LOCTITE ECCOBOND UF 3811 Epoxy Underfill for BGA and CSP Protection

LOCTITE ECCOBOND UF 3811 Underfill for Reliable Electronics Protection

LOCTITE ECCOBOND UF 3811 Underfill is a one-component, halogen-free epoxy encapsulant developed to reinforce Ball Grid Array and Chip Scale Package components on printed circuit boards. Its low-viscosity formulation flows beneath electronic packages at room temperature through capillary action, eliminating the additional board or component preheating often required by conventional underfill materials. This streamlined processing can reduce equipment requirements, simplify production control, and improve manufacturing throughput.

The product is supplied as a black, heat-curing liquid and is designed for applications where solder joints require improved resistance to thermal cycling, mechanical impact, and drop testing. Although the cured epoxy has a relatively high glass-transition temperature, it retains sufficient flexibility to reduce concentrated stress around solder connections. This combination is especially valuable in compact electronic devices where package and board materials expand at different rates during temperature changes.

Key Benefits of LOCTITE ECCOBOND UF 3811 Underfill

LOCTITE ECCOBOND UF 3811 Underfill has a typical viscosity of approximately 354 mPa·s at 25°C and a specific gravity of about 1.16. Its low viscosity promotes rapid capillary penetration into the narrow space between the component and circuit board. Because the product flows effectively at room temperature, manufacturers can avoid a separate preheating stage before dispensing, helping reduce thermal exposure for nearby heat-sensitive components.

The uncured material has a published pot life of approximately three days at 25°C. Henkel provides several heat-curing schedules, including 60 minutes at 100°C, 30 minutes at 110°C, 10 minutes at 130°C, or seven minutes at 150°C. These schedules provide manufacturers with flexibility to balance component sensitivity, production speed, oven capacity, and required throughput. Actual curing conditions should be validated using the intended board design, package size, material volume, oven loading, and measured bond-line temperature.

After curing, the material has a typical glass-transition temperature of 124°C. Its coefficient of thermal expansion is approximately 61 ppm/°C below Tg and 190 ppm/°C above Tg. The cured underfill also has a typical storage modulus of 2,445 MPa at 25°C and thermal conductivity of approximately 0.23 W/m·K. These properties help reinforce the component while distributing mechanical and thermal stress across the package area.

Applications for LOCTITE ECCOBOND UF 3811 Underfill

LOCTITE ECCOBOND UF 3811 Underfill is specially designed for BGA and CSP assemblies used in mobile devices, wearable electronics, smart-home products, portable instruments, communication equipment, and other high-density electronic systems. Underfill materials reinforce interconnect arrays and help protect solder joints from movement, warpage, moisture, thermal stress, and mechanical loading.

The reworkable formulation can support manufacturing and repair processes where a defective or damaged component may need to be removed after underfill curing. Rework conditions must be developed carefully because the required temperature, tools, and removal method depend on the circuit board, package type, nearby components, solder alloy, and equipment available. Production trials should confirm both initial reliability and the complete rework process.

How to Apply LOCTITE ECCOBOND UF 3811 Underfill

Before dispensing LOCTITE ECCOBOND UF 3811 Underfill, ensure the assembled circuit board is clean, dry, and free from flux residue, dust, oil, moisture, and other contamination that could interfere with capillary flow or adhesion. Apply a controlled bead along one or more edges of the BGA or CSP package. Capillary force draws the low-viscosity epoxy beneath the component and through the interconnect array.

The dispensing volume should be sufficient to fill the package underside and create the required fillet without excessive overflow onto neighboring components. Flow time, dispense pattern, needle size, package clearance, board temperature, and material condition should be standardized for repeatable production. After filling, cure the assembly using a validated temperature profile based on Henkel’s recommended schedules.

Storage of LOCTITE ECCOBOND UF 3811 Underfill

Store unopened LOCTITE ECCOBOND UF 3811 Underfill in a dry location at the recommended temperature of approximately -20°C. Henkel lists a shelf life of 365 days under these storage conditions. Material removed from its original container should not be returned because contamination can affect flow, curing, and reliability. Before use, follow the approved thawing and handling procedure and review the current safety data sheet.

For electronics manufacturers requiring a low-viscosity, room-temperature-flowing and reworkable encapsulant, LOCTITE ECCOBOND UF 3811 Underfill provides effective BGA and CSP reinforcement, flexible curing options, stable electrical performance, and dependable solder-joint protection. Explore our electronic underfill encapsulants for BGA, CSP, WLCSP, flip-chip, mobile-device, wearable and circuit-board protection.