JP3882645B2 - Infrared sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an infrared sensor configured to detect transmitted infrared rays through a filter that selectively transmits infrared rays.
[0002]
[Prior art]
Conventionally, as this type of infrared sensor, one described in JP-A-11-337414 has been proposed. In this device, an infrared detecting element is mounted on one surface of a stem, and a metal cap is coated on the infrared detecting element to constitute a package. Here, the cap has an opening formed in a portion facing the infrared detection element, and a filter that selectively transmits infrared light is provided in the opening.
[0003]
In such a sensor, infrared rays that pass through the filter are received by the infrared detection element. And the temperature of a to-be-measured body etc. can be measured by calculating | requiring the temperature difference of the temperature of the detection part of this detection element, and the temperature of the other reference | standard part, and calculating | requiring the amount of received infrared rays.
[0004]
Here, in the conventional sensor, infrared rays are emitted from a filter whose temperature has been increased by infrared rays, and the infrared rays are radiated to the detection element. Then, due to the infrared radiation, the temperature of the detection part of the infrared detection element is not only changed by the infrared rays that should be measured, but also the change caused by the infrared radiation, and an error occurs in the sensor output.
[0005]
For example, even after the object to be measured is removed from the infrared sensor, infrared radiation from the filter whose temperature has increased may continue, and this may be received by the infrared detection element, resulting in an error in sensor output.
[0006]
For this reason, in the above-described conventional one, a thermistor for detecting the temperature of the filter is attached to the filter, and an output error factor caused by the difference between the temperature of the infrared detection element and the temperature of the filter is removed.
[0007]
[Problems to be solved by the invention]
However, in order to remove the above error factors, the detection temperature of the infrared detection element is corrected. However, a temperature correction circuit is required, and the sensor configuration becomes complicated.
[0008]
An object of the present invention is to provide an infrared sensor capable of reducing an output error without using a temperature correction circuit.
[0009]
[Means for Solving the Problems]
To achieve the above object, according to the first aspect of the present invention, a stem (10) having a through hole (11) penetrating from one surface to the other surface, and a filter (20) joined to the stem so as to close the through hole. ) And an infrared detecting element (40) bonded to the surface of the filter located on one side of the stem, and the infrared rays incident from the other side of the stem through the through hole are transmitted through the filter and infrared rays. The detection element is configured to receive light.
[0010]
According to this, since the filter and the infrared detection element are integrated, the temperature difference between the filter temperature and the infrared detection element temperature can be minimized.
[0011]
Further, in the infrared sensor described in the above-mentioned conventional publication, a filter is attached to the cap, but the cap is originally made of a thin metal because it is welded to the stem that is the support portion. Therefore, the thermal conductivity of the cap is small and the temperature of the filter is likely to increase.
[0012]
In that respect, in the present invention, since the filter is directly joined to the stem capable of relatively increasing the heat capacity, the temperature rise of the filter can be suppressed.
[0013]
Therefore, according to the present invention, it is possible to suppress an output error factor caused by the difference between the temperature of the infrared detection element and the temperature of the filter, and to provide an infrared sensor capable of reducing the output error without using a temperature correction circuit. Can do.
[0014]
In addition, it is preferable to hermetically seal the infrared detection element with a package in order to eliminate disturbance given to the sensor output such as the external environment temperature. However, as described above, conventionally, a metal cap is used as the package. I used it. This is to improve the heat dissipation of the filter as much as possible to reduce the temperature difference with the infrared detection element.
[0015]
On the other hand, in the present invention, the difference between the filter temperature and the infrared detection temperature can be minimized, and the heat radiation of the filter can be secured by the stem, so that it is not particularly necessary to use a metal cap as a package.
[0016]
Therefore, in the present invention, as a package, at one side of the stem (10), and with a filter (20) and a resin package (70) provided so as to seal over the infrared detection element (40).
[0017]
According to this, since it is easier to mold than a conventional metal cap, there is an advantage that the design flexibility of the package shape is increased.
[0024]
In addition, the code | symbol in the bracket | parenthesis of each said means is an example which shows a corresponding relationship with the specific means as described in embodiment mentioned later.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments shown in the drawings will be described below. In the following embodiments, the same parts are denoted by the same reference numerals in the drawings.
