| HS Code | 895233 |
| Product Name | Flux Electronic/EL Grade |
| Appearance | Clear liquid |
| Color | Light amber to pale yellow |
| Odor | Mild alcoholic/resinous odor |
| Density | 0.80 - 0.82 g/mL at 25°C |
| Viscosity | 1 - 5 cP at 25°C |
| Flash Point | Approximately 12°C (closed cup) |
| Boiling Point | 78 - 82°C initial boiling point |
| Solids Content | 20 - 35% by weight |
| Halide Content | Less than 0.05% (EL-grade low halide) |
| Ph | 5.0 - 6.0 as 10% solution in DI water |
| Water Extract Resistivity | ≥ 100,000 Ω·cm |
| Surface Insulation Resistance | ≥ 1 × 10^11 Ω after soldering |
| Shelf Life | 12 months from date of manufacture in sealed container |
| Storage Temperature | 5°C to 35°C |
As an accredited Flux Electronic/EL Grade factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Packaged as a 1 L HDPE bottle with tamper-evident closure, hazard labeling, and batch traceability for electronic/EL grade flux. |
| Container Loading (20′ FCL) | 20′ FCL loading of EL Grade Electronic Flux, with secure, clean packaging ensuring safe transport and chemical compatibility. |
| Shipping | Shipping of Flux Electronic/EL Grade requires compliance with hazardous materials regulations. Use approved containers, secure packing, and proper labeling. Transport via ground freight only; air shipment is restricted. Include Safety Data Sheets and declare as limited quantity if applicable. Ensure spill containment and temperature protection during transit. |
| Storage | Store Flux Electronic/EL Grade in a tightly sealed, original container in a cool, dry, well-ventilated area away from direct sunlight, heat, and ignition sources. Keep separated from strong oxidizers and acids. Maintain stable temperatures between 15–25°C to preserve purity. Avoid moisture contamination, and use proper grounding during dispensing to prevent static discharge. |
| Shelf Life | Shelf life typically 12 months unopened, stored at room temperature in original airtight container, away from moisture, heat, and sunlight. |
On a dual-wave soldering line configured for 2 mm–6 mm mixed-technology PCB thicknesses, the electronic/EL-grade flux is deposited by an ultrasonic spray fluxer operating with transducer frequencies of 480–520 kHz and atomizing air pressure of 0.1–0.3 MPa. The spray head traverses a single-axis gantry over a palletized panel, and droplet size distribution, measured by laser diffraction with D50 below 20 µm, governs film uniformity inside high-aspect-ratio plated through-holes. A top-side preheat cycle of 100–120 °C for 40–70 s removes the volatile carrier solvent before the PCB contacts the first solder wave. Insufficient preheat below 90 °C leaves solvent trapped within the flux film and induces solder balling at the wave front; preheat above 130 °C may pre-polymerize rosin acids and reduce flux activity. The first turbulent wave is maintained at 260–265 °C for Sn63/Pb37 or 270–280 °C for SAC305, with contact length of 30–60 mm and conveyor speed of 1.2–1.8 m/min. A second laminar wave, when present, operates 2–4 °C lower and 20–30 mm shorter to limit copper dissolution. Hole-fill performance is evaluated against IPC-A-610 class 2 or class 3 criteria, requiring minimum 75% vertical fill for class 2 and full through-hole wetting for class 3. Solder pot analysis at shift start, typically by X-ray fluorescence or optical emission spectroscopy, tracks copper accumulation; copper loadings above 0.7 wt% increase solder viscosity and reduce drain-off. Flux film weight on the PCB underside is held at 200–700 µg/cm² when measured gravimetrically or by beta backscatter. Halide-free electronic-grade formulations reduce solder ball rejection rates in this application but require higher preheat because their activator systems are less thermally stable than halide-containing types.
