Determination of anions on the surface of printed circuit boards by IPC-TM-650 Method 2.3.28 using HPIC

Importance of the topic

The ionic cleanliness of printed circuit board (PCB) surfaces influences corrosion, electrochemical migration, dendritic growth, leakage currents, and reliability in both testing and field operation. Traditional bulk conductivity methods such as ROSE cannot differentiate among ionic species. High-pressure ion chromatography (HPIC) with suppressed conductivity detection provides selective, sensitive measurement of individual anions and weak organic acids at ppm–ppb levels, enabling targeted troubleshooting and quality control in PCB manufacturing.

Study objectives and overview

This work adapts IPC-TM-650 Method 2.3.28 for quantifying specific anionic residues on PCBs using a Thermo Scientific Dionex ICS-5000+ HPIC system with IonPac AS11-HC-4 µm column. The aim is to separate and measure 14 anions (bromide, chloride, fluoride, nitrate, nitrite, phosphate, sulfate, acetate, adipate, formate, glutamate, malate, methanesulfonate, succinate, and phthalate) present after a standardized isopropanol/water extraction.

Methodology and used instrumentation

Sample preparation followed IPC-TM-650 extraction in sealed low-ion bags with 75/25 IPA/H₂O at 80 °C for 1 h. Extracts were cooled, filtered (0.2 µm), and injected (5 µL). Separation used a KOH gradient (1 mM to 60 mM) with a methanol modifier to resolve coeluting organic acids. Key instrument modules:

• Dionex ICS-5000+ HPIC system: DP pump, EG eluent generator (500 mM KOH cartridge), CR-ATC trap column, AERS 500e suppressor
• IonPac AS11-HC-4 µm guard (2 × 50 mm) and analytical (2 × 250 mm) columns
• AS-AP autosampler, 250 µL syringe, 0.2 µm PES filters
• Chromeleon™ CDS software

Main results and discussion

Separation of 14 anions was achieved in a 60 min run. Calibration covered 0.05–50 mg/L with quadratic fits (r² > 0.999). Limits of detection ranged from <0.01 to 0.115 mg/L; quantitation limits from <0.04 to 0.383 mg/L. Precision (n = 7) showed retention time RSD < 0.1% and peak area RSD < 3%. Recovery tests (20–150% spike) for acetate, adipate, and sulfate in three PCB assemblies yielded 87–114%. Real samples revealed assembly-dependent levels of acetate (0.30–0.68 µg/cm²), formate (0.41–0.52 µg/cm²), chloride (0.24–0.77 µg/cm²), nitrate (0.10–0.61 µg/cm²), sulfate (0.08–0.26 µg/cm²), plus methanesulfonate, adipate, and bromide in varying amounts. Nitrite, phosphate, malate, and phthalate were below quantitation.

Benefits and practical applications

• Selective detection of individual anions and organic acids improves root-cause analysis of PCB failures.
• Sensitivity down to sub-ppm levels supports stringent cleanliness standards.
• Automated eluent generation and suppression reduce reagent handling and background conductivity.
• Validated precision and accuracy ensure reliable QC assessments.

Future trends and applications

Advances may include higher-throughput columns, multiplexed detectors, and automated sample handling to further reduce cycle times. Lower-pressure column chemistries and alternative suppressor formats could extend instrument lifespan and simplify maintenance. Integration with real-time monitoring and data analytics will enhance predictive quality control in electronics manufacturing.

Conclusion

This application demonstrates a robust HPIC approach for comprehensive anion analysis on PCB surfaces per IPC-TM-650. The method delivers high specificity, sensitivity, and reproducibility for monitoring inorganic and organic ionic contaminants, supporting improved product reliability and process optimization.

Reference

1. IPC-TM-650, Test Method 2.3.28 Ionic Analysis of Circuit Boards by Ion Chromatography.
2. Thermo Fisher Scientific. Eluent Generator Cartridges Product Manual, P/N 065018, 2012.
3. Thermo Fisher Scientific. Continuously Regenerated Trap Columns (CR-TC) Product Manual, Doc No 031910, 2010.
4. Thermo Fisher Scientific. Dionex ERS 500 Suppressor Product Manual, Doc No 031956, 2013.
5. Thermo Scientific Application Note 1157: Determination of Organic Acids in Kombucha Using HPIC, 2016.
6. Brinkmann T., Specht C.H., Frimmel F.H. J. Chromatogr. A 2002, 957:99–109.