Method of Electrochemically Fabricating Multilayer Structures Having Improved Interlayer Adhesion

Abstract

Multi-layer microscale or mesoscale structures are fabricated with adhered layers (e.g. layers that are bonded together upon deposition of successive layers to previous layers) and are then subjected to a heat treatment operation that enhances the interlayer adhesion significantly. The heat treatment operation is believed to result in diffusion of material across the layer boundaries and associated enhancement in adhesion (i.e. diffusion bonding). Interlayer adhesion and maybe intra-layer cohesion may be enhanced by heat treating in the presence of a reducing atmosphere that may help remove weaker oxides from surfaces or even from internal portions of layers.

1 . A fabrication process for forming a multi-layer three-dimensional structure, comprising:
 (a) forming and adhering a layer to a previously formed layer and/or to a substrate, wherein the layer comprises a desired pattern of at least one material; and   (b) repeating the forming and adhering operation of (a) at least once to build up a three-dimensional structure from a plurality of adhered layers;   (c) after formation of at least a plurality of layers, subjecting the multi-layer structure to a heat treatment, wherein a maximum effective temperature during heat treatment is less than a recrystallization temperature of at least one metal forming part of the structure, and wherein the heat treatment is applied for a sufficient time and at a sufficient temperature and in an environment that allows interlayer adhesion to be enhanced a substantial amount, and   wherein the forming and adhering of at least one layer comprises use of an adhered mask in the selective patterning of at least one material.   
   
   
       2 . The process of  claim 1  wherein the substantial amount comprises at least a factor of two. 
   
   
       3 . The process of  claim 1  wherein the substantial amount comprises at least a factor of five. 
   
   
       4 . The process of  claim 1  wherein the substantial amount corresponds to the interlayer adhesion strength being greater than about 50% of the yield strength of the interlayer material. 
   
   
       5 . The process of  claim 1  wherein the substantial amount corresponds to the interlayer adhesion strength being greater than about the yield strength of the interlayer material. 
   
   
       6 . The process of  claim 1  wherein the substantial amount corresponds to the interlayer adhesion strength being greater than about 50% of the ultimate tensile strength of the intra-layer material. 
   
   
       7 . A fabrication process for forming a multi-layer three-dimensional structure, comprising:
 (a) forming and adhering a layer to a previously formed layer and/or to a substrate, wherein the layer comprises a desired pattern of at least one material; and   (b) repeating the forming and adhering operation of (a) at least once to build up a three-dimensional structure from a plurality of adhered layers;   (c) after formation of at least a plurality of layers, subjecting the multi-layer structure to a heat treatment, wherein the heat treatment is applied to the structure for a temperature, a time, and in an environment such that a substantial increase in interlayer adhesion results without significantly reducing the yield strength of the intra-layer material, and   wherein the forming and adhering of at least one layer comprises use of an adhered mask in the selective patterning of at least one material.   
   
   
       8 . The process of  claim 7  wherein the substantial increase comprises at least a factor of two and the reducing is no more than 50% of the yield strength prior to heat treatment. 
   
   
       9 . The process of  claim 7  wherein the substantial amount comprises at least a factor of five and the reducing is no more than 75% of the yield strength prior to heat treatment. 
   
   
       10 . The process of  claim 7  wherein the substantial amount corresponds to the interlayer adhesion strength being greater than about 50% of the yield strength prior to heat treatment and the yield strength after heat treatment is no less than 75% of the yield strength prior to heat treatment. 
   
   
       11 . The process of  claim 7  wherein the substantial amount corresponds to the interlayer adhesion strength being greater than about the yield strength after heat treatment and the yield strength after heat treatment being no less than 75% of its value prior to heat treatment. 
   
   
       12 . The process of  claim 7  wherein the substantial amount corresponds to the interlayer adhesion strength being greater than about 50% of the ultimate tensile strength of the intra-layer material and the ultimate tensile strength of the interlayer material being no less than 75% of its value prior to heat treatment. 
   
   
       13 . A fabrication process for forming a multi-layer three-dimensional structure, comprising:
 (a) forming and adhering a layer to a previously formed layer and/or to a substrate, wherein the layer comprises a desired pattern of at least one material; and   (b) repeating the forming and adhering operation of (a) at least once to build up a three-dimensional structure from a plurality of adhered layers;   (c) after formation of at least a plurality of layers, subjecting the multi-layer structure to a heat treatment, wherein the heat treatment results in the formation of a structure which behaves monolithically up to at least 50% of the yield strength of the intra-layer material, and wherein the forming and adhering of at least one layer comprises use of an adhered mask in the selective patterning of at least one material.   
   
   
       14 . The process of  claim 13  wherein yield strength of the intra-layer material is that of the intra-layer material prior to heat treatment. 
   
   
       15 . The process of  claim 13  wherein yield strength of the intra-layer material is that of the intra-layer material after heat treatment. 
   
   
       16 . The process of  claim 13  wherein monolithic behavior exists when stresses are at or below 50% of the yield strength of the intra-layer material and inter-layer adhesion failure is no more likely to occur than intra-layer cohesion failure. 
   
   
       17 . The process of  claim 13  wherein monolithic behavior exists when stresses are at or below about 50% of the ultimate yield strength of the intra-layer. 
   
   
       18 . The process of  claim 17  wherein yield strength of the intra-layer material is that of the intra-layer material prior to heat treatment. 
   
   
       19 . The process of  claim 17  wherein yield strength of the intra-layer material is that of the intra-layer material after heat treatment. 
   
   
       20 . A fabrication process for forming a multi-layer three-dimensional structure, comprising:
 (a) forming and adhering a layer to a previously formed layer and/or to a substrate, wherein the layer comprises a desired pattern of at least one material; and   (b) repeating the forming and adhering operation of (a) at least once to build up a three-dimensional structure from a plurality of adhered layers;   (c) after formation of at least a plurality of layers, subjecting the multi-layer structure to a heat treatment, wherein the heat treatment results in the formation of a structure which is no more likely to experience interlayer adhesion failure than intra-layer cohesion failure when applied stress is at least 50% of the yield strength of the intra-layer material.   
   
   
       21 . The process of  claim 20  wherein yield strength of the intra-layer material is that of the intra-layer material prior to heat treatment. 
   
   
       22 . The process of  claim 20  wherein yield strength of the intra-layer material is that of the intra-layer material after heat treatment.