Heat Sink

LEDs don't fail like incandescent bulbs — there's no filament to snap. Instead, they degrade gradually from heat. The LED chips themselves produce relatively little heat compared to incandescent, but what heat they do produce is concentrated in a tiny area. Without a path to escape, that heat builds up and accelerates phosphor degradation, reduces light output, and eventually kills the driver electronics.

The heat sink is that escape path. Usually made from aluminum (for its combination of thermal conductivity, low weight, and low cost), the heat sink draws heat away from the LED chips and spreads it across a larger surface area where it can dissipate into the surrounding air. In LED bulbs, the heat sink is the solid metal section between the base and the globe.

This is why enclosed fixtures are an LED's worst enemy. A bulb rated for 25,000 hours in open air might last only 10,000 hours in an enclosed globe or recessed can with no airflow. Always check for "enclosed fixture rated" on the box if your fixture traps heat — or better yet, choose fixtures designed for LED from the start.