Overview
ISO 9455-15:2017 - Soft soldering fluxes - Test methods - Part 15: Copper corrosion test - specifies a qualitative laboratory method to evaluate the corrosive properties of flux residues on copper. The standard applies to type 1 fluxes (see ISO 9454‑1) and defines sample preparation, exposure and microscopic assessment under controlled temperature and humidity to detect corrosion caused by flux residues.
Key topics and requirements
- Scope: Qualitative determination of corrosion caused by flux residues on a copper substrate under controlled environmental conditions.
- Test principle: A small solder pellet is placed in contact with the flux on a prepared copper test piece, melted, cooled, then exposed to damp heat. Corrosion is assessed microscopically.
- Specimens & materials:
- Copper sheet: 0.5 mm phosphorus-deoxidized copper per ISO 197‑1.
- Solder mass: typically ~1.00 g of solder wire/pellets or defined amounts for flux-cored solder and solder paste (solder paste ~0.50 g).
- Flux amounts: solids/pastes ~0.035–0.040 g non-volatile matter; liquid flux volumes adjusted to provide equivalent non-volatile content.
- Reagents: ammonium peroxodisulfate and diluted sulfuric acid for surface pretreatment; analytical-grade solvents and water.
- Apparatus:
- Solder bath at alloy-specific temperatures (commonly ~235 °C for traditional Sn–Pb alloys, ~255 °C for common lead‑free alloys such as Sn96.5Ag3Cu0.5; other alloys tested at ~35 °C above liquidus).
- Humidity chamber conforming to IEC 60068‑2‑78 (damp heat, steady state).
- Cupping device to form a 3 mm depression in test pieces; low-power stereomicroscope (×20) for evaluation.
- Procedure highlights:
- Careful degreasing, acid etch and etchant treatments to prepare uniform copper surfaces.
- Flux and solder placement, melting on the copper, photographic recording of surface appearance.
- Conditioning: preheat then expose specimens vertically at ~40 °C and 90–95% relative humidity for 3 days.
- Visual/microscopic assessment of corrosion growth at flux boundaries, cracks or under residues; comparison with a blank.
- Results & reporting: Qualitative assessment with photographic records and description of corrosion features; test report content is defined in the standard.
Applications and users
ISO 9455-15:2017 is used by:
- Flux manufacturers for product qualification and reformulation.
- Solder manufacturers and electronic assembly suppliers for compatibility testing.
- Quality and reliability laboratories performing corrosion screening for PCBs, connectors and copper-plated components.
- Standards bodies and procurement teams specifying flux performance for electronics or general soldering processes.
Keywords: ISO 9455-15, soft soldering fluxes, copper corrosion test, flux residues, type 1 fluxes, humidity chamber, solder alloys, corrosion assessment.
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