| HS Code | 576271 |
| Product Name | Ammonium Persulfate Electronic/EL Grade |
| Chemical Formula | (NH4)2S2O8 |
| Molecular Weight | 228.18 g/mol |
| Cas Number | 7727-54-0 |
| Einecs Number | 231-786-5 |
| Appearance | White crystalline powder |
| Assay | ≥99.0% |
| Chloride Cl | ≤0.001% |
| Iron Fe | ≤0.0005% |
| Heavy Metals As Pb | ≤0.0005% |
| Water Insoluble Matter | ≤0.005% |
| Ph 5 Aqueous Solution | 3.0-5.0 |
| Density | 1.98 g/cm³ |
| Solubility In Water | Soluble |
As an accredited Ammonium Persulfate Electronic/EL Grade factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Packaged as 25 kg net in double polyethylene-lined bags inside a sealed fiber drum, ensuring purity and safe handling. |
| Container Loading (20′ FCL) | 20′ FCL: Ammonium Persulfate Electronic/EL Grade packed in sealed, labeled drums on pallets, secured and segregated to prevent contamination. |
| Shipping | Ammonium Persulfate Electronic/EL Grade ships as UN1444, Class 5.1 oxidizer, PG III. Pack in sealed, corrosion-resistant containers to maintain high purity. Keep dry, cool, and away from combustibles, reducing agents, and incompatible materials. Label as oxidizing solid; use grounded, ventilated transport and avoid contamination during handling. |
| Storage | Store Ammonium Persulfate Electronic/EL Grade in a cool, dry, well-ventilated area away from direct sunlight, heat, and moisture. Keep the container tightly sealed to prevent contamination and decomposition. Maintain temperatures below 25°C (77°F). Segregate from combustibles, reducing agents, organic materials, and metal powders. Use compatible, non-reactive containers and inspect regularly for damage. |
| Shelf Life | Shelf life is 12 months from manufacture when stored in the original, tightly sealed container in a cool, dry area. |
In high-density interconnect (HDI) printed circuit board fabrication, low-sodium ammonium persulfate electronic/EL grade is metered into a sulfuric acid spray module immediately upstream of dry film photoresist lamination and solder mask coating. Horizontal conveyorized spray tools are configured with flood-bar nozzles of 0.8–1.2 mm diameter and fluid pressure between 0.8 bar and 1.4 bar; bath temperature is held at 25–35 °C, and the working concentration is typically 60–150 g/L ammonium persulfate with 1.5–5.0 vol% sulfuric acid. The sulfuric acid component suppresses hydrolysis of the persulfate anion and prevents the formation of cuprous hydroxide precipitates on the copper surface. Copper removal is controlled to 0.3–0.8 µm per pass, measured by cross-sectional microscopy, while surface roughness is maintained at Ra 0.30–0.50 µm as determined by contact profilometry in accordance with ISO 4287:1997. The resulting topography provides mechanical anchoring for dry film photoresist. Production-scale failure modes include nozzle crystallization after idle periods below 15 °C and feed-line blockages from lumpy crystals when hopper vibration is not maintained. For fine-line patterning, this pretreatment is used before dry film resist lamination, UV exposure, development, and acid copper electroplating; terminal features include line/space dimensions down to 30 µm/30 µm, with acceptance governed by IPC-6012E.
Substitution with technical-grade sodium persulfate in this step is avoided because residual sodium accumulates at the copper-resist interface and can migrate under humid bias during downstream electrical testing. Electronic/EL grade ammonium persulfate is therefore specified with sodium and iron limits at or below 0.1 mg/kg, and chloride below 0.5 mg/kg to prevent pitting during spray impingement. Rinsing after microetching uses ultrapure water at 18 MΩ·cm resistivity meeting ASTM D1193-06 Type E-1.
