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.
您需要了解的信息
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.
您需要了解的原因
之所以要监测卤化物的浓度，是因为卤化物有可能腐蚀焊料，在施加电偏压和潮湿的情况下会导致树枝状生长。当免洗产品通过 J-STD-004 SIR 和 ECM 测试并正确使用时，就不会出现这种问题。对于必须清洗的助焊剂残留物（水溶性），使用彻底、有效的清洗过程应能防止任何腐蚀。必须重申的是，含卤化物的助焊剂本身并不会对组件造成危害。只是必须对卤化物的存在进行鉴定，以促进电化学可靠设备的设计和组装。
相比之下，制造商之所以决定只使用无卤素产品，则是出于对环境的考虑。助焊剂化学成分中的卤素通常是卤代碳化物，当含卤素助焊剂残留物的组件处理不当时，可能会污染环境。虽然全球每天都在使用含卤素的助焊剂，但个别公司可能会选择自行制定法规，拒绝使用含卤素的助焊剂，以完全避免这一问题。目前还没有政府法规完全禁止在电子产品中使用所有含卤素的焊接材料。由于在技术上不需要对卤素含量进行鉴定，因此卤素测试是可选的。
令人困惑之处
对于那些对技术有更多好奇心的人来说，这里有一个更深入的探索：
- 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.
更多阅读
有关 J-STD-004 焊剂表征的更多信息，请参阅这些文章：
