Method of making a product with improved material properties by moderate heat treatment of a metal incorporating a dilute additive

Abstract

Deposition of metal in a preferred shape, including coatings on parts, or stand-alone materials, and subsequent heat treatment to provide improved mechanical properties. In particular, the method gives products with relatively high yield strength. The products often have relatively high elastic modulus, and are thermally stable, maintaining the high yield strength at temperatures considerably above 25° C. This technique involves depositing a material in the presence of a selected additive, and then subjecting the deposited material to a moderate heat treatment. This moderate heat treatment differs from other commonly employed “stress relief” heat treatments in using lower temperatures and/or shorter times, preferably just enough to reorganize the material to the new, desired form. Coating and heat treating a spring-shaped substrate provides a resilient, conductive contact useful for electronic applications.

What is claimed is:  
     
         1 . A method of fabricating a resilient structure comprising the steps of 
 providing an elongate member,    depositing a coating on the elongate member to give a coated elongate member, the coating comprising at least one metal and at least one additive, the additive capable of codepositing with the at least one metal, and    heat treating the coated elongate member at a combination of time and temperature that gives a coating with improved material properties.    
     
     
         2 . The method of    claim 1   , wherein the elongate member comprises a wire skeleton.  
     
     
         3 . The method of    claim 2   , wherein the wire skeleton is attached to a pad on a semiconductor.  
     
     
         4 . The method of    claim 2   , wherein the wire skeleton is attached to a pad on a carrier.  
     
     
         5 . The method of    claim 1   , wherein the elongate member comprises a sacrificial substrate.  
     
     
         6 . The method of    claim 1   , wherein the elongate member comprises a sacrificial substrate coated with a seed layer of material to promote plating.  
     
     
         7 . The method of    claim 1   , wherein the elongate member comprises a metal skeleton.  
     
     
         8 . The method of    claim 1   , wherein the coating is formed by electroplating.  
     
     
         9 . The method of    claim 8   , wherein the electroplating is performed in a bath which includes the at least one metal and the at least one additive.  
     
     
         10 . The method of    claim 1    further comprising, before said coating step, preparing said desired substrate for electroplating.  
     
     
         11 . The method of    claim 1   , wherein the method of depositing the coating is selected from the group consisting of electroplating, chemical vapor deposition (CVD), physical vapor deposition (PVD), electrolytic or electroless aqueous solution plating of metals, and any process that causes deposition of materials through decomposition or reaction of gaseous, liquid or solid precursors.  
     
     
         12 . The method of    claim 1    wherein the coating is sufficiently thick that the increased yield strength imparts resiliency to the coated substrate.  
     
     
         13 . The method of    claim 1    wherein said at least one metal comprises a metal selected from the group consisting of nickel, cobalt, iron, rhodium, palladium, tungsten, copper, chromium, titanium, aluminum, gold and platinum.  
     
     
         14 . The method of    claim 1    wherein said at least one metal comprises a metal selected from the group consisting of nickel, cobalt and iron.  
     
     
         15 . The method of    claim 1    further comprising coating with a material including at least two metals, said two metals selected from the group consisting of Ni—Co, Co—Mn, Ni—Mn, Pd—Au, Pd—Co, W—Co, Ti—N and Ti—W.  
     
     
         16 . The method of    claim 1   , wherein the coating comprises an alloy.  
     
     
         17 . The method of    claim 10   , wherein the coating comprises a Ni—Co alloy.  
     
     
         18 . The method of    claim 1    further comprising coating with a material including at least three metals, said three metals selected from the group consisting of Ni—Co—Mn and Ni—W—B.  
     
     
         19 . The method of    claim 1    wherein the at least one additive is a relatively minor component.  
     
     
         20 . The method of    claim 1    wherein the at least one additive or a derivative of the at least one additive is capable of codepositing with the at least one metal and capable of coexisting with the at least one metal upon moderate heat treating to organize the structure of the coating to provide an increase in yield strength of the coated substrate.  
     
     
         21 . The method of    claim 1   , wherein the at least one additive comprises a sulfur-containing compound.  
     