Copper build-up, not initial ammonium persulfate concentration, determines process stability in horizontal conveyorized etching lines. Above approximately 30–45 g/L dissolved copper, spray impingement uniformity at the copper surface degrades because solution density increases and persulfate consumption shifts toward side reactions with accumulated cuprous species. For fixed flood-bar pressure tools, operators observe a reduction of 15–25 % in gravimetric copper removal when the bath is run beyond the rated copper loading window. Published data for exact limiting concentrations varies by tool configuration, because nozzle throw distance, oscillation speed, and bath reheating capacity all modify local mass transfer; the stated 30–45 g/L range is derived from production etch-floor specifications rather than a single universal threshold.
Bath control relies on oxidation-reduction potential rather than operator visual inspection. A platinum electrode is held at 500–650 mV versus Ag/AgCl to track persulfate activity; ORP falls sharply as persulfate is depleted below 20 g/L. Copper concentration is measured every 4 h by matrix-matched UV-VIS absorbance at 800 nm, and sulfuric acid is titrated with sodium hydroxide to maintain a minimum of 2.0 vol%. Chloride ingress above 2 mg/L from tap-water rinse drag-in creates localized pitting and interferes with ORP reproducibility; this is why electronic/EL grade ammonium persulfate and chloride-free make-up water are adopted. Bath life extension by electrochemical copper removal is available but seldom used for fine-line work because regeneration can introduce organic stabilizers that remain on the dry film adhesive interface.
| Parameter | Representative electronic/EL grade lot-release limit | Analytical method |
|---|---|---|
| Active oxygen assay | ≥ 6.90 wt% | iodometric titration |
| Chloride | ≤ 0.5 mg/kg | ion chromatography |
| Sodium | ≤ 0.1 mg/kg | ICP-MS |
| Iron | ≤ 0.1 mg/kg | ICP-MS |
| Copper | ≤ 0.05 mg/kg | ICP-MS |
| Residue after ignition | ≤ 0.02 wt% | gravimetric |
Ammonium persulfate electronic/EL grade is used as a water-soluble thermal initiator for aqueous acrylic binders in multilayer ceramic capacitor green tape. The binder is synthesized in a glass-lined reactor equipped with a turbine agitator operating at 3.0–5.0 m/s tip speed. A pre-emulsion of acrylic acid, methacrylic acid, and C1–C4 alkyl acrylates is fed over 2.5–4.0 h into deionized water at 70–85 °C, while ammonium persulfate is introduced as a separate aqueous solution at 0.2–0.8 wt% relative to total monomer. The persulfate anion undergoes first-order thermal homolysis at the peroxo bond, generating sulfate radical anions that initiate chain growth in the aqueous phase and at the particle-water interface. Reaction temperature and initiator feed rate are interlocked: a jacket temperature overshoot of +3 °C during feed reduces persulfate half-life sufficiently to cause batch-to-batch molecular weight reduction and low-viscosity latex.
Electronic/EL grade ammonium persulfate is specified because residual sodium, iron, and copper from technical initiators become ionic contaminants in the binder after ammonia neutralization. In multilayer ceramic capacitor green tape, the binder is loaded at 5–8 wt% relative to barium titanate powder and must burn out cleanly before sintering at 1100–1200 °C. Sulfate end groups from persulfate initiator are controlled through diafiltration; residual sulfate above 0.05 wt% in the dried binder can leave sulfate ash that contributes to insulation resistance failures under MIL-PRF-55681 life testing. Redox initiation with sodium metabisulfite lowers polymerization temperature to 35–45 °C but raises total sulfur content and is therefore restricted to non-dielectric binder grades unless a post-reaction ultrafiltration step is qualified.
A standard fan-out wafer-level packaging flow deposits a 200–500 nm physical-vapor-deposited copper seed layer over a titanium barrier after polymer dielectric patterning. After photo-patterning and copper redistribution layer electroplating to 5–10 µm, the photoresist is stripped and the exposed copper seed is removed with an acidic ammonium persulfate wet etch. Single-wafer spray processors are configured with recirculating bath temperature at 30–40 °C and ammonium persulfate concentration at 20–50 g/L, with sulfuric acid below 3 vol% to limit titanium attack before the subsequent barrier etch step. Endpoint detection is based on colorimetric copper concentration or open-circuit potential shift; the process is stopped when redistribution layer surface profilometry indicates less than 300 nm of unintended copper loss, measured on monitor wafers before and after each lot. Published tool-specific etch-rate data for this configuration is limited, so production control relies on monitor-wafer profilometry rather than fixed immersion time.
