| HS Code | 999666 |
| Appearance | Clear colorless liquid |
| Chemical Family | Aqueous organic acid mixture |
| Ph At 25c | 3.0 - 4.0 |
| Specific Gravity At 25c | 1.02 - 1.05 |
| Total Acid Content | 15 - 20 wt% |
| Metal Impurities Each | < 0.5 ppm |
| Chloride Content | < 1 ppm |
| Particle Count Per Ml | < 50 particles at 0.5 µm |
| Shelf Life | 12 months from date of manufacture |
| Storage Temperature | 5°C to 30°C |
As an accredited Pre-Treatment Solution for Metal Deposition Electronic/EL Grade factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Packaged in a 1 L HDPE bottle with a secure, tamper-evident closure for safe handling and precise dispensing of the electronic-grade pre-treatment solution. |
| Container Loading (20′ FCL) | 20′ FCL: palletized, UN-approved drums/cartons securely braced, labeled for electronic-grade pre-treatment solution, segregated from incompatible materials, clean and dry container. |
| Shipping | Ship in sealed, compatible HDPE containers with secondary containment to prevent leaks. Label as electronic-grade pre-treatment solution; include SDS and hazard markings if corrosive/oxidizer. Keep upright, away from moisture and incompatible metals. Transport at ambient temperature in authorized vehicles. Ensure spill response equipment available and emergency contact information is documented. |
| Storage | Store in a tightly sealed original container in a cool, dry, well-ventilated area away from direct sunlight and incompatible materials. Maintain temperatures between 15–30°C, avoiding freezing and excessive heat. Ensure container remains undamaged, keep away from moisture and ignition sources, and segregate from oxidizers and foodstuffs. |
| Shelf Life | Shelf life: 12 months from production if kept in original, unopened container at controlled room temperature, away from direct sunlight. |
For high-density interconnect PCB production, the Electronic/EL Grade pre-treatment solution is charged at 14–18 vol% into ASTM D1193 Type E-1 deionized water in a horizontal conveyorized immersion module operating at 68–72°C with a residence time of 240–360 s. The working bath is circulated through 0.1 µm polypropylene cartridge filters at 3–4 tank volumes/h and the pH is controlled at 11.8–12.2 with 45–55 g/L potassium carbonate rather than sodium hydroxide to prevent sodium silicate precipitation on glass-reinforced epoxy. The bath is loaded at 0.8–1.2 m²/L; manufacturing-line records show that above 1.5 m²/L, desmear uniformity across panel edges degrades because the permanganate redox potential drifts below -250 mV versus Ag/AgCl and produces epoxy smear residues in blind vias. Industry compliance for the downstream electroless copper deposit is governed by IPC-6012DA Class 3, adhesion is evaluated under IPC-TM-650 method 2.4.8, and final ENIG thicknesses are verified to IPC-4552 where applicable. The process sequence is alkaline permanganate desmear, neutralization, hot-water rinse, pre-dip, palladium/tin activation, acceleration, and electroless copper at 32–38°C. The electrolyte is maintained with continuous air agitation and low-sodium drag-out recovery; sodium levels above 20 mg/L are incompatible with the glass-reinforced epoxy surface because silicate precipitation blocks the subsequent palladium/tin nucleation. Terminal products include 4–10 layer HDI smartphone boards, automotive ADAS camera modules, and chip-on-flex circuits where fine-line capability is specified at 30–50 µm line/space.