     
         22 . The method of    claim 1   , wherein said at least one additive is selected from the group consisting of saccharin, napthalene-tri-sulfonic acid (NTSA), 2-butyne-1,4-diol, and thiourea.  
     
     
         23 . The method of    claim 1    further comprising coating in the presence of a material selected from the group consisting of NiCl, NiBr, a Class 1 brightener and a Class 2 brightener.  
     
     
         24 . The method of    claim 1   , wherein the coating undergoes an exothermic transformation in microstructure from a less organized to a more organized state, an exothermic transformation which be readily detected using differential scanning calorimetry and has a peak temperature, and wherein the temperature of heat treating is between about 0° C. above and about 100° C. above the peak temperature.  
     
     
         25 . The method of    claim 1   , wherein the coating comprises an amorphous material before the heat treating step.  
     
     
         26 . The method of    claim 25   , wherein the heat treating step causes a significant although not necessarily complete transformation in the coating from the amorphous material to an ordered material.  
     
     
         27 . The method of    claim 1   , wherein a significant but not necessarily complete portion of the coating is an ordered material after the heat treating step.  
     
     
         28 . The method of    claim 1   , wherein the coated substrate comprises an electrical interconnection.  
     
     
         29 . The method of    claim 1   , further comprising coating the elongate member such that the coated and annealed substrate is attached to a larger structure wherein the coated substrate comprises a resilient electrical contact.  
     
     
         30 . The method of    claim 1    further comprising fully enveloping the elongate member during the coating step.  
     
     
         31 . The method of    claim 1    further comprising removing the substrate, in whole or in part, after the coating step and before or after the heat treating step.  
     
     
         32 . The method of    claim 1   , wherein the elongate member comprises a material selected from the group consisting of gold, silicon, aluminum, and titanium-tungsten.  
     
     
         33 . The method of    claim 1   , wherein the coated substrate has higher yield strength after heat treating than before heat treating.  
     
     
         34 . The method of    claim 33   , wherein the heat treating is at a combination of time and temperature to give a final, coated substrate with a yield strength near the maximum for that coating, such that significant further heat treating will reduce the yield strength significantly from that maximum.  
     
     
         35 . The method of    claim 1   , wherein the improved material property of the coating comprises increased yield strength compared with the yield strength of the coating before heat treating.  
     
     
         36 . The method of    claim 1   , wherein the improved material property of the coating comprises increased elastic modulus compared with the elastic modulus of the coating before heat treating.  
     
     
         37 . The method of    claim 1   , wherein the improved material property of the coating comprises increased temperature stability under load at temperatures above 100° C. compared with the temperature stability of the coating before heat treating.  
     
     
         38 . The method of    claim 1    wherein the elongate member is less resilient before heat treatment than the coating after heat treatment.  
     
     
         39 . A method of fabricating a resilient structure comprising the steps of 
 providing an elongate member,    depositing a coating on the elongate member to give a coated elongate member, the coating comprising at least one metal and at least one additive, the additive capable of codepositing with the at least one metal, 
 the metal comprising a metal selected from the group consisting of nickel and cobalt, and the additive selected from the group consisting of saccharin and 2-butyne-1,4-diol, and  
 heat treating the coated elongate member at a combination of time and temperature that increases the yield strength of the coating.  
   
     
     
         40 . The method of    claim 39   , wherein the elongate member comprises a wire skeleton.  
     
     
         41 . The method of    claim 39   , wherein the elongate member comprises a metal skeleton.  
     
     
         42 . The method of    claim 39    further comprising using a plating bath to deposit said coating wherein said additive is saccharin at a concentration in the plating bath of more than about 20 mg/L.  
     
     
         43 . The method of    claim 39    further comprising using a plating bath to deposit said coating wherein said additive is 2-butyne-1,4-diol at a concentration in the plating bath of more than about 5 mg/L.  
     
     
         44 . The method of    claim 39   , wherein the coating undergoes an exothermic transformation in microstructure from a less organized to a more organized state, an exothermic transformation which be readily detected using differential scanning calorimetry and has a peak temperature, and wherein the temperature of heat treating is between about 0° C. above and about 100° C. above the peak temperature.  
     
