Overview
EN ISO 9455-11:2017 - Soft soldering fluxes - Test methods - Part 11: Solubility of flux residues (ISO 9455-11:2017) specifies a qualitative test to assess the solubility of flux residues in a selected solvent. It is applicable to all Type 1 fluxes (see ISO 9454-1) and is intended for use in laboratory quality control and process validation for soldering and flux cleaning operations. The method evaluates how effectively a chosen solvent removes residues by measuring electrical continuity across a cleaned brass test plate.
Key topics and technical requirements
- Scope and limitation
- Qualitative assessment only; the standard notes the test does not guarantee that very small post‑cleaning residues will not affect long‑term assembly performance.
- Test specimen and preparation
- Brass test plates (60 mm × 60 mm, nominally 0.5 mm, alloy CuZn37) with a 3 mm central depression.
- Plates are acid‑cleaned, rinsed, marked and loaded with a defined amount of flux (liquid or paste).
- Conditioning and heating
- One plate is heated by floating on a solder bath (300 ± 10 °C) to simulate soldering; the other serves as an unheated control. Both are conditioned in a humidity oven (23 ± 2 °C, 50 ± 5 % RH) for 24 h.
- Solvent selection and immersion
- The solvent is chosen per flux manufacturer recommendations (solvent can vary with flux composition). Immersion time is specified depending on flux type and may be 1 min or 10 min as reported.
- Apparatus and electrical detection
- Test uses a 6 V DC source, variable resistor, milliammeter and a probe with Pd‑Ag tip. A steady full‑scale current indicates efficient residue removal (pass); unsteady or reduced current indicates failure.
- Reagents
- Analytical‑grade reagents and distilled/deionized water; acid cleaning solution composition is specified (sulfuric + nitric acid mix).
- Reporting
- Test report must identify sample, solvent used, immersion time, results, deviations and date.
Applications and users
- Flux manufacturers validating recommended cleaning solvents and formulations.
- Electronics assembly and rework laboratories for flux residue removal verification.
- Process engineers and QA teams in automotive, aerospace, telecommunications and consumer electronics for soldering process qualification and maintenance of assembly reliability.
- Standards bodies and testing laboratories performing comparative flux evaluations.
Related standards
- ISO 9454-1 - Classification and requirements for soft soldering fluxes (defines Type 1).
- Other parts of the ISO 9455 series covering additional flux test methods.
Keywords: EN ISO 9455-11:2017, soft soldering fluxes, solubility of flux residues, flux residue removal, Type 1 flux, test methods, flux cleaning, soldering quality control.
