Mechanical durability of flexible printed circuit boards containing thin coverlays fabricated with poly(Amide-imide-urethane)/epoxy interpenetrating networks

Jeongah Kim, Bo Young Kim, Seong Dae Park, Ji Hun Seo, Chan Jae Lee, Myong Jae Yoo, Youngmin Kim

Research output: Contribution to journalArticlepeer-review

Abstract

Because electronics are becoming flexible, the demand for techniques to manufacture thin flexible printed circuit boards (FPCBs) has increased. Conventional FPCBs are fabricated by attaching a coverlay film (41 μm) onto copper patterns/polyimide (PI) film to produce the structure of coverlay/Cu patterns/PI film. Given that the conventional coverlay consists of two layers of polyimide film and adhesive, its thickness must be reduced to generate thinner FPCBs. In this study, we fabricated 25-μm-thick poly(amide-imide-urethane)/epoxy interpenetrating networks (IPNs) to re-place the thick conventional coverlay. Poly(amide-imide-urethane) (PAIU) was synthesized by re-acting isocyanate-capped polyurethane with trimellitic anhydride and then mixed with epoxy resin to produce PAIU/epoxy IPNs after curing. Thanks to the soft segments of polyurethane, the elongation of PAIU/epoxy IPNs increased with increasing PAIU content and reached over 200%. After confirming the excellent thermal stability and chemical resistance of the PAIU/epoxy IPNs, we fabricated FPCBs by equipping them as coverlays. The mechanical durability of the FPCBs was evaluated through an MIT folding test, and the FPCB fabricated with PAIU/ep-2 was stable up to 164 folding cycles because of the balanced mechanical properties.

Original languageEnglish
Article number943
JournalMicromachines
Volume12
Issue number8
DOIs
Publication statusPublished - 2021 Aug

Keywords

  • Coverlay
  • Flexible printed circuit boards
  • Interpenetrating network
  • MIT folding test
  • Poly(amide-imide-urethane)

ASJC Scopus subject areas

  • Control and Systems Engineering
  • Mechanical Engineering
  • Electrical and Electronic Engineering

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