Why are Polybrominated Biphenyls and Polybrominated Diphenyl Ethers Exceeding the Standard in Flux Components?
2021-12-28
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Abstract
There are two toxic and hazardous substances specified in ROHS, which are polybrominated biphenyls (PBB) and polybrominated diphenyl ethers (PBDE). These two substances are the products of the polymerization reaction of bromine and benzene or ether, which are often used as flame-retardant materials in electronic information products. They exist in a completely different form and manner than halogen or bromide ions. Testing restricted substances with the wrong test method often result in test results with excessive levels of harmful substances in the flux.
Key words
Flux, ROHS, Polybrominated Biphenyls, Polybrominated Diphenyl Ethers, Excessive Bromine Content, Test Methods
What is the relationship between bromine, bromide ions, halogens, and ROHS-regulated polybrominated biphenyls and polybrominated diphenyl ethers?
Excessive bromine levels in flux have been explained to customers more than once. Some customers are confused with the impacts of bromine, bromide ions, halogens, and ROHS-regulated polybrominated biphenyls and polybrominated diphenyl ethers.
When adding flux, a small amount of organic brominated amine salts or other brominated substances are often added as surfactants. However, bromine in the flux exists as an organic compound rather than in the form of monomer ions. After high-temperature soldering, the organic additives will produce organic acid salts, water, carbon dioxide, etc., part of which will be decomposed, and the rest will be compounded with copper or solder joints to form a stable protective layer. Therefore, although bromine-containing organic compounds are added to the flux, an ion tester in accordance with national standards cannot detect the independent halogen ion residues on the surface of the boards, ensuring reliability after soldering. This flux can also be marked as halogen-free. Of course, halide ions will still decompose if excessive or the wrong type of addition is added. This halogen index can be measured by potentiometric titration, but the measured halogen content refers not only to the bromine content but also to the chlorine content.
Why are toxic and hazardous substances exceeding the standard?
After the introduction of the lead-free packaging process, a problem needed to be explained. There are two kinds of toxic and hazardous substances stipulated in ROHS, which are polybrominated biphenyls (PBB) and polybrominated diphenyl ethers (PBDE). These two substances are the products of the polymerization reaction of bromine and benzene or ether and are often used as flame-retardant materials in electronic products. They exist in a completely different form and manner than the above-mentioned halogen or bromide ions.
Why are many customers currently reporting excess bromine in flux? It is because of the inconsistency between the test methods and the ROHS directives and national standards for testing restricted substances. For example, SGS uses an atomic absorption spectrometer to determine polybrominated biphenyls or polybrominated diphenyl ethers (most fluxes do not contain either, so they are usually labeled ND in SGS reports). Many manufacturers have introduced more expensive test instruments after the popularization of lead-free packaging, and the most common equipment is the direct-reading X-ray fluorescence instrument. After a few years of observation, the instrument measures the content of lead elements relatively accurately, but cadmium (CD) and hexavalent chromium (Cr6+) results are often inaccurate. The worse thing is that the so-called bromine content detected by this instrument is the total content of bromine in the entire test substance. Besides, PBB and PBDE stipulated by ROHS cannot be completely distinguished and accurately tested.
Fitech determines hazardous substances with an atomic absorption spectrometer.
Fitech has invested a lot of resources in scientific research and innovation and has more than 40 professional testing equipment related to solder paste, flux, and solder powder, including an atomic absorption spectrometer (AAS) for the development, research, testing, and verification of solder products. Fitech uses an atomic absorption spectrometer to detect the content of polybrominated biphenyls and polybrominated diphenyl ethers in the flux to ensure the experimental data accuracy of hazardous contents and product quality. In addition, the atomic absorption spectrometer plays an auxiliary role in solder paste/epoxy solder product development and production and solder powder alloy system design.
In some companies, operators or quality controllers are not very clear about halogen issues, and they report to suppliers that bromine level exceeds the standards. In fact, there is an unnecessary worry. If worrying whether the flux contents of PBB and PBDE can meet the requirements of the ROHS directive, companies can send the flux samples to SGS or a third-party authoritative organization for toxic and hazardous substances testing.
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