JPH0680139U - Pyroelectric infrared detector - Google Patents

Abstract

(57) [Abstract] [Purpose] An object of the present invention is to obtain a pyroelectric infrared detector with little malfunction even when high-frequency electric field noise with a large transmission output is incident. [Structure] The printed wiring board 2 to which the pyroelectric element 1 and the circuit components 21 and 22 are attached is connected to lead terminals 31 and 3.
It is mounted on the base 3 in which 2, 33 are planted. A light incident window 41 is provided in the cap 4 that hermetically seals the base 3, and an optical filter 5 is attached to the inside of this window.
The optical filter 5 has a structure in which a frequency selective insulating film 52 for transmitting only infrared rays is formed on the front and back surfaces of a non-insulating substrate 51. On the pyroelectric element side in the vicinity of the outer periphery of this optical filter, a notch 5a is formed in which the non-insulating substrate 51 under the insulating film 52 is exposed. By applying the conductive bonding material S2 to the cutout portion, the cap 4
And the optical filter 5 are connected electrically and mechanically.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a pyroelectric infrared detector used in a human body detection system or the like, and more particularly to a pyroelectric infrared detector that eliminates the influence of external noise as much as possible.

[0002]

[Prior art]

 As is well known, when a pyroelectric material receives infrared rays, it absorbs its heat energy and causes a temperature change, spontaneous polarization changes, and a charge is generated on the surface. In this way, an electric charge is induced on the surface in proportion to a slight temperature change, and this electric charge is detected as an electric current or voltage by an external circuit. The pyroelectric infrared detector utilizes such a pyroelectric effect and is used for human body detection and the like.

A configuration example of a conventional pyroelectric infrared detector will be described with reference to FIG. Three lead terminals 731, 732, 733 are projected on the upper surface of a metal base 73, a printed wiring board 72 is supported at three points on these lead terminals, and a circuit component 721 is provided on the upper and lower surfaces of this board. , 722 and supports 761 and 762 are mounted to support the pyroelectric element 71 on this support. The optical filter 75 on the flat plate is joined to the metallic cap 74 having the light incident window, and the cap 74 covers each of these parts. The optical filter 75 has a non-insulating substrate made of a conductor such as a silicon wafer or a semiconductor as a substrate, and a frequency-selective insulating film (not shown) for transmitting infrared rays is formed on at least one of the front and back surfaces thereof. Then, it is obtained by cutting into a predetermined size and shape. Since a conductor or a semi-conductor portion is exposed at this cut surface (that is, a side surface), the cap 74 and the optical filter are made conductive by the conductive bonding material S including the cut surface. Conducts, and can be electrically shielded. In addition, as shown in FIG. 4, when the optical filter 75 is bonded to the cap, first, for example, an epoxy resin-based insulating bonding material S1 is preliminarily bonded in order to improve airtightness, and then, By electrically bonding with the conductive bonding material S2, the same electrical shielding can be performed. The optical filter 75 has a configuration in which a frequency selective insulating film 752 is provided on the front and back surfaces of a non-insulating substrate 751.

[0004]

[Problems to be solved by the device]

 Not only infrared rays but also other electromagnetic waves emitted from various electric devices enter the infrared detector as described above through an optical filter. These other electromagnetic waves became harmful noises for the infrared detector and were a factor that caused malfunction in infrared detection. By performing the above electric shield, other electromagnetic waves are grounded from a specific lead terminal through a metal cap and a metal base. Therefore, it has been possible to reduce the malfunction to a certain level. However, due to the recent rapid increase in mobile communication and the like, the high-frequency electric field noise generated from them has a large transmission output, and the above-mentioned shield may not be sufficient. That is, since the conductor or semiconductor portion exposed on the cut surface of the optical filter has a small surface area and the surface tension is difficult to obtain, sufficient conduction cannot be obtained, and thus a sufficient shielding effect cannot be obtained. , Causing a malfunction. Further, as shown in the partially enlarged cross-sectional view of the vicinity of the light incident window in FIG. 4, when pre-bonding is performed with an insulating bonding material, this bonding material for pre-bonding does not protrude from the bonding surface of the cap and the optical filter. However, it sometimes covered a lot of the cut surface of the optical filter. In such a case, the conductive bonding material, which was applied later, 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 a pyroelectric red line detector with less malfunction even when high frequency electric field noise with a large transmission output is incident on this infrared detector. The purpose is to obtain.

[0006]

[Means for Solving the Problems]

 In order to solve the above-mentioned problems, the pyroelectric infrared detector according to the present invention has a metallic cap having a light incident window, a non-insulating substrate as a base body, and a frequency selection for transmitting an infrared ray to at least the surface thereof. The optical filter with a conductive insulating film is attached, a pyroelectric element is provided at the position corresponding to this optical filter, and the necessary electronic components that amplify and output the electromotive force output from this pyroelectric element are installed. The optical filter is housed, and a part or the whole of the vicinity of the outer periphery on the pyroelectric element side is cut out to provide a thin portion in which a part of the non-insulating substrate is exposed. It is characterized in that the non-insulating portion and the cap are joined at least with a conductive joining material. In order to improve the airtightness, the cap and the optical filter may be first pre-bonded with an insulating bonding material and then bonded with a conductive bonding material.

