Correlation between the characteristics of printed sinter paste and the quality of sintered interconnects through non-destructive analysis techniques

Solid-state sintering has emerged as the preferred process for high-temperature applications. To improve the quality of sintered compounds, this paper wants to build up a correlation between the properties of printed sintering paste and the quality of sintered compounds. For this purpose, different sintering pastes of silver and copper with micro- and nanoparticles are used. The paste is printed with different printing parameters, such as printing speed and strokes. Then the paste is predried, and a chip is placed and sintered on. This process is accompanied by non-destructive measurement methods. The paste is characterized by height, uniformity and surface quality using an optical profilometer. The interconnect is inspected using the SAM. This shows that some irregularities in printing are not compensated even during sintering under pressure and can cause defects in the interconnect. A double stroke printing process is observed to provide better print quality and consistency than single stroke. Microparticle-based pastes that can be either stored at room temperature or at most refrigerated (2-8°C) are observed to be more stable than nanoparticle-based pastes that needed deep-freeze (-40°C) storage. In conclusion, profilometer analysis of the sinter pastes offers a possible solution for in-line inspection, subject to, however, desired resolution and inspection time.