No abstract

A method for fabricating a Si-based packaging platform with a reflector and electrode-guided interconnections is proposed for the packaging component of a high-power light-emitting diode (LED) module. The reflector is fabricated by Ni/Au/Ag-electroplating which is patterned by SU-8 2075 and 4620 negative photo-resistors and the electrical interconnections are formed by Cu/Au-electroplating in the same body. The heat generated by the LED chip is dissipated directly to the Si body through the large metal-plated platform. This method is suitable for high-efficiency and low-cost LED packaging.Introduction: In recent years the use of GaN-based LEDs for solid-state lighting has increased tremendously owing to their long guaranteed lifetime, low power consumption, high brightness, low cost, and little harmfulness. To this end, high-power LEDs are expected to replace traditional incandescent bulbs and fluorescent lights in many application areas such as household illumination, automotive lights, backlight units, and traffic signals [1]. However, for these near-future applications, cost and thermal design are the key parameters in high-power LED package design. The design of good packaging by using proper materials and structures is important to ensure both the thermal and the mechanical reliabilities of LED packages. With the improvement in LED packaging, several packaging methods for improving high-power LED performance have been presented [2, 3]. However, these methods need more complicated fabrication processes and come at higher cost. In this Letter we propose a method for packaging high-power LEDs that uses Si substrate and electroplating technology. A reflector and electrode-guided interconnections are integrated in one packaging body with excellent mechanical stability and heat dissipation. The packaging body is composed of Si substrate, Cu and Au, all of which have excellent thermal conductivities. The thermal conductivities (at 300 K) are 148, 401 and 317 W . m 21 . K 21 , respectively. An undoped Si wafer is used as a packaging substrate and electroplated Cu/Au with patterns of electrode for the electrical interconnection. The SU-8 barrier formed between the connection plates provides electrical isolation and a protective passivation layer for the ground metal pad. The reflector is formed by Ni/Au/Ag electroplating with an angle of 608 -708, which is patterned by SU-8 2075 and 4620 photo-resistors (PRs). The heat generated by the LED will be directly dissipated through the large Cu-plated platform to the whole body of the Si substrate and the light emitted from the LED can be reflected by the reflector. The LED chip will be connected with the Zener diode and covered with fluorescent material and accommodated inside the reflector by wire-bonding. The lens will be built up by injecting epoxy in the form of a dome.