The 1N6020C: Rated for 500 mW continuous power dissipation at 25°C ambient — the DO-35 body's glass-sealed junction handles that without external heatsinking, but derate above 25°C per the thermal resistance curve in the datasheet.
Zener voltage, tolerance, and leakage
Nominal Zener voltage is 68 V with a ±2% tolerance — the tightest bin in the 1N6020 family, so the regulation point stays between 66.64 V and 69.36 V over the operating range. That matters when the Zener sets the clamp threshold in a supply rail or the reference in a shunt regulator. Reverse leakage is specified at 100 nA maximum with 52 V applied across the junction — 16 V below the nominal Zener voltage, so the leakage current in the off-state is negligible for most bias networks. At 175°C the leakage climbs, but the glass package keeps the junction dry and stable.
Impedance and forward drop
Maximum Zener impedance (Zzt) is 240 Ohms at the test current — a relatively high figure for a 68 V device, meaning the regulation voltage shifts more with load current than a lower-impedance part. If the load draws variable current, budget the IR drop across this impedance in the output tolerance stack. Forward voltage is 1.1 V maximum at 200 mA forward current — typical for a Zener in this voltage class. The forward drop is not the primary operating mode, but it matters if the diode is used as a bidirectional clamp or in a reverse-polarity protection string.
Temperature range and reliability
Operating junction temperature spans -65°C to +175°C — a military-grade range that covers avionics cold-soak and engine-bay heat alike. The glass DO-35 hermetic seal keeps moisture out, so the Zener holds its leakage spec through thermal cycling that would crack a plastic package.