AuSn (Gold-Tin) Solder

AuSn (Gold-Tin) Solder offers the following features:

High-Purity Gold
4N (99.99%) purity for reliable bonding performance

Ultra-Thin Plate
Minimum thickness of
10µm with advanced processing

Superior Bonding
Reduced oxide film for
enhanced adhesion

Sumitomo Metal Mining's AuSn (Gold-Tin) solder uses high-purity gold (Au, 4N: 99.99%) that is refined in-house. We manufacture each product entirely in-house—from melting and casting to high-precision press processing. Advanced rolling and high-precision press technologies enable ultra-fine processing, which achieves a minimum thickness of 10 µm and an outer diameter of less than 1 mm.
We can produce a range of shapes (including frames, washers, ribbons, balls, and plates) to meet customer requirements.

AuSn (Gold-Tin) solder is an alloy that is composed mainly of gold (Au) and tin (Sn). This alloy offers excellent thermal and electrical conductivity. Because of its high gold content, manufacturers use this solder as a bonding material for electronic components that require high reliability, such as crystal oscillators and optical communication devices. With a melting point of 280°C, AuSn solder is suited to high-temperature soldering and minimizes thermal impact on electronic components during bonding. Sumitomo Metal Mining has developed an S-type AuSn solder that offers superior wettability compared with conventional products. The S-type maintains excellent wettability even on thermally oxidized plated substrates, because of a proprietary process that reduces the oxide film thickness on the solder surface. This reduction improves yield during step soldering and helps prevent void formation.

AuSn (Gold-Tin) Solder Wettability Test

Our developed product, shown on the right, exhibits superior wetting spread while retaining its shape.

Sumitomo Metal Mining's AuSn (Gold-Tin) solder series.
If our standard lineup does not meet your requirements, please contact us for custom solutions.

For detailed product information and specifications, download the data sheets below.

AuSn (Gold-Tin) solder is used as a sealing and bonding material for crystal oscillators, communication devices, and semiconductor lasers. It also serves as an electrode material for LEDs and as mounting solder for electronic components.

What is the melting point of AuSn (Gold-Tin) solder?

A: The melting point of AuSn (Gold-Tin) solder is 280°C for the eutectic composition of Au-20 wt% Sn. For Au-22 wt% Sn, melting starts at 280°C and ends at 315°C.

What are the precautions for using AuSn (Gold-Tin) solder?

A: Depending on the components you use, gold plating can affect wetting. When you use gold-plated components, some of the surface gold diffuses into the AuSn solder as the solder melts.
This can raise the gold concentration in the solder, precipitate a high-melting-point phase, and prevent the solder from wetting properly.
For this reason, Au-22 wt% Sn is the recommended composition when you use gold-metallized components.

Can AuSn (Gold-Tin) solder be made into a wire?

A: We do not currently manufacture wire. However, we can supply ribbons with a width of 0.3 mm and a thickness of 15 µm.

Is AuSn (Gold-Tin) solder lead-free?

A: Yes. AuSn (Gold-Tin) solder is an alloy of gold (Au) and tin (Sn), making it an environmentally friendly, lead-free solder material.

Does AuSn (Gold-Tin) solder contain any substances restricted by the RoHS directive?

A: No. AuSn (Gold-Tin) solder does not contain any substances restricted under the RoHS directive.