| Process variable | Lower control limit | Upper control limit | Test designation |
|---|---|---|---|
| Pre-treatment bath addition ratio | 14 vol% | 18 vol% | In-line conductivity calibration |
| Bath pH | 11.8 | 12.2 | ASTM D1293 |
| Residence time | 240 s | 360 s | Line-speed log |
| Bath loading | 0.8 m²/L | 1.2 m²/L | Production lot tracking |
| Post-treatment average surface roughness | 0.35 µm | 0.60 µm | ISO 25178 |
| Copper peel strength after electroless copper | 6.0 N/cm | 8.0 N/cm | IPC-TM-650 method 2.4.8 |
The limiting variable on high-volume decorative metallization lines is not the etch rate of the chromic-free medium but the half-life of the palladium/tin colloid after repeated drag-in of etchant neutralizer. The pre-treatment solution is applied in two stages: first as a swell conditioner at 180–220 mL/L in Type E-1 deionized water at 60–66°C for 180–240 s, then as an etch formulation at 5–8 vol% at 63–68°C for 240–360 s. The swell step produces a root-mean-square roughness of 0.4–0.8 µm on ABS/PC blends; below 0.3 µm, peel adhesion falls below 8 N/25 mm when tested according to ASTM B533-85, and above 1.0 µm the polycarbonate phase exhibits stress crazing after thermal cycling. The etched parts are neutralized with a pH 6.5–7.0 buffer, activated in a low-palladium colloid at 38–42°C, accelerated, and then plated with 8–12 µm of electroless nickel followed by 15–20 µm of electrolytic copper. Compliance with REACH Annex XVII entry 47 and RoHS Directive 2011/65/EU requires the complete absence of hexavalent chromium in the etch step, and ISO 4525 defect classes are applied for plated-plastic acceptance sampling. Incompatible process conditions include amine-based neutralizers below pH 6.8, which cause premature acceleration and burn deposits in high-current-density recesses; nitrate drag-in above 50 mg/L also coagulates the colloid and shortens the activation bath to less than 72 h. Terminal products include 5G antenna trays, ADAS sensor housings, and EMI shield covers produced on vertical reel-to-reel lines running at 0.6–1.0 m/min.
When through-silicon vias are revealed by back grinding and chemical mechanical planarization, a mixed residue of copper, silicon, and slurry organics remains on the wafer edge and bevel. The pre-treatment solution is formulated at 0.8–1.5 wt% in buffered deionized water with pH 6.8–7.2 and is dispensed through single-wafer spray tools with 0.3 mm nozzle pitch, 1.0–1.5 L/min flow, and 150–300 rpm chuck rotation at 22–25°C for 25–40 s. The pH ceiling is set by the aluminum bond-pad etch rate: above pH 8.0, aluminum removal exceeds 0.5 nm/min and creates post-bond pull strength losses. The formulation is therefore free of amine-based additives, which lower surface tension but increase pH drift and attack exposed AlCu bond pads. After cleaning, the wafer proceeds to physical vapor deposition of a Ti/Cu barrier seed stack, photoresist patterning, and electrochemical copper redistribution layer growth at 1.5–3.0 A/dm². Compliance is governed by SEMI C1 high-purity chemical specifications, cleanroom particulate limits under ISO 14644-1 Class 3, and wafer-surface metallic contamination monitored by vapor-phase decomposition inductively coupled plasma mass spectrometry with ≤5×10¹⁰ atoms/cm² Cu. The process sequence serves 20–40 µm pitch copper pillar bumps, fan-out wafer-level packages, and power management ICs. Published performance data for this specific configuration is limited; qualification on product wafers is therefore required for each TSV aspect ratio and die map.
On tin-doped indium oxide layers deposited by magnetron sputtering, the pre-treatment solution is injected at 1.5–3.0 vol% into an in-line ultrasonic spray manifold operating at 40 kHz and 40–50°C. The spray dwell is 30–60 s, followed by a cascade rinse with 18 MΩ·cm deionized water and warm-air drying. The treatment lowers the water contact angle from above 60° to below 15° measured by ASTM D5946, allowing uniform coverage of the subsequent electroplated copper seed or seed-free direct metallization process. The bath is filtered to 0.1 µm and maintained at total organic carbon below 50 ppb to prevent surface haze. The process is used on 120–150 nm indium tin oxide-coated n-type silicon heterojunction wafers before patterned copper metallization; residual peroxide is excluded because it consumes the palladium-based activator and creates void defects in fine-line grids. The pH is maintained at 9.0–9.8 to avoid indium extraction from the transparent conductive oxide. Compliance for downstream module performance is evaluated under IEC 61215-1:2021 for design qualification and under ASTM D5946 for surface energy. Terminal products include bifacial silicon heterojunction solar cells with copper grid line widths of 25–40 µm, transparent touch-sensor electrodes, and electrochromic display electrodes. The main incompatibility is with storage tanks containing copper metal surfaces, where trace chloride in the formulation can cause stress-corrosion cracking over extended contact; all wetted parts are therefore specified in PVDF or polypropylene.
