Overview
ISO 9455-14:2017 specifies a qualitative method for assessing the tackiness of flux residues left after soft soldering processes. The method applies to all flux forms: solid and paste fluxes, liquid fluxes, solder pastes and flux-cored solder wires. It is particularly appropriate where residues remain in situ on electrical and electronic equipment, supporting quality control and reliability assessments.
The principle is simple: a standard mass of solder (or solder form) and a defined amount of flux are melted on a prepared copper test piece. After cooling, the residue is dusted with powdered chalk and the ease of chalk removal by light brushing determines whether the residue is tacky or not tacky.
Key Topics
- Scope and applicability: All soft solder fluxes, solder pastes and flux-cored wires; focused on residues left on electronic assemblies.
- Principle: Melt flux/solder on a copper test piece; cool; apply powdered chalk; brush and observe removal.
- Test pieces and preparation:
- 0.5 mm thick copper sheet test pieces with a central depression are cleaned and degreased according to the method.
- Flux quantities are controlled so that non-volatile matter is between 0.035 g and 0.040 g where applicable.
- Heating and solder selection:
- Typical solder options in the standard include Sn60Pb40 at (235 ± 3) °C and Sn96Ag3Cu0.5 at (255 ± 3) °C, or an agreed temperature 35 ± 3 °C above the alloy liquidus.
- Evaluation criterion:
- If chalk powder is easily removed by brushing → not tacky.
- If chalk cannot be removed, or only with difficulty → tacky.
- Test reporting: Identification of sample, reference to ISO 9455-14, results, unusual features, any deviations, and date.
Applications
- Electronics assembly quality assurance and incoming flux inspection.
- Comparative screening during flux formulation and supplier evaluation.
- Field or in-situ assessments where residues remain on PCBs or components and residue tack influences handling or reliability.
- Supporting process control decisions for cleaning requirements and post-soldering treatments.
Related Standards
- ISO 9455-1 - Determination of non-volatile matter, gravimetric method (referenced for liquid flux preparation).
- ISO 9455-2 - Determination of non-volatile matter, ebulliometric method.
- ISO 9453 - Soft solder alloys - chemical compositions and forms (solder specifications used for temperature selection).
- ISO 197-1 - Copper and copper alloys - terms and definitions - materials (copper test piece specification).
This concise method offers a rapid, qualitative indicator of tacky residues that can affect handling, cleaning decisions and long-term performance of electronic assemblies.
Open preview (PDF)Soft soldering fluxes — Test methods — Part 14: Assessment of tackiness of flux residues