JPH06101581B2 - Method of forming photo interrupter - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming a photo interrupter suitable for a small device such as a camera and a floppy disk drive.

2. Description of the Related Art A perspective view showing the appearance of a conventional double mold type photo interrupter is shown in FIG. 7, and a sectional view thereof is shown in FIG. Two
The heavy mold type is realized for downsizing of the photo interrupter, and the holder case is eliminated by adopting the secondary molding structure of the light-shielding resin to achieve downsizing. Light-shielding resin 6 used for secondary molding
Has a role of integrating the light emitting element 7L and a light receiving element 7P and a role of blocking ambient light. In order to form the window portion 10 serving as a light entrance / exit, in the primary mold for forming the light emitting element 7L and the light receiving element 7P, the protruding portion 8 having a predetermined width is provided on the facing surface side of the outer shell of the transparent resin. A slit is provided as a photo interrupter to improve the resolution. The groove 9 formed in the light-shielding resin 6 is used as a secondary molding die for the light-emitting element 7L and the light-receiving element 7P that are primary-molded so that the light-shielding resin 6 does not cover the window portion 10. It is a groove formed by pressing the formed protrusion. Therefore, the window portion 10 and the light receiving and emitting elements 7P, 7
The positional relationship with L is determined when the primary molding is completed. The light-emitting element 7L and the light-receiving element 7P that are primary-molded have the shapes shown in the perspective view of FIG.

In order to improve the resolution of the photointerrupter, it is desirable to make the window portion 10 serving as a light entrance / exit as small as possible, and actually a dimension of about 0.2 mm to 0.3 mm is required. However, since the size of the light emitting element substrate 1L, which is the main constituent of the photointerrupter, is also around 0.3 mm square, the width of the window portion 10 and the size of the light emitting element substrate 1L are almost the same, and the window portion 10 and the light receiving and emitting element substrate are the same. If the positional relationship between the light emitting element and the light receiving element is deviated, a part of the optical path between the light emitting element and the light receiving element is blocked by the light shielding resin 6, which causes a problem that the effective transmission of the optical signal is hindered.

By the way, as a cause of the positional relationship between the window portion 10 and the light emitting / receiving element substrates 1P and 1L being shifted, there is a deviation when the element substrate is mounted on the lead frame in the manufacturing process and a deviation during the primary molding. Especially, it becomes the deviation at the time of primary molding that becomes dominant. The primary molding of the light emitting / receiving element is performed with the light receiving / emitting element substrate mounted on the multiple lead frames, and the curing temperature of the resin at this time is generally set to 100 ° C. or higher. Therefore, due to the difference in the thermal expansion coefficient between the lead frame material and the primary molding die, the lead frame and the protrusion 8 of the primary mold are displaced from each other, and this displacement causes the light emitting / receiving element substrates 1P and 1L and the windows. A displacement of the portion 10 occurs. The thermal expansion coefficient of Fe, which is a typical material for lead frames, is 1.2 x 1
0 ^-5 / ° C. The thermal expansion coefficient of Cu is 1.7 × 10 ^-5 / ℃. On the other hand, the coefficient of thermal expansion of Al used for the mold in the casting method is 2.3 × 10
^-5 / ° C.

Therefore, in the conventional double-mold type photointerrupter, when the secondary molding with the light-shielding resin 6 is completed, a part of the light path between the light receiving and emitting elements is blocked by the light-shielding resin 6, and the effective window area is reduced. However, there is a problem in that the efficiency of the light transfer characteristic is reduced due to the decrease of the light transmission efficiency. The cross-sectional view of FIG. 8 illustrates the reduction of the effective window area, and the light emitting element substrate 1L or the light receiving element substrate 1P is displaced from the window portion 10.

Further, when the primary molding is performed by the casting method, the shape of the protruding portion is limited due to the restriction of the die. That is,
The protrusion 11 as shown in FIG. 10 can be molded, but the protrusion 11 as shown in FIG. 11 cannot be molded. Therefore, the seventh
Although the resolution in the X-axis direction shown in the figure can be improved by the window shape, the resolution in the Y-axis direction could not be improved by the window shape.

Means for Solving the Problems In order to solve the problems of the conventional techniques described above, the method for manufacturing a photointerrupter of the present invention is such that a taper portion is provided on the upper surface and the front surface is a flat surface. A step of forming a light emitting element and a light receiving element which are primary-molded with a light-transmissive resin, and into a secondary molding die having a protrusion reaching the upper surface at a position corresponding to the front surface of the light emitting element and the light receiving element. A step of secondly molding the light emitting element and the light receiving element so as to face each other and forming a window portion for forming an optical path by the tapered portion and the projecting portion between both elements. It is characterized by.

According to the forming method of the present invention, the window portion is formed by the taper portion 12 formed by the primary mold and the protrusion portion formed on the mold for the secondary molding, and therefore the secondary portion of the position of the window portion is formed. The positional displacement of the window portion with respect to the outer shape of the molded photo interrupter is uniquely determined by the processing accuracy of the secondary molding die, and therefore is extremely small.

Even if the primary mold is used as a casting method, by changing the window shape dimension in the Y-axis direction, which has been difficult in the past, by changing the length of the protrusion of the secondary mold and the shape of the taper of the primary mold, You can change it freely.

Example An example of a method for forming a photo interrupter of the present invention will be described below.

First, as shown in FIG. 4, the light emitting element substrate 1L is fixed to the lead frame 2, and furthermore, the electrodes of the light emitting element substrate 1L and the external leads are connected by the thin metal wires 3. Next, as shown in FIG. 5, a light-transmissive resin 4 is provided with a tapered portion on the upper surface, and the light emitting element 5L is completed by performing a primary molding in which the front surface is flat. The light receiving element is also formed by the same method.

