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What it is. This ammonium fluoride solution contains 40 g of ammonium fluoride (NH4F) per 100 mL and is supplied ready to use in a 500 mL size. It saves time, weighing, and dust exposure compared with dissolving the toxic solid salt in-house, and it delivers a consistent fluoride concentration from batch to batch.
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Concentration in practical terms. At 400 g of NH4F per liter and a molecular weight of 37.04 g/mol, the solution is about 10.8 molar in ammonium fluoride (calculated). That high fluoride concentration is what makes it effective as an etch buffer and a fluoride source with small additions.
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Why 40%. Forty percent is the standard ammonium fluoride concentration for preparing buffered oxide etch (BOE), also called buffered HF. Mixing 40% NH4F with 49% hydrofluoric acid at common volume ratios such as 6:1, 7:1, or 10:1 produces an etchant that removes silicon dioxide at a steady, predictable rate. Lab Pro also offers Hydrofluoric Acid 49% ACS and pre-mixed Hydrofluoric Acid 6:1.
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How it buffers the etch. Hydrofluoric acid consumes fluoride as it dissolves silicon dioxide. Ammonium fluoride replenishes fluoride and keeps the solution's acidity steady, so the etch rate stays uniform across a wafer and over the bath's life. It also limits HF penetration into photoresist, reducing resist lifting and undercut compared with straight hydrofluoric acid.
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Weight per volume versus weight per weight. This product is specified as 40% w/v, meaning 40 g per 100 mL of solution. Many semiconductor-grade solutions are specified as 40% w/w, 40 g per 100 g of solution. The two are close but not identical, so confirm which basis a process recipe uses before substituting.
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How it behaves. The solution is clear and colorless with a faint ammonia odor. Fluoride ions are toxic through skin contact, ingestion, and inhalation of mist, and they etch glass and silica. Contact with acids releases hydrogen fluoride, and heating or decomposition can release ammonia, nitrogen oxides, and hydrogen fluoride gas.
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Where it is used. Beyond semiconductor oxide etching, 40% ammonium fluoride is used for glass and quartz surface treatment, metal and ceramic cleaning formulations, and analytical work that calls for a fluoride ion source. Because it is pre-dissolved, it meters more accurately into baths than solid salt.
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Handling at a glance. Treat ammonium fluoride solution with hydrofluoric acid precautions: HF-rated gloves, goggles, a face shield, and calcium gluconate gel within reach. Mix etchants only in polyethylene, polypropylene, or fluoropolymer labware inside a ventilated hood.
Technical Specifications
| Active Ingredient |
Ammonium fluoride |
| CAS Number |
12125-01-8 (ammonium fluoride); 7732-18-5 (water) |
| EC Number (active) |
235-185-9 |
| Formula (active) |
NH4F |
| Molecular Weight (active) |
37.04 g/mol |
| Concentration |
40% (w/v), 400 g/L |
| Solvent |
Water |
| Appearance |
Clear, colorless liquid |
| Odor |
Faint ammonia odor |
| Water Solubility |
Completely miscible |
| Package Size |
500 mL |
Applications / Common Uses
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Buffered oxide etch preparation: Blended with 49% HF to strip silicon dioxide at a controlled rate.
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Semiconductor wafer processing: Supports oxide removal, patterning, and pre-diffusion cleans.
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Glass and quartz surface treatment: Provides fluoride for light etching and surface activation.
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Analytical fluoride source: Used where methods call for a known fluoride ion concentration.
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Metal and ceramic cleaning: Removes oxide films and silicate residues in specialty cleaning formulations.
Storage, Handling & Shipping
Caution: Ammonium fluoride solution is toxic if swallowed, contacts skin, or is inhaled. Fluoride penetrates skin and can cause delayed deep-tissue injury and systemic effects. Wear chemical goggles, a face shield, HF-rated gloves, and a chemical-resistant apron, work in a ventilated area, and keep calcium gluconate gel available.
Store the solution tightly closed in a cool, ventilated area away from acids and strong oxidizers, and keep Calgonate 2.5% Calcium Gluconate Gel wherever it is handled. Fluoride attacks glass, so transfer and mix only in polyethylene, polypropylene, or fluoropolymer labware. Do not let the solution dry on benches or containers, since dried residues remain toxic and can become airborne.
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Incompatible materials: Acids (release HF), strong oxidizers, strong bases, glass and silica, and reactive metals.
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Exposure limit (fluorides): OSHA PEL 2.5 mg/m3 as F (TWA).
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Spill response: Absorb with an inert or calcium-based absorbent, collect in a plastic container, and keep away from acids.
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First aid: Skin: flush with water, apply calcium gluconate gel, and get medical attention. Eyes: flush for 15 minutes and seek immediate care.
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GHS signal word: Danger. Toxic if swallowed, in contact with skin, or if inhaled.
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