Patent ID: 8927122
Filing Date: 2015-01-06
Classification: C23F,G11B,H05K,Y10T

Abstract:
1. A substrate for suspension, comprising: a metallic substrate, an insulating layer formed from an insulating-layer-forming material on the metallic substrate, a conductor layer formed on the insulating layer, and a cover layer formed from a cover-layer-forming material on the insulating layer, covering at least a part of the conductor layer, wherein the insulating-layer-forming material and the cover-layer-forming material are formed of an identical polyimide precursor solution including an identical acid anhydride and an identical diamine, and include identical amounts of the anhydride and the diamine, wherein the insulating-layer-forming material and the cover-layer-forming material are subjected to a heat treatment so that the insulating-layer-forming material and the cover-layer-forming material have coefficients of hygroscopic expansion of 0/% RH to 30×10 wherein the insulating-layer-forming material and the cover-layer-forming material have a repeating unit represented by the following formula: wherein R 1 is a tetravalent organic group, R 2 is a divalent organic group, R 1 and R 2 being either a single structure or a combination of two or more structures, and n is a natural number of 1 or more, wherein the insulating-layer-forming material and the cover-layer-forming material have coefficients of thermal expansion of 15×10 wherein the metallic substrate has an open area formed by etching in the metallic substrate so as to expose the insulating layer outside through the open area and to decrease a rigidity of the substrate for suspension, and a warpage of a 50 mm×10 mm strip of the metallic substrate is 0.5 mm or less when placed in a thermo-hygrostat at 85° C. and 85% RH for one hour.