| HS Code | 457455 |
| Product Name | Marking Ink Electronic/EL Grade |
| Color | Black or custom color |
| Viscosity | 20-50 cP at 25°C |
| Specific Gravity | 0.95-1.10 g/cm³ |
| Solid Content | 30-40% by weight |
| Purity | Low ionic impurities; ≤10 ppm total heavy metals |
| Adhesion | Excellent to PCB substrates, glass, ceramics, and epoxy surfaces |
| Curing Condition | Thermal cure: 130-150°C for 20-30 minutes; or UV cure: 3-5 seconds |
| Solvent Base | Alcohol and glycol ether mixture; halogen-free |
| Flash Point | >60°C (closed cup) |
| Electrical Insulation | Volume resistivity >1×10¹² Ω·cm when cured |
| Chemical Resistance | Resistant to IPA, flux cleaners, mild acids, and alkalis after cure |
| Abrasion Resistance | High; withstands handling and PCB processing without smearing |
| Operating Temperature Range | -40°C to +150°C after full cure |
| Shelf Life | 12 months from date of manufacture when unopened |
| Storage Condition | Store in sealed container at 5-35°C, away from direct sunlight |
| Application Method | Screen printing, pad printing, inkjet, or marker pen delivery |
As an accredited Marking Ink Electronic/EL Grade factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Marking Ink Electronic/EL Grade supplied in a 1-liter amber glass bottle with secure lid, ensuring purity and safe handling. |
| Container Loading (20′ FCL) | 20′ FCL: Marking Ink Electronic/EL Grade packed in drums/pails on pallets, loaded securely for safe transport. |
| Shipping | Marking Ink Electronic/EL Grade is a flammable liquid requiring hazardous materials shipping. Transport via ground freight only in UN-approved packaging with correct labels and documentation. Air transport is prohibited. Regulatory compliance is mandatory and may affect delivery times. Keep away from ignition sources. |
| Storage | Store Marking Ink Electronic/EL Grade in a tightly sealed original container in a cool, dry, well-ventilated area away from direct sunlight, heat, sparks, and open flames. Keep away from incompatible oxidizers. Maintain temperatures between 15–25°C, avoid freezing, and inspect containers regularly for leaks or damage. |
| Shelf Life | Shelf life is typically 12 months from manufacture date when stored sealed, cool, and away from direct sunlight. |
On high-density QFN, TSSOP, and BGA assembly lines, two-component epoxy-based Electronic/EL Grade marking ink is pad-printed onto transfer-molded epoxy packages before singulation. The formulation addition ratio of base ink to hardener is maintained at 100:10.5 by weight, corresponding to 90.5 wt% Electronic/EL Grade marking ink in the final wet mixture. When the hardener fraction exceeds 11.0 parts, crosslink density rises to a threshold where the cured film cannot relieve thermal stress during subsequent 260°C peak solder reflow, producing edge cracking on 0.4 mm pitch packages. When the hardener fraction falls below 10.0 parts, residual unreacted epoxy oligomers migrate during reflow and create interfacial delamination between the ink body and the mold compound. The cured film is qualified to JEDEC JESD22-B107E for mark permanence after solder float and MIL-STD-883 Method 2015 for solvent resistance; production lots are evaluated by crosshatch adhesion to ASTM D3359-17 Method B and must reach classification 5B. The pad-printing operation uses a 90 mm closed-cup cliché with 0.018 mm etch depth and a 60 Shore A transfer pad. Viscosity is checked each shift with DIN 53211 cup 4 and held at 30,000–45,000 mPa·s at 25°C. Terminal components produced under this application include QFP, QFN, BGA, SOIC, and TSSOP integrated circuits for consumer, industrial, and computing substrates.
