JPH0579908A - Pyroelectric element - Google Patents

Abstract

PURPOSE:To provide a pyroelectric element having corrosion resistance and excellent durability when it is used for a flame detector. CONSTITUTION:Electrodes 10, 11 formed by deposition and the like on the upper and lower faces of a pyroelectric body 1 are divided into absorbing electrode sections 10c, 11c and extracting electrodes 10d, lid. The electrodes 10, 11 rarely having a short circuit at boundary portions of conducting adhesives 12, 13 are obtained while the thickness or material of them is changed and an infrared absorbing function is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pyroelectric element used in a flame detector for detecting infrared rays.

[0002]

2. Description of the Related Art In recent years, as infrared sensors and heat-sensitive elements,
Pyroelectric elements are widely used. The pyroelectric body used in this pyroelectric element is generally made of a polymer material or a ceramic material having spontaneous polarization. When electrodes are formed on both sides of the pyroelectric film, a potential difference occurs between the electrodes due to temperature change. There is an action. In general, an infrared sensor generates a voltage according to the amount of heat of incident infrared rays by such a pyroelectric element and appropriately amplifies this voltage to detect a flame or a human body.

As an example of such a pyroelectric element, there is an element whose cross-sectional view is shown in FIG. The pyroelectric body 1 is PZT,
A film made of pyroelectric material such as lithium tantalate, lead titanate, PVDF and its copolymer,
The printed circuit board 3 is mounted on the printed circuit board 3 via the frame-shaped element substrate 2 serving as a base. Similarly, the printed circuit board 3 is provided with an electric circuit section 4 such as an FET for extracting the potential difference of the pyroelectric body 1. It is configured. Alumina is used as the material of the base 2 and the printed circuit board 3.

The printed circuit board 3 is connected to the ends of three terminals 7 that penetrate the stem 5 (via an insulator 6 if necessary), and the periphery thereof is airtightly covered by a can 9 having a window formed by a filter 8. It is being appreciated. The filter 8 is made of a material having infrared transmissivity such as silicon, and is shielded by the filter 8, the metal stem 5 such as steel, and the can 9.

The vicinity of the pyroelectric body 1 will be described in detail with reference to the schematic enlarged view of FIG. 5. Keyhole-shaped electrodes 10 and 11 are formed on the upper and lower surfaces of the pyroelectric body 1 by vapor deposition or the like, and circular portions 10a, 11a is located at an overlapping position. The protruding portions 10b and 11b are circular portions 10a and 11a.
To the left and right ends of the pyroelectric body 1. Electrode 1
An infrared absorbing material such as nickel-chromium alloy or gold black is used as the material of 0 and 11.

The pyroelectric body 1, the base 2 and the printed circuit board 3 are adhered and fixed to each other by an appropriate material.
The electrodes 10 and 11 on the upper and lower surfaces and a circuit pattern (not shown) of the printed circuit board 3 are electrically connected by applying conductive adhesives 12 and 13. Conductive adhesive 12, 1
As 3, there is used a material containing a silver filler.

[0007]

In such a pyroelectric element, the electrodes 10 and 11 formed on the surface of the pyroelectric body 1 are further connected to the pyroelectric body 1 by the action of electrical connection. It has a function of confining infrared rays incident on the electric body 1. That is, ideally, the electrode 10 on the light-receiving surface absorbs infrared light without reflecting it, and the electrode 11 on the back surface reflects infrared light without transmitting it, whereby the infrared absorption efficiency to the pyroelectric body 1 is increased. Improve. Therefore, each of the electrodes 10 and 11 has a predetermined optimum thickness.

A conductive adhesive 12,
13 is applied, and tension is applied to the electrodes 10 and 11 when it is cured. Since the electrodes 10 and 11 cannot absorb the infrared rays, the electrodes 10 and 11 and the adhesives 12 and 13 are thin and thin due to corrosion or vibration.
It may be easily cut at the boundary surface with. In particular, when using such a pyroelectric element for a flame sensor that detects infrared rays, not only the stipulations regarding durability are strict, but the actual installation environment may be extremely bad conditions, which may cause failure. ..

[0009]

The present invention has been made in view of the above points, and as a first invention, when the electrodes 10 and 11 are formed on the upper and lower surfaces of the pyroelectric body 1, the absorbing electrode portion is formed. 10
c and 11c are formed in a thin layer, and the extraction electrode portions 10d and 11d are formed.
Is thicker than the absorption electrode portions 10d and 11d.

Further, as a second invention, the absorbing electrode portion 10
An infrared absorbing material such as nickel-chromium alloy is used as the material of e and 11e, and a good conductor such as platinum or a conductive material having corrosion resistance is used as the material of the extraction electrode portions 10f and 11f.

[0011]

In the first aspect of the invention, the electrodes 10 and 11 are formed in two steps to change the thickness thereof. In the second aspect of the invention, when the electrodes 10 and 11 are formed, two kinds of materials are used. The electrode 1 formed by applying the conductive adhesives 12 and 13 without reducing the infrared absorption efficiency of the pyroelectric body 1.
The electrical connection between 0 and 11 and the printed circuit board 3 is ensured.

The electrodes 10 and 11 are made of nickel-chromium alloy as an infrared absorbing material for the pyroelectric body 1,
Gold black, nickel, gold, indium antimony, or the like can be used, and platinum, aluminum, gold, silver, copper, or the like can be used as a good conductor or a corrosion-resistant conductive material for the conductive adhesives 12 and 13.

