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February 2014 • SMT Magazine 39 TeSTING INTerMeTaLLIC FraGILITy ON eNIG uPON aDDITION OF LIMITLeSS Cu continues FEATUrE Peak load to failure and failure mode in HBP testing was nearly identical for all solder and ball attach variations. The HBP testing method developed for this research has mitigated the in- termetallic morphology variability during ball attach and alloy selection as shown in Figure 16. Ultimately all solder joints failed in a brittle failure mode with similar fracture morphologies as shown in Figure 16 and Figure 17. Inspection of the fracture surfaces revealed that fractures Figure 15: hbP brittle failure mode example. Figure 17: hbP Short profile fracture morphology comparison to Intel 845. Figure 18: hbP long profile fracture morphology comparison to Intel 845. Figure 16: hbP test results between all alloy and pro- cess variations. Figure 14: 10,000x SEM inspection of hbP intermetallic morphologies for Intel and long ball attach profiles (A) Intel 845, (b) SnPb, (C) SnAg, (D) SAC304. a b C D