Introduction
Gold based alloys, particularly the eutectic 80Au 20Sn alloy, provide a variety of advantages that offset the cost of the gold. It can be used in many applications that require high reliability and high temperature, as well as a need for Pb-free.
Features of AuSn Solder
- Provides great joint strength
- Superior resistance to corrosion
- Superior thermal conductivity compared to standard solders
- Compatible with precious metals
- Pb-free
- High temperature (280°C)
- Excellent wetting properties
- Superior thermal fatigue resistance
Product Data Sheets
| Fluxless Soldering |
| Substrate Metallization Considerations for Soldering |
| Eutectic Gold/Tin Solder |
| Gold Tin - The Unique Eutectic Solder Alloy |
| Indalloy 182 Gold-Tin Solder Paste |
When to Use AuSn Solder
Thermal requirements often mandate a high-melting solder in die attach applications. With a melting temperature of 280°C, AuSn can satisfy this demand.
In high reliability applications such as microwave systems, medical and aerospace, AuSn has proven long-term reliability. It is also compatible with gold metallizations, unlike standard SnPb or SAC alloys where the tin will leach the gold, compromising the solder joint.
The eutectic AuSn also exhibits one of the highest tensile strength measurements in the soldering world. The 40,000 lbs per square inch provides a great alternative to brazing alloys when high strength must be achieved at soldering temperatures.
AuSn also provides an excellent seal which works well in lid sealing applications.
Gold based solders can be used without flux because of the metal’s resistance to oxides. However, reduction of oxides in the manufacturing process is key to producing a high quality solder that thoroughly wets the designated area.
Forms of AuSn
AuSn is a very versatile alloy and can be formed into solder wire (including very fine .025mm (.001”) wire), solder ribbon, solder paste, and various sizes and shapes of solder preforms.
Solder preforms in particular are made to exacting tolerances and to thicknesses down to .0127mm (.0005”) to allow for the placement of precise, repeatable solder volumes each time.
More information on the eutectic solder paste can be found on the data sheet: Eutectic Gold Tin Solder Paste, #98127.
| Physical Properties of Eutectic AuSn | |
|---|---|
| Composition | 80Au 20Sn |
| Melting Point | 280°C/536°F |
| Density | 14.51 grams/cm3 |
| Tensile Strength | 40,000 psi |
| Shear Strength | 40,000 psi |
| Coefficient of Thermal Expansion | 16 ppm/°C@20°C |
| Thermal Conductivity | 0.57 w/cm°C@85°C |
| Young’s Modulus | 8.57 x 106 psi |
For more information contact gold@indium.com.
