S1XBIG Alloy and SAC305: Difference is “Low-cost” and “High reliability”

In conventional low-Ag solder alloys, reducing Ag content often results in compromised joint reliability.
However, The S1XBIG58-HF1200B overcomes this trade-off.
Through the optimized addition of Bi and Ni—each providing distinct metallurgical benefits—The S1XBIG58-HF1200B achieves joint strength comparable to SAC305 while maintaining excellent reliability.

At the same time, its lower Ag content helps manufacturers minimize solder paste cost fluctuations driven by rising Ag prices, enabling a more stable and cost-efficient production strategy.

2 Approaches to Achieve Superior Durability

Precipitation Strengthening: Nickel (Ni)
Fine intermetallic compounds with high melting points precipitate within the Sn crystal lattice to prevent dislocations from propagating beyond the grain boundaries.

Solid Solution Strengthening: Bismuth (Bi)
Atomic level strengthening by scattering of elements which have significantly larger atomic diameter in the Sn phase to generate strains in the crystalline lattice to prevent dislocation propagation.

Outperforms SAC305 in Thermal Cycle Resistance and Joint Strength

The strengthening elements suppress microstructural changes in the solder joint and intermetallic compound (IMC) growth during thermal cycling.
Compared to SAC305, The S1XBIG58-HF1200B exhibits less strength degradation after thermal cycling and maintains high solder joint reliability.

■Shear strength and thermal cycle testing（-30/+80℃）

Compatible with the Same Reflow Profile as SAC305

By preventing the typical drawback of low-Ag solder alloys—namely an increase in melting temperature—the S1XBIG58-HF1200B can be reflowed under the same peak temperature conditions as SAC305, while offering lower material costs.

■DSC chart

Struggling with Voiding or Wettability?

With advancements in PCB and component quality and performance in SMT industry, the demands on solder materials have also increased.

In response to the industry’s growing need to address voiding and wettability challenges, we have newly developed a unique product featuring two groundbreaking technologies, the ‘2-Step Flux Gas Discharge Effect’ and ‘2-Step Activation Boost Effect’ delivering unprecedented level of assembly quality!

What is “the Dual 2-step Technology”? – S3X58-HF1200

Low-void Solder Joins regardless of the Component Type and Size

Flux gas release feature reduces void occurrence in a void prone components, such as components with electrode on the bottom.
Same stable soldering results can be obtained regardless of the component size or the type of PCB pad surface finish.

■Void condition

Addresses Various Surface Mounting Challenges

The performance required in a soldering material for surface mount assembled products has become higher in terms of quality and function.
The flux used in S1XBIG58-HF1200B is unique with KOKI selecting a flux which fulfills versatile requirements using a newly introduced core technology.

HF1200 is available in following variations.

The HF1200 series

・S3X58-HF1200　　　　Multi-feature Halogen-free Solder Paste (SAC305 / Type 4)
・S3X70-HF1200　　　　Multi-feature Halogen-free Solder Paste for fine-pitch printing (SAC305 / Type 5)
・S01XBIG58-HF1200B　 Ultra Cost-effective, High-reliability Low Ag Lead Free Solder Paste (0.1Ag / Type 4)

“Halogen-Free” – Addressing Environmental Requirements

One key aspect of environmental measures is “halogen-free”; today, many companies require final products to be halogen-free.
The halogen-free S1XBIG58-HF1200B meets these requirements while providing both reliability and workability.