Overview
ISO 9455-3:2019 is an internationally recognized standard that specifies test methods for determining the acid value of soft soldering fluxes, specifically types 1 and 2 as defined in ISO 9454-1. The standard presents two methods for measuring the acid value:
- Method A: Potentiometric titration method (reference method)
- Method B: Visual end-point titration method (alternative procedure)
Both methods provide accurate and reliable ways to quantify the acid value-a key parameter that impacts flux performance during soldering operations. This standard is essential for manufacturers, quality control laboratories, and researchers working with soft soldering fluxes.
Key Topics
Acid Value Determination
- The acid value indicates the amount of acidic substances present in the soldering flux. It is expressed in milligrams of potassium hydroxide (KOH) per gram of non-volatile matter.
- Measuring acid value is critical for ensuring fluxes meet performance standards and help maintain reliable solder joints.
Method A – Potentiometric Titration
- Involves titrating a prepared flux solution with a standard solution of tetrabutylammonium hydroxide using a glass electrode and pH or millivoltmeter readings.
- The acid value is calculated based on the titration curve’s inflection point, which signals the completion of neutralization.
- Suitable solvents for sample dissolution include propan-2-ol, ethanol, toluene, or an ethanol/toluene mixture depending on solubility.
- Supports both manual and automated titration procedures for laboratory flexibility.
Method B – Visual Titration
- Utilizes an indicator (phenolphthalein) to visually detect the endpoint of titration with potassium hydroxide solution in an alcohol medium.
- Considered an alternative to potentiometric titration, suitable where instrumentation is limited.
- Requires careful solvent selection for flux solubility and accurate endpoint detection.
Sampling and Preparation
- Flux samples must be accurately weighed and dissolved without loss of volatile components.
- Tests are performed in triplicate to ensure reproducibility.
Calculation and Reporting
- Acid values are computed using standardized formulas considering sample weight, titrant volume, and solution normality.
- Results are averaged from replicate tests and include blank determinations to ensure accuracy.
Applications
- Quality Control: Ensures flux acid levels comply with manufacturing specifications, which affects solderability and corrosion resistance.
- Material Certification: Validates flux batches prior to shipment and use in electronics manufacturing.
- Research and Development: Assists in assessing the effect of flux composition on solder joint quality by monitoring acid levels.
- Compliance Testing: Meets regulatory requirements for flux performance and safety in international markets.
Implementing the ISO 9455-3:2019 testing protocols enhances production reliability and maintains consistent soldering quality, minimizing failures in electronic assemblies.
Related Standards
- ISO 9454-1: Defines flux types 1 and 2, providing classification relevant to acid value testing.
- ISO 9455-1 and ISO 9455-2: Provide complementary test methods for determining non-volatile content in soft soldering fluxes, which is foundational for accurate acid value calculations.
- ISO/IEC Directives: Guidelines for the development and harmonization of ISO standards and test procedures.
Adhering to ISO 9455-3:2019 alongside these related ISO standards ensures comprehensive evaluation of soldering flux quality and supports standardization efforts in electronics manufacturing worldwide.
Open preview (PDF)Soft soldering fluxes — Test methods — Part 3: Determination of acid value, potentiometric and visual titration methods