Analysis of Electrical Resonance of a Hard Disk Drives Suspension Interconnect and Invasion Into Read Signal Path

Disk drives' high data rate required wide bandwidth for read signal path. Some mechanical parts inside hard disk drives have electrical resonances. Suspension interconnect's tail is one of them. The root cause of the resonance is that it has no connection between suspension tail stainless-steel (SST) Ground (GND) and flex finger GND. The substrate of the suspension interconnect's tail SST GND connects to the base/arm, however, the tip of the suspension interconnect's tail SST GND near the amplifier is open. Preamp power and GND noise flow on the suspension interconnect's tail, and suspension interconnect's tail creates an open ground structure that has quarter wavelength resonances. The interference signals that resonant on the open ground tail structure are then picked up as common mode signals, that invade into the read signal path, which transfers to differential mode of the interference signals through imbalances in the interconnect and amplifier. Therefore, the solution to remove the quarter wavelength resonance is to connect the tip of the suspension tail SST GND and flex finger GND near the read amplifier's GND.