Influence of adhesive viscoelasticity on the thermal bending of a magneticrecording slider

In the magnetic recording head gimbal assembly, the ceramic slider is attac hed to the stainless-steel flexure of the suspension by a thin layer of adh esive. The mismatch of the thermal expansion coefficients between the stain less 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 att itude of the slider as well as interface tribology. For a viscoelastic adhe sive, both time and temperature are coupled during the evolution of the cro wn. We develop a viscoelastic solution for slider deflection based on our p reviously 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 v iscoelastic master curve and time-temperature shift factors define the adhe sive properties. The model calculation provides the deflection of the bonde d assembly for an arbitrary thermal history. The calculated deflection is c ompared with test results using several adhesives with different viscoelast ic properties. Our results are in qualitatively good agreement with the mea sured slider crown sensitivity.