2N3418 Transistor Derating Curve

2N3418U4 Temperature-Power Derating Curve [2N3419U4, 2N3420U4, 2N3421U4]
NPN Medium Power Switching Silicon Transistor. Package, Surface Mount Device [SMD].

2N3418U4 Surface Mount Operational Limits

Use the Graph to determine how much to derate power [wattage] based on ambient operational temperature, in this case case temperature. Transistor Derating Curves
Temperature derating is a standard design practice for electrical engineers.

Refer to MIL-PRF-19500/393H; Semiconductor Device, Transistor, NPN, Silicon Power, Types 2N3418, 2N3418S, 2N3418U4, 2N3419, 2N3419S, 2N3419U4, 2N3420, 2N3420S, 2N3420U4, 2N3421, 2N3421S, and 2N3421U4, JAN, JANTX, JANTXV, JANS, JANSM, JANSD, JANSP, JANSL, JANSR, JANSF, JANSG, JANSH, JANHCA, JANHCB, JANKCA, JANKCB, JANKCBM, JANKCBD, JANKCBP, JANKCBL, JANKCBR, JANKCBF, JANKCBG, and JANKCBH, [U4 package]

Maximum Ratings:
Collector Emitter Voltage = 80 volts
Power Dissipation 25⁰C = 1Watt
Operating Temperature = -65 to +175⁰C
Maximum Junction Temperature = 200⁰C

Transistor Manufacturers

How to Derate; Guideline for Derating Electronic Components