Overview
EN ISO 9455-5:2020 - "Soft soldering fluxes - Test methods - Part 5: Copper mirror test" specifies a qualitative method to assess the aggressiveness of fluxes towards copper. Published by CEN/ISO, this test is applicable to fluxes of type 1 (see ISO 9454-1) and is intended to detect the presence of free halide activators that can attack copper films used in electronic and soldering assemblies.
Key topics and requirements
- Test principle: A flux test solution is applied to a vacuum‑deposited copper film (a “copper mirror”) on glass; flux reactivity is judged by whether the copper film is removed (becomes transparent).
- Sample preparation
- Liquid fluxes: used full strength.
- Solid/paste fluxes: dissolve or dilute to 25 % (m/m) solids (propan-2-ol is the usual solvent).
- Flux‑cored solder: extract flux (Soxhlet) and adjust extract to 25 % solids after determining non‑volatile matter (ISO 9455‑1 or ISO 9455‑2).
- Copper mirror: vacuum‑deposited copper ~50 nm thick; transmittance at 500 nm between 5 % and 15 %. Mirrors must be stored under dry nitrogen and cleaned immediately before test.
- Cleaning and conditioning: brief immersion (≤ 5 s) in EDTA 0.1 % to remove oxide, rinse, acetone wipe, then place one drop (≤ 0.05 ml) of flux test solution and one drop of rosin reference solution (25 % colophony in propan‑2‑ol) on separate mirror areas. Maintain at 25 °C ± 2 °C and (50 ± 5) % RH for 24 h.
- Assessment: a flux passes if no removal (no visible white background through the film) occurs on either mirror. If the rosin control fails, repeat using fresh mirrors.
- Limitations/notes: the method is qualitative and amines in fluxes can mask reactivity, producing misleading pass results.
Applications and users
- Quality control and acceptance testing of soft soldering fluxes for electronics and electrical assemblies.
- Product development and stability testing by flux manufacturers and formulators.
- Solder process engineers, metallurgists, and independent test laboratories evaluating flux compatibility with copper substrates.
- Procurement and compliance teams specifying flux performance in manufacturing specifications.
Related standards
- ISO 9454‑1 - Definition and classification of flux types (type 1).
- ISO 9455‑1 / ISO 9455‑2 - Methods for determination of non‑volatile matter used when preparing flux extracts.
- Use keywords when searching or documenting: EN ISO 9455-5:2020, copper mirror test, soft soldering fluxes, flux aggressiveness, free halide activators.
This standard provides a straightforward, industry‑accepted qualitative check to screen fluxes for copper‑attacking behavior prior to use in sensitive soldering and electronic assembly processes.