[0007]

[Action]

 The surface near the outer periphery of the optical filter on the side of the pyroelectric element is partially cut out to form a cutout portion having a thin portion and a thick portion.The cutout portion is a conductor or semiconductor portion of the optical filter. Since it is largely exposed, by applying a conductive bonding material to this part and conductively bonding it to the cap, the conductive state is improved and the electrical shield is strengthened. Therefore, it is possible to sufficiently ground unnecessary electromagnetic waves that become noise. Also, since a large surface tension can be obtained, the mechanical connection strength can be enhanced.

In addition, in the case of joining the cap and the optical filter, in the case where the insulating bonding material is first preliminarily bonded and then the conductive bonding material is used to bond the both, as shown in FIG. 2, the bonding is performed first. Insulating bonding material stops by surface tension at the edge of the thin part. Therefore, it is possible to secure the exposed state of the notch (cut surface) of the thick portion, and by applying the next conductive bonding material to the notch of the thick portion, a sufficient electric shield can be obtained. You can do it.

[0009]

【Example】

 An embodiment according to 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 is made of lead titanate-based pyroelectric ceramic, is polarized in the plate thickness direction, and is cut into a rectangular shape. Although not shown, two metal film electrodes (Cr or Ni-Cr) for light reception are provided on the surface of the pyroelectric element 1 at a predetermined interval, and on the back surface, the metal film for light reception is provided. A metal film electrode (Ag or the like) corresponding to the electrode is 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. Further, circuit components 21, 22 such as FETs and resistors forming a circuit are attached to the back surface of the printed wiring board 2 to make necessary electrical connection with the pyroelectric element. In the base 3, lead terminals 31 and 32 are implanted in a metallic shell 3a via insulating glass, and a lead terminal 33 is implanted in a state of being electrically connected to the shell 3a. The printed wiring board is mounted on top of these lead terminals to make the necessary electrical connections.

The cap 4 that seals each of these components is made of metal, and a light incident window 41 is provided on the upper surface. 2 is an enlarged cross-sectional view of the optical filter portion of FIG. 1. As shown in FIG. 2, the optical filter 5 mounted inside the light incident window 41 is a non-insulating substrate such as silicon. 51 (conductor or semiconductor) has a structure in which a frequency-selective insulating film 52 for transmitting only infrared rays is formed on the front and back surfaces, and the pyroelectric element side in the vicinity of the outer periphery of the optical filter is cut out to form the insulating film. 52. The non-insulating substrate 51 under 52 is exposed to form a notch 5a having a thin portion and a thick portion. Then, an epoxy resin-based insulating bonding material S1 is first applied to the opposing surfaces of the cap 4 and the optical filter 5, and they are brought into contact with each other to perform mechanical pre-bonding. 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. When a conductive bonding material having excellent airtightness is used, pre-bonding is not required as described above, and electromechanical bonding may be performed only with the conductive bonding material.

If necessary, an epoxy-based bonding material or the like may be applied to the upper part of the conductive bonding material to enhance mechanical bonding or airtightness. As described above, the printed wiring board on which the pyroelectric element and the like are mounted is mounted on the base, and the cap is hermetically sealed to complete the pyroelectric infrared detector.

[0013]

[Effect of device]

 According to the present invention, the surface near the outer periphery of the optical filter on the side of the pyroelectric element is partially notched to form a notched portion having a thin portion and a thick portion, whereby the conductor of the optical filter is formed. Alternatively, since the semiconductor portion is largely exposed, the conductive state is improved and the electrical shield is strengthened by applying a conductive bonding material to this portion and conducting conductive bonding with the cap. In particular, in the case of joining the cap and the optical filter, when pre-bonding with an insulating bonding material first and then bonding them with a conductive bonding material, the insulating bonding material first bonded should be It can be stopped by surface tension at the edge. Therefore, it is possible to secure the exposed state of the notch (cut surface) of the thick portion, and by applying the next conductive bonding material to the notch of the thick portion, a sufficient electric shield can be obtained. You can do it. As a result, it is possible to sufficiently shield unnecessary electromagnetic waves that become noise and to ground them, and when high-frequency electric field noise with a large transmission output from mobile communication equipment, which has been rapidly increasing in recent years, is incident on this infrared detector. However, a pyroelectric infrared detector with few malfunctions can be obtained. Moreover, since a large surface tension can be obtained, the mechanical connection strength can be strengthened, and the airtight effect of the cap is also improved.

[Brief description of drawings]

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

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3 is a sectional view showing a conventional example.

FIG. 4 is a partially enlarged cross-sectional view showing another conventional example.

[Explanation of symbols]

1, 71 Pyroelectric element 2, 72 Printed wiring board 3, 73 Base 31, 32, 33, 731, 732, 733 Lead terminal 4, 74 Cap 5, 75 Optical filter 5a Notch

Claims (1)

[Scope of utility model registration request] 1. A metallic cap having a light incident window,
An optical filter having a frequency-selective insulating film for transmitting infrared rays on at least the surface of a non-insulating substrate as a base is attached, and a pyroelectric element is provided at a position corresponding to the optical filter. A pyroelectric infrared detector comprising a necessary electronic component for amplifying and outputting an electromotive force output from an element, wherein the optical filter cuts a part or all of the vicinity of the outer periphery of the pyroelectric element side. Due to the lack, a thin portion where a part of the non-insulating substrate is exposed is provided,
A pyroelectric infrared detector characterized in that the non-insulating portion of the cut-out optical filter and the cap are bonded with at least a conductive bonding material.