Henkel LOCTITE 3629C Surface Mount Adhesive for PCB Assembly

LOCTITE 3629C Surface Mount Adhesive Performance

The adhesive is engineered to produce consistent deposits during automated PCB production. Its rheology helps each dot retain a controlled height and footprint after dispensing, supporting accurate component placement without excessive spreading. Henkel reports a Casson yield point of approximately 165 Pa·s at 25°C and a typical specific gravity of 1.38. These properties support precision dots beneath electronic components before board population and thermal processing.

LOCTITE 3629C Surface Mount Adhesive remains uncured until exposed to sufficient heat. Recommended curing requires a bond-line temperature above 100°C, with reference schedules of at least 150 seconds at 120°C or 90 seconds at 150°C. Actual cure rate and final strength depend on PCB construction, component population, oven ramp rate, adhesive volume, and residence time at the required temperature.

PCB Assembly and Wave Soldering Applications

The primary application is bonding surface-mounted devices to printed circuit boards before wave soldering. After the adhesive dot is dispensed and the component is placed, the board passes through a validated heat-curing process. The cured epoxy holds the component in position when the populated side of the PCB is exposed to wave-soldering forces, helping reduce movement, displacement, or component loss.

Typical uses include power-supply boards, appliance controllers, automotive electronic modules, communication equipment, industrial control boards, and lighting electronics. The product can be applied through high-speed dispensing systems using qualified nozzles and machine settings. Henkel recommends a dispensing temperature of 30°C to 35°C for optimum results, although each production line should be optimized for its equipment, dot dimensions, board design, and cycle time.

7 Benefits of LOCTITE 3629C Surface Mount Adhesive

• Halogen-free formulation: Supports electronic manufacturing with controlled material requirements.
• Fast heat curing: Reference cycles include 150 seconds at 120°C or 90 seconds at 150°C.
• High-speed dispensing: Designed for automated dot placement in volume PCB production.
• Controlled dot geometry: Helps maintain repeatable deposit size, shape, and component support.
• High thermomechanical strength: Retains compatible SMD components during wave soldering.
• One-component processing: Requires no resin-and-hardener measuring or mixing.
• Visible red color: Supports inspection of adhesive presence and placement accuracy.

Dispensing and Process-Control Guidance

Allow refrigerated containers to reach room temperature before use, normally for two to four hours, while preventing condensation. Keep nozzles, adapters, reservoirs, and feed components clean to avoid cross-contamination. Dispensed volume is influenced by pressure, time, nozzle size, machine settings, and adhesive temperature, so production parameters should be documented and monitored.

At 25°C and 55% relative humidity, Henkel states that the material can remain dispensable for a maximum of approximately two days of continuous machine operation. Higher temperature or humidity can shorten this period. Uncured adhesive can be removed with isopropanol, MEK, ester blends, or a compatible cleaner such as LOCTITE 7360, subject to board compatibility testing.

Cured Properties, Storage, and Packaging

After a reference cure of 30 minutes at 150°C, the product has a glass-transition temperature of at least 118°C. Typical cured density is approximately 1.4 g/cm³, while the coefficient of thermal expansion is about 45 ppm/°C below Tg and 144 ppm/°C above Tg. These values help engineers evaluate dimensional response during soldering and thermal cycling.

Store unopened LOCTITE 3629C Surface Mount Adhesive in a dry location between 2°C and 8°C. The official Henkel page lists 30 ml syringe and 300 ml cartridge formats, subject to regional availability. Do not return dispensed or potentially contaminated material to the original package.

Official Resources and Related PCB Adhesives

Review the official Henkel LOCTITE 3629C product page and the official LOCTITE 3629C technical data sheet for current properties, processing instructions, storage guidance, and regulatory documents.

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