JP2001066184A - Pyroelectric infrared sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a contact area between a sensor element and sensor element supports, and to thereby reduce radiation of heat of an infrared ray at the minimum, by forming the sensor element supports in a spherical shape, in a pyroelectric infrared sensor. SOLUTION: A sensor element 3 and sensor element supports 8, and also the sensor element supports 8 and a circuit board 5 are equally fixed each other by a conductive adhesive or the like. The spherical sensor element supports 8 are fixed on prescribed positions of the circuit board 5 by the conductive adhesive, and thereafter the conductive adhesive is coated on the upper parts of the spherical sensor element supports 8, and the sensor element 3 is placed on the spherical sensor element supports 8, and the conductive adhesive is hardened. In order to prevent radiation of heat from adhesion parts, an anisotropic adhesive capable of securing conductivity in the pressing direction is preferable as the conductive adhesive. In order to prevent radiation of heat, as material of the sensor element supports 8, the material having low thermal conductivity, for example, the material formed by forming a metal thin film on the surface of a resin, is preferable, on condition that conduction of the surface is secured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pyroelectric infrared sensor having a small pyroelectric infrared sensor element for detecting infrared radiation radiated from an object such as a human body.

[0002]

2. Description of the Related Art In recent years, pyroelectric infrared sensors have been widely used as human body detection sensors and the like.

FIGS. 1 and 2 are cross-sectional views of a typical pyroelectric infrared sensor according to the prior art.

The pyroelectric infrared sensor shown in FIG. 1 has a structure in which a sensor element 3 is directly attached to a circuit board 5 with a conductive adhesive or the like. Reference numeral 1 denotes an infrared filter, and a comparative voltage generated by the pyroelectric effect of the sensor element 3 is attached to the base 6 through the substrate 5 by projecting infrared rays of a certain frequency passing through the infrared filter 1 onto the sensor element 3. It is structured to be taken out from the lead 4.
The base 6 and the lead 4 are insulated by a hermetic seal or the like. In addition, 2 is a cap.

The pyroelectric infrared sensor shown in FIG. 2 has a structure in which a sensor element 3 is supported on a circuit board 5 by a sensor element support 7. The sensor element support 7 is made conductive by a conductive material or conductive plating.
The conduction between the sensor element support 7 and the circuit board 5 is ensured by a conductive adhesive or the like.

In the pyroelectric infrared sensor shown in FIG. 1, the sensor element 3 can be fixed to the circuit board 5 at a low cost because there is no sensor element support. However, since the sensor element 3 is in contact with the circuit board 5, there is a disadvantage that the heat of infrared rays projected on the sensor element 3 is radiated through the circuit board 5 and the sensor sensitivity is reduced. The pyroelectric infrared sensor shown in FIG. 2 has a structure in which a sensor element support 7 is provided to reduce heat radiation from the sensor element 3 to the circuit board 5 and improve sensitivity, and is mainly used.

[0007]

As described in the prior art, the sensor element is mounted on the circuit board when the sensor element is directly mounted on the circuit board as in the pyroelectric infrared sensor of FIG. Heat dissipation to the
A pyroelectric infrared sensor having the sensor element support structure shown in FIG. 2 has become common. Problems to be solved by the present invention will be described based on the sensor element support structure of the pyroelectric infrared sensor in FIG. Sensor element support 7 of FIG.
Has a structure that supports the sensor element 3 and is supported by the circuit board 5. The sensor element 3 and the sensor element support 7, and the sensor element support 7 and the circuit board 5 are connected by a conductive adhesive or the like in order to secure conductivity. FIG. 5 is a perspective view of a general sensor element support, and FIG.
Is a columnar shape, (b) is a rectangular parallelepiped shape, and (c) is a T-shaped shape. There are various other shapes, but the sensitivity also varies due to the effect of heat radiation depending on the contact area between the sensor element and the sensor element support and the amount of adhesive, so the sensor element must be mounted on the sensor element support. It is necessary to reduce the contact area between the sensor element support and the sensor element support and to reduce the variation in the contact area. In addition, it is of course important that the sensor element support is easily incorporated into the circuit board, and that it is also important to suppress variations in characteristics and reduce man-hours.
An object of the present invention is to solve the above problems.

[0008]

A pyroelectric infrared sensor comprising at least a sensor element, a sensor element support, and a circuit board, wherein the sensor element is fixed to the circuit board via the sensor element support. The spherical shape and the present invention make the sensor element support spherical.

[0009]

FIG. 3 is a cross-sectional view showing an embodiment of a pyroelectric infrared sensor according to the present invention. FIG. 4 is an enlarged view around a sensor element support, and FIG. 6 is a spherical view used in the present invention. It is a perspective view of a sensor element support. Hereinafter, the present invention will be described in detail with reference to FIGS. 3 is a sensor element and 5 is a circuit board. Reference numeral 8 denotes a spherical sensor element support of the present invention, and the sensor element 3, the sensor element support 8, the sensor element support 8, and the circuit board 5 are all fixed with a conductive adhesive or the like.

A spherical sensor element support 8 is fixed at a predetermined position on the circuit board 5 with a conductive adhesive, and then a conductive adhesive is applied on the spherical sensor element support 8 to change the sensor element to a spherical sensor. The assembly of the sensor element is completed by placing the element on the element support 8 and curing the conductive adhesive. In order to prevent heat radiation at the bonding portion, the conductive adhesive is preferably an anisotropic adhesive capable of securing conductivity in the pressing direction.

In order to prevent heat radiation through the sensor support, the material of the sensor element support 8 should preferably have low thermal conductivity as long as the surface conduction is ensured. For example, a resin in which a metal thin film is formed on the surface, a conductive resin alone or a conductive resin plated on the surface is preferable.

Although the sensor element support is spherical in the present invention, it goes without saying that the same effect can be obtained if the contact point between the sensor element and the sensor element support is pinpointed.

[0013]

By making the sensor element support spherical, the contact area between the sensor element and the sensor element support can be reduced, and the radiation of infrared radiation can be minimized. Also, since the shape is spherical, it can be easily attached to a circuit board, which leads to a reduction in assembly cost. Further, since the mounting accuracy is easily obtained, the variation in sensitivity can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a typical pyroelectric infrared sensor according to the prior art.

FIG. 2 is a cross-sectional view of a typical pyroelectric infrared sensor according to the prior art.

FIG. 3 is a sectional view showing an embodiment of a pyroelectric infrared sensor according to the present invention.

FIG. 4 is an enlarged view around a sensor element support.

FIG. 5 is a perspective view of a general sensor element support;
(A) is cylindrical, (b) is rectangular parallelepiped, (c) is T-shaped

FIG. 6 is a perspective view of a spherical sensor element support used in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Infrared filter 2 Cap 3 Sensor element 4 Lead 5 Circuit board 6 Base 7 Sensor element support 8 Sensor element support

Claims (1)

[Claims] 1. A pyroelectric infrared sensor comprising at least a sensor element, a sensor element support, and a circuit board, wherein the sensor element is fixed to the circuit board via the sensor element support, wherein the sensor element support is spherical. A pyroelectric infrared sensor characterized by the following.