Coated and magnetic particles and applications thereof

Abstract

A method of using coated and/or magnetic particles to deposit structures including solder joints, bumps, vias, bond rings, and the like. The particles may be coated with a solderable material. For solder joints, after reflow the solder material may comprise unmelted particles in a matrix, thereby increasing the strength of the joint and decreasing the pitch of an array of joints. The particle and coating may form a higher melting point alloy, permitting multiple subsequent reflow steps. The particles and/or the coating may be magnetic. External magnetic fields may be applied during deposition to precisely control the particle loading and deposition location. Elements with incompatible electropotentials may thereby be electrodeposited in a single step. Using such fields permits the fill of high aspect ratio structures such as vias without requiring complete seed metallization of the structure. Also, a catalyst consisting of a magnetic particle coated with a catalytic material, optionally including an intermediate layer.

What is claimed is:  
     
         1 . A method of making a solder joint, the method comprising the steps of: 
 depositing particles comprising at least one coating on a substrate; and    reflowing the particles to at least partially melt the coating, thereby forming a substantially continuous solidified solder material.    
     
     
         2 . The method of  claim 1  wherein the depositing step comprises depositing via a process selected from the group consisting of electrodeposition, electrophoresis, electroplating, evaporation, screen printing, and photostencil bumping.  
     
     
         3 . The method of  claim 1  wherein the depositing step comprises blending the particles into a paste or ink.  
     
     
         4 . The method of  claim 1  wherein the depositing step comprises electrodepositing in one deposition step at least two materials with incompatible electropotentials.  
     
     
         5 . The method of  claim 1  wherein the solder material comprises unmelted particles in a solidified matrix.  
     
     
         6 . The method of  claim 5  wherein the unmelted particles increase at least one strength of the solder material.  
     
     
         7 . The method of  claim 6  wherein the strength is selected from the group consisting of shear strength and compressive strength.  
     
     
         8 . The method of  claim 6  wherein the solder material is reinforced by the unmelted particles.  
     
     
         9 . The method of  claim 1  wherein the reflowing step comprises forming an alloy.  
     
     
         10 . The method of  claim 9  wherein the reflowing step comprises forming an alloy which comprises substantially all of the coating of the particles.  
     
     
         11 . The method of  claim 10  wherein the alloy has a substantially higher melting temperature than the coating.  
     
     
         12 . The method of  claim 9  wherein the solder material contains a substantially uniform distribution of stoichiometries.  
     
     
         13 . The method of  claim 12  wherein the solder material is substantially uniform in composition.  
     
     
         14 . The method of  claim 1  wherein the depositing step comprises controlling a concentration of the particles, thereby reducing a size of the solder joint in directions parallel to the substrate surface.  
     
     
         15 . The method of  claim 14  further comprising the step of decreasing the pitch of solder joints on the substrate.  
     
     
         16 . The method of  claim 1  wherein the particles are magnetic.  
     
     
         17 . The method of  claim 16  wherein the depositing step comprises controlling a particle loading with at least one external magnetic field.  
     
     
         18 . The method of  claim 16  wherein the depositing step comprises controlling a deposition location with at least one external magnetic field.  
     
     
         19 . The method of  claim 16  wherein the reflowing step comprises controlling a particle distribution in the solder joint with at least one external magnetic field.  
     
     
         20 . A solder material comprising particles that were coated before being deposited on a substrate.  
     
     
         21 . A method of co-depositing particles comprising the steps of: 
 suspending the particles in a suspension;    applying at least one magnetic field to the particles;    co-depositing the particles along with at least one component of the suspension; and    forming a desired structure.    
     
     
         22 . The method of  claim 21  wherein the applying step comprises controlling at least one deposition location of the particles.  
     
     
         23 . The method of  claim 21  wherein the applying step comprises controlling a particle loading.  
     
     
         24 . The method of  claim 21  wherein the particles are magnetic.  
     
     
         25 . The method of  claim 22  wherein the particles have been coated with at least one coating.  
     
     
         26 . The method of  claim 25  wherein the coating is magnetic.  
     
     
         27 . The method of  claim 21  wherein the suspending step comprises suspending the particles in an electrolytic solution.  
     
     
         28 . The method of  claim 27  wherein the co-depositing step comprises co-depositing in one deposition step at least two materials with incompatible electropotentials.  
     
     
         29 . The method of  claim 21  wherein the suspending step comprises suspending the particles in an ink or paste.  
     
     
         30 . The method of  claim 22  wherein the forming step comprises filling a via.  
     
     
         31 . The method of  claim 30  wherein the forming step comprises accelerating a fill rate by controlling particle loading.  
     
     
         32 . The method of  claim 30  wherein the forming step further comprises controlling the particle location with at least one external magnetic field, thereby permitting fill electrodeposition within the via without the presence of prior seed metallization of an entire surface of the via.  
     
     
         33 . A method of making a via comprising the steps of: 
 providing seed metallization to only a portion of a surface of the via;    filling the via with a material comprising conducting particles.    
     
     
         34 . A via comprising a seed metallization layer only partially coating a surface of the via.  
     
     
         35 . A catalyst comprising a magnetic particle coated with at least one catalytic material.  
     
     
         36 . An electrode comprising at least one surface layer deposited using the catalyst of  claim 35 .  
     
     
         37 . The catalyst of  claim 35  further comprising a first coating of the particle, wherein said first coating comprises a stable barrier to prevent diffusion of elements comprising the particle into the catalytic material.