Electronic/EL grade ammonium persulfate is mandatory because sodium and chloride residues from lower-purity grades remain on the polyimide or PBO dielectric surface after rinse and cause bias-humidity failure or copper migration. Incoming specification limits for sodium at ≤0.1 mg/kg and chloride at ≤0.5 mg/kg are reconciled against wafer-level inductively coupled plasma mass spectroscopy extraction tests after clean. The ammonium persulfate etch must balance seed-layer clearing with minimal redistribution layer sidewall attack; process conflict arises when bath copper loading exceeds 10 g/L, at which point the etch rate becomes non-uniform at the wafer edge. Periodic batch replenishment with fresh ammonium persulfate solution and overflow cascade rinse is employed to prevent edge-to-center non-uniformity. Terminal product is a reconstituted wafer or panel with high-density copper redistribution layer ready for die placement, molding, and ball attach.
Copper-gate thin-film transistor liquid-crystal display arrays are wet-etched with a hydrogen peroxide-based copper etchant followed by a dilute acid molybdenum or titanium barrier etch. After the barrier etch, a short ammonium persulfate treatment oxidizes residual copper species and organic post-etch residues from the gate edge, preventing copper ion migration into the silicon nitride insulator. Batch spray tools apply the solution at 25–35 °C for 60–180 s, followed by ultrapure water rinsing at >18.2 MΩ·cm resistivity conforming to ASTM D1193-06. Ammonium persulfate concentration is held at 10–30 g/L with pH below 2.0; this is intentionally lower than printed circuit board microetch baths because excessive copper removal would undercut the gate line edge.
Sodium is the critical contaminant in this application. A sodium increase on the glass array can manifest as threshold-voltage shift after negative-bias temperature stress. Consequently, the electronic/EL grade ammonium persulfate used upstream of chemical-vapor-deposited gate insulator must be low-sodium and low-chloride; many array fabs require sodium below 0.05 mg/kg and chloride below 0.2 mg/kg at the point of use. The terminal array substrate proceeds to silicon nitride deposition, amorphous silicon channel formation, source-drain patterning, and pixel electrode integration.
For conductive polymer dispersions used in printed supercapacitor electrodes and antistatic coatings, ammonium persulfate electronic/EL grade functions as an oxidant in the oxidative polymerization of aniline to polyaniline. In a jacketed reactor held at 0–5 °C, aniline hydrochloride is polymerized in 1 M hydrochloric acid while ammonium persulfate dissolved in 1 M hydrochloric acid is added at a controlled rate to maintain a final molar ratio of ammonium persulfate to aniline between 1.0:1 and 1.25:1. The addition time ranges from 2 h to 4 h, followed by continued stirring for 4–6 h at low temperature. The resulting emeraldine salt precipitate is filtered, washed with dilute acid and deionized water, and neutralized or dedoped as required. Electronic/EL grade ammonium persulfate is used because trace iron and copper in technical grades alter the oxidation state and reduce final conductivity; polyaniline electrode films are characterized by four-point probe resistance or surface resistivity according to ASTM D257-14. Because concentrated persulfate and aniline hydrochloride react exothermically, the oxidant solution is added through a cooled dip tube and is never reverse-charged into neat aniline solution.
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Ammonium Persulfate Electronic/EL Grade, CAS 7727-54-0 and EINECS 231-786-5, is a controlled-purity peroxydisulfate supplied as a white crystalline solid with the formula (NH4)2S2O8 and molecular weight 228.20 g mol−1. The EL designation identifies a low-metal, low-halide material intended for printed circuit board copper microetching, adhesion promotion before dry-film lamination, and cleaning steps in which residual cation contamination directly influences electrical test yield. Commercial electronic/EL certificates of analysis generally specify assay by iodometric titration at not less than 99.0%, water content not more than 0.05 wt%, and residue after ignition not more than 0.02 wt%. Packaging is typically 25 kg fiber drums with polyethylene liners or 500 kg bulk sacks with moisture-barrier construction, because exposure to humidity above 60% RH produces caking and localized decomposition.
