JP2001308372A - Reflection optical sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problems that an optical path length is extended for a wire-bonding loop and the efficiency of light is reduced in a reflection optical sensor and, if the sensor is miniaturized by reverse bonding, diffuiculty is increased in mounting of the sensor, and moreover, a light shading member is required between a light emitting element and a light-receiving element and the number of components is increased. SOLUTION: A light emitting element 32 and a light receiving element 33 are respectively mounted on both surfaces of a substrate 31 close to the ends of the substrate 31. Hereby, both elements 32 and 33 are separated from each other via the substrate and a special light shading member for the elements 32 and 33 is unnecessary. The element 32 is laid sideways so that a light emitting layer 32a is formed vertically to the substrate without wire-bonding to mount the element 32 on the substrate by soldering or with a conductive bonding agent 36, and bumps 35 are formed on the element 33 to mount the element 33 on the substrate. The element 33 is formed one side of its sides into a mesa structure and contrives to receive light on slanted surfaces 33b to enhance its sensitivity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a reflection type optical sensor for detecting light reflected from the surface of an object to be detected.

[0002]

2. Description of the Related Art A reflection type optical sensor is a sensor for detecting the presence or absence of an object in a non-contact manner.
It is used to detect the position of paper, film, etc., and the edge.
FIG. 4 shows a principle configuration of a reflection type optical sensor. A package 1 contains a light emitting element 2 (for example, an infrared LED) and a light receiving element 3 (for example, a phototransistor). The light receiving element 3 detects that the light emerges as shown by the arrow and is reflected by the object 4 to be detected. As a result, the output from the light receiving element 3 changes according to the presence or absence and the position of the object 4 in the vicinity of the reflection type optical sensor, and this is used as a detection signal.

FIGS. 5 and 6 show examples of a reflection type optical sensor proposed by the inventors. 5A is a perspective view, and FIG. 5B is a cross-sectional view taken along the line BB of FIG. 5A. A light emitting element 2 and a light receiving element 3 are formed on a conductive pattern on a substrate 9 made of epoxy resin containing glass fiber or the like. Is die-bonded, wire-bonded with a metal wire 13, and sealed with a light-transmitting sealing resin 11. The sealing resin 11 has a trapezoidal shape, and has a side surface covered with a light-shielding film 14 such as a metal plating layer. The upper surface of the sealing resin 11 has no light-shielding film and is a window through which light enters and exits. By reducing the area of this window, detection accuracy can be increased. The conductive portion 12 on the side surface of the substrate 9 is formed by forming a conductive layer in an arc-shaped depression by a through-hole technique, thereby connecting the conductive pattern on the upper surface of the substrate 9 to the terminal electrode on the lower surface of the substrate.

FIG. 6A is a perspective view, and FIG. 6B is a sectional view taken along line BB of FIG. A light-shielding frame 10 made of a light-shielding resin is joined to a substrate 9, and the light-shielding frame 10 has two windows 8 penetrating therethrough. The light emitting element 2 and the light receiving element 3 are die-bonded to the conductive pattern on the substrate 9 inside each of the windows 8 and wire-bonded with the metal wires 13, and the window 8 is filled with a translucent sealing resin 11. Is sealed. Wire bonds are
Normally, a ball is formed at the tip of the metal wire 13 and bonded to the surface of the light emitting element 2 or the light receiving element 3, but in FIG. 4, reverse bonding is performed to bond the ball to the substrate side. It suppresses the increase in component height due to a loop.

The light emitting element 2 and the light receiving element 3 are provided in contact with a central partition wall of the light shielding frame 10 as shown in FIG. The elements can be bonded to the substrate 9 at the center of the window 8 away from the wall. However, in this case, the distance between the elements tends to vary, and the optical path length, and thus the performance of the optical sensor, tends to vary. In that respect, positioning is easy if the element is brought into contact with the wall. The conductive pattern on the upper surface of the substrate is connected to the terminal electrode on the lower surface by the conductive portion 12 on the side surface of the substrate 9. The light emitted from the light emitting element 2 exits through the window 8 on the light emitting element side and irradiates the object to be detected, and the reflected light returns from the window 8 on the light receiving element side to reach the light receiving element 3 and is detected.

