JPH07120314A - Sunshine sensor - Google Patents

Abstract

PURPOSE:To achieve curtailing of the number of parts and upgrading of positioning accuracy. CONSTITUTION:A photodiode chip 23 etched to be diaphragm-like is die-mounted on the undersurface of a lead frame 22. An electrode formed on the undersurface of the photodiode chip 23 and the lead frame 22 are wire-bonded on the lead frame 22 and the work is molded as a whole with a transparent mold body 25 made of an epoxy resin or the like. A light introduction hole 26 is formed at the center of the lead frame 22 and positioned right above the photodiode chip 23. In this case, the photodiode chip 23 is set with a PN junction part as photodetecting part facing down while it 23 is formed into a diagram-shape. This can reduce the thickness of an Si layer on the PN junction part to be photodetecting part, thereby allowing light to reach the PN junction part sufficiently even from the Si layer on the PN junction part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar radiation sensor in which solar radiation is detected by a photodiode.

[0002]

2. Description of the Related Art In a conventional solar radiation sensor, for example, as shown in FIG. 12, a photodiode chip 12 is die-mounted on a lead frame 11 so that a light receiving portion (PN junction portion) faces upward, and both of them are wire-mounted. The structure is such that they are electrically connected by bonding and are entirely molded with a transparent mold body 13 such as epoxy. This solar radiation sensor is used, for example, as a sensor that corrects the air conditioning control of an automobile in accordance with the solar heat load.

Here, since the amount of solar radiation entering the passenger compartment changes according to the solar radiation direction (solar radiation azimuth / solar altitude), it is preferable that the solar radiation sensor also have output characteristics depending on the solar radiation direction. From this point of view, for example, JP-A-2-998
As described in Japanese Patent Laid-Open No. 35-35, there is a type in which a specially shaped lens is mounted above a photodiode and the sensor output characteristic is dependent on the direction of the solar radiation depending on the shape of this lens. In addition, as described in Japanese Patent Application Laid-Open No. 2-216402, a diffuser above the light receiving element,
There is also a device provided with a light modulator and a light shield.

[0004]

By the way, since the photodiode chip used in the solar radiation sensor is as small as several mm square, the positioning accuracy of another component such as a lens with respect to the photodiode chip (light receiving element) is equivalent. If it is not raised to the desired value, the desired output characteristics cannot be obtained. For this reason, the process control for increasing the positioning accuracy of another component such as a lens becomes very troublesome, and in combination with the need for another component such as a lens having a special shape, the manufacturing cost becomes high. is there.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a solar radiation sensor capable of reducing the number of parts and facilitating positioning, and improving productivity and cost. To do.

[0006]

In order to achieve the above-mentioned object, the solar radiation sensor of the present invention comprises a photodiode chip for detecting solar radiation and a pedestal supporting the photodiode chip. The photodiode chip is formed in a diaphragm shape, and the solar light can be incident on the light receiving portion of the photodiode chip from the pedestal side.

[0007]

According to the above construction, the photodiode chip is formed in the shape of a diaphragm, so that the light receiving portion P can be formed.
The thickness of the Si layer on the back surface side of the N-junction portion can be reduced, and the light receiving portion (P
Light can reach the N-junction). Therefore, if a hole or a notch for introducing light is formed in a part of the pedestal that supports the photodiode chip, or if a transparent material is used for at least a part of the pedestal, the light is emitted from the pedestal side (back side). Since the light can be incident on the light receiving portion of the chip, desired output characteristics can be obtained by limiting the range of light passing through this pedestal by the shape of the hole for introducing light.

In this case, light can be detected from either the front side or the back side of the photodiode chip. Therefore, if the photodiode chip is set upright and the front and back surfaces of the photodiode chip are oriented in the left-right direction, the direction of solar radiation can also be detected. can do.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS. First, the structure of the optical sensor element 21 will be described with reference to FIG. On the lower surface of the lead frame 22,
A photodiode chip 23 etched in a diaphragm shape is mounted by a process described later. As shown in FIG. 2, the photodiode chip 23 is fixed such that the PN junction portion 18 serving as a light receiving portion faces downward, and therefore the outer peripheral thick portion 23a faces upward. The electrodes 27 (GND) and 28 (Vcc) formed on the lower surface of the photodiode chip 23 and the lead frame 22 are electrically connected by a bonding wire 24,
All of them are molded by a transparent mold body 25 such as an epoxy resin. The lower surface of the photodiode chip 23 is covered with the oxide insulating film 20 (SiO ₂ film), and the electrode 27 (GND) is the photodiode chip 2.
3 is conducted to the N ⁺ layer formed on the lower surface of the electrode 3, and the electrode 28 (Vc
c) is electrically connected to the P layer of the PN junction 18.

In the first embodiment, the lead frame 22
Corresponds to a “pedestal” that supports the photodiode chip 23, and in order to allow light to enter the PN junction 18 of the photodiode chip 23 from the lead frame 22 side, the center portion of the lead frame 22 has a light source. Introduction hole 2
6 is formed, the light introducing hole 26 is located right above the photodiode chip 23, and the distance between the two is equal to the thickness of the outer peripheral thick portion 23a of the photodiode chip 23 (for example, 40 mm).
About 0 μm). This light introduction hole 2
As shown in FIGS. 3 (a) and 3 (b), the shape of No. 6 is formed so as to be divided into a plurality of annular regions, or is formed into another specific shape, so that the output characteristic is dependent on the solar radiation direction. Can have

In this case, the photodiode chip 23
Is installed so that the PN junction portion 18 serving as a light receiving portion faces downward, but since the photodiode chip 23 is formed in a diaphragm shape, the PN junction portion 1 serving as a light receiving portion is formed.
The thickness of the Si layer on the back surface side (upper side) of 8 can be reduced to about 10 μm, for example, and light can sufficiently reach the PN junction portion 18 even from the Si layer on the back surface side of the PN junction portion 18. ing.

Next, a method of manufacturing the photodiode chip 23 will be described with reference to FIG. First, a thermal oxide film (SiO ₂ film) is formed on the surface of a Si wafer by thermal oxidation, a hole for forming an N ⁺ channel stopper layer is opened in this thermal oxide film by photoetching, and impurities are diffused from this hole. Forming an N ⁺ channel stopper layer. Next, photo etching for forming a P ⁺ layer is performed, and a P ⁺ layer is formed by ion implantation. After that, the oxide insulating film 20 is formed again by thermal oxidation, and then a phosphorus treatment is performed to form a PSG film on the surface thereof. A hole for forming an electrode is formed in this oxide insulating film 20 by photoetching, and aluminum is formed. Electrodes 27 (GND) and 28 (Vcc) are formed by the above, aluminum wiring is performed, and electrode sintering is performed to ensure electrical connection.

Thereafter, before moving to the step of photoetching the back surface of the Si wafer into a diaphragm shape, the surface of the portion not to be photoetched is protected (masked) with wax or the like, and the back surface of this Si wafer is photoetched to form the diaphragm shape. To form. When an electric field in the opposite direction is applied to the PN junction 18 during this photoetching, the etching stops when the depletion layer spreads (stop etching method), and a diaphragm with a thickness of, for example, about 10 μm is formed. In this way, one Si
After forming many diaphragms on the wafer,
The wafer is diced and cut into, for example, photodiode chips 23 each having a size of 2 to 3 mm.

The photodiode chip 23 thus manufactured is die-mounted on the lead frame 22, and is subjected to a wire bonding process, an epoxy molding process,
The optical sensor element 21 is manufactured through a cutting and homing step (a step of cutting the lead frame 22 and bending the leads 22a).

The structure of the entire solar radiation sensor incorporating this optical sensor element 21 will be described with reference to FIG. Inside the sensor case 30, a sensor holder 32 made of an insulating resin in which two terminals 31 are insert-molded is provided, and the optical sensor element 21 is mounted on the sensor holder 32. Each lead 22a of the optical sensor element 21 is electrically connected to each terminal 31 by welding or the like. A transparent cover 29 is mounted on the sensor case 30. On the other hand, a connector housing 33 is provided below the sensor case 30.
The terminal 31 is electrically connected to the connector pin 34 in the terminal 3.

Although not shown, the solar radiation sensor constructed as described above is attached, for example, in the vicinity of the windshield on the dashboard of an automobile so that the optical sensor element 21 faces upward. In order to detect the output of the optical sensor element 21, as shown in FIG. 6, the output voltage Vs of the optical sensor element 21 (voltage divided by the two resistors Ra and Rb of the voltage dividing circuit 35) is controlled by air conditioning. Microcomputer 36 for
Entered in. The microcomputer 36 determines the solar heat load based on the output voltage Vs of the optical sensor element 21, and executes the solar radiation correction control for correcting the air conditioning control according to the solar heat load. The optical sensor element 21 is connected in parallel with the resistor Ra of the voltage dividing circuit 35, and as the amount of received light increases, the photocurrent generated at the PN junction 18 increases,
The output voltage Vs rises.

