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Gold/Mining/Energy : Silver prices

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To: TheBusDriver who wrote (3196)	12/20/2000 9:37:55 AM
From: long-gone	Read Replies (1) of 8010

Home Alloys Solder Alloys and the Industries They Serve ALLOY MELTING RANGE (°C) INDUSTRY SERVED SnAg 221 -226 Automotive SnAgBi 206 - 213 Military/Aerospace Consumer SnAgBiCu - Military/Aerospace SnAgBiCuGe - Consumer SnAgBiX 206 - 213 Consumer SnAgCu 217 Automotive Telecommunications SnBi 138 Consumer SnCu 227 Consumer Telecommunications SnZn 198.5 Consumer -------------------------------------------------------------------------------- Some Industry Organizations and the Alloys They're Investigating ORGANIZATION ALLOY NEMI SnCu0.7 SnAg3.5 SnAgCu NCMS SnAg3.5 SnBi58 SnAg3.2Bi2.0 CASTIN SnAg3.4Bi4.8 SnIn20Ag2.8 (Indalloy) SnAg3.5Cu0.5Zn1.0 ITRI SnAgCu SnAg2.5Cu0.8Sb0.5 SnCu0.7 SnAg3.5 SnBiAg SnBiZn -------------------------------------------------------------------------------- Alloy Material Cost, As Compared to Eutectic Tin-Lead Solder ALLOY PRICE MULTIPLIER REFERENCED TO TIN-LEAD* USE SnAgCu 2.2 to 2.7 Considered a benchmark SnCu 1.5 Low-cost alternative for wave soldering SnAgBi 2.2 to 2.7 Possible Pb replacement (especially for SMT). Bi concern for SnPb finish boards. Avoid any Pb! SnZn 2.2 to 2.7 Concerns with corrosion resistance. Requires special fluxes. No long-term reliability data available. SnAg 2.2 to 2.7 Extensive data *NOTE: Price is compared to SnPb at current metals market price. -------------------------------------------------------------------------------- Lead-Free Solder Alloys Potential alloys with high percentage of tin: +silver (Ag) 0.1 to 5.0% +bismuth (Bi) 1.0 to 5.0% +antimony (Sb) 0.2 to 5.0% +copper (Cu) 0.2 to 2.0% +zinc (Zn) 0.5 to 9.0% +indium (In) 0.5 to 20.0% +magnesium (Mg) 0.5 to 2.0% -------------------------------------------------------------------------------- Common Alloys Being Used or Evaluated to Replace Lead & Their Melting Points Sn96.5Ag3.5 (221 C) Sn95Sb5 (232-240 C) Sn95.5Ag3.8Ci0.7 (~217 C) Sn95.8Ag3.5Cu0.7 (~217 C) NIST Alloy Sn99.3Cu0.7 (227 C) Sn96.2Ag2.5Cu0.8Sb0.5 (213-218 C) Sn97Cu2.0Sb0.8Ag0.2 (226-228 C) Sn91.8Ag3.4Bi4.8 (202-215 C) Sn42Bi58 (138 C) -------------------------------------------------------------------------------- Physical Properties of Lead-Free Alloys: I High tin content alloys like Sn90+: + Typically have much higher melting points than traditional Sn63Pb37 + Are stronger and less ductile than lead or Indium-bearing alloys + Typically exhibit poor wetting when compared to Sn63Pb37 Moderate bismuth content alloys: + Typically have lower melting points than Sn63Pb37 + Typically are very brittle + Wetting and joint appearance is relatively poor Physical Properties of Lead-Free Alloys: II Effect of certain elements such as copper on high tin content solder: (as in Sn95.5Ag3.8Cu0.7): + Retards the dissolution rate of copper. + Can improve the wettability. + Can improve the thermo-mechanical properties of solder joints. + Reduces the melting point slightly. Indium-bearing solders compare favorably to lead-bearing solders. Both are ductile materials. Typically, indium-bearing solders (e.g., Sn48In52) tend to be slightly expensive compared to other alternatives. Indium-bearing solders are often used when soldering to gold substrates. Note that where Sn-Au intermetallics are brittle, Au-In intermetallics are relatively thin and much more tolerant of thermal cycling. Bi-containing Alloys Fatigue life is reduced when soldered to hot air solder leveled (HASL) boards. Lead from Hot Air Leveling (HAL) coatings can diffuse through the grain boundaries of alloy. This lead can form a eutectic composition of Bi52Pb32Sn16 in the grain boundaries. The melting point of the eutectic alloy is 95 °C. The overall result is a large decrease in the strength of the joint. Fillet lifting of PTHs due to pasty range (206-213 °C) Avoid any Pb!! The Effect of Lead on Sn42Bi58 Lead from hot air leveling (HAL) coatings can diffuse through the grain boundaries of the alloy. This lead can form a eutectic composition of Bi52Pb32Sn16 in the grain boundaries. The melting point of the eutectic alloy is 95 °C. The overall result is a large decrease in the strength of the joint. In-containing Alloys In reduces the melting temperature of an alloy In alloys offer good strength and physical properties In very expensive and in short supply Also forms a ternary compound with SnPb finishes that has a phase change at 114°C. kester.com

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