Abstract
The development of printing technologies has enabled the realization of electric circuit fabrication on a flexible substrate. However, the current technique remains restricted to single-layer patterning. In this paper, we demonstrate a fully solution-processable patterning approach for multi-layer circuits using a combined method of laser sintering and ablation. Selective laser sintering of silver (Ag) nanoparticle-based ink is applied to make conductive patterns on a heat-sensitive substrate and insulating layer. The laser beam path and irradiation fluence are controlled to create circuit patterns for flexible electronics. Microvia drilling using femtosecond laser through the polyvinylphenol-film insulating layer by laser ablation, as well as sequential coating of Ag ink and laser sintering, achieves an interlayer interconnection between multi-layer circuits. The dimension of microvia is determined by a sophisticated adjustment of the laser focal position and intensity. Based on these methods, a flexible electronic circuit with chip-size-package light-emitting diodes was successfully fabricated and demonstrated to have functional operations.
Highlights
Functional-ink-based printing technology has greatly advanced in recent years for use with flexible electronics [1,2]
We developed a fully solution-processable fabrication process for a multi-layer circuit on a flexible substrate using a combined method of selective laser sintering (SLS) and ablation (SLA)
A solid state Nd:YAG continuous wave (CW) laser with a wavelength of 532 nm was implemented for the SLS, which has a maximum power of 1.6 W, power stability of
Summary
Functional-ink-based printing technology has greatly advanced in recent years for use with flexible electronics [1,2]. As printing technologies have matured, electronic applications, such as resistor–capacitor circuits [16], radio frequency identification [17], sensors [18], displays [19], organic field-effect transistors [20,21], and solar cells [22], have been reported. These techniques support only single-layer circuit printing and are not well-suited for the manufacturing of multi-layer circuits. Previous studies suggested an interconnection method by dry etching [23,24], which is slow, expensive, and harmful to the Materials 2018, 11, 268; doi:10.3390/ma11020268 www.mdpi.com/journal/materials
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