Room temperature gold wire bonding

Abstract

The present invention is a method for bonding gold wire to gold bond pads at temperatures lower than 125 degrees Celsius, and more particularly at room temperature, defined to be 25 degrees Celsius. By applying compressive force and ultrasonic energy, an intermetallic bond can be formed between a gold wire and a gold bond pad without elevating the temperature. Furthermore, the present invention uses ultrasonic energy with frequencies low enough to be in the range of commercially available wire bonders.

We claim:  
     
         1 . A method for bonding gold wire to a gold bond pad, comprising the steps of: 
 pressing a gold wire against a gold bond pad; and    vibrating the gold wire at a frequency lower than 200 kHz and at a power less than 1 watt, to form a metallic bond between the gold wire and gold bond pad.    
     
     
         2 . The method of  claim 1 , wherein the step of vibrating is performed at a frequency less than 140 kHz.  
     
     
         3 . The method of  claim 2 , wherein the step of vibrating is performed at a frequency in the range of 100 kHz through 138 kHz, inclusive.  
     
     
         4 . The method of  claim 1 , wherein the step of vibrating is performed with a power not more than 220 mW.  
     
     
         5 . The method of  claim 4 , wherein the step of vibrating is performed with a power in the range of 75 to 220 mW, inclusive.  
     
     
         6 . The method of  claim 1 , wherein the step of pressing is performed with a static force not more than 150 grams.  
     
     
         7 . The method of  claim 6 , wherein the step of pressing is performed with a static force in the range of 40 to 150 grams, inclusive.  
     
     
         8 . The method of  claim 1 , wherein the step of vibrating is performed for an amount of time not more than 70 milliseconds.  
     
     
         9 . The method of  claim 8 , wherein the step of vibrating is performed for an amount of time in the range of 20 through 70 milliseconds, inclusive.  
     
     
         10 . The method of  claim 1 , wherein the steps of pressing and vibrating are performed at temperatures in the range of 20 to 30 degrees Celsius, inclusive.  
     
     
         11 . The method of  claim 1 , wherein the gold bond pad has been plated using an electrolytic process.  
     
     
         12 . An apparatus for bonding gold wire to a gold bond pad, comprising: 
 a holder for holding a gold bonding wire;    a vibration source for vibrating the holder at a frequency lower than 200 kHz and with a power less than 1 watt; and    a pressure source for pressing the holder towards a gold bond pad.    
     
     
         13 . The apparatus as in  claim 12 , wherein the vibration source vibrates the holder at a frequency less than 140 kHz.  
     
     
         14 . The apparatus as in  claim 13 , wherein the vibration source vibrates the holder at a frequency in the range of 100 kHz to 138 kHz, inclusive.  
     
     
         15 . The apparatus as in  claim 12 , wherein the vibration source vibrates the holder with a power not more than 220 mW.  
     
     
         16 . The apparatus as in  claim 15 , wherein the vibration source vibrates the holder with a power in the range of 75 to 220 mW, inclusive.  
     
     
         17 . The apparatus as in  claim 12 , wherein the pressure source presses the holder towards the gold bond pad with a static force not more than 150 grams.  
     
     
         18 . The apparatus as in  claim 17 , wherein the pressure source presses the holder towards the gold bond pad with a static force in the range of 40 to 150 grams, inclusive.  
     
     
         19 . The apparatus as in  claim 12 , wherein the vibration source vibrates the holder for an amount of time not more than 70 milliseconds.  
     
     
         20 . The apparatus as in  claim 12 , wherein the gold bond pad has been plated using an electrolytic process.