CASTIN(patent right):96.2%Tin,2.5%Silver,0.8%copper,0.5%antimony. LF218:96.5%Tin,3%Silver,0.5%copper. Why is there a push for lead-free solders in electronics soldering applications? The health and liability risks associated with the use of lead have led to government regulations concerning the elimination of lead from certain manufacturing processes. Lead already has been banned from paint, plumbing, and gasoline. Solder is likely to be regulated in the near future as well. Why should some lead-free alloys be approached cautiously? The compositions and traits of lead-free solder alloys vary greatly. However, some alloys should be approached cautiously: *Tin migration during high temperature thermocycling is often associated with tin-silver alloys. *Alloys with a high percentage of exotic or expensive metals may be cost prohibitive. *Very high melting temperatures, which may damage parts, exist with some tin-silver and tin-copper alloys. *The inevitable damage or destruction of parts during repair, such as with conductive adhesives, is something to be wary of. Are lead-free alloys as durable as tin-lead alloys? Many of the available lead-free alloys offer significant durability advantages over tin-lead alloys. Benefits such as higher joint strength, better fatigue resistance, improved high temperature life, and harder solder joints are common to some of these alloys. However, these benefits vary greatly among the various lead-free alloys, and research is required in order to choose the correct alloy. How do lead-free alloys compare to tin-lead alloys for application temperature requirements? Typically, lead-free alloys have higher melting points than tin-lead alloys. These range from 215C to 240C. It is very important to consider the melting point while choosing a lead-free alloy, as many components and materials cannot withstand the very high reflow peak temperatures (upwards of 260C) of some tin-silver and tin-copper alloys. Are lead-free alloys compatible with all flux types? In general, lead-free alloys may be used with most flux chemistries. Again, however, these alloys vary greatly, and compatibility with solder paste, cored wire solder, and liquid flux chemistry is dependent upon the melting point and composition of the alloy. In what solder forms can lead-free alloys be produced? Most lead-free alloys are available in all solder forms, including solder paste, cored wire solder, solid wire, bar solder, spheres and preforms. Exceptions to this are alloys that contain a high amount of indium or bismuth, which cannot be produced as cored wire solder due to manufacturing issues. What are the attributes that one should look for while searching for a lead-free solder alloy? Lead-free solder alloys should possess the following characteristics: No current or future negative environmental impact Low cost Melting temperature similar to Sn63/Pb37 Easily repaired Compatibility with existing parts and processes No toxic or exotic consitituents What does AIM recommend for a lead-free alloy? AIM¡¦s patented lead-free alloy, CASTIN has proven to be an excellent alternative to lead-bearing alloys.CASTIN is a tin-silver-copper alloy that has the lowest cost of all acceptable lead-free solder alloys. CASTIN?has a low melting temperature (215-217C)for a lead-free solder, does not contain exotic or toxic metals, is not prone to oxidation or corrosion, has low alpha emissions, and is acceptable for landfill disposal. In addition, unlike tin-silver alloys, CASTIN will not suffer from tin migration during high temperature thermocycling. Is CASTIN as durable an alloy as tin-lead and other lead-free alloys? CASTIN has proven to be equal or superior to tin-lead and other popular lead-free alloys, such as tin-silver, tin-copper, and tin-silver-copper in the following categories: Joint Strength Fatigue Resistance High Temperature Life Hardness of Solder Joints Ultimate Tensile Strength Yield Strength Percent Elongation Adaptability to Stress Thermal Fatigue Properties Intermetallic Growth Rates Thermal and Electrical Conductivity Wetting to gold, HASL, copper & lead How does CASTIN?compare to tin-lead alloys for application temperature requirements? One of the advantages of CASTIN is that it is a near drop-in for tin-lead solder applications: Wave Soldering- same pot temperature: 250C - 260C SMT- slightly higher peak temperature: 235C vs. 220C Hand Soldering- same to slightly higher tip temperature: 750C vs. 650C - 750C The temperature requirements of an alloy are very important, as many components cannot withstand the very high peak temperatures (upwards of 260C)required by some tin-silver and tin-copper alloys. Is CASTIN compatible with all flux types? CASTIN may be used with all flux chemistries, including AIM¡¦s popular line of no clean ,water-soluble and RMA fluxes. In what solder forms can CASTIN be produced? CASTIN is available in solder paste, cored wire solder, bar solder, spheres and preforms. How does the price of CASTIN compare to tin-lead alloys and other lead-free alloys? As lead is one of the least expensive elements on earth, replacing it with any other metal in a solder alloy will result in a price increase. CASTIN is no exception to this. However, it is important to note that CASTIN is the least expensive of any of the tin-silver-copper alloys. Furthermore, CASTIN is less expensive than Sn/Ag alloys. The result of this lower cost is substantial savings for bar solder and wire solder, and a reduction in the cost of solder paste. How reliable are solder joints made with CASTIN? That is a difficult question to answer, because there is such a wide variety of electronics assemblies and applications. However, all "real world" and laboratory experiments conducted thus far demonstrate that CASTIN is a very durable alloy. Products assembled with CASTIN over five years ago are still working today with zero degradation to performance or reliability. In laboratory