High reliability, low voiding: the Indium Durafuse® HR Advantage
As electronics operate at higher power and under more demanding conditions, solder-joint reliability is increasingly critical. Automotive electronics, high-performance computing, and 5G infrastructure require solder materials capable of extended thermal cycling beyond traditional SAC alloys. At the same time, high-reliability alloys can present challenges such as increased voiding, particularly in bottom-terminated components (BTCs).
Durafuse® HR was developed to help address both challenges. Its mixed-alloy technology combines low-voiding and high-reliability alloy constituents during reflow to support solderability and produce a robust, high-reliability solder joint.
Lower voiding than SAC305
A study compared SAC305 with Durafuse® HR using QFN68 assemblies on an industry-standard Jabil test board. Under a traditional SAC305 reflow profile, Durafuse® HR demonstrated lower average overall voiding than SAC305:
• Fresh Cu-OSP boards: 16.7% with Durafuse® HR vs. 19.3% with SAC305
• Pre-baked Cu-OSP boards: 18.2% with Durafuse® HR vs. 22.5% with SAC305
• Modified ramp profile: 16.1% with Durafuse® HR vs. 21.7% with SAC305
Under the modified ramp profile, Durafuse® HR also reduced the average largest single void
to 1.9%, compared with 3.1% for SAC305.
Optimized processing drives voiding even lower
Further reflow optimization demonstrated the potential for even lower voiding with Durafuse® HR.
Three profiles with peak temperatures of approximately 249°C–256°C produced average overall voiding of about 13% or less.
The best-performing condition achieved 12.5% average overall voiding and an average largest single void of 1.7%, meeting the study target of less than 15% average overall voiding.
These results highlight the importance of optimizing the entire soldering process including reflow conditions, flux chemistry, and surface finish to maximize performance.
A flexible platform for low voiding and high reliability
The study demonstrates that Durafuse® HR can combine extended thermal-cycling performance with low voiding. Under optimized process conditions, Durafuse® HR achieved average overall voiding as low as 12.5%.
Voiding performance depends on the interaction of alloy technology, flux chemistry, surface finish, and reflow conditions. Durafuse® HR can also be paired with other suitable flux vehicles to optimize low-voiding performance for specific applications and process requirements.
For demanding automotive, computing, telecommunications, and other high-reliability applications, Durafuse® HR provides a flexible mixed-alloy platform. It enables manufacturers to balance solder-joint reliability, process compatibility, and low-voiding performance.
Following the success demonstrated in this study, ongoing work is evaluating Durafuse® HR under standard reflow profiles and with additional surface finishes. This work aims to expand low-voiding process options across a broader range of applications.
This article summarizes findings from the Indium Corporation technical study“Enhancing PCB Reliability: Voiding Reduction with a Mixed-Alloy Solder Paste,” authored by Thuy Nguyen and presented at APEX 2025. Commercial product names have been used to connect the experimental materials described in the study with their corresponding Indium Corporation technologies.