JPH05157618A - Infrared detector - Google Patents

Abstract

PURPOSE:To obtain an infrared detector having high responsiveness and detection sensitivity and, at the same time, to improve the productivity of the detector. CONSTITUTION:Detection electrodes 48 of thermister chips 44 and 46 are formed in the chips 44 and 46 and output electrodes 50 connected to the electrodes 48 are connected to an electrode pattern 54 on a supporting substrate 42. A recessed section 52 is provided on the substrate 42. Because of the section 52, the occurrence of an increase in heat capacity and heat dissipation can be reduced and the sensitivity and responsiveness are improved. Since the electrodes 48 do not crop out, the change with time of electric characteristics can be prevented without using any hermetic case and no sealing is required. Since the electrodes are connected to the pattern 54, no thin lead wire is required.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of an infrared detector for detecting infrared rays by a thermistor chip, and more particularly to improvement of a support structure for the thermistor chip.

[0002]

2. Description of the Related Art As an infrared detector, a structure is known in which a thermistor chip is placed on a supporting substrate and housed in a hermetic case. FIG. 5 shows a cross section of an infrared detector having such a configuration.

The infrared detector shown in this figure includes two thermistor chips 10 and 12. Since the electric resistance of the thermistor chips 10 and 12 changes depending on the temperature, the temperature can be detected by outputting this resistance change as a voltage or current change.

The thermistor chips 10 and 12 are mounted and fixed on an electrically insulating support substrate 14. Support substrate 1
Further, 4 is mounted and fixed on the stem 16. The stem 16 is fitted with the cap 18 to form a hermetically sealed case (so-called hermetic case) 20 as shown in FIG. The hermetic case 20 is filled with an inert gas or is in a substantially vacuum state. As a result, the thermistor chips 10 and 12
It is possible to prevent secular changes in the electrical characteristics of the.

The thermistor chip 10 is a thermistor chip for infrared detection. For infrared detection, the thermistor chip 10 is arranged under the infrared incident window 22 formed on the ceiling of the cap 18 and made of silicon, polyethylene, or the like, that is, so as to receive infrared rays.

On the other hand, the thermistor chip 12 is a temperature compensating thermistor chip. The thermistor chip usually has a certain temperature characteristic, and its output varies depending on its operating temperature. The difference in electric resistance between the thermistor chip 12 that is not irradiated with infrared rays and the thermistor chip 10 that is irradiated with infrared rays indicates a temperature rise due to infrared rays, which improves the infrared detection sensitivity.

However, in this conventional example, the thermistor chips 10 and 12 are placed in contact with each other on the support substrate 14. Therefore, the equivalent heat capacity of the thermistor chips 10 and 12 becomes large, resulting in a problem in responsiveness. Further, when the thermal energy generated by the irradiation of infrared rays is transferred from the thermistor chip 10 to the thermistor chip 12 via the support substrate 14 and the stem 16, the temperature difference between the thermistor chips 10 and 12 decreases, which causes a problem in sensitivity. ..

In order to solve such a problem, a structure in which the thermistor chip is kept in contact with other members as little as possible is being studied. As such a configuration, for example, the configuration shown in FIG. 7 can be cited.

As shown in FIG. 7B, the thermistor chip used in this conventional example has a structure in which the detection electrodes 26 and 28 are adhered to both ends of the surface of the thermistor chip body 24. Lead wires 30 and 32 are electrically connected to the detection electrodes 26 and 28. The lead wires 30 and 32 are thin lead wires formed of Pt or the like with a diameter of about 0.03 to 0.05φ, and these are the detection electrodes 26 and 28 by a method such as baking a conductive paste such as Pt.
Fixed to each.

The thermistor chip having such a structure is housed in the hermetic case as the infrared detection thermistor chip 34 and the temperature compensation thermistor chip 36. As shown in FIG. 7 (A), the thermistor chips 34, 36 include an output terminal 38 and lead wires 30, 32.
Connected by.

At this time, the connection position with the output terminal 38 is
The position is set so as to float from the stem 16. This way,
Since the thermistor chips 34 and 36 are thermally insulated by the atmosphere inside the case, the equivalent heat capacity is not increased and the temperature difference reduction due to heat transfer is avoided. In addition, lead wire 3
Since 0 and 32 are thin lead wires of about 0.03 to 0.05φ, it is also possible to prevent heat energy from being dissipated through the output terminal 38.