[0026]
(First embodiment)
FIG. 1 is a schematic cross-sectional view of an infrared sensor S1 according to the first embodiment of the present invention. The stem 10 has a through hole 11 penetrating from one surface (upper surface in the drawing) to the other surface (lower surface in the drawing), and is formed by cutting or pressing a metal plate. .
[0027]
On one surface of the stem 10, a filter 20 that selectively transmits infrared rays is directly bonded to the stem 10 with an adhesive 30 so as to close the through hole 11 of the stem 10.
[0028]
The filter 20 is made of a single crystal or ceramic that is transparent to infrared rays such as silicon or germanium, and is formed by a cutting process such as dicing. An aluminum wiring 21 formed by sputtering, vapor deposition, or the like is formed on a surface of the filter 20 that is located on one side of the stem 10, that is, the upper surface of the filter 20.
[0029]
An infrared detection element 40 such as a thermopile type is mounted on and bonded to the upper surface of the filter 20. In this example, the infrared detection element 40 is electrically and mechanically joined to the aluminum wiring 21 via the solder bumps 22.
[0030]
In this example, the infrared detecting element 40 is a thermopile type in which a membrane as a thin portion is formed on a semiconductor substrate such as silicon. The thick portion of the semiconductor substrate is used as a reference point, and the temperature of the reference point and the membrane are determined. The voltage signal corresponding to the temperature difference with the temperature of the infrared detection part 41 located in is generated.
[0031]
The stem 10 is provided with a lead pin 50 for outputting a voltage signal from the detection element 40 to the outside. The lead pin 50 is inserted into an insertion hole provided around the through hole 11 in the stem 10 and has a structure sealed with a hermetic glass 51.
[0032]
The lead pin 50 protruding to one surface side of the stem 10 and the aluminum wiring 21 formed on the upper surface of the filter 20 are connected and electrically connected by a bonding wire 60 such as gold or aluminum. Thereby, the voltage signal from the infrared detecting element 40 can be output to the outside through the aluminum wiring 21, the bonding wire 60 and the lead pin 50.
[0033]
A cap 70 made of resin or metal is provided on one surface of the stem 10, and the filter 20 and the infrared detection element 40 are covered with the cap 70 and hermetically sealed. In this example, unlike the conventional metal, a resin package made by molding a resin such as an epoxy resin is used as the cap 70.
[0034]
When the cap 70 is a metal, the cap 70 is joined to the stem 10 by welding, but the cap 70 as a resin package of this example is bonded to one surface of the stem 10 with an adhesive or the like.
[0035]
The airtight space between the cap 70 and the stem 10 is sealed with a vacuum atmosphere or nitrogen or inert gas that does not absorb infrared rays so as not to absorb infrared rays that pass through the filter 20. . As described above, it is preferable to hermetically seal the infrared detection element 40 with a package in order to eliminate disturbances applied to the sensor output such as the external environment temperature.
[0036]
It is preferable that the airtight space is evacuated because it has the best heat insulation efficiency, but nitrogen or an inert gas is enclosed in order to avoid fluctuations in the vacuum due to leakage from a certain part of the package structure. Is also done.
[0037]
In such an infrared sensor S 1, as indicated by the white arrow in FIG. 1, infrared rays that are incident from the other surface side of the stem 10 through the through hole 11 are transmitted through the filter 20 and the infrared detection element 40. The infrared detector 41 receives light. The received infrared energy is converted into a voltage signal and output from the lead pin 50 to the outside.
[0038]
For example, the infrared sensor S1 is provided with a stem 10 having a through hole 11 and a lead pin 50. After the filter 20 and the infrared detection element 40 are assembled to the stem 10, wire bonding is performed in vacuum or nitrogen or The cap 70 can be assembled in an inert gas atmosphere.
[0039]
By the way, according to this embodiment, since the filter 20 and the infrared detection element 40 are integrated, the temperature difference between the filter temperature and the infrared detection element temperature can be minimized.
[0040]
In this embodiment, since the filter 20 is directly joined to the stem 10 that can have a relatively large heat capacity, the filter attached to the metal cap having a relatively low heat capacity as in the prior art. In comparison, the temperature increase of the filter 20 can be suppressed.
[0041]
Therefore, according to the present embodiment, an output error factor caused by the difference between the temperature of the infrared detection element 40 and the temperature of the filter 20 can be suppressed, and an infrared sensor S1 that can reduce the output error without requiring a temperature correction circuit. Can be provided.
