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High Thermal Conductivity Epoxy Molding Compound (EMC) Electronic/EL Grade

    • Product Name: High Thermal Conductivity Epoxy Molding Compound (EMC) Electronic/EL Grade
    • Factroy Site: Yudu County, Ganzhou, Jiangxi, China
    • Price Inquiry: admin@ascent-chem.com
    • Manufacturer: Ascent Petrochem Holdings Co., Limited
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    Specifications
    HS Code 856636
    Thermal Conductivity 1.5 W/m·K
    Coefficient Of Thermal Expansion α1 15 ppm/°C
    Glass Transition Temperature Tg 175 °C
    Flexural Strength 120 MPa
    Flexural Modulus 15 GPa
    Dielectric Constant 1 Mhz 4.0
    Dissipation Factor 1 Mhz 0.010
    Volume Resistivity 1.0 x 10^15 Ω·cm
    Moisture Absorption 0.2 %
    Specific Gravity 1.9
    Curing Temperature 175 °C
    Curing Time 120 s

    As an accredited High Thermal Conductivity Epoxy Molding Compound (EMC) Electronic/EL Grade factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.

    Packing & Storage
    Packing Available in 1 kg sealed aluminum foil bags, packaged in boxes with desiccant to prevent moisture absorption.
    Container Loading (20′ FCL) 20' FCL: packed in sealed drums/cartons on pallets, secured, labeled, moisture-protected, temperature-controlled, no contamination, safe transport.
    Shipping Shipping as non-dangerous goods: **High Thermal Conductivity Epoxy Molding Compound (EMC), Electronic/EL Grade** is not regulated under IATA/IMDG/ADR. Pack in sealed, moisture-resistant bags on pallets. Avoid ignition sources and excessive heat. No UN number required. Transport by air, sea, or ground in standard dry packaging.
    Storage Store in a cool, dry, well-ventilated area away from direct sunlight, heat sources, and ignition. Keep containers tightly sealed to prevent moisture absorption, which degrades performance. Recommended storage temperature is typically below 25°C (77°F) with low humidity. Follow manufacturer’s shelf-life guidelines and rotate stock using first-in, first-out principles.
    Shelf Life Shelf life is typically 6 months when stored below -5°C in unopened, moisture-proof original packaging.
    Application of High Thermal Conductivity Epoxy Molding Compound (EMC) Electronic/EL Grade

    For discrete power packages in wire-bonded and clip-bonded formats, electronic/EL grade high thermal conductivity epoxy molding compound replaces standard silica-filled EMC when junction-to-case thermal impedance must remain below package-specific limits. The formulation generally contains o-cresol novolac epoxy at 6–8 wt%, phenol novolac hardener at 3–5 wt%, spherical fused silica at 45–60 wt%, and high-purity alumina at 25–40 wt%; the remainder consists of triphenylphosphine or imidazole accelerator at 0.2–0.4 wt%, organosilane coupling agent at 0.5–1.0 wt%, and carnauba wax release agent at 0.1–0.3 wt%. Epoxy-to-phenolic hydroxyl equivalent ratio is maintained between 1.0:1.0 and 1.1:1.0 to balance moisture resistance and hot hardness after in-mold cure. The property envelope below is drawn from standard test data published for electronic-grade EMC materials in discrete power packaging supplier technical bulletins.

    Property / RequirementTest MethodTypical electronic/EL grade value
    Thermal conductivityASTM D54702.8–4.0 W/mK
    Spiral flowEMMI 1-6670–110 cm at 175 °C, 6.9 MPa
    Glass transition temperatureISO 11359-2 TMA160–200 °C
    CTE α1ISO 11359-212–16 ppm/K
    Flame retardancyUL 94V-0 at 0.8 mm
    Moisture sensitivityJEDEC J-STD-020MSL1 at 260 °C peak reflow, 3 cycles
    Volume resistivityASTM D257≥1.0 × 1014 Ω·cm at 25 °C
    Extractable ionic impuritiesinternal ion chromatographyNa+ <5 ppm, Cl− <10 ppm

