Patent Application
20140087498
The present application is based on Japanese patent application Nos.2012-210571 and 2013-146729 filed on Sep. 25, 2012 and Jul. 12, 2013, respectively, the entire contents of which are incorporated herein by reference.
1. Field Of The Invention
The invention relates to a method of manufacturing a light-emitting device.
2. Description Of The Related Art
A conventional light-emitting device is known in which an LED chip is mounted in a case and inner side surfaces of a recessed portion of the case is covered with a coating member formed of a highly-reflective resin so as to efficiently extract light emitted from the LED chip (see, e.g., JP-A-2005-136378).
In the light-emitting device disclosed in JP-A-2005-136378, a resin case has a two-stage structure or a dam shape on the side portion thereof or a lead electrode has a wall portion in a region around an LED chip-mounting region in order to prevent a decrease in light output which is caused because the coating member applied to the side surfaces of the recessed portion of the case flows and comes into contact with the LED chip.
Meanwhile, another known conventional light-emitting device is an LED device having a resin case in which a black resin is used for the outside and a white resin is used for the inside (see, e.g., JP-A-2006-130714).
In addition, yet another known conventional light-emitting device is an LED device having a resin case in which a black resin is used for the outside, a white resin is used for the inside and an edge at a boundary between the outside and the inside is covered with a covering member (see, e.g., JP-A-2010-206039).
The light-emitting device disclosed in JP-A-2005-136378, JP-A-2006-130714 and JP-A-2010-206039 needs to be equipped with the resin case or lead electrode having the special shape. Therefore, a special mold, etc., is required in manufacturing the resin case or lead electrode. This may cause an increase in manufacturing cost.
It is an object of the invention to provide a method of manufacturing a light-emitting device that allows a light-emitting device with high light extraction efficiency to be manufactured at low cost.
(1) According to one embodiment of the invention, a method of manufacturing a light-emitting device comprises:
mounting an LED chip on a bottom surface of a recessed portion of a case; and
after mounting the LED chip, forming a highly-reflective sidewall so as to be in contact with side surfaces and the bottom surface of the recessed portion and to be spaced from the LED chip,
wherein the highly-reflective sidewall comprises a higher light reflectance than the side surfaces of the recessed position of the case and an outwardly convex surface as a surface exposed in the recessed portion.
(2) According to another embodiment of the invention, a method of manufacturing a light-emitting device comprises:
forming a highly-reflective sidewall on a surface of a core plate of an injection mold;
forming a case including a resin case that is formed by injecting a resin into a space between the core plate having the highly-reflective sidewall formed thereon and a cavity plate of the injection mold; and
mounting an LED chip on a bottom surface of a recessed portion of the case,
wherein the highly-reflective sidewall is transferred from the core plate to the resin case so as to be provided on side surfaces of the recessed portion of the case.
In the above embodiment (1) or (2) of the invention, the following modifications and changes can be made.
(i) A height of the highly-reflective sidewall is smaller than that of the case.
(ii) The bottom surface of the recessed portion is flat.
(iii) The side surfaces of the recessed portion comprise two first side surfaces and two second side surfaces respectively facing each other with the LED chip interposed therebetween,
wherein a distance between the first side surface and the LED chip is smaller than that between the second side surface and the LED chip, and
wherein the highly-reflective sidewall is formed in a region other than between the first side surface and the LED chip.
(iv) A power-supply wire is connected to the LED chip,
wherein the side surfaces of the recessed portion comprise two first side surfaces and two second side surfaces respectively facing each other with the LED chip interposed therebetween,
wherein a distance between the second side surface and the wire is smaller than that between the first side surface and the wire, and wherein the highly-reflective sidewall is formed in a region other than between the second side surface and the LED chip.
(v) The highly-reflective sidewall is molded outside the case and is then placed so as to be in contact with the side surfaces and the bottom surface of the recessed portion and to be spaced from the LED chip.
