• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.1
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• pp.56-62
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• 2013

The laser cutting process which is flexible and rapid usually provides a better result in cutting of flexible printed circuit boards (FPCB). However, circuit-short by the re-deposition of debris from laser ablation or its heat affect zone (HAZ) on the cutting surfaces can be a problem. A laser cutting process of FPCB in the presence of liquid can minimize these negative effects. The temperature distribution of copper and polymer parts of FPCB was analyzed with numerical simulation and the experimental results were presented to evaluate this process. Generally, laser cutting under liquid has advantages of less re-deposition of carbides and less HAZ on the cutting edges. However, bubble generation and laser beam control through the liquid media should be considered carefully to obtain a successful result.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.37 no.4
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• pp.420-426
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• 2024

This study proposes an innovative methodology for developing flexible printed circuit boards (FPCBs) capable of conforming to three-dimensional shapes, meeting the increasing demand for electronic circuits in diverse and complex product designs. By integrating a traditional flat plate-based fabrication process with a subsequent three-dimensional thermal deformation technique, we have successfully demonstrated an FPCB that maintains stable electrical characteristics despite significant shape deformations. Using a modified polyimide substrate along with Ag flake-based conductive ink, we identified optimized process variables that enable substrate thermal deformation at lower temperatures (~130℃) and enhance the stretchability of the conductive ink (ε ~30%). The application of this novel FPCB in a prototype 3D-shaped sensor device, incorporating photosensors and temperature sensors, illustrates its potential for creating multifunctional, shape-adaptable electronic devices. The sensor can detect external light sources and measure ambient temperature, demonstrating stable operation even after transitioning from a planar to a three-dimensional configuration. This research lays the foundation for next-generation FPCBs that can be seamlessly integrated into various products, ushering in a new era of electronic device design and functionality.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.26 no.4
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• pp.371-377
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• 2017

In this study, the heat dissipation performances of metal printed circuit boards (MPCBs) and flexible printed circuit boards (FPCBs) used in light-emitting diode (LED) lights were compared and analyzed by performing a heat dissipation simulation using a thermal flow analysis program. The results were summarized graphically. The temperature distribution of the MPCB was found to be better than that of the FPCB, indicating the better heat dissipation performance of the MPCB. For the two FPCB structures studied, we confirmed the LED temperature and temperature distribution by thermal flow analysis and found that for better overall heat dissipation performance, PCBs should preferably have an asymmetric structure. We confirmed the possibility of using FPCBs, which are characterized by a flexible structure, for LED lighting.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.1
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• pp.61-70
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• 2008

This paper presents the flexible MEMS transmitter based on flexible printed circuit board or FPCB, which can be transformed to arbitrary shape. The FPCB is suitable to fabricate light weight and small size modules with the help of its thin thickness. Moreover a module based on FPCB can be attached on the arbitrary curved surface due to its flexible enough to be lolled up like paper. In this paper, the flexible MEMS transmitter integrated on FPCB for a short-distance sensor network which is based on orthogonal frequency division multiplexing(OFDM) communication system is proposed. The active device of the proposed flexible MEMS transmitter is fabricated on InGaP/GaAs HBT process which has been used for power amplifier design to take advantages of high linear and high efficient characteristics. Moreover, the passive devices such as the filter and signal lines are integrated and fabricated on the FPCB board. The performance of the fabricated flexible MEMS transmitter is analyzed with EVM characteristics of the output signal.

• Journal of Institute of Control, Robotics and Systems
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• v.2 no.4
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• pp.337-343
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• 1996

In this paper, we investigate the defect detection by making use of pre-made reference image data and classify the defects by using the artificial neural network. The approach is composed of three main parts. The first step consists of a proper generation of two reference image data by using a low level morphological technique. The second step proceeds by performing three times logical bit operations between two ready-made reference images and just captured image to be tested. This results in defects image only. In the third step, by extracting four features from each detected defect, followed by assigning them into the input nodes of an already trained artificial neural network we can obtain a defect class corresponding to the features. All of the image data are formed in a bit level for the reduction of data size as well as time saving. Experimental results show that proposed algorithms are found to be effective for flexible defect detection, robust classification, and high speed process by adopting a simple logic operation.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.10
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• pp.14-22
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• 2010

The most costly and time-consuming process in the fabrication of today's multi-layer circuit board is drilling interconnection holes between adjacent layers and via holes within a layer. Decreasing size of via holes being demanded and growing number of via holes per panel increase drilling costs. Component density and electronic functionality of today's multi-layer circuit boards can be improved with the introduction of cost-effective, variable depth laser drilled blind micro via holes, and interconnection holes. Laser technology is being quickly adopted into the circuit board industry but can be accelerated with the introduction of a true production laser drilling system. In order to get optimized condition for drilling to FPCB (Flexible Printed Circuit Board), we use various drill pattern as drill step. For productivity, we investigate drill path optimization method. And for the precise drilling the thermal drift of scanner and temperature change of scan system are tested.