Production-scale failure data from this configuration indicates that solvent retention is the primary process conflict. When cliché flooding extends beyond 1.5 s at 40% relative humidity, solvent evaporation at the cliché edge creates starved transfer and low-contrast stroke voids. If the solvent-rich ink is deposited onto packages without sufficient predry, the subsequent solder reflow drives solvent vapor through the curing film, forming microvoids and reducing adhesion from 5B to 3B after 96 h of biased humidity testing. Amine-containing mold release residues are incompatible; they react with the epoxy hardener to yield soft, uncured patches. If the package surface is not plasma-cleaned after mold release, crosshatch adhesion falls from 5B to 3B within 24 h.
| Test standard | Condition | Minimum acceptance criterion |
|---|---|---|
| JEDEC JESD22-B107E | Solder float and solvent exposure | Legible mark without lift-off |
| MIL-STD-883 Method 2015 | Immersion in solvent mixture | Mark remains legible |
| ASTM D3359-17 Method B | Crosshatch tape adhesion | 5B |
| ASTM D3363-20 | Pencil hardness | 2H min |
High-speed MLCC production lines require the Electronic/EL Grade marking ink to survive furnace profiles before nickel–tin terminal sintering and to maintain legibility after chip resistor laser trimming. The formulation addition ratio of Electronic/EL Grade marking ink to low-sodium reactive diluent is 100:3.0 by weight, giving the ink a 97.1 wt% loading in the final mixture before printhead filtration. For continuous inkjet cells, this ratio yields a viscosity of 8–12 cP at 40°C printhead temperature. For pad-transfer cells, the ink is adjusted to 100:2.0 by weight, producing 25–35 s on DIN 53211 cup 4. Compliance verification includes AEC-Q200 passive component qualification after destructive solder heat testing, EU RoHS 2015/863, and REACH SVHC candidate list conformance. Halogenated flame retardants are absent from the cured mark. The downstream production process uses continuous inkjet printheads with 55 μm nozzles running at 300 m/min line speed. The primary failure mode is nozzle plate wetting from low-boiling diluents, causing satellite drop formation and unreadable component codes. Terminal finished products include MLCCs, chip resistors, chip inductors, thermistors, and varistors used in mobile devices, automotive modules, and power converters.
In LED and optocoupler assembly, the marking operation is performed after wire bonding and before final encapsulation, which means the Electronic/EL Grade marking ink must not release acidic volatiles that can corrode silver-plated leadframes or induce microarcing across the die attach. White epoxy-based Electronic/EL Grade marking ink is loaded at 91.3 wt% of the final pad-print mixture, corresponding to a 100:9.5 base-to-hardener ratio, and thinned with 4.0 wt% anhydrous butyl cellosolve acetate to a pad-print viscosity of 28–36 s on DIN 53211 cup 4. Compliance testing includes JEDEC JESD22-A102C autoclave exposure at 121°C and 100% RH for 96 h, after which the mark must remain legible and adhesion must remain above 4B by ASTM D3359-17. The downstream process uses a 120 mm cup pad printer with a 0.022 mm cliché depth and a 55 Shore A pad. Operators report that excess thinners above 5.0 wt% cause ink misting between the cliché and package surface, lowering line yield. Finished product types include indicator LEDs, white LED packages, optocouplers, IR receivers, and RGB module assemblies.
Double-sided surface-mount PCB assemblies require the Electronic/EL Grade marking ink to be screen-printed after solder mask cure and before component placement, creating component designators, polarity marks, and board serialization. The formulation addition ratio of ink to slow-evaporating viscosity reducer is 100:2.5 by weight, yielding 97.6 wt% ink loading before screen-printing. Reducer levels above 3.5 parts extend the UV cure window but cause residual monomer retention that fails the IPC-TM-650 2.3.25 ROSE cleanliness test. Qualified boards are tested to IPC-SM-840E Class T for legend durability, UL 94 V-0 for flame classification, and EU RoHS 2015/863. The screen-printing operation uses a 77T polyester mesh and a 75 Shore A squeegee at 15° attack angle. Production logs show that stencil flooding longer than 2.0 s causes solvent loss and a viscosity increase from 18,000 mPa·s to 32,000 mPa·s, producing incompletely cured legends after the UV cure tunnel at 8 m/min. Because the material is applied on bare or OSP copper pads and cured in-line, ionic extractables are monitored by IPC-TM-650 2.3.25; boards with chloride contamination above accepted limits are rejected before stencil wipe cycles. Terminal parts include router line PCBs, power supply boards, LED driver modules, and communication modules.