[0013]

EXAMPLES Examples according to the present invention will be described below. 1 is a plan view of the inside of a pyroelectric element according to the present invention, FIG. 2 is a schematic sectional view of FIG. 1 showing a first embodiment, and FIGS. 3 and 4 are the same as FIG. 2 showing a second embodiment. FIG.
The same or corresponding parts as those in FIGS. 5 and 6 are designated by the same reference numerals, and the description thereof will be omitted.

In the first embodiment, the electrodes 10 and 11 are
The absorption electrodes 10c, 11 are formed on the upper and lower surfaces of the pyroelectric body 1 and have circular absorption electrode portions 10c, 11 on the surface through the pyroelectric body 1 as shown in FIG.
c appear to overlap, and the extraction electrode parts 10d and 11
d is protruding. The conductive adhesives 12 and 13 are attached to the lead electrode portions 10d and 11d, and are electrically connected to a circuit pattern (not shown) of the printed circuit board 3 located below the lead electrode portions 10d and 11d.

When the electrode 10 is formed, first, a thin layer having a predetermined thickness is formed on one surface of the pyroelectric body 1 in a keyhole shape by vapor deposition or the like. After that, further lamination is similarly performed only on the portion protruding from the circle. Then, the absorption electrode portion 10c having a predetermined thickness is formed in the circular portion, and the extraction electrode portion 10d having a thickness larger than that of the circular portion is formed in the protruding portion. Electrode 11
Also, the electrode 10 is formed similarly to the electrode 10. As a result, the conductivity and durability of the lead-out electrode portions 10d and 11d formed to have a small width are improved.

The method of forming the electrodes 10 and 11 is not limited to the above, and a layer to some extent is first formed on the projecting portions (lead-out electrode portions 10d and 11d), and the absorbing electrode is formed thereon to have a predetermined thickness. The parts 10c and 11c may be created. Further, both may be created individually.

In the second embodiment, the structure of the electrodes 10 and 11 and the method of making them are almost the same as in the first embodiment.
The difference is that when a keyhole-shaped first thin layer (absorption electrode portions 10e, 11e) is formed by vapor deposition or the like, an infrared absorbing material such as nickel-chromium alloy is used in a circular shape, and the protruding portion (extraction electrode portion 10f , 11f) is laminated on the end of the circular portion using a good conductor such as platinum or another material having corrosion resistance. Therefore,
On the surface, a keyhole-shaped circular portion (absorption electrode portions 10e, 11
The nickel-chromium alloy is visible in e) and platinum is visible in the protruding portions (lead-out electrode portions 10f and 11f), and the conductive adhesives 12 and 13 are applied to the platinum portions. As a result, the conductivity and durability of the extraction electrode portions 10f and 11f are improved as in the first embodiment. In addition, the keyhole shape is nickel
A chromium alloy may be formed and platinum may be formed thereon.

There are various methods for forming the electrodes 10 and 11 as in the first embodiment. Finally, a nickel-chromium alloy and a conductive adhesive 12, 1 are formed on the light receiving surface of the pyroelectric body 1.
It suffices that platinum is arranged on the joint surface of No. 3.

As described above, in each embodiment, the electrodes 10, 11
The shape of is not limited to the above, but the absorption electrode portions 10c, 10e, 1
1c and 11e may be widely formed on the light receiving surface of the pyroelectric body 1, and the extraction electrode portions 10d, 10f, 11d and 11f may be only the portions where the conductive adhesives 12 and 13 are joined, and the electrodes 10 and 11 may be formed. Needless to say, it is not necessary to configure the same.

[0020]

INDUSTRIAL APPLICABILITY The present invention relates to an electrode formed on the upper and lower surfaces of a thin film of a pyroelectric material in a pyroelectric element. By changing the thickness of the electrode or the material of the electrode for each part, it is resistant to corrosion and durable. There is an effect that an excellent pyroelectric element is obtained.

[Brief description of drawings]

FIG. 1 is a plan view of the inside of a pyroelectric element according to a first embodiment of the present invention.

2 is a schematic cross-sectional view of FIG.

FIG. 3 is a sectional view similar to FIG. 2 according to a second embodiment of the present invention.

FIG. 4 is a sectional view similar to FIG. 2, showing another configuration of the second embodiment.

5 is a sectional view similar to FIG. 2 showing a conventional example.

FIG. 6 is a vertical sectional view showing the overall structure of a pyroelectric element.

[Explanation of symbols]

 1 Pyroelectric body 3 Printed circuit board 10, 11 Electrode 12, 13 Conductive adhesive

Claims (4)

[Claims] 1. An absorption electrode portion formed in a thin layer such as a circle on the upper and lower surfaces of a thin film made of a pyroelectric material, and an extraction electrode portion which is formed in a layer thicker than the absorption electrode portion in communication therewith. A pyroelectric element comprising an electrode made of 2. An absorption electrode portion made of infrared absorbing material formed in a thin layer such as a circle on the upper and lower surfaces of a thin film made of a pyroelectric material, and another conductive material formed in communication with the absorbing electrode portion. And a lead electrode section for forming an electrode. 3. The pyroelectric element according to claim 1, wherein the material of the absorbing electrode portion is nickel-chromium alloy or gold black. 4. The pyroelectric element according to claim 1, wherein the material of the extraction electrode portion is noble metal or aluminum.