| HS Code | 469464 |
| Deposit Composition | 90% nickel / 10% phosphorus |
| Phosphorus Content | 10-11% by weight |
| Nickel Content | 89-90% by weight |
| Density | 7.9 g/cm³ |
| Melting Point | 890 °C |
| Hardness As Plated | 550 VHN100 |
| Hardness After Heat Treatment | 950 VHN100 |
| Electrical Resistivity | 70 µΩ·cm |
| Corrosion Resistance | Excellent |
| Solderability | Good with suitable flux |
| Deposition Rate | 15 µm/hour |
| Internal Stress | Low compressive |
As an accredited Electroless Nickel Electronic/EL Grade factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Packaged in 5-gallon (18.9 L) polyethylene pails with sealed lids, containing 15 kg net of Electroless Nickel Electronic/EL Grade solution. |
| Container Loading (20′ FCL) | 20′ FCL container loading of Electroless Nickel Electronic/EL Grade, securely packed, properly labeled, ensuring safe transport and stability. |
| Shipping | Ship Electroless Nickel Electronic/EL Grade as hazardous/non-hazmat depending on formulation; consult SDS. Use corrosion-resistant, leak-proof containers with secure closures. Label clearly, avoid incompatible materials, and follow local, national, and international transport regulations. Ensure proper documentation and training for handlers. |
| Storage | Store Electroless Nickel Electronic/EL Grade in tightly sealed original containers in a cool, dry, well-ventilated area, ideally at 15–30°C. Protect from direct sunlight, freezing, and contamination. Keep away from strong oxidizers, acids, and food materials. Inspect for leaks regularly and use dedicated, clean equipment to maintain solution purity and shelf life. |
| Shelf Life | Electroless Nickel Electronic/EL Grade shelf life is 6 to 12 months if stored unopened at room temperature, away from sunlight. |
For printed circuit board final finishing operations targeting Class 2 and Class 3 assemblies, electroless nickel electronic/EL grade is deposited over copper pads at a controlled thickness of 3–6 µm and phosphorus content of 6.5–9.0 wt% before immersion gold is applied to 0.05–0.12 µm. The immersion gold layer functions as an oxidation barrier, while the nickel layer supplies the primary solderable and diffusion-barrier interface. In horizontal conveyorized lines with bath volumes of 300–600 L and panel loads up to 0.4 dm²/L, dissolved nickel is maintained at 4.5–5.5 g/L and sodium hypophosphite at 20–28 g/L to prevent skip plating on high-aspect-ratio microvias. EL-grade impurity control reduces zinc below 5 mg/L, copper below 5 mg/L, and iron below 20 mg/L in the working bath, which minimizes particulate co-deposition that creates soldering voids after SAC305 reflow at peak temperatures of 245–250 °C. Process pH is held at 4.4–4.8 and bath temperature at 82–86 °C, with control limits of ±0.3 pH and ±1 °C, because phosphorus content shifts approximately 0.3 wt% per 0.1 pH unit in this range. Continuous filtration through 1 µm absolute cartridges is required because fine nickel particulates adhering to the copper surface appear as solder wetting failure under J-STD-003 after steam aging.
Black pad failure is suppressed by maintaining phosphorus above 6.5 wt% and by keeping dissolved copper below 10 mg/L; phosphorus above 9.0 wt% depresses solderability after multiple reflow cycles because nickel-phosphide enrichment at the solder interface raises the intermetallic shear path. Immersion gold thickness is kept below 0.15 µm, and the Au/Ni thickness ratio is held below 0.03 for high-reliability telecommunication boards because thicker gold embrittles the SAC305 joint under IPC-9701A thermal cycling from -40 °C to 125 °C. RoHS Directive 2011/65/EU as amended by Delegated Directive (EU) 2015/863 restricts lead, cadmium, mercury, and hexavalent chromium in homogeneous materials; the nickel-phosphorus deposit with trace lead below 0.1 wt% and cadmium below 0.01 wt% meets the restriction without exemption.
| Control parameter | Working range | Verification method |
|---|---|---|
| Nickel ion concentration | 4.5–5.5 g/L | EDTA titration |
| Sodium hypophosphite concentration | 20–28 g/L | Iodometric titration |
| Bath pH | 4.4–4.8 | Glass electrode, two-point calibration |
| Bath temperature | 82–86 °C | PT100 immersion sensor |
| Deposit phosphorus | 6.5–9.0 wt% | XRF or EDS per IPC-4552A |
| Nickel thickness | 3–6 µm | XRF |
| Immersion gold thickness | 0.05–0.12 µm | XRF |
| Trace copper | <5 mg/L | ICP-MS |
| Trace iron | <20 mg/L | ICP-MS |
| Trace zinc | <5 mg/L | ICP-MS |
An ENEPIG finish for quad-flat no-lead leadframes places electroless nickel electronic/EL grade beneath electroless palladium and immersion gold. The nickel layer is maintained at 3–6 µm, palladium at 0.05–0.12 µm, and gold at 0.03–0.08 µm. In reel-to-reel plating lines operating at take-up speeds of 0.8–1.5 m/min, nickel bath pH is controlled at 4.5–4.8, temperature at 83–86 °C, and agitation by air sparging at 0.3–0.5 L/min per m² of bath surface. Palladium thickness below 0.05 µm creates pinholes through which nickel oxidizes; gold wire bond pull force then falls below the 3 gf acceptance threshold for 25 µm wire under MIL-STD-883 TM 2011 because oxidized nickel no longer forms a reliable Au-Al intermetallic. Palladium thickness above 0.12 µm raises cost without improving solder joint reliability and can create a Pd-rich interface that accelerates solder spread but reduces shear resistance after 500 h of high-temperature storage at 150 °C per JESD22-A103.
The EL-grade nickel bath for ENEPIG uses sulfur-free stabilizer packages because sulfur co-deposition above 0.005 wt% in the nickel layer inhibits Au-Al wire bond formation and increases the coefficient of variation of pull strength across a strip. Copper contamination from exposed leadframe areas is controlled below 8 mg/L by in-line electrolytic dummy plating at 0.2–0.4 A/dm². On production strips with silver-plated leads and bare copper heat slugs, the bath must be dosed with a chelator that suppresses spontaneous deposition on silver; otherwise nickel nodules form at tie-bar edges and cause wire bond capillary damage. Solder ball shear after SAC305 attachment is evaluated per JESD22-B117, with a minimum shear force of 4.0 N for 300 µm ball size on 0.25 mm pitch packages.
Chip resistor and multilayer ceramic capacitor terminations are barrel-plated with the same EL-grade nickel chemistry after firing of screen-printed silver paste. The nickel barrier thickness is held at 1.5–3.0 µm with phosphorus at 7–10 wt%, followed by tin at 3–5 µm; this stack prevents silver migration into the solder fillet during wave soldering at 260 °C for 5–10 s. Barrel lines run at 4–8 rpm, bath temperature 88–92 °C, pH 4.2–4.6, and loadings of 0.5–1.0 dm²/L. EL-grade impurity limits are tighter than decorative-grade chemistries because tin contamination above 5 mg/L produces rough, dark nickel and a solderability spread that fails AEC-Q200 qualification testing under J-STD-002 after steam aging for 8 h.
| Impurity element | Maximum concentration in working bath | Analytical method |
|---|---|---|
| Zinc | <5 mg/L | ICP-MS |
| Copper | <5 mg/L | ICP-MS |
| Iron | <20 mg/L | ICP-MS |
| Lead | <5 mg/L | ICP-MS |
| Tin | <5 mg/L | ICP-MS |
| Aluminium | <5 mg/L | ICP-MS |
Termination edge coverage is verified by cross-sectioning per IEC 60384-1; a nickel layer below 1.5 µm permits molten tin-bismuth solder to leach silver from the termination, while nickel thickness above 3.0 µm increases internal stress and causes chip cracking during thermal shock from -55 °C to 125 °C. The bath is operated at high hypophosphite concentration of 28–35 g/L to maintain the higher phosphorus content required for solder leach resistance, and metal turnover is limited to 4 in production to avoid orthophosphite accumulation that slows deposition and shifts phosphorus.
Electromagnetic compatibility enclosures produced from die-cast aluminium ADC12 are prepared through alkaline zincate double immersion, then plated with EL-grade nickel at 12.5–25 µm thickness. The deposit for housing interiors is specified at 10–12 wt% phosphorus to remain non-magnetic and to pass neutral salt spray testing per ASTM B117-19 for 96–168 h without red rust when sealed. Adhesion is evaluated by bend testing per ASTM B571-18 on witness coupons; blistering indicates zincate rinse water contamination above 200 µS/cm. A post-plate bake at 150–160 °C for 1 h is applied to reduce hydrogen uptake on high-strength aluminium fasteners, although published data for hydrogen embrittlement relief on aluminium enclosures is limited. Coating thickness uniformity across deep cavities is maintained with solution agitation at 0.3–0.5 L/min per L bath volume, and the EL-grade low-metal impurities avoid pitting that creates RF leakage slots above 10 µm.
In optoelectronic packaging and hermetic hybrid housings, EL-grade nickel is deposited on Kovar and Alloy 42 lead frames before seam welding or AuSn soldering. The nickel thickness is held at 2.5–5.0 µm with phosphorus of 6.5–8.5 wt% to balance solder wetting and wire bond pull force. Laser diode submounts require surface roughness below 0.4 µm Ra after plating, measured by contact profilometry on witness flats, to avoid optical axis tilt; EL-grade filtration through 0.5 µm cartridges removes particulate nickel that would otherwise form hard nodules. Solderability of AuSn preforms at 280–300 °C is tested per MIL-STD-883 TM 2020.1, while hermeticity is confirmed after seam welding by helium leak testing per MIL-STD-883 TM 1014 with a leak rate below 5×10⁻⁸ atm·cc/s. The bath is operated at pH 4.6–4.8 and temperature 82–84 °C; lower temperature reduces deposition rate below 8 µm/h and extends cycle time beyond 20 min.
Compression and transfer moulds used for epoxy molding compound encapsulation in semiconductor assembly receive EL-grade nickel at 25–50 µm thickness. The as-plated hardness of 550–600 HV for 10–12 wt% phosphorus deposits is raised to 900 HV after heat treatment at 400 °C for 1 h; this hardness permits mould chase surfaces to withstand abrasive silica filler in epoxy formulations. Sulfur from stabilizer by-products above 2 mg/L in the bath causes micro-pitting at the mould parting line, which transfers to encapsulated devices as flash defects. The bath is therefore operated with sulfur-free stabilizer systems and is filtered through 1 µm absolute cartridges. Surface roughness after plating is specified below 0.1 µm Ra on polished insert areas, verified by ISO 4287:1997, to preserve demoulding performance without external release agents. Dimensional control on critical gate features is held to ±2 µm through selective plating on masked tool steel, because high-phosphorus nickel deposits of 50 µm thickness can close gates below 0.5 mm width.
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Electroless Nickel Electronic/EL Grade is a high-purity, mid-phosphorus autocatalytic nickel-phosphorus deposition system supplied as a three-component replenishment package. It is intended for ENIG, ENEPIG, and other solderable and wire-bondable finishes on printed circuit boards and semiconductor packaging. The working bath is maintained at 5.0–6.5 g/L nickel, 25–35 g/L sodium hypophosphite, pH 4.5–5.2, and 82–90 °C; under these conditions the formulation plates at 8–14 µm/h and yields a deposit with 7–10 wt% phosphorus. Filtration through 0.2 µm absolute-rated polypropylene cartridges and use of electronic-grade nickel salts reduce codeposited lead and cadmium to below 0.01 wt% when measured by IEC 62321-5. The deposit satisfies IPC-4552 for ENIG when nickel thickness is held between 3 µm and 6 µm and the immersion gold layer is controlled at 0.05–0.1 µm. The model designation Electronic/EL Grade identifies a process variant with separate nickel, reducer, and stabilizer concentrates, chloride minimized by raw-material purity, and a filtration loop capable of 0.2 µm absolute retention.
| Parameter | Reference range | Analytical method | Controlling standard or specification |
|---|---|---|---|
| Nickel concentration | 5.0–6.5 g/L | ICP-OES | Manufacturer control plan |
| Sodium hypophosphite | 25–35 g/L | Iodometric titration | Manufacturer control plan |
| pH | 4.5–5.2 | Calibrated glass electrode | ISO 4527 |
| Temperature | 82–90 °C | RTD or calibrated thermocouple | ISO 4527 |
| Plating rate | 8–14 µm/h | XRF thickness divided by dwell time | IPC-4552 |
| Deposit phosphorus content | 7–10 wt% | ICP-OES after acid digestion | IPC-4552 |
| ENIG nickel thickness | 3–6 µm | XRF or metallographic cross-section | IPC-4552 |
| Immersion gold thickness | 0.05–0.1 µm | XRF | IPC-4552 |
Deposit qualification for the Electronic/EL Grade includes hardness, stress, phosphorus content, and solderability. As-plated hardness is 500–600 HV when measured by ASTM E384 at 50 gf load. After heat treatment at 350 °C for 1 h, hardness increases to 850–950 HV because of Ni3P precipitation. Tensile stress is measured by spiral contractometer and maintained below 50 MPa on copper; high tensile stress above 100 MPa can cause line cracking on thin substrates. Porosity testing per ASTM B733 or ISO 4527 is performed on copper coupons, and the acceptance limit is set by the final assembly specification.
Routine operation of the formulation is governed by the ratio of nickel ion to hypophosphite rather than by nickel concentration alone. When the hypophosphite concentration falls below 25 g/L, plating rate decreases nonlinearly and deposit phosphorus content shifts toward the lower bound of 7 wt%. The stabilized bath uses a lead-free additive package; residual stabilizer concentration is monitored by differential pulse voltammetry to avoid stabilizer carryover into the deposit. Process conflicts arise when pH is adjusted with ammonium hydroxide: ammonia can complex copper and increase nickel porosity. Electronic-grade variants use potassium hydroxide or a proprietary alkali to maintain pH without introducing nitrogen-bearing species. On vertical conveyorized lines with bath volumes of 200–500 L, pH drift is typically 0.05–0.10 per 8 h shift when the bath is operated at 0.5–1.0 dm²/L load. Copper, iron, and zinc impurities partition into the deposit more readily when dissolved oxygen is present; continuous filtration through 0.2 µm absolute-rated cartridges and nitrogen blanketing reduce oxygen uptake. Orthophosphite accumulation remains the rate-limiting breakdown product. At orthophosphite concentrations above 80–100 g/L, plating rate falls below 8 µm/h even with normal replenishment. Published data for this specific configuration is limited beyond 5 metal turnovers.
In ENIG surface finishing, the electroless nickel layer functions as a diffusion barrier between copper and immersion gold and as the primary solderable cap for assembly. IPC-4552 defines the acceptable nickel thickness as 3–6 µm; values below 3 µm increase the risk of copper diffusion and solder joint voiding, while values above 6 µm can raise deposit stress and reduce solder joint fatigue resistance. Immersion gold thickness is held at 0.05–0.1 µm. Gold above 0.1 µm may embrittle solder joints, whereas gold below 0.05 µm may not protect nickel from oxidation during storage. The plating rate of the Electronic/EL Grade is linear between 10 min and 30 min on copper surfaces, allowing thickness control by dwell time in conveyorized equipment. On high-density interconnect substrates with pad pitch below 0.4 mm, thickness uniformity is controlled by solution agitation and panel racking; edge effects of 10–15% have been recorded on vertical lines when rack isolation is inadequate. Solderability is verified by wetting balance per IPC J-STD-003 and by thermal stress per IPC-TM-650 method 2.6.8. Dewetting failures are correlated with phosphorus enrichment exceeding 10 wt% in the Ni3Sn4 intermetallic region after reflow.
For assemblies requiring wire bonding or high-frequency signal transmission, surface cleanliness and nickel grain structure are as critical as thickness. Ionic contamination on finished ENIG boards is controlled below 1.56 µg/cm² NaCl equivalent when measured by IPC-TM-650 method 2.3.25. Surface insulation resistance testing per IPC-TM-650 method 2.6.3.7 is used to verify that the formulation does not leave hygroscopic ionic residues. The amorphous nickel-phosphorus matrix minimizes grain-boundary attack by alkaline cleaners and microetchants prior to soldering. Immersion gold coverage is inspected by XRF; incomplete coverage on blind vias results from low agitation and should be corrected by increasing solution flow rather than by extending dwell time, which can produce gold overplate and subsequent solder embrittlement.
In ENEPIG sequences, Electroless Nickel Electronic/EL Grade is followed by electroless palladium and immersion gold. The nickel deposit must have uniform phosphorus distribution because the palladium layer is typically 0.05–0.15 µm and cannot mask local nickel variation. Rinse water resistivity above 18 MΩ·cm is specified to prevent drag-in of nickel ions into the palladium bath; particulate filtration at 0.2 µm on the nickel bath reduces cross-contamination. Gold-wire pull testing per MIL-STD-883 method 2011 is used to verify wire-bond acceptance on ENEPIG surfaces.
When solder paste is reflowed over an ENIG finish, the immersion gold dissolves rapidly into molten solder and exposes the nickel-phosphorus layer to tin. The interfacial reaction forms Ni3Sn4 intermetallic compound and leaves a phosphorus-enriched layer beneath the interface. Phosphorus content in electroless nickel is the primary variable controlling the thickness and morphology of that phosphorus-enriched layer. Deposits at 7–10 wt% phosphorus produce a compact Ni3Sn4 layer with slow growth. Deposits below 7 wt% accelerate nickel dissolution and can create thick phosphorus-enriched zones, while deposits above 10 wt% can reduce wetting speed and have been associated with black pad fracture when nickel surface oxidation precedes gold deposition. The Electronic/EL Grade is therefore maintained in a mid-phosphorus band rather than the high-phosphorus compositions used for corrosion-resistant wear coatings. The phosphorus-enriched layer is measured by cross-section EDS after reflow; a layer above 3 µm or containing microvoids is rejected under internal criteria aligned to IPC-4552.
| Characteristic | Mid-phosphorus 7–10 wt% P | High-phosphorus 10–13 wt% P | Test method or standard |
|---|---|---|---|
| As-plated hardness | 500–600 HV | 450–550 HV | ASTM E384 |
| Magnetic response | Weakly ferromagnetic to non-magnetic | Non-magnetic | Magnetic susceptibility meter |
| Concentrated nitric acid resistance | Lower | Higher | ASTM B733 nitric acid test |
| Solder wetting time after ENIG | Shorter | Longer | IPC J-STD-003 |
| Phosphorus-enriched layer growth after reflow | Moderate | Reduced | EDS cross-section |
Unlike general-purpose electroless nickel processes intended for wear, corrosion, or mold release, the Electronic/EL Grade removes brightening and stress-control additives that introduce sulfur, lead, or cadmium into the deposit. General-purpose baths may use lead or cadmium stabilizers at 1–10 mg/L; the electronic formulation substitutes lead-free stabilizers and controls codeposited lead and cadmium below 0.01 wt% when measured by IEC 62321-5. This difference is significant because mobile ionic contamination on a PCB surface can produce electrochemical migration in surface insulation resistance testing per IPC-TM-650 method 2.6.3.7. The formulation is also filtered to remove particles larger than 0.2 µm, whereas many general-purpose systems use 5–10 µm filtration; particles above 1 µm in a solder joint can act as void nucleation sites. Deposit tensile stress is maintained below 50 MPa on copper when measured by spiral contractometer; general-purpose baths used for wear liners often accept tensile stress above 100 MPa. The Electronic/EL Grade is supplied with separate nickel, reducer, and stabilizer concentrates to allow bleed-and-feed operation; conventional single-package baths cannot independently adjust stabilizer concentration as metal turnover increases.
Compliance with RoHS 2011/65/EU is maintained by controlling lead and cadmium in the deposit below 0.1 wt% and 0.01 wt%, respectively; the process contains no hexavalent chromium or mercury. Under REACH, nickel sulfate is classified as Skin Sens. 1 and Repr. 1B; the plating line must have local exhaust ventilation and ion-exchange treatment for nickel removal from rinsewater.
Installation of ultrafiltration or dialysis on a production line changes the impurity profile of aged electroless nickel baths. Ultrafiltration with 10,000–100,000 Da molecular weight cutoff membranes removes colloidal nickel-phosphite particles and suspended solids, but does not remove dissolved orthophosphite or sulfate. Dialysis using anion-exchange membranes can remove orthophosphite and sulfate selectively. When the orthophosphite concentration is reduced from 80 g/L to below 40 g/L, the plating rate recovers to 10–12 µm/h in baths that had slowed to 7 µm/h. However, the same membrane removes hypophosphite if not operated with a compensating feed; a phosphorus mass balance is therefore required. On a 1,000 L ENIG line processing 40 m²/day, membrane fouling by nickel particles is controlled by backpulsing every 15 min and by maintaining a crossflow velocity of 3–4 m/s. Published data for this specific configuration is limited beyond 10 metal turnovers; process qualification should therefore include solderability and wire-bond pull testing after each turnover extension.
