Pulsed LED application like flash LEDs requires adequate thermal management to counter the heavy heat caused by larger current, here’s an app note from OSRAM discussing on thermal management of LEDs. Link here (PDF)
This application note focuses on how to develop an adequate thermal management for LEDs in camera flash applications. It provides information on critical factors and the thermal properties of LEDs during a range of operation modes as well as information on how to develop an adequate thermal management in flashlight applications.