1 kV PIV, 4 A — the board-fit numbers
The KBU4M-E4/51: The KBU4M-/51 is a Vishay single-phase bridge rectifier rated for 1 kV peak reverse voltage and 4 A average rectified output. The forward drop is 1 V maximum at the 4 A rated current, which sets the conduction loss at roughly 4 W for a full-wave bridge — the KBU package's copper lead frame and through-hole mounting sink that into the board or a clip-on heatsink. Reverse leakage is specified at 5 µA when the full 1 kV is applied across the bridge. That figure climbs with junction temperature — at the 150 °C absolute maximum it is roughly an order of magnitude higher — but for a 50/60 Hz mains rectifier operating below 100 °C junction, the leakage contribution to the thermal budget is negligible.
Package and mounting — through-hole, no reflow
The 4-SIP KBU package has four through-hole leads on a 5.08 mm pitch. The body is moulded epoxy with the die bonded to a copper lead frame that extends as the centre two pins — those carry the AC input and the DC output, and the copper cross-section handles the 4 A continuous without exceeding the lead-temperature rise. No reflow profile applies; wave solder or hand-solder only. Supplied in bulk tube — no tape-and-reel option for this order code. For pick-and-place assembly the KBU package is not suited; it is a manual-insertion or wave-solder part.
Storage range matches the operating limits.