Head gimbal assembly with a flexible printed circuit having a serpentine substrate

Abstract

A head gimbal assembly includes a suspension of the type supporting a slider and a flex circuit. The suspension is formed of a load beam that supports the flex circuit, and a resilient flexure which is secured to the load beam and which supports the slider. The flex circuit is comprised of conductive traces formed on a compliant, dielectric substrate. The substrate includes a body portion and a head portion for supporting the conductive traces. The substrate head portion is patterned such that selected portions are removed to leave bare conductive trace sections on a generally serpentine insulation layer, in order to compensate for variations effected by heat and humidity. The serpentine insulation layer is S-shaped with a periodic pattern, and overlays but does not touch the load beam tip. The substrate body portion overlays and is secured to the load beam at selected locations. This design enables the flex circuit to provide support for the conductive traces, to insulate the conductive traces from the load beam, to minimize the stiffness effect of the flex circuit on the gimbal, to direct the expansion and contraction of the substrate in a controlled fashion while retaining the mechanical connectivity of traces to the substrate, and to minimize the effect of the expansion and contraction on the slider flying characteristics.