Overview
EN ISO 9455-10:2012 - "Soft soldering fluxes - Test methods - Part 10: Flux efficacy test, solder spread method" specifies a laboratory test to determine the efficacy of soft soldering fluxes. Known as the solder spread method, the test measures how well a flux promotes the spreading (wetting) of a molten filler metal on a prepared metal surface. The method is applicable to all flux classes defined in ISO 9454-1 and is standardized by CEN/ISO for consistent, repeatable results.
Key topics and requirements
- Scope and principle
- Measures flux performance by applying a fixed quantity of flux and a standard solder sample to a prepared brass test plate, immersing briefly in a solder bath, then measuring the spread area of the solidified solder.
- Test specimens
- Brass test plates (40 × 40 mm, CuZn37 or CuZn40, 0.5 mm thick) are specified; oxidized copper plates are allowed as an alternative.
- Solder wire straightened and cleaned, wound into a flat spiral; specific solder alloys and temperatures are listed (e.g., Sn60Pb40 at 235 °C ±3 °C, Sn96Ag3Cu1 at 255 °C ±3 °C).
- Apparatus and reagents
- Requirements include a solder bath (depth and temperature control), microsyringe/micropipette (25 µL), planimeter for area measurement, micrometer for height measurement, and cleaning/acid solutions.
- Procedure
- Detailed cleaning and surface preparation of plates (degrease, acid preparation solution cycles, rinsing).
- Application of measured flux (0.025 mL for liquids or 0.025 g for pastes/solids) and standard solder; immerse for a controlled time (spread measured after ~5 s of spreading and cooling).
- Result expression and precision
- Spread area measured (planimeter) or height measured (micrometer) and expressed as a spread ratio/percentage. The standard includes precision guidance and options for comparison with a reference flux.
Applications and users
- Who uses this standard
- Flux manufacturers and R&D teams evaluating product performance.
- Third‑party test laboratories performing quality control and acceptance testing.
- Soldering process engineers and quality assurance (QA) personnel in electronics manufacturing, HVAC/plumbing, and other industries that use soft soldering.
- Spec writers and procurement teams requiring an objective flux efficacy metric.
- Practical value
- Provides a repeatable, comparative measure of a flux’s wetting ability on brass/copper substrates - useful for product development, batch acceptance, and troubleshooting solderability issues.
Related standards
- ISO 9454-1 - Classification and requirements for soft soldering fluxes (flux classes referenced by this test).
- ISO 9455-16 - Alternative efficacy test for liquid fluxes using the wetting balance method.
- ISO 9453 - Chemical compositions and forms of soft solder alloys used in testing.
Keywords: EN ISO 9455-10:2012, soft soldering fluxes, flux efficacy test, solder spread method, brass test plates, solderability testing, wetting balance method, ISO 9454-1.
