Influence of adhesive viscoelasticity on the thermal bending of a magnetic recording slider

Abstract

In the magnetic recording head gimbal assembly, the ceramic slider is attached to the stainless-steel flexure of the suspension by a thin layer of adhesive. The mismatch of the thermal expansion coefficients between the stainless steel and the ceramic causes thermal bending, or crown sensitivity, as a result of temperature variation. Crown sensitivity is a measure of crown change with temperature. The crown plays a critical role in the flying attitude of the slider as well as interface tribology. For a viscoelastic adhesive, both time and temperature are coupled during the evolution of the crown. We develop a viscoelastic solution for slider deflection based on our previously derived elastic analysis. The elastic-viscoelastic correspondence principal and Laplace transformation techniques are employed to extend the elastic solution to the viscoelastic regime. The experimentally measured viscoelastic master curve and time-temperature shift factors define the adhesive properties. The model calculation provides the deflection of the bonded assembly for an arbitrary thermal history. The calculated deflection is compared with test results using several adhesives with different viscoelastic properties. Our results are in qualitatively good agreement with the measured slider crown sensitivity.