Optical module and method for manufacturing same

Abstract

A light-receiving element (2) and a processing device (3) are mounted on the main surface of a printed circuit board (1). The processing device (3) processes an output signal of the light-receiving element (2). A cap (4) covers the light-receiving element (2) and the processing device (3). A lens (13) is provided to the upper surface of the cap (4) directly above the light-receiving element (2) and condenses light onto the light-receiving element (2). Edges (14) of the cap (4) have adhesive surfaces (14a) bonded to the main surface of the printed circuit board (1) by means of an adhesive (15). The width of the adhesive surface (14a) on the light-receiving element (2) side is narrower than the width of the adhesive surface (14a) on the processing device (3) side.

Description

Optical module and manufacturing method thereof

[0001] The present disclosure relates to an optical module and a method for manufacturing the same.

[0002] In an optical module, a light-receiving element and a processing device are mounted on the main surface of a printed circuit board, and the light-receiving element and processing device are covered with a cap. The cap is provided with a lens that focuses light onto the light-receiving element (see, for example, Patent Document 1). When the cap is attached to the main surface of the printed circuit board, a collet is used to press the cap against the printed circuit board via an adhesive.

[0003] Japanese Patent Application Publication No. 2011-203221

[0004] The collet had to be pressed on the area on the top surface of the cap where the lens was not installed, and it was not possible to press the collet on the center of the top surface of the cap. As a result, the cap was attached to the printed circuit board at an angle, causing a tilt in which the central axis of the lens was tilted from the perpendicular direction to the light-receiving surface of the light-receiving element. This caused the lens to shift focus, resulting in insufficient light collection on the light-receiving element and a deterioration in light-receiving performance.

[0005] The present disclosure has been made to solve the above-mentioned problems, and its object is to provide an optical module that can prevent deterioration of light receiving performance and a method for manufacturing the same.

[0006] The optical module according to the present disclosure comprises a printed circuit board, a light receiving element mounted on a main surface of the printed circuit board, a processing device mounted on the main surface of the printed circuit board and processing an output signal of the light receiving element, a cap covering the light receiving element and the processing device, and a lens provided on the upper surface of the cap directly above the light receiving element and focusing light onto the light receiving element, wherein the edge of the cap has an adhesive surface adhered to the main surface of the printed circuit board with an adhesive, and the width of the adhesive surface on the light receiving element side is narrower than the width of the adhesive surface on the processing device side.

[0007] In this disclosure, the width of the adhesive surface on the light-receiving element side is narrower than the width of the adhesive surface on the processing device side. This ensures that the load per unit area applied to the adhesive on the light-receiving element side and the processing device side when the cap is attached is the same. As a result, the thickness of the adhesive on the light-receiving element side and the processing device side is the same, so lens tilt does not occur and deterioration of light-receiving performance can be prevented.

[0008] FIG. 1 is a cross-sectional view showing an optical module according to a first embodiment. FIG. 2 is a top view showing an optical module according to the first embodiment. FIG. 3 is a cross-sectional view showing a manufacturing process of the optical module according to the first embodiment. FIG. 4 is a cross-sectional view showing an optical module according to a comparative example. FIG. 5 is a top view showing an optical module according to a comparative example. FIG. 6 is a cross-sectional view showing an optical module according to a second embodiment. FIG. 7 is a bottom view of a cap according to a third embodiment. FIG. 8 is a side view of a cap according to the third embodiment. FIG. 9 is a cross-sectional view showing an optical module according to the third embodiment. FIG. 10 is a bottom view of a modified example of the cap according to the third embodiment. FIG. 11 is a top view showing an optical module according to a fourth embodiment.

[0009] An optical module and a method for manufacturing the same according to an embodiment will be described with reference to the drawings. The same or corresponding components are designated by the same reference numerals, and repeated description may be omitted.

[0010] 1 is a cross-sectional view showing an optical module according to embodiment 1. Fig. 2 is a top view showing the optical module according to embodiment 1. This optical module is, for example, a thermal diode infrared sensor that measures the temperature of an object in a non-contact manner.

