Crown Sensitivity of the Magnetic Recording Head Gimbal Assembly Bonded by a Viscoelastic Adhesive

The temperature excursions inside a magnetic recording disk drive can be as much as 20 to 60°C. When subjected to these temperature changes, thermal expansion coefficient mismatch between the ceramic slider and the stainless steel suspension causes bending. This thermal bending is mediated by the viscoelastic properties of the polymeric adhesive attaching the slider and the suspension. We employ the elastic-viscoelastic correspondence principle to model thermal bending. We calculate thermal bending up to 30 nm for a high-modulus adhesive and only 0.8 nm for a low-modulus adhesive over typical temperature variations. The low-modulus adhesive exhibited remarkable time-dependent oscillations during a successive ramp-and-hold temperature profile. These oscillations are expected to be a general phenomenon that should be observed under similar conditions of length, time, temperature, and mechanical properties of the bonded beams and adhesive. The calculated rate of temperature-dependent thermal bending was in good agreement with that measured on actual magnetic recording head gimbal assemblies. This is the first analysis that employs a viscoelastic adhesive model and the correspondence principle to describe slider crown phenomenon.