Selective soldering machines from multi-axis gantry platforms use needle or micro-jet fluxing heads to dispense volumes of 0.8–2.5 µL per joint onto through-hole component leads protruding from bottom-side pads. The dispensed droplet must remain wholly within the circular pad annulus; drift beyond the annular ring, even by 0.3 mm, creates residues that bridge adjacent lands and violate IPC-A-610 cleanliness requirements unless a post-solder cleaning step is added. The electronic/EL-grade flux used in this process is formulated with 2–5 wt% solids in an alcohol or glycol-ether carrier. Solids content below 2 wt% reduces residues but may cause stochastic wetting failures on oxidized leads; solids content above 8 wt% deposits a visible film that can foul the solder nozzle shield. During the subsequent contact sequence, a solder nozzle of 3–8 mm internal diameter is raised to the board underside for 0.8–1.5 s under a molten solder flow rate of 1.5–3.5 kg/min. Flux activation must complete before the solder front arrives; because thermal mass is lower than in wave soldering, preheat is delivered by short-wavelength IR emitters to reach 110–130 °C topside within 60–90 s. The flux must also survive fast evaporation without crystallizing inside the dispenser needle; needle clogging from flux solids accumulation is a primary downtime cause in high-mix lines. Viscosity, measured by cone-plate viscometer at 25 °C, is adjusted to 15–35 mPa·s, balancing droplet tailing, satellite formation, and needle retention.
| Variable | Dual-wave soldering | Selective soldering |
|---|---|---|
| Flux deposition method | Ultrasonic spray film | Needle or micro-jet droplet |
| Flux film weight or volume | 200–700 µg/cm² | 0.8–2.5 µL per joint |
| Top-side preheat | 100–120 °C | 110–130 °C |
| Solder bath temperature | 260–270 °C | 295–320 °C |
| Contact time | 2.0–4.0 s per wave | 0.8–1.5 s per joint |
The 85 °C / 85% RH damp-heat chamber exposes a standardized comb pattern with 0.32 mm line spacing under a 50 V DC bias for 168 h according to IPC-TM-650 2.6.3.3. Surface insulation resistance is considered acceptable when the value remains above 100 MΩ throughout the bias period; failure occurs if dendrite growth produces a current spike exceeding a decade increase in leakage current. Halide activators such as chloride and bromide dominate ionic species that lower the threshold humidity for water monolayer formation and accelerate electrochemical migration. EL-grade formulations are therefore specified with halide content below 0.05 wt%, and in many cases below 0.01 wt%, equivalent to a J-STD-004B L0 designation. The copper mirror corrosion test defined in IPC-TM-650 2.6.15, conducted at 40 °C and 93% RH for 72 h, further checks whether residues attack copper traces. Because halide-free electronic-grade flux often contains difunctional carboxylic acids or non-halogenated amine salts, it must be evaluated for pH drift and copper ion leaching. Cleaning after soldering, when required, is performed with saponified aqueous cleaners at 55–65 °C under spray pressure of 0.2–0.4 MPa; wash solution conductivity is maintained below 50 µS/cm to prevent ionic redeposition.
| Designation | Residue chemistry | Halide level | Typical SIR outcome after no-clean soldering |
|---|---|---|---|
| ROL0 | Rosin, low activity | <0.05 wt% | >100 MΩ |
| ROL1 | Rosin, low activity | 0.05–0.50 wt% | >100 MΩ, but humidity margin is reduced |
| ORL0 | Organic acid, low activity | <0.05 wt% | >100 MΩ |
| ORH1 | Organic acid, high activity | 0.50–2.00 wt% | <100 MΩ when left uncleaned |
Electronic/EL-grade flux in solder paste performs three simultaneous functions: oxide removal, oxygen barrier during reflow ramping, and tack retention from stencil printing to component placement. In high-mix SMT lines where a paste is exposed to 22–27 °C and 50–60% RH for up to 8 h, tack force must remain above 0.8 N according to IPC-TM-650 2.4.44, using a 6.35 mm diameter probe at 0.5 mm/s pull speed. A drop below 0.6 N causes component shift during rapid conveyor acceleration and tombstoning of 0402 and 0201 components. The flux solvent system governs open-time; glycol-ether carriers with boiling points above 200 °C reduce evaporation but may increase slump and bridge formation. Slump measured by IPC-TM-650 2.4.35 at 150 °C for 15 min must not exceed 20% of the initial print width on 0.4 mm pitch lands. Reflow ramps for SAC305 paste require a flux activity window that survives the 150–190 °C preheat slope of 0.5–1.5 °C/s without premature volatilization of activator species. Premature activator loss between 120–150 °C causes wetting defects on OSP-finished pads because the final reflow stage retains insufficient oxide removal capacity. The electronic-grade quality constraint additionally limits zinc, calcium, and magnesium residuals because these elements form refractory oxides that suppress solder spread. Solder paste powder size type 4, with D50 near 25 µm, requires flux rheology yielding viscosity of 180–250 Pa·s at 10 s⁻¹ and 25 °C for screen printing; at 1 s⁻¹ the viscosity may reach 800–1200 Pa·s to retain shape. The flux component must also be supported by compliance data under RoHS Directive 2015/863 for lead, cadmium, mercury, hexavalent chromium, PBB, and PBDE in homogeneous material.
