Abstract:

This paper reports preliminary finite element analysis (FEA) simulations conducted to support a study on durability risk in BGA assemblies due to sequential combination of temperature cycling (TC) and harmonic vibration loading. Experimental results, presented in a companion paper, showed that the resulting damage modes are a combination of two damage modes: (i) solder-IMC interfacial fracture and (ii) copper trace fatigue. Printed Wiring Assemblies (PWAs) with a BGA416 package and daisy-chained copper traces along one package edge, were designed, fabricated and tested under sequential combined loading. Copper trace width was varied to quantify how the degradation risk scaled with trace width. Copper trace failures were restricted to the vibration segments of the test matrix and did not occur during TC. Sequential combination of vibration and TC loading was seen to increase the damage accumulation in copper traces, compared to individual application of either vibration or TC. Consequently, the FEA simulations focus here on the vibration response. The experimental results are first briefly summarized in this paper for completeness and the methodology for dynamic FEA of the tested BGA416 PWA are presented. The FEA approach uses a multiscale global-local approach, to quantify the stresses and strains in the copper trace near the observed failure site. Preliminary model calibration efforts are presented and future work is discussed.

This article is available online here and to CALCE Consortium Members for personal review.