A new microelectronic package was designed for a high-power light-emitting diode (LED). The objective was to build a package that enables the LED to operate with currents as high as 2 Amps. An innovative thin-film interface has been developed to electrically connect the cathode of the LED die to a 22AWG Cu wire. This thin-film interface is wirebondable and solderable, and consists of three layers: Au, Ni93/V7, and Si. Four 1 mil Au wirebonds, supporting 2A of maximum current, connect the Au thin-film to the LED die cathode. Sn96Ag4 solder is used for connecting the Ni93/V7 thin-film to the 22AWG Cu wire. To provide an electrical, mechanical and thermal platform for the anode of the LED die, a sub-assembly was developed. This sub-assembly utilizes a Cu substrate on which the anode of the LED die is attached with Au80Sn20 solder. The LED die, thin-film interface and Cu substrate integrate into the sub-assembly, which then solders onto a Cu heatsink. Electrical current flows into the heatsink, through the LED, across the thin-film interface, then out the Cu wire. All-metal interfaces from the LED anode to the heatsink provide a thermally conductive path. However, testing results show that the LED fails with currents of 815 mAmps or less. It appears that the failure was caused by thermal management within the die and is not due to the design of the package.
Available at: http://works.bepress.com/rsavage/6/