ISO 9455-2:1993

Overview

ISO 9455-2:1993 specifies a standardized test method for determining the content of non-volatile matter in soft soldering fluxes using an ebulliometric technique. This method applies specifically to liquid fluxes of classes 1.1.1, 1.1.2, and 1.1.3 that contain solvents with relatively high volatility, such as propan-2-ol. The standard focuses on fluxes with a non-volatile content of 10% or more. Accurate measurement of non-volatile matter is crucial for quality control and performance assessment in soldering applications, ensuring flux efficacy and minimizing issues such as corrosion and residue build-up.

Key Topics

• Ebulliometric Method: The procedure revolves around evaporating a weighed sample of soldering flux in an ebulliometer until the volatile components are fully driven off, tracing the distillation temperature against time to identify the endpoint. The remaining residue is the non-volatile content of the flux.

• Applicability: Suitable for liquid soft soldering fluxes with volatile solvents, especially those with non-volatile matter above 10%. Not recommended for fluxes containing less volatile solvents than propan-2-ol, which require alternative gravimetric methods (ISO 9455-1).

• Apparatus Requirements:

  • Martin ebulliometer with a spherical distillation flask for efficient heat exchange.
  • Thermostatically controlled heater.
  • Laboratory thermometer or corrosion-resistant thermocouple covering 50°C to 150°C.
  • Precise laboratory balance with 0.1 mg accuracy.

• Test Procedure: Sample preparation includes weighing 40 to 50 grams of flux in the distillation flask, heating to boiling, and collecting condensate at a controlled rate while recording temperature at two-minute intervals. Distillation stops when the temperature falls to 75°C, and the non-volatile residue is weighed after cooling.

• Precision and Reliability: Interlaboratory tests confirm repeatability and reproducibility with low standard deviation values, underscoring the method’s validity for consistent flux characterization.

• Quality Verification: Annex A of ISO 9455-2 provides a procedure to prepare standard rosin-based reference fluxes with 25% non-volatile matter for laboratories to verify accuracy and reliability of their measurements.

Applications

• Manufacturing Quality Control: Ensures soldering flux batches meet consistent non-volatile content specifications critical to solder joint quality and flux performance.

• Soldering Process Optimization: Accurate knowledge of non-volatile matter helps optimize flux formulations for improved solder flow, wetting, and residue minimization.

• Flux Classification and Compliance: Assists manufacturers and laboratories in classifying fluxes per ISO 9454-1, meeting international standards for labeling, packaging, and use.

• Failure Analysis and Reliability Testing: Identifies improper flux compositions contributing to solder joint defects or corrosion, supporting corrective actions in electronics manufacturing.

• Research and Development: Enables development of new flux formulations by providing reliable measurement techniques for non-volatile content impacting flux activity and residue behavior.

Related Standards

• ISO 9454-1:1990: Classification, labeling, and packaging of soft soldering fluxes, providing definitions and categories relevant to ISO 9455-2 testing.

• ISO 9455-1: Gravimetric method for determining non-volatile matter in fluxes with less volatile solvents.

• ISO 4791-1:1985: Vocabulary for laboratory apparatus including specifications for ebulliometer components used in testing.

• ISO 9455 Parts 3, 5, 6, 8, 9, 10, 12, 13, 14, 15, 16, 17, 18: Additional test methods related to acid value, halide content, corrosion tests, flux efficacy, and residue characteristics complementing the non-volatile matter determination.

Keywords: ISO 9455-2, soft soldering fluxes, non-volatile matter, ebulliometric method, soldering flux testing, flux quality control, soldering process, flux classification, solder joint reliability, flux residue analysis.