News Column

Patent Issued for Light Emitting Diode Package Structure and Manufacturing Method

July 23, 2014



By a News Reporter-Staff News Editor at Electronics Newsweekly -- According to news reporting originating from Alexandria, Virginia, by VerticalNews journalists, a patent by the inventor Lin, Hsien Chia (New Taipei, TW), filed on May 27, 2011, was published online on July 8, 2014.

The assignee for this patent, patent number 8772807, is Everlight Electronics Co., Ltd. (TW).

Reporters obtained the following quote from the background information supplied by the inventors: "The present disclosure relates to a semiconductor package structure and a manufacturing method thereof. More particularly, the present disclosure relates to a light emitting diode (LED) package structure and a manufacturing method thereof.

"LEDs generally offer a number of advantageous characteristics such as long product life, compact size, high shock resistance, low heat generation and low power consumption, etc. As a result LEDs are widely employed in household applications and as the light source or indicator of a variety of equipment. Recent developments of new LEDs are in the areas of multiple colors and high brightness. Accordingly, LEDs are further employed in applications such as large outdoor bulletin boards, traffic signals and related fields. In the future, LEDs may even become the primary light source for illumination that not only conserve electricity but also are environmentally friendly.

"Among the white-light LED package structures commonly adopted in the market, a type of white-light LED is composed of a blue-light LED chip and yellow phosphor. A prior art manufacturing method of a white-light LED package structure typically disposes a blue-light LED chip on a base and wire bonds the blue-light LED chip with the base. Afterwards, using spin coating, dispensing, spray coating, molding or any other suitable process on the base, a yellow fluorescent layer is formed on the blue-light LED chip. A portion of the yellow fluorescent layer emits yellow light upon excitation by the blue light emitted by the blue-light LED chip, and in turn the yellow light, combined with the blue light emitted by the blue-light LED chip, produces white light. However, a yellow fluorescent layer formed by spin coating, dispensing, spray coating or the like tends to suffer from excessive usage of phosphor powder and results in uneven thickness of the layer. That is, when the blue light emitted by the blue-light LED chip traverses through a yellow fluorescent layer of a greater thickness, the white-light LED package structure may produce a yellowish halo, causing the color of the light emitted by the LED package structure to be uneven overall.

"In order to address the problem associated with uneven spin-coating of the fluorescent layer, U.S. Pat. No. 6,395,564 and U.S. Patent Publication No. 2009/0261358 disclose a technique that involves spraying the fluorescent layer directly on wafers and forming white-light LED package structures after cutting the wafers. However, such prior art technique suffers from the problem of lowered scattering efficiency during the process of the yellow fluorescent layer emitting yellow light upon excitation by the blue light. Additionally, as difference in wavelengths may result from crystalline growth on wafers, manufacturing costs tend to increase if the difference in wavelengths is to be rectified by way of spin-coating fluorescent layer on wafers.

"In order to address the problem associated with low scattering efficiency, U.S. Pat. No. 6,630,691 discloses a manufacturing method of a phosphor layer. Ceramic glass and phosphor are combined under high temperature to result in a eutectic process that forms a fluorescent substrate, which is pasted to LED chips to avoid the issue of low scattering efficiency and enhance the uniformity of light generated by the LED package structure. However, as such prior art technique provides no electrode design for the fluorescent substrate, the use of this technique is limited to flip chip LED chips."

In addition to obtaining background information on this patent, VerticalNews editors also obtained the inventor's summary information for this patent: "The present disclosure provides an LED package structure and a manufacturing method thereof that can help enhance the uniformity in the color of light generated by LED chips.

"In one aspect, an LED package structure may comprise a fluorescent substrate, a first electrically conductive pattern, a second electrically conductive pattern, at least one electrically conductive component, and an LED chip. The fluorescent substrate may have a first surface and a second surface opposite the first surface. The fluorescent substrate may comprise a fluorescent material and a glass material. The first electrically conductive pattern may be disposed on the first surface of the fluorescent substrate. The second electrically conductive pattern may be disposed on the second surface of the fluorescent substrate. The at least one electrically conductive component may connect the first electrically conductive pattern and the second electrically conductive pattern. The LED chip may be disposed on the second surface of the fluorescent substrate. The LED chip may have a light extraction surface coupled to the second electrically conductive pattern such that the LED chip is electrically coupled to the first electrically conductive pattern via the at least one electrically conductive component.

