Low-Temperature and Low-Pressure Cu-Cu Bonding by Highly Sinterable Cu Nanoparticle Paste

Area of Science:

• Materials Science
• Nanotechnology
• Joining Technology

Background:

• Copper-copper (Cu-Cu) bonding is crucial for electronic packaging.
• Traditional bonding methods face challenges with miniaturization and thermal management.
• Developing novel, low-temperature bonding techniques is essential.

Purpose of the Study:

• To achieve a reliable Cu-Cu bonding joint using a highly sinterable copper nanoparticle paste.
• To characterize the properties of the synthesized copper nanoparticles and the resulting Cu-Cu joint.
• To evaluate the thermal stability and electrical performance of the bonded joint.

Main Methods:

• Synthesis of pure copper nanoparticles with an average size of 60.5 nm via simple routes.
• Preparation of a copper nanoparticle paste.
• Sintering the paste under an Ar-H₂ gas mixture atmosphere at 300°C.
• Applying a pressure of 1.08 MPa during sintering.
• Evaluating shear strength, electrical resistivity, and elemental composition post-bonding and after aging.

Main Results:

• Achieved large areas of fusion in the copper nanoparticle paste after sintering at 300°C.
• Obtained a low electrical resistivity of 11.2 μΩ cm for the sintered paste.
• Formed a compact Cu-Cu bonding joint with a shear strength of 31.88 MPa at 300°C and 1.08 MPa.
• The bonded joint exhibited excellent thermal stability, with shear strength and elemental composition remaining largely unchanged after aging.

Conclusions:

• A reliable and high-performance Cu-Cu bonding joint can be achieved using a low-temperature sintering process with copper nanoparticle paste.
• The developed method offers a promising solution for advanced electronic packaging applications requiring high thermal stability and conductivity.
• The synthesized copper nanoparticles and bonding process demonstrate excellent potential for industrial implementation.