| HS Code | 127167 |
| Product Type | Electronic/EL Grade Underfill Adhesive |
| Base Chemistry | Epoxy resin |
| Viscosity | Low, 400–800 mPa·s at 25°C |
| Glass Transition Temperature | 160°C |
| Coefficient Of Thermal Expansion | Alpha 1: 25 ppm/°C; Alpha 2: 90 ppm/°C |
| Dielectric Constant | 3.2 at 1 MHz |
| Volume Resistivity | 1.0 x 10^14 ohm·cm |
| Thermal Conductivity | 0.4 W/m·K |
| Cure Time | 30 minutes at 150°C |
| Operating Temperature Range | -55°C to 150°C |
| Adhesion Strength | High die shear strength > 15 MPa |
| Moisture Resistance | Excellent, JEDEC MSL-1 rated |
| Filler Content | 70–75% silica filler |
| Color | Black |
| Shelf Life | 6 months at -40°C storage |
As an accredited Underfill Adhesive Electronic/EL Grade factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Packaged in sealed syringes for precise application, 10 mL per syringe, with desiccant pouch and nitrogen purge. |
| Container Loading (20′ FCL) | 20′ FCL transport of electronic-grade underfill adhesive, securely packed in sealed drums, ensuring stability and safe handling. |
| Shipping | Ship underfill adhesive as sensitive electronic-grade chemical. Use clean, sealed containers, avoiding moisture and contamination. Protect from extreme temperatures and direct sunlight. Ensure compliance with hazardous goods regulations if applicable. Clearly label with product name and safety data. Use qualified carriers for safe, traceable delivery. |
| Storage | Store tightly sealed in original container in a clean, cool, dry environment away from direct sunlight, heat, and moisture. For electronic/EL grade, refrigeration at recommended temperature may extend stability; allow to warm to room temperature before opening to prevent condensation. Avoid contamination and follow manufacturer’s shelf-life guidelines. |
| Shelf Life | Shelf life is typically 6 months if stored unopened at recommended cool, dry conditions. |
Production lines dispensing EL-grade capillary underfill for 55 µm pitch flip-chip CSP devices on FR-4 laminate begin with a substrate prebake at 125 °C for 2 h or 150 °C for 1 h when incoming board moisture exceeds 0.10 wt% measured by Karl Fischer titration. The board is then exposed to argon/oxygen plasma at 100 W for 30–60 s to raise the surface energy of the solder mask and die passivation above 45 dyn/cm. An auger valve with a 0.25–0.40 mm needle deposits a single fillet along one or two adjacent die edges at a substrate temperature of 80–100 °C, which reduces the material viscosity from 8,000–14,000 mPa·s at 25 °C to 0.8–2.0 Pa·s during flow through the 40–60 µm standoff gap. The formula addition ratio for this gap class is set at 62–70 wt% spherical silica with a maximum individual particle diameter of 2.0 µm, liquid anhydride hardener at 0.85–1.00 stoichiometric ratio to epoxy equivalents, 0.2–0.5 phr imidazole adduct, 0.5–1.0 phr glycidoxypropyltrimethoxysilane, and 0.1–0.3 phr carbon black for batch-to-batch color consistency. Dispense weight for an 8×8 mm die is held between 6–10 mg, with fillet width controlled to 0.5–1.5 mm; underfill mass below 5 mg produces incomplete edge encapsulation and premature bump failure, while dosage above 12 mg creates fillet overflow onto adjacent passives and increases board-level warpage. Compatibility with no-clean flux residues must be verified because amine-based flux chemistries accelerate the imidazole cure and shorten open time at 90 °C to less than 20 min. Cure is executed in an in-line convection oven with a staged profile of 100 °C for 10 min followed by 165 °C for 30 min; void content is inspected by scanning acoustic microscopy and accepted only when the void area remains below 0.5 % of the die footprint. Compliance anchors for this application include IPC/JEDEC J-STD-020E MSL 3, JESD22-A104F thermal cycling condition G from −40 °C to +125 °C, IPC-A-610G Class 2/3 fillet criteria, RoHS Directive 2011/65/EU, and UL 746E for flammability. Syringes are stored at −20 °C and must not exceed 3 freeze-thaw cycles; in-line material is held at 25 °C for no more than 48 h before viscosity drift exceeds 5 %. Terminal finished product types include mobile application processors, baseband processors, GPU die in consumer handhelds, DRAM-on-CPU stacked packages, and RF front-end modules on 0.3–0.4 mm pitch CSP substrates.
| Filler loading | Viscosity at 25 °C | CTE α1 below Tg | Elastic modulus | Moisture uptake |
|---|---|---|---|---|
| 60 wt% | 8,000–12,000 mPa·s | 28–32 ppm/°C | 7–9 GPa | 0.18–0.22 % |
| 65 wt% | 15,000–22,000 mPa·s | 22–26 ppm/°C | 9–11 GPa | 0.14–0.18 % |
| 70 wt% | 35,000–50,000 mPa·s | 16–20 ppm/°C | 11–13 GPa | 0.10–0.14 % |
In fan-out wafer-level packaging, B-stage epoxy underfill film is vacuum-laminated onto a reconstituted wafer at 80–110 °C under 0.5–1.0 MPa for 5–10 min, then the wafer is back-ground and diced before die attach. The film contains 60–68 wt% spherical silica filler and a latent imidazole-blocked curing agent at 2–5 phr, leaving the resin B-staged with a degree of conversion below 10 % measured by differential scanning calorimetry at 10 °C/min ramp rate. After lamination, the underfill thickness is controlled to 25–50 µm between the silicon device and the reconstituted epoxy molding compound; final cure occurs at 175 °C for 20 min in a vacuum lamination press to remove entrapped air. Compliance for wafer-level underfill is verified against IPC/JEDEC J-STD-020E for moisture sensitivity, JESD22-A104F thermal cycling condition G, JESD22-B111 board-level drop testing, and ASTM E595 outgassing for optical sensor variants. Terminal wafer-level chip-scale packages include power management integrated circuits, RF filters, MEMS sensor WLCSP, and fan-out package variants for portable electronics.
Mass-limited closed-loop dispense control is required for automotive camera modules and ECU packages because underfill mass variance beyond ±5 % creates fillet asymmetry that shifts board-level drop-test failure from the bulk solder to the solder mask interface. The production line uses a heated vacuum chuck at 80 °C, a jet valve calibrated to 3.5–8.0 mg per pass for a 7×7 mm CSP, and a staged cure of 100 °C for 10 min followed by 150 °C for 60 min to minimize board warpage. The underfill compound is loaded with 58–65 wt% spherical silica, coupled with 0.5–1.0 phr epoxysilane and 0.2–0.5 phr imidazole adduct, with anhydride hardener stoichiometry held at 0.85–0.95; total hydrolyzable chloride is controlled below 50 ppm by ion chromatography. Qualification is anchored to AEC-Q100 Rev H Grade 1, JESD22-A104F thermal cycling condition G, ISO 16750-4, and J-STD-020E MSL 3 preconditioning. Terminal finished types include surround-view camera modules, ABS/ESC electronic control units, radar MMIC modules, and transmission control modules.
| Stress item | Method / standard | Condition | Pass criterion |
|---|---|---|---|
| Preconditioning | J-STD-020E | MSL 3, 30 °C / 60 % RH | No delamination after reflow simulation |
| Temperature cycling | JESD22-A104F | Condition G, −40 °C to +125 °C, 1,000 cycles | No opens, no fillet cracking |
| Biased HAST | JESD22-A110 | 130 °C / 85 % RH, 96 h | No leakage current drift beyond datasheet limit |
| High-temperature storage | JESD22-A103C | 150 °C, 1,000 h | No degradation in die shear below 80 % initial |
The qualification sequence for avionics ceramic column grid array modules begins with ionic cleanliness verification per IPC J-STD-001DS and continues with thermal cycling from −65 °C to +150 °C per MIL-STD-883H Method 1010.8 condition C for 1,000 cycles, followed by random vibration per MIL-STD-883H Method 2026 and mechanical shock per MIL-STD-810H. The underfill is formulated at 65–72 wt% spherical silica in a novolac epoxy matrix with anhydride hardener at 0.90–1.00 stoichiometric ratio and 0.1–0.3 phr cobalt-free accelerator, yielding a glass transition temperature above 160 °C measured by differential scanning calorimetry. Dispensing onto ceramic interposers uses a needle auger valve with substrate temperature at 90–110 °C; the fill volume for a 32×32 mm CCGA is 0.35–0.55 mL, and capillary fill time is 60–180 s under nitrogen. Outgassing is limited to <1.0 % total mass loss and <0.1 % collected volatile condensable material per ASTM E595. Terminal finished products include flight control computers, radar transmit/receive modules, satellite communication converters, and inertial measurement units.
For 1,200 V SiC MOSFET modules with copper baseplates, EL-grade underfill is injected after wire bonding and before final transfer molding; the injection chamber is evacuated to 1–10 mbar and then pressurized to 0.4–0.6 MPa to eliminate voids larger than 50 µm in areas under the gate and source ribbons. The compound uses 60–68 wt% spherical alumina plus 5–10 wt% fused silica hybrid filler to balance thermal conductivity with viscosity; the total filler loading must not exceed 72 wt% because flow length through 100–150 µm die-to-substrate gaps drops below process limits and void rejection rises above 3 % at inspection. Published flow-length data for hybrid alumina-silica underfill at 72 wt% loading in 100–150 µm gaps is limited; incoming inspection should therefore verify spiral flow length against a validated reference standard before line release. Compliance is verified against IEC 60747-9 for insulated-gate bipolar transistors, JESD22-A104F condition H for non-hermetic power package temperature cycling, IEC 60068-2-14 test Na, and UL 1557 for electrical isolation. Terminal product types are traction inverters, industrial motor drives, photovoltaic string inverters, and on-board chargers.
After thermocompression bonding of HBM stacks to a silicon interposer, capillary underfill is dispensed along two adjacent edges of the stack array at 90–110 °C; the material must travel through 14–25 µm gaps without segregating filler particles at the bump interconnects. Viscosity at 90 °C is held at 0.5–1.5 Pa·s and the filler loading is restricted to 55–62 wt% with a maximum individual particle diameter of 0.5 µm to prevent particle bridging in narrow gaps. Low alpha filler grade is specified at 0.002 α/(cm²·h) measured per JESD89A for soft error rate control in high-density memory stacks. The dispensed volume for a 20×30 mm interposer is 0.15–0.25 mL; void ratio is inspected by scanning acoustic tomography with acceptance at <0.5 % of bump area. Compliance for board-level reliability includes JESD22-B111 drop testing, JESD22-B110 mechanical shock, and JESD22-A104F thermal cycling condition G. Finished types include HBM graphics processors, AI accelerator modules, 2.5D field-programmable gate array interposers, and high-end networking processors.
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Underfill Adhesive Electronic/EL Grade, designated EL-100, is a one-component, anhydride-cured epoxy adhesive filled with spherical fused silica. The formulation is intended for post-reflow capillary underfill of flip-chip packages, chip-scale packages, and 2.5D interposer structures with die standoff distances from 15 μm to 60 μm. At 25 °C, cone-and-plate rheometry per ISO 3219:1994 gives a viscosity of 3,000–7,000 mPa·s; on a 90 °C substrate, the viscosity drops below 1,200 mPa·s. A cure schedule of 150 °C for 30 min followed by 165 °C for 30 min produces a glass transition temperature of 135–160 °C by differential scanning calorimetry per ASTM D3418-15. Coefficient of thermal expansion is 22–30 ppm/°C below Tg and 80–110 ppm/°C above Tg per ASTM E831-19. Filler loading is controlled at 55–65 wt% by ignition loss per ASTM D2584-18, and the maximum filler particle size is ≤10 μm by laser diffraction per ISO 13320-1:2020. The EL grade differs from no-flow and corner-bond products by being dispensed only after solder reflow; it differs from molded underfill by selective application and fillet formation along die edges. Electronic-grade ionic purity limits for chloride, sodium, and potassium are specified on the certificate of analysis as <10 ppm total chloride and <5 ppm combined alkali metals by ion chromatography, which distinguishes this material from general-purpose epoxy adhesives that do not carry equivalent limits.
