Loctite D 125 F

Loctite D 125 F is a high-performance, one-component, epoxy adhesive specifically engineered for high-speed dispensing in surface mount technology (SMT). This yellow, non-sagging paste is designed to secure passive components—such as chip capacitors, resistors, SOTs, and SOICs—onto printed circuit boards before wave soldering. It offers a unique combination of high hot strength and low-temperature curing, ensuring that components remain precisely positioned during the rapid thermal transitions of electronic assembly.

In its uncured state, the adhesive exhibits an extremely high viscosity of 1,750,000 mPa·s (at 1 rpm), providing excellent dot profile stability and eliminating “stringing” during high-speed needle dispensing. It features a high yield point of 350,000 mPa·s, which prevents the adhesive from slumping or spreading after placement. The material is optimized for processing flexibility, capable of curing in as little as 1.5 minutes at 150°C in a convection oven, or through infrared (IR) conveyor systems. To maintain its chemical integrity, it should be stored between 0°C and 8°C and allowed to reach room temperature before use.

Once heat-cured, Loctite D 125 F forms a robust mechanical bond with a lap shear strength exceeding 1,160 psi (8 N/mm²) on aluminium. It possesses a glass transition temperature of 85°C and a low coefficient of thermal expansion 58 ppm/°C below Tg, which minimizes mechanical stress on delicate solder joints. Its electrical reliability is supported by a volume resistivity of 1×10¹⁴ and low water absorption, ensuring the adhesive does not interfere with the electrical signals of high-density circuits even in humid operating environments.