Copper ribbon in photovoltaic stringer lines is coated with electronic/EL-grade flux by a felt wheel or ultrasonic nozzle immediately before entering an IR soldering tunnel. The soldering temperature at the ribbon-cell interface is 220–240 °C for Sn60Pb40 and 240–260 °C for Sn62Pb36Ag2 or Sn96.5Ag3Cu0.5. Contact time is kept between 2.0–3.5 s because prolonged heat above 260 °C increases silver grid metal dissolution and reduces cell fill factor. The flux must wet both the tin-coated copper ribbon and the silver printed busbar under low oxygen atmosphere below 30 ppm O₂ to prevent re-oxidation of the molten solder. Halide-free formulations are mandatory in photovoltaic modules because residual chloride ions accelerate corrosion of the silver grid under IEC 61215 damp-heat conditions at 85 °C / 85% RH for 1000 h. After soldering, flux solids must remain below 1.5 wt% of the joint area to avoid interfering with EVA lamination adhesion. Lamination peel strength of the encapsulant to glass and backsheet, tested by IEC 61215-2 at 180 °C and 0.1 MPa for 15 min, can drop if volatile flux residue forms a low-molecular-weight interlayer. Stringer cycle time demands solvent flash-off below 2.0 s so that the ribbon enters the solder wave without liquid carryover; low-boiling azeotropic solvent blends in the EL-grade flux are controlled to meet this window while maintaining OSHA permissible exposure limits.
Wetting balance testing according to IEC 60068-2-54 or IPC-J-STD-003 records wetting force and time for copper coupons coated with ENIG, OSP, or immersion tin. Electronic/EL-grade flux with high activity but halide-free chemistry typically produces wetting time below 2.0 s at 255 °C on ENIG. On OSP finishes, wetting time increases because the organic protective film decomposes above 130 °C and the flux must then remove the exposed Cu₂O layer. The two-stage activator package in EL-grade material is formulated so that the first decomposition peak occurs between 110–140 °C and the second between 180–220 °C, matching the preheat and spike intervals of a reflow or wave profile. On immersion tin, excessive activator strength promotes tin dissolution and the formation of Cu₃Sn intermetallic within 60 s of liquid contact; this can degrade solder joint shear strength if immersion tin thickness is below 0.6 µm. Flux pH measured after dilution in deionized water by ASTM E70 is usually specified between 3.0 and 4.5 for halide-free organic formulations. A pH below 2.5 increases corrosion risk on bare copper lands, while a pH above 5.0 usually fails to remove SnO₂ from tin-based finishes. Solder spread area is measured by IPC-TM-650 2.4.46 using 0.2 g of SAC305 on a 25 mm × 25 mm copper coupon; spread factors above 90% are expected for ROL0 electronic-grade material at 260 °C, provided the copper substrate was cleaned with 10 vol% sulfuric acid and rinsed to conductivity below 20 µS/cm. Published data for this specific configuration is limited when flux chemistry is customized; qualification runs on the actual soldered board stack-up are required before setting wetting time acceptance limits.
