OPTICAL DEVICE AND METHOD OF MANUFACTURING OPTICAL DEVICE

Abstract

An optical device includes: an optical element that is rectangular as seen in a top view, and that has a light-receiving portion at a top surface thereof; a wiring substrate on which the optical element is mounted; wires electrically connecting the optical element and the wiring substrate at from one to three sides of the rectangular optical element; a resin portion formed at a periphery of the optical element, and covering a portion of the top surface of the optical element including the wires; and an opening portion that is concave, that is provided in the resin portion, and that is formed by a molding die such that at least the light-receiving portion and the top surface at a periphery of the light-receiving portion are exposed, wherein the resin portion that structures a bottom surface at the opening portion is flush with the top surface.

Claims

1. An optical device, comprising: an optical element that is rectangular as seen in a top view, and that has a light-receiving portion at a top surface thereof; a wiring substrate on which the optical element is mounted; wires electrically connecting the optical element and the wiring substrate at from one to three sides of the rectangular optical element; a resin portion formed at a periphery of the optical element, and covering a portion of the top surface of the optical element including the wires; and an opening portion that is concave, that is provided in the resin portion, and that is formed by a molding die such that at least the light-receiving portion and the top surface at a periphery of the light-receiving portion are exposed, wherein the resin portion that structures a bottom surface at the opening portion is flush with the top surface.

2. The optical device of claim 1, wherein: connection terminals that connect the wires are not provided at two sides among four sides of the optical element, and light-receiving portions are provided respectively along the two sides at which the connection terminals are not provided.

3. The optical device of claim 2, wherein the light-receiving portions are formed in elongated shapes along the sides, and pluralities of pixels are arrayed along length directions of the light-receiving portions.

4. The optical device of claim 1, wherein: a through-portion, which passes through the resin portion and exposes a surface of a portion of the wiring substrate, is provided at a portion of the opening portion, and a light-emitting element is provided at the wiring substrate that is exposed from the through-portion.

5. A method of manufacturing an optical device that includes an optical element having a light-receiving portion, and a wiring substrate on which the optical element is mounted and that is electrically connected to the optical element via wires, the method comprising: a resin molding step of molding at least the wires and a portion of the optical element by a resin by using a molding die, wherein the molding die has a cavity portion that is concave and into which resin for molding is filled, and wherein the cavity portion has a contacting portion that is planar, that contacts the light-receiving portion and a surface of the optical element at a periphery of the light-receiving portion such that the light-receiving portion and the surface of the optical element at the periphery of the light-receiving portion are not covered by the resin, and that forms an optical element periphery portion that is formed by the resin and is flush with the surface.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Preferred embodiments will be described in detail based on the following figures, wherein:

[0037] FIG. 1 is a perspective view illustrating an optical device relating to a first embodiment.

[0038] FIG. 2A is a cross-sectional view along line 2A-2A of the optical device illustrated in FIG. 1.

[0039] FIG. 2B is a cross-sectional view along line 2B-2B of the optical device illustrated in FIG. 1.

[0040] FIG. 2C is a cross-sectional view of a molding die that carries out resin molding (a cross-sectional view along line 2C-2C of FIG. 4A).

[0041] FIG. 3A is a plan view illustrating the optical device relating to the first embodiment.

[0042] FIG. 3B is an enlarged plan view illustrating a portion of a light-receiving portion of the optical device relating to the first embodiment.

[0043] FIG. 4A is an explanatory drawing illustrating a step of carrying out resin molding.

[0044] FIG. 4B is an explanatory drawing illustrating a step of carrying out resin molding.

[0045] FIG. 4C is an explanatory drawing illustrating a step of carrying out resin molding.

[0046] FIG. 4D is an explanatory drawing illustrating a step of carrying out resin molding.

[0047] FIG. 5 is a cross-sectional view illustrating a continuous substrate on which resin molding has been carried out.

[0048] FIG. 6 is a cross-sectional view illustrating optical devices that have been individually cut.

