Gold-
tin alloy is a kind of electronic welding, which has a good market and prospect. Gold-tin alloy uses gold-tin alloy solder in electronic applications. Gold-tin alloy is made by brazing technology, which is an important technology for assembling electronic products. In order to get the ideal brazing connection, the choice of brazing material is very important. The solderability, melting point, strength, Young's modulus, thermal expansion coefficient, thermal fatigue, creep and creep resistance of brazing materials can all affect the quality of brazing connections.
Eutectic gold 80% tin 20% brazing alloys (melting point 280°C) have been used in semiconductor and other industries for many years. Due to its excellent physical properties, gold-tin alloy has gradually become the best brazing material for optoelectronic device packaging. So what are the unique advantages and uses of gold-tin alloy solder?
1. Advantages and disadvantages of (gold-tin alloy) Au-Sn solder
Advantages of Au-Sn Solder
1. Moderate brazing temperature
The brazing temperature is only 20-30°C (ie about 300-310°C) higher than its melting point. During the brazing process, the alloy-based
Eutectic composition, the alloy can be melted and infiltrated with a small degree of superheat; the solidification process of the alloy is very fast. Therefore, the use of gold-tin alloy can greatly shorten the whole brazing process. 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 low temperatures. The assembly temperature of these solders is around 260°C. Eutectic gold-tin solder (Au80Sn20) offers a temperature operating range up to 200°C.
2. High strength
The yield strength of gold-tin alloy is very high, even at the temperature of 250 ~ 260 ℃, its strength is also capable of air tightness
requirements.
3. No flux required
Gold accounts for a large proportion (80%) in the alloy composition, and the oxidation degree of the material surface is low. If a vacuum or a reducing gas mixture such as nitrogen is used during the brazing process, there is no need to use chemical fluxes. This is one of the most compelling features and most important for electronics, especially optoelectronic device packaging.
4. Infiltration
It has good wettability and corrosion phenomenon of lead-free tin solder on the gold-plated layer. The gold-tin alloy is close to the composition of the gold-plated layer, so the degree of leaching of the thin layer by diffusion is very low, and there is no migration phenomenon like silver.
5. Low viscosity
The liquid gold-tin alloy has very low viscosity, which can fill some very large voids. Illiquid in most cases.
6. Au80%Sn20% solder has high corrosion resistance, high creep resistance, good thermal conductivity and electrical conductivity, and the thermal conductivity reaches 57 W/m·K.
7. Lead-free.
8. Form a temperature gradient with low-melting solder.
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