Here you will find all the frequently asked questions and answers that we have put together for you.
A suitable flux must ensure good soldering properties without interfering with the wave or selective soldering process. At the same time, it must be possible to process it reliably within the defined process parameters. For nickel surfaces, protection against re-oxidation is also required.
Specially formulated fluxes are required for nickel surfaces that are difficult to wet. Emil Otto has developed fluxes based on a carboxylic acid complex that can remove the oxide layer while simultaneously protecting the surface from further contamination and surface changes.
Relevant factors include the surface and drill holes of the printed circuit board, the PCB alloy and layout, storage conditions, component plating, preheating temperature and duration, the dwell time of the THT component in the solder, and the nitrogen atmosphere during selective soldering.
The flux helps remove oxides from the solder pads, thereby contributing to a clean, oxide-free surface and better wetting. Good wetting, in turn, can help reduce the formation of pores within the solder joint.
SAC alloys have higher surface tension, which makes it more difficult for trapped gases to escape from the solder. In addition, the higher process temperatures can promote gas formation from the flux, the printed circuit board, and the components. The wetting properties of SAC solders also play a role.
Possible causes include organic inclusions in the surface metallization, flux components, or oxides dissolved in the solder. Void formation is also influenced by the interaction between the printed circuit board, component metallization, solder alloy, and process control.
Voids can compromise the electrical and mechanical quality of a solder joint. Additional stress caused by vibration or temperature differences can destabilize the solder joint and, in the worst case, cause the connection between the substrate and the component to fail.
The flux must remain sufficiently active throughout the required temperature range of the soldering process. This is particularly important at higher solder bath temperatures and in processes where wire strand coatings are thermally removed during soldering.
Any remaining flux residue must not impair the electrical performance or long-term functionality of the cable connection. Of particular concern are potential corrosion and an excessively low surface electrical resistance (SIR).
The flux must allow for controlled tin plating so that only the specified length of the strand is wetted. At the same time, it must not damage the cable or strand insulation, nor have a corrosive effect on the resulting connection.