[0011] A light-receiving element 2 and a processing device 3 are mounted side by side along the longitudinal direction of the printed circuit board 1 on the main surface of the printed circuit board 1, which is rectangular in plan view. The printed circuit board 1 is made of glass epoxy. An output electrode 5 of the light-receiving element 2 is connected to an input terminal 7 of the processing device 3 by a gold wire 6. An output terminal 8 of the processing device 3 is connected to a surface electrode 10 of the printed circuit board 1 by a gold wire 9. The surface electrode 10 and a back electrode 12 are connected through a via 11 that passes through the printed circuit board 1.

[0012] The light receiving element 2 is a thermal diode infrared sensor with multiple pixels arranged in a matrix that receives infrared light and converts it into an electrical signal, for example an infrared sensor with 80 x 60 pixels. Since there is variation in the output signal from each pixel even when measuring the same temperature, the processing device 3 processes the output signal from the light receiving element 2 so that the output corresponds to the same temperature. The output signal from the processing device 3 is output to the outside via the gold wire 9, the front surface electrode 10, the via 11, and the back surface electrode 12.

[0013] A cap 4, which is approximately rectangular in plan view, covers the light-receiving element 2 and processing device 3. The cap 4 is made of plastic. Since the surface of the printed circuit board 1 is covered with resist (not shown), the light-receiving element 2, processing device 3, and cap 4 are adhered to the resist of the printed circuit board 1. A lens 13 is provided on the upper surface of the cap 4 directly above the light-receiving element 2, and focuses light onto the light-receiving element 2. The lower surface of an edge 14 of the cap 4 forms an adhesive surface 14a that is adhered to the main surface of the printed circuit board 1 with an adhesive 15. The adhesive 15 is an acrylic or epoxy adhesive.

[0014] To increase the area of ​​the adhesive surface 14a, the edge 14 of the cap 4 extends outward beyond the side wall of the cap 4. The width of the edge 14 of the cap 4 differs between the light-receiving element 2 side and the processing device 3 side, with the width of the adhesive surface 14a on the light-receiving element 2 side being narrower than the width of the adhesive surface 14a on the processing device 3 side. The width of the edge 14 along the longitudinal direction of the cap 4 gradually changes from the width of the edge 14 on the processing device 3 side to the width of the edge 14 on the light-receiving element 2 side.

[0015] 3 is a cross-sectional view showing a manufacturing process of the optical module according to embodiment 1. The center X of the area on the top surface of the cap 4 where the lens 13 is not provided is vacuum-sucked by the collet 16. That is, the center of the collet 16 is aligned with the center X of the area, and vacuum suction is performed. In this state, the collet 16 is moved to align the cap 4 and the printed circuit board 1 so that the lens 13 is positioned on the top surface of the cap 4. The cap 4 is adhered to the main surface of the printed circuit board 1 by pressing the collet 16 against the main surface of the printed circuit board 1 via the adhesive 15.

[0016] Next, the effects of this embodiment will be described in comparison with a comparative example. FIG. 4 is a cross-sectional view of an optical module according to the comparative example. FIG. 5 is a top view of an optical module according to the comparative example. In the comparative example, the width of the adhesive surface 14a on the light-receiving element 2 side is the same as the width of the adhesive surface 14a on the processing device 3 side. As shown in FIG. 3, the collet 16 presses the processing device 3 side more than the center of the top surface of the cap 4. The pressure from the collet 16 is weaker at portions of the adhesive surface 14a on the edge 14 of the cap 4 that are farther from the center of the collet 16. As a result, the force applied to the processing device 3 side of the cap 4 is greater than the force applied to the light-receiving element 2 side of the cap 4. Therefore, more of the adhesive 15 on the processing device 3 side of the cap 4 is discharged from between the cap 4 and the printed circuit board 1, making it thinner than the adhesive 15 on the light-receiving element 2 side of the cap 4. As a result, the cap 4 is adhered to the printed circuit board 1 at an angle, causing a "tilt" in which the central axis of the lens 13 is tilted from the perpendicular direction to the light-receiving surface of the light-receiving element 2. This tilt causes the lens 13 to shift its focus, resulting in insufficient light collection by the lens 13 onto the light receiving element 2, and thus deteriorating the light receiving performance.