According to the first embodiment described above, the diaphragm-shaped photodiode chip 23 is attached to the lower surface of the lead frame 22 which is the "pedestal", and the light introducing hole 2 for introducing the solar radiation into the lead frame 22 is provided.
6 is formed, the lead frame 22 can be effectively used as a light shielding means for limiting the light passage range, and the shape of the light introducing hole 26 of the lead frame 22 is shown in FIG.
Desired output characteristics can be obtained by forming a specific shape as shown in (a) and (b). Moreover, since the positioning accuracy between the light introducing hole 26 of the lead frame 22 and the photodiode chip 23 can be sufficiently increased by the normal semiconductor manufacturing process, the difficulty of positioning which is a conventional problem can be solved. Therefore, mass productivity can be improved, and in combination with the fact that a separate component such as a conventional lens having a special shape is not required, it is possible to satisfy the demand for cost reduction.

On the other hand, FIGS. 7 to 9 show a second embodiment of the present invention. In the second embodiment, the photodiode chip 23 is set upright so that the front surface and the back surface of the photodiode chip 23 are oriented in the left-right direction and the solar radiation direction can be detected.

In the second embodiment, the Pyrex glass 41 is used as a "pedestal" for supporting the photodiode chip 23, and the thick peripheral portion 23a of the photodiode chip 23 is anodically bonded to the Pyrex glass 41. ing. Also in this second embodiment, the lead frame 42 (see FIG. 8) is the same as in the first embodiment.
Using a light guide hole (not shown) formed, the Pyrex glass 41 is aligned and bonded to the part of the light guide hole, and the photodiode chip 23 and the lead frame 42 are wire-bonded to form the whole. After molding with a transparent epoxy, a cutting and homing process (a process of cutting the lead frame 42 and bending the leads 42a) is performed to manufacture the optical sensor element 43.

As shown in FIG. 8, the optical sensor element 43 is placed on the sensor holder 32 in a state where the photodiode chip 23 is erected and the front and back surfaces of the odd chip 23 are oriented in the left-right direction. The lead 42a is electrically connected to each terminal 31 by welding or the like. This second
In the embodiment, the photodiode chip 23 also has an electrode Vcc (not shown) formed on the back surface thereof, and a bias voltage is applied from both front and back surfaces to cause both the front and back surfaces to function as light receiving portions, and output voltage Vs1, As shown in FIG. 9, Vs2 is input to the microcomputer 36. This microcomputer 36 has an output voltage Vs
The magnitude relationship between 1 and Vs2 is determined to determine the left and right of the solar radiation direction, and the solar heat load is determined based on the total value of the output voltages Vs1 and Vs2. The detection circuit for the output voltages Vs1 and Vs2 has the same configuration as that of the first embodiment.

In the second embodiment, an electrode Vcc (not shown) is also formed on the back surface of the photodiode chip 23,
Both the front and back surfaces are made to function as light receiving portions, but the electrodes GND and V are provided only on the front surface side as in the first embodiment.
cc may be formed so that only the front surface side functions as a light receiving portion. Even in this case, by forming the photodiode chip 23 in a diaphragm shape, the thickness of the Si layer on the back surface side of the PN junction portion 18 serving as the light receiving portion can be reduced, so that the Si layer on the back surface side of the PN junction portion 18 can be thinned. However, sufficient light can reach the PN junction portion 18. On this occasion,
Since the light attenuates in the process of passing through the Si layer on the back surface side, the output voltage varies depending on which side the light enters, the front surface side or the back surface side. If you take advantage of this property,
Even when a photodiode chip having only the front surface side as a light receiving portion is used, the solar radiation direction can be detected based on the magnitude of the output voltage by using the photodiode chip upright.

By the way, conventionally, when detecting the direction of solar radiation, as described in Japanese Patent Laid-Open No. 1-136811, two optical sensor elements are installed so as to be inclined in opposite directions to each other, or , Actual Kaihei 4-38532
As described in Japanese Patent Laid-Open Publication No. 2004-242242, a light-shielding means is provided on a plurality of optical sensor elements so that the light receiving area of each optical sensor element changes in accordance with the direction of sunlight. However, in any of these configurations, a plurality of optical sensor elements are required or a light shielding means is required, so that there is a problem of an increase in the number of parts and positioning accuracy, and it is necessary to meet the demand for cost reduction. I can't.