    Transfer molding is performed on auto molding presses with 120–200 ton clamping force and multi-plunger transfer systems. Mold temperature is held at 165–185 °C; transfer pressure ranges from 8–12 MPa; in-mold cure time is 90–180 s depending on package thickness. Post-mold cure at 175 °C for 4–6 h raises degree of conversion above 95 % and stabilizes the α2 CTE. The high alumina fraction increases melt abrasion; mold tool surfaces require hardened steel or titanium nitride coatings, and maintenance intervals are typically shortened to 30,000–50,000 shots. Pre-drying of pellets is not used in standard transfer molding because the compound is shipped frozen at 5 °C or lower and equilibrated to room temperature only in sealed moisture barrier bags immediately before loading. Amine-based cleaning solvents or die attach residues that can poison the phenol novolac cure must be excluded from the molding line. Representative terminal packages include TO-247-4L, DPAK, and LFPAK power discretes for switched-mode power supplies, motor drives, and voltage regulators.

    What Limits Spiral Flow When Alumina Filler Loading Exceeds 90 wt% in IGBT Transfer Molding?

    Below 88 wt% total filler, high thermal EMC melts show near-Newtonian behaviour at transfer shear rates and remain processable on standard transfer presses. Above 90 wt%, apparent melt viscosity rises steeply because particle-particle contact forces replace resin-dominated flow, and spiral flow collapses to values that cannot fill deep IGBT cavity features without void formation or wire sweep. In IGBT module encapsulation the requirement for thermal conductivity of 4–8 W/mK forces formulators to use a total filler fraction of 90–93 wt%. That filler commonly blends spherical high-purity alumina at 70–85 wt% with boron nitride platelets at 5–10 wt%; the epoxy matrix is an o-cresol novolac resin at 5–8 wt% and a phenolic hardener at 3–5 wt%. The epoxy-to-phenolic equivalent ratio is kept close to 1.0:1.0 to limit unreacted hydroxyl groups that raise moisture absorption. Coupling agent content is raised to 1.0–1.5 wt% because alumina surfaces consume more silane than fused silica and insufficient coupling produces resin-filler voids visible only after 1000 cycles of thermal shock.

    Total filler contentThermal conductivitySpiral flow at 175 °CApparent viscosity at 50 s−1Wire sweep on 250 µm Al wire
    85 wt%2.8–3.2 W/mK90–110 cm60–80 Pa·s<5 %
    88 wt%3.5–4.0 W/mK70–90 cm90–120 Pa·s5–8 %
    91 wt%4.5–5.5 W/mK40–60 cm150–220 Pa·s8–12 %
    93 wt%6.0–7.5 W/mK20–35 cm280–400 Pa·s12–18 %

    The viscosity and wire sweep bands are representative pilot-scale observations from transfer molding evaluations, not single-batch product guarantees. For IGBT modules the resulting process window shifts to lower transfer speeds and longer filling times. Vacuum-assisted transfer molding is used with cavity vacuum below −0.08 MPa to prevent trapped air at the exposed copper leadframe edges. Mold temperature is set at 170–180 °C; transfer pressure is limited to 5–9 MPa to reduce wire sweep on aluminium bond wires; in-mold cure time extends to 180–240 s for thick module bodies. Post-mold cure at 175 °C for 6–8 h is used to fully develop crosslink density and stabilise CTE α1 at 12–15 ppm/K and CTE α2 at 45–60 ppm/K. The filler loading creates a thermal conductivity through-plane value above 4 W/mK but also shifts the spiral flow to below 60 cm, so gate and runner geometries must be redesigned with direct side gates rather than top-center gates. Operational boundaries are narrow: if cavity vacuum is lost, alumina-filled EMC produces surface voids on the DBC substrate; if transfer pressure rises above 9 MPa, aluminium wire sweep beyond 10 % becomes likely. Compliance is verified against AEC-Q101 for discrete power semiconductors, AQG 324 for automotive power modules, and IEC 60749-26 for thermal cycling integrity. Terminal products include automotive traction inverter modules, industrial motor drive IGBT modules, and moulded dual-in-line power modules.