[0049] FIG. 7 is a plan view illustrating an optical device relating to a second embodiment.

[0050] FIG. 8 is a cross-sectional view illustrating the optical device relating to the second embodiment (a cross-sectional view along line 8-8 of FIG. 7).

[0051] FIG. 9 is a plan view illustrating an optical device relating to a third embodiment.

[0052] FIG. 10 is a cross-sectional view illustrating the optical device relating to the third embodiment (a cross-sectional view along line 10-10 of FIG. 9).

DETAILED DESCRIPTION

First Embodiment

[0053] An optical device 10 relating to a first embodiment of the present invention is described by using FIG. 1 through FIG. 6. Note that the up-down distinction in the following description is made for convenience, but does not limit the upward and downward directions at the time of actual use of the optical device.

[0054] In the present embodiment, for convenience, the arrow U direction side in the drawings is the upper side, the arrow D direction side in the drawings is the lower side, the arrow L direction side in the drawings is the left side, the arrow R direction side in the drawings is the right side, the arrow F direction side in the drawings is the front side, and the arrow B direction side in the drawings is the rear side. Further, the arrow U direction in the drawings is called the upward direction, the arrow D direction in the drawings is the called the downward direction, the arrow L direction in the drawings is called the leftward direction, the arrow R direction in the drawings is called the rightward direction, the arrow F direction in the drawings is called the frontward direction, and the arrow B direction in the drawings is called the rearward direction.

(Structure of Optical Device)

[0055] As illustrated in FIG. 1, FIG. 2A and FIG. 2B, the optical device 10 of the present embodiment is structured to include a wiring substrate 12, an optical element 14, a light-emitting element 16, a resin portion 18 formed of a resin for molding, and the like, and is structured as a so-called reflective-type photo interrupter, and is used at an encoder or the like as an example.

[0056] The wiring substrate 12 is formed in a rectangular shape. As illustrated in FIG. 1 and FIG. 3A, the optical element 14 that is formed in a rectangular shape is mounted to the top surface of the wiring substrate 12.

[0057] The optical element 14 is formed to be smaller than the wiring substrate 12. Plural electrode pads 20 are provided at the optical element 14 of the present embodiment on the top surface thereof (the surface at the arrow U direction side in FIG. 2A) along the side at the arrow L direction side, the side at the arrow B direction side, and the side at the arrow R direction side.

[0058] As illustrated in FIG. 3A, a rectangular (elongated) light-receiving portion 22 is provided at the top surface of the optical element 14 along the side at the arrow F direction side at which the electrode pads 20 are not provided. The surface area of the light-receiving portion 22 when the optical element 14 is seen in a top view is smaller than that of the top surface of the optical element 14 that is exposed at an opening portion 28.

[0059] The length direction of the light-receiving portion 22 is parallel to the side at the arrow F direction side of the optical element 14. As illustrated in FIG. 3B, photodiodes 22A that are an example of plural pixels are disposed at the light-receiving portion 22 of the present embodiment at a uniform interval along the length direction of the light-receiving portion 22. In other words, the light-receiving portion 22 of the present embodiment functions as a line sensor.

[0060] As illustrated in FIG. 3A, plural electrode pads 24 are provided at the wiring substrate 12 at the periphery of the optical element 14 at positions adjacent to the electrode pads 20 of the optical element 14.

[0061] The electrode pads 20 of the optical element 14 and the electrode pads 24 of the wiring substrate 12 are electrically connected by bonding wires 26.

[0062] As illustrated in FIG. 1 through FIG. 3, a portion of the wiring substrate 12, a portion of the optical element 14, and the bonding wires 26 are covered by the resin portion 18. The top surface of the resin portion 18 is positioned further upward than the upper ends of the bonding wires 26, such that the bonding wires 26 are embedded in the resin. The top surface of the resin portion 18 is formed in the shape of a plane that is parallel to the wiring substrate 12. Note that, as an example, a black resin that is used in general semiconductor packages is used at the resin portion 18 of the present embodiment.

