Manufacturing method of connecting structure and package structure

A method for forming a connecting structure, comprising:

• forming a conductive pad in a substrate and exposed from the substrate;
• forming a mask layer over the substrate and with an opening exposing the conductive pad;
• forming a first metal layer over the conductive pad and in the opening of the mask layer, wherein the first metal layer comprises copper;
• forming a second metal layer on the first metal layer in the opening, wherein the second metal layer comprises tin;
• forming a third metal layer on the second metal layer in the opening, wherein the third metal layer comprises nickel or cobalt;
• forming a fourth metal layer on the third metal layer in the opening, wherein the fourth metal layer comprises tin;
• removing the mask layer;
• and
• performing a thermal process to form a connecting structure, comprising:
• heating and turning the first metal layer into a first metallic layer;
• heating and turning the fourth metal layer into a fourth metallic layer;
• and
• forming a first intermetallic compound layer and a second intermetallic compound layer between the first metallic layer and the fourth metallic layer.

A method, comprising:

• forming a conductive pad in a substrate and exposed from the substrate;
• forming a connecting structure on the conductive pad, comprising:
• forming a mask layer over the substrate and with an opening exposing the conductive pad;
• forming a first metal layer over the conductive pad and in the opening of the mask layer, wherein the first metal layer comprises copper;
• forming a second metal layer on the first metal layer in the opening, wherein the second metal layer comprises tin and silver;
• forming a third metal layer on the second metal layer in the opening, wherein the third metal layer comprises nickel or cobalt;
• forming a fourth metal layer on the third metal layer in the opening, wherein the fourth metal layer comprises tin;
• removing the mask layer;
• and
• performing a thermal process to form the connecting structure by turning the first metal layer into a first metallic layer, the fourth metal layer into a fourth metallic layer and forming a first intermetallic compound layer and a second intermetallic compound layer between the first metallic layer and the fourth metallic layer;
• providing a die having a connector thereon;
• and
• performing a bonding process to connect the connector with the connecting structure to form a connected structure.