| HS Code | 587861 |
| Product Name | Cu Pretreatment Electronic/EL Grade |
| Grade | Electronic/EL |
| Main Composition | Copper pretreatment chemical formulation |
| Physical State | Liquid |
| Appearance | Clear liquid |
| Color | Colorless to pale blue |
| Odor | Mild characteristic odor |
| Specific Gravity | 1.05 - 1.15 at 20°C |
| Ph | 1.0 - 2.5 |
| Water Solubility | Completely miscible |
| Trace Metal Impurities | ≤ 10 ppb each |
| Storage Temperature | 15 - 25°C |
| Shelf Life | 6 months from date of opening |
As an accredited Cu Pretreatment Electronic/EL Grade factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Packaged in 1 L and 4 L HDPE containers with tamper-evident caps, certified for electronic-grade purity and safe handling. |
| Container Loading (20′ FCL) | 20′ FCL: palletized, upright chemical drums securely braced with dunnage, labeled, ventilated, and protected from leakage and movement. |
| Shipping | Shipping as hazardous material (Class 8 corrosive/oxidizer) in UN-approved containers. Ground transport only; not authorized for air. Requires proper hazardous materials declaration, labeling, and upright securement. Keep away from incompatible materials, moisture, and direct sunlight. Ensure leak-tight packaging with secondary containment for spill protection. |
| Storage | Store Cu Pretreatment Electronic/EL Grade in its original, tightly sealed container in a clean, cool, dry, well-ventilated area. Protect from moisture, physical damage, and direct sunlight. Keep away from incompatible materials, strong oxidizers, and food items. Avoid contamination; use dedicated equipment. Maintain temperatures within manufacturer recommendations, typically 15–30°C, and monitor expiration dates. |
| Shelf Life | Shelf life is typically 12 months from manufacture date when stored sealed in original containers at room temperature. |
On horizontal conveyorized inner-layer etch lines, Cu Pretreatment Electronic/EL Grade is metered into a microetch module before dry film photoresist lamination. The fluid is circulated through a heated sump and sprayed onto moving panels at 1.0–2.0 kg/cm² manifold pressure. A cupric chloride working bath is controlled at 28–32 °C, cupric ion below 30 g/L, and sodium chloride between 50–80 g/L; a sulfuric-peroxide alternative is operated at 20–28 °C with 5–10 vol% sulfuric acid and 0.5–2.0 vol% hydrogen peroxide. Copper removal is maintained at 0.4–0.8 µm/min, and total etch depth per side is held between 0.3–1.0 µm depending on foil profile and reverse-treated or low-profile copper type. Spray dwell time is 30–60 s on conveyorized modules. Surface roughness measured according to ISO 25178-2 typically falls between Ra 0.25–0.45 µm after pre-treatment. The microetch is followed by a two-stage cascade rinse; rinse water conductivity above 5 µS/cm is rejected because sulfate or chloride drag-out reduces dry film resist polymerization and adhesion. After lamination and development, peel strength is verified by IPC-TM-650 2.4.8B, with failures traced to insufficient microetch depth or non-uniform panel speed. End products are inner-layer cores for multilayer printed circuit boards built to IPC-6012 Class 2 and Class 3.
EL-grade purity limits for this application define chloride contamination below 1.0 µg NaCl equivalent/cm² by IPC-TM-650 2.3.25C, sodium below 0.5 µg/cm², and total sulfate residue below 1.0 µg/cm². The innerlayer pre-treatment is incompatible with amine-based organic corrosion inhibitors introduced before lamination because amine residues interfere with diazo film photoinitiator chemistry in dry film resist. Holding time after microetch is limited to 4 h at 45–55% relative humidity; panel storage above 60% RH accelerates copper oxide regrowth and reduces resist adhesion. The process is used on FR-4, halogen-free epoxy laminate, and low-loss hydrocarbon or PTFE laminates where foils include electrodeposited and reverse-treated low-profile copper.
A sodium persulfate microetch is applied to copper surfaces immediately before liquid photoimageable solder mask coating. The Cu Pretreatment Electronic/EL Grade bath is maintained at 25–30 °C with sodium persulfate at 80–120 g/L and sulfuric acid at 2–5 vol%; immersion dwell time is 60–90 s and spray dwell time is 30–45 s. Copper removal is controlled at 0.8–1.2 µm per side to generate Ra 0.35–0.55 µm while preserving fine-line cross-section. Bath parameters are adjusted when immersion tin is specified downstream because trapped sulfate species at the solder mask-copper edge increase white spot defects after immersion tin deposition. Iron contamination is controlled below 2 mg/L because iron catalyzes persulfate decomposition and increases free-radical attack on mask adhesion promoters. The post-pretreatment rinse water is maintained at 0.5–1.0 µS/cm conductivity, and final ionic contamination is measured according to IPC-TM-650 2.3.25D.