• Proceedings of the KWS Conference
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• 2010.05a
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• pp.81-81
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• 2010

전자 패키징은 미세화, 경량화, 저가화를 지향하고 신뢰성의 향상을 위해 발전해 왔다. 이러한 경향은 전자부품 자체의 성능 향상 뿐 아니라 전자부품을 장착, 고정할 수 있게 하는 인쇄회로 기판(PCB : Printed Circuit Board)의 성능에 많은 관심을 가지게 되었다. 전기적 신호의 손실을 줄이기 위해 전기, 전자 산업체에서는 가볍고 굴곡성이 우수한 연성인쇄회로기판(FPCB : Flexible PCB)과 가격이 싸고 신뢰성이 입증된 경성인쇄회로기판(RPCB : Rigid PCB)이 그 대상이다. 본 논문에서는 이 PCB중에서도 RPCB와 FPCB간의 열압착 방식으로 접합 시 전극간의 접합 양상을 보았다. 이 열압착 방식은 기존에 PCB를 접합하는데 사용하고 있는 connector를 이용한 체결법을 대체하는 기술로써 솔더를 중간층(interlayer)로 이용하여 열과 압력으로 접합하는 방식이다. 이 방식을 connector를 사용하는 방식에 비해 그 부피가 작고 I/O개수에 크게 영향 받지 않으며 자동화 공정이 쉬운 장점을 가지고 있다. 접합의 대상 중 RPCB의 경우는 무전해 니켈 금도금(ENIG : Electroless Nickle Immersion Gold)로 제작하였으며 FPCB의 경우는 ENIG와 유기보호피막(OSP : Organic solderability preservation) 처리하였다. 실험에 사용한 PCB는 $300\;{\mu}m$ pitch의 미세피치이며 솔더의 조성은 Sn-3.0Ag-0.5Cu (in wt%)과 Sn-3.0Ag (in wt%)를 사용하였다. 접합 온도와 접합 시간 그리고 접합 압력에 따라 최적의 접합 조건을 도출하였다. 접합 강도는 $90^{\circ}$ Peel Test를 통해서 측정하였으며 접합면 및 파괴면은 SEM과 EDS를 통하여 분석하였다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2001.11a
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• pp.3-3
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• 2001

Two companies plating baths were selected for plating on phenol and epoxy resin boards as well as on flexible p polyimide boards. After plating, deposited i&IIk&.ness al1d physical properties, as well as solder wettabilities by aging with $150^{\circ}C$ heating and 100% humidity were compared. After plating and aged with two different tin baths, deposited thickness and physical properties were not so great differences, but solder wettabilities were superior used polymer catalyst than the other. Furthermore depend upon the compactness and fineness of metallic sturctures of the base copper, the amounts of the plated copper were big differel1lces. These differences seems to be inherited from the kind and amount of additives. as well as current densities, which are influences upon structures of Copper layers. Generally the tin thickness are hetween 0.5 to $1.0\mu\textrm{m}$ and thicker the solder wettabilities are the better, and also me compact structures of deposits showed gooo soidierabiiities. In this study, with our own deveiotaedl plating equipment could get more than $0.5\mu\textrm{m}$ of till thickness and piating speed was $0.1\mu\textrm{m}$ per minutes.

• Journal of the Microelectronics and Packaging Society
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• v.25 no.2
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• pp.25-30
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• 2018

Sn-Pb solder has been used in automotive electronics for decades. However, recently, due to the environmental and health concerns, some international environmental organizations such as the end-of-life vehicle (ELV) enacted legislation banning of the Pb usage in automotive electronics. For this reason, many studies to develop and promote Pb-free soldering have been significantly reported. Meanwhile, because of flexibility and lightweight, flexible printed circuit boards (FPCBs) have been increasingly used in automotive electronics for lightweight to improve fuel efficiency and space utilization. Although the properties of lead-free solders for automotive electronics have been widely studied, there is a lack of research on the reliability performance of the lead-free solder joint on FPCB under user conditions. This study reported the properties of solder joints between Pb-free solders such as Sn3.0Ag0.5Cu, Sn0.7Cu and Sn0.5Cu0.01Al (Si), and various FPCBs finished with organic solderability preservative (OSP) and electroless nickel immersion gold (ENIG). To evaluate on joint properties and reliabilities with different solder compositions and surface-finishing materials, pull strength test, thermal shock test, and bending cycle test were performed and analyzed. After the bending cycle test of solder joint on OSP-finishing, the fractures were occurred in solder and the lifetime of Sn3.0Ag0.5Cu solder joint was the longest.

• ETRI Journal
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• v.32 no.5
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• pp.713-721
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• 2010

E-textile technology has earned a great deal of interest in many fields; however, existing wearable network protocols are not optimized for use with conductive yarn. In this paper, some of the basic properties of conductive textiles and requirements on wearable personal area networks (PANs) are reviewed. Then, we present a wearable personal network (WPN), which is a four-layered wearable PAN using bus topology. We have designed the WPN to be a lightweight protocol to work with a variety of microcontrollers. The profile layer is provided to make the application development process easy. The data link layer exchanges frames in a master-slave manner in either the reliable or best-effort mode. The lower part of the data link layer and the physical layer of WPN are made of a fabric serial-bus interface which is capable of measuring bus signal properties and adapting to medium variation. After a formal verification of operation and performances of WPN, we implemented WPN communication modules (WCMs) on small flexible printed circuit boards. In order to demonstrate the behavior of our WPN on a textile, we designed a WPN tutorial shirt prototype using implemented WCMs and conductive yarn.