In automotive power modules and under-hood sensor housings, the cured ink film is subjected to thermal cycling from -40°C to +150°C, vibration, and aggressive transmission fluids, so the Electronic/EL Grade marking ink is selected only after surviving 1,000 h PCT and 1,000 cycles air-to-air thermal shock. The formulation addition ratio of base to hardener is 100:14 by weight, placing the Electronic/EL Grade ink at 87.7 wt% of final wet mix. No solvent is added when the viscosity falls within 40,000–55,000 mPa·s at 25°C; if ambient temperature drops below 18°C, a 2.0 wt% slow-evaporating reactive diluent is incorporated via closed mixing. Qualification includes AEC-Q100 Rev H for IC-level reliability, AEC-Q200 for passive support components, and ISO 16750-4 for climate loads. The downstream production cell uses a 150 mm sealed pad printer with 0.025 mm cliché depth and a 70 Shore A transfer pad. Molded body roughness from Ra 1.2 μm to Ra 2.8 μm requires doubling the stroke dwell to fill microvoids without entrapping air. Completed products include ECU microcontrollers, ABS sensor modules, electric power steering controllers, and battery management system boards.
Medical telemetry systems and avionic line-replaceable units require the Electronic/EL Grade marking ink to pass outgassing screening and non-ionic contamination checks under IPC-J-STD-001 ROL0 assembly conditions. The formulation addition ratio is set at 100:12 by weight epoxy base to hardener; the Electronic/EL Grade ink comprises 89.3 wt% of the mix, and the mixed viscosity is 35,000–48,000 mPa·s at 25°C. No thinning solvent is permitted because residual solvent is classified as a non-conformance in avionics conformal coating adhesion tests. The production process is a low-speed 80 mm cup pad printer with 0.015 mm cliché depth and 55 Shore A pad, operating under 30% relative humidity to suppress condensation-induced amine blush on ceramic substrates. Terminal product types include patient monitors, implant programmers, cockpit warning units, and flight control modules.
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Marking Ink Electronic/EL Grade, model designation EL-700 Series, is a one-part, solvent-borne, heat-cured epoxy-based pigmented ink assigned to identification legends on high-density printed circuit assemblies, ceramic hybrid circuits, and electroluminescent lamp bus structures. Qualified colours are EL-701 white, EL-702 yellow, and EL-703 black. Viscosity at 25 °C is specified as 8 000–12 000 mPa·s per ISO 2555 using a Brookfield RV spindle 14 at 20 min⁻¹. Non-volatile content is 68 ± 2 wt% per ISO 3251, fineness of grind is < 5 µm per ISO 1524, and density is 1.25 ± 0.05 g/cm³ per ASTM D1475. The wet ink exhibits a closed-cup flash point above 40 °C when tested per ISO 3679.
For impedance-sensitive assemblies, the EL-700 Series is controlled for total ionic extractables below 1.0 µg NaCl equivalence/cm² per IPC-TM-650 2.3.25 and for total halogen content below 50 ppm per EN 14582. Post-cure volume resistivity is above 1 × 10¹⁴ Ω·cm per ASTM D257, and dielectric strength is above 20 kV/mm per ASTM D149. Surface insulation resistance after 168 h at 85 °C/85 % RH and 100 V DC is specified above 1 × 10⁸ Ω per IPC-TM-650 2.6.3.7.
This product is not a solder mask or conformal coating. It is applied by screen printing as a legend or polarity marking, then thermally cured before soldering and cleaning operations. Published data for direct contact with electroluminescent phosphor encapsulation layers is limited; qualification coupons under 85 °C/85 % RH bias are required for lamp-specific designs.
