Small Aircraft; Low Wing; 2 Eng; Retractable Gear
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 1.9
Communication Breakdown; Confusion; Distraction
ATC Issue All Types; Airspace Violation All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Airspace Structure; Procedure
Aircraft X was about to depart IFR and NCT Coordinator called us about his beacon code. This led us to forget to obtain IFR departure release because I did not remember that Diablo Sector is open. Normally; when Diablo is not open we have auto releases on prop departures on NIMI or H315 departures. It was not until we had the next IFR departure that I inquired to the trainee if we got a release on Aircraft X and she said she just launched him.We should have been using the CFR placard when Diablo is open to avoid forgetting.
OAK Tower Controller describes situation where an aircraft departed without a release.  Controller also states there is a placard to remind them to obtain the release that they weren't using.