WO2009005257A2

WO2009005257A2 - Method for manufacturing led package

Info

Publication number: WO2009005257A2
Application number: PCT/KR2008/003728
Authority: WO
Inventors: Jung Hoo Seo; Do Hyung Kim; Moon Ho Cho; Min Gyu Jeon
Original assignee: Seoul Semiconductor Co Ltd
Current assignee: Seoul Semiconductor Co Ltd
Priority date: 2007-06-29
Filing date: 2008-06-27
Publication date: 2009-01-08
Anticipated expiration: 2009-12-29
Also published as: WO2009005257A3; TWI451594B; TW200913325A; KR20090001036A; KR101380385B1

Abstract

Disclosed herein is a method for manufacturing LED packages based on a batch encapsulation process in which a plurality of encapsulation members are simultaneously formed to protect LED chips in the LED packages in manufacturing the LED packages on a lead frame strip. The method includes preparing a lead frame strip having a plurality of lead frames defined by pattern-holes and connected to each other; mounting LED chips on predetermined regions of the lead frame strip; disposing a dummy frame on the lead frame strip to overlap each other, the dummy frame closing the pattern-holes while exposing the predetermined regions of the lead frame strip; positioning the lead frame strip overlapping the dummy frame inside a mold; and simultaneously encapsulating the LED chips located on the predetermined regions of the lead frame strip by injecting a liquefied resin into the mold.

Description

METHOD FOR MANUFACTURING LED PACKAGE

Technical Field

[1] The present invention relates to a method for manufacturing light emitting diode

(LED) packages, and more particularly, to a method for manufacturing LED packages based on a batch encapsulation process in which a plurality of encapsulation members are simultaneously formed to protect LED chips disposed in respective LED packages in manufacturing the plurality of LED packages on a lead frame strip. Background Art

[2] Generally, light emitting diodes (LEDs) generate light based on recombination between electrons and holes in a P-N semiconductor junction upon application of an electric current. The LEDs are manufactured in a package structure, generally called an "LED package", in which an LED chip is mounted. The LED package is configured to emit light upon application of an electric current from an exterior power source.

[3] The LED packages are generally classified into "printed circuit board (PCB) type

LED package" wherein an LED chip is mounted on a conductive pattern of a PCB to receive an electric current supplied from the exterior, and "a lead frame type LED package" wherein the electric current is applied through a lead frame. For the PCB type LED package, a plurality of LED chips are formed on a single large PCB and encapsulation members are then provided to cover the plurality of LED chips, followed by cutting the PCB into a plurality of individual LED packages. For the lead frame type LED package, a plurality of LED chips are mounted at several locations on a plate-shaped lead frame strip which has a hole pattern for defining a plurality of lead frames, and encapsulation members and/or housings are then formed to cover the LED chips, followed by cutting the lead frame strip to provide a plurality of LED packages.

[4] The applicant of the present invention has developed a technique for forming a plurality of encapsulation members in a batch process. In this technique called "transfer molding", an epoxy tablet is liquefied via application of pressure and heat, and is then simultaneously supplied around each of LED chips located at several locations on a PCB.

[5] This conventional technique is selectively employed in the case where the encapsulation member is formed on a substrate (particularly, PCB), as in the PCB type LED package, which has entirely closed front and rear sides. However, the process of manufacturing the lead frame type LED packages requires formation of plural encapsulation members on a single lead frame strip before cutting, and has a difficulty in batch formation of the plural encapsulation members due to the hole pattern which defines the lead frames. This is attributed to a problem that, when forming the encapsulation members by supplying a liquid resin to a mold with the lead frame strip located therein, the liquid resin tends to leak through holes arranged in a predetermined pattern.

[6] For this reason, when manufacturing the plural LED packages on the lead frame strip, a plurality of LED chips are formed at plural locations on the lead frame, a plurality of housings including cavities surrounding the LED chips are prepared, and the liquid resin is then injected into the respective cavities of the housings, thereby forming the encapsulation members. However, such an injection method for forming the encapsulation members is complicated and is both costly and time consuming. Disclosure of Invention Technical Problem

[7] Therefore, the present invention has been made in view of the above problems of the conventional technique, and an object of the present invention is to provide a method for manufacturing LED packages based on batch formation of a plurality of encapsulation members on a lead frame strip with pattern-holes closed. Technical Solution

[8] In accordance with an aspect of the present invention, the above and other objects of the present invention can be achieved by the provision of a method for manufacturing LED packages, including: preparing a lead frame strip having a plurality of lead frames defined by pattern-holes and connected to each other; mounting LED chips on predetermined regions of the lead frame strip; disposing a dummy frame on the lead frame strip to overlap each other, the dummy frame closing the pattern-holes while exposing the predetermined regions of the lead frame strip; positioning the lead frame strip overlapping the dummy frame inside a mold; and simultaneously encapsulating the LED chips located on the predetermined regions of the lead frame strip by injecting a liquefied resin into the mold.

