Overview
ISO 9455-5:2020 - "Soft soldering fluxes - Test methods - Part 5: Copper mirror test" specifies a qualitative laboratory method to assess the aggressiveness of a soft‑soldering flux toward copper. The test detects flux reactivity caused by free halide activators and is applicable to all type 1 fluxes as defined in ISO 9454‑1. A rosin reference solution is used as a control to verify test validity.
Key topics and requirements
- Test principle: A flux test solution is applied to a vacuum‑deposited copper film (“copper mirror”) on glass; attack is judged by partial or complete removal of the film (increased transparency).
- Sample preparation
- Liquid fluxes: tested full strength.
- Solid/paste fluxes: dissolved to 25 % (m/m) solids (propan-2-ol normally used).
- Flux‑cored solder: extract flux by Soxhlet with propan-2-ol, adjust non‑volatile matter to 25 % using ISO 9455‑1 or ISO 9455‑2 methods.
- Copper mirrors: copper vacuum‑deposited to ~50 nm; transmittance at 500 nm between 5 % and 15 %. Store under dry nitrogen.
- Pre‑test cleaning: brief EDTA dip (≤5 s), rinse, acetone wipe, dry with warm air.
- Test conditions: place a drop (≤0.05 ml) of test solution and a rosin reference (25 % colophony in propan-2-ol) on mirror; condition 24 h at 25 °C ±2 °C and 50 % ±5 % RH.
- Pass criterion: no removal of the copper film on either mirror. If the rosin reference fails, repeat with fresh mirrors.
- Notes and cautions: presence of amines can mask aggressive behaviour and give misleading pass results. Use analytical‑grade reagents and document any solvent substitutions.
Practical applications and users
- Quality control and acceptance testing of soft‑soldering fluxes in electronics manufacturing.
- Flux and solder manufacturers validating formulations for copper compatibility.
- Test laboratories performing conformity testing to ISO standards.
- R&D teams evaluating flux formulations for PCB assembly and soldering processes.
- Procurement/specification writers referencing objective test methods for supplier acceptance.
Keywords: ISO 9455-5, copper mirror test, soft soldering fluxes, flux aggressiveness, halide activators, flux test solution, type 1 fluxes, rosin reference solution.
Related standards
- ISO 9454-1 - Classification and requirements for soft soldering fluxes (type 1).
- ISO 9455-1 and ISO 9455-2 - Methods for determining non‑volatile matter used when preparing flux test solutions.
