In today’s electronic device manufacturing processes, many factories use lead-free solder flux composed mainly of rosin, resin, halogen-containing activators, additives, and organic solvents. While such fluxes offer good solderability and low cost, they leave behind high levels of residues after soldering. These residues contain halide ions, which gradually decrease electrical insulation performance and may lead to short circuits. To address this issue, it’s essential to thoroughly clean the rosin-based solder flux residues on the printed circuit boards (PCBs). However, the cleaning agents used to remove such residues mainly consist of fluorine-chlorine chemicals, which are ozone-depleting substances and are banned or phased out due to environmental concerns. Nevertheless, due to various reasons, many companies still use a process involving rosin-based lead-free solder flux soldering followed by cleaning with fluorinated cleaning agents, resulting in low efficiency, high costs, and severe environmental pollution.
Detaillierte Zusammensetzung des bleifreien Lötflussmittels
Currently, the most widely used and higher-grade option is a no-clean lead-free solder flux, composed of various materials dissolved in various liquids to form a homogeneous and transparent mixed solution. The specific ingredients include:
- Organic solvents: A mixture of ketones, alcohols, and esters, commonly including ethanol, propanol, butanol, acetone, methyl isobutyl ketone, ethyl acetate, butyl acetate, etc. These solvents dissolve the solid components of the lead-free solder flux, creating a homogeneous solution for uniform application to solder joints. Additionally, they can remove light dirt and oil contamination from metal surfaces.
- Natural resins and their derivatives or synthetic resin surfactants: Surfactants containing halogens have strong activity and soldering ability but are not suitable for use as raw materials in no-clean lead-free solder flux due to difficulties in cleaning, increased ionic residues, and corrosive properties. Surfactants without halogens have slightly lower activity but leave fewer ionic residues. These surfactants are typically non-ionic surfactants of the fatty acid or aromatic series, which reduce surface tension between solder and lead wires, enhance surface wetting, increase the penetration of organic acid activators, and may also act as foaming agents.
- Organic acid activators: Comprising organic acid diacids or aromatic acids, such as adipic acid, sebacic acid, p-toluene sulfonic acid, salicylic acid, azelaic acid, caprylic acid, malic acid, succinic acid, etc. These activators remove oxides from lead wires and molten solder surfaces, serving as important components of solder flux.
- Corrosion inhibitors: Reduce the residual substances left after the decomposition of solid components such as resins and activators at high temperatures.
- Solubilizers: Prevent the solid components like activators from precipitating out of the solution and ensure their uniform distribution.
These are the main components of lead-free solder flux. We hope this information is helpful to you!