The EL grade is a capillary-flow underfill. It is dispensed along one or two edges of the die after solder reflow and relies on substrate heating to lower viscosity and promote flow into the chip gap. No-flow underfill is deposited before component placement and cures during solder reflow; corner-bond adhesive is applied as a discrete fillet only at package corners; molded underfill is formed at wafer level by compression or transfer molding and covers the entire wafer surface. Because the EL grade must penetrate a 15–60 μm gap with a filler loading of 55–65 wt%, the maximum filler particle size is controlled to ≤10 μm per ISO 13320-1:2020. No-flow formulations typically use lower filler loading to avoid interfering with solder wetting. Corner-bond products use higher thixotropy to hold fillet shape after dispensing. The EL grade is formulated for adhesion to polyimide, silicon nitride, benzocyclobutene, and solder mask, with die shear strength after full cure specified per MIL-STD-883 Method 2019.8 at 12–25 MPa on representative silicon nitride and polyimide surfaces. The material cannot be used for direct-chip-attach structures that are not reflowed before underfilling; this is an operational boundary that distinguishes it from no-flow grades.
On high-volume surface-mount lines, the EL grade is jetted or needle-dispensed onto substrates held at 90 °C ± 2 °C by a pulse-heated stage with closed-loop thermocouple feedback. Needle dispensing uses a 0.20 mm internal diameter stainless steel needle at 1.0–1.8 bar; jetting uses a piezoelectric jet valve with a 0.05–0.10 mm nozzle at 150–250 Hz, producing shot volumes of 2.0–3.5 nL. The viscosity reduction at 90 °C allows a 6 mm × 6 mm die with a 25 μm standoff to fill in 45–90 s. The processing window is narrow: substrate temperature below 85 °C raises viscosity above 1,500 mPa·s, increasing fill time beyond 120 s and raising void risk at the die exit edge. Sustained temperature above 95 °C shortens open time and can raise viscosity through premature epoxy homopolymerization before flow-front convergence. A 10 °C overcool causes incomplete fill at the far edge; a 5 °C overheat causes stringing and tailing with needle valves. Filler settling is suppressed by the yield stress of the filled resin; after standing at 25 °C for 72 h, no visible supernatant forms, and viscosity after remixing returns within 5% of the initial value by ISO 3219:1994. The dispense pattern uses an L-shaped pass along two adjacent die edges; for die larger than 10 mm, a U-shaped pattern is required to avoid entrapment at the far edge.
| Property | Test method | EL-grade range | Standard capillary-flow reference range |
|---|---|---|---|
| Viscosity at 25 °C, 5 s−1 | ISO 3219:1994 | 3,000–7,000 mPa·s | 2,000–15,000 mPa·s |
| Glass transition temperature, DSC midpoint | ASTM D3418-15 | 135–160 °C | 120–170 °C |
| CTE α1 below Tg | ASTM E831-19 | 22–30 ppm/°C | 25–40 ppm/°C |
| CTE α2 above Tg | ASTM E831-19 | 80–110 ppm/°C | 90–140 ppm/°C |
| Flexural modulus at 25 °C | ASTM D790-17 | 8.0–10.0 GPa | 6.0–9.0 GPa |
| Water absorption, 24 h immersion | ASTM D570-22 | 0.10–0.25% | 0.20–0.40% |
| Maximum filler particle size, laser diffraction | ISO 13320-1:2020 | ≤10 μm | ≤20 μm |
| Filler loading, ignition loss | ASTM D2584-18 | 55–65 wt% | 40–60 wt% |
The property envelope is not independent of cure. Under-cure at 150 °C for less than 20 min leaves conversion below 90% and lowers Tg below 120 °C; over-cure at 165 °C for more than 60 min raises crosslink density but can accelerate oxidation of epoxy methylene groups at the fillet surface. The filler loading drives the low CTE needed for solder bump strain reduction, but it also raises the flexural modulus above 8 GPa, increasing package warpage stress on thin organic substrates. This trade-off is more severe than in standard capillary-flow reference products with lower filler loading and higher bulk expansion.