Solder mask adhesion is tested by tape pull per IPC-TM-650 2.4.1, and cured film qualification follows IPC-SM-840E. Mask delamination at excursions above Ra 0.7 µm is avoided by limiting etch depth and controlling peroxide decomposition. End products are rigid and flexible printed wiring boards with LPI solder mask qualified for HASL, ENIG, immersion silver, and immersion tin surface finishes. The pre-treatment line rejects panels with water-break failure after rinse because organic residues reduce mask UV adhesion. For white solder mask production, copper particulate is removed through 1 µm absolute cartridge filtration to prevent black speck contamination after final cure.
Before ionic palladium catalyst immersion, through-hole metallization lines require removal of interfacial copper oxide and desmear residues from innerlayer capture pads. Cu Pretreatment Electronic/EL Grade is applied after desmear and before catalyst. The bath contains sodium persulfate at 80–100 g/L, sulfuric acid at 1–3 vol%, and copper sulfate up to 10 g/L to moderate etch rate; temperature is 26–32 °C and immersion time is 45–75 s. Copper removal of 0.5–0.8 µm removes oxide without severe attack on laser-drilled microvia sidewalls. Bath life is terminated when copper loading exceeds 8–10 g/L or when etch rate drops below 0.3 µm/min, whichever occurs first. After pre-treatment, cascading rinses reduce conductivity below 5 µS/cm, and the panel passes a water-break test before entering the catalyst bath. Electroless copper flash thickness of 0.5–1.0 µm is verified gravimetrically or by cross-section per IPC-TM-650 2.4.8B.
End products are through-hole and blind via panels for automotive and high-density interconnect multilayer boards under IPC-6012 Class 3. The pre-treatment is incompatible with alkaline cleaner residues entering the persulfate bath because pH shock precipitates copper hydroxide and consumes persulfate through side reactions. Panel-to-panel etch depth variation on vertical hoist lines is minimized by rack movement agitation at 0.5–1.0 m/min and by maintaining copper content below 10 g/L with continuous bleed-and-feed. Production-scale HDI line data show that copper loading above 12 g/L increases via wall over-etch by 0.15–0.25 µm and reduces backlight ratings because redeposited copper interferes with via coverage.
| Parameter | Sodium persulfate | Cupric chloride | Sulfuric-peroxide |
|---|---|---|---|
| Operating temperature | 25–35 °C | 40–55 °C | 20–30 °C |
| Primary active component | Na₂S₂O₈ 80–150 g/L | CuCl₂·2H₂O 150–200 g/L | H₂SO₄ 5–10 vol% + H₂O₂ 0.5–2.0 vol% |
| Typical etch rate | 0.3–0.8 µm/min | 1.0–2.0 µm/min | 0.5–1.5 µm/min |
| Copper loading limit | 10–15 g/L | 30–50 g/L | 20–30 g/L |
| Preferred process mode | Immersion or spray | Spray or conveyorized | Immersion or spray |
In pattern plating cells, residual benzotriazole and triazole-based anti-tarnish films are removed by a dilute sulfuric-peroxide or persulfate pre-dip immediately before acid copper electroplating. The working solution contains 5–10 vol% sulfuric acid and 0.3–1.0 vol% hydrogen peroxide at 20–25 °C; immersion time is limited to 30–60 s. Copper removal is held below 0.3 µm per side to preserve fine line geometry and avoid undercut of dry film edges. The bath is agitated with nitrogen or oil-free air because oxygen depletion reduces etch uniformity and allows local cuprous oxide reformation. After pre-dip, the surface is rinsed with deionized water at conductivity below 1 µS/cm and dried with filtered compressed air or nitrogen. Acid copper electroplating follows using a bright acid copper bath; plated deposit adhesion is verified by tape pull according to IPC-TM-650 2.4.1 after deposition. Typical terminal products are pattern-plated copper traces, plated through holes, and copper pillar base layers on rigid and flex PCB. The pre-dip is incompatible with palladium activator drag-in because palladium ions precipitate as black residues when sulfuric acid concentration falls below 5 vol% or when chloride contamination exceeds 20 mg/L.
