마이크로전자및패키징학회지 (Journal of the Microelectronics and Packaging Society)

  • 제25권4호
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  • Pages.111-118
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  • 2018
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  • 1226-9360(pISSN)
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  • 2287-7525(eISSN)
한국마이크로전자및패키징학회 (The Korean Microelectronics and Packaging Society)
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신축성 전자패키지용 강성도 국부변환 신축기판의 계면접착력 향상공정

Interfacial Adhesion Enhancement Process of Local Stiffness-variant Stretchable Substrates for Stretchable Electronic Packages

  • 박동현 (홍익대학교 공과대학 신소재공학과) ;
  • 오태성 (홍익대학교 공과대학 신소재공학과)
  • Park, Donghyeun (Department of Materials Science and Engineering, Hongik University) ;
  • Oh, Tae Sung (Department of Materials Science and Engineering, Hongik University)
  • 투고 : 2018.12.19
  • 심사 : 2018.12.27
  • 발행 : 2018.12.31
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초록

강성도가 서로 다른 두 polydimethylsiloxane (PDMS) 탄성고분자와 flexible printed circuit board (FPCB)로 이루어진 soft PDMS/hard PDMS/FPCB 구조의 강성도 국부변환 신축기판을 개발하기 위해 PDMS와 FPCB를 acrylic-silicone 양면테이프를 사용하여 접합한 후 접합공정에 따른 PDMS/FPCB 계면접착력을 분석하였다. 완전 경화된 PDMS에 acrylic-silicone 양면테이프의 silicone 접착제로 접착한 FPCB의 pull 강도는 259 kPa이었으며, pull 시험시 PDMS와 silicone 접착제 사이에서 박리가 발생하였다. 반면에 $60^{\circ}C$에서 15~20분 유지하여 반경화시킨 PDMS에 acrylic-silicone 양면테이프의 silicone 접착제로 FPCB를 접착 후 $60^{\circ}C$에서 12시간 유지하여 PDMS를 완전 경화시키면 pull 강도가 1,007~1,094 kPa로 크게 향상되었으며, pull 시험시 계면 박리가 acrylic-silicone 양면테이프의 acrylic 접착제와 FPCB 사이에서 발생하였다.

In order to develop a local stiffness-variant stretchable substrate with the soft PDMS/hard PDMS/FPCB configuration consisting of two stiffness-different polydimethylsiloxane (PDMS) parts and flexible printed circuit board, a FPCB was bonded to PDMS using the acrylic-silicone double-sided tape and the interfacial adhesion of the PDMS/FPCB was evaluated. The pull strength of the FPCB, which was bonded to the fully cured PDMS using the silicone adhesive of the double-sided tape, was 259 kPa and the delamination during the pull test occurred at the interface between the PDMS and the silicone adhesive. On the contrary, the bonding process, for which the FPCB was bonded using the silicone adhesive to the PDMS partially cured for 15~20 minutes at $60^{\circ}C$ and then the PDMS was fully cured for 12 hours at $60^{\circ}C$, exhibited the remarkably enhanced pull strength of 1,007~1,094 kPa. With the above mentioned bonding process, the delamination during the pull test was observed at the interface between the FPCB and the acrylic adhesive of the acrylic-silicone double sided tape.

키워드

MOKRBW_2018_v25n4_111_f0001.png 이미지

Fig. 1. Schematic illustration of the process flow for a locally stiffness-variant stretchable substrate consisting of soft PDMS, hard PDMS, and FPCB: (a) attach the acrylicsilicone double-sided tape to FPCB, (b) attach the FPCB to a partially cured hard PDMS using the silicone adhesive of the double-sided tape, (c) fully cure the hard PDMS, and (d) after placing the FPCB-bonded hard PDMS into a mold, pour and fully cure the soft PDMS.

MOKRBW_2018_v25n4_111_f0002.png 이미지

Fig. 2. Schematic illustration of the stretchable substrate consisting of soft PDMS, hard PDMS, and FPCB after chip bonding.

MOKRBW_2018_v25n4_111_f0003.png 이미지

Fig. 3. Engineering stress-strain (σ-ε) and true stress-strain (σt-εt) curves of (a) hard PDMS and (b) soft PDMS.

MOKRBW_2018_v25n4_111_f0004.png 이미지

Fig. 4. Images of ink penetration into the delaminated interface between the FPCB and the fully cured hard PDMS, which were bonded together using the double-sided tape, at an applied tensile strain of (a) 3%, (b) 15%, (c) 22%, (d) 24%, (e) 28%, and (f) 30%.

MOKRBW_2018_v25n4_111_f0005.png 이미지

Fig. 5. Pull strength of the FPCB bonded using the double-sided tape to the PDMS fully cured or partially cured for 15~25 minutes and then fully cured after bonding

MOKRBW_2018_v25n4_111_f0006.png 이미지

Fig. 6. Optical images of the (a) FPCB side and (b) PDMS side after the pull test. The FPCB was bonded using the double-sided tape to the PDMS partially cured for 15 minutes before full curing of the PDMS..

MOKRBW_2018_v25n4_111_f0007.png 이미지

Fig. 7. Optical images of the (a) FPCB side and (b) PDMS side after the pull test. The FPCB was bonded using the double-sided tape to the PDMS partially cured for 20 minutes before full curing of the PDMS.

MOKRBW_2018_v25n4_111_f0008.png 이미지

Fig. 8. Optical images of the (a) FPCB side and (b) PDMS side after the pull test. The FPCB was bonded using the double-sided tape to the PDMS partially cured for 25 minutes before full curing of the PDMS.

MOKRBW_2018_v25n4_111_f0009.png 이미지

Fig. 9. Images to illustrate the deformation behavior of the locally stiffness-variant stretchable substrate at an applied strain of (a) 0%, (b) 10%, (c) 20%, and (d) 30%.

MOKRBW_2018_v25n4_111_f0010.png 이미지

Fig. 10. Actual strain of each part of the locally stiffness-variant stretchable substrate as a function of the applied tensile strain.

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