(vi) The case is formed reusing a thermoplastic resin that is collected after molding other molded parts.
Effects of the invention
According to one embodiment of the invention, a method of manufacturing a light-emitting device can be provided that allows a light-emitting device with high light extraction efficiency to be manufactured at low cost.
Next, the present invention will be explained in more detail in conjunction with appended drawings, wherein:
The case 10 includes a resin case 11 and a lead frame 12 which is exposed on the bottom surface 13a of the recessed portion 13. Electrodes of the LED chip 14 and the lead frame 12 are electrically connected by wires 15. In the case 10, the bottom surface 13a is formed of the resin case 11 and the lead frame 12, and the side surface 13b is formed of the resin case 11.
The resin case 11 is formed of, e.g., a thermoplastic resin such as polyphthalamide resin, LCP (liquid crystal polymer) or PCT (polycyclohexylene dimethylene terephthalate), etc., or a thermosetting resin such as silicone resin, modified silicone resin, epoxy resin or modified epoxy resin, etc., and is formed by injection molding. The resin case 11 may contain light-reflecting particles of titanium dioxide, etc., to improve light reflectance.
Preferably, the bottom surface 13a of the recessed portion 13 of the case 10 does not have a special shape including protrusion or recess and is flat. In this case, it is possible to use an existing mold to form the resin case 11 and the lead frame 12 and it is thus not necessary to prepare a special mold, which allows the manufacturing cost to be kept low.
Although the LED chip 14 in
The entire lead frame 12 or a surface thereof is formed of, e.g., Ag, Cu or Al. Alternatively, for example, a substrate having a conductor pattern on a surface thereof may be used in place of the lead frame 12.
The highly-reflective sidewall 16 is formed of a resin material containing light-reflecting particles of titanium dioxide, etc. The resin material constituting the highly-reflective sidewall 16 is, e.g., a thermoplastic resin such as polyphthalamide resin, LCP or PTC, etc., or a thermosetting resin such as silicone resin, modified silicone resin, epoxy resin or modified epoxy resin, etc. A concentration of the light-reflecting particles contained in the highly-reflective sidewall 16 is higher than a concentration of the light-reflecting particles contained in the resin case 11 and light reflectance of the highly-reflective sidewall 16 is higher than that of the resin case 11, e.g., that of the side surfaces 13b of the recessed portion 13 of the case 10.
The highly-reflective sidewall 16 is formed by applying and curing a liquid resin containing light-reflecting particles. A surface of the highly-reflective sidewall 16 exposed in the recessed portion 13 is an outwardly convex surface, which is because of a property, such as viscosity, of the liquid resin before curing.
In addition, a height of the highly-reflective sidewall 16 is smaller than that of the case 10. Accordingly, a decrease in light emission amount caused by narrowing an opening area of the case 10 can be suppressed.
It is preferable that the highly-reflective sidewall 16 be formed in as much area around the LED chip 14 as possible in order to further improve light extraction efficiency. When a planar shape of the recessed portion 13 of the case 10 is, e.g., square as shown in
The sealing member 17 is formed of, e.g., a resin material such as silicone-based resin or epoxy-based resin, etc., or glass. In addition, the sealing member 17 may contain phosphor particles. For example, when emission color of the LED chip 14 is blue and that of the phosphor contained in the sealing member 17 is yellow, emission color of the light-emitting device 1 is white.
Alternatively, the highly-reflective sidewall 16 may be formed so as to partially cover the wires 15, as shown in
An example of a method of manufacturing the light-emitting device 1 will be described below.
Firstly, as shown in
Next, as shown in
Next, as shown in
At this time, although the bottom surface 13a of the recessed portion 13 is flat, it is possible to prevent the liquid resin from flowing and coming into contact with the LED chip 14 by controlling viscosity, etc., of the liquid resin.
