1. Field of the Invention
The present invention generally relates to a light-emitting diode (LED) package structure, and in particular to an LED package structure that separately arranges a light-emitting die and a voltage regulation diode in different sections.
2. The Related Arts
A liquid crystal display (LCD) is a flat panel display (FPD) that uses the nature of liquid crystals to display an image and shows, as compared to other known displays, several advantages in respect of being light and thin, low drive voltage, and low power consumption, making it a main stream product in the whole consumer market. However, the liquid crystal used in the liquid crystal display does not emit light by itself and must be provided with an external light source. Consequently, a liquid crystal display is additionally combined with a backlight module to provide the desire light source.
Generally, the backlight module is classified in two forms, namely an edge type backlight module and a direct type backlight module. The existing backlight modules use a cold cathode fluorescent lamp (CCFL), a hot cathode fluorescent lamp (HCFL), or a semiconductor based lighting device to serve as a light source. The semiconductor based lighting device generally uses light-emitting diode (LED) to emit light and, as compared to the cathode fluorescent lamps, can reduce more power consumption and save more energy and has a longer service life and a compacter size, making it increasingly replace the cathode fluorescent lamps. The LEDs will be the main stream light source for the backlighting of future LCDs.
Currently, an LED is subjected to semiconductor packaging in the form of a die to make an LED package, which is eventually coupled to a retention board of a backlight module. Categories of the product package structure of LED are divided according to characteristic factors including light color, die material, brightness, and size. A single die often constructs a point light source, while a combination of multiple dies may form a planar light source or a linear light source to provide indication and display of message and status. A light-emitting display also uses multiple dies and is formed by proper connection of the dies (including series connection and parallel connection) and suitable optic structures, which constitute a light-emitting section and a light-emitting spot of the light-emitting display. Among these devices, a surface-mount-device (SMD) LED is laid flat on a surface of a circuit board, making it suitable for surface mounting technology (SMT) processing and allowing for reflow soldering so as to be capable of solving problems in association with brightness, view angle, planarity, reliability and consistency, and also making it possible to eliminate the carbon steel lead pins of the pinned LED and reduce the quantity of epoxy resin filled in the display reflective layer, due to adoption of printed circuit boards (PCBs) and reflective layer materials that are lighter. The SMD LED can easily reduce the product weight by half, making it perfect for final application. As a result, the SMD LED is increasingly replacing the pinned LED, making the application and design thereof more flexible and taking a certain share of the LED display market with a trend of accelerated development.
Reference is made to FIG. 1. FIG. 1 shows a cross-sectional view of a conventional light-emitting diode (LED) package structure. As shown in FIG. 1, a conventional LED package structure 90 comprises a housing 91, a first electrode plate 92, a second electrode plate 93, a light-emitting diode 94, a voltage regulation diode 95, and a light-transmitting package portion 96. The housing 91 has a top surface forming a cavity 911. The first electrode plate 92 has a portion exposed on a bottom of the cavity 911 and another portion extending outside the housing 91 for external electrical connection. The second electrode plate 93 has a portion exposed on the bottom of the cavity 911 and another portion extending outside the housing 91 for external electrical connection. The light-emitting diode 94 is exposed inside the cavity 911 and has a first electrode electrically connected to the first electrode plate 92 and a second electrode electrically connected to the second electrode plate 93 through a first lead 941. The light-transmitting package portion 96 fills the cavity 911 and encloses components located inside the cavity 911. Light from the light-emitting diode 94 is allowed to transmit through the light-transmitting package portion 96 for upward emission.
However, in the conventional LED package structure 90, to protect the light-emitting diode 94 from being punctured by static electricity, a single one or a set of voltage regulation diodes 95 is set in parallel connection therewith to solve the problem. Reference is made to both FIGS. 1 and 2, wherein FIG. 2 shows a schematic circuit diagram of the conventional LED package structure shown in FIG. 1. In the LED package structure 90, the voltage regulation diode 95 is set on the housing 91, namely on the second electrode plate 93, with a first electrode thereof located on the underside to electrically connect to the second electrode plate 93 and a second electrode located on the upper side electrically connected to the first electrode plate 92 through a second lead 951. In other words, the voltage regulation diode 95 and the light-emitting diode 94 are in parallel connection, wherein the voltage regulation diode 95 is arranged as being reversely biased. As such, the voltage regulation diode 95 provides a function of protecting the light-emitting diode 94 from being punctured by static electricity. However, the voltage regulation diode 95 is positioned on the second electrode plate 93, namely in the upper portion of the housing 91, and is thus located inside the light-transmitting package portion 96. Further, since the voltage regulation diode 95 has an outside appearance that is not light transmittable and is often of a black color, the voltage regulation diode 95 shows a characteristics of blocking and absorbing light, causing influence on some light flux of the light-emitting diode 94 and thus lowering the lighting performance of the LED package structure 90.
Thus, it is desired to provide an LED package structure that overcomes the existing technical problems.