[0012]

However, in the configuration as shown in FIG. 7, although the response and the detection sensitivity are improved, the assembly work is inefficient because the very thin lead wire must be handled. Therefore, there was a problem of low productivity. In addition, a hermetic case must be used in order to avoid secular change of the detection electrode, and highly accurate processing of the sealing part is required, which complicates the manufacturing equipment. This further increases the manufacturing cost and price.

The present invention has been made in order to solve such a problem, and an object thereof is to provide an inexpensive infrared detector having high responsiveness and detection sensitivity and high productivity.

[0014]

In order to achieve such an object, the present invention provides a thermistor chip in which a detection electrode is formed and an output electrode electrically connected to the detection electrode is covered at both ends. The support plate is formed into a flat plate shape, a recess is formed on at least one surface of the support substrate, electrodes for output terminals are formed on both sides of the recess, and the output electrodes are electrically connected to the electrodes for output terminals across the recesses. As described above, the thermistor chip is mounted and fixed on the support substrate.

[0015]

In the present invention, a recess is formed on at least one surface of the support substrate, and the thermistor chip is mounted and fixed on the support substrate so as to straddle the recess. Therefore, increase in equivalent heat capacity of the thermistor chip and dissipation of heat energy due to irradiation of infrared rays are prevented. Further, since the output electrode is electrically connected to the output terminal electrode on the surface of the supporting substrate, it is not necessary to use a thin lead wire. Further, the detection electrode of the thermistor chip is formed inside thereof. Therefore, since the detection electrode is not exposed to the external atmosphere, it is not necessary to use a hermetic case or the like.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. The same components as those of the conventional example shown in FIGS. 5 to 7 are designated by the same reference numerals and the description thereof will be omitted.

FIG. 1 shows the structure of an infrared detector according to the first embodiment of the present invention. As shown in this figure, the case 40 is not a hermetic case in this embodiment. The case 40 has a structure in which the infrared incident window 22 is provided on the ceiling, and the bottom surface is sealed by the support substrate 42. In this embodiment, the contact portion between the case 40 and the support substrate 42 needs to be hermetically sealed. Without
It is possible to prevent the production cost from being generated due to the precise sealing.

The reason why the hermetic seal is not necessary is that the thermistor chips 44 and 46 mounted and fixed on the support substrate 42 have the detection electrodes 48 inside, and the detection electrodes 48 are exposed to the external atmosphere. Because it is not exposed to. FIG. 2 shows such a thermistor chip 4
4, 46 configurations are shown.

As shown in FIG. 2A, the thermistor chip used in this embodiment has a detection electrode 48 inside and is electrically connected to the detection electrode 48.
It has an individual output electrode 50. As a method of forming the detection electrode 48 in this way, for example, there is a method of embedding a metal layer by stacking sheets. By thus forming the detection electrode 48 inside, it is prevented from being exposed to the outside atmosphere and is prevented from aging.

The thermistor chips 44 and 46 having such a structure are placed on the support substrate 42. Similar to the first conventional example, the mounting position is set so that the thermistor chip 44 used for temperature detection is below the infrared incident window 22, and the thermistor chip 46 is used for temperature compensation.

The supporting substrate 42 is an insulating flat plate such as alumina, and has a recess 52 formed on the thermistor chip mounting surface as shown in FIG. 2B. Support substrate 4
2 thermistor chip mounting surface, thermistor chip 4
An electrode pattern 54 is formed by applying and baking a conductive paste (for example, Ag paste) so that the output electrodes 50 come into contact with each other when 4, 4 are placed across the recess 52. The electrode pattern 54 is electrically connected to the output terminal 38.

Therefore, the thermistor chips 44 and 46 are mounted on the support substrate 42 as shown in FIG. 2B, and the output electrode 50 is connected to the electrode pattern 54 by a conductive paste or soldering to detect the A configuration in which the electrode 48 is isolated from other components (for example, the support substrate 42) is obtained. As a result, the equivalent heat capacity of the thermistor chips 44 and 46 becomes small, and the thermal energy due to infrared rays is prevented from being dissipated from the infrared detection thermistor chip 44.

