Fabrication of copper nanoparticles based ink for printed electronics

The fabrication of electrical circuits by printing conductive inks is gaining interest,
due to its promising capacity to simplify the traditional production process and
reduce costs. However, the high price of silver, the most commonly used metal
for conductive inks, poses a barrier for wide industrial implementation of this
technology.
Copper inks are an attractive alternative, due to their low price. However, their
fabrication is limited owing to the requirement of strong reducing agents in the
preparation of nanoparticle (NP) inks or from low copper content in metal organic
decomposition (MOD) inks.
Here, we established a process that resolves these limitations by taking
advantage of the self-reduction mechanism existing in MOD ink in order to form
nanoparticles ink, without using strong reducing agents.
Copper ink was printed on various substrates, and sintered by thermal heating,
while examining the effect of different parameters including: the ligands used to
form the copper complex, the stabilizing agents and temperatures. The inks and
obtained copper films were characterized by SEM, EDS, XRD, XPS, TGA-DSC
and electrical measurements.
A two steps procedure was yielded for achieving conductive electrical circuits.
First, complexation of copper formate with 2-amino-2-methyl-1-propanol in the
presence of n-octylamine to give ~100-300nm nanoparticles. Secondly, the ink
was deposited, followed by nanoparticles sintering in 170 - 250°C.