For OSP final finish lines, the copper pre-treatment must remove oxide without depositing halide species. Cu Pretreatment Electronic/EL Grade formulated as a halide-free sulfamic or sulfuric-peroxide system is operated at 25–35 °C, pH below 2, and etch depth 0.3–0.6 µm. The working preparation is 8–12 vol% sulfamic acid or 5–10 vol% sulfuric acid with 0.3–1.0 vol% hydrogen peroxide and a non-halide stabilizer at 0.1–0.5 g/L. Chloride concentration is monitored by ion chromatography; chloride levels above 5 mg/L are rejected because chloride residues degrade OSP film uniformity and accelerate edge creep corrosion after thermal cycling. The microetch is followed by a 1–2 min deionized water rinse and an acid post-dip at pH 1.0–1.5 to remove sulfate or persulfate residues. OSP coating thickness is controlled at 0.1–0.3 µm and verified by UV-Vis or HPLC; solderability is tested per J-STD-003C. End products are OSP-finished printed circuit boards for consumer, telecommunications, and industrial assemblies. The final bath must not be topped up with chloride-containing city water because even trace halide levels reduce OSP protection against copper oxidation during reflow soldering.
Because cuprous oxide and stamping lubricant residues remain on copper alloy leadframes, wire bond lift and die attach void failures increase before silver spot plating. Cu Pretreatment Electronic/EL Grade is applied in immersion or electrolytic modes using a low-chloride acid formulation at 25–40 °C. For immersion cleaning, dwell time is 20–40 s; for electrolytic cleaning, current density is 0.5–2.0 A/dm². Copper removal is held at 0.1–0.3 µm per side to avoid altering leadframe dimensional tolerances and pad co-planarity. Chloride is monitored below 2 mg/L because chloride residues on silver-plated leadframes induce wire bond lift after 175 °C die attach cure. Surface oxide removal is verified by XPS or water contact angle below 15°; wire bond pull strength is tested after assembly by MIL-STD-883 Method 2011. End products are QFN, QFP, and SOIC leadframes for power and automotive packages. The process is incompatible with high-pH cleaning before die attach because sodium residues reduce wire bond shear strength and increase package popcorning risk.
| Test / Requirement | Standard / Method | Typical Control Window |
|---|---|---|
| Dry film peel strength | IPC-TM-650 2.4.8B | ≥ 0.70 N/mm |
| Ionic contamination | IPC-TM-650 2.3.25C | ≤ 1.0 µg NaCl eq/cm² |
| Solder mask adhesion | IPC-TM-650 2.4.1 | No removal beyond tape test limit |
| Solderability after OSP | J-STD-003C | Class 3 wetting balance pass |
| Microetch roughness | ISO 25178-2 | Ra 0.25–0.55 µm |
| Wire bond pull | MIL-STD-883 Method 2011 | Device-specific minimum |
In advanced packaging wafer fabs, single-wafer spin processors apply Cu Pretreatment Electronic/EL Grade for post-CMP and pre-plating clean on copper pillar structures and redistribution layers. The chemistry is dispensed at 20–23 °C for 15–30 s, followed by a 30 s ultrapure water rinse and nitrogen spin dry. The EL-grade specification limits total trace metals to below 10 µg/L and critical alkali metals to below 1 µg/L to prevent transistor threshold shifts. Etch amount on electroplated copper is limited to 0.05–0.15 µm per side to avoid degrading pillar height uniformity. Process controls include zeta potential measurement for particle removal efficiency and surface roughness measurement by atomic force microscopy reported as Sa under ISO 25178-2. Published data for this specific configuration is limited; qualification therefore uses test vehicles with bump height standard deviation below ±1.0 µm and reflow voiding below 5% by X-ray inspection. End products are flip-chip copper pillar bumps with tin-silver caps, fan-out wafer-level packaging, and high-density interconnects for 5G and automotive radar. The pre-clean is incompatible with benzimidazole-containing copper complexing agents when subsequent solder wetting must achieve J-STD-003C Class 3 wetting balance thresholds.