Physical data include true density 1.98 g cm−3, bulk density 1.1–1.3 g cm−3, and water solubility near 80 g per 100 mL at 20°C. A 5 wt% aqueous solution at 25°C has pH 3.0–4.0 because the ammonium ion equilibrium maintains an acidic response. Thermal decomposition begins above 120°C, releasing oxygen and acidic sulfate-bearing decomposition products. The solid is classified as UN 1444, Class 5.1, and must be segregated from reducing agents, strong alkalis, transition-metal salts, and combustible organic fines.
Thermal decomposition in aqueous solution proceeds by scission of the peroxo bond to sulfate radical anion SO4•−. Peer-reviewed kinetic studies generally report uncatalyzed activation energy near 140–160 kJ mol−1 for peroxydisulfate decomposition in deionized water. Dissolved iron and copper lower the apparent activation energy by redox cycling, which is why low metal content in the EL grade directly affects bath life. A solution containing 0.5 mg/L dissolved iron can have a materially longer decomposition half-life at 40°C than the same solution containing 5 mg/L iron. The practical consequence on a production line is less oxygen off-gassing, lower turbidity, and reduced nozzle blockage in spray systems.
Analytical verification of Electronic/EL Grade is performed by iodometric titration for assay, ICP-MS for trace metals, ion chromatography for chloride, and Karl Fischer titration for water. Incoming inspection for printed circuit board shops typically uses a 10 wt% solution filtered through a 0.45 µm membrane to monitor undissolved residue and turbidity. Particle counts above 10 particles per mL at ≥0.5 µm are often used as a quarantine limit in high-volume lines. These are contract quality controls rather than universally binding specifications, so lot-specific certificate-of-analysis data and retained samples are maintained.
Compared with technical-grade ammonium persulfate, the Electronic/EL Grade reduces iron, copper, nickel, zinc, and chloride through additional purification. In a microetch bath, trace iron and copper accelerate persulfate decomposition and release particulates into fine-line spaces; chloride at the copper-resist interface can promote pitting and undercut. The following representative acceptance bands are compiled from merchant datasheets; individual vendor limits may be narrower.
| Parameter | Electronic/EL Grade | Technical Grade |
|---|---|---|
| Assay as (NH4)2S2O8 | ≥99.0 wt% | ≥98.5 wt% |
| Iron Fe | ≤2 mg/kg | ≤20 mg/kg |
| Copper Cu | ≤1 mg/kg | ≤10 mg/kg |
| Nickel Ni | ≤1 mg/kg | ≤5 mg/kg |
| Zinc Zn | ≤1 mg/kg | ≤10 mg/kg |
| Chloride Cl | ≤5 mg/kg | ≤20 mg/kg |
| Residue after ignition | ≤200 mg/kg | ≤500 mg/kg |
| Water | ≤0.05 wt% | ≤0.10 wt% |
In multilayer printed wiring production, the EL grade is applied as a microetchant before dry-film lamination, solder mask coating, or electroless copper deposition. A typical horizontal spray recipe operates at 80–150 g/L ammonium persulfate in deionized water, 30–40°C, spray pressure 1.8–2.5 bar, and residence time 30–90 s. Copper removal of 0.8–1.5 µm per pass produces uniform microroughening for resist anchoring. Etch depths below 0.5 µm can leave insufficient topography for adhesion, while removal above 2.0 µm on fine-line circuitry causes conductor width loss and impedance drift. The bath is not adjusted with mineral acid; persulfate oxidation and sulfate accumulation drive the pH into the acidic range during operation.
