JPH06147979A - Pyroelectric infrared detector - Google Patents

Abstract

PURPOSE:To make the visual field characteristic of a pyroelectric infrared detector uniform and improve the reliability of the detector by connecting electrodes respectively formed on a circuit board and pyroelectric body to each other by using solder. CONSTITUTION:A circuit board 3 housed in a metallic case 1 is constituted by forming a circuit pattern on a substrate and electrodes 4 and 5 and FET 6 and resistor 7 are respectively provided on the upper and lower surfaces of the board 3. Upper and lower-surface electrodes 9a and 9b and 10a and 10b which are composed of thin films are respectively formed on the upper and lower surfaces of a pyroelectric body 8. In addition, lead-out electrode connecting sections 11a and 11b connected to the electrodes 10a and 10b are provided on the lower surface of the body 8 and the surfaces of the sections 11a and 11b are coated with metallic films of copper or gold so as to improve the solder wettability of the surfaces. The electrodes 4 and 5 are connected to the sections 11a and 11b with solder 12. Therefore, the electrical and mechanical connections between the electrodes become sure and the circuit of the pyroelectric body is rigidly supported by the board 3. As a result, this detector can withstand impacts and the visual field characteristic of the detector is made uniform.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a pyroelectric type in which a circuit board having an FET and a resistor is provided in a case having an infrared transmitting window, and a pyroelectric body is supported on the circuit board. Regarding infrared detectors.

[0002]

2. Description of the Related Art In a conventional pyroelectric infrared detector,
When a pyroelectric body is supported on a circuit board provided with an FET and a resistor, an electrode formed on the circuit board and an electrode formed on the pyroelectric body are electrically connected to each other. There is a method disclosed in Japanese Patent Laid-Open No. 193030.

FIG. 4 shows the pyroelectric infrared detector disclosed in the above publication. In this figure, 31 is a case provided with an infrared transmission window 32, inside which an FET and a resistor (both are shown). A circuit board 33 including (not shown) is provided, and an electrode 34 is formed on the upper surface thereof. Three
Reference numeral 5 denotes a pyroelectric body, on which electrodes 36 and 37 are formed on both upper and lower surfaces thereof, which are held by a paste-like conductive resin adhesive 38 in which a metal filler such as silver is dispersed in an epoxy resin, With the resin adhesive 38, the electrode 3
4, 37 are electrically connected. In addition, 39 is a stem provided so as to close the lower part of the case 31, 4
0 and 41 are lead terminals.

[0004]

However, the pyroelectric infrared detector shown in FIG. 4 has the following problems. That is, the pyroelectric body 35 is the circuit board 33.
Is supported by a conductive resin adhesive 38 on the above, but in this case, if the positional accuracy of the pyroelectric body 35 with respect to the circuit board 33 is not good, the visual field characteristics vary. However, when the conductive resin adhesive 38 is applied, the positional accuracy is likely to vary, and thus such a pyroelectric infrared detector has a problem in that the field of view characteristics are uniform. .

Further, it takes a considerable amount of time to cure the conductive resin adhesive 38, which lowers the productivity, and the electrodes 34 and 3 on the circuit board 33 and the pyroelectric body 35.
There is a problem in that the electrical connection of No. 7 may not be made completely, resulting in lack of reliability.

The present invention has been made in view of the above matters, and an object of the present invention is to obtain a highly reliable pyroelectric infrared detector having a uniform visual field characteristic.

[0007]

To achieve the above object, in the pyroelectric infrared detector according to the present invention, electrodes formed on a circuit board and a pyroelectric body are connected to each other by using solder. .

[0008]

By connecting the electrodes formed on the circuit board and the pyroelectric body to each other by using solder, the electric and mechanical connection between the electrodes can be surely performed. In particular, the pyroelectric body is used as the circuit board. Since it is rigidly supported by, it becomes strong against impact. In addition, the solder is hardened quickly and the working efficiency is improved.

Further, when the solder is melted, the self-alignment effect causes a slight positional deviation when the pyroelectric body is mounted, and the solder is positioned at a predetermined position.
It is possible to obtain a pyroelectric infrared detector with less variation in visual field characteristics. Further, since the adhered portion of the solder to the unnecessary portion becomes a solder ball and separates, there is a self-cleaning effect, and thus a pyroelectric infrared detector having high productivity and reliability can be easily obtained.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

1 to 3 show an embodiment of the present invention. FIG. 1 is a sectional view showing a pyroelectric infrared detector, and FIG.
Is a plan view showing the internal structure of the detector, FIG.
(B) is a plan view showing an upper surface electrode and a lower surface electrode, respectively.

First, in FIG. 1, reference numeral 1 is a metal case, in which an infrared transmitting window 2 is formed. Three
Is a circuit board housed in the case 1 and is formed by forming a circuit pattern on a board made of alumina, for example. Electrodes 4 and 5 are formed on the upper surface of the circuit board 3,
The FET 6 and the resistor 7 are provided on the lower surface.