The adhesion of EL-grade underfill to a reflowed no-clean flux residue is lower than to a plasma-cleaned surface. Flux residue can create an interphase with a surface energy below 38 mN/m, measured by contact angle with diiodomethane according to DIN 55660-2; below this value, capillary wetting becomes sluggish and void formation at the solder mask–underfill boundary increases. An Ar/O₂ plasma treatment at 13.56 MHz, 0.3 mbar, 150 W for 60 s removes rosin and organic acid residues but can oxidize copper pillar surfaces and reduce wire-bond pad bondability. If plasma cleaning is not available, a solvent wipe with a 70/30 v/v isopropanol/deionized water mixture can reduce residue thickness, but its efficacy on high-viscosity no-clean residues is process-specific; published data for this specific configuration is limited. Avoid combining EL grade with amine-based flux activators: residual primary or secondary amines catalyze epoxy homopolymerization at dispense temperature and may raise viscosity before the flow front reaches the far die edge. Acid anhydride cure chemistry is also sensitive to residual carboxylic acid flux; excess acid can consume the latent imidazole catalyst and produce under-cure, observed as DSC residual exotherm above 8 J/g after the standard 165 °C hold per ASTM E2160-17. Each flux and underfill combination requires qualification by die shear testing per MIL-STD-883 Method 2019.8 after moisture sensitivity level preconditioning per IPC/JEDEC J-STD-020E.
Void formation is minimized by a stepwise cure profile in which the assembly ramps from 25 °C to 120 °C at 3 °C/min and holds for 20 min before the main 150 °C hold. The gel point occurs between 105 °C and 115 °C; once gelation occurs, volatile escape is limited and any remaining low-mass outgassing forms stable voids. A ramp rate above 5 °C/min can produce a temporary viscosity drop that allows filler particles to migrate toward the die exit edge before the network builds yield stress; this is observed as a filler-rich region by scanning acoustic microscopy. Residual exotherm after the 165 °C hold should be below 8 J/g when scanned at 10 °C/min per ASTM E2160-17. A 20-unit production lot in a forced-air oven with an air velocity of 1.5 m/s at the package surface shows a maximum package-to-package Tg spread of 4 °C when oven loading is maintained below 0.5 m² projected package area per m³ chamber volume. Void area fraction below 0.5% by scanning acoustic microscopy at 30 MHz after JEDEC MSL3 preconditioning is used as the acceptance criterion for radio-frequency packages. Assemblies should not be cooled below 0 °C within 30 min after cure because the CTE mismatch through the glass transition can create edge delamination.
After 1,000 h of aging at 85 °C and 85% RH, the EL grade typically retains above 80% of initial die shear strength on copper pillar surfaces according to supplier data using MIL-STD-883 Method 2019.8; this is a more severe interface test than bulk tensile retention per ASTM D638-14. Moisture uptake is 0.10–0.25% after 24 h immersion per ASTM D570-22; moisture content above 0.35% correlates with lower adhesion after reflow at 260 °C peak and should be flagged before component placement. The low chloride and alkali metal limits reduce electrochemical migration risk on fine-pitch redistribution layers; surface insulation resistance is tested at 85 °C, 85% RH, 100 V DC per IPC-TM-650 Method 2.6.3.3 and remains above 10⁸ Ω after 168 h. The material is not recommended for direct contact with bare copper wire bonds if the assembly is exposed to sulfur dioxide or hydrogen sulfide atmospheres because surface corrosion can proceed without visual solder mask degradation.
For halogen-free and high-reliability builds, the following compliance limits apply.
| Criterion | Method or standard | Acceptance limit | Validation source |
|---|---|---|---|
| RoHS restricted substances | 2011/65/EU as amended by (EU) 2015/863 | Pb <1000 ppm, Hg <1000 ppm, Cd <100 ppm, Cr(VI) <1000 ppm, PBB/PBDE <1000 ppm | Supplier declaration |
| REACH SVHC content | Regulation (EC) No 1907/2006 | <0.1% w/w per SVHC | Certificate of analysis |
| Halogen content | IEC 61249-2-21 | Cl ≤900 ppm, Br ≤900 ppm, total ≤1,500 ppm | Certificate of analysis |
| Moisture sensitivity level | IPC/JEDEC J-STD-020E | MSL 3, floor life 168 h at ≤30 °C/60% RH | Package-level test |
| Surface insulation resistance | IPC-TM-650 Method 2.6.3.3 | ≥10⁸ Ω at 85 °C/85% RH, 100 V DC after 168 h | Comb pattern |
| Die shear after thermal shock | JESD22-A104 Condition B, 500 cycles −55/125 °C | No loss greater than 20% from initial | Supplier qualification lot |
Storage is at 2–8 °C with a supplier shelf life of 6 months from date of manufacture. The syringe is warmed to 25 °C for 4 h before opening and is not used if barrel condensate remains after the warm-up period. Frozen storage is not permitted because ice crystal formation can rupture the filler–resin interface and increase viscosity variability.
