ISO 9455-18:2024

Overview

ISO 9455-18:2024 - Soft soldering fluxes - Test methods - Part 18 specifies test methods to assess the cleanliness of soldered printed circuit assemblies (PCBs) before and/or after soldering and cleaning. Published in 2024, this first-edition ISO standard applies to all flux types defined in ISO 9454-1 and defines a structured approach to detect, identify and evaluate flux residues and their impact on electrical reliability.

Key topics and technical requirements

• Scope and principle
  • Methods cover visual and instrumental detection, identification and reliability testing of flux residue and white residue on soldered assemblies.
• Two-step test flow (Figure 1 / Table 1)
  • Step 1: Presence/absence checks by microscope (×20–×100) and/or SEM.
  • Step 2 (optional): Identification and reliability tests - users select methods to meet requirements.
• Identification techniques
  • SEM/EDX for elemental mapping (C, O, Cl, Br, Sn, Ag, Cu …).
  • FT‑IR (ATR or reflection) for functional groups (‑COOH, ‑NH, etc.) and residue vs. substrate discrimination.
• Reliability and electrical tests
  • Ionic contamination test (ROSE / process ionic contamination) - conductivity-based, expressed as μg‑NaCl/cm.
  • Surface insulation resistance (SIR) testing (references: ISO 9455-17, IEC 61189-5-501).
  • Dielectric property measurements (LCR meter) where applicable.
• Apparatus and reagents
  • SEM‑EDX, FT‑IR, ionic contamination tester, SIR tester, controlled temperature/humidity oven.
  • Use analytical‑grade reagents and manufacturer‑recommended cleaning solvents.
• Reporting
  • Test sample ID, methods used, results, anomalies, any optional operations, and cleaning conditions must be recorded.

Practical applications and users

ISO 9455-18:2024 is intended for:

• PCB manufacturers and assembly houses validating cleaning processes and post‑reflow cleanliness.
• Flux and solder paste suppliers qualifying products and supporting datasheets.
• Reliability engineers and failure‑analysis labs assessing contamination risk (ionic residue, insulating films).
• Quality, compliance and procurement teams establishing acceptance criteria for supplier audits.

Practical uses include process validation, supplier qualification, root‑cause analysis of corrosion or dendritic growth, and ongoing process control to mitigate field failures.

Related standards

• ISO 9454-1 - Flux classification, labelling and packaging (applicability).
• ISO 9455-17 - SIR comb test and electrochemical migration of flux residues.
• IEC 61189-5-501 - SIR testing procedure.
• IEC 61189-5-504 - Process ionic contamination testing (PICT).

Annexes A and B provide example test workflows, results, and FT‑IR guidance. Keywords: ISO 9455-18:2024, soft soldering fluxes, cleanliness testing, PCB flux residue, SEM/EDX, FT‑IR, ionic contamination, SIR, ROSE test.