700 V SuperMESH MOSFET in a full-pack TO-220
The 700 V Vdss gives a healthy margin for universal-input (85-265 VAC) flyback converters, where the reflected voltage plus leakage spike typically peaks around 600-650 V. The 30 W maximum power dissipation in the TO-220FP package is the real limiter — at 2.5 A the conduction loss alone is over 11 W, so the switching frequency and thermal interface to the heatsink need careful budgeting. The ±30 V maximum gate-source rating gives headroom for gate-drive overshoot in noisy environments, but a 12-15 V gate clamp is still good practice. Input capacitance is 930 pF typical at 25 V drain-source — moderate for a 700 V device, meaning the gate-driver sees a manageable load.
New designs should not target this order code.
Finding a replacement for the STF6NK70Z
A functionally similar replacement would need to match the 700 V Vdss, 5 A Id, TO-220FP package, and SuperMESH or equivalent technology. Within ST's portfolio, look at the current SuperMESH 3 or MDmesh series in the same package — the STF7NK70Z or STF5NK70Z are close parametric matches but verify pin compatibility and gate charge differences before committing.