Low temperature soldering technology based on superhydrophobic copper microlayer.

Area of Science:

• Materials Science
• Nanotechnology
• Joining Technology

Background:

• Traditional reflow soldering of copper (Cu) faces challenges with high temperatures, leading to thermal stress and signal delay.
• Existing Cu-Cu soldering methods require high temperatures, limiting their application in sensitive electronic components.
• Need for advanced soldering techniques that ensure high joint strength while minimizing thermal impact.

Purpose of the Study:

• To develop a low-temperature Cu-Cu soldering process using silver (Ag) film modification.
• To investigate the microstructural evolution and mechanical properties of Ag-modified Cu microlayer joints.
• To address the limitations of high-temperature soldering in electronic packaging.

Main Methods:

• Copper microlayers were modified with a silver film via electrodeposition, creating nano cone-shaped protrusions.
• Soldering was performed under specific pressure and low-temperature conditions using the modified Cu-Cu couple.
• Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and shear testing analyzed joint morphology and strength.

Main Results:

• Optimal soldering parameters (220°C, 20 MPa, 20 min) resulted in interlocked nano-conical Cu projections and a silver buffer layer.
• The Ag film effectively connected the Cu layers, significantly increasing the average shear strength of the joints.
• Low-temperature soldering was achieved due to the unique Cu microlayer morphology and the nano-size effect of the Ag layer.

Conclusions:

• Silver film modification provides an effective route for low-temperature Cu-Cu soldering with enhanced joint strength.
• The developed method overcomes the drawbacks of high-temperature soldering, offering good interface quality and miniaturization potential.
• This technique is promising for advanced electronic packaging applications requiring high reliability and thermal management.