[9] The lead frame strip may be formed with housings including cavities each surrounding the corresponding predetermined region, and in the encapsulating of the LED chips, the liquefied resin injected into the mold may fill the cavities to encapsulate the LED chips located inside the respective cavities.

[10] The dummy frame may be a plate-shaped frame having exposure holes fitted onto the housings to expose the predetermined regions. The mold may be configured to define a runner communicating with the cavities between the mold and the dummy frame. The mold may include a plurality of molding shapes determining shapes of encapsulation members which encapsulate the LED chips. The resin may be a silicone resin.

Advantageous Effects [11] According to exemplary embodiments of the present invention, when encapsulating

LED chips with a liquid resin after mounting the LED chips on plural regions of the lead frame strip having pattern-holes, the pattern-holes are closed by a dummy frame and the liquid resin is then simultaneously supplied to the respective regions where the LED chips are located, so that the plural LED chips can be simultaneously encapsulated without leakage of the liquid resin through the pattern-holes of the lead frame strip. In particular, such a batch encapsulation process using the dummy frame is suitable for application using a silicone resin, which conventionally requires a long period of time for curing and thereby makes it difficult to form encapsulation members by transfer molding. Brief Description of the Drawings

[12] Fig. 1 is a plan view illustrating a single lead frame strip on which LED packages are formed;

[13] Fig. 2 is a cross-sectional view taken along line I-I in Fig. 1;

[14] Figs. 3 to 6 are sectional views illustrating a batch process of encapsulating LED chips mounted on plural regions of a lead frame strip with a resin; and

[15] Fig. 7 is views of exemplary dummy frames placed to overlap the lead frame strip for the batch process of encapsulating LED chips with a liquid resin.

[16] <Description of Reference Numerals>

[17] 10: lead frame strip 12: pattern-holes

[18] 14: lead frame 20: LED package

[19] 22: housing 24: LED chip

[20] 26: encapsulation member

Best Mode for Carrying Out the Invention

[21] Exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The embodiments are given by way of illustration for full understanding of the present invention by those skilled in the art. Hence, the present invention is not limited to these embodiments and can be realized in various forms. Further, for convenience of description, width, length, and thickness of components are not drawn to scale in the drawings. Like components are indicated by like reference numerals throughout the specification.

[22] Fig. 1 is a plan view illustrating a single lead frame strip on which LED packages are formed. Fig. 2 is a cross-sectional view taken along line I-I in Fig. 1.

[23] Referring to Fig. 1 and 2, a lead frame strip 10 has a substantially plate-shaped structure and is formed with a plurality of pattern-holes 12. Further, a plurality of LED packages 20 are integrated with the lead frame strip 10. The pattern-holes 12 define lead frames 14, which will be cut from the lead frame strip 10. The lead frame strip 10 is cut to constitute a portion of a separate LED package 20.

[24] As shown in enlarged circle A of Fig. 1, the LED package 20 includes a housing 22 which supports the lead frame 14. The housing 22 has a cavity 22a, which accommodates the corresponding one of LED chips 24 mounted on plural regions of the lead frame strip 10. Alternatively, each of the cavities 22a may accommodate plural LED chips 24. In this embodiment, the LED chip 24 is mounted on a single lead frame 14, which is electrically wired to other adjacent lead frames 14 via boding wires. By cutting the respective lead frames 14 at predetermined locations from the lead frame strip 10, the respective LED packages 20 are separated from the lead frame strip 10.

[25] As shown in Figs. 1 and 2, encapsulation members 26 are formed inside the cavities

22a of the housings 22 to protect the LED chips 24 mounted on the plural regions of the lead frame strip 10. Here, the encapsulation members 26 are simultaneously formed by injecting a liquid resin into a mold, which will be described below in detail. Next, the method for simultaneously forming the encapsulation members 26 will be described in detail with reference to Figs. 3 to 6.

[26] First, as shown in Fig. 3, a plate-shaped lead frame strip 10 is prepared. The lead frame strip 10 has LED chips 24 mounted on predetermined regions thereof and hous ings 22 each having a cavity 22a for accommodating the corresponding LED chip 24. The lead frame strip 10 is formed with a plurality of pattern-holes 12, and includes a plurality of lead frames 14 which are connected to each other and have predetermined shapes defined by the pattern-holes 12.