[0017] In contrast, in this embodiment, the width of the adhesive surface 14a on the light-receiving element 2 side is narrower than the width of the adhesive surface 14a on the processing device 3 side. The narrower the width of the adhesive surface 14a of the edge 14 of the cap 4, the stronger the load per unit area applied to the adhesive 15. Therefore, the load per unit area applied to the adhesive 15 on the light-receiving element 2 side and the processing device 3 side when the cap 4 is adhered is the same. As a result, the thickness of the adhesive 15 on the light-receiving element 2 side and the adhesive 15 on the processing device 3 side are the same, so tilting of the lens 13 does not occur, and deterioration of light-receiving performance can be prevented.

[0018] Furthermore, it is preferable to set the ratio of the width of the adhesive surface 14a on the processing device 3 side to the width of the adhesive surface 14a on the light-receiving element 2 side to the ratio of the distance from the center X of the area on the top surface of the cap 4 where the lens 13 is not provided to the end Y of the cap 4 on the processing device 3 side to the distance from the center X to the end Z of the cap 4 on the light-receiving element 2 side. For example, if the ratio of the distance from the center X to the end Z of the cap 4 on the light-receiving element 2 side to the distance from the center X to the end Y of the cap 4 on the processing device 3 side is 3:1, the width of the adhesive surface 14a on the light-receiving element 2 side should be set to 1 / 3 of the width of the adhesive surface 14a on the processing device 3 side. This ensures that the load per unit area applied to the adhesive 15 on the light-receiving element 2 side and the processing device 3 side when the cap 4 is bonded is the same.

[0019] Second Embodiment FIG. 6 is a cross-sectional view of an optical module according to a second embodiment. The width of the edge 14 of the cap 4 is the same on the light-receiving element 2 side and the processing device 3 side. However, the edge 14 on the light-receiving element 2 side has a taper 14b that moves away from the main surface of the printed circuit board 1 as it moves outward from the cap 4. The portion of the underside of the edge 14 of the cap 4 other than the taper 14b serves as the adhesive surface 14a. Therefore, as in the first embodiment, the width of the adhesive surface 14a on the light-receiving element 2 side is narrower than the width of the adhesive surface 14a on the processing device 3 side. This ensures that the load per unit area applied to the adhesive 15 when adhering the cap 4 is the same on the light-receiving element 2 side and the processing device 3 side. As a result, the thickness of the adhesive 15 on the light-receiving element 2 side and the processing device 3 side are the same, preventing tilting of the lens 13 and preventing deterioration of light-receiving performance.

[0020] The width of the adhesive surface 14a along the longitudinal direction of the cap 4 gradually changes from the width of the adhesive surface 14a on the processing device 3 side to the width of the adhesive surface 14a on the light-receiving element 2 side. A taper 14b may also be provided on the edge 14 on the processing device 3 side, but the size of the taper 14b on both sides must be adjusted so that the width of the adhesive surface 14a on the light-receiving element 2 side is narrower than the width of the adhesive surface 14a on the processing device 3 side. Furthermore, the taper 14b causes the adhesive 15 to creep up the side wall of the edge 14 of the cap 4 at an angle greater than 90°. This makes it difficult for the adhesive 15 to creep up the side wall, and therefore the adhesive 15 is less likely to creep up onto the cap 4.

[0021] Embodiment 3 Fig. 7 is a bottom view of a cap according to embodiment 3. Fig. 8 is a side view of a cap according to embodiment 3. Fig. 9 is a cross-sectional view showing an optical module according to embodiment 3. A plurality of protrusions 17 are formed on the adhesive surface 14a of the cap 4. The plurality of protrusions 17 have the same size, but the spacing between the protrusions 17 on the adhesive surface 14a on the light-receiving element 2 side is wider than the spacing between the protrusions 17 on the adhesive surface 14a on the processing device 3 side. Therefore, the area ratio of the protrusions 17 on the adhesive surface 14a on the light-receiving element 2 side is smaller than the area ratio of the protrusions 17 on the adhesive surface 14a on the processing device 3 side.