Reference numeral 8 denotes a pyroelectric body made of a pyroelectric material such as lead zirconate titanate-based ceramics (PZT) or lithium tantalate. The upper and lower surfaces of the pyroelectric material are shown in FIGS. ), Upper surface electrodes 9a and 9b and lower surface electrodes 10a and 10b are formed, respectively. These electrodes 9a to 10b are formed of, for example, chromium into a thin film of about several hundred to several thousand liters by a sputtering method or a vapor deposition method. And on the lower surface of the pyroelectric body 8,
Lead-out electrode connecting portions 11a and 11b are formed so as to be continuous with the lower surface electrodes 10a and 10b. The lead electrode connecting portions 11a and 11b are formed in the same manner as the electrodes 9a to 10b, but the surface thereof is further covered with a metal film such as copper or gold to improve the wettability of the solder 12 described later. It is preferable to allow it.

Referring again to FIG. 1, reference numeral 12 denotes electrodes 4, 5 on the side of the circuit board 3 and lead-out electrode connecting portions 11a on the side of the pyroelectric body 8,
Solder that connects 11b electrically and mechanically,
Reference numeral 13 is a stem, and 14 is a lead pin.

In the pyroelectric infrared detector constructed as described above, the electrodes 4, 5 and the extraction electrode connecting portion 11 are provided.
When soldering a and 11b, when applying a cream-like solder, a positional deviation occurs, and it adheres to unnecessary portions around the electrodes 4 and 5, or pulls out when the pyroelectric body 8 is mounted. Pyroelectric body 8 other than the electrode connecting portions 11a and 11b
Even if creamy solder adheres to the front and bottom electrodes 10a and 10b, the electrodes 4 and 5 and the lead-out electrode connecting portion 11
Except for a and 11b, the wettability with respect to solder is low, so such solder becomes a solder ball and is removed, and the self-cleaning effect is exhibited.

Further, a slight positional deviation when the pyroelectric body 8 is mounted is naturally corrected by the effect of self-alignment during solder melting.

In the above embodiment, the extraction electrode connecting portion 11
Although a and 11b were provided, they are omitted and the electrodes 4,
5 and the lower surface electrodes 10a and 10b may be directly connected by the solder 12.

By the way, the PZT which constitutes the pyroelectric body 8
In general, pyroelectric materials such as lithium tantalate and the like may exceed the Curie temperature, or have a thermal history close to the Curie temperature, the pyroelectricity may be significantly reduced or disappear.

In particular, PZT has a Curie temperature of 200 to 300 ° C., which is relatively low depending on its composition, so that it may be heated to about 230 ° C. by the soldering step, and the sensitivity as a detector may be lowered. is there. Therefore, if the polarization treatment is performed after the soldering process to activate the pyroelectricity, the original performance can be fully exhibited.

Since lithium tantalate has a Curie temperature of about 600 ° C., which is a relatively high temperature, the pyroelectricity does not deteriorate, and it is not necessary to perform polarization treatment after the soldering process.

If a low melting point solder (melting point is about 150 ° C.) is used as the solder, the decrease in pyroelectricity can be avoided.

[0022]

As described above, in the present invention, since the electrodes formed on the circuit board and the pyroelectric body are connected to each other by using solder, the electrodes can be electrically and mechanically connected to each other. It is performed reliably, and in particular, since the pyroelectric body is rigidly supported by the circuit board, the pyroelectric body becomes strong against impact. In addition, the solder is hardened quickly and the working efficiency is improved.

When the solder is melted, the self-alignment effect causes a slight positional deviation when the pyroelectric body is mounted, and the solder is positioned at a predetermined position.
It is possible to obtain a pyroelectric infrared detector with less variation in visual field characteristics. Further, since the adhered portion of the solder to the unnecessary portion becomes a solder ball and separates, there is a self-cleaning effect, and thus a pyroelectric infrared detector having high productivity and reliability can be easily obtained.

[Brief description of drawings]

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

FIG. 2 is a plan view showing an internal structure of the detector.

3A and 3B are plan views showing an upper surface electrode and a lower surface electrode, respectively.

FIG. 4 is a sectional view showing a conventional pyroelectric infrared detector.

[Explanation of symbols]

1 ... Case, 2 ... Infrared transmitting window, 3 ... Circuit board, 4, 5
... electrodes of circuit board, 6 ... FET, 7 ... resistor, 8 ... pyroelectric body, 9a, 9b ... electrodes of pyroelectric body, 12 ... solder.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akira Shintaku 2 Higashimachi, Kichijoin Miya, Minami-ku, Kyoto-shi, Kyoto

Claims (1)

[Claims] 1. An FE is provided in a case having an infrared transmitting window.
In a pyroelectric infrared detector comprising a circuit board provided with T and a resistor, and supporting a pyroelectric body on the circuit board, electrodes formed on the circuit board and the pyroelectric body are soldered together. A pyroelectric infrared detector characterized by being connected by using.