[27] Then, as shown in Fig. 4, a plate-shaped dummy frame 30 is positioned on the top of the lead frame strip 10 to overlap each other. The dummy frame 30 includes exposure holes 32, which will be fitted onto the housings 22 such that the cavities 22a of the housings 22 can be exposed upward through the exposure holes 32, respectively. Conversely, it can be contemplated to allow the encapsulation member to act as the housing instead of providing the housing 22, and in this case, the exposure holes 32 expose the plural regions of the lead frame strip 10 on which the LED chips 24 are mounted.

[28] In this embodiment, the exposure hole 32 has a rectangular shape corresponding to an outer shape of the housing 22, as shown in Fig. 7 (a). However, when the housing 22 has a circular shape 22, the exposure hole 32 may also have a circular shape as shown in Fig. 7 (b). Further, the exposure holes 32 may have various geometrical shapes corresponding to the shapes of the housings 22. While overlapping the lead frame strip 10, the dummy frame 30 entirely closes the plurality of pattern-holes 12 formed on the lead frame strip 10.

[29] Next, as shown in Fig. 5, with the pattern-holes 12 closed by the dummy frame 30, the lead frame strip 10 is placed inside a mold 40 used for molding encapsulation members 26 (see Fig. 2). The mold 40 may be composed of an upper mold 42 and a lower mold 44 which can be open or closed by a certain drive means. In a closed state, the mold 40 defines a space for accommodating the dummy frame 30 and the lead frame strip 10 which overlap each other. The shape and size of the space defined inside the mold 40 are determined by the shapes and sizes of the lead frame strip 10, dummy frame 30, and housings 22.

[30] Particularly, the upper mold 42 is formed with substantially semicircular molding shapes 422 which will determine respective shapes of the encapsulation members 26. Further, a runner 424 is provided between the upper mold 42 and the dummy frame 30 and communicates with all spaces defined between the molding shapes and the cavities 22a. The runner 424 communicates with a resin injection port 425 formed through the upper mold 42.

[31] Then, the encapsulation members 26 are formed inside the cavities 22a with a liquid resin, preferably, a silicone resin, as shown in Fig. 6. Here, the silicone resin is liquefied by heat and injected into the mold 40 through the resin injection port 425. Then, the liquid resin is supplied to respective predetermined regions on the lead frame strip 10, on which the LED chips 24 are located, through the runner 424, and fills the cavities 22a, so that the liquid resin is formed into semicircular shapes by the molding shapes 422. When the liquid resin is cured inside the spaces defined between the cavities 22a and the molding shapes 422, the encapsulation members 26 are formed as shown in Figs. 1 and 2.

[32] Next, the upper mold 42 and/or the lower mold 44 are shifted to open the mold 40, and the lead frame strip 10 with the plural encapsulation members 26 covering the respective LED chips 24 is removed from the mold 40. Finally, the lead frames 14 of the lead frame strip 10 are cut at predetermined locations, thereby providing LED packages, each of which has two lead frames 14. In each of the LED packages, the LED chip 24 is mounted on one of the two lead frames 14 and is encapsulated by the encapsulation member 26. Here, the encapsulation members 26 are simultaneously formed by a batch encapsulation process using the dummy frame 30 as described above.

Claims

[1] A method for manufacturing LED packages, comprising steps of: preparing a lead frame strip having a plurality of lead frames defined by pattern- holes and connected to each other; mounting LED chips on predetermined regions of the lead frame strip; disposing a dummy frame on the lead frame strip to overlap each other, the dummy frame closing the pattern-holes while exposing the predetermined regi ons of the lead frame strip; positioning the lead frame strip overlapping the dummy frame inside a mold; and simultaneously encapsulating the LED chips located on the predetermined regions of the lead frame strip by injecting a liquefied resin into the mold.

[2] The method according to claim 1, wherein the lead frame strip is formed with housings including cavities each surrounding the corresponding predetermined region, and in the step of encapsulating of the LED chips, the liquefied resin injected into the mold fills the cavities to encapsulate the LED chips located inside the respective cavities.

[3] The method according to claim 2, wherein the dummy frame is a plate-shaped frame having exposure holes fitted onto the housings to expose the predetermined regions.

[4] The method according to claim 3, wherein the mold is configured to define a runner communicating with the cavities between the mold and the dummy frame.

[5] The method according to claim 3, wherein the mold comprises a plurality of molding shapes determining shapes of encapsulation members which encapsulate the LED chips.

[6] The method according to any one of claims 1 to 5, wherein the resin is a silicone resin.