Parts of a pump head of a scroll pump facilitate an assembly process in which the stationary and orbiting scroll blades of the pump are angularly aligned or synchronized with one another. A metallic bellows of the pump head provides a primary means of synchronizing the stationary and orbiting scroll blades. The assembly process may be carried out using a fixture configured to be mountable to an assemblage including the bellows and the orbiting plate scroll. The fixture has a reference feature, and the orbiting plate scroll or the frame has another reference feature that can be aligned with the reference feature of the fixture, in the circumferential direction of the bellows, during the course of the assembly process.