Compact electric brake booster

The servo-motor (1) has an electric motor (2) whose clutch shaft (4) extends along a central axis (5). A push rod extends along another central axis (6). Driving units drive the rod, and are formed of wheels (7, 8) and pinions (9, 10). The driving units cooperate with the clutch shaft and the push rod to move the rod in a direction of a master cylinder. The former central axis extends in a plane, and the latter central axis extends in another plane. The electric motor is arranged with respect to the push rod with the planes, which cut with respect to each other perpendicularly. An independent claim is also included for a method for assembling an electric servo-motor of a vehicle.