Purpose – In land grid array hybrid or system in package type products passive integration on silicon dies are flip chip mounted on a laminate substrate using Pb‐free solder. To increase the solder bump fatigue life, underfill is applied. The application of underfill resulted in the occurrence of an unexpected and unwanted phenomenon: solder flowing out of the underfill during a second level reflow test. The occurrence of solder flow‐out seemed associated with moisturizing as part of a moisture sensitivity level assessment. The solder flow‐out is preceded by delamination, initiated by mismatch in coefficient of thermal expansion between copper through‐holes and laminate. This paper aims to describe the phenomenon and possible solutions by combining experiments with finite element (FE) simulations.Design/methodology/approach – Ways to prevent this kind of overstress failures are investigated by design of experiments and observed trends are compared with thermo‐mechanical FE simulations. A significant contr...
[1]
Sven Rzepka,et al.
Time-independent elastic-plastic behaviour of solder materials
,
2004,
Microelectron. Reliab..
[2]
W.D. van Driel,et al.
Influence of material combinations on delamination failures in a cavity-down TBGA package
,
2004,
IEEE Transactions on Components and Packaging Technologies.
[3]
H. Reichl,et al.
Stress analysis and design optimization of a wafer-level CSP by FEM simulations and experiments
,
2001,
2001 Proceedings. 51st Electronic Components and Technology Conference (Cat. No.01CH37220).
[4]
Ching-Ping Wong,et al.
Study on underfill/solder adhesion in flip-chip encapsulation
,
2002
.