A major challenge in printed electronics is the inability to solder directly on Ag paste (the most common ink and paste material) because no intermetallic layer is formed. With Cu, this can be different.
Here, Copprint is showing results, demonstrating that one can directly solder onto their Cu pastes with good shear test results, even if sometimes the wetting is not the best. It also shows how a strong intermetallic layer is formed during the solder, for example, with the standard SAC305 solder on an FR4 substrate.
This is an important advancement of the art because it makes printed electronics more compatible with standard SMT processes. Furthermore, the Cu ink is compatible with low-T solders too, enabling one to solder components directly onto a PET substrate with printed Cu lines.
In general, Cu inks have had issues in the past. The conductivity has not been high enough, meaning more material is needed thereby eroding their $/Kg advantage vs. Ag. They have also required novel sintering steps with a new learning curve and with new equipment. The data from Copprint suggests that their ink can be sintered very fast and achieve conductivity levels outperforming those of classic Ag suppliers.
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