     
         45 . The method of    claim 39   , further comprising coating the elongate member such that the coated and annealed substrate is attached to a larger structure wherein the coated substrate comprises a resilient electrical contact.  
     
     
         46 . A resilient structure manufactured by the method comprising the steps of 
 providing an elongate member,    depositing a coating on the elongate member to give a coated elongate member, the coating including at least one metal and at least one additive, and    heat treating the coated elongate member at a combination of time and temperature that increases the yield strength of the coating.    
     
     
         47 . The resilient product of    claim 46   , wherein the elongate member comprises a wire skeleton.  
     
     
         48 . The resilient product of    claim 46   , wherein the elongate member comprises a sacrificial substrate.  
     
     
         49 . The resilient product of    claim 46   , wherein the elongate member comprises a sacrificial substrate coated with a seed layer of material to promote plating.  
     
     
         50 . The resilient product of    claim 46   , wherein the elongate member comprises a metal skeleton.  
     
     
         51 . The resilient product of    claim 46   , wherein the coating is formed by electroplating.  
     
     
         52 . The resilient product of    claim 51   , wherein the electroplating is performed in a bath which includes the at least one metal and the at least one additive.  
     
     
         53 . The resilient product of    claim 46    wherein said at least one metal comprises a metal selected from the group consisting of nickel, cobalt, iron, rhodium, palladium, tungsten, copper, chromium, titanium, aluminum, gold and platinum.  
     
     
         54 . The resilient product of    claim 46    wherein said at least one metal comprises a metal selected from the group consisting of nickel, cobalt and iron.  
     
     
         55 . The resilient product of    claim 46    further comprising coating with a material including at least two metals, said two metals selected from the group consisting of Ni—Co, Co—Mn, Ni—Mn, Pd—Au, Pd—Co, W—Co, Ti—N and Ti—W.  
     
     
         56 . The resilient product of    claim 55   , wherein the coating comprises a Ni—Co alloy.  
     
     
         57 . The resilient product of    claim 46    further comprising coating with a material including at least three metals.  
     
     
         58 . The resilient product of    claim 46    wherein the at least one additive is a relatively minor component.  
     
     
         59 . The resilient product of    claim 46    wherein the at least one additive or a derivative of the at least one additive is capable of codepositing with the at least one metal and capable of coexisting with the at least one metal upon moderate heat treating to organize the structure of the coating to provide an increase in yield strength of the coated substrate.  
     
     
         60 . The resilient product of    claim 46   , wherein the at least one additive comprises a sulfur-containing compound.  
     
     
         61 . The resilient product of    claim 46   , wherein said at least one additive is selected from the group consisting of saccharin, napthalene-tri-sulfonic acid (NTSA), 2-butyne-1,4-diol, and thiourea.  
     
     
         62 . The resilient product of    claim 46   , wherein the coating is an ordered material after the heat treating step.  
     
     
         63 . The resilient product of    claim 46   , further comprising coating the elongate member such that the coated and annealed substrate is attached to a larger structure wherein the coated substrate comprises a resilient electrical contact.  
     
     
         64 . The resilient product of    claim 46   , wherein the coated substrate has higher yield strength after heat treating than before heat treating.  
     
     
         65 . The resilient product of    claim 64   , wherein the heat treating is at a combination of time and temperature to give a final, coated substrate with a yield strength near the maximum for that coating, such that significant further heat treating will reduce the yield strength significantly from that maximum.  
     
     
         66 . The resilient product of    claim 46   , wherein the coated substrate has higher temperature stability after heat treating than before heat treating.  
     
     
         67 . A method of fabricating a resilient structure comprising the steps of 
 providing an elongate member,    depositing a metastable coating on the elongate member to give a coated elongate member, the metastable coating comprising at least one metal and at least one additive, the additive capable of codepositing with the at least one metal, and    heat treating the coated elongate member at a combination of time and temperature to initiate a transition in the metastable coating to give a stable coating.    
     
     
         68 . The method of    claim 67    wherein said stable coating has a yield strength greater than that of the metastable coating.  
     
     
         69 . The method of    claim 67    wherein said stable coating has an elastic modulus greater than that of the metastable coating.