JPH09126883A - Infrared detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the malfunction of an infrared detector even when high-frequency electric field noise enters the detector by grounding transparent conductive films and a metallic cap while the films and cap are electrically connected to each other. SOLUTION: A pyroelectric element 1 is mounted on a printed wiring board 2 with supporting bodies 61 and 62 in between and circuit parts 21 and 22, such as the FET, resistor, etc., constituting a circuit are fitted to the rear surface of the board 2. An optical filter 5 forms a light ray entrance window 41 and a frequency-selective insulating film 52 at the light ray entrance window section of an infrared detector sealed with a metallic cap 4. In the detector, at least one main surface of the filter 5 is coated with transparent conductive films 71 and 72, electrically connected to the cap 4, and grounded. Even in the part of the filter 5, therefore, high-frequency electric field noise which hinders the detection of infrared rays is grounded through the films 71 and 72 and cap 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared detector using a pyroelectric element or the like used in a human body detection system or the like, and more particularly to an infrared detector in which the influence of external noise is eliminated as much as possible.

[0002]

2. Description of the Related Art For example, a pyroelectric element is well known as an infrared detecting element. When a pyroelectric element receives infrared rays, it absorbs its thermal energy and causes a temperature change, which causes a change in spontaneous polarization and an electric charge on the surface. In this way, charges are induced on the surface in proportion to the minute temperature change, and the charges are detected as a current or a voltage by an external circuit. The pyroelectric infrared detector utilizes such a pyroelectric effect and is used for human body detection and the like.

An example of the configuration of a conventional pyroelectric infrared detector is shown in FIG.
It will be explained together. Three lead terminals 31, 32, 33 are projected on the upper surface of the metal base 3, the printed wiring board 2 is supported at three points on these lead terminals, and circuit components 21, 22 are further provided on the upper and lower surfaces of this board. And the support 61,
62 is mounted and supports the pyroelectric element 1 on this support. The optical filter 5 on the flat plate is bonded to the metallic cap 4 having the light incident window, and the cap 4 covers each of these parts. The optical filter 5 has a non-insulating substrate made of a conductor such as silicon or a semiconductor as a base, and a frequency-selective insulating film for transmitting infrared rays is formed on one or both surfaces of the front and back surfaces, and then a predetermined size is formed. , Obtained by cutting into a shape. A portion of the optical filter near the outer periphery of the pyroelectric element is cut away to form the insulating film 5.
2 The lower non-insulating substrate 51 is exposed to form a cutout portion 5a having a thin portion and a thick portion. Then, first, an epoxy resin-based insulating bonding material S1 is applied to the facing surfaces of the cap 4 and the optical filter 5, and the both are bonded. Next, the cap 4 and the optical filter 5 are electrically connected and the mechanical connection is strengthened by applying the conductive bonding material S2 to the notch 5a of the thick portion.
This makes the metal cap and the optical filter conductive,
Can be electrically shielded.

[0004]

The infrared ray detector as described above receives not only infrared rays but also other electromagnetic waves emitted from various electric devices through an optical filter. These other electromagnetic waves have become a harmful noise to the infrared detector, and have been a factor that causes malfunction in infrared detection. By performing the electrical shield as described above, other electromagnetic waves are grounded from a specific lead terminal via the metal cap and the metal base. Therefore, it is possible to reduce the malfunction to a certain level. However, recently, mobile communication represented by mobile phones and the like has rapidly increased, and high-frequency electric field noise generated from them has a large transmission output, so that the shield may not be sufficient. That is, the conductor or semiconductor portion exposed on the cut surface of the optical filter may have a small surface area and may not have sufficient conduction. Therefore, a sufficient shielding effect cannot be obtained, which may cause a malfunction. Was there. Further, when the bonding is performed with an insulating bonding material, the bonding material for pre-bonding sometimes protrudes from the bonding surface of the cap and the optical filter and covers a large part of the cut surface of the optical filter. . In such a case, the conductive bonding material applied afterwards did not sufficiently adhere to this cut surface, and the necessary conduction could not be obtained.

The present invention has been made in order to solve the above-mentioned problems, and it is, for example, to obtain a pyroelectric infrared detector having a small malfunction even when high frequency electric field noise having a large transmission output is incident on the infrared detector. It is intended.

[0006]

In order to solve the above problems, a pyroelectric infrared detector according to the present invention is equipped with an infrared detecting element and a base having a plurality of external lead terminals.
A metal cap that covers the infrared detection element and has a light incident window for injecting infrared rays to be detected by the infrared detection element, and a metal cap attached to the light incident window and using a non-insulating substrate as a substrate, at least its surface An infrared detector including at least an optical filter having a frequency-selective insulating film for transmitting infrared rays, wherein at least one main surface of the optical filter is covered with a transparent conductive film, and the transparent conductive film is formed. The membrane is electrically connected to the metallic cap and is grounded. The transparent conductive film is made of, for example, ITO (Indium Tin Oxide) and may be provided on the inner side, the outer side, or both sides of the metallic cap of the optical filter, but both of them must be electrically bonded to the metallic cap. I have to.