Lot-release properties are consolidated in Table 1. Values are determined on cured films at 25 ± 2 °C and 50 ± 10 % RH unless otherwise stated.
| Property | Test Method | Specification |
|---|---|---|
| Viscosity at 25 °C | ISO 2555 | 8 000–12 000 mPa·s |
| Non-volatile content | ISO 3251 | 68 ± 2 wt% |
| Fineness of grind | ISO 1524 | < 5 µm |
| Density | ASTM D1475 | 1.25 ± 0.05 g/cm³ |
| Flash point, closed cup | ISO 3679 | > 40 °C |
| Total ionic extractables | IPC-TM-650 2.3.25 | < 1.0 µg NaCl eq/cm² |
| Total halogen content | EN 14582 | < 50 ppm |
| Surface insulation resistance after 168 h | IPC-TM-650 2.6.3.7 | > 1 × 10⁸ Ω |
| Volume resistivity after cure | ASTM D257 | > 1 × 10¹⁴ Ω·cm |
| Dielectric strength | ASTM D149 | > 20 kV/mm |
| Adhesion, cross-hatch, FR-4 | ASTM D3359 | 5B |
| Pencil hardness after full cure | ASTM D3363 | 6H |
| Cure schedule | Supplier-qualified profile | 30 min at 150 °C or 60 min at 120 °C |
| Shelf life, unopened | Supplier retention data | 6 months at 5–25 °C |
Conventional industrial solvent-borne marking inks are frequently released with total ionic extractables of 2.0–5.0 µg NaCl equivalence/cm² because they are not qualified for high-impedance surfaces or bare-copper clearance regions. The EL-700 Series is manufactured without silicone-based defoamers and without amine-based pigment dispersants; both additive classes have been associated with conformal coating delamination and premature epoxy crosslinking when carried into downstream coating processes. Halogen content is controlled below 50 ppm, whereas general industrial inks often permit total chlorine and bromine levels above 300 ppm.
Against UV-curable electronic marking inks, the heat-cured EL-700 Series avoids residual photoinitiator by-products that can contribute to leakage and electrochemical migration under humid bias. The trade-off is production throughput: a thermal tunnel requires 30 min at 150 °C while UV units reach tack-free state in 1–3 s at 600 mJ/cm². Table 2 compares representative values under common test conditions.
| Parameter | EL-700 Series Electronic/EL Grade | Conventional Industrial Marking Ink | UV-Curable Electronic Marking Ink |
|---|---|---|---|
| Total ionic extractables | < 1.0 µg NaCl eq/cm² | 2.0–5.0 µg NaCl eq/cm² | 1.0–2.5 µg NaCl eq/cm² |
| Total halogen | < 50 ppm | 200–600 ppm | < 900 ppm |
| Cure response | 30 min at 150 °C | 10 min at 120 °C or 24 h at 25 °C | 1–3 s at 600 mJ/cm² |
| SIR after 168 h, 85 °C/85 % RH | > 1 × 10⁸ Ω | > 1 × 10⁶ Ω | > 1 × 10⁷ Ω |
| Adhesion to FR-4, cross-hatch | 5B | 4B–5B | 3B–4B |
On a mixed-technology line using a 350 mm × 350 mm screen printer with vision alignment repeatability of ±12.5 µm, EL-701 white was printed through a 230 mesh per inch stainless-steel mesh with 25 µm emulsion thickness. At 25 °C and 45 % RH, print definition remained stable for 2 h; ambient excursions above 30 °C or below 20 % RH shortened useful working time to 45–60 min because evaporation raised viscosity beyond 15 000 mPa·s. The same line recorded mesh clogging when squeegee speed exceeded 250 mm/s at mesh tension below 25 N/cm, indicating that shear rate and screen tension must be controlled together.
A butyl acetate-based thinner is used at 0–5 wt%. Pot life after thinning is 8 h at 25 °C; viscosity doubling requires thinning or retarding additive, but addition of reactive amine retarders is prohibited because the system undergoes premature crosslinking within 15 min at 25 °C.
