JPS6047542B2 - Infrared detection element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an infrared detection element using a polymer pyroelectric film, which has a simple structure, can obtain a large output,
Furthermore, the present invention provides an infrared detection element that is easy to assemble.

Conventional infrared detection elements include quantum and thermal infrared detectors that utilize semiconductor photoconduction and photovoltaic force.

Thermal types include a thermistor type that detects resistance changes due to temperature rise due to infrared light reception, thermopile types that use thermoelectromotive force, and pyroelectric types that use changes in surface charge. The thermistor type and thermopile type have disadvantages of requiring cooling with liquid nitrogen and bias voltage, as well as slow response speed. On the other hand, the pyroelectric type is sensitive to infrared rays in a wide range of 1 to 20 μm and can be operated at room temperature.

Recently, excellent pyroelectric materials have been developed, and high-performance detection elements have been developed. These mainly use single crystal or ceramic ferroelectric materials. For example, PbTiO3, LiT
aO. pn゛ etc. However, these devices need to be made thinner and thermally insulated to increase infrared detection sensitivity, but they have reached their limits. The present invention is intended to eliminate the above-mentioned drawbacks of the conventional art, and one embodiment of the present invention will be described below with reference to FIGS. 1 and 2. Figures 1 and 2
In the figure, 1 is a cylindrical metal cap, and a hole 2 is formed in the top plate of this metal cap 1.

A silicon crystal plate 3 is bonded to the edge of the hole 2 in the metal cap 1.

This silicon crystal plate 3 transmits infrared rays, and in addition to the silicon crystal plate 3, it may be an organic film, such as a polyethylene film, that transmits mid-infrared and far infrared rays well. The metal cap 1 is made of iron or an iron-nickel-cobalt alloy having a coefficient of thermal expansion comparable to that of silicon, and the silicon crystal plate 3 and the metal cap 1 are bonded using epoxy resin. However, in order to further improve the sealing degree, a gold-silicon alloy layer is formed on the surface of the adhesive part at the outer periphery of the silicon crystal plate 3, and a nickel layer is further provided on this gold-silicon alloy layer. , it may be soldered using solder.
Reference numeral 4 denotes an annular spacer made of metal such as nickel silver or phosphor bronze, and this spacer 4 is arranged on the lower surface of the silicon crystal plate 3 and is fixed to the inner peripheral surface of the metal cap 1.

5 is a cylindrical insulating tube housed in the metal cap 1, and this insulating tube 5 is made of a resin with very high volume resistance and surface resistance, such as polytetrafluoroethylene, modified PPO, or other material with excellent heat resistance. used.

6 is an annular metal frame, and a polymer pyroelectric film 7 is adhered to the upper surface of the metal frame 6.

This metal frame 6 is inserted above the insulating tube 5, and the upper surface of the polymer pyroelectric film 7 bonded onto the metal frame 6 is in contact with the lower surface of the spacer 4. The polymer pyroelectric film 7 is made by uniaxially stretching a polyvinylidene fluoride film, depositing a nickel-chromium alloy as an electrode metal, and polarizing the film.The electrode formed on the top surface of the polymer pyroelectric film 7 is a spacer 4 to the metal cap 1. 8 is a ring-shaped wave spring arranged at the bottom of the metal frame 6, and this wave spring 8 is made of stainless steel for springs, nickel silver for springs, etc., and is formed into a ring shape with a punch press. The upwardly protruding portion of the wave spring 8 is the metal frame 6
It is in contact with the bottom surface of.

Reference numeral 9 denotes a cylindrical insulating stand, which is made of ceramic such as alumina or resin such as modified RpO.

This insulating stand 9 is adhesively fixed to the upper surface of a metal base 10. Note that the insulating stand 9 and the insulating cylinder 5 may be formed integrally. Reference numeral 11 denotes an infrared reflecting plate placed on the upper surface of the insulating table 9.

12 is a semiconductor element such as a field effect transistor for impedance conversion fixed on the metal base 10;
The gate of this semiconductor element 12 is connected to the infrared reflecting plate 11.

13, 14, 15 are terminals implanted in the metal base 10, the terminals 13, 14 and the metal base 10 are insulated, and the sources of the semiconductor element 12,
Drain is connected.

The metal base 10 is fixed so as to cover the lower end opening of the metal cap 1.

In the completed state, the wave spring 8 is interposed between the infrared reflector 11 and the metal frame 6, the elastic force of the wave spring 8 urges the metal frame 6 upward, and the polymer pyroelectric film 7 is attached to the spacer 4. Pressed against the bottom surface. Further, the electrode on the upper surface of the polymer pyroelectric film 7 is connected to the terminal 15 via the spacer 4, the metal cap 1, and the metal base 10, and the electrode on the lower surface of the polymer pyroelectric film 7 is connected to the metal frame 6,
Semiconductor element 12 via wave spring 8 and infrared reflector 11
connected to the gate. In Figures 1 and 2,
When infrared rays enter the polymer pyroelectric film 7 through the hole 2 of the metal cap 1, an electric charge is generated in the polymer pyroelectric film 7. In addition, charges are also generated by the infrared rays that pass through the polymer pyroelectric film 7, are reflected by the infrared reflector 11, and re-enter the polymer pyroelectric film 7, and a voltage is generated between the front and back electrodes of the polymer pyroelectric film. It is something that occurs. The following table compares the output voltages of the infrared detection element of the present invention and the conventional infrared detection element.

Conventional Example 1 is an element using lead titanate as a pyroelectric substance, Conventional Example 2 is an element using lithium tantalate as a pyroelectric substance, and Conventional Example 3 is an element using polyvinyl fluoride as a pyroelectric substance. FIG. 4 shows a measurement system for measuring the output voltage of each element in the table above. A is a heat source with a temperature of 400'K, B is a chopper rotated by motor C, and D is heat source J.
This is an infrared detection element set at a location 50 CTfL away from A, and the output of element D at a chopper frequency of 3 Hz is measured with an AC voltmeter. As is clear from the above table, the infrared detecting element of the present invention uses a polyvinylidene fluoride film and an infrared reflector, so that the output voltage is increased.

In addition, since the metal frame to which the polymer pyroelectric film is adhered is pressed against the spacer by a ring-shaped wave spring, it has the advantage that the connection of the polymer pyroelectric film to other electrodes is reliable. It is. Further, according to the present invention, the device can be easily assembled by sequentially inserting the parts into the metal cap.

[Brief explanation of the drawing]

FIG. 1 is a plan view of an infrared detection element according to an embodiment of the present invention, FIG. 2 is a sectional view of the same side, and FIG. 3 is a schematic diagram of a measurement system for measuring the output voltage of the infrared detection element. 1...metal cover, 2...hole, 3...
...Silicon crystal plate, 4...Spacer, 5
...Insulating tube, 6...Metal frame, 7.
...Polymer pyroelectric film, 8 ... Waveform spring, 9 ... Insulation stand, 10 ... Metal base, 11 ... Infrared reflection plate , 12... semiconductor element, 13, 14, 15... terminal.

Claims (1)

[Claims] 1. A cylindrical metal cap with a hole formed in the top plate, an infrared transmitting body attached to the edge of the hole, an annular spacer fixed inside the metal cap, and electrodes formed on both sides. An annular metal frame supporting a polymer pyroelectric film, a ring-shaped wave spring, a metal base fixed to an opening at one end of the metal cap, an insulating stand fixed on the metal base, and an insulating base fixed to the metal cap. An infrared detection element comprising an infrared reflection plate supported on a table, and the metal frame and the wave spring are interposed between the infrared reflection plate and the spacer.