Novel bonding structure for a hard disk drive suspension using anisotropic conductive film

Abstract

A plurality of bonding structures and their forming methods for bonding a FPC to a bonding pad, in particular a bonding pad of a wireless suspension in a head gimbal assembly, using anisotropic conductive adhesive; such structures eliminate the spring-back force in typical anisotropic bonding to ensure durable bonding. At the same time, these structures also allow for reworkability under which the bonded parts can be separated easily.

1 - 26 . (canceled)  
   
   
       27 . A head gimbal assembly (HGA) circuit structure attached to a bonding pad on a suspension of a head gimbal assembly for use in a hard disk drive using anisotropic conductive adhesive, comprising: 
 a base film;    a conductive layer situated below the base film, a part of said conductive layer attached to the bonding pad using said anisotropic conductive adhesive; and    an overcoat layer situated below a portion of the conductive layer, a bottom surface of said overcoat layer not overlapping a top surface of the bonding pad.    
   
   
       28 . The HGA circuit structure of  claim 27 , further comprising a conductive ball positioned above the bonding pad forming an electric conduit between the conductive layer and the bonding pad.  
   
   
       29 . The HGA circuit of  claim 28 , wherein the conductive ball comprises gold.  
   
   
       30 . The HGA circuit structure of  claim 27 , wherein the anisotropic conductive adhesive comprises anisotropic conductive film.  
   
   
       31 . The HGA circuit structure of  claim 27 , wherein a portion of said conductive layer is bonded to the top surface of the bonding pad directly using said anisotropic conductive adhesive.  
   
   
       32 . A method for bonding a flex-print circuit to a suspension in a head gimbal assembly, comprising the steps of: 
 Forming a conductive structure between a bonding pad and a conductive layer of the flex-print circuit; and    Bonding the conductive layer to the bonding pad via the conductive structure using anisotropic conductive adhesive.    
   
   
       33 . The method of  claim 32 , wherein the anisotropic conductive adhesive comprises anisotropic conductive film.  
   
   
       34 . The method of  claim 32 , wherein the conductive structure comprises a gold ball.  
   
   
       35 . The method of  claim 32 , wherein the conductive structure comprises a solid conductive material filling.  
   
   
       36 . The method of  claim 34 , wherein the gold ball is formed using stud bump bonding (SBB).  
   
   
       37 . The HGA circuit structure of  claim 27 , wherein the overcoat layer comprises two sections separated by a plating of conductive material, each of said two sections overlapping an end of a top surface of the bonding pad.  
   
   
       38 . A HGA circuit structure according to  claim 37  wherein the filling is thinner than the overcoat layer.  
   
   
       39 . A HGA circuit structure according to  claim 37  wherein the base film extends beyond a first end of the conductive layer and wherein the overcoat layer does not overlap any portion of the bonding pad when the bonding device is attached to the bonding pad.