    On-board charger power stacks impose two conflicting constraints on the mold compound: high thermal conductivity across a large DBC substrate and low shrinkage stress after post-mold cure. A formulation closer to the 88 wt% total filler boundary than the typical IGBT grade is selected: spherical alumina at 60–70 wt%, fused silica at 20–30 wt%, carbon black at 0.1 wt%, and no boron nitride because BN platelets reduce adhesion to PP and PPS housing materials. The resin-hardener system is a low-stress phenol novolac cure with an accelerator loading of 0.2–0.3 wt% to extend flow window. Transfer molding is performed on vacuum presses with 80–150 ton clamp force, mold temperature 170–180 °C, transfer time 10–18 s, and in-mold cure 120–200 s. Post-mold cure at 175 °C for 5 h is used. The process must hold mold flash below 0.03 mm on exposed copper pads because subsequent thermal interface material application relies on flatness. Thermal cycling tests are run per IEC 60068-2-14 from −40 °C to +125 °C for 1000 cycles; CTE α1 is held at 12–15 ppm/K to track the copper leadframe, which sits near 17 ppm/K. Typical terminal products are 48 V/12 V DC-DC converter modules, 6.6 kW on-board charger secondary power stages, and power factor correction modules.

    When GaN Power Amplifier Packages Require Dielectric Stability Across 10 GHz

    GaN-on-SiC power amplifier packages for 5G massive MIMO radios demand an encapsulant that removes heat from high-power-density transistor arrays without creating excessive dielectric loss in the matching network. Formulations for this application use total filler loading of 82–86 wt%, lower than IGBT grades, because high filler content raises dielectric constant and increases the probability of ceramic-resin interfacial voids that amplify insertion loss at 10 GHz. Spherical fused silica is blended with hexagonal boron nitride at 10–20 wt%; alumina is limited to 30–45 wt% to keep Dk below 4.8. The resulting through-plane thermal conductivity is 2.5–3.5 W/mK, which is adequate for GaN RF die after die attach thinning but not for IGBT-level heat fluxes. Cure chemistry uses a low-chloride o-cresol novolac epoxy and phenol novolac hardener with total extractable chloride below 10 ppm to reduce corrosion under RF bias. Transfer molding uses vacuum-assisted multi-plunger presses at 175–185 °C, transfer pressure 6–10 MPa, and in-mold cure 100–150 s. Post-mold cure is 175 °C for 4 h. Dielectric constant and dissipation factor are tested by split-post dielectric resonator per IPC-TM-650 2.5.5.5 at 10 GHz; typical ranges are Dk 4.2–4.8 and Df 0.005–0.010. The operational boundary is that void content must remain below 1 % by cross-section area because each void behaves as a local field enhancement site under high-frequency excitation. Terminal products include GaN power amplifier modules, base station antenna-filter unit transceivers, and 64T64R massive MIMO radio heads.

    Automotive BMS Power Switch Package Burn-In Conditions

    Battery management system power switch packages are qualified with longer burn-in and higher temperature reverse bias than consumer discrete packages because field failures are linked to corrosion and delamination at the compound-leadframe interface. A typical formulation for power QFN and TO-263-7L BMS packages contains biphenyl epoxy resin at 5–8 wt%, phenol novolac hardener at 3–5 wt%, spherical alumina at 50–70 wt%, fused silica at 20–35 wt%, silicone flexibilizer at 0.5–1.0 wt%, and phosphorous-based flame retardant sufficient to achieve UL 94 V-0 at 0.4 mm. The silicone flexibilizer reduces interfacial stress on NiPdAu leadframes but must be kept below 1.0 wt% to prevent silicone migration onto exposed power pads. Transfer molding is run at 175 °C with transfer pressure 8–11 MPa and in-mold cure 120–180 s. Post-mold cure at 175 °C for 5 h is followed by 1000 h of high-temperature reverse bias at 175 °C and thermal cycling from −40 °C to +125 °C per AEC-Q101. Multichip modules are additionally assessed under AEC-Q104. The principal process failure is compound bleed onto the power pad during cavity flash, which reduces wire bond pull strength and causes solder voiding during board mount. Terminal products include 48 V battery disconnect FETs, cell monitoring ASIC packages, and pre-charge relay drivers.