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Cu Pretreatment Electronic/EL Grade functions as a stabilized acidic hydrogen peroxide microetch for copper surfaces in printed circuit board, IC substrate, and wafer-level packaging flows. The material is blended as a liquid concentrate with a nominal specific gravity of 1.13–1.16 at 25 °C under ASTM D4052-22. Incoming lot certification for electronic/EL grade material controls sodium, potassium, calcium, and iron to < 1.0 mg/L, chloride to < 5.0 mg/L, and liquid-borne particle counts at ≥ 0.2 µm to < 100 counts/mL using an optical particle counter calibrated per ISO 21501-4:2018. The low alkali-metal specification separates the product from general industrial copper etchants because mobile ion residues on wafer-level redistribution layers or organic substrates can shift electrical test values and contribute to electrochemical migration under bias in humid environments. The product is used in two primary positions: after copper deposition and before photoresist lamination to produce a uniformly roughened surface, and immediately before electrolytic or electroless copper deposition to remove oxide and adsorbed organic contamination.
Within horizontal conveyorized spray equipment fitted with 0.5 µm polypropylene cartridge filtration and titanium heater coils, the working bath is applied through low-pressure spray bars at 1.0–1.5 bar. Contact time is set to 45–75 seconds depending on copper thickness; longer exposure on thin seed layers causes breakthrough in isolated high-mass-transfer zones. The bath is replenished from concentrate via an automatic dosing system that monitors specific gravity and hydrogen peroxide concentration. Exhaust ventilation above the spray module is required because aerosolized peroxide at concentrations above 5.0 wt% can deposit on guide rollers and drive frictional oxidation in downstream dry-film lamination.
The electronic/EL grade designation is not a single test but a chain of incoming quality checks tied to specific methods. Table 1 summarizes representative acceptance windows that distinguish the material from industrial-grade copper microetchants. The limits are intended for lot release and are derived from supplier certificates of analysis for products classified as electronic grade; actual values for a specific drum may lie below the listed maxima.
| Parameter / Test Method | Electronic/EL Grade | Industrial Grade Microetchant |
|---|---|---|
| Specific gravity at 25 °C (ASTM D4052-22) | 1.13–1.16 | 1.10–1.18 |
| Sodium by ICP-MS (ASTM D5673-16) | < 1.0 mg/L | < 50 mg/L |
| Potassium by ICP-MS (ASTM D5673-16) | < 1.0 mg/L | < 50 mg/L |
| Iron by ICP-MS (ASTM D5673-16) | < 0.5 mg/L | < 25 mg/L |
| Chloride by ion chromatography (ASTM D512-23) | < 5.0 mg/L | 50–200 mg/L |
| Particle count ≥ 0.2 µm | < 100 counts/mL | Not routinely specified |
| Etch rate at 30 °C | 0.8–1.4 µm/min | 1.5–3.0 µm/min |
Chloride is the most operationally significant difference. At concentrations above 20 mg/L, chloride accelerates localized pitting on 5–12 µm electrodeposited copper and produces non-uniform micro-roughening after film lamination. In the electronic/EL grade, chloride is reduced by selecting chloride-free raw material sources and by avoiding hydrochloric acid pH adjustment. The etch rate is also deliberately set lower than industrial grades; a lower rate improves uniformity in horizontal lines where conveyor speed varies by ±0.2 m/min across the belt width. The resulting removal depth standard deviation remains below 0.15 µm across a 610 × 610 mm panel when measured by contact profilometry.
The micro-roughened surface after treatment is characterized by an arithmetic average roughness of 0.25–0.45 µm and a peak-to-valley roughness of 1.5–2.5 µm on 1 oz copper foil, measured by contact profilometry with a 5 µm tip radius. This roughness window is narrow by design: values below 0.20 µm do not provide enough mechanical interlock for dry-film photoresist adhesion, while values above 0.50 µm can entrap developer residues and create undercut during etching. In fine-line patterning below 25 µm line/space, the lower half of the roughness range is preferred to maintain sidewall control after develop-etch-strip.
For integrated circuit package redistribution layers, the copper seed is often deposited by physical vapor deposition at 80–200 nm. The acceptable loss before plating is typically limited to 10–30 nm because the seed must sustain uniform current distribution during subsequent electrolytic copper initiation. Cu Pretreatment Electronic/EL Grade at full concentration exceeds this budget in less than 5 seconds. The recommended procedure is therefore to operate a separate diluted bath containing 10–20 vol% of the standard solution in ultrapure water meeting ASTM D1193-06 Type II resistivity ≥ 1 MΩ·cm at 25 °C. At 20 °C the diluted bath removes less than 5 nm/min, allowing a 60-second exposure to remove surface oxide without breaching the seed. Bath sampling by ICP-OES for dissolved copper provides a real-time indication of etch extent; dissolved copper rises linearly with substrate throughput until the bath reaches 5–10 g/L, at which point the etch rate slows and the bath is replaced.
