Indium Blog

Back to Basics: Au-Based Alloys

In history, “The Gold Standard” was a monetary system in which countries fixed their currencies to a specified amount of gold. Here at Indium, we also use the phrase, however, to reference something a little different. To us, “The Gold Standard” refers to the overall reliability and quality you can expect from our gold-based solder materials. Gold-based alloys offer strong solder joints, excellent corrosion and oxidation resistance, and good thermal and electrical transfer. The most common applications that often require the use of a gold-based solder alloy include die-attach and hermetic sealing in the medical, aerospace, optoelectronics, RF infrastructure, and automotive industries.  

So why are gold-based solder alloys so sought after for these applications? This can be answered by gold’s superior physical, mechanical, electrical, and thermal properties. Gold-based alloys are generally labeled as ‘high-temp,’ and their higher melting points allow them to withstand extreme temperatures and environments while maintaining their strength and stability. In addition to meeting the thermal requirements these applications often require, gold-based solder materials also deliver the highest tensile strength of any solder, are Pb-free and RoHS compliant, have superior thermal fatigue resistance, and possess excellent wetting properties.

With all the wonderful properties gold-based solder materials can deliver, why does it seem like they are reserved for such specific applications? It is no secret that gold is a precious metal, and as such, would have a higher cost associated with it. Gold is not a rare metal by any means, but it is difficult to find, mine, extract, and purify. The high cost of production associated with gold is what makes it more expensive than other metals that have lower manufacturing costs, such as aluminum or copper. While using gold would most likely incur a higher price, the benefits and longevity of the material generally levels out the cost over time. For less vulnerable or more short-term use devices the cost/reliability trade-off may not be worthwhile, in which case, lower-cost solders are more likely to be used.

A leading gold solder innovator, Indium’s gold-based portfolio includes wire, paste, preforms, spheres, shot, and ribbon manufactured with cutting-edge technology to ensure supreme quality and the utmost precision. The most commonly used gold-based alloy is 80Au20Sn: the pillar alloy of the microelectronics industry with a melting point of 280°C, 80Au20Sn works great in the majority of die-attach and lid sealing applications. However, our gold-based alloy library includes many others suitable for any application at hand, such as 88Au12Ge, 96.8Au3.2Si, 82Au18In, and 100Au. For all of our high-temp based alloys, including silver-based alloys, click here.