Study flags “no-clean” flux as TOPCon corrosion risk under damp heat

• UNSW research links “no-clean” solder flux residues to contact corrosion and efficiency loss in TOPCon cells under damp-heat, with guidance for manufacturers.

Researchers at the University of New South Wales found that residues from certain “no-clean” soldering fluxes can trigger severe corrosion in the silver-aluminum front contacts of TOPCon cells during damp-heat (85°C/85% RH) testing—raising series resistance and eroding efficiency. Fluxes with halogens proved especially corrosive; denser metallization and lower aluminum content improved resilience.

The team recommends unencapsulated, cell-level DH screening to catch flux-related issues early and selecting formulations with minimal halogens and optimized acid content. Rear-side Ag pastes showed far less degradation, underscoring the chemistry-dependent nature of the failure mode.

Why it matters: As TOPCon has become the mainstream n-type architecture, module-assembly details like flux choice can make or break long-term reliability—and warranty claims. The results add to a growing body of evidence connecting interconnection chemistry to performance drift in both TOPCon and HJT devices.

For manufacturers, the near-term action items are straightforward: revisit approved flux lists, intensify incoming QC, and incorporate rapid DH checks before full-line runs. For buyers, ask suppliers for flux specifications and reliability data specific to your BOM—not just generic certifications.