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Solder Paste – Alloys

Much to the surprise of the SnPb and SAC alloy consuming world, there are a number of alloys available in solder paste, each with their own unique melting points and soldering and mechanical properties. Below is a table containing some of the alloys possible in solder paste (not exhaustive).

 

Alloy Composition

Melting Temperature (Solidus/Liquidus)

46Bi 34Sn 20Pb

96C (Eutectic)

52In 48Sn

118C (Eutectic)

58Bi 42Sn

138C (Eutectic)

57Bi 42Sn 1Ag

139C/140C

97In 3 Ag

143C (Eutectic)

80In 15Pb 5Ag

149C/154C

100In

157 (Melting Point)

43Pb 43Sn 14Bi

144C/163C

70In 30Pb

165C/175C

62Sn 36Pb 2Ag

179C

60In 40Pb

173C/181C

63Sn 37Pb

183C (Eutectic)

50In 50Pb

184C/210C

Sn Ag Cu (SAC alloys)

217C/220C

96.5Sn 3.5Ag

221C (Eutectic)

95Sn 5Sb

235C/240C

80Au 20Sn

280C (Eutectic)

88Pb 10Sn 2Ag

267C/299C

92.5Pb 5Sn 2.5Ag

287C/296C

92.5Pb 5In 2.5Ag

300C/310C

95Pb 5Sn

308C/312C

 

None of these individual metals are found pure on the planet. They have to be mined, refined and then alloyed to the proper proportion with the other metals to create these solder alloys. Oftentimes a wet chemical technique is required after alloying to validate that the alloy meets the allowable tolerances and purities spelled out in J-STD-006 or a customer specific specification.