[0022] The manufacturing process of the optical module is the same as that of the first embodiment, except that the thickness of the adhesive 15 applied to the printed circuit board 1 before bonding the cap 4 is made thicker than the thickness of the protrusions 17. The cap 4 is adhered to the main surface of the printed circuit board 1 by pressing the adhesive 15 against the main surface of the printed circuit board 1 with a collet 16. After bonding the cap 4, the adhesive 15 is crushed, and both the protrusions 17 on the light-receiving element 2 side and the protrusions 17 on the processing device 3 side come into contact with the main surface of the printed circuit board 1.

[0023] The effects of this embodiment will be explained by comparing it with a comparative example. In the comparative example, the area ratio of the protrusions 17 is the same on the light-receiving element 2 side and the processing device 3 side. As described above, the collet 16 presses the processing device 3 side of the top surface of the cap 4 more than the center, so the force applied to the processing device 3 side of the cap 4 is greater than the force applied to the light-receiving element 2 side of the cap 4. Therefore, in the comparative example, more adhesive 15 on the processing device 3 side of the cap 4 is discharged from between the cap 4 and the printed circuit board 1, making it thinner than the adhesive 15 on the light-receiving element 2 side of the cap 4. As a result, tilt occurs, deteriorating light-receiving performance.

[0024] In contrast, in this embodiment, the area ratio of the protrusions 17 on the light-receiving element 2 side is reduced. The protrusions 17 come into contact with the adhesive 15 when the cap 4 is attached, and the smaller the area of ​​the protrusions 17, the stronger the load per unit area applied to the adhesive 15. This makes the load per unit area applied to the adhesive 15 the same on the light-receiving element 2 side and the processing device 3 side. As a result, the thickness of the adhesive 15 on the light-receiving element 2 side and the processing device 3 side are the same, so tilting of the lens 13 does not occur, and deterioration of light-receiving performance can be prevented.

[0025] 10 is a bottom view of a modified cap according to the third embodiment. The spacing between the multiple protrusions 17 is constant, but the length of the protrusions 17 along the edge 14 on the adhesive surface 14a on the light-receiving element 2 side is shorter than the length of the protrusions 17 along the edge 14 on the adhesive surface 14a on the processing device 3 side. Even in this case, the spacing between the protrusions 17 on the adhesive surface 14a on the light-receiving element 2 side is wider than the spacing between the protrusions 17 on the adhesive surface 14a on the processing device 3 side. Therefore, the area ratio of the protrusions 17 on the adhesive surface 14a on the light-receiving element 2 side is smaller than the area ratio of the protrusions 17 on the adhesive surface 14a on the processing device 3 side. The area ratio of the protrusions 17 on the edge 14 along the longitudinal direction of the cap 4 gradually changes from the area ratio of the protrusions 17 on the processing device 3 side to the area ratio of the protrusions 17 on the light-receiving element 2 side. This achieves the same effect as described above.

[0026] Furthermore, it is preferable to set the ratio of the area ratio of the protrusions 17 on the processing device 3 side to the area ratio of the protrusions 17 on the light-receiving element 2 side to the ratio of the distance from the center X of the region on the top surface of the cap 4 where the lens 13 is not provided to the end Y of the cap 4 on the processing device 3 side to the distance from the center X to the end Z of the cap 4 on the light-receiving element 2 side. For example, if the ratio of the distance from the center X to the end Z of the cap 4 on the light-receiving element 2 side to the distance from the center X to the end Y of the cap 4 on the processing device 3 side is 3:1, the area ratio of the protrusions 17 on the light-receiving element 2 side is set to 1 / 3 of the area ratio of the protrusions 17 on the processing device 3 side. This ensures that the load per unit area applied to the adhesive 15 when bonding the cap 4 is the same on the light-receiving element 2 side and the processing device 3 side.