[0063] The opening portion 28 that is concave is formed in the center of the resin portion 18. An opening edge 28AE of the opening portion 28 at the top surface of the resin portion 18 is formed in a rectangular shape. The opening portion 28 has a bottom surface 30 that is flush with the top surface of the optical element 14, and a through-portion 32 that is provided at the arrow F direction side of the bottom surface 30 and exposes a portion of the top surface of the wiring substrate 12.

[0064] Note that the resin portion that has the bottom surface 30 and stands-up from the top surface of the wiring substrate 12 is an example of the optical element periphery portion of the present invention.

[0065] As illustrated in FIG. 2A and FIG. 2B, a side surface 28F at the arrow F direction side, a side surface 28B at the arrow B direction side, a side surface 28L at the arrow L direction side, and a side surface 28R at the arrow R direction side of the opening portion 28 respectively are substantially orthogonal to the wiring substrate 12. Note that the reason why these surfaces are made to be substantially orthogonal is in order to provide the side surface 28F, the side surface 28B, the side surface 28L and the side surface 28R with draft angles for pulling the resin portion 18 out from an upper molding die 40A that is described later and that is for forming the opening portion 28. Note that angles that are larger than usual draft angles that are provided at the time of resin molding may be provided at the side surface 28F, the side surface 28B, the side surface 28L and the side surface 28R.

[0066] As illustrated in FIG. 1 through FIG. 3, the optical element top surface at the periphery of the light-receiving portion 22 except for the area where the bonding wires 26 are disposed at the optical element 14, and the top surface of the bottom surface 30, are exposed at the opening portion 28. In further detail, the top surface of the bottom surface 30 is exposed at the arrow L direction side, the arrow F direction side and the arrow R direction side of the optical element 14 that are exposed at the opening portion 28.

[0067] As illustrated in FIG. 2A and FIG. 3A, length LO of the bottom surface 30 in the left-right direction is longer than length L1 of the optical element 14 in the left-right direction (which is also the length exposed at the bottom surface 30). Width W0 of the bottom surface in the front-rear direction is wider than width W1, in the front-rear direction, of the optical element 14 that is exposed at the bottom surface 30 of the opening portion 28.

[0068] As illustrated in FIG. 3A, at the optical element 14 that is used in the optical device 10 of the present embodiment, length L2 of the light-receiving portion 22 in the left-right direction is shorter than the length L1 of the optical element 14 in the left-right direction, and width W2 of the light-receiving portion 22 in the front-rear direction is narrower than the width W1, in the front-rear direction, of the optical element 14 that is exposed at the bottom surface 30.

[0069] Accordingly, at the optical element 14 illustrated in FIG. 3A, there is leeway for lengthening the light-receiving portion 22 at the both sides in the left-right direction of the light-receiving portion 22, and there is leeway for widening the light-receiving portion 22 toward the rear side of the light-receiving portion 22.

[0070] In FIG. 3A, the two-dot chain line illustrates the light-receiving portion 22 whose length and width have been increased.

[0071] Further, in FIG. 3A, the one-dot chain line illustrates the optical element 14, the length and width of which have been increased.

[0072] Further, at the optical device 10 of the present embodiment, as illustrated in FIG. 2A, FIG. 2B and FIG. 3A, given that, at the interior of the opening portion 28, of the resin portion 18 that surrounds the periphery of the optical element 14 at the bottom surface 30 of the opening portion 28,

[0073] The width of the resin portion 18 between the through-portion 32 and one side of the optical element 14 that faces the through-portion 32 is A, and the width of the resin portion 18 between the wall surface 28L, 28R of the opening portion 28 and another side that is adjacent to that one side of the optical element 14 is B, the dimensions are set such that A>B.

[0074] In other words, at the interior of the opening portion 28, thickness A [W0W1] of the resin portion 18 that is positioned at a length direction side of the light-receiving portion 22 is set to be greater than thickness B [(L0L1)/2], which is measured along the width direction of the light-receiving portion 22, of the resin portion 18 that is positioned at a width direction side of the light-receiving portion 22.

