Substrate for suspension, process for producing the same, suspension for magnetic head, and hard disk drive

Abstract

A substrate for suspension comprises a metallic substrate, an insulating layer formed on the metallic substrate, a conductor layer formed on the insulating layer, and a cover layer covering the conductor layer. The insulating layer and the cover layer are formed from different materials, whose coefficients of hygroscopic expansion are in the range between 3×10 −6 /% RH and 30×10 −6 /% RH. The difference between the coefficients of hygroscopic expansion of the two materials is 5×10 −6 /% RH or less.

1 . A process for producing a substrate for suspension, comprising:
 a step of laminate preparation in which a laminate of a metallic substrate, an insulating layer, and a metal deposit that are situated in this order is prepared; and   a first metal etching step in which after forming patterned resist layers on the surfaces of the metallic substrate and of the metal deposit, the metallic substrate and the metal deposit are etched, thereby making a jig hole in the metallic substrate and forming a conductor pattern layer from the metal deposit.   
     
     
         2 . The process for producing a substrate for suspension according to  claim 1 , further comprising:
 a step of cover layer formation in which a cover layer having openings so made that the surface of the conductor pattern layer is partly exposed, is formed from a covering material on the conductor pattern layer;   a step of insulating layer etching in which the insulating layer is etched after forming the cover layer;   a step of protective deposit formation in which a protective deposit is formed on those portions of the surface of the conductor pattern layer that are exposed because of the openings in the cover layer; and   a step of second metal etching step in which the external side of the metallic substrate is processed after the step of insulating layer etching and the step of protective deposit formation.   
     
     
         3 . The process for producing a substrate for suspension according to  claim 1 , wherein a difference between the maximum thickness and the minimum thickness of the metal deposit is 2 μm or less. 
     
     
         4 . The process for producing a substrate for suspension according to  claim 2 , wherein a difference between the maximum thickness and the minimum thickness of the cover layer on the conductor pattern layer is 1 μm or less. 
     
     
         5 . The process for producing a substrate for suspension according to  claim 2 , wherein in the step of cover layer formation, the cover layer is formed from a liquid covering material.