[0027] 11 is a top view of an optical module according to a fourth embodiment. The width of the edge 14 of the cap 4 is the same on the light-receiving element 2 side and the processing device 3 side. When applying adhesive 15 to the main surface of the printed circuit board 1 using a dispenser, the adhesive 15 is applied discretely on the light-receiving element 2 side and continuously on the processing device 3 side. Therefore, the area ratio of the adhesive 15 on the underside of the edge 14 on the light-receiving element 2 side is smaller than the area ratio of the adhesive 15 on the underside of the edge 14 on the processing device 3 side. By reducing the amount of adhesive 15 on the light-receiving element 2 side, the load per unit area applied to the adhesive 15 during bonding of the cap 4 is the same on the light-receiving element 2 side and the processing device 3 side. As a result, the thickness of the adhesive 15 on the light-receiving element 2 side and the processing device 3 side are the same, preventing tilting of the lens 13 and preventing deterioration of light-receiving performance.

[0028] 1 printed circuit board, 2 light receiving element, 3 processing device, 4 cap, 13 lens, 14 edge, 14a adhesive surface, 14b taper, 15 adhesive, 17 protrusion

Claims

1. An optical module comprising: a printed circuit board; a light receiving element mounted on a main surface of said printed circuit board; a processing device mounted on the main surface of said printed circuit board and processing an output signal of said light receiving element; a cap covering said light receiving element and said processing device; and a lens provided on the upper surface of said cap directly above said light receiving element and for focusing light onto said light receiving element, wherein the edge of said cap has an adhesive surface adhered to the main surface of said printed circuit board with an adhesive, and the width of said adhesive surface on the light receiving element side is narrower than the width of said adhesive surface on the processing device side.

2. An optical module as described in claim 1, characterized in that the edge of the cap extends outward beyond the side wall of the cap, and the edge on the light-receiving element side tapers away from the main surface of the printed circuit board as it moves toward the outside of the cap.

3. An optical module as described in claim 1 or 2, characterized in that the ratio of the width of the adhesive surface on the processing device side to the width of the adhesive surface on the light receiving element side is the same as the ratio of the distance from the center of the area on the top surface of the cap where the lens is not provided to the end of the cap on the processing device side to the distance from the center to the end of the cap on the light receiving element side.

4. An optical module comprising: a printed circuit board; a light receiving element mounted on a main surface of the printed circuit board; a processing device mounted on the main surface of the printed circuit board and processing an output signal of the light receiving element; a cap covering the light receiving element and the processing device; and a lens located on the upper surface of the cap directly above the light receiving element and focusing light onto the light receiving element, wherein the edge of the cap has an adhesive surface that is adhered to the main surface of the printed circuit board with an adhesive, and a plurality of protrusions are formed on the adhesive surface, and the area ratio of the protrusions on the adhesive surface on the light receiving element side is smaller than the area ratio of the protrusions on the adhesive surface on the processing device side.

5. The optical module according to claim 4, wherein the spacing between the protrusions on the adhesive surface on the light receiving element side is wider than the spacing between the protrusions on the adhesive surface on the processing device side.

6. An optical module as described in claim 4, characterized in that the length along the edge of the protrusion on the adhesive surface on the light receiving element side is shorter than the length along the edge of the protrusion on the adhesive surface on the processing device side.

7. An optical module described in any one of claims 4 to 6, characterized in that the ratio of the area ratio of the protrusion on the processing device side to the area ratio of the protrusion on the light receiving element side is the same as the ratio of the distance from the center of the area on the top surface of the cap where the lens is not provided to the end of the cap on the processing device side to the distance from the center to the end of the cap on the light receiving element side.

8. An optical module comprising: a printed circuit board; a light receiving element mounted on a main surface of the printed circuit board; a processing device mounted on the main surface of the printed circuit board and processing an output signal of the light receiving element; a cap covering the light receiving element and the processing device; and a lens provided on the upper surface of the cap directly above the light receiving element and focusing light onto the light receiving element, wherein the edge of the cap has an adhesive surface adhered to the main surface of the printed circuit board with an adhesive, and the area ratio of the adhesive on the underside of the edge on the light receiving element side is smaller than the area ratio of the adhesive on the underside of the edge on the processing device side.

9. A method for manufacturing an optical module according to any one of claims 1 to 8, characterized in that the center of an area on the top surface of the cap where no lens is provided is vacuum-sucked with a collet, and the cap is pressed against the main surface of the printed circuit board using the collet via the adhesive, thereby adhering the cap to the main surface of the printed circuit board.

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