[0075] As illustrated in FIG. 1, FIG. 2B and FIG. 3A, the light-emitting element 16 that is an LED or the like is mounted to the central portion of the top surface of the wiring substrate 12 that is exposed by the opening portion 28. As illustrated in FIG. 2B and FIG. 3A, the light-emitting element 16 and the wiring substrate 12 are electrically connected by a bonding wire 34. The light-emitting element 16 of the present embodiment can emit light toward the upward direction of the wiring substrate 12.

(Method of Manufacturing Optical Device)

[0076] A molding die 40 for forming the resin portion 18 of the optical device 10 is illustrated in cross-sectional views in FIG. 2 and FIG. 4.

[0077] The molding die 40 is structured to include the upper molding die 40A and a lower molding die 40B. A cavity portion 42, which is concave and is for forming a continuous wiring substrate 12A (see FIG. 4C, FIG. 4D), the optical elements 14 and the resin portions 18, is formed in the molding die 40. Note that what is called the continuous wiring substrate 12A here means a substrate at which the individual wiring substrates 12 illustrated in FIG. 1 are connected continuously, and becomes the individual wiring substrates 12 by being cut later. Note that the light-emitting elements 16 are not mounted to the continuous wiring substrate 12A that is placed in the molding die 40.

[0078] (1) First, as illustrated in FIG. 4B, a synthetic resin sheet 44 that is flexible and peelable is laminated on the lower surface of the upper molding die 40A. As an example, a fluorine resin sheet can be used as the synthetic resin sheet 44. Note that, in FIG. 4B, the synthetic resin sheet 44 is drawn to be thick in order to facilitate understanding of the structure.

[0079] (2) As illustrated in FIG. 4C, the continuous wiring substrate 12A on which the plural optical elements 14 are mounted is placed on the lower molding die 40B, and the molding die 40 is closed. Note that, at the continuous wiring substrate 12A, wiring of the bonding wires 26, which electrically connect the optical elements 14 and the wiring substrates, has been completed.

[0080] (3) Next, as illustrated in FIG. 4D, resin in a molten state is injected into the interior of the cavity portion 42, and the bonding wires 26 and other necessary places are sealed by resin. Due thereto, the remaining portions that are other than the light-receiving portions 22 of the optical elements 14, and portions of the top surfaces of the optical elements at the peripheries of the light-receiving portions 22, and portions of the top surface of the continuous wiring substrate 12A on which the light-emitting elements 16 are to be mounted, are sealed by resin. Note that the bonding wires 26 are completely embedded within the resin.

[0081] (4) After the resin cures, the molding die 40 is opened, and, as illustrated in FIG. 5, the continuous wiring substrate 12A is removed from the molding die 40, and the light-emitting elements 16 are mounted to portions of the wiring substrate 12A which portions are not sealed by the resin portions 18.

[0082] (5) Thereafter, the continuous wiring substrate 12A is cut by an unillustrated dicing blade, and as illustrated in FIG. 6, the individual optical devices 10 are separated.

[0083] The optical device 10 illustrated in FIG. 1 is completed by the above-described steps.

(Operation, Effects)

[0084] At the optical device 10 of the present embodiment, the light emitted from the light-emitting element 16 is emitted via the through-portion 32 of the opening portion 28 (see FIG. 2B and FIG. 3A) toward an object of illumination (not illustrated) provided at the exterior, and the reflected light that is reflected at the object of illumination is received at the light-receiving portion 22 of the optical element 14.

[0085] Note that the optical device 10 of the present embodiment can be used at an encoder or the like as an example.

[0086] As illustrated in FIG. 2A and FIG. 3A, the length L1 in the left-right direction of the optical element 14 that is mounted to the wiring substrate 12 of the present embodiment is shorter than the length L0 of the bottom surface 30 in the left-right direction.