testing, CASTIN has proven equal or superior to tin-lead and other popular lead-free alloys, such as tin-silver, tin-copper, and other tin-silver-copper alloys, in the following categories: Joint Strength Fatigue Resistance Yield Strength High Temperature Life Solder Joints Hardness Intermetallic Growth Rates Ultimate Tensile Strength Percent Elongation Adaptability to Stress Thermal Fatigue Properties Thermal and Electrical Conductivity Are any OEMs or EMSs currently using CASTIN? Yes. Despite the fact that lead-free solders are not yet mandated by law, CASTIN already has been used across the electronics industry in a variety of applications. Furthermore, many independent organizations have performed extensive testing with CASTIN?and have had excellent results. As of today, some of the users of CASTIN have been a top-ten EMS, a leading global telecommunications company, and one of the largest automotive manufacturers in the world. This is in addition to several small- to mid-size companies using and experimenting with CASTIN. Is CASTIN compatible with no clean flux chemistries? Yes. Many users of fluxes and solder pastes have (justifiably) wondered if they will have to switch chemistries when they switch to a lead-free process. The answer is: It depends. If you switch to a high melting point alloy such as tin-silver or tin-copper, then it is likely that a change will have to be made. However, with lower melting point lead-free alloys, such as CASTIN? it is much more likely that you can continue to use the same flux chemistry, including no clean chemistries. CASTIN?has proven to work well with AIM's no clean solder paste and flux chemistries without resulting in charred residues, dewetting, cleaning difficulties, etc. Is nitrogen required to process CASTIN through a reflow oven or wave solder machine? No. A great deal of tests have been performed with CASTIN.which demonstrate acceptable wetting when processed in air. However, as with tin-lead alloys, the use of nitrogen may be useful in certain applications depending on the parts and chemistry being used. With which printed circuit board and lead finishes is CASTIN?compatible? CASTIN? is compatible with all of the currently available surface finishes. CASTIN?has been tested with HASL, gold over nickel, silver, palladium, pure tin, OSP, and bare copper finishes and has proven to work well with each of these. Of course, as with tin-lead alloys, the solderability and processing characteristics of these finishes varies greatly when using a lead-free alloy. Does CASTIN contain any toxic elements? No. CASTIN?is a ternary tin-silver-copper (SnAgCu) alloy with a dopant of 0.5% antimony. Antimony was used as an additive in CASTIN. because of its melting temperature reduction, grain-refining, and thermal fatigue resistance-improving characteristics. For a variety of reasons, antimony is a very misunderstood element. However, antimony in an alloyed form is safe to be used in soldering and recycling applications. In fact, 3rd party data indicates that antimony is no more "toxic", often is far less-stringently regulated, and is classified as less of a health threat than many of the "safe" elements that comprise the majority of lead-free solders, including silver, copper, zinc, and various compounds of tin. For additional information, please request a copy of "A Study of Antimony" from AIM. What is the refrigerated shelf-life of CASTIN solder paste? The same as AIM's tin-lead solder pastes: one year for no clean pastes, three to six months for water soluble pastes. It is of interest to note that some alloys, such as tin-zinc, offer greatly reduced shelf-lives due to corrosion and oxidation issue (less than one week!). How does CASTIN compare to conductive adhesives? Although they appear intriguing, there are several drawbacks associated with conductive adhesives. In general, conductive adhesives do not self-correct, generally have poor shock resistance, contain costly silver flake, cannot be reworked without damaging the component and/or PCB, are not nearly as electrically conductive as solders. What happens if a CASTIN solder interconnect is exposed to lead? This is a critical issue to resolve before the implementation of a lead-free alloy, as during the transition period to lead-free solders it is very likely that lead-bearing component leads and board coating will still be prevalent. In fact, these may be used for years to come. In addition, there is the risk that a lead-bearing solder will be used if an assembly is repaired after it is in the field. CASTIN has been tested with 0.5% lead contamination (this has been determined to be a realistic amount of lead exposed from Sn/Pb coated leads and boards to solder joints), with no degradation to its thermal or mechanical properties. Therefore, CASTIN is considered "safe" to be used with lead-free or lead-bearing parts. This is in direct contrast to bismuth containing alloys, because if these are exposed to lead, then a secondary eutectic at 96C will be formed. This result of this is a substantial reduction in the thermal fatigue resistance of the interconnect. What tip temperature is required hand soldering with CASTIN? A variety of solder iron manufacturers and EMSs have tested CASTIN in hand soldering applications and have concluded that CASTIN?is a drop-in for tin-lead alloys. In general, a tip temperature of 600 to 700 C is sufficient to hand solder with the CASTIN alloy. This low tip temperature ensures that the components being hand soldered today with tin-lead may be safely hand soldered with CASTIN. Furthermore, these drop-in temperatures ensure that the same cored wire flux chemistries currently used with tin-lead cored wires may be used with CASTIN cored wire. Is CASTIN?available in spheres for BGA and CSP applications? Yes. CASTIN is available in all solder forms, including solder paste, bar solder, cored and solid wire, preforms, and spheres.