The liquid resin exhibits low wettability to the bottom surface 13a and the side surfaces 13b of the recessed portion 13 and has a relatively small contact angle. Therefore, a surface of the highly-reflective sidewall 16 formed by curing the liquid resin (a surface which is exposed in the recessed portion 13) is an outwardly convex surface.
In addition, since the highly-reflective sidewall 16 is formed after the LED chip 14 is mounted in the case 10, a space required for mounting the LED chip 14 or for connecting the wires 15 between the LED chip 14 and the highly-reflective sidewall 16 does not need to be provided unlike the case where the LED chip 14 is mounted after forming the highly-reflective sidewall 16, and it is therefore possible to downsize the case 10.
Alternatively, the highly-reflective sidewall 16 may be preliminarily molded outside the case 10 and then placed in the case 10. A method of molding the highly-reflective sidewall 16 in this case is a molding method with high dimensional accuracy, e.g., such as injection molding or a molding method in which a resin is potted in a mold by screen printing.
The LED chip 14 is sealed with the sealing member 17 after forming the highly-reflective sidewall 16, thereby obtaining the light-emitting device 1 shown in
Effects of the First Embodiment
In the first embodiment, light emitted from the LED chip 14 is efficiently reflected by providing the highly-reflective sidewall 16 having a high light reflectance and it is thereby possible to improve light extraction efficiency of the light-emitting device 1.
In addition, flow of the liquid resin toward the LED chip 14 is suppressed by controlling viscosity, etc., of the liquid resin and it is thereby possible to prevent a decrease in light output of the LED chip 14 which is caused because the resin covers the LED chip 14.
Furthermore, since the flow of the liquid resin toward the LED chip 14 can be suppressed even though the bottom surface 13a of the recessed portion 13 is flat, it is not necessary to provide a protrusion or a recess on the resin case 11 and the lead frame 12 which constitute the case 10. Therefore, it is possible to use an existing mold to form the resin case 11 and the lead frame 12 and it is thereby possible to keep the manufacturing costs low.
In addition, providing the highly-reflective sidewall 16 allows light resistance of the light-emitting device 1 to be maintained, regardless of a material of the resin case 11. When, for example, an inclined angle of the side surface 13b of the recessed portion 13 is small, it is necessary to use a resin with high flowability in order to sufficiently spread the resin in a mold used for forming the resin case 11. However, in general, a resin with high flowability often has low light resistance, resulting in low light resistance of the resin case 11. Even in such a case, deterioration of the resin case 11 due to light can be suppressed by covering the exposed portion of the resin case 11 with the highly-reflective sidewall 16.
In addition, when a thermoplastic resin such as nylon or PCT is used as a material of the resin case 11, the thermoplastic resin left over in the molding of the resin case 11 can be collected, melted and reused as a material of another resin case 11. In this regard, discoloration of the thermoplastic resin occurs by repeating such reuse, which leads to change in color of the resin case 11 and resulting change in emission color of the light-emitting device 1. However, even in such a case, the change in emission color of the light-emitting device 1 due to the change in color of the resin case 11 can be suppressed by covering the exposed portion of the resin case 11 with the highly-reflective sidewall 16.
The second embodiment is different from the first embodiment in the position of placing the highly-reflective sidewall. Note that, the explanation for the same configuration as the first embodiment will be omitted or simplified.
A light-emitting device 2 has a case 20, an LED chip 24, highly-reflective sidewalls 26 and a sealing member 27. The case 20 includes a resin case 21 and a lead frame 22. The LED chip 24 is connected to the lead frame 22 via, e.g., wires 25. Note that, a planar shape of a recessed portion of the case 20 is rectangular, as shown in
The light-emitting device 2 has two side surfaces 23a facing each other with the LED chip 24 interposed therebetween and two side surfaces 23b also facing each other with the LED chip 24 interposed therebetween, and the highly-reflective sidewalls 26 are formed only on the side surfaces 23b. In the light-emitting device 2, a distance between the side surface 23a and the LED chip 24 is smaller than that between the side surface 23b and the LED chip 24. Therefore, if the highly-reflective sidewalls 26 are formed on the side surfaces 23a, the highly-reflective sidewalls 26 may come into contact with the LED chip 24 and block emission of light from the LED chip 24.
