Overview
ISO 9455-10:2012 specifies a laboratory method to determine the efficacy of soft soldering fluxes using the solder spread method (also called the flux efficacy test). The method measures how well a flux promotes wetting and spreading of a defined filler metal on a prepared test surface. It is applicable to all flux classes defined in ISO 9454-1 and is intended for quality control, product development and comparative evaluation of flux performance.
Keywords: ISO 9455-10, soft soldering fluxes, flux efficacy test, solder spread method, flux testing.
Key topics and requirements
- Test principle: A cleaned brass test plate is dosed with a fixed amount of flux and a standard solder sample; the plate is lowered onto a molten solder bath so the solder melts and spreads. The spread area (or calculated ratio of spread) quantifies flux efficacy.
- Test specimens and materials:
- Brass plates: 40 mm × 40 mm, 0.5 mm thick, alloy CuZn37 or CuZn40 (10 plates per flux).
- Solder sample: 1 mm diameter wire, 0.49–0.50 g, wound into a flat spiral.
- Flux dosing: 0.025 ml (liquid) or 0.025 g (paste/solid) measured by microsyringe or balance.
- Standard solder grades and temperatures:
- Sn60Pb40 at 235 °C ± 3 °C
- Sn96Ag3Cu1 at 255 °C ± 3 °C
- Other alloys/temperatures by agreement.
- Preparation & cleaning: Degrease in acetone, treat in an acid preparation solution (specified in the standard), rinse, dry-procedure includes safety warnings for corrosive reagents.
- Measurement & expression of results:
- Measure spread area with a planimeter or determine height and compute spread ratio.
- Report arithmetic mean and standard deviation for 10 replicates.
- Test report must include sample ID, solder grade, test temperature, area/ratio results and any deviations.
- Precision data: Interlaboratory precision (repeatability/reproducibility) is provided for different flux types; Annex A gives a method to prepare standard reference rosin-based fluxes for comparison.
Applications and users
ISO 9455-10 is used by:
- Flux manufacturers for product development and batch quality control.
- Electronics assemblers and PCB manufacturers evaluating flux performance for soldering processes.
- Independent test laboratories performing standardized flux efficacy testing.
- R&D teams comparing halide-activated vs. non-activated fluxes and leaded vs. lead-free solder interactions.
Practical benefits include objective comparison of wetting performance, validation of flux claims, and conformity testing in procurement or regulatory contexts.
Related standards
- ISO 9454-1 - Flux classification, labelling and packaging
- ISO 9455-16 - Flux efficacy test, wetting balance method (alternative for liquid fluxes)
- ISO 9453 - Soft solder alloys - chemical compositions and forms
Using ISO 9455-10 helps ensure consistent, comparable flux efficacy data across laboratories and product lines.
Open preview (PDF)Soft soldering fluxes — Test methods — Part 10: Flux efficacy test, solder spread method