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.
您需要知道的事
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.
為什麼您需要知道
之所以要監控鹵化物的濃度，是因為鹵化物具有腐蝕焊料的潛力，在外加電氣偏壓和濕氣的情況下，可能會導致樹枝狀生長。當免清洗產品通過 J-STD-004 SIR & ECM 測試，並正確使用時，就不需要擔心這個問題。對於必須清洗（水溶性）的助焊劑殘留物，使用徹底、有效的清洗程序應可防止任何腐蝕。必須重申的是，含鹵化物的助焊劑並不是對組件有害的。只需對鹵化物的存在進行特性分析，即可促進電化學可靠裝置的設計與組裝。
相反，製造商決定完全使用無鹵素產品則是基於環境考量。助焊劑化學中的鹵素通常是鹵碳化合物，當含鹵素助焊劑後殘留的組件被不當處理時，有可能污染環境。雖然全球每天都在使用含鹵素的助焊劑，但個別公司可以選擇自行制定法規，拒絕使用含鹵素的助焊劑，以完全避免這個問題。目前並沒有政府法規完全禁止在電子產品中使用所有含鹵素的焊接材料。由於在技術上沒有表征鹵素含量的需要，因此鹵素測試是可選的。
令人困惑的地方
對於有更多技術好奇心的人，這裡有更深入的探索：
- 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.
進一步閱讀
如需更多關於 J-STD-004 通量特性的資訊，請隨時查看這些文章：