[0006]

Each of the above-mentioned conventional reflection-type optical sensors is useful but has problems.
In FIG. 5, since the optical element is wire-bonded and the sealing resin 11 has a trapezoidal shape, the height of the component is more than a certain level. The optical path length of the light returning to the light receiving element 3 cannot be shortened. Since the energy of light is inversely proportional to the square of the optical path length, a long optical path length is disadvantageous because the light use efficiency is reduced.

FIG. 6 has a flat upper surface and is more suitable for thinning than that of FIG. 5. However, if the mounting method is a normal wire bonding in which a ball is formed at the end of the metal wire 13 and bonded to the element. If the height of the component, that is, the optical path length is increased due to the formation of a loop in the metal wire 13 and the height is reduced by performing reverse bonding by another method, the device side tends to be wedge bonded and the device tends to be damaged. Work becomes difficult. The present invention solves these problems and realizes a high-performance, low-cost reflective optical sensor with a simple structure.

[0008]

According to the present invention, the light emitting element and the light receiving element are not arranged on the same surface of the substrate as in each of the above-mentioned prior arts, but are sandwiched between the substrates near the ends of the substrate. Mount on both sides. As a result, the two elements are isolated from each other by the substrate, so that there is no need to provide a special light shielding means between the elements. Then, without performing wire bonding, the light emitting element is laid down on the substrate with solder or conductive paste, with the light emitting layer formed by the pn junction lying down so as to be perpendicular to the substrate,
On the other hand, the light receiving element is mounted with bumps formed on the surface. This eliminates an increase in the optical path length due to the formation of a loop by the metal wire for wire bonding. The light receiving element is 1
The side has a mesa structure and a slope suitable for light reception is provided to increase the light reception sensitivity.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view illustrating an embodiment of the reflection type optical sensor of the present invention in a perspective view. A light emitting element 32 such as an LED is mounted on one surface of a substrate 31, and a light receiving element 33 such as a phototransistor is mounted on the opposite surface, and both elements are sealed with a light-transmitting sealing resin 34. It is. The light emitting element 32 is formed on the substrate 31 by soldering or conductive adhesive.
The bumps 35 are formed on the light receiving element 33 and mounted on the substrate 31. The substrate 31 is provided with a terminal pattern 36 for connection to a target circuit.

FIG. 2A is a plan view of the reflection type optical sensor of FIG. 1, and FIG. 2B is a front view. As shown in FIG. 2B, the light emitting element 32 and the light receiving element 33 are respectively mounted on the front and back of the substrate at a position near the upper edge of the substrate 31, and are sealed with a sealing resin. The light emitting element 32 is, for example, an LED and emits light from the light emitting layer 32a which is a pn junction. In the case of normal wire bonding mounting, the light emitting layer 32a is parallel to the substrate 31 and the semiconductor base is die-bonded to the substrate 31 to perform wire bonding. In the present invention, the light emitting element 32 is turned over so that the light emitting layer 32a is perpendicular to the substrate surface, and the light emitting element 32 is mounted on the substrate 31 with a conductive adhesive 36 such as solder or silver paste.

On the other hand, the light receiving element 33 is mounted on the substrate surface on the side opposite to the light emitting element 32. Similarly, a required number of bumps 35 are provided on the element surface and bonded to connection pads on the substrate 31 without using wire bonding. . When the light receiving element 33 is, for example, a phototransistor, the base region becomes a light receiving layer. As shown in FIG. 2B, the light receiving element 33 has a mesa structure on the upper edge side to form an inclined surface 33b. 33
a is exposed on the slope 33b.

