36 V Zener — 500 mW power dissipation in a MELF package
The 1N6013UR/TR is a 36 V Zener diode from Microchip Technology, rated for 500 mW continuous power dissipation in the DO-213AA surface-mount package. The 36 V nominal Zener voltage (Vz) sets the regulation point — at that voltage the maximum continuous current before hitting the power limit is roughly 14 mA, so the designer sizes the series resistor to keep the Zener current below that ceiling across the input voltage range.
DO-213AA MELF — surface-mount integration
The DO-213AA is a glass-passivated MELF (Metal Electrode Leadless Face) package. It is a cylindrical body with metallized end caps — the board footprint is a pair of rectangular pads, and the solder profile follows standard reflow for MELF components. The tape-and-reel format (7-inch reel, 8 mm tape, 4 mm pitch typical for DO-213AA) feeds into automatic pick-and-place without issue, though the cylindrical shape can roll during placement if the nozzle vacuum is marginal. The package is rated for the full -65°C to 175°C temperature range, so the solder joint fatigue life at the high end is driven by the CTE mismatch between the MELF body and the PCB.