Thermomechanical head performance

Mismatch of thermal expansion of various materials used in the transducer and slider of giant magnetoresistive (GMR) recording heads causes, at higher operating head temperature, mechanical stresses and, in particular, protrusion toward the media [thermal pole tip recession (T-PTR)]. Low T-PTR is necessary for low head-media spacing without mechanical contact. Impact of the magnitude of the Poisson´s ratio of a photoresist coil insulator on thermal protrusion is shown to be large, due to large variation of the volume compressibility. Three-dimensional FE (3-D FE) thermomechanical modeling shows that the distribution of thermal stress in shields caused by mismatch of coefficient of thermal expansion changes completely close to the air bearing surface due to protruded head surface. During head operation, the primary heat source arises from the writer coil. The maximum temperature and the particular temperature distribution depends on the ability of the head components to dissipate effectively the generated heat. As the transducer continues to scale down in size with increasing areal density and data rate, the power dissipated per unit volume grows due to the larger coil resistance in the core region.