Gold-tin eutectic (AuSn20), also known as gold-tin alloy, is to deposit the sub-gold and stannous ions in the plating solution according to the mass fraction of Au 80% and tin 20% on the position specified by the order through electrolysis. Au-Sn eutectic contains AuSn(δ) and Au5Sn(ζ) two phases of low-temperature eutectic noble metal solder, the thickness of which can be controlled according to the deposition time, and can be directly welded with the gold layer at 300℃ without flux.
Moderate brazing temperature
The brazing temperature is only 20-30°C higher than its melting point (ie, about 300-310°C). During the brazing process, based on the eutectic composition of the alloy, a small degree of superheat can melt and infiltrate the alloy; in addition, the solidification process of the alloy proceeds very quickly. Therefore, the use of gold-tin alloy can greatly shorten the whole brazing process cycle. The brazing temperature range of gold-tin alloys is suitable for component assembly that requires high stability. At the same time, these components can also withstand subsequent assembly using lead-free solder at relatively lower temperatures. The assembly temperature of these solders is around 260℃
High strength
The yield strength of gold-tin alloys is very high. Even at a temperature of 250 to 260 ° C, its strength can meet the requirements of air tightness.
No flux required
Gold accounts for a large proportion (80%) in the alloy composition, and the degree of oxidation on the surface of the material is low. The use of chemical fluxes is not necessary if a vacuum, or a reducing gas such as a mixture of nitrogen and hydrogen, is used in the brazing process.
Low viscosity
Liquid gold-tin alloys have very low viscosity, which allows them to fill some large voids.
Good wettability
It has a good corrosion phenomenon of lead-free tin solder on the gold-plated layer
The composition of the gold-tin alloy is close to that of the gold-plated layer, so the degree of infiltration of very thin layers by diffusion is very low, and there is no migration phenomenon like silver.
In addition, Au80%Sn20% solder also has high corrosion resistance, high creep resistance and good thermal and electrical conductivity.
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