Printed circuit board, package substrate comprising same, and method for manufacturing same

1. A printed circuit board comprising:

an insulating substrate;

a pad disposed on at least one surface of the insulating substrate;

a first protective layer disposed on the insulating substrate, the first protective layer having an opening exposing an upper surface of the pad therethrough;

a first solder bump disposed on the pad exposed by the first protective layer and including a solder, the first solder bump protruding upward from a top surface of the first protective layer;

a metal layer disposed on the first solder bump; and

a second solder bump disposed on the metal layer and including a solder, and configured to directly couple to a lower surface of a second protective layer of an upper printed circuit board,

an electronic device attached onto the insulating substrate;

a molding layer provided to encapsulate the electronic device, the first solder bump and a part of the metal layer to be buried in the molding layer,

wherein a melting point of the first solder bump is different from a melting point of the second solder bump,

wherein the first solder bump is formed as a material having a heterogeneous element comprising at least one selected from the group consisting of Al, Sb, Bi, Cu, Ni, In, Pb, Ag, Sn, Zn, Ga, Cd, and Fe is contained in a solder comprising at least one of SnCu, SnPb, and SnAgCu,

wherein the second solder bump is formed as a material having a heterogeneous element comprising at least one selected from the group consisting of Al, Sb, Bi, Cu, Ni, In, Pb, Ag, Sn, Zn, Ga, Cd, and Fe is contained in a solder comprising at least one of SnCu, SnPb, and SnAgCu, and

wherein a content of the heterogeneous element of the first solder bump and a content of the heterogeneous element of the second solder bump are adjusted such that the melting point of the second solder bump is different from the melting point of the first solder bump,

wherein an entire top surface of the second solder bump is in direct physical contact with the lower surface of the second protective layer,

wherein a top surface of the first solder bump is positioned at a lower level than a top surface of the molding layer,

wherein a bottom surface of the metal layer is positioned at a lower level than the top surface of the molding layer, and

wherein the top surface of the molding layer is positioned at a lower level than a top surface of the metal layer.

2. The printed circuit board according to claim 1 , wherein the melting point of the first solder bump is higher than that of the second solder bump.

3. The printed circuit board according to claim 1 , further comprising:

a first surface treatment layer disposed between the first solder bump and the metal layer; and

a second surface treatment layer disposed between the metal layer and the second solder bump.

4. The printed circuit board according to claim 1 , wherein the first solder bump further comprises a plating seed layer disposed on an inner wall of the opening and a partial upper surface of the protective layer.

5. A package substrate comprising:

a lower substrate having a first chip mounted thereon;

an upper substrate disposed on the lower substrate, the upper substrate having a second chip mounted thereon, and

a molding layer disposed between the lower substrate and the upper substrate, the molding layer allowing the first chip of the lower substrate to be buried therein,

wherein the lower substrate comprises:

an insulating substrate;

a pad disposed on at least one surface of the insulating substrate;

a first protective layer disposed on the insulating substrate, the first protective layer having an opening exposing an upper surface of the pad therethrough;

a first solder bump disposed on the pad exposed by the first protective layer;

a metal layer disposed on the first solder bump; and

a second solder layer formed on the metal layer and configured to directly couple to a lower surface of a second protective layer of the upper substrate,

wherein a melting point of the first solder bump is different from a melting point of the second solder bump,

wherein the first solder bump is formed as a material having a heterogeneous element comprising at least one selected from the group consisting of Al, Sb, Bi, Cu, Ni, In, Pb, Ag, Sn, Zn, Ga, Cd, and Fe is contained in a solder comprising at least one of SnCu, SnPb, and SnAgCu,

wherein the second solder bump is formed as a material having a heterogeneous element comprising at least one selected from the group consisting of Al, Sb, Bi, Cu, Ni, In, Pb, Ag, Sn, Zn, Ga, Cd, and Fe is contained in a solder comprising at least one of SnCu, SnPb, and SnAgCu,

wherein a content of the heterogeneous element of the first solder bump and a content of the heterogeneous element of the second solder bump are adjusted such that the melting point of the second solder bump is different from the melting point of the first solder bump,

wherein an entire top surface of the second solder bump is in direct physical contact with the lower surface of the second protective layer,

wherein a top surface of the first solder bump is positioned at a lower level than a top surface of the molding layer,

wherein a bottom surface of the metal layer is positioned at a lower level than the top surface of the molding layer, and

wherein the top surface of the molding layer is positioned at a lower level than a top surface of the metal layer.

6. The package substrate according to claim 5 , further comprising:

a first surface treatment layer disposed between the first solder bump and the metal layer; and

a second surface treatment layer disposed between the metal layer and the second solder bump.

7. A method for manufacturing a package substrate, the method comprising:

preparing a base substrate;

forming a pad on at least one surface of the prepared base substrate;

forming, on the base substrate, a first protective layer having an opening exposing a surface of the pad therethrough;

forming, on the first protective layer, a mask having a window exposing the surface of the pad;

forming, on the pad, a first solder bump buried in the opening and a portion of the window;

forming, a metal layer, on the first solder bump;

forming, on the metal layer, a second solder bump buried in the window; and

forming, on the base substrate, a molding layer provided to encapsulate the first solder bump and a part of the metal layer to be buried in the molding layer,

wherein a melting point of the first solder bump is different from a melting point of the second solder bump,

wherein the first solder bump is formed as a material having a heterogeneous element comprising at least one selected from the group consisting of Al, Sb, Bi, Cu, Ni, In, Pb, Ag, Sn, Zn, Ga, Cd, and Fe is contained in a solder comprising at least one of SnCu, SnPb, and SnAgCu,

wherein the second solder bump is formed as a material having a heterogeneous element comprising at least one selected from the group consisting of Al, Sb, Bi, Cu, Ni, In, Pb, Ag, Sn, Zn, Ga, Cd, and Fe is contained in a solder comprising at least one of SnCu, SnPb, and SnAgCu,

wherein a content of the heterogeneous element of the first solder bump and a content of the heterogeneous element of the second solder bump are adjusted such that the melting point of the second solder bump is different from the melting point of the first solder bump,

wherein the second solder bump is configured to directly couple to a lower surface of a second protective layer of an upper printed circuit board,

wherein an entire top surface of the second solder bump is in direct physical contact with the lower surface of the second protective layer,

wherein a top surface of the first solder bump is positioned at a lower level than a top surface of the molding layer,

wherein a bottom surface of the metal layer is positioned at a lower level than the top surface of the molding layer, and

wherein the top surface of the molding layer is positioned at a lower level than a top surface of the metal layer.

8. The method according to claim 7 , further comprising:

forming a first surface treatment layer between the first solder bump and the metal layer; and

forming a second surface treatment layer between the metal layer and the second solder bump.

9. The method according to claim 7 , further comprising performing a reflow process based on the melting point of the second solder bump, thereby attaching an upper substrate onto the second solder bump,

wherein, in the reflow process, the shape of the first solder bump is maintained as it is.