[0042]
Further, in this embodiment, the difference between the filter temperature and the infrared detection temperature can be minimized, and the heat dissipation of the filter 20 can be secured by the stem 10, so that it is necessary to use a metal cap as a package as in the past. Disappear.
[0043]
Therefore, in the present embodiment, a resin package is used as the cap 70 as a preferable example. However, since this resin package is easier to mold than a conventional metal cap, the advantage that the design flexibility of the package shape is increased. There is.
[0044]
(Second Embodiment)
FIG. 2 is a schematic cross-sectional view of an infrared sensor S2 according to the second embodiment of the present invention. Hereinafter, the difference from the first embodiment will be mainly described. Also in this embodiment, the infrared detection element 40 performs infrared detection based also on a temperature difference between a detection unit such as a thermopile type and a reference point.
[0045]
Also in this example, the infrared detection element 40 is a thermopile type in which a membrane as a thin part is formed on a semiconductor substrate such as silicon, and the temperature of the reference point is determined by using the thick part of the semiconductor substrate as a reference point. And a voltage signal corresponding to the temperature difference between the temperature of the infrared detector 41 located on the membrane.
[0046]
A filter 20 that selectively transmits infrared rays is mounted on and bonded to the infrared detection element 40. As a bonding method, an adhesive, anodic bonding, direct bonding (such as bonding via an oxide film), solder bonding, or the like can be employed.
[0047]
The filter 20 has a concave portion 23 on one surface (the lower surface in the drawing), and is made of a single crystal or ceramic transparent to infrared rays such as silicon and germanium, as in the first embodiment.
[0048]
Here, the recess 23 of the filter 20 can be made by applying, for example, a manufacturing process of a silicon semiconductor sensor. For example, the recess 23 can be formed by processing a silicon substrate using anisotropic etching or dry etching. In this example, as a preferred embodiment, as shown in FIG. 3, the bottom surface of the recess 23 in the filter 20 has a convex lens shape.
[0049]
Such a convex lens shape is formed by forming a thick part and a thin part on the mask when making an etching mask using a photolithographic technique, and performing dry etching using such a mask, thereby forming the concave part 23. This is formed because the bottom surface has a convex shape.
[0050]
And the recessed part 23 is covered by the infrared detection element 40 joined to the one surface side of the filter 20, and the cavity part 80 as an obstruction | occlusion space is formed. Here, when the filter 20 and the infrared detection element 40 are joined, the atmosphere is made nitrogen or an inert gas, so that the inside of the cavity 80 is an airtight space filled with nitrogen or the like.
[0051]
Thereby, the heat conduction in the vicinity of the infrared detection part 41 of the infrared detection element 40 is suppressed. That is, the infrared detecting unit 41 is provided inside the cavity 80 as an airtight space with low heat conduction. As described above, in this embodiment, an airtight structure is realized in which disturbance of the sensor output is suppressed in a chip state in which the infrared detection element 40 and the filter 20 are joined without using a conventional package structure.
[0052]
The infrared detection element 40 integrated with the filter 20 is mounted on the bottom surface of the resin package 90, and the infrared detection element 40 and the bottom surface are bonded and fixed with an adhesive or the like. The resin package 90 has a container shape made by molding a resin such as an epoxy resin.
[0053]
In this example, the infrared detection element 40 has an infrared detection unit 41 provided on a membrane, and a cavity as an airtight space is formed between the resin package 90 and the membrane of the infrared detection element 40 by joining the membrane. A portion 81 is formed.
[0054]
Here, in the membrane-type infrared detection element 40, since the temperature difference between the membrane part and the thick part in the element 40 is used for the measurement, the cavity 81 under the membrane is also highly heat-insulating. Is preferred.
[0055]
Therefore, it is preferable that the bonding atmosphere between the resin package 90 and the infrared detection element 40 is nitrogen, an inert gas, or the like, similar to the bonding between the infrared detection element 40 and the filter 20. As a result, the inside of the cavity 81 is filled with nitrogen or the like to form an airtight space with low thermal conductivity.
[0056]
A lead 91 made of metal or the like is provided at an appropriate position of the resin package 90 by insert molding or the like. The lead 91 and the infrared detection element 40 are connected by a bonding wire 60 and are electrically connected. . Thereby, the voltage signal from the infrared detection element 40 can be output to the outside through the bonding wire 60 and the lead 91.
