LED感应局部加热封装试验研究

采用感应局部加热技术,对大功率发光二极管(LED)封装进行了试验研究。结果表明,由于感应加热对材料和结构具有选择性,封装过程中仅Cu-Sn合金焊料层加热,实现了芯片和覆铜陶瓷基板间的热键合。封装后的LED性能测试表明,该封装技术不仅降低了热阻,使LED在高电流下(4倍电流)仍能保持较低的工作温度,而且降低了热应力和整体高温对芯片结构的损坏,提高了器件性能和可靠性。

Research on Localized Induction Heating for LED Packaging

Light-emitting diodes (LEDs) are a strong candidate for the next-generation general illumination applications. LEDs are making great strides in brightness performance and reliability; however, the barrier to widespread use in general illumination still remains the cost (dollars per lumen). For increasing the luminous flux of LED, the input power for chip of LED needs to be greater than before, and the thermal density inside LED will increase violently. However, the luminous efficiency and the life of chip will decrease at the high temperature condition, even the chip may be out of order or damaged. A good packaging technology is the way to solve the heat dissipation problem, but it is a challenge to develop this technology in the limited space of LED. The purpose of heat dissipating technology for LED is to decrease the working temperature of LED's chip. It is necessary to reduce the thermal resistance of LED package. The efficiency and reliability of solid-state lighting devices depends strongly on successful thermal management, because the junction temperature of the chip is the prime driver for effective operation. As the power density continues to increase, the integrity of the package electrical and thermal interconnects becomes extremely important.In this work, packaging experiments of high-power LEDs were studied using localized induction heating technique. The results show that, owing to the selectivity of induction heating with materials and geometry, only the electroless plated Cu-Sn alloy solder layer in chip area is heating and solder bonding between chip and copper-coated ceramic substrate is promised. Because of high thermal conductivity of Cu-Sn alloy, this novel packaging technique not only decrease the thermal resistance, making the p-n junction of LED kept at a low temperature even with a high current (four-fold of rated current), but also decrease thermal stress and avoid the damage of the chip, all of which will improve the performance and reliability of LED.