Disk drive comprising a double sided flex circuit wherein a first side lead provides an etching mask for a second side lead

Abstract

A method of manufacturing a flex circuit is disclosed for a disk drive comprising a disk, a head actuated radially over the disk, and control circuitry. The flex circuit is for electrically coupling the head to the control circuitry and comprises a substrate. An electrical coating applied to a first side of the substrate is etched to form a first electrical lead. The first side of the substrate is irradiated with radiation such that the first electrical lead masks the radiation from passing through the substrate to prevent curing of a photoresist applied to the second side of the substrate to form an uncured photoresist and a cured photoresist on the second side of the substrate. The uncured photoresist is removed from the second side of the substrate to form a groove, and the groove is filled with electrically conductive material to form the second electrical lead.

1 . A method of manufacturing a flex circuit for a disk drive, the disk drive comprising a disk, a head actuated radially over the disk, and control circuitry, wherein the flex circuit is for electrically coupling the head to the control circuitry and comprises a substrate, the method comprising:
 etching an electrical coating applied to a first side of the substrate to form a first electrical lead;   irradiating the first side of the substrate with radiation such that the first electrical lead masks the radiation from passing through the substrate to prevent curing of a photoresist applied to the second side of the substrate to form an uncured photoresist and a cured photoresist on the second side of the substrate;   removing the uncured photoresist from the second side of the substrate to form a groove; and   filling the groove with electrically conductive material to form the second electrical lead.   
   
   
       2 . The method as recited in  claim 1 , wherein the first electrical lead is substantially aligned with the second electrical lead such that the substrate forms a capacitive dielectric. 
   
   
       3 . The method as recited in  claim 1 , wherein the substrate comprises a polyimide. 
   
   
       4 . The method as recited in  claim 3 , wherein the polyimide is sufficiently transparent to pass the radiation. 
   
   
       5 . The method as recited in  claim 1 , wherein the radiation comprises ultraviolet light. 
   
   
       6 . The method as recited in  claim 1 , wherein the radiation comprises visible light. 
   
   
       7 . A disk drive comprising:
 a disk;   a head actuated radially over the disk;   control circuitry; and   a flex circuit for electrically coupling the head to the control circuitry, the flex circuit comprising:
 a substrate; 
 a first electrical lead coupled to a first side of the substrate, wherein the first electrical lead is operable to conduct a first signal of a differential signal; 
 a second electrical lead coupled to a second side of the substrate opposite the first side, wherein the second electrical lead is operable to conduct a second signal of the differential signal; and 
 wherein the first electrical lead provides an etching mask for etching the second electrical lead and the first electrical lead is substantially aligned with the second electrical lead such that the substrate forms a capacitive dielectric. 
   
   
   
       8 . The disk drive as recited in  claim 7 , wherein the substrate comprises a polyimide. 
   
   
       9 . The disk drive as recited in  claim 8 , wherein the polyimide is sufficiently transparent to pass a curing radiation. 
   
   
       10 . The disk drive as recited in  claim 7 , wherein the radiation comprises ultraviolet light. 
   
   
       11 . The disk drive as recited in  claim 7 , wherein the radiation comprises visible light. 
   
   
       12 . The disk drive as recited in  claim 7 , further comprising an actuator arm, wherein:
 the head is coupled to a distal end of the actuator arm;   the control circuitry comprises a preamp circuit mounted on the actuator arm; and   the flex circuit for electrically coupling the head to the preamp circuit.   
   
   
       13 . The disk drive as recited in  claim 7 , wherein the control circuitry is mounted on a printed circuit board.