Electroless copper deposition lines for high-aspect-ratio through-holes use the pretreatment solution after alkaline permanganate desmear and before palladium catalyzation. The role changes from oxide removal to surface conductance preservation. Residual peroxide on the dielectric can oxidize the tin-palladium colloid and suppress the subsequent electroless copper initiation, so the rinse sequence after pretreatment must include a warm deionized water cascade at 40–50 °C for at least 60 seconds. A final rinse in 0.5–1.0 vol% sulfuric acid is used to neutralize drag-out from the alkaline desmear line. Incompatibility with amine-based accelerators is documented: residual amine films on the panel react with the acidic peroxide bath to form off-gassing and localized exothermic decomposition, which increases pitting near the hole mouths.
Hydrogen peroxide decomposition in Cu Pretreatment Electronic/EL Grade is influenced by dissolved copper, bath temperature, and the presence of insoluble particles. The stabilizer system is selected to maintain peroxide concentration above 80% of the initial steady-state level over 72 hours in a 200 L polypropylene holding tank with 0.2–0.5 L/min air sparging. At copper loading exceeding 50 g/L, the decomposition half-life shortens to less than 24 hours and the exotherm can raise bath temperature by 5–8 °C if the cooling circuit is undersized. Production lines are advised to install titanium plate heat exchangers sized for 0.15–0.25 kW/L of bath heat load under worst-case copper loading. Filtration through 0.5 µm polypropylene cartridges at 3–5 turnovers per hour removes precipitated copper sulfate particles that otherwise catalyze local peroxide decomposition. Bath life is additionally limited by the accumulation of dissolved copper; when copper reaches 60 g/L, chelation by the stabilizer is insufficient and the etch uniformity degrades. At this point the bath is either decanted and treated or run in bleed-and-feed mode at 5–10 vol% per hour.
Routine bath control uses iodometric titration for hydrogen peroxide, acid-base titration for free acid, and density measurement for specific gravity. Hydrogen peroxide concentration is maintained at 3.0–5.0 wt%, free sulfuric acid at 4.5–6.0 wt%, and cupric ion at 0.5–25 g/L depending on the application. The electronic/EL grade also requires periodic ICP-MS verification of sodium, potassium, iron, and calcium in the working bath, because drag-in from substrate surfaces can elevate mobile ion residues even when the virgin product meets specification. For semiconductor passivation applications, the working bath should meet the same trace metal limits as the incoming product, and weekly sampling is recommended.
| Control Point | Standard or Method | Acceptance Criterion |
|---|---|---|
| Preplate cleaning practice | ASTM B322-99(2020) | Copper surface free of oxide and organic contamination |
| Trace element analysis | ASTM D5673-16 | ICP-MS quantification of Na, K, Ca, Fe |
| Chloride determination | ASTM D512-23 | Ion chromatography or mercuric nitrate titration |
| Specific gravity | ASTM D4052-22 | Digital density meter at 25 °C |
| Dilution water resistivity | ASTM D1193-06 Type II | ≥ 1 MΩ·cm at 25 °C |
| Particle counter calibration | ISO 21501-4:2018 | Optical particle counter for liquid-borne particles |
Sodium persulfate and cupric chloride alternatives are used in lower-grade shops. Sodium persulfate baths create sodium sulfate drag-out that precipitates on unheated lower tank walls, whereas the electronic/EL grade contains no added sodium or potassium salts. Cupric chloride etchants leave chloride residues that can promote corrosion under dry-film resist edges; the electronic/EL grade is formulated to avoid chloride addition and to hold chloride below 5.0 mg/L in the as-supplied concentrate.
Compliance documentation for Cu Pretreatment Electronic/EL Grade aligns with the cleaning and surface preparation guidance of ASTM B322-99(2020) and with cleanroom particulate control practices described in ISO 14644-1:2015 Class 5. The product is not recommended for direct use on aluminum, nickel, or other non-copper base metals because hydrogen peroxide in acidic media may generate surface oxides with unpredictable adhesion. It is also incompatible with strong reducing agents such as metabisulfite and with ammonia-containing strippers that can generate chloramine-like by-products if chloride is present. Published data for performance on additive-manufactured copper surfaces with porosity greater than 2% is limited, and qualification testing on production-intent substrates is required.
