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Eutectic Alloys

September 23, 2016

Eutectic brazing alloys are a distinct group of alloys that combine the bonding characteristics of the component metals with the superior flow properties of pure metals. Eutectic alloys melt and solidify at the same temperature. This instantaneous phase change from solid to liquid makes eutectic alloys free-flowing and ideal for a wide range of electrical, electronic and plumbing manufacturing applications.

Eutectic is defined as an isothermal reversible reaction in which a liquid solution is converted into two or more intimately mixed solids on cooling; the number of solids formed  being the same as the number of components in the system.

Phase diagrams are used to understand the various phase transformations that occur during the solidification process of a given alloy. The ratio of an alloy’s component metals determines the eutectic point, as illustrated below. For component metals A and B, the eutectic is the precise ratio at which instant liquidity or solidity is achieved. Any alteration of the ratio introduces a wider and longer metling range.

Not every alloy has a eutectic mix. While binary eutectic alloys are most widely used, eutectic alloys with three or four components, such as P&I Bi49-Pb18-Sn12-In21, are available.

Common Eutectic Brazing Alloys

Silver Braze 72a  1410 Submit RFQ
Silver Braze 72 1435 Submit RFQ
Gold Braze 8020TM 1635 Submit RFQ
Gold Braze 8218TM 1740 Submit RFQ
Pure Silver 1761 Submit RFQ
BCu-1 1981 Submit RFQ
BCu-1a 1981 Submit RFQ
BCu-2 1981 Submit RFQ
CDA 102 1981 Submit RFQ
CDA 110 1981  Submit RFQ

Common Eutectic Soldering Alloys

Au88/Ge12  673 Submit RFQ
Sn96.5/Ag3.5  430 Submit RFQ
Au80/Sn20  536 Submit RFQ
Sn99 450 Submit RFQ
Bi49/Pb18/Sn12/In21  136 Submit RFQ
Sn63/Pb37  361 Submit RFQ
In52/Sn48  244 Submit RFQ


Due to their free-flowing properties and excellent wettability, eutectic alloys are excellent for sealing long narrow joints and high-throughput joining processes such as electronic component housings, vacuum brazing of metallized ceramics to metals, or for processes that demand minimal presence of detrimental volatile impurities. Examples of eutectic alloy uses include:

  • Semiconductors: Bonding silicon chips to gold-plated substrates using Gold-Silicon brazes
  • Fire sprinklers: Wood’s Metal, a Bismuth-Lead-Tin-Cadmium alloy, melts in fire to activate water valves
  • Film metallization 
  • Industrial coatings
  • Crack repair
  • Filling blow holes
  • Dental solder
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