Microcrystalline-to-amorphous gold alloy and plated film, and plating solution for those, and plated film formation method

Abstract

Disclosed is a microcrystalline-to-amorphous gold alloy-plated film having excellent electrical properties and excellent mechanical properties. Physical properties including both the advantageous properties of a crystalline structure and the advantageous properties of an amorphous structure can be obtained by allowing a microcrystalline phase and an amorphous phase to exist in a mixed state at a specific ratio. The average particle diameter of the microcrystals is 30 nm or smaller, the volume fraction of the microcrystals is 10 to 90%, the knoop hardness is Hk 180 or more, the specific resistivity is 200 μΩ-cm or less. In the film, hardness and abrasion resistance can be improved while maintaining a good specific resistivity value and chemical stability both inherent to gold at practically insignificant levels. Therefore, the film is useful as a material for connecting an electric or electronic component such as a connector and a relay.

1 . A gold alloy plated film formed so that a crystalline phase and an amorphous phase are mixed. 
     
     
         2 . The plated film according to  claim 1 , wherein the volume fraction of the crystalline phase is 10% to 90%. 
     
     
         3 . The plated film according to  claim 1 , wherein the average particle size of the crystalline phase is no greater than 30 nm. 
     
     
         4 . The plated film according to  claim 1 , wherein a peak half-width at around 2θ=40 degrees in an X-ray diffraction pattern is at least 1 degree. 
     
     
         5 . The plated film according to  claim 1 , wherein the Knoop hardness is at least Hk  180 . 
     
     
         6 . The plated film according to  claim 1 , wherein the specific resistance is no greater than 200 μΩ·cm. 
     
     
         7 . The plated film according to  claim 1 , wherein it is represented by the compositional formula Au 100-x-y M x C y ,wherein Au or M is a main component, M at least one of Ni and Co, C is carbon, 1 atom %≦x≦80 atom %, and 1 atom %≦y≦30 atom %. 
     
     
         8 . The plated film according to  claim 1 , wherein it is used as an electrical contact material. 
     
     
         9 . An electroplating solution for forming a gold alloy film with a mixed crystalline phase and amorphous phase, the solution comprising:
 a gold cyanide salt,   at least one of a nickel salt and a cobalt salt,   a complexing agent, and;   a pH adjusting agent.   
     
     
         10 . The electroplating solution according to  claim 9 , wherein the complexing agent comprises one or more agents selected from the group consisting of citric acid, tartaric acid, malic acid, pyrophosphoric acid, phosphoric acid, sulfamic acid, and a sodium salt, potassium salt, and ammonium salt thereof, and the pH adjusting agent is aqueous ammonia or potassium hydroxide. 
     
     
         11 . The electroplating solution according to  claim 10 , wherein the complexing agent is citric acid, and the pH adjusting agent is aqueous ammonia. 
     
     
         12 . A method for forming a gold alloy plated film, the method comprising forming a gold alloy plated film on an article to be plated using the electroplating solution according to  claim 9 , the gold alloy plated film being formed so that a crystalline phase and an amorphous phase are mixed. 
     
     
         13 . An electrical/electronic component employing the plated film according to  claim 1 .