Investigation on Chemical Etching Process of FPCB With 18 μm Line Pitch

Abstract

Flexible printed circuit boards (FPCB) are widely used in smart devices with high wiring density and light weight. In this paper, the chemical etching process of FPCB with 18 μm line pitch is investigated. A geometric model of the FPCB circuit with the shape of "T" is established and simulated by the finite element method. The time evolution of the etching cavity, concentration field and velocity field of CuCl2 solution are studied, as well as the effects of initial concentrations and inlet velocities on the etching cavity profile. Finally, the FPCB sample with 18 μm line pitch is successfully fabricated by employing process parameters from the etching simulation. The results show that as the increase in the etching cavity, recirculating eddies form at the bottom of the photoresist in the corners of the etching cavity, resulting in more etching on the top sides of sidewalls over time. Higher initial concentration of the etching solution will result in a larger etching cavity profile, but the inlet velocity cannot affect the etching cavity profile significantly. Finally, the effectiveness of the simulation model is verified by comparing the etching cavity profiles with four experiments. INDEX TERMS FPCB, chemical etching, transport of diluted species

One‐Step Soft Templated Selective Milling‐Based Circuit Patterning for Eco‐Friendly and High‐Throughput Manufacturing of Flexible Electronics

“…The photochemical etching process patterns circuits by etching away exposed conductors, and takes a dominant position in patterning processes in recent years due to its reliable performance and high resolution. [20][21][22][23][24][25] However, its chemical emission causes severe chemical pollution [26,27] and its complex steps also limit its throughput. In contrast, the direct printing process patterns circuits by additive depositing various conductive inks on flexible substrates.…”

Investigation into Photolithography Process of FPCB with 18 µm Line Pitch

“…Bearing the benefits of good portability [ 1 ], light weight, small size, and excellent bending performance, flexible printed circuit boards (FPCBs) are widely used in mobile communication equipments, flexible wearable devices [ 2 ], and automotive electronic products [ 3 ]. With increasing demand in the FPCB market, the photolithography process [ 4 ] has been a crucial driving force for achieving a narrower FPCB line pitch.…”

“…However, none of these studies have investigated 3D photolithography simulations based on the finite difference time domain (FDTD) method. Moreover, at present, many companies have achieved the manufacturing of FPCBs with a 20 μm line pitch, such as the LG company in South Korea, Chipbond Technology Co., Ltd., Taiwan, China and FLEXCEED Co., Ltd., Naka-shi, Japan [ 2 ]. The breakthrough in the production process of an FPCB with a 20 μm line pitch plays an extremely important driving role in the development of the flexible electronics field.…”

Analysis of Microstrip Line with Asymmetric Arch Type Cross-Sectional Structure Using Micro Pattern Transfer Printing Method

“…Recently, the industry has taken great interest in reducing the weight and space charge of the circuit boards used for signal transmission of the sensors [ 1 , 2 , 3 , 4 ]. Therefore, studies to solve this problem by replacing the regularly printed circuit boards (PCBs) with flexible printed circuit boards (FPCBs) are now drawing attention [ 5 , 6 , 7 , 8 , 9 ]. If the regular PCBs are replaced by FPCBs, fuel efficiency is expected to be improved, reducing the weight of circuit boards connected to the vehicle.…”