Preparation of conductive silver paste using bimodal particles.

Area of Science:

• Materials Science
• Nanotechnology
• Electrical Engineering

Background:

• Achieving low electrical resistivity in silver paste is crucial for microelectronics.
• Particle networking and density significantly impact silver paste performance.
• Improving packing density, interconnectivity, and conductivity at low sintering temperatures is a key challenge.

Purpose of the Study:

• To develop a silver paste with enhanced electrical conductivity using bimodal silver particles (micro- and nano-sized).
• To investigate the effect of nano-silver particle size and content on paste properties.
• To optimize sintering conditions for low electrical resistivity.

Main Methods:

• Preparation of nano-silver particles (100-300 nm) via chemical reduction.
• Formulation of silver paste using bimodal silver powders, Pb-free frit, and vehicle.
• Screen printing of the paste onto alumina substrates.
• Sintering the printed paste at temperatures ranging from 400-500°C.

Main Results:

• Increased nano-silver content and sintering temperature enhanced packing density and electrical conductivity.
• Nano-silver particles effectively filled interstices between micro-silver particles, improving interconnectivity and densification.
• The lowest electrical resistivity achieved was 3.9 microomega cm at 500°C sintering temperature.

Conclusions:

• Bimodal silver particle mixtures are effective in enhancing the electrical properties of silver paste.
• The developed silver paste demonstrates compatibility with microelectronics device requirements.
• Optimizing the ratio of micro- and nano-silver particles and sintering temperature is key to achieving superior performance.