Multi-solder techniques and configurations for integrated circuit package assembly

1. A method comprising:

depositing a plurality of solder balls on a plurality of pads of a package substrate, the plurality of solder balls corresponding with the plurality of pads;

performing a first solder reflow process to form a solder joint between the plurality of solder balls and the plurality of pads, wherein individual solder balls of the plurality of solder balls include a first solder material and a second solder material, the first solder material having a liquidus temperature that is greater than a peak temperature of the first solder reflow process and the second solder material having a liquidus temperature that is less than the peak temperature of the first solder reflow process; and

performing a second solder reflow process to form a solder joint between the plurality of solder balls and a circuit board, wherein the first solder material is an off-eutectic alloy having a liquidus temperature that is greater than a peak temperature of the second solder reflow process and a solidus temperature that is less than the peak temperatures of the first solder reflow process and the second solder reflow process, and the second solder material has a liquidus temperature that is less than the peak temperature of the second solder reflow process.

2. The method of claim 1 , further comprising:

depositing a flux material including a solder paste on the plurality of pads of the package substrate prior to depositing the plurality of solder balls, wherein depositing the plurality of balls comprises depositing the plurality of balls on the flux material disposed on the plurality of pads.

3. The method of claim 1 , wherein the peak temperatures of the first solder reflow process and the second solder reflow process are temperatures from 230° C. to 250° C.

4. The method of claim 1 , wherein the individual solder balls include a core composed of a polymer or metal that is configured to provide a structural barrier that provides a collapse distance between the package substrate and the circuit board during said performing the second solder reflow process to prevent collapse or bridging defects.

5. The method of claim 4 , wherein, prior to performing the first reflow process, the first solder material is disposed to substantially surround the core and the second solder material is disposed to substantially surround the first solder material.

6. The method of claim 1 , wherein performing the second solder reflow process forms the solder joint between the first solder material and the second solder material of the plurality of solder balls and a corresponding plurality of pads on the circuit board.

7. The method of claim 1 , wherein depositing the plurality of solder balls comprises:

placing one or more solder balls composed of a single, contiguous alloy material on corresponding one or more pads of the plurality of pads that are disposed in a central region of the package substrate; and

placing one or more of the individual solder balls on corresponding one or more pads of the plurality of pads that are disposed in a peripheral region of the package substrate.

8. The method of claim 1 , wherein:

the first solder material includes an off-eutectic alloy of tin (Sn) and copper (Cu) having a liquidus temperature greater than 260° C.; and

the second solder material includes an alloy of tin (Sn), silver (Ag), and copper (Cu).

9. A method comprising:

depositing a plurality of solder balls on a plurality of pads of a package substrate, the plurality of solder balls corresponding with the plurality of pads; and

performing a solder reflow process to form a solder joint between the plurality of solder balls and the plurality of pads, wherein individual solder balls of the plurality of solder balls include a first solder material and a second solder material, the first solder material having a liquidus temperature that is greater than a peak temperature of the solder reflow process and the second solder material having a liquidus temperature that is less than the peak temperature of the solder reflow process, wherein:

the first solder material includes an off-eutectic alloy of tin (Sn) and copper (Cu) having a liquidus temperature greater than 260° C. and a solidus temperature that is less than the peak temperature of the solder reflow process; and

the second solder material includes an alloy of tin (Sn), silver (Ag), and copper (Cu).

10. A method comprising:

depositing a plurality of solder balls on a plurality of pads of a package substrate, the plurality of solder balls corresponding with the plurality of pads; and

performing a solder reflow process to form a solder joint between the plurality of solder balls and the plurality of pads, wherein individual solder balls of the plurality of solder balls include a first solder material and a second solder material, the first solder material having a liquidus temperature that is greater than a peak temperature of the solder reflow process and the second solder material having a liquidus temperature that is less than the peak temperature of the solder reflow process, wherein:

the first solder material has a solidus temperature that is greater than the peak temperature of the solder reflow process;

the first solder material includes an alloy of bismuth (Bi) and silver (Ag), an alloy of cadmium (Cd) and Zinc (Zn), or an alloy of tin (Sn), silver (Ag) and antimony (Sb); and

the second solder material includes an alloy of tin (Sn), silver (Ag), and copper (Cu).