Longitudinal Ultrasonic Bonding of Electrodes between Rigid and Flexible Printed Circuit Boards

Lee, Jong-Bum; Koo, Jaseung; Hong, Seong Uk; Shin, Ho-Jun; Moon, Young-Jun; Jung, Jae Pil; Yoo, Chang D.; Jung, Seung-Boo

doi:10.1143/jjap.47.4300

Cited by 9 publications

(4 citation statements)

References 6 publications

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“…On the other hand, the application of FPC is extending toward increasingly complicated devices such as membrane switch matrices 10) and bare chip mounting. 11,12) Recent requirements for reducing the line width of the circuits and minimizing the thickness of the base film have come to a point where the thickness of the adhesive layer can no longer be neglected. Moreover, the adhesive layer exerts a harmful effect on the long-term reliability of FPCs.…”

Section: Introductionmentioning

confidence: 99%

Copper cladding on polymer surfaces by ionization-assisted deposition

Kohno¹,

Tanaka²,

Usui³

2018

Jpn. J. Appl. Phys.

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Copper thin films were prepared on poly(ethylene terephthalate) (PET) and polyimide (PI) substrates by an ionization-assisted vapor deposition method. The films had a polycrystalline structure, and their crystallite size decreased with increasing ion acceleration voltage Va. Ion acceleration was effective in reducing the surface roughness of the films. Cross-sectional transmission electron microscopy revealed that the copper/polymer interface showed increased corrugation with increasing Va. The increase in Va also induced the chemical modification of polymer chains of the PET substrate, but the PI substrate underwent smaller modification after ion bombardment. Most importantly, the adhesion strength between the copper film and the PET substrate increased with increasing Va. It was concluded that ionization-assisted deposition is a promising technique for preparing metal clad layers on flexible polymer substrates.

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Section: Introductionmentioning

confidence: 99%

Copper cladding on polymer surfaces by ionization-assisted deposition

Kohno¹,

Tanaka²,

Usui³

2018

Jpn. J. Appl. Phys.

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“…[1][2][3][4] FPCBs can be applied to various electronic products, such as portable electronics and display modules etc., due to their many advantageous properties including lightness, small thickness, high glass transition temperature, and superior exibility. [5][6][7][8][9] On the other hand, RPCBs have a low cost, high packaging density, and considerably better established reliability data.…”

Section: Introductionmentioning

confidence: 99%

“…1,2) Of these bonding methods, mechanical connections, using a connector, have been widely used due to their advantageous simplicity, low-cost, and high reliability. In spite of this, mechanical connections continue to have some problems, such as large volumes, dif cult automation processes, and limited input/output (I/O) counts.…”

Section: Introductionmentioning

confidence: 99%

Effect of Hygrothermal Treatment on Reliability of Thermo-Compression Bonded FPCB/RPCB Contact Joints

Yoon

Jung

2016

Mater. Trans.

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In this study, electrodes on a exible printed circuit board (FPCB) and rigid printed circuit board (RPCB) were bonded together by thermo-compression (TC) bonding, using a Sn-3.0Ag-0.5Cu solder as an interlayer. In order to investigate the hygrothermal reliability of the TC bonded FPCB/RPCB joints, a temperature-humidity (TH) test of 85 C/85% relative humidity, and a 90 peel test, were conducted. The relationships between the TH treatment, peel strength, and failure analysis result were discussed. The peel strength signi cantly decreased as TH time increased. In contrast, a signi cant variation in electrical resistance was not observed during TH testing. Thin and uniform (Ni,Cu) 3 Sn 4 intermetallic compound (IMC) layers were formed at both FPCB/Sn-3.0Ag-0.5Cu/RPCB interfaces. After a TH test for 500 h, the thickness of the IMC layer was slightly increased. In the case of the joint without TH treatment, a fracture occurred at the polyimide of the FPCB. After the TH test, the degradation of the adhesion between the polyimide and Cu in the FPCB occurred, due to the hygrothermal treatment, resulting in a switch of failure mode, from a polyimide failure to a brittle polyimide/Cu interface failure. X-ray photoelectron spectroscopy (XPS) analyses showed that the decrease in C-O and C=O bond ratios caused a decrease in peel strength of the TC bonded FPCB-RPCB joints, after the TH test. When comparing the TH and HTS tests, the TH test signi cantly deteriorated the integrity of the TC bonded FPCB-RPCB joints.

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“…, 2005a). Ultrasonic bonding of RPCB and FPCB pads with longitudinal vibration at a heated state was carried out by the author et al (Lee et al , 2008). However, ultrasonic bonding with transverse vibration at ambient temperature between Sn and Au, the outer layers of the respective pads of the FPCB and RPCB in this work, or between Sn and Ni, the subsequent layers under Au, was not reported.…”

Section: Introductionmentioning

confidence: 99%

Ultrasonic bonding of flexible PCB to rigid PCB using an Sn interlayer

Kim

Jung²,

Zhou³

2009

Soldering &Amp; Surface Mount Technology

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Purpose-The aim of the paper is to study the feasibility of direct ultrasonic bonding between contact pad arrays on flexible printed circuit boards (FPCB) and rigid printed circuit boards (RPCB) at ambient temperature. Design/methodology/approach-Metallization layers on the RPCB comprised Sn on Cu while the pads on the FPCB consisted of Au/Ni/Cu. Prepared RPCB and FPCB were bonded by ultrasound at ambient temperature using an ultrasonic frequency of 20 kHz, a power of 1,400 W, and 0.62 MPa of bonding pressure. The bonded samples were cross-sectioned and the joints and microstructures were observed by Field Emission Scanning Electron Microscopy (FE-SEM) and Energy Dispersive Spectroscopy (EDS). The soundness of the joints was evaluated by pull testing. Findings-Robust bonding between FPCB and RPCB was obtained by bonding for 1.0 and 1.5 s. This result has confirmed that direct room temperature ultrasonic bonding of Au and Sn is feasible. At a longer bonding time of 3.0 s, cracks and voids were found in the joints due to excessive ultrasonic energy. The IMC (intermetallic compound) between the Sn layer and pads of the RPCB was confirmed as Cu 6 Sn 5. On the FPCB side, Cu 6 Sn 5 and Ni 3 Sn 4 were formed by contact with the facing Sn coating, and mechanically alloyed Cu 0.81 Ni 0.19 was found within the pads. Meanwhile, the strength of bonded joints between FPCB and RPCB increased with bonding time up to 1.5 s and the maximum value reached 12.48 N. At 3.0 s bonding time, the strength decreased drastically, and showed 5.75 N. Footprints from the fracture surfaces showed that bonding started from the edges of the metal pads, and extended to the pad centers as ultrasonic bonding time was increased. Originality/value-Direct ultrasonic bonding with transverse vibration at ambient temperature between the surface layers of the pads of FPCB and RPCB has been confirmed to be feasible.

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Longitudinal Ultrasonic Bonding of Electrodes between Rigid and Flexible Printed Circuit Boards

Cited by 9 publications

References 6 publications

Copper cladding on polymer surfaces by ionization-assisted deposition

Copper cladding on polymer surfaces by ionization-assisted deposition

Effect of Hygrothermal Treatment on Reliability of Thermo-Compression Bonded FPCB/RPCB Contact Joints

Ultrasonic bonding of flexible PCB to rigid PCB using an Sn interlayer

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