posted on 2022-02-04, 18:03authored byChing-Ping Hsiao, Jhewn-Kuang Chen, Chia-Chen Li
In-mold
electronics (IME) is a revolutionary way to form three-dimensional
molded films with printed circuitry. However, thermoforming and molding
processes inevitably cause microcracks in the printed circuit lines
that lower the electronic conductivity. Here, two types of microcapsules
containing liquid metals, gallium (Ga) and gallium-indium (Ga-In),
in a poly(urea-formaldehyde) shell are synthesized, and their potential
as an additive in restoring the conductivity of circuit lines for
IME is assessed. Because the microcapsules have good chemical compatibility
with Ag paste, they are uniformly distributed in the circuit lines.
Tensile test results show that both Ga and Ga-In microcapsules efficiently
reduce the resistance increase due to fractured structures after stretching.
Nevertheless, incorporating an excess amount of microcapsules results
in a fragile matrix in Ag lines, and the aggravated damage causes
the resistance to exceed that without microcapsule addition. Compared
to the Ga microcapsules, the Ga-In microcapsules perform better in
restoring circuit lines, and the reason is discussed.