Au/Sn Eutectic Material Properties

• The gold/tin eutectic material has a melting temperature of 284 degrees Celsius (543 degrees Fahrenheit) and a density of 14.5g/cm3. The material is known for its excellent thermal conductivity, which makes it the solder of choice for several applications. The thermal conductivity value is 57.0 W/mk, which is very high. The electric conductivity is also excellent, with a value of 7.7 percent IACS. The bonds formed by the gold/tin 80/20 solder are very strong due to the high tensile strength of this material at 276 MPa. Other properties of this eutectic material include a temperature coefficient of expansion of 16.0 m/mK and resistivity of 160 n ohm m.
  
  

Integrated Au/Sn (80/20) Eutectic Solder

• The integrated gold/tin 80/20 eutectic solder has a thickness range of 80 -- 200 µ″ with the most common thickness being 160 µ″. When eutectic pad is inboard of conductor, the solder pad pullback from gold metallization is .0015″. The gold metallization pullback from the substrate edge is .002″ even though termination at the edge is available from some manufacturers. The eutectic solder also has a minimum feature size of .005″ and a minimum substrate thickness of the same size and no solder pad placement.
  
  

Spluttered Material

• Gold/tin eutectic solder is a spluttered material, which gives the user superior flatness and thickness control. The sizing of gold/tin pads during manufacture is very important, and the manufacturers usually ask their customers to specify what they want according to die size and tolerance. There are also pre-deposited and patterned gold/tin solders that are very cost- effective in eliminating pre-forms when used on designs with multiple solder hierarchy or multiple perform sites.
  
  

Other Properties

• The gold/tin 80/20 solder alloy is used in integrated circuit chip or die bonding. This is due to characteristics such as high bond strength, adhesion and good thermal conductivity. The material also has low stress, corrosion resistance to creep and does not form whiskers when used. It reflows at 280 degrees Celsius (536 degrees Fahrenheit) and exhibits good wettability.