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38 SMT Magazine • January 2015 the first considerations is its physical properties. A comparison of some of the physical proper- ties of 1233zd(E) with CFC-113 and a few exist- ing solvents used today, are shown in Table 1, where Perc is used as an abbreviation for per- chloroethylene. One seeming disadvantage of 1233zd(E) is its slightly lower boiling point as compared to many of the current solvent used in the mar- ketplace. However, this sometimes turns out to be an advantage in certain applications because the cleaned parts will dry faster. Another advan- tage of 1233zd(E) is its high heat of vaporiza- tion, which does not vaporize very rapidly de- spite its low boiling point. So contrary to a per- ception that the solvent will readily evaporate at room temperature, it has been found that if one pours the solvent in a beaker at room tem- perature around 25°C, the solvent takes quite a while to evaporate. Because of its higher vapor pressure, 1233zd(E) requires special shipping and han- dling instructions that are different from many of the existing materials. It will be shipped in a pressure-rated drum or cylinder. It also requires some changes to some existing cleaning equip- ment, but it can be nearly a drop-in substitute in some low emission degreaser incorporating minor modifications. Besides being non-flammable, as evident by the lack of flash points, and no flame limits in air, 1233zd(E) also has a very low surface ten- sion. 1233zd(E) has a surface tension of 12.7 dynes/cm which is the lowest among solvents shown in the Table 1. It has a Kauri-Butanol value of 25, providing it with a balance of pen- etration ability (low surface tension, compared to water at 72.1 dynes/cm) and solvent power (Kauri-Butanol (KB) value, compared to CFC- 113 which has a KB value of 31) that makes it an excellent candidate to become the new en- vironmentally friendly workhorse of solvents. The low surface tension of 1233zd(E) helps to make this compound excellent for use in appli- cations where there is a need to penetrate nar- row spacings and thus would be able to clean under surface mounts. Environmental Properties In today's world of environmental aware- ness and preferences for environmentally safe products, it is very important to discuss envi- ronmental properties of new chemicals. A com- parison of 1233zd(E) environmental properties with that of several other solvents is provided in Table 2. Table 1: Selected physical properties of solvents. (hFCs and hFes are mostly used in blends with Tr-1,2- dicholoroethylene or other substances, so their values in this table are not representative of material used in practice.) an aLTErnaTIvE SOLvEnT WITH LOW GLOBaL WarMInG POTEnTIaL continues artiCle