Recently, I’ve fielded several requests to clarify the distinction between “halide-free” and “halogen-free.” Both terms apply to the composition of soldering fluxes in the electronics assembly industry. While some may use the terms interchangeably without any repercussions, the definitions are not synonymous. This topic can get a bit confusing, so in this article, I’ll outline the difference between halides and halogens in the context of both industry standards and general chemistry.
Was Sie wissen müssen
Understanding these terms in the context of industry standards is crucial. For a standardized definition of “halide-free,” we refer to J-STD-004 (Rev. C). J-STD-004C defines “halide-free” as a flux that contains less than 0.05% of combined halide ions (F-, Cl-, Br-, I-) as a weight percentage of the solid portion of the flux. The analytical test method “ion chromatography” is performed on flux in the unheated state. The halide content of a flux is designated by the final character in the flux classification: 0 for halide-free, 1 for halide-containing.
On the other hand, IEC 61249 defines “halogen-free” as a material with residue that contains less than 0.09% of chlorine (all forms), less than 0.09% of bromine (all forms), and less than 0.15% of chlorine and bromine combined. The analytical test method (per J-STD-004C) “bomb calorimetry,” followed by ion chromatography, is performed on flux residue in the final reflowed residue form. The halogen test is optional, and there is no standardized character designation.
Warum Sie das wissen müssen
Die Konzentration der Halogenide wird überwacht, weil Halogenide das Potenzial haben, das Lot zu korrodieren, was bei Vorspannung und Feuchtigkeit zu dendritischem Wachstum führen kann. Wenn No-Clean-Produkte die J-STD-004 SIR- und ECM-Tests bestehen und korrekt verwendet werden, ist dies kein Problem. Bei Flussmittelrückständen, die gereinigt werden müssen (wasserlöslich), sollte ein gründliches, effektives Reinigungsverfahren jegliche Korrosion verhindern. Es ist wichtig zu wiederholen, dass ein halogenidhaltiges Flussmittel nicht per se schädlich für eine Baugruppe ist. Das Vorhandensein von Halogeniden muss lediglich charakterisiert werden, um die Konstruktion und Montage eines elektrochemisch zuverlässigen Geräts zu fördern.
Im Gegensatz dazu ist die Entscheidung eines Herstellers, ausschließlich halogenfreie Produkte zu verwenden, von Umweltüberlegungen geleitet. Bei den Halogenen in der Chemie eines Flussmittels handelt es sich in der Regel um Halogenkohlenwasserstoffe, die die Umwelt verschmutzen können, wenn Baugruppen mit halogenhaltigen Flussmittelrückständen unsachgemäß entsorgt werden. Obwohl halogenhaltige Flussmittel weltweit täglich verwendet werden, kann sich ein einzelnes Unternehmen dafür entscheiden, selbst Vorschriften zu erlassen, die die Verwendung halogenhaltiger Flussmittel ablehnen, um dieses Problem gänzlich zu vermeiden. Es gibt keine staatlichen Vorschriften, die die Verwendung aller halogenhaltigen Lötmittel in der Elektronik vollständig verbieten. Da es aus technischer Sicht nicht notwendig ist, den Halogengehalt zu charakterisieren, ist die Halogenprüfung optional.
Wo es verwirrend wird
Für technisch Interessierte gibt es hier einen tieferen Einblick:
- In general chemistry, halogens are the elements in group 17 of the periodic table. A “halide” is any halogen-containing compound. Halides can be broken down into two main categories: ionically bonded and covalently bonded. In ionically bonded compounds, atoms with opposing charges (positive and negative) attract each other. If the negatively-charged atom is a halogen, it’s considered a “halide ion.” However, in the electronics industry and its standards, the term “halide” technically refers to a “halide ion.” The ion chromatography analysis does not detect the concentration of all halide species, only ionic halide species.
- Based on standard definitions, a flux could technically be classified as both “halide-free” and “halogen-containing.” Activators, one of the primary components of fluxes, are the chemicals that dissolve and remove oxides to enable soldering. Typically, activators are halocarbons or organic acids, and halocarbons are particularly effective at removing oxides. If a flux is formulated with halocarbons, halide ions can form within the flux due to side reactions. This is why many flux-containing products, notably solder paste, will be halide-containing if they are halogen-containing. However, it shouldn’t be assumed that a halide-free flux is also halogen-free.
- Using the same analytical method for halogen content, J-STD-004 defines flux residues as “low halogen” if Br ≤ 0.1% and Cl ≤ 0.1%. Yet, it’s uncommon to see a flux-containing material labeled as “low halogen.”
- A common question I get asked is, “What does the ‘HF’ in [product name] stand for?” Indium Corporation offers many solder pastes and fluxes with “HF” in the title (like Indium8.9HF, for example). The HF stands for halogen-free. However, not all halogen-free products have “HF” in their name. If a product is halogen-free, it will be noted on it’s product data sheet.
While this is a lot of information to digest, it’s important not to overthink it. For many assemblies, choosing between halide-free and halide-containing, or halogen-free and halogen-containing, is not going to make or break the device. There are many more factors to consider when selecting the optimal solder material. If you’re in the market for flux and solder, we encourage you to have a conversation with a member of our technical support team. We’ll be happy to discuss your project and help you navigate our portfolio of electronics assembly materials.
Weitere Lektüre
Weitere Informationen zur Flussmittelcharakterisierung nach J-STD-004 finden Sie in diesen Artikeln:
