Development of low CHE, negative-tone, photo-definable polyimide for HDD suspension

A negative-tone photo-definable polyimide with a low CHE has been developed for coating suspension heads in HDD applications. In order to select the low CHE polyimide, the stabilization energy of hydration calculated from the polyimide and water by Gaussian 03 was used as an indicator. A good correlation between the stabilization energy and CHE value of the polyimide was obtained and which resulted in the development of a low CHE, negative-tone, photo-definable polyimide. The developed material has a low CHE of 9 ppm/%RH, a CTE of 17 ppm/°C (matching that of stainless steel) and good lithographic properties.