Journal of Electronic Materials

, Volume 44, Issue 4, pp 1220–1237 | Cite as

Hygro-thermo-mechanical Behavior of Adhesive-Based Flexible Chip-on-Flex Packaging

  • Hsien-Chie ChengEmail author
  • Ho-Hsiang Huang
  • Wen-Hwa ChenEmail author
  • Su-Tsai Lu


Although adhesive-based chip-on-flex (COF) packaging technologies have many advantageous features, such as flexibility and compatibility with standard semiconductor and microelectronics packaging processes, the low hygro-thermal resistance leads to reliability concerns. Thus, finite element (FE) modeling and experimental testing have been used to investigate the effects of temperature and humidity conditions on the hygro-thermo-mechanical behavior of a thin flexible anisotropic conductive adhesive (ACA)-based COF packaging technology. The investigation starts from process modeling of the thermo-mechanical behavior of the technology during the ACA bonding process. The validity of the process modeling is demonstrated by temperature and warpage experiments. Furthermore, three-dimensional (3-D) transient moisture diffusion FE analysis through a thermal–moisture analogy based on the “wetness” technique is performed to evaluate the moisture distribution, in which the moisture properties of the polyimide (PI) substrate are obtained through a moisture absorption experiment. Then, the effect of the moisture properties of the ACA adhesive and PI substrate on the moisture diffusion behavior is examined. Finally, following process modeling, 3-D hygro-thermo-mechanical FE analysis under a constant temperature and humidity condition is undertaken to assess the influence of hygro-thermal aging and stress relaxation of the ACA adhesive on the long-term contact performance of the interconnects.


Chip-on-flex anisotropic conductive adhesive (ACA) finite element modeling transient moisture diffusion hygro-thermo-mechanical analysis hygro-thermal aging 


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The work is partially supported by the Ministry of Science and Technology, Taiwan, ROC, under Grants MOST 103-2221-E-035-024-MY3 and NSC 101-2221-E-007-009-MY3.


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Copyright information

© The Minerals, Metals & Materials Society 2015

Authors and Affiliations

  1. 1.Department of Aerospace and Systems EngineeringFeng Chia UniversityTaichungTaiwan
  2. 2.Department of Power Mechanical EngineeringNational Tsing Hua UniversityHsinchuTaiwan
  3. 3.Electronics and Optoelectronics Research LaboratoriesITRIHsinchuTaiwan

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