Whether a Flux paste contains halogens is not a simple yes-or-no question, but depends on the specific halogen types, content levels, and customer certification standards. For example, IPC-J-STD-004B explicitly defines halogen-free as chlorine and bromine each ≤900ppm and their total ≤1500ppm, while some automotive electronics customers require stricter limits of chlorine ≤300ppm and bromine ≤500ppm. This means that during selection, we must check the halogen test reports in the TDS item by item rather than only looking at the "halogen-free" label.

Testing halogen-free flux paste cannot be done by visual inspection or simple test strips; it must use ion chromatography combined with microwave-assisted water extraction. The key is that sample weighing accuracy must be controlled within ±0.1mg, and the extraction temperature must be strictly set to 95°C and held constant for 30 minutes. Otherwise, low temperature will cause insufficient dissolution of bromide, while high temperature may cause decomposition of organic halides and interfere with peak shape. We once encountered a batch with test result fluctuations of up to 200ppm, which was ultimately found to be caused by pressure leakage due to aging of the extraction tank seal ring.

Common errors in actual operation include using deionized water instead of ultrapure water for dilution, failing to perform daily activation of the IC instrument suppressor, and the standard curve not covering the full 0.1–10ppm range. All of these will worsen the repeatability of chloride ion peak area. Especially when the flux paste background contains trace ammonium chloride-type activators, if the standard solution is not supplemented with the same matrix synchronously, it will cause quantitative deviation exceeding ±15%.

For on-line self-inspection, it is recommended to first verify the consistency of the supplier's factory reports. The method is to randomly draw three flux pastes from the same batch and perform parallel extraction respectively. If RSD > 8%, retesting must be conducted and check whether the filter membrane pore size is still 0.22μm and whether the mobile phase flow rate is stable at 1.0mL/min, because any parameter drift may cause the bromide ion retention time to shift by more than 0.3 minutes, thereby affecting integration accuracy.

If whitening solder joints or leakage in ICT testing occur after stencil printing of halogen-free flux paste, it is not necessarily due to excessive halogens; it may also be surface passivation caused by rosin residue oxidation or insufficient nitrogen purity. At this time, FTIR should be used first to compare the intensity changes of the C=O characteristic peaks in the solder joint area before and after cleaning, and then decide whether to initiate the halogen retesting process, to avoid misjudging process problems as material problems.