Overview
ISO 9454-2:2020 specifies the performance requirements for soft‑soldering fluxes delivered as solids, liquids or pastes. It defines how fluxes intended for use with soft solders must perform in laboratory tests (wetting, halide content, acid index, residue behaviour, etc.) and links those requirements to the classification system set out in ISO 9454‑1 (labelling, packaging and coded classification). The standard is intended for fluxes used in general brazing/soldering and electronic and other industrial applications; some fluxes for inert‑gas or vapour‑phase soldering may require purchaser–supplier agreement where criteria are not fully applicable.
Key topics and requirements
- Scope and flux forms: Applies to solid, liquid and paste fluxes; requires homogeneity and freedom from detrimental impurities or deposits.
- Flux types and codes: Covers resin (rosin)‑based fluxes (type 1), organic non‑resin fluxes (type 2) and inorganic fluxes (type 3), with further subdivision by activation (e.g., halide‑activated) and activity grades (W, X, Y, Z).
- Performance test methods: Specifies tests referenced to the ISO 9455 series, including:
- Non‑volatile matter and tolerance (ISO 9455‑1/‑2)
- Acid number / index determination (ISO 9455‑3) - tolerance example: ±10% on acid index for non‑volatile basis
- Copper mirror test and silver‑chromate paper test (oxidation/activation behaviour)
- Halide (chloride, bromide, iodide) content measurement (ISO 9455‑6) - numeric limits are set per flux class (examples in tables: 0.01 % up to >1.0 % expressed on non‑volatile basis)
- Spreading/wetting (ISO 9455‑10 A/B) - minimum spread area and spread ratio values are given per class
- Residue solubility, spattering, tackiness, and copper corrosion tests (ISO 9455 parts 11–15)
- Numeric performance tables: Tables 1–3 in the standard provide class‑specific numeric limits for acid index, non‑volatile content tolerances, halogen limits, minimum wetting/spread area and pass/fail criteria for residue and corrosion tests.
Applications and users
ISO 9454‑2 is used by:
- Flux manufacturers for product formulation, labeling and classification to meet international performance benchmarks.
- Electronics assemblers and PCB manufacturers to select fluxes with required wetting, residue and halide properties.
- Metal fabricators and solder process engineers who need predictable solderability and corrosion performance.
- Procurement, quality and test laboratories for specification compliance, acceptance testing and supplier evaluation.
Practical benefits include consistent flux selection, reduced risk of corrosion or residue issues, and clearer buyer–supplier agreements when specialised processes (e.g., inert or vapour‑phase soldering) are used.
Related standards
Open preview (PDF)Soft soldering fluxes — Classification and requirements — Part 2: Performance requirements