Henkel LOCTITE 3619 Low-Temperature Surface Mount Adhesive for PCB Assembly

LOCTITE 3619 Low-Temperature Surface Mount Adhesive Performance

LOCTITE 3619 is supplied as a ready-to-use, de-aerated epoxy in syringes compatible with common pressure-and-time dispensing systems. The single-component formulation eliminates weighing, mixing, and resin-to-hardener ratio errors. It remains uncured until exposed to sufficient heat, allowing the adhesive to be dispensed and components to be accurately positioned before the curing process begins.

The uncured product is a red, high-viscosity paste with a typical specific gravity of approximately 1.22 at 25°C. Its Casson viscosity is listed at approximately 1 to 4 Pa·s, while the yield point is approximately 200 to 450 Pa under the specified cone-and-plate test method. The thixotropic behavior helps each adhesive deposit retain a useful height and shape after dispensing, reducing excessive spreading beneath the component.

LOCTITE 3619 Low-Temperature Surface Mount Adhesive Applications

The primary application is securing surface-mounted electronic components to printed circuit boards before wave soldering. During production, controlled adhesive dots are dispensed onto the PCB, components are placed over the deposits, and the adhesive is heat cured. The cured epoxy holds the devices in position while the populated side of the board passes over the solder wave.

Typical bonded components include chip resistors, capacitors, diodes, small integrated circuits, and other compatible SMD packages. The product is suitable for power-supply boards, automotive electronic modules, appliance controllers, industrial control systems, communication devices, lighting electronics, and consumer products requiring repeatable automated assembly.

LOCTITE 3619 is particularly valuable when the board includes components that cannot tolerate the higher or longer curing cycles associated with some conventional surface-mount adhesives. The low-temperature curing profile can help reduce thermal exposure while maintaining the component-retention strength required for subsequent soldering operations.

7 Benefits of LOCTITE 3619 Low-Temperature Surface Mount Adhesive

• Low-temperature curing: Supports PCB assemblies containing heat-sensitive electronic components.
• Short curing cycles: Helps improve production throughput in high-volume electronics manufacturing.
• One-component processing: Eliminates weighing, mixing, and adhesive-ratio variation.
• High-speed dispensing: Supports approximately 25,000 to 40,000 adhesive dots per hour under qualified conditions.
• High wet strength: Helps prevent component movement after placement and before heat curing.
• Controlled dot profile: High-viscosity rheology helps deposits retain useful height and geometry.
• Electrical insulation: Provides strong dielectric and resistivity properties after complete curing.

LOCTITE 3619 Low-Temperature Surface Mount Adhesive Cure Guidance

Henkel recommends curing through exposure to heat at approximately 100°C or above. A typical short production cycle is approximately 90 to 120 seconds at 100°C after the adhesive itself reaches the required temperature. The total oven time may need to be longer because the PCB, components, fixtures, and adhesive require time to warm to the selected bond-line temperature.

The technical data also reports at least 70% isothermal DSC conversion after approximately three minutes at 90°C. Longer cycles may be used when greater cure development or standardized property testing is required. Henkel’s published cured-property data frequently uses reference cycles such as five or 30 minutes at 100°C.

The correct production profile depends on component size, PCB thickness, solder-mask construction, adhesive-dot volume, oven design, airflow, conveyor speed, and component heat sensitivity. Manufacturers should measure the temperature at the actual adhesive location rather than relying only on the oven’s displayed air temperature.

Dispensing and Process-Control Recommendations

After refrigerated storage, keep the syringe closed and allow it to reach room temperature for approximately two to four hours before use. This helps prevent condensation and restores consistent dispensing behavior. Henkel recommends controlling the dispensing temperature at approximately 30°C to 35°C for optimum high-speed performance.

The amount dispensed is controlled by pressure, dispensing time, nozzle diameter, material temperature, and equipment design. Positive-displacement pump systems may also be used. Pin-transfer dispensing is not recommended for this product. Nozzles, adapters, and equipment components must be clean and free from residues of other adhesives to prevent contamination and inconsistent deposits.

Uncured material may be removed from suitable PCB surfaces using isopropanol, MEK, compatible ester blends, or an approved cleaner such as LOCTITE 7360. Cleaner compatibility must be tested with the solder mask, component body, markings, plastics, and other materials used in the actual assembly.

Electrical Strength and Wave-Soldering Resistance

Published electrical properties after curing include volume resistivity of approximately 1.2 × 10¹⁵ Ω·cm and dielectric breakdown strength of approximately 30 kV/mm. These characteristics support electrically non-conductive component fixing on properly designed PCB assemblies.

Under Henkel’s reference conditions, LOCTITE 3619 provides push-off strength of at least 25 N for C-1206 components on bare FR-4 after curing for 90 seconds at 100°C. Published steel lap-shear strength is at least 14 N/mm² after a 30-minute cure at 100°C. Actual component retention depends on package type, dot dimensions, solder-mask grade, surface condition, and degree of cure.

The cured material also passed a referenced hot-solder-dip test in which an R-1206 component was held above a 260°C solder bath for 60 seconds and then immersed for ten seconds. This supports its intended use during qualified wave-soldering processes.

Storage and Official Product Resources

Store unopened LOCTITE 3619 between 2°C and 8°C in a dry location. Temperatures below or above this range may adversely affect product properties. Do not return dispensed or potentially contaminated adhesive to the original syringe or container.

Review the official Henkel LOCTITE 3619 product page and the official LOCTITE 3619 technical data sheet for current processing instructions, storage guidance, safety documentation, and regional availability.

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