Intermetallic Spring Structure

Abstract

A spring structure in which the transition of a metal layer from a solid solution to an intermetallic compound is utilized either to bend a spring finger into a curved shape, or to increase the yield point of the spring finger. The spring finger has an anchor portion attached to a substrate, and a cantilever portion extending over the substrate surface. The metal layer forms at least a portion of the spring finger. The metal layer is initially formed as a solid solution including a primary and secondary elements that transform to an intermetallic compound upon annealing, thereby generating a bending force that causes the cantilever portion of the spring finger to bend relative to the substrate, and/or to increase the yield point of the bent cantilever portion. The metal layer is formed by plating and/or sputtering, and annealing is performed before and/or after release of the cantilever portion.

1 . A spring structure comprising: 
 an elongated spring finger having an anchor portion attached to the substrate, a cantilever portion extending from the anchor portion, and a tip located at a distal end of the cantilever portion,    wherein said spring finger includes a metal layer comprising an intermetallic compound including two or more elements.    
   
   
       2 . The spring structure according to  claim 1 , wherein the spring finger is entirely formed by said metal layer.  
   
   
       3 . The spring structure according to  claim 1 , wherein the spring finger comprises a lower layer and an upper layer formed on the lower layer, wherein at least one of the lower layer and the upper layer comprise the intermetallic compound.  
   
   
       4 . The spring structure according to  claim 3 , 
 wherein said two or more elements include a primary metal and a secondary metal,    wherein both the lower layer and the upper layer comprise the intermetallic compound, and    wherein a first ratio of the secondary metal to the primary metal associated with the lower layer is different from a second ratio of the secondary metal to the primary metal associated with the upper layer.    
   
   
       5 . The spring structure according to  claim 3 , wherein one of the lower layer and the upper layer comprises one of a stress-engineered metal layer, an intermetallic compound layer, a bimetallic structure, and a bimorph structure.  
   
   
       6 . The spring structure according to  claim 1 , wherein the spring finger comprises a spring core, and wherein the metal layer comprises an intermetallic coating formed over the spring core.  
   
   
       7 . The spring structure according to  claim 6 , wherein the spring core comprises one of an intermetallic compound layer, a stress-engineered metal layer, a bimetallic structure, and a bimorph structure.  
   
   
       8 . The spring structure according to  claim 6 , wherein said intermetallic coating has a thickness in the range of 0.1 to 20 μm.  
   
   
       9 . The spring structure according to  claim 6 , further comprising a non-intermetallic coating formed over the intermetallic coating.  
   
   
       10 . The spring structure according to  claim 6 , further comprising a first non-intermetallic coating formed between the intermetallic coating and the spring core.  
   
   
       11 . The spring structure according to  claim 10 , further comprising a second non-intermetallic coating formed over the intermetallic coating.  
   
   
       12 . A spring structure comprising: 
 an elongated spring core having an anchor portion attached to the substrate, a cantilever portion extending from the anchor portion, and a tip located at a distal end of the central section; and    an intermetallic coating formed over the spring core.    
   
   
       13 . The spring finger according to  claim 12 , wherein the spring core comprises one of an intermetallic compound layer, a stress-engineered metal layer, a bimetallic structure, and a bimorph structure.  
   
   
       14 . The spring finger according to  claim 12 , wherein said intermetallic coating has a thickness in the range of 0.1 to 20 μm.  
   
   
       15 . The spring structure according to  claim 12 , further comprising a non-intermetallic coating formed over the intermetallic coating.  
   
   
       16 . The spring structure according to  claim 12 , further comprising a first non-intermetallic coating formed between the intermetallic coating and the spring core.  
   
   
       17 . The spring structure according to  claim 16 , further comprising a second non-intermetallic coating formed over the intermetallic coating.