[0087] Further, at the cavity portion 42 of the upper molding die 40A in which the resin is filled, as illustrated in FIG. 2C, length L3 in the left-right direction of a convex portion 42A for forming the bottom surface 30 of the optical element 14 is equivalent to the length L0 of the bottom surface 30 in the left-right direction. (Note that the thickness of the synthetic resin sheet 44 that is thin is ignored.) Note that the peak surface (the bottom surface in FIG. 2C) of the convex portion 42A corresponds to the contacting portion of the present invention.

[0088] As illustrated in FIG. 2A, the length L1 of the optical element 14 of the present embodiment in the left-right direction is shorter than the length L3 in the left-right direction of the convex portion 42A of the upper molding die 40A. Therefore, even if the length L1 of the optical element 14 in the left-right direction is lengthened up to the length L0 of the bottom surface 30 in the left-right direction, the left and right upper surfaces of the optical element 14 are not covered by the resin portion 18.

[0089] In other words, by employing the structure of the optical device 10 of the present embodiment, the necessary places of the wiring substrate 12 on which is mounted the large-sized optical element 14, whose left-right length is longer than that of the optical element 14 of the size illustrated in FIGS. 1 through 3A and whose left and right top surfaces are not covered by the resin portion 18, can be sealed by resin without changing the molding die 40.

[0090] Namely, by making the optical device 10 have the structure of the above-described present embodiment, the molding die 40 can be used in common (standardized) for the light-receiving portions 22 and the optical elements 14 of various sizes, and manufacturing costs can be reduced.

[0091] Further, by making the length L1 of the optical element 14 in the left-right direction long, the length L2 in the left-right direction of the light-receiving portion 22 that is provided on the top surface of the optical element 14 can be made to be longer by the amount by which the left-right direction length of the optical element 14 is lengthened, and due thereto, the number of the photodiodes 22A (pixels) of the light-receiving portion 22 can be increased.

[0092] Note that it suffices to determine the dimensions (in the left-right direction and the front-rear direction) of the opening portion 28 and the bottom surface 30 in advance while taking into consideration the optical element 14 of the largest size that will be mounted on the wiring substrate 12. In other words, at the time of designing the molding die 40, it suffices to suppose the largest optical element 14, and to set in advance the dimensions of the portion that forms the opening portion 28.

[0093] Further, in accordance with the structure of the optical device 10 of the present embodiment, the width W2 of the light-receiving portion 22 in the front-rear direction is narrower than the width W1 in the front-rear direction of the optical element 14 that is exposed at the bottom surface 30. Therefore, the width W2 of the light-receiving portion 22 in the front-rear direction also can be made wider.

[0094] In accordance with the structure of the optical device 10 of the present embodiment, because the light-receiving portion 22 is small as compared with the size of the optical element 14 that is exposed at the bottom surface 30, the degrees of freedom in placement of the light-receiving portion 22 are large.

[0095] Note that, in the optical device 10 of the present embodiment, as illustrated in FIG. 2A, FIG. 2B and FIG. 3A, of the resin portion 18 that surrounds the periphery of the optical element 14, width A of the resin portion 18 between the through-portion 32 and one side of the optical element 14 is greater than width B of the resin portion 18 between the wall surface 28L, 28R of the opening portion 28 and another side that is adjacent to the one side of the optical element 14. However, the relationship of the magnitudes of width A and width B can be changed as needed, and may be set such that width Awidth B.

[0096] Note that, among this type of optical device, there are optical devices of a structure in which the resin molding is carried out such that the light-receiving portion and the wires are covered by a transparent resin. As compared with black resin that is used in general semiconductor devices, with a transparent resin, it is often the case that the reliability thereof with respect to reflow and temperature cycles and the like is low, and there are cases in which breakage of the bonding wires or the like occurs.

[0097] However, at the optical device 10 of the present embodiment, the light-receiving portion 22 is exposed by the opening portion 28, and a black resin that is highly reliable and is used at general semiconductor devices can be used at the resin portion 18. Therefore, high reliability that is similar to that of general semiconductor devices is obtained.

