Principle
The Coulomb moisture titrator is based on Faraday's law of electrolysis, and its core principle is to quantitatively determine the moisture content in a sample through the electrolysis process. When the instrument works, the water in the sample reacts with the iodine in the electrolytic cell, and the iodine consumed is supplemented by electrolyzed iodine ions, and the amount of electricity required for electrolysis is directly proportional to the moisture mass. The process can be described by a formula:
m = (Q × M) / (2 × F)
where m represents the water mass (unit: grams), Q is the total amount of electricity consumed by electrolysis (unit: coulomb), M is the molar mass of water (18.015 g/mol), and F is the Faraday constant (96485 C/mol). By accurately measuring the electrolytic power, the absolute water content in the sample can be directly calculated without the need for pre-calibration, with high accuracy and sensitivity.
Moisture detection of electronic components
Electronic components may adsorb or retain moisture during production, storage and use. The presence of moisture can cause problems such as corrosion of metal leads, solder joint failure, degradation of insulation properties, and changes in dielectric constant in high-frequency circuits. Especially in precision components such as microelectronic packaging, multilayer ceramic capacitors, and semiconductor chips, even trace amounts of moisture can affect their long-term reliability and life. Therefore, testing the moisture content of components is a key link to ensure product quality and reliability.
Applicability
Coulomb moisture titrators are suitable for the detection of trace to trace levels of moisture in electronic components, with a typical detection range from 1 to 1 percent per million. This method has good applicability to solid, powder and paste samples (such as solder paste, packaging materials, ceramic substrates, etc.). During testing, the sample is usually released through a heating furnace under an inert gas carrier band, and the dry carrier gas is introduced into the titration cell for determination. This method does not damage the sample body and avoids environmental humidity interference, making it suitable for production line quality control and laboratory analysis.
Operation process
Typical testing processes include: sample preparation, instrument preheating and blank calibration, sample heating to release moisture, electrolytic titration and data logging. Key operating parameters need to be adjusted according to the characteristics of the sample, mainly involving heating temperature, carrier gas flow rate and electrolysis end point determination. The following is the reference parameter range for sample testing of common electronic components:
| Sample type | Heating temperature range |
| Plastic encapsulation | 120°C to 200°C |
| Ceramic substrate | 200°C to 300°C |
| Solder paste and flux | 80°C to 150°C |
| Silicon wafer coating | 150°C to 250°C |
Notes:
The Coulomb moisture titrator has the advantages of high detection sensitivity, direct mass representation, and no need for standard calibration. In the inspection of electronic components, it can distinguish between surface adsorption water and internally bound water, and achieve segmented determination by controlling the pyrolysis temperature. During operation, it should be noted that the sample should be representative to avoid environmental humidity interference; The heating temperature should not be too high to prevent sample decomposition and interfering substances. Change electrolytes and desiccants regularly to maintain system tightness.
Epilogue
Coulomb moisture titrators provide an accurate and reliable solution for moisture detection of electronic components. By reasonably setting parameters and standardizing operations, this method can effectively monitor the moisture content of materials and components during the production process, providing data support for improving the reliability of electronic products. With the development of electronic devices in the direction of miniaturization and high density, the requirements for moisture control will be stricter, and the application value of this method will be further highlighted.
References
1. National standard: GB/T 6283 Determination of moisture content in chemical products Karl Fischer method
2. International Electrotechnical Commission standard: IEC 60749 Semiconductor devices - Mechanical and climatic test methods
3. Technical Handbook of Analytical Instruments: Principles and Applications of Coulomb Moisture Determination, Chemical Industry Press
4. Electronic Material Testing Technology, Science Press