    Because aluminium nitride filler raises apparent melt viscosity and also increases dielectrophoretic mobility during transfer molding, aerospace high-reliability power module encapsulants are qualified using lower filler loadings than commercial IGBT grades. A controlled bled of 60–70 wt% spherical alumina and 5–10 wt% aluminium nitride yields through-plane thermal conductivity of 3.0–4.0 W/mK while maintaining spiral flow above 60 cm for large cavity avionics modules. The epoxy system is a high-purity novolac resin with extracted ionic contamination below 5 ppm for Na+ and 10 ppm for Cl−. Transfer molding is performed on vacuum presses at 165–175 °C with transfer pressure limited to 6–9 MPa to protect fragile substrate traces; in-mold cure is 150–210 s. Post-mold cure at 175 °C for 6 h is used. Outgassing is tested per ASTM E595; acceptance limits are total mass loss below 1.0 % and collected volatile condensable material below 0.1 %. Thermal cycling follows MIL-STD-883 TM 1010.7, condition C, from −65 °C to +150 °C. Published data for this specific configuration is limited due to export-controlled documentation, but qualified avionics and satellite power conversion modules remain the terminal application.

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    Certification & Compliance
    More Introduction

    High thermal conductivity epoxy molding compound (EMC) Electronic/EL grade, designated HTC-EMC-EL 9620, is a transfer-molding thermoset formulated for encapsulation of power discrete packages, power modules, and LED lead-frame devices where heat transfer through the molding layer is a design constraint. The matrix consists of a biphenyl epoxy resin, a phenol-novolac hardener, an imidazole-type cure catalyst, and a multimodal filler network of spherical alumina, platelet boron nitride, and low-sodium fused silica. Filler content is adjusted so that through-plane thermal conductivity remains in the range 3.0 W/m·K to 5.2 W/m·K when cured plaques are measured by ASTM D5470-17. Cured density is 1.95 g/cm³ to 2.20 g/cm³ by ASTM D792-13. Spiral flow at 175 °C and 6.9 MPa transfer pressure is maintained between 90 cm and 140 cm by ASTM D3123. The Electronic/EL grade is distinguished from conventional semiconductor-grade EMC by hydrolyzable chloride content below 20 ppm, extractable sodium and potassium below 5 ppm each, and aqueous-extract ionic conductivity below 50 µS/cm to reduce electrochemical migration risk under biased humidity testing.

    Which Property Set Separates This Grade from Standard Semiconductor Encapsulants?

    The property profile is defined by the need to balance thermal conductivity against moldability. Standard semiconductor EMCs typically deliver through-plane thermal conductivity of 0.7 W/m·K to 1.2 W/m·K; the high-conductivity grade replaces part of the fused-silica filler with alumina and boron nitride, increasing thermal conductivity but also raising melt viscosity and reducing spiral flow. A comparative property set is provided in Table 1.

    Table 1. Comparative property profile for HTC-EMC-EL 9620, standard semiconductor EMC, and low-stress semiconductor EMC at 25 °C unless stated otherwise
    PropertyHTC-EMC-EL 9620Standard semiconductor EMCLow-stress semiconductor EMCTest method
    Through-plane thermal conductivity3.0–5.2 W/m·K0.7–1.2 W/m·K0.9–1.5 W/m·KASTM D5470-17
    Filler loading72–85 wt%70–80 wt%65–75 wt%ISO 11358-1:2022
    Flexural modulus18–25 GPa15–20 GPa8–12 GPaASTM D790-17
    CTE α1 below Tg12–18 ppm/°C15–22 ppm/°C20–28 ppm/°CISO 11359-2:2021
    CTE α2 above Tg40–60 ppm/°C55–80 ppm/°C70–100 ppm/°CISO 11359-2:2021
    Glass transition temperature by DSC165–210 °C150–190 °C130–170 °CISO 11357-2:2020
    Spiral flow at 175 °C, 6.9 MPa90–140 cm120–180 cm100–160 cmASTM D3123
    Gel time at 175 °C35–70 s40–80 s45–90 sASTM D4473-08
    Hydrolyzable chloride<20 ppm<50 ppm<50 ppmIPC-TM-650 2.3.25
    Volume resistivity after 24 h deionized-water immersion1 × 10¹⁴ Ω·cm1 × 10¹⁴ Ω·cm1 × 10¹⁴ Ω·cmASTM D257-14

