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LOCTITE 3621 – Heat-curing red epoxy adhesive for SMD bonding in electronics manufacturing applications

  • Item Name: LOCTITE 3621
  • Manufacturer: Henkel
  • Product Category: Surface Mount Adhesive
  • Technologies: Epoxy-based, Heat Cure
  • Applications: Bonding surface-mounted devices (SMD) to printed circuit boards (PCB) before wave soldering, small parts bonding
  • Color: Red (viscous gel)
  • Cure Type: Heat cure (typically 90-120 seconds at 150°C)
  • Package Size: Contact Techniq VN for details.
  • Shelf Life: Contact Techniq VN for details.

1. Product Overview

LOCTITE 3621 is a one-component, heat-curing epoxy adhesive designed for bonding surface-mounted devices (SMDs) to printed circuit boards (PCBs) before wave soldering. It offers high wet strength, excellent electrical characteristics, and is particularly suited for high-speed dispensing applications (>35,000 dots/h). The adhesive is compatible with lead-free soldering processes using water- and alcohol-based fluxes.


2. Applications

  • Bonding SMD components to PCBs
  • Small parts bonding
  • High-speed dispensing applications (25,000 – 50,000 dots/h)

3. Typical Properties

Uncured Material

Property Value
Specific Gravity (25°C) 1.22
Yield Point (Pa) 130 – 280
Casson Viscosity (Pa∙s) 0.5 – 3
Particle Size (µm) <150
Appearance Red viscous gel

Curing Performance

Condition Cure Time
150°C 90 – 120 sec
125°C 5 min (≥90% cure conversion)
150°C 30 min (full cure)

Cured Material

Property Value
Glass Transition Temp (°C) 110
Thermal Conductivity (W/m·K) 0.3
Density (g/cm³) 1.16
Coefficient of Thermal Expansion (K⁻¹) 100×10⁻⁶ (25–70°C) / 218×10⁻⁶ (90–150°C)

Electrical Properties

Property Value
Volume Resistivity (Ω·cm) 1.3×10¹⁵
Surface Resistivity (Ω) 52×10¹⁵
Dielectric Breakdown Strength (kV/mm) 40
Dielectric Constant (1kHz) 2.94

Adhesive Strength

Test Condition Strength
Pull-off Strength (C-1206 on FR4) 50 N (13 lb)
Torque Strength (C-1206 on FR4) 60 N·mm (9.6 in.oz)
Push-off Strength (3 min @150°C) ≥27 N (≥6.0 lb)
Lap Shear Strength (Mild Steel) ≥15 N/mm² (≥2,175 psi)

Environmental Resistance

  • Hot Strength: Maintains strength up to 150°C
  • Resistance to Hot Solder Dip: Passes 260°C wave solder test
  • Surface Insulation Resistance (SIR): Retains high electrical insulation after 1000 hours at 85°C/85% RH

4. Storage & Handling

  • Store between 2°C – 8°C
  • Floor life at 22°C – 28°C: 1 month
  • Allow 2–4 hours to reach room temperature before use
  • Ideal dispensing temperature: 30°C – 35°C
  • Clean uncured adhesive with isopropanol, MEK, or ester blends (e.g., LOCTITE® 7360™)

BERGQUIST microTIM mTIM 1028 Thermal Interface Coating High performance thermal management solution for nickel finished heat sinks, optical transceivers, and data center liquid cooling systems

BERGQUIST microTIM mTIM 1028 is purpose built for riding cage assemblies in servers, switches, and routers, interfacing with electroless nickel plated copper or aluminum heat sinks. It ensures stable operation in high power transceiver modules while also extending applicability to liquid cooling components, heat pipes, and fin based dissipative structures.

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