Method for producing wiring board having through hole or non-through hole

Abstract

There is provided a circuit board including a substrate having a hole. Inside the hole, a metal wiring is formed. The wiring is made of a solder alloy having a melting point of 100 to 600° C., and the metal wiring includes a polycrystalline region of the solder alloy. The metal wiring of the present invention is superior in conductivity.

What is claimed is: 
     
         1 . A method for preparing a circuit board, comprising;
 providing a substrate having a hole;   providing metal particles made of an alloy, including a polycrystalline region, having a sphericity of −10% to +10%, having a melting point of 100 to 600° C.,   heating the metal particles at a temperature between the melting point and 10% higher than the melting point, to melt the metal particles;   filling the hole with the molten metal particles; and   solidifying the molten metal particles to form a metal wiring inside the hole.   
     
     
         2 . A method for preparing a circuit board according to  claim 1 , wherein the metal wiring includes a polycrystalline region. 
     
     
         3 . A method for preparing a circuit board according to  claim 1 , wherein the particle has a composite structure. 
     
     
         4 . A method for preparing a circuit board according to  claim 1 , wherein the metal particles have a size of 1 to 300 μm. 
     
     
         5 . A method for preparing a circuit board according to  claim 1 , wherein the metal particles have a size of less than 1 μm. 
     
     
         6 . A method for preparing a circuit board according to  claim 1 , wherein a supersonic wave is applied to the substrate when the hole is filled with the molten solder alloy. 
     
     
         7 . A method according to  claim 1 , wherein the solder alloy is a Sn based lead free alloy. 
     
     
         8 . A method according to  claim 1 , wherein the substrate is housed inside a chamber, and the hole is filled with the molten metal particles while increasing the pressure inside the chamber and while applying ultrasonic wave to the substrate.