By the way, as is apparent from FIG. 5 showing the shape of the primary-molded element, in the photointerrupter formed by the manufacturing method of the present invention, the shape of the window portion which becomes the passage of light is not determined by the primary molding. The portion of the secondary molding die against which the protrusion is pressed is flat. Further, the tapered portion 12 is used to adjust the size of the window portion in the Y-axis direction.

That is, in FIG. 2, the dimension of the window portion 15 in the Y-axis direction is an important factor that determines the detection accuracy in the Y-axis direction.
If the dimension in the axial direction is small, the detection accuracy is improved (movement or presence / absence of a minute range of the detection target can be detected). For this reason, the taper portion 12 is made to have a large inclination so that the window portion 15 has a small dimension in the Y-axis direction, and the taper portion 12 has a small inclination so that the window portion 15 has a large Y-direction dimension. It will be possible.

Further, as another effect of the tapered surface, when the secondary molding with the light-shielding resin 13 which will be described later is further performed, the tapered portion 12 forms the window portion 15 between the light emitting element 5L and the light receiving element 5P which are arranged to face each other. This has the effect of smoothly inserting the tip of the protruding portion along the tapered portion 1 when the protruding portion of the secondary molding die is inserted.

The primary mold may be either a transfer molding method or a casting method.

Next, the light-emitting element 5L and the light-receiving element 5P whose primary molding has been completed
Are placed opposite to each other in a mold for secondary molding having protrusions at positions corresponding to the front surfaces of both elements, and a light-shielding resin 13 is used as a resin for the secondary molding to integrate the two. Do. The secondary mold resin may be either a thermoplastic resin or a thermosetting resin, and the molding method may be either an injection molding method, a transfer molding method or a casting method. A perspective view of a photo interrupter formed by injection molding using a thermoplastic resin is shown in FIG. 1, and sectional views thereof are shown in FIGS. 2 and 3.
The light-shielding resin 13 used for the secondary mold has a structural role of integrating the light emitting element 5L and the light receiving element 5P and a role of blocking ambient light. The recesses 14 provided on the back surfaces of the light emitting element 5L and the light receiving element 5P are
The light emitting element 5L and the light receiving element 5P are respectively pushed forward by a die having a protruding portion, and the window forming portion of the light emitting and light receiving element is pressed to prevent the light shielding resin 13 from wrapping around the window portion 15. It was created to have.

In FIG. 3, the dimension of the window portion 15 in the X-axis direction is determined by the width dimension of the protrusion of the secondary molding die, and
In FIG. 2, the dimension of the window portion 15 in the Y-axis direction is determined by the length dimension of the protruding portion of the secondary molding die and the shape of the taper portion of the primary-molded element.

By the way, according to the manufacturing method of the present invention, as shown in FIG. 3, the deviation in the X-axis direction in the light-emitting element 5L of the light-emitting element substrate 1L and the X-axis direction in the light-receiving element 5P of the light-receiving element substrate 1P are observed. Even if the deviation is large, the window part after the secondary molding
Since the position of 15 and the positions of the light emitting / receiving element substrates 1L and 1P are determined separately for the primary mold and the secondary mold, they can be accurately matched.

It is needless to say that the transparent resin 4 described in the above embodiments may be a type of resin that blocks visible light when an infrared light emitting diode is used as a light emitting element.

The photo interrupter formed may also have a plurality of windows on the light emitting side and the light receiving side, as shown in FIG.

As described above, according to the present invention, the size of the window portion can be freely determined by the taper portion at the time of forming the primary mold and the protruding portion at the time of forming the secondary mold. It could not be realized with a conventional photointerrupter with a double mold structure in which the protruding portion provided on the enclosure serves as a light emitting / receiving window.
It is possible to produce a double-molded photointerrupter with high precision and high transmission characteristics at a low cost and with excellent mass productivity.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a photo interrupter formed by the method of the present invention, FIGS. 2 and 3 are sectional views of the photo interrupter shown in FIG. 1, and FIG. 4 is an assembly before primary molding. FIG. 5 is a perspective view showing a state of the structure, FIG. 5 is a perspective view showing a light emitting element after the primary molding, and FIG. 6 is a perspective view showing another embodiment of the photo interrupter formed by the method of the present invention. FIG. 8 is a perspective view showing a conventional photointerrupter, FIG. 8 is a cross-sectional view of the photointerrupter shown in FIG. 7, and FIG. 9 is a perspective view showing the structure of the element after the primary molding forming the conventional photointerrupter. FIG. 10 is a sectional view showing an example of a primary mold by a casting method or transfer molding method, and FIG. 11 is a sectional view showing an example of a primary mold by a transfer molding method. 1L: Light emitting element substrate, 1P: Light receiving element substrate, 2 ... Lead frame, 3 ... Metal wire, 4 ... Translucent resin for primary mold, 5L, 7L ... Light emitting element, 5P, 7P ……Light receiving element,
6,13 …… Light-shielding resin, 8 …… Projection of primary mold, 9
...... Grooves, 10,15 ・ ・ ・ Window parts, 11 …… Projections formed by transfer molding, 12 …… Primary mold taper parts, 14 …… Concave parts.

Claims (1)

[Claims] 1. A step of forming a light emitting element and a light receiving element which are primary-molded with a transparent resin so that a taper portion is provided on the upper surface and the front surface becomes a flat surface, and the light emitting element and the light receiving element. The light emitting element and the light receiving element are arranged to face each other in a mold for secondary molding having a protrusion reaching the upper surface at a position corresponding to the front surface of the element, and the light emitting resin is secondarily molded, and the element between the both elements is described above. A method of forming a photo interrupter, comprising: forming a window portion for forming an optical path with a tapered portion and the protruding portion.