The path of light during operation of the above-mentioned reflection type optical sensor is as shown by an arrow in FIG. That is, the light emitted from the light emitting element 32 is reflected on the surface of the detection target object 4 and turns to the opposite side of the substrate 31 to the slope 33 of the light receiving element 33.
b, the end of the light receiving layer 33a is located in this portion. When the surface of the light receiving element 33 is brought into close contact with the substrate 31, light does not reach the light receiving layer 33a. However, the light receiving element surface slightly floats from the substrate surface by mounting using the bump 35, and a mesa structure is provided on the upper edge of the element. Is provided, the light receiving layer 33a takes an appropriate position with respect to the light path.

In the structure of the present invention, since the light emitting element 32 and the light receiving element 33 are on both sides of the substrate 31 and are separated by the substrate, it is necessary to provide a special member for shielding light between the two optical elements as in the conventional example. There is no. Further, since the mounting of the optical element is not wire bonding, the metal wire does not form a loop and the resin sealing portion is not bulky, so that the optical path is shortened and the performance is improved.

As the substrate 31, a flexible circuit board having a conductive pattern provided on a flexible resin thin plate can be used. Also, the outer surface other than the upper surface of the sealing resin 34 is coated with a metal light-shielding film by plating or vapor deposition, etc.
Light loss can also be reduced.

FIG. 3 shows a second embodiment of the present invention, in which the light emitting element 32 is rotated by 90 ° around an axis perpendicular to the surface of the substrate 31 with respect to that of FIG. Thus, the light emitting layer 32a of the light emitting element 32 is perpendicular to the surface of the object 4 in FIG. 2, but the light emitting layer 32a is parallel to the surface of the object 4 in FIG.

[0016]

According to the reflection type optical sensor of the present invention, the following effects can be obtained. That is, 1. Since the light emitting element and the light receiving element are mounted near the edge of the substrate, the light emitting element and the light receiving element can be arranged close to the object to be detected, and the optical path length can be minimized to increase the light coupling efficiency and the S / N ratio. 2. Since it does not rely on wire bonding, mounting reliability is increased. 3. Since the optical path length is shortened, the spread of light is reduced, so that the light receiving portion, that is, the light receiving element can be reduced, the junction capacitance can be reduced, and the frequency characteristics of detection can be improved. 4. Since the element can be made smaller, the substrate can be made thinner and the sealing can be made less bulky, it is easy to make the product smaller and thinner. 5. Since the substrate separates the optical elements from each other, it is not necessary to separately provide a light-blocking member, and the manufacturing cost can be reduced. As described above, according to the present invention, a small-sized, high-performance, and highly reliable reflection-type optical sensor can be provided at low cost.

[Brief description of the drawings]

FIG. 1 is a perspective view of a reflection type optical sensor of the present invention.

FIG. 2 is a drawing of the embodiment of FIG. 1, wherein (A) is a top view,
(B) is a front view.

3A and 3B are drawings of another embodiment of the present invention, wherein FIG. 3A is a top view and FIG. 3B is a front view.

FIG. 4 is a view showing the principle configuration of a reflection type optical sensor.

5A is a perspective view of a conventional example of a reflection type optical sensor, FIG.
(B) is BB sectional drawing of (A).

6A is a perspective view and FIG. 6B is a cross-sectional view taken along the line BB of FIG.

[Explanation of symbols]

 2, 32 light emitting element 3, 33 light receiving element 8 window 9, 31 substrate 10 light shielding frame 11, 34 sealing resin 14 light shielding film 32a light emitting layer 33a light receiving layer 33b slope 35 bump 36 solder, conductive adhesive

Claims (2)

[Claims] 1. A light-emitting element and a light-receiving element are mounted on both sides of a substrate at positions close to an edge of the substrate, respectively, and are sealed with a resin. The light-receiving element was mounted on the board with an adhesive or the like, and the light-receiving element was mounted on the board with bumps with the mesa structure on one side, the slope of the mesa structure facing the edge of the board, and the light-receiving layer facing the board side. The reflection type optical sensor characterized by the above-mentioned. 2. The reflection type optical sensor according to claim 1, wherein the substrate is a flexible circuit board.