Title :
Effect of underfill on BGA reliability
Author :
Pyland, James ; Pucha, Raghuram ; Sitaraman, Suresh
Author_Institution :
George W. Woodruff Sch. of Mech. Eng., Georgia Inst. of Technol., Atlanta, GA, USA
Abstract :
The effect of underfill on various thermomechanical reliability issues in SBGA (super ball grid array) packages is studied in this paper. Nonlinear finite element models with underfill and no underfill have been developed, taking into consideration the process-induced residual stresses. In this study, the solder is modeled as time and temperature-dependent, while other materials are modeled temperature and direction-dependent, as appropriate. The stress/strain variations in solder joints due to thermal cycling are analyzed. The effect of underfill is studied with respect to magnitude and location of time-independent plastic strain, time-dependent creep strain and total inelastic strain in solder balls. The possibility of delamination at the interposer-underfill interface as well as board-underfill interface is studied with the help of qualitative interfacial stress analysis. Results on SBGA packages indicate that the underfill does not always enhance the BGA and that the properties of the underfill have a significant role in the overall reliability of the BGA solder balls
Keywords :
ball grid arrays; creep; delamination; encapsulation; finite element analysis; integrated circuit interconnections; integrated circuit modelling; integrated circuit packaging; integrated circuit reliability; internal stresses; microassembling; plastic deformation; soldering; stress analysis; stress-strain relations; thermal stresses; BGA reliability; BGA solder balls; SBGA packages; board-underfill interface; delamination; interposer-underfill interface; material temperature/direction-dependent models; nonlinear finite element models; process-induced residual stresses; qualitative interfacial stress analysis; reliability; solder balls; solder joints; solder time/temperature-dependent model; stress/strain variations; super ball grid array packages; thermal cycling; thermomechanical reliability; time-dependent creep strain; time-independent plastic strain; total inelastic strain; underfill; Capacitive sensors; Creep; Electronics packaging; Finite element methods; Plastics; Residual stresses; Soldering; Temperature; Thermal stresses; Thermomechanical processes;
Conference_Titel :
Advanced Packaging Materials: Processes, Properties and Interfaces, 2001. Proceedings. International Symposium on
Conference_Location :
Braselton, GA
Print_ISBN :
0-930815-64-5
DOI :
10.1109/ISAOM.2001.916601