In this respect, according to the above-described second embodiment, one photodiode chip 2 is provided by vertically installing the diaphragm-shaped photodiode chip 23.
3, the solar radiation direction can also be detected, so that the number of parts can be reduced, and the conventional problem of positioning difficulty can be solved, productivity can be improved, and cost reduction can be satisfied. You can

On the other hand, FIG. 10 shows a third embodiment of the present invention. In the third embodiment, the photodiode chip 23
When photoetching the diaphragm into a diaphragm shape, the rib-shaped or annular light-shielding portion 23 is formed inside the outer peripheral thick portion 23a.
b is formed, and this light-shielding portion 23b is the Pyrex glass 4
1 functions as a light blocking unit that limits the incident range of the light that has passed through 1. The configuration other than this is the same as that of the second embodiment described above. In this case, since the light-shielding portion 23b can be integrally formed with the photodiode chip 23 by photoetching, the positional accuracy of the light-shielding portion 23b can be remarkably increased as compared with the case where a separate light-shielding means is provided.

In the second and third embodiments described above, the Pyrex glass 41 is anodically bonded to the outer peripheral thick portion 23a on the back surface side of the photodiode chip 23.
As in the fourth embodiment of the present invention shown in FIG. 1, the Pyrex glass 41 may be anodically bonded to the front surface side of the photodiode chip 23. In this case, before the anodic bonding of the Pyrex glass 30, a poly-Si layer 42 is formed on the outer peripheral portion of the surface of the photodiode chip 23, and the surface of the photodiode chip 23 and the Pyrex glass 4 are formed.
It secures a gap with 1.

Also in the fourth embodiment, when the photodiode chip 23 is photoetched into a diaphragm shape, the rib-shaped or annular light-shielding portion 23b is formed inside the thick outer peripheral portion 23a. Light-shielding portion 23b
It goes without saying that it is also possible to adopt a configuration in which the above is not formed.

Further, in any of the above-described embodiments, desired output characteristics can be obtained by appropriately changing the shape and size of each part according to the circumstances of the place where the solar radiation sensor is installed. In addition, the solar radiation sensor of the present invention is not limited to the one used in the air conditioning system for automobiles, and can be widely modified as a solar radiation sensor for detecting the solar radiation direction and the solar radiation intensity in various places. Needless to say.

[0028]

As is apparent from the above description, according to the present invention, the photodiode chip is formed in a diaphragm shape, and the solar radiation can be incident on the light receiving portion of the photodiode chip from the pedestal side. Therefore, the sensor output characteristics can have azimuth dependence without using special parts such as lenses and light-shielding members, and the number of parts can be reduced, and the difficulty of positioning, which is a problem in the past, can be achieved. Can be solved, productivity can be improved, and cost reduction requirements can be satisfied.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an optical sensor element showing a first embodiment of the present invention.

FIG. 2 is a vertical sectional view of a photodiode chip.

FIG. 3 is a diagram showing two types of patterns of light introduction holes of a lead frame.

FIG. 4 is a diagram showing a manufacturing process of a photodiode chip.

FIG. 5 is a vertical sectional view showing the assembly structure of the entire solar radiation sensor.

FIG. 6 is an electric circuit diagram showing a photodetector circuit.

FIG. 7 is a vertical sectional view of an optical sensor element (before molding) showing a second embodiment of the present invention.

FIG. 8 is a vertical sectional view showing the assembly structure of the entire solar radiation sensor.

FIG. 9 is an electric circuit diagram showing a photodetector circuit.

FIG. 10 is a vertical sectional view of an optical sensor element (before molding) showing a third embodiment of the present invention.

FIG. 11 is a vertical sectional view of an optical sensor element (before molding) showing a fourth embodiment of the present invention.

FIG. 12 is a vertical sectional view of a conventional optical sensor element.

[Explanation of symbols]

18 ... PN junction part, 21 ... Photosensor element, 22 ... Lead frame (base), 23 ... Photodiode chip, 2
3b ... Light-shielding part, 25 ... Transparent mold body, 26 ... Light introduction hole, 32 ... Sensor base, 41 ... Pyrex glass (base), 43 ... Photosensor element.

Claims (1)

[Claims] 1. A solar radiation sensor comprising a photodiode chip for detecting solar light and a pedestal supporting the photodiode chip, wherein the photodiode chip is formed in a diaphragm shape, and the solar light is emitted from the pedestal side. A solar radiation sensor, wherein the solar radiation sensor is configured to be able to enter the light receiving portion of the photodiode chip.