Soft ESD phenomena in GMR heads in the HDD manufacturing process

GMR heads used for hard disk drives (HDD) are very sensitive to ESD. A kind of ESD damage makes a soft magnetic degradation of head performance with time. We report examples of head degradation modes by ESD damage and other damage modes as head Scratch damage, electro migration effects and corrosion of GMR stack, which are usually difficult to be distinguished explicitly by QST and Spinstand measurement test.