With the above structure, the optical filter portion is also covered with the transparent conductive film, and high frequency electric field noise harmful to infrared detection is absorbed by the transparent conductive film and grounded through the metallic cap. Therefore, harmful high frequency electric field noise does not enter the infrared detector, and malfunction of infrared detection can be prevented. The transparent electrode film may be formed on one main surface (front surface or back surface) of the optical filter, but by providing it on both surfaces, a more reliable shield effect can be obtained.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings, taking a pyroelectric infrared detector as an example. FIG. 1 is a sectional view of a pyroelectric infrared detector. The pyroelectric element 1 serving as an infrared detection element is made of a lead titanate-based pyroelectric ceramic, is polarized in the thickness direction, and is cut into a rectangular shape. On the surface of the pyroelectric element 1, although not shown, two metal film electrodes (Cr or Ni-C) for receiving light are provided.
r, etc.) are provided at a predetermined interval, and a metal film electrode (Ag) corresponding to the metal film electrode for light reception is provided on the back surface.
Etc.) are provided. The electrodes for receiving light are commonly connected.

The pyroelectric element 1 is mounted on the printed wiring board 2 via supports 61 and 62. Circuit components 21 and 22 such as an FET and a resistor constituting a circuit are attached to the back surface of the printed wiring board 2, and necessary electric connection with the pyroelectric element is made. The base 3 has lead terminals 31 and 32 electrically independent from each other implanted on a metal shell 3a via an insulating glass G.
The lead terminals 33 are implanted in a state where they are electrically connected to the shell 3a. This lead terminal 33 functions as a ground terminal. The printed wiring board is mounted on these lead terminals, and necessary electrical connections are made.

The cap 4 for sealing each of these components is made of metal, and a light incident window 41 is provided on the upper surface. The optical filter 5 attached to the inside of the light incident window 41 has a frequency-selective insulating film 52 for transmitting only infrared rays formed on the front and back surfaces of a non-insulating substrate 51 (conductor or semiconductor) such as silicon. Configuration,
In addition, the pyroelectric element side near the outer periphery of this optical filter is cut out, the non-insulating substrate 51 under the insulating film 52 is exposed, and a cutout portion 5a having a thin portion and a thick portion is formed. And the cap 4 and this optical filter 5
First, an epoxy resin-based insulative bonding material S1 is applied to the opposing surfaces of the above, and these are brought into contact with each other to mechanically pre-bond them. Even if the insulating bonding material S1 used here has a large coating amount, it stops at the edge portion of the thin portion of the cutout portion 5a due to its surface tension. Then, by applying the conductive bonding material S2 to the notch 5a in the thick portion, the cap 4 and the optical filter 5 are electrically connected and the mechanical connection is strengthened. Note that when a conductive bonding material having excellent airtightness is used, electrical and mechanical bonding may be performed using only the conductive bonding material without the need for two-time bonding as described above. Also,
The optical filter may have a normal cross section (side surface) in which the cutout portion is not formed.

IT is provided on the front and back surfaces of such an optical filter 5.
The transparent conductive films 71 and 72 made of O are covered. The transparent conductive film can be formed by applying it to the surface of the optical filter by a method such as coating or vapor deposition, and then hardening it by a certain heat treatment. The covering range covers the entire surface of the optical filter and the vicinity of the light incident window 41 of the cap 4. As a result, the high frequency electric field noise is grounded via the lead terminal 33. Then, a printed wiring board on which a pyroelectric element and the like are mounted is mounted on the base, and the cap is hermetically sealed to complete the pyroelectric infrared detector.

[0012]

According to the present invention, at least one main surface of the optical filter is coated with a transparent conductive film, and the transparent conductive film is electrically connected to the metallic cap and is grounded. Therefore, also in the optical filter portion, high frequency electric field noise harmful to infrared detection is grounded through the transparent conductive film and the metallic cap. Therefore, harmful high frequency electric field noise does not enter the infrared detector, malfunction of infrared detection can be prevented, and a highly reliable infrared detector can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a pyroelectric infrared detector according to the present invention.

FIG. 2 is a sectional view showing a conventional example.

[Explanation of symbols]

 1 Pyroelectric element (infrared ray detecting element) 2 Printed wiring board 3 Base 31, 32, 33 Lead terminal 4 Cap 5 Optical filter 5a Cutout 7 Transparent conductive film

Claims (1)

[Claims] 1. A metal having an infrared detection element mounted thereon, a base having a plurality of external lead-out terminals, a light-incident window for covering the infrared detection element, and a light-incident window for allowing infrared rays to be detected to enter the infrared detection element. An infrared detector equipped with a cap and an optical filter which is attached to the light incident window and has a frequency-selective insulating film for transmitting infrared rays on at least the surface of the non-insulating substrate as a base, An infrared detector characterized in that at least one main surface of the optical filter is coated with a transparent conductive film, and the transparent conductive film is electrically connected to the metallic cap and grounded.