface or inside of the insulating layer 16. The material, hardness, and thickness of the metal thin film and conductive plastic sheet are determined so as not to interfere with pressure detection.

Furthermore, by forming a conductive thin film of titanium, chromium, etc. on the pressing surface of the semiconductor substrate 98 itself via an insulating layer such as silicon dioxide or nitride film, and setting the conductive thin film to a ground potential, static electricity can be achieved. Electrical shielding may also be provided.

In this case, instead of the entire pressing surface of the semiconductor substrate 98,
Although it is necessary to form a conductive thin film except for the pad for bonding the bonding wire 114, it is sufficient if it is formed so as to cover at least the pressure sensitive element 100. The material and thickness of the conductive thin film are also determined so as not to interfere with pressure detection.

The above-mentioned embodiment is merely one embodiment of the present invention, and various modifications may be made to the present invention without departing from its purpose.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the pulse wave sensor of FIG. 2 in detail. FIG. 2 is a longitudinal cross-sectional view showing a pulse wave detection device according to an embodiment of the present invention. 3 is a perspective view showing a sensor body included in the pulse wave sensor of FIG. 2. FIG. Figure 4 shows
FIG. 4 is a diagram illustrating the structure of a pressure sensitive element provided on the negative side of the semiconductor substrate in FIG. 3; 8: Semiconductor substrate 00: Pressure sensitive element 118: Shield layer

Claims (1)

[Claims] A semiconductor substrate having a pressure-sensitive element formed on one side, and by pressing one side of the semiconductor substrate against the skin of a living body, detects pressure pulse waves generated from arteries located under the skin. A pulse wave detection device comprising: a shield layer made of a conductive material provided on one surface of the semiconductor substrate.