Composite metal and composite metal alloy microstructures

Abstract

Several advantages result from the incorporation of nanoparticulates into the plating bath when electrodepositing metal composite microstructures or metal alloy composite microstructures. Adding even relatively small quantities of nanoparticulates can enhance the rate of alloy deposition, cause the deposition of smoother structures, and produce composites having superior properties as compared to otherwise similar alloys lacking the particulates—for example, composites having greater hardness. These techniques are useful for plating composites into deep recesses of a microstructure.

We claim:  
     
         1 . A process for making a metal composite microstructure comprising at least one metal selected from the group consisting of nickel, copper, iron, tungsten, cobalt, molybdenum, gold, zinc, silver, chromium, tin, and lead; said process comprising the steps of: 
 (a) supplying into a mold an aqueous solution comprising a salt of the metal and comprising suspended particulates; wherein the shape of the mold is complementary to the shape of the microstructure to be made, and wherein the mold includes one or more deep recesses having a depth of at least about 10 μm, and having an aspect ratio greater than about 1; and wherein the particulates have a number-average diameter less than about 500 nm; and    (b) depositing the metal from the aqueous solution into the mold by pulsed electroplating; wherein the electroplating pulses have an on time that is sufficiently short, and a duty cycle that is sufficiently low, that the products of the electroplating reactions and the products of any side reactions do not accumulate in concentrations that are sufficiently high to substantially interfere with the electroplating of the desired metal into the deep recesses; and wherein said depositing step is continued until a metal composite microstructure has been formed having a height of at least about 10 μm, and having an aspect ratio greater than about 1; wherein the composite microstructure comprises an intermixture of metal and particulates; wherein the concentration of the particulates is such that the rate at which the metal is deposited is faster than the metal would be deposited in an otherwise identical process lacking the particulates; and wherein the depositing of at least one of the metals is under mass transport control.    
     
     
         2 . A process as recited in  claim 1 , wherein the duty cycle is less than about 0.2.  
     
     
         3 . A process as recited in  claim 1 , wherein the duty cycle is less than about 0.1.  
     
     
         4 . A process as recited in  claim 1 , wherein the on time is greater than about 0.1 second.  
     
     
         5 . A process as recited in  claim 1 , wherein the on time is greater than about 1 second.  
     
     
         6 . A process as recited in  claim 1 , wherein the on time is less than about 60 seconds.  
     
     
         7 . A process as recited in  claim 1 , wherein the mold includes one or more deep recesses having a depth between about 50 μm and about 2000 μm deep.  
     
     
         8 . A process as recited in  claim 7 , wherein at least one of the deep recesses has an aspect ratio greater than about 5.  
     
     
         9 . A process as recited in  claim 1 , wherein a metal alloy composite microstructure is produced; wherein the alloy comprises two or more metals as recited, and wherein the aqueous solution comprises salts of each of the metals comprising the alloy.  
     
     
         10 . A process as recited in  claim 9 , wherein the alloy comprises nickel and copper.  
     
     
         11 . A process as recited in  claim 9;  wherein the composition of the alloy varies as a function of depth in the microstructure.  
     
     
         12 . A process as recited in  claim 1;  wherein the metal is deposited substantially faster than the metal would be deposited in a process that was otherwise identical, except that no suspended particulates were present.  
     
     
         13 . A process as recited in  claim 1;  wherein the concentration of particulates varies as a function of depth in the microstructure.  
     
     
         14 . A process as recited in  claim 1;  wherein the particulates have a number-average diameter between about 10 nm and about 50 nm.  
     
     
         15 . A microstructure produced by the process of  claim 1 .  
     
     
         16 . A microstructure produced by the process of  claim 2 .  
     
     
         17 . A microstructure produced by the process of  claim 3 .  
     
     
         18 . A microstructure produced by the process of  claim 4 .  
     
     
         19 . A microstructure produced by the process of  claim 5 .  
     
     
         20 . A microstructure produced by the process of  claim 6 .  
     
     
         21 . A microstructure produced by the process of  claim 7 .  
     
     
         22 . A microstructure produced by the process of  claim 8 .  
     
     
         23 . A microstructure produced by the process of  claim 9 .  
     
     
         24 . A microstructure produced by the process of  claim 10 .  
     
     
         25 . A microstructure produced by the process of  claim 11 .  
     
     
         26 . A microstructure produced by the process of  claim 12 .  
     
     
         27 . A microstructure produced by the process of  claim 13 .  
     
     
         28 . A microstructure produced by the process of  claim 14 .  
     
     
         29 . A composite comprising a nickel-copper alloy intermixed with alumina particles, wherein said alumina particles have a number-average diameter less than about 500 nm.  
     
     
         30 . A microstructure comprising at least one feature comprising a composite as recited in  claim 29 , wherein said feature has a height between about 10 μm and about 2000 μm, and wherein said feature has an aspect ratio greater than about 1.  
     
     
         31 . A microstructure comprising at least one feature comprising a composite; wherein said feature has a height between about 10 μm and about 2000 μm; wherein said feature has an aspect ratio greater than about 1; wherein said composite comprises a metal alloy intermixed with particulates having a number-average diameter less than about 500 nm; wherein said particulates have a composition that differs from the composition of said alloy; and wherein the composition of said feature varies as a function of height.  
     
     
         32 . A microstructure as recited in  claim 31 , wherein the composition of said alloy varies as a function of height in said feature.  
     
     
         33 . A microstructure as recited in  claim 31 , wherein the concentration of said particulates varies as a function of height in said feature.