High-strength and high-conductivity Cu-(Ni, Co, Fe)-Si copper alloy for use in leadframes

Abstract

A high-strength and high-conductivity copper alloy is disclosed which contains essentially of: (a) from 0.5 to 2.5 wt % of Ni; (b) from 0.5 to 2.5 wt % of Co; (c) from 0.5 to 0.8 wt % of Si; (d). from 0.05 to 0.15 wt % of either Mg or P or both; and (e) the balance of Cu. The amounts of Co, Ni, and Si satisfy the following equations: 2%≦(Ni+Co)≦4%, and 0.8≦(Ni/4+Co/6)/Si≦1.2. The new copper alloy exhibits substantially improved electrical conductivity, greater than 65% IACA, than the commercially available C7025 copper alloy, while maintaining a satisfactory tensile strength (greater than 600 MPa), and, thus, can be most advantageously used for preparing leadframes for use in high pin-number (greater than 100 pins) IC application.

What is claimed is:  
     
         1 . A copper alloy consisting essentially of: 
 (a) from 0.5 to 2.5 wt % of Ni;    (b) from 0.5 to 2.5 wt % of Co;    (c) from 0.5 to 0.8 wt % of Si;    (d) from 0.05 to 0.15 wt % of either Mg or P or both; and    (e) the balance of Cu;    (f) wherein the amounts of Co, Ni, and Si satisfy the following equations:    2%≦(N+Co)≦4%, and 0.8≦(Ni/4+Co/6)/Si≦1.2.    
     
     
         2 . The copper alloy according to  claim 1  which consists essentially of: from 0.5 to 2.5 wt % of Ni, from 0.5 to 2.5 wt % of Co, from 0.4 to 0.8 wt % of Si, from 0.05 to 0.15 wt % of (Mg and/or P), and the balance of Cu, wherein the sum of Ni and Co is between 2.0 and 4.0 wt %.  
     
     
         3 . The copper alloy according to  claim 1  which is formed from a process comprising the following steps: 
 (a) melting constituting metals using a high frequency induction furnace followed by rapid cooling to form ingots of desired sizes;  
 (b) homogenizing said ingots at about 800 to 950° C. for about ½ to 5 hours;  
 (c) hot working said homogenized ingots to form copper alloy plate at a hot reduction ratio of 70% or greater in thickness, followed by water quenching and then milled to remove oxide and scales;  
 (d) cold rolling said copper alloy plate to a thickness reduction of 50% or greater, followed by annealing at about 800 to 950° C. for 30 seconds to 30 minutes then rapidly cooling said copper alloy plate;  
 (e) cold rolling said copper alloy plate to a thickness reduction of 50% or greater; and  
 (f) aging said copper alloy plates at about 300 to 600° C. for 30 minutes to 5 hours.  
 
     
     
         4 . The copper alloy according to  claim 3  wherein said process for making said copper alloy further comprises the step of subjecting said copper alloy plate to additional cold rolling after aging.  
     
     
         5 . The copper alloy according to  claim 1  wherein said process for making said copper alloy further comprising the following steps: 
 (a) melting constituting metals using a high frequency induction furnace followed by rapid cooling to form ingots of desired sizes;  
 (b) homogenizing said ingots at about 800 to 950° C. for about ½ to 5 hours;  
 (c) hot working said homogenized ingots to form copper alloy plates at a reduction ratio of 70% or greater in thickness, followed by water quenching and then milled to remove oxide and scales;  
 (d) cold rolling said copper alloy plates to a cold reduction of 50% or greater; and  
 (e) aging said copper alloy plates at about 300 to 600° C.  
 
     
     
         6 . The copper alloy according to  claim 5  wherein said process for making said copper alloy further comprises the step of subjecting said copper alloy plate to additional cold rolling after aging.  
     
     
         7 . The copper alloy according to  claim 1  which has a tensile strength of at least 600 MPa and an electrical conductivity of at least 65% IACS.  
     
     
         8 . A process for preparing copper alloy comprising the following steps: 
 (a) preparing a metal mixture consisting essentially of 
 (i) from 0.5 to 2.5 wt % of Ni;  
 (ii) from 0.5 to 2.5 wt % of Co;  
 (iii) from 0.5 to 0.8 wt % of Si;  
 (iv) from 0.05 to 0.15 wt % of either Mg or P or both; and  
 (v) the balance of Cu;  
 (vi) wherein the amounts of Co, Ni, and Si satisfy the following equation:  
 2%≦(Ni+Co)≦4%, and 0.8≦(Ni/4+Co/6)/Si≦1.2.  
   (b) melting constituting metals using a high frequency induction furnace followed by rapid cooling to form ingots of desired sizes;    (c) homogenizing said ingots at about 800 to 950° C. for about ½ to 5 hours;    (d) hot working said homogenized ingots to form copper alloy plate at a hot reduction ratio of 70% or greater in thickness, followed by water quenching and then milled to remove oxide and scales;    (e) cold rolling said copper alloy plate to a thickness reduction of 50% or greater, followed by annealing at about 800 to 950° C. for 30 seconds to 30 minutes then rapidly cooling said copper alloy plate;    (f) cold rolling said copper alloy plate to a thickness reduction of 50% or greater; and    (g) aging said copper alloy plates at about 300 to 600° C. for 30 minutes to 5 hours.    
     
     
         9 . The process for preparing copper alloy according to  claim 8  wherein said metal mixture consists essentially of: from 0.5 to 2.5 wt % of Ni, from 0.5 to 2.5 wt % of Co, from 0.4 to 0.8 wt % of Si, from 0.05 to 0.15 wt % of (Mg and/or P), and the balance of Cu, wherein the sum of Ni and Co is between 2.0 and 4.0 wt %.  
     
     
         10 . process for preparing copper alloy according to  claim 8  which further comprises the step of subjecting said copper alloy plate to additional cold rolling after aging.  
     
     
         11 . A process for preparing copper alloy comprising the following steps: 
 (a) preparing a metal mixture consisting essentially of: 
 (i) from 0.5 to 2.5 wt % of Ni;  
 (ii) from 0.5 to 2.5 wt % of Co;  
 (iii) from 0.5 to 0.8 wt % of Si;  
 (iv) from 0.05 to 0. 15 wt % of either Mg or P or both; and  
 (v) the balance of Cu;  
 (vi) wherein the amounts of Co, Ni, and Si satisfy the following equations:  
 2%≦(Ni+Co)≦4%, and 0.8≦(Ni/4+Co/6)/Si≦1.2.  
   (b) melting constituting metals using a high frequency induction furnace followed by rapid cooling to form ingots of desired sizes;    (c) homogenizing said ingots at about 800 to 950° C. for about ½ to 5 hours;    (d) hot working said homogenized ingots to form copper alloy plates at a reduction ratio of 70% or greater in thickness, followed by water quenching and then milled to remove oxide and scales;    (e) cold rolling said copper alloy plates to a cold reduction of 50% or greater; and    (f) aging said copper alloy plates at about 300 to 600° C.    
     
     
         12 . The process for preparing copper alloy according to  claim 11  wherein said metal mixture consists essentially of: from 0.5 to 2.5 wt % of Ni, from 0.5 to 2.5 wt % of Co, from 0.4 to 0.8 wt % of Si, from 0.05 to 0.15 wt % of (Mg and/or P), and the balance of Cu, wherein the sum of Ni and Co is between 2.0 and 4.0 wt %.  
     
     
         13 . The process for preparing copper alloy according to  claim 11  which further comprises the step of subjecting said copper alloy plate to additional cold rolling after aging.