Second Embodiment

[0098] The optical device 10 relating to a second embodiment of the present invention is described in accordance with FIG. 7 and FIG. 8. Note that structures that are the same as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

[0099] In the optical device 10 of the present embodiment, the opening portion 28 that is formed in the resin portion 18 is formed in the shape of a rectangle that is long and narrow in the front-rear direction, and the optical element 14 that is long and narrow in the left-right direction is mounted to the wiring substrate 12. In the present embodiment, the bonding wires 26 are wired at the left and right both sides of the optical element 14.

[0100] In the optical device 10 of the present embodiment as well, the top surface of the optical element 14 that is exposed at the opening portion 28 is flush with the bottom surface 30 of the opening portion 28.

[0101] The light-receiving portion 22 that is rectangular is provided at the top surface of the optical element 14 toward the arrow B direction side.

[0102] The length L2 of the light-receiving portion 22 of the optical element 14 of the present embodiment in the left-right direction is shorter than the length L0 of the bottom surface 30 in the left-right direction. Therefore, in the same way as in the first embodiment, the optical element 14, which has the light-receiving portion 22 whose length L2 is longer, can be mounted to the wiring substrate 12 and sealed by resin, without changing the molding die.

Third Embodiment

[0103] The optical device 10 relating to a third embodiment of the present invention is described in accordance with FIG. 9 and FIG. 10. Note that structures that are the same as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

[0104] In the same way as the optical device 10 of the second embodiment, at the optical device 10 of the present embodiment as well, the opening portion 28 that is formed in the resin portion 18 is formed in the shape of a rectangle that is long and narrow in the front-rear direction, and the optical element 14 that is long and narrow in the left-right direction is mounted to the wiring substrate 12. Further, the bonding wires 26 are wired at the left and right both sides of the optical element 14.

[0105] In the optical device 10 of the present embodiment as well, the top surface of the optical element 14 that is exposed at the opening portion 28 is flush with the bottom surface 30 of the opening portion 28.

[0106] The light-receiving portions 22 that are long and narrow in the left-right direction are provided at the top surface of the optical element 14 toward both the arrow F direction side and the arrow B direction side.

[0107] In the optical element 14 of the present embodiment as well, the length L2 of the light-receiving portions 22 in the left-right direction is shorter than the length L0 of the bottom surface 30 in the left-right direction. Therefore, in the same way as in the second embodiment, the optical element 14, which has the light-receiving portions 22 whose length L2 is longer, can be mounted to the wiring substrate 12 and sealed by resin, without changing the molding die.

Other Embodiments

[0108] Although embodiments of the present invention have been described above, the present invention is not limited to the above, and can, of course, be implemented by being modified in various ways other than the above, within a scope that does not depart from the gist thereof.

[0109] In the above-described first embodiment, the bonding wires 26 are wired at three sides of the optical element 14 that is formed in a rectangular shape. In the second embodiment and the third embodiment, the bonding wires 26 are wired at two sides of the optical element 14. However, the present invention is not limited to this, and it suffices for the bonding wires 26 to be wired at one side of the optical element 14.

[0110] The light-receiving portion 22 of the above-described embodiments is a structure in which the plural photodiodes 22A are arrayed along the length direction of the light-receiving portion 22. However, the arrangement of the photodiodes 22A is not particularly limited, and further, the light-receiving portion 22 may be a single photodiode 22A.

[0111] In the optical device 10 of the above-described embodiments, the light-emitting element 16 is provided at the wiring substrate 12. However, the light-emitting element 16 may be provided or may not be provided, as needed. At the optical device 10 at which the light-emitting element 16 is not provided, the through-portion 32 does not have to be provided at the opening portion 28.

[0112] In the optical device 10 of the above-described embodiments, the shape of the light-receiving portion 22 as seen in plan view is rectangular, but may be a shape other than rectangular, such as hexagonal, circular-arc-shaped, or the like.