[0057]
Further, the peripheral portion of the infrared detection element 40 and the bonding 60 and the connection portion between the wire 60 and the lead 91 are covered with a gel 100 such as silicone gel. In the case where an amplification circuit for signal processing or the like is formed around the infrared detection element 40, the gel 100 is provided as protection. The gel 100 may be provided as necessary or not.
[0058]
In this way, the integrated filter 20 and infrared detection element 40 are encapsulated and sealed by the resin package 90 and the gel 100 with the other surface of the filter 20 corresponding to the recess 23 exposed. .
[0059]
A resin cover 92 is bonded and fixed to the resin package 90 by adhesion or the like so as to cover the opening of the resin package 90 with the other surface side of the filter 20 corresponding to the recess 23 exposed. The resin cover 92 can also be made of the same material and method as the resin package 90.
[0060]
In such an infrared sensor S2, as indicated by the white arrow in FIG. 2, the infrared rays transmitted through the filter 20 from the other surface side of the filter 20 corresponding to the recess 23 are detected by the detection unit of the infrared detection element 40. 41 is made to receive light. The received infrared energy is converted into a voltage signal and output from the lead 91 to the outside.
[0061]
The infrared sensor S2 is prepared, for example, by a resin package 90 including leads 91. After the integrated filter 20 and infrared detection element 40 are assembled to the resin package 90, wire bonding is performed, and the gel 100 is attached. It can be manufactured by coating and curing, and finally assembling the resin cover 92.
[0062]
By the way, according to the present embodiment, the infrared detecting element 40 is joined to the filter 20 having the concave portion 23 on the one surface side, and the concave portion 23 is covered with the infrared detecting element 40 to cover the concave portion 23. 80 is formed.
[0063]
Thereby, the cavity 80 can be made an airtight space in the state of a chip in which the filter 20 and the infrared detection element 40 are integrated. And the infrared detection part 41 of the infrared detection element 40 becomes the form provided in the inside of the said cavity part 80, and can implement | achieve the airtight structure which suppressed the disturbance of the sensor output.
[0064]
Also in this embodiment, since the filter 20 and the infrared detection element 40 are joined and integrated, the temperature difference between the filter temperature and the infrared detection element temperature can be minimized. Therefore, it is possible to provide the infrared sensor S2 that can reduce the output error without using the temperature correction circuit.
[0065]
Furthermore, in this embodiment, a resin package 90 is provided for sealing so as to wrap the filter 20 and the infrared detection element 40 in a state where the other surface side of the filter 20 corresponding to the recess 23 is exposed. According to this, by using the resin package 90, an airtight structure can be easily formed as compared with the conventional metal package, and the design flexibility of the package shape is also increased.
[0066]
Furthermore, in the present embodiment, as a preferred form, the bottom surface of the concave portion 23 in the filter 20 has a convex lens shape. According to this, the infrared rays from the measurement object can be easily condensed on the detection unit 41 of the infrared detection element 40, which is advantageous in improving the output sensitivity.
[0067]
In the present embodiment, an infrared sensor may be configured by only the integrated filter 20 and the infrared detection element 40 as shown in FIG. 2, and as a result, disturbance of the sensor output is suppressed as described above. It is possible to provide an infrared sensor capable of realizing an airtight structure and reducing an output error without using a temperature correction circuit.
[0068]
Then, such an integrated filter 20 and infrared detection element 40 may be packaged by molding with resin.
[0069]
As described above in each embodiment, the structure in which the filter 20 and the infrared detection element 40 are joined and integrated can reduce the temperature difference between the filter temperature and the infrared detection element temperature as much as possible. It is possible to provide an infrared sensor that can reduce an output error without using a correction circuit.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of an infrared sensor according to a first embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view of an infrared sensor according to a second embodiment of the present invention.
FIG. 3 is a diagram showing an example of a cross-sectional configuration of a single filter according to the second embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Stem, 11 ... Through-hole, 20 ... Filter, 23 ... Recessed part, 40 ... Infrared detector, 70 ... Cap, 90 ... Resin package.

Claims (1)

A stem (10) having a through hole (11) penetrating from one surface to the other surface;
A filter (20) joined to the stem so as to close the through hole;
An infrared detection element (40) joined to the surface of the filter located on one side of the stem;
Infrared light incident through the through hole from the other surface side of the stem is transmitted through the filter and received by the infrared detection element ,
One surface of the stem (10) is provided with a resin package (70) made of resin for covering and sealing the filter (20) and the infrared detection element (40). Sensor.

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