High-density circuits with 50 µm conductor spacing and electroluminescent lamp elements are sensitive to ionic residues because absorbed moisture forms a conductive electrolyte under DC bias. The cured ink film contributes to the ionic load of the surface; the EL-700 Series is therefore batch-released using IPC-TM-650 2.3.25 extraction and measured by ion chromatography. Acceptable sodium and potassium extractables are below 5 ppm each, and total chloride is below 30 ppm.
In addition to extraction data, the product is qualified on an interdigitated comb pattern with 0.4 mm pitch per IPC-TM-650 2.6.3.7. The coupon is biased at 100 V DC for 168 h; pass criterion is > 1 × 10⁸ Ω with no dendrite formation and no measurable leakage increase of more than one decade. Electrochemical migration failure in conventional inks appears as metallic dendrites across 0.4 mm gaps under 85 °C/85 % RH, which is the primary failure mode this grade was designed to reduce.
For electroluminescent lamp designs, the ink is specified only for the non-illuminated legend area and not for dielectric isolation between front and rear electrodes. Direct contact with indium tin oxide or silver flake conductors is acceptable after cure, but the ink must not be used as a replacement for the dielectric layer. Published data for phosphor encapsulation direct contact is limited.
The rheological profile of EL-700 Series is pseudoplastic with a thixotropic index of 2.2–2.8 calculated from Brookfield viscosity at 1 min⁻¹ and 10 min⁻¹. The index is intentional: it allows the ink to shear-thin under a 70–80 Shore A squeegee at 100–250 mm/s while recovering rapidly after mesh departure, limiting bleed on 100 µm line characters. Dynamic viscosity at 10 s⁻¹ is approximately 4 000–6 000 mPa·s, which corresponds to clean mesh release on 200–325 mesh per inch stainless-steel screens.
Cure kinetics were evaluated by differential scanning calorimetry per ISO 11357-1 at 10 K/min; the main exotherm peak occurs between 142 °C and 158 °C. Full cure is defined as 30 min at 150 °C forced-air or 60 min at 120 °C. Under-cure below 120 °C leaves residual solvent and depresses pencil hardness from 6H to below 3H, with corresponding loss of chemical resistance.
In conveyorised ovens, oven zones set to 130/150/160 °C with 30 min total residence satisfy the cure specification. Board mass above 2.0 kg requires profiling because thermal lag can reduce actual ink temperature by 10–15 °C below setpoint.
Cross-hatch adhesion per ASTM D3359 is 5B on FR-4 laminate, 4B on untreated polyimide, and 5B on alumina ceramic after solvent wipe. The same ink printed on low-surface-energy substrates below 38 mN/m without plasma treatment drops to 2B–3B; air plasma at 200–300 W for 30 s is used on polyimide and ceramic to restore the specification.
After three reflow cycles with a peak temperature of 260 °C per J-STD-020 profile, adhesion on FR-4 remains 5B, and colour shift is limited to ΔE below 3 when measured by a spectrophotometer with D65 illumination and 10° observer. Solder float at 288 °C for 10 s produces no blistering or delamination.
Adhesion is reduced when the ink is applied over uncured acrylic conformal coating or over benzil alcohol flux residues. Substrates must be cleaned to < 1.5 µg NaCl eq/cm² before printing.
Cured EL-700 Series withstands 50 double rubs with 99 % isopropanol per ASTM D5402 without breakthrough. Immersion in aqueous saponifier at 55 °C for 10 min does not reduce adhesion below 5B on FR-4. The cured film is also tested after 1 h contact with terpene hydrocarbon flux removers at 40 °C, with no visible edge attack and no change in pencil hardness.
The operational boundary is defined by chlorinated solvent immersion: methylene chloride paint stripper and dichloromethane-based cleaners produce edge lifting and softening after 5 min. Alkaline cleaners with pH above 12 at 70 °C cause adhesion loss on ceramic and glass-passivated substrates. The product is not specified for immersion in strong acid pickling baths or for direct contact with benzyl alcohol flux activators above 2 wt%. Avoid post-cure exposure to ultraviolet ozone systems longer than 30 min because pigment binders may chalk.
