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60 SMT Magazine • November 2014 offer benefits purely based on single element addition with respect to creep resistance. This, however, is offset by the synergistic effect of Ni in conjunction with Bi further improving the alloy performance by precipitation hard- ening (i.e., formation of Ni-Bi intermetallic compounds). The optimisation process needed to ensure that the final alloy composition ex- hibited the desired thermal cycle resistance at the target temperature of 150°C without com- promising the suitability of the alloy for use in standard soldering processes (excessive eleva- tion of melting point). Figure 4 presents the re- lationship between alloy composition, solder- ing temperature and creep resistance. Confirmation of the physical properties of the novel senary element alloy as a direct com- parison to standard SAC387 and SnPb alloys is shown in Figure 5. The creep resistance of the new high-reliability alloy at ~150°C is equiva- lent to that of SnPb at 80°C as defined by s k (creep stress as a function of temperature). alloy testing Extensive testing of the alloy for reliability using a range of test vehicles and conditions de- signed to promote alloy failure (thermal cycling, thermal shock, vibration, drop testing etc.) has been widely reported elsewhere [6] . This paper highlights particular data presented as part of the LIVE collaborative project where the new alloy not only gave significant improvements over both standards (SAC and SnPb), but the results also highlighted the phenomena of the relative reliability of SnPb versus SAC alloys in- terchanging depending on the test conditions. Figure 6 details the failure rate (50% failure) ver- sus delta T on two different passive devices. It is evident that the six-part alloy shows increased reliability over the reference alloys, the SAC al- loys shows increased reliability under low cycle thermal shock with SnPb giving improvements when exposed to high cycle thermal shock test- ing. The point of intersection between the reli- ability data of the SnPb and SAC alloys (delta T at which failure rate is equal) occurs at 140°C and 90°C for 1206 and 2512 components, re- spectively. Flux Development Flux formulations underpin the entire per- formance of the solder material, the organic HigH-reLiabiLity, Pb-Free, HaLogen-Free soLDer continues arTiCle Figure 4: Solder temperature and creep resistance as a function of alloy composition.