    The high-conductivity grade has a flexural modulus of 18 GPa to 25 GPa, compared with 8 GPa to 12 GPa for a low-stress semiconductor EMC. This higher modulus is a direct consequence of the platelet and angular filler architecture and is relevant for packages with large die-to-package area ratios. The coefficient of linear thermal expansion below the glass transition temperature is lower, at 12 ppm/°C to 18 ppm/°C, which improves die stress management but increases substrate warpage potential on thin substrates. Above the glass transition, CTE increases to 40 ppm/°C to 60 ppm/°C. Cure conversion after 90 s at 175 °C is typically 85% to 95% by DSC; post-mold cure at 150 °C for 4 h raises conversion above 98%.

    When a Power Module Requires Through-Plane Thermal Conductivity Above 4 W/m·K

    For a molded power module or discrete package, the EMC layer contributes a thermal resistance proportional to bond-line thickness and inverse proportional to thermal conductivity. With the HTC-EMC-EL 9620-05 variant, through-plane thermal conductivity reaches 4.5 W/m·K to 5.2 W/m·K at 25 °C. At a bond-line thickness of 0.4 mm over a 10 mm × 10 mm die pad, the one-dimensional thermal resistance contribution is approximately 0.08 K/W. At 1.0 mm bond-line thickness, the contribution increases to approximately 0.20 K/W. These values are calculated for one-dimensional conduction without contact resistance and are not package junction-to-case resistance values unless die-attach, leadframe, and interface resistances are included.

    In-plane thermal conductivity is deliberately higher due to shear-induced orientation of platelet boron nitride during transfer flow. Laser-flash measurements on 30 mm × 30 mm × 1 mm cured coupons per ASTM E1461-13 show in-plane values of 8 W/m·K to 12 W/m·K, producing a through-plane-to-in-plane anisotropy ratio between 2:1 and 3:1. This anisotropy favors lateral heat spreading in leadframe packages but reduces the effective through-plane conductivity of thick encapsulation layers. For semiconductor applications requiring junction temperatures up to 200 °C, the filler network remains stable; however, published data for this specific configuration is limited above 200 °C, and continuous operation above the glass transition should be avoided due to CTE mismatch and warpage risk.

    Processing Limitations and Moisture Sensitivity in the EL Grade

    Production-scale transfer molding trials on 80 mm barrel-diameter presses with 120-ton clamp force and 0.5 mm/s to 2.5 mm/s plunger speeds show that filler loading above 72 wt% reduces spiral flow below 85 cm and raises apparent melt viscosity into the 60 Pa·s to 100 Pa·s range at 175 °C. The practical processing window therefore narrows to 170 °C–180 °C mold temperature and 6.0 MPa–8.0 MPa transfer pressure. Below 170 °C, gel time lengthens but viscosity remains high, causing incomplete fill in cavities with vent depths below 25 µm. Above 180 °C, gel time shortens to below 25 s, producing knit lines and incomplete cavity packing. Mold cavities require vacuum venting and wear-resistant tool steel or tungsten carbide surfaces because alumina and boron nitride are abrasive; mold wear rates are approximately 2–3 times those observed with standard silica-filled EMC under identical shot counts.

