JPS60128312A - Pyroelectric sensor - Google Patents

Abstract

PURPOSE:To obtain a titled sensor which is stable and has a high sensitivity by forming the center part of the opposite side to the photodetecting surface of a pyroelectric body, in a recessed shape, providing an electrode layer on said part, and also sticking the circumferential edge part of the outside of its recessed part onto a flat substrate. CONSTITUTION:The surface of the opposite side to the photodetecting surface of a pyroelectric body wafer is formed in a recessed shape, and thereafter, it is cut to a prescribed size, and also the center part is formed in a small thickness so that the heat capacity becomes small enough by polishing the photodetecting surface side. A blackened film 12 is formed in the center part of the photodetecting surface of this pyroelectric body 11, and also an electrode layer 14 is formed on a recessed part 13 formed on the opposite side to the photodetecting surface. Subsequently, a conductive paste is applied to the circumferential edge part of the outside of the recessed part 13 of the pyroelectric body 11, and it is stuck to about the center part of a flat substrate 15. An FET16 and resistances 17, 18 are stuck to the opposite surface of the substrate 15.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a pyroelectric sensor that detects light or infrared rays.

[Technical background of the invention and its problems] Conventionally, as shown in FIG. 1, a pyroelectric sensor has been constructed by forming a black layer 1 or 2 on the upper surface of a pyroelectric body 1 and forming an electrode layer 3 on the lower surface. It is known that the electrode layer 3 is fixed to the upper surface of a flat substrate 5 with a hole 4 in the center so as to close the hole 4.

In addition, 6 in the figure is FET (field effect transistor),
7.8 are resistors, which are fixed to the lower surface of the substrate 5. FIG. 2 is a basic circuit diagram of a pyroelectric sensor, in which the drain and source of the field effect transistor 6 are connected to the terminals TI and T2, respectively, and the source is connected to the paper R.
8 to the terminal T3, and further, its gate is connected to the terminal T3 via a parallel circuit of the pyroelectric body 1 and the resistor 7.

That is, in this sensor 4, the pyroelectric body 1 is the blackened film 2.
When it receives light or infrared rays, it converts it into heat, changes its polarization slightly, and generates an electric charge. The impedance of this is converted by FET6 and a signal is output.

By the way, in order to obtain high sensitivity in this sensor, the pyroelectric material 1 must cause a thermal change even with a small amount of light or infrared rays, and therefore, the heat capacity must be reduced, and the thickness must be extremely thin, 100 μm or less. Moreover, it was necessary to make holes 4 in the substrate 5 to prevent heat from escaping through the substrate 5. However, when a hole is made like this, it is difficult to place the pyroelectric material directly above the hole and fix it firmly. Therefore, if the pyroelectric material is shifted, heat will be transferred from the pyroelectric material to the board. occurs and the sensitivity changes,
Additionally, the contact surface between the pyroelectric body and the substrate may increase, resulting in a problem of decreased sensitivity.

Because pyroelectric materials are extremely thin, they break easily and are difficult to handle, creating difficulties in the manufacturing process.

[Object of the Invention] The present invention was made in order to solve such problems, and an object thereof is to provide a pyroelectric sensor that can always obtain stable and high sensitivity and is strong in strength.

[Summary of the Invention] This invention forms a concave central portion on the side opposite to the light-receiving surface of a pyroelectric substance, forms an electrode layer in the concave portion, and fixes the peripheral portion outside the concave portion on a flat substrate. This is a pyroelectric sensor made by

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

In FIG. 3, reference numeral 11 denotes a pyroelectric material having a concave cross-section in the center opposite to the light-receiving surface. After forming it into a concave shape, it is cut to a predetermined size, and the light-receiving surface side is polished to form a central portion thin enough to have a sufficiently small heat capacity. By doing so, the central portion can be formed extremely thin while maintaining sufficient strength. A blackened film 1 is provided at the center of the light-receiving surface of the pyroelectric body 11.
2 and an electrode layer 14 is formed in a recess 13 formed on the side opposite to the light receiving surface.

Then, a conductive paste is applied to the outer peripheral edge of the recess 13 of the pyroelectric body 11, and the pyroelectric body 11 is fixed to the substantially central portion of the flat substrate 15. A FET (field effect transistor) 16 and resistors 17 and 18 are fixed to the opposite surface of the substrate 15.

Note that the operation of the pyroelectric sensor of this embodiment is the same as the conventional one, so a description thereof will be omitted.

With such a configuration, the concave portion 13 of the pyroelectric body 11 can sufficiently prevent heat from escaping. Moreover, since the peripheral portion is thick, sufficient strength can be maintained, and the central portion, which is irradiated with light and infrared rays, can be made extremely thin. Therefore, the heat capacity of the pyroelectric body 11 can be made sufficiently small, and a highly sensitive sensor can be manufactured. Further, in order to fix the pyroelectric body 11 on the substrate 15, it is sufficient to apply the conductive paste only to the outer peripheral edge of the recess 13, and the paste does not protrude. Furthermore, the fixed positioning of the pyroelectric body 11 to the substrate 15 is easy because there are no holes, and there is no positional shift of the pyroelectric body with respect to the hole as in the conventional case. No more decline.

In the above embodiments, a pyroelectric body having a square cross section was used, but the present invention is not necessarily limited to this, and the entire non-electric body may have a curved shape.

Even in this case, the intensity is strong because the stress t=1 applied to the pyroelectric body is dispersed to the peripheral portion.

[Effects of the Invention] As described in detail above, according to the present invention, it is possible to provide a pyroelectric sensor that always provides stable high sensitivity and has improved strength.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a conventional example, FIG. 2 is a basic circuit diagram of a sensor, and FIG. 3 is a sectional view showing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 11... Pyroelectric material, 12... Blackened film, 13... Recessed part, 14... Electrode layer, 15... Substrate. Applicant's agent Patent attorney Takehiko Suzue

Claims (2)

[Claims] (1) The central part of the pyroelectric body opposite to the light-receiving surface is formed into a concave shape, an electric field is formed in the concave part, and the peripheral part outside the concave part is fixed on a flat substrate. Features a pyroelectric sensor. (2) The pyroelectric sensor according to claim 1, wherein the pyroelectric body is formed so that its center portion is thinner than its peripheral portion.