Fluoride-free microetching at pH 5.8–6.2 removes 0.2–0.5 µm of the top copper oxide from unpatterned direct-bond copper surfaces without attacking alumina grain boundaries. The pre-treatment solution is charged at 0.6–1.2 vol% in Type E-1 deionized water at 28–32°C, with an immersion time of 45–90 s in a cascade line followed by two overflow rinses and forced-air drying. The etched copper surface is then coated with 4–6 µm electroless nickel-phosphorus and 0.05–0.10 µm immersion gold, with the nickel layer evaluated under ASTM B733 for phosphorus content and coating thickness, and the final solderability of the immersion gold verified under IEC 60068-2-58. The process is qualified for power-module substrates in accordance with IEC 60672-2 for ceramic insulating materials and ISO 4527 for autocatalytic nickel-phosphorus coatings. Removal below 0.2 µm leaves residual cuprous oxide that lowers nickel adhesion, while removal above 0.5 µm produces undercut at the copper-alumina interface and creates plating voids in subsequent wire-bond regions. The fluoride-free formulation eliminates hydrogen fluoride exposure and prevents the formation of aluminum fluoride residues that would reduce thermal conductivity at the ceramic-metal interface. Terminal products include 650 V to 1700 V IGBT power modules, silicon carbide MOSFET baseplates, and thermoelectric generator substrates where the alumina thickness is 0.32–0.64 mm and the copper thickness is 0.20–0.30 mm.
Solder stencil electroforming requires the pre-treatment solution to penetrate photoresist apertures with aspect ratios exceeding 1.5:1 before the initial nickel strike. The solution is sprayed at 2.0–4.0 vol% in deionized water through 80 psi fan nozzles positioned 100 mm from a rotating mandrel at 20–25°C for 60–120 s. The low-chloride chemistry removes photoresist scum and lowers the dynamic surface tension to ≤38 mN/m measured by maximum bubble pressure tensiometry, ensuring wetting of 20–50 µm apertures without foam entrainment in the subsequent sulfamate nickel bath. The mandrel is then rinsed with cascading deionized water at 1.5–2.0 L/min and transferred directly into a nickel sulfamate bath maintained at 50–55°C with a current density of 5–15 A/dm². Compliance for the electroformed product is verified under ASTM B489-85 for ductility and ASTM B568-98 for coating thickness, while final stencil aperture dimensions are checked against IPC-7525 stencil design requirements. The solution must not be recirculated through copper heat exchangers because trace chloride promotes stress-corrosion cracking; all pump housings and manifolds are specified in PVDF. Terminal products include fine-line solder stencils for 01005 component placement, wafer probe cards, and micro-mesh filters with 25–100 µm openings.
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Pre-Treatment Solution for Metal Deposition Electronic/EL Grade, model designation PT-EL 718, is an acidic persulfate-based conditioning chemistry specified for copper surfaces before electroless copper, electrolytic copper, electroless nickel, and related deposition sequences in printed circuit board, IC substrate, and high-density interconnect fabrication. The product is filled through a 0.1 µm absolute-rated polypropylene filter into 20 L or 200 L high-density polyethylene containers under an ISO 14644-1:2015 Class 5 cleanroom environment. It is formulated to remove light organic residues, copper oxides, and process films while producing a micro-roughened copper topography compatible with palladium activation and subsequent metal adhesion. When diluted as specified with ASTM D1193 Type I reagent water, the working bath operates as a controlled copper microetch containing no free ammonia, no amine-based surfactants, and no quaternary ammonium compounds. The exclusion of these cationic and amine species reduces interference with tin-palladium catalyst adsorption and avoids the formation of passive organic films after rinsing.
The term Electronic/EL grade is defined by limits on trace metals, chloride, nonvolatile residue, and liquid-borne particles rather than by a single pH or etch-rate value. The as-supplied concentrate has a specific gravity of 1.140 at 25 °C, a pH of 0.90–1.30, and an active persulfate content of 9.0 wt% as sodium persulfate. Each production lot is released against a fixed specification profile and is accompanied by a certificate of analysis that reports the measured values shown in the table below.
| Parameter | Limit | Test Method |
|---|---|---|
| Appearance | Clear, colorless to pale straw liquid | Visual |
| pH, as supplied at 25 °C | 0.90–1.30 | ASTM E70 |
| Specific gravity, 25 °C | 1.120–1.160 | ASTM D4052 |
| Chloride, Cl⁻ | ≤ 0.5 mg/L | ASTM D512 |
| Iron, Fe | ≤ 0.5 mg/L | ASTM D5673 |
| Nickel, Ni | ≤ 0.2 mg/L | ASTM D5673 |
| Total organic carbon | ≤ 300 mg/L | ASTM D7573 |
| Nonvolatile residue | ≤ 0.08 wt% | ASTM D1353 |
| Liquid-borne particles ≥ 0.5 µm | ≤ 200 particles/mL | Laser light-scattering counter |
| Working bath copper loading tolerance | ≤ 20 g/L | Atomic absorption or ICP-OES |
Each production lot is released using calibrated laboratory instrumentation. pH is measured after thermal equilibration at 25 °C with a glass electrode calibrated under ASTM E70. Density is measured by digital oscillating U-tube under ASTM D4052. Chloride is determined by ASTM D512. Trace metals are determined by ICP-MS under ASTM D5673. Total organic carbon is measured by high-temperature catalytic oxidation under ASTM D7573. Nonvolatile residue is gravimetric at 105 °C under ASTM D1353. Liquid-borne particle counts are obtained with a laser light-scattering counter at a detection threshold of 0.5 µm after the container has been agitated for 30 s.
Bath make-up uses demineralized water with resistivity of 18 MΩ·cm at 25 °C. Lower-resistivity water introduces calcium and magnesium that precipitate as sulfate sludges and clog spray nozzles or recirculation filters. The working bath is monitored by specific gravity, pH, and copper concentration rather than by a single redox potential because the persulfate–sulfuric acid system does not show a simple linear ORP response across the usable operating window.
In a horizontal conveyorized electroless copper line, the PT-EL 718 working bath is prepared at 10–15 vol% in ASTM D1193 Type I water. The bath is held in a 316L stainless steel or polypropylene sump with a quartz-sheathed immersion heater and recirculated through a 10 µm guard filter and a 0.5 µm polishing filter. Spray bar pressure is maintained between 1.2 bar and 1.8 bar. Conveyor speed is set to produce a contact time of 45 s to 75 s. Under these conditions the bath removes approximately 0.8 µm to 1.2 µm of copper from rolled annealed and electrodeposited foil; the exact removal rate depends on copper loading, temperature, and local spray impingement. For fine-line work below 20 µm line/space, the recirculation loop is equipped with a magnetic flowmeter and a specific gravity controller that maintains concentration within ±0.5% of set point. The concentrate is dosed from a diaphragm metering pump into the recirculation return line, never directly into the spray bar suction line, because localized high acidity at the suction side produces copper pitting at the point of impingement.
Drag-in of cupric ion from upstream etch rinses changes the etching equilibrium and should not exceed 5 g/L in the working bath. When copper loading reaches 20 g/L, the etch rate drops and the surface topography shifts from a uniform microcrystalline texture to deep grain-boundary attack. Production records from high-density interconnect lines indicate that bath life between dumps falls from 36 h to 14 h when copper loading exceeds 18 g/L and solution temperature fluctuates by more than ±2 °C. After the pre-treatment stage, the panel is rinsed in a three-stage cascade rinse with final conductivity below 5 µS/cm; the panel is not allowed to dry before entering the electroless copper bath. Drying after this pre-treatment produces nonuniform cuprous oxide and is a known source of skip plating on high-aspect-ratio through-holes.
In electrolytic acid copper plating lines, the same working bath can be installed as a spray pre-dip immediately before the acid copper tank. The bath removes anti-tarnish films and light fingerprints from dry-film resist apertures without measurable attack on the photoresist when contact time is kept below 30 s. Longer contact at temperatures above 35 °C can produce resist lifting at fine-pitch apertures. The rinse after the pre-dip is maintained below 10 µS/cm to minimize sulfate drag-in into the acid copper electrolyte.
Surface quality after pre-treatment is assessed by contact profilometry or laser scanning confocal microscopy. The target roughness range is 0.25 µm to 0.45 µm Ra on innerlayer copper after 60 s exposure. The cleaned surface should show a water break-free surface; contact angle with deionized water is typically below 10° when measured within 60 s after final rinse. Surfaces that exceed 0.55 µm Ra or that show localized pitting indicate chloride contamination, excessive copper loading, or aged bath solution; in this case the bath is dumped and recharged rather than replenished.
The primary differences are not limited to etch rate. General-purpose acid cleaners used in decorative and industrial metal finishing frequently carry chloride, iron, and nonvolatile residue levels that are acceptable for barrel plating but introduce defects in high-reliability circuits. The general-purpose values shown in the comparison table are representative ranges reported in supplier literature for non-electronic metal finishing cleaners and do not identify any single product.
| Parameter | PT-EL 718 Electronic/EL Grade | General-Purpose Acid Cleaner |
|---|---|---|
| Chloride | ≤ 0.5 mg/L | 10–50 mg/L |
| Iron | ≤ 0.5 mg/L | 5–100 mg/L |
| Nickel | ≤ 0.2 mg/L | Not specified |
| Nonvolatile residue | ≤ 0.08 wt% | 1.0–5.0 wt% |
| Liquid-borne particles ≥ 0.5 µm | ≤ 200 particles/mL | Not specified |
| Working bath pH control tolerance | ±0.3 pH units | ±1.0 pH units |
| Filtration at container fill | 0.1 µm absolute | 5 µm nominal or unfiltered |
| Amine-based surfactant content | None | May be present |
The low chloride limit is operationally significant because chloride concentrations above 3 mg/L in the working bath increase pitting on 10 µm copper foil and can leave residues that reduce wire-bond pull strength measured under MIL-STD-883 Method 2011.9. The low iron and nickel limits prevent metal contamination from shifting the mixed potential between copper and palladium during activation. Nonvolatile residue control is required because organic films above 0.1 wt% in the as-supplied product can survive a two-stage rinse and produce a hydrophobic surface that repels the aqueous electroless copper bath. The deliberate absence of amine-based surfactants is a formulation difference rather than a single lot parameter; in palladium-catalyzed processes, cationic amines can compete with tin-palladium colloid adsorption and cause skip plating or edge pullback in high-aspect-ratio through-holes.
At copper loading above 20 g/L, the persulfate etching reaction becomes mass-transport limited at the copper surface. The measured etch depth on 35 µm copper foil drops from 1.0 µm to 0.4 µm at the same conveyor speed, while the coefficient of variation across a 400 mm panel increases from 4% to 15%. The resulting surface is characterized by isolated deep grain-boundary attack rather than uniform micro-roughening. In high-density interconnect lots with 50 µm blind vias, this nonuniform attack generates undercut at the base of thicker copper pads and increases the likelihood of inner-layer separation after electroless copper deposition. Production lines mitigate this condition by installing continuous copper recovery cells operating at 2–4 A/dm² cathode current density and by lowering the working temperature from 32 °C to 27 °C during low-throughput shifts.
Analytical control is performed every 4 h during three-shift operation. Acid normality is determined by automatic titration with 0.1 N sodium hydroxide. Copper concentration is measured by atomic absorption spectroscopy following ASTM D1688. Persulfate concentration is determined by iodometric titration and maintained between 8.0 wt% and 10.0 wt% as sodium persulfate. Replenishment is made by dosing PT-EL 718 concentrate through a diaphragm metering pump controlled by the specific gravity signal. The dilution and replenishment points are separated by at least 3 m of return pipe to ensure complete mixing before the solution reaches the spray manifold.
Because the as-supplied concentrate is acidic and oxidizing, continuous-contact materials are fluoropolymers, polypropylene, 316L stainless steel, or quartz. Natural rubber, nitrile rubber, and epoxy-coated mild steel are not acceptable for continuous contact. Titanium heating coils are acceptable only after passivation; unpassivated titanium can reduce persulfate and release titanium ions that deposit as insoluble films on copper surfaces. The working bath should be segregated from ammoniacal or cyanide-containing rinsewaters because mixing liberates toxic gases and destabilizes the persulfate oxidizer. Spent baths are treated by neutralization with sodium hydroxide to pH 8.5–9.5; copper hydroxide precipitation is followed by clarification and filter press dewatering. The formulation does not contain chelating agents that would prevent conventional hydroxide precipitation.
In vertical electroless nickel immersion gold lines, the PT-EL 718 pre-treatment is operated at 25–30 °C with eductor recirculation of 4–6 turnovers per hour. Parts are processed in fluoropolymer baskets with controlled withdrawal at 0.2 m/min. The bath is filtered through a 1 µm polypropylene cartridge, and DI water rinsing after the bath is continuous with final resistivity above 18 MΩ·cm. This sequence occurs before palladium activation; the absence of amine surfactants prevents catalyst poisoning. Compared with general-purpose acid cleaners, fewer skip-plating defects are observed on 0.4 mm pitch ball-grid-array substrates after 72 h of bath aging. Published data for this specific configuration is limited, but the operational trend is consistent with the lower trace-metal and nonvolatile residue limits of the electronic/EL grade product.