FIG. 3 shows the configuration of a bridge circuit for confirming this effect. As shown in this figure, a constant voltage E is applied to both ends of the thermistor chips 44 and 46 connected in series, and resistors R1 and R2 are connected in parallel with the constant voltage E.
And the connection point between the thermistor chips 44 and 46,
The voltage between the connection point of the resistors R1 and R2 and the unbalanced voltage of the bridge circuit is measured. When adopting the configuration of this embodiment, E = 5V, R1 = R2 = 4.7kΩ, 5
An unbalanced voltage of 1 mV is obtained at 10 cm from a 0 ° C. blackbody radiation source. On the other hand, in the configuration of the first conventional example, the unbalanced voltage was 0.05 mV under the same conditions. That is, in this embodiment, the sensitivity is improved 20 times.
Further, the result of measurement on the responsiveness shows that the time constant is 3 seconds in the first conventional example, whereas it is 0.5 second in the present embodiment, and the responsiveness (time constant) is improved to 1/6. There is.
The dimension setting is as described later.

Further, in the configuration of this embodiment, the output terminal 3
8 is provided so as to penetrate the insulating support substrate 42. In the hermetic case, since the stem is generally made of metal, an electrically insulating layer has to be provided between the output terminal and the stem. In the present embodiment, there is no such need.

Further, the detection electrodes of the thermistor chips 44 and 46 and the output terminal 38 are electrically connected by the output electrode 50.
And the electrode pattern 54, and no thin lead wire is interposed. Therefore, the workability at the time of manufacturing can be improved, and the manufacturing cost and the price can be reduced. Further, by setting the width of the concave portion 52 (the interval between the electrode patterns 54 of the support substrate 42) to a value close to the length of the thermistor chips 44 and 46, it is possible to prevent heat from being dissipated through the output electrode 50. For example, if the thermistor chips 44 and 46 have a length of 6
In the case of (mm) × width 1 (mm) × thickness 0.08 (mm), the width of the recess 52 may be 5.8 (mm).

Although the thermistor chips 44 and 46 are mounted on the same support substrate 42 in this embodiment, they may be mounted on different substrates.

FIG. 4 shows the configuration of an apparatus according to the second embodiment of the present invention. This device has a structure in which the support substrate 42 having the thermistor chips 44 and 46 mounted and fixed as shown in FIG. 2 is fixed on the circuit board 56. Other electric components are mounted on the circuit board 56.

That is, according to the structure of the present invention in which the detection electrode is formed inside the thermistor chip, it can be mounted on the circuit board without using a hermetic case, and the entire circuit is housed in the case 58 as shown in FIG. If so, you do not need the case for infrared detectors only. That is, the degree of freedom in designing the circuit and the infrared detector increases.

[0029]

As described above, according to the present invention,
Since the detection electrode of the thermistor chip is formed inside,
Since a hermetic case is not necessary and the cost of sealing does not occur, an inexpensive infrared detector is realized and the degree of freedom in design increases. In addition, since the support substrate is provided with a recess and the thermistor chip is placed on the support substrate so as to straddle the recess,
Since the equivalent heat capacity of the thermistor chip can be reduced and heat dissipation can be prevented, responsiveness and sensitivity can be improved. Furthermore, since the output of the thermistor chip is taken out by connecting the output electrode and the electrode for the output terminal, it is possible to prevent heat from being dissipated from the output terminal without using thin lead wires. Cost reduction can be realized.

[Brief description of drawings]

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

FIG. 2A is a side view showing a structure of a thermistor chip used in this embodiment, and FIG. 2B is a perspective view showing a structure and a mounting mode of a support substrate which points the thermistor chip.

FIG. 3 is a circuit diagram of a bridge circuit for verifying the effect of improving the sensitivity according to this embodiment.

FIG. 4 is a cross-sectional view showing the configuration of the circuit device according to the first embodiment of the present invention.

FIG. 5 is a cross-sectional view showing a configuration of an infrared detector according to a first conventional example.

FIG. 6 is a perspective view showing a configuration of a hermetic case.

7A is a cross-sectional view showing the configuration of an infrared detector according to a second conventional example, and FIG. 7B is a perspective view showing the configuration of a thermistor chip used in this conventional example.

[Explanation of symbols]

 42 Support Substrate 44,46 Thermistor Chip 48 Detection Electrode 50 Output Electrode 52 Recess 54 Electrode Pattern

Claims (1)

[Claims] 1. A flat plate thermistor chip having a detection electrode formed inside and an output electrode formed on both ends and electrically connected to the detection electrode, and a recess formed on at least one surface of the thermistor chip. An output terminal electrode is adhered and formed on both sides, and an electrically insulating support substrate on which a thermistor chip is mounted and fixed so that the output electrode is electrically connected to the output terminal electrode across the recess. An infrared detector characterized in that