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JWJ > Volume 37(5); 2019 > Article
Journal of Welding and Joining 2019 October;37(5) :477-481.
Published online September 19, 2019.
Investigations of Material Properties of Underfill Material for Mechanical Reliability Improvement of Electronic Devices
Byung-Seung Yim1  , Jin-Nam Kim1, Jong-Min Kim2 
1School of Mechanical System Engineering, Kangwon National University, Gangwon-do, 25913, Korea
2School of Mechanical Engineering, Chung-Ang University, Seoul, 06974, Korea
Correspondence: Jong-Min Kim  Email:
Received July 5, 2019  Revised July 29, 2019  Accepted August 8, 2019  Published online September 19, 2019
In this paper, two types of underfill with different additive contents were formulated to investigate the effects of the underfill properties on the mechanical reliability of electronic packages in portable electronic devices. Dynamic mechanical analyses (DMA), tensile tests and shear tests were conducted to examine the material properties of the underfill, such as the storage modulus (E′), glass transition temperature (Tg), mechanical strength, stiffness and modulus of toughness. In the DMA and tensile test results for cured underfill specimens, Underfill 1 without a flexible additive showed a low modulus of toughness, and Underfill 2 with a small amount of flexible additive exhibited a high modulus of toughness. For underfills with a similar Tg value, the underfill with the higher modulus of toughness exhibited better mechanical reliability than the underfills with high strength, stiffness and low modulus of toughness, due to their fracture resistance to crack propagation. Therefore, the modulus of toughness of the underfill should be predominantly considered, when developing or selecting an underfill to enhance the mechanical reliability of electronic devices, rather than excessively high mechanical strength or stiffness.
Keywords: Area array packaging | Electronic device | Mechanical strength | Reliability | Toughness | Underfill
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