Therefore, in the light-emitting device 2, the highly-reflective sidewalls 26 are formed only on the side surfaces 23b and are not formed between the side surfaces 23a and the LED chip 24 so that light extraction efficiency of the light-emitting device 2 is improved while preventing the highly-reflective sidewalls 26 from coming into contact with LED chip 24.
The light-emitting device 3 has two side surfaces 33a facing each other with the LED chip 34 interposed therebetween and two side surfaces 33b also facing each other with the LED chip 34 interposed therebetween, and the highly-reflective sidewalls 36 are formed only on the side surfaces 33a. In the light-emitting device 3, each wire 35 runs from the LED chip 34 toward a side surface 33b and a distance between the side surface 33b and the wire 35 is smaller than that between the side surface 33a and the wire 35. Therefore, if the highly-reflective sidewalls 36 are formed on the side surfaces 33b, a needle of a potting system may come into contact with and cut the wire 35.
Therefore, in the light-emitting device 3, the highly-reflective sidewalls 36 are formed only on the side surfaces 33a and are not formed between the side surfaces 33b and the LED chip 34 so that light extraction efficiency of the light-emitting device 3 is improved while preventing the wires 35 from being cut during the potting.
Note that, materials of the resin cases 21 and 31, the lead frames 22 and 32, the LED chips 24 and 34, the wires 25 and 35, the highly-reflective sidewalls 26 and 36 and the sealing members 27 and 37 are respectively the same as the materials of the resin case 11, the lead frame 12, the LED chip 14, the wire 15, the highly-reflective sidewall 16 and the sealing member 17 in the first embodiment.
The third embodiment is different from the first embodiment in that the highly-reflective sidewall is placed during the molding of the resin case. Note that, the explanation for the same configuration as the first embodiment will be omitted or simplified.
The case 40 includes a resin case 41 and a lead frame 42. The LED chip 44 is connected to the lead frame 42 via wires 45.
Materials of the resin case 41, the lead frame 42, the LED chip 44, the wire 45 and the sealing member 47 are respectively the same as the materials of the resin case 11, the lead frame 12, the LED chip 14, the wire 15 and the sealing member 17 in the first embodiment.
The highly-reflective sidewall 46 is formed of a resin material such as acrylic resin or silicone resin.
The highly-reflective sidewall 46 has the same function as the highly-reflective sidewall 16 in the first embodiment. In addition, the highly-reflective sidewall 46 may be formed on all side surfaces 43b of the recessed portion 43 in the same manner as the first embodiment or may be formed on some of the side surfaces 43b in the same manner as the second embodiment.
An example of a method of manufacturing the light-emitting device 4 will be described below.
Firstly, as shown in
Next, as shown in
Next, as shown in
Next, as shown in
Next, as shown in
As described above, a dedicated special mold is not required to form the case 40 in which the highly-reflective sidewall 46 is provided on the side surfaces 43b of the recessed portion 43.
After that, the LED chip 44 is mounted in the case 40 and is then sealed with the sealing member 47, thereby obtaining the light-emitting device 4.
A modification of the method of manufacturing the light-emitting device 4 will be described below.
Firstly, as shown in
Next, as shown in
Next, as shown in
Next, as shown in
After that, the LED chip 44 is mounted in the case 40 and is then sealed with the sealing member 47, thereby obtaining the light-emitting device 4.
The present invention is not intended to be limited to the above-mentioned embodiments, and the various kinds of modifications can be implemented without departing from the gist of the invention.
In addition, the invention according to claims is not to be limited to the above-mentioned embodiments. Further, please note that all combinations of the features described in the embodiments are not necessary to solve the problem of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012-210571 | Sep 2012 | JP | national |
| 2013-146729 | Jul 2013 | JP | national |
