Development of Multimodal Metal Particle Pastes Using Computer Simulation Technology

Compared with soldering technology, metal particle sinter-joining technology can provide better thermodynamic performance and higher packaging reliability. It is considered one of the most promising technologies for achieving interconnects with high reliability and heat resistance for wide-band gap semiconductor devices. However, sinter-jointed layers are usually porous structures, and the porosity inevitably affects the sinter-joints' thermal and mechanical properties. Compared with traditional unimodal metal particle pastes, multimodal particle pastes can reduce the sinter-jointed layers' porosity and improve their performance effectively. In order to obtain the optimal ratio of multimodal micro/nanoparticle materials, a Monte Carlo simulation method was developed to achieve their random stacking. The results show that regardless of radius ratios between bimodal spherical particles, their stacking density gets the highest value when the mass of the small particles comprises ~30%. When the spherical particles with
$r_{1}=0.5$
and non-spherical (elliptical) particles with the principal axis
$2a=10,2b=8$
, thickness
$2d=1.5$
and
$\theta_{max}=10^{\circ}$
were used, the stacking density gets the highest value when the spherical particles account for ~70%. Overall, the computer simulation method for evaluating the stacking density of multimodal spherical or non-spherical particles is provided and proved useful.