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On mixed-metal printed circuit assemblies where surface finishes vary among organic solderability preservative, immersion silver, immersion tin, and electrolytic nickel-gold, the decision to use a no-clean flux is usually linked to post-reflow residue behavior and electrochemical reliability rather than to wetting force alone. Flux Electronic/EL Grade is supplied as a low-solids, halide-free, rosin-bearing liquid with a low-boiling alcohol carrier. The product identifier—Electronic/EL Grade—appears on certificates of analysis and packaging labels as the primary model/grade designation; the EL suffix denotes an electronic-grade purity envelope in which chloride, sulfate, and non-volatile residue are held below levels customarily accepted for industrial brazing or plumbing fluxes. When classified under IPC J-STD-004B, the standard spray formulation falls within the ROL0 category: rosin-bearing, low activity, and halide-free by design. The product is intended for spray, dip, and selective soldering systems, not for stencil-printable solder paste applications.
The functional difference from aggressive halide-activated industrial fluxes is not only activity; it is the residue chemistry remaining after the soldering process. Zinc chloride and ammonium chloride fluxes used in structural soldering and plumbing retain chloride-equivalent concentrations above 2 wt%. Their residues are hygroscopic and can produce visible corrosion and electrochemical migration when trapped beneath low-standoff components. Flux Electronic/EL Grade is controlled to a chloride equivalent below 0.05 wt% when tested by IPC-TM-650 method 2.3.35. This restriction lowers the wetting speed on heavily oxidized copper. It does not make the product a drop-in replacement for high-activity RA or organic acid water-washable fluxes on thermally aged boards; the operational boundary is the degree of surface oxidation at the time of assembly. Wave soldering records from production-scale equipment show acceptable soldering results on boards processed within 48 h of air exposure after fabrication.
In wave soldering, the flux is applied by spray fluxing at a solids deposition of 15–40 µg/cm² across the board surface. The alcohol carrier in the standard configuration has a closed-cup flash point between 12 °C and 15 °C when measured by ASTM D56. This creates a strict process boundary: the fluxer zone must be interlocked with exhaust and fire suppression, and the preheat section must remove carrier before the board contacts the solder wave. Top-side preheat temperatures below 100 °C are associated with solvent entrapment at via walls and under component standoffs, producing solder balling and micro-spatter on solder mask. Raising the top-side preheat to 115–135 °C while maintaining bottom-side preheat at 90–110 °C stabilizes wetting in a conventional SAC305 wave soldering operation with a solder pot held at 260–270 °C. Conveyor speed is normally set between 1.2 m/min and 1.8 m/min for a 2.5 m tunnel, but the profile must be re-verified when board thickness exceeds 1.6 mm or when large copper planes create heat-sink zones.
The activity of the Electronic/EL Grade is derived from rosin acids and non-halide activators carried in a low-boiling alcohol blend. The residue is designed to remain as a thin, non-tacky film on the soldered side; for dense SMT assemblies with through-hole connectors, this residue can remain in place if surface insulation resistance testing is conducted on the specific bare board material and solder mask combination. The process window narrows when the board exit temperature after preheat is not measured. Thermal profiling with a wired bare board is necessary because the flux decomposition behavior is a function of peak ramp rate, not only final temperature. The recommended ramp from room temperature to preheat plateau is 2–4 °C/s; ramp rates below 1.5 °C/s can leave a partially dried flux layer that is too viscous to flow into plated through-holes.
The ROL0 classification does not imply zero residue; it implies the residue mass is small and the formulation is free of intentionally added halides. When the flux is over-applied to more than 50 µg/cm² solids, the thin-film assumption breaks down. The residue becomes visible as a sticky film and the product no longer behaves as no-clean; surface insulation resistance risk increases and automated optical inspection may falsely flag it as foreign material. Deposition calibration is therefore performed gravimetrically on glass coupons before each shift, using a sectioned board mask to measure flux solids per unit area.
