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.
知っておくべきこと
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.
なぜ知っておく必要があるのか
ハロゲン化物ははんだを腐食する可能性があるため、ハロゲン化物の濃度が監視されます。ハロゲン化物は、印加される電気バイアスや水分の存在下で樹枝状成長を引き起こす可能性があります。無洗浄製品がJ-STD-004 SIR & ECMテストに合格し、正しく使用されている場合、この心配はありません。洗浄が必要なフラックス残留物（水溶性）については、徹底的かつ効果的な洗浄プロセスを使用することで、腐食を防ぐことができます。ハロゲン化物を含むフラックスが本質的にアセンブリに有害であるわけではないことを再確認することは極めて重要である。ハロゲン化物の存在は、電気化学的に信頼できるデバイスの設計と組立を促進するために、単に特性評価されなければならない。
これとは対照的に、ハロゲンを含まない製品のみを使用するというメーカーの決定は、環境への配慮が原動力となっている。フラックスの化学的性質に含まれるハロゲンは通常ハロカーボンであり、ハロゲンを含むフラックス残渣を含むアセンブリが不適切に廃棄された場合、環境を汚染する可能性がある。ハロゲン含有フラックスは世界的に毎日使用されているが、個々の企業は、この問題を完全に回避するために、ハロゲン含有フラックスの使用を拒否する自主規制を選択することができる。電子機器におけるすべてのハロゲン含有はんだ材料の使用を全面的に禁止する政府規制はありません。ハロゲン含有量を評価する技術的な必要性はないため、ハロゲン試験は任意である。
混乱するところ
より技術的な好奇心が強い人のために、ここでさらに深く掘り下げてみよう：
- 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.
さらに読む
J-STD-004によるフラックス特性評価の詳細については、以下の記事をご覧ください：