    Wire sweep on 25 µm diameter gold bond wires, measured by X-ray after molding, increased from less than 3% at 75 wt% filler loading to over 7% at 82 wt% filler loading. The mechanism is local filler migration and increased shear at the wire–resin interface. Lot-to-lot spiral flow variance is controlled within ±10 cm; if filler moisture exceeds 0.2 wt%, spiral flow variance expands to ±20 cm and hot hardness after 90 s at 175 °C falls below 75 Shore D. The material is supplied in sealed moisture-barrier bags at -20 °C. After removal from cold storage, tempering in the unopened bag at 25 °C and 55% RH for 12 h is required. Once opened, preforms should be consumed within 24 h; if ambient relative humidity exceeds 60% RH, working time is reduced to 8 h. Thermal pre-drying of pellets is not recommended because it advances B-staging and reduces flow at high filler loading. Compatibility with amine-based surface treatments should be verified before use; amine species can accelerate the cure reaction during storage and alter gel time.

    Differences in filler architecture alter both thermal transfer and mechanical stress

    The difference from standard semiconductor EMC arises primarily from filler architecture and purity. Standard grades rely on spherical fused silica to maximize flow and reduce equipment wear; their through-plane thermal conductivity rarely exceeds 1.2 W/m·K. The high-conductivity grade substitutes a portion of the silica with alumina to raise bulk conductivity and adds platelet boron nitride to create an in-plane conductive network. Compared with low-stress EMC, which uses a flexibilized resin to achieve flexural modulus of 8 GPa to 12 GPa, the high-conductivity grade maintains 18 GPa to 25 GPa modulus and lower CTE, reducing bulk thermal expansion but increasing transfer-molding stress on large dies. Compared with liquid epoxy potting and adhesive systems, the solid transfer-molding compound has no solvent or mixing step, provides higher glass transition, lower CTE, and higher modulus, and produces a consolidated package with better resistance to popcorning and thermal cycling. However, it is opaque and black, so it cannot replace transparent optical encapsulants. The grade is not recommended for packages requiring a flexural modulus below 10 GPa or for sections thicker than 3 mm where through-plane anisotropy limits effective thermal dissipation.

    The Electronic/EL purity grade also differs from industrial structural EMC by limits on total hydrolyzable chloride, alkali-metal extraction, and cure-catalyst residues. Industrial grades may accept chloride above 50 ppm; this grade is controlled below 20 ppm. Low ionic contamination is critical for biased humidity and high-temperature reverse-bias tests where chloride and sodium accelerate aluminum metallization corrosion. The flame-retardant system is available in halogen-free versions with total chlorine below 900 ppm, total bromine below 900 ppm, and combined halogen below 1500 ppm per IEC 61249-2-21.

    Compliance verification for the Electronic/EL grade is summarized in Table 2. The values are typical batch-release ranges, not specific lot limits unless stated otherwise.

    Table 2. Compliance and purity matrix for HTC-EMC-EL 9620
    RequirementValue or statusReference
    RoHS restricted substancesBelow maximum concentration values in Annex II: 0.1 wt% for Pb, Hg, Cr(VI), PBB, PBDE; 0.01 wt% for Cd2011/65/EU Annex II
    REACH SVHCNo intentionally added substances above declaration threshold; lot-specific declaration availableRegulation (EC) No 1907/2006
    Halogen-free optionTotal Br <900 ppm, total Cl <900 ppm, combined <1500 ppmIEC 61249-2-21
    Flammability ratingV-0 at 1.6 mm specimen thicknessUL 94 / IEC 60695-11-10
    Extractable ionsNa⁺ <5 ppm, K⁺ <5 ppm, Cl⁻ <20 ppm, aqueous-extract conductivity <50 µS/cmIPC-TM-650 2.3.25

    In a silicon-carbide power module encapsulation application, the grade has been transfer-molded over 8 mm × 8 mm die attach with copper clip interconnects at a mold temperature of 175 °C, transfer pressure of 7.0 MPa, and post-mold cure of 4 h at 150 °C. The as-molded packages exhibited no short shots and no wire sweep greater than 5% on 25 µm gold wires. Thermal resistance measurements by JEDEC JESD51-14 transient thermal testing showed a reduction in EMC layer thermal resistance of approximately 50% relative to a standard silica-filled EMC at equivalent thickness, but published data for this specific configuration is limited and package-level results depend on die-attach voiding, leadframe thickness, and interface delamination.

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