Circuit board and manufacturing method thereof

A manufacturing method of a circuit board, comprising:

• providing a substrate;
• forming a patterned copper layer on the substrate, wherein the patterned copper layer covers the substrate and exposes a portion of the substrate;
• forming a phosphorous-containing electroless plating palladium layer on the patterned copper layer, wherein the phosphorous-containing electroless plating palladium layer covers the patterned copper layer, and in the phosphorous-containing electroless plating palladium layer, a weight percentage of phosphorous is in a range from 4% to 6%, and a weight percentage of palladium is in a range from 94% to 96%;
• forming an electroless plating palladium layer on the phosphorous-containing electroless plating palladium layer, wherein the electroless plating palladium layer covers the phosphorous-containing electroless plating palladium layer, and in the electroless plating palladium layer, a weight percentage of palladium is at least 99% or more;
• and
• forming an immersion plating gold layer on the electroless plating palladium layer, wherein the immersion plating gold layer covers the electroless plating palladium layer.