"In one embodiment, a thickness of the fluorescent substrate may be approximately constant throughout the fluorescent substrate.

"In one embodiment, the fluorescent material may comprise yellow phosphor.

"In one embodiment, the fluorescent material may comprise phosphors of at least two different wavelengths.

"In one embodiment, the phosphors may comprise at least two of yellow phosphor, red phosphor, and green phosphor.

"In one embodiment, the LED package structure may further comprise an underfill disposed between the light extraction surface of the LED chip and the second surface of the fluorescent substrate, the underfill covering at least partially the light extraction surface of the LED chip. In one embodiment, the underfill may cover a plurality of side surfaces of the LED chip. In one embodiment, the LED chip may comprise a sapphire substrate.

"In one embodiment, the LED package structure may further comprise a circuit line substrate where a back surface of the LED chip opposite the light extraction surface is disposed on the circuit line substrate. In one embodiment, the LED package structure may further comprise at least one bonding wire that electrically couples the circuit line substrate and the first electrically conductive pattern.

"In another aspect, a manufacturing method of an LED package structure may comprise: providing a fluorescent substrate having a first surface and a second surface opposite the first surface, the fluorescent substrate containing therein a plurality of electrically conductive components that connect the first surface and the second surface, the fluorescent substrate comprising a mixture of at least one fluorescent material and a glass material; forming a first electrically conductive pattern on the first surface and a second electrically conductive pattern on the second surface, at least some of the electrically conductive components connecting the first electrically conductive pattern and the second electrically conductive pattern; and bonding a plurality of LED chips on the second surface of the fluorescent substrate, each of the LED chips having a respective light extraction surface coupled to the second electrically conductive pattern, each of the LED chips electrically coupled to the first electrically conductive pattern via a corresponding one of the electrically conductive components.

"In one embodiment, the plurality of electrically conductive components may be formed by: forming a plurality of through holes in the fluorescent substrate, the through holes connecting the first surface and the second surface; galvanizing the through holes to form a plurality of electrically conductive pillars protruding out of the first surface of the fluorescent substrate; milling the electrically conductive pillars to provide the electrically conductive components that are flush with the first surface of the fluorescent substrate. In one embodiment, the milling comprises cutting the fluorescent substrate with a cutting device to reduce a thickness of the fluorescent substrate and to expose the electrically conductive components.

"In one embodiment, the plurality of electrically conductive components may be formed by: forming a plurality of electrically conductive bumps in a recess of a carrier base; filling the recess of the carrier base with the at least one fluorescent material and the glass material, the at least one fluorescent material and the glass material covering the electrically conductive bumps; heating the electrically conductive bumps, the at least one fluorescent material, and the glass material together to form the fluorescent substrate with the electrically conductive bumps buried therein; and milling the fluorescent substrate and the electrically conductive bumps to form the electrically conductive components that are flush with the first surface of the fluorescent substrate.

"In one embodiment, the method may further comprise: forming a plurality of circuit lines on the second surface after forming the second electrically conductive pattern, the circuit lines connecting the second electrically conductive pattern.

"In one embodiment, the method may further comprise: forming an underfill between the light extraction surface of the LED chips and the second surface of the fluorescent substrate after bonding the LED chips on the second surface of the fluorescent substrate, the underfill covering at least partially the light extraction surface of the LED chips. In one embodiment, the method may additionally comprise: after forming the underfill, carrying out a cutting process to form a plurality of LED package structures. In one embodiment, the underfill may cover at least partially a plurality of side surfaces of the LED chips. In one embodiment, the method may also comprise: after forming the underfill, carrying out a cutting process to form a plurality of LED package structures.

"These and other features, aspects, and advantages of the present disclosure will be explained below with reference to the following figures. It is to be understood that both the foregoing general description and the following detailed description are by examples, and are intended to provide further explanation of the present disclosure as claimed."

For more information, see this patent: Lin, Hsien Chia. Light Emitting Diode Package Structure and Manufacturing Method. U.S. Patent Number 8772807, filed May 27, 2011, and published online on July 8, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8772807.PN.&OS=PN/8772807RS=PN/8772807

Keywords for this news article include: Light-emitting Diode, Everlight Electronics Co. Ltd..

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Source: Electronics Newsweekly


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