caa a22 4500 445828196 CHVBK 20180317145305.0 cr unu---uuuuu 170323e20110801xx s 000 0 eng 10.1007/s10854-010-0248-y doi (NATIONALLICENCE)springer-10.1007/s10854-010-0248-y Chen K. United Microelectronics Corporation, No. 3, Li-Hsin Rd. II, 300, Hsinchu Science Park, ROC, Taiwan aut Ultra low-k die crack study for lead free solder bump flip-chip packaging [Elektronische Daten] [K. Chen] Ultra low-K (ULK) dielectric has lower mechanical strength (E<8 GPa), lower cohesive strength and lower adhesion (<5J/m2) than low-K and SiO2 dielectric material. The packaging reliability test has shown that delamination between copper (Cu) and ULK is a major concern. In addition to the Cu and ULK delamination issue, the ULK die crack after temperature cycling test (TCT) showed die crack failure to be another issue. ULK die crack failure can be detected by C-mode scanning acoustic microscopy (CSAM). The CSAM image of the die crack mostly shows a crescent moon shape. The crack initiates at the upper edge of the underfill fillet penetrating the sidewall of the die, and then propagates toward the inside of the die. Finite element simulation indicates that the die crack failure starts at the backside edge of the die. The ULK die crack is caused by two mechanisms. First is the bending stress at the backside of the die, which is the result of the coefficient of thermal expansion (CTE) mismatch between the silicon die and the organic substrate. Second is the thermo-mechanical stress, which is the result of the local CTE mismatch between the silicon die and the underfill. The finite element simulation parametric study performed in this paper shows that a low underfill fillet height and a small fillet tip angle reduce the thermo-mechanical stress. In addition, attaching a heat sink to the surface of the flip-chip die increases packaging stiffness and resists the bending stress induced by the shrinkage of the substrate. Experimental results demonstrate that lowering the height of the underfill fillet, reducing the angle of the fillet tip and attaching a heat sink to the flip-chip die are effective ways to solve the ULK die crack issue. Springer Science+Business Media, LLC, 2010 Journal of Materials Science: Materials in Electronics Springer US; http://www.springer-ny.com 22/8(2011-08-01), 988-994 0957-4522 22:8<988 2011 22 10854 https://doi.org/10.1007/s10854-010-0248-y text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s10854-010-0248-y text/html Onlinezugriff via DOI NATIONALLICENCE 100 1- Chen K. United Microelectronics Corporation, No. 3, Li-Hsin Rd. II, 300, Hsinchu Science Park, ROC, Taiwan aut NATIONALLICENCE 773 0- Journal of Materials Science: Materials in Electronics Springer US; http://www.springer-ny.com 22/8(2011-08-01), 988-994 0957-4522 22:8<988 2011 22 10854 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer