마이크로전자및패키징학회지 (Journal of the Microelectronics and Packaging Society)

  • 제30권3호
  • /
  • Pages.40-50
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  • 2023
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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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인터포저를 이용한 Stacked PCB의 휨 및 솔더 조인트 강도 연구

Warpage and Solder Joint Strength of Stacked PCB using an Interposer

  • 김기풍 (서울과학기술대학교 나노IT융합공학과) ;
  • 황보유환 (서울과학기술대학교 나노IT융합공학과) ;
  • 좌성훈 (서울과학기술대학교 지능형반도체공학과)
  • Kipoong Kim (Department of Nano IT Fusion Engineering, Seoul National University of Science and Technology) ;
  • Yuhwan Hwangbo (Department of Nano IT Fusion Engineering, Seoul National University of Science and Technology) ;
  • Sung-Hoon Choa (Department of Intelligent Semiconductor Engineering, Seoul National University of Science and Technology)
  • 투고 : 2023.08.11
  • 심사 : 2023.09.13
  • 발행 : 2023.09.30
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초록

최근 스마트폰의 부품 수는 급격히 증가하고 있는 반면, PCB 기판의 크기는 지속적으로 감소하고 있다. 따라서 부품의 실장밀도를 개선하기 위해 PCB를 쌓아서 올리는 stacked PCB 구조의 3D 실장 기술이 개발되어 적용되고 있다. Stacked PCB에서 PCB 간 솔더 접합 품질을 확보하는 것이 매우 중요하다. 본 연구에서는 stacked PCB의 신뢰성을 향상시키기 위하여, 인터포저(interposer) PCB 및 sub PCB의 프리프레그의 물성, PCB 두께, 층수에 대한 휨의 영향을 실험과 수치해석을 통해 분석하였다. 또한 솔더 접합부의 응력을 최소화하기 위해 인터포저 패드 설계 구조에 따른 접합강도를 분석하였다. 인터포저 PCB의 휨은 프리프레그의 열팽창계수가 적을수록 감소하였으며, 유리전이온도(Tg)가 높을수록 감소하였다. 그러나 온도가 240℃ 이상이면 휨의 개선 효과는 크지 비교적 크지 않다. 또한 FR-4 프리프레그에 비하여 FR-5을 적용할 경우에 휨은 더 감소하였으며, 프리프레그의 층수와 두께가 높을수록 휨은 감소하였다. 한편 sub PCB의 경우, 휨은 프리프레그의 Tg 보다 열팽창계수가 더 중요한 변수임을 확인하였고, 두께를 증가시키는 것이 휨 감소에 효과적이었다. 솔더 접합력을 향상시키기 위하여 다양한 인터포저 패드 디자인을 적용하여 전단력 시험을 수행한 결과, 더미 패드를 추가하면 접합강도가 증가하였다. 또한 텀블 시험 결과, 더미 패드가 없을 때의 크랙 발생율은 26.8%이며, 더미 패드가 있으면 크랙 발생율은 0.6%로 크게 감소하였다. 본 연구의 결과는 stacked PCB의 설계 가이드라인 제시를 위한 유용한 결과로 판단된다.

Recently, the number of components of smartphones increases rapidly, while the PCB size continuously decreases. Therefore, 3D technology with a stacked PCB has been developed to improve component density in smartphone. For the s tacked PCB, it i s very important to obtain solder bonding quality between PCBs. We investigated the effects of the properties, thickness, and number of layers of interposer PCB and sub PCB on warpage of PCB through experimental and numerical analysis to improve the reliability of the stacked PCB. The warpage of the interposer PCB decreased as the thermal expansion coefficient (CTE) of the prepreg decreased, and decreased as the glass transition temperature (Tg) increased. However, if temperature is 240℃ or higher, the reduction of warpage is not large. As FR-5 was applied, the warpage decreased more compared to FR-4, and the higher the number and thickness of the prepreg, the lower the warpage. For sub PCB, the CTE was more important for warpage than Tg of the prepreg, and increase in prepreg thickness was more effective in reducing the warpage. The shear tests indicated that the dummy pad design increased bonding strength. The tumble tests indicated that crack occurrence rate was greatly reduced with the dummy pad.

키워드

과제정보

본 연구는 2023년도 정부(산업통상자원부)의 재원으로 한국산업기술진흥원의 지원(P0008458, 2023년 산업혁신인재성장지원사업)을 받아 수행된 연구임

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