The specification envelope is defined by three interconnected variables: viscosity, acid number, and halide concentration. Viscosity controls spray droplet size and penetration into capillary gaps; acid number approximates the oxide removal potential of the rosin acid fraction; halide content governs post-reflow electrochemical reliability. A representative certificate of analysis for a low-solids electronic-grade flux in this product class reports a dynamic viscosity of 2.0–5.0 mPa·s at 25 °C when measured by ISO 3104, with density of 0.805–0.835 g/cm³ at 25 °C by ASTM D4052. Acid number typically falls between 25 mg KOH/g and 40 mg KOH/g, which is lower than many rosin-activated fluxes but sufficient for immersion tin and silver finishes when the board is processed within the specified shelf exposure window. Solids content in the standard spray formulation is 2.0–4.5 wt%, with a nominal value of 3.2 wt%.
| Property | Test method | Typical control range |
|---|---|---|
| Appearance | Visual inspection | Clear pale amber, free of sediment |
| Solids content | IPC-TM-650 2.3.13 | 2.0–4.5 wt%, nominal 3.2 wt% |
| Density at 25 °C | ASTM D4052 | 0.805–0.835 g/cm³ |
| Dynamic viscosity at 25 °C | ISO 3104 | 2.0–5.0 mPa·s |
| Acid number | ISO 9455-1 | 25–40 mg KOH/g |
| Chloride equivalent | IPC-TM-650 2.3.35 | < 0.05 wt% |
| Flash point, closed cup | ASTM D56 | 12–15 °C |
| Surface insulation resistance | IPC-TM-650 2.6.3.3 | > 100 MΩ after 96 h at 85 °C/85% RH |
| Copper mirror corrosion | IPC-TM-650 2.3.32 | No breakthrough |
These values are material-class reference ranges rather than guaranteed lot limits; the product-specific certificate of analysis governs each batch. The Electronic/EL Grade should not be diluted with non-virgin solvent, because altering the carrier balance depresses the viscosity below the spray-transfer threshold and can generate localized halide concentration on the board surface.
The low dynamic viscosity permits droplet formation through a nozzle orifice; however, it also means that airless spray systems operating above 0.6 MPa can shear the alcohol carrier and produce satellite droplets that drift into areas without preheat. The practical spray air pressure is therefore kept between 0.15 MPa and 0.35 MPa for a typical reciprocating spray head with a nozzle speed of 300–600 mm/s. At pressures above 0.45 MPa, the measured droplet size distribution narrows but overspray losses rise; at pressures below 0.10 MPa, incomplete wetting occurs in high-density via fields.
Conditioned storage should be maintained at 18–25 °C and below 60% RH. Containers must be resealed immediately after dispensing because the alcohol carrier absorbs atmospheric moisture and evaporates unevenly; a water uptake as low as 1.0 wt% can destabilize the activator package and reduce SIR performance. Bulk dispensing lines should use stainless steel or fluoropolymer wetted parts; brass and zinc-plated fittings are incompatible because rosin acids and the alcohol carrier will leach metal ions into the flux and depress water-extract resistivity. Water-extract resistivity is an indirect purity indicator. The Electronic/EL Grade maintains a resistivity above 50,000 Ω·cm for the flux itself before drying, which is relevant for closed-loop spray reservoirs. If the reservoir liquid falls below 20,000 Ω·cm, ionic contamination from the barrel or air supply has increased and the charge should be replaced.
Although the Electronic/EL Grade is classified as no-clean, the classification applies only to the residue produced at recommended deposition volumes. In high-reliability assemblies containing carbon sensors, open-wound relays, or non-hermetic optical devices, a thin residue can adsorb moisture and alter impedance. Under these conditions, the residue is removed with a vapor degreaser using a fluorinated solvent blend rated for no-clean rosin residue at 40–60 °C in the boil sump and 20–30 °C in the rinse sump. The cleaning process should be qualified by measuring post-wash ionic contamination below 1.56 µg NaCl equivalent/cm² in accordance with IPC-TM-650 method 2.3.25. If washing is added after soldering, water-extract resistivity testing alone will not detect localized flux residues trapped beneath low-standoff components; visual inspection with a prism or 90° endoscopic probe is required for standoff heights below 0.10 mm.
In a screening trial based on IPC-TM-650 method 2.6.3.3, the Electronic/EL Grade residue typically maintains SIR above 100 MΩ at 85 °C and 85% RH after 96 h. High-halide RA fluxes can drop below 10 MΩ in the same test, while organic acid water-washable fluxes pass only after cleaning. Electrochemical migration testing carried out under 85 °C/85% RH with 50 V bias for 500 h shows no dendritic growth for the Electronic/EL Grade on a representative FR-4 test pattern. The margin is lower on bare copper coupons with intentionally degraded organic solderability preservative; therefore the product should not be used as a remedial flux for heavily oxidized test boards.
| Flux class | Typical halide content | Residue behavior | Typical SIR after 96 h at 85 °C/85% RH | Cleaning requirement |
|---|---|---|---|---|
| Electronic/EL Grade (ROL0) | < 0.05 wt% chloride equivalent | Thin, non-tacky, low residue | > 100 MΩ | No clean for standard assemblies |
| Rosin-activated RA | 0.5–1.0 wt% chloride equivalent | Active rosin residue, potentially corrosive | < 10 MΩ | Cleaning required |
| Organic acid water-washable | Low or halide-free | Hygroscopic residue | Pass after aqueous cleaning | Cleaning mandatory |
| Industrial zinc chloride | > 2 wt% chloride equivalent | Corrosive, hygroscopic | Fail | Not suitable for electronics |
For selective soldering nozzles with internal diameters from 2.0 mm to 6.0 mm, the flux is applied as a jet or micro-spray directly to the pin field. The transfer efficiency is influenced by nozzle height, liquid pressure, and board preheat. A nozzle height of 3–5 mm above the board surface and a flux flow rate of 1.5–3.0 mL/min are typical starting values for a four-axis selective soldering cell processing through-hole connectors at a soldering iron or induction nozzle temperature of 320–350 °C. Dwell time per joint is usually 1.5–3.5 s, depending on hole fill requirement and pin mass. Excessive flux application in selective soldering produces halo residues beyond the nozzle path, which complicates automated optical inspection and can increase the risk of solder ball attachment to adjacent SMT passives.
Drop-jet fluxing is used for through-hole connectors with cavity depths below 5 mm. The Electronic/EL Grade can be jetted at room temperature if the fluid pressure is maintained at 0.05–0.15 MPa; higher pressure causes hammer bounce and satellite contamination on adjacent lands. The jet nozzle must be cleaned with virgin solvent at shift end because the evaporation of alcohol inside the nozzle forms rosin skins that change the droplet trajectory.
The flux is compatible with immersion tin, immersion silver, and OSP board finishes when board storage is controlled. It is not recommended for bare copper that has been exposed to uncontrolled temperature-humidity excursions, because the low halide level cannot reliably reduce thick cuprous oxide. Compatibility with conformal coatings must be verified by coating adhesion testing; some silicone-based coatings show delamination over visible flux residue. Published product-specific data for the Electronic/EL Grade in vapor phase soldering is limited; its use in vapor phase systems should be preceded by a carrier volatility and condensation test in the specific machine geometry.
The product is not compatible with amine-containing additives or with strong alkaline cleaning concentrates, because the rosin acid fraction will saponify and leave an insoluble metal soap residue. It should not be combined with high-acid organic acid fluxes to boost activity, because mixed residue systems can absorb moisture at 70% RH and produce electrochemical migration failures. Regulatory documentation is maintained under REACH Regulation 1907/2006/EC and RoHS Directive 2011/65/EU as applicable to the final assembly. For aerospace use, additional qualification under the applicable military performance specification or J-STD-004C may be required. The material should be stored in the original container with a nitrogen blanket if the ambient relative humidity exceeds 75% RH.