Copper loading is the primary process-control variable. As cupric ion accumulates above 30–40 g/L, etch-rate suppression and non-uniform roughening are reported on production lines, requiring bleed-and-feed at 10–20% of bath volume per shift or inline copper recovery. Raising temperature above 45°C does not provide a proportionate rate increase; instead, accelerated oxygen evolution can cause nozzle cavitation and spray non-uniformity. Below 25°C, etch rate in some horizontal systems falls below 0.3 µm/min. The practical processing window is therefore narrower than for commodity persulfate because the controlled impurity profile makes decomposition products and bath instability more visible as pressure or turbidity excursions.
Even at chloride ceilings of ≤5 mg/kg in the dry salt, chloride drag-out can concentrate in rinse water and dry at the copper surface if final rinsing is not maintained with hot deionized water or if panels wait more than 8 h before resist application. Microsections then show local pitting of 2–5 µm diameter at resist edges. In electroless copper initiation, halide contamination above 1–2 mg/L in the activator bath can destabilize palladium colloid. The EL grade is preferred over technical grade when the same microetch solution immediately precedes plating, because iron, nickel, and copper impurities in the salt can otherwise be trapped in residual sulfate films and migrate into solder-mask interfaces during cure above 150°C.
After microetching, final cascade rinses are maintained below 20 µS/cm conductivity at 15–25°C to prevent sulfate redeposition. For semiconductor packaging and ceramic substrates, alkali-metal contamination budgets are commonly ≤1×1010 atoms cm−2 for sodium and potassium by total reflection X-ray fluorescence. Ammonium persulfate introduces no sodium or potassium, unlike sodium persulfate, and its ammonium residue can be removed by thermal exposure during die-attach or solder reflow. This is a key differentiator from sodium and potassium persulfate grades.
Wafer bump and redistribution-layer copper etching exclude sodium persulfate because mobile sodium ions under bias migrate toward silicon oxide interfaces and shift flatband voltage. Potassium persulfate is similarly restricted in MOS-compatible lines. Ammonium persulfate offers an alkali-metal-free persulfate chemistry, but it must be operated acidic at pH 2.5–4.0 to maintain copper-to-barrier selectivity; ammonia-containing formulated etchants above pH 8.5 can attack titanium-tungsten barrier layers. Published data for this specific configuration is limited for advanced wafer-level packaging because most formulated copper etchants are proprietary blends rather than single-salt solutions. Qualification therefore requires patterned-wafer etch tests with tin-silver bump metallurgy and barrier-metal undercuts reviewed by cross-section.
Compared with hydrogen peroxide–sulfuric acid microetchants, ammonium persulfate is a solid one-component oxidizer that avoids liquid peroxide stabilizers and reduces the risk of runaway decomposition in concentrated form. However, persulfate baths operate at a lower oxidation-reduction state and require thorough sulfate rinsing. The EL grade is selected not because it etches faster than technical grade, but because its impurity ceiling is compatible with downstream palladium catalysts, dry-film adhesion, and fine-line yield.
In high-purity acrylic and methacrylic polymer synthesis, persulfate initiation is carried out at 60–80°C with initiator levels of 0.1–0.5 wt% on monomer. Sulfate radical anions derived from aqueous decomposition initiate chain growth; residual ammonium and sulfate end groups affect latex stability. Electronic/EL Grade is selected only when the final polymer cannot tolerate iron or copper residues from technical grade at the mg/kg level. For general emulsion polymer production, technical grade remains cost-effective and sufficient.
Storage and dissolution for Electronic/EL Grade follow UN 1444 oxidizer requirements, with additional contamination control. Bulk storage bins are grounded, vented, and protected from humidity above 60% RH; partially opened bags should be resealed under dry nitrogen if ambient moisture exceeds 50% RH. Dissolution skids use 316L stainless steel or polypropylene, and titanium heat exchangers where heating is required; brass, copper, and unlined carbon steel are incompatible because dissolved transition metals accelerate persulfate decomposition. Local exhaust ventilation is required at bag dump stations and dust collectors because the salt is a respiratory irritant and strong oxidizer. Amine-based additives should not be blended with solid ammonium persulfate before addition to water; exothermic redox reactions can occur unless the formulation has been tested and diluted in the intended sequence.
