Microstructural and thermal characterizations of light emitting diode employing a low temperature die bonding material
Abstract A Sn/Bi bilayer was deposited on a hot air solder leveling (HASL) treated metal core printed circuit board (MCPCB) using electroplating as a low temperature die bonding material for light emitting diode (LED) The eutectic feature of the Sn/Bi contact enabled the die bonding process to accomplish through a liquid/solid reaction at 185 degC with a proper compression force. A high temperature die bonding structure composed of a Bi layer sandwiched by two intermetallic compounds (IMCs) formed after thermocompression. Employment of the Sn/Bi bilayer for low temperature die bonding prevented the LEDs from thermal stress problems, and the resulting high temperature IMC/Bi/IMC die bonding structure was capable of withstanding multiple bonding reactions and high temperature/current operation environment. Durability tests including mechanical, thermal, and optical performance were systematically performed and compared with other commercially available die bonding materials (Ag paste and solder alloys)
Microelectron. Reliab.