The STTH30RQ06D: Through-hole TO-220AC package with the anode on the tab — the tab is electrically live, so the heatsink must be electrically isolated or the tab must be tied to the correct potential. The standard 2.54 mm pitch between the two leads matches the common TO-220 footprint; the body stands off the board about 4 mm when fully seated.
What the 55 ns trr means for your switching loop
55 ns reverse recovery time at rated conditions puts this in the ultrafast class — the diode clears the stored charge fast enough to keep the switching node from ringing into the MOSFET body diode in a 100 kHz PFC stage. The 2.95 V forward drop at 30 A is the conduction loss floor; at 30 A the dissipation is about 88 W, so the junction temperature climbs quickly without a heatsink rated for that thermal load. The 175 °C maximum junction temperature gives headroom for high ambient or marginal thermal design.
The ECOPACK® series designation